单位阶跃响应的时域求解方法

我们国多数教材中重点讨论系统的单位冲激响应时域求解方法,然后利用阶跃响应与冲激响应的微积分关系求解系统阶跃响应,关于直接求解单位阶跃响应的时域方法总结较少。本文分别从冲激响应与阶跃响应关系、微分方程求解以及时域规范化方法的角度出发,归纳了连续时间系统单位阶跃响应求解方法,并以实例说明其正确性。     

一种新的gyrator变换的快速算法

为了研究gyrator变换在光学信息处理中的应用,提出了一种采用两次快速傅里叶变换实现快速计算gyrator变换的新算法.在量纲归一化条件下,研究了gyrator变换离散化过程,获得了空域、傅里叶变换域和gyrator变换域的采样间隔,形成了一种能避免尺度变换的算法.采用该算法进行了数值模拟实验,实验结果与相关文献中报道的计算结果一致.结果表明,该算法可以应用于gyrator变换的研究中.     

光反馈自混合干涉信号预处理方法

为了提高参数估计的精确度,根据光反馈自混合干涉信号的特点,采用对原始光反馈自混合实验信号进行滤波和归一化等预处理方法,有效地滤除了噪声,使信号平坦化,而且预处理后的实验信号与理论模型仿真数据更加吻合。分别利用原始实验信号和预处理后的信号对参数进行估计,比对结果表明,使用预处理后的光反馈自混合信号进行参数估计,线宽展宽因数和光反馈水平因子C的测量精度分别提高了5.52%和4.55%。     

抗多径噪声归一化合并SFH／MFSK系统在短波信道中的性能

分析了具有抗多径措施的噪声归一化合并ＳＦＨ／ＭＦＳＫ接收机在存在部分边带干扰的多径瑞利衰落信道中的性能，着重研究了多径加权因子ω对该系统性能的影响．结果表明，最佳加权困子ω与多径干扰强度、分集重数、调制阶数和信道热噪声有关．对多径合适地加权可明显地降低比特误码率Ｐｂ，在分集和编码相结合时，能使Ｐｂ下降２～３个数量级．     

关系模式规范化的几个算法

本文在不计算函数依赖集闭包的情况下,给出了求关系模式关键字、BCNF判定和分解、寻找BCNF分解中丢失的函数依赖等几个算法。     

Combining multivariate analysis and geochemical approaches for assessing heavy metal level in sediments from Sudanese harbors along the Red Sea coast

Multivariate statistical analysis and geochemical approaches were exploited for the assessment of the level of some heavy metals (Mn, Fe, Ni, Cu, Zn and Pb) in sediments from Sudanese harbors along the Red Sea coast. Principal component analysis, as a multivariate statistical analysis approach, was applied to identify contribution sources by heavy metals in sediments. While a single source (crustal) was recorded in the bulk sediments and coarse sediment grains (grain-size 1000-500 µm), two sources (crustal and anthropogenic) were recorded in fine sediment grains (grain-size < 500 µm). Furthermore, enrichment factor (EF), as a geochemical approach, appointed polluted sites by heavy metals in the study area. Based upon a previous study addressed the interpretation of EF values, minor to moderate anthropogenic enrichment were recorded in sediments from some sites in the study area. The main anthropogenic activities that believed to be the major sources of pollution by heavy metals in the study area are discharges from oil refinery, industry, shipping activity and domestic waste. Hierarchical cluster analysis (HCA), as another multivariate statistical analysis approach, was applied for the concentrations of heavy metals in bulk sediments to group sediments according to their mineralogical composition. The output of HCA is that sediments from the Port-Sudan harbor can be divided mainly into three areas — east, west and south. For the Sawakin harbor, no apparent trend for the spatial distribution of heavy metals in sediments was recorded.     

基于编辑距离和相似度改进的汉字字符串匹配

为解决中文字符串匹配精度较低的问题,提出了一种基于编辑距离和相似度改进的汉字字符串近似匹配算法,针对汉字字符串特点,使用汉字拼音和五笔编码计算;通过改进动态规划算法,能够有效提高编辑距离的计算准确度以及执行效率;再引入考虑交换问题的归一化算法,以语义编辑距离与长句长度的比值作为归一化结果,以此来提高近似匹配算法的准确度。实验结果表明,改进后算法计算的相似度质量要优于改进前的算法结果,且对提高算法效率和查全率、查准率和时间性能等指标均有明显改善,证明该算法的可行性和有效性。     

Genome-wide predicting disease-related protein complexes by walking on the heterogeneous network based on data integration and laplacian normalization

BackgroundAssociating protein complexes to human inherited diseases is critical for better understanding of biological processes and functional mechanisms of the disease. Many protein complexes have been identified and functionally annotated by computational and purification methods so far, however, the particular roles they were playing in causing disease have not yet been well determined.ResultsIn this study, we present a novel method to identify associations between protein complexes and diseases. First, we construct a disease-protein heterogeneous network based on data integration and laplacian normalization. Second, we apply a random walk with restart on heterogeneous network (RWRH) algorithm on this network to quantify the strength of the association between proteins and the query disease. Third, we sum over the scores of member proteins to obtain a summary score for each candidate protein complex, and then rank all candidate protein complexes according to their scores. With a series of leave-one-out cross-validation experiments, we found that our method not only possesses high performance but also demonstrates robustness regarding the parameters and the network structure. We test our approach with breast cancer and select top 20 highly ranked protein complexes, 17 of the selected protein complexes are evidenced to be connected with breast cancer.ConclusionsOur proposed method is effective in identifying disease-related protein complexes based on data integration and laplacian normalization.     

谈谈物理实验课的教学管理

为了提高物理实验课的教学质量．有必要加强实验教学的规范化、制度化建设。我们对此作了初步的实践和探索。     

Statistical properties of two-dimensional periodic Lorentz gas with infinite horizon

We study the asymptotic statistical behavior of the 2-dimensional periodic Lorentz gas with an infinite horizon. We consider a particle moving freely in the plane with elastic reflections from a periodic set of fixed convex scatterers. We assume that the initial position of the particle in the phase space is random with uniform distribution with respect to the Liouville measure of the periodic problem. We are interested in the asymptotic statistical behavior of the particle displacement in the plane as the timet goes to infinity. We assume that the particle horizon is infinite, which means that the length of free motion of the particle is unbounded. Then we show that under some natural assumptions on the free motion vector autocorrelation function, the limit distribution of the particle displacement in the plane is Gaussian, but the normalization factor is (t logt)^1/2 and nott ^1/2 as in the classical case. We find the covariance matrix of the limit distribution.