Accurate Polarization Energies from Force Fields

The distributed point polarizable water model (DPP2) [Ref 1] which was recently developed in our group, has explicit terms for induction, charge penetration, and charge transfer. It is a refinement of the DPP model [Ref 2] which was also developed in our group. The DPP2 model has been found to accurately describe the interaction energy in water clusters. In this work, we aim to further improve the accuracy of DPP2 in calculating the induction energy. There are two ways to model higher-order polarization effects, one is through distributed atomic dipole polarizabilities, the other is through single-center expansion with higher multipoles. We developed a fitting method which can map the distributed dipole polarizabilities into the dipole-dipole (α), dipole-quadrupole (A) and quadrupole-quadruple (C) polarizabilities. DPP2 uses three distributed atomic polarizabilities〖 α〗_O,α_H1,α_H2 which are located on oxygen and hydrogen atoms to describe induction effects. We show that the A and C values associated with the DPP2 model differ appreciably from the results of high level ab-inito methods [Ref 3, 4, 5, 25]. We have explored several strategies for improving on the DPP2 results. We describe a 4-site polarizable model, in which we split the polarizability of oxygen onto its two lone-pair sites, and which gives results in good agreement with the ab-initio calculations

Relationship of rock microscopic parameters with the elastic modulus and strength

The microscopic damage of materials will induce changes in the macroscopic mechanical characteristics of rock material. When simulating engineering problems using the discrete element method, to explore the macroscopic mechanical response of rock material, the microscopic parameters that match the macro material characteristics must be obtained. In this paper, the influence of macroscopic mechanical properties of rock materials is studied through the variation of microscopic parameters, and the quantitative relation between macroscopic parameters of rock material is discussed. The results show that, (1) In accordance with the order of influencing factors, the parameters affecting the elastic modulus of the specimen are parallel bond elastic modulus, particle contact modulus, and parallel bond stiffness ratio. (2) The Poisson’s ratio of the specimen was most influenced by the parallel bond stiffness ratio, and their relation was nonlinear. The influence of parallel bond modulus and friction factor on the Poisson’s ratio was negatively correlated. (3) The effect of particle contact stiffness ratio, parallel bond stiffness ratio, and particle contact modulus on the uniaxial compressive strength was less than that of the particle friction factor

The impact of pension insurance types on the health of older adults in China: a study based on the 2018 CHARLS data

IntroductionPension insurance is an essential safeguard for the quality of life and health of older adults because it provides a stable and dependable source of income after retirement. China has constructed a multi-level social security system to accommodate the diverse needs of older adults, and offers various levels of pension insurance to maximize their interests.MethodsThis study uses propensity score matching and ordinary least squares techniques to analyze 7,359 data from the 2018 China Health and Retirement Longitudinal Study (CHARLS) in order to explore the relationship between different pension insurance categories and the health of older individuals.ResultsThe research findings reveal that advanced insurances greatly benefit the health of older adults more than basic pension insurances, and the findings pass the robustness test. In addition, the effect was found to be heterogeneous, depending on the location of retirement and the marital status of older adults.Our findings suggest that both material and non-material consumption may be potential mechanisms by which pension insurance affects the health of older adults, providing new evidence for the causal mechanism between pension insurance and the health of older adults.DiscussionThis study expands the scope of research on the health effects of pension insurance by covering a large representative sample across the country. The results show the important impact of the level of pension insurance on the health of older adults and can contribute to the development of social policies to promote the physical and mental health of older adults

Human 3D Avatar Modeling with Implicit Neural Representation: A Brief Survey

A human 3D avatar is one of the important elements in the metaverse, and the modeling effect directly affects people's visual experience. However, the human body has a complex topology and diverse details, so it is often expensive, time-consuming, and laborious to build a satisfactory model. Recent studies have proposed a novel method, implicit neural representation, which is a continuous representation method and can describe objects with arbitrary topology at arbitrary resolution. Researchers have applied implicit neural representation to human 3D avatar modeling and obtained more excellent results than traditional methods. This paper comprehensively reviews the application of implicit neural representation in human body modeling. First, we introduce three implicit representations of occupancy field, SDF, and NeRF, and make a classification of the literature investigated in this paper. Then the application of implicit modeling methods in the body, hand, and head are compared and analyzed respectively. Finally, we point out the shortcomings of current work and provide available suggestions for researchers.Comment: A Brief Surve