Suppression of the domain structure in uniaxial ferromagnetic films with a superconducting coating

Specific models of domain walls are used to investigate conditions for the single-domain state and quasi-single-domain states in structures with magnetic materials having a quality factor higher than one. It is shown that the critical thickness of the magnetic film in a tangentially magnetized system decreases monotonically as the magnetizing field increases from zero to the transition from the collinear to the homogeneous angular phase and then increases monotonically with increasing external field. In a thin isolated magnetic film, the size of the domains increases exponentially with decreasing thickness. This dependence is logarithmic near the transition to the single-domain state for a film coated on two sides and obeys a power law for a film coated on one side. The establishment of a single-domain state and characteristic features in the asymptotic behavior of the domain structure in magnetic films with and without coatings can be attributed to differences in the asymptotic behavior of the field of a single domain wall. Fiz. Tverd. Tela (St. Petersburg) 40, 1068–1074 (June 1998)     

SPE电极上Pt单组分及Pt-Au双组分还原态CO_2阳极剥离电化学氧化行为研究

采用循环伏安法，对ＳＰＥＰｔ电极以及ＳＰＥＡｕ－Ｐｔ电极上还原态ＣＯ２的电化学氧化行为研究表明，此类电极的电化学特性与光滑Ｐｔ电极一致：ＣＯ２在氢原子吸附电位区０～２５０ｍＶ（ｖｓ．ＲＨＥ）处，可与电极上化学吸附的氢反应，生成还原态的ＣＯ２，通过线性扫描，还原态ＣＯ２即发生一不可逆电化学氧化过程（阳极剥离）．在ＳＰＥＰｔ系列及ＳＰＥＡｕ－Ｐｔ系列上ＣＯ２的电化学行为表明，当ＳＰＥＰｔ系列上Ｐｔ的载量为２．５ｍＬ的０．０１ｍｏｌ·Ｌ－１Ｈ２ＰｔＣｌ６的Ｐｔ时，对还原态ＣＯ２的电催化活性最好，当Ｐｔ的载量相同时，在ＳＰＥＡｕ－Ｐｔ上，催化剂对还原态ＣＯ２的电化学氧化行为比ＳＰＥＰｔ电极更强，这是由于预先沉积的Ａｕ对后沉积的Ｐｔ有调制作用．     

Effect of the susceptibility on the magnetic phase diagrams of a ferrimagnet with magnetic instability

The magnetic phase diagrams of a two-sublattice ferrimagnet with a magnetically unstable subsystem are calculated taking account of the susceptibility. Analytic expressions are obtained for the phase-transition fields and critical values of the parameters of the ferrimagnet. The evolution of the magnetic phase diagrams as the susceptibility of the unstable sublattice increases is analyzed.     

Enhancement of the quantum characteristics of light from an inversionless three-level Λ-laser in cascade schemes

We show that when a three-level laser is excited by Poisson light the lasing remains sub-Poisson, as asserted by H. Ritsch, M. A. M. Marte, and P. Zoller [Europhys. Lett. 19, 7 (1992)], only if there is no reciprocal action on the exciting laser (weak coupling). In cascade schemes in which each three-level Λ-laser excites each succeeding Λ-laser with its light, any desired degree of shot-noise suppression can be achieved. Zh. éksp. Teor. Fiz. 114, 1971–1992 (December 1998)     

On variable stepsize Runge-Kutta approximations of a Cauchy problem for the evolution equation

We consider a Cauchy problem for the sectorial evolution equation with generally variable operator in a Banach space. Variable stepsize discretizations of this problem by means of a strongly A(φ)-stable Runge-Kutta method are studied. The stability and error estimates of the discrete solutions are derived for wider families of nonuniform grids than quasiuniform ones (in particular, if the operator in question is constant or Lipschitz-continuous, for arbitrary grids).     

“Horizontal” and “vertical” quantum-dot molecules

An analysis is made of a two-electron system of two adjacent quantum dots (QD) with a two-dimensional parabolic lateral confining potential, and of two coupled or double, spatially separated QDs (a “horizontal” and a “vertical” QD molecule), and of their behavior in an external transverse magnetic field. The ground-state energies and energy spectra of the system have been determined by various methods (Heitler-London, molecular-orbital, variational approach, and numerical diagonalization of Hamiltonian), with inclusion of electron-electron interaction, and for a broad range of confining-potential steepness, QD-center spacing (interlayer distance), and external magnetic field. Fiz. Tverd. Tela (St. Petersburg) 40, 2127–2133 (November 1998)     

Response of a YBaCuO/MgO bolometer structure at high levels of laser excitation. Nonlinear model and experiment

A nonlinear model is developed for the photoresponse of a bolometric structure taking into account the temperature dependences of the thermal constants of the YBaCuO/MgO structure and its boundary thermal resistance. The model also allows for the specific form of the currentvoltage characteristic of YBaCuO and the heat release from the transport current flow. A comparison between the experimental data and the model showed that the nonlinear thermal model accurately describes the temporal characteristics of the photoresponse. Fiz. Tverd. Tela (St. Petersburg) 40, 191–194 (February 1998)     

Stress state of infinite medium with elastic paraboloidal inclusion

S. P. Timoshenko Institute of Mechanics, Ukrainian Academy of Sciences, Kiev. Translated from Prikladnaya Mekhanika, Vol. 29, No. 12, pp. 15–21, December, 1993.     

前馈PMD补偿实验中从偏振度椭球获得差分群时延的研究

运用偏振度(DOP)椭球法从实验的有限样点数据中获得了差分群时延和偏振主态方向,这为前馈补偿实验提供了最关键的技术因素.在实验中获得了偏振主态方向和DGD,而且当DGD较小时,从实验所获得的DGD值与理论模拟的变化趋势基本一致.结果表明当DGD较小时,可以用偏振度椭球法从实验上得到正确的DGD和偏振主态方向.     

New numerical methods and some applied aspects of the p-regularity theory

The theory of p-regularity is applied to optimization problems and to singular ordinary differential equations (ODE). The special variant of the method of the modified Lagrangian function proposed by Yu.G. Evtushenko for constrained optimization problems with inequality constraints is justified on the basis of the 2-factor transformation. An implicit function theorem is given for the singular case. This theorem is used to show the existence of solutions to a boundary value problem for a nonlinear differential equation in the resonance case. New numerical methods are proposed including the p-factor method for solving ODEs with a small parameter.