Nonlinear fluctuations in a plasma with Coulomb interaction

The theory of thermodynamic plasma fluctuations is now fairly well developed [1–31]. However, in practice, one often comes across plasma states which are very far from being in equilibrium. Flucuations in such nonequilibrium states have been investigated by a series of authors [4–9] in terms of a linear approximation.It must, however, be noted that, under specific conditions, neglect of nonlinear effects may turn out to be unjustified. This relates particularly to plasma states which are close to being unstable. In this region the fluctuations of various physical quantities are very large. A similar situation occurs, for example, in the experimentally observed critical opalescence in plasma, i.e., the anomalously strong scattering of electromagnetic waves by an unstable plasma [10]. The dependence of the transport coefficient on ion-sound oscillations at a fairly large ratio of electron and ion temperatures [11] is another example illustrating the insufficiency of the linear approximation. Finally, nonlinear effects may be significant in a plasma with highly developed turbulence.All this points to the necessity of expressing the various correlation functions characteristic of fluctuation processes in terms of higher correlation functions. In doing so, it is natural to confine oneself, for a start, to the first approximation in order of nonlinearity.The present paper solves this problem for plasma with Coulomb interaction.     

A rigorous method for solving the problems of diffraction of monochromatic electromagnetic waves by periodic structures

We present a rigorous method for solving the problems of diffraction of monochromatic electromagnetic waves on periodic structures of many types. The method is based on transformation of the Helmholtz equation and the boundary conditions to a certain system of integral equations and a subsequent rigorous solution of this system.     

Plasmons in a planar graphene superlattice

Plasmon collective excitations are studied in a planar graphene superlattice formed by periodically alternating regions of gapless graphene and of its gapped modification. The plasmon dispersion law is determined both for the quasi-one-dimensional case (the Fermi level is located within the minigap) and for the quasi-two-dimensional case (the Fermi level is located within the miniband). The problem concerning the absorption of modulated electromagnetic radiation at the excitation of plasmons is also considered.     

Electron gas energy in narrow-gap semiconductors in a magnetic field

The correlation energy of electron gas in narrow-gap semiconductors in a magnetic field was analytically calculated in the random-phase approximation. The results obtained allow calculation of the ground state energy and determination of the electron density corresponding to the energy minimum.     

Low-Frequency Asymptotic Analysis of Seismic Reflection from a Fluid-Saturated Medium

Reflection of a seismic wave from a plane interface between two elastic media does not depend on the frequency. If one of the media is poroelastic and fluid-saturated, then the reflection becomes frequency-dependent. This paper presents a low-frequency asymptotic formula for the reflection of seismic plane p-wave from a fluid-saturated porous medium. The obtained asymptotic scaling of the frequency-dependent component of the reflection coefficient shows that it is asymptotically proportional to the square root of the product of the reservoir fluid mobility and the frequency of the signal. The dependence of this scaling on the dynamic Darcy’s law relaxation time is investigated as well. Derivation of the main equations of the theory of poroelasticity from the dynamic filtration theory reveals that this relaxation time is proportional to Biot’s tortuosity parameter.     

Magnetoelasticity and effect of thermal phonons on the magnetic properties of ferromagnets

The experimental data for a series of ferromagnets are analyzed to determine quantitatively the magnetoelasticity-reduced effects of thermal phonons on the magnetic properties of ferromagnets. It is shown that thermal phonons have an anomalously strong effect on the magnetic properties of Invar iron-platinum alloys. The effect is governed by shear magnetoelasticity. Pis'ma Zh. éksp. Teor. Fiz. 64, No. 1, 33–37 (10 July 1996)     

ΠN-scattering at high energies in the quasipotential approach

Experimental data on πN scattering in the momentum transfer region 0.01?|t|?1.0 (GeV/c)² and P_L?10 GeV/c are described in the framework of the quasipotential approach. The parameters of the quasipotential are found which allow the data to be described satisfactorily.     

Theory of the temperature relaxation of an electron-ion plasma in a high-frequency electric and constant magnetic field

The effective collision frequency of electrons and ions which leads to temperature equalization in a plasma in a constant magnetic field and a weak high-frequency electric field when the gyroscopic radius of the electrons is less than the Debye screening radius is determined. The corresponding values of the relaxation time are determined over a wide range of values of the ratio between the electron and ion temperatures, over a wide range of values of the magnetic and electric fields, and also as a function of the frequency of the external electric field.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 41–48, November–December, 1970.     

Effects of benzene,cyclo-hexane and n-hexane addition to methane on soot yields in high-pressure laminar diffusion flames

Effects of doping high pressure methane diffusion flames with benzene, cyclo-hexane and n-hexane were investigated to assess the sooting propensity of three hydrocarbons with six carbons at elevated pressures. Amount of liquid hydrocarbons added to methane constituted 7.5% of the total carbon content of the fuel stream. The pressure range investigated extended up to 10 bar and the experiments were carried out in a high pressure combustion chamber capable of establishing stable laminar diffusion flames with various fuels at elevated pressures and was used in similar experiments previously. Temperatures and soot volume fractions were measured using the spectral soot emission technique capturing spectrally-resolved line-of-sight intensities which were subsequently inverted using an Abel type algorithm to obtain radial distributions assuming that the flames are axisymmetric. The total mass carbon flow of the fuel stream was kept constant at 0.524 mg/s in neat methane, benzene-doped methane, cyclo-hexane-doped methane, and n-hexane-doped methane flames to have tractable measurements at all pressures. Measured maximum soot volume fractions and evaluated maximum soot yields showed that benzene-doped methane flame had the higher values than cyclo-hexane doped methane flames which in turn had higher values than n-hexane doped methane flames at all pressures. Sooting propensity dependence of the three hydrocarbons on pressure can be ranked as, in descending order, n-hexane, cyclo-hexane, and benzene; however, the difference between pressure dependencies of n-hexane and cyclo-hexane was within the measurement error margins. Ratio of soot yields of benzene to n-hexane doped flames changed from about 2 at 2 bar to 1.2 at 10 bar; the ratio of benzene to cyclo-hexane doped flames showed similar trends.     

钒-棓酸配合物吸附波

在含有0.1mol/L氟化铵、6.0×10~(-5)mol/L棓酸的Britton-Robinson缓冲液溶(pH6.1)中,钒在单扫示波极谱仪上产生一灵敏的配合物吸附波。峰电位在-0.66V(vs.SCE)左右。二次导数波高与钒浓度在0.001—0.30μg/ml范围内呈线性关系。方法已应用于煤飞灰中痕量钒的测定。