基于奇偶树型交互学习机与遗传算法的密文优化系统

为使图像加密系统具备优化功能,并解决当前遗传算法无法实现全局最优、收敛速率慢等问题,提出奇偶树型交互学习机耦合全局离散遗传算法的密文优化系统。定义权值更新机制,耦合混沌映射,构造奇偶树型交互学习机及其互扰模型。将切断型轮盘赌择取机制引入均匀交叉算子中,以图像分块的相邻像素相关系数和密文信息熵为目标,根据权重理论设计加权适应度函数,提出一种全局离散遗传算法,最终形成"初始加密-密文优化"的加密结构。实验结果表明,与超混沌算法、离散遗传算法、元胞自动机相比,该系统的加密质量较好,并且具备全局优化功能,可优化所有迭代结果,使最终输出密文的信息熵最大,相关系数最小。     

802.11 DCF协议引入信道预约机制的必要性分析

论文对802.11 DCF协议引入信道预约机制的必要性问题进行了探讨.通过分析信道预约机制与隐藏/暴露终端问题之间的关系,提出一种比较隐藏终端和暴露终端出现概率大小的等效方法,并给出了相应的数值估算结果.理论分析结果验证了802.11 DCF协议引入信道预约机制的有效性.     

工作流系统性能分析与优化方案

随着企业业务流程信息化建设的推进,对核心业务领域的流程化管理已成为实现信息化水平进一步提升的重要基础,工作流系统作为基础设施,其性能在一定程度上决定了业务流程流转的效率.本文通过对工作流系统性能的量化分析,得出其性能指标与数据库规模的量化关系,从而为性能优化工作提出关键因素和技术切入点,在此基础上,本文结合数据库机制对工作流性能优化方案进行了研究和实现,提出了一种有效的算法,实现了归档机制,从而达到提升工作流系统性能优化的最终目的.     

网络在线文化信息监控平台建设与服务机制研究

针对高速网络环境下网络文化信息传输内容监控的需要,提出了实现拥有自主版权的能够在边界路由器上监测运行的网络文化信息监控系统的3种设计方法、3个层面的设计思想,以及数据采集结构、模块功能实现、服务机制创新的方法和理念,试图有效监测特征敏感性在线文化信息的来源与去向,创新监控应对策略,提高监控安全事件处理的效能。     

图像增强技术在安防监控系统中的应用

数字化的图像处理技术里面对于各个综合知识的跨度是相当大的,对于各个知识面的要求也是十分高的。那么图像处理技术在实际的生活应用中也是被广泛运用。随着科技时代的到来,人们对于图像的画质要求更高,所以对于图像处理技术的研发已经是整个行业必须解决的问题。那么在这样一个要求越来越高的情形下,在视频监控行业里面图像处理技术起到了那些作用？是怎么样去应用到安防监控行业里面的？本文针对这些问题作出了一些简单的讨论和研究。     

A minimum variance distortionless response filter based on the bifrequency spectrum for single-channel noise reduction

This paper deals with the problem of single-channel noise reduction in the short-time Fourier transform (STFT) domain. Many algorithms have been developed to solve this important problem, most of which generally assume that the STFT coefficients in different frequency bands are uncorrelated, so the noise reduction is achieved by applying a gain function to the STFT of the noisy speech in each frequency band. However, this assumption is not accurate and the STFT coefficients of speech signals between neighboring frequency bands are correlated in practice due to the use of small lengths of the fast Fourier transform (FFT) and overlap add/save techniques in implementation. This paper formulates the noise reduction problem by taking into account the interband correlation using the so-called bifrequency spectrum. Based on this formulation, a single-channel minimum variance distortionless response (MVDR) filter is derived, which is shown to be able to significantly improve the signal-to-noise ratio (SNR) and meanwhile maintain the desired speech not much distorted. Simulations are presented to justify the claimed merits of the developed MVDR filter.     

视频图像增强关键技术研究

随着社会的飞速发展,采集保存视频/图像已经成为人类日常生活的一部分。视频图像的质量高低,对人类识别图像对象起着非常重要的作用。为了改善图像的视觉效果,有目的地强调图像的某些特征,增加图像的可读性与可识别性,提出采取融合增强术来提高视频图像的对比度与清晰度,提高图像增强质量。     

Effect of fretting amplitudes on fretting wear behavior of steel wires in coal mines

Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.     

潜器Stewart平台动力学仿真

建立了Stewart平台的动力学模型,对潜器的动力学特征进行分析,对其运动进行动力学仿真研究.以Stewart平台的任意支腿为研究对象,考虑各支腿的重力和惯性力,利用牛顿-欧拉方法建立了支腿及动平台的力和力矩平衡方程,推导出了Stewart平台的动力学方程及支腿所受的支反力.以潜艇模拟器并联机构为例,运用动力学模型进行了实际计算并绘制了支腿驱动力的变化曲线,将驱动力与支腿运动速度相乘得到支腿功率输出的变化曲线,为液压油缸的功率设计提供了依据,也为潜器的精确动力学解耦奠定了基础.