ALBERT

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Maxim Rakhuba, Alexander Novikov, Ivan Oseledets〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Such problems as computation of spectra of spin chains and vibrational spectra of molecules can be written as 〈em〉high-dimensional eigenvalue problems〈/em〉, i.e., when the eigenvector can be naturally represented as a multidimensional tensor. Tensor methods have proven to be an efficient tool for the approximation of solutions of high-dimensional eigenvalue problems, however, their performance deteriorates quickly when the number of eigenstates to be computed increases. We address this issue by designing a new algorithm motivated by the ideas of 〈em〉Riemannian optimization〈/em〉 (optimization on smooth manifolds) for the approximation of multiple eigenstates in the 〈em〉tensor-train format〈/em〉, which is also known as matrix product state representation. The proposed algorithm is implemented in TensorFlow, which allows for both CPU and GPU parallelization.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Chen Liu, Florian Frank, Faruk O. Alpak, Béatrice Rivière〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Permeability estimation of porous media from directly solving the Navier–Stokes equations has a wide spectrum of applications in petroleum industry. In this paper, we utilize a pressure-correction projection algorithm in conjunction with the interior penalty discontinuous Galerkin scheme for space discretization to build an incompressible Navier–Stokes simulator and to use this simulator to calculate permeability of real rock samples. The proposed method is accurate, numerically robust, and exhibits the potential for tackling realistic problems.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Mustapha Malek, Nouh Izem, M. Shadi Mohamed, Mohammed Seaid, Omar Laghrouche〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An efficient partition of unity finite element method for three-dimensional transient diffusion problems is presented. A class of multiple exponential functions independent of time variable is proposed to enrich the finite element approximations. As a consequence of this procedure, the associated matrix for the linear system is evaluated once at the first time step and the solution is obtained at subsequent time step by only updating the right-hand side of the linear system. This results in an efficient numerical solver for transient diffusion equations in three space dimensions. Compared to the conventional finite element methods with 〈em〉h〈/em〉-refinement, the proposed approach is simple, more efficient and more accurate. The performance of the proposed method is assessed using several test examples for transient diffusion in three space dimensions. We present numerical results for a transient diffusion equation with known analytical solution to quantify errors for the new method. We also solve time-dependent diffusion problems in complex geometries. We compare the results obtained using the partition of unity finite element method to those obtained using the standard finite element method. It is shown that the proposed method strongly reduces the necessary number of degrees of freedom to achieve a prescribed accuracy.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Lahbib Bourhrara〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This document presents a new numerical scheme dealing with the Boltzmann transport equation. This scheme is based on the expansion of the angular flux in a truncated spherical harmonics function and the discontinuous finite element method for the spatial variable. The advantage of this scheme lies in the fact that we can deal with unstructured, non-conformal and curved meshes. Indeed, it is possible to deal with distorted regions whose boundary is constituted by edges that can be either line segments or circular arcs or circles. In this document, we detail the derivation of the method for 2D geometries. However, the generalization to 2D extruded geometries is trivial.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Yadan Guo, Chenxi Li, Yiqin Guo, Xuegang Wang, Xiaomeng Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Graphitic carbon nitride (g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉) is a new type of nonmetal polymeric semiconductor photocatalyst for removal of pollutants. To overcome the low BET surface and the low electron–hole recombination rate of the g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 photocatalysts, we successfully synthesized g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/Na-bentonite composites using an ultrasonic-assisted method. The XRD showed that the composite was composed of g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 and Na-bentonite. The analyses of TEM and XPS indicated that graphite carbon nitride was successfully intercalated on Na-bentonite via the ultrasonic-assisted strategy, and the g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/Na-bentonite nanocomposites presented remarkable light absorption capacities and mesoporous structure observed by UV–vis DRS and BET method. In addition, the as-prepared composites can be used for the photocatalytic removal of single RhB or Cr(VI), and the efficiencies of the Cr(VI) reduction are increased from 53.2% to 88.6% in RhB/Cr(VI) mix-system. Superior stability and high efficiencies of g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/Na-bentonite composites were also exhibited for up to 4 cycles. The photocatalytic enhancement was due to the strong adsorption and the higher charge separation efficiency of as-prepared g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/Na-bentonite composites.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719306065-ga1.jpg" width="219" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Lifeng Chen, Zhen Qian, Liang Li, Meilong Fu, Hui Zhao, Lipei Fu, Gang Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water production is getting worse along with the continuous water injection in the reservoir with fracture, but common hydrogels cannot be successfully applied for water shutoff due to its poor resident ability in fracture. In this work, an interpenetrating network hydrogel has been developed innovatively by polyvinyl alcohol (PVA) fiber and common polyacrylamide (PAM) hydrogel. Plugging ability, long-term thermal stability and the interaction between PVA fiber and hydrogel were detailedly studied. Results show that PVA fiber is beneficial to the stability of the PAM hydrogel, and the syneresis rate can be decreased from 30% to 3% on the 120〈sup〉th〈/sup〉 day. PVA fiber accelerates the hydrogel gelation, and the high concentration of fiber leads to good hydrogel strength. PVA fiber increases the amount of the bound water in hydrogel, leading the hydrophilcity increase of hydrogel. An interpenetrating network is formed on the micrometer level, resulting from the three-group crosslinking among polymer, cross-linker and fiber. Compared with common PAM hydrogel, the interpenetrating network hydrogel has better water shutoff effect and EOR performance. Core flow experiment and micromodel test show that the interpenetrating network hydrogel forms an effective bridge in fracture, and it is hard to be moved due to the water washing. The introduction of fiber to hydrogel is an innovative research, which not only improves the water shutoff effect of hydrogel in fracture, but also provides reference to increase the performance of drilling fluid, fracturing solution and EOR polymer utilized in petroleum engineering.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Micropresentation of synergistic effect of PVA fiber on PAM solution (A, B) and hydrogel (C, D).〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719305928-ga1.jpg" width="252" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Krzysztof Kolman, Zareen Abbas〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Molecular dynamics (MD) simulations provide molecular level information about the interaction of organic molecules with the solid surfaces. There has been much development of this method to simulate the interaction of organic molecules with neutral surfaces but relatively less information is available regarding the interactions with charged surfaces. In this study we have developed MD model for the charged silica surface and have investigated the interactions of different benzoic acid derivatives with the charged silica surface in pure and saline water at acidic, neutral and basic pH. The investigated molecules were 2,3-dihydroxybenzoic acid (23DHBA), 3,4-dihydroxybenzoic acid (34DHBA), 1,2,4-benzenetricarboxylic acid (BTCA) and phthalic acid (PHTHA). To simplify the analysis of results, three different simulation systems were considered. Clustering simulations showed how molecules aggregate in solution, pulling simulations provided quantitate information regarding the interactions of single molecule with the silica surface, whereas adsorption simulations focused on the adsorption of multiple molecules on the surface. In general, at pH 2–3, all investigated molecules were clustering and were attracted towards the surface. At pH 7, due to arising electrostatic repulsion, the interactions became weaker which prevented 23DHBA, 34DHBA and BTCA from clustering, however, they continued to adsorb on the silica surface. The adsorption of 23DHBA and 34DHBA decreased significantly at pH 9–10 due to electrostatic repulsion between the molecules and charged silica surface, while BTCA adsorbed slightly stronger due to interactions with ions close to the surface. PHTHA molecules behaved differently by clustering stronger and adsorbing weaker at higher pH. The results of MD simulations presented in this work by using pulling and adsorption approaches provide possibility to compare the results with experimental data.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719301748-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): José G. Parra, Héctor Domínguez, Yosslen Aray, Peter Iza, Ximena Zarate, Eduardo Schott〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Structural characteristics, interfacial distribution and molecular interactions of the components of the CO〈sub〉2〈/sub〉(gas)/SDS/water/SDS/CO〈sub〉2〈/sub〉(gas) systems as a function of the CO〈sub〉2〈/sub〉(gas)/water interface coverage by the SDS surfactant to different amounts of the CO〈sub〉2〈/sub〉 were studied with molecular dynamics simulations and the NVT ensemble. Initially, the repulsive nonbonding parameter between the water oxygen and CO〈sub〉2〈/sub〉 oxygen was adjusted to improve the prediction of the solvation free energy, solubility of the CO〈sub〉2〈/sub〉 gas in water and the behavior of the CO〈sub〉2〈/sub〉(gas)/SDS/water/SDS/CO〈sub〉2〈/sub〉(gas) systems at molecular level. Our results show that the stability of the studied foams can be improved incrementing of the vapor/water interface coverage with the SDS surfactant and the amount of CO〈sub〉2〈/sub〉 in the system. With the highest interface coverage, the sulfate group has a molecular array more compact at the interface. Furthermore, CO〈sub〉2〈/sub〉 gas have a reduction of the diffusion across of the hydrocarbon chains to the water layer with an increment of the number of CO〈sub〉2〈/sub〉 molecules in the system, indicating a behavior more hydrophobic of the CO〈sub〉2〈/sub〉 gas. The tendencies obtained of the simulations are consistent with the reported experimental results.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719305989-ga1.jpg" width="239" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): M. Jinish Antony, C. Albin Jolly, K. Rohini Das, T.S. Swathy〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report here the synthesis of polyaniline (PANI) nanomaterials using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) micelles assisted chemical oxidative interfacial polymerization. We have employed two interfaces (chloroform-water and hexane-water) and two oxidizing agents (ammonium persulfate and ferric chloride). The anionic surfactant sodium bis (2-ethylhexyl) sulfosuccinate (AOT) forms normal micelles in aqueous solution and reverse micelles in hydrophobic solvents like hexane or chloroform. The factors influencing the properties and morphologies of polyaniline nanomaterials such as monomer: surfactant ratio, monomer: oxidant ratio, types of interfaces and oxidants used have been studied. Powder X-ray diffraction of the polyaniline nanomaterials have revealed that polyaniline samples were semi-crystalline in nature. Morphology of polyaniline samples studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have revealed that most of the polyaniline nanomaterials synthesized using ferric chloride possess spherical nature, whereas polyaniline samples synthesized using ammonium persulfate (APS) possess short nanofibers especially at lower aniline/AOT mole ratio in feed (12.5–6.5). The four probe electrical conductivity of the samples were found to be of the order of 1.8 × 10〈sup〉−1〈/sup〉 to 8.6 × 10〈sup〉−1〈/sup〉 S/cm. Thermal stability of the polyaniline samples recorded by thermogravimetric analysis (TGA) have revealed that polyaniline samples were thermally stable up to 275 °C for 10% weight loss. Interfacial polymerization of aniline monomer using reverse micelles of AOT in hexane phase and ammonium persulfate as oxidizing agent in aqueous phase have been proved to be efficient method for the synthesis of short polyaniline nanofibers.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719306090-ga1.jpg" width="316" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Feng Zhao, Shibin Wang, Xin Shen, Jianchun Guo, Yuxuan Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Inhibiting acid-rock reaction rate is an important key in the field of acid fracturing. Based on the acid-rock reaction mechanism and the performance characteristics of surfactant, the surfactant is applied to cover the rock surface for forming an adsorption layer, which can keep H〈sup〉+〈/sup〉 from contacting the surface of rock during acid fracturing. In this paper, a series of cationic Gemini surfactants with different hydrophobic chain length are synthesized (C〈sub〉n〈/sub〉-4-C〈sub〉n〈/sub〉, n = 12, 14, 16).The surface tension, adhesion work, and AFM are used to investigate the effect of hydrophobic chain length and concentration of surfactant on surface activities, adsorption morphology and adsorption capacities. The static acid-rock reaction rate is measured and the surface of the rock plate is digitally characterized by 3D scanning. The results show that Gemini surfactants have the high surface activities. It can be recognized from AFM that as the length of the carbon chain increases, the aggregation of Gemini surfactants on the surface to form micelles becomes more and more obvious, resulting in a decrease in the density and area of the adsorption. However there are few differences for adsorption capacities. Therefore, 12-4-12 can restart H〈sup〉+〈/sup〉 most efficiently. This conclusion is proved by static acid-rock reaction. In addition, H〈sup〉+〈/sup〉 only reacted with the rock from the micro fractures of the adsorption layer formed by 12-4-12, the surface morphology of the rock plate after etching is the best rugged. In conclusion, it is believed that using the Gemini surfactant to form an adsorption layer on the rock surface is a new approach for inhibiting acid rock reaction rate and has great potential in oil field application.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Inhibiting acid-rock reaction rate is an important key in the field of acid fracturing. The morphology of the surfactant on the rock controls the rate between acid and rock. The properties of the different chain length surfactant form different layered structure on the substrate. 12-4-12 can play an efficacious role to adsorb on the rock surface to prevent H〈sup〉+〈/sup〉 from contacting the surface of rock.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719306119-ga1.jpg" width="295" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Zhao Mu, Jianhao Hua, Sai Kumar Tammina, Yaling Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In current investigation, we synthesized a new Cu, N co-doped carbon dots/Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 (Cu, N-CDs/Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉) nanocomposite by one-step thermolysis and precipitation method. In addition, we evaluated the activity of Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 and Cu,N-CDs/Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 nanomaterials in degrading an environmental pollutant called neutral red under visible radiations. Compared to the pure Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉, Cu, N-CDs/Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 had shown high degradation efficiency by more than 25% and shown good recyclability. The synthesized nanocomposite was characterized by XRD, HRTEM, FT-IR, Raman and XPS techniques. The optical property of Cu, N-CDs/Ag〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉 nanocomposite was examined with UV–vis DRS (Diffuse Reflectance Spectroscopy). And the excellent photocatalytic performance of this Cu, N-CDs system was ascribed to the increased conversion of ·O〈sub〉2〈/sub〉〈sup〉−〈/sup〉 under visible light irradiations and effective separation of electron-hole pairs, results in inhibited photocorrosion of the system. Also, this nanocomposite could successfully degrade the neutral red dye (mention the concentration) about 95.5% under LED irradiations within 60 min.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719306193-ga1.jpg" width="222" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Juan David Beltrán, Camilo Eduardo Sandoval-Cuellar, Katherine Bauer, María Ximena Quintanilla-Carvajal〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liposomes are spherical vesicles which can be used as encapsulation systems for transporting and releasing many biocomposites which can be affected by conditions in the gastrointestinal tract; such affectation means that the dominant degradation mechanisms and the factors influencing such degradation must be identified by means of digestion studies. This study was thus aimed to evaluate the physical stability and intestinal digestibility of nanoliposomes (NLs) produced by microfluidization (MF) and ultrasound (US) for high oleic palm oil (HOPO) encapsulation. A standardized 〈em〉in vitro〈/em〉, three-stage (〈em〉i.e.〈/em〉 oral, gastric and intestinal) static model of the gastrointestinal tract was used which had been published by the INFOGEST research network. No statistically significant changes were observed concerning any of the properties regarding stability during the oral phase; however, both types of NL studied here became destabilized during the gastric phase by environmental conditions, such as acid pH and high ion concentration. This was reflected by increased average particle size, the polydispersity index and the Z potential. Decreased particle size was observed during intestinal digestion regarding both technologies compared to gastric phase. MF-produced NLs were larger than US-produced ones during this phase. Intestinal enzymes degraded the system’s triglycerides, leading to 116.04 ± 2.62%w MF and 80.39 ± 2.26%w US free fatty acid release.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719305862-ga1.jpg" width="389" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Chengwei Wang, Lili Ma, Qingkun Wen, Baoxiang Wang, Rongjiang Han, Chuncheng Hao, Kezheng Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, an electrorheological (ER) fluid containing titanium oxide@ H〈sub〉2〈/sub〉Ti〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanotube core/shell nanocomposite was prepared via the combination of hydrothermal and solvo-thermal method. The morphological evolution was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Furthermore, the structural characteristics of the as-obtained core/shell nanoparticles were confirmed by x-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) and nitrogen adsorption measurements respectively. Titanium oxide@H〈sub〉2〈/sub〉Ti〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 nanotube core/shell nanocomposite is showed to possess tube-like and core-shell structure and enhanced ER properties under external electric fields.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930617X-ga1.jpg" width="235" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 396〈/p〉 〈p〉Author(s): Luigi Brugnano, Juan I. Montijano, Luis Rández〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper we study arbitrarily high-order energy-conserving methods for simulating the dynamics of a charged particle. They are derived and studied within the framework of 〈em〉Line Integral Methods (LIMs)〈/em〉, previously used for defining 〈em〉Hamiltonian Boundary Value Methods (HBVMs)〈/em〉, a class of energy-conserving Runge-Kutta methods for Hamiltonian problems. A complete analysis of the new methods is provided, which is confirmed by a few numerical tests.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 578〈/p〉 〈p〉Author(s): Jincheng Mao, Jizhen Tian, Wenlong Zhang, Xiaojiang Yang, Heng Zhang, Chong Lin, Yang Zhang, Zhaoyang Zhang, Jinzhou Zhao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gemini cationic surfactants, which have two cationic surfactant molecules connected by a spacer, have received increased attention in recent years as very good thickeners for clean fracturing fluids. We synthesized four Gemini cationic surfactants with three, four, five, and six methylene groups in the spacers. Salts can promote micelle aggregation of viscoelastic surfactants (VESs) and affect their performance and we used potassium chloride (KCl) to study the performance differences of the surfactants with different spacer lengths. The results showed that the surfactant with three methylene groups in its spacer had the lowest critical micelle concentration, and when combined with KCl in solution, it had the best salt tolerance and apparent viscosity in KCl concentrations ranging from 0.2 wt% to 2.6 wt%. In addition, the solution also exhibited an excellent viscoelasticity and a tighter network microstructure, which was confirmed by SEM observation and oscillatory measurement. We conducted rheological measurements for the four Gemini cationic surfactant fracturing fluid formulations with a shear rate of 170 s〈sup〉−1〈/sup〉 at up to 100 °C. The solution with KCl and the surfactant with the shortest spacer had distinctly superior rheological properties, and its viscosity could be maintained above 58 mPa.s after 120 min. Finally, we did proppant suspension tests, gel breaking property tests, and core matrix permeability damage rate tests on the four optimized fracturing fluid systems. The solution prepared by KCl and the surfactant with the shortest spacer was found to have the most favorable properties for fracturing fluids. These results demonstrate that decreasing the spacer length of a Gemini cationic surfactant leads to better performance in fracturing fluids.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The effect of counter-ion salt (KCl) concentrations on 21-(3,4,5,6)-21 surfactants that the surfactant solutions were transparent at low salt concentrations, but with increasing counter-ion concentrations above a peak viscosity, the phase separation occurred in all surfactant solutions. Meanwhile, this also shows that increasing the number of carbon atoms on the spacer of the surfactants lead to a greater sensitivity to the phase separation phenomenon.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719306016-ga1.jpg" width="227" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Zechen Liu, Yangchao Xia, Qingteng Lai, Maoyan An, Yinfei Liao, Yongtian Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this investigation, a mixed collector (MC) of dodecane and n-valeric acid was used to improve low rank coal flotation. Fourier transformation infrared spectroscopy (FTIR) measurements and contact angle measurements were conducted to explain flotation responses. Furthermore, using a molecular dynamics (MD) simulation, the changes of water/collector (dodecane or MC)/coal systems were studied before and after adsorption to indicate the absorption behavior and mechanism. The results showed that a better flotation performance of low-rank coal was obtained using the MC compared to a conventional collector of dodecane. The hydroxyl (-OH) or carbonyl (C = O) or carboxyl (COOH) migration of the coal with the MC was stronger than that with dodecane as a solo collector, and the MC can enhance the hydrophobicity and lipophilicity of the coal surface. MD simulation results revealed the adsorption behavior of the MC on low-rank coal surfaces. Dodecane was mainly adsorbed on the hydrophobic surface of coal, and n-valeric acid was more inclined to act on the oxygen-containing functional group of coal, i.e., a hydrophilic surface. The mobility of = dodecane molecules on the coal surface was reduced owing to the presence of n-valeric acid, which increased the lipophilicity and hydrophobicity of the low-rank coal surface, thus attracting dodecane molecules of the MC and restricting their movement, and accelerating the departure of water molecules from the low-rank coal surfaces. There was also a higher interaction energy between the MC and low-rank coal. The simulation results are in good agreement with the measured results; this effectively explains the flotation results.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308283-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Xing-An Luo, Pei Zhao, Hai Zhang, Shu-Yi Feng, Ke-Xian Chen, Zhong-Xiu Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dietary macromolecules are often used for food formulation. Most of the published literature usually focuses on a certain polysaccharide reducing lipid digestion, but the non-specific physical effects such as the excluded volume effect of the surrounding macromolecules, which will possibly enhance the hydrolysis of lipids, is rarely discussed. As the influence of polysaccharides on the gastrointestinal fate of α-tocopherol acetate (VE-A) encapsulated in emulsion have not been conducted so far, in this research, we study the effect of crowded medium created by polysaccharides (Ficoll400) on the hydrolysis of VE-A and its bioaccessibility. The results show that the presence of Ficoll400 increased the bioaccessibility and conversion of VE-A 1.6 times that of a dilute buffer. An enzyme-catalyzed kinetic reaction rate of VE-A hydrolysis is increased up to 3.5 times. Both the improved thermodynamic conversion yields and kinetic rates of the hydrolysis of the VE-A emulsion was further observed in a synthetic macromolecule PEG2000 medium. This research improves our understanding of the crowding effect of macromolecules on VE-A/lipid emulsion digestion.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308258-ga1.jpg" width="323" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Konstantin Pieper, K. Chad Sockwell, Max Gunzburger〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A framework for exponential time discretization of the multilayer rotating shallow water equations is developed in combination with a mimetic discretization in space. The method is based on a combination of existing exponential time differencing (ETD) methods and a careful choice of approximate Jacobians. The discrete Hamiltonian structure and conservation properties of the model are taken into account, in order to ensure stability of the method for large time steps and simulation horizons. In the case of many layers, further efficiency can be gained by a layer reduction which is based on the vertical structure of fast and slow modes. Numerical experiments on the example of a mid-latitude regional ocean model confirm long term stability for time steps increased by an order of magnitude over the explicit CFL, while maintaining accuracy for key statistical quantities.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Stéphane Zaleski, Feng Xiao〈/p〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Dario Collia, Marija Vukicevic, Valentina Meschini, Luigino Zovatto, Gianni Pedrizzetti〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The fluid dynamics inside the left ventricle of the human heart is considered a potential indicator of long term cardiovascular outcome. In this respect, numerical simulations can play an important role for integrating existing technology to reproduce flow details and even conditions associated to virtual therapeutic solutions. Nevertheless, numerical models encounter serious practical difficulties in describing the interaction between flow and surrounding tissues due to the limited information inherently available in real clinical applications.〈/p〉 〈p〉This study presents a computational method for the fluid dynamics inside the left ventricle designed to be efficiently integrated in clinical scenarios. It includes an original model of the mitral valve dynamics, which describes an asymptotic behavior for tissues with no elastic stiffness other than the constrain of the geometry obtained from medical imaging; in particular, the model provides an asymptotic description without requiring details of tissue properties that may not be measurable 〈em〉in vivo〈/em〉.〈/p〉 〈p〉The advantages of this model with respect to a valveless orifice and its limitations with respect to a complete tissue modeling are verified. Its performances are then analyzed in details to ensure a correct interpretation of results. It represents a potential option when information about tissue mechanical properties is insufficient for the implementations of a full fluid-structure interaction approach.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Ping Ding, Serafim Bakalis, Zhibing Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Foaming in high viscous and non-Newtonian aqueous phase is generally difficult to be realised. In this work, a surfactant (Sodium Linear Alkylbenzene Sulphonate with alkyl chain lengths varying from C10 to C16) named LAS paste mixed with a co-polymer solution of acrylic acid and maleic acid denoted by Polymer solution was used to generate foam under conditions of sparging without or with agitation, which aims to be used as a coating material of detergent powders. The foam structure/morphology, bubble size, gas holdup and liquid drainage in such surfactant-copolymer system were investigated. It was found that two different types of foam were generated: 1) dispersed spherical air bubbles in highly viscous mixtures of LAS paste and Polymer solution with median size d50 in a range of 20 – 50 μm and gas holdup of 0.20 - 0.44 depending on LAS concentration, 2) bubbles with polyhedral structure in a mixture of LAS paste and Polymer solution diluted with water and size d50 = 7.0 ± 0.4 mm and gas holdup of 0.93 ± 0.05. The generated foam structures depended on the energy input, air superficial velocity, surfactant concentration and the liquid viscosity. Besides, they even depended on liquid mixing procedures before the foam was generated, resulting from different transfer rates from LAS paste phase to Polymer solution. The comparison of foam behaviours in such complex system and in single-phase liquid was made. For dispersed spherical bubbles, the median size has been correlated to energy input whilst for bubbles with polyhedral structure the characteristic size has been predicted by considering the balance between their buoyancy and viscous forces generated in the system. Based on the results, the mechanism of foam stabilisation is proposed.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308052-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 22 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): L. Nouveau, M. Ricchiuto, G. Scovazzi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose an extension of the embedded boundary method known as “shifted boundary method” to elliptic diffusion equations in mixed form (e.g., Darcy flow, heat diffusion problems with rough coefficients, etc.). Our aim is to obtain an improved formulation that, for linear finite elements, is at least second-order accurate for both flux and primary variable, when either Dirichlet or Neumann boundary conditions are applied. Following previous work of Nishikawa and Mazaheri in the context of residual distribution methods, we consider the mixed form of the diffusion equation (i.e., with Darcy-type operators), and introduce an enrichment of the primary variable. This enrichment is obtained exploiting the relation between the primary variable and the flux variable, which is explicitly available at nodes in the mixed formulation. The proposed enrichment mimics a formally quadratic pressure approximation, although only nodal unknowns are stored, similar to a linear finite element approximation. We consider both continuous and discontinuous finite element approximations and present two approaches: a non-symmetric enrichment, which, as in the original references, only improves the consistency of the overall method; and a symmetric enrichment, which enables a full error analysis in the classical finite element context. Combined with the shifted boundary method, these two approaches are extended to high-order embedded computations, and enable the approximation of both primary and flux (gradient) variables with second-order accuracy, independently on the type of boundary conditions applied. We also show that the the primary variable is third-order accurate, when pure Dirichlet boundary conditions are embedded.〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Natalya Sankova, Viktoriya Semeykina, Ekaterina Parkhomchuk〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we have studied the growing mechanism of polystyrene microspheres with a small amount of cross-linking agent (0.2–2 wt%) during dispersion polymerization (DP) in 1-butanol in presence of PVP-40 steric stabilizer. Scanning electron microscopy and dynamic light scattering showed that particles take anomalous form at first several hours due to the growth predominantly by homo- and hetero-coagulation mechanism. The duration of the coagulation process is estimated to be of about a minute. Understanding of the mechanism of particle formation in the above systems will help to overcome the problem of irreproducibility, control the preparation of anisotropic particles during DP and extend the application of these particles.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307332-ga1.jpg" width="496" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Xiaobo Nie, Wei Jiang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A facile method is introduced to tune the aggregate morphologies of ABC triblock copolymer in selective media by combining the self-assembly and hydrogen bonding. Poly(styrene)-〈em〉block〈/em〉-poly(1,4-butadiene)-〈em〉block〈/em〉-poly(2-vinyl pyridine), abbreviated for PS-〈em〉b〈/em〉-PBd-〈em〉b〈/em〉-P2VP and used as an ABC triblock copolymer, self-assembles in toluene and methanol mixture to form discoid micelles with PBd as the disk containing part of PS domains in the core, other PS as bumps and P2VP as corona, respectively. When oleic acid (OA) is added in the assembly system, supramolecular polymer PS-〈em〉b〈/em〉-PBd-〈em〉b〈/em〉-P2VP(OA) is prepared by the hydrogen bonding between OA and P2VP of triblock copolymer. As a result, biscuit-like and mushroom-like micelles are formed with assistance of hydrogen bonding. Interestingly, the biscuit-like and mushroom-like micelles can transform reciprocally by fission and fusion mechanism through varying the volume ratio of toluene and methanol. Thus, it provides a simple and convenient approach to control the aggregate morphologies of block copolymers by tuning the hydrogen bonding and selective solvent content. The multicompartment micelles from ABC triblock copolymer may present potential applications in drug delivery, targeting, catalysis and others.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308271-ga1.jpg" width="247" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Badr M. Thamer, Ali Aldalbahi, Meera Moydeen A, Abdullah M. Al-Enizi, Hany El-Hamshary, Mandeep Singh, Vipul Bansal, Mohamed H. El-Newehy〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Activated electrospun carbon nanofibers (A-ECNFs) with micro/mesoporous structures and high surface areas (1615 m〈sup〉2〈/sup〉 g〈sup〉-1〈/sup〉) were prepared using an electrospinning technique followed by carbonization and alkali activation. The adsorption of Congo red (CR) and methylene blue (MB) dyes by A-ECNFs from aqueous solutions was investigated and compared with those of pristine ECNFs. The textural characteristics and morphology of the prepared pristine and activated ECNFs were characterized using various techniques. The adsorption performance was found to be associated to the surface area, porosity, and surface charges of the prepared adsorbents; the nature and molecular size of the dyes; and the pH and temperature of the solution. Six nonlinear isotherm models were applied to analyze the adsorption equilibrium data, and the results showed that the adsorption behavior could be appropriately described using the Redlich–Peterson isotherm model. The kinetic results for the adsorption of CR and MB onto A-ECNFs were fitted reasonably well to the Elovich model and were fitted by a pseudo-second order (PSO) model onto the pristine ECNFs. According to the thermodynamic results, the adsorption of CR and MB onto the A-ECNFs was endothermic and spontaneous. In addition, the reusability of the A-ECNFs was evaluated over five adsorption-desorption cycles.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308234-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 21 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Walter Boscheri, Dinshaw S. Balsara〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In this work we present a conservative WENO Adaptive Order (AO) reconstruction operator applied to an explicit one-step Arbitrary-Lagrangian-Eulerian (ALE) discontinuous Galerkin (DG) method. The spatial order of accuracy is improved by reconstructing higher order piecewise polynomials of degree 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mi〉M〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉〉〈/mo〉〈mi〉N〈/mi〉〈/math〉, starting from the underlying polynomial solution of degree 〈em〉N〈/em〉 provided by the DG scheme. High order of accuracy in time is achieved by the ADER approach, making use of an element-local space-time Galerkin finite element predictor that arises from a one-step time integration procedure. As a result, space-time polynomials of order 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mi〉M〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉+〈/mo〉〈mn〉1〈/mn〉〈/math〉 are obtained and used to perform the time evolution of the numerical solution adopting a fully explicit DG scheme.〈/p〉 〈p〉To maintain algorithm simplicity, the mesh motion is restricted to be carried out using straight lines, hence the old mesh configuration at time 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mi〉n〈/mi〉〈/mrow〉〈/msup〉〈/math〉 is connected with the new one at time 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈msup〉〈mrow〉〈mi〉t〈/mi〉〈/mrow〉〈mrow〉〈mi〉n〈/mi〉〈mo linebreak="badbreak" linebreakstyle="after"〉+〈/mo〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/math〉 via space-time segments, which result in space-time control volumes on which the governing equations have to be integrated in order to obtain the time evolution of the discrete solution. Our algorithm falls into the category of 〈em〉direct〈/em〉 Arbitrary-Lagrangian-Eulerian (ALE) schemes, where the governing PDE system is directly discretized relying on a space-time conservation formulation and which already takes into account the new grid geometry 〈em〉directly〈/em〉 during the computation of the numerical fluxes. A local rezoning strategy might be used in order to locally optimize the mesh quality and avoiding the generation of invalid elements with negative determinant. The proposed approach reduces to direct ALE finite volume schemes if 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mi〉N〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mn〉0〈/mn〉〈/math〉, while explicit direct ALE DG schemes are recovered in the case of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.svg"〉〈mi〉N〈/mi〉〈mo linebreak="goodbreak" linebreakstyle="after"〉=〈/mo〉〈mi〉M〈/mi〉〈/math〉.〈/p〉 〈p〉In order to stabilize the DG solution, an 〈em〉a priori〈/em〉 WENO based limiting technique is employed, that makes use of the numerical solution inside the element under consideration and its neighbor cells to find a less oscillatory polynomial approximation. By using a 〈em〉modal basis〈/em〉 in a reference element, the evaluation of the oscillation indicators is very easily and efficiently carried out, hence allowing higher order modes to be properly limited, while leaving the zero-〈em〉th〈/em〉 order mode untouched for ensuring conservation.〈/p〉 〈p〉Numerical convergence rates for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si7.svg"〉〈mn〉2〈/mn〉〈mo〉≤〈/mo〉〈mi〉N〈/mi〉〈mo〉,〈/mo〉〈mi〉M〈/mi〉〈mo〉≤〈/mo〉〈mn〉4〈/mn〉〈/math〉 are presented as well as a wide set of benchmark test problems for hydrodynamics on moving and fixed unstructured meshes.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Ali Zidane, Abbas Firoozabadi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Non-planar fractures are often created in hydraulic fracturing. These irregular shape fractures may reduce the penetration into the formation; they may also improve the reservoir reach. Accurate flow simulation of two-phase compositional flows in domains with complex non-planar fractures is beyond the capabilities of current numerical models. In this work we present a higher-order numerical model for compositional two-phase flow in a domain with non-planar fractures. Fully unstructured gridding in 3D is a natural choice for description of geometry with irregular fracture shapes. We apply the concept of fracture cross-flow equilibrium (FCFE) in simulations of porous media flows with non-planar fractures. FCFE allows accurate flow and composition calculations at low CPU cost. Our implementation is in the context of the hybridized form of the mass conservative mixed finite element (MFE) and the higher-order discontinuous Galerkin (DG) method. In this work we introduce a simple and effective approach for design of non-planar fractures through the mesh interface that connects computer-aided-design (CAD) software to the mesh generator. In our algorithm we can simulate all ranges of fracture permeability accurately as opposed to other approaches where low permeability fractures affect the accuracy.〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Hitomi Kobara, Kaoru Nakatsuka, Akihiro Wakisaka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Size selected synthesis of gold nanoparticle (AuNP) was carried out by use of an ultra-fine liquid droplet as a reaction field. The ultra-fine liquid droplets were generated by electrospraying in a liquid medium. The electrospraying in the liquid medium had a great advantage over the conventional electrospraying in the air. The size of electrosprayed liquid droplets can be varied with the supplied electric voltage beyond the range of the electrospraying in the air. When the AuNPs synthesis through the chemical reduction of Au〈sup〉3+〈/sup〉 was carried out by use of this electrospraying in the liquid medium for the mixing of Au〈sup〉3+〈/sup〉 solution and the reducing agent solution, the size of AuNPs was controlled by the supplied electric voltage. Two types of reaction field equipped with a single and double electrospray nozzles were designed to be demonstrated.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The size distribution of gold nanoparticles was controlled in the ultra-small reaction field generated by the electrospray in a liquid medium.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308246-ga1.jpg" width="440" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Kenji Aramaki, Misaki Fujii, Yuichi Sakanishi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the major drawbacks of ionic-surfactant-based wormlike micelles (WLMs) is their poor low-temperature stability, which severely limits their application. Generally, an ionic surfactant with a linear C12–C16 alkyl chain has a Krafft point around or above room temperature. Therefore, there is a demand for ionic-surfactant-based WLMs with greater lowtemperature stability. Silicone surfactants have flexible hydrophobic chain structures. Hence, they are expected to be suitable candidates for WLMs that can be stable at low temperatures. Sodium trimethylsilyl tetra(dimethylsiloxane) decyl sulfate (Si〈sub〉5〈/sub〉C〈sub〉10〈/sub〉SO〈sub〉4〈/sub〉Na) and benzyltrimethylammonium chloride (BTAC) were used as surfactant and electrolyte, respectively, to obtain the WLM system with desired properties. No precipitation of surfactant crystals was observed in the WLM system obtained in this study when temperature was decreased to as low as 0 °C, indicating excellent low-temperature stability. Steady rheological measurements on the viscous solutions show shear thinning corresponding nearly to a power law relation (viscosity ∝ [shear rate]〈sup〉−1〈/sup〉). Zero shear viscosity (〈em〉η〈/em〉〈sub〉0〈/sub〉) increased with increase in 〈em〉R〈/em〉, reaching a maximum at around 〈em〉R〈/em〉 = 0.3 and decreasing thereafter. Oscillatory shear measurements for the viscoelastic samples, formed around the maximum-viscosity composition, show that the storage modulus (〈em〉G′〈/em〉) and the loss modulus (〈em〉G′′〈/em〉), with respect to the oscillation frequency (〈em〉ω〈/em〉), cross each other and fit the Maxwell model very well in the low-〈em〉ω〈/em〉 region. The normalized Cole-Cole plot of 〈em〉G′′〈/em〉 / 〈em〉G′′〈/em〉〈sub〉max〈/sub〉 against 〈em〉G′〈/em〉 / 〈em〉G′′〈/em〉〈sub〉max〈/sub〉 was obtained as a semicircle centered at 〈em〉G′〈/em〉 / 〈em〉G′′〈/em〉〈sub〉max〈/sub〉 = 1, as is typical for WLM systems.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308295-ga1.jpg" width="356" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 20 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Jian Xiao, Honglin Luo, Haiyong Ao, Yuan Huang, Fanglian Yao, Quanchao Zhang, Yizao Wan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although recombinant human bone morphogenetic protein-2 (rhBMP-2) has been widely applied for bone regeneration, finding an ideal delivery system with optimal dose and minimal side effects is still a challenge. In this context, a novel mesoporous bioactive glass nanotubular (MBG-NT) scaffold loaded with rhBMP-2 was developed using a template-assisted sol-gel method. The obtained MBG-NT scaffold showed a notable 3D network structure and the nanotubes had an outer diameter of approximately 45 nm and a wall thickness of 15 nm. X-ray photoelectron spectroscopy (XPS) certified that the rhBMP-2 was successfully loaded into the MBG-NT scaffold with a quantity of 184.3 〈strong〉±〈/strong〉 5 ng mg〈sup〉-1〈/sup〉, and the MBG-NT scaffold exhibited a sustained release of rhBMP-2 for 28 days due to the presence of mesoporous structures. Moreover, the rhBMP-2-loaded MBG-NT scaffold exhibited enhanced proliferation, alkaline phosphatase (ALP) activity and osteogenic-related gene expression of human bone marrow stromal cells (hBMSCs) when compared to bare MBG-NT scaffold. We believe that the rhBMP-2-loaded MBG-NT scaffold can be a promising scaffold for regeneration of large bone defects.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930826X-ga1.jpg" width="285" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Razieh Zahedi, Zahra Asadi, Fahimeh Dehghani Firuzabadi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel heterogeneous catalyst was developed via the immobilization of a copper complex by covalent anchoring of the ligand on the surface of magnetic nano particles. The catalyst was characterized by various techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron micrograph (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), a vibrating sample magnetometer (VSM) and inductively coupled plasma (ICP) spectroscopy. The prepared catalyst demonstrated high catalytic activity, stability, reproducible dispersibility, and recycability in the O-arylation reactions. Moreover, the catalyst could be easily recovered under the outside magnetic field and reused without noticeable decreasing in its catalytic performance upon five consecutive runs.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307162-ga1.jpg" width="271" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Akram Abbasi, Arijit Bose〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The high electrical conductivity of multilayer graphene (MLG) and their sheet like morphology results in a low percolation threshold, and makes it an attractive filler for inducing electrical conductivity in an insulating polymer at small filler loadings. However, strong van der Waals forces between the flat faces of multilayer graphene cause agglomeration, making it difficult to disperse them in a polymer. The loading required for forming a percolating network of these MLGs then increases dramatically, and the advantage of their sheet-like morphology is lost. To enhance the dispersion of MLGs, carbon black nanoparticles (CB) were added as secondary fillers to a polystyrene (PS) matrix containing 2.5 vol% MLG. The electrical conductivity of the composite increased from 10〈sup〉−9〈/sup〉 S/m with no CB to 10〈sup〉-4〈/sup〉 S/m with 1.5 vol% CB, asymptoting to 10〈sup〉3〈/sup〉 S/m at ∼12 vol% CB. Using Raman spectroscopy and wide-angle X-ray diffraction, we confirmed that the CB particles act as dispersion aids and prevent MLG restacking, reducing agglomeration and enhancing dispersion of the MLG sheets in PS. This leads to an increase of several orders of magnitude in electrical conductivity.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307150-ga1.jpg" width="269" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Jiaoyuan Lian, Suxia Zheng, Cong Liu, Zhongbin Xu, Xiaodong Ruan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a co-flowing step emulsification strategy for the on-line control of micro-droplet generation. The effects of four parameters including wall contact angle, plateau length, channel distance and diameter are investigated numerically and experimentally in this study. The results indicate that the wall contact angle, whose applicable range can be expanded to 90°–180° by co-flow, is critical to droplet formation. The effect of the plateau length on droplet generation is reduced by the co-flow, and the droplet diameter is almost independent of the plateau length, which ranges from 0.7 to 1.5 mm. In addition, the droplet diameter increases significantly with increasing channel distance and diameter. Combining these results with those of our previous study, we derived an explicit equation for droplet diameter prediction. The predicted droplet diameter based on this equation has good agreement with the simulation and experimental results. Furthermore, we proposed a coefficient 〈em〉α〈/em〉 as a function of physical and dimensional parameters to predict the regimes and modes in the co-flowing step emulsification process. The conclusion of this study not only provides an important reference for the design and improvement of step emulsification chips, but also offers a new idea and a scientific basis for tuneable monodisperse micro-droplet production.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307216-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Biao Zhang, Xiaojuan Li, Yang Zhao, Hua Song, Huan Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oxygen doped mesoporous graphitic carbon nitride(O-mpg-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉) was innovatively prepared through facile two-step synthesis and characterized through different characterization tools, such as XRD、SEM、XPS etc. These characterizations confirm that the as-prepared sample has separated plate-like structure with lots of gaps and oxygen atoms have been successfully doped into them. Evaluated by photodegradation of Rhodamine B and Methyl Orange, the O-mpg-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 photocatalyst exhibits higher photocatalytic degradation efficiency, which is attributed to the added active spots, shorter electronic transmission distance and wider range of light absorption. In addition, the photocatalytic activity of the as-prepared catalysts didn’t decrease significantly after five photodegradation cycles, showing a high photocatalytic stability.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Oxygen doped mesoporous g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 was firstly prepared by a facile calcination-solvothermal method and exhibits excellent photocatalytic degradation performance, which is ascribed to the change of morphology and intrinsic electronic structure.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307241-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Wenjie Liu, Kun Yuan, Peipei Liu, Ming Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this article, magnetically responsive catalysts were successfully synthesized by host-guest chemistry and self-assembly strategy. Firstly, β-cyclodextrin (β-CD) was bound directly to the surface of core/shell magnetic Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@C (MFC) using chemical bonding methods. Then, in view of the host-guest recognition, p-aminothiophenol (pATP) was captured by β-CD to form inclusion complex on the surface of MFC. Lastly, pre-synthesized gold, silver, platinum nanoparticles (AuNPs, AgNPs, PtNPs) could be adsorbed on the surface of MFC@β-CD-pATP through self-assembly strategy to fabricate ternary composites MFC@β-CD-pATP@metal nanoparticles. Catalytic reduction reaction of methylene blue using NaBH〈sub〉4〈/sub〉 as reducing agent evaluates the catalytic performance of three as-prepared magnetic nanocomposites. MFC@β-CD-pATP@AuNPs catalyst showed the fast catalytic reaction rate constant. Significantly, we have explored the separation of magnetic supports and novel metal nanoparticles under mild conditions. This strategy will become a green and environmental way for highly efficient separation of precious metals catalysts, and recycle and reuse of catalyst carriers.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307174-ga1.jpg" width="362" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Piero De Leonardis, Francesco Cellesi, Nicola Tirelli〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We explored a versatile enzyme nanoencapsulation process based on the synthesis of silica gel nanoparticles, decorated with a dense hydrophilic poly(glycerol monomethacrylate) (PGMMA) shell for biological and therapeutic applications. These hybrid enzyme-SiO〈sub〉2〈/sub〉-polymer nanoparticles were obtained through an aqueous sol-gel process, followed by the adsorption of cationic macroinitiators by electrostatic complexation. Surface-initiated Atom Transfer Radical Polymerisation (ATRP) was applied to obtain a dense hydrophilic (protein repellent) PGMMA layer of tunable size, under conditions which are compatible with the nanoencapsulation of horseradish peroxidase. The sol-gel synthetic procedure, the composition and molecular weight of the macroinitiators, the polymer adsorption and purification methods, and the final ATRP conditions, were optimised to control the properties of these nanoparticles, in terms of particle size, Z-potential, PGMMA decoration, while preserving enzymatic activity.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307228-ga1.jpg" width="489" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Enzyme-SiO〈sub〉2〈/sub〉-polymer nanoparticle obtained by enzyme (HRP) nanoencapsulation in silica gel nanoparticles, adsorption of a cationic macroinitiator, and final polymer shell generation (PGMMA) by ATRP.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): F. Salerni, D. Orsi, E. Santini, L. Liggieri, F. Ravera, L. Cristofolini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We employ Diffusing Wave Spectroscopy (DWS) to characterize microscopic structure, internal dynamics and rheological properties of a paradigmatic emulsion formed by water and dodecane stabilized by the anionic surfactant Sodium Dodecyl Sulfate (SDS).〈/p〉 〈p〉We focus on ageing and stability in the regime of low surfactant concentration, well below the Critical Micellar Concentration (CMC). In the long-time ageing regimes differentiate in stable and unstable, depending on surfactant concentration. For the stable case, ageing affects the dynamics following a power law with an exponent independent on surfactant concentration, presumably related to the late stages of the water drainage process. On the contrary, at constant ageing, the dependence of the dynamics from surfactant concentration shows a slowdown, corresponding to a maximum in the bulk shear mechanical modulus, around 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si25.svg"〉〈mo〉[〈/mo〉〈mi〉S〈/mi〉〈mi〉D〈/mi〉〈mi〉S〈/mi〉〈mo〉]〈/mo〉〈mo〉=〈/mo〉〈mn〉2〈/mn〉〈mi〉m〈/mi〉〈mi〉M〈/mi〉〈/math〉 which is reminiscent of a similar maximum found by drop tensiometry in the dilational modulus of the single interface.〈/p〉 〈p〉This suggests a consistent picture of the mechanisms (de)stabilizing the emulsion, explained in terms of elementary process at the interface. These results show furthermore that DWS can be a reliable diagnostic for the study of the aging and of the mechanical properties of concentrate emulsions. This might be relevant to control stability of emulsions when a low concentration of surfactant is desired, e.g. for economical or environment reasons.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719301876-ga1.jpg" width="334" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Huijian Ye, Xuanhe Zhang, Chunfeng Xu, Lixin Xu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The polymer film capacitor has been widely applied in electronics and stationary power system due to the large power density and graceful dielectric reliability. The current requirements for flexible film capacitor are mainly on the development of polymer nanocomposite with high energy density and charge-discharge efficiency during applied electric field. Here we employed the fluoro hyperbranched polyethylene-graft-poly(trifluoroethyl methacrylate) (HBPE-〈em〉g〈/em〉-PTFEMA) copolymer to exfoliate the boron nitride nanosheets (BNNSs) in low-boiling-point solvent, and then, the flexible poly(vinylidene fluoride-trifluoroethylene) (P(VDF-CTFE)) nanocomposite film incorporated with BNNSs was prepared by the simple solution casting. The stable BNNSs dispersion was obtained with assistance of fluoro hyperbranched copolymer as the stabilizer, which was adsorbed on the nanosheets via the noncovalent CH-π interaction against aggregation. The presence of fluoro segments improves the compatibility of BNNSs/P(VDF-CTFE) nanocomposite, which contributes to the large interfacial polarization. The energy density in 0.4 wt% nanocomposite achieves 6.8 J/cm〈sup〉3〈/sup〉 with charge-discharge efficiency of 66% at 300 MV/m, which is ascribed to the large content of electroactive phase and the enhanced interfacial polarization. The fluoro hyperbranched copolymer functionalized BNNSs/P(VDF-CTFE) nanocomposite film exhibits high electric storage capability as well as lightweight feature and flexibility, which is benefit to potential applications for portable and implantable electrical devices where both the weight and size are primary concerns.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930723X-ga1.jpg" width="287" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Mohammad M. Hassan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, multifunctional wool fabrics were produced by treating them with silver (Ag) nanoparticles in a single-stage treatment using trisodium citrate (TSC) as a reducing and capping agent. The effects of treatment parameters, such as Ag〈sup〉+〈/sup〉 concentration, pH, temperature and time on the colour strength, antibacterial and antistatic properties, and UV radiation absorption by the treated fabric were carried out. It was found that the wool fabric treated with Ag nanoparticles formed by using Ag〈sup〉+〈/sup〉 concentration of less than 1.11% on the weight of wool fibres produced very pale shade. The colour strength and UV radiation absorption capacity of the treated wool fibres increased with an increase in the concentration of Ag〈sup〉+〈/sup〉, and Ag〈sup〉+〈/sup〉 to citrate anion ratio, and also with a decrease in the treatment pH. The treatment temperature had a great effect on the colour strength of the treated fabrics and the size of Ag nanoparticles. The colour strength increased from 1.59 for the fabric treated at 55 °C to 7.74 for the fabric treated at 95 °C. The surface resistance of the treated wool fibres decreased with an increase in the concentration of Ag〈sup〉+〈/sup〉, while the colour fastness to washing decreased for the fabric treated at a higher pH. The treated fibres showed excellent antibacterial activity, UV radiation absorption capacity, and also very good antistatic properties along with an excellent colourfastness to washing. Moreover, the developed treatment is highly durable to washing as after 20 washes the treated fibres lost their colour and antibacterial activity only marginally.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308076-ga1.jpg" width="415" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Yixing Wang, Taijun He, Mengyun Liu, Jianqi Ji, Yu Dai, Yang Liu, Longbo Luo, Xiangyang Liu, Jiaqiang Qin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fast and efficient oil-water separation materials under harsh conditions become urgent requirement for eliminating destruction of environment from offshore oil spill, oily wastewater produced in industry and life. Here, we designed and prepared polyimide (PI) aerogel with strong hydrogen bond by introducing benzimidazole structure. The hydrogen bond increases the intermolecular interactions to overcome the expansion force and capillary force during ice crystal growth and sublimation. The obtained PI aerogel has a mutually interleaved sheet three-dimensional network structure of thin pore walls (about 85 nm), interconnected pores and tortuous channels with a low shrinkage (about 7.8%). Moreover, due to the high hydrophobicity and morphological characteristics, the PI aerogel can be used for oil-water separation continuously under different harsh conditions, such as high viscosity oil (above 570 mPa·s), oil in cold/hot water (0 °C/120 °C), corrosive solution and emulsion. The separation efficiency and maximum oil flux can reach 99. 9% and 14320 L·m〈sup〉-2〈/sup〉 h〈sup〉-1〈/sup〉, respectively. Because of their fast and efficient oil-water separation performance in harsh environments, this PI aerogel shows great potential in the field of petroleum, municipal and industrial wastewater treatment.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307976-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Junmei Tian, Zhijia Zhu, Baojiang Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Photocatalysts with heterojunctions had attracted much attention in the field of photocatalysis due to their strong charge separation and transfer capabilities. In this work, a novel Bi〈sub〉2〈/sub〉MoO〈sub〉6〈/sub〉/Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉/MWCNTs Z-scheme photocatalyst was firstly prepared by one-step hydrothermal method. A series of characterization results showed that the ternary flower-like Bi〈sub〉2〈/sub〉MoO〈sub〉6〈/sub〉/Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉/MWCNTs photocatalyst was successfully synthesized. The photocatalytic property of Bi〈sub〉2〈/sub〉MoO〈sub〉6〈/sub〉/Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉/MWCNTs composite was evaluated by photo-degradation of reactive blue 19 (RB-19) dye under visible light irradiation. The results manifested that Bi〈sub〉2〈/sub〉MoO〈sub〉6〈/sub〉/Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉/MWCNTs composite presented the better photocatalytic property than pure Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉 and Bi〈sub〉2〈/sub〉MoO〈sub〉6〈/sub〉/Bi〈sub〉2〈/sub〉WO〈sub〉6〈/sub〉. Additionally, in the photocatalytic process free radical and hole scavenging experiments indicated that h〈sup〉+〈/sup〉 and ·O〈sub〉2〈/sub〉- played an indispensable role. Finally, possible mechanisms for the photocatalytic enhancement of the composite were put forward.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307861-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Chao Zhang, Siyao Liu, Shuangxi Li, Yue Tao, Panpan Wang, Xinyue Ma, Lanzhou Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The magnetic chitosan microspheres immobilized 〈em〉Aspergillus sydowii〈/em〉 (MCMAs) was prepared and characterized by SEM, BET, XRD and VSM analyses, and used to adsorb Cu(II) from aqueous solution under different influence factors such as contact time, initial Cu(II) concentration and biosorbent dose. Characterization results showed that MCMAs had large specific surface area and were rapidly separated from aqueous solution by using an adscititious magnetic field. Batch adsorption experiments showed that Cu(II) adsorption capacity of MCMAs was up to 119.21 mg g〈sup〉−l under the optimal condition. The CO, OH and NH〈/sup〉〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉 groups played an important role in Cu(II) chelation observed from FTIR spectra. Cu(II) adsorption onto MCMAs was well described by pseudo-second-order kinetics and Langmuir isotherm, and the adsorption process involved surface and intra-particle diffusion. In addition, MCMAs showed good recyclable efficiency after four adsorption-desorption cycles.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308015-ga1.jpg" width="334" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Suvendu Manna, Snigdha Prakash, Papita Das〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article presents the process of synthesizing a value added product from a carbonaceous industrial waste. For this a carbonaceous industrial waste was coated with graphene oxide (GO) and then thermally activated at 800 °C. The GO and the GO-coated biochar were characterized with atomic force microscope, raman spectroscope, fourier transform infrared spectroscopy, field-emission scanning electron microscope, x-ray Diffraction and transmission electron microscope. This GO-coated biochar was then utilized to investigate removal capacity of phenol present in wastewater. The data indicated that the GO-coated biochar showed better phenol removal efficacy then that of the GO itself. The isotherm analysis indicated that the data could be described best with Langmuir isotherm indicating that the phenol separation was a monolayer surface adsorption. The kinetic analysis indicated that the phenol separation process was followed by pseudo second order kinetics. Also, it was evident from the intra-particle diffusion kinetic analysis that diffusion plays a significant role in phenol separation. From thermodynamic analysis it was evident that the phenol separation process was endothermic as well as spontaneous in nature. The GO-coated biochar showed better separation efficacy in the presence of salt.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308064-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Yong-li Yan, Qi Xi, Christian-chibuike Una, Bing-cheng He, Chun-sheng Wu, Long-long Dou〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The serious fingering and nonuniform injectivity profile of acid liquid result from the features of heterogeneity in most carbonate reservoir, leading to a poor effect on the acidizing process. In the present contribution, for the first time, we report a novel diversion acidizing strategy that uses acid-rock reaction between the acidizing fluid itself and carbonate core to produce CO〈sub〉2〈/sub〉 at supercritical state. Under the action of a mixture of foaming agent and stabilizer contained in this working fluid, a CO〈sub〉2〈/sub〉 foamed acid fluid is in-situ formed in the acidizing layer, which would play a diverting role in carbonate matrix acidizing operations. Experiments on in-situ formation of CO〈sub〉2〈/sub〉 microfoams (emulsions) were performed utilizing a visible acid-rock reaction simulation device and a self-made high pressure and temperature foam generator. A series of divided-flow experiments were undertaken by the core displacement setup.〈/p〉 〈p〉Results based on these experiments indicate that with 0.5% SDBS as a foaming agent and 0.15% CMC as a stabilizing agent, the supercritical CO〈sub〉2〈/sub〉 microfoams (emulsions) could be created in-situ in the process of acidizing through the carbonate reservoirs. The foamed acid has the accumulating and plugging effects, with divided-flow selectivity not only in the parallel cores of oil saturation and water saturation, but also in the parallel cores of different permeability. This foamed acid fluid could provide better diversion acidizing operations for heterogeneous carbonate formation. Finally, the mechanism of this novel diversion acidizing technology was uncovered in detail. It is suggested that the whole working process is actually an interface effect in the dynamic system of gas/liquid/solid multiphase fluid. Such findings are potentially important for a better understanding on the mechanisms of in-situ formation of CO〈sub〉2〈/sub〉 foamed acid and its self-diversion. Looking out to the future, our report attempts to provide a new and efficient technology for the improvement of acid stimulation in the carbonate reservoirs.〈/p〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉A novel diversion acidizing technology using in-situ microfoams to meet the challenge of serious fingering and poor backflow of acid liquid existing in application of diverting acid technology in heterogeneous formations. This technology uses a chemical reaction between conventional acid and carbonate cores to produce CO〈sub〉2〈/sub〉 at supercritical state. Under the action of a mixture of foaming agent and stabilizer, a CO〈sub〉2〈/sub〉 foam fluid was in-situ formed, which would play a diverting role in carbonate matrix acidizing operations. It is suggested that the whole working process is actually an interface effect in the dynamic system of gas/liquid/solid multiphase fluid.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307757-ga1.jpg" width="200" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Tao Ma, Haishun Feng, Hairong Wu, Zhe Li, Jiatong Jiang, Derong Xu, Ziyu Meng, Wanli Kang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gemini surfactant has a good application prospect in the field of enhanced oil recovery (EOR) due to the advantages of high interfacial activity, low critical micelle concentration (CMC) and good wettability alteration. In this paper, ethylenediamine, sodium 2-bromoethanesulphonate and fatty alcohol polyoxyethylene ether are used as raw materials to synthesize a new kind of anionic-nonionic gemini surfactant which hydrophilic group consists of two parts nonionic and anionic groups through a mild reaction of amination. The surface tension, interfacial tension, wettability and oil displacement of the synthesized anionic-nonionic gemini surfactants were evaluated. Parameters of surfactant the saturated adsorption amount 〈em〉Γ〈/em〉〈sub〉max〈/sub〉 and the minimum molecular occupied area 〈em〉A〈/em〉〈sub〉min〈/sub〉 were calculated. The structures of the optimal product were characterized by IR and 〈sup〉1〈/sup〉H-NMR. The results showed that the critical surface tension of the synthesized anionic-nonionic gemini surfactant was as low as 28.94 mN/m, and the critical micelle concentration was 4.9 × 10〈sup〉−5〈/sup〉 mol/L. An interfacial tension between the aqueous solution of 600 mg/L optimal surfactant and Dagang crude oil was 0.0804 mN/m. 1500 mg/L aqueous solution can reduce the surface contact angle of lipophilic low permeability core from 144.5° to 71.5°. The anionic-nonionic gemini surfactant (1000 mg/L; 0.4 PV) can improve oil displacement efficiency by 7.03%. The current study opens a new pathway for designing enhancing oil recovery applicable gemini surfactants with excellent performance, wide source of raw materials and low dosage.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307885-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Zengzi Wang, Runtao Hu, Gaihuan Ren, Gongrang Li, Shangying Liu, Zhenghe Xu, Dejun Sun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The application of conventional alkalis (NaOH or Na〈sub〉2〈/sub〉CO〈sub〉3〈/sub〉) in alkali/surfactant/polymer (ASP) flooding is rather limited due to their intrinsic drawbacks, including precipitating during injection into formation water with a high divalent ion concentration and enhancing the dispersibility of clays (e.g., montmorillonite (MMT) or kaolinite) in water, which lead to damage to reservoir formations and bring about difficulties in treating produced fluids. Here, we propose polyetheramine D 230 as an alternative alkali to avoid these problems. D 230 is a diamine linked by poly(oxypropylene) backbones. Interfacial tension and emulsification measurements proved that D 230 can neutralize the acidic components in crude oil to generate surface-active soaps, which facilitate oil emulsification in water. Contact angle measurements indicated that an oil-contaminated quartz surface treated with D 230/SP blends was successfully altered from oil-wet to water-wet. Sand pack flooding measurements demonstrated that a D 230/SP injection was able to mobilize 19.23% of the original oil in place (OOIP) after thorough water flooding. Rheograms of alkali/polymer blends showed a reduced impact of D 230 on viscosity. Static bottle tests indicated that no precipitation occurred after D 230 was injected into formation water with a high Ca〈sup〉2+〈/sup〉 concentration. Colloidal stability measurements of clay dispersions suggested that D 230 can inhibit clay dispersibility. As an alternative alkali in ASP flooding, D 230 not only facilitates enhanced oil recovery (EOR) but also solves problems such as precipitation, high biotoxicity, reduced fluid viscosity and enhanced clay dispersibility brought about by conventional inorganic and organic alkalis. These advantages make D 230 an eco-friendly choice as an alkali for ASP flooding.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308088-ga1.jpg" width="362" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Mohsin Ali Marwat, Bing Xie, Yiwei Zhu, Pengyuan Fan, Kai Liu, Meng Shen, Malik Ashtar, Suwadee Kongparakul, Chanatip Samart, Haibo Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The sandwich-structured barium titanate/poly(ether imide) (BT/PEI) nanocomposites are fabricated layer-by-layer, with outer two insulation layers (ILs) for high breakdown strength and a middle polarization layer (PL) for high dielectric constant, using solution casting technique. Consequently, the sandwich-structured BT/PEI nanocomposites with optimum BT NPs concentration in ILs and PL showed tremendously enhanced discharge energy density (〈em〉U〈/em〉〈sub〉e〈/sub〉) of 5.7 J/cm〈sup〉3〈/sup〉, which is ∼256% and ∼307% higher than the pristine PEI (with 1.6 J/cm〈sup〉3〈/sup〉) and its single-layered counterpart, i.e., 9 wt.% BT/PEI (with 1.4 J/cm〈sup〉3〈/sup〉), respectively. The similar sandwich structure also displayed a significantly higher discharge efficiency of ∼62% at very high electric field. In addition, the high-temperature hysteresis loops for optimal sandwich structure nanocomposites revealed considerably high-temperature endurance until 150 °C at 200 MV/m. The present work paves the way for using sandwich-structured linear nanocomposites in thermally stable energy storage devices.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307903-ga1.jpg" width="267" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Sabrina Matos de Carvalho, Carolina Montanheiro Noronha, Cleonice Gonçalves da Rosa, William Gustavo Sganzerla, Ismael Casagrande Bellettini, Michael Ramos Nunes, Fabiano Cleber Bertoldi, Pedro Luiz Manique Barreto〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Natural antioxidants can be incorporated into polymers to the production of active packaging, preventing the formation of off-flavors and undesirable textures in foods, increasing the foods shelf life. In this study was developed polymeric films based on poly (vinyl alcohol) (PVA) incorporated with 30, 50 and 70% of solid lipid nanoparticles entrapped α-tocopherol. PVA films were produced by the casting technique and characterized by their physicochemical, morphological, thermal and antioxidant characteristics. PVA films with nanoparticles demonstrated higher hydrophilic compared to the control film. Thermal analysis of the films showed that nanoparticles incorporation has changed the structure, decreasing the crystallinity. Moreover, films with solid lipid nanoparticles entrapped α-tocopherol demonstrated a higher antioxidant capacity, and the α-tocopherol controlled release confirmed the possibility of its use as active packaging to application in food conservation.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307812-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 19 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Yudai Chizawa, Yayoi Miyagawa, Mao Yoshida, Shuji Adachi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mayonnaise is a preferred dressing that is routinely used in many regions. Distribution of products containing frozen mayonnaise is highly desirable due to the development of cold chain and changing lifestyle. However, freezing and thawing of mayonnaise result into separate oil and aqueous phases. A detailed mechanism of this phenomenon is still unknown. In this study, the destabilization of frozen emulsions, using rapeseed, safflower, olive, rice bran, and soybean oils as the oil phase was examined, in which these oil phases crystallize at lower temperature than the aqueous one. The vegetable oils exhibit different crystallization behavior. Irrespective of the type of vegetable oil, it was found that smaller the difference between the storage temperature and the melting point of the oil, which was estimated from the fatty acid composition, quicker was the destabilization of the emulsion prior to the growth of the oil crystal. We consider that the change in the crystallization process of the oil phase increases the energy at the oil–water interface and destabilizes the emulsion.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930812X-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Pablo Llombart, Mauricio Alcolea Palafox, Luis G. MacDowell, Eva G. Noya〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Controlled CTAB self-assembly is an essential prerequisite for the formation of gold nanorods with tailored shape and monodispersity. In this paper, we exploit the use of salt concentration and co-surfactant decanol for the preparation of CTAB aggregates with different morphologies. To this end we use a model of CTAB recently developed by ourselves, and perform electronic structure calculations in order to improve current point charge parametrization of decanol. Using molecular dynamics simulations with the new models, we find a sequence of structural transitions of CTAB aggregates induced by salt concentration and added cosurfactant. In pure solutions, CTAB aggregates form spherical micelles with a compact ionic shell and a diffuse double layer that can be qualitatively described with Poisson–Boltzmann theory. Addition of decanol as a cosurfactant induces a sequence of dramatic structural transitions at low surfactant concentration and allows the stabilization of compact ordered bilayers in a well defined range of intermediate decanol/CTAB ratios. At low and high decanol/CTAB ratios spherical micelles are transformed into wormlike cylindrical micelles. At intermediate decanol/CTAB ratios, fully formed bilayers are observed, with surfactants exhibiting a compact structure with strong positional and orientational order. We discuss how the controlled self-assembly of compact CTAB bilayers at low global CTAB concentration can pave the way for the selective passivation of gold facets and the controlled formation of monodisperse gold nanorods.〈/p〉〈/div〉 〈div〉 〈h6〉Graphical abstract〈/h6〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307186-ga1.jpg" width="275" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Tülin Gürkan Polat, Kayhan Ateş, Süleyman Bilgin, Osman Duman, Şükrü Özen, Sibel Tunç〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, gelatin-based conductive hydrogels doped with carbon nanotube (CNT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and silver (Ag) nanoparticle were prepared for use in biopotential measurements. Gelatin was modified by various concentrations of methacrylic anhydride (MA) to obtain photo-crosslinkable gelatin methacrylate (GelMA) polymer with low (21%), medium (44%) and high (78%) methacrylation degree. Chemical modification of gelatin was characterized by 〈sup〉1〈/sup〉H-NMR spectroscopy. It was observed that mechanical properties of the GelMA hydrogels were highly dependent on methacrylation degree. Ultimate compressive stress of low, medium and high methacrylated gelatin hydrogel was measured to be 9.97 ± 0.14 kPa, 17.83 ± 1.73 kPa and 38.23 ± 2.96 kPa, respectively. Surface morphology of hydrogels was visualized by scanning electron microscope (SEM). The pore size of methacrylated gelatin hydrogel significantly reduced with the addition of CNT, PEDOT:PSS and Ag nanoparticle into the hydrogel matrix. The results of thermal gravimetric analysis showed that conductive hydrogels were of higher thermal stability than nonconductive GelMA hydrogel. The suitability of the prepared hydrogels for biopotential measurements was determined by equivalent impedance measurements. Impedance values of hydrogel samples were obtained in the frequency range of 20 Hz–500 Hz. The hydrogel materials prepared in this study exhibited high impedance at low frequencies and low impedance at high frequencies. The results of this study showed that the hydrogels produced with Ag nanoparticle are more suitable electrode materials for physiological measurement systems such as electrocardiography (ECG) and electroencephalography (EEG).〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307393-ga1.jpg" width="438" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Siddhesh Kamat, Runxing Lin, Yee C. Chiew〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Reduction of interfacial tension caused by surfactants at oil/water interfaces plays a crucial role in many technological processes and industrial applications such as detergency, food processing, cosmetics and personal care, wastewater treatment, pharmaceutical and oil industries. The properties and behavior of dispersions, foams, and emulsions are determined by the interfacial properties stabilized by the surfactants. We carried out molecular dynamics simulations to study the interfacial properties, structure and dynamics of dodecanedioic dicarboxylic acids at hexane/water interface over a wide range of surface coverage (area per molecule). Unlike monocarboxylic acid whose hydrocarbon tail points to the oil phase normal to the oil/water interface, the two carboxyl groups of the dicarboxylic acid are attached to the aqueous phase while its slightly curved carbon backbone lies parallel to the interface. The dodecanedioic dicarboxylic acid adopts a slightly curved linear conformation in the interfacial region. The adsorbed acids undergo a first-order gas-to-liquid phase transition as the density of acid increases. The characteristic thickness of the acid layer remains practically constant at large area per molecule (or, low surface density) until surface coverage reaches a “critical” value above which the thickness of the acid layer increases markedly deviating from its low density value. This layering transition has a significant influence on the spreading pressure, interfacial structure, and lateral diffusion coefficient of the acids. Additionally, we modeled a system of fully deprotonated negatively charged acids balanced by positively charged sodium counterions. We found that the interfacial tension of the charged acid interface is consistently lower than uncharged acid at moderate to higher surface density; however, at low densities, we observe little difference in interfacial tension between these two systems within the accuracy of the MD results. Additionally, we found that the rotational relaxation of the charged acids is significantly slower than that of uncharged acids owing to strong electrostatic interactions between the carboxyl groups COO〈sup〉−〈/sup〉and sodium Na〈sup〉+〈/sup〉cations which restrain the rotational motion of the acid. This molecular dynamics study has provided information and insights at the molecular level on the structure, equilibrium, and dynamic properties of dicarboxylic dodecanedioic acids at hexane/water interface.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307137-ga1.jpg" width="494" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Martin Pollack, Michele Pütz, Daniele L. Marchisio, Michael Oevermann, Christian Hasse〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The evolution of polydisperse systems is governed by population balance equations. A group of efficient solution approaches are the moment methods, which do not solve for the number density function (NDF) directly but rather for a set of its moments. While this is computationally efficient, a specific challenge arises when describing the fluxes across a boundary in phase space for the disappearance of elements, the so-called zero-flux. The main difficulty is the missing NDF-information at the boundary, which most moment methods cannot provide. Relevant physical examples are evaporating droplets, soot oxidation or particle dissolution.〈/p〉 〈p〉In general, this issue can be solved by reconstructing the NDF close to the boundary. However, this was previously only achieved with univariate approaches, i.e. considering only a single internal variable. Many physical problems are insufficiently described by univariate population balance equations, e.g. droplets in sprays often require the temperature or the velocity to be internal coordinates in addition to the size.〈/p〉 〈p〉In this paper, we propose an algorithm, which provides an efficient multivariate approach to calculate the zero-fluxes. The algorithm employs the Extended Quadrature Method of Moments (EQMOM) with Beta and Gamma kernel density functions for the marginal NDF reconstruction and a polynomial or spline for the other conditional dimensions. This combination allows to reconstruct the entire multivariate NDF and based on this, expressions for the disappearance flux are derived. An algorithm is proposed for the whole moment inversion and reconstruction process. It is validated against a suite of test cases with increasing complexity. The influence of the number of kernel density functions and the configuration of the polynomials and splines on the accuracy is discussed. Finally, the associated computational costs are evaluated.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Antoine Vermeil de Conchard, Huina Mao, Romain Rumpler〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effective treatment of unbounded domains using artificial truncating boundaries are essential in numerical simulation, e.g. using the Finite Element Method (FEM). Among these, Perfectly Matched Layers (PML) have proved to be particularly efficient and flexible. However, an efficient handling of frequency sweeps is not trivial with such absorbing layers since the formulation inherently contains coupled space- and frequency-dependent terms. Using the FEM, this may imply generating system matrices at each step of the frequency sweep. In this paper, an approximation is proposed in order to allow for efficient frequency sweeps. The performance and robustness of the proposed approximation is presented on 2D and 3D acoustic cases. A generic, robust way to truncate the acoustic domain efficiently is also proposed, tested on a range of test cases and for different frequency regions.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Maxime Theillard, David Saintillan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a new framework for the efficient simulation of the dynamics of active fluids in complex two- and three-dimensional microfluidic geometries. Focusing on the case of a suspension of microswimmers such as motile bacteria, we adopt a continuum mean-field model based on partial differential equations for the evolution of the concentration, polarization and nematic tensor fields, which are nonlinearly coupled to the Navier-Stokes equations for the fluid flow driven by internal active stresses. A level set method combined with an adaptive mesh refinement scheme on Quad-/Octree grids is used to capture complex domain shapes while refining the solution near boundaries or in the neighborhood of sharp gradients. A hybrid finite volumes/finite differences method is implemented in which the concentration field is treated using finite volumes to ensure mass conservation, while the polarization and nematic alignment fields are treated using a combination of finite differences and finite volumes for enhanced accuracy. The governing equations for these fields are solved along with the Navier-Stokes equations, which are evolved using an unconditionally stable projection solver. We illustrate the versatility and robustness of our method by analyzing spontaneous active flows in various two- and three-dimensional systems. Our results show excellent agreement with previous models and experiments and pave the way for further developments in active microfluidics.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Jiangming Xie, M. Yvonne Ou, Liwei Xu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Poroelastic materials play an important role in biomechanical and geophysical research. In this paper, we investigate wave propagation in orthotropic poroelastic media by studying the time-domain poroelastic wave equations. Both the low frequency Biot's (LF-Biot) equations and the Biot-Johnson-Koplik-Dashen (Biot-JKD) model are considered. In LF-Biot equations, the dissipation terms are proportional to the relative velocity between the fluid and the solid by a constant. Contrast to this, the dissipation terms in the Biot-JKD model are in the form of time convolution (memory) as a result of the frequency-dependence of fluid-solid interaction at the underlying microscopic scale in the frequency domain. The dynamic tortuosity and permeability described by Darcy's law are two crucial factors in this problem, and highly linked to the viscous force. In the Biot model, the key difficulty is to handle the viscous term when the pore fluid is viscous. In the Biot-JKD model, the convolution operator involves order 1/2 shifted fractional derivatives in the time domain, which is challenging to discretize.〈/p〉 〈p〉In this work, a new method of the multipoint Padé (or Rational) approximation for Stieltjes function is applied to approximate the JKD dynamic tortuosity and then an augmented system of Biot-JKD model is obtained, where the kernel of the memory term is replaced by the finite auxiliary variables satisfying a local system of ordinary differential equations. The Runge-Kutta discontinuous Galerkin (RKDG) method with the un-splitting method is used to compute the numerical solution, and numerical examples are presented to demonstrate the high order accuracy and stability of the method. Compared with the existing approaches for solving the Biot-JKD equations, the augmented system presented here require neither the storage of solution history nor the computation of the flux of the auxiliary variables.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): William C. Tyson, Gary K. Yan, Christopher J. Roy, Carl F. Ollivier-Gooch〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A higher-order accurate discretization error estimation procedure for finite-volume schemes is presented. Discretization error estimates are computed using the linearized error transport equations (ETE). ETE error estimates are applied as a correction to the primal solution. The ETE are then relinearized about the corrected primal solution, and discretization error estimates are recomputed. This process, referred to as ETE relinearization, is performed in an iterative manner to successively increase the accuracy of discretization error estimates. Under certain conditions, ETE relinearization is shown to correct error estimates, or equivalently the entire primal solution, to higher-order accuracy. In terms of computational cost, ETE relinearization has a competitive advantage over conventional higher-order discretizations when used as a form of defect correction for the primal solution. Furthermore, ETE relinearization is shown to be particularly useful for problems where the error incurred by the linearization of the ETE cannot be neglected. Results are presented for several steady-state inviscid and viscous flow problems using both structured and unstructured meshes.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Yu Li, Richard Mikaël Slevinsky〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a unified treatment of the Fourier spectra of spherically symmetric nonlocal diffusion operators. We develop numerical and analytical results for the class of kernels with weak algebraic singularity as the distance between source and target tends to 0. Rapid algorithms are derived for their Fourier spectra with the computation of each eigenvalue independent of all others. The algorithms are trivially parallelizable, capable of leveraging more powerful compute environments, and the accuracy of the eigenvalues is individually controllable. The algorithms include a Maclaurin series and a full divergent asymptotic series valid for any 〈em〉d〈/em〉 spatial dimensions. Using Drummond's sequence transformation, we prove linear complexity recurrence relations for degree-graded sequences of numerators and denominators in the rational approximations to the divergent asymptotic series. These relations are important to ensure that the algorithms are efficient, and also increase the numerical stability compared with the conventional algorithm with quadratic complexity.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Xinyu Zheng, Huaili Zheng, Yuhao Zhou, Yongjun Sun, Rui Zhao, Yongzhi Liu, Shixin Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Wastewater containing dyes poses a severe threat to human health and to environmental safety. Hence, finding an effective way to treat this wastewater has attracted wide attentions. In this study, quaternary ammonium group-rich magnetic nanoparticles (MNPs), Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@SiO〈sub〉2〈/sub〉-MPS-g-DAC (FSMD), were facilely prepared by grafting polymerization and served as a cationic adsorbent to remove anionic dye Orange G from aqueous solutions. Being compared with Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@SiO〈sub〉2〈/sub〉-MPS MNPs, the adsorption capacity of FSMD MNPs was notably enhanced and it could be maintained in a high level under a wide solution pH range. The dependency on pH and the sensitivity to ionic strength indicated that the main adsorption mechanism was the electrostatic interaction. The adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherms were well described with the Langmuir model. According to the thermodynamic analysis, the adsorption process was spontaneous and endothermic. FSMD MNPs were proved to have advantages of fast adsorption rate, high adsorption capacity, easy separation ability under external magnetic field, and satisfactory reusability, therefore they can be applied in the removal of anionic dyes from wastewater.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307344-ga1.jpg" width="370" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Hua Shen, Matteo Parsani〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We construct a space-time conservation element and solution element (CESE) scheme for solving the compressible Euler equations on moving meshes (CESE-MM) which allow an arbitrary motion for each of the mesh points. The scheme is a direct extension of a purely Eulerian CESE scheme that was previously implemented on hybrid unstructured meshes (Shen et al. (2015) [43]). It adopts a staggered mesh in space and time such that the physical variables are continuous across the interfaces of the adjacent space-time control volumes and, therefore, a Riemann solver is not required to calculate interface fluxes or the node velocities. Moreover, the staggered mesh can significantly alleviate mesh tangles so that the time step can be kept at an acceptable level without using any rezoning operation. The discretization of the integral space-time conservation law is completely based on the physical space-time control volume, thereby satisfying the physical and geometrical conservation laws. Plenty of numerical examples are carried out to validate the accuracy and robustness of the CESE-MM scheme.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Du Ren, Yujie Chen, Hua Li, Hafeez Ur Rehman, Yunli Cai, Hezhou Liu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Shape memory assisted self-healing polymeric networks have been numerously explored due to their multi-functionality and sustainability. In this study, we prepare a kind of electrical and thermal dual-responsive shape memory assisted self-healing polymeric composites fabricated with polycaprolactone/thermoplastic polyurethane (PCL/TPU) and carbon nanotubes (CNTs) via a facile method. The CNTs/PCL/TPU composites use PCL/TPU blend as shape memory polymer matrix, PCL as healing agent and CNTs as reinforcement networks. CNTs greatly enhance mechanical strength of the composites with good electrical and thermal conductivity. Interestingly, the CNTs/PCL/TPU composites can be healed via electricity and heating respectively in tens of seconds with corresponding optimal healing efficiencies about 96% and 94%. Meanwhile, the composites can exhibit remarkable electro-active shape recovery property that assist to diminish the crack openings and then the healing agent would be molten to fill in the crack. Therefore, the proposed materials can offer great potential applications in biomedical, aerospace and microelectronics.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307198-ga1.jpg" width="343" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): J. Carneiro, J.B.L.M. Campos, J.M. Miranda〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study reports the generation and characterization of polydimethylsiloxane (PDMS) microparticles. Droplets are produced in the jetting regime by hydrodynamic flow focusing technique in a PDMS square-section microchannel and afterwards thermally cured. Both the droplets and microparticles size distributions are characterized and compared. During the curing process, there is no appreciable shrinking of the droplets/microparticles. Droplets are generated with a maximum frequency of 1.3 kHz and their diameter ranges from 27 to 59 μm depending on the flow rate ratio. After the cure, the microparticles are chemically and optically characterized. The results show that the droplet generation method and the curing process are able to produce PDMS microparticles with low size, low dispersity and optimal optical properties for visualization and velocimetry experiments.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307253-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Li Duan, ChenChen Qin, Anhe Wang, Shengtao Wang, Jieling Li, Shuo Bai〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, uniform and porous gelatin microgels with various functional nano-objects (platinum nanoparticles and magnetic nanoparticles) were prepared by a ‘casting’ strategy in a controllable manner. During the microgels fabrication, two kinds of nanoparticles can be simultaneously introduced into the microgels without mutual influence, endowing the microgels with the combined functionality of nano-objects. Experimental data showed that the microgels with various nano-objects are stable enough in strong base or acidic solution, and can be taken as an efficient catalysis system and conveniently separated from the reaction medium by magnetic field. The method proposed here is certified to be facile, efficient and low cost to fabricate stable multifunctional microgels.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307472-ga1.jpg" width="259" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Yaya Ma, Cuiqing Zhang, Chengyu Li, Feng Qin, Lin Wei, Changyuan Hu, Quanhong Hu, Shuwang Duo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 is a newly found semiconductor photocatalyst with visible-light response property; however, due to its large particle size, the photocatalytic efficiency is greatly limited. Reducing the particle size down to nanoscale is an efficient way to enhance the photocatalytic ability, but still challenging. Herein, the firework-shaped hierarchical TiO〈sub〉2〈/sub〉 microsphere was used as the framework to spatially confine the growth of Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉. SEM characterization results reveal nanosized Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 particles are successfully inserted into the TiO〈sub〉2〈/sub〉 microsphere, forming enormous Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/TiO〈sub〉2〈/sub〉 heterojunctions. Benefitted from the nanoscaled Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 and the formation of Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/TiO〈sub〉2〈/sub〉 type II heterojunction, both the separation efficiency of charge carriers and the quantum yield are improved. As a result, Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/TiO〈sub〉2〈/sub〉 heterojunctions show much higher photocatalytic activity than that of pristine Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 in the degradation of methyl orange and tetracycline under visible light. Radical capture experimental results imply that hole is the dominant reactive species for the degradation of methyl orange. The present work paves the way for designing nanosized photocatalyst via the space-confined effect.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉A space-confined strategy is developed to restrict the size of Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉 down to nanoscale level and as-constructed Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉/TiO〈sub〉2〈/sub〉 heterojunctions display superior photocatalytic performance than pure Bi〈sub〉2〈/sub〉O〈sub〉4〈/sub〉.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307459-ga1.jpg" width="283" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): S. Dargaville, A.G. Buchan, R.P. Smedley-Stevenson, P.N. Smith, C.C. Pain〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper describes an angular adaptivity algorithm for Boltzmann transport applications which uses P〈sub〉〈em〉n〈/em〉〈/sub〉 and filtered P〈sub〉〈em〉n〈/em〉〈/sub〉 expansions, allowing for different expansion orders across space/energy. Our spatial discretisation is specifically designed to use less memory than competing DG schemes and also gives us direct access to the amount of stabilisation applied at each node. For filtered P〈sub〉〈em〉n〈/em〉〈/sub〉 expansions, we then use our adaptive process in combination with this net amount of stabilisation to compute a spatially dependent filter strength that does not depend on 〈em〉a priori〈/em〉 spatial information. This applies heavy filtering only where discontinuities are present, allowing the filtered P〈sub〉〈em〉n〈/em〉〈/sub〉 expansion to retain high-order convergence where possible. Regular and goal-based error metrics are shown and both the adapted P〈sub〉〈em〉n〈/em〉〈/sub〉 and adapted filtered P〈sub〉〈em〉n〈/em〉〈/sub〉 methods show significant reductions in DOFs and runtime. The adapted filtered P〈sub〉〈em〉n〈/em〉〈/sub〉 with our spatially dependent filter shows close to fixed iteration counts and up to high-order is even competitive with P〈sup〉0〈/sup〉 discretisations in problems with heavy advection.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Jingwei Hu, Shi Jin, Ruiwen Shu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Boltzmann equation may contain uncertainties in initial/boundary data or collision kernel. To study the impact of these uncertainties, a stochastic Galerkin (sG) method was proposed in [18] and studied in the kinetic regime. When the system is close to the fluid regime (the Knudsen number is small), the method would become prohibitively expensive due to the stiff collision term. In this work, we develop efficient sG methods for the Boltzmann equation that work for a wide range of Knudsen numbers, and investigate, in particular, their behavior in the fluid regime.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Qing Pan, Timon Rabczuk, Gang Xu, Chong Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the isogeometric analysis for surface PDEs based on the extended Loop subdivision approach. The basis functions consisting of quartic box-splines corresponding to each subdivided control mesh are utilized to represent the geometry exactly, and construct the solution space for dependent variables as well, which is consistent with the concept of isogeometric analysis. The subdivision process is equivalent to the 〈em〉h〈/em〉-refinement of NURBS-based isogeometric analysis. The performance of the proposed method is evaluated by solving various surface PDEs, such as surface Laplace-Beltrami harmonic/biharmonic/triharmonic equations, which are defined on the limit surfaces of extended Loop subdivision for different initial control meshes. Numerical experiments show that the proposed method has desirable performance in terms of the accuracy, convergence and computational cost for solving the above surface PDEs defined on both open and closed surfaces. The proposed approach is proved to be second-order accuracy in the sense of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msup〉〈mrow〉〈mi〉L〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/math〉-norm with theoretical and/or numerical results, which is also outperformed over the standard linear finite element by several numerical comparisons.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Arthur E.P. Veldman〈/p〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): A.M. Hezma, A. Rajeh, Mohammed A. Mannaa〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Zinc oxide nanoparticles were prepared by a sol-gel method and characterized by XRD, SEM, TEM and EDX. A series of chitosan and polyvinyl alcohol (Cs/PVA) blend films doped with various concentrations of Zinc oxide nanoparticles (ZnO NPs) were prepared by solution casting method. These samples were characterized by various analytical techniques. XRD patterns of the prepared samples showed increasing in amorphousity of the polymer blend with increasing the content of ZnO NPs in Cs/PVA blend. The FT-IR analysis confirmed the complexation between Cs/PVA blend and ZnO NPs. From the UV–vis results, the optical energy gap was calculated. The TGA analysis displayed that the thermal stability of all the samples improved after the addition of the ZnO NPs. By the tensile universal testing machine, the mechanical properties of the prepared films were determined. The antimicrobial analysis showed that all nanocomposite films exhibited enhanced antimicrobial efficacy as compared to pure Cs/PVA film and it is linearly related to the amount of ZnO nanoparticles in the matrix. The sample containing 10 and 15 wt.% ZnO NPs exhibited the highest thermal stability, mechanical strength, and antibacterial activity. This nanocomposite with excellent thermal stability, tensile and antibacterial properties can be potentially utilized for antimicrobial packaging purposes and can be widely used in medical applications.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930809X-ga1.jpg" width="256" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Ya Di, Kunling Lu, Yaling Tian, Yan Liu, Yunwang Zhao, Yue Zheng〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two-phase synthesis is an advantageous alternative to the traditional synthetic method, due to its less toxicity, controllable, mild synthetic conditions and easy large-scale synthesis. However, meeting novel synthesis, the conventional trial-and-error approach could not provide a clear understanding. We herein report synthesis and mechanism investigation of CdS quantum dots in octadecene/glycerol two-phase system. The effects of different reaction parameters and conditions including reaction temperature, reaction time, reactant concentrations, and synthesis routes (one-step and two-step approach) on both nucleation and particle growth were investigated. It was found that the synthesis course was a growth dominated process depending on both CdS(monomer) and CdS(nuclei), and controlled by the interface of ODE/glycerol. The present work provided a new and clear understanding about two-phase system synthesis on semiconductor quantum dots, noble metal nanocrystals and some alloy nanomaterials.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308003-ga1.jpg" width="377" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Massimiliano Ferronato, Andrea Franceschini, Carlo Janna, Nicola Castelletto, Hamdi A. Tchelepi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work discusses a general approach for preconditioning the block Jacobian matrix arising from the discretization and linearization of coupled multiphysics problem. The objective is to provide a fully algebraic framework that can be employed as a starting point for the development of specialized algorithms exploiting unique features of the specific problem at hand. The basic idea relies on approximately computing an operator able to decouple the different processes, which can then be solved independently one from the other. In this work, the decoupling operator is computed by extending the theory of block sparse approximate inverses. The proposed approach is implemented for two multiphysics applications, namely the simulation of a coupled poromechanical system and the mechanics of fractured media. The numerical results obtained in experiments taken from real-world examples are used to analyze and discuss the properties of the preconditioner.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Huey-Shan Hung, Da-Tian Bau, Chun-An Yeh, Mei-Lang Kung〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉〈strong〉Gold〈/strong〉nanoparticles (AuNPs) have well applied in imaging and carriers of drugs and/or biomolecules for diseases and cancers therapeutics, due to their tunable physicochemical properties, easy functionalized with biomolecules and biocompatibility. AuNPs conjugated with biopolymer such as collagen has been demonstrated that increased the cell proliferation, migration and cell differentiation. Avemar (Ave) is a nutraceutical from natural components and dietary supplement for healthcare of tumor related anorexia/cachexia. Moreover, Ave has revealed the excellent bio-efficacy of anti-proliferation, cell cycle disturbing and apoptosis induction in numerous types of tumor cells in 〈em〉in vivo〈/em〉 and 〈em〉in vitro〈/em〉. However, the effects of Ave on cellular uptake mechanisms still unclear. In this study, we fabricate the Ave-deposited AuNP-collagen nanocarrier (AuNP-Col-Ave) and investigate their endocytic mechanisms in transformed SCC oral cancer cells and non-transformed BAEC and HSF cell lines. By using DLS assay, Ave-deposited AuNP-Col have shown a particle size of 303 ± 35.2 nm. Both UV–vis absorption assay and FTIR spectrum analysis were also demonstrated that the Ave conjugated onto AuNP-Col. Further, both MTT assay and Calcein AM assay were revealed that AuNP-Col-Ave induced a significant cytotoxicity in cancerous SCC cells and showed nontoxicity and biocompatibility for non-transformed BAEC and HFS cells. In addition, AuNP-Col-Ave has showed an excellent uptake capacity in all these cell lines as compared to AuNP-Col group. Further uptake mechanisms analysis demonstrated that the macropinocytosis seems to be the favorite endocytic mechanism during AuNP-Col-Ave internalized into these transformed and non-transformed cell lines. Altogether, this study is first validating the endocytic mechanisms of AuNP-Col-Ave in transformed and non-transformed cell lines. Our findings will provide a novel insight for endocytic mechanisms of cellular uptake nutraceuticals during nutrition therapy and cancer prevention.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Schematic diagram illustrated that AuNP-Col-Ave-mediated cellular uptake mechanisms and cell fates in both transform and non-transformed cell lines.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307794-ga1.jpg" width="217" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Edoardo Zoni, Yaman Güçlü〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A common strategy in the numerical solution of partial differential equations is to define a uniform discretization of a tensor-product multi-dimensional logical domain, which is mapped to a physical domain through a given coordinate transformation. By extending this concept to a multi-patch setting, simple and efficient numerical algorithms can be employed on relatively complex geometries. The main drawback of such an approach is the inherent difficulty in dealing with singularities of the coordinate transformation.〈/p〉 〈p〉This work suggests a comprehensive numerical strategy for the common situation of disk-like domains with a singularity at a unique pole, where one edge of the rectangular logical domain collapses to one point of the physical domain (for example, a circle). We present robust numerical methods for the solution of Vlasov-like hyperbolic equations coupled to Poisson-like elliptic equations in such geometries. We describe a semi-Lagrangian advection solver that employs a novel set of coordinates, named pseudo-Cartesian coordinates, to integrate the characteristic equations in the whole domain, including the pole, and a finite element elliptic solver based on globally 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msup〉〈mrow〉〈mi mathvariant="script"〉C〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈/mrow〉〈/msup〉〈/math〉 smooth splines (Toshniwal et al., 2017). The two solvers are tested both independently and on a coupled model, namely the 2D guiding-center model for magnetized plasmas, equivalent to a vorticity model for incompressible inviscid Euler fluids. The numerical methods presented show high-order convergence in the space discretization parameters, uniformly across the computational domain, without effects of order reduction due to the singularity. Dedicated tests show that the numerical techniques described can be applied straightforwardly also in the presence of point charges (equivalently, point-like vortices), within the context of particle-in-cell methods.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Maria Giuseppina Chiara Nestola, Barna Becsek, Hadi Zolfaghari, Patrick Zulian, Dario De Marinis, Rolf Krause, Dominik Obrist〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We present a novel framework inspired by the Immersed Boundary Method for predicting the fluid-structure interaction of complex structures immersed in laminar, transitional and turbulent flows.〈/p〉 〈p〉The key elements of the proposed fluid-structure interaction framework are 1) the solution of elastodynamics equations for the structure, 2) the use of a high-order Navier–Stokes solver for the flow, and 3) the variational transfer (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msup〉〈mrow〉〈mi〉L〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/math〉-projection) for coupling the solid and fluid subproblems.〈/p〉 〈p〉The dynamic behavior of a deformable structure is simulated in a finite element framework by adopting a fully implicit scheme for its temporal integration. It allows for mechanical constitutive laws including inhomogeneous and fiber-reinforced materials.〈/p〉 〈p〉The Navier–Stokes equations for the incompressible flow are discretized with high-order finite differences which allow for the direct numerical simulation of laminar, transitional and turbulent flows.〈/p〉 〈p〉The structure and the flow solvers are coupled by using an 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈msup〉〈mrow〉〈mi〉L〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/math〉-projection method for the transfer of velocities and forces between the fluid grid and the solid mesh. This strategy allows for the numerical solution of coupled large scale problems based on nonconforming structured and unstructured grids. The transfer between fluid and solid limits the convergence order of the flow solver close to the fluid-solid interface.〈/p〉 〈p〉The framework is validated with the Turek–Hron benchmark and a newly proposed benchmark modelling the flow-induced oscillation of an inert plate. A three-dimensional simulation of an elastic beam in transitional flow is provided to show the solver's capability of coping with anisotropic elastic structures immersed in complex fluid flow.〈/p〉 〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): Min Chai, Kun Luo, Changxiao Shao, Haiou Wang, Jianren Fan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper proposes a finite difference discretization method for simulations of heat and mass transfer with Robin boundary conditions on irregular domains. The level set method is utilized to implicitly capture the irregular evolving interface, and the ghost fluid method to address variable discontinuities on the interface. Special care has been devoted to providing ghost values that are restricted by the Robin boundary conditions. Specifically, it is done in two steps: 1) calculate the normal derivative in cells adjacent to the interface by reconstructing a linear polynomial system; 2) successively extrapolate the normal derivative and the ghost value in the normal direction using a linear partial differential equation approach. This method produces second-order accurate solutions for both the Poisson and heat equations with Robin boundary conditions, and first-order accurate solutions for the Stefan problems. The solution gradients are of first-order accuracy, as expected. It is easy to implement in three-dimensional configurations, and can be straightforwardly generalized into higher-order variants. The method thus represents a promising tool for practical heat and mass transfer problems involving Robin boundary conditions.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Allan Gomez-Flores, Scott A. Bradford, Lei Wu, Hyunjung Kim〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Particles of various shapes (e.g., spheres or rods), sizes (e.g., nm to microns), interiors (e.g., solid or hollow), and materials are used in many industrial and environmental applications. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory has commonly been used to calculate and predict the adhesive interaction of these particles with solid surfaces. However, DLVO theory treats these particles as equivalent spheres for simplicity ignoring shape in numerous cases. The surface element integration (SEI) approach allows DLVO theory to be extended for different particle shapes, orientations, and interiors. In this study, the SEI approach was applied to calculate the interaction energy between hollow and solid cylinders with a flat surface. The effect of aspect ratio and particle orientation on interaction energies was investigated under different solution chemistry conditions. Our study is relevant for an extensive range of particle aspect ratios, ranging from nanosized particles such as carbon nanotubes or nanowires, which have high aspect ratios, to micron-sized particles such as bacteria, which have low aspect ratios. The energy barrier tended to increase when the angle that the larger axis of the particle made with the normal to the surface changed from perpendicular (0 rad) to parallel (π/2 rad). The aspect ratio did not affect the trend of the energy barrier for solid (200–1000) and hollow (25–1000) cylinders of relatively high aspect ratios, but it produces a non-monotonic trend for solid (2–100) and hollow (2–10) cylinders of low aspect ratios. The present study advances our understanding of adhesive interactions for particles having a wide range of aspect ratios and interior properties at various orientations with the surface.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307691-ga1.jpg" width="310" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Xiaoqin Huang, Yanli Niu, Zeping Peng, Weihua Hu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Core–shell structured BiOCl@polydopamine (BiOCl@PDA) hierarchical hollow microspheres were synthesized as an efficient photocatalyst towards degradation of pollutants under visible light. As-prepared BiOCl@PDA features hierarchical hollow microsphere structure formed by aggregated BiOCl nanosheets with PDA thin film coated on their surface. It exhibits excellent photocatalytic activity and recycling durability for photodegradation of pollutants under visible light illumination. Detail investigation suggests that the introduction of PDA significantly improves the specific surface areas and enhances the light absorption and interfacial separation, together to improve the photocatalytic efficiency. This work may provide a valuable strategy for the synthesis of highly efficient photocatalysts.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307356-ga1.jpg" width="222" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Sanaz Ghiasi, Ali Behboudi, Toraj Mohammadi, Samaneh Khanlari〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, negatively charged Polyethersulfone (PES)/Polyimide (PI) ultrafiltration membranes were fabricated in order to enhance membrane performance. Moreover, the surface properties such as surface charge and roughness were studied as essential properties which can enhance Polyethyleneimine (PEI) nanofiltration layer assembly. Due to the possibility and observation of phase segregation, for the first time, PES/PI blend was investigated and approved both thermodynamically and experimentally via DSC and FESEM analysis. Highly charged surface of fabricated ultrafiltration (UF) blend membranes were able to reject BSA more than 95% due to smaller pores, surface roughness, and electrostatic forces according to the AFM and zeta potential analyses. Fouling parameters depicted lower fouling with increasing the PI content. Further investigations provided evidence that the presence of PI greatly affected membrane morphology, phase separation behavior, and pore size distribution. According to zeta potential and AFM analysis, the presence of negative charge along with increased roughness of blend membrane surface drastically enhanced the formation of positively charged hyperbranched polyethyleneimine NF layer. As seen in FESEM images, using the blend membranes as substrate enhanced the NF layer assembly by increasing the interfacial affinity resulting in more efficient layer assembly of the NF layer. The NF membranes exhibited high flux (52 LMH/bar) at low pressure (2 bar) in salt removal filtration tests along with increased performance in salts rejection in order of MgSO〈sub〉4〈/sub〉 (72%) 〉MgCl〈sub〉2〈/sub〉 (62%) ≥NaCl (61.4%).〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307411-ga1.jpg" width="242" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Weidong Li, Wei Li, Pai Song, Hao Ji〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents an efficient, low memory cost, implicit finite volume lattice Boltzmann method (FVLBM) based on conservation moments acceleration for steady nearly incompressible flows. In the proposed scheme, not as the conventional implicit schemes, both the micro lattice Boltzmann equations (LBE) and the associated conservation moment equations are solved by the matrix-free, lower-upper symmetric Gauss-Seidel scheme (LUSGS) and the conservation moment equations are used to predict equilibrium distribution functions at the new time, which eliminates the storage of the Jacobian matrix of the collision term in the implicit LBE system and provides a driving force for the fast convergence of the LBE. Moreover, by utilizing the projection matrix and the collision invariant, we can construct the fluxes of the moment equations efficiently from the fluxes of the LBE and avoid the time-consuming reconstruction procedure for obtaining the fluxes of the moment equations. To demonstrate the accuracy and high efficiency of the proposed scheme, comparison studies of simulation results of several two-dimensional testing cases by the present scheme and an explicit FVLBM are conducted and numerical results show that the proposed implicit scheme can be as accurate as its explicit counterpart with 1 or 2 orders times speedup.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Laurent Muscat, Guillaume Puigt, Marc Montagnac, Pierre Brenner〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper addresses how two time integration schemes, the Heun's scheme for explicit time integration and the second-order Crank-Nicolson scheme for implicit time integration, can be coupled spatially. This coupling is the prerequisite to perform a coupled Large Eddy Simulation/Reynolds Averaged Navier-Stokes computation in an industrial context, using the implicit time procedure for the boundary layer (RANS) and the explicit time integration procedure in the LES region. The coupling procedure is designed in order to switch from explicit to implicit time integrations as fast as possible, while maintaining stability. After introducing the different schemes, the paper presents the initial coupling procedure adapted from a published reference and shows that it can amplify some numerical waves. An alternative procedure, studied in a coupled time/space framework, is shown to be stable and with spectral properties in agreement with the requirements of industrial applications. The coupling technique is validated with standard test cases, ranging from one-dimensional to three-dimensional flows.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Benjamin Stadlbauer, Andrea Cossettini, José A. Morales E., Daniel Pasterk, Paolo Scarbolo, Leila Taghizadeh, Clemens Heitzinger, Luca Selmi〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Massively parallel nanosensor arrays fabricated with low-cost CMOS technology represent powerful platforms for biosensing in the Internet-of-Things (IoT) and Internet-of-Health (IoH) era. They can efficiently acquire “big data” sets of dependable calibrated measurements, representing a solid basis for statistical analysis and parameter estimation.〈/p〉 〈p〉In this paper we propose Bayesian estimation methods to extract physical parameters and interpret the statistical variability in the measured outputs of a dense nanocapacitor array biosensor. Firstly, the physical and mathematical models are presented. Then, a simple 1D-symmetry structure is used as a validation test case where the estimated parameters are also known 〈em〉a-priori〈/em〉. Finally, we apply the methodology to the simultaneous extraction of multiple physical and geometrical parameters from measurements on a CMOS pixelated nanocapacitor biosensor platform.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Meiling Zhao, Na Zhu〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We study the problem of electromagnetic scattering by multiple open cavities embedded in an infinite ground plane with high wave numbers. The problem can be described by a series of Helmholtz equations with coupled boundary conditions. We develop a sixth-order finite difference scheme to discretize the coupled Helmholtz equations. By Gaussian elimination in the vertical direction and Fourier transform in the horizontal direction, we can reduce the multiple cavity scattering problem to an aperture linear system. However, in the situation of high wave numbers, the condition number of the coefficient matrix of the reduced linear system is especially large and the system tends to be ill-conditioned. The convergence histories of most iterative methods become oscillating which consume considerable computations and memory spaces. In order to overcome the difficulty caused by high wave numbers, we develop an efficient preconditioned iterative method based on the Krylov subspace, which greatly improves the eigenvalue distributions and reduces the number of iterations. Numerical experiments show the validity and efficiency of the proposed sixth-order fast preconditioned algorithm for solving the scattering by multiple cavities with high wave numbers.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): YuFeng Shi, Yan Guo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we propose an alternative formulation of conservative fifth order finite difference compact Weighted Essentially Non-Oscillatory (WENO) schemes to solve compressible Euler equations. Comparing with the classical conservative finite difference Compact-WENO scheme, its reconstruction procedure is applied to the point values rather than the traditional flux functions, then the HLLC (Harten, Lax and van Leer) and the local Lax-Friedrichs flux functions can be used to compute the interface fluxes in this framework. To maintain positivity of density and pressure, the parametrized positivity satisfying flux limiter is coupled with the proposed scheme for problems with extreme conditions. A number of testing cases including Titarev-Toro problem, the planar Sedov blast-wave problem, Riemann problems, double Mach reflection problem, shock diffraction problem and Kelvin-Helmholtz instability problem are presented to demonstrate the high resolution of the proposed compact scheme.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Alexandre Noll Marques, Jean-Christophe Nave, Rodolfo Ruben Rosales〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We introduce a technique that simplifies the problem of imposing jump conditions on interfaces that are not aligned with a computational grid in the context of the 〈em〉Correction Function Method〈/em〉 (CFM). The CFM offers a general framework to solve Poisson's equation in the presence of discontinuities to high order of accuracy, while using a compact discretization stencil. A key concept behind the CFM is enforcing the jump conditions in a least squares sense. This concept requires computing integrals over sections of the interface, which is a challenge in 3-D when only an implicit representation of the interface is available (e.g., the zero contour of a level set function). The technique introduced here is based on a new formulation of the least squares procedure that relies only on integrals over domains that are amenable to simple quadrature after local coordinate transformations. We incorporate this technique into a fourth order accurate implementation of the CFM, and show examples of solutions to Poisson's equation with imposed jump conditions computed in 2-D and 3-D.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Qian Kong, Yan-Fei Jing, Ting-Zhu Huang, Heng-Bin An〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The main aim of this paper is to develop two algorithms based on the Scheduled Relaxation Jacobi (SRJ) method (Yang and Mittal (2014) [7]) for solving problems arising from the finite-difference discretization of elliptic partial differential equations on large grids. These two algorithms are the Alternating Anderson-Scheduled Relaxation Jacobi (AASRJ) method by utilizing Anderson mixing after each SRJ iteration cycle and the Minimal Residual Scheduled Relaxation Jacobi (MRSRJ) method by minimizing residual after each SRJ iteration cycle, respectively. Through numerical experiments, we show that AASRJ is competitive with the optimal version of the SRJ method (Adsuara et al. (2017) [9]) in most problems we considered here, and MRSRJ outperforms SRJ in all cases. The properties of AASRJ and MRSRJ are demonstrated. Both of them are promising strategies for solving large, sparse linear systems while maintaining the simplicity of the Jacobi method.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 398〈/p〉 〈p〉Author(s): Karim Shawki, George Papadakis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a preconditioner that can accelerate the rate of convergence of the Multiple Shooting Shadowing (MSS) method [1]. This recently proposed method can be used to compute derivatives of time-averaged objectives (also known as sensitivities) to system parameter(s) for chaotic systems. We propose a block diagonal preconditioner, which is based on a partial singular value decomposition of the MSS constraint matrix. The preconditioner can be computed using matrix-vector products only (i.e. it is matrix-free) and is fully parallelised in the time domain. Two chaotic systems are considered, the Lorenz system and the 1D Kuramoto Sivashinsky equation. Combination of the preconditioner with a regularisation method leads to tight bracketing of the eigenvalues to a narrow range. This combination results in a significant reduction in the number of iterations, and renders the convergence rate almost independent of the number of degrees of freedom of the system, and the length of the trajectory that is used to compute the time-averaged objective. This can potentially allow the method to be used for large chaotic systems (such as turbulent flows) and optimal control applications. The singular value decomposition of the constraint matrix can also be used to quantify the effect of the system condition on the accuracy of the sensitivities. In fact, neglecting the singular modes affected by noise, we recover the correct values of sensitivity that match closely with those obtained with finite differences for the Kuramoto Sivashinsky equation in the light turbulent regime. We notice a similar improvement for the Lorenz system as well.〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Paola Fincheira, Olga Rubilar, Javier Espinoza, Washington Aniñir, Loreto Méndez, Amedea B. Seabra, Andrés Quiroz〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oil-in-water (O/W) multilayer emulsions have been used to encapsulate volatile organic compounds (VOCs). Nevertheless, research associated with application in horticulture has been poorly studied. The objective of this study was to develop O/W emulsions for releasing VOCs to induce vegetable growth. Emulsions were prepared with vegetable oil, soybean lecithin and polysaccharides to formulate a stable product. The results indicated that O/W emulsions formulated with chitosan and sodium alginate were stable in a wide range of pH, temperature, and ionic strength. Furthermore, a direct relation between emulsions stability and VOC carbon was observed. The 2-nonanone (50–250 ppm) released from O/W emulsions increased the foliar length on L. 〈em〉sativa〈/em〉 and 〈em〉S. lycopersicum〈/em〉. Additionally, root lateral number was increased in 〈em〉S. lycopersicum〈/em〉 after exposition to released 2-nonanone. Surface elements as carbon, oxygen, and nitrogen were increased on leaves. It empathized that total nitrogen of both vegetables increased with exposition to 2-nonanone. Therefore, O/W emulsions can be an effective tool to microencapsulate VOCs with potential horticulture application.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307265-ga1.jpg" width="442" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 580〈/p〉 〈p〉Author(s): Qidong Huang, Xin Li, Sili Ren, Wuhui Luo〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Xanthate is a widely used collector in the flotation of sulfide minerals and discharge of xanthate-bearing solution could cause detrimental effects on ecological balance. In this study, the cationic gemini surfactant, butane-1,4-bis(dodecyl dimethyl ammonium bromide) (gBDDA), was applied to modify montmorillonite (Mt) for removal of ethyl, isobutyl, and isoamyl xanthates from aqueous solution. Different amounts of gBDDA that were stoichiometrically equivalent to 0.5 and 1.0 times the cation exchange capacity of Mt were used to investigate the effects of gBDDA dosage on xanthates removal by the obtained products (gOMt). Characterization results of gOMt by X-ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis showed the successful intercalation of gBDDA into the interlayer space and the higher content of gBDDA on the external surface of gOMt-1.0. Ion exchange and hydrophobic interaction accounted for the similar adsorption capacities of gOMt-1.0 for three xanthates (ca., 0.6 mmol/g), regardless of the molecular structure of xanthates. The rapid adsorption rate and high selectivity of gOMt to xanthates were obtained as supported by the complete removal within 60 min and the stable uptake in the sulfate-coexisting system, respectively, suggesting that gOMt could be a promising adsorbent for removal of xanthates from aqueous solution.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307125-ga1.jpg" width="424" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 6 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Yi Xiao, Zeqing He, Renshan Wang, Xueqin Tao, Benxia Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Notwithstanding intensive research in recent decade, the conspicuous restrictions in photocatalysts still remain as low utilization of visible light, poor charge transfer/separation, and insufficient surface active sites. Designing semiconductor heterostructures as photocatalysts is a promising approach to enhance the photocatalytic efficiency for degrading organic pollutants. In this work, a novel WO〈sub〉3〈/sub〉/BiOCl p–n heterostructure photocatalyst with optimal molar ratio was successfully fabricated by growing BiOCl nanosheets on WO〈sub〉3〈/sub〉 nanofibers through the electrospinning method followed with a solvothermal process. The optical properties and photoelectrochemical tests indicated that the WO〈sub〉3〈/sub〉/BiOCl heterostructures possess high ability of photogenerated charge separation. The photocatalytic performance of the as-obtained materials was assessed by the degradations of rhodamine B (RhB) and phenol in water under visible light. Compared with pure WO〈sub〉3〈/sub〉 nanofibers and BiOCl nanosheets, the WO〈sub〉3〈/sub〉/BiOCl heterostructure catalysts showed improved photocatalytic efficiencies, and the apparent rate constant of RhB degradation is 0.259 min〈sup〉−1〈/sup〉 on the optimal WO〈sub〉3〈/sub〉/BiOCl(2) sample, which is about 2.3 times that of pure BiOCl (0.113 min〈sup〉-1〈/sup〉). The roles of different active species in the photocatalytic system were determined by active-species-eliminating experiments, revealing that the photogenerated holes play a leading function in the degradation of organic pollutants. The enhanced photocatalysis of WO〈sub〉3〈/sub〉/BiOCl(2) heterostructures results from the joint effect of high activity of BiOCl nanosheets, anti-agglomeration of WO〈sub〉3〈/sub〉 nanofibers, and well-matched straddling band-structures for charge separation. This photocatalyst presents great potential in the removal of organic pollutants from aquatic environment.〈/p〉〈/div〉 〈h5〉Graphical Abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S092777571930740X-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉The novel WO〈sub〉3〈/sub〉/BiOCl heterostructure photocatalyst exhibits improved photocatalysis for degrading organic pollutants under visible light.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): Jian Yu, Chao Yan, Zhenhua Jiang, Wu Yuan, Shusheng Chen〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An adaptive non-intrusive reduced basis (RB) method based on Gaussian process regression (GPR) is proposed for parametrized compressible flows. Adaptivity is pursued in the offline stage. The reduced basis by proper orthogonal decomposition (POD) is constructed iteratively to achieve a specified tolerance. For GPR, active data selection is used at each iteration, with standard deviation as the error indicator. To improve accuracy for shock-dominated flows, a properly designed simplified problem (SP) is considered as input of the regression models in addition to using parameters directly. Furthermore, a surrogate error model is constructed to serve as an efficient error estimator for the GPR models. Several two- and three-dimensional cases are conducted, including the inviscid nozzle flow, the inviscid NACA0012 airfoil flow and the inviscid M6 wing flow. For all the cases, the trained models are able to make efficient predictions with reasonable accuracy in the online stage. The SP-based approach is observed to result in biased sampling towards transonic regions. The regression models are further applied in sensitivity analysis, from which the solution of the two-dimensional cases are shown to be significantly more sensitive to input parameters than the wing flow. This is consistent to the comparison of convergence histories between the parameter-based and the SP-based models. For cases of high sensitivity, the SP-based approach is superior and can help to significantly reduce the number of required snapshots to achieve a prescribed tolerance.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics, Volume 397〈/p〉 〈p〉Author(s): T. Allen, M. Zerroukat〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the increasing resolution of numerical weather prediction models the slopes of orographic features such as hills and mountains is becoming much better resolved with the consequence that the gradients encountered are becoming ever steeper. The commonly used terrain following coordinate, which actually becomes singular at 90°, is becoming more problematic due to the resulting stiffness making the elliptic boundary value problem difficult to solve. Even when a solution is obtainable the feedback of the pressure correction onto the momentum will generally cause instabilities and/or unphysical solutions. This paper uses an alternative representation of the orography, namely the immersed boundary method, in a semi-implicit-semi-Lagrangian model of the inviscid compressible Euler equations. The results show that the method not only performs well but, due to the chosen method of implementation, that the computational overhead of the geometry can be decoupled from implicit treatment of the vertical gravity wave component.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): François Forgues, Lucian Ivan, Alexandre Trottier, James G. M〈sup〉c〈/sup〉Donald〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The accurate prediction of multiphase flow when particles are differentiated by a set of “internal” variables, such as size or temperature, can pose modelling and numerical challenges. Although Lagrangian particle methods can provide predictive simulations of a wide spectrum of complex multiphase problems, they can become prohibitively expensive as the number of particles becomes large. Alternatively, Eulerian approaches have the potential to improve the computational efficiency of multiphase flows, but classical methods produce modelling artifacts or do not properly treat the local statistical dependence between the particle velocities and internal variables, or between the internal variables themselves. In this paper an extension is proposed of the classical Gaussian ten-moment model from gaskinetic theory to a model for the treatment of a dilute particle phase with an arbitrary number of internal variables based on an entropy-maximization argument. Unlike previous formulations, this new model provides a set of first-order robustly-hyperbolic balance laws that include a direct treatment for the local statistical variance of each variable, as well as the covariance between the internal variables or the internal variables and particle velocity. A study of the wave speeds of the general hyperbolic system is presented. To demonstrate an example application, the model is then specialized for polydisperse flows that are subject to viscous fluid drag as well as gravitational and buoyancy forces. The complete eigenstructure of this fifteen-moment polydisperse Gaussian model (PGM) is presented and the PGM is shown to maintain a physically realizable distribution function for all admissible initial conditions. Finally, several illustrative low-dimensional problems are studied to demonstrate the predictive capabilities of the new model.〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): O. Gmach, A. Bertsch, C. Bilke-Krause, U. Kulozik〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aim of this study was to investigate the effect of oil type, i.e. sunflower, rapeseed, peanut and corn oil on the emulsification effect. Knowledge about the impact of the different oils on the emulsification process in a head-to-head comparison is lacking. The hypothesis was that various oils as such or with their special compositions of by-products will have an impact on the properties of the resulting emulsion. As a novel aspect, a single fraction of egg yolk (EY), i.e. the egg yolk granules, were used as emulsifier. Because of their different sources and production processes, the oils differ in composition of fatty acids, degree of saturation and contain various surface-active components like cell membrane fragments, phospholipids and vitamins which influence the emulsification process and therefore the emulsions. In addition, the pH value of the aqueous phase was varied in a broad range. The dynamic interfacial tension between oil and water as well as the adsorption behavior of granules at the interface was analyzed by drop shape analysis. Oil-in-water emulsions with high ratio of dispersed phase (80%) were produced using a colloid mill. The resulting particle size distribution was determined by laser diffraction. There were significant differences in interfacial tension and adsorption of surface-active components at the interface among the oils due to their composition, fatty acid chain length and ratio of mono-, di-, and triglycerides, resulting in different droplet sizes ascribable to the oils. A correlation could be found for the initial decrease of the analytically measured interfacial tension at the oil-water interface and the resulting emulsion droplet size. Furthermore, it could be shown that the droplet size of the emulsions decreased with increasing pH-value of the continuous phase.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307769-ga1.jpg" width="482" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Yulia V. Kuznetsova, Ilse Letofsky-Papst, Benedikt Sochor, Bernhard Schummer, Alexander A. Sergeev, Ferdinand Hofer, Andrey A. Rempel〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simple shell-creating technique for the synthesis of CdS nanoparticles covered by ZnS is presented, which also contributes to the understanding of their low quantum yield and luminescence intensity in water, which is usually below 0.01%. The CdS nanoparticles with about 0.8 nm thick ZnS shell were synthesized in a colloidal aqueous solution and stabilized by EDTA. The CdS carrier lifetime and the quantum efficiency is greatly increased. For the latter, values up to 2.7% were achieved. A mechanism for the CdS nanoparticle luminescence in the aqueous solution is proposed, which is based on radiative recombination of charge carriers with structural defects. It was found that the synthesis of CdS in air leads to the inclusion of oxygen atoms in the structure of nanoparticles, which strongly effects the luminescence spectrum. These results show that most of the CdS luminescence centers are localized inside the nanoparticle.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308027-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Ali Esfandyari Bayat, Reza Shams〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent decades, utilizing of water-based muds (WBMs) in drilling oil and gas wells is ever increasing comparing to oil-based muds and synthetic-based muds due to the lower environmental issues. However, the main drawbacks with WBMs are rheological properties inefficiency and shale swelling which have caused attentions turn to improvement of WBMs’ rheological properties. In this study, the effects of various nanoparticles (NPs) namely titanium dioxide (TiO〈sub〉2〈/sub〉), silicon dioxide (SiO〈sub〉2〈/sub〉), and zinc oxide (ZnO) on improving rheological properties and shale recovery rate of a WBM sample at two temperatures (25 and 50 °C) were investigated. The concentrations of NPs in the base mud were set at 0.01, 0.05, 0.1 and 0.5 wt%. The results revealed that by adding NPs, the plastic viscosity (PV) of base mud was noticeably increased at the both temperatures. The optimum concentration of all NPs for increasing PV was found to be 0.01 wt%. Furthermore, by increasing concentration of ZnO and SiO〈sub〉2〈/sub〉 NPs up to 0.5 wt%, the base mud yield point value was considerably risen to around 13.3%, while by increasing concentration of TiO〈sub〉2〈/sub〉 NPs, the mud yield point values were reduced to 23.5 and 20.2 (lb/100 ft〈sup〉2〈/sup〉) at 25 and 50 °C, respectively. The optimum ZnO, TiO〈sub〉2〈/sub〉, and SiO〈sub〉2〈/sub〉 NPs concentrations for this purpose were found to be 0.05, 0.01, and 0.1 wt%, respectively. Moreover, ZnO and SiO〈sub〉2〈/sub〉 NPs at concentrations below 0.05 wt% had the best performances for filtration loss control. The related reason is higher stability of these NPs in the aqueous phase and consequently, better mud cake pores filling act by them which caused the mud cakes permeabilities were noticeably reduced. Besides that, SiO〈sub〉2〈/sub〉 NPs caused the highest 10 sec and 10 min gel strength values and ZnO and TiO〈sub〉2〈/sub〉 NPs in order had the lowest 10 sec and 10 min gel strength values at all applied concentrations and temperatures. Finally, by increasing concentrations of all NPs, shale recovery rates have noticeably risen comparing to the base mud. SiO〈sub〉2〈/sub〉, ZnO and TiO〈sub〉2〈/sub〉 NPs in order were successful additives for shale recycling.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307800-ga1.jpg" width="292" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 13 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Ming Yang, Qianhui Bai〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water pollution has become a great problem and aroused worldwide concern. As a new class of materials, metal-organic frameworks (MOFs) exhibit significant potential for wastewater treatment due to their high surface area, porosity, stability and tunability. In this work, flower-like hierarchical Ni-Zn MOF microspheres were synthesized via a facile solvothermal method. The mole ratio of Ni to Zn had a great influence on the morphology and microstructure of the final products. With the increase mole ratio of Zn to Ni, the morphology of MOFs gradually changed from spheroidal structure to rod-like structure. Using the Congo red (CR) experiment to evaluate the adsorption performance, Ni-Zn MOF displayed superior adsorption capacity towards CR (460.90 mg g〈sup〉-1〈/sup〉), compared with Ni MOF (276.70 mg g〈sup〉-1〈/sup〉) and Zn MOF (132.20 mg g〈sup〉-1〈/sup〉). Besides the tuned morphology and pore structure, electron transferring from Zn species to Ni species would also favor the physicochemical adsorption of Ni-Zn MOF towards CR.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307836-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈p〉Ni-Zn MOF synthesized via solvothermal method exhibited a superior adsorption performance towards Congo red. Due to the synergistic effect of Ni and Zn species, the Ni-Zn MOF exhibited a superior adsorption performance compared with Ni MOF and Zn MOF.〈/p〉 〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Yanyan Pei, Zhuwu Jiang, Liangjie Yuan〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently, MgO has been demonstrated to be a promising adsorption material for dye removal from wastewater due to its unique characteristics. However, the low surface area and recyclability have seriously limited its practical application in water treatment. Herein, MgO was introduced to mesoporous MCM-41 to improve its surface properties. A series of MCM-41/MgO nanocomposites with high surface areas (˜1000 m〈sup〉2〈/sup〉/g) and mesostructures were synthesized by a facile in situ method. Compared with pure MgO and MCM-41, the mesoporous MCM-41/MgO exhibited enhanced adsorption capacity and superior recycling stability for fast removal of an organic dye from water. The maximum adsorption capacity for crystal violet (CV) can reach 1861.38 mg/g, which is several times higher than that of MgO itself and of most other adsorbents. Even after five consecutive cycles, the removal efficiency is still up to 90%. It is expected that the mesoporous MCM-41/MgO materials will have a considerable potential in wastewater treatment.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉A facile synthetic strategy was developed to fabricate MCM-41/MgO nanocomposities with ultrahigh adsorption performance and excellent recycling stability.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719308040-ga1.jpg" width="403" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉

Description: 〈p〉Publication date: 20 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 581〈/p〉 〈p〉Author(s): Shasha Ai, Xu Guo, Lei Zhao, Dan Yang, Hanming Ding〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Prussian blue analogues (PBAs) have gained extensive attention for peroxymonosulfate (PMS) activation. However, the poor recovery ability of PBAs has limited their practical applications. In this work, PBA was firstly immobilized using zeolitic imidazolate framework-8 (ZIF-8) 〈em〉via〈/em〉 a facile 〈em〉in-situ〈/em〉 growth method. The decoration of PBA onto the surface of ZIF-8 was well confirmed by TEM, XRD, FTIR and XPS. The catalytic efficiency of the PBA-ZIF8 composite was significantly higher than that of pure PBA and ZIF-8 on the activation process of peroxymonosulfate when rhodamine B (RhB) was employed as a target contaminant. RhB degradation efficiency was effectively promoted at relatively high PBA-ZIF8 dosage and PMS concentration, as well as in near-neutral pH medium. Sulphate radicals obviously played a predominant role in attacking RhB during the whole reaction. In addition, PBA-ZIF8 also possessed good stability and reusability with negligible cobalt leaching. Therefore, the PBA-ZIF8 composite was a conveniently prepared and promising catalyst that may be employed to remediate contaminated water due to its excellent catalytic activity and recyclability.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307848-ga1.jpg" width="408" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Colloids and Surfaces A: Physicochemical and Engineering Aspects〈/p〉 〈p〉Author(s): Qingsong Hu, Sheng Yin, Yi Ding, Ting Wu, Ming Li, Bin Wang, Yong Chen, Jun Di, Jiexiang Xia, Huaming Li〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel sphere-like g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉/PbBiO〈sub〉2〈/sub〉Cl 2D-3D composite photocatalyst was fabricated 〈em〉via〈/em〉 a reactive ionic liquid 1-hexadecyl-3-methylimidazolium chlorine ([C〈sub〉16〈/sub〉mim]Cl) assisted one-pot solvothermal method. [C〈sub〉16〈/sub〉mim]Cl could act as Cl source, dispersing and template agent in the meantime, which ensured the construction of PbBiO〈sub〉2〈/sub〉Cl porous microspheres and high dispersity of ultrathin g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉. Various techniques were adopted to investigate the morphology, structure, optical and electrochemical properties of the obtained catalysts. It could be observed that ultrathin g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 was dispersed evenly around PbBiO〈sub〉2〈/sub〉Cl microspheres. The colorless contaminants including bisphenol A (BPA), ciprofloxacin (CIP) and colored rhodamine B (RhB) were selected as the model pollutants to appraise the photocatalytic performance of the as-prepared samples. Compared with single PbBiO〈sub〉2〈/sub〉Cl, the composites presented obviously enhanced photocatalytic performance under the irradiation of visible light, and the optimum mass ratio of g-C〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 was around 3 wt%. The improvement of photocatalytic activity could be ascribed to the tight interfacial contact between the two components that could promote the separation and transfer of photogenerated electron-hole pairs. Superoxide radical (•O〈sub〉2〈/sub〉-), holes and hydroxyl radical (•OH) all participated in the photocatalytic reactions on account of radicals quenching experiments and electron spin resonance (ESR). This research extends the knowledge into the construction of other 2D-3D composite photocatalysts with preferable photocatalytic activities in the field of environmental remediation.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0927775719307927-ga1.jpg" width="301" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 16 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Computational Physics〈/p〉 〈p〉Author(s): S. Danilov, A. Kutsenko〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Computational wave branches are common to linearized shallow water equations discretized on triangular meshes. It is demonstrated that for standard finite-volume discretizations these branches can be traced back to the structure of the unit cell of triangular lattice, which includes two triangles with a common edge. Only subsets of similarly oriented triangles or edges possess the translational symmetry of unit cell. As a consequence, discrete degrees of freedom placed on triangles or edges are geometrically different, creating an internal structure inside unit cells. It implies a possibility of oscillations inside unit cells seen as computational branches in the framework of linearized shallow water equations, or as grid-scale noise generally.〈/p〉 〈p〉Adding dissipative operators based on smallest stencils to discretized equations is needed to control these oscillations in solutions. A review of several finite-volume discretization is presented with focus on computational branches and dissipative operators.〈/p〉 〈/div〉