Double pyrovanadates CaMgV2O7: Formation mechanism,phase structure,and thermodynamic properties

A double pyrovanadate CaMgV₂O₇ sample was synthesized via a facile solid-state route under an air atmosphere. The nonequilibrium formation pathways of the CaMgV₂O₇ were investigated via powder X-ray diffraction. A multistep reactions path (metavanadates–pyrovanadates–double pyrovanadate CaMgV₂O₇) was proposed to describe the formation of the CaMgV₂O₇ considering the thermodynamic and kinetic factors. The cell unit parameters of the CaMgV₂O₇ sample indicated the crystallization according to a monoclinic system with space group P12/c1(14), and the lattice parameters of a = 6.756 Å, b = 14.495 Å, c = 11.253 Å, β = 99.12, and V = 108.806 Å³. X-ray photoelectron spectroscopy also confirmed the +5 oxidation state vanadium in CaMgV₂O₇. The endothermic effects at 1033 and 1143 K were related to the incongruent melting and liquidus temperatures of CaMgV₂O₇, respectively. The comprehensive thermodynamic properties of CaMgV₂O₇ were established in both low- and high-temperature regions, utilizing a physical property measurement system and multi-high-temperature calorimetry (96 lines). The heat capacity (200 J mol K⁻¹) and entropy (198 J mol K⁻¹) at 298.15 K were computed based on the low-temperature heat capacity values, and the enthalpy of formation at 298.15 K was also estimated. The fitted high-temperature capacity can be used to obtain the changes in the enthalpy, entropy, and Gibbs free energy. This study is part of building a reliable thermodynamic database of the CaO–MgO–V₂O₅ system.     

Simultaneous fractionation of multiple classes of polyphenols from honeybush tea using solid-phase extraction

The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min⁻¹ of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.     

Montmorillonite-perlite-iron ceramic membranes for the adsorption/removal of As(III) and other constituents from surface water

In this study, ceramic membranes made of montmorillonite, perlite and iron were used to remove As(III) from water. Membranes prepared with 0.0, 0.5, 1.0, and 1.5 wt% of iron content were used to filtrate As(III) synthetic water and surface water solutions. As(III) adsorption capacity and removal efficiency, and other parameters such as cations and anions content, turbidity, pH, electrical conductivity were used to evaluate the membranes' performance. Results show that the As(III) adsorption/removal capacity of membranes was improved by the addition of iron. Adsorption capacity of 7.5 μg As(III)/g and removal efficiency of 97% can be achieved in membranes with 1.0 wt% of iron filings content for surface water; however, a greater amount of iron in the membrane structure limits the adsorption capacity of As(III). Besides the capacity of ceramic membranes to adsorb/remove As(III), membranes were also effective to remove other ions, turbidity, and electrical conductivity from the surface water. The addition of iron to the ceramic membranes enhanced their capacity to remove such surface water constituents. These results are important from the practical viewpoint showing the potential of ceramic membranes for the removal of metalloids and other water constituents. Langmuir isotherm model best described the adsorption process in ceramic membranes, suggesting that adsorption of As(III) happened on a monolayered surface of the ceramic membrane.     

两种混合单元混合机理的数值模拟

为了研究SV型和SX型混合单元在全静态乳化器的混合机理,使用群体平衡模型对乳化器内部流场进行模拟分析。结果表明,SV型与SX型混合单元的混合机理是油相与水相材料通过混合单元时其空间流动方向改变,在流场内形成大量的漩涡,从而达到乳化的目的;通过比较流体在经过SV型和SX型混合单元后的水相索特平均直径(d_(32)),得出SV型混合单元的乳化效果更强,但同时消耗更多的能量,压降更大。     

Anchor plate bearing capacity in flexible mesh facings

This work addresses the problem of the loading capacity of an anchor plate coupled with a steel wire mesh in soil retaining applications. The interaction mechanism between the flexible mesh facing, the underlying soil layer and the plate is studied starting from the results of several laboratory punch tests involving both the plate and the mesh only, and the whole soil-mesh-plate system. The experimental tests have been reproduced by adopting a 3D discrete element model where also the wire mesh is discretized as an assembly of interconnected nodal particles. The interaction between these particles is ruled by elasto-plastic tensile force–displacement laws in which a distortion is introduced in a stochastic manner to account for the wires’ geometrical irregularities. The mesh model is then validated with reference to a set of punch tests in which the shape and size of the punching element as well as the nominal wire diameter were varied. Subsequently, the model is extended to a punch against soil test configuration permitting an insight into the nontrivial local mechanism between the mesh facing and the underlying granular layer. The good agreement between the numerical predictions and the experimental observations at the laboratory scale allowed us to extend the model towards more realistic field conditions for which the role of the mesh panel boundary conditions, the mesh mechanical properties, the soil mechanical properties and the anchor plate geometry is investigated.     

Consolidation considering increasing soil column radius for dredged slurries improved by vacuum preloading method

Soil column is often investigated in the improvement of dredged slurries. Different from the smear zone, the soil column forms gradually and has extremely low permeability. This study presents an analytical solution for soil consolidation considering the increasing radius of the soil column and time-dependent discharge capacity. Based on the solution, the influence of the radius' increase on the consolidation behavior is found significant when the soil column has low permeability and large final radius, and the increase of formation time can lead to the increase of consolidation speed and final consolidation degree.     

Finite element limit analysis of load-bearing performance of reinforced slopes using a non-associated flow rule

This paper presents a numerical study on the load-bearing performance of reinforced slopes under footing load using a finite element limit analysis (FELA) method where a non-associated flow rule is assumed in the analysis. The method was validated against results from full-scale model tests and a limit equilibrium (LE) analytical method. A series of parametric analyses was subsequently carried out to examine the influences that the soil dilation angle, footing location, and reinforcement design (i.e. length, tensile strength, and vertical spacing) could have on the load-bearing performance of reinforced slopes. Results indicate that dilation angle has a significant influence on the predicted magnitudes of bearing capacity, slope deformation, and mobilized reinforcement load. The predicted values of bearing capacity using the FELA are smaller than those from the Meyerhof's analytical method for unreinforced semi-infinite foundation, especially for larger friction angle values. Additionally, the ultimate bearing capacity of the slope and its corresponding horizontal deformation increase with the reinforcement tensile strength. Finally, the slip planes under the applied footing load are found to be y-shaped and primarily occur in the upper half of the slope.     

堆本体抗震试验动力相似关系推导与验证

为确保堆本体抗震试验中流体对流效应、脉冲效应和堆本体结构响应的准确性，需保证重力、流体与固体惯性力、结构弹性力和结构应变的相似性。本文从固体结构的振动方程、不可压牛顿流体的动力学方程、流固交界面的边界条件和环形柱体域内液体线性晃动的动力学公式出发，基于控制方程的量纲分析法，推导了考虑液体晃动效应的堆本体地震响应动力相似关系。基于上述相似关系建立了堆容器堆内构件和堆容器内自由液面流体域的缩尺模型，通过有限体积法分析堆容器堆内构件原型和缩尺模型中液体的晃动固有频率、晃动波高、压力以及液体晃动对堆容器支承裙的倾覆力矩。结果表明本文动力相似关系具有合理性和准确性，可用于堆本体缩尺模型的抗震试验研究。     

Thermodynamic properties of sodium hexatitanate (Na2Ti6O13) at high temperature (298.15–1573 K)

Sodium hexatitanate (Na₂Ti₆O₁₃) was reported as an anode side material for Sodium ion batteries owing to low material cost, high energy efficiency, good thermal stability and long cycle life. Therefore, studies pertaining to the thermodynamic properties of Na₂Ti₆O₁₃ are indispensable for improving its service performance. However, a significant number of literature reviews concerning thermodynamic properties indicated that heat capacity of Na₂Ti₆O₁₃ at high temperatures should be confirmed. In this study, the 99.5% purity of Na₂Ti₆O₁₃ sample was successfully prepared via solid-state reaction using TiO₂ and Na₂CO₃ as initial materials. Heat capacity of the as-synthesized samples in the temperature range of 573–1523 K was measured using a multi-high temperature calorimeter 96 line. Heat capacity, Cp, from 298.15 to 1573 K was modeled as a polynomial formula with a prediction error of 3%: Cp = 474.08143 + 0.06286T-8.04068 × 10⁶ T⁻² (J⋅mol⁻¹⋅K⁻¹). In combination with the low-temperature data, heat capacity of Na₂Ti₆O₁₃ from 0 to 1573 K was given in present study. Values of changes in enthalpy, Gibbs free energy and entropy in the temperature range of 298.15–1573 K were calculated based on the temperature dependence of heat capacity.     

分方位地震勘探研究现状及进展

从地震采集、处理和解释三方面总结了分方位角勘探的研究现状：1综合使用螺旋和蜗牛道集与震源同时激励，能够降低勘探成本并高效完成分方位地震野外采集；2炮检距向量片（OVT，Offset Vector Tile）技术是针对分方位观测带来的方位各向异性问题提出的，在处理过程中可以保留炮检距和方位角信息，提高地震成像精度；3充分利用地震波在裂缝型地层中传播时的能量衰减、相位和频率的方位各向异性信息是提高裂缝预测精度的有效手段，但目前在地震资料的处理中应用的实例很少。为了提高裂缝预测的准确性，今后应重点研究地震波的方位各向异性问题；4将多种随方位变化属性（如AVAZ等）与相干一致性融合，可有效检测地下裂缝和地层岩性，提高预测精度。