A group priority earliest deadline first scheduling algorithm

In most priority scheduling algorithms, the number of priority levels is assumed to be unlimited. However, if a task set requires more priority levels than the system can support, several jobs must in practice be assigned the same priority level. To solve this problem, a novel group priority earliest deadline first (GPEDF) scheduling algorithm is presented. In this algorithm, a schedulability test is given to form a job group, in which the jobs can arbitrarily change their order without reducing the schedulability. We consider jobs in the group having the same priority level and use shortest job first (SJF) to schedule the jobs in the group to improve the performance of the system. Compared with earliest deadline first (EDF), best effort (BE), and group-EDF (gEDF), simulation results show that the new algorithm exhibits the least switching, the shortest average response time, and the fewest required priority levels. It also has a higher success ratio than both EDF and gEDF.     

一种基于声起伏特性的水面干扰抑制方法

利用水面目标和环境噪声起伏较大,而水下目标的声信号起伏较小的特性,可以有效抑制水面干扰,提高水下目标的检测概率。对于单基元频谱分析采用非线性滤波器,进而针对阵列信号处理提出一种基于非线性滤波的连续时间方位历程水面干扰抑制方法。最后,对Swell96的实验数据进行了处理,单基元信号处理结果表明,振幅非线性滤波器和复声压非线性滤波器对于稳定线谱的信噪比(Signal to Noise Ratio,SNR)增益可达15 d B和30 d B;阵列信号处理结果显示所提出的方法能够有效抑制水面声源的航迹,提高水下声源的发现概率。     

缓冲区溢出的安全隐患

本文主要介绍缓冲区溢出和输入检查漏洞利用技术,还介绍了计算机病毒是如何利用这些技术。     

一种新的基于EMD模态相关的信号去噪方法

基于模态相关的准则,提出了一种新的信号去噪方法。首先对原信号进行经验模态分解（EMD）,其次根据各阶固有模态与原信号的相关系数曲线中第一个极小值点的位置作为标准定出噪声主导性模态与信号主导性模态的分界点,最后将固有模态函数（IMF）中信号起主导作用的模态成分进行重构来实现去噪。将该方法应用于仿真信号与实际光辐射强度信号的去噪,结果表明该方法在有效去噪的同时能较好地保持原信号的细节信息,具有较好的推广性。     

压力管道腐蚀灾变检测的应变敏度比法

基于结构振动模态测试理论和有限元方法提出了压力管道腐蚀检测的应变敏度比法。首先,通过位移模态及应变模态建立了腐蚀管道的定位检测判据。其次,制备不同缺陷的管道,应用应变敏度比法检测判断缺陷位置,结果表明,检测位置与实际损伤位置完全一致。最后,通过数值算例证实用前1阶模态分量数据检测的结果与实际缺陷基本一致。通过实测和数值算例证明了只测试损伤及未损伤结构的低阶模态参量,便可进行有效的检测,而低阶参量是相对简单易测,从而使该方法应用于工程实际更显便利。     

目标识别中信息融合的准则和方法

本文用信息论的观点，给出了在设计单个分类器时使系统性能得以提高的条件，基于群组决策理论和模糊积分方法提出了一种多证据条件下进行信息融合的方法．该方法被用于被动声纳目标分类，数值模拟表明了该方法的有效性.     

舰炮人工弹幕反导射击效力计算

针对舰炮人工弹幕反导射击效力计算的需要,分析了舰炮人工弹幕射击的特点,建立了人工弹幕射击误差分析模型,给出了舰炮人工弹幕布反导射击效力计算方法。以某型小口径舰炮为例,仿真计算了集火射击和人工弹幕射击对6种机动导弹目标的射击效力,结果表明：对于大机动导弹目标,人工弹幕射击比集火射击在射击效力上更具优势,仿真结论与人工弹幕射击的实际特点一致,证明了射击效力仿真方法的有效性。     

基于反对称高斯小波的水下目标回声信号检测

针对目标回声检测中信号背景的混响干扰问题,基于反对称连续高斯小波变换空间上的模极大值传播特性与信号奇异点的关系,提出用小波影响锥锥尖和最佳尺度的自动检索来实现目标回声检测的方法.通过大量海上现场数据验证该方法的有效性,结果表明,由于对目标信号头和尾位置的准确定位,基于W igner分布特征和模糊分类器的分类识别效果理想,显示本方法在实现目标回声的自动检测方面具有应用前景.     

无人机保障单座舰炮对单个目标作战效果分析

无人机通过侦察向舰炮提供目标信息,将舰炮武器与无人机作为一个完整的作战系统,用状态向量表征作战过程的动态变化,用状态概率描述系统作战效能及战斗结果,导出了系统状态概率的计算公式,给出了系统作战效果的评价方法.结果表明,当2架无人机保障1座舰炮对1个岸上运动目标作战时,0.2 s左右即可消灭目标.若要确保作战取得胜利,无人机最好在3架以上,此时舰炮摧毁目标的概率为0.8.研究成果对于无人机保障舰炮对岸作战具有重要的参考价值.     

Wear behavior of natural diamond tool in cutting tungsten-based alloy

Natural diamond tool is quickly worn out while cutting a workpiece made of a tungsten-based alloy. This paper presents a new approach to reduce tool wear: ultrasonic vibration cutting of a workpiece made of a tungsten-based alloy based on gas–liquid atomization cooling. An atomizer is a device which mixes carbon dioxide gas with vegetable oil and changes the liquid into minute droplets, which are carried by a stream of gas. Atomizer is also a device that incorporates a venture device to translate liquid into a gas stream. The atomized minute droplets act as the cooling and lubricating medium to protect the tools. The system is designed to ensure that droplets can spread all over the surface of a work piece. At a constant spindle speed, feed rate, and cutting depth, the experiments were carried out for investigating the effects of the tool vibration parameters, carbon tetrachloride liquid flow rate, carbon dioxide gas flow, and gas–liquid mass ratio on the tool wear. The experiments showed that the technology of ultrasonic vibration with gas–liquid atomization cooling effectively prolongs the tool life in cutting tungsten-based alloy.