The internal friction of longitudinal oscillations in ferromagnetic materials

The paper deals with the theory of the new magnetomechanical phenomenon in an alternating field [6, 7]. The first part concerns the internal friction of longitudinal oscillations of a ferromagnetic material in the shape of a wire in a constant magnetic field. It is assumed that the medium in which the sample oscillates is conducting and has a certain permeability. Equations defining the magnetic field in the oscillating material are derived from the basic thermodynamic relations. The term describing the non-conservative force component in a complex formulation is used to determine the internal friction. A general relation between the internal friction and the magnetic field is derived, as well as other expressions, which are a simplification of it. The second part of the paper deals with internal friction in an alternating field. It is shown that the solution can be transformed to the sum of the internal frictions of the different harmonic oscillations, which are obtained as a partial solution of the problem on the assumption that the elastic oscillations in interaction with the field oscillations are separated into their harmonic components. The calculation then becomes that of the internal friction considered in the first part of the paper. In this case the internal friction significantly depends on the field amplitude. The functional dependence of the internal friction peak on the frequency of the mechanical oscillations is also calculated. The agreement of the theory with experiment is satisfactory.

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Phases and reactions in the Li x Mn3−x O y system

The dissociation and oxidation processes occurring in Li _x Mn_3–x O _y in air in a temperature range between 0 and 12 000°C were examined by means of thermographic and X-ray methods. Lithium and manganese form oxides with a spinel structure in a broad interval of the oxidation degree of manganese ions. As consequences of the oxidation degree and of the temperature, changes of the lattice parameters, of the cation distribution in the spinel lattice and the occurrence or disappearance of a tetragonal deformation of the lattice are experienced. In the temperature range between 950 and 1100°C probably the Li₂Mn₄O₇ compound and its solid solutions with Mn₃O₄ occur.The authors wish to express their gratitude to A. ápová, J. Mikulíková and E. Kitzinger for their helpful cooperation.     

ПЛОТНОСТЬ ТОКА В АНОД НЫХ ПЯТНАХ ИСКРОВЫХ РАЗРЯДОВ В ВОЗДУХЕ ПР И АТМОСФЕРНОМ ДАВЛЕН ИИ

annapamyp, . .     

A theorem of Šarkovskii on the existence of periodic orbits of continuous endomorphisms of the real line

Two theorems are proved—the first and the more important of them due to ?arkovskii—providing complete and surprisingly simple answers to the following two questions: (i) given that a continuous mapT of an interval into itself (more generally, into the real line) has a periodic orbit of periodn, which other integers must occur as periods of the periodic orbits ofT? (ii) given thatn is the least odd integer which occurs as a period of a periodic orbit ofT, what is the “shape” of that orbit relative to its natural ordering as a finite subset of the real line? As an application, we obtain improved lower bounds for the topological entropy ofT.     

Thermopower and conductivity of semiconducting vitreous system CdTlxAs2

The d.c. conductivity and thermoelectric power of vitreous system CdTl _x As₂ have been investigated as a function of temperature. Experimental data are analyzed in terms of a random phase model.     

Measurements of frequency of ionization waves in axial magnetic field

The observations of the frequency change of selfexcited ionization waves in an axially electric field are present. The typical results obtained in Ne discharge are discussed.On leave fromCharles University, Dept. of Electronics and Vacuum Physics, Prague, Ke Karlovu 5, 121 16 Praha, Czechoslovakia.     

Internal conversion coefficients in the Hartree-Fock atomic model. Calculations and experiments for199Hg

The internal conversion coefficients were calculated for the transitions in¹⁹⁹Hg using both Hartree-Fock and Hartree-Fock-Slater atomic models. The relative conversion line intensities were measured with the magnetic spectrometers in Prague and Heidelberg. The multipolarities were determined to be:M1+(0.20±0.03)%E2, pure E2 and M 1+ (13.4 ±0.4)%E2 for the 50, 158 and 208 keV transitions, respectively. Allowing for the nuclear structure effect in M1 component we obtained: M1+(0.15±0.03) %E2,λ = 2.4±1.0 for the 50 keV and M1+ (10.9±0.7)% E2, λ=3.8±0.5 for the 208 keV transitions. Very good agreement was found between theory and experiment for the atomic subshells,K, L_1?3,M _1?5,N, andO + P.     

Über die Möglichkeiten der intramolekularen Wechselwirkung in (2-Hydroxyäthyl)- und (2-Chloräthyl)aryidimethylsilanen

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