20～6000 K温度范围内二氧化碳配分函数的计算

在20～6000 K温度范围内,通过乘积近似计算了二氧化碳及其同位素的总的配分函数.其中振动配分函数用谐振子近似,转动配分函数考虑了离心扭曲修正.20～6000 K温度范围被划分为五个小区间.在每一个小区间,计算的总的配分函数被拟合到一个温度T的四阶或五阶多项式,从而获得五个或六个拟合系数.通过这些拟合系数可以快速准确的获得分子在所研究温度范围内任意温度下的总配分函数.     

A microscopic theory of the lambda transition,II

The previously proposed finite temperature field theory of the lambda transition based on the Schwinger functional method is investigated further. A systematic method for calculating the higher-order loop terms is presented by introducing the one-loop Green's functions, which are found to be a natural finite temperature extension of the Beliaev-Hugenholtz-Pines-Gavoret-Nozières zero-temperature Green's functions. The application of the finite temperature loop expansion to the dynamical properties is presented by calculating the retarded density correlation functions at the one-loop level. The result gives a microscopic basis for the form of the dynamical structure factor recently proposed by Woods and Svensson. From a general point of view, without using any approximations or model interactions, Goldstone's theorem for the lambda transition at finite temperature is presented.     

Application of the real space dynamic renormalization group method to the one-dimensional kinetic ising model

We apply the recently developed real space dynamic renormalization group method to the one-dimensional kinetic Ising model. We show how one can develop block spin methods that lead to recursion relations for the space and time dependent correlation functions that correspond to the observables for this system. We point out the importance of carefully choosing the appropriate parameters governing the behavior of individual blocks of spins and the necessity of worrying about the high temperature properties of the temperature recursion relations if one is to obtain the proper exponential decay of correlation functions at large distances away from the critical point at zero temperature. We systematically investigate the accuracy of our approximate recursion relations for various correlation functions by checking them against the known exact results. Our simple methods work surprisingly well over a wide range of temperatures, wavenumbers and frequencies.     

二氧化硅分子配分函数的研究

在低温20K到高温6000K温度范围内,计算了¹⁶O²⁸Si¹⁶O分子稳定结构的的总配分函数.其中,转动配分函数考虑了离心扭曲修正,振动配分函数采用谐振子近似.把20—6000K的温度范围划分为五区间段,计算的总配分函数在这五个温度区间分别被拟合到一个温度T的四阶多项式,从而在每个区间均得到五个拟合系数.由这些拟合系数就可以快速、准确地获得分子在所研究温度范围内任意温度的总的配分函数. 关键词： 总配分函数 二氧化硅分子 转动配分函数 振动配分函数     

A new method to eliminate the influence of the backward defect infection and the position-dependent of the coefficient on distributed Brillouin fiber sensor

Two theoretical problems associated with the measurement of temperature or strain from the normalized power of Brillouin signal in a distributed fiber sensor are studied. One problem is the position-dependent of the coefficient relating the Brillouin power to the local temperature or strain. The other problem is the backward infection of the defect (local temperature or strain change). These two problems will degrade the measurement accuracy of a distributed Brillouin fiber sensor by changing the distribution of pump power. To eliminate these two problems, new reference functions are proposed to normalize the Brillouin signal. Simulation results by using fourth-order Runge-Kutta algorithm show that these new reference functions can eliminate the influence of these two problems on distributed Brillouin fiber sensor.     

The thermodynamic functions and the regions of (P,T)-states of dense carbon and boron nitride modifications

Abstract

For the first time the thermodynamic functions for boron nitride and carbon were defined in the temperature range 300 to 4000K by a computational procedure which was impossible in the previous empirical approach. This involved the application of the theoretical functions from Refs. 1, 2, and 3. There the temperature dependence of the heat capacity is characterized by a sum of two Debye functions that reflect the contribution of vibration modes of different characteristic temperature to the heat capacity. The above-mentioned theoretical functions make it possible to calculate the thermodynamic function without allowing for the anharmonic effect in the temperature range rather wider th-an the one wherein the initial experiments were conducted. It is sufficient for their computation to define Debye characteristic temperatures. One of the procedures of their calculation using experimental enthalpy data is described in Ref. 4. Besides, this work contains the majority of known experimental and theoretical data which enable various methods of the thermodynamic function characterizations for carbon and boron nitride to be compared.     

On the derivation of the entropy of ideal quantum gases confined in a three-dimensional harmonic potential

In this work,the entropy functions of ideal quantum gases in a three-dimensional harmonic trap are analytically calculated using temperature as an explicit variable.Afterward,the applicability of the analytical formulas is validated by comparison with the numerical calculation.The results illustrate that the obtained functions could be applied for the whole temperature regime with a maximum relative deviation of less than 7.5%in the vicinity of the critical temperature Tcin the case of Bose gases.Meanwhile,for Fermi gases,although the analytical formula fits well at very low-and high-temperature regimes,it cannot be applied at temperature in the range[0.3-0.5]T_F,where T_F is the Fermi temperature.In addition,the consistency between our formulas and classical ones at significantly high temperatures is also discussed.     

The scaling limit and Osterwalder-Schrader axioms for the two-dimensional Ising model

From a Feynman-Kac formula in a Fermion Fock space for the Schwinger functions of the infinite lattice periodic two-dimensional Ising model, scaled and scaling limit Schwinger functions are defined and shown to admit an absolutely convergent series representation. As the critical temperature is attained, it is shown that the scaled Schwinger functions converge and that the resulting scaling limit Schwinger functions obey the Osterwalder-Schrader axioms.     

Active Q-switching of the Alexandrite laser

An alexandrite-laser rod was actively Q-switched in the transversal fundamental mode at λ = 758 nm with an double crystal KD^*P Pockels cell. Pulse width, pulse energy and optical pulse delay (the build-up time of the photon field in the resonator) were measured as functions of pumping energy, rod temperature and reflectivity of the output coupling mirror. As the laser gain of alexandrite strongly depends on temperature, the pulse width and pulse energy were also investigated as functions of the temperature of the active material. A comparison of experimental data with theory was made.     

On the dynamics of impure classical Heisenberg chains

We present theoretical results on dynamic correlation functions of impure, classical, one-dimensional Heisenberg magnets with both ferromagnetic and antiferromagnetic coupling. The results are obtained in the framework of Mori's theory and in an approximation which includes correctly all moments of the relaxation function to lowest order in impurity concentration and temperature and which preserves the rotational symmetry of the system even at zero temperature. Explicit results are given for lineshifts and linewidths of quasi-spinwaves and the behaviour of correlation functions in the hydrodynamic limit is discussed.     

On the determination of the Debye temperature from experimental data

It is shown that the Debye temperature as a function of temperature must satisfy certain equations in order for the thermodynamic functions calculated in terms of the Debye temperature to satisfy both the third law of thermodynamics and the law of equipartition of energy. A general expression for the Θ(T) function satisfying these thermodynamic laws is found.     

Theory of the Ionization Equilibrium in Nonideal Alkali Plasmas

With the help of local pseudopotentials and binary distribution functions bound and scattering state parts of the thermodynamic functions of nondegenerate nonideal alkali plasmas with a large interaction parameter are calculated. The one-particle distribution functions for the atomic levels are obtained by reinterpretation from the bound state part of the binary distribution functions. The ionization equilibrium is described by a Saha equation which is evaluated for certain ranges of temperature and density. The transition to high conducting states is discussed.     

How many constitutive functions are necessary to determine a thermoelastic material?

The independence of the constitutive functions of a thermoelastic material compatible with the Clausius-Duhem inequality is analysed. The constitutive functions for the absolute temperature and entropy are shown to be determined (to within a change of a unit for the absolute temperature and the entropy constant) by the constitutive functions for the stress tensor and the heat flux vector. Hence two constitutive functions are sufficient to specify a thermoelastic material.     

Dynamic mean field in the Hubbard model

In the framework of the one-impurity problem formulated for the nondegenerate Hubbard Hamiltonian, general expressions are derived for all its principal correlation functions, as well as its retarded and advanced thermodynamic (Matsubara) Green functions. These results are analyzed for the case of zero temperature.     

Construction of the distribution functions of the oh radicals in the H2-O2 flame

In the present paper the construction of the distribution functions for OH radicals in the H₂-O₂ flame is dealt with. The construction is based on the fact stated in [1] that there are two groups of OH radicals in the flame. It is shown here that the method for temperature determination used in [1] can be considered as the first approximation only. According to this fact the method of determining the parameters of the flame (temperature etc.) solving system of equations for line intensities is presented here. In practice it is possible under certain conditions, discussed here, to use an improved method in order to determine the flame parameters and distribution functions of OH radicals. Also the reduction of the temperatures of the cold group of OH radicals based on above mentioned improved method is discussed here. The values of the temperature of the cold group of OH radicals to be reduced are taken from [1].     

Consideration of the temperature dependence of infrared spectra in the context of classical specific heat theory

The dependence of harmonic frequencies on the temperature and broadening of vibrational energy levels is considered in the context of classical Debye and Einstein specific heat theories. Analytical expressions for the vibrational thermodynamic functions are derived with allowance for these factors. It is shown that consideration of these two factors leads to the fact that the average energy of low-frequency oscillators differs from the statistical temperature, and the high-frequency fluctuations give a nonzero contribution to the specific heat. These expressions are used to calculate the thermodynamic functions of liquid water, and reliable agreement with the experiment is obtained. Voronezh State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 81–88, June, 2000.     

Unification of the quantum and classical theories of methyl NMR.

The existing low and high temperature theories of methyl NMR are not linked because two conditions imposed on state functions in the low temperature theory are not compatible with the classical rotations on which the high temperature theory is based. The conditions do not occur in a geometrical theory of quantum phenomena in which particles and waves have separate roles. When applied to methyl dynamics, this theory covers the whole temperature range.     

Statistical model for the structure functions of the nucleon

The deep-inelastic structure functions of the nucleon are calculated in a statistical model considering the nucleon to be composed of a gas of quarks and gluons. Several differences with the standard parton-model approach are pointed out. To zeroth order in perturbative QCD, the model is worked out completely. A fit to the large-x part of the structure functions requires a temperature of about 40–50 MeV for the quarks and gluons and a chemical potential around 200 MeV.     

Effect of magnetic field and radiative condensation on the Jeans instability of dusty plasma with polarization force

The Jeans instability of self-gravitating dusty plasma with polarization force is investigated considering the effects of magnetic field, dust temperature and radiative condensation. The condition of Jeans instability and expression of critical Jeans wave number are obtained which depend upon polarization force and dust temperature but these are unaffected by the presence of magnetic field. The radiative heat-loss functions also modify the Jeans condition of instability and expression of critical Jeans wave number. It is observed that the polarization force and ratio of radiative heat-loss functions have destabilizing while magnetic field and dust temperature have stabilizing influence on the growth rate of Jeans instability.     

Universal low-temperature properties of frustrated classical spin chain near the ferromagnet-helimagnet transition point

The thermodynamics of the classical frustrated spin chain near the transition point between the ferromagnetic and the helical phases is studied. The calculation of the partition and spin correlation functions at low temperature limit is reduced to the quantum mechanical problem of a particle in potential well. It is shown that the thermodynamic quantities are universal functions of the temperature normalized by the chiral domain wall energy. The obtained behavior of the static structure factor indicates that the short-range helical-type correlations existing at low temperatures on the helical side of the transition point disappear at some critical temperature, defining the Lifshitz point. It is also shown that the low-temperature susceptibility in the helical phase near the transition point has a maximum at some temperature. Such behavior is in agreement with that observed in several materials described by the quantum s = 1/2 version of this model.