无证书强指定验证者签名的分析与改进

对Hafizul等提出的无证书强指定验证者签名方案进行安全分析,指出该方案不能抵抗授权攻击和恶意但被动的KGC(Key Generation Center)的普遍伪造攻击。同时也指出了另外一个缺陷,即不仅指定验证者的私钥可以验证签名,而且签名者的私钥也可以验证签名。提出改进的方案,改进方案克服了原方案的安全缺陷,提高了系统的安全性。     

基于热释电红外传感技术的目标定位研究

利用配备有多重反射光学装置的热释电红外传感器感知节点接收运动人体的红外辐射能量.通过采集和分析红外传感器输出的模拟信号的特征,可以提取人体的位置信息.当受试者沿离红外感知节点不同距离的路径通过节点观测区域时,红外信号的最大峰值会随人体与节点距离的增大而下降.在此基础上,设计了一种基于红外信号最大峰值的定位方法.与质心定...     

Fabrication and characterization of a biphasic scaffold for osteochondral tissue engineering

A biphasic scaffold with a stratified structure for osteochondral tissue engineering was developed. The chondral phase was a collagen-chitosan composite. The osseous phase was a composite of bioactive glass and collagen. Collagen integrated in the two respective phases was connected by cross-linking agents. Both layers of the scaffold showed interconnected porous structures. After being immersed into stimulated body fluid, precipitation of spherulitic grains could be found on the surface of the osseous phase and this precipitation was proved to be hydroxyapatite by X-ray diffraction and Fourier transform infrared spectroscopy. Inversion, fluorescence and scanning electron microscopy further confirmed that bone marrow stromal cells could anchor on this scaffold with healthy spreading. As the consequence, this biphasic scaffold may have significant potential as an alternative for osteochondral tissue engineering.     

橡胶膜密封气柜侧壁与顶盖同步安装法

橡胶膜密封气柜由于自身的结构特点,其施工方法与稀油密封气柜的施工方法有很大的区别,施工的重点和难点是侧壁和顶盖。目前常用的两种施工方法都是安装完侧壁后再提升安装顶盖。这种方法不仅费工费时、难度大,而且安装精度难以保证。还有一种方法虽然是侧壁与顶盖同步施工,但仍然还有不少缺点。新的施工方法是利用鸟形钩和手拉葫芦,同时将气柜的顶盖用作施工安装平台,实施侧壁和顶盖同步施工。这种安装方法不仅简单可靠,省时省力,而且有利于整个气柜安装质量的提高。     

探讨步行街商铺的设计

阐述了国内近几年来城市商业步行街实践中常见的一些问题,对步行街商铺设计要点尽心了探讨。     

一种加速度计冲击校准系统

介绍了一套加速度计冲击校准系统的测试原理和方法,该系统可产生半正弦冲击脉冲,可对压电式、内置电路式和压阻式等多种加速度计的冲击灵敏度进行校准.其中冲击比较校准器通过弹体碰撞装有标准传感器和被校传感器的砧子,进行背靠背式比较校准,其可产生低量程的冲击加速度,可对加速度计进行精确、可控的校准;高g值冲击校准器可产生可控的冲击激励脉冲,共基于Hopkinson棒原理,通过高压气加速弹体碰撞Hopkinson棒,使棒中产生压缩波,并传到装有被校传感器的棒的另一端,系统通过贴在棒中部的应变片测得该点的应变,通过应变与加速度之间的关系式计算出棒末端被校传感器处所受到的冲击加速度值.     

FLEXIBLE 2-DOF STEERING MODEL OF MULTI-AXLE HEAVY-DUTY VEHICLE

A flexible two degrees of freedom (2-DOF) steering model of multi-axle vehicle (MAV) is presented with considering the effect of frame flexibility based on the classic 2-DOF model. A method to calculate the frame flexibility is derived by using three moments equation. The steering stability of MAV is analyzed. The steering performance of MAV is also researched in frequency domain. Simulation results show that the dynamic effects of flexible model are more severe than rigid model and the flexible effect of frame will weaken the steering stability of MAV. Different disposals of steering axles lead to different steering characteristics of MAV. The in-phase steering mode improves the steering characteristics and stability at high speed. The anti-phase steering mode increases the steering mobility at low vehicle speed.     

宽频锁相的一种实现方法

将PWM整流器用于小型风力发电机时,宽频率范围锁相技术是其关键环节。针对此需求,文中将基于二阶广义积分(SOGI)锁相环与过零测频功能结合,并根据频率变化和频率适应范围实时调整PI参数,使相位跟踪快速准确。仿真表明所提方法在输入信号频率、幅值和谐波等多扰动源工况下都能准确实现相位和频率跟踪。