A robust ensemble data method for identification of human joint mechanical properties during movement

This paper describes a perturbation method for the identification of linear time-varying systems with an unknown input (voluntary joint input) using ensemble data. The method separates the unknown input and the perturbation through high-pass filtering and recasts the multi-input single-output system identification into single-input single-output system identification. The method is robust to intertrial variation, and can track changes of system dynamics up to 5 Hz. Analysis and simulation are given for the conditions similar to those for the human arm experiments. Experiments show that mechanical properties of the human elbow joint change with voluntary movement speed and that the mean stiffness with voluntary movement is in the range of the posture and is higher than reported before.     

A statistical method for the measurement of muscle activationintervals from surface myoelectric signal during gait

The aim of this work is to present an original double-threshold detector of muscle activation, specifically developed for gait analysis. This detector operates on the raw myoelectric signal and, hence, it does not require any envelope detection. Its performances are fixed by the values of 3 parameters, namely, false-alarm probability (P_fa), detection probability, and time resolution. Double-threshold detectors are preferable to single-threshold ones because, for a fixed value of the P_fa, they yield higher detection probability; furthermore, they allow the user to select the couple false alarm-detection probability with a higher degree of freedom, thus, adapting the performances of the detector to the characteristics of the myoelectric signal of interest and of the experimental situation. Here, first the authors derive the detection algorithm and describe different strategies for selecting its parameters, then they present the performances of the proposed procedure evaluated by means of computer simulations, and finally they report an example of application to myoelectric signals recorded during gait. The characterization of the proposed double-threshold detector demonstrates that, in most practical situations, the bias of the estimates of the on-off transitions is smaller than 10 ms, the standard deviation may be kept lower than 15 ms, and the percentage of erroneous patterns is below 5%. These results show that this detection approach is satisfactory in research applications as well as in the clinical practice     

一种阵列天线的约束最优化综合方法

为同时满足对方向性系数,阵列效率,方向图旁瓣等参数的要求,提出了一种效率和旁瓣约束下的最优方向性综合法.该方法适用于任意的阵列形式,以最大化阵列方向性系数为目标,通过对加权向量的二次约束控制了阵列效率,并采用迭代的方法满足了方向图旁瓣的要求,实现了阵列效率和旁瓣约束下的方向性系数最优化.对多种阵列在不同要求下的仿真结果以及5元圆阵列的实验结果表明了这种方法的有效性和灵活性.     

生物医学表面信息检测新方法研究

本文在血液等液体的表面上，激振出了一维表面波光栅，当激光束照射时，形成一列线阵分布的衍射光斑，它包含了生物表面特性的光信息，用电荷耦合器件等光电系统采集光信息与处理数据，从而为定量地表征生物表面信息，开创了新的研究途径。     

Iterative method of movement estimation for television signals

An iterative method for accurate movement estimation of television signals is analyzed. The method considered is based on an iterative process applied to the conventional gradient method. It is known that the gradient method has some problems both in its stability and in its accuracy for movements larger than 2 or 3 pel/frame. It is shown that when an iterative process is used, the estimated movement converges to the actual movement rapidly and is exponentially stable. It is also shown that the asymptotic accuracy of the iterative estimate is determined by the smoothness of the gradient and by the amount of the frame-to-frame noise. Some experimental results are given and compared to the theoretical result     

A sparse representation method for image-based surface defect detection

In this paper, an efficient sparse representation-based method is presented for detecting surface defects. The proposed method uses the sparse degree of coefficient in the redundant dictionary for checking whether the test image is defective or not, and the binary representation of the defective images is obtained, according to the global coefficient feature. Owing to the requirements for the efficiency and detecting quality, the block proximal gradient operator is introduced to speed up the online dictionary learning. Considering the correlation among the testing samples, prior knowledge is applied in the orthogonal-matching-pursuit sparse representation algorithm to improve the speed of sparse coding. Experimental results demonstrate that the proposed detection method can effectively detect and extract the defects of the surface images, and has broad applicability.     

一种无触点快速测量表面粗糙度的方法

提出一种使用激光束快速测量表面粗糙度的无触点光学方法。一束照射在样品表面的激光束随着表面粗糙度的增大反射光的密度分布将被扩展,可用PCD测出从铝制样品表面反射光的密度分布。被反射光的密度曲线可通过高斯函数近似地求出。密度分布曲线的宽度由高斯曲线系数的标准差计算出来,此标准差近似等于密度曲线的高斯函数的标准差,密度曲线的中线平均粗糙度随着高斯曲线系数的增加而增加。粗糙度Ra在0.1～0.5μm的范围内,可利用实验公式Ra=0.088GCP+0.032通过测量GCP得到。     

A method of surface clutter cancellation for an underground CWradar

An RF signal similar to the undesired signals is synthesized and used to cancel the undesired portion of the received signal from the antenna before it reaches the receiver. With a progressing degree of cancellation, the transmitter power is accordingly increased to expand the dynamic range of the radar. A canceller subsystem is proposed to eliminate undesired signals such as surface reflection and mutual coupling between antennas     

A method for the optimal pattern synthesis of linear arrays withprescribed nulls

A new L_∞ optimal method for the synthesis of equispaced linear array functions with asymmetrical far-field pattern functions is proposed. This iterative method provides for the exact specification of the beam width, while at the same time allowing for the specification of the relative levels of individual sidelobes by index or as a function of bearing (e.g., angularly-extended nulls), as well as the realization of specified narrowband nulls. The resulting array factors are optimal in the weighted L_∞ sense and, in general, have complex coefficients. This new Remez-type method employs multiple objective functions to provide the degrees of freedom that are required for exact null placement. Examples which demonstrate the design flexibility offered by the method are included for various sum and difference patterns, including superdirective and shaped-beam arrays     

一种测量激光跃迁截面和荧光寿命的新方法

本文介绍了利用激光弛豫振荡频率和激光参数的关系来测量激光跃迁截面和荧光寿命的方法。利用该方法测量了Nd:YAG 1.0642μm和Nd:YAP1.0795μm的激光跃迁截面及荧光寿命,其结果分别为43×10~(-20)—cm~2,253μs和46×10~(-20)cm~2,142μs。