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排序方式: 共有3218条查询结果,搜索用时 15 毫秒
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2.
The effect of the charge fluctuation of dust particles on ion acoustic wave (IAW) excited through ionization instability was investigated. The hydrodynamic equations and linear time-dependent perturbation theory served as the starting point of theory, by which the dispersion relation and growth rate of the IAW were given. By comparing the results with the case of constant dust charges, it was found that the charge fluctuation of dust particles reduces the instability of the wave mode. 相似文献
3.
Ting-Ting Gao Dan Wu Ying-Ling Huang De-Zhong Yao 《中国电子科技》2007,5(3):272-277
A nonlinear method named detrended fluctuation analysis (DFA) was utilized to investigate the scaling behavior of the human electroencephalogram (EEG) in three emotional music conditions (fear, happiness, sadness) and a rest condition (eyes-closed). The results showed that the EEG exhibited scaling behavior in two regions with two scaling exponents β1 and β2 which represented the complexity of higher and lower frequency activity besides α band respectively. As the emotional intensity decreased the value of β1 increased and the value of β2 decreased. The change of β1 was weakly correlated with the 'approach-withdrawal' model of emotion and both of fear and sad music made certain differences compared with the eyes-closed rest condition. The study shows that music is a powerful elicitor of emotion and that using nonlinear method can potentially contribute to the investigation of emotion. 相似文献
4.
尺度目标识别中的若干技术问题 总被引:1,自引:0,他引:1
从工程应用的角度阐述了现代鱼雷常用的尺度目标识别原理,讨论了影响识别距离的若干因素和措施,提出了小尺度模拟靶通过亮点延时算法以弥补尺度不足及其试验技术,试验结果表明,该方法可以获得良好效果。 相似文献
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6.
D. Bergmann U. KaiserS. Wagner 《Journal of Wind Engineering & Industrial Aerodynamics》2003,91(4):543-550
The determination of dynamic wind loads on buildings, i.e. pressure and deflection, has gained increasing interest (European Prestandard ENV 1991-2-4, Eurocode 1: basis of design and actions on structures—Part 2-4: actions on structures—wind actions, European Committe for Standardization, Brussels, 1995; DIN 1055 Teil 4 Lastannahmen für Bauten, Verkehrslasten, Windlasten bei nicht schwingungsanfälligen Bauwerken, 1991; N. Hölscher, M. Hortmanns, J. Sahlem, Praxisnahe Erfassung von Windwirkung an Industrie- und Hochbauten, Windwirkung im Bauwesen, Braunschweig, 7, Dreiländertagung D-A-CH 2001, Windtechnologische Gesselschaft, 2001 [1], [2] and [3]). Therefore, the spectral distributions of velocity and pressure fluctuations in wind tunnels are an important quality aspect. While velocity fluctuations can be manipulated by the obstacles used to create the turbulence, pressure fluctuations are influenced by acoustic noise as well. Especially, the first eigenfrequency of the longitudinal mode of the wind tunnel tends to disturb the pressure spectrum.In this paper, a solution for the reduction of low-frequency acoustic pressure fluctuation is presented and its application in the atmospheric boundary layer wind tunnel at the IAG is shown. 相似文献
7.
用瞬态频率波动法诊断齿轮故障 总被引:4,自引:0,他引:4
利用瞬态频率波动法实现频率调制信号的解调,提取齿轮的局部裂纹信息,并通过黄河TN252型汽车变速器疲劳试验的信号分析来验证。 相似文献
8.
L. FAN‡ D. PATERSON† I. McNULTY‡ M. M. J. TREACY & J. M. GIBSON‡ 《Journal of microscopy》2007,225(1):41-48
Measuring medium‐range order is a challenging and important problem in the structural study of disordered materials. We have developed a new technique, fluctuation x‐ray microscopy, that offers quantitative insight into medium‐range correlations in disordered materials at nanometre and larger length scales.In this technique, which requires a spatially coherent x‐ray beam, a series of speckle patterns are measured at a large number of locations in a sample using various illumination sizes. Examination of the speckle variance as a function of the illumination spot size allows the structural correlation length to be measured. To demonstrate this technique we have studied polystyrene latex spheres, which serve as a model for a dense random‐packed glass, and for the first time have measured the correlation length in a disordered system by fluctuation X‐ray microscopy. We discuss data analysis and procedures to correct for shot noise and detector noise. This approach could be used to explore medium‐range order and subtle spatial structural changes in a wide range of disordered materials, from soft matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. 相似文献
9.
Deterministic chaos theory offers useful quantitative tools to characterize the non-linear dynamic behavior of a fluidized bed and the developed complexity theory presents a new approach to evaluate finite sequences. In this paper,the non-linear,hydrodynamic behavior of the pressure flutuation signals in a reactor was discussed by chaos parameters and complexity measures.Coherent results were achieved by our multi-scale analysis,which further exposed the behavior in a gas-solid two-phase system. 相似文献
10.
为研究液压系统管路泄漏对压力脉动信号的影响,提出利用改进的小波消噪算法和小波包对压力脉动信号进行消噪和特征提取;针对传统小波变换阈值函数在去噪处理中存在的恒定偏差、不连续等缺点,提出一种改进阈值函数和新阈值相结合的新方法,将该方法与平移不变量方法相结合,避免了传统小波变换去噪时在不连续点存在的Pseudo-Gibbs现象;通过利用改进小波消噪方法和小波包对FESTO试验系统采集的正常和故障压力脉动信号进行分析比较,研究结果表明,不同工况下压力脉动信号3个主要能量频带的分布特性,可以作为泄露检测和识别的故障特征。 相似文献