On the thermodynamic potentials for superconductors of second type
On the thermodynamic potentials for superconductors of second type
F.F. Ternоvskii
Within the framework of the Ginzburg - Landau theory, a study is conducted of the local equilibrium expressions for the free energy and Gibbs potential of a superconductor of the second kind (arbitrarily shaped) in an external field and carrying a transport current. It is shown how the London magnetic field $H_L$ and the intrinsic field $H_V$ of vortex filaments may be determined in this general case. Terms isolated from expressions for the thermodynamic potentials are proportional to the circulation sums $H_V$(in the case of free energy) or $H_V$ + + $2H_L$ (in the case of the Gibbs potential) along closed circuits that bound sections connecting the axial lines of the vortex filaments to the superconductor surface. If $H_V$,$H_L$≪$H_{c2}$, these terms yield the basic (dependent on the configuration of the vortex filaments) contribution to the thermodynamic potentials.
Show AbstractNeutrino production by two photon in a strong external field
Neutrino production by two photon in a strong external field
Yu.M. Loskutov, V.V. Skobelev
A loop diagram with a single "weak" and two "vector" vertices is computed within the framework of a proposed asymptotic treatment of the Green's electron function for a strong magnetic field. The process of two - photon production of neutrino pairs is studied, and their angular distribution and total production cross section are found. The contribution of this process to the neutrino luminosity of pulsars is estimated.
Show AbstractOn the radiation migration in crystal
On the radiation migration in crystal
V.I. Grigоriev
An exact solution of the evolution problem for a boson packet in a " model " ideal infinitely extended crystal constructed of identical twolevel centers is obtained and studied: dissipative and temperature effects are ignored. A technique is proposed for the microscopic desrcription of the dynamics of the propagation of both long - wave as well as short - wave emission packets, as a result of which qualitative features of processes in the case of different ratios of the scale of microscopic inhomogeneities to the emission wavelength are identified.
Show AbstractSmall low frequency underwater transducers based on discrete periodic structures
Small low frequency underwater transducers based on discrete periodic structures
M.A. Коneva, P.N. Kravchun, К.V. Сhernуshev
A piezoelectric hydroacoustic radiator consisting of a discrete periodic structure with assemblies whose inertial elements are piezoelectrically active and whose elastic elements are passive is considered. Formulas for the resonance frequencies of the radiator and the oscillation amplitudes of its radiating surface are analyzed. Optimal phase shifts between the voltages fed to the piezoelectric elements are found. Experimental results are presented for the case of a three-assembly structure that demonstrates that the above systems may be used as multifrequency radiators.
Show AbstractThe synthesis of continious matching transitions between rods-like wave guides
The synthesis of continious matching transitions between rods-like wave guides
E.V. Imenitova, К.V. Chernyshev
The form of amatching transition is determined by the wave propagation equation for a rod of variable cross section and must correspond to a deep enough local minimum of the local (in a specified frequency band) mismatch factor. The fundamental system of solutions of this equation is used, so that it is possible to find the mismatch factor. Then, based on some initial approximation, the form of the transition is determined by means of the method of steepest descent. In the article, examples are considered which relate to the most interesting case of short transitions, to which a nonmonotone relation between the radius of the bar and the longitudinal coordinate corresponds.
Show AbstractEnergy of ordering in alloys of Mg—In and Mg—Cd, calculation using the pseudopotential approximation and comparison with experiment
Energy of ordering in alloys of Mg—In and Mg—Cd, calculation using the pseudopotential approximation and comparison with experiment
A.A. Katsnelson, L.A. Safrоnоva, V.M. Silоnоv
The ordering energy is computed by means of the pseudopotential method for Mg-In and Mg-Cd alloys. The computation results are compared to the ordering energy determined from diffuse scattering of X - rays. Over significant concentration intervals, the theoretical and experimental values of the ordering energy for the first coordination sphere are close in magnitude.
Show AbstractSome features of the antiferromagnetic resonance in MnCl(2)
Some features of the antiferromagnetic resonance in MnCl(2)
M.О. Kostryukova, Iоnov A.V.
Resonance absorption in $MnCl_2$ corresponding to the low-frequency branch of the antiferromagnetic resonance is studied. Measurements are performed at frequencies of 9.2 and 38 GHz in the temperature region 1.4- 4.2° K. The experimental data are compared to the conclusion of the theory of light-plane antiferro magnetics. Effects which tend to alter the size of the gap in the low-frequency branch are discussed.
Show AbstractThe five-wave model of the coherent Raman mixing
The five-wave model of the coherent Raman mixing
Yu.E. Dyakov, V.A. Nekhaenko, S.Yu. Nikitin
A five-wave model of coherent Raman mixing is considered for the case in which a test wave with frequency $ω_t$ is scattered by vibrations of the medium $ω_o$ both in the stokes ($ω_t$ → $ω_ir$ = $ω_t$ - $ω_o$) and in the anti-Stokes ($ω_t$ → $ω_α$ = $ω_t$ + $ω_o$) region in the case of pumping of forced lattice vibrations($ω_p$ → $ω_sin$ = $ω_p$ - $ω_o$). The fifth wave ($ω_ir$ or $ω_o$) is important to take into account for media with relatively weak dispersion (for example, gases). An analytic and numerical study of the model is performed for experimental conditions with production of tuned infrared radiation in hydrogen. It is shown that the inclusion of a fifth wave ($ω_a$) radically alters the pattern of interaction due to strong energy pumping into this wave. An approximate solution of the coherent Raman mixing equations is obtained, making it possible to compute the frequency conversion efficiency as a function of the field frequencies, gas pressure, and pumping intensity.
Show AbstractThe study of sapphire cylinders torsional vibrations
The study of sapphire cylinders torsional vibrations
V.P. Mitrofanov, О.I. Pоnоmarevа
An electrostatic method of excitation and registration of torsional vibrations of mechanical cylindrically-shaped cavities made of sapphire is described. Calculated amplitudes of the excited vibrations and the transducer response are given. Torsional vibrations of a sapphire cavity with Q-factor 7.5-10$^7$ is achieved at room temperature.
Show AbstractThe study of superposed Raman lines in cyclohexane using method of coherent ellipsometry
The study of superposed Raman lines in cyclohexane using method of coherent ellipsometry
L.S. Aslanyan, A.F. Bunkin, S.A. Chupryna
The structure of an irregularly broadened band at 1445 cm$^{-1}$ in cyclohexane is resolved by means of coherent Raman ellipsometry. The threshold capabilities of the method for the purpose of resolving superposed Raman lines are discussed.
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