Papers by Александр Старков
Thermodynamics of electrocaloric effect
Elsevier eBooks, 2023
Direct and inverse problems of the scattering of modes in a waveguide with rough boundaries
Radiophysics and Quantum Electronics, 1991
Journal of Engineering Physics, 1991
We propose a method for the calculation of the principal coefficients of the heat-conduction sens... more We propose a method for the calculation of the principal coefficients of the heat-conduction sensor of a flat orthotropic layer, based on results from a nonsteady experiment.
The local resonance interaction of normal waves in coupled waveguides
ABSTRACT
Journal of Mathematical Sciences
The high-frequency wave field of a point source situated near the interface of two homogeneous me... more The high-frequency wave field of a point source situated near the interface of two homogeneous media and placed in a faster medium is considered. A description of the wave field in a neighborhood of the critical ray in a slower medium is found by the parabolic-equation method. The result involves a Pearcey-type integral. The approach is not based on the Fourier method and can be generalized to inhomogeneous media with curved interfaces. Bibliography: 14 titles.
Asymptotical Description of the Time and Temperature Hysteresis in the Framework of Landau-Khalatnikov Equation
Thermodynamic Foundations of Solid-State Cooler Based on Multiferroic Materials
Reflection of a plane wave from a smoothly irregular layer
Optics and Spectroscopy
Influence of PFM Tip Shape on the Electrostatic Field Distribution
Ferroelectrics
We study the dependence of the electric field induced by the tip of a piezoresponse force microsc... more We study the dependence of the electric field induced by the tip of a piezoresponse force microscope over a ferroelectric sample on its shape. It is assumed that the probe needle is thin, i.e. its largest diameter is much smaller than the length. The microscope tip is considered as a surface of revolution. The accuracy of the proposed approach depends on the ratio of the dielectric constants of the dielectric and ferroelectric (air and sample).
Diffraction by dielectric wedge
International Seminar. Day on Diffraction '2001. Proceedings (IEEE Cat.No.01EX477)
The scattering of a plane monochromatic wave by a infinite dielectric wedge is discussed for arbi... more The scattering of a plane monochromatic wave by a infinite dielectric wedge is discussed for arbitrary direction of incidence. The wave velocities in the interior and exterior of the wedge are distinct. At the boundary of the wedge there is a pair of transmissions conditions. We also impose Meixner's condition at the edge. The wave field should also satisfy the radiation condition at infinity. Here we follow the approach based on Sommerfeld transforms and first applied in scalar problem by Maliuzhinets (1955, 1957, 1958) in his study of diffraction by wedge with impedance boundary conditions. Maliuzhinets reformulated the diffraction problem in the form of functional equations for Sommerfeld transform. Budaev (1995) reduced the diffraction problem for an elastic wedge to two decoupled systems of two functional equations and then to two singular integral equations. The Sommerfeld-Maliuzhinets method is used to represent the field in the interior and exterior regions of the wedge by means of two spectral functions. The original problem is decoupled into two, symmetric and antisymmetric. A pair of functional equations are obtained for these unknown spectral functions.
Technical Physics Letters, 2010
Investigations of the electrocaloric effect in ferroelectric materials are of interest for applic... more Investigations of the electrocaloric effect in ferroelectric materials are of interest for applications and of importance for an adequate description of the electrical properties of ferroelectric films, in particular, their switching dynamics. A theoretical approach is developed based on the Landau-Khalatnikov model, which can be used to describe the dynamic spontaneous polarization of a ferroelectric material and the influ ence of this polarization on the character of the temperature dependence of the electrocaloric effect.
Technical Physics, 2010
A thermodynamic cycle in a solid state cooling line including two ferroelectric capacitors which ... more A thermodynamic cycle in a solid state cooling line including two ferroelectric capacitors which exhibit the electrocaloric (EC) effect is considered. Expressions are derived for determining the cooling factor and the efficiency of the EC cooling line in terms of the Carnot cycle. Numerical estimates obtained for bar ium-strontium titanate ferroelectric capacitors make it possible to determine the cooling efficiency upon a change in temperature by ΔT = 2 K. At the initial temperature of 272 K, the efficiency is 0.6 Carnot, which considerably exceeds the efficiency of vapor compression refrigerators.
Physics of the Solid State, 2009
The dynamics of change in temperature at the edges of a layered structure consisting of one or mo... more The dynamics of change in temperature at the edges of a layered structure consisting of one or more electrocaloric and heat conducting elements in response to pulses of a periodic electric field has been studied with the use of the finite element method. The possibility of using ceramic materials and (Ba,Sr)TiO 3 films as electrocaloric and heat conducting elements of linear and radial cooling structures is considered. The difference between the temperatures at the center and periphery of the radial film microstructure with two interdigital circular electrode lines is 2.5 K. An increase in the number of lines and the electric field frequency leads to an increase of the thermal effect.
Physics of the Solid State, 2009
The electrocaloric response of a ferroelectric capacitor to a periodic electric field has been an... more The electrocaloric response of a ferroelectric capacitor to a periodic electric field has been ana lyzed in terms of the nonstationary heat conduction equation. A linear physical model is considered for an electrocaloric element in which one end (x = 0) is thermally insulated and a constant temperature T 0 is main tained at the boundary x = l. The effect of a periodic electric field on the capacitor gives rise to temperature oscillations about a decreasing average value that reaches saturation. A relatively simple analytic expression is derived for the temperature distribution along the electrocaloric element and the heat flux density under stationary conditions. The calculations are carried out using the results obtained from measurements per formed for a PMN-PT relaxor ferroelectric in the temperature range of the phase transition. A temperature gradient and a heat flux of ~150 W/cm 2 are observed in an electric field of 2.4 V/µm at a frequency of 10 Hz.
Microelectronics Reliability, 2014
In this paper, we have investigated the turn-around effect of the threshold voltage (V th ) shift... more In this paper, we have investigated the turn-around effect of the threshold voltage (V th ) shift in the case of an n-type long channel MOSFET during hot-carrier stress. This effect is explained by the interplay between interface states and oxide traps, i.e. by the partial compensation of the rapidly created oxide charges by the more slowly created interface states. Significant hole trapping is observed from the negative shift of the threshold voltage during the first seconds of stress. Afterwards, V th has switched to the positive voltage direction due to the negative charging of interface traps after relatively long stress time. To analyze this phenomenon in detail, a refined extraction technique for the defect distribution from charge-pumping measurements has been employed. Additionally, the obtained results have been explained by our physics-based model of hot-carrier degradation which considers not only channel electrons but also secondary holes generated by impact ionization. In spite of the small hole contribution (compared to that of electrons) to the total defect creation, its impact on the threshold voltage shift is comparable with the electronic one. The reason behind this trend is that hole-induced traps are shifted towards the source, thereby more severely affecting the device behavior.
Layered ceramic structure based on the electrocaloric elements working as a solid state cooling line
Journal of the European Ceramic Society, 2007
The temperature response in the solid state cooling line composed of electrocaloric (EC) and ther... more The temperature response in the solid state cooling line composed of electrocaloric (EC) and thermoconductive elements was investigated using analytical approach and computational experiment. A periodical bias electric field applied to ferroelectric capacitor caused their heating and cooling, however, alternative adiabatic and isothermal switching of the EC elements allowed to generate the directed heat flux and the temperature decrease ΔT at one edge of the solid state structure. Thin film topologies are expediently to be used because thin electrocaloric elements are most appropriate to enhance switching frequency and increase ΔT. The temperature decrease ∼20° was obtained at one edge of the cooling line with (Ba,Sr)TiO3 EC elements. The serial connection of the EC lines can give a considerable cooling effect.
Journal of Soviet Mathematics, 1982
space of numerical sequences (4), and convergence of the method of reduction is guaranteed. After... more space of numerical sequences (4), and convergence of the method of reduction is guaranteed. After solving system (12) the coefficients of the series (I) for the desired field are determined from formulas (3). LITERATURE CITED i. W.D. Collins, "Some scalar diffraction problems for a spherical cap," Arch. Rat. Mech. Anal., i0, No. i, 249-266 (1962). 2. W. D. Collins, "On some triple series equations and their applications," Arch. Rat. Mech. Anal., ii, No. 2, 122-137 (1962). A.M. Radin and V. P. Shestopalov, "Diffraction of waves on a sphere with aperatures, ~' Dokl. Akad. Nauk SSSR, 212, No. 4, 838-841 (1973). 4. S. S. Vinogradov and V. P. Shestopalov, "Solution of a vector diffraction problem for a sphere with aperature," Dokl. Akad. Nauk SSSR, 237, No. i, 60 (1977). 5. S.S. Vinogradov, Yu. A. Tuchkin, and V. P. Shestopalov, "Effective solution of paired summation equations with a kernel in the form of associated Legendre functions," Dokl. Akad. Nauk SSSR, 242, No. i, 80 (1978). 6. V.S. Gubenko and V. I. Mossakovskii, "The pressure of an axially symmetric annular die on an elastic half space," Prikl. Mat. Mekh., 24, No. 2, 334-340 (1960).
Journal of Mathematical Sciences, 1998
An approach to the solution of inverse problems of wave propagation at a fized frequency based on... more An approach to the solution of inverse problems of wave propagation at a fized frequency based on using transform operators is suggested. A system of integral equations of the Gelfand-Levitan type is obtained. The uniqueness theorem for the refraction index in the analytic case is proved. Bibliography: 6 titles. It is well known that Gelfand-Levitan's solution of the one-dimensional inverse scattering problem for an ordinas T differential equation is based on the existence of an integral transform operator with "triangular" kernel . As was shown in , is it difficult to extend the "triangularity" property of the kernel to the multidimensional case. For the first time the multidimensional analog of Gelf~nd-Levitan's equation appeared in , where the boundary-control method was used. It should be noted that the approach used in this paper has some important features in common with the one-dimensional approach. Similarly to the Gelfand-Levitan method, our considerations are based on the analiticity of the solution and the existence of transform operators. As a result we obtain a system of integral equations resembling Gelfand-Levitan's integral equations. However, comparing the approach used in this paper with other approaches based on analiticity ideas, we can indicate the following significant distinctions. (1) We use the kernel with a different "triangularity" property. This distinction is caused by using sin Xx/X and cos Xx rather than an exponential function (in a multidimensional problem, X is a function of some parameters and has branch points). (2) We use the integral operator that transforms the solution of the Laplace equation into the solution of a perturbed SchrSdinger equation, i.e., the Laplace equation is chosen as the unperturbed equation. (3) The proof of the uniqueness theorem is based on the expansion of the kernel in smoothness.
On recovering density in a plane domain from incomplete spectral data
Journal of Mathematical Sciences, 1999
The inverse spectral problem of recovering density in a bounded domain is considered. The first N... more The inverse spectral problem of recovering density in a bounded domain is considered. The first N eigenvalues and traces on the boundary of the normal derivatives of the eigenfunctions of the Dirichlet problem are considered as the input data. It is shown that the error of the density recovery does not exceed cln−Β N, where c and Β are certain positive constants.
Journal of Mathematical Sciences, 1999
ABSTRACT The acoustic field of a source moving at a subsonic velocity in a regular waveguide with... more ABSTRACT The acoustic field of a source moving at a subsonic velocity in a regular waveguide with perfectly reflecting boundaries is considered. The acceleration of the source is assumed to be small. In a moving coordinate system, the asymptotics of the wave field is obtained. This asymptotics is inapplicable near the critical cross sections, for which the Doppler frequency of the source coincides with the frequency of the waveguide mode under consideration. It is demonstrated that, in this case, the wave field can be represented locally by a special type of integral, which is analyzed by the saddle-point method.
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Papers by Александр Старков