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171.
用激光外差测振装置测量了扬声器纸盆振动幅度与激励电压及激励频牢之间的关系。为扬声器结构及振动特性的研究提供了一种精度高、重复性好的可靠测量方法。 相似文献
172.
Modeling, analysis, and implementation of parallel multi-inverter systems with instantaneous average-current-sharing scheme 总被引:16,自引:0,他引:16
Xiao Sun Yim-Shu Lee Dehong Xu 《Power Electronics, IEEE Transactions on》2003,18(3):844-856
Parallel multi-inverter systems can be designed to have the advantages of expandable output power, improved reliability, and easy N+X redundancy operation. However, a current-sharing control scheme has to be employed to enable the inverters to share the load current equally. A multi-inverter system with instantaneous average-current-sharing scheme is presented in this paper. By introducing a disturbance source to represent all the sources that may cause current unbalances, a model of the system can be built. Some key issues are discussed based on the model, including stability of the current-sharing controller, impedance characteristics and voltage regulation. Three experimental 110 VAC/1.1 kVA inverters are built and paralleled to verify the theoretical predictions. 相似文献
173.
174.
格基约减在许多应用上是一个非常有力的数学工具。本文详细介绍了有关格基约减算 法的概念、定义和著名的LLL算法,并在此基础上通过一个对低阶RSA算法的攻击过程对约减算法 的应用进行了简要介绍。 相似文献
175.
Suppose that the signal X to be estimated is a diffusion process in a random medium W and the signal is correlated with the observation noise. We study the historical filtering problem concerned with estimating the signal path up until the current time based upon the back observations. Using Dirichlet form theory, we introduce a filtering model for general rough signal X
W
and establish a multiple Wiener integrals representation for the unnormalized pathspace filtering process. Then, we construct a precise nonlinear filtering model for the process X itself and give the corresponding Wiener chaos decomposition. 相似文献
176.
Kae-Oh Sun Min Ki Choi van der Weide D. 《Microwave and Wireless Components Letters, IEEE》2005,15(6):440-442
We describe a simple PIN diode controlled variable attenuator that employs a 0-dB branch line directional coupler. The response of the attenuator was measured between 1.3 GHz and 2.6 GHz. At the center frequency, the attenuation monotonically varied from 0.7 dB to 23 dB with the control voltage, and the distributed branch-line coupler structure resulted in low input reflection. Our attenuator is easier to design, smaller in area than a double hybrid coupled attenuator, and has comparable or better reflection and attenuation performance characteristics. 相似文献
177.
关于Echelon空间无穷矩阵变换集的有界性 总被引:1,自引:1,他引:0
无穷矩阵变换是研究序列空间理论的重要工具.研究一个空间到另一个空间无穷矩阵变换的形式,是序列空间理论中的重要内容,并且已有众多工作.本文将进一步研究一般的Echelon空间到空间lp(1≤p≤∞),c、c0的无穷矩阵变换集的有界性.所得结果的特例正是Echelon空间到lp(1≤p≤∞)c、c0无穷矩阵变换的形式,同时概括了前人的许多结果. 相似文献
178.
A novel interference suppression scheme for global navigation satellite systems using antenna array 总被引:2,自引:0,他引:2
This paper considers interference suppression and multipath mitigation in Global Navigation Satellite Systems (GNSSs). In particular, a self-coherence anti-jamming scheme is introduced which relies on the unique structure of the coarse/acquisition (C/A) code of the satellite signals. Because of the repetition of the C/A-code within each navigation symbol, the satellite signals exhibit strong self-coherence between chip-rate samples separated by integer multiples of the spreading gain. The proposed scheme utilizes this inherent self-coherence property to excise interferers that have different temporal structures from that of the satellite signals. Using a multiantenna navigation receiver, the proposed approach obtains the optimal set of beamforming coefficients by maximizing the cross correlation between the output signal and a reference signal, which is generated from the received data. It is demonstrated that the proposed scheme can provide high gains toward all satellites in the field of view, while suppressing strong interferers. By imposing constraints on the beamformer, the proposed method is also capable of mitigating multipath that enters the receiver from or near the horizon. No knowledge of either the transmitted navigation symbols or the satellite positions is required. 相似文献
179.
A method has been developed for the qualitative analysis of paeonol, paeoniflorin and their derivatives in Paeoniae Radix by high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS). Gradient elution with acetonitrile-water solvent system was employed in an HPLC-ESI-MS study. The negative-ion ESI mode was suitable for these compounds. The peaks were identified by their mass spectra, UV spectra and fragments of their MS2 spectra. The structures of three unknown compounds are inferred in this paper. 相似文献
180.
In this paper, existence criteria are established for the existence of periodic solutions of a second order sublinear differential equation with delay and forcing function. Our method is based on careful a priori estimation and continuation theorems, and our sublinear condition is an improvement of the boundedness condition in some recent results. 相似文献