共查询到20条相似文献,搜索用时 771 毫秒
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研究了基于关联噪声的带时滞项的非对称双稳系统的随机共振,在小时滞量及绝热近似理论下得到了信噪比的精确解析表达式,表明由于时滞量的存在系统出现了随机共振.讨论了系统的时滞量、噪声相关系数及系统的非对称性对系统的信噪比的影响. 相似文献
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提出了调制随机共振方法,实现了在大参数条件下从强噪声中检测微弱周期信号.将混于噪声中的较高频率的弱信号经调制变为一差频的低频信号作用于随机共振体系,该低频信号满足绝热近似理论,因而能产生随机共振;再经解调可获得埋于噪声中的原较高频率的弱信号.对埋于噪声中的未知频率,可采用连续改变调制振荡器的频率,以获得一个适当的差频信号输入到随机共振体系,根据输出信号共振谱峰的变化经解调而得待检弱信号的未知频率.该方法应具有较高的应用前景.
关键词:
调制与解调
非线性双稳系统
随机共振
微弱信号检测 相似文献
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M. C. Valsakumar 《Journal of statistical physics》1985,39(3-4):347-365
The diffusion of a particle set near an unstable point in a bistable potential is considered. The scaling theory of fluctuations proposed originally for onedimensional systems driven by Gaussian white noise is extended to arbitrary dimensions. The merits and drawbacks of the scaling theory are discussed by taking a model problem in one dimension. It is shown in passing that the saddle point approximation enables one to get analytic expressions for various moments of the stochastic process. The two different methods to include asymptotic fluctuations-which are absent in the usual scaling solution-are shown to be equivalent. An alternate way of including asymptotic fluctuations is attempted by solving the associated Fokker-Planck equation using the Fer formula. The reason for the failure of this method is traced. After this, it is argued that the unified scaling theory should be applicable for treatment of colored noise as well, for the scaling assumption is independent of the statistical property of the driving noise. Explicit Monte Carlo simulation of a model onedimensional system driven by exponentially correlated Gaussian noise is performed and compared with the scaling solution to bolster this point. The agreement is very good. 相似文献
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G.G. Martin 《Ultrasonics》1983,21(3):127-133
The background noise generated by servo-hydraulic machines commonly used in laboratory tests of materials prevents the extraction of the maximum amount of acoustic emission data during fatigue experiments. Some of the solutions for removing background noise during monotonic tests are not applicable, and modern acoustic emission (ae) monitoring systems cannot detect all ae generated in the presence of continuous background noise. The best technique for reducing the background noise appears to be the insertion of a noise attenuating barrier between the noise source and the test specimen.Multilayer sound transmission theory is outlined to show that noise attenuators must be designed for the particular frequency at which the ae system is to operate. The theoretical basis for obtaining (for a given application) the optimum attenuation from attenuators constructed on an acoustic impedance mismatch basis is provided. Finally, physical properties of materials suitable for use in attenuator construction are tabulated. 相似文献
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Synchronization between two different noise-perturbed chaotic systems with unknown parameters
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In this paper, a general method of synchronizing noise-perturbed chaotic systems with unknown parameters is proposed. Based on the LaSalle-type invariance principle for stochastic differential equations and by employing a combination of feedback control and adaptive control, some sufficient conditions of chaos synchronization between these noise-perturbed systems with unknown parameters are established. The model used in the research is the chaotic system, but the method is also applicable to the hyperchaotic systems. Unified system and noise-perturbed RSssler system, hyperchaotic Chen system and nolse-perturbed hyperchaotic RSssler system are taken for illustrative examples to demonstrate this technique.[第一段] 相似文献
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MAA Dah-You 《声学学报:英文版》1994,(2)
I.IntroductionThereverberantnoisesmaybereducedwithanactivenoisecontrol(ANC)systcmformedbyacornermicrophonc-amplifier-1oudspcakersystemina.oom.lllThismeth-odbascdonthenormalmodccancelingprincip1chasalreadybeenclarifiedbothinthco-ryandexperimcnts,andthclimitationandpotcntialityofitsapp1icationalsodiscussedinapreviouspaper.Thediscussionsinthepastlimitedmost1ytothesteadyconditionofnoiscfield,andthisisextendedtothetransientcondihoninthcprcsentwork,viz.thein-llucnceofthecornerANCsystemwhenthenois… 相似文献
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An essential feature of first-order paraxial theory is the assumption that if the potential along the axis of an axially symmetric system is known, then the potential (fields) near the axis can be obtained by a power-series expansion about points lying on axis. However, in traditional first-order theory, which commonly assumes systems with cylindrical symmetry, only terms up to second-order in the coordinate transverse to the beam axis are retained. In this letter we argue that a consequence of this restriction is that traditional first-order paraxial theory should not be applicable to electron and ion sources with pointed or needle-type geometries. In order to treat non-parallel trajectories which occur in the pointed geometries present, say, in field emission liquid metal ion sources, a modified paraxial theory is suggested which describes two-dimensional particle dynamics.This work has been supported in part by the Division of Materials Research, National Science Foundation, Grant No. DMR-81008829 相似文献
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Analyses of an air conditioning system with entropy generation minimization and entransy theory
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In this paper,based on the generalized heat transfer law,an air conditioning system is analyzed with the entropy generation minimization and the entransy theory.Taking the coefficient of performance(denoted as COP) and heat flow rate Q~(out) which is released into the room as the optimization objectives,we discuss the applicabilities of the entropy generation minimization and entransy theory to the optimizations.Five numerical cases are presented.Combining the numerical results and theoretical analyses,we can conclude that the optimization applicabilities of the two theories are conditional.If Q~(out) is the optimization objective,larger entransy increase rate always leads to larger Q~(out),while smaller entropy generation rate does not.If we take COP as the optimization objective,neither the entropy generation minimization nor the concept of entransy increase is always applicable.Furthermore,we find that the concept of entransy dissipation is not applicable for the discussed cases. 相似文献
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The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for magnetic resonance imaging (MRI) acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely, the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20-dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction. 相似文献
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《Physics letters. [Part B]》1986,173(3):303-308
Radiative corrections to the effective scalar potential are studied in no-scale supergravity models with local supersymmetry spontaneously broken by a gravitino mass. A simple proof is given that gauge non-singlet scalar fields acquire no supersymmetry breaking masses at the one-loop level, and a general argument is given extending this result to all orders of perturbation theory in the effective low-energy theory, proving also that no trilinear soft supersymmetry breaking terms in the effective potential are generated. These results are applicable to the four-dimensional no-scale supergravity theory obtained from the superstring after compactification, and support suggestions that the dominant source of global supersymmetry breaking in this theory may be the gaugino mass. 相似文献