傍轴光束截面的内能是一个不变量

本文从描写光束传输的流体模型中建立了内能概念.证明,对于任何一个在真空中稳态传输的傍轴光束,光束截面的内能与截面的位置无关,即在传输过程中,内能是一个不变量.     

先有手性均一性还是先有生命？

先有手性均一性还是先有生命？民间谚语说：“万物都在转、转、转”．但这要通过什么途径？为什么？这是科学之谜，１９９５年２月１５－１７日美国洛杉矶召开了“生命中手性起源”问题的国际讨论会［１］，来自世界各地的２４位物理学家、化学家和天文学家出席了会议。会...     

声强的有旋性与表面声强

本文应用复声强的概念,讨论了复声强的实部即有功声强的有旋性质。指出:在声场中真正传递声能量者仅是有功声强中的无旋分量。所以在应用双传声器声强测量法测量声功率时将受到有旋性的影响。有功声强的无旋分量与表面声强有关,因此测量表面声强可避免有旋性的影响。本文从自功率谱的角度给出了表面声强的有关计算公式,为表面声强测量提供了理论基础。     

编者的话

“标量”一词在基础物理中和理论物理中通常有不同的含义 .在基础物理中 ,一般理解标量是可用 1个实数描写的物理量 .因此 ,质量、温度、劲度系数等都是标量 ,这一点本文已经说清楚了 .在理论物理中 ,标量、矢量和张量都是按这个量在坐标转动下的变换性质来定义的 .例如位置矢量r ,在坐标系A中的分量是x ,y,z ,即x1,x2 ,x3 .在坐标系A′中的分量是x′1,x′2 ,x′3 ,二者的关系是x′i= jaijxj (1 )式中aij(共 9个 )是描写坐标转动 ,即A与A′的关系的量 ,满足detaij=1所以 ,在理论物理中 ,矢量的定义是 :矢量是用 3个实数x ,y,z描写的、在坐…     

电子等离子体波反射点附近的有质动力效应

本文首次研究了电子等离子体波反射点附近的有质动力效应,确定了描写这一效应的各特征参量之间的联系,并自洽地求出位于该区域的等离子体密度台阶及相应的电子等离子体波。     

孰先孰后判定的6种方法

孰先孰后即比较物体运动时间长短的问题，是高中物理中常见的问题．由于这类问题的物理情景往往比较新颖，涉及的知识跨度较大，同学们解答起来颇感棘手．本文拟结合典型例题的解析，说明比较时间的6种方法．     

高斯轨迹参量的线性变换对于电子光学象差的影响

本文从比较普遍的观点出发,采用矢量形式描写高斯轨迹,运用矩阵形式表示象差,从而讨论了普遍的高斯轨迹参量线性变换下的电子光学系统的三级象差和象差系数及其偏微商。由此得到了电子光学广义的Fraunhofer条件(即消除各向同性和各向异性彗差的条件),证明了在此条件下,象散和场曲取极值或稳定值。利用上述的普遍公式和结果,讨论了固定束和扫描束电子光学系统中光阑位置变化的影响,还讨论了阴极发射系统中磁浸没的影响。 关键词：     

力学里需要一个新的基本概念──“急动度”吗?

读到了黄沛天《一个描写机械运动的新概念──急动度》的文章[1].文中声称这个问题是“牛顿力学留下的小空白”;并且由于急动度(jerk)等于加速度的时间变率,就需要引进对时间的三阶微分方程来描述机械运动,还必须修正现行对惯性和相互作用等概念的理解等等.总之,使人得到的印象     

在科学探究中建构物理概念的意义——再析“规律-概念一体化探究”教学模式

1 一体化探究模式的结构 从图中可以看出,"一体化探究"模式包含的重要特征要素有:问题、概念、规律(知源性要素)与科学探究(过程性要素).其中问题蕴含概念和规律,概念与规律紧密相联,概念支撑规律的发现、问题的解决;反过来规律、问题又为概念意义的建构(即概念是什么、概念为什么)提供定向与参照,三者交织在探究活动这一共同的"过程载体"中,形成一个"三位一体"的教学模式结构.     

湍流两相流动有燃烧颗粒相概率密度函数输运方程理论

由有燃烧的湍流气粒两相流动的瞬态方程和统计力学概率密度函数概念出发,推导了有燃烧颗粒相的质量－动量－能量联合概率密度函数（ＰＤＦ）输运方程,并对方程中条件期望项用梯度模拟概念进行了模拟封闭。封闭后的ＰＤＦ方程可作为建立颗粒拟流体模型方程和封闭二阶矩模型的基础,也可以通过Ｍｏｎｔｅ－Ｃａｒｌｏ 法求解用以直接计算颗粒雷诺应力和湍流动能,以便和二阶 矩模型的结果相对照,改善二阶矩模型。     

A possible approach to the description of topological transitions in the quantum theory of gravitation

Russian Physics Journal - One of the problems generated in attempts of describing topological transitions in the quantum theory of gravitation is the introduction of variables describing the...     

Microstructure of excited nuclear states in the vicinity of an yrast line

The microscopic model describing the wobbling motion in fast rotating nuclei is presented and the connection of the parameters describing it with the Coriolis effects at low spins is discussed.     

Interference effects in the coherent X-ray radiation of relativistic electrons in two- and three-layer targets

A dynamic theory of the coherent X-ray radiation of relativistic electrons in “amorphous medium–single-crystal” and “amorphous medium–free-space–single-crystal” targets is developed. Expressions for the spectral-angular distributions of diffracted transition radiation (DTR), parametric X-ray radiation, and a term describing their interference are obtained. The spectral-angular density of the DTR is represented as a sum of terms describing the diffracted transition radiation from various boundaries and a term describing the interference of these components. Interference effects in the spectral-angular and angular densities of radiation are studied.     

Travelling with/against the Flow. Deterministic Diffusive Driven Systems

We introduce and study a deterministic lattice model describing the motion of an infinite system of oppositely charged particles under the action of a constant electric field. As an application this model represents a traffic flow of cars moving in opposite directions along a narrow road. Our main results concern the Fundamental diagram of the system describing the dependence of average particle velocities on their densities and the Phase diagram describing the partition of the space of particle configurations into regions having different qualitative properties, which we identify with free, jammed and hysteresis phases. This research has been partially supported by Russian Foundation for Fundamental Research, CRDF and French Ministry of Education grants.     

Self-sputtering of thin films (Application of the invariant immersion method)

The analytic solution to the problem of self-sputtering of thin homogeneous films is considered. Invariant immersion principles were used for deriving integral equations describing the flow of sputtered atoms. Approximate solutions of the integral equation are found for the functions describing the spectra of atoms emitted from the film surface in the case of self-sputtering.     

Quantum Damped Oscillator in Probability Representation

The probability distribution describing quantum states of the damped oscillator in the framework of the Caldirola-Kanai model is introduced. The probability distributions for coherent states and Fock states of the damped oscillator are found explicitly. The transition probability for the damped oscillator is expressed in terms of distributions describing initial and final states.     

DECONFINEMENT TRANSITION OF NONTOPOLOGICAL SOLITON MODEL AT FINITE TEMPERATURE

The temperatrure dependence of the σ_vac describing the extent of gluon condensation,and that of the color-dieletric constant K_vac describing the confinement of quarks,are discussed in nontopological soliton model at finite temperature; The mechanism of deconfinement transition is analysed.     

Diffusion in crystals with traps: A simple phenomenological model

We present a phenomenological model describing the trapping and release of mobile defects at random inhomogeneities. The traps are characterized by two parameters, the capture radiusR _t, describing the range of the interaction and the binding energyE _b describing the escape. We give an integral representation of the correlation function of the mobile particles in the presence of traps. For large distances the correlation function can be described by a simple diffusional process with an effective diffusion constant. Finally we discuss the neutron scattering by mobile defects resulting from this trapping model.     

Flory approximant for self-avoiding walks on fractals

A Flory approximant for the exponent describing the end-to-end distance of a self-avoiding walk (SAW) on fractals is derived. The approximant involves the fractal dimensionalities of the backbone and of the minimal path, and the exponent describing the resistance of the fractal. The approximant yields values which are very close to those available from exact and numerical calculations.     

Exact eigenstates for a class of models describing two-mode multiphoton processes

We present an efficient approach to studying the spectra and eigenstates for nonlinear models describing multiphoton processes. We obtain the exact explicit analytical expressions of all the energy spectra and eigenstates in terms of a parameter for a class of models describing two-mode multiphoton processes. The parameter is shown to be determined by the roots of a simple polynomial.