值得重视的田口式参数设计法

本文着重论述了田口式参数设计法在半导体制造中对线宽的质量控制.通过田口式参数设计法,可以优化线宽控制对光刻过程步骤中的可控参数的条件,以便将不可控因素的影响降到最低.     

How a moving passive observer can perceive its environment ? The Unruh effect revisited

We consider a point-like observer that moves in a medium illuminated by noise sources with Lorentz-invariant spectrum. We show that the autocorrelation function of the signal recorded by the observer allows it to perceive its environment. More precisely, we consider an observer with constant acceleration (along a Rindler trajectory) and we exploit the recent work on the emergence of the Green’s function from the cross correlation of signals transmitted by noise sources. First we recover the result that the signal recorded by the observer has a constant Wigner transform, i.e. a constant local spectrum, when the medium is homogeneous (this is the classical analogue of the Unruh effect). We complete that result by showing that the Rindler trajectory is the only straight-line trajectory that satisfies this property. We also show that, in the presence of an obstacle in the form of an infinite perfect mirror, the Wigner transform is perturbed when the observer comes into the neighborhood of the obstacle. The perturbation makes it possible for the observer to determine its position relative to the obstacle once the entire trajectory has been traversed.     

Singularities and spectral asymptotics of a random nonlinear wave in a nondispersive system

In this paper, we study the propagation of high-intensity acoustic noise in free space and in waveguide systems. A mathematical model generalizing the Burgers equation is used. It describes the nonlinear wave evolution inside tubes of variable cross-section, as well as in ray tubes, if the geometric approximation for heterogeneous media is used. The generalized equation transforms to the common Burgers equation with a dissipative parameter, known as the “Reynolds–Goldberg number”. In our model, this number depends on the distance travelled by the wave. With a zero “viscous” dissipative term, the model reduces to the Riemann (or Hopf) equation. Its solution presents the field by an implicit function. The spectral form of this solution makes it possible to derive explicit expressions for both dynamic and statistical characteristics of intense waves. The use of a spectral approach allowed us to describe the high-intensity noise in media with zero and finite viscosity. Applicability conditions of these solutions are defined. Since the phase matching is fulfilled for any triplet of interacting spectral components, there is an avalanche-like increase in the number of harmonics and the formation of shocks. The relationship between these discontinuities and other singularities and the high-frequency asymptotic of intense noise is studied. The possibility is shown to enhance nonlinear effects in waveguide systems during the evolution of noise.     

Experimental study of the cavitation noise and vibration induced by the choked flow in a Venturi reactor

In this paper, the cavitation performance and corresponding pressure pulsation, noise and vibration induced by the choked cavitating flow in a Venturi reactor are investigated experimentally under different cavitation conditions by using high-speed camera and high frequency sensors. Based on the instantaneous continuous cavitation images, the Proper Orthogonal Decomposition (POD), a tool to analyze the large-scale cavitation flow structure, is applied to investigate the choked cavitating flow dynamics. The POD results show that two mechanisms, re-entrant jet flow mechanism and shock wave mechanism, govern the shedding and collapse of cavitation cloud at different pressure ratios. These mechanisms contribute to the variation of pressure pulsation, noise and vibration at different pressure ratios. The pressure pulsation spectrum behaves differently in various cavitation regions induced by the choked cavitating flow. Due to the existence of low pressure in re-entrant region, the influence of high frequency fluctuation on pressure pulsation caused by re-entrant flow is small. Moreover, with the increase of pressure ratio, the induced noise and vibration intensity decreases gradually, then increases and reaches a maximum value. Finally, it drops to a low and stable level. Despite different inlet pressures, the intensity of cavitation noise and vibration reaches the maximum value at the same pressure ratio. Specifically, the FFT analysis of noise and vibration signals indicates that low frequency component prevails at small pressure ratio owing to the re-entrant jet mechanism, while high frequency component prevails at large pressure ratio owing to the shock wave mechanism. The relationship between the choked cavitation dynamics and the induced pressure pulsation, noise and vibration in the Venturi reactor is highlighted. The results can provide guidance for the optimal operation condition of the Venturi reactor for cavitation applications such as water treatment.     

基于小波的恒电量瞬态响应信号的滤波处理

利用小波变换的阈值法对恒电量响应信号进行滤波处理, 同时与传统的时域和频域的滤波方法进行分析比较, 并且讨论了小波变换的分解层数对恒电量响应信号滤波效果的影响. 结果表明, 利用小波变换可以在时域和频域同时对恒电量响应信号取得良好的去噪效果. 这不仅能提高时域曲线拟合的精度, 还大大地提高了恒电量频谱解析的可靠性. 在实际应用中, 小波变换的分解层数取5～7层可以收到满意的效果.     

HgCdTe光伏探测器抑制背景通量的研究

对于长线列焦平面器件，简单的单孔冷屏往往不能有效地抑制背景，本文在Hg1-xCdxTe光伏探测器背面镀制微孔冷屏的办法来降低背景。测试结果表明，探测器镀制微孔冷屏之后，可以使背景辐射通量大幅度减少，同时减少了光串音。从而证明微孔冷屏的确可以有效地抑制背景通量，减少光敏元响应面积扩大的问题，对于红外焦平面器件的性能提高有帮助。     

一种实用的信号类型诊断方法及其在船舶辐射噪声中的应用

对一种基于ＫＳＷ理论的信号类型诊断方法进行了深入的研究,并将此方法用于船舶辐射噪声的分析中,为进一步了解船舶辐射噪声的特性提供了新的途径。另外,还发现,本方法不仅可以准确地诊断信号的类型,而且可以用来检验信号重构的质量．     

HgCdTe光伏探测器抑制背景通量的研究

对于长线列焦平面器件，简单的单孔冷屏往往不能有效地抑制背景，本文在Hg1-xCdxTe光伏探测器背面镀制微孔冷屏的办法来降低背景。测试结果表明，探测器镀制微孔冷屏之后，可以使背景辐射通量大幅度减少，同时减少了光串音。从而证明微孔冷屏的确可以有效地抑制背景通量，减少光敏元响应面积扩大的问题，对于红外焦平面器件的性能提高有帮助。     

基于经验模态分解的SO_2浓度检测信号处理方法

荧光法测量SO2浓度是大气监测中常用的检测手段.双光路技术可以消除光源和光路的噪音干扰,但光电转换器件在激发光照射下产生的背景噪音也会影响定量分析的准确度.本文采用经验模态分解滤波算法降低检测中存在的各种噪音,在实现有效降噪的基础上较好地保存了有用的原始信号.仿真结果表明,针对SO2浓度检测系统,利用经验模态分解去噪后信号的信噪比达到204.273 6,均方误差为0.007 0.与小波去噪法相比,经验模态分解检测效果更佳.最后将经两组不同方法处理后的信号应用于气体检测系统中,实验数据的线性关系更好地验证了经验模态分解方法应用到浓度检测系统的可行性.     

分配网络中的反向入侵噪声及其防范措施

从实践的角度,分析分配网络中入侵噪声进入反向回路的主要途径,并提出防范措施.