共查询到20条相似文献,搜索用时 15 毫秒
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N. V. Atanov A. S. Dmitriev E. V. Efremova N. A. Maksimov 《Technical Physics Letters》2006,32(8):645-646
The effect of a periodic drive signal on a chaotic rf oscillator is considered. The possibility to obtain chaotic pulse trains (rf pulses) of a preset duration is experimentally demonstrated. 相似文献
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The behavior of a bistable oscillator under the action of a chaotic signal from a Rössler oscillator with a spiral attractor is considered. The influence of the width of the main spectral line of the chaotic drive signal on the signal to noise ratio at the response system’s output has been studied. 相似文献
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The motion of high-energy electrons in a gas-discharge gap filled by nitrogen at atmospheric pressure has been simulated. Electrons were driven by a subnanosecond high-voltage pulse with an amplitude of 150 kV. It is established that the injected electrons can reach the anode only for a very high initial energy, which cannot be provided by means of explosive emission. Therefore, under usual experimental conditions, electron emission from the cathode cannot account for the main fraction of electrons generated in a gas-filled diode at atmospheric pressure. 相似文献
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We study on non-linear localized waves on continuous wave background in a dispersion and non-linearity management fibre. We find a stable supercontinuum pulse can be generated from a small modulation on continuous wave in a proper management way, for which the pulse spectrum width and its growth rate can be controlled well by the management parameters. Additionally, we demonstrate a Kuznetsov–Ma breather like non-linear localized wave can exist in a periodic dispersion management fibre, and its spectrum evolution is distinctive from the Kuznetsov–Ma breather’s. 相似文献
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Hayashi Y Fukumi A Matsukado K Mori M Kotaki H Kando M Chen LM Daito I Kondo S Kanazawa S Yamazaki A Ogura K Nishiuchi M Kado M Sagisaka A Nakamura S Li Z Orimo S Homma T Daido H 《Radiation protection dosimetry》2006,121(2):99-107
The authors obtain a new equation to estimate the forward component of a photon dose generated through the interaction between a target and a short pulse high power laser. As the equation is quite simple, it is useful for calculating the photon dose. The equation shows that the photon dose is proportional to the electron temperature in the range>3 MeV and proportional to the square of the electron temperature in the range<3 MeV. The dose estimated with this method is roughly consistent with the result of Monte Carlo simulation. With some assumptions and corrections, it can reproduce experimental results obtained and the dose result calculated at other laboratories. 相似文献
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G. A. Mesyats V. V. Osipov N. B. Volkov V. V. Platonov M. G. Ivanov 《Technical Physics Letters》2003,29(9):771-774
Experimental data on the nonlinear dynamics of a plasma torch generated by a laser pulse of large width acting upon a graphite target are presented and discussed. The mushroom shape of the luminous region and the duration of emission observed in experiment are explained by the development of the Richtmyer-Meshkov instability at the carbon plasma-air interface and by the formation of nanoparticles in the plasma expanding into the buffer gas. 相似文献
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K. R. Murali 《Journal of Materials Science》2007,42(4):1321-1324
GaAs is a III-V compound possessing high mobility and a direct band gap of 1.43 eV , making it a very suitable candidate for
photovoltaic applications. Thin GaAs films were prepared at room temperature by plating an aqueous solution containing GaCl3 and As2O3 at a pH of 2. The current density was kept as 50 mA cm−2 and the duty cycle was varied in the range 10–50%. The films were deposited on titanium and tin oxide coated glass substrates.
Films exhibited polycrystalline nature with peaks corresponding to single phase GaAs. Optical absorption measurements indicated
a direct band gap of 1.40 eV. The surface roughness of the films varied from 3 nm to 6 nm as the duty cycle increased. Raman
spectra indicated both the LO and TO phonons for the films deposited at duty cycles above 25%. Photoelectrochemical studies
indicated that the current and voltage output are higher than earlier reports on thin film electrodes. 相似文献
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Honghua Dai Zipu Yan Xuechuan Wang Xiaokui Yue Satya N. Atluri 《International journal for numerical methods in engineering》2023,124(2):458-481
Periodic dynamical systems ubiquitously exist in science and engineering. The harmonic balance (HB) method and its variants have been the most widely-used approaches for such systems, but are either confined to low-order approximations or impaired by aliasing and improper-sampling problems. Here we propose a collocation-based harmonic balance framework to successfully unify and reconstruct the HB-like methods. Under this framework a new conditional identity, which exactly bridges the gap between frequency-domain and time-domain harmonic analyses, is discovered by introducing a novel aliasing matrix. Upon enforcing the aliasing matrix to vanish, we propose a powerful reconstruction harmonic balance (RHB) method that obtains extremely high-order (>100) nonaliasing solutions, previously deemed out-of-reach, for a range of complex nonlinear systems including the cavitation bubble dynamics, the three-body problem and the two dimensional airfoil dynamics. We show that the present method is 2–3 orders of magnitude more accurate and simultaneously much faster than the state-of-the-art method. Hence, it has immediate applications in multidisciplinary problems where highly accurate periodic solutions are sought. 相似文献
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Rémi Cornaggia Cédric Bellis 《International journal for numerical methods in engineering》2020,121(14):3178-3205
This works concerns the propagation of waves in periodic media, whose microstructure is optimized to obtain specific dynamical properties (typically, to maximize the dispersion in given directions). The present study, focusing on scalar waves in two dimensions, for example, antiplane shear waves, aims at setting a generic optimization framework. The proposed optimization procedure relies on a number of mathematical and numerical tools. First, the two-scale asymptotic homogenization method is deployed up to second-order to provide an effective dispersive model. Simple dispersion indicators and cost functionals are then considered on the basis of this model. Then, the minimization of these functionals is performed thanks to an algorithm that relies on the concept of topological derivative to iteratively perform phase changes in the unit cell characterizing the material. Finally, fast Fourier transform-accelerated solvers are extensively used to solve the cell problems underlying the homogenized model. To illustrate the proposed approach, the resulting procedure is applied to the design of anisotropic media with maximal dispersion in specific directions, and to the reconstruction of unknown microstructures from effective phase velocity data. 相似文献
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Phenomena accompanying the propagation of a short bipolar radio pulse with duration of ~1 ns through the Earth’s ionosphere are considered. Such pulses can be generated by a cascade shower caused by an ultrahigh-speed cosmic particle on the Moon’s surface. It is shown that the width of the radio pulse increases by almost two orders of magnitude as a result of dispersion. A method is proposed for retaining the real sensitivity of a detector. The possibility of using dispersion for separating informative signals from local interferences is considered. The power of a cosmic-particle-induced radio signal is compared to the power of cosmic radio-frequency interferences. 相似文献
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O. I. Moskalenko 《Technical Physics Letters》2007,33(10):841-843
Intermittent behavior has been studied near the boundary of phase synchronization in an autooscillatory system with periodic dynamics under the action of an external chaotic signal. It is shown that the intermittency obeys the same scenario as that observed in the case of interaction between two coupled chaotic oscillators. 相似文献
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The development of pulse tube coolers has progressed significantly during the past two decades. A single piston linear compressor is used to in order to reduce the size and mass of a high frequency pulse tube cryocooler. The pulse tube achieved a no-load temperature of 61 K and a cooling power of 1 W@80 K with an operating frequency of 80 Hz and an electrical input power of 50 W. By itself, the single piston compressor generates a large vibration, so a set of leaf springs with an additional mass is used to reduce the vibration. The equation relating the mass, the elasticity coefficient of leaf spring and the working frequency is obtained through an empirical fit of the experimental data. The vibration amplitude is reduced from 55 mm/s to lower than 5 mm/s by using a proper leaf spring. This paper demonstrates that a single piston compressor with vibration reduction provides a good choice for a PTC. 相似文献
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Yang Xiang Hongmin Liu Jing Lu Yueping Niu Shangqing Gong 《Journal of Modern Optics》2013,60(8):613-619
We theoretically investigate the high-order harmonic generation (HHG) driven by laser pulses with tri-color carrier wave in the multi-cycle regime. Through the modulation of the carrier wave, the peak of the return kinetic energy of the electron near the pulse center extends dramatically and the other peaks are suppressed by the envelope. Thus, a very broad continuum spectrum appears in the HHG. Moreover, due to the propagation effect, the long path of the electron for the continuum spectrum is eliminated effectively. Hence, the continuum spectrum is well-phase locked, from which an isolated sub-50 attosecond pulse could be obtained even for the driver pulse with duration of 30 fs. 相似文献
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We perform a comprehensive study of the ionization of hydrogen atom by a few-cycle laser pulse with a fixed carrier-envelop in phase space through calculating the Wigner functions. The results show that the electrons always locate around the nucleus before the laser electric field force reaches a certain intensity. While as the force of the laser electric field increases, the electrons are gradually deviated away from the nucleus. The ionized electrons are driven back to the core region and make a wiggling motion because of the variation of the laser electric field force with time. Moreover Wigner functions enable us to clearly show the classical and quantum behaviours during ionization process are presented in phase space, and explicitly attribute the arc fringes to the interference effect between the electronic wavepackets born at different ionization times. 相似文献
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The beam quality of an optical parametric oscillator (OPO) within a singly resonant, confocal-positive branch unstable resonator is investigated. Resonator configurations have been found in which the beam quality of the outgoing signal exceeds the beam quality of the pump. Cavity magnification and pump-pulse duration are found to determine the signal beam quality. It is shown that signal M2 decreases with increasing pump-pulse duration for a given cavity magnification. In an experimental demonstration of a LiNbO3 OPO within an unstable resonator, pumped by a multitransversal mode beam, a signal beam with an almost-single transversal mode has been generated, whereas the multitransversal mode behavior of the pump beam is projected on the idler beam. 相似文献