共查询到20条相似文献,搜索用时 15 毫秒
1.
The one-dimensional Brownian motion and the Brownian motion of a spherical particle in an infinite medium are described by
the conventional methods and integral transforms considering the entrainment of surrounding particles of the medium by the
Brownian particle. It is demonstrated that fluctuations of the Brownian particle velocity represent a non-Markovian random
process. A harmonic oscillator in a viscous medium is also considered within the framework of the examined model. It is demonstrated
that for rheological models, random dynamic processes are also non-Markovian in character.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 66–74, February, 2009. 相似文献
2.
A. A. Vertiy S. P. Gavrilov D. S. Armaan I. ?l?er 《International Journal of Infrared and Millimeter Waves》1997,18(2):405-429
In the present paper a time response of a quasi-optical open resonator when exciting it by a pulse signal with a radiofrequency
filling has been investigated using an inverse Fourier transformation. The radiofrequency filling corresponds to millimeter
wavelengths region. Fourier image of the time response of the resonator is calculated from a product of two frequency’s functions.
One of these functions is the Fourier image of a pulse signal at the resonator input, and the second is a calculated or measured
amplitude — phase characteristic of the resonator. When calculating the amplitude- phase characteristic of the resonator (a
complex transfer coefficient) a plane — layered model of the resonator was used.
Experimental investigation has been conducted in millimeter wavelengths with Fabry-Perot type open resonator. Amplitude- phase
characteristic of the resonator were measured in “on passage“ regime in wide frequency band.
It was shown that presence of weakly absorbing layer in the resonator leads to changing of the time response of the resonator.
The obtained results can be used in the dielectric measurements, defectoscopy of stratiform materials, relaxometry, non-destructive
control of materials and structures, etc. 相似文献
3.
S Rajasekar 《Pramana》1995,44(2):121-131
In this paper we investigate numerically the possibility of conversion of a chaotic attractor into a nonchaotic but strange
attractor in both a discrete system (an one dimensional map) and in a continuous dynamical system — Bonhoeffer—van der Pol
oscillator. In these systems we show suppression of chaotic property, namely, the sensitive dependence on initial states,
by adding appropriate i) chaotic signal and ii) Gaussian white noise. The controlled orbit is found to be strange but nonchaotic
with largest Lyapunov exponent negative and noninteger correlation dimension. Return map and power spectrum are also used
to characterize the strange nonchaotic attractor. 相似文献
4.
Shaoqiu Xiao Dongqing Hou Jinzhang Peng Bing-Zhong Wang 《International Journal of Infrared and Millimeter Waves》2005,26(10):1417-1425
In this paper, a millimeter wave Gunn diode oscillator is analyzed and designed by the finite-difference time-domain (FDTD)
method. The design results indicate that the oscillator has an oscillation frequency of 45.0GHz and a higher oscillation voltage.
Based on the circuit equations and an integral transform, an improved matrix method is utilized for the oscillator design.
This method is also extended to model the hybrid network which is constructed by the high order linear elements and the nonlinear
elements with arbitrary connections. The experience shows that the improved FDTD method is stable with the time step length
Δt based on the Courant condition.
*This work was supported by the National Natural Science Foundation of China. 相似文献
5.
N. Safta A. Sakly H. Mejri Y. Bouazra 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(1):75-78
We report a numerical simulation of the conduction and valence band edges of
Cd1-xZnxS nanocrystallites using a one — dimensional potential
model. Electron — hole pairs are assumed to be confined in nanospheres of
finite barrier heights. Optical absorption measurements are used to fit the
bandgap of the Cd1-xZnxS nanocrystal material. A theoretical
analysis is also made to calculate the energy location of bound excitons and
the oscillator strength of interband transitions as a function of zinc
composition. The aim of the latter study is to investigate the optical
behavior of Cd1-xZnxS nanocrystals. An attempt to explain all the
results is presented. 相似文献
6.
7.
Özgür Özcan Ethem Aktürk Ramazan Sever 《International Journal of Theoretical Physics》2008,47(12):3207-3218
The time dependent entropy (or Leipnik’s entropy) of harmonic and damped harmonic oscillator systems is studied by using time
dependent wave function obtained by the Feynman path integral method. The Leipnik entropy and its envelope change as a function
of time, angular frequency and damping factor. Our results for simple harmonic oscillator are in agreement with the literature.
However, the joint entropy of damped harmonic oscillator shows remarkable discontinuity with time for certain values of damping
factor. The envelope of the joint entropy curve increases with time monotonically. These results show the general properties
of the envelope of the joint entropy curve for quantum systems. 相似文献
8.
Milena Davidović Mirjana Bozić Dusan Arsenović 《Journal of Russian Laser Research》2006,27(3):220-224
It is shown that the Fourier integral of the function exp(−ux
2) exists not only for u satisfying Re u > 0 but also for u that satisfies Re u ≥ 0. The proof is given by evaluating this integral for imaginary u. 相似文献
9.
By applying the standard analytical techniques of solving partial differential equations, we have obtained the exact solution in terms of the Fourier sine series to the time-dependent Schrödinger equation describing a quantum one-dimensional harmonic oscillator of time-dependent frequency confined in an infinite square well with the two walls moving along some parametric trajectories. Based upon the orthonormal basis of quasi-stationary wave functions, the exact propagator of the system has also been analytically derived. Special cases like (i) a confined free particle, (ii) a confined time-independent harmonic oscillator, and (iii) an aging oscillator are examined, and the corresponding time-dependent wave functions are explicitly determined. Besides, the approach has been extended to solve the case of a confined generalized time-dependent harmonic oscillator for someparametric moving boundaries as well. 相似文献
10.
We give the first explicit construction of the quadratic algebra for a 3D quantum superintegrable system with nondegenerate
(4-parameter) potential together with realizations of irreducible representations of the quadratic algebra in terms of differential—differential
or differential—difference and difference—difference operators in two variables. The example is the singular isotropic oscillator.
We point out that the quantum models arise naturally from models of the Poisson algebras for the corresponding classical superintegrable
system. These techniques extend to quadratic algebras for superintegrable systems in n dimensions and are closely related to Hecke algebras and multivariable orthogonal polynomials. 相似文献
11.
A memcapacitor is a new type of memory capacitor. Before the advent of practical memcapacitor, the prospective studies on its models and potential applications are of importance. For this purpose, we establish a mathematical memcapacitor model and a corresponding circuit model. As a potential application, based on the model, a memcapacitor oscillator is designed, with its basic dynamic characteristics analyzed theoretically and experimentally. Some circuit variables such as charge, flux, and integral of charge, which are difficult to measure, are observed and measured via simulations and experiments. Analysis results show that besides the typical period-doubling bifurcations and period-3 windows, sustained chaos with constant Lyapunov exponents occurs. Moreover, this oscillator also exhibits abrupt chaos and some novel bifurcations.In addition, based on the digital signal processing(DSP) technology, a scheme of digitally realizing this memcapacitor oscillator is provided. Then the statistical properties of the chaotic sequences generated from the oscillator are tested by using the test suit of the National Institute of Standards and Technology(NIST). The tested randomness definitely reaches the standards of NIST, and is better than that of the well-known Lorenz system. 相似文献
12.
V. L. Gilyarov A. I. Slutsker V. P. Volodin A. I. Laius 《Physics of the Solid State》1998,40(8):1404-1406
The dependence of the temperature on the external adiabatic deformation is determined for a one-dimensional model of a solid
— chains of atoms with an anharmonic interaction. The resulting dependences of the average kinetic and potential components
of the internal energy on this deformation are compared with a model of adiabatic loading of a single oscillator.
Fiz. Tverd. Tela (St. Petersburg) 40, 1548–1551 (August 1998) 相似文献
13.
In this work, a poly(o-toluidine) “POT” was synthesized by chemical oxidative polymerization method in aqueous media. High uniform and good adhesion thin films of POT have been successfully deposited by the spin coating technique. The films were characterized by X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectroscopy. The XRD pattern of the POT shows the semi-crystalline nature of the films. FTIR studies show the information of functional groups in POT. The optical transmittance and reflectance of POT film was measured in the 200–2500 nm wavelength range. The absorption coefficient analysis shows that the optical band gaps of POT film are direct allowed transition band gaps with 1.2 and 2.6 eV. Other optical absorption parameters such as extinction molar coefficient, oscillator strength and electric dipole strength were also calculated. The dispersion parameters were determined and discussed based on the single oscillator model. According to the analysis of dispersion curves some important parameters such as dispersion energy (Ed), oscillator energy (Eo), high frequency dielectric constant (ε∞) and lattice dielectric constant (εL) were also evaluated. Discussion of the obtained results and their comparison with the previous published data were also given. The obtained desirable results of POT thin film can be useful for the optoelectronic applications. 相似文献
14.
M. A. Sheremet 《Thermophysics and Aeromechanics》2011,18(3):447-458
The mathematical modelling of unsteady regimes of natural convection in a closed cylindrical region with a heat-conducting
shell of finite thickness was carried out in the presence of a local heat source under the conditions of convective heat exchange
with the ambient medium. The mathematical model was constructed in dimensionless variables “stream function — vorticity vector
— temperature” in the cylindrical coordinate system. The influence of the Rayleigh number, 104 ≤ Ra ≤ 106, of the unsteadiness factor 0 < τ < 300, of the thermal conductivity ratio λ
2,1 = 5.7·10−4, 4.3·10−2, and the energy source sizes on both local characteristics (streamlines and temperature fields) and on the integral complex
(the mean Nusselt number on typical boundaries) was analysed in detail. Thermohydrodynamic peculiarities due to the geometry
of the object of research were established. 相似文献
15.
C. P. Burgess 《Pramana》1995,45(1):47-63
Bound state population dynamics in a diatom modelled by an appropriate Morse oscillator with a time-dependent well-depth is
investigated perturbatively both in the absence and presence of high intensity radiation. For sinusoidally oscillating well-depth,
the population of themth bound vibrational level,P
mm(t), is predicted to be a parabolic function of the amplitude of the oscillation of the well-depth (ΔD
0) at a fixed laser intensity. For a fixed value of ΔD
0,P
mm(t) is also predicted to be quadratic function of the field intensity (ɛ
0). Accurate numerical calculations using a time-dependent Fourier grid Hamiltonian (TDFGH) method proposed earlier corroborate
the predictions of perturbation theory. As to the dissociation dynamics, the numerical results indicate that the intensity
threshold is slightly lowered if the well-depth oscillates. Possibility of the existence of pulse-shape effect on the dissociation
dynamics has also been investigated. 相似文献
16.
By expanding the hard-aperture function into a finite sum of complex Gaussian functions, we derive approximate analytical formulae for Lorentz and Lorentz-Gauss beams propagating through an apertured fractional Fourier transform (FRT) optical system. As an application example, properties of a Lorentz-Gauss beam in the FRT plane after propagating through a squarely or annularly apertured FRT optical system are studied numerically. The results obtained using the approximate analytical formula are in good agreement with those obtained using numerical integral calculation. The FRT optical system provides a convenient way for laser beam shaping. 相似文献
17.
Exact solutions of the Klein—Gordon equation with ring-shaped oscillator potential by using the Laplace integral transform 下载免费PDF全文
Sami Ortakaya 《中国物理 B》2012,21(7):70303-070303
We present exact solutions for the Klein-Gordon equation with a ring-shaped oscillator potential. The energy eigenvalues and the normalized wave functions are obtained for a particle in the presence of non-central oscillator potential. The angular functions are expressed in terms of the hypergeometric functions. The radial eigenfunctions have been obtained by using the Laplace integral transform. By means of the Laplace transform method, which is efficient and simple, the radial Klein-Gordon equation is reduced to a first-order differential equation. 相似文献
18.
Yu. M. Poluéktov 《Russian Physics Journal》2009,52(1):33-45
A modified perturbation theory is formulated for an asymmetric anharmonic oscillator based on a choice of the main approximation
constructed by analogy with the self-consistent field model. This perturbation theory has a much wider range of application
in comparison with the standard approach and considers a finite number of energy levels in the potential well already in the
main approximation. This approach is used for the construction of a two-atomic model of a quantum crystal. A quantum analog
of the Lindeman criterion is obtained.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 30–40, January, 2009. 相似文献
19.
利用Duffing振 子从混沌到间歇混沌的相变及其对策动力和待检测信号频差较小的周期信号的敏感性, 研究了强海洋背景噪声下微弱周期信号的检测. 通过构造混沌振子列的方法对频率未知信号进行扫频, 从而提取待检测信号的频率范围, 最后利用希尔伯特变换, 实现对间歇混沌的包络检测, 并计算出待检测信号的频率. 计算机仿真与实测水声信号处理结果表明, 利用基于希尔伯特变换的间歇混沌振子对水声微弱信号检测, 其检测信噪比比一般的间歇混沌振子提高了至少4.4 dB, 验证了所提方法的有效性. 相似文献
20.
On the basis of the known reflection spectrum, we calculate a complete set of fundamental optical functions for cubic boron
nitride (c-BN) in the region of 2–23 eV. The integral spectrum of dielectric permeability is decomposed into 16 elementary
components. Three main parameters (maximum energy, half-width, and oscillator force) for each of the components are determined.
Using the well-known theoretical calculations for bands of boron nitride as the base we suggest a scheme of the nature of
these dielectric permeability components.
To whom correspondence should be addressed.
Udmurtiya State University, 1, Universitetskaya Str., Izhevsk, 426034, Russia:e-mail: sobolev@matsim.udmurtia.su. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 579–583, July–August, 1999. 相似文献