Molecular mechanics and dynamics simulation of hydrogen diffusion in aluminum melt

The main impurities in aluminum melt are hydrogen and Al_2O_3,which can deteriorate melt quality and materials performance.However,the diffusion process of H atoms in aluminum melt and the interactions among Al atoms,Al_2O_3 and hydrogen have been studied rarely.Molecular mechanics and dynamics simulations are employed to study the diffusion behaviors of different types of hydrogen,such as free H atoms,H atoms in H_2 and H^+ions in H_2O using COMPASS force field.Correspondingly,force field types h,h1h and h1o are used to describe different types of hydrogen which are labeled as H_h,H_(h1h) and H_(h1o).The results show that the adsorption areas are maximum for H_(h1o),followed by H_(h1h) and H_h.The diffusion ability of H_(h1o) is the strongest whereas H_h is hard to diffuse in aluminum melt because of the differences in radius and potential well depth of various types of hydrogen.Al_2O_3 cluster makes the Al atoms array disordered,creating the energy conditions for hydrogen diffusion in aluminum melt.Al_2O_3 improves the diffusion of H_h and H_(h1o),and constrains H_(h1h) which accumulates around it and forms gas porosities in aluminum.H_(h1o) is the most dispersive in aluminum melt,moreover,the distance of Al-H_(h1o) is shorter than that of Al-H_(h1h),both of which are detrimental to the removal of H_(h1o).The simulation results indicate that the gas porosities can be eliminated by the removal of Al_2O_3 inclusions,and the dispersive hydrogen can be removed by adsorption function of gas bubbles or molten fluxes.

Clinical Data-Driven Finite Element Analysis of the Kinetics of Chewing Cycles in Order to Optimize Occlusal Reconstructions Dedicated to Professor Karl Stark Pister for his 95th birthday

The occlusal design plays a decisive role in the fabrication of dental restorations.Dentists and dental technicians depend on mechanical simulations of mandibular movement that are as accurate as possible,in particular,to produce interference-free yet chewing-efficient dental restorations.For this,kinetic data must be available,i.e.,movements and deformations under the influence of forces and stresses.In the present study,so-called functional data were collected from healthy volunteers to provide consistent information for proper kinetics.For the latter purpose,biting and chewing forces,electrical muscle activity and jaw movements were registered synchronously,and individual magnetic resonance tomograms(MRI)were prepared.The acquired data were then added to a large complex finite element model of the complete masticatory system using the functional information obtained and individual anatomical geometries so that the kinetics of the chewing process and teeth grinding could be realistically simulated.This allows developing algorithms that optimize computer-aided manufacturing of dental prostheses close to occlusion.In this way,a failure-free function of the dental prosthesis can be guaranteed and its damage during usage can be reduced or prevented even including endosseous implants.

Modeling and simulation of temperature control system in plant factory using energy balance

Closed production systems,such as plant factories and vertical farms,have emerged to ensure a sustainable supply of fresh food,to cope with the increasing consumption of natural resource for the growing population.In a plant factory,a microclimate model is one of the direct control components of a whole system.In order to better realize the dynamic regulation for the microclimate model,energy-saving and consumption reduction,it is necessary to optimize the environmental parameters in the plant factory,and thereby to determine the influencing factors of atmosphere control systems.Therefore,this study aims to identify accurate microclimate models,and further to predict temperature change based on the experimental data,using the classification and regression trees(CART)algorithm.A random forest theory was used to represent the temperature control system.A mechanism model of the temperature control system was proposed to improve the performance of the plant factories.In terms of energy efficiency,the main influencing factors on temperature change in the plant factories were obtained,including the temperature and air volume flow of the temperature control device,as well as the internal relative humidity.The generalization error of the prediction model can reach 0.0907.The results demonstrated that the proposed model can present the quantitative relationship and prediction function.This study can provide a reference for the design of high-precision environmental control systems in plant factories.

AN EXPERIMENTAL SIMULATION ON THE MECHANICAL EFFECT OF TIBETAN PLATEAU ON ZONAL CIRCULATION OF STRATIFIED ATMOSPHERE

The present work is intended to simulate, in a rotating annulus of stratified liquid, the me-chanical effect of the Xizang (Tibetan) Plateau on the zonal circulation. The main featuresof three flow patterns around the plateau for different Rossby number R and rotating Eulernumber E are analysed. and a division diagram of the flow pattern in (R, E) plane is given.It has been found that under the condition that similarity criterions R and E of the experimentalfluid are the same as those existing in the atmosphere for monthly mean states in spring, au-tumn and winter months, the experimental results are satisfied for the following weathersystems over the plateau and its vicinities: the low vortex, trough and shear line over thesoutheast part of the plateau, the tilted ridge over the northwest part of the plateau, the troughpatterns over the upstream and dewnstream of the plateau, the vertical circulation structure, thejets on both north and southeast sides of the plateau, and so on. This shows that the

Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity,ionic strength and pH.A mathematical model was used to simulate the mass transfer mechanism,taking film mass transfer,pore diffusion and axial dispersion into account.The model predictions were consistent with the experi-mental data and were consequently used to determine the mass transfer coefficients.

Research on mechanics properties of crop stalks:A review

As one of the foundational research areas in agricultural engineering,the study of agricultural materials includes an important branch:mechanics properties of crop stalks.This branch is now widely associated with design and improvement of agricultural equipment,breeding of new species,and development of reinforced composites.This article presents an overview of research on mechanics properties of crop stalks,including the mechanics measurement experiments,mechanics model and theory,microstructure and composition,and mechanics simulation experiments.The current research relies mainly on the mechanics theory of engineering material,neglects the fact that crop stalk is a biological material with complex structure,anisotropy,viscoelasticity and rheology.In addition,some simulation experiments are conducted in idealized conditions,beyond the application.Hence,the paper proposes to create new material models for crop stalks,conduct more practical and effective simulation experiments,and promote cooperation in interdisciplinary studies for the development of mechanics properties of crop stalks in the future research.