一种改进小波收缩阈值的信号消噪算法

小波变换是一种时频分析的方法,在信号处理领域广泛应用.文章在经典的小波软、硬阈值消噪方法的基础上,提出了一种基于小波分析的改进阈值信号消噪方法.Matlab仿真结果表明,此法同时克服了软、硬阈值方法的缺点,其消噪效果较好.     

计算机在医学领域的应用

根据医学领城应用计算机技术的现状,对医学实验、辅助诊断、图像处理、医院综合管理等方面的应用做简要概述,并举例说明计算机在医疗领域的具体应用.     

一种基于RSSI的车载WiFi相遇时间预测方法

随着WiFi技术的普及,在移动车辆上使用路边AP进行数据通信变得越来越容易.使用车载WiFi通信有一个关键问题是如何选择最优的AP.针对该问题,提出了一种通过监测AP接收信号强度RSSI的变化趋势来预测车辆与AP相遇时间的算法.车载WiFi通过预测不同AP的相遇时间选择预测时间较长的AP.实验分析表明,在确定无线电信号衰减因子的情况下, 通过多次采样可以减小误差,相遇时间预测结果的准确性较高.算法提高了平均连接时间,减少了切换次数,增强了通信稳定性.     

A novel color image watermarking scheme in nonsampled contourlet-domain

Geometric distortion is known as one of the most difficult attacks to resist, for it can desynchronize the location of the watermark and hence causes incorrect watermark detection. It is a challenging work to design a robust color image watermarking scheme against geometric distortions. Based on the support vector regression (SVR) and nonsubsampled contourlet transform (NSCT), we propose a new color image watermarking algorithm with good visual quality and reasonable resistance toward geometric distortions in this paper. Firstly, the geometrically invariant space is constructed by using color image normalization, and a significant region is obtained from the normalized color image by utilizing the invariant centroid theory. Then, the NSCT is performed on the green channel of the significant region. Finally, the digital watermark is embedded into host color image by modifying the low frequency NSCT coefficients, in which the HVS masking is used to control the watermark embedding strength. In watermark detection, according to the high correlation among different channels of the color image, the digital watermark can be recovered by using SVR technique. Experimental results show that the proposed color image watermarking is not only invisible and robust against common image processing operations such as filtering, noise adding, and JPEG compression etc., but also robust against the geometrical distortions.     

Priority-based target coverage in directional sensor networks using a genetic algorithm

Sensor networks have been applied in a wide variety of situations. Recently directional sensor networks consisting of directional sensors have gained attention. As for the traditional target coverage problem, the limited sensing angle of directional sensors makes it even more challenging. Moreover, individual targets may also be associated with differentiated priorities. Considering the distance between the directional sensors and targets influences sensing quality, this paper proposes the priority-based target coverage problem and strives to choose a minimum subset of directional sensors that can monitor all targets, satisfying their prescribed priorities. Due to the NP-Complete complexity, the minimum subset of directional sensors is approximated by using a genetic algorithm. Simulation results reveal the effects of multiple factors on the size of the resulting subset.     

DCS电源供电系统的可靠性定量分析

根据DCS电源系统的现状,对目前几种不同的电源设计方案进行可靠性定量分析.通过建立不同DCS电源系统可靠性框图并估算相关的可靠性指标,比较了不同方案下的平均无故障工作时间 (MTBF),给出了系统可靠性的分析结果和改进措施,定量分析了改进后的方案.结果表明电源系统的MTBF有了明显的改善.     

基于模式驱动和模糊查询的模式发现方法

在蛋白质序列的比对研究中,拥有相似模式的蛋白质常常具有相似的功能.通过已知的蛋白质序列模式可以很方便地对新蛋白质序列的功能结构进行研究和确认.蛋白质序列的发现已成为一个很有意义的题目.对基于模式驱动Pratt算法进行改进以提高其效率,在原来基础上引入模糊查询方法,能够更为快捷地从互不相关的蛋白质序列集合中找出最具代表性的蛋白质模式.