共查询到20条相似文献,搜索用时 15 毫秒
1.
Yu. A. Morozov 《Technical Physics》2000,45(5):584-590
The spectral density of intensity fluctuations of quasi-single-mode heterolaser radiation under pseudorandom pulsed modulation
of the pumping current has been studied for the first time by numerical methods. In the limit of the second-order dispersion
theory, the effect of the chromatic dispersion of an optical fiber on the noise characteristics of laser radiation (spectral
density of fluctuations and signal-to-noise ratio in the operating range of the photodetector) was investigated. The effect
of the laser parameters and modulation on the transformation of the intensity fluctuations in a fiber-optic communication
line was studied. 相似文献
2.
L. A. Kulakova N. A. Pikhtin S. O. Slipchenko I. S. Tarasov 《Journal of Experimental and Theoretical Physics》2007,104(5):689-695
The radiation of a semiconductor laser has been modulated in frequency by variable strain. The strain is excited by injecting bulk or surface ultrasonic waves. Dynamic and static analyses of the variations in the spectral characteristics of the radiation in the presence of sound are performed. A model is suggested and the data obtained are analyzed theoretically. The radiation frequency modulation in InGaAsP/InP heterostructures produced by surface waves is shown to be determined mainly by the band gap modulation of the active region. 相似文献
3.
This paper presents a theoretical analysis of a two-layered pyroelectric detector which can be used in photopyroelectric spectroscopy where one of the two layers is an air gap. The analysis was performed using a recently developed one-dimensional two-layer model. It was shown theoretically and numerically that the presence of an air gap between the substrate and the pyroelectric material simplifies the photopyroelectric spectroscopic technique. 相似文献
4.
Gulis I. M. Komyak A. I. Saechnikov K. A. Tsvirko V. A. 《Journal of Applied Spectroscopy》1989,50(3):257-262
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 3, pp. 385–391, March, 1989. 相似文献
5.
K. A. Barantsev A. N. Litvinov E. N. Popov 《Journal of Experimental and Theoretical Physics》2017,124(1):1-9
The variational Monte Carlo method is applied to investigate the ground state and some excited states of the lithium atom and its ions up to Z = 10 in the presence of an external magnetic field regime with γ = 0–100 arb. units. The effect of increasing field strength on the ground state energy is studied and precise values for the crossover field strengths were obtained. Our calculations are based on using accurate forms of trial wave functions, which were put forward in calculating energies in the absence of magnetic field. Furthermore, the value of Y at which ground-state energy of the lithium atom approaches to zero was calculated. The obtained results are in good agreement with the most recent values and also with the exact values. 相似文献
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7.
A. I. Bazhin D. V. Grankin V. V. Styrov V. I. Tyutyunnikov 《Bulletin of the Russian Academy of Sciences: Physics》2008,72(7):915-918
An increase in the ionoluminescence intensity from a ZnS-CdS:Ag sample by a factor of more than 20 upon additional electronic
excitation by UV light has been found. The effect decreases in magnitude with an increase in the energy of bombarding H2+ ions and peaks at an energy below 175 eV. This effect manifests itself in samples having a system of shallow electron traps
and is due to the relaxation of highly excited anharmonic atomic vibrations, caused by the ion impact, through the electronic
channel. A mechanism is proposed and computed for the phenomenon revealed. 相似文献
8.
B. A. Veklenko 《Russian Physics Journal》1984,27(11):918-920
The transition radiation in excited dispersing media is determined by the quantum index of refraction found in this paper. In the resonant-frequency region it is not related to the dielectric constant of the medium and cannot be calculated on the basis of the semiclassical radiation theory.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 11–14, November, 1984.The author is grateful to the participants in the seminar conducted by V. L. Bonch-Bruevich for their attention to this paper. 相似文献
9.
The influence of defects coupling linearly to the order parameter on the critical behaviour of structural phase transitions is studied. A continuum model for the statics and dynamics is introduced and is investigated by the renormalization group theory. If the defects are slow a central peak is found, the characteristic width of which is determined by the defects. Concerning the critical behaviour the dynamical model belongs to the same universality class as the one studied previously by Grinstein, MA, and Mazenko. The concentration dependence of the central peak response is discussed inside and outside the critical region. 相似文献
10.
《Physics letters. A》2006,359(4):285-289
The spiking properties of a subcritical Hopf oscillator with a time delayed nonlinear feedback is investigated. Finite time delay is found to significantly affect both the statistics and the fine structure of the spiking behavior. These dynamical changes are explained in terms of the fundamental modifications occurring in the bifurcation scenario of the system. Our mathematical model can find useful applications in understanding the dynamical behavior of various real life excitable systems where propagation delay effects are ubiquitous. 相似文献
11.
A. V. Lebedev 《Acoustical Physics》2002,48(3):339-346
The possibility of using the resonant acoustic spectroscopy method for testing the internal state of rock is considered. This method can be used for the determination of the concentration of defects and their spatial distribution. A rock specimen with defects is characterized by a high loss of vibrational energy, which leads to the overlapping of the resonant responses. In this case, the complex resonant frequencies are determined as the parameters of a model that describes the measured transfer function of the response of the mechanical system. The linearity of the vibratory system is used as the a priori information for presetting the functional dependences of the model. An algorithm is developed for the determination of the parameters of the resonances in conditions of their partial overlapping. Examples are presented to demonstrate the possibility of analyzing the complex elastic constant tensor of rock by the acoustic spectroscopy method. The proposed method of experimental data processing provides the possibility for the determination of the weak anisotropy that occurs in the velocity of sound because of a partial fracture of rock. 相似文献
12.
Fine hexaferrite particles for perpendicular recording prepared by the coprecipitation method in the presence of an inert component 总被引:3,自引:0,他引:3
V.V. Pankov M. Pernet P. Germi P. Mollard 《Journal of magnetism and magnetic materials》1993,120(1-3):69-72
The modified coprecipitation method has been shown to be suitable for preparing BaFe2y−2χCoχTiχO19 powder with narrow particle size distribution (50–80 nm). The phase composition of the intermediate products during the synthesis has been investigated by DTA, TG, X-ray analysis and Mössbauer spectroscopy. The dependence of the dc measured specific magnetization and coercivity on the Ti-Co content and annealing temperature is presented. 相似文献
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14.
Transient processes associated with gas bubble excitation by ultrasonic pulses are investigated based on the numerical solution
to the Rayleigh-Plesset equation. The results are used to consider ultrasonic methods of gas bubble detection and sizing in
liquids and biological tissues on the basis of linear and nonlinear bubble properties. The possibility of frequency separation
of signals received from bubbles with different sizes in the case of their pulsed excitation is experimentally demonstrated. 相似文献
15.
在超声快速制取组织细胞病理切片的过程中,发现激励信号对切片制取效果有明显的影响.为了掌握超声激励信号对组织细胞的影响规律,达到快速制取病理切片的最佳状态,从气泡空化模型入手,通过改变激励信号频率、声压、气泡初始半径和液体黏滞系数等参量,研究了声孔效应中气泡动力学激励机制.数值计算表明:空化泡振动随激励声压增强而升高,随液体黏滞系数增强而减弱;一定频率范围内空化泡振动能保持在膨胀、收缩和振荡的稳定空化状态,存在空化泡稳态振动的最佳激励频率;一定初始半径能保证空化泡产生稳定的振动,存在空化泡稳态振动幅度最大的初始半径.实际操作中,在频率、声压、初始半径和黏滞系数综合作用的若干空化阈内,声孔效应使超声快速法制取细胞组织切片获得最佳效果.
关键词:
声孔效应
超声空化
气泡振动
稳态空化域 相似文献
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17.
Birkin PR Offin DG Vian CJ Leighton TG 《The Journal of the Acoustical Society of America》2011,130(5):3379-3388
Bubble dynamics in water close to the tip of an ultrasonic horn (~23 kHz, 3 mm diameter) have been studied using electrochemistry, luminescence, acoustics, light scattering, and high-speed imaging. It is found that, under the conditions employed, a large bubble cluster (~1.5 mm radius) exists at the tip of the horn. This cluster collapses periodically every three to four cycles of the fundamental frequency of the horn. Following the collapse of the cluster, a short-lived cloud of small bubbles (each tens of microns in diameter) was observed in the solution. Large amplitude pressure emissions are also recorded, which correlate temporally with the cluster collapse. Bursts of surface erosion (measured in real time using an electrochemical technique) and multibubble sonoluminescence emission both also occur at a subharmonic of the fundamental frequency of the horn and are temporally correlated with the bubble cluster collapse and the associated pressure wave emission. 相似文献
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Harmonics generation of high-frequency radiation in a plasma embedded in a constant electric field is investigated theoretically. It is shown that the electron directed motion due to the static electric field yields the appearance in the plasma emission spectrum of high-frequency radiation even harmonics. The conditions are established when the even harmonics generation is as effective as that of the odd ones. At variance with the odd harmonics, the even harmonics polarization plane is found to rotate with respect to that of the fundamental field. The basic dependencies concerning the rotation angle and the generation efficiency on the plasma and field parameters are established.Received: 3 May 2004, Published online: 14 September 2004PACS:
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.) - 52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.) 相似文献
20.
I. O. Zolotovskii D. A. Korobko V. A. Lapin D. I. Sementsov 《Optics and Spectroscopy》2016,121(2):256-262
The conditions for the onset of modulation instability of wave packets in an optical waveguide in the presence of the traveling refractive index wave are investigated. An expression governing the growth rate of a small harmonic perturbation at the early development stage of the modulation instability is obtained. Based on numerical analysis, the behavior of the wave packet at the developed modulation instability stage is studied for different parameters of the waveguide and the refractive index wave. 相似文献