Calculation of radiation characteristics of diatomic and some triatomic molecules

A mathematical model and a software package that permit calculation of the chemical composition of complex mixtures in a wide range of temperatures and densities are developed. A thermodynamic databank for a large number (about 300) of molecules and radicals up to pentatomic ones inclusive is set up. The chemical composition is determined in the approximation of local thermodynamic equilibrium. A mathematical model and a software package for calculating electron-vibration-rotation spectra of diatomic molecules are proposed. A databank of optical characteristics of molecules makes it possible to calculate spectra of about 50 of the most important molecules. The calculation is performed in the approximation of Morse potential—nonrigid rotator. A version for calculating spectra in the approximation of the Rydberg—Klein—Reese potential is also set up.     

Radiation-conduction heat transfer in fibrous heat-resistant insulation under thermal effect

The conjugate diffusion model of radiation transfer and the approximation of radiant thermal conductivity are used to investigate the radiation-conduction heat transfer in a flat layer of fibrous heat-resistant insulation under the effect of fire. The results of calculation of the characteristics of unsteady-state heat transfer and of the duration of heat resistance of the substrate demonstrate the accuracy of the approximation of radiant thermal conductivity which is good for practical applications. The fireproof efficiency of fibrous quartz heat insulation is investigated. The calculation results demonstrate that the application of this insulation provides for high limits of fire resistance of metal structures.     

Extension of geometrical-optics approximation to on-axis Gaussian beam scattering. I. By a spherical particle

The geometrical-optics approximation of light scattering by a transparent or absorbing spherical particle is extended from plane wave to Gaussian beam incidence. The formulas for the calculation of the phase of each ray and the divergence factor are revised, and the interference of all the emerging rays is taken into account. The extended geometrical-optics approximation (EGOA) permits one to calculate the scattering diagram in all directions from 0 degrees to 180 degrees. The intensities of the scattered field calculated by the EGOA are compared with those calculated by the generalized Lorenz-Mie theory, and good agreement is found. The surface wave effect in Gaussian beam scattering is also qualitatively analyzed by introducing a flux ratio factor. The approach proposed is particularly important to the further extension of the geometrical-optics approximation to the scattering of large spheroidal particles.     

Electrical resistivity of titanium in the temperature range from 290 to 1800 K

Studies into the electrical resistivity of titanium in the solid state are reviewed, analyzed, and generalized. The experimental data in the high-temperature region of the α-phase (290–1150 K) are approximated by an equation obtained within the two-band model approximation, and in the region of the β-phase—by linear dependence. The calculation results reveal the regularities of the effect of the defect concentration due to impurities and dislocations on the conductivity of titanium at high temperatures.     

偶极子模型在磁流变液中的使用误差研究

为了提高使用偶极子模型分析磁流变液流变性能的准确性,采用偶极子模型与有限元模型对比的方法,分析了偶极子模型的适用范围,计算了不同体积分数磁流变液偶极子模型表面磁场的误差大小,并进行了实验验证.研究结果表明,磁流变液中软磁性颗粒主要受其相邻颗粒影响;偶极子模型表面磁场最大误差为62%,出现在两颗粒表面距离最近处,在磁流变...     

The Possibility of Using Repulsive Interaction Potentials for the Calculation of High-Temperature Integrals of Collisions between Atoms and Molecules

The possibility is demonstrated of using exponential repulsive interaction potentials for the calculation of high-temperature integrals of collisions between atoms and molecules. An analytical formula is suggested, and the values of employed parameters are determined. The difference between the calculation results for complex interaction potentials with due regard for repulsion, potential well, and long-range attraction and the calculation results for the repulsive exponential interaction potential in the entire range of impact parameters is investigated. The dependence of the calculation accuracy on the choice of the region of approximation of the model potential by the exponential one is noted.     

Quasi-specular model for calculating the reflection of atmospheric-emitted infrared radiation from a rough water surface

A numerical model is developed for computation of the reflection of atmospheric-emitted IR radiance from a wind-roughened water body. The model assumes the Kirchhoff approximation for rough surface scattering. This allows application of the postulates of geometrical optics to determine the reflection of rays from an ensemble of wave facets. We performed the hemispherical integration with Gaussian quadrature by using an uplooking fast transmittance model. This calculation is simplified further through the concept of a reflection-diffusivity angle. The model compares favorably with observed radiance spectra obtained from the Marine-Atmospheric Emitted Radiance Interferometer during the Combined Sensor Program research cruise.     

Self-Consistent Calculation of the Compressibility and Viscosity of Dense Gases in the Lattice-Gas Model

A self-consistent calculation is performed of generalized diagrams of compressibility and shear viscosity of simple gases in a wide range of pressure (from rarefied states to 10P _c) and temperature (from subcritical to supercritical) on the basis of unified potential functions of interparticle interaction. A modified lattice-gas model is used which takes into account the nonideality of gases, the eigenvolume of atoms, and interactions between atoms in a quasi-chemical approximation conserving the effects of direct correlations of short-range order. The calculation results are compared with generalized diagrams of compressibility and viscosity constructed by experimental data. Quantitative agreement is obtained with experimental data for neon and oxygen.     

Influence of coating permeability in thin-film pulse recording

A modified model ofM(H)curves which uses a more realistic family of minor loops has been designed for a theory of pulse recording. The loops are defined by the initial and maximal permeability,mu aandmu m, as well as by the reversible permeabilitymu rof the tape. The calculation of the demagnetizing field, the magnetization transition, and the effective flux through the reproduce head is carried out by solving the Poisson differential equation, taking into account the boundary conditions of a two-dimensional head model. The calculation is carried out for an isolated linear magnetization transition of nonzero width. It results in Fourier integrals, the solution being provided by series expansion or approximation. The pulse amplitude and pulsewidth are given as simplified analytical functions of the tape permeability.     

Scattering of electromagnetic radiation by a metal nanoparticle

The scattering cross section of electromagnetic radiation by a small spherical metal particle has been calculated in the framework of the standard kinetic theory in a dipole approximation. The calculation has been performed for relatively small (～10 nm) particles, which allows the skin effect to be ignored. A mechanism of mixed specular-diffuse reflection of conduction electrons from the particle surface is considered. It is established that, at certain angles of scattering, the mechanism of magnetic-dipole scattering becomes dominating. The influence of kinetic effects on the differential scattering cross section is analyzed.     

Planar optical array with a spatial-integration feature

A planar optical array is presented that provides a selective concentration of the light incident upon the system onto a given area. Several alternative designs are analyzed and explained geometrically. The photometric calculation is presented for three different levels of approximation. A prototype of the proposed system is tested, showing good accordance with the theoretical predictions.     

Calculation of the optical characteristics of a multicomponent multiply charged plasma

A theoretical model is developed and results of calculations of thermodynamic and optical characteristics of a plasma in the approximation of a radiative-collisional model that allows their calculation in wide temperature and density ranges are reported. Energy levels, ionization potentials, probabilities of transitions are calculated by quantum-mechanical methods in the Hartree-Fock-Slater approximation. For some chemical elements use is also made of extensive experimental spectroscopic information that provides the possibility of determining the energy levels and wavelengths of optical transitions with a high accuracy.     

Aspects concerning the choice of measuring points and specificationof parameters needed for a proper determination of magnetic fields

Laplacian fields approximated by a finite series based on an orthogonal set of spherical harmonics are treated. A procedure for estimating the optimal shape of an approximation model, showing not only the variety of degrees but also the highest significant order and a possible order absence of involved field functions, is developed. The restrictions on the distribution of field observations are specified, and a way to ensure a distribution respecting these restrictions that leads to a reduction of necessary field observations is proposed. On the basis of computer simulation, rules for the estimation of the minimal number and distribution of observation points necessary for a proper analysis of a field determination by a particular approximation model are specified. The approach substantially reduces time and calculation effort for magnetic field analysis     

Shock-wave compaction of the granular medium initiated by magnetically pulsed accelerated striker

The experimental and theoretical investigation of the granular medium shock-wave compaction process is made. The striker acceleration in the experiments is realized by pulsed magnetic field force action. The granular medium is alumina nanopowder. The mathematical model of the process describes the energy dissipation, which is stipulated by the work made to compact the powder, considering the loss for the non-ideal reflection of the shock wave from the discontinuity surfaces on the borders of the body being compacted. There is a satisfactory fit of the theoretical calculations and the final compact’s density experimental data. In terms of the low-energy shock front approximation the problem of the time dynamics calculation of the granular medium state is narrowed down to the system of ordinary non-linear differential equations. The limitation the striker to low energies linearizes the system, allowing to take its rigorous solution. The influence of such parameters as starting voltage of the capacitor, powder and striker masses and wave resistances of contacting materials on the compaction process is analyzed.     

Calculation of cyclotron rf systems

An approximate calculation of the characteristic properties of resonators for cyclotron rf systems is described. Formulas for the characteristic impedence of line segments are evaluated and an approximation for a dee-dummy dee system is given. A computer program has been written which also takes into account the capacity due to line discontinuities. The computed resonance frequency for cyclotrons in Eindhoven and Jülich agrees within 5% with experimental data. The power consumption is also computed and analyzed.     

Improved confidence limits for low-dose carcinogenic risk assessment from animal data

An improved procedure is presented for estimating low-dose risks from dichotomous animal data. Based on the multistage model of cancer, the procedure gives a maximum likelihood fit to the experimental data. Because the model is approximately linear in the low-dose range, the procedure may be considered to be a generalized method for linear extrapolation which uses all of the data. The extrapolation procedure is different from an earlier procedure based upon the multistage model in that two improved methods are put forward for calculating statistical confidence limits. (One is a linearized approximation of the other.) A further innovation is a recommendation for the integration of several data sets in the calculation of risk levels.     

A New Approach to Calculating the Potential Energy of Interaction between Two Atoms

A Fourier component of the potential energy of interaction between two atoms has been presented as a polynomial of the biquadratic atomic form factor. A numerical calculation has been performed in the screened Coulomb potential approximation. It is demonstrated that the account for the Pauli principle leads to the occurrence of a potential barrier and an additional region of attraction of two atoms. This model is shown to agree qualitatively with the results of the density-functional-theory calculation.     

一维复合波入射的固-固界面接触特性分析

基于弹性波理论,针对接触面非线性相互作用,建立了一个非线性刚度模型,利用接触应力描述非线性刚度特性。引入包含基波和谐波的一维复合波入射,在二阶微扰近似以及非线性边界条件下,给出了界面的反射波和透射波的表达式,得到反射系数和透射系数。结合界面线性刚度和接触应力的幂律关系,定义了四个非线性系数。通过数值计算分析了固-固界面的非线性特性以及谐波对于接触应力的依赖性。