变参数波振器中小信号增益公式

利用微扰展开技术推导出变参数波振器的小信号增益两个近似求积表达式并将其计算结果与数值模拟结果进行了比较,二者吻合很好。利用近似解析式对小信号增益进行了初步探讨,得到了电子入射能量可低于初始谐振能,能散度允许范围受波振器设计影响以及降低锥度改变率可提高小信号增益等新结论。     

Detecting emboli from Doppler ultrasound signals with the wavelet packet analysis method

A Doppler ultrasound analysis method based on wavelet package transform was proposed for embolic detection. The embolic Doppler signal was firstly decomposed using the wavelet packet. Then the sensitive characteristics were calculated from each sub-band signal and used in the emboli classification. This method was applied to analyze 300 cases simulated and 163 cases clinical Doppler signals. The minimum error ratio of embolic detection using this method was 13 percents lower than that using the traditional spectrogram analysis method.It was shown that this method overcame the limit between the time and frequency resolution in the short time Fourier transform, improved the accuracy of embolic detection greatly and extracted more reliable parameters for the clinical diagnosis.     

An approach to the detection of underwater remote target

An approach to the detection of underwater remote target by estimating its backscattering coefficient is presented. The key to this approach is that the echo signal is represented in state-variable model and the back-scattering coefficients of target are contained in dynamic noise of this model, thus underwater target can be detected by estimating this dynamic noise, i.e., deconvolving this model. When all noise statistics are a priori known, an optimum deconvolution algorithm based on the optimum state filter is derived, or else, an adaptive deconvolution algorithm based on the adaptive state filter of alternatively estimating the vector state and the noise statistics is developed. In the final simulation test, an echo signal with SNR equal to -6.1 dB is proceeded using the aforementioned two deconvolution algorithms, respectively, and the results demonstrate good performance of the approach.     

Cascade Grating Structure for Increasing the Channel Number on Holographic Demultiplexer

The expansion capability of the channel number in the optical demultiplexer using two cascaded photopolymer volume gratings is reported. It could be accomplished by designing of two gratings with different spectral range. As a result of the experiment, a 0.4-nm-spaced 130-channel demultiplexer with the channel uniformity of 3.5 dB, the 3 riB-bandwidth of 0.12nm, and the channel crosstalk of-20 dB is experimentally demonstrated.     

弱信号提取中门积分器的设计

介绍动平稳仪中弱信号提取的门积分器的设计。讨论了门脉冲宽度（Ｔｇ）、信号周期（Ｔ）、时间常数（ＲＣ）和信噪比改善的关系，并在实际电路中进行了检测。     

美国开发出食品保质检测新装置

不久前，美国开发出一种全新的食品保质检测装置，该装置由传感器与传感器与扫描器构成。据悉，传感器的主要材料是铅，包装食品时，将它置于食品匣内。检测时，扫描器对食品发射的无线电波信号会使食品产生振动，同时发出乐谱波。乐谱波先反射到食品盒壁上，后传导给传感器，通过标准数据库标定振动程度、振动传导时间及乐谱波的传导速度，瞬间即可确定所检测食品发生变质的时间。     

一种可以观测化学反应过程中物质形态的分析测试装置以及方法

本发明公开了一种可以观测化学反应过程中物质形态的分析测试装置以及方法，包括充满电解质溶液的液池、光学棱镜、镀金属载波片、激光发生器、信号接收器及计算机处理系统；液池底面设置载波片，其上表面设有金属薄膜，待测样品设置在金属薄膜上；光学棱镜固定设置在液池底部下表面处；激光发生器和信号接收器分别设置在光学棱镜两侧，液池内还设有电极和扫描器以及串连设置在扫描器和电极之间的电流表和电压表，扫描器的下端部固定连接有探针；计算机处理系统与信号接收器、电流表、电压表电气连接，本发明不仅能够在线监测物质的形貌特征，而且可以测试物质的厚度，具有结构简单，使用方便、检测灵敏度高等优点。     

倒导数计时电位法研究

本文推导出倒导数计时电位法理论,实验结果与理论基本相符.本工作结果使计时电位法的信号灵敏度提高约一个数量级.     

基于模糊理论的空间屏蔽滤波信号去噪

基于模糊理论提出了一种空间屏蔽滤波信号去噪方法.对信号进行二进小波变换后,对信号进行空间屏蔽滤波,对于未通过滤波器的系数进行模糊阈值处理实现去噪.通过对含噪HeaviSine和Doppler信号的去噪仿真,表明,该方法对噪音具有良好的抑制作用,能较好地保持信号在间断点处的信息.与传统空间屏蔽滤波相比,该方法对不同种类的含噪信号均具有良好的去噪效果.