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1.
叶贞成  蔡钧  张书令  刘洪来  胡英 《物理学报》2005,54(9):4044-4052
应用Yethiraj的加权密度近似泛函理论研究平板狭缝中方阱链流体的密度分布,系统的Helm holtz自由能泛函分为理想气体的贡献利剩余贡献两部分,其中剩余贡献部分分别采用刘洪 来等人建立的基于空穴相关函数的方阱链流体状态方程和Gil-Villegas等人提出的统计缔合 流体理论状态方程(SAFT-VR)结合简单加权密度近似计算.考察了不同链长、温度、系统密度 和壁面吸引强度下平板狭缝中方阱链流体的密度分布,并与Monte Carlo(MC)模拟结果进行 了比较.结果表明采用不同的状态方程对密度分布的计算有明显的影响,对于受限于硬壁狭 缝中的方阱链流体,温度和密度比较高时,两种状态方程计算的结果均与MC模拟符合得比较 好,在低温和低密度下效果变差,SAFT-VR方程的计算结果更接近于MC模拟结果.对于受限于 方阱壁狭缝中的方阱链流体,由于系统密度分布的非均匀性加强,采用两种状态方程计算的 结果均与MC模拟结果有一定偏差,寻找更合适的权重函数是进一步改进的关键. 关键词: 密度泛函理论 非均匀流体 密度分布 固液界面 方阱链  相似文献   

2.
本文应用物质分子聚集与解集理论阐述了高压流体相平衡机理并提出了分子聚集型状态方程.应用此方程能精确地描述流体高压下的PVT关系,且用于预测相平衡数据也获得了满意结果.  相似文献   

3.
 根据Ross变分微扰理论以及硬球流体Percus-Yevick(PY) 径向分布函数表达式,建立了广义Morse势流体的解析状态方程。与模拟结果的比较一方面证实了广义Morse 势模型的合理性;另一方面表明了解析Ross变分微扰理论的精度相当或略好于非解析的Weeks-Chandler-Anderson (mWCA)理论,而优于复杂的优化超网络链积分方程理论(RHNC)。该解析状态方程被应用于拟合处于环境温度和压强小于1 GPa情形流体氮的实验数据,所得到的势能参数被用于预测高温高密度情形氮流体的压强,预测结果证实,该解析状态方程可以很好地适用于较宽的压强和温度范围。  相似文献   

4.
低温流体状态方程研究   总被引:6,自引:2,他引:4  
本研究了可用于低温流体热力学性质计算的状态方程,提出一个改进型的Patel-Teja状态方程,给出了24种常用低温流体的方程常数、其中包括氢、氦等量子气体。用新方程对24种常用低温流体的饱和蒸汽压,饱和蒸汽比容,饱和液体比容等进行了计算并与传统方程进行了比较。  相似文献   

5.
格鲁尼森数是一个无量纲的热力学参数,通常被用来描述固体的热力学性质.由于其对流体的临界点不敏感,它对于检验非理想流体的热力学性质也有指导意义.本文通过计算多种流体在不同温度和压力下的格鲁尼森数,发现其数值在宽广区域里变化稳定,进而论述了格鲁尼森数与其他热力学参数的关系.以PR方程和BWR方程为例,阐述了格鲁尼森数对于检验状态方程完善性的标尺性作用.  相似文献   

6.
混沌时间序列全局预测新方法——连分式法   总被引:13,自引:0,他引:13       下载免费PDF全文
张森  肖先赐 《物理学报》2005,54(11):5062-5068
拓展了多项式逼近理论,利用连分式法建立了混沌时间序列非线性全局预测模型,此模型替代混沌序列的动力学方程,实现对其动力学特性分析,达到预测目的. 理论分析和仿真实验表明,连分式法能够有效预测一些混沌序列,该方法预测精度高,并且能得到显式的预测表达式. 关键词: 混沌时间序列 全局预测 连分式  相似文献   

7.
基于Bernstein多项式的自适应混沌时间序列预测算法   总被引:3,自引:0,他引:3       下载免费PDF全文
闫华  魏平  肖先赐 《物理学报》2007,56(9):5111-5118
提出了利用Bernstein多项式对混沌时间序列的动力学方程进行建模的方法,并将该方法与递推最小二乘(RLS)算法相结合,从而可以自适应地逼近混沌时间序列的动力学特性,以达到预测的目的.理论分析和仿真实验表明该方法对一些常见的混沌时间序列具有较高的预测精度和较理想的准确预测率.由于RLS算法的收敛速度较快,因此该方法比较适合于对短混沌时间序列进行实时预测. 关键词: 混沌 预测 Bernstein多项式 RLS算法  相似文献   

8.
一种新的蔡氏电路设计方法与硬件实现   总被引:8,自引:0,他引:8       下载免费PDF全文
李亚  禹思敏  戴青云  刘明华  刘庆 《物理学报》2006,55(8):3938-3944
提出了一种基于蔡氏无量纲状态方程新的电路设计方法.首先对蔡氏无量纲状态方程各变量进行比例压缩变换、微分-积分转换和时间尺度变换.其次根据变换后的方程设计出各模块电路,再将各模块按方程中各状态变量的对应关系联结起来.整个电路只由反相加法器、积分器和反相器三大模块构成,电路结构对称.与现有其他的混沌电路设计相比,该方法具有三个主要特点:(1)直观性强,实现了电路的模块化设计,并总结出了这类混沌电路更一般的设计原理,具有普适性,可用于其他无量纲连续状态方程的电路设计;(2)由于采用了反相加法器,各个电路参数独立 关键词: 蔡氏电路 多项式 模块化设计 硬件实验  相似文献   

9.
一、引 言 临界点是气液相变的终点.在该点附近流体显示出奇异特性.奇异特性使得临界点附近流体热力学性质的实验测量与理论计算变得非常困难. 为了更好地表示临界点附近的热力学性质,状态方程应能表达流体在临界点的奇异性.Schofield首先提出能满足上述要求的参数标度状态方程——线性模型与立方模型两种.该方程用两个参变数R,θ表示.可以证明:在限定立方模型中,等温压缩率KT仅与R有关,与θ无关,所以R是KT大小的直接度量.KT具有强烈发散性,且又与密度涨落相关.从而,KT更能表征流体的临界特性.可见,从理论上讲,限定立方模型能更好地表…  相似文献   

10.
本文研究二维多相反应流的数值模拟方法.对于非完全流体,考虑两种状态方程:刚性气体状态方程和JWL(Jones-Wilkins-Lee)型的状态方程.针对这些非完全流体,研究一种混合单元物理量重构法,它由单元内的已知物理量出发,应用单元内不同相的物理量之间的关系:混合密度与各自密度之间的关系、及混合内能与各物质内能之间的关系,再由温度与压强平衡条件,建立关于单变量的非线性方程,对所得方程通过"移动跟踪法"求解,得到单元内的压力、温度及声速等.再利用HLLC解法器,求解各个单元边界数值通量,从而构造一种高效的数值方法.数值结果表明:该算法能清晰地捕捉爆轰波的结构特征,胞格排列有序,三波点的特征明显.  相似文献   

11.
This paper proposes a solution to Bloch NMR flow equations in biomedical fluid dynamics using a new set of real polynomials. In fact, the authors conjugated their efforts in order to take benefit from similarities between independent Bloch NMR flow equations yielded by a recent study and the newly proposed characteristic differential equation of the m-Boubaker polynomials. The main goal of this study is to establish a methodology of using mathematical techniques so that the accurate measurement of blood flow in human physiological and pathological conditions can be carried out non-invasively and becomes simple to implement in medical clinics. Specifically, the polynomial solutions of the derived Bloch NMR equation are obtained for use in biomedical fluid dynamics. The polynomials represent the T2-weighted NMR transverse magnetization and signals obtained in terms of Boubaker polynomials, which can be an attractive mathematical tool for simple and accurate analysis of hemodynamic functions of blood flow system. The solutions provide an analytic way to interpret observables made when the rF magnetic fields are designed based on the Chebichev polynomials. The representative function of each component is plotted to describe the complete evolution of the NMR transverse magnetization component for medical and biomedical applications. This mathematical technique may allow us to manipulate microscopic blood (cells) at nano-scale. We may be able to theoretically simulate nano-devices that may travel through tiny capillaries and deliver oxygen to anemic tissues, remove obstructions from blood vessels and plaque from brain cells, and even hunt down and destroy viruses, bacteria, and other infectious agents.  相似文献   

12.
R. Schmitz 《Physica A》1980,102(1):161-178
We present a general theorem for the force multipole moments of arbitrary order induced in a spherically symmetric particle immersed in a fluid whose motion satisfies the linear Navier-Stokes equation for steady incompressible viscous flow. The multipole moments are expressed in terms of the unperturbed fluid velocity field. It is shown that for a particle with a finite extension only a few terms give rise to fluid perturbations which are not confined to the interior of the particle. We give explicit results for a polymer satisfying the Debye-Bueche-Brinkman equations and for a hard sphere with mixed slip-stick boundary conditions.  相似文献   

13.
We report the derivation of a wave equation for coherence in "dark state" two-photon-resonance spectroscopy. One of its consequences is a dark state area theorem. The dark area theorem is a single ordinary differential equation which is globally equivalent, in a way we describe, to the full set of five coupled nonlinear partial differential equations that govern space-time evolution of two-pulse coherence in a lambda medium. The predictions of the dark area theorem are open to test via laser spectroscopy in dilute vapors and inhomogeneously broadened solids.  相似文献   

14.
Macroscopic field equations, boundary conditions and equations of state are derived for the non-linear, macroscopic elastic and dielectric response of an insulator. A centrosymmetric polynomial representation of order four is introduced for the energy density; the equations of state for the electric field and stress tensor are then deduced as polynomials of degree three in the displacement gradients and electric displacement field. The results are applied to the special case of m3m material symmetry.

A finite, point-charge model of a centrosymmetric ionic crystal is introduced and used to determine 0°K microscopic expressions for the electric field and stress tensor equation of state coefficients introduced in the macroscopic analysis. The results are used to calculate the full set of second and third-order non-linear coefficients for NaI, based on a Born-Mayer potential and the 4·2°K elastic stiffness data of Claytor and Marshall.  相似文献   

15.
The transport equations associated with radiation damage studies are often solved using expansions in Legendre polynomials. The radiation damage distribution functions which satisfy these equations may be sharply peaked in the forward direction, while the Legendre polynomials, as a set, are isotropic. This situation requires the use of many terms in the Legendre expansion in order to adequately represent the distribution functions. The Jacobi polynomials, on the other hand, can have strong peaking built into their associated weight function. To test the usefulness of the Jacobi polynomials we use them to solve the simple, one-speed, neutron transport equation. The results are then compared to the exact theory and to the results of applying Legendre methods to the same problem. This sample calculation demonstrates the advantage of the Jacobi polynomials in strongly non-isotropic situations.  相似文献   

16.
范洪义  楼森岳  潘孝胤  笪诚 《物理学报》2013,62(24):240301-240301
提出量子力学算符Hermite多项式方法,即将若干常用的特殊函数的宗量由普通数变为算符,并用它来发现涉及Hermite多项式(单变数和双变数)的二项式定理和涉及Laguerre多项式的负二项式定理,它们在计算若干量子光场的物理性质时有实质性的应用. 该方法不但具有简捷的优点,而且能导出很多新的算符恒等式,成为发展数学物理理论的一个重要分支. 关键词: 量子力学 Hermite多项式 二项式定理 Laguerre多项式  相似文献   

17.
In spherical polar coordinates, double ring-shaped oscillator potentials have supersymmetry and shape invariance for θ and r coordinates. Exact bound state solutions of Klein—Gordon equation with equal double ring-shaped oscillator scalar and vector potentials are obtained. The normalized angular wavefunction expressed in terms of Jacobi polynomials and the normalized radial wavefunction expressed in terms of the Laguerre polynomials are presented. Energy spectrum equations are obtained.  相似文献   

18.
Stimulating the biquaternionic generalization of electric and magnetic fields in electromagnetism, a new model has been proposed to present the Maxwell type equations of compressible fluids. The fluid wave equation has been expressed in a compact and elegant manner. Similarly, the generalized Poynting theorem for fluids has been derived analogous to electromagnetism and linear gravity. Moreover, a brief survey on biquaternionic matrices and the corresponding matrix representations of fluid equations have been given.  相似文献   

19.
The properties of self-gravitating distributions of an ideal fluid charged by a vector field which is either massive or massless, i.e., electromagnetic, are considered taking account of the spin properties of the vector field in the framework of the Einstein-Cartan theory of gravitation. Conditions for equilibrium are found and the corresponding exact solutions are obtained. A complete system of first integrals of the corresponding equations of motion is found for dynamical distributions in the absence of pressure. A theorem on the correspondence between the dynamics of an electrically charged ideal fluid with a limiting equation of state and the dynamics of a free massive vector field is also proved.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 7–11, August, 1979.  相似文献   

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