随机介质的声散射(Ⅰ)——广义Born近似反演

运用泛函微分方法给出弱随机介质中散射问题的散射幅度Ｂｏｒｎ近似的推广形式。讨论了关于阻尼最小二乘法反演介质参数的各价相关函数的方法,并讨论具有有限支集势函数扰动的逆问题的唯一性,其结果对运用Ｎｅｗｔｏｎ法等数值方法有实际意义。     

Histopathology alterations and histochemistry measurements in mussel, Mytilus edulis collected offshore from an aluminium smelter industry (Norway)

Histopathological characteristics of specific organs express condition, and represent time-integrated impacts on the organism stemming from alterations at lower levels of biological organisation. As integrative parameters, histochemical investigations have proved to be sensitive tools to detect effects of chemical compounds.The objective of this study was to determine changes in the tissues of mussels collected at a PAH contaminated site compared to a reference site using histopathological and histochemical parameters: lipofuscin (LF) accumulation in mussel digestive gland, and lysosomal membrane stability (LMS), and using additional information provided by body burden analysis to compare the sensitivity of these parameters.The histochemical measurements for both LF and LMS gave a clear indication of a high level of stress in animals from the PAH contaminated site. This LF accumulation in lysosomes is the result of peroxidation of autophagocytosed proteins associated with protein aggregates and oxidatively damaged organelles. These measurements were able to detect the effects of PAHs, and showed a strong relationship with the body burden results.     

A simple LMS‐based approach to the structural health monitoring benchmark problem

A structure's health or level of damage can be monitored by identifying changes in structural or modal parameters. However, the fundamental modal frequencies can sometimes be less sensitive to (localized) damage in large civil structures, although there are developing algorithms that seek to reduce this difficulty. This research directly identifies changes in structural stiffness due to modeling error or damage using a structural health monitoring method based on adaptive least mean square (LMS) filtering theory. The focus is on computational simplicity to enable real‐time implementation. Several adaptive LMS filtering based approaches are used to analyze the data from the IASC–ASCE Structural Health Monitoring Task Group Benchmark problem. Results are compared with those from the task group and other published results. The proposed methods are shown to be very effective, accurately identifying damage to within 1%, with convergence times of 0.4–13.0 s for the twelve different 4 and 12 degree of freedom benchmark problems. The resulting modal parameters match to within 1% those from the benchmark problem definition. Finally, the methods developed require 1.4–14.0 Mcycles of computation and therefore could easily be implemented in real time. Copyright © 2004 John Wiley & Sons, Ltd.     

罗兰C信号中的窄带干扰抑制与仿真

窄带干扰（NBI）是罗兰C接收机接收信号中普遍存在的一种干扰。这种窄带干扰经常淹没有用的罗兰C信号,因此,去掉NBI对罗兰C接收机的正常工作尤为重要。分别采用最小均方误差（LMS）自适应算法和二阶自适应格型滤波器算法对带有窄带干扰的罗兰C信号进行处理。仿真结果得出：LMS自适应滤波器对同步干扰和近同步干扰都有很好的效果;但是由于罗兰C信号本身的编码信息而比较难获取期望信号,加上LMS自适应滤波器实现阶数较高,实现相对困难。二阶格型自适应滤波器由于是完全除去干扰频率点,不能用于同步干扰,但其对近同步干扰和非同步干扰仍然有很好的效果,且其实现较为简单,易于在工程上应用。     

两种GPS天线阵列抗干扰算法研究及仿真

介绍了自适应天线阵列信号响应的数学描述,论述了在GPS抗干扰应用中广泛采用的基于最小均平方（LMS）的自适应算法的原理和实现过程,并对算法进行了仿真。提出了一种优于LMS算法的自适应数字波束形成（DBF）技术,推导出了其最优权系数矢量的计算方法,并对该算法进行了仿真。仿真结果表明：4阵元LMS的自适应调零算法对于单干扰的抑制和双干扰的抑制都达到了较好的效果,同时也体现了该算法零陷的优点。     

Assessment of lysosomal membrane stability and peroxisome proliferation in the head kidney of Atlantic cod (Gadus morhua) following long-term exposure to produced water components

There is a need for sensitive biological effect methods by which to detect impacts of chronic exposure to low concentrations of contaminants. Two methods shown to be potentially useful for monitoring purposes in fish include lysosomal membrane stability and peroxisome proliferation. These biological endpoints were assessed in Atlantic cod (Gadus morhua) head kidney following exposure to a mixture of produced water components including polycyclic aromatic hydrocarbons, phenol, and alkylphenols. Lysosomal damage of head kidney cells occurred within the first two weeks and did not recover during the entire exposure period (32 weeks). Lysosomal membrane stability was not affected by gender and was responsive at low concentrations of contamination, indicating that lysosomal membrane stability measured in the head kidney could be a useful biomarker for effects of offshore pollution. Peroxisome proliferation, measured as acyl-CoA oxidase activity in the head kidney, appeared to be a potential biomarker in male cod exposed less than 16 weeks.     

基于两步最小均方的宽带波束形成算法

针对空时二维滤波器结构,提出了修正两步最小均方波束形成算法,通过修正每次迭代运算中的期望阵列响应幅度和方向矩阵,显著地减少了矩阵运算量,达到快速准确求解期望方向图的相位和相应权矢量的目的。该算法在不改变天线阵元数的情况下,比传统空域滤波增加了时域处理维数,提高了波束形成质量,并利用了期望方向图相位的随机性,通过迭代更新期望方向图的相位和相应权矢量,实现了方向图的旁瓣控制,理论上可以形成任意控制的旁瓣波束,满足不同应用场合的需求。经计算机仿真实验,算法可以很好的收敛到期望的方向图,验证了该算法的有效性。该算法可广泛应用于多天线的GNSS导航接收机或抗干扰接收机中,在提高接收机在复杂环境下的可用性和灵敏度上具有重要的意义。     

具有LMS稳健初值的选权迭代法

基于选权迭代法的基本理论,文中提出先用LMS稳健估计来确定残差的初值,然后再进行选权迭代方法。其估计结果既继承LMS方法的高失效点(BP)稳健性,又具有选权迭代法的高估计效率,其计算结果与无异常点时最小二乘估计结果基本一致。     

基于最小均方误差算法消除GPS接收机噪声

从解决GPS接收机受干扰的实际需求出发,阐述了基于LMS算法的自适应滤波器基本原理和不同的噪声产生方式,并对GPS接收机仿真信号与噪声进行叠加。最后用基于LMS算法的自适应滤波器对仿真信号进行消噪处理,得到良好的消噪效果,证明了基于LMS算法的自适应滤波器能够应用于GPS接收机滤波系统。