ALBERT

Description: The article presents problem of non-uniform foundation of structures in weak wet subsoil. The problem is illustrated with the case study of two-chamber-reinforced concrete water tank constructed in 1920s of 20th century, which cracked during construction. Under part of foundation, where the peat was found, the concrete piles were introduced.The results of five-year measurement of crack widths with crack gauges and geodesic measurements of vertical displacement of tank were presented. These results indicate that the tank is not stable and part of broken tank supported on piles is movable.On the basis of the presented data, the general conclusions concerning the non-uniform founding of tanks are formulated.

Description: The inclusions of geosynthetic materials (fibers, geomembranes and geotextiles) is a new improvement technique that ensures uniformity in the soil during construction. The use of tension resisting discreet inclusions like polypropylene fibers has attracted a significant amount of attention these past years in the improvement of soil performance in a cost-efficient manner. A series of direct shear box tests were conducted on unreinforced and reinforced Chlef sand with different contents of fibers (0, 0.25, 0.5 and0.75%) in order to study the mechanical behavior of sand reinforced with polypropylene fibers. Samples were prepared at three different relative densities 30%, 50% and 80% representing loose, medium dense and dense states,respectively, and performed at normal stresses of 50, 100 and 200 kPa. The experimental results show that the mechanical characteristics are improved with the addition of polypropylene fibers. The inclusion of randomly distributed fibers has a significant effect on the shear strength and dilation of sandy soil. The increase in strength is a function of fiber content, where it has been shown that the mechanical characteristics improve with the increase in fiber content up to 0.75%, this improvement is more significant at a higher normal stress and relative density.

Description: The present article examines the problem related to the axisymmetric torsion of an elastic layer by a circular rigid disc at the symmetry plane. The layer is sandwiched between two similar elastic half-spaces with two penny-shaped cracks symmetrically located at the interfaces between the two bonded dissimilar media. The mixed boundary-value problem is transformed, by means of the Hankel integral transformation, to dual integral equations, that are reduced, to a Fredholm integral equation of the second kind. The numerical methods are used to convert the resulting system to a system of infinite algebraic equations. Some physical quantities such as the stress intensity factor and the moment are calculated and presented numerically according to some relevant parameters. The numerical results show that the discontinuities around the crack and the inclusion cause a large increase in the stresses that decay with distance from the disc-loaded. Furthermore, the dependence of the stress intensity factor on the disc size, the distance between the crack and the disc, and the shear parameter is also observerd.

Description: A characteristic feature of soil-steel structures is that, unlike in typical bridges, the backfill and the carriageway pavement with its foundation play a major role in bearing loads. In the soil-steel structure model, one can distinguish two structural subsystems: the shell made of corrugated plates and the backfill with the pavement layers. The interactions between the subsystems are modelled as interfacial interactions, that is, forces normal and tangent to the surface of the shell. This is a static condition of the consistency of mutual interactions between the surrounding earth and the shell, considering that slip can arise at the interface between the subsystems. This paper presents an algorithm for determining the internal forces in the shell on the basis of the unit strains in the corrugated plates, and subsequently, the interfacial interactions. The effects of loads arising during the construction of a soil-steel bridge when, for example, construction machines drive over the structure, are taken into account in the analysis of the internal forces in the shell and in the surrounding earth. During construction, the forces in the shell are usually many times greater than the ones generated by service loads. Thus, the analytical results presented in this paper provide the basis for predicting the behaviour of the soil medium under operational loads.

Description: This article presents the results of laboratory tests on soft, normally consolidated soils from the Vistula Marshlands. Samples of high-plasticity organic soils (muds) taken from 3.2–4.0 m and 9.5–10.0 m depth, as well as peat deposit at 14.0 m, are analysed. Presented case study confirms the applicability of the Norwegian Institute of Technology (NTH) method based on Cone Penetration Tests (CPTU) and allows for a conservative estimation of effective friction angle for muds. The plastification angle equal to 14.5° for organic silt, applied in the modified NTH method, fits well the triaxial test (TX) results. Moreover, the dilative-contractive behaviour according to the CPTU soil classification based on the Robertson’s proposal from 2016 corresponds well with volumetric changes observed in the consolidated drained triaxial compression tests. The internal friction angles of the Vistula Marshlands’ muds and peats are lower in comparison with the database of similar soft soils.

Description: Based on the response of small-scale model square footing, the present paper shows the results of an experimental bearing capacity of eccentrically loaded square footing, near a slope sand bed. To reach this aim, a steel model square footing of (150 mm × 150 mm) and a varied sand relative density of 30%, 50% and 70% are used. The bearing capacity-settlement relationship of footing located at the edge of a slope and the effect of various parameters such as eccentricity (e) and dimensions report (b/B) were studied. Test results indicate that ultimate bearing capacity decreases with increasing load eccentricity to the core boundary of footing and that as far as the footing is distant from the crest, the bearing capacity increases. Furthermore, the results also prove that there is a clear proportional relation between relative densities –bearing capacity. The model test provides qualitative information on parameters influencing the bearing capacity of square footing. These tests can be used to check the bearing capacity estimated by the conventional methods.

Description: Tunnel construction below or adjacent to piles will affect the performance and eventually the stability of piles due to ground deformation resulting in the movement of piles and changes in the axial force distribution along the piles. A three dimensional finite element analysis using PLAXIS 3D (2013) was performed to study the behaviour of a single pile and 3 x 3 piles group during the advancement of shield tunnelling in ground. The 10-node tetrahedral elements were used to model both the soil and the tunnel lining. The Hardening Soil (HS) model was used to simulate the soil structure interaction at the tunnel-soil interface. An isotropic elastic model was used for the pile, piles cap, tunnel lining and tunnel boring machine shield (TBM). Several parametric studies were attempted including the longitudinal, lateral, and vertical tunnel location relative to pile embedded in different types of soil (clay or sand). The results showed that the pile head settlement increases during the tunnelling advancement in larger values than that for ground surface settlement. A zone of influence was determined in the range of twice the tunnel diameter in the longitudinal direction (forward and backward of the pile), and transverse direction (left and right of the tunnel centreline). If the tunnel boring is kept off this zone then there is no fear of pile collapse.

Description: The paper evaluates the effectiveness of reinforcing a damaged earth structure with making counterfort drains in its slope. The system of counterfort drains changed the soil properties significantly over a long-term use. The evaluation was based on many years of field and laboratory tests and stability analysis. The field tests concerned the observation of N WST probing resistance change, and the laboratory tests concerned the change in soil consistency and water content. The paper presents the results of tests that were conducted over 13 years.

Description: The article describes a computer analysis of the pull-out test used to calculate the force needed to pull out a rock fragment and determine the shape of this broken fragment. The analyzed material is sandstone and porphyry. The analysis included the first approach to using own subroutine in the Simulia Abaqus system, that is, which task is undertaken to accurately determine the crack path of the Finite Element Method model. The work also contains a description of laboratory tests and analytical considerations.

Description: At present, the suspended monorail systems constitute a very common means of transportation in the Polish hard coal mines. The main advantages of the suspended monorail include the independence of the route from the working floor surface irregularities and the possibility to transport cargo of significant mass and size.The masses and dimensions of machines and devices transported via monorail have increased considerably in recent times. This particularly concerns the transport of longwall system elements. In Poland, the maximum speed of suspended monorail travel is 2 m/s. Due to the fact that preparations are currently underway to increase the maximum speed above 2 m/s, it is necessary to inspect what influence it will have on work safety and mining support stability.Current operational experience and tests have shown that dynamic loads induced by the suspended monorail transportation have a significant influence on the roadway support stability, working protection durability and on the monorail operators. This is particularly true during the emergency braking of a suspended monorail by means of a braking trolley, where the overloads reach 3g.Bench tests of the selected steel arch and rock bolt support elements utilised in the Polish hard coal mines were conducted in order to determine the resistance of steel arch and rock bolt supports to static and dynamic loads.The article presents the results of the tests conducted on a steel arch support in the form of the sliding joints of an ŁP/V29 yielding roadway support, which is commonly employed in the Polish hard coal mines. Tests of elements of the threaded bolts with trapezoidal threads over the entire rod length were conducted as well.The conducted strength tests of steel arch and rock bolt support elements under static and dynamic loading have shown that dynamic loading has decisive influence on the support’s retaining of its stability. Support element stability decreases along with the increase of the impact velocity. This concerns both the steel arch support and the rock bolt support.

Description: We show that the global non-linear stability threshold for convection in a double-diffusive couple-stress fluid saturating a porous medium is exactly the same as the linear instability boundary. The optimal result is important because it shows that linearized instability theory has captured completely the physics of the onset of convection. It is also found that couple-stress fluid saturating a porous medium is thermally more stable than the ordinary viscous fluid, and the effects of couple-stress parameter (F ) , solute gradient ( S f ) and Brinkman number ( D a ) on the onset of convection is also analyzed.

Description: This paper discusses the pull-out laboratory tests and the monitoring of expansion-shell bolts with a length of 1.82 m. The bolts comprised the KE-3W expansion shell, a rod with a diameter of 0.0183 m and a profiled, circular plate with a diameter of 0.14 m, and a gauge of 0.006 m. The bolts were installed in a concrete block with a compressive strength of 75 MPa. The tests were conducted on a state-of-the-art test stand owned by the Department of Underground Mining of the AGH University of Science and Technology. The test stand can be used to test roof bolts on a geometric scale of 1:1 under static and rapidly varying loads. Also, the stand is suitable for testing rods measuring 5.5 m in length. The stand has a special feature of providing the ongoing monitoring of bolt load, displacement and deformation. The primary aim of the study was to compare the results recorded by two different measurement systems with the innovative Self-Excited Acoustic System (SAS) for measuring stress variations in roof bolts. In order to use the SAS, a special handle equipped with an accelerometer and exciter mounted to the nut or the upset end of the rod was designed at the Faculties of Mining and Geoengineering and Mechanical Engineering and Robotics of the AGH University of Science and Technology. The SAS can be used for nondestructive evaluation of performance of bolts around mining workings and in tunnels. Through laboratory calibration tests, roof bolt loads can be assessed using the in-situ non-destructive method.

Description: This paper presents an experimental investigation of the discharge flow pressure in the vertical silo and the hopper due to the use of insert (top cone with trunk cone bottom). Using the Insert inside the silos is one of the proposed solutions to avoid the problems of having funnel flow pattern, which has a significant effect on the distribution of flow pressure exerted on the silo wall and the hopper. The experiments were performed on a metal cylinder prototype; corn was used as a granular material, and the wall and hopper pressure distribution was measured by a special pressure transducer. The experiments revealed an important result in the flow pressure due to the change in the location of the insert. The experiments were conducted in Damascus University laboratories.

Description: Water seepage is one of the most important features of embankment dams. To prevent and reduce seepage, it is necessary to seal the dam. Plastic concrete cutoff walls are one of the most efficient methods in waterproofing the foundation of embankment dams on permeable alluvial substrates. Sufficient resistance to loads, low permeability to maintain dam sealing, high ductility compatible with the foundation and deformation under load without cracking are the main requirements in plastic concrete cutoff walls. In this paper, the construction and implementation of the cutoff wall of Karkheh Dam, which is one the world’s largest water sealing projects, was studied. In addition, a numerical model using Seep-3D software was developed to evaluate the efficiency of the cut-off wall to decrease the seepage over the dam’s foundation. The numerical results validated by instrumentation statistics resulted from 17-years dam operation. According to the results, after the drainage of the reservoir, the cutoff wall optimally reduced the hydraulic gradient by 0.08 from 2.35 and the water leakage by 3.1 m/s from 18.3 m/s.

Description: The main issue of the paper is the estimation of soil hydraulic permeability based on the DMT test. DMTA, DMTC and SASK methods performed in the Nielisz dam, Stegny and the SGGW Campus of the Warsaw University of Life Sciences sites are described. The article presents the implementation of the dilatometer Marchetti test (DMT) in the determination of soil fraction and effects of its occurrence in the subsoil, tested in the Nielisz dam located in the Wieprz river valley in the Lublin province, and in various sites in Warsaw (Stegny site and SGGW Campus of the Warsaw University of Life Sciences). In order to acquire the needed data, the flat dilatometer test (DMT) method was used. A direct and indirect pressure methodology of interpreting soil swelling was characterized in the article. The paper shows the possibilities of determining sand, silt and clay soil fractions based on po and p1 pressures from dilatometer tests (DMT) and the effective (σ’vo) and total (σvo) vertical in situ overburden stress. Additionally, the main advantage of this paper is the proposal of use of a new chart to determine hydraulic permeability and soil fraction, based on DMT tests.

Description: This article deals with the vibrations of a nonprismatic thin-walled beam with an open cross section and any geometrical parameters. The thin-walled beam model presented in this article was described using the membrane shell theory, whilst the equations were derived based on the Vlasov theory assumptions. The model is a generalisation of the model presented by Wilde (1968) in ‘The torsion of thin-walled bars with variable cross-section’, Archives of Mechanics, 4, 20, pp. 431–443. The Hamilton principle was used to derive equations describing the vibrations of the beam. The equations were derived relative to an arbitrary rectilinear reference axis, taking into account the curving of the beam axis and the axis formed by the shear centres of the beam cross sections. In most works known to the present authors, the equations describing the nonprismatic thin-walled beam vibration problem do not take into account the effects stemming from the curving (the inclination of the walls of the thin-walledcross section towards to the beam axis) of the analysed systems. The recurrence algorithm described in Lewanowicz’s work (1976) ‘Construction of a recurrence relation of the lowest order for coefficients of the Gegenbauer series’, Applicationes Mathematicae, XV(3), pp. 345–396, was used to solve the derived equations with variable coefficients. The obtained solutions of the equations have the form of series relative to Legendre polynomials. A numerical example dealing with the free vibrations of the beam was solved to verify the model and the effectiveness of the presented solution method. The results were compared with the results yielded by finite elements method (FEM).

Description: This paper presents the results obtained from an experimental programme and numerical investigations conducted on model tests of strip footing resting on reinforced and unreinforced sand slopes. The study focused on the determination of ultimate bearing capacity of strip footing subjected to eccentric load located either towards or opposite to the slope facing. Strip footing models were tested under different eccentricities of vertical load. The obtained results from tests conducted on unreinforced sand slope showed that the increase in eccentricity of applied load towards the slope facing decreases the ultimate bearing capacity of footing. Predictions of the ultimate bearing capacity obtained by the effective width rule are in good agreement with those proposed from the consideration of total width of footing subjected to eccentric load. The ultimate bearing capacity of an eccentrically loaded footing on a reinforced sand slope can be derived from that of axially loaded footing resting on horizontal sand ground when adopting the effective width rule and the coefficient of reduction due to the slope. When increasing the distance between the footing border to the slope crest, for unreinforced and reinforced ground slope by geogrids, the ultimate bearing capacity of footing is no more affected by the slope ground.

Description: In urban areas, the control of ground surface settlement is an important issue during shield tunnel-boring machine (TBM) tunneling. These ground movements are affected by many machine control parameters. In this article, a finite difference (FD) model is developed using Itasca FLAC-3D to numerically simulate the whole process of shield TBM tunneling. The model simulates important components of the mechanized excavation process including slurry pressure on the excavation face, shield conicity, installation of segmental lining, grout injection in the annular void, and grout consolidation. The analysis results from the proposed method are compared and discussed in terms of ground movements (both vertical and horizontal) with field measurements data. The results reveal that the proposed 3D simulation is sufficient and can reasonably reproduce all the operations achieved by the TBM. In fact, the results show that the TBM parameters can be controlled to have acceptable levels of surface settlement. In particular, it seems that moderate face pressure can reduce ground movement significantly and, most importantly, can prevent the occurrence of face-expected instability when the shield crosses very weak soil layers. The shield conicity has also an important effect on ground surface settlement, which can be partly compensated by the grout pressure during tail grouting. Finally, the injection pressure at the rear of the shield significantly reduces the vertical displacements at the crown of the tunnel and, therefore, reduces the settlement at the ground surface.

Description: This paper presents an enhanced constitutive model integrating deviatoric hardening with a modified yield surface for overconsolidated clayey soils in a general framework of Cam-clay type models. Its performance was assessed with the simulation of drained and undrained triaxial tests on three clays at different consolidation states in comparison to two critical state models. The proposed model satisfactorily estimates the shear resistance, while capturing the smooth nonlinearity of the soil response.Shear triaxial tests at constant mean pressure were performed on an overconsolidated marl to study the shear response. Their simulation attests the importance of deviatoric hardening integration.

Description: The present study investigates the onset of penetrative convection in- duced by selective absorption of radiation in a magnetic nanofluid saturated porous medium. The influence of Brownian motion, thermophoresis, and magnetophoresis on magnetic nanofluid treatment is taken into consideration. The Darcy’s model is selected for the porous medium. We conduct a linear stability analysis to examine the onset of instability and evaluate the results for two different configurations, namely, when the layer is heated from below and when the layer is heated from above. The numerical investigations are carried out by applying the Chebyshev pseudospectral method. The effect of the porosity parameter E, parameter Y (represents the ratio of internal heating to boundary heating), Lewis number Le, concentration Rayleigh number Rn, Langevin parameter αL, width of nanofluid layer d, diffusivity ratio η, and modified diffusivity ratio NA is examined at the onset of convection. The results indicate that the convection commences easily with an increase in the value of Y, Le, and NA but opposite in the case with a decrease in the value of E, αL, η and d for both the two configurations. The parameter Rn advances the onset of convection when the layer is heated from below, while delays the onset of convection when the layer is heated from above.

Description: This article presents the results of tests on the energy properties of sedimentary rocks in the Upper Silesian Coal Basin. The rocks were tested both in an air-dry state and in a water saturation state. Samples of sedimentary rocks were collected from boreholes drilled in the underground workings of coal mines located within the area of the city of Jastrzębie, in the areas of the Chwałowice Trough and Rybnik Trough (south-western part of the Upper Silesian Coal Basin) and in the Main Trough. Influence of saturation condition on the values of the tested energy parameters was observed. The values of elastic energy and dissipated energy obtained for the samples tested in water saturation were lower compared to the values obtained for samples tested in air-dry state. As observed, an increase in the values of the given types of specific energy corresponds to an increase in the uniaxial compression strength in air-dry state and in water saturation state. Results of the tests are original and they can be applied while analysing the possibility of the occurrence of some dynamic phenomena and hazards in mine workings in Carboniferous rock mass in the Upper Silesian Coal Basin, caused by mining operations.

Description: Different types of foundations are used in steel, above-ground cylindrical storage tanks for liquids. If a sand-gravel foundation is used under the entire bottom of the tank or only in the central part of the tank, settlement can be expected, and it increases after many years of operation. The paper presents the typical kinds and types of soil settlements under the bottoms of the tanks, in which different types of foundations were used. Numerical analyses of the effect of the soil settlement on the state of deformations and stresses in steel sheets of the bottom under one of the real tanks, in which different types of foundations and different cases of settlement were assumed. The results of numerical analyses indicated the possibility of evaluating the state of the soil settlement and bottom sheet deformations on the basis of simple measurements of deformations of the lower part of the tank cylinder. These measurements can be very useful in assessing the possible risk of failure of the tank bottom during each period of its operation, as measurements of settlement of the bottom of a filled tank are not feasible in practice. It has been proposed that in each steel tank, the deformation of the cylinder’s sheets should be measured even before the beginning of exploitation, and that in subsequent periodical measurements, the influence of the soil settlement under the tank on the state of the cylinder deformation and bottom’s strain should be assessed more accurately.

Description: Sands reinforced by hydraulic binders (cement) have constituted in recent decades a major asset for the expansion of several areas of engineering. The mechanical behavior of sand-cement mixtures has undergone some controversies studied on the Chlef sand. In this paper, we present an experimental study to investigate the mechanical behavior of a sandy soil reinforced by a hydraulic binder (cement), using the direct shear apparatus emphasizing on the shear strength characteristics and the vertical deformation variation of cemented reinforced sand. The parameters used in this study are mainly: relative density (Dr = 80%), normal stress (σn = 100, 200, 400 kPa), water content (3, 7 and 10%), cement content (2.5, 5, 7.5 and 10 %) and cure time (7, 14 and 28 days). The experimental results show that the mechanical characteristics in terms of internal cohesion (C) and internal frication angle (φ) give a better mechanical performance with the binder inclusion, and the cure conditions play an effective role on the improvement of the shear strength. This result also showed that 10% of the cement content gave us a maximum value of shear strength and an optimal influence on the mechanical characteristics. The addition of cement not only improves the shear strength of soil, but also provides diversity in the resistance against the deformations imposed load, which can be established by a dilatant character.

Description: Extractive industries often use explosives to destroy rocks, and productivity requirements tend to increase the charges of the explosives. The blasts induce vibrations, which result in a potential damage of the surrounding structures. Therefore, the prediction of vibrations should be described with accuracy, in order to ensure the safety of engineered structures. However, the prediction of vibrations’ levels remain a complicated issue, because it involves numerous parameters correlated to the quarry site. In this paper, statistical analysis based on the peak particle velocity (PPV) and the attenuation law has been carried out to assess the safety charges (Q) for different distances (R) between the blast and the considered structure to secure. Moreover, the experimental investigations were conducted on the quarry site of “Sococim”, which is located on the south coast of Senegal. To ensure the safety of the “Conveyor belt” and “Panel 1 (Upper exploitation level)” sites, the PPV should be less than 10 mm/s. In fact, the attenuation model has been used to assess the safe charge weights of the explosive (Q) to be used at the “Conveyor belt” site and at the “Panel 1 (Upper exploitation level)” site. Therefore, the safe charge weights per delay (Q) were respectively 116 kg and 13.75 kg.

Description: This work presents the geotechnical problems occurring in the interaction area between road embankments and the bridge structures in case a subsoil characterised by complex and complicated geological and engineering conditions. These significant problems that occur during the design, performance and exploitation of the abutment structures, are illustrated on the example of engineering practice in Lower Silesia, concerning a road embankment that constitutes access to the bridge. The results of numerical analyses concerning the process of consolidation of low-strength soils and their impact on the settlements of road embankment indicate the need to carry out such analyses also in the cases, when the soft soils occur in the direct geotechnical layer under the designed embankment. The Authors included in this article a discussion regarding other effective actions and solutions that can be used in the design and performance phase, leading to the elimination or reduction of problems concerning the connection of engineering structures with road embankments, which have been recurring for years, ultimately resulting in the improvement of quality, comfort and safety of road exploitation.

Description: Understanding the quality of intact rock is one of the most important parts of any engineering projects in the field of rock mechanics. The expression of correlations between the engineering properties of intact rock has always been the scope of experimental research, driven by the need to depict the actual behaviour of rock and to calculate most accurately the design parameters. To determine the behaviour of intact rock, the value of important mechanical parameters such as Young’s modulus (E), Poisson’s ratio (ν) and the strength of rock (σcd) was calculated. Recently, for modelling the behaviour of intact rock, the crack initiation stress (σci) is another important parameter, together with the strain (σ). The ratio of Young’s modulus and the strength of rock is the modulus ratio (MR), which can be used for calculations. These parameters are extensively used in rock engineering when the deformation of different structural elements of underground storage, caverns, tunnels or mining opening must be computed. The objective of this paper is to investigate the relationship between these parameters for Hungarian granitic rock samples. To achieve this goal, the modulus ratio (MR = E/σc) of 50 granitic rocks collected from Bátaapáti radioactive waste repository was examined. Fifty high-precision uniaxial compressive tests were conducted on strong (σc 〉100 MPa) rock samples, exhibiting the wide range of elastic modulus (E = 57.425–88.937 GPa), uniaxial compressive strength (σc = 133.34–213.04 MPa) and Poisson’s ratio (ν = 0.18–0.32). The observed value (MR = 326–597) and mean value of MR = 439.4 are compared with the results of similar previous researches. Moreover, the statistical analysis for all studied rocks was performed and the relationshipbetween MR and other mechanical parameters such as maximum axial strain $left( {{varepsilon }_{ext{a,},ext{max}}} ight)$for studied rocks was discussed.

Description: Waste material such as used tires is increasing every year, which poses environmental problems. However, such material has been used in several geotechnical applications as alternative lightweight backfill in highway embankments and/or behind retaining walls, providing environmental, economic and technical benefits. These applications require knowledge of engineering properties of soil-tire rubber mixtures. The present study aims to show the possibility of tire rubber usage in sand by evaluating the shear strength and deformability of sand mixed with granulated rubber, in weight percentages between 0 and 50%. The tire rubber content was found to influence the stress-strain and deformation behavior of the mixtures. The shear strength of sand mixed with 10% or 20% tire rubber was higher than that measured for sand only. However, the trend for TRC = 30–50% was different. Samples with a rubber content of 30-50% exhibited a rapid decrease in the stress ratio compared with that of sand. The major principal strain at maximum stress ratio was found to increase with increasing tire rubber content. However, it was observed that the lateral strains (minor and intermediate principal strains) of samples reduced significantly with the addition of tire rubber to the sand.

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 153〈/p〉 〈p〉Author(s): Ayoub H. Jaafar, N.T. Kemp〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper reports on the first optically tunable graphene oxide memristor device. Modulation of resistive switching memory by light opens the route to new optoelectronic devices that can be switched optically and read electronically. Applications include integrated circuits with memory elements switchable by light and optically reconfigurable and tunable synaptic circuits for neuromorphic computing and brain-inspired, artificial intelligence systems. In this report, planar and vertical structured optical resistive switching memristors based on graphene oxide are reported. The device is switchable by either optical or electronic means, or by a combination of both. In addition the devices exhibit a unique wavelength dependence that produces reversible and irreversible properties depending on whether the irradiation is long or short wavelength light, respectively. For long wavelength light, the reversible photoconductance effect permits short-term dynamic modulation of the resistive switching properties of the light, which has application as short-term memory in neuromorphic computing. In contrast, short wavelength light induces both the reversible photoconductance effect and an irreversible change in the memristance due to reduction of the graphene oxide. This has important application in the fabrication of cloned neural networks with factory defined weights, enabling the fast replication of artificial intelligent chips with pre-trained information.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306943-fx1.jpg" width="485" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 153〈/p〉 〈p〉Author(s): C.M. Ramos-Castillo, M.E. Cifuentes-Quintal, E. Martínez-Guerra, R. de Coss〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Energy gap engineering in graphene nanostructures is one of the most important topics towards development of graphene-based electronics. In this work, based on the density functional theory, the role of the edge magnetism on the size dependence of Kohn-Sham gap and fundamental energy gap for 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"〉〈mrow〉〈msub〉〈mrow〉〈mtext〉C〈/mtext〉〈/mrow〉〈mrow〉〈mn〉6〈/mn〉〈mtext〉nn〈/mtext〉〈/mrow〉〈/msub〉〈msub〉〈mrow〉〈mtext〉H〈/mtext〉〈/mrow〉〈mrow〉〈mn〉6〈/mn〉〈mtext〉n〈/mtext〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈mtext〉n〈/mtext〉〈mo linebreak="badbreak"〉=〈/mo〉〈mn〉2〈/mn〉〈mo linebreak="goodbreak" linebreakstyle="after"〉−〈/mo〉〈mn〉16〈/mn〉〈/mrow〉〈/math〉) hexagonal graphene quantum dots (GQDs) with zigzag edges is studied. We found a transition from a nonmagnetic to an antiferromagnetic state at a certain critical diameter (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si3.svg"〉〈mrow〉〈mo〉∼〈/mo〉〈/mrow〉〈/math〉 3 nm), characterized by the opening of a Kohn-Sham gap as a consequence of the exchange interaction between localized edge states. Furthermore, the fundamental gap is obtained from the difference between the calculated vertical ionization and electron affinity energies. Such approximation includes relaxation in the exchange correlation potential when the electron is added to the system, which might be useful for GQDs transport properties interpretation. We found a scaling rule for the fundamental gap dependence on quantum dot size, providing a practical way to predict this property for large GQDs with zigzag edges, which currently in most demanding approaches, such as GW, is unfeasible.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306876-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Marine Systems, Volume 199〈/p〉 〈p〉Author(s): Peisheng Huang, Kerry Trayler, Benya Wang, Amina Saeed, Carolyn E. Oldham, Brendan Busch, Matthew R. Hipsey〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effective short- and long-term estuarine water quality management decisions require a holistic view of estuarine response to multiple stressors that may be achieved through the integration of numerical modelling and observed data. Such an approach has been developed for the Swan-Canning Estuary system, a eutrophic urban estuary in Western Australia under threat from nutrient enrichment and a drying climate. Numerical modelling was integrated with long-term monitoring to develop the system Swan-Canning Estuary Virtual Observatory (SCEVO), which has been used to facilitate water quality management and streamline prediction workflows of hindcast, forecast, and environmental response functions. The system is based on a validated 3D water quality model, integrated within a data management system and related environmental models. A machine-learning method to improve the patchy and time-lagged catchment inputs is also highlighted. This work has identified that the key challenge associated with estuarine water quality prediction is the capability to (1) simulate internal physical and biogeochemical processes at suitable spatial resolution to resolve the gradients along the freshwater-ocean continuum; and (2) transition from using routine monitoring data as the basis for management decisions to using a diverse and integrated set of data streams as the basis for real-time operational decisions. Recommendations for high-frequency monitoring to support water quality modelling and dynamic integration between numerical and observed data for improved forecasting are discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Marine Systems, Volume 199〈/p〉 〈p〉Author(s): Arseny A. Kubryakov, Alexander S. Mikaelyan, Sergey V. Stanichny〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Bio-Argo measurements of the backscattering coefficient (〈em〉bbp〈/em〉) were used to investigate the time-depth evolution of coccolithophore blooms in the Black Sea. Five years of Bio-Argo data obtained in 2014–2018 revealed two distinct peaks of 〈em〉bbp〈/em〉 corresponding to the winter and early summer coccolithophore blooms. The latter started in the upper mixed layer (UML) in April–May and was characterized by the highest coccolithophore concentrations. During the most extensive summer bloom in 2017, its estimates reach 10 × 10〈sup〉6〈/sup〉 cells l〈sup〉−1〈/sup〉. The summer blooms occupied the UML (0–10 m) and a seasonal thermocline (10–30 m). The lower boundary of the bloom was related to the position of isopycnal 1014 kg m〈sup〉−3〈/sup〉, which deepens in May–July due to summer heating. Consequently, the coccolithophore bloom deepened to 20–30 m and terminated rapidly in July. Bloom termination was accompanied by a significant rise in light attenuation (〈em〉kd〈/em〉) in the sea basin. This peak was attributed to the release of dissolved organic carbon (DOC), which was possibly related to viral lysis and the exudation of lipids from coccolithophore cells. Data on the 〈em〉kd〈/em〉 was used to estimate the seasonal variability in DOC in the Black Sea. Maximal estimated values of DOC were observed at 15–35 m depth in June-August and coincided with the early summer coccolithophore bloom termination.〈/p〉 〈p〉The winter coccolithophore bloom started in October–November in the UML. The maximum 〈em〉bbp〈/em〉 was observed in January. High values of 〈em〉bbp〈/em〉 were observed down to a depth of 60 m during the maximal deepening of the mixed layer. The winter blooms were distinctly observed in MODIS satellite images, where they were characterized by high reflectance and relatively low chlorophyll concentrations. The estimated coccolithophore concentration in winter was lower than that in summer, but column-averaged 〈em〉bbp〈/em〉 values were comparable. The winter coccolithophore bloom reached a peak within one month after the autumn peak of chlorophyll A, indicating the possible importance of the nutrients recycled after the diatom autumn bloom. In contrast to summer, the maximum DOC observed at the surface preceded the winter coccolithophore bloom, and the mass DOC production was probably attributed to the excretion and lysis of the non-calcified phytoplankton cells.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Marine Systems, Volume 199〈/p〉 〈p〉Author(s): Yuanyi Li, Huan Feng, Haiwen Zhang, Jian Sun, Dekui Yuan, Lei Guo, Jing Nie, Jinglong Du〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The time required for water exchange characterizes the hydrodynamic condition of a water body, which is related to its self-purification ability. In this study, a numerical model based on a three-dimensional hydrodynamic model is established and implemented to calculate the age of water. Using the model, the spatial distribution and seasonal variation of the age of the water discharged into the New York/New Jersey (NY/NJ) Harbor from the Passaic River and the Hackensack River are calculated. The hydrodynamic conditions and the characteristics of water exchange in the harbor are analyzed from the perspective of age. The results indicate that the monthly-averaged age at the entrance of the NY/NJ Harbor is approximately 26 days and 40 days during the wet season and the dry season, respectively. River discharge has a significant impact on the spatial distribution of water age in the NY/NJ Harbor. Generally, high river discharge results in better water exchange and flushes contaminants out of the harbor quickly. However, discharges from several rivers flowing into the harbor interact and interfere with one another. Such interactions can improve or inhibit water and contaminant flushing from the harbor. The analysis of age variations and residual flows indicates that the Kill van Kull is one of the key channels controlling the contaminant transport and water quality in the Newark Bay. This study demonstrates the advantages of using water age to study the water exchange and physical self-purification ability of this complex harbor.〈/p〉〈/div〉 〈/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 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: 1 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Continental Shelf Research, Volume 184〈/p〉 〈p〉Author(s): Israel Medina-Gómez, Ana Aguilar Trujillo, Ismael Marino-Tapia, Giuliana Cruz, Jorge Herrera-Silveira, Cecilia Enriquez〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Inorganic nutrients and phytoplankton (chlorophyll-〈em〉a〈/em〉 concentration and community variables) were studied under a hydrologic scenario defined by a joint topographic-hydrodynamic upwelling event and an algal bloom in the southeast Gulf of Mexico. To do so three oceanographic cruises (GOMEX series) were undertaken throughout the Yucatan shelf during: September 11th-21st of 2010, September 23rd-October 3 〈sup〉rd〈/sup〉 of 2011, and November 29th-December 9th〈sup〉,〈/sup〉 2012 (named as GOMEX-1, GOMEX-2 and GOMEX-3, respectively). We aim to assess the spatial inorganic nutrients and Chl-a patterns corresponding to each cruise to explore potential biochemical consequences of the temporal variability of the vertical inflow in the eastern shelf boundary (Cape Catoche: CC) and further spatial propagation of water featuring this hydrographic signature onto a shallow shelf, marked also by a high algal bloom incidence. This framework allows tackling the implications of the interplay between coastal variability and oceanographic processes on the phytoplankton biomass and community parameters. The spatial pattern of surficial Chl-a, as well as sub-surface maxima of ≈10 mgm〈sup〉−3〈/sup〉 concurrent with the 22.5 °C isotherm over the southeastern shelf area of CC supports the fact that vertical nutrients supply is removed from the euphotic layer through phytoplankton uptake. This scenario indicates a biochemical setting consistent with rapid transfer of external resources advected from deep levels, capable not only to enhance phytoplankton growth, but also to change its species composition. Vertical mixing conditions associated with N-NW winds (locally known as “nortes”) and a lack of upwelling scenario during GOMEX-3 in 2012 lead to relatively more homogeneous nitrate spatial distribution with overall high concentrations in deep, oceanic areas subject to nutrients entrainment. The distribution of specific richness among diatoms and dinoflagellates and relative abundance within such groups, as well as Chl-〈em〉a〈/em〉 concentrations are considered normal with regards to what has been observed in other studies for the Gulf of Mexico. The potential implications of large-scale, inter-annual climatic processes (e.g., El Niño-Southern Oscillation) on marine resources relevant to regional primary productivity variability (changes in the phytoplankton community) are discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Shuai Zhao, Wanfen Pu, Mikhail A. Varfolomeev, Chengdong Yuan, Shan Qin, Liangliang Wang, Dmitrii A. Emelianov, Artashes A. Khachatrian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Because the thermal release correlates directly with the success of in-situ combustion (ISC) technology, this research performs a series of investigations concerning thermal behavior and kinetics of heavy crude oil during combustion using high pressure differential scanning calorimetry (HP-DSC) and accelerating rate calorimetry (ARC). The results obtained from HP-DSC profiles indicated that for oil alone and its mixtures with quartz sand/crushed core, the peak temperature was lowered, and the heat flow increased with increasing oxygen partial pressure. The heat enthalpy of low temperature oxidation (LTO) was higher than that of high temperature oxidation (HTO) under oxygen partial pressures of 0.5, 1 and 1.5 MPa, and the increase in heat enthalpy of LTO with oxygen partial pressure was more pronounced than that of HTO. Unlike the crushed core, the addition of quartz sand delayed exothermic oxidation reactions. Compared with oil only and oil + quartz sand, the LTO and HTO peak temperatures of oil + crushed core were considerably lowered, and the effect of crushed core on increasing heat release for LTO at oxygen partial pressure of 1.5 MPa was more prominent. It was observed that the heat enthalpy of LTO and HTO increased quasi-linearly with the oxygen partial pressure in both the presence and absence of quartz sand/crushed core. ISC might be considered as an appropriate candidate for Jiqi block, based on exothermic continuity of the ARC curves, with the near-wellbore zone of target block heated to 180 °C where the exothermic oxidation activity is notably intensified. The kinetic results showed that the LTO and HTO intervals were divided into 6 and 2 subintervals, respectively, which facilitated more precise modelling of the ISC process.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Zan Chen, Menglu Lin, Shuhua Wang, Shengnan Chen, Linsong Cheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Studies have shown that the gas huff and puff injection potentially perform better than the continuous gas flooding in enhancing the hydrocarbon recovery in the liquid rich tight reservoirs. During the fracturing stimulation, only part of the induced hydraulic fractures is propped because proppants cannot be carried to the fracture tips. Moreover, some secondary and tertiary fractures may be too narrow to accommodate any proppants. The conductivity of the unpropped fractures is highly dependent on the variation of the in-situ pressure and may be open and close periodically during the huff-n-puff cycles. In this study, the stress-dependent fracture conductivity and its impact on the produced gas huff-n-puff performance are investigated in a liquid rich tight reservoir, considering the existence of the large amount of the unpropped fractures. The experimental data of stress-dependent fracture conductivity is employed first to simulate the dynamic conductivity during the depletion and the gas huff and puff cycles. A reservoir model is then constructed and history-matched based on the reservoir fluid samples and the field production data collected from the Montney liquid rich tight reservoir in Western Canada. Performance of the produced gas huff-n-puff is examined in the targeted reservoir and results show that contributions of the unpropped fractures cannot be ignored, which leads to 7.8% more condensate (i.e., oil) production and 2.8% higher in barrel of oil equivalent (BOE), compared to the case with propped fractures only. The effects of complex fracture geometry and the cluster completion are also investigated and results show that the unpropped fracture contributions towards the condensate production and BOE are even more pronounced in the complicated scenarios. The condensate oil and BOE are 42.0% and 22.9% higher in complex fracture geometry case and 12.4% and 5.6% higher in the fractures with multiple clusters than those scenarios with propped fractures only. This paper provides a better understanding on the potential performance of enhanced hydrocarbons recovery in liquid rich tight gas reservoirs via gas huff-n-puff operations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Abdelrahman Elkhateeb, Reza Rezaee, Ali Kadkhodaie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Traditionally, prediction of facies and permeability for a reservoir rock was one of many challenges in the industry that necessitates advanced and sophisticated evaluation for effective reservoir description. Three wells have been studied in the Perth Basin in Western Australia across the shaly sand of the Irwin River Coal Measures Formation, which contain a comprehensive suite of advanced and conventional logs. Due to the reservoir heterogeneity and the clay distribution, it is very challenging to resolve the effective pore volume, the reservoir facies and how the high permeability zones are distributed within the formation.〈/p〉 〈p〉In this paper, a new technique has been successfully tested on the Shaly Sand by integrating the nuclear magnetic resonance (NMR) and the conventional density log. The method allows the establishment of high-resolution facies classification for the reservoir using an Equivalent Flow Zone Indicator Index (EFZI). The studied core facies have been integrated with the EFZI into a new workflow to distribute facies on a larger scale in the uncored wells.〈/p〉 〈p〉Four hydraulic flow units (HFU) have been defined from one cored well using Flow Zone Indicator approach, with each has a unique FZI value and different permeability model based on core measurements. The EFZI-based high-resolution facies have been validated at several formation depths using the core thin sections to ensure the best calibration will be obtained for facies log, hence the permeability log-to-core match.〈/p〉 〈p〉The methodology will help running an advanced petrophysical analysis for the zone of interest and will reduce the parameters uncertainty. Application of this methodology in the uncored wells has shown very encouraging results, which is believed it can be used in the absence of any core data to resolve the rock typing from the well logs.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Atousa Heydari, Kiana Peyvandi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, the stainless steel mesh was used to study the effect of metallic porous media on the formation of methane hydrate and some parameters such as induction time, the kinetics growth and the mole of gas consumed have been investigated at a temperature of 3 °C (276.15 K) and a pressure of 760 psi (5.24Mpa). The metallic porous media was able to show better results on the methane hydrate formation relative to the silica gel. Hence the induction time and, eventually, the total time of the hydrate formation process decreased by about 60%. The kinetics growth and the amount of gas consumed increased significantly. Also, the effect of two types of anionic and nonionic surfactants as kinetics promoters studied in this porous media. The result of adding SDS and SDBS at a concentration near the CMC designated that the induction time lasted nearly zero and the total time of the process by SDBS was minimal. It should be noted that the non-ionic surfactant SPAN 80 could not have a positive effect on this porous media. In general, therefore, the results of this research attempts to show that the stainless steel mesh with SDBS possessed high potential in obtaining the industrial purpose of gas hydrate growth and also was significant in the field of energy storage and transport.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0920410519306473-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Shuaishuai Jiang, Xuehua Chen, Yingkai Qi, Wei Jiang, Jie Zhang, Zhenhua He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The frequency-dependent attenuation and velocity dispersion of seismic responses are closely related to hydrocarbon reservoirs. To further investigate the characteristics of seismic responses caused by pore fluid-bearing reservoirs, the role of gas saturation is analyzed in seismic responses of sand reservoirs characterized by the patchy saturation model. To this end, a novel wave extrapolation method is developed based on the diffusive-viscous wave equation (DVWE) as well as a scheme for an extended local Rytov Fourier (ELRF) approximation within the extrapolation depth interval. Our proposed method considers the presence of fluid mixtures in the porous media, resulting in seismic attenuation and dispersion by the mechanism generally known as wave-induced fluid flow (WIFF). This method enables an accommodation for the lateral variations in slowness, diffusion coefficient and viscosity. Subsequently, the extrapolation is adopted to model the synthetic seismic data of a distributary channel model. During this modeling, a gas-water saturated sand reservoir embedded into one of the channels was used to comparatively analyze the distinct features on its seismic synthetic data. We exhibited the numerical simulation results using the proposed wave extrapolation method here and the traditional acoustic wave equation (AWE) method. A comparison of the simulation results, demonstrates that our proposed numerical method can depict the seismic dispersion and frequency-dependent attenuation as well as the phase delay effects associated with gas-water-saturated sand reservoirs. Furthermore, we compare the seismic responses by changing the gas saturations of the sand reservoir. The gas saturation of the reservoir has significant effects on the seismic characteristics of the numerical modeling data. The numerical modeling method improves our understanding of the mechanisms of seismic frequency-dependent characteristics associated with gas saturations and potentially contributes to better insights into gas reservoir indicators derived from seismic field data.〈/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: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 125〈/p〉 〈p〉Author(s): Ahmet Hilmi Deringöl, Esra Mete Güneyisi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigates the influence of the friction pendulum bearing (FPB) isolator characteristics on the nonlinear response of the buildings under various seismic excitations. To represent a wide range of assessment, 3, 6, and 9-storey steel framed buildings with twenty seven different isolation models of FPB were studied by identifying the local and global deformations. Three important parameters such as isolation period T (as 2, 2.5, and 3 s), effective damping ratio ß (as 0.05, 0.15, 0.25), and yield strength ratio Fy/W (as 0.025, 0.05, and 0.10) were used in the modelling of FPB. Two-dimensional model of the base-isolated steel frames were created and the nonlinear time history analysis was performed through a number of earthquake ground motions. The behaviour of the isolated frames was measured by the variation of isolator displacement, roof drift ratio, relative displacement, interstorey drift ratio, absolute acceleration, base shear, base moment, hysteretic curve, and dissipated energy. The benefits obtained through the adoption of the base isolation system were discussed. It was found that the seismic response of the base-isolated frames could be estimated accurately by adjusting the proper isolation period, yield strength ratio, and effective damping ratio for the case studied structures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 125〈/p〉 〈p〉Author(s): Jinbao Yao, Rutao Zhao, Nan Zhang, Dujuan Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉An in-filled trench barrier is usually used to reduce the damages from train-induced environmental vibrations. To find the vibration isolation effect of an in-filled trench barrier, this paper analyses the reflection coefficients and transmission coefficients of the Rayleigh wave at the interface between in-filled trenches and the soil. In our calculation formulas of ground vibrations, a single point and a single frequency excitation, as well as multi-point and multi-frequency excitation, are simultaneously derived in a soil-in-filled-trench system.〈/p〉 〈p〉Using these formulas and a numerical analysis, the effects of an in-filled trench barrier on the environmental vibrations induced by running trains are analyzed. The results show that the reflection coefficients increase, while the transmission coefficients decrease, with the density and elastic modulus of the in-filled material. The vibration isolation effect is clearly better than that without trenches. In a certain width range, the transmission coefficient and vertical acceleration levels decrease with the increase of trench width. The influences of the transmission coefficient and the vibration isolation effects are not clear with the trenches’ depth variation. The vertical vibrations of the ground pick-up point are all smaller than those without in-filled trenches.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 124〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering, Volume 125〈/p〉 〈p〉Author(s): Benshun Shao, Stephen A. Mahin, Victor Zayas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉By interpreting the seismic responses of two seismically isolated low-rise case-study buildings probabilistically using FEMA P695 methodology, the study indicates for the design of seismically isolated structures, providing isolator capacities equal to risk-targeted maximum considered earthquake (MCE〈sub〉R〈/sub〉) demand does not achieve targeted levels of reliability specified in ASCE 7–16. To do so, isolation system capacities beyond average MCE〈sub〉R〈/sub〉 demand are required. The minimum required capacities for using three types of enhanced isolation system (isolator without displacement restraint, isolator combined with external hard-stopping mechanism, and isolator with internal stiffening behavior at large horizontal displacement) are calculated with nonlinear response history analysis following probabilistic framework for different design risk categories numerically. The results indicate that isolator displacement capacities ranging from 1.5 to 2.60 times the average MCE〈sub〉R〈/sub〉 demand and isolation system shear capacities ranging from 1.5 to 5 times the average MCE〈sub〉R〈/sub〉 demand are required, depending on seismic risk categories and isolation system types. The use of an isolator with internal stiffening behavior is an efficient option to provide the required capacities for achieving reliability goals, especially for high risk-category design.〈/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〉 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: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 332〈/p〉 〈p〉Author(s): Farzaneh Shakerardakani, Xian-Hua Li, Xiao-Xiao Ling, Jiao Li, Guo-Qiang Tang, Yu Liu, Behzad Monfaredi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-precision secondary-ion mass spectrometry (SIMS) U–Pb and Hf–O isotopic microanalyses of zircons from the central Sanandaj–Sirjan metamorphic zone (SSMZ) of the Zagros orogen, Iran, provide evidence of the presence of 2.7 Ga xenocrystic zircons, suggesting that the SSMZ records Neoarchean crustal components that have not previously been reported in Iran. The two amphibolite samples analyzed from the Muteh–Golpaygan metamorphic complex during this study include one sample (GQ-10) that yielded xenocrystic zircons with ages clustered around 〈em〉ca〈/em〉 2.7 Ga. The second sample (GC-15) contains zircons that show two distinct xenocrystic zircon domains with ages of (i) 〈em〉ca〈/em〉 2.7 and 2.5 Ga, and (ii) 〈em〉ca〈/em〉 52 Ma. The 〈em〉ca〈/em〉 2.7 Ga zircons and zircon domains have homogeneous, mantle-like δ〈sup〉18〈/sup〉O values with a mean of 6.10 ± 0.69‰. They have εHf(t) values that vary between +0.2 to +6.8 with T〈sub〉DM〈/sub〉〈sup〉C〈/sup〉 ages of 3.1–2.7 Ga, suggesting they crystallized from granitoid melts derived from juvenile components. However, the younger 〈em〉ca〈/em〉 2.5 Ga zircons yield an average δ〈sup〉18〈/sup〉O value of 6.17 ± 0.24‰ and have evolved Hf isotopic compositions (εHf(t) −0.8 to −3.4; T〈sub〉DM〈/sub〉〈sup〉C〈/sup〉 = 3.2–3.1 Ga), indicating that the older crust in this region underwent more intense later reworking than is the case for crustal material formed at 〈em〉ca〈/em〉 2.7 Ga. These data provide evidence of Neoarchean basement rocks in this region, indicating that the SSMZ records ancient crustal growth events. The youngest 〈em〉ca〈/em〉 52 Ma xenocrystic zircons within these samples most likely reflect the late Paleocene–Eocene magmatic ‘flare-up’ within Iran. These zircons have slightly elevated δ〈sup〉18〈/sup〉O values (7.69 ± 0.21‰) and negative Hf isotopic compositions (εHf(t) −8.3 to −12.1; T〈sub〉DM〈/sub〉〈sup〉C〈/sup〉 = 1.9–1.6 Ga), suggesting intensive crustal reworking at 〈em〉ca〈/em〉 50 Ma.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 332〈/p〉 〈p〉Author(s): Kelsey G. Lamothe, Paul F. Hoffman, J. Wilder Greenman, Galen P. Halverson〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Islay carbon isotope anomaly is a late Tonian negative δ〈sup〉13〈/sup〉C excursion that has been documented in marine carbonates globally. It has in the past been thought to be causally linked to the onset of Cryogenian glaciation ca. 717 Ma. However, recent work suggests that this anomaly is instead closer to ca. 739–735 Ma and that it may be one of two distinct late Tonian carbon isotope anomalies. Here we present the litho- and chemo-stratigraphy of the late Tonian Ugab Subgroup of the Otavi/Swakop Group in northwestern Namibia. Carbon isotope data from two separate outcrop belts, the Summas Mountains and the Vrede Domes, indicate that the Ugab Subgroup strata exposed in the former inlier are older than those of the latter, with only approximately 100 m of stratigraphic overlap. We use detailed measured sections to develop a sequence stratigraphic framework for the Ugab Subgroup in each outcrop belt, and correlate strata across the two exposures to construct a composite carbonate δ〈sup〉13〈/sup〉C record for the late Tonian in Namibia. This carbon isotope profile of the Ugab Subgroup shows two separate pre-Sturtian negative anomalies, consistent with findings in northern Canada, Svalbard, Scotland, and Ethiopia. Our results are an important contribution to the pre-Cryogenian carbon isotope record, as these data may serve as the first definitive documentation of both anomalies within a single basin.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 332〈/p〉 〈p〉Author(s): V.S. Shatsky, Q. Wang, S.Yu. Skuzovatov, A.L. Ragozin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To clarify the tectonic-thermal evolution of the Anabar tectonic province in the central Siberian Craton, we performed an isotope-geochemical study of 20 xenoliths from the Udachnaya, Zarnitsa, and Komsomolskaya kimberlite pipes to represent different crustal levels. Most mafic granulites have Proterozoic Nd model ages and geochemical characteristics close to those of intraplate basalts, whereas some mafic and intermediate granulites with Archean model ages exhibit geochemical features of supra-subduction ophiolitic basalts. Analysis of U-Pb ages and hafnium isotopic composition of zircon indicates that the main tectonic-thermal events modified the crust at 2.7 and 1.9–1.8 Ga, which is consistent with ages of mantle depletion events from previous studies. All zircons have Archean Hf model ages (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"〉〈mrow〉〈msubsup〉〈mi〉T〈/mi〉〈mrow〉〈mi mathvariant="italic"〉DM〈/mi〉〈/mrow〉〈mi〉C〈/mi〉〈/msubsup〉〈mspace width=".25em"〉〈/mspace〉〈mn〉3.6〈/mn〉〈mo linebreak="badbreak" linebreakstyle="after"〉-〈/mo〉〈/mrow〉〈/math〉3.2 Ga). Overall, thermal events with ages of 2.9–2.8, 2.7, 2.4, 1.97 and 1.8 Ga have remarkable influence on the studied zircons. Tectono-thermal events at 2.4 1.97, 1.9 and 1.8 Ga with no addition of juvenile material are recorded by zircons from xenoliths of mafic and intermediate granulites and metadiorites. A compilation of isotope-geochemical data demonstrates that instead of age-stratified, the crust of the Anabar tectonic province consists of variably reworked Paleoarchean rocks and juvenile Proterozoic rocks at all crustal levels. Hence the crust and mantle of the Siberian Craton has been coupled since the Paleoarchean.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research〈/p〉 〈p〉Author(s): B.R. Choudhary, R.E. Ernst, Y-G. Xu, D.A.D. Evans, M. de Kock, J.G. Meert, A. Ruiz, G.A. Lima〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉1110 Ma Large Igneous Province (LIP) fragments in the Kalahari craton, southern Africa (Umkondo LIP); Dronning Maud Land, Antarctica; Bundelkhand portion of Indian craton (Mahoba dolerite dykes); Congo craton (Huila-Epembe dolerite dykes); and Amazonia (Rincon del Tigre-Huanchaca LIP) have been reconstructed as a single LIP with plume centre beneath the NW part of the Kalahari Craton. This paper offers the best estimates for the paleoposition of the〈/p〉 〈p〉Indian and Amazonian cratons along with conjoined Kalahari-SF/Congo reconstruction. This 1110 Ma mafic magmatism is dominantly tholeiitic, ranging from basalt to andesitic basalt in composition, generated over a range of mantle melting depths [(Gd/Yb)N =1.2 to 2.3], exhibit low to high contamination with crustal components (negative Nb anomalies, eNd (0 to -12), and elevated Th/Yb). The data fall into two Groups based on TiO2 content, with Group 1 (low Ti) of andesitic basalt composition, and Group 2 (high Ti) exhibiting a basaltic affinity. Group 1 magmas were generated in the spinel lherzolite field followed by significant contamination likely during passage through metasomatised lithospheric mantle in crustal magma chambers. A greater melting depth reaching into the garnet lherzolite field is proposed for the Group 2 magmas. The majority of Group 2 units are located in the Kalahari and Congo cratons, and this reflects onset of deeper melting closer to the interpreted plume axis in our reconstruction.〈/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: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research〈/p〉 〈p〉Author(s): Vladimir N. Sergeev, J. William Schopf, Anatoliy B. Kudryavtsev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Subtidal cherts from phosphorite-bearing basal strata of the Early Cambrian Shabakta (Dzhylandy) Formation, Tamda Group of the Maly Karatau Range of South Kazakhstan, contain a diverse assemblage of acanthomorph acritarchs and other well-preserved organic-walled microfossils. Acanthomorphs of the Shabakta lowermost layers are taxonomically essentially identical to those of many similarly aged Early Cambrian organic-walled compression-preserved and permineralized microbiotas preserved in rocks deposited in relatively open marine settings and are biostratigraphically correlative with acanthomorph-containing microfloral assemblages of the Vergale and Rausve Horizons (Regional Stages) of the East European Platform as well as with other assemblages known worldwide from the upper Atdabanian (Series 2 of the International Union of Geological Sciences [IUGS]). Although lower Atdabanian deposits of the Talsy (Lükati) horizon are missing from the Maly Karatau succession studied here, Nemakit-Daldynian through Tommotian (the IUGS Terranovian) microbiotas both of the Shabakta-underlying Berkuta Member of the Kyrshabakta Formation and phosphoritic Chulaktau Formation are comparable to those of the pre-trilobite Rovno and Lontova Horizons (Regional Stages) of the East European Platform. Thus, the phosphatized and chert-permineralized Shabakta assemblages date from of the Early Cambrian part of the Precambrian-Cambrian phosphogenic event, an interpretation supported also by associated small shelly fossils.〈/p〉 〈p〉The studies reported here of the Shabakta microfossils – based on the use of optical microscopy, confocal laser scanning microscopy (CLSM) and Raman spectroscopy – provide information in three dimensions at high spatial resolution about their organismal morphology, cellular anatomy, kerogenous composition, taphonomy, and mode and fidelity of preservation. The combined use of CLSM and Raman, techniques introduced to Precambrian paleobiology only rather recently, is shown to reveal morphological characters of taxonomic, biostratigraphic and palaeoenvironmental significance.〈/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-S0301926818306260-ga1.jpg" width="274" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 110〈/p〉 〈p〉Author(s): Walid A. Makled, Ahmed A. Abd El Ghany, Soheir I. Soliman〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Productivity, redox conditions and sedimentation rate constrain the enrichments of organic matters and under suitable conditions they can trigger larger enrichments. These parameters are tracked in the subsurface Miocene sediments in four wells on east to west transect across north Sinai. These wells are Abu Roda-1, Misfaq-1, Teffah-1 and Einab-1. The Miocene sections cover the Aquitanian, Burdigalian, Langhian, Serravalian and Tortonian. The tracking is based on the proxies of planktonic and benthic foraminifera that offer many solutions in the application of the equations used to calculate these parameters. The first of these parameters is the sedimentation rate which is calculated for different time segments based on the planktonic foraminifera bioevents. The sedimentation rates are correlated throughout the basin. The second parameter is the water depth that is obtained from conversion of the scores of component 1 resulted during the routine statistical analysis of the benthic foraminifera by cluster and principal component analyses. These analyses are used also in assessment of redox condition and eutrophication. The sedimentation rates and water paleobathymetry alongside the measured C〈sub〉org〈/sub〉 are used to calculate the paleoproductivity and to determine four stratigraphic sequences (Seq1, Seq2, Seq3 and Seq4). The tracking of these parameters reveal higher productivity levels in the Seq1 (Aquitanian and Burdigalian) accompanied with dysoxic and mesotrophic conditions, however the lower sedimentation rates are not optimum to stimulate enough burial efficiency that reduced values of C〈sub〉org〈/sub〉. In the younger sequences (Seq2-4), the higher sedimentation rates increase the burial efficiency and values of C〈sub〉org〈/sub〉 despite the lower paleoproductivity and oxic oligotrphic conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 110〈/p〉 〈p〉Author(s): Marwa Yousef, Mohamed Yousef, Adel Sehim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-quality three-dimensional (3D) seismic reflection and borehole data are used to characterize in detail the structural style and evolution of inversion structures in Horus oil field. This field lies in the central part of Alamein Basin, northern Western Desert of Egypt, in the hanging-wall of a major Jurassic-Early Cretaceous normal fault. This fault delineates the northwestern margin of the basin and extends in an ENE-WSW direction, bounding a half-graben trough in its hanging-wall. This trough had continued subsidence during Early Cretaceous time with depositional thickening of the Lower Cretaceous Alam el Bueib Formation. Fault displacement had ceased near the top of Barremian level. Aptian-Lower Senonian seismically traced levels show a major NE-plunging asymmetrical anticline overlying the Jurassic-Barremian half-graben. This anticline is sub-parallel to the inherited Jurassic rifting fault. At shallower Cretaceous levels, this fault is replaced by a set of WNW-ESE-trending en echelon faults of considerable displacements, which probably indicates a strike-slip component of deformation. These faults display normal separation on all displaced stratigraphic levels and tip upwards in the upper part of the Upper Cretaceous succession. This marks a considerable change in the tectonic mode of the area. NW-SE extensional faults were developed perpendicular to the fold axis, dissecting the anticline into several blocks entrapping hydrocarbons. Detailed seismic structural analysis of growth strata indicates that the fold initiated in Early Senonian time was associated with the inversion of the earlier Jurassic-Barremian half-graben. This basin inversion is attributed to the Syrian-Arc event that dominated North Africa during the Late Cretaceous time and continued through to the Early Miocene. Low fold amplitude coupled with normal displacements on the deep-seated ENE-WSW-trending Jurassic-Barremian fault indicate a mild phase of positive inversion. The Upper Senonian-Eocene stratigraphic sequences increased in thickness in the back-troughs that were associated with basin inversion.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0264817219303198-fx1.jpg" width="57" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Jingzhe Wang, Jianli Ding, Danlin Yu, Xuankai Ma, Zipeng Zhang, Xiangyu Ge, Dexiong Teng, Xiaohang Li, Jing Liang, Ivan Lizaga, Xiangyue Chen, Lin Yuan, Yahui Guo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Soil salinization is one of the most important causes for land degradation and desertification and is an important threat to land management, farming activities, water quality, and sustainable development in arid and semi-arid areas. Soil salinization is often characterized with significant spatiotemporal dynamics. The salt-affected soil is predominant in the Ebinur Lake region in the Northwestern China. However, detailed local soil salinity information is ambiguous at the best due to limited monitoring techniques. Nowadays, the availability of Multi-Spectral Instrument (MSI) onboard Sentinel-2, offers unprecedented perspectives for the monitoring and mapping of soil salinity. The use of MSI data is an innovative attempt for salinity detection in arid land. We hypothesize that field observations and MSI data and MSI data-derived spectral indices using the partial least square regression (PLSR) approach will yield fairly accurate regional salinity map. Based on electrical conductivity of 1:5 soil:water extract (EC) of 72 ground-truth measurements (out of 116 sample sites) and various spectral parameters, such as satellite band reflectance, published satellite salinity indices, red-edge indices, newly constructed two-band indices, and three-band indices from MSI data, we built a few inversion models in an attempt to produce the regional salinity maps. Different algorithms including Pearson correlation coefficient method (PCC), variable importance in projection (VIP), Gray relational analysis (GRA), and random forest (RF) were applied for variable selection. The results suggest that both the newly proposed normalized difference index (NDI) [(B12 − B7) / (B12 + B7)] and three-band index (TBI4) [(B12 − B3) / (B3 − B11)] show a better correlation with validation data and could be applied to estimate the soil salinity in the Ebinur Lake region. The established models were validated using the remaining 44 independent ground-based measurements. The RF-PLSR model performed the best across the five models with R〈sup〉2〈/sup〉〈sub〉V〈/sub〉, RMSE〈sub〉V〈/sub〉, and RPD of 0.92, 7.58 dS m〈sup〉−1〈/sup〉, and 2.36, respectively. The result from this model was then used to map the soil salinity over the study area. Our analyses suggest that soil salinization changes quite significantly in different seasons. Specifically, soil salinity in the dry season was higher than in the wet season, mostly in the lake area and nearby shores. We contend that the results from the study will be useful for soil salinization monitoring and land reclamation in arid or semi-arid regions outside the current study area.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 110〈/p〉 〈p〉Author(s): Shuheng Du, Yapu Zhao, Jun Jin, Gen Kou, Yongmin Shi, Xianfu Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Perthite is a special type of skeleton mineral in tight oil sandstone which cannot be ignored. However, few attention was paid to the secondary pores in perthite and their contributions in tight oil reservoir. This study reveals the perthite's significance in unconventional oil flow characterizes comprehensively and quantitativel by combining the Field Emission Scanning Electron Microscope (FE-SEM) with high resolution, Energy Dispersive Spectrometer (EDS) analysis, high precision image processing, comprehensive parameters construction and calculation. Typical perthite samples of Chang 7 tight oil reservoir of Ordos basin were selected for this study. Our results demonstrate that the growth of K-feldspar and Na-feldspar in perthite is complementary. The mixing process of the two types of stripes promotes each other rather than inhibiting each other. As to the development of secondary pores of perthite, there are clear differences in the area and number of pores, medium differences in the porosity, radius and perimeter, and small differences in other parameters. The more regular and uniform growth of Na-feldspar, the more likely the perthite is to form regular and normalized secondary pore. At least 56.7% of the secondary pore of perthite contributes to oil flow in the process of oil migration or development, and its scientific significance cannot be ignored. The conclusion could provide the geological basis for the effective development of the unconventional hydrocarbon reservoirs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 9 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geochemistry〈/p〉 〈p〉Author(s): Yu Zhang, Xianghong Meng, Duoyun Wang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Ordos Basin is a large interior continental sedimentary basin in western China； its Mesozoic evolution was controlled by surrounding orogenic belts. To constrain the evolution of the southern Ordos Basin, four samples from the southern Ordos Basin were analyzed for U-Pb ages. Similar detrital zircon U-Pb age patterns of the samples suggest no provenance change occurred during the Middle Triassic. Detrital zircons from the samples are divided into three major groups based on their U-Pb ages: 360-250 Ma, 2000-1600 Ma and 2800-2200 Ma. The first group of zircons is consistent with Paleozoic igneous zircons from the northern margin of the North China Craton (NCC). Detrital zircons of the second and third groups are likely derived from the basement of the NCC northern margin. In the Middle Triassic, detritus from the Qinling Orogenic belt may only have reached the piedmont deep depression. The absence of the Qilian Mountain source suggests that the Ordos Basin may not have been connected with the Hexi Corridor Basin in the Middle Triassic. Combining our results with those of previous studies, we suggest that the southern borderline of the Ordos Basin may not have reached the Qinling Orogenic Belt. The northern margin of the NCC, the Qinling Orogenic Belt and the pre-Middle Triassic sedimentary rocks of the eastern NCC provided sources for the Southern Ordos Basin in the Late Triassic. The rapid uplift of the Qinling Orogenic belt occurred in the Late Triassic. This event was response to collision between the NCC and the South China Block. The deposition and evolution of the Ordos Basin were controlled by the Indosinian movement. The change in source areas for the Southern Ordos Basin was closely related to the development and evolution of the Qinling Orogenic Belt. The Qinling Orogenic Belt shows good coupling with the sedimentation and structures of the Southern Ordos Basin.〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Applied Geophysics, Volume 169〈/p〉 〈p〉Author(s): Zhiqu Lu, Glenn V. Wilson, Mark W. Shankle〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For soil exploration in the vadose zone, a high-frequency multi-channel analysis of surface waves (HF-MASW) method with three enhanced techniques has been developed. In this paper, we apply this enhanced HF-MASW method to re-process field testing data that were collected over the past several years on five different sites. These sites are selected for their different soil properties and data acquisition configurations. The derived overtone images, extracted dispersion curves, and inverted soil profiles of these soil sites are shown and discussed. Penetration tests were conducted and comparisons are made between the soil profiles taken from the HF-MASW tests and those from the penetration tests. One of the objectives of the paper is to determine the optimal data acquisition parameters, including the source parameters and sensor array geometric configuration through the discussions of these case studies. Practical concerns of the HF-MASW method and lessons learnt from these tests are addressed. Recommendations for data acquisition, signal processing, and inversion are provided.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 346–347〈/p〉 〈p〉Author(s): Rohit Pandey, Ashutosh Pandey, N.V. Chalapathi Rao, B. Belyatsky, A.K. Choudhary, B. Lehmann, Dinesh Pandit, Prashant Dhote〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present petrology, geochemistry and radiogenic isotope (Sr and Nd) data of thirteen post-Deccan lamprophyre dykes in the Narmada rift zone from the Chhotaudepur alkaline province of the Deccan Large Igneous Province (DLIP). Mineralogically, these dykes show affinity towards alkaline (sannaite and camptonite) as well as ultramafic (damtjernite) varieties of lamprophyres. Their major oxides and certain trace element ratios increase with increasing silica content highlighting the strong influence of fractionation processes. Their Nb/U and Ce/Pb ratios are similar to the mantle array defined by MORBs and OIBs and suggests an uncontaminated nature. Major oxide (K〈sub〉2〈/sub〉O, Na〈sub〉2〈/sub〉O, SiO〈sub〉2〈/sub〉 and TiO〈sub〉2〈/sub〉) contents show geochemical similarity towards shoshonitic volcanic series, whereas elevated Zr/Hf and Nb/La coupled with suppressed Rb/Nb and Zr/b display their affinity towards HIMU-type intraplate basalts. Their radiogenic initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr (0.706034–0.710582) and sub-chondritic initial ɛNd (−8.6 to 2.1) are akin to those of the (i) ca. 65 Ma Ambadongar carbonatite, NW India, and (ii) ca. 65 Ma orangeites from Bastar Craton, central India, highlighting an enriched lithospheric mantle source. REE inversion modeling suggests ~3% enrichment of an undepleted mantle followed by small degrees of melting of this enriched mantle source are sufficient- as in the case of ocean island basalts (OIB)- to reproduce their observed REE concentrations. Their T〈sub〉DM〈/sub〉 Nd model ages (564–961 Ma) are consistent with widespread convergent margin-related magmatism during the amalgamation of the Rodinia supercontinent. We propose that enriched lithospheric mantle developed during the Neoproterozoic was metasomatized by small-volume CO〈sub〉2〈/sub〉-rich melts imparting a HIMU-type geochemical character during Late Cretaceous, when the mantle plume (viz., Réunion) responsible for the flood basalt eruption, impinged at the base of the NW Indian lithosphere. From the presence of F-rich apatite and high K/Rb in mica, we infer the (i) presence of F-phlogopite in their source regions, and (ii) that the depth of post-Deccan lithosphere-asthenosphere boundary (LAB) beneath NW India was at least ~100 km at ca. 65 Ma.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 346–347〈/p〉 〈p〉Author(s): Babita Rani Choudhary, M. Santosh, Benedetto De Vivo, Gajananrao Jadhav, E.V.S.S.K. Babu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Silicate melt inclusions (MI) trapped in minerals provide direct tools to evaluate source characteristics and magma evolution including magma chamber processes. Here we present results from the study of MIs in basalts from the Western Ghats region of the Deccan Large Igneous Province (LIP) in India. The MIs in plagioclase and clinopyroxene phenocrysts were analyzed. The MIs exhibit post-entrapment modification by in situ crystal fractionation, chemical interaction with the host phenocryst (plagioclase or clinopyroxene), degassing/decrepitation, and crystallization of daughter minerals during cooling. The MIs display variable silica (SiO〈sub〉2〈/sub〉 41–68 wt%), low potassium, and high Fe〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉Ti contents, corresponding to differentiation of basaltic to andesitic magma. Our data indicate H〈sub〉2〈/sub〉O content of about 2 wt% which is consistent with recent evidence for elevated primary H〈sub〉2〈/sub〉O content in the Deccan and other LIPs, corresponding to elevated H〈sub〉2〈/sub〉O in the lithospheric mantle and plumes passing through the mid-mantle inheriting the hydrous nature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 523〈/p〉 〈p〉Author(s): Yuichiro Hayashi, Takeshi Mitani, Naoyoshi Komatsu, Tomohisa Kato, Hajime Okumura〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We investigated the surface roughening in 4H-SiC solution growth from the following two aspects: the roughening of the seed surface before seeding and the roughening caused by the adhesion of SiC particles during growth. First, we investigated the morphological changes of the seed surface before and after the melt-back process. The seed surface just before seeding was covered with macrosteps and 6H-SiC hillocks with a height of several micrometers. This surface roughening was caused by condensation of droplets of vaporized solvent on the seed surface. We found that the 6H-SiC hillocks were the origins of trench defects. The melt-back process completely removed the hillocks and produced a smooth surface adequate for successive bulk growth. Second, we investigated surface roughening caused by the formation of SiC particles. The adhesion of SiC particles on the growth surface introduced trench defects and polytype inclusions. The adhesion of SiC particles was suppressed by controlling the distribution of carbon supersaturation in the solvent.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 December 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 346–347〈/p〉 〈p〉Author(s): Rosana Silveira Resende, Carlos Alberto Tello Sáenz, Luiz Augusto Stuani Pereira, Elton Luiz Dantas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding the chemical etching effects in the crystalline structure of zircon grains is crucial to know their chemical composition, morphology and isotopic geochemistry. After chemical etching, the zircon grain can be classified as homogeneous heterogeneous, hybrid and anomalous depending on the surface fission-track density observed under an optical microscope. The complementary techniques such as optical microscopy, micro-Raman spectroscopy, scanning electron microscopy (imaging by cathodoluminescence and secondary electrons) and electron microprobe, were employed to characterize the zircon grain surfaces from Igneous, Metamorphic and Sedimentary rocks before and after chemical etching, except for Raman spectroscopy. Measurements of U-Pb age are concordant in areas on the grain surface with uniform fission-track density. The chemical and isotopic analyses show that the etching is capable of revealing the different layer imperfections of the zircon crystalline structure, which can be inherent in its crystallization or acquired during its geological history. Therefore, identification of crystallographic preserved areas on the zircon surface, which are associated with uniform fission-track density, helps to get highly concordant U-Pb ages. In general, the results showed that the U-Pb system depends significantly on the amorphization degree of the zircon crystalline structure, which in most cases can only be revealed by etching.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Applied Geophysics, Volume 169〈/p〉 〈p〉Author(s): Rakoto Heritiana A., Rajaomahefasoa Riva, Razafiarisera Ralay, Razafindrakoto Boni〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Multiple electrical geophysical survey techniques were used to evaluate the flaky graphite reserves found along the east coast of Madagascar. Self-potential (SP) combined with induced polarization (IP) and electrical resistivity tomography (ERT) methods were applied and provide information about the graphite ore spatial distribution. Unlike conventional geophysical survey methods that use SP and electromagnetic (EM) methods for exploration of this type of metal, the addition of IP and ERT offers a geoelectrical map and section which indicate correlations with the graphite content.〈/p〉 〈p〉The obtained SP map enabled us to delineate the mineralized area whereas the geoelectrical sections obtained from ERT and IP provide additional information on the vertical extent of the mineral of interest, in this case flake-graphite. We overlaid the graphite content, as measured on samples, on the SP map in order to verify the effectiveness of the geophysical methodology. Good correlation between negative SP anomalies and positive indication of graphite content confirms that the methods used in this study (SP, ERT and IP) are sensitive for delineation of the mineralized zone and consequent evaluation of the ore reserve. Resistivity and chargeability obtained from the inversion of the ERT/IP data are low and high, respectively, within the saturated zone inside SP-anomalous zones.〈/p〉 〈p〉The principal ore body is located in the lateritic zone composed of clay-rich formations derived from the weathering of gneiss and migmatite rocks. Negative SP anomalies, along with low electrical resistivity and high chargeability values, are found mainly in areas where the graphitic content exceeds 5%.〈/p〉 〈/div〉 〈/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: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Biomass and Bioenergy, Volume 127〈/p〉 〈p〉Author(s): Shuping Zhang, Shuguang Zhu, Houlei Zhang, Xinzhi Liu, Huiyan Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Effect of combined pretreatment on the mechanism of pyrolysis behavior and pyrolysis products (bio-oil, non-condensable gas and char) of rice husk was investigated using thermogravimetric analyzer (TGA) and laboratory-scale fixed-bed reactor. A coupling method combining iso-conversional method and model-fitting method was used to obtain the pyrolysis kinetic parameter. Pyrolysis kinetics results indicated that activation energy (〈em〉E〈/em〉) gradually increased with the increase of conversion rate (〈em〉α〈/em〉), which was due to the differences in thermal stability of biomass components. Acid washing pretreatment slightly increased the average activation energy (〈em〉E〈/em〉〈sub〉a〈/sub〉), and then subsequent torrefaction process further increased it. The entire pyrolysis reaction process of all the rice husk samples can be described by the reaction-order model. In addition, a laboratory-scale fixed-bed reactor was used to investigate the yields and detailed characteristics of pyrolysis products. The results suggested that phenols and sugars contents in bio-oil increased, while that of small-molecule components with high thermal instability decreased, which was favor for the storage and subsequent utilization of bio-oil. Rice husk char obtained from pyrolysis also has the potential for preparation of silica products. We concluded that combined pretreatment of washing and torrefaction significantly improved the thermochemical utilization potential of rice husk for fuels and chemicals by pyrolysis.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0961953419302429-fx1.jpg" width="307" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Geology, Volume 416〈/p〉 〈p〉Author(s): Pedro Terrinha, Henrique Duarte, Pedro Brito, João Noiva, Carlos Ribeiro, Rachid Omira, Maria Ana Baptista, Miguel Miranda, Vitor Magalhães, Cristina Roque, Tagusdelta cruise team〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The stratigraphy of the Tagus river ebb-tidal delta off Lisbon (Portugal) is investigated using high resolution multichannel seismic reflection profiles with the purpose of searching for sedimentary or erosive features associated with landslides. The Tagus delta is sub-divided in two prograding seismic units of 17 ky to 13 ky and 13 ky to Present based on the calibration of seismic lines using gravity and box-cores in the Tagus pro-delta. We report the existence of a buried landslide with 11 km of length, 3.5 km of width and a maximum thickness of 20 m that accounted for the collapse of half of the upper unit of the Tagus river delta front in Holocene times. The non-collapsed half of the delta front contains extensive shallow gas of still unknown origin and nature. An estimated age of ~8 ky BP for the Tagus delta landslide is proposed based on stratigraphic correlation. The trigger mechanisms of the newly identified Tagus landslide are discussed as well as of the several landslides also found in the lower delta unit. These findings present a first step towards a future assessment of the susceptibility of the nearby coastal areas and the off-shore infrastructures to hazards related to such large collapses.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 214〈/p〉 〈p〉Author(s): Daniela Polag, Frank Keppler〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Methane (CH〈sub〉4〈/sub〉) is a potent greenhouse gas released to the atmosphere by various natural and anthropogenic sources. Numerous studies have been conducted to quantify the major and minor CH〈sub〉4〈/sub〉 sources on spatial and temporal time scales. A minor source of the atmospheric global CH〈sub〉4〈/sub〉 budget is the direct release of CH〈sub〉4〈/sub〉 from the living human body. Based on available data from recent publications, for the first time, CH〈sub〉4〈/sub〉 emissions from human breath and flatus are estimated on a global scale taking into account dominant factors influencing emission, such as age, ethnicity, and gender. Human CH〈sub〉4〈/sub〉 emissions are compared between preindustrial times (1750), present age (2017) and future prediction (2100) using demographic data based on World Population Prospects 2017 of the United Nations (UN 2017). In preindustrial times the global CH〈sub〉4〈/sub〉 release by humans is estimated at 34 ± 28 Gg and then substantially increase by a factor of ten reaching 344 ± 255 Gg by 2017. Emissions are estimated to further increase by almost fourfold to a value of 1221 ± 672 Gg by 2100, even though the rise in population is predicted to only increase by 50%. This nonlinear relationship is related to the predicted change in population structure affecting the number of CH〈sub〉4〈/sub〉 producers. In contrast, for the year 2100 the simplified non-weighted estimation which merely considers the expected increase in population would only account for 612 ± 169 Gg. The discrepancy between the simplified non-weighted and weighted estimations of human CH〈sub〉4〈/sub〉 emissions emphasises the importance of factor-based calculations in order to compile more accurate data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 8 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Palaeogeography, Palaeoclimatology, Palaeoecology〈/p〉 〈p〉Author(s): William J. Freimuth, David J. Varricchio〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We describe the diversity and abundance of insect (specifically hymenopterans and coleopterans) pupation structures in the Upper Cretaceous (Campanian) Two Medicine Formation at the Egg Mountain locality, western Montana, U.S.A., an important dinosaur nesting site. The study interval comprises a massive calcareous siltstone and indurated silty limestone horizons interpreted as the product of cumulative paleosols. A 7 m by 11 m area was quarried with a jackhammer at intervals of 12.5 cm thickness for a 1.5 m thick stratigraphic section. The ichnoassemblage comprises four morphotypes (small, medium, large, and wide) assigned to 〈em〉Fictovichnus sciuttoi〈/em〉, of which three represent wasp (hymenopteran) cocoons while the fourth (wide) type potentially was produced by a coleopteran. Medium and small 〈em〉F. sciuttoi〈/em〉 are dominant while large and wide 〈em〉Fictovichnus〈/em〉 are less common and absent in some sample intervals. Other probable insect traces include partial perforations in cocoons (〈em〉Tombownichnus〈/em〉), isolated burrows, and an enigmatic hemispherical trace. Material is representative of a depauperate 〈em〉Celliforma〈/em〉 ichnofacies. Pervasive cocoons and other traces throughout the sequence suggest persistent soil conditions suitable for insect nesting and pupation, and suggest an absence of sediment pulses of sufficient thickness to prohibit thorough colonization. Peaks in pupation chamber abundance may reflect episodes of reduced sedimentation rates otherwise unseen in the absence of primary bedding structures. Well-drained and friable soil conditions favorable for insect nesting also may help explain the abundance of dinosaur nests and other vertebrate nesting events in associated strata as well as the presence of small terrestrial forms.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Geodynamics, Volume 129〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Jingyi Zhu, Zhaozhong Yang, Xiaogang Li, Zhichao Song, Ziwei Liu, Shiyi Xie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liquid foam is an alternative to water-based fracturing fluid due to its great proppant suspension ability. In this work, theoretical and experimental investigations on the settling behavior of the proppants in viscoelastic foams were analyzed on bubble scale. Settling trajectory was captured over time by optical microscope to calculate proppant settling velocity. At room temperature, proppants kept suspended well, but noticeable changes in proppant position could be observed at 70 °C. We concluded that the sedimentation of the proppants at high temperature was divided into three stages, that were drainage-dominated, structure-dominated and fluid-dominated regimes. For the large proppants, quick settling velocity was seen at first due to fast drainage rate. Then bubble pressure force and network force served as drag force exerting on the proppants when the proppants stretched or squeezed the liquid films. During this regime, bubble distribution, the existence of nodes, the length and the orientation of Plateau border leaded to the fluctuation in settling velocity. Lastly, the proppants would also flow freely along Plateau border over time, and the properties of the foam fluid such as viscosity and elasticity provided the drag force to prevent the proppants from settling. It's more likely for small proppants to change to this stage called fluid-dominated regime, but elasticity also guaranteed their low settling velocity. Moreover, in the existence of proppants, the analysis into drainage rate and bubble structure demonstrated the high stability of viscoelastic foams. These results helped understand the sedimentation of proppants in wet foams and broadened the application of viscoelastic foams in hydraulic fracturing.〈/p〉〈/div〉 〈/div〉

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

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 181〈/p〉 〈p〉Author(s): Zhong-Zhen Chen, Hong-Ze Gang, Jin-Feng Liu, Bo-Zhong Mu, Shi-Zhong Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A thermal-stable and salt-tolerant biobased zwitterionic surfactant 〈em〉N, N〈/em〉-Dimethyl-〈em〉N〈/em〉-[2-hydroxy-3-sulfo-propyl]-〈em〉N〈/em〉′-phenyloctadecanoyl-1, 3-diaminopropane (SPODP) was successfully obtained from modification of oleic acids which can be regenerated from waste cooking oils, and its structure was characterized using GC-MS, ESI-MS and 〈sup〉1〈/sup〉H NMR approaches. The biobased zwitterionic surfactant demonstrated a strong interfacial activity at high salinity and high temperature conditions at a very low surfactant dosage in formation brine. The ultralow interfacial tension (≤10〈sup〉−3〈/sup〉 mN/m) between crude oil and brine was reached at 0.5 g/L in brine with a wide range compatibility of NaCl up to saturation, Ca〈sup〉2+〈/sup〉 up to 500 mg/L, and temperature up to 95 °C. Meanwhile, it also exhibited strong wetting ability and resistance against adsorption on sands. All the results from this study suggest that the biobased zwitterionic surfactant is promising over varieties of traditional surfactants in applications in alkali free systems in enhanced oil recovery (EOR).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews〈/p〉 〈p〉Author(s): Henrik Kalliomäki, Thomas Wagner, Tobias Fusswinkel, Dina Schultze〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Orogenic style gold mineralizations in the Archean Hattu schist belt (E Finland) are present in all major host rock lithologies including epiclastic sedimentary rocks, volcanic rocks, and felsic intrusives. The gold deposits are related to extensive quartz-dominated vein networks and the gold mineralization occurs as dissemination in altered wall rocks and within hydrothermal quartz veins. The quartz-dominated veins frequently contain calcite, which is also present within the country rocks. We analyze and compare the major and trace element chemistry of these calcites and test whether they carry the signatures of the origin of hydrothermal fluids associated with the gold deposits or record fluid interaction with the local wall rocks. The calcites show textural growth and chemical zoning, considerable chemical variations within samples and the chemical data do show some overlap between the samples. All calcites contain dominantly Ca with other elements being typically below 2 wt.%, and they are accordingly classified as rather pure calcites. Amongst minor elements, both Mg and Fe show larger variations than Mn. The concentrations of most trace elements analyzed are relatively low, except for Sr and Y, which can attain values up to 1 wt.% and 200 ppm, respectively. Some of the trace elements or trace element ratios in hydrothermal calcite, including Sr, Y, Mn, (La/Lu)〈sub〉N〈/sub〉 and ∑REE, show correlations with the respective host rock lithologies. This indicates that interaction between hydrothermal fluids and adjacent and diverse host rocks has strongly affected the trace element chemistry of calcite. Chemically variable growth zones in large calcite crystals and distinct grain populations within individual samples cannot be readily explained by host rock control, but instead they are interpreted to reflect changes in fluid composition over time. The hydrothermal calcites have chondrite-normalized REE patterns that are mostly HREE enriched relative to LREE, with very few exceptions that show unfractionated flat or LREE enriched (relative to the HREE) patterns. The REE patterns of the calcites are very different from those of their immediate host rocks, suggesting that they are inherited from the hydrothermal fluid(s) from which they precipitated. The HREE enrichment relative to the LREE visible in the patterns resembles the REE patterns of calcites from hydrothermal vein type deposits of metamorphic origin elsewhere and contrasts with the REE patterns of calcites from magmatic-hydrothermal environments. The REE patterns of the hydrothermal calcites in the Hattu schist belt deposits would therefore be compatible with formation from a fluid system that is essentially derived from metamorphic sources, in agreement with conclusions drawn from the fluid inclusion chemistry.〈/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-S0169136818309636-ga1.jpg" width="86" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Deep Sea Research Part II: Topical Studies in Oceanography〈/p〉 〈p〉Author(s): Stacey A. McCormack, Jessica Melbourne-Thomas, Rowan Trebilco, Julia L. Blanchard, Andrew Constable〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years, there has been a shift away from the long-standing paradigm in which a short, krill-dominated food chain was considered to be the central element in Southern Ocean food webs. Instead, there is now increasing recognition that alternative energy pathways through mid-trophic level groups (mesopelagic fish and squid) may be equally (if not more) important than the krill pathway in many regions. Ecosystem models are a valuable tool to synthesise existing data on the structure of marine food webs and to visualise and quantify alternative energy pathways. In this study we develop a static mass balance food web model for the southern Kerguelen Axis region (Prydz Bay and Princess Elizabeth Trough) to evaluate the importance of alternative energy pathways through mid-trophic level groups, including fish, squid and krill, in maintaining energy flow to top predators within East Antarctica. Our model reveals several major trophic pathways distinct from, and equally important to the Antarctic krill (〈em〉Euphausia superba〈/em〉) pathway. Using simple scenarios of reductions in krill biomass, we investigate how the system might switch to a state dominated by fish and squid pathways with the response of krill-reliant predators strongly dependent on their ability to switch to other prey sources. We conclude by discussing what these findings might suggest for the future vulnerability of East Antarctic food webs and the implications for future modelling work in the region.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Ore Geology Reviews, Volume 111〈/p〉 〈p〉Author(s): Wenyuan Liu, Nigel J. Cook, Cristiana L. Ciobanu, Sarah E. Gilbert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Enargite, Cu〈sub〉3〈/sub〉AsS〈sub〉4〈/sub〉, is a relatively common sulphide mineral and is considered diagnostic for deposits of intermediate- to high-sulphidation type. Analysis of enargite-bearing samples from deposits in the Zijinshan porphyry – high-sulphidation epithermal Cu-Au orefield, southeastern China, provides evidence for the diversity of trace elements that may be hosted within enargite and their range of concentrations. Enargite is shown to host Sb, Te, Sn, Zn and Ge at concentrations up to several thousand ppm. The mineral also incorporates measurable concentrations of Mo, Cd, Bi, Pb, Fe, Se, Ag, Au W, Ga and In. Element mapping (electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry) provides evidence for grain-scale heterogeneity in enargite in the form of oscillatory, grain-scale compositional zonation with respect to Sb, Sn, Te and several other trace elements. Element mapping also clearly shows an inverse correlation between the concentrations of As and Te, and between As and Sn. Incorporation of Sn and Te into the enargite structure is achieved by substitution of Sn〈sup〉4+〈/sup〉 and Te〈sup〉4+〈/sup〉 for As〈sup〉5+〈/sup〉. Charge balance is maintained by incorporation of Fe〈sup〉2+〈/sup〉, Zn〈sup〉2+〈/sup〉 and other divalent cations (potentially including Cu〈sup〉2+〈/sup〉) into the Cu〈sup〉+〈/sup〉 site. The complex intra-grain zoning results from evolving fluids, multiple phases of growth – in turn leading to an overprinting of primary distribution patterns. Observed patterns are also influenced by equilibrium partitioning between enargite and co-existing minerals. Nevertheless, trace element signatures in enargite from different parts of the Zijinshan ore system show notable differences. Enargite from the high-sulphidation stage typically shows a marked enrichment in Te and Sn whereas enargite from intermediate-sulphidation stage is relatively depleted in Te and Sn, and comparatively enriched in Sb and Se. These differences represent a potential vector for exploration within porphyry – high-sulphidation epithermal systems. Furthermore, the presence of Te-rich enargite may be a prospective guide to high Au-grade mineralization. The notable concentrations of precious metals (Au, Ag) and critical elements (notably Te and Ge) within enargite make this mineral of particular interest from the perspective of potential recovery of these economically important elements. The observed grain-scale zoning and inherent variability within any given sample emphasize that spot analysis of trace elements alone without consideration of such heterogeneity may provide quantitative data of limited use and potentially, lead to misleading interpretations.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉LA-ICP-MS element maps of zoned enargite from the Zijinshan high-sulphidation Cu-Au deposit reveal often spectacular grain-scale zonation that track changes in fluid composition. Enargite also concentrates several elements of interest, including Ag, Au, Te and Ge, relative to associated minerals.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0169136819303750-ga1.jpg" width="292" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 153〈/p〉 〈p〉Author(s): A-Young Kim, Ryanda Enggar Anugrah Ardhi, Guicheng Liu, Ji Young Kim, Hyun-Jin Shin, Dongjin Byun, Joong Kee Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A hierarchical hollow SnO/SnO〈sub〉2〈/sub〉 heterostructure anode surrounded by a dual carbon layer (DCL@SnO/SnO〈sub〉2〈/sub〉), inner (host) and outer carbon layers, was successfully designed 〈em〉via〈/em〉 a simple hydrothermal method with a single Sn precursor to achieving high-performance Li-ion batteries (LIBs) and Li-ion capacitors (LICs). The carbon nanotube (CNT)-based inner carbon host and an ultrathin outer amorphous carbon layer introduced at the SnO/SnO〈sub〉2〈/sub〉 heterostructure had good elasticity and high electrical properties to prevent volume change and ensure fast Li-ion transport during cycling, respectively. Meanwhile, the SnO/SnO〈sub〉2〈/sub〉 heterostructure comprising p-type SnO and n-type SnO〈sub〉2〈/sub〉 facilitated further fast interfacial Li-ion transfer within the p–n SnO/SnO〈sub〉2〈/sub〉 heterojunction anode 〈em〉via〈/em〉 the acceleration effect induced by the built-in electric field (BEF). The resulting half cells LIBs consisting DCL@SnO/SnO〈sub〉2〈/sub〉 anode shows a high reversible specific capacity of 902.1 mAh g〈sup〉−1〈/sup〉 after 500 cycles at a current density of 1400 mA g〈sup〉−1〈/sup〉. The specific capacity of 347.04 mAh g〈sup〉−1〈/sup〉 was still maintained even at a high current density of 10 000 mA g〈sup〉−1〈/sup〉. Moreover, the maximum energy and power density of 125 W kg〈sup〉−1〈/sup〉 and 200 Wh kg〈sup〉−1〈/sup〉, respectively, were achieved from the half cells LIC comprising DCL@SnO/SnO〈sub〉2〈/sub〉 anode (LIC-DCL@SnO/SnO〈sub〉2〈/sub〉).〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉A hierarchical hollow SnO/SnO〈sub〉2〈/sub〉 heterostructure anode surrounded by a dual carbon layer (DCL@SnO/SnO〈sub〉2〈/sub〉) is prepared by a simple hydrothermal method using a single Sn precursor. The CNT-based inner carbon host layer is equipped by a nanotail CNT to form a tadpole-like structure. The ultrathin elastic amorphous outer carbon layer buffers the cyclic volume change of the SnO/SnO〈sub〉2〈/sub〉 heterostructure, while its natural properties could realize the formation of thin, instead of thick, solid-electrolyte interphase (SEI) layer to enhance e〈sup〉−〈/sup〉/Li〈sup〉+〈/sup〉 reversibility and transport kinetics during charge charge–discharge cycles. The p–n heterojunction created from SnO/SnO〈sub〉2〈/sub〉 heterostructure facilitates the creation of the built-in electric field (BEF) to promote e〈sup〉−〈/sup〉/Li〈sup〉+〈/sup〉 transport rate during charge–discharge cycling and to maintain a reversible high capacity at a high current density.〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306888-fx1.jpg" width="288" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 153〈/p〉 〈p〉Author(s): Chen Han, Xiaoguang Duan, Mingjie Zhang, Wenzhao Fu, Xuezhi Duan, Wenjie Ma, Shaomin Liu, Shaobin Wang, Xinggui Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanocarbon-catalyzed advanced oxidation processes for wastewater remediation are green and state-of-the-art methods, nevertheless, the origins of carbocatalysis remain unresolved. In this study, carbon nanotubes (CNTs) are employed as typical metal-free catalysts for catalytic peroxymonosulfate (PMS) activation and phenol oxidation. The surface chemistry and electronic properties of CNTs are deliberately tailored by liquid acid oxidation and subsequent thermal treatment. It is unveiled that the electron-rich carbon surface and carbonyl groups can affect organic adsorption capacity of the carbocatalysts and modulate persulfate activation in different catalytic manners. Furthermore, the relationship between the surface chemistry (oxygen functionality and electron density) and carbocatalysis is established, which is decisive to regulate the radical/nonradical pathways in the catalytic oxidation for water purification. This study provides new insights to carbon-catalyzed persulfate activation with manipulated reaction pathways and redox potentials.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622319306839-fx1.jpg" width="260" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Volcanology and Geothermal Research, Volume 384〈/p〉 〈p〉Author(s): Chiou Ting Tan, Benoît Taisne, Jurgen Neuberg, Ahmad Basuki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Magma opening new fluid pathways through the crust can generate migrating seismic sources following the trail of the magma. By using Seismic Amplitude Ratio Analysis (SARA), it is possible to detect this seismic migration simply from the amplitudes of continuous data recorded at different stations in a network, without having to do any picking of seismic phases. In this study, we present a modified method – Red-flag SARA, which adapts SARA for real-time monitoring. Red-flag SARA provides a quantitative tool to analyse amplitude ratios between stations in a network and detect temporal changes in these ratios. Since such changes imply seismic source location variations, Red-flag SARA is a handy tool during seismic crises to quickly answer the question of whether seismic activity, and therefore magma, is migrating or not. We tested Red-flag SARA on synthetic data and validated it using real data from two volcanoes – Piton de la Fournaise, Reunion Island, and Gede, Indonesia, for three scenarios: 1) magma migration ending as intrusion, 2) migration leading to eruption and 3) a burst of seismicity with no magma migration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 533〈/p〉 〈p〉Author(s): Wenhui Wang, Linna Zhang, Hao Liu, Xin Deng, Jingqiang Tan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study presents a new analysis of three species of the Ordovician graptolite genus 〈em〉Azygograptus〈/em〉 Nicholson & Lapworth from the Wenxiakou section in the Zhongxiang area of Hubei Province. The paleogeographic occurrences of the genus within South China were plotted on an up-to-date paleogeographic map based on a revised data set of graptolite occurrences from 68 localities compiled by the online Geobiodiversity Database (GBDB). The paleogeographic distribution of 〈em〉Azygograptus〈/em〉 follows a nearshore-offshore trend, and the taxonomic diversity of 〈em〉Azygograptus〈/em〉 is higher in nearshore high-energy environments than in offshore low-energy environments. However, graptolites also gathered in deeper-water environments surrounding oldlands partly due to the high-nutrient inputs and rapid deposition. 〈em〉Azygograptus〈/em〉 is found not only in high-latitude cold-water regions as endemic taxa but also in low-latitude regions. Oceanic circulation may account for the rapid dispersal of 〈em〉Azygograptus〈/em〉 from high-latitude regions, such as Britain and Scandinavia, to low-latitude regions, such as South China, eventually resulting in their observed paleogeographic distribution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Geology, Volume 416〈/p〉 〈p〉Author(s): Manli Zhang, Changsong Lin, Min He, Zhongtao Zhang, Hao Li, Xuan Feng, Hongxun Tian, Hanyao Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The early-stage shelf-margin prism in the Pearl River Mouth Basin (PRMB), northern South China Sea, formed from the Late Oligocene to Early Miocene, comprises a set of shelf-edge delta and slope fan wedges of the Zhuhai Formation and records the development of the continental slope in response to the interaction of sea-level change, tectonic subsidence and sediment supply. Based on integrated analysis of seismic, well logging and core data, the stratigraphic architecture, depositional systems and controlling processes are documented. The Zhuhai Formation is a composite sequence bounded by regional unconformity, and can be further divided into five sequences (CS3-1-CS3-5). The depositional genetic units (transgression, ascending normal regression and descending forced regression) are identified within sequences based on variation in shelf edge trajectories. The shelf deltaic clinoforms are characterized by oblique-tangential reflections in seismic profiles with a thickness of 100–150 m. In contrast, the shelf-margin delta and slope clinoforms generally are 300–1200 m thick and mainly display as sigmoid or sigmoid-tangential seismic reflections. The delta deposits usually consist of thick beds of delta front deposits and prodelta slump and deformed sediments, and are associated with sandy slope fan systems. Eleven delta complexes are distinguished by tracking the distribution of the deltaic clinoforms in each sequence, and these deltaic deposits tend to extend along their strike direction which may be related to the reworking of strong waves and coastal currents. Slope fan systems consist mainly of turbidite channel fills, frontal splay and debris flow deposits, and generally develop along the slope in CS3-3-CS3-5, which may be triggered by steep shelf margin slope and fault activity. The stratigraphic pattern of the shelf margin prism and depositional evolution of the deltaic systems from the Late Oligocene to Early Miocene were controlled by the interaction of sea level changes, sediment supply and tectonic subsidence. The ascending trajectory from the CS3-1 (30 Ma) to the top of the CS3-5 indicates that the relative sea level continued to rise generally but the shelf margin prograded basinward rapidly due to the great amount of sediment supply and lower subsidence rate. Tectonic uplift of the source area and strengthened physical erosion during this period may be the reason for the large sediment supply.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Mengxue Li, Haibo Liu, Tianhu Chen, Lin Wei, Can Wang, Wei Hu, Hanlin Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The transformation of Al-substituted goethite in oxidative and reductive atmosphere, which models natural fire, was investigated in detail. Various characterization results indicated that Al-substituted goethite transformed into hematite in an oxidative atmosphere and magnetite followed by zero-valent iron in a reductive atmosphere. Interestingly, the substitution of Al for Fe not only changed the crystal morphology affecting crystal surface reactivity, but also restrained the transformation of goethite into hematite, magnetite and zero-valent iron. In addition, the Al in the goethite was embedded into the crystal structure of thermally formed hematite and magnetite, considerably influencing their surface reactivity. The macroscopic adsorption results indicated that the substitution of Al for Fe increased the adsorption capacity of goethite and the corresponding derivatives except zero-valent iron. For the same Al amount, the adsorption capacity followed an order of goethite 〉 hematite 〉 magnetite, implying a loss of phosphate in goethite-rich soil after experiencing natural fire. However, with increasing in temperature in the reductive atmosphere, Al-magnetite transformed into a mixture of Al-magnetite and zero-valent iron which displayed excellent phosphate adsorption capacities increasing to 1.21–5.96 mg/g. The phosphate adsorption behaviors to thermally formed products were fitted well by surface complexation modeling with five complexation sites, which were more obvious for goethite than for hematite and magnetite. These findings presented in this study represent significant progress toward an understanding of the migration, enrichment and transformation of phosphate in Al-substituted goethite-rich soil in cases experiencing natural fire.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 524〈/p〉 〈p〉Author(s): Xue-Feng Hu, Jing-Long Zhao, Pei-Feng Zhang, Yong Xue, Bo-Nian An, Fang Huang, Hui-Min Yu, Gan-Lin Zhang, Xiang-Jun Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To probe Fe isotopic signatures of the Quaternary Red Clay (QRC) in subtropical southeastern China, two QRC profiles located in southern Anhui Province, Southeast China, were studied. The whole profiles were generally in a narrow range in δ〈sup〉56〈/sup〉Fe of −0.040 ± 0.061‰—0.117 ± 0.048‰. The Yellow-brown Earth (YBE) and Uniform Red Clay (URC) of the upper profiles were similar in δ〈sup〉56〈/sup〉Fe to the Xiashu Loess along the Yangtze River, Southeast China, and the loess, paleosols and Tertiary red clay in the Chinese Loess Plateaus, Northwest China, as well as the baseline of terrestrial igneous rocks. The slight variation of δ〈sup〉56〈/sup〉Fe from the YBE to the URC suggests that the chemical weathering and rubification on the aerobic surface did not fractionate Fe isotopes significantly. The Reticulate Red Clay (RRC) underlying the YBE and URC fluctuated in δ〈sup〉56〈/sup〉Fe to some extent. The white veins separated from the lower RRC were depleted of Fe oxides and heavier in Fe isotopes, and the red veins, on the contrary, were isotopically lighter in Fe. δ〈sup〉56〈/sup〉Fe of the white veins, 0.345 ± 0.053‰ on average, was significantly higher than the bulk samples, 0.033 ± 0.044‰ on average, and the red veins, −0.021 ± 0.046‰ on average. This suggests that the reticulate textures of the RRC were formed by the reductive removal/re-precipitation of Fe due to the cyclical changes of redoxic conditions. Fe isotopic composition of the QRC was dominantly controlled by the redoxic mobility of Fe, rather than the degree of weathering. δ〈sup〉56〈/sup〉Fe of the profiles was not correlated with the paleoclimatic events, and thus cannot be used as a paleoclimatic proxy. The fractionation of Fe isotopes in the lower RRC, however, indicated the occurrence of over-humid paleoclimate with alternations between drought and wetness in Southern China during the Pleistocene.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of African Earth Sciences, Volume 158〈/p〉 〈p〉Author(s): Sayed Mosaad, El Sayed El Abd, Alan E. Kehew〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Middle Eocene carbonate aquifer constitutes the major source of groundwater for the expansion of reclamation projects outside the Nile Valley southeast of Beni-Suef, Egypt. In the past few decades, groundwater abstraction from the Middle Eocene carbonate aquifer has increased, leading to the deterioration of groundwater quality. The current study combines geochemical methods and multivariate statistical analysis to assess the factors controlling the deterioration of groundwater quality in this aquifer. The results show that the total dissolved solids (TDS) varies between 263.7 and 4214 mg/l. The groundwater is dominantly of Na–Ca–Cl SO〈sub〉4〈/sub〉 type. Various plots were used to assess processes such as carbonate and evaporite dissolution, silicates weathering and/or cation exchange controlling groundwater quality. Geochemical modelling with NETPATH indicates that recharge sources and mixing of groundwater within the aquifer result from occasional storms over the eastern watershed. These rainfall events account for ~32% of aquifer recharge, along with infiltration of Nile water in the west, which contributes ~36% of the recharge. The groundwater salinity is controlled by precipitation of calcite, dissolution of dolomite, gypsum and halite and ion exchange along the groundwater flow path. Multivariate statistical analysis highlights that the Ca, Na, Cl and SO4 ions control groundwater salinity within the aquifer through water-rock reactions and mixing of Nile water from the western side of the study area with subsurface recharge from mountainous areas in the eastern portion of the watershed. Integration of hydro-geochemical data and multivariate statistical analysis leads to better understanding of geochemical processes controlling regional groundwater quality in the Middle Eocene carbonate aquifer near Beni-Suef, Egypt and in areas with comparable conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 332〈/p〉 〈p〉Author(s): Lucía E. Gómez-Peral, María Julia Arrouy, Daniel G. Poiré, Claudia E. Cavarozzi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The limestones of the Loma Negra Formation provide an excellent opportunity to examine the behaviour of rare earth elements plus yttrium (REY) due to the near-zero diagenetic alteration of the carbonate system. The terrigenous supply to this unit was minimal or scarce in relation to the depth of seawater in which the limestones accumulated. The interpreted palaeoenvironment suggests that limestones could have originated by suspension fall-out in a shallow, open marine ramp. The diagenetic features, composition, and original microtextures are considered good criteria for investigating their REY composition. Burial diagenesis products were limited and limestones largely preserved their original texture and organic matter, as well as their isotope and trace element composition. The study of REY distribution in the Loma Negra Formation in different settings of the Tandilia System revealed systematic chemostratigraphic patterns related to uniform palaeo-redox conditions. The general light rare-earth element depletion, marked positive La, Y, and Gd anomalies, as well as the clear negative Ce anomalies, are further features typically ascribed to oxidizing seawater conditions. From these results, it can be concluded that the Loma Negra Formation documents an oxygenation event that stands out in the overall anoxic Ediacaran ocean. This record may be correlated with the mid-Ediacaran oxygenation event (ca. 580 Ma). This may support the hypothesis that the Clymene Ocean was well oxygenated and connected during the Ediacaran, at least in the southwestern border of Gondwana.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 353〈/p〉 〈p〉Author(s): Roozbeh Moazenzadeh, Babak Mohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Root zone temperature is one of the most important soil characteristics, controlling many of the physical, chemical and biological processes in the soil. Temperature varies by soil depth, and exerts a profound impact on plant germination and growth. In this study, the accuracy of two artificial intelligence models including support vector regression (SVR) and elman neural network (ENN) and their hybrids with firefly algorithm (SVR-FA and ENN-FA) and krill herd algorithm (SVR-KHA and ENN-KHA) was assessed in estimating soil temperature (Ts) at 5, 10, 20, 30, 50 and 100 cm depths at Maragheh meteorological station in north-western Iran. The results of the models were evaluated under 5 scenarios with various inputs including the main meteorological parameters measured at the station (air temperature, sunshine hours, relative humidity, wind speed and saturation vapour pressure deficit). Daily Ts data recorded from January 1, 2006 to December 30, 2012 and from January 1, 2013 to December 30, 2015 were used for model training and testing, respectively. The results showed that error rates have decreased from 5 to 10 cm soil depth (root mean square error (RMSE) reduced by 2.97, 4.68 and 3.19% for the best scenarios of SVR, SVR-FA and SVR-KHA models, respectively), whereas error rates have been increasing from 10 to 100 cm soil depths (RMSE increased by 62.4, 80.9 and 73.6% for the best scenarios of SVR, SVR-FA and SVR-KHA models, respectively). For the best scenarios of ENN, ENN-FA and ENN-KHA models, RMSE values decreased by 2.1, 1.6 and 3.1% from 5 to 10 cm depth and increased by 61.1, 84.1 and 81.1% from 10 to 100 cm depth, so that all six models reached their best performance at 10 cm soil depth. Examination of the results in terms of under-estimation or over-estimation of Ts indicated that the lowest and highest differences in performance between under- and over-estimation sets were 0.01 °C (SVR-FA at 5 cm depth) and 1.64 °C (SVR at 100 cm depth) for SVR-based models and 0 °C (ENN at 10 cm depth) and 0.56 °C (ENN at 100 cm depth) for ELM-based models, respectively. According to the results from the best scenarios of SVR, SVR-FA and SVR-KHA models in the under-estimation set at 100 cm depth, all the three models have exhibited a poorer performance over the temperature range 15–25 °C (RMSE increased by 56.7, 47 and 61.3% for SVR, SVR-FA and SVR-KHA, respectively) compared to temperature values outside that range. Exactly the same trend was also observed for ELM-based models, where the mentioned increases in RMSE were about 37.7, 59.4 and 55.5% for ELM, ELM-FA and ELM-KHA, respectively. According to the results, bio-inspired metaheuristic optimisation algorithms based on SVR and ENN which use appropriate meteorological parameters as inputs can have a relatively satisfactory performance in estimating Ts under climatic conditions similar to our study area, especially in lower depths, and can be used as an alternative to direct measurement of this important parameter.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 6 July 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology〈/p〉 〈p〉Author(s): Momotaj Begum, Mahmood Reza Yassin, Hassan Dehghanpour, University of Alberta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉We evaluated the wettability of organic-rich shale plugs from 6 wells drilled in the Duvernay Formation, which is a self-sourced reservoir. We divided our samples into Upper (UD) and Lower (LD) Duvernay based on the variations in depth and kerogen maturity levels. UD and LD samples belong to oil and gas windows, respectively. We measured and compared spontaneous imbibition of oil and brine into 17 twin plugs with wide range of kerogen maturity level and total organic carbon (TOC) content. We also characterized the shale samples by conducting tight-rock analysis (TRA), x-ray diffraction (XRD), and rock-eval pyrolysis tests to identify the petrophysical properties, mineralogy, and organic-carbon properties, respectively. To investigate the size, abundance, and morphology of pores, we analyzed scanning electron microscopy (SEM) of the shale samples. Finally, we investigated the relationships between the results of spontaneous-imbibition tests and geochemical properties to understand the effect of kerogen maturity level on shale wettability.〈/p〉 〈p〉The results of wettability tests show higher normalized imbibed volume of oil (I〈sub〉o〈/sub〉) compared with that of brine (I〈sub〉w〈/sub〉), suggesting that the uncleaned dry plugs are strongly oil-wet. The positive correlations of TOC content with effective porosity and pressure-decay permeability indicate that a significant fraction of the pore space is within the organic matter, supported by the SEM images. The abundance of organic pores may explain the strong wetting affinity of the shale samples to oil. We observed negative and positive correlations between TOC content and equilibrated I〈sub〉o〈/sub〉 (I〈sub〉o〈/sub〉〈sup〉eq〈/sup〉) of UD and LD samples, respectively. This discrepancy can be explained by the smaller number of organic pores of UD samples with lower thermal maturity (oil window), confirmed by the results of SEM analysis and pore size distribution (N〈sub〉2〈/sub〉 sorption) tests. Furthermore, the free hydrocarbons content (S〈sub〉1〈/sub〉 in rock-eval data) in the form of oil in the UD samples is higher than that in the LD samples. The existence of free hydrocarbons content may reduce the pore space available for oil imbibition, leading to lower I〈sub〉o〈/sub〉〈sup〉eq〈/sup〉 for the UD samples with higher TOC content.〈/p〉 〈/div〉 〈/div〉