椭球壳及椭球体转动惯量的简易推导

本文利用微积分方法,给出计算球壳、球体转动惯量的一种简易办法,又利用正交轴定理,给出椭球壳、椭球体的转动惯量.     

含有密集随机分布内核的椭球粒子光散射特性研究

给出了一种结合射线追踪和蒙特卡罗方法计算含核粒子光散射的方法,内核粒子可以为稀疏分布也可为浓密分布.粒子外边界的反射和折射由射线追踪方法计算,而粒子内部的多次散射过程由蒙特卡罗方法模拟;当内核粒子为浓密随机分布时,其单次散射特性由基于静态结构因子（static structure factor）的浓密介质光散射理论计算.最后讨论了含核椭球粒子模型的单次散射特性. 关键词： 射线追踪技术 蒙特卡洛方法 光散射 椭球粒子     

取向比对椭球气溶胶粒子散射特性的影响

利用T矩阵和离散坐标法研究了取向比对椭球粒子散射特性的影响, 计算了小尺度范围内椭球粒子的散射特征参量, 包括消光效率因子、不对称因子、单次散射反照率、散射相矩阵及双向反射函数(BRDF). 结果表明, 椭球粒子的散射特性与取向比密切相关, 粒子取向比会影响散射参量的振荡频率和振幅, 与球形粒子散射参量的相对差异也呈周期振荡趋势. 研究还发现, 某些特殊粒子尺寸的散射参量与粒子取向比基本无关. 在多次散射条件下, 分析不同取向比粒子群的BRDF随反射角和光学厚度的变化特性. 结果显示: 不同取向比粒子群的BRDF随反射角的变化趋势基本一致, 球形粒子群比非球形粒子群的BRDF曲线波动振幅更大; 球形-非球形粒子的BRDF相对差异随光学厚度和取向比的增大而减小, 随入射角的增大而增大.     

随机取向双层椭球粒子偏振散射特性研究

基于T矩阵方法,给出了随机取向、轴对称、含核椭球粒子的散射计算方法.散射体的核和外壳均可为非球形粒子,整个粒子具有轴对称性.以含核椭球粒子为模型,计算了含有吸收性内核(黑炭,black carbon)的水凝物气溶胶的散射特性,分析了核的大小、形状对消光系数、散射系数、吸收系数、不对称因子、单次散射反照率以及Muller矩阵等的影响. 关键词： 光散射 T矩阵 Muller矩阵 椭球粒子     

随机取向群聚椭球粒子光散射特性研究

利用离散偶极子近似方法,考虑单元粒子之间的电磁相互作用,数值计算了随机取向的不同尺度参数、不同纵横比的群聚椭球粒子的缪勒矩阵元素,给出了各个缪勒矩阵元素的角分布曲线,探讨了随机取向的群聚椭球粒子的尺度参数、纵横比、基本粒子相对位置对其缪勒矩阵元素的影响。并将随机取向群聚椭球粒子的光散射特性与单个等效球形粒子的数值结果进行了比较。结果表明,随机取向群聚椭球粒子的光散射特性与等效球形粒子的光散射特性存在很大差别,基本粒子的形状越偏离球形,这种差别就越大; 随机取向群聚椭球粒子中椭球粒子的纵横比和相对位置对整个群聚粒子的缪勒矩阵元素存在不同程度的影响,并且此影响随着粒子尺度参数的增大而变得更加显著。     

随机取向纳米石墨椭球粒子的红外消光特性

利用离散偶极子近似(DDA)方法研究了椭球形的纳米石墨粒子的红外消光特性。计算了不同形状的椭球粒子红外消光截面随波长变化规律,并与等效球形粒子的消光性能进行了比较,分析了不同入射波长时,椭球粒子形状和粒径对消光的影响。结果表明,椭球状的纳米石墨粒子红外消光性能好于等效球粒子的消光性能,椭球粒子的最佳消光等效粒径与轴长比和入射波长有关。     

随机取向群聚椭球粒子光散射特性研究

利用离散偶极子近似方法,考虑单元粒子之间的电磁相互作用,数值计算了随机取向的不同尺度参数、不同纵横比的群聚椭球粒子的缪勒矩阵元素,给出了各个缪勒矩阵元素的角分布曲线,探讨了随机取向的群聚椭球粒子的尺度参数、纵横比、基本粒子相对位置对其缪勒矩阵元素的影响。并将随机取向群聚椭球粒子的光散射特性与单个等效球形粒子的数值结果进行了比较。结果表明,随机取向群聚椭球粒子的光散射特性与等效球形粒子的光散射特性存在很大差别,基本粒子的形状越偏离球形,这种差别就越大; 随机取向群聚椭球粒子中椭球粒子的纵横比和相对位置对整个群聚粒子的缪勒矩阵元素存在不同程度的影响,并且此影响随着粒子尺度参数的增大而变得更加显著。     

带电导体椭球的电势和电荷分布

介绍用椭球坐标系求带电导体椭球所产生的电势和它上面电荷分布的方法,并讨论一些特殊情况.     

均匀带电旋转椭球体的静电能及电势分布

本文利用特殊函数－勒让德函数计算了均匀带电旋转椭球体的静电能及其在远处所产生的静电势。     

电介质椭球内极化场强方向的研究

导出了椭球体内极化场强方向与外电场方向之间夹角大小的表达式,并对其进行了数值计算,分析认为对于椭球体而言,其体内的极化场强方向并不一定严格和外电场方向相反。     

约束条件下胶球间排空力的研究

用MonteCarlo方法对处于两平行硬板约束下三个浓度的大小胶球系统进行了模拟,通过对大胶球表面小胶球密度的统计,由密度积分公式获得了大胶球所受的排空力.研究结果显示,因为平行硬板的存在或当改变两平行硬板的距离时,同浓度下,排空力在硬板距离小的时候最明显;三个浓度中,浓度高的,排空力受硬板距离影响最大;有硬板约束比无该约束的时候,排空力效果更显著.     

Confinement limit of a Dirac particle in two and three dimensions

Consider a particle that is in a stationary state described by the Dirac equation with a finite-range potential. In two and three dimensions the particle can be confined to an arbitrarily small spatial region. This is in contrast to the one-dimensional case in which the confinement region cannot be much narrower than the Compton wavelength.     

Confined Quantum Hard Spheres

We present computer simulation and theoretical results for a system of N Quantum Hard Spheres (QHS) particles of diameter σ and mass m at temperature T, confined between parallel hard walls separated by a distance Hσ, within the range 1≤H≤∞. Semiclassical Monte Carlo computer simulations were performed adapted to a confined space, considering effects in terms of the density of particles ρ*=N/V, where V is the accessible volume, the inverse length H−1 and the de Broglie’s thermal wavelength λB=h/2πmkT, where k and h are the Boltzmann’s and Planck’s constants, respectively. For the case of extreme and maximum confinement, 0.5<H−1<1 and H−1=1, respectively, analytical results can be given based on an extension for quantum systems of the Helmholtz free energies for the corresponding classical systems.     

Confinement models for gluons

Confinement model for gluons using a ‘colour super current’ is formulated. An attempt has been made to derive a suitable dielectric function corresponding to the current confinement. A simple inhomogeneous dielectric confinement model for gluons is studied for comparison. The model Hamiltonians are second quantized and the glueball states are constructed. The spurious motion of the centre of confinement is accounted for. The results of the current confinement scheme is found in good agreement with experimental candidates.     

Confinement of tensor gluons — a classical approach

We look at the confinement of tensor gluons (f _μν ^(c) field) in a strong gravity background and find that the strong gravity provides a trap for the confinement of colour waves of selected frequencies. We assume that the tensorf _μν ^(c) field (mediating quanta: tensor 2⁺ f-meson) satisfies Einstein-like equations with a cosmological constant. The colour field satisfy equations resembling Maxwell form of the linear theory of gravitation and see the effect off _μν ^(c) field as playing the role of a medium having space dependent dielectric permeabilities. The solution of colour field equations resemble harmonic oscillator type wave functions with equispaced energy levels (no continuum) leading to confinement.     

Ordering kinetics in quasi-one-dimensional Ising-like systems

We present results of a Monte Carlo simulation of the kinetics of ordering in the two-dimensional nearest-neighbor Ising model in anL xM geometry with two free boundaries of length ML. This model can be viewed as representing an adsorbant on a stepped surface with mean terrace widthL. We follow the ordering kinetics after quenches to temperatures 0.25 T/T_c 1 starting from a random initial configuration at a coverage of=0.5 in the corresponding lattice gas picture. The systems evolve in time according to a Glauber kinetics with nonconserved order parameter. The equilibrium structure is given by a one-dimensional sequence of ordered domains. The ordering process evolves from a short initial two-dimensional ordering process through a crossover region to a quasi-one-dimensional behavior. The whole process is diffusive (inverse half-width of the structure factor peak 1/q_{¦¦ t}), in contrast to a model proposed by Kawasakiet al., where an intermediate logarithmic growth law is expected. All results are completely describable in the picture of an annihilating random walk (ARW) of domain walls.     

A fast random walk algorithm for computing the pulsed-gradient spin-echo signal in multiscale porous media

A new method for computing the signal attenuation due to restricted diffusion in a linear magnetic field gradient is proposed. A fast random walk (FRW) algorithm for simulating random trajectories of diffusing spin-bearing particles is combined with gradient encoding. As random moves of a FRW are continuously adapted to local geometrical length scales, the method is efficient for simulating pulsed-gradient spin-echo experiments in hierarchical or multiscale porous media such as concrete, sandstones, sedimentary rocks and, potentially, brain or lungs.     

中子引起单粒子翻转过程中能量沉积统计分析

利用Monte Carlo方法,对14MeV中子引起存储器单粒子翻转过程进行了计算模拟,从而对引起单粒子翻转的关键因素——存储器灵敏区中的能量沉积进行了统计分析,为了解单粒子翻转随机过程提供了详细的能量沉积统计信息。The process of the single event upset induced by 14 MeV neutrons in SRAM silicon chip is simulated by using a Monte Carlo method. The deposited energies in sensitive volumes in the chip, which is an important factor in the single event upset, are statistically analysed. The statistic information about the deposited energies is provided for understanding the detailed random process of the single event upset.     

Confinement and dynamical chiral symmetry breaking in a non-perturbative renormalizable quark model

Inspired by the construction of the Gribov–Zwanziger action in the Landau gauge, we introduce a quark model exhibiting both confinement and chiral symmetry aspects. An important feature is the incorporation of spontaneous chiral symmetry breaking in a renormalizable fashion. The quark propagator in the condensed vacuum turns out to be of a confining type. Besides a real pole, it exhibits complex conjugate poles. The resulting spectral form is explicitly shown to violate positivity, indicative of its unphysical character. Moreover, the ensuing quark mass function fits well to existing lattice data. To further validate the physical nature of the model, we identify a massless pseudoscalar (i.e. a pion) in the chiral limit and present estimates for the ρ$\rho$ meson mass and decay constant.     

强流质子束辐照形成的冲击波

 对强流质子束在铝材料中引起的冲击波进行了数值模拟，其中强流质子束在铝中的能量沉积行为采用蒙特卡罗方法模拟，而能量的非均匀沉积后引起的力学效应采用一维流体弹塑性模型进行计算。计算给出了强流质子束在铝材料中的能量沉积曲线和引起的冲击波的时间演化规律。