ALBERT

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Energy Conversion and Management, Volume 196〈/p〉 〈p〉Author(s): Zhendong Zhang, Hui Qin, Yongqi Liu, Liqiang Yao, Xiang Yu, Jiantao Lu, Zhiqiang Jiang, Zhongkai Feng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a renewable and clean energy, wind energy plays an important role in easing the increasingly serious energy crisis. However, due to the strong volatility and randomness of wind speed, large-scale integration of wind energy is limited. Therefore, obtaining reliable high-quality wind speed prediction is of great importance for the planning and application of wind energy. The purpose of this study is to develop a hybrid model for short-term wind speed forecasting and quantifying its uncertainty. In this study, Minimal Gated Memory Network is proposed to reduce the training time without significantly decreasing the prediction accuracy. Furthermore, a new hybrid method combining Quantile Regression and Minimal Gated Memory Network is proposed to predict conditional quantile of wind speed. Afterwards, Kernel Density Estimation method is used to estimate wind speed probabilistic density function according to these conditional quantiles of wind speed. In order to make the model show better performance, Maximal Information Coefficient is used to select the feature variables while Genetic Algorithm is used to obtain optimal feature combinations. Finally, the performance of the proposed model is verified by seven state-of-the-art models through four cases in Inner Mongolia, China from five aspects: point prediction accuracy, interval prediction suitability, probability prediction comprehensive performance, forecast reliability and training time. The experimental results show that the proposed model is able to obtain point prediction results with high accuracy, suitable prediction interval and probability distribution function with strong reliability in a relatively short time on the prediction problems of wind speed.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0196890419306958-ga1.jpg" width="159" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

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: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Contaminant Hydrology, Volume 226〈/p〉 〈p〉Author(s): Mehrdad Bastani, Thomas Harter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Nitrate in drinking water may cause serious health problems for consumers. Agricultural activities are known to be the main source of groundwater nitrate contaminating rural domestic and urban public water supply wells in farming regions. Management practices have been proposed to reduce the amount of nitrate in groundwater, including improved nutrient management practices and “pump and fertilize” with nitrate-affected irrigation wells. Here, we evaluate the feasibility and long-term impacts of agricultural managed aquifer recharge (Ag-MAR) in the source area of public water supply wells. A numerical model of nitrate fate and transport was developed for the Modesto basin, part of California's Central Valley aquifer system. The basin is representative of semi-arid agricultural regions around the world with a diversity of crop types, overlying an unconsolidated sedimentary aquifer system. A local public supply well in an economically disadvantaged community surrounded by farmland was the focus of this study. Model scenarios implemented include business as usual, alternative low-impact crops, and Ag-MAR in the source area of the public supply well. Alternative nutrient management and recharge practices act as remediation tools in the area between farmland and the public supply well. Improved agricultural source area management practices are shown to be an effective tool to maintain or even enhance groundwater quality in the targeted supply well while remediating ambient groundwater.〈/p〉 〈p〉Best results are obtained when lowering nitrate load while also increasing recharge in the source area simultaneously. This scenario reduced nitrate in the supply well's drinking water by 80% relative to the business as usual scenario. It also remediated ambient groundwater used by domestic wells between the source area farmlands and the supply well and showed 60% more reduction of nitrate after 60 years of application. Increasing recharge led to shorter initial response time (five years) and showed the most sustainable impact. Our analysis further suggests that Ag-MAR in a highly discontinuous, wide-spread pattern leads to slow water quality response and may not yield sufficient water quality improvements.〈/p〉 〈/div〉 〈/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: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Contaminant Hydrology〈/p〉 〈p〉Author(s): Héloïse A.A. Thouement, Tomasz Kuder, Timo J. Heimovaara, Boris M. Van Breukelen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Back-diffusion of chlorinated ethenes (CEs) from low-permeability layers (LPLs) causes contaminant persistence long after the primary spill zones have disappeared. Naturally occurring degradation in LPLs lowers remediation time frames, but its assessment through sediment sampling is prohibitive in conventional remediation projects. Scenario simulations were performed with a reactive transport model (PHT3D in FloPy) accounting for isotope effects associated with degradation, sorption, and diffusion, to evaluate the potential of CSIA data from aquifers in assessing degradation in aquitards. The model simulated a trichloroethylene (TCE) DNAPL and its pollution plume within an aquifer-aquitard-aquifer system. Sequential reductive dechlorination to ethene and sorption were uniform in the aquitard and did not occur in the aquifer. After 10 years of loading the aquitard through diffusion from the plume, subsequent source removal triggered release of TCE by back-diffusion. In the upper aquifer, during the loading phase, δ〈sup〉13〈/sup〉C-TCE was slightly enriched (up to 2‰) due to diffusion effects stimulated by degradation in the aquitard. In the upper aquifer, during the release phase, (i) source removal triggered a huge δ〈sup〉13〈/sup〉C increase especially for higher CEs, (ii) moreover, downstream decreasing isotope ratios (caused by downgradient later onset of the release phase) with temporal increasing isotope ratios reflect aquitard degradation (as opposed to downstream increasing and temporally constant isotope ratios in reactive aquifers), and (iii) the carbon isotope mass balance (CIMB) enriched up to 4‰ as lower CEs (more depleted, less sorbing) have been transported deeper into the aquitard. Thus, enriched CIMB does not indicate oxidative transformation in this system. The CIMB enrichment enhanced with more sorption and lower aquitard thickness. Thin aquitards are quicker flushed from lower CEs leading to faster CIMB enrichment over time. CIMB enrichment is smaller or nearly absent when daughter products accumulate. Aquifer CSIA patterns indicative of aquitard degradation were similar in case of linear decreasing rate constants but contrasted with previous simulations assuming a thin bioactive zone. The Rayleigh equation systematically underestimates the extent of TCE degradation in aquifer samples especially during the loading phase and for conditions leading to long remediation time frames (low groundwater flow velocity, thicker aquitards, strong sorption in the aquitard). The Rayleigh equation provides a good and useful picture on aquitard degradation during the release phase throughout the sensitivity analysis. This modelling study provides a framework on how aquifer CSIA data can inform on the occurrence of aquitard degradation and its pitfalls.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Ocean Modelling, Volume 140〈/p〉 〈p〉Author(s): Oleg Druzhinin, Yuliya Troitskaya, Wu-ting Tsai, Po-chen Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study is concerned with direct numerical simulation (DNS) of turbulent air flow over a waved water surface. Three-dimensional, turbulent Couette flow is considered in DNS as a model of a constant-flux layer in the marine atmospheric surface layer. Two-dimensional stationary waves at the water surface are prescribed and assumed to be unaffected by the air-flow. We consider capillary-gravity water surface waves and are interested in the influence of “parasitic” capillary ripples riding on the carrier, energy-containing waves, on the properties of the air-flow. The surface waves are prescribed and considered to be stationary, the capillaries being in phase with the carrier wave. The surface elevations spectra are also prescribed and mimicking stationary capillaries riding on Stokes waves observed in a 2D numerical simulation of water-surface capillary-gravity waves by Hung & Tsai (2009). The bulk air velocity and the carrier water surface waves lengths are considered in our DNS in the range of 3 to 5 m/s and 3 to 7 cm, respectively. Under these conditions, the capillaries are found to be submerged within the viscous sublayer of the atmospheric boundary layer. Our DNS results show that although the flow fields are characterized by instantaneous separations of the boundary layer, the ensemble (wave-phase) averaged flow fields are non-separating and well predicted by a quasilinear theoretical model. We find also that capillaries mitigate the development of coherent (horse-shoe) vortex structures as compared to the no-ripples flow-case. We further use DNS results and quasilinear model formulation to parameterize the water surface roughness height in terms of critical layer thickness and the amplitude of a dominant, energy-containing harmonic of the water surface elevation spectrum.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: July–August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Today, Volume 27〈/p〉 〈p〉Author(s): George F. Vander Voort〈/p〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Hiral D. Shah, J.A. Bhalodia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this communication, we report the structural and electrical transport properties of (1-〈em〉x〈/em〉) La〈sub〉0.7〈/sub〉Sr〈sub〉0.3〈/sub〉Mn〈sub〉0.95〈/sub〉Co〈sub〉0.05〈/sub〉O〈sub〉3〈/sub〉 (LSMCO) + (〈em〉x〈/em〉) ZnO (〈em〉x〈/em〉 = 0%, 6%, 9%, 12%, 15% & 18%) composites. For the preparation of (1-〈em〉x〈/em〉) LSMCO + (〈em〉x〈/em〉) ZnO (〈em〉x〈/em〉 = 6%, 9%, 12%, 15% & 18%) composites, sample of LSMCO was prepared by the auto combustion technique/inexpensive modified sol-gel technique. The results of Rietveld refined XRD data show that LSMCO sample possesses a rhombohedral structure with the 〈em〉R-3c〈/em〉 space group whereas ZnO compound remains with hexagonal structure with the 〈em〉P6〈/em〉〈sub〉〈em〉3〈/em〉〈/sub〉〈em〉mc〈/em〉 space group in all the composite samples. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that no any extra unwanted phase was observed in each composite excluding the LSMCO and ZnO phases. ZnO is mostly distributed at the grain boundaries and on the surface of the LSMCO grains. Elemental presence and ratio was confirmed through the EDX analysis. The electrical resistivity of LSMCO and each composite was measured in the temperature range of 2 K–320 K at 0 Oe, 10 kOe, 50 kOe & 90 kOe magnetic field. The results indicate that the ZnO addition increases the resistivity of all the composites compare to that of pure LSMCO. The electrical resistivity explored by the theoretical model below 〈em〉T〈/em〉〈sub〉MI〈/sub〉 and fitting enlightenment for the observed behavior is transmitted here in detail.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Dezhi Yang, Weihua Liu, Dingfu Cheng, Jieshi Chen, Hao Lu, Chun Yu, Jijin Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉(Co, Cr)23C6 type carbide is a typical metallic compound in many cobalt bearing alloys, and it acts as the strengthening phase in the form of bulk eutectic carbides or precipitated carbides. In this work, first-principles calculations were carried out to investigate the electronic structure, phase stability, mechanical and magnetic properties of (Co, Cr)23C6 with different cobalt occupation. Some of the calculated values are compared with previous studies and, they are found to be in a good agreement. The method considering curvature radius is firstly used to describe the degree of anisotropy. The hardness calculated through elastic constants presents an approximate downtrend with the cobalt concentration. Analysis of the density of states (DOS), overlapped population and electron density maps, indicates that the bonds in (Co, Cr)23C6 are the mixture of covalent, ionic and metallic bonds, the interactions of 〈em〉d-d〈/em〉 orbits between metallic atoms contribute most to the hybridization mode. According to the population analysis, the reduction in hardness can attribute to the increase of metallicity and iconicity of the interacted metallic atoms. In addition, the formation of a large quantity of antibonding also plays a negative role in intrinsic hardness of (Co, Cr)23C6 when massive substitution of cobalt atom.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Morteza Alizadeh, Andisheh Shakery, Erfan Salahinejad〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this research, the structure and mechanical properties of 1050 aluminum strips reinforced with E-glass fibers, processed by the cross accumulative roll bonding (CARB) process, were investigated from microscopic, hardness, tensile and peeling viewpoints. The results indicated that the incorporation of the glass fibers in the Al matrix increases strength and micro-hardness but decreases elongation. In addition, it was realized that some of these fibers are broken and changed to short fibers during the CARB process. The presence of the glass fibers strongly also reduces the bond efficiency of the Al strips, typically from 50% to 5%. To compensate this deleterious effect, it was found that at least 25% should be increased to the normal thickness reduction used in CRAB.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Astronautica〈/p〉 〈p〉Author(s): Bing Xiong, Xiao-qiang Fan, Yi Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To improve the performance of a hypersonic inward turning inlet, an optimization design method was proposed. A parameterization methodology was developed for an axisymmetric basic flowfield, and the geometry of a basic flowfield can be easily generated in several parameters. Preliminarily, an optimization targeting on the basic flowfield performance was conducted. As a result, the total pressure recovery of the basic flowfield was improved 7.65% compared with the referred one under the same constraints. The corresponding stream-traced inlet performance was also improved 5.65%. For further optimization, an optimization directly targeting on the 3-D inlet performance was carried out. The method of calculating along streamlines (MCS), which is for the fast calculation of a stream-traced inlet flowfield, was proposed and confirmed before this optimization. The result shows that the 3-D inlet total pressure can be further enhanced 6.74% than the previous one, and it is 12.78% higher than the referred one. That is to say, it is more reasonable to target on the inlet performance directly for an optimization, rather than targeting on the basic flowfield performance. By statistically analyzing the optimization data, it was found that the opinion “A better basic flowfield means a better stream-traced inlet” is statistically correct, but not exactly correct. The steam-traced inlet performance is not exactly determined by a basic flowfield, and it is determined by a combination of all the flow tubes the inlet captures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Transportation Research Part F: Traffic Psychology and Behaviour, Volume 64〈/p〉 〈p〉Author(s): Kayla Fleskes, David S. Hurwitz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One proposed benefit of automated vehicles (AVs) is their potential to mitigate the occurrence of serious crashes due to human error or poor decision making while driving. However, there are still many concerns associated with the use of SAE Level 3 AVs, which require intervention by a human driver after a take-over request (TOR). These concerns intensify when vulnerable road users, such as bicyclists, are introduced to the driving environment. The objective of this research was to investigate how human drivers of AVs interact with bicyclists during a right-turn maneuver after receiving a TOR. Changes in driver performance, including visual attention and crash avoidance behavior, were measured by using a high-fidelity driving simulator, with 43 participants each completing 18 right-turn maneuvers. Three independent variables were studied: the bicyclist’s proximity to the intersection, the driver’s proximity from the intersection when the TOR was received, and the driver’s engagement in a distracting secondary task (a game on a tablet). In general, the results showed that the introduction of the secondary task led to decreased driver performance with respect to time-to-collision and the time that it took a driver to first identify the bicyclist on the roadway. When given more time to react before the intersection, drivers generally had safer interactions with the bicyclist.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S136984781830411X-ga1.jpg" width="426" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Jingqi Tan, Jianjian Wei, Tao Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Onset and damping processes that characterize the transition of a thermoacoustic engine between the stationary and periodic oscillating states have attracted much research effort. In this work, the onset and damping characteristics of a closed two-phase thermoacoustic engine are investigated, where a regenerator is inserted between the cold and hot heat exchangers to reduce the irreversible loss caused by heat transfer. Additionally, a branch resonator, which consists of a load tube and a gas reservoir, is introduced to form the closed system and to adjust the acoustic field. A lumped parameter model is proposed to quantitatively analyze the performance of the thermoacoustic engine. Upon optimization, an onset temperature difference as low as 8.2 °C can be achieved in the experiments with R134a as the working fluid, which is the lowest one ever reported in the literatures. Besides, hysteresis phenomenon is found during the onset and damping processes. The present work aims to provide better understanding of the onset and damping behaviors of a two-phase thermoacoustic engine.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Bin Zou, Yiqiang Jiang, Yang Yao, Hongxing Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since various optical factors, including sunshape and optical errors, coexist in practice, their coupling effects on the PTC’s optical performance deserve in-depth explorations. Previous studies mainly focused on individual effects of several typical optical errors or simple description of optical errors using a unified Gaussian model. Thus, this study is committed to investigating the coupling effects of multiple optical factors on the PTC’s optical performance based on the theoretically individual characterization of each optical factor. The Monte Carlo Rays Tracing method was adopted, and the effective sunshape model was established for sampling of incident rays by convolving the incident sunshape model with the specularity error model. It is revealed that larger circumsolar ratio and specularity error produced more uniform heat flux distribution on the absorber. The advantage of high optical quality reflectors in improving optical efficiency was more outstanding in clearer weather. As circumsolar ratio was more than 0.2, improving specular quality to very high degree (〈3 mrad) reduced instead the optical efficiency. When tracking error and slope error were maintained respectively less than 4 mrad and 2 mrad, the weakening of optical efficiency was limited. The optical efficiency was more sensitive to slope error than to tracking error. The offset direction along positive Y-axis caused at maximum 2.19 times increase in heat flux density than that without optical errors, which causes threat of overheating to the absorber. When alignment error and tracking error were in the opposite direction, the optical loss could be compensated, whereas that in the same direction enlarged the optical loss. The slope error weakened the compensation effect and aggravated the weakening effect.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary International〈/p〉 〈p〉Author(s): Brian F. Codding, Adrian R. Whitaker, Nathan E. Stevens〈/p〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Athanassios Athanassiou, Alexandra A.E. van der Geer, George A. Lyras〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Eastern Mediterranean islands, most of which belong to the Aegean archipelago, have a complex biogeographic history, which puts its stamp on their fauna and flora. A now extinct but most important faunal component, in terms of geographic spread and taxonomic diversity, are the elephants. The Eastern Mediterranean islands are particularly rich in Pleistocene endemic elephant localities, which preserve samples of extinct endemic populations. These were either descendants of the European straight-tusked elephant 〈em〉Palaeoloxodon antiquus〈/em〉 or the Southern mammoth, 〈em〉Mammuthus meridionalis〈/em〉. Their presence, history and palaeobiogeography has been documented only for Cyprus, Crete, Kasos, Rhodes, Tilos, Kýthera, Naxos, and Delos. For six other islands only anecdotal references exist in the literature: Kálymnos, Astypálaia, Milos, Sériphos, Kýthnos and Paros. Here, we provide an update on previously published specimens and taxa, describe previously undescribed specimens that were relocated in museum collections, as well as recently excavated specimens, and put these in the context of island palaeobiogeography. We conclude that dwarf elephants, endemic to their palaeo-island, lived on the islands of palaeo-Cyclades, Astypálaia, Crete, Kasos–Kárpathos–Saría, Tilos, Rhodes and Cyprus, whereas the elephants from Kephallenía, Kálymnos and Kýthera are indistinguishable on the species level from mainland 〈em〉Palaeoloxodon antiquus〈/em〉. Elephant fossils of unresolved taxonomic status are reported from five present-day islands. The Eastern Mediterranean endemic elephants likely derived from separate and independent colonisation events from the mainland. No island supported more than one proboscidean species at any time. We found that isolation had no effect on the degree of dwarfism, but that there exists a threshold of about 6–10 km distance between the island and the mainland, below which no dwarfism evolved, likely as a result of genetic contact with the mainland population. We also found that although island area is correlated with the degree of dwarfism in elephants, other factors, such as the level of interspecific competition, may limit this degree.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Remote Sensing of Environment〈/p〉 〈p〉Author(s): Julie A. Fortin, Jeffrey A. Cardille, Elijah Perez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The ongoing march toward freely available, highly pre-processed satellite imagery has given both researchers and the public unprecedented access to a vast and varied data stream teeming with potential. Among many sources, the multi-decade Landsat archive is certainly the best known, but legacy and current data from other sensors is available as well through the USGS data portals: these include CBERS, ASTER, and more. Though the particular band combinations or non-global missions have made their integration into analyses more challenging, these data, in conjunction with the entire Landsat record, are available to contribute to multi-decade surveys of land-cover change.〈/p〉 〈p〉With the goal of tracing forest change through time near the Roosevelt River in the state of Mato Grosso, Brazil, we used BULC and Google Earth Engine to fuse information from 13 space-borne imagers capturing 140 images spanning 45 years. With high accuracy, the resulting time series of classifications shows the timing and location of land-use/land-cover change—both deforestation and regrowth—at sub-annual time scales. Accuracy estimates showed that the synthesized BULC classification time series was better than nearly all of the single-day image classifications, covering the entire study area at sub-annual frequency while reducing the impact of clouds and most unwanted noise as it fused information derived from a wide array of imaging platforms. The time series improved and gradually sharpened as the density of observations increased in recent decades, when there were three or more clear, higher-resolution views of a pixel annually from any sensor combination. In addition to detailing the methodology and results of multi-source data fusion with the BULC approach, this study raises timely points about integrating information from early satellite data sources and from sensors with footprints smaller than Landsat's. There are decades of research deriving sensor-specific techniques for classifying land use and land cover from a single image in a variety of settings. The BULC approach leverages the many successes of single-sensor research and can be used as a straightforward, complementary tool for blending many good-quality mapped classifications from disparate sources into a coherent, high-quality time series.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary International〈/p〉 〈p〉Author(s): Xiaolin Ren, Duowen Mo, Michael Storozum, Ximena Lemoine, Yanyan Yu, Wanfa Gu, Xingshan Lei, Jiaqiang Zhang, Jianqing Lü, Tristram R. Kidder〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Archaeologists have focused on the social conditions surrounding the development of urbanism around the world, however the environmental impact of these ancient cities remains unclear. In this paper, we present palynological data from the early Bronze Age city of Dongzhao, Henan Province, China. Our data indicate that vegetation change and the development of early urban settlements are closely linked, with the advent of urban development significantly accelerating deforestation and altering the composition of local vegetation communities. The pollen record from Dongzhao provides new evidence to support the claim that urban expansion, coupled with a drying climate and the expansion of agriculture, dramatically reconfigured the landscapes of Bronze Age China.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Geosciences, Volume 132〈/p〉 〈p〉Author(s): T. Carlotto, P.L.B. Chaffe〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Streamflow recession analysis is crucial for understanding how catchments release water in periods of drought and therefore is important for water resources planning and management. Despite there being several theories on how to model recession curves, few studies compare the different approaches to that problem. In this work, we developed the Master Recession Curve Parameterization tool (MRCPtool), which brings together a set of automated methods for the analysis of recession periods based only on streamflow data. The methods include: (i) hydrograph separation using numerical filters; (ii) automatic extraction of recession periods; (iii) creation of the MRC with the matching strip method; (iv) creation of the MRC for different flow classes defined from the flow duration curve; (v) analysis of flow recession rates 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" altimg="si1.svg"〉〈mrow〉〈mo〉(〈/mo〉〈mo linebreak="goodbreak" linebreakstyle="after"〉−〈/mo〉〈mi〉d〈/mi〉〈mi〉Q〈/mi〉〈mo〉∕〈/mo〉〈mi〉d〈/mi〉〈mi〉t〈/mi〉〈mo〉)〈/mo〉〈/mrow〉〈/math〉 as a function of flow 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" altimg="si2.svg"〉〈mrow〉〈mo〉(〈/mo〉〈mi〉Q〈/mi〉〈mo〉)〈/mo〉〈/mrow〉〈/math〉 and (vi) creation of the MRC from simulated recession curves with different analytical approaches, including linear and nonlinear models. The MRCPtool contains a graphical user interface developed in MATLAB software that facilitates the analysis of streamflow datasets. Finally, we present an example application of the MRCPtool using a streamflow dataset of 44 years. The MRCPtool is an open source tool that can be downloaded from the site: 〈a href="http://www.labhidro.ufsc.br/static/software/MRCPtool.rar" target="_blank"〉http://www.labhidro.ufsc.br/static/software/MRCPtool.rar〈/a〉.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computer Methods in Applied Mechanics and Engineering, Volume 355〈/p〉 〈p〉Author(s): Jean-Lou Pfister, Olivier Marquet, Marco Carini〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The stability analysis of elastic structures strongly coupled to incompressible viscous flows is investigated in this paper, based on a linearization of the governing equations formulated with the Arbitrary-Lagrangian–Eulerian method. The exact linearized formulation, previously derived to solve the unsteady non-linear equations with implicit temporal schemes, is used here to determine the physical linear stability of steady states. Once discretized with a standard finite-element method based on Lagrange elements, the leading eigenvalues/eigenmodes of the linearized operator are computed for three configurations representative for classical fluid–structure interaction instabilities: the vortex-induced vibrations of an elastic plate clamped to the rear of a rigid cylinder, the flutter instability of a flag immersed in a channel flow and the vortex shedding behind a three-dimensional plate bent by the steady flow. The results are in good agreement with instability thresholds reported in the literature and obtained with time-marching simulations, at a much lower computational cost. To further decrease this computational cost, the equations governing the solid perturbations are projected onto a reduced basis of free-vibration modes. This projection allows to eliminate the extension perturbation, a non-physical variable introduced in the ALE formalism to propagate the infinitesimal displacement of the fluid–solid interface into the fluid domain.〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Advances in Water Resources, Volume 131〈/p〉 〈p〉Author(s): Shaokun He, Shenglian Guo, Kebing Chen, Lele Deng, Zhen Liao, Feng Xiong, Jiabo Yin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The optimal impoundment operation of cascade reservoirs can dramatically improve the utilization of water resources. However, their complex non-convexity and computational costs pose challenges to optimal hydroelectricity output and limit further development of joint operation within larger-scale cascade reservoirs. In recent decades, parallel dynamic programming (PDP) has emerged as a means of alleviating the ‘curse of dimensionality’ in the mid-long term reservoir operation with more involved computing processors. But it still can't effectively solve the daily impoundment operation of more than three reservoirs. Here, we propose a novel method called importance sampling-PDP (IS-PDP) algorithm in which the merits of PDP are integrated with importance sampling and successive approximation strategy. Importance sampling is first used to construct the state vectors of each period by introducing ‘Manhattan distance’ in the discrete state space. Then the PDP recursive equation is used to find an improved solution during the iteration. The IS-PDP method is tested to optimize hydropower output for the joint operation of an 11-reservoir system located in the upper Yangtze River basin of China after establishing impoundment operation by advancing impoundment timings and rising water levels. We find that our methodology could effectively deal with the ‘curse of dimensionality’ for such mega reservoir systems and make better use of water resources in comparison to the Standard Operation Policy (SOP). Given its computational efficiency and robust convergence, the methodology is an attractive alternative for non-convex operation of large-scale cascade reservoirs.〈/p〉〈/div〉

Description: 〈p〉Publication date: July–August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Today, Volume 27〈/p〉 〈p〉Author(s): Laurie Donaldson〈/p〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 254〈/p〉 〈p〉Author(s): Zhi-Hu Wang, Hong-Wei He, Guo-Sai Liu, Xu Yan, Xin Ning, Yun-Ze Long〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In conventional electrospinning (e-spinning) process, the curing mechanism can be attributed to the volatilization of solvent or the melt cooling of the jets, which were merely physical processes. To develop novel e-spinning curing mechanism, we propose a conjugate e-spinning one, in which the e-spinning precursors, solution A containing some active monomers, oxidant and solution B containing reductant, are loaded into two different syringes connected with opposite high voltage supplier, respectively. The opposite charged jets attract each other and then meet when flying from spinneret tip to collector. The redox reaction occurs when two jets meet and radicals are produced in situ which can initiate polymerization of active monomers. Then the conjugate jets solidify into fibers under reaction curing mechanism. The new method may give a new approach to produce composite functional fibers.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Two solutions containing oxidant and reductant, respectively are electrospun into fibers via a conjugate electrospinning process under a reaction curing mechanism.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0167577X19309954-ga1.jpg" width="271" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): J.Y. Oh, Tien M. Le, A.T. Pham, D.H. Tran, D.S. Yang, B. Kang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, we investigated a correlation between superconductivity and interlayer coupling of two different alkaline (Na and K)-substituted Bi〈sub〉1·6〈/sub〉Pb〈sub〉0·4〈/sub〉Sr〈sub〉2〈/sub〉Ca〈sub〉2〈/sub〉Cu〈sub〉3〈/sub〉O〈sub〉10+δ〈/sub〉 (BSCCO) polycrystalline samples. The excess conductivity analysis by the Aslamazov-Larkin (AL) and Lawrence-Doniach (LD) theories showed that Na substitution at the Ca site induced a gradual broadening of 3D fluctuation region with increasing interlayer coupling strength, which explains a systematic increase of 〈em〉T〈/em〉〈sub〉〈em〉c〈/em〉〈/sub〉 and a decrease of normal state resistivity. On the other hand, exactly the opposite results were observed in the K-substituted samples in place of Sr. Extended x-ray absorption fine structure (EXAFS) studies revealed that substitution of Na and K generated completely different effects on the local structure around Cu atoms. It is noticeable that the Cu–O bond distance was found to decrease monotonically with the varying amounts of Na, which indicates that the CuO〈sub〉2〈/sub〉 layer is stabilized. On the while, the opposite was observed to occur with the varying amounts of K. Unlike the Cu–Ca bond which was the least affected by the substitution, the Cu–Sr bond distance increased drastically with K substitution. All these findings indicate that Na substitution at the Ca site enhances superconductivity with no loss of interlayer interaction, while K substitution at the Sr site weakens superconductivity due to the diminished interlayer interaction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Moara M. Castro, Shima Sabbaghianrad, Pedro Henrique R. Pereira, Eric M. Mazzer, Augusta Isaac, Terence G. Langdon, Roberto B. Figueiredo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A magnesium/aluminium composite was produced by room temperature consolidation through high-pressure torsion (HPT) processing. Half-discs of the pure metals were placed side-by-side and subjected to different numbers of turns. The initially reduced interface between the phases gradually increased with increasing rotation. The composite displayed a significant ductility even after 10 turns. The distribution of hardness in the HPT-processed discs was bi-modal in the early stages of processing. As the number of turns increased and the thickness of the phases decreased there was a noticeable increase in hardness. The hardness values of the composite further increased after thermal treatment due to the formation of intermetallics within the interface between the magnesium and aluminium-rich phases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Lipeng Xu, Fei Zhou, Jizhou Kong, Haobin Zhou, Qian Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of testing temperature on the electrochemical properties of Li(Ni〈sub〉0.6〈/sub〉Mn〈sub〉0.2〈/sub〉Co〈sub〉0.2〈/sub〉)O〈sub〉2〈/sub〉 are investigated in detail. When the testing temperature is 40 °C, the Li(Ni〈sub〉0.6〈/sub〉Mn〈sub〉0.2〈/sub〉Co〈sub〉0.2〈/sub〉)O〈sub〉2〈/sub〉 cathode material possesses the highest initial discharge capacity of 162.4 mAh·g〈sup〉−1〈/sup〉 at 0.5C rate, but their cycling stability decreases markedly. When the test temperature rises up to 60 °C, the side reaction between electrolyte and cathode material becomes serious, and the Li(Ni〈sub〉0.6〈/sub〉Mn〈sub〉0.2〈/sub〉Co〈sub〉0.2〈/sub〉)O〈sub〉2〈/sub〉 cannot work. When the testing temperature decreases, the electrochemical impedances like R〈sub〉ct〈/sub〉 values increase, and then the discharge capacity at 0 °C, −10 °C and −20 °C is only 80%, 53% and 23% of that at 25 °C. Based on the electrochemical impedance spectra at different temperatures, four kinds of equivalent circuit models are classified. The cycle and rate performance of Li(Ni〈sub〉0.6〈/sub〉Mn〈sub〉0.2〈/sub〉Co〈sub〉0.2〈/sub〉)O〈sub〉2〈/sub〉 cathode material could be improved obviously through Ti〈sub〉3〈/sub〉C〈sub〉2〈/sub〉(OH)〈sub〉2〈/sub〉 modification in an extreme environment, and especially in sub-zero environment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Materials Processing Technology, Volume 273〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Kenji Yoshii, Naoshi Ikeda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Dielectric and magnetocaloric measurements are carried out for the chromite TmCrO〈sub〉3〈/sub〉. This oxide was reported to be multiferroic below the Néel temperature (〈em〉T〈/em〉〈sub〉N〈/sub〉) of ∼125 K, likely due to a structural transformation. The dielectric response shows large dielectric constants below 300 K. However, from the analyses of loss tangent, AC conductivity and dielectric modulus, this behavior is rooted in hopping of charge carriers rather than electric dipoles, as proposed for some other chromites. No dielectric anomaly is found at 〈em〉T〈/em〉〈sub〉N〈/sub〉. The magnetocaloric effect shows that the magnetic transitions at 〈em〉T〈/em〉〈sub〉N〈/sub〉 as well as the spin reorientation temperature are of a second order. This result strongly suggests the absence of magnetostructural transition at 〈em〉T〈/em〉〈sub〉N〈/sub〉 in accord with no observation of ferroelectric transition at this temperature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Rattiya Hongtong, Panya Thanwisai, Rattakarn Yensano, Jeffrey Nash, Sutham Srilomsak, Nonglak Meethong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Core-shell olivine-type electrospun and doped LiFePO〈sub〉4〈/sub〉/FeS/C composite fibers were synthesized via a single-step process employing an electrospinning method using LiOH·H〈sub〉2〈/sub〉O, metal sul phates, H〈sub〉3〈/sub〉PO〈sub〉4〈/sub〉, citric acid, and polyvinylpyrrolidone (PVP) as the starting materials. Electron microscopy studies showed that the mean diameter of the core-shell composite fibers was about 280 ± 20 nm with a LiFePO〈sub〉4〈/sub〉 phase forming a core with a diameter of about 100 ± 20 nm and a carbon shell with a thickness of 80 ± 20 nm. An FeS phase was formed by a direct reduction of iron (II) sulfate (FeSO〈sub〉4〈/sub〉) that was evenly distributed within the core region of the composite fibers and further improved the electronic conductivity of the fibers. Na〈sup〉1+〈/sup〉, Mg〈sup〉2+〈/sup〉, and Al〈sup〉3+〈/sup〉 doping ions affected fiber morphology and electrochemical performance. All composite fibers showed excellent electrochemical performance. However, Al〈sup〉3+〈/sup〉 ions improved the electrochemical performance of the composite fibers to a significantly greater degree than Na〈sup〉1+〈/sup〉 and Mg〈sup〉2+〈/sup〉 doping ions, increasing the electronic and ionic conductivities of the material while maintaining their core-shell composite fiber characteristics.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉Electrospun LiFePO〈sub〉4〈/sub〉/FeS/C and 5% doped 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈mi〉L〈/mi〉〈mi〉i〈/mi〉〈mi〉F〈/mi〉〈msubsup〉〈mrow〉〈mi〉e〈/mi〉〈/mrow〉〈mrow〉〈mn〉1〈/mn〉〈mo linebreak="badbreak"〉−〈/mo〉〈mrow〉〈mo stretchy="false"〉(〈/mo〉〈mi〉n〈/mi〉〈mi〉x〈/mi〉〈mo linebreak="badbreak"〉/〈/mo〉〈mn〉2〈/mn〉〈mo stretchy="false"〉)〈/mo〉〈/mrow〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈mo linebreak="badbreak"〉+〈/mo〉〈/mrow〉〈/msubsup〉〈msubsup〉〈mrow〉〈mi〉M〈/mi〉〈/mrow〉〈mrow〉〈mi〉x〈/mi〉〈/mrow〉〈mrow〉〈mi〉n〈/mi〉〈mo linebreak="badbreak"〉+〈/mo〉〈/mrow〉〈/msubsup〉〈mi〉P〈/mi〉〈msub〉〈mrow〉〈mi〉O〈/mi〉〈/mrow〉〈mrow〉〈mn〉4〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉/FeS/C (M = Na〈sup〉1+〈/sup〉, Mg〈sup〉2+〈/sup〉, Al〈sup〉3+〈/sup〉) composites with a unique core-shell structure were synthesized via a simple single-step process to improved electrochemical properties for high performance and low cost Li-ion batteries.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0925838819324946-fx1.jpg" width="287" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): L.V.B. Diop, O. Isnard〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of Fe substitution on the structural and magnetic properties of the HoCo〈sub〉12-〈em〉x〈/em〉〈/sub〉Fe〈sub〉〈em〉x〈/em〉〈/sub〉B〈sub〉6〈/sub〉 (0 ≤ 〈em〉x〈/em〉 ≤ 2) series of intermetallic compounds have been studied. All of the compounds form in the rhombohedral SrNi〈sub〉12〈/sub〉B〈sub〉6〈/sub〉-type structure, the lattice constants increasing linearly with 〈em〉x〈/em〉. These compounds are ferrimagnets with a small transition metal magnetic moment and exhibit a spin reorientation transition. The Curie temperature decreases from 147 K for 〈em〉x〈/em〉 = 0–105 K for 〈em〉x〈/em〉 = 2. The Fe for Co substitution leads also to a progressive decrease of the spontaneous magnetization. The spin reorientation transition temperature is significantly reduced upon Fe for Co substitution whereas the compensation temperature is much less sensitive to the Fe composition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Hoheok Kim, Tatsuki Yamamoto, Yushi Sato, Junya Inoue〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigate the viability of establishing low-cost surrogate structure-property (S–P) linkages by introducing a Bayesian model selection method to extend the Materials Knowledge Systems (MKS) homogenization framework, which employs the n-point spatial correlation function, principal component analysis, and regression techniques. In particular, we place emphasis not only on choosing the important structural features but also on interpreting their implications for the property under consideration. First, the yield strengths of synthetic microstructures with various morphological characteristics are estimated by physics-based crystal plasticity simulation. Then, the dimension-reduced microstructural features are revealed by a combination of 2-point spatial correlations and principal component analysis. The Bayesian model selection method is further applied to establish a microstructure-to-yield-strength surrogate model. Finally, the model is validated with an independent dataset and its constituent features are interpreted with a morphology reconstruction based on a Monte Carlo algorithm. The method is found to be capable of interpreting the key microstructural features as well as modeling the mechanical response of a dual-phase metallic composite in consideration of the diverse microstructural factors.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304367-fx1.jpg" width="274" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Maxim S. Likhanov, Vladislav O. Zhupanov, Valeriy Yu Verchenko, Andrei A. Gippius, Sergei V. Zhurenko, Alexey V. Tkachev, Dina I. Fazlizhanova, David Berthebaud, Andrei V. Shevelkov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a new Fe〈sub〉1–〈em〉x〈/em〉〈/sub〉Re〈sub〉〈em〉x〈/em〉〈/sub〉Ga〈sub〉3〈/sub〉 solid solution, in which a 5〈em〉d〈/em〉-metal––rhenium––partially substitutes for iron to the limiting composition of 〈em〉x〈/em〉 = 0.10. The crystal structure refined for the composition Fe〈sub〉0.91〈/sub〉Re〈sub〉0.09〈/sub〉Ga〈sub〉3〈/sub〉 shows the expected increase in the unit cell parameters compared to the parent FeGa〈sub〉3〈/sub〉 compound, however the M–M (M = Fe, Re) distance decreases within the M–M dumbbell, indicating an increased M–M bonding density. Therein, investigation of the local structure by means of 〈sup〉69,71〈/sup〉Ga NQR spectroscopy revealed the formation of homonuclear Fe–Fe and Re–Re dumbbells. Transport and thermoelectric properties have been investigated for the Re-substituted FeGa〈sub〉3〈/sub〉. Electrical transport measurements showed preservation of the nonmetallic conductivity of Fe〈sub〉1–〈em〉x〈/em〉〈/sub〉Re〈sub〉〈em〉x〈/em〉〈/sub〉Ga〈sub〉3〈/sub〉 despite the decrease of the valence electron concentration from 17 to 16.9 electrons per formula. At low temperatures, Fe〈sub〉1–〈em〉x〈/em〉〈/sub〉Re〈sub〉〈em〉x〈/em〉〈/sub〉Ga〈sub〉3〈/sub〉 is a 〈em〉p〈/em〉-type semiconductor with the band gap of 0.4 eV, but with increasing temperature the sign of the dominant charge carriers changes. Owing to the alloying effect, Fe〈sub〉1–〈em〉x〈/em〉〈/sub〉Re〈sub〉〈em〉x〈/em〉〈/sub〉Ga〈sub〉3〈/sub〉 displays 1.5 times lower thermal conductivity than FeGa〈sub〉3〈/sub〉, which increases at high temperatures because of the growing contribution of the electronic term.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0925838819325198-fx1.jpg" width="454" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Jiashu Zhang, Weiyao Zhao, Zhenjie Feng, Jun-Yi Ge, Jincang Zhang, Shixun Cao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the crystal growth, structure analysis and magnetic phase transitions in the single crystal Sm〈sub〉0.15〈/sub〉Dy〈sub〉0.85〈/sub〉FeO〈sub〉3〈/sub〉. The high-quality of the crystal is verified by X-ray diffraction technique. Our research reveals that: 1) the iron sublattice spin reorientation (SR) transition emerges at 25 K, and ends at 10 K; 2) the rare earth antiferromagnetic (AF) order transition happens at 2.6 K; 3) there is a special wasp-waist hysteresis loop at low temperatures. Knowledge of such phase transitions in rare earth orthoferrite system is of potential importance for applications and theoretical studies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 253〈/p〉 〈p〉Author(s): Ji Soo Yu, Sung Hun Kim, Minh Tan Man, Hong Seok Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have successfully demonstrated the colloidal hot-injection process to easily obtain the Mn-doped ZnSe quantum dots (QDs) with a size of about 4–5 nm, and 〈em〉d〈/em〉-spacing is 0.31 nm, corresponding to the (1 1 1) lattice plane of ZnSe. Experimental results show that UV–vis absorption and fluorescence spectra were recorded to elucidate the role of Mn〈sup〉2+〈/sup〉 ions substituted into ZnSe, which resulted in the carrier transfer of luminescent sites by a small amount of Mn〈sup〉2+〈/sup〉 dopant. The small size of the Mn-doped ZnSe QDs offers intriguing opportunities for their application in photonic, bioimaging, and spintronics devices.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0167577X19309905-ga1.jpg" width="298" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 254〈/p〉 〈p〉Author(s): Mohamad Fahrul Radzi Hanifah, Juhana Jaafar, M.H.D. Othman, A.F. Ismail, M.A. Rahman, Norhaniza Yusof, Farhana Aziz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocluster-like Pt nanoparticles/reduced graphene oxide nanocomposite catalyst (NC-PtNPs/RGO) was synthesized through a novel one-step process of chemical reduction-assisted hydrothermal reaction by using formic acid as reducing agent. The crystallinity, morphology and composition of the NC-PtNPs/RGO catalysts were extensively characterized. The as-prepared NC-PtNPs/RGO catalysts exhibited higher electro-catalytic activity towards methanol oxidation than carbon black (CB)/PtNPs catalyst and could be ascribed to the high dispersion of NC-Pt NPs with large electrochemical surface area, release more exposure of active sites by NC-PtNPs structure and synergy effect of RGO.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 253〈/p〉 〈p〉Author(s): Zhenhua Wang, Yi Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Σ3 boundaries improve the intergranular corrosion resistance of high nitrogen austenitic stainless steels. However, the regeneration of these boundaries is, unfortunately, accompanied by significant grain coarsening. 18Mn18Cr0.5N and 18Mn18Cr0.6N steels were thermo-mechanically processed and the corresponding microstructures were evaluated. Formation mechanisms were proposed for Σ1 boundaries in different R-Σ3-Σ1-type junctions. These boundaries formed during grain growth accompanying Σ3 formation and reaction. After 30% cold tension and cyclic heating between 500 °C and 1100 °C, numerous Σ1 boundaries were formed and disrupted the high angle grain boundary network efficiently. Moreover, a small grain size was maintained. Σ1 boundaries have significant application potential in grain boundary engineering.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 254〈/p〉 〈p〉Author(s): Rui Wang, Dongdong Gu, Lixia Xi, Kaijie Lin, Meng Guo, Hongmei Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Selective laser melting (SLM), as a rapidly developed layer-by-layer 3D printing technology, has been demonstrated that it can be used for additive manufacturing of multi-materials. In this work, TiB〈sub〉2〈/sub〉/Ti6Al4V multi-materials were manufactured by SLM. The results showed that interfacial microstructures consisting of un-melted TiB〈sub〉2〈/sub〉 powders, columnar TiB crystals, and acicular TiB crystals were formed in the molten pool. Meanwhile, a variation nanohardness was developed with chemical compositions at the interfacial regions, owing to an in-situ reaction of Ti and TiB〈sub〉2〈/sub〉. The first-principle calculations were used to reveal the axial growth of TiB crystals as well as the different hardness of this system.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0167577X19310006-ga1.jpg" width="346" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 253〈/p〉 〈p〉Author(s): Siyao Xie, Ruidi Li, Linjun Tang, Tiechui Yuan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The diffusion behavior of Al in FeCoCrNiMo〈sub〉x〈/sub〉 high-entropy alloys (HEAs) at temperatures ranging from 773 to 873 K with and without pulse current was studied in this paper. The diffusion coefficients 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mi〉D〈/mi〉〈/math〉 was determined based on the Fick’s law and corresponding pre-exponential factor 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msub〉〈mi〉D〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈/math〉, as well as activation energy 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈msub〉〈mi〉Q〈/mi〉〈mi〉D〈/mi〉〈/msub〉〈/math〉. It was found that the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mi〉D〈/mi〉〈/math〉 under pulse current dramatically increased about hundreds of times in contrast with that without current. In addition, the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msub〉〈mi〉D〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈msub〉〈mi〉Q〈/mi〉〈mi〉D〈/mi〉〈/msub〉〈/math〉 were determined to reduce from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si5.svg"〉〈mrow〉〈msubsup〉〈mrow〉〈mn〉1.369〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉0.324〈/mn〉〈/mrow〉〈mrow〉〈mo〉+〈/mo〉〈mn〉0.424〈/mn〉〈/mrow〉〈/msubsup〉〈mo〉×〈/mo〉〈msup〉〈mrow〉〈mn〉10〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉13〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si17.svg"〉〈mrow〉〈msubsup〉〈mrow〉〈mn〉5.016〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉1.984〈/mn〉〈/mrow〉〈mrow〉〈mo〉+〈/mo〉〈mn〉3.284〈/mn〉〈/mrow〉〈/msubsup〉〈mo〉×〈/mo〉〈msup〉〈mrow〉〈mn〉10〈/mn〉〈/mrow〉〈mrow〉〈mo〉-〈/mo〉〈mn〉15〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉 m〈sup〉2〈/sup〉/s, and from 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si6.svg"〉〈mrow〉〈mn〉39.7〈/mn〉〈mo〉±〈/mo〉〈mn〉1.8〈/mn〉〈/mrow〉〈/math〉 to 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si18.svg"〉〈mrow〉〈mn〉21.6〈/mn〉〈mo〉±〈/mo〉〈mn〉3.4〈/mn〉〈/mrow〉〈/math〉 kJ/mol respectively with the Mo contents increasing from Mo〈sub〉0〈/sub〉 to Mo〈sub〉0.2〈/sub〉 without pulse current. The introduction of pulse current into the diffusion couples dramatically promoted the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈msub〉〈mi〉D〈/mi〉〈mn〉0〈/mn〉〈/msub〉〈/math〉 at all the diffusion couples. However, the pulse current was ascertained to obviously increase the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si4.svg"〉〈msub〉〈mi〉Q〈/mi〉〈mi〉D〈/mi〉〈/msub〉〈/math〉 in contrast to that of diffusion couples without pulse current.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0167577X19309899-ga1.jpg" width="271" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Yuliang Jiang, Xueyan Fu, Zidong Zhang, Wei Du, Peitao Xie, Chuanbing Cheng, Runhua Fan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Carbon nanofibers embedded with magnetic Fe〈sub〉3〈/sub〉C nanoparticles have been synthesized using electrospinning technique, followed by one-step carbonization. By using Fe〈sub〉3〈/sub〉C/C nanofibers as filler with 10% content, the sample can achieve a minimum reflection loss (RL) of −54.94 dB with a thickness of 1.36 mm, as well as the broad effective absorption bandwidth (EAB) can reach to 4.5 GHz (13.3–17.8 GHz) at the thickness of 1.55 mm. The superior properties might be due to the synergistic effects of dielectric loss, magnetic loss, multiple scattering and reflection. This work presents a facile and promising method to produce high performance microwave absorption materials with thin thickness, light weight and strong absorption.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): E.J. Pickering, K.A. Christofidou, H.J. Stone, N.G. Jones〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to reduce the environmental impact of air travel, it is desirable that the efficiencies of gas turbine engines are increased. One way to achieve this goal is to increase the operating temperatures of the engine cores. Unfortunately for aero-engine manufacturers, the temperature capability limits of the Ni-base superalloys used currently have been reached. Hence, new alloys need to be developed that are capable of operating at significantly higher temperatures. In this article, the potential of tantalum-base superalloys is discussed and explored. A suite of alloys based on the Ta-Al-Co system was investigated. It was found that an array of fine carbide precipitates was formed in the Ta-rich matrix in a subset of the alloys, which is promising in terms of developing a strong and damage-tolerant microstructure, but that the elemental partitioning of Al out of the matrix accompanying precipitation is likely to degrade environmental resistance. Nevertheless, it is believed that the design principles described have the potential to facilitate the development of the next generation of high-temperature alloys based on systems of this type.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): C.Q. Zhou, Q.A. Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to understand the effect of Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 nanoparticles on crystallite growth kinetics of nanocrystalline Mg, the crystallite growth characteristics in a Mg−Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 composite and a pure Mg sample were comparatively investigated in this work. The crystallite growth exponents of nanocrystalline Mg in the Mg−Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 composite and pure Mg were determined as 〈em〉n〈/em〉 = 5 and 〈em〉n〈/em〉 = 4, respectively. Meanwhile, the activation energy for crystallite growth in Mg−Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 composite was calculated to be 118.8 kJ/mol, which is higher than 97.1 kJ/mol in pure nanocrystalline Mg. Further studies reveal that the rise of crystallite growth exponent and increase of activation energy in the Mg−Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 composite are primarily attributed to the pinning effect of Pr〈sub〉3〈/sub〉Al〈sub〉11〈/sub〉 nanoparticles at crystallite boundaries of Mg.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Alloys and Compounds, Volume 804〈/p〉 〈p〉Author(s): Liming Tan, Yunping Li, Wenkai Deng, Yong Liu, Feng Liu, Yan Nie, Liang Jiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Three Ni-base powder metallurgy superalloys have been developed recently, and tensile tests at temperatures ranging from room temperature (RT) to 815 °C were conducted on them. The results conformed their excellent tensile properties, in comparison with several other existed polycrystalline superalloys. In this work, by means of microstructure characterization, thermal dynamic calculations, and theoretical modeling, different strengthening mechanisms including precipitation strengthening, grain boundary strengthening, solid solution strengthening, and Orowan strengthening, were found to contribute to the yield strength in different degrees, which would help to further enhance the tensile properties of these alloys through composition design and processing optimization thereafter.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0925838819324892-fx1.jpg" width="459" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Materialia, Volume 176〈/p〉 〈p〉Author(s): Denise C. Ford, David Hicks, Corey Oses, Cormac Toher, Stefano Curtarolo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metallic glasses are excellent candidates for biomedical implant applications due to their inherent strength and corrosion resistance. However, use of metallic glasses in structural applications is limited because bulk dimensions are challenging to achieve. Glass-forming ability (GFA) varies strongly with alloy composition and becomes more difficult to predict as the number of chemical species in a system increases. Here, we present a theoretical model — implemented in the AFLOW framework — for predicting GFA based on the competition between crystalline phases. The model is applied to biologically relevant binary and ternary systems. Elastic properties of Ca- and Mg-based systems are estimated for use in biodegradable orthopedic support applications. Alloys based on Ag〈sub〉0.33〈/sub〉Mg〈sub〉0.67〈/sub〉, Cu〈sub〉0.5〈/sub〉Mg〈sub〉0.5〈/sub〉, Cu〈sub〉0.37〈/sub〉Mg〈sub〉0.63〈/sub〉, and Cu〈sub〉0.25〈/sub〉Mg〈sub〉0.5〈/sub〉Zn〈sub〉0.25〈/sub〉, and in the Ag-Ca-Mg and Ag-Mg-Zn systems, are recommended for further study.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359645419304380-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Letters, Volume 254〈/p〉 〈p〉Author(s): C.Q. Zhang, W. Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Al〈sub〉3〈/sub〉Ti intermetallic compound (IMC) layer growth kinetics at Al-Ti interface was investigated. Surprisingly an abnormal effect of temperature was observed with a thicker IMC layer formed at lower annealing temperature due to the much faster Al〈sub〉3〈/sub〉Ti grain coarsening at a higher temperature, the IMC layer growth at 630 °C became slower than that at 600 °C after a certain annealing time. The quantitative influence of grain size on effective diffusion coefficient was analysed. Calculations showed that the lattice diffusion makes little contribution to the effective diffusion coefficient. Grain boundary diffusion, therefore, dominates for all the annealing conditions studied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: July–August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Today, Volume 27〈/p〉 〈p〉Author(s): David Bradley〈/p〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Scripta Materialia, Volume 171〈/p〉 〈p〉Author(s): Guang Wang, Xiannian Sun, Jinhai Xu, Yingchun Shan, Xiaoguang Han, Jiujun Xu, Jiangtao Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two transparent AlON ceramics substrates were successfully pressureless joined at 1880 °C for 80 min by using a powder interlayer of parent material. The grains on the interface of the joint were simultaneously shared by both interlayer and substrates due to grain growth and coalescence, which can evidently be categorized as thermal diffusion bonding under pressureless condition. The identical phase assemblage and microstructure for both interlayer and substrates lead to a bending strength of the joint (229.1 MPa) nearly equal to that of substrates, which is much higher than that of the reported AlON joints.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359646219303835-ga1.jpg" width="242" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 ISPRS Journal of Photogrammetry and Remote Sensing, Volume 154〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Ocean Modelling, Volume 139〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Jiaxu Wang, Xuefeng Liu, Siwei Chen, Hanghang Jiang, Guanyu Fang, Wenjing Chen, Shiming Deng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The current work study the heat dissipation characteristics and airflow distribution in a power cabin. By simplifying the cable structure, a 1:5 reduced-scale model was constructed based on the Archimedes number. Computational fluid dynamics (CFD) simulations were applied to the prototype power cabin. The 3D steady-state Reynolds average Navier-Stokes (RANS) equation is used to solve the ventilation flow, where the turbulence model is realizable k–ε. The CFD simulation of the prototype has been verified by the reduced-scale model. On this basis, several conclusions were drawn. The airflow distribution in the power cabin and cable arrangement cause a difference in the temperature distribution between the cables. The strong turbulence at the air inlet causes a significant temperature drop. The mechanical fan can effectively cool the cable to a certain extent, but cable temperature control should take into account the effects of ampacity and ventilation, as well as cable location.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Wenwu Zhou, Lin Yuan, Xin Wen, Yingzheng Liu, Di Peng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study explored and examined the piezoelectric (PE) jet: an active cooling concept that can be actuated in demand, which had an oscillating flow and extremely low power consumption. The heat transfer and flow characteristics of the PE jet were quantified at various Reynolds numbers (〈em〉Re〈/em〉 = 5000, 10,000, 18,000) and spacings (〈em〉H〈/em〉/〈em〉D〈/em〉 = 4.5, 5.5, 6.5; corresponding gap 〈em〉G〈/em〉/〈em〉D〈/em〉 = 0.1, 1.1, 2.1). The temperature sensitive paint technique was used to study the heat transfer, and the particle image velocimetry technique was applied to resolve the flow characteristics and to further correlate the heat transfer results. Measured results show that the impingement cooling of the PE jet increased as the 〈em〉Re〈/em〉 increased and as the 〈em〉H〈/em〉/〈em〉D〈/em〉 decreased. Compared with a circular jet, the PE jet exhibited a greatly improved heat transfer at 〈em〉H〈/em〉/〈em〉D〈/em〉 = 4.5 (i.e., 〈em〉G〈/em〉 = 0.1〈em〉D〈/em〉), with a maximum of 20% enhancement in area-averaged 〈em〉Nu〈/em〉. Due to the fan oscillation, the turbulent kinetic energy level in the PE jet was significantly higher than in the circular jet, which greatly promoted the heat transfer at a narrow gap. In general, the new PE jet can provide superior heat transfer performance at a small gap and a high Reynolds number.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 World Development, Volume 123〈/p〉 〈p〉Author(s): Adriana Camacho, Emily Conover〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Small-scale farmers in developing countries often make production and sale decisions based on imprecise, informal, and out-of-date sources of information, such as family, neighbors, or tradition. Lack of timely and accurate information on climate and prices can lead to inefficiencies in the production, harvesting, and commercialization of agricultural products, which in turn can affect farmers’ revenues and well-being. We did a Randomized Controlled Trial (RCT) experiment with 500 small-scale farmers in a rural area of Colombia where there is nearly full mobile phone usage and coverage. Treated farmers received around 8 text messages per week with prices in the main markets for crops grown in the region, and customized weather forecasts. Compared to a control group, we find that treated farmers were more likely to report that text messages provide useful information for planting and selling, and more likely to always read their messages, indicating an increase in appreciation and use of this type of technology. We also found heterogeneous effects by farmer size. Smaller farmers try to make use of the intervention by planting more crops for which they have price information. Larger farmers seek new markets and increase conversations with other producers. Despite these positive effects, we do not find a significant difference in farmers reporting a price, price differential with the market price, or sale prices received. Our results indicate that farmers are amenable to learning and using new technologies, but that the introduction of these technologies do not always translate into short-run welfare improvements for them. Given the increased interest in incorporating information and communication technologies into agriculture, our findings indicate that prior to a large-scale implementation it is necessary to better understand what prevents farmers from more directly profiting from this new information.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Remote Sensing of Environment, Volume 232〈/p〉 〈p〉Author(s): Yue Ma, Nan Xu, Jinyan Sun, Xiao Hua Wang, Fanlin Yang, Song Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Currently, 〈em〉in-situ〈/em〉 data and the time duration of altimeter data are limitations in calculating the water level and water volume of lakes and reservoirs from remotely sensed data. A novel method is proposed to estimate the temporal change in water levels and water volumes for lakes with only remotely sensed data. First, the surface profiles, including the ground and the underwater bottom, were extracted from the MABEL (Multiple Altimeter Beam Experimental Lidar) photon-counting lidar raw data via a new surface detecting algorithm. Second, the lake boundaries between land and water in different years were identified using a thresholding method based on the annual median Landsat composite. Third, water levels were calculated by matching the lidar surface profiles with the lake boundaries based on the nearby georeferenced coordinates. Finally, the water volumes in different years were estimated via the contours (i.e., lake boundaries) with different elevations. Lake Mead was selected as the study area, which is the largest reservoir in the United States in terms of water capacity. With only one day measuring lidar points in February 2012 and over 20 years of Landsat images (from 1987 to 2007), the water levels and water volumes in different years were estimated and compared with the 〈em〉in-situ〈/em〉 data. Our results performed well in accordance with the 〈em〉in-situ〈/em〉 measurements; the R-square of the water levels and water volumes were both over 0.99; the RMSE of the interannual variations of water levels and water volumes were 0.96 m and 0.31 km〈sup〉3〈/sup〉, respectively. The MABEL was used as a technology demonstrator for the satellite photon-counting laser altimeter and had similar data to the ICESat-2 dataset. Future ICESat-2 datasets will broaden this method to estimate water volumes for remote lakes from the 1980s, where no 〈em〉in-situ〈/em〉 data are available (such as the Tibetan Plateau and polar regions with thousands of remote and wild lakes), which could not be achieved in previous studies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of the Mechanics and Physics of Solids, Volume 131〈/p〉 〈p〉Author(s): Amir Ashkan Mokhtari, Yan Lu, Ankit Srivastava〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, we consider the operator properties of various phononic eigenvalue problems. We aim to answer some fundamental questions about the eigenvalues and eigenvectors of phononic operators. These include questions about the potential real and complex nature of the eigenvalues, whether the eigenvectors form a complete basis, what are the right orthogonality relationships, and how to create a complete basis when none may exist at the outset. In doing so we present a unified understanding of the properties of the phononic eigenvalues and eigenvectors which would emerge from any numerical method employed to compute such quantities. We show that the phononic problem can be cast into linear eigenvalue forms from which such quantities as frequencies, wavenumbers, and desired components of wavevectors can be directly ascertained without resorting to searches or quadratic eigenvalue problems and that the relevant properties of such quantities can be determined apriori through the analysis of the associated operators. We further show how the Plane Wave Expansion (PWE) method may be extended to solve each of these eigenvalue forms, thus extending the applicability of the PWE method to cases beyond those which have been considered till now. The theoretical discussions are supplemented with supporting numerical calculations. The techniques and results presented here directly apply to wave propagation in other periodic systems such as photonics.〈/p〉〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Weather and Climate Extremes, Volume 25〈/p〉 〈p〉Author(s): Jeremy Diaz, Maxwell B. Joseph〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tornadoes are the most violent of all atmospheric storms. In a typical year, the United States experiences hundreds of tornadoes with associated damages on the order of one billion dollars. Community preparation and resilience would benefit from accurate predictions of these economic losses, particularly as populations in tornado-prone areas increase in density and extent. Here, we use a zero-inflated modeling approach and artificial neural networks to predict tornado-induced property damage using publicly available data. We developed a neural network that predicts whether a tornado will cause property damage (out-of-sample accuracy = 0.821 and area under the receiver operating characteristic curve, AUROC, = 0.872). Conditional on a tornado causing damage, another neural network predicts the amount of damage (out-of-sample mean squared error = 0.0918 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msup〉〈mrow〉〈mi〉R〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈/mrow〉〈/math〉  = 0.432). When used together, these two models function as a zero-inflated log-normal regression with hidden layers. From the best-performing models, we provide static and interactive gridded maps of monthly predicted probabilities of damage and property damages for the year 2019. Two primary weaknesses include (1) model fitting requires log-scale data which leads to large natural-scale residuals and (2) beginning tornado coordinates were utilized rather than tornado paths. Ultimately, this is the first known study to directly model tornado-induced property damages, and all data, code, and tools are publicly available. The predictive capacity of this model along with an interactive interface may provide an opportunity for science-informed tornado disaster planning.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 24〈/p〉 〈p〉Author(s): Johnson U. Kitheka〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉This study was undertaken in the Athi-Sabaki river basin in Kenya in East Africa.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The study focused on the determination of the influence of streamflow variability on salt fluxes. This involved monitoring of river discharge and river salinity in the period between 2012 and 2018.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights〈/h6〉 〈p〉: This study demonstrates that Athi-Sabaki river discharges significant quantity of salt to the sea. There are significant seasonal and inter-annual variations in salt fluxes that are due to variations in river discharge and rainfall in the basin. The relationship between streamflow variations and variations of salinity in the river was inverse with highest salinity concentrations and fluxes occurring during low flow conditions. The river salinity and TDS concentrations decreased with an increase in river discharge due to dilution effect and flushing of salt from the river. The highly polluted sub-basins draining through the City of Nairobi exhibited relatively higher salinity and salt fluxes as compared to non-polluted ones draining rural areas. The total salt flux in the basin ranged between 29 × 10〈sup〉3〈/sup〉 and 261 × 10〈sup〉3〈/sup〉 tons year〈sup〉−1〈/sup〉. The relatively high salinity and salt fluxes were attributed to the discharge of wastewaters, seepage of groundwater and irrigation return flows. The study calls for water pollution control, sustainable irrigation and landuse practices in the basin.〈/p〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoforum, Volume 105〈/p〉 〈p〉Author(s): Arnab Roy Chowdhury, Kuntala Lahiri-Dutt〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hirashasan is the term used for governance of diamond mining and trade – with a small bureaucracy and an exclusive set of rules and regulations – by the district administration of Panna in the state of Madhya Pradesh in India. Diamond mining in Panna encompasses diverse extractive practices that range from fully mechanised large-scale mining operations owned by the state, to small-scale and semi-mechanised mining carried out by farmers and landowners in groups, to individuals carrying out seasonal and part-time mining of diamonds in an artisanal manner. Based on an ethnographic study was undertaken from September 2016 to April 2017, we argue that Hirashasan has created an “extractive assemblage” that comprises four genres of mining and production systems: large-scale, small-scale, licensed artisanal and unlicensed artisanal. This assemblage is a product of historical, cultural and geographical contingencies as much as place-specificities, and does not lend itself to a single mode of governance. Mineral resource governance in a particular place, therefore, necessitates understanding and internalising the variegated and pluri-form extractive assemblages, such as that of the diamond economy in Panna.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Technological Forecasting and Social Change〈/p〉 〈p〉Author(s): Sorin M.S. Krammer, Alfredo Jiménez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We posit that the investments in political connections made by a firm in an emerging market will impact differently its propensity to introduce radical and incremental innovations. In addition, we argue that this effect will be moderated by alternate non-market firm strategies, such as bribery. Using a dataset of more than 9000 firms in 30 emerging economies from Eastern Europe and Central Asia we find that political connections increase the probability of radical innovation but have no significant impact on incremental innovation. Moreover, larger bribing reduces the positive impact of political connections on radical innovation. Our results confirm the importance of political connections for firm activities, but also caution firms on their heterogeneous impact on various types of innovations, and their detrimental interplay with other non-market strategies.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Transportation Research Part A: Policy and Practice〈/p〉 〈p〉Author(s): Amit Agarwal, Dominik Ziemke, Kai Nagel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Bicycle is a sustainable low-carbon transport mode. However, insufficient or unplanned infrastructure leads to decrease in the share of bicycle in many cities of developing nations. In order to increase the bicycle share and to provide safer, faster and more direct routes, a bicycle superhighway is proposed for urban areas. This study identifies the potential of increase in the bicycle share. For maximum utilization of the new infrastructure, an algorithm is presented to identify the optimum number and locations of the connectors between proposed new infrastructure and existing network. Household income levels are incorporated into the decision making process of individual travellers for a better understanding of the modal shift. A real-world case study of Patna, India is chosen to show the application of the proposed superhighway. It is shown that for Patna, the bicycle share can escalate as high as 48% up from 32% by providing this kind of infrastructure. However, together with bicycles, allowing motorbikes on the superhighway limits the bicycle share to 44%. The increase in bicycle share is mainly a result of people switching from motorbike, public transport and walk to the bicycle. Further, to evaluate the benefits of the bicycle superhighway, this study first extends an emission modelling tool to estimate the time-dependent, vehicle-specific emissions under mixed traffic conditions. Allowing only bicyclists on the superhighway improves congested urban areas, reduces emissions, and increases accessibility. However, allowing motorbikes on the superhighway increases emissions significantly in the central part of the urban area and reduces accessibilities by bicycle mode to education facilities which are undesirable. This study elicits that a physically segregated high-quality bicycle superhighway will not only attract current non-cyclist travellers and increase the share of the bicycle mode, but will also reduce negative transport externalities significantly.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biomaterials, Volume 218〈/p〉 〈p〉Author(s): Yuwei Liu, Biao Kuang, Benjamin B. Rothrauff, Rocky S. Tuan, Hang Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mesenchymal stem cells (MSCs) embedded in their secreted extracellular matrix (mECM) constitute an exogenous scaffold-free construct capable of generating different types of tissues. Whether MSC-mECM constructs can recapitulate endochondral ossification (ECO), a developmental process during 〈em〉in vivo〈/em〉 skeletogenesis, remains unknown. In this study, MSC-mECM constructs are shown to result in robust bone formation both 〈em〉in vitro〈/em〉 and 〈em〉in vivo〈/em〉 through the process of endochondral ossification when sequentially exposed to chondrogenic and osteogenic cues. Of interest, a novel trypsin pre-treatment was introduced to change cell morphology, which allowed MSC-mECM constructs to undergo the N-cadherin-mediated developmental condensation process and subsequent chondrogenesis. Furthermore, bone formation by MSC-mECM constructs were significantly enhanced by the ECO protocol, as compared to conventional 〈em〉in vitro〈/em〉 culture in osteogenic medium alone. This was designed to promote direct bone formation as seen in intramembranous ossification (IMO). The developmentally informed method reported in this study represents a robust and efficacious approach for stem-cell based bone generation, which is superior to the conventional osteogenic induction procedure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 343〈/p〉 〈p〉Author(s): Wenmin Yao, Changdong Li, Qingjun Zuo, Hongbin Zhan, Robert E. Criss〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Variations of reservoir water level and seasonal precipitation have resulted in significant movement and destabilization of landslides in the Three Gorges Reservoir (TGR) region of China since reservoir impoundment in 2003. An example is the Baijiabao landslide, a large, actively creeping landslide located in the steep lower valley of the Xiangxi River, about 55 km upstream of the TGR dam in the Yangtze River. Twelve years of monthly monitoring at four GPS stations and routine, monthly field observations show cumulative GPS displacements as large as 〉1.5 m and widely developed ground cracks. GPS monitoring results show that most movement takes place in rapid steps that coincide with the rainy season and the period of annual reservoir drawdown, with particularly large steps in 2009, 2012 and 2015. This step-like pattern of displacement is also shown by daily data from an automatic monitoring system installed in 2017. The total period of acceleration shown by these daily data was about six weeks long, with rapid movement starting during rapid reservoir drawdown, and terminating when the reservoir began to rise again. In particular, most of the 2018 displacement occurred in only two weeks. Different subzones of the landslide move at different rates and exhibit different features of deformation. The neighborhood rough set theory is used to identify the triggering factors responsible for landslide deformation. The most important triggering factors vary between different sites, data types and the time interval used to define them. The surface deformation and ground crack widening are controlled by the combination of rainfall and variations in the reservoir water levels, whereas the deformation of the sliding zone is most sensitive to the latter. The results show that daily data are needed to capture important, short-term landslide responses. The neighborhood rough set theory for determination of triggering factors is suggested for deformation prediction, stability evaluation, and prevention and control of reservoir landslides in this and other regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Applied Earth Observation and Geoinformation, Volume 83〈/p〉 〈p〉Author(s): Sergio Sánchez-Ruiz, Álvaro Moreno-Martínez, Emma Izquierdo-Verdiguier, Marta Chiesi, Fabio Maselli, María Amparo Gilabert〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Growing stock volume (GSV) is one of the most important variables for forest management and is traditionally estimated from ground measurements. These measurements are expensive and therefore sparse and hard to maintain in time on a regular basis. Remote sensing data combined with national forest inventories constitute a helpful tool to estimate and map forest attributes. However, most studies on GSV estimation from remote sensing data focus on small forest areas with a single or only a few species. The current study aims to map GSV in peninsular Spain, a rather large and very heterogeneous area. Around 50 000 wooded land plots from the Third Spanish National Forest Inventory (NFI3) were used as reference data, whereas more than 8 000 Landsat-5 TM and Landsat-7 ETM + scenes covering both the study period (1997–2007) and area were chosen as a compromise between availability and suitable temporal and spatial resolution to estimate GSV. Google Earth Engine (GEE) was used to handle the huge amount of remotely sensed data. A total of 805 predictors were calculated from Landsat spectral reflectances. Guided regularized random forests algorithm (RF) was used to deal with the arising multicolinearity and identify the most important predictors by comparing with NFI3 plot-level GSV data. As a result, to model the relationship between spectral information and GSV, the original 805 predictors were reduced to only 29 (highlighting texture metrics, vegetation indices and band ratios involving short wave infrared reflectance) while maintaining the accuracy level (〈em〉R〈/em〉〈sup〉2〈/sup〉 ≈ 0.4 and RMSE ≈ 60 m〈sup〉3〈/sup〉 ha〈sup〉–1〈/sup〉). A 30-m spatial resolution wall-to-wall GSV map over Peninsular Spain was obtained from a standard RF with the 29 selected predictors through GEE. Its accuracy was evaluated against NFI3 province-level GSV data, resulting in 〈em〉R〈/em〉〈sup〉2〈/sup〉 ≈ 0.91 and RMSE ≈ 15 m〈sup〉3〈/sup〉 ha〈sup〉–1〈/sup〉.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0303243419301898-ga1.jpg" width="298" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Astronautica, Volume 164〈/p〉 〈p〉Author(s): Hao-Yang Peng, Wei-Dong Liu, Shi-Jie Liu, Hai-Long Zhang, Wei-Yong Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Methane-air Continuous Rotating Detonation (CRD) has been firstly achieved in this paper in the hollow chamber with a Laval nozzle, and the diameter of the chamber is just 100 mm. The contraction ratio of the Laval nozzle is a key factor for the CRD realization. CRD can only be obtained when the contraction ratio is no less than 4, but its ER operating range decreases in the increase of contraction ratio from 4 to 10. For all the success cases, the average propagation frequency and velocity are in the ranges of 5.32–5.65 kHz and 1670.48–1774.10 m/s, respectively, and the velocity deficits are less than 10%. Based on the high-speed photography images, the approach of chemiluminescence intensity integral is proposed in this paper, and the propagation characteristics of the flame are analyzed quantitatively. The propagation velocities of the flame and shock wave are agreed well with each other, indicating that the typical feature of detonation wave, i.e., the coupling of the flame and the shock wave, is verified quantitatively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Acta Astronautica〈/p〉 〈p〉Author(s): Jie Huang, Wei-Xing Yao, Ning Qin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The spiked blunt body is usually adopted to reduce the aerodynamic heating of hypersonic vehicles. In this paper, the heat reduction mechanism of hypersonic spiked blunt body with installation angle at large angle of attack is studied by the CFD numerical method. The AUSM+ scheme and Menter's SST 〈em〉k〈/em〉-〈em〉ω〈/em〉 turbulent model are adopted for the spatial discretization and turbulent simulation respectively. The results show that the maximum wall heat flux of blunt body is sensitive to the angle of attack. The increase of angle of attack causes the aerodynamic heating to rise sharply. The installation angle of the spike can effectively reduce the maximum heat flux of blunt body at large angle of attack, which is very beneficial to the thermal protection of blunt body. There is an optimal installation angle to minimize the maximum heat flux of blunt body. The optimal installation angle is about 1.5° greater than the angle of attack. All the investigations in this paper show the feasibility and advantages of spiked blunt body with installation angle in the engineering applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Sanaz Tabasi, Hossein Yousefi, Younes Noorollahi, Mohamad Aramesh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the performance of a photovoltaic panel integrated with a reflecting mirror is investigated. In this regard, the effects of panel and mirror tilt angles, and the mirror length on the system performance are modeled. The cell temperature rises have also been considered. Moreover, by a 3D model, the lighting and shading statuses are studied in detail, and all the possible conditions are presented and modeled. The resulting model can calculate the amount of incident solar energy on the panel and the generated electrical power in every moment during a year. This amount is dependent on the system configuration and capacity and its location. A 250-W photovoltaic panel and the city of Tehran have been considered the basics of calculations to assess the model results. By employing the genetic algorithm method, the optimum configuration has been found to have 69.084° and 0° tilt angles for the panel and the mirror, respectively, at the mirror length of 2 m. This configuration can generate 2.38 GJ (613.89 kWh) of electrical energy annually. It was also found that the optimum configuration had 0.024 GJ of annual energy losses due to the effects of cell temperature rise.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Su Min Hoi, An Liang Teh, Ean Hin Ooi, Irene Mei Leng Chew, Ji Jinn Foo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The flow across the plate-fin heat sink under the influence of 2D planar space-filling square fractal grid-induced turbulence at Reynolds number 〈em〉Re〈sub〉Dh〈/sub〉〈/em〉 of 2.0 × 10〈sup〉4〈/sup〉 is numerically characterized. Fractal thickness ratio 〈em〉t〈sub〉r〈/sub〉〈/em〉, plate-fin inter-fin distance 〈em〉δ〈/em〉 and grid-fin separation 〈em〉ℓ〈/em〉 are numerically explored and optimized via Response Surface Optimization (RSO) with the objective of maximizing the Nusselt number 〈em〉Nu〈/em〉. Results reveal that, thanks to highly interactive, small and comparable turbulence length scale 〈em〉L〈sub〉t〈/sub〉〈/em〉, strong turbulence intensity 〈em〉T〈sub〉u〈/sub〉〈/em〉 and high velocity adjacent to the fin surfaces, thermal dissipation of plate-fin heat sink enhances significantly. An optimum fractal grid and plate-fin geometrical combination having 〈em〉t〈sub〉r〈/sub〉〈/em〉 = 9.77, 〈em〉δ〈/em〉 = 0.005 m and 〈em〉ℓ〈/em〉 = 0.01 m is proposed. It delivers 〈em〉Nu〈/em〉 of 3661.0 which is 6.1% and 16.3% greater than the reference case and least favorable configuration, respectively. Sensitivity analysis discovered that 〈em〉δ〈/em〉 effectively dominates the thermal dissipation improvement while 〈em〉t〈sub〉r〈/sub〉〈/em〉 contributes the most on the pressure drop. Interestingly, fractal grid may not necessarily augmenting plate-fin forced convective heat transfer. Without proper-tuning the fluid flow structures within the fins may worsen the thermal dissipation instead of strengthening it. In short, the interaction between plate-fin heat sink and the fluid flow structures within the fins contributes greatly to heat transfer performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 World Development, Volume 123〈/p〉 〈p〉Author(s): Alwin Keil, Archisman Mitra, Amit K. Srivastava, Andrew McDonald〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sustainable intensification (SI) approaches to agricultural development are urgently needed to meet the growing demand for crop staples while protecting ecosystem services and environmental quality. However, SI initiatives have been criticized for neglecting social welfare outcomes. A recent review found that better-off farmers benefitted disproportionately from SI and highlighted the dearth of studies assessing the equity of outcomes. In this study, we explore the social inclusiveness of zero-tillage (ZT) wheat adoption in Bihar, India. ZT is a proven SI technology for enhancing wheat productivity while boosting profitability and reducing greenhouse gas emissions from agricultural machinery in the densely populated Indo-Gangetic Plains. With an average landholding size of 0.39 ha, most farmers in Bihar depend on custom-hiring services to access the technology. While service provision models should foster inclusive growth by reducing financial barriers to technology adoption, early evidence suggested that smallholders remained at a disadvantage. Building on this previous research, we use a panel dataset from 961 wheat-growing households that spans a six-year period to analyze ZT adoption dynamics over time while accounting for the role of social networks and access to service provision. Using a heckprobit approach to correct for non-exposure bias, we compare determinants of ZT awareness and use in 2012 and 2015. We apply a multinomial logit model to identify determinants of early adoption, recent adoption, non-adoption, and dis-adoption. Furthermore, we explore the quality of ZT services as an additional dimension of socially-inclusive technology access. We find that the strong initial scale bias in ZT use declined substantially as awareness of the technology increased and the service economy expanded. Land fragmentation replaced total landholding size as a significant adoption determinant, which also affected the quality of ZT services received. Hence, farmers with small but contiguous landholdings appear to have gained a significant degree of access over time. We conclude that early-stage assessments of SI may be misleading, and that private sector-based service provision can contribute to socially inclusive development outcomes as markets mature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 World Development, Volume 123〈/p〉 〈p〉Author(s): Chiara Ravetti, Mare Sarr, Daniel Munene, Tim Swanson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper analyses the ways in which ethnic identity and labour institutions shape favouritism and discrimination among workers. We conduct a lab experiment in the field with South African coal miners from various ethnic groups and with different trade union membership status. Our analysis suggests that union identity and ethnic identity are two social constructs that operate in a distinct and opposite fashion. Unionization acts as a factor of workers solidarity beyond the confine of union membership. Conversely, ethnicity operates as the linchpin through which discrimination among workers is infused not only between ethnic majority and minorities, but also within the majority group itself. We find that the widespread practice of subcontracting in the mining sector exacerbates ethnic discrimination among workers both between and within ethnic groupings.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Mark Baldry, Victoria Timchenko, Chris Menictas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metal additive manufacturing technologies are increasingly being adopted for rapid prototyping and to build geometrically complex designs for thermal management. This paper develops and experimentally validates a numerical model to design a high performance, small-scale heat sink for use with a thermoelectric cooling cap. The design was constrained by a heat load of 2.15 W, and a target average base temperature of 45 °C as a compromise between avoiding burn injury and reducing heat dissipation requirements. Over successive numerical iterations, an optimal natural convection heat sink was developed with an estimated thermal resistance of 10.9  K·W〈sup〉−1〈/sup〉 and base temperature of 44.4 °C. This design featured an internal cavity in a tapered pin array, and was able to achieve a steady state base temperature that was 11.7 °C cooler than a conventional design, with 51% less surface area and significantly less material.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 World Development, Volume 123〈/p〉 〈p〉Author(s): Vanesa Jordá, Miguel Niño-Zarazúa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Despite the growing interest in global inequality, assessing inequality trends is a major challenge because individual data on income or consumption is not often available. Nevertheless, the periodic release of certain summary statistics of the income distribution has become increasingly common. Hence, grouped data in form of income shares have been conventionally used to construct inequality trends based on lower bound approximations of inequality measures. This approach introduces two potential sources of measurement error: first, these estimates are constructed under the assumption of equality of incomes within income shares; second, the highest income earners are not included in the household surveys from which grouped data is obtained. In this paper, we propose to deploy a flexible parametric model, which addresses these two issues in order to obtain a reliable representation of the income distribution and accurate estimates of inequality measures. This methodology is used to estimate the recent evolution of global interpersonal inequality from 1990 to 2015 and to examine the effect of survey under-coverage of top incomes on the level and direction of global inequality. Overall, we find that item non-response at the top of the distribution substantially biases global inequality estimates, but, more importantly, it might also affect the direction of the trends.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary Science Reviews, Volume 218〈/p〉 〈p〉Author(s): Weizhe Chen, Dan Zhu, Philippe Ciais, Chunju Huang, Nicolas Viovy, Masa Kageyama〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Climate and atmospheric CO〈sub〉2〈/sub〉 strongly influence the vegetation distribution and the terrestrial carbon storage. Process-based dynamic global vegetation models (DGVM) are important tools for simulating past vegetation dynamics and carbon cycle; yet the link between spatial gradients of climate and vegetation cover in geological past has received less attention. In this study, we simulate the distribution of vegetation under three CO〈sub〉2〈/sub〉 levels for two climate states, the Last Glacial Maximum (LGM) and Pre-industrial (PI) climate with fire activated or deactivated using the ORCHIDEE-MICT DGVM. Results show that elevated CO〈sub〉2〈/sub〉 and warmer climate promote global total tree cover but the impacts are different between forest biomes. Regional tree cover is highly regulated by mean annual precipitation (MAP) especially in the tropics, and by temperature for the boreal-arctic tree line. Based on quantile nonlinear regressions, we analyze the MAP threshold at which maximum tree cover is reached. This threshold is significantly reduced with elevated CO〈sub〉2〈/sub〉 for tropical and temperate trees. With higher CO〈sub〉2〈/sub〉, increased tree cover leads to reduced fire ignition and burned area, and provides a positive feedback to tree cover, especially in Africa. Besides, in our model, increasing CO〈sub〉2〈/sub〉-induced enhancement of gross primary productivity (GPP) is more prominent for tropical trees than for temperate and boreal trees, and for dry regions than wet regions. This difference explains why CO〈sub〉2〈/sub〉 is the major factor influencing forest cover in the tropics. It also highlights that special attention should be paid to collect paleo-vegetation data across savannas-forest transition in dry regions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 World Development, Volume 123〈/p〉 〈p〉Author(s): Ben Siegelman, Nora Haenn, Xavier Basurto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper relates how fishermen in San Evaristo on Mexico’s Baja peninsula employ fabrications to strengthen bonds of trust and navigate the complexities of common pool resource extraction. We argue this trickery complicates notions of social capital in community-based natural resource management, which emphasize communitarianism in the form of trust. Trust, defined as a mutual dependability often rooted in honesty, reliable information, or shared expectations, has long been recognized as essential to common pool resource management. Despite this, research that takes a critical approach to social capital places attention on the activities that foster social networks and their norms by arguing that social capital is a process. A critical approach illuminates San Evaristeño practices of lying and joking across social settings and contextualizes these practices within cultural values of harmony. As San Evaristeños assert somewhat paradoxically, for them “lies build trust.” Importantly, a critical approach to this case study forces consideration of gender, an overlooked topic in social capital research. San Evaristeña women are excluded from the verbal jousting through which men maintain ties supporting their primacy in fishery management. Both men’s joke-telling and San Evaristeños’ aversion to conflict have implications for conservation outcomes. As a result, we use these findings to help explain local resistance to outsiders and external management strategies including land trusts, fishing cooperatives, and marine protected areas.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Nae-Hyun Kim, Cheol-Hwan Kim, Yousaf Shah, Wei Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In a parallel flow heat exchanger, significant mal-distribution of flow occurs due to phase separation. In this study, various insert devices (perforated tube, perforated tube with perforated plate, orifice and perforated tube, concentric perforated tube) were investigated to obtain an improved flow distribution in a 36 channel parallel flow heat exchanger. The test section was made to closely simulate an actual heat exchanger. Tests were conducted for upward flow for the mass flux from 57 to 241 kg m〈sup〉−2〈/sup〉 s〈sup〉−1〈/sup〉 and quality from 0.2 to 0.4 using R-410A. Of the investigated insert devices, concentric perforated tube yielded the best flow distribution. Insertion of the concentric perforated tube reduced the thermal degradation from 61% to 14%. Furthermore, the preferred number of holes of the concentric perforated tube was dependent on the mass flux. At a low mass flux, an insert having small number of holes was preferred, whereas the reverse was true at a high mass flux. At a low mass flux, the effect of inlet vapor quality on flow distribution was significant. At a high mass flux, however, the effect of vapor quality on flow distribution was minimal. Possible explanations on the flow distribution behavior were provided through flow visualization in the header.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Quaternary International〈/p〉 〈p〉Author(s): Rodrigo Loyola, Lautaro Núñez, Isabel Cartajena〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It has often been assumed that a link exists between climate change and human dispersion during the initial peopling of the Atacama Desert. However, there is little understanding of how hunter-gatherers acquired and processed environmental information. We examine paleoenvironmental and archaeological data to propose that the early peopling of the highlands of the south-central Atacama was a gradual process modulated by landscape learning. Evidence suggests that initial occupations at the end of the Pleistocene were limited to intermediate altitude levels, where the ecological structure was more easily legible and productive. This allowed human groups to make use of general, transferrable landscape knowledge, based mainly on the hunting of wild camelids and the gathering of plant resources in azonal formations. However, the arid event of the Early Holocene led to successive episodes of abandonment and relocation to new areas, consolidating complementary land-use between the desert lowlands and the high puna. Two complementary strategies for the acquisition and transmission of information can be identified: (1) scouting as part of logistical hunting parties; and (2) information-pooling rooted in broad, flexible social networks. We conclude that in the face of uncertain conditions, hunter-gatherers invested more effort in learning the landscape and sharing environmental knowledge.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Space Policy〈/p〉 〈p〉Author(s): Bergit Uhran, Catharine Conley, J. Andy Spry〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Planetary protection, or the protection of celestial bodies from potentially harmful contamination, has been required by international law since the ratification of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space in 1967. At that time, scientists were concerned about the potential of contaminating the Moon or bringing back a life form of lunar origin when astronauts returned to Earth with samples. The evidence is that the Moon does not contain indigenous life, but other celestial bodies may. Mars is of particular concern because of its habitability and plans to carry out a robotic sample return mission and even potentially human crewed missions in the near future (next 20–30 years). This article (recognizing that other national and international tasks are ongoing with detailed studies of technical aspects of containment and sample analysis) provides an overview of the policy aspects of planetary protection and sample return, discussing the history of planetary protection, lessons learned from the Apollo missions, and a potential strategy to ensure prevention contamination if a robotic sample return mission is carried out. It is recommended that the capability performed in the 1960s by the Interagency Committee on Back Contamination be reestablished, that regulations be developed to allow quarantine of anyone exposed to the samples, that scientific and technical personnel be trained in a receiving laboratory for at least 2 years prior to sample return, and that a test protocol be established for examining the samples. This will protect our biosphere while enabling groundbreaking research into conditions on Mars and any possible signs of life.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Space Policy〈/p〉 〈p〉Author(s): Harald Köpping Athanasopoulos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article discusses the Moon Village concept within the context of the increasing momentum to return human beings to the surface of the Moon. The article follows a dual objective. Firstly, the Moon Village is probably the most misunderstood among the plethora of ideas to explore the Moon scientifically and commercially. The article is therefore intended to explore what the Moon Village actually is. Secondly, the article explores the strengths and weaknesses of the Moon Village. The article is divided into three sections. The first section reviews the current Moon projects of public and private space actors, including the United States, Russia, China, SpaceX and Blue Origin. It sets the scene for the argument that the Moon Village has entered global discourse on space within a positive political environment. The second section discusses the premises of ESA chief Jan Wörner’s Moon Village concept, putting forward that the Moon Village is intended as an open concept rather than as a concrete plan. It is a process rather than a project and it is meant to initiate a global conversation on humanity’s future on the Moon. As such, the world café is an appropriate metaphor to illustrate the idea behind the Moon Village. In the third and final section a SWAT/PEST analysis is conducted to assess the feasibility of the Moon Village, highlighting that one of the major opportunities of the project is to promote international cooperation. The article concludes by supporting the institutionalist hypothesis that the Moon Village is arguably a translation of the ESA system to the global level, as participation is voluntary and as it builds on the strengths of each cooperation partner. As such, the Moon Village in indeed a new way of doing space on the global level.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Heat and Mass Transfer, Volume 141〈/p〉 〈p〉Author(s): D.Y. Yeo, H.C. NO〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, two-phase drag models for a packed bed of uniform-size particles were suggested, and they were applied to the calculation of pressure drop and dryout heat flux. We provided physical basis for the two-phase flow regime model through the analysis of the interfacial friction (〈em〉F〈sub〉i〈/sub〉〈/em〉). The suggested model provides flow patterns representing bubbly, slug, and channel flow and considering three criteria including d〈sup〉2〈/sup〉〈em〉F〈sub〉i〈/sub〉〈/em〉/d〈em〉α〈/em〉〈sup〉2〈/sup〉 = 0, 〈em〉F〈sub〉i〈/sub〉〈/em〉 = maximum, and 〈em〉F〈sub〉i〈/sub〉〈/em〉 = 0. The results obtained from the three criteria were drawn with several observation-based experimental ones to generate the flow regime map (void fraction vs. particle diameter). Through the current flow regime map, we clearly saw the existence of channel flow in a packed bed with particles smaller than around 3.5 mm. Then, mechanistic interfacial friction models were developed on basis of the current two-phase flow map of bubbly flow, slug flow, channel flow and annular flow. The suggested interfacial friction models were validated with top- and bottom-flooding air-water experiments and boiling experiments. We found out that the capability of pressure drop estimation by the current model were significantly improved for a bed with small particles. Finally, a zero-dimensional dryout heat flux (DHF) model was derived using the suggested interfacial friction models, and validated against DHF experimental data for beds with 1-D configuration. The root-mean-square error (RMSE) of the suggested DHF model was 35%, which was the smallest among the RMSEs of the previous DHF models.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Fluids and Structures, Volume 90〈/p〉 〈p〉Author(s): Julien Cisonni, Anthony D. Lucey, Novak S.J. Elliott〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Flutter instability of flexible cantilevers axially immersed in channel flow has been studied mainly for slender bodies with uniform properties. The present study addresses the stability of one-dimensional stepped cantilevers comprising two sections of different thickness immersed in two-dimensional viscous channel flow. The influence of the relative mass and rigidity of the two sections on the motion of the cantilever is explored through variations of length and thickness ratios. The parametric investigation shows that, for instance, making the free end of the cantilever twice thinner or thicker than the clamped end over a short fraction can produce structures that are either more stable or more unstable, depending on the fluid-to-solid mass ratio. In the case of a heavy and stiff free section and a light and flexible clamped section of comparable length, the excitation of lower structural modes by slower flows is significantly destabilising as compared to a uniform cantilever of same length and total mass. Strong destabilisation and weak stabilisation of the fluid–structure interaction system can result from either thinning or thickening the cantilever free-end which can also lead to changes in the flutter mode shape. These complex variations are quantitatively presented through stability maps.〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Heat and Mass Transfer, Volume 141〈/p〉 〈p〉Author(s): Tianyu Ma, Lei Feng, Hu Wang, Haifeng Liu, Mingfa Yao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spray impingement has aroused more and more interests in recent years with the increase of injection pressure in internal combustion engines. In this paper, the near wall combustion after fuel spray impingement is studied based on an updated film development model and experiment in constant volume vessel. Relationship between spray injection and flame development under different ambient temperature is analyzed as well as the near wall distribution of combustion products. In the first part, a mathematical model that considered the effects of surface tension on spray impingement is built for better prediction of film development. Reasonable results are obtained at room temperature spray impingement case, and the split distribution of film depth is also well captured. In the second part, flame development in the near wall region is investigated based on the proposed numerical model and experiments. The result shows that the flame becomes circumferentially nonuniformed at lower ambient temperature (723 K) and the evolution of downstream flame become sensitive to the wall temperature. At lower ambient temperature (723 K), increasing wall temperature could enlarge the high temperature zone, which is helpful to accelerate the film evaporation and soot oxidation. At higher ambient temperature condition, the spray impact angle should be reduced to create more concentrated combustion (stronger stratification), which could improve the combustion efficiency in the near wall region.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Progress in Aerospace Sciences〈/p〉 〈p〉Author(s): Dantong Ge, Pingyuan Cui, Shengying Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As small celestial body exploration advances, higher requirements with regard to system safety and landing precision are proposed for future landing and sample return missions. However, due to limited prior information about the target, the complex dynamics environment, and significant time-delay, performing a descent and landing on the small body surface is challenging. Among all the techniques required for achieving a safe landing, onboard guidance, navigation, and control (GNC) is of paramount importance in determining mission success. In this paper, a systematic survey of the autonomous GNC technologies for descent and landing on small bodies is carried out. First, based on an analysis of the technical challenges in the process, an overview of typical small body landing and sample return missions is given. Then, an elaboration of the state-of-the-art GNC technologies is presented. Specifically, autonomous navigation methods in unknown environments with highly-nonlinear dynamics are introduced. Descent guidance and control algorithms that take into account landing performance optimization and system robustness against model uncertainties are discussed. Touchdown dynamics and control methods proposed for precise and safe surface contact under weak gravity are analyzed. And safe strategies for onboard detected emergencies such as collision threats and system malfunctions are explained. Besides the prevalent methods, innovative techniques with respect to observability-based optimization, edge curve matching, online landing site selection, collision probability-based hazard avoidance, and trajectory curvature guidance proposed for improving system safety and landing performance are elucidated. At last, based on the growing system autonomy and operational complexity demands, a prospect of future research directions for small body GNC technologies is given.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Geosciences, Volume 132〈/p〉 〈p〉Author(s): Hongxing Zhang, Mingliang Zhang, Yongpeng Ji, Yini Wang, Tianping Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vegetation exerts a significant damping effect on tsunami wave run-up on coastal beaches, thus effectively mitigating the tsunami hazard. A depth-integrated two-dimensional numerical model (HydroSed2D, Liu et al., 2008; Liu et al., 2010) is developed to investigate tsunami wave run-up and land inundation on coastal beaches covered with 〈em〉Pandanus odoratissimus〈/em〉 (〈em〉P. odoratissimus〈/em〉). The present model is based on a finite volume Roe-type scheme, that solves the non-linear shallow water equations with the capacity of treating the wet or dry boundary at the wave front. The momentum equations in this model are modified by adding a drag force term, thus considering the resistance effects of vegetation on tsunami waves. The accuracy of the numerical scheme and the vegetation drag force are validated by three experimental cases of dam-break flow propagation in a dry channel, solitary wave propagation in a vegetated flume, and tsunami run-up over an uneven bed. Subsequently, a numerical model is applied to simulate tsunami run-up and land inundation on actual-scale vegetated beaches and a series of sensitive analyses are conducted by comparing numerical results. The obtained numerical results suggest that 〈em〉P. odoratissimus〈/em〉 can effectively attenuate tsunami run-up and land inundation distance on coastal beaches, and a higher attenuation rate for tsunami wave can be achieved by increasing both vegetation width and vegetation density. The tsunami wave height is also an important factor that impacts the tsunami wave run-up and land inundation on vegetated beaches.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computer Methods in Applied Mechanics and Engineering, Volume 355〈/p〉 〈p〉Author(s): Zhao Wang, Amit Subhash Shedbale, Sachin Kumar, Leong Hien Poh〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A localizing gradient damage model with micro inertia effect is proposed for the dynamic fracture of quasi-brittle materials. The objective is to achieve mesh independent solutions, and to avoid spurious effects associated with the conventional nonlocal enhancement. The proposed localizing gradient damage model closely resembles the conventional gradient enhancement, albeit with an interaction domain that decreases with damage, complemented by a micro inertia effect. We first consider a classical crack branching problem, where the localizing gradient damage model is shown to resolve the mesh sensitivity issue, as well as to correctly reproduce the crack profile. Moreover, the micro inertia effect is observed to retard the crack velocity. Next, the tensile loading of a Polymethyl Methacrylate plate is considered. It is shown that the proposed model effectively captures the experimentally observed transition of crack profiles as the loading rate increases, i.e. from a straight crack propagation, to sub-branching, and finally to macro branching. Numerical results in terms of crack patterns, crack velocities, and fracture energies are in good agreement with the experimental data. To furthermore demonstrate the superior performance of the localizing gradient damage model, the macro branching problem is solved using the conventional gradient enhancement with micro inertia. It is shown that a spurious damage growth and an erroneous interaction between closely spaced cracks suppress the development of macro branching, even though reasonable values are obtained for the fracture energy and crack velocity. The localizing gradient damage model is able to fully resolve these issues.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computer Methods in Applied Mechanics and Engineering, Volume 355〈/p〉 〈p〉Author(s): D. Xiao〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A novel error estimation method for the parametric non-intrusive reduced order model (P-NIROM) based on machine learning is presented. This method relies on constructing a set of response functions for the errors between the high fidelity full model solutions and P-NIROM using machine learning method, particularly, Gaussian process regression method. This yields closer solutions agreement with the high fidelity full model. The novelty of this work is that it is the first time to use machine learning method to derive error estimate for the P-NIROM. The capability of the new error estimation method is demonstrated using three numerical simulation examples: flow past a cylinder, dam break and 3D fluvial channel. It is shown that the results are closer to those of the high fidelity full model when considering error terms. In addition, the interface between two phases of dam break case is captured well if the error estimator is involved in the P-NIROM.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computer Methods in Applied Mechanics and Engineering, Volume 355〈/p〉 〈p〉Author(s): M. Goudarzi, A. Simone〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report the results of a comparative analysis of mesh independent discrete inclusion models and point out some shortcomings of classical approaches in the approximation of the strain field across an inclusion (artificial continuity) and the slip profile along an inclusion (oscillatory behavior). We also present novel embedded reinforcement models based on partition of unity enrichment strategies, adaptive 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" altimg="si246.svg"〉〈mi〉h〈/mi〉〈/math〉-refinement, and order/regularity extensions. These novel models are assessed by means of mesh convergence studies and it is shown that they improve the quality of the solution by significantly decreasing local spurious oscillations in the slip profile along an inclusion.〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computer Methods in Applied Mechanics and Engineering, Volume 355〈/p〉 〈p〉Author(s): C. Hermange, G. Oger, Y. Le Chenadec, D. Le Touzé〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A 3D fluid–structure coupling between Smoothed Particle Hydrodynamics (SPH) and Finite Element (FE) methods is proposed in this paper, with its application to complex tire hydroplaning simulations on rough ground. The purpose of this work is to analyze the SPH–FE coupling capabilities for modeling efficiently such a complex phenomenon. On the fluid side, the SPH method is able to handle the three complex interfaces of the hydroplaning phenomenon: free-surface, ground/fluid and fluid/tire interfaces. On the solid side, the FE method is used for its ability to treat tire–ground contact. A new algorithm dedicated to such SPH–FE coupling strategies is proposed to optimize the computational efficiency through the use of differed time steps between fluid and solid solvers. This way, the number of calls to the FE solver is minimized while maintaining the accuracy and stability of the coupling. The ratio between these respective time steps relies on a control procedure based on pressure loading. The present 3D SPH–FE model is first validated with different academic test cases and experimental data before considering the complex problem of the 3D hydroplaning simulations. Hydroplaning simulations are performed and analyzed on 3D configurations involving both smooth and rough grounds.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 343〈/p〉 〈p〉Author(s): Nieves G. Valiente, Robert Jak McCarroll, Gerd Masselink, Tim Scott, Mark Wiggins〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Predicting the future behavior of beach and nearshore systems requires an accurate delineation and understanding of coastal cell boundaries, sediment transport pathways, and sediment sources and sinks. Unfortunately, there is a paucity of field datasets on beach and nearshore morphological change that extend fully from the top of the dunes to beyond the depth of closure to enable quantification of the sediment budget. Here, for the first time, we employ a total sediment budget approach, examining a sandy and embayed beach located in the north coast of SW England, to investigate inter- and multi-annual embayment scale sediment dynamics over a 10-year period that includes extreme storm erosion and post-storm recovery. We demonstrate that, despite the deeply embayed nature of the beach, the shoreline orientation roughly parallel to the dominant wave direction and the overwhelmingly cross-shore forcing of the inter-tidal beach volume, the system is neither closed, nor balanced. The very significant net changes in the recorded sediment volume from dune top to depth of closure (−14.5 m ODN), representing a loss of c. 100 m〈sup〉3〈/sup〉 m〈sup〉−1〈/sup〉 during the extreme storm period and a gain of c. 200 m〈sup〉3〈/sup〉 m〈sup〉−1〈/sup〉 during the recovery period, indicate that significant sediment transport occurs seaward of the base of the terminating headlands and beyond the morphological depth of closure. The results further indicate that the inter-tidal region is partly uncoupled from the sub-tidal region, with the former region dominated by cross-shore sediment fluxes, whereas the subtidal region is also significantly affected by longshore sediment fluxes. A conceptual model is presented that balances the observed volume changes with inferred fluxes, forced by variations in total and alongshore wave power. This study contradicts the general assumption that when sediment exits the inter-tidal, it rests undisturbed in the sub-tidal, waiting for a period of low-moderate energy to bring it onshore. The large sediment volumetric variations across the lower shoreface (depth of 5–20 m), which are of the same order of magnitude as, but uncorrelated with, those occurring in the inter-tidal region, are suggestive of an energetic longshore transport system across this deeper region. It is possible that this transport system extends along the whole north coast of SW England and this finding may lead to a shift in understanding of sediment budgets along exposed and macrotidal embayments globally.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169555X19302739-ga1.jpg" width="439" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 13 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Sound and Vibration, Volume 458〈/p〉 〈p〉Author(s): Xiao-Dong Yang, Zhen-Kun Guo, Wei Zhang, Yuan Ren, Melnik V.N. Roderick〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although the substitution idea has been used occasionally in some engineering structures to study vibration characteristics, it is still short of systematic study in the vibrational engineering field. We summarize the techniques of the substitution method in this paper and apply such skill further to continuous and nonlinear systems, by which the dimension of the system can be reduced. By illustrated examples of frequency analysis on Timoshenko beam and composite sandwich structure, the substitution method has verified to be valid and efficient. The gyroscopic systems, represented by both rotating structures and orbits around libration points have also been presented to show the power of substitution method. Illustrated by the current examples, it is concluded that the substitution method has wide potential applications via studying the functional relations among all the degree-of-freedoms (DOFs) of non-gyroscopic or gyroscopic systems.〈/p〉〈/div〉 〈/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: July–August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Materials Today, Volume 27〈/p〉 〈p〉Author(s): 〈/p〉

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: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Fluids, Volume 191〈/p〉 〈p〉Author(s): Tibing Xu, Yee-Chung Jin〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper incorporates an improved Laplacian model for the pressure Poisson equation, a stabilization technique and a newly proposed advanced conditional collision force model in a projection-based particle method of the Moving Particle Semi-implicit (MPS) method. The Laplacian model is used to calculate pressure field and is able to predict more accurate results. The stabilization technique is used to eliminate density variation, which is developed from the continuity equation and transport theorem. The conditional collision force model is developed to handle approaching particles in simulations. With the conditional collision force model and the stabilization technique, the density calculation is improved in the dam-breaking flow and the number of separate jumping particles in the flow is greatly reduced due to the stabilization technique. By using the conditional collision force model, the Laplacian model can calculate the rotation of a square fluid patch. The stabilization technique further enhances the calculation, allowing the method to predict the evolution of the fluid patch in long duration. Including the three techniques, the present MPS is able to predict accurate pressure in the dam-breaking flow and rotation of the fluid patch. The energy variation in the impact of two rectangular fluid patches is also reproduced by the implemented techniques.〈/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〉