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Tucker R.S. Baney D.M. Sorin W.V. Flory C.A. 《IEEE journal of selected topics in quantum electronics》2002,8(1):88-97
In this paper, we examine thermal noise and radiation-pressure effects in MEMS tunable Fabry-Perot etalons. We show that thermal noise causes a jitter in the center wavelength in very high finesse etalons. In turn, the jitter causes an effective increase in the time-averaged filter bandwidth. Radiation pressure is of little consequence in conventional Fabry-Perot etalons, but it can give rise to nonlinearities and hysteresis in the tuning response of high-finesse MEMS filters. We develop models of noise and optical nonlinearities and compare the models with a series of measurements on commercial tunable high-finesse MEMS Fabry-Perot etalons 相似文献
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Formal models of communicating and concurrent systems are one of the most important topics in formal methods, and process
calculus is one of the most successful formal models of communicating and concurrent systems. In the previous works, the author
systematically studied topology in process calculus, probabilistic process calculus and pi-calculus with noisy channels in
order to describe approximate behaviors of communicating and concurrent systems as well as randomness and noise in them. This
article is a brief survey of these works. 相似文献
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This work presents digital noise in signal integrity and clarifies noise margin issues in digital electronics education. For the static noise margin, the traditional definition violates the basic principle of noise. The embedded rectangle method to define the static noise margin is a more reliable criterion. For the dynamic noise margin (DNM), several approaches have been evaluated. The best way to teach the student DNM is suggested. 相似文献
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随着对输变电工程环境影响的重视,噪声影响及其治理问题是其中较为突出的问题。介绍了变电站主要噪声源变压器、输电线路和换流站噪声及其治理的国外情况,主要对国内外降低变压器本体噪声及辅助冷却装置噪声采取的技术措施、变压器有源消声法、在导线表面采取缠绕扰流线或直接使用低噪声导线以降低导线噪声的方法、换流站主要噪声源设备(换流变压器、平波电抗器、滤波器组等设备)降噪研究和措施作了阐述。 相似文献
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噪声是衡量吸尘器研制水平的重要标志.本文从频率分析的角度剖析了吸尘器噪声的组成情况,讨论了各噪声成分的产生根源和传播路径,分析了吸尘器噪声的主要影响因素并进行了试验验证.继而从减振、吸声和隔声三个方面探讨了吸尘器噪声控制的策略与方法. 相似文献
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本文以负压波信号采集滤波为例,介绍了基于LMS算法的自适应滤波器的基本原理和该滤波器几个关键参数设定的基本方法。实践证明,在采集随机不确定信号时,采用此滤波器进行信号调理具有比传统滤波器不可比拟的优越性。 相似文献
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锅炉出口参数、机炉压降和主蒸汽管道压降计算的规范化问题 总被引:1,自引:0,他引:1
张建中 《电力标准化与技术经济》2003,12(1):29-37
对锅炉出口参数、机炉压降及主蒸汽管道压降计算规范的现状、存在的问题进行了分析讨论,并提出了改进建议。 相似文献
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The authors discuss electromagnetic compatibility (EMC) and electromagnetic interference (EMI). After a brief look at the causes of EMI, they describe conductive coupling and electromagnetic radiative coupling. Career opportunities in EMC problem solving are looked at 相似文献
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Peter T. While Jose R. Teruel Igor Vidić Tone F. Bathen Pål Erik Goa 《Magma (New York, N.Y.)》2018,31(3):425-438
Objective
To explore the relationship between relative enhanced diffusivity (RED) and intravoxel incoherent motion (IVIM), as well as the impact of noise and the choice of intermediate diffusion weighting (b value) on the RED parameter.Materials and methods
A mathematical derivation was performed to cast RED in terms of the IVIM parameters. Noise analysis and b value optimization was conducted by using Monte Carlo calculations to generate diffusion-weighted imaging data appropriate to breast and liver tissue at three different signal-to-noise ratios.Results
RED was shown to be approximately linearly proportional to the IVIM parameter f, inversely proportional to D and to follow an inverse exponential decay with respect to D*. The choice of intermediate b value was shown to be important in minimizing the impact of noise on RED and in maximizing its discriminatory power. RED was shown to be essentially a reparameterization of the IVIM estimates for f and D obtained with three b values.Conclusion
RED imaging in the breast and liver should be performed with intermediate b values of 100 and 50 s/mm2, respectively. Future clinical studies involving RED should also estimate the IVIM parameters f and D using three b values for comparison.13.
J. Vandewalle H. De Man J. Rabaey 《International Journal of Circuit Theory and Applications》1981,9(1):77-88
Given a linear network of capacitors, periodically controlled switches and sources we derive its adjoint network and show how it can be used to reduce the computational complexity of the frequency, noise and sensitivity analysis. The construction of the adjoint switched capacitor circuit turns out to be quite simple, even for switched capacitor networks with more than two phases or with a continuous input-output path. Moreover this construction can be performed equivalently in the time domain or on the equivalent circuit. In order to facilitate the implementation in a computer-aided-design program all derivations are performed in the modified nodal analysis formulation (MNA). 相似文献
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Angelo Brambilla Giambattista Gruosso Massimo Redaelli Giancarlo Storti Gajani 《International Journal of Circuit Theory and Applications》2010,38(7):689-708
In this paper it is shown that a numerical method largely adopted for the simulation of noise in autonomous circuits is affected by singularities that manifest when the frequency at which the noise analysis is carried out approaches a harmonic of the autonomous circuit. The resulting noise power spectral density (PSD) is thus characterized by spurious spikes. The presence of these singularities is for the first time justified from an analytical standpoint and their effects are shown by simulating some oscillators, employed as benchmarks. Furthermore, the presented approach justifies the 1/(fs?f)2 shape of the PSD of noise at the output when the fs frequency approaches the f fundamental of a stable oscillator and the 1/|fs?f|3 shape when the effects of flicker noise are manifest. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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管道电机噪声有源控制系统研究 总被引:1,自引:0,他引:1
针对直流电机运行噪声的频谱特点,设计管道电机噪声有源控制的物理系统和软件硬件系统.对直流电机运行噪声,通过实验进行单通道有源噪声控制算法主要参数包括泄漏参数、迭代步长和滤波器长度的最优化设计.根据优化后的算法参数,进行管道电机噪声单通道和多通道有源控制实验.实验结果表明,电机转速为1 200r/min和1 500r/m... 相似文献
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C. Pennetta M. Tizzoni A. Carbone L. Reggiani 《Journal of Computational Electronics》2012,11(3):287-292
Measurements of electrical transport and excess current noise in semiconducting films of polyacenes revealed a superquadratic increase of the current and a sharp peak of the relative noise at voltage values corresponding to the trap-filling transition region. Recently, we formulated an explanation of these findings in terms of trapping and detrapping processes of the injected carriers by deep defect states. This interpretation was based on a phenomenological model that takes as input the measured I?CV characteristic curve. Here we introduce a new percolative approach to transport and noise in these materials. In particular we develop two percolation models, differing in the voltage dependence of the trapping and detrapping rates: precisely, one model neglects and the other accounts for the Poole-Frenkel effect. We then discuss the results of both models in connections with experimental findings. 相似文献
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针对变电站噪声有源控制技术中存在的算法性能较差和易受周边环境影响的问题,本文利用人工神经网络、小波技术及遗传算法对该技术进行改进。首先结合小波技术和人工神经网络来预测噪声控制系统的参考输入信号,然后根据小波去噪原理滤除进入误差传感器的混合噪声中由周边环境引起的高频干扰噪声,并将剩余噪声反馈至系统控制器中,最后利用遗传算法优化控制器中小波神经网络的参数,实现变电站噪声的最佳控制。对变电站内变压器振动和噪声数据进行仿真,结果表明改进后的方法有效地提高了系统的噪声跟踪速度、降噪量及稳定性,可以使变电站降噪达到满意的效果。 相似文献
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Scott R.P. Langrock C. Kolner B.H. 《IEEE journal of selected topics in quantum electronics》2001,7(4):641-655
We describe techniques for making sensitive and high-dynamic-range measurements of laser amplitude and envelope phase noise (timing jitter) in the frequency domain at the shot-noise limit. Examples of amplitude noise measurements on continuous-wave argon-ion and diode-pumped solid-state lasers used for pumping a femtosecond Ti:sapphire laser are presented. Amplitude and phase noise measurements for the Ti:sapphire laser are also presented, showing correlation between pump laser amplitude modulation (AM) spectra and the resulting AM and phase noise. Characteristics of the measurement system components are discussed, along with examples of the impact these have on achieving reliable high-dynamic-range measurement capability 相似文献