Dynamics of Vesicle Suspensions in Shear Flow Between Walls

The behaviour of a vesicle suspension in a simple shear flow between plates (Couette flow) was investigated experimentally in parabolic flight and sounding rocket experiments by Digital Holographic Microscopy. The lift force which pushes deformable vesicles away from walls was quantitatively investigated and is found to be rather well described by a theoretical model by Olla (J Phys II (France) 7:1533, 1997). At longer shearing times, vesicles reach a steady distribution about the center plane of the shear flow chamber, through a balance between the lift force and shear induced diffusion due to hydrodynamic interactions between vesicles. This steady distribution was investigated in the BIOMICS experiment in the MASER 11 sounding rocket. The results allow an estimation of self-diffusion coefficients in vesicle suspensions and reveal possible segregation phenomena in polydisperse suspensions.     

Transport in Fermi Liquids Confined by Rough Walls

I present theoretical calculations of the thermal conductivity of Fermi liquid \(^3\) He confined to a slab of thickness of order \(\sim \) 100 nm. The effect of the roughness of the confining surfaces is included directly in terms of the surface roughness power spectrum which may be determined experimentally. Transport at low temperatures is limited by scattering off rough surfaces and evolves into the known high-temperature limit in bulk through an anomalous regime in which both inelastic quasiparticle scattering and elastic scattering off the rough surface coexist. I show preliminary calculations for the coefficients of thermal conductivity. These studies are applicable in the context of electrical transport in metal nanowires as well as experiments that probe the superfluid phase diagram of liquid \(^3\) He in a slab geometry.     

Gas Flow in a Plane Channel with Oscillating Walls

Gas oscillations occurring in a plane channel in excitation of elastic walls which is symmetric relative to the longitudinal axis are investigated by the methods of numerical modeling. The spatial localization of transverse and longitudinal waves has been revealed and the character of resonance oscillations of the gas in the vicinity of the excitation region for different velocities of the flow has been established.     

A Mineral Liberation Model for Confined Particle Bed Breakage

ABSTRACT

The advent of High Pressure Grinding Rolls technology in the minerals industry has created an interest in the particle bed mode of breakage, not only because of its energy saving qualities, but also due to its apparent enhanced mineral liberating properties. Little scientific evidence exists to substantiate any enhanced liberation properties. Automated image analysis and stereological correction methods have now made it possible to measure mineral liberation quite accurately. A population balance mineral liberation model, based on QEM*SEM liberation data of confined particle bed breakage products of a binary ion oxide core, is presented. The selective breakage observed, due to the differential breakage properties of the respective phases, is described. Preferential breakage is incorporated into a liberation model for the first time.     

Finite-Size Effects of Surface Tension in Two Segregated BECs Confined by Two Hard Walls

The finite-size effects of the surface tension in two segregated Bose–Einstein condensates limited by two hard walls are studied respectively in canonical ensemble and grand canonical ensemble by means of the Gross–Pitaevskii theory in the modified double-parabola approximation. The analytical formulae of surface tensions and their finite-size effects are found together with a new type of long-range forces acting on two walls.     

A Field-Network Model of a Linear Oscillating Motor and Its Dynamics Characteristics

We describe a method of modeling of the dynamics characteristics for linear oscillating motors. We used electromagnetic finite-element analysis in the network model, which contains the electric circuit and mechanical equations. We compared the integral parameters of the electromagnetic field with the measured ones. We also compared the calculated and measured waves of the stator current for two values of supply voltage. The comparison yields a good agreement.     

杜仲胶/天然橡胶共混物的分子动力学模拟和耗散粒子动力学模拟

应用分子动力学(MD)和耗散粒子动力学(DPD)模拟方法对杜仲胶(TPI)、天然橡胶(NR)的相容性进行了研究.采用MD模拟方法,在COMPASS力场下,对纯物质在不同聚合度下的溶度参数、一系列共混比的TPI/NR共混物内聚能密度、Flory- Huggins作用参数进行了模拟计算,确定了纯物质单链的聚合度,经判断各比例共混物的相容性均较好;采用DPD模拟方法对TPI/NR共混体系的相结构进行了研究,从等密度图可以进一步判断共混体系的相容性;分析比较两种纯物质的径向分布函数,揭示了其相互作用的本质;经过分析比较静态力学性能,发现共混比为1/3的TPI/NR共混物性能最佳,其结论与实验结果一致.     

Dynamics of Vortices and Solitons in a Bose-Einstein Condensate by an Oscillating Potential

We study numerically the dynamics of quantized vortices and solitons induced by an oscillating potential inside a trapped Bose-Einstein condensate. The dynamics of the topological defects is much different from the case for a linear uniform moving object; the metamorphosis between vortices and solitons is characteristic of the dynamics. We discuss how vortices are nucleated by an oscillating potential.     

基于粒子滤波的液态场环境声源定位方法

研究了石油储罐罐底腐蚀声发射源的定位方法.针对有限空间液态场中水声信号的多途效应严重影响声源目标定位问题,提出一种基于粒子滤波的到达时间差(TDOA)声源定位方法,充分考虑广义互相关结果中多途效应导致的多个峰值,采用高斯似然函数进行重要性采样,实现对多途效应影响的抑制.水池实验结果表明这种方法比传统的Chan方法具有更高的定位准确性和精度,定位结果的均方根误差(RMSE)为Chan方法的10%,提高了定位性能.     

Interaction Between Domain Walls in Chiral p-Wave Superfluids

We calculate microscopically the interaction energy of domain walls separating degenerate ground states in a chiral p-wave fermionic superfluid. The interaction is mediated by the quasiparticles experiencing Andreev scattering at the domain walls. As a by-product, we derive a useful general expression for the free energy of an arbitrary nonuniform texture of the order parameter in terms of the quasiparticle scattering matrix.     

Nonlinear Dynamics of Spin Structure in Confined Bose–Einstein Condensates

Nonlinear wave propagations in spinor Bose–Einstein condensates confined strongly along an axial direction are studied. Due to the confinement induced effects, there exist a variety of soliton solutions with the magnetic properties.     

MPP并行机上数亿粒子规模的分子动力学模拟

提出一种基于“块-单元-链表”数据结构和HSFC动态负载平衡的并行分子动力学算法,实现了大规模、非均匀分子动力学模拟的基于MPI的可扩展并行计算,以辅助物理学家实现具有实验意义的纳米级模拟。具体地,在某MPP并行机的240个CPU上,计算3．84亿(二维)和2．76亿(三维)个粒子规模的金属微喷射问题,均获得了209倍以上的加速比。     

Transverse Motion of a Particle with an Oscillating Charge and Variable Mass in a Magnetic Field

The problem of motion of a particle with an oscillating electric charge and variable mass in an uniform magnetic field has been solved. Three laws of mass variation have been considered: linear growth, oscillations, and stepwise growth. Analytical expressions for the particle velocity at different time dependences of the particle mass are obtained. It is established that simultaneous consideration of changes in the mass and charge leads to a significant change in the particle trajectory.     

Dielectric Spectroscopy of Water Confined Between Aerosil Nanoparticles and in Vycor Nanoporous Glass

The dynamic properties of water dispersed in compacted aerosils and confined in Vycor porous glass have been investigated by means of dielectric relaxation spectroscopy. The measurements were performed in the frequency range from 10⁻² to 10⁷ Hz and in the temperature range from 123 to 300 K. Multiple relaxation processes in bulk water, in water dispersed with aerosil particles, and in Vycor glass were observed. By comparing the presence and absence of the processes in the different samples, it was established that part of the water in confinement crystallizes to a bulk-like ice, whereas the water close to the surfaces evolved to a different phase.     

激光粒度分析和筛分法测粒径分布的比较

分别采用筛分法和马尔文激光粒度分析仪两种方法对16种颗粒的粒径分布进行了测量。通过比较,发现两种测量手段得到的粒径分布结果存在较大的差异,马尔文激光粒度方法对颗粒粒径的测量结果偏小,受颗粒形状的影响很大;筛分法对微细颗粒的测量误差较大,但对大粒径颗粒的测量较为准确。通过对不同粒径段灰颗粒的显微照相,发现细颗粒的团聚是筛分法测量小颗粒结果偏小的主要原因。     

柔性悬吊平台光电系统动力学分析

提出了一种基于地平式光电经纬仪并带有姿态稳定装置的柔性悬吊平台光电系统的结构,以实现精密指向.根据系统各部件之间的运动学关系,采用通路矩阵,约束力元矩阵等方法描述了系统的拓扑构型.采用拉格朗日方法建立了系统的多刚体动力学模型.仿真实验研究了平台绕垂线的转动以及垂线-地平面内的摆动对视轴指向精度的影响.仿真结果:若系统沿垂线方向的转动惯量在10~3kg·m~2量级,反捻机构残余力矩10~(-2)N·m的量级,方位轴的控制指向精度与光电传感器的分辨率精度相当,可以达到10~(-5)rad.如果缆绳的长度在10 m数量级,系统绕摆动轴的转动惯量将达到10~5～10~7kg·m~2量级.平台的摆动幅度在0.017 rad时,视轴的指向控制精度可以控制在10~(-4) rad量级.仿真结果表明:反捻机构开启,光电系统指向控制能力强时,可以不对平台进行姿态控制.另外,摆动将造成经纬仪两个轴系的耦合.     

Dissipative Particle Dynamics investigation of parameters affecting planar nanochannel flows

The method of Dissipative Particle Dynamics is applied to investigate the effect of the parameters involved in a nano-channel Poisseuille flow. The parameters considered here include (a) fluid/wall interactions, (b) wall material, (c) range of interaction of fluid particles and wall particles, and (d) external applied force. The computed macroscopic quantities include density, velocity, pressure and temperature profiles. Fluid particle localization near the solid wall is affected by the conservative force (fluid/wall interactions), the wall number density, and the range of atomic interactions (cut-off radius). The external driving force magnitude does not affect the number density distribution. Fluid velocity increases as the conservative force and the wall density increase and the cut-off radius decreases. Pressure distribution is mainly affected by the conservative force and the interaction cut-off radius. Temperature is uniform across most of the channel but presents an increase close to the solid walls especially when increasing the external driving force. We believe that the detailed knowledge of the fluid behaviour under variation of the system parameters obtained from the DPD simulations could be helpful in the design of nanodevices such as lab-on-a-chip devices and nanomixers.     

Superfluid Confined to the Space Between Rotating Spheres. I. Equilibrium States

The critical velocity of the first vortex generation in a superfluid confined to the space between two rotating concentric spheres as well as the width of an irrotational area and the equilibrium number of vortices are determined.     

粉碎能耗与粒度分布指数的相关性

利用分形和分维数基本概念,导出粉粒度分布的分维数和分裂比、粉碎概率互相存在的简单关系,从能耗与颗粒表面分维数相关出发,推出单位体积粉碎能耗与粒度分布的值指数的相关性;同时推出单位体积粉碎能耗的分维数.当粉碎粒度分布的分维数近似小于0.89时,粉碎能耗呈现自然分形的特征.