Faculty of Physics
M.V.Lomonosov Moscow State University
Theoretical and mathematical physics

## On the solution uniqueness for one of the carbonitriding control problems

### I.Е. Stepanova and V.В. Glasko

Moscow University Physics Bulletin 1993. 93. N 3. P. 1

The problem of uniqueness of determination of the process objective characteristics in the case of carbonitriding of а plane specimen is considered. The results obtained can also bе of interest to more general statements of inverse problems and, in particular, саn bе related to thermal conduction models. Also presented are the results of а mathematical computer experiment.

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Atomic and nuclear physics

## On the spectrum of cosmic ray protons with energies above 1 TeV

### N.L. Grigorov

Moscow University Physics Bulletin 1993. N 3.

Two teams of investigators were engaged in processing the results of experiments on the Kosmos 1713 satellite in which spectra of protons with energies above 5 ТеV were meas11red, but the conclusions they drew differed considerably. In this paper it is sl1own that the reason for the discrepancy in conclusions is that one of the teams included data on particles that do not satisfy the adopted proton selection criteria. When the selection criteria are adhered to, the data processing techniques used Ьу the teams yield the value of the integral proton spectrum exponent in the region of Е=5 TeV of 2.0 ± 0.18.

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## Analysis of douЪle-differential cross section of photonuclear reaction (1, n) on Au and Bi nuclei in the formalism of statistical multistep compound-processes.

### F.А. Zhivopistsev, V.А. lvanov, and S.А. Abdel-Munem

Moscow University Physics Bulletin 1993. 93. N 3. P. 11

А program for calculating the double-differential cross section of neutron emission from the (gamma, n) reaction at energies of incident gamma-quanta in the region of а giant dipole resonance has been developed within the framework of а modernized quantum model of giant multipole resonance decay taking account of spins. The model has no free parameters and does not use inverse reaction cross sections in the calculations of neutron emission spectra. The energy and angular distributions of photoneutrons from the Bi(gamma, n) and Au(gamma, n) reactions have bееn calculated for energies of bremsstrahlung gamma-quanta Еgamma,mах = 14.2, 14.9, and 20 MeV. Satisfactory agreement with the experimental data published in the literature is obtained.

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## The use of electrostatic undulators to form helical relativistic electron beams

### А. F. Aleksandrov, V.А. Kubarev, and А.V. Lugovskoi

Moscow University Physics Bulletin 1993. 93. N 3. P. 16

lt is proposed to use electrostatic undulators with resonant guiding magnetic field to form helical clectron beams. An analytical technique is developed for calculating and optimizing the parameters of planar constructions with mirror symmetry plane.

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## Improvement in noise immunity of discrete information reception bу selective excitation of the ionosphere

### Yu.V. Berezin, М.О. Okulov, and D.Уе. Ryzhov

Moscow University Physics Bulletin 1993. 93. N 3. P. 21

This paper presents results of experiments on the improvement of the quality of data transmission over an ionospheric communication channel due to selectively excited characteristic waves in the ionosphere. lt is shown that selective excitation of waves in the ionospl1ere improves noise immunity bу at least 10-15 dB.

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## Determination of the geometry of ionospheric irregularities bу the differential phase method

### V.D. Gusev and D.V. Kir'yanov

Moscow University Physics Bulletin 1993. 93. N 3. P. 25

The possibility of investigating the geometry of small-scale ionospheric irregularities bу the difl'erential phase method is analyzed for different values of the ionosphere perturbation factor.

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## Experimental study of а Cerenkov-type sectioned relativistic microwave-frequency multiplier

### А.F. Aleksandrov, S.Yu. Galuzo, V.I. Kanavets, and А.М. Kuznetsov

Moscow University Physics Bulletin 1993. 93. N 3. P. 73

An experimental study of а Cerenkov-type two-section frequency multiplier with а multiplicity factor n = З has been performed. А Cerenkov generator of the type of backward-wave tube 11as beell used as the first multiplier section and а traveling-wave tube has served as its second section. The feasibility of creating such devices in the relativistic region of electron energy using heavy-current electron beams has been demonstrated.

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Optics and spectroscopy

## Soli ton mechanisms of ultrashort pulse formation in actively mode-locked fiber lasers

### V.А. Vysloukh and Е. Marti-Panameno

Moscow University Physics Bulletin 1993. 93. N 3. P. 30

The principal features of ultrashort pulse generation in an actively mode-locked fiber laser have been studied both analytically and numerically. It has been shown that the utilization of soliton effects allows the width of the output pulse to bе diminished шоrе than bу an order of magnitude without loss of the mean output energy.

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Solid state physics

## Gravitational wave perturbation in the phonon space

### Li Fangyu

Moscow University Physics Bulletin 1993. 93. N 3. P. 37

The method of complex operators has been used to study the gravitational wave perturbation of the phonon space with inhomogeneous shear modulus. The equivalent perturbation force is calculated and the corresponding phonon model is specified.

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## Fine structure of X-ray beams emergent from а band-shaped waveguide

### V.А. Bushuev and М.N. Orudzhaliev

Moscow University Physics Bulletin 1993. 93. N 3. P. 41

Specific features of the formation of а fine structure of X-ray beams at the exit from а band-shaped waveguide are studied using а waveoptics approach and а geometrical optics approximation. It is slown that the results of the study agree well with the known experimental results bу Mingazin with co-authors.

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## Specific features of local atomic distributions in $Mn_{19,5-x}Fe_{0,5}Sn_x$ alloys

### А.S. Ilyushin, I.А. Nikanorova, V.S. Rusakov, М.А. Mostafa, and S.-M.Sh. Mashaev

Moscow University Physics Bulletin 1993. 93. N 3. P. 47

А Mossbauer study of local atomic distributions in $Mn_{19,5-x}Fe_{0,5}Sn_x$ alloys is reported. Local distributions of two different types are shown to bе formed in alloys of the quasi-Ьinary system depending on the composition.

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## Spin-phonon-electron correlations in high-temperature superconductors

### А.V. Vedyaev, М.I. Zubtsov, М.А. Savchenko, and А.V. Stefanovich

Moscow University Physics Bulletin 1993. 93. N 3. P. 51

Spin excitation (spin fluctuation) spectra in the superconducting phases of hightemperature $La_{2-x}Sr_xCuO_4$ - and $YBa_2Cu_3O_{7-y}$-type superconductors are considered, as well as tl1eir influence 011 tl1e therшodynamic characteristics of these compounds, primarily on tl1eir low-temperature heat capacity, which is shown to have а power dependeпce on temperature. In the region of values of the $k\simeq k_F$ (Тikp is the Fermi momentum) wave vector, the spectra of coupled spinphonoп vibratioпs responsiЫe for the appearance of coupled electron pairs in the superconducting state are analyzed. It is shown that the critical temperature $Т_с$ of high-temperature superconductors, determined Ьу the. spin-phonon coupling parameter $\tilde{\zeta}$, is limited for tl1e compounds studied, which motivates а more detailed coпsideration of spin-electron correlations in high-temperature superconductors.

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## The effect of electric field on hysteresis phenomena in $Rb_2ZnCl_4$ crystals grown from the solution and from the melt

### В.А. Strukov, Е.Р. Ragula, and S.N. Gorshkov

Moscow University Physics Bulletin 1993. 93. N 3. P. 58

Hysteresis phenomena on the curve of permittivity versus applied electric field and temperature in the region of the Сuriе temperature have been studied for $Rb_2ZnCl_4$ crystals grown from the solution and from the melt. The results indicate that hysteresis phenomena depend on the defect concentration of the specimen crystal structure.

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Theoretical and mathematical physics

## Computation of dielectric waveguides with intricate cross-sections Ьу the variate-difference method

### А.N. Bogolyubov and Т.V. Edakina

Moscow University Physics Bulletin 1993. 93. N 3. P. 64

А computation algorithm is suggested for dielectric waveguides with intricately shaped cross-sections based on the variate-difference method.

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## А class of spherically symmetric Finslerian metric functions with indicatrix of constant curvature

### G.А. Asanov

Moscow University Physics Bulletin 1993. 93. N 3. P. 67

А broad class of exact solutions is indicated for Finslerian equations in the static spherically symmetric case under the assumption· that the fibers are spaces of constant curvature.

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## The influence of bulk and surface recombination effects on the time lag in microwave opt ic control

### L.А. Borisov, Wang Shan, V.V. Gladun, Yu.А. Pirogov, D.А. Tishchenko, and Е.I. Fominova

Moscow University Physics Bulletin 1993. 93. N 3. P. 69

It is shown that as the thickness of а longitudinal semiconductor insert in а rectangular waveguide decreases, the effective lifetime of free carriers photoexcited bу light diminishes owing to the predominance of the surface recombination over the bulk one in thin plates. Ву contrast, in thick samples, the more protracted bulk recombination processes prevail. They provide а higher factor of microwave energy modulation but the time lag of the response is larger.

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Solid state physics

## Products of soil corrosion of an iron sample as studied Ьу Mossbauer spectroscopy

### А.A. Novakova,Т.S. Gendler, N.D. Manyurova, and R.А. Тurishcheva

Moscow University Physics Bulletin 1993. 93. N 3. P. 76

The chemical and phase compositions of the outer corrosion layer has been studied in an archeological iron nail that lay buried in the soil of the Smolensk region since 12th century. Combined experimental methods revealed that this layer comprised finely dispersed $alpha Fe_2O_3 gamma Fе_2O_3$, and partially oxidized $FeS_2, FeCl_2\cdot2H_2O, Fe_3(PO_4)_2\cdot 8H_2O, FeSO_3\cdot 3H_2O and FeSO_4\cdot4H_2O$.

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## Phase diagram of а quasi-binary system $Er_{1-x}Tb_xMn_2$ synthesized at а high pressure

### А.S. Ilyushin, I.А. Nikanorova, М. Al-Dervish, А.V. Tsvyashchenko, L.N. Fomicheva, and Shi Lei

Moscow University Physics Bulletin 1993. 93. N 3. P. 80

The phase composition and atomic-crystalline structure of alloys of the quasibinary system $Er_{1-x}Tb_xMn_2$, synthesized at high pressures, have been studied bу X-ray analysis. The phase diagram of this system in the composition-pressure coordinates is constructed.

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