We investigate collision characteristics of micro-sized particles (diameter less than 100 microns) via numerical simulations and experiments. Discrete element method (DEM) simulations, based on improved hard-sphere model, are performed to explore effect of initial velocity, surface energy, size, mass concentration, and wind speed on cohesive collisions and non-cohesive collisions between micro-sized particles. Aggregation and settlement process are considered as well. It is found that simulated cohesive collision rate agrees with experimental results of self-settlement of micro-sized particles.

The core philosophy of Material Genome Initiative is transition of way of new material design from traditional "try-and-error" approach to in-silico material design approach where intensive computing and material informatics are employed. It aims to effectively speed up discovery, development, production and deployment of new material two times faster as it is now. It means a culture shift of new material discovery:simulation and prediction first, followed by experiment. An integrated computational material platform that can facilitate high-throughput quantum mechanical simulations and manage simulation lifecycle data is therefore vital. This paper depicts a high throughput computational material platform and software framework, namely, MatCloud, which effectively integrates individual quantum mechanical simulation tasks, data extraction and data storage into an automatic flow in an end-to-end manner without direct human control. Especially, core data curation activities are also integrated into this flow rather than happening at post-simulation stage separately. MatCloud is demonstrated in an example of disorder binary alloy design to be valid and effective.

Based on two-grid discretizations,three two-level subgrid stabilized finite element algorithms for stationary Navier-Stokes equations at high Reynolds numbers are proposed and compared. Basic idea of the algorithms is to solve a fully nonlinear Navier-Stokes problem with a subgrid stabilization term on a coarse grid,and then solve a subgrid stabilized linear fine grid problem based on one step of Newton,Oseen or Stokes iterations for Navier-Stokes equations.It shows that with suitable stabilization parameters and coarse and fine grid sizes,those algorithms yield an optimal convergence rate. Finally, numerial results are given to show efficiency of the algorithms.

One of key issues in high energy density physics is clarification of transport and energy deposition of laser-produced fast electrons traveled through dense plasma. However, modeling these systems numerically is still a great challenge. In this paper, we introduce a PIC/fluid hybrid model. In this hybrid method, fast electrons are modeled by a relativistic Fokker-Planck equation, which numerically solved by reducing it to equivalent stochastic differential equations. Background electrons and ions are treated as two-fluid model. Collisions, electric and magnetic fields, and evolutions of resistivity due to heating of background are included. Treatment is valid for fast electron number densities much less than that of background, fast electron energies much greater than background temperature, and time scales short enough that magnetic diffusion and thermal conduction can be negligible. Model of ionization and resistivity also determine validity of the model.

Effects of gate underlap on electronic properties of conventional single-material-gate CNTFET (C-CNTFET) and heteromaterial-gate CNTFET (HMG-CNTFET) are investigated theoretically in a quantum kinetic model.The model is based on twodimensional non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that intrinsic cutoff frequency of C-CNTFETs reaches a few THz.In addition,a comparison study was performed about C-and HMG-CNTFETs.Calculated results show that,C-CNTFETs with longer underlap have better switching speed but less on/off current ratios.For HMG-CNTFET,gate underlap improves sub-threshold performance and switching delay times,and decreases output conductance significantly.

Ballistic performance of single-material-gate and triple-material-gate graphene nanoribbon field effect transistors (GNRFETs) with various doping profiles is studied in a quantum kinetic model based on non-equilibrium Green's functions (NEGF) solved self-consistently with Poisson's equations.It shows that triple-material-gate GNRFET with linear doping (TL-GNRFET) exhibits significant advantage in reducing SCEs and DIBL effects,as well as achieving better subthreshold slope and better on/off current ratio.In addition,asymmetric gate underlap is also discussed.It is revealed that as top and bottom gates are both shifted towards source on/off state current performance is improved.

To understand performance of molten salt heat transfer and thermal storage in solar thermal power system, thermodynamic properties of cubic KNO₂ under atmospheric pressure and temperatures between 300 and 725 K are studied with density functional theory combined with a quasi-harmonic Debye model. Temperature dependence of isobaric heat capacity, isochoric heat capacity, entropy, Debye temperature, volume thermal expansion coefficient, equilibrium volumes and bulk modulus under ambient pressure are calculated. It shows that calculated isobaric heat capacities are in good agreement with experiments under ambient pressures. Both entropy vary greatly. The average volume thermal expansion coefficient-is 1.837 8×10^-5K^-1 and Debye temperature is 667.13K at ambient temperatures, respectively.

To design a high-order accurate shock capturing method for hyperbolic conservation laws,we introduce a new power limiter to obtain a second-order power NND scheme and a third order power WNND scheme based on modification of NND scheme and WNND scheme.By applying the limiter to first-order differences of the candidate stencils,the power NND scheme and the power WNND scheme reduce the smearing near discontinuities.The power NND scheme and the power WNND scheme show less dissipation and less spurious oscillations,and catch the discontinuities more accurately than NND scheme and WNND scheme.The results of power NND scheme are similar to those of WNND scheme,and even better in some examples.The simulation of forced oscillation of the NACA0012 airfoil by power WNND scheme is in good agreement with experiments.

A practical and efficient computation method for stable and unstable manifolds is proposed.Pictures of unstable (stable) manifolds are obtained easily.Thus one can investigate geometrically dynamics of a dynamical system and features of stability regions.The algorithm consists of two steps:Firstly,calculate on well distributed points in the unstable manifold by means of integration so that details of the unstable manifold are shown.Secondly,draw a picture of the manifold with these points by means of triangle partition.

Results of existence,uniqueness and stability recovering the domain from a measured data of Poisson equation are obtained.The results of determining the shape of unknown domain are proven with Sobolev theory and the fundamental solution of Poisson equation.

The laminar flow and heat transfer of water in periodic fully-developed divergent-convergent channels has been investigated numerically.The SIMPLE algorithm and body-fitted coordinates (BFC) are used.The periodic boundary condition is treated using the method proposed by Amano.It is found that under the range of Re=100~1 000,the friction factor is about 10%~200% more than that of parallel plate channel,while the average Nusselt number is about 40%~320% more than that of parallel plate channel.

Based on Delaunay triangulation an algorithm is presented for generation triangle mesh over any planar domain which have complicated characteristic constraints.Charateritic constraints in a planar domain can be constructed by point,line,circle,arc,spline curves,open loops and closed loops which are made up of them.