Molecular Volume of Phosphates, Arsenates and Vanadates

The present paper discusses some characteristics of the molecular volumes of phosphates, arsenates and vanadates. In the salts, the volumes of per acid radical ((?)) quantitatively depend on the radii, charges, numbers of cations and anions. The functional relations between the (?) values of phosphates, arsenates, vanadates and the factors mentioned above are obtained. The molecular volumes of these salts are equal to the sum of the topological volumes of cations and anions. The authors have got a series of universally united topological volume values of cations and anions. It confirms that the topological molecular volume of the crystal water (H_2O) in the hydrates of the salts approximates to a constant, 244 (?)~3 with σ_(n-1)= 2.1. The topological volume of the hydroxide ion (OH~-) approximates to a constant too. The average value is 16.89 (?)~3 with σ_(n-1)=1.68.     

空洞敏感材料有限变形中的横向变形系数

讨论了空沿敏感韧性及超塑性材料由于变形损伤引起的体积膨胀，提出了弹塑性有限变形下表征体积膨胀特性的横向主形系数在各向同性损伤条件下的解析表达式。     

Minimal volume invariants,topological sphere theorems and biorthogonal curvature on 4‐manifolds

The goal of this article is to establish estimates involving the Yamabe minimal volume, mixed minimal volume and some topological invariants on compact 4‐manifolds. In addition, we provide topological sphere theorems for compact submanifolds of spheres and Euclidean spaces, provided that the full norm of the second fundamental form is suitably bounded.     

Solution property preserving reconstruction for finite volume scheme: a boundary variation diminishing+multidimensional optimal order detection framework

The purpose of this work is to build a general framework to reconstruct the underlying fields within a finite volume (FV) scheme solving a hyperbolic system of PDEs (Partial Differential Equations). In an FV context, the data are piecewise constants per computational cell and the physical fields are reconstructed taking into account neighbor cell values. These reconstructions are further used to evaluate the physical states usually used to feed a Riemann solver which computes the associated numerical fluxes. The physical field reconstructions must obey some properties linked to the system of PDEs such as the positivity, but also some numerically based ones, like an essentially nonoscillatory behavior. Moreover, the reconstructions should be highly accurate for smooth flows and robust/stable for discontinuous solutions. To ensure a solution property preserving reconstruction, we introduce a methodology to blend high-/low-order polynomials and hyperbolic tangent reconstructions. A boundary variation diminishing algorithm is employed to select the best reconstruction in each cell. An a posteriori MOOD detection procedure is employed to ensure the positivity by recomputing the rare problematic cells using a robust first-order FV scheme. We illustrate the performance of the proposed scheme via the numerical simulations for some benchmark tests which involve vacuum or near vacuum states, strong discontinuities, and also smooth flows. The proposed scheme maintains high accuracy on smooth profile, preserves the positivity and can eliminate the oscillations in the vicinity of discontinuities while maintaining sharper discontinuity with superior solution quality compared to classical highly accurate FV schemes.     

A grid-based algorithm in conjunction with a gaussian-based model of atoms for describing molecular geometry

A novel grid-based method is presented, which in conjunction with a smooth Gaussian-based model of atoms, is used to compute molecular volume (MV) and surface area (MSA). The MV and MSA are essential for computing nonpolar component of free energies. The objective of our grid-based approach is to identify solute atom pairs that share overlapping volumes in space. Once completed, this information is used to construct a rooted tree using depth-first method to yield the final volume and SA by using the formulations of the Gaussian model described by Grant and Pickup (J. Phys Chem, 1995, 99 , 3503). The method is designed to function uninterruptedly with the grid-based finite-difference method implemented in Delphi, a popular and open-source package used for solving the Poisson–Boltzmann equation (PBE). We demonstrate the time efficacy of the method while also validating its performance in terms of the effect of grid-resolution, positioning of the solute within the grid-map and accuracy in identification of overlapping atom pairs. We also explore and discuss different aspects of the Gaussian model with key emphasis on its physical meaningfulness. This development and its future release with the Delphi package are intended to provide a physically meaningful, fast, robust and comprehensive tool for MM/PBSA based free energy calculations. © 2019 Wiley Periodicals, Inc.     

增加一种反应物浓度对反应物转化率影响的研究

通过建构模型探讨了多反应物平衡体系中增加反应物浓度对转化率的影响,并用曲线进行表征。模型表明,转化率的变化与反应物和生成物化学计量数相对大小关联紧密。文中结论澄清了某些错误认知,对中学化学教学有一定的指导意义。     

Positron annihilation and electrical studies on the influence of loading magnesia nanoribbons on PVA-PVP blend

This work aims to study the effect of loading magnesia (0.5–2.0 wt%) on the positron annihilation parameters and electrical properties of the PVA-PVP blend. The films were synthesized by solution casting and checked by different techniques. XRD and HR-TEM of sol-gel prepared magnesia revealed that the average crystallite size was 14.29 nm with ribbon-like morphology with varying widths and lengths up to a few micrometers. SEM showed that the blend surface appeared smooth and homogenous and this confirmed the compatibility between PVA and PVP. However, loading magnesia increased surface roughness. TGA confirmed the thermal stability enhancement of blend film with magnesia incorporation. Ortho–positronium lifetime τ₃ and the free volume $V_f$ decrease with loading magnesia while the intensity I₃ is nearly constant. These features were interpreted in view of the hole-filling mechanism, the interaction between magnesia & blend and magnesia morphology. The equilibrium swelling ratio ESR was found for the studied films and a positive correlation between ESR and $V_f$ was reported. The current density-electric field, J-E, characteristics were of non-ohmic type. J increased with increasing magnesia levels and heating. The Richardson-Schottky effect was the dominant dc conduction mechanism at low temperature and low magnesia loading levels while it changed to Poole–Frenkel emission at higher values. Finally, a correlation between Log J and the intensity I₂ was reported.     

Isomorph Invariance of Higher-Order Structural Measures in Four Lennard–Jones Systems

In the condensed liquid phase, both single- and multicomponent Lennard–Jones (LJ) systems obey the “hidden-scale-invariance” symmetry to a good approximation. Defining an isomorph as a line of constant excess entropy in the thermodynamic phase diagram, the consequent approximate isomorph invariance of structure and dynamics in appropriate units is well documented. However, although all measures of the structure are predicted to be isomorph invariant, with few exceptions only the radial distribution function (RDF) has been investigated. This paper studies the variation along isomorphs of the nearest-neighbor geometry quantified by the occurrence of Voronoi structures, Frank–Kasper bonds, icosahedral local order, and bond-orientational order. Data are presented for the standard LJ system and for three binary LJ mixtures (Kob–Andersen, Wahnström, NiY2). We find that, while the nearest-neighbor geometry generally varies significantly throughout the phase diagram, good invariance is observed along the isomorphs. We conclude that higher-order structural correlations are no less isomorph invariant than is the RDF.     

DVC analysis of a polymer material subjected to tensile loading with synchrotron radiation tomography

Subsurface deformation behavior of a polymeric material is studied through the digital volume correlation (DVC) technique. Fundamental principles of the DVC technique are presented and the supplemental state-of-the-art algorithmic schemes to improve the efficiency and accuracy of the DVC analysis are also introduced. Tensile tests on an epoxy material are performed in conjunction with synchrotron radiation tomography. In order to create randomly distributed grayscale values in the tomograms for the following image analysis, microscale high-density particles are embedded when the epoxy specimens are fabricated. 3D tomographic images taken at multiple loading steps are utilized for the DVC analysis. The performance of the present DVC analysis is evaluated with the experimental data.