Propagation of radiation in a fluctuating medium with discrete inclusions

The structure and solutions of the Markov approximation equations are considered for the first two moments of radiation propagating in a medium with continuous fluctuations and discrete inclusions. Corrections associated with taking the second-order correlations of the scatterers into account are described. Conditions for the black screen models to be used in describing discrete inclusions are estimated.Radiotechnical Institute, Russian Academy of Sciences. Translated from Izvestiya Vysshika Uchebnykh Zavedenii, Radiofizika, Vol. 36, Nos. 3–4, pp. 275–285, March–April, 1993.     

On the current distribution in a shielded superconducting film

The current distribution is investigated theoretically in a shielded superconducting film, which is a film deposited on an insulating superconducting ground plate. An exact result is obtained in the case of a thin and wide film on the basis of London's equation.     

Quantum hall effect in inhomogeneous media: Effective characteristics and local current distribution

An analysis is made of the problem of current flow in heterophase inhomogeneous media in the quantum Hall effect regime. Duality relations are derived and expressions are obtained for the effective conductivity of inhomogeneous media over the entire range of concentrations. Local current distributions (fields) are determined in the quantum Hall effect regime.     

Effective permittivity of a discrete random medium with anisotropic inclusions

We use the method of substitution of field variables in the bilocal approximation to find the effective permittivity of a two-phase composite random medium in the form of an ensemble of small, arbitrarily anisotropic spherical inclusions distributed inside an isotropic matrix. To illustrate the results we calculate the damping of the plane waves of the mean field in such a medium. Zh. éksp. Teor. Fiz. 114, 1188–1201 (October 1998)     

Antiferromagnetic hall effect nonlinear in the electric current

A new galvanoantiferromagnetic effect is predicted—the Hall effect nonlinear in the electric current, i.e., a potential difference that is transverse to the current and is associated with the antisymmetric contribution to the resistivity tensor, which violates Ohm’s law, for example, of the form Δρij=?Δρji∝LE, where L is the antiferromagnetism vector and E is the electric field. The indicated contribution is characteristic for centrally antisymmetric antiferromagnets and can lead to a Hall field that is quadratic in the current: ΔE ^⊥ ∝ LJ ². Similarly, the effect ΔE ^⊥∝LJ ³ can exist in centrally symmetric antiferromagnets even in a state where the ordinary Hall effect, which is linear in J, is absent (for example, in hematite below the Morin point).     

Kinetic theory of the hall effect in the self-magnetic field of a current

The Hall effect induced by the self-magnetic field of a current is considered in weak longitudinal fields in an electron-hole plasma on the basis of the solution for the kinetic equation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 108–112, September, 1972.     

On the probability distribution for rays in a medium having random inhomogeneities

Radiophysics and Quantum Electronics -     

Propagation of longitudinal elastic waves in a fluid-saturated porous medium with spherical inclusions

The Frenkel-Biot theory is used to study the propagation of a longitudinal harmonic wave of the first kind in an isotropic porous matrix with inclusions contrasting in elastic properties and hydrodynamic permeability. The generation of elastic waves of the second kind at the boundaries of inclusions is taken into account. The effective wave number of the longitudinal wave is calculated using the equations of multiple scattering theory. The characteristic size of inhomogeneities is assumed to be much greater than the size of pores. The parameters of the model used for calculations correspond to sandstone with centimeter-scale inhomogeneities. The presence of such inhomogeneities is typical of sedimentary rocks. Calculations show that, in the frequency range of acoustic logging, the effective attenuation factor of the longitudinal wave may noticeably exceed the attenuation factors of longitudinal waves of the first kind in both matrix and inclusions. From the results obtained, it follows that, when studying the propagation of elastic waves in fluid-saturated porous media, it is necessary to take into account the hydrodynamic effects associated with the filtration overflows that arise at the boundaries of inhomogeneities.     

早期声在厅堂中的分布

厅堂内早期反射声能分布与厅堂的容积、体形、吸声布置及接收点的位置等有关,其形成的早期声场与完全扩散声场有较大的差别。因而有关与早期反射声能相关的音质参量在厅堂中的分布情况无法用扩散场的理论来预计。本文通过对四个厅的测量结果,来分析早期反射声能在厅堂中分布的特性。     

Self-consistent structure of a dc discharge with a closed hall current in crossed electric and magnetic fields

A dc glow discharge with a closed Hall current in crossed electric and magnetic fields in helium is investigated. It is shown that the main features of an unmagnetized dc discharge [1] (such as the separation of the discharge into a space charge sheath and a quasineutral plasma, the formation of a cathode fall region and a negative glow, the appearance of a region with a reversed electric field producing a potential well for low-energy electrons and resulting in the formation of a Faraday dark space, and the formation of three pronounced groups of electrons in the electron distribution function) are also retained in a discharge in crossed fields. It is found that the sheath length is almost independent of the magnetic field, while the length of the negative glow region decreases appreciably with increasing magnetic field. The measured electron distribution function agrees well with the nonlocal theory, according to which the current in the Faraday dark space is carried by the intermediate electrons that are not trapped in the potential well and the energies of which are lower than the first excitation energy.     

On thermal method of character of inclusions structure rating in semiinfinitely medium volume

In this Letter the thermal contact scanning method of restoration of volumetric coordinates of defects latent in depth of a semiinfinitive body is considered. Due to the increased temperature sensitivity and absence of a handicap from spatial heterogeneity of a surface of a researched body the method allows to find out defects having the characteristic size much more smaller, than the depth of their immersing and thus is removed the requirement to a transparency of a body in infra-red or radiofrequency range. There is an opportunity of using this method as absolutely safe in a task of detection of pathological changes in body of a man is considered.     

Effects of hall current on MHD Couette flow in a rotating system with arbitrary magnetic field

Author has studied the MHD Couette flow in a rotating environment with non- conducting walls in the presence of an arbitrary magnetic field. The solution in dimensionless form contains four pertinent flow parameters, viz. the Hartmann number, the rotation parameter which is the reciprocal of the Ekman number, the Hall current parameter, and the angle of inclination of the magnetic field to the positive direction of the axis of rotation. An interplay of hydromagnetic force and Coriolis force with an inclusion of Hall current plays a significant role in determining the MHD flow behaviour. The velocity and induced magnetic field distributions are depicted graphically. Also, the numerical results of shear stresses and the rate of mass flows are presented graphically.     

Magnetoconductance oscillations and hall current for a two-dimensional electron gas with harmonic confining potential

Summary In the present paper we calculate exactly the density of states of an ideal 2DEG in uniform magnetic and electric fields with parabolic confining potential. From the density of states, we obtain the magnetoconductance oscillations. Consequently, we get the Hall current by means of the Feynman-Hellman theorem and study its quantization.

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Riassunto In questo lavoro si calcola esattamente la densità degli stati di un ideale 2DEG in campi uniformi magnetici ed elettrici con potenziale confinante parabolico. Dalla densità degli stati si ottengono le oscillazioni di magnetoconduttanza. Di consequenza si ricava la corrente di Hall per mezzo del teorema di Feynman-Hellman e si studia la sua quantizzazione.

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Резюме В этой работе мы проводим точное вычисление плотности состояний идеального даумерного электронного газа в однородных магнитных и электрических полях с параболическим удерживаущим потенциалом. Из плотности состояний мы получаем осцилляции магнитной проводимости. Таким образом, мы определяем ток Холла с помощью теоремы фейнмана-Гелмана и исследуем его квантование.

     

On the quantization of the hall impedance

The quantized Hall impedence is shown to relate to the ratio of two period integrals which are identified as the familiar period integrals of flux and electric charge if their domain of definition is extended to the realm of spacetime.     

临界装置实验大厅散射中子分布研究

采用蒙特卡罗方法,通过MCNP5程序对实验大厅内不同散射体产生的散射贡献及散射中子分布进行了计算。结果表明,散射中子强度随离开临界中子源距离先呈减小趋势,在接近大厅墙壁处则出现增加,呈现明显的W形状。同时设计并验证了模拟结果的正确性,结果表明模拟计算与实验测量结果的趋势相同,证明了计算结果的可靠性。