Quantum Chaos,Random Matrices,and Irreversibility in Interacting Many-Body Quantum Systems

The Pauli master equation describes the statistical equilibration of a closed quantum system. Simplifying and generalizing an approach developed in two previous papers, we present a derivation of that equation using concepts developed in quantum chaos and random-matrix theory. We assume that the system consists of subsystems with strong internal mixing. We can then model the system as an ensemble of random matrices. Equilibration results from averaging over the ensemble. The direction of the arrow of time is determined by an (ever-so-small) coupling to the outside world. The master equation holds for sufficiently large times if the average level densities in all subsystems are sufficiently smooth. These conditions are quantified in the text, and leading-order correction terms are given.     

无界集值上鞅的Riesz逼近

研究了弱紧凸集值上鞅及无界集值上鞅的Ｒｉｅｓｚ逼近，以及鞅型集序列的若干收敛定理．     

A primitive-variable Riemann method for solution of the shallow water equations with wetting and drying

A Riemann flux that uses primitive variables rather than conserved variables is developed for the shallow water equations with nonuniform bathymetry. This primitive-variable flux is both conservative and well behaved at zero depth. The unstructured finite-volume discretization used is suitable for highly nonuniform grids that provide resolution of complex geometries and localized flow structures. A source-term discretization is derived for nonuniform bottom that balances the discrete flux integral both for still water and in dry regions. This primitive-variable formulation is uniformly valid in wet and dry regions with embedded wetting and drying fronts. A fully nonlinear implicit scheme and both nonlinear and time-linearized explicit schemes are developed for the time integration. The implicit scheme is solved by a parallel Newton-iterative algorithm with numerically computed flux Jacobians. A concise treatment of characteristic-variable boundary conditions with source terms is also given. Computed results obtained for the one-dimensional dam break on wet and dry beds and for normal-mode oscillations in a circular parabolic basin are in very close agreement with the analytical solutions. Other results for a forced breaking wave with friction interacting with a sloped bottom demonstrate a complex wave motion with wetting, drying and multiple interacting wave fronts. Finally, a highly nonuniform, coastline-conforming unstructured grid is used to demonstrate an unsteady simulation that models an artificial coastal flooding due to a forced wave entering the Gulf of Mexico.     

脉冲软X光辐射三种材料的喷射冲量实验研究

 在强光一号脉冲加速器上进行了国内首次的实验室软X光辐射三种材料的喷射冲量研究。结果表明，在能量为(0.2～0.33)keV、平均脉宽为39ns左右的X光辐射下，对灰漆、白漆和硬铝，在能注量分别为(92～152)J/cm²、(115～136)J/cm²和(163～192)J/cm²时，它们的冲量耦合系数分别为(0.61～0.80)Pa·s/(J·cm^-2)、(0.58～0.97)Pa·s/(J·cm^-2)和(0.61～0.84)Pa·s/(J·cm^-2)。     

The effects of cubic potentials on discrete breathers in a mixed Klein－Gordon /Fermi－Pasta－Ulam chain

Nonlinearity has a crucial impact on the symmetry properties of dynamical systems. This paper studies a one-dimensional mixed Klein--Gordon/Fermi--Pasta--Ulam diatomic chain using the expanded rotating plane-wave approximation and numerical calculations to determine the effect of cubic potentials on the symmetry properties of discrete breathers in this system. The results will be very useful to researchers in the field of numerical calculations on discrete breathers.     

Be-composition effect on structure, electronic and optical properties of BexZn1-xO alloys

This paper carries out first principles calculation of the structure,electronic and optical properties of Be x Zn 1 x O alloys based on the density-functional theory for the compositions x = 0.0,0.25,0.5,0.75,1.0.The lattice constants deviations of alloys obey Vegard’s law well.The Be x Zn 1 x O alloys have the direct band gap(Γ-Γ) character,and the bowing coefficients are less than the available theoretical values.Moreover,it investigates in detail the optical properties(dielectric functions,absorption spectrum and refractive index) of these ternary mixed crystals.The obtained results agree well with the available theoretical and experimental values.     

随机取向烟幕凝聚粒子的消光特性

采用蒙特卡罗方法根据团簇-团簇凝聚(CCA)模型对由球形原始微粒凝聚而成的烟幕凝聚粒子进行模拟,用离散偶极子近似(DDA)方法研究随机取向烟幕凝聚粒子的消光特性.结果表明,凝聚粒子的消光特性受到原始微粒数量以及粒径的影响,粒子的凝聚将减弱烟幕的消光性能;当凝聚结构中原始微粒的数目一定时,存在使烟幕消光性能达到最大的原始微粒粒径.     

矩形微槽道纳米流体饱和沸腾临界热流密度特性

针对纳米流体在微小尺度传热领域的应用,在常压下对微槽道中纳米流体的流动沸腾临界热流密度进行实验研究。分别以体积浓度为0.2%、0.5%的水基Al2O3纳米流体为工质进行试验,研究不同质量流速、槽道尺寸以及体积浓度等因素对沸腾CHF的影响。对比水为工质实验结果,表明:槽道尺寸、质量流速对于水-Al2O3纳米流体和纯水的CHF影响一致。其它参数一定的工况下,纳米流体CHF比纯水大,且随着纳米流体体积浓度增大,出口壁面过热度会增大。最后介绍一个微槽道沸腾CHF的预测模型,在评价其不足的基础上提出一个关于CHF的预测公式,与实验数据进行对比,验证该公式的适用性。     

Design of square-shaped heat flux cloaks and concentrators using method of coordinate transformation

A square-shaped heat flux cloak and a square-shaped heat flux concentrator have been designed theoretically according to the invariance symmetry of steady state thermal conductive equation. The direction of heat flux in these devices can be modulated as desired. Using the method of coordinate transformation, the inhomogeneous and anisotropic thermal conductivity in the transformation region have been acquired. Two-dimensional finite element simulations were performed to confirm the theoretical results.     

气粒混合物非灰辐射特性合并宽窄谱带K分布模型

气粒混合物辐射问题具有全场性、非灰性、耦合性等特点,准确预估高温燃气/粒子非灰辐射特性是非常重要的。本文将合并宽窄谱带K分布模础(CWNBCK)与离散坐标法(DOM)结合,开展了非灰气粒混合物辐射换热问题的模拟工作,分别验证了一维和三维情况下应用该模型的准确性,给出不同工况下的热流源项、壁面热流或辐射热流等。结果表明:该模型能够给出与SNB模型精度基本相同的结果,考虑其计算效率的提高,可以在工程实际中应用该模型计算非灰气粒混合物辐射换热。