陶瓷球栅阵列封装的有限元模拟与焊点应力分析

文章运用有限元分析软件ANSYS,建立了陶瓷球栅阵列(CBGA)封装的三维有限元模型,模拟出热载荷作用下CBGA封装的三维热应力应变分布,研究了焊点的形状对焊点的应力、应变的影响,为在实际焊接过程中,从焊点形态的角度去控制焊点质量提供了理论依据.     

无线传感器网TPSN的优化方案

文章在介绍无线传感器网络的时间同步协议TPSN(Timing-sync Protocol for Sensor Networks)的基础上.针对无线传感器网络中隐终端和冲突可能导致TPSN的不可靠、同步周期短、同步开销较大等问题.提出了TPSN的优化方案,可以提高其时间同步可靠性、估计时间误差、延长同步周期、并可大大减少其同步开销.     

一种新型电话自动语音报警装置的设计与开发

设计开发了一种新型电话自动语音报警装置,提出利用EPROM和少量通用数字集成电路．通过硬逻辑实现电话报警触发、自动摘（挂）机、自动拨号、自动提取报警语音信息和自动停机的功能,旨在利用较为简单的设计平台,通过多种手段集成,以实现智能化、多功能的目的。     

环型二元序列的赋权对换排序问题

研究了环型二元序列的赋权对换排序问题。定义一个长度为l的对换的费用是f(l)=lα,0≤α<1,对环型二元序列的赋权对换排序问题给出了一个O(logn)近似算法,其中n是环型二元序列的长度。     

IPv6校园网组网模式探讨及隧道代理的实现

在分析IPv6过渡技术的基础上,总结提出了IPv6校园网的几种组网模式,并给出了一个隧道代理的具体实现方法.     

基于核密度估计的干接缝装配式桥墩概率性地震损伤特性分析

为研究装配式桥墩的地震损伤特性,建立了干接缝拼装桥墩的纤维模型,以150条近场地震动为激励,开展了不同混凝土强度、初始预应力水平及节段个数的预制拼装桥墩增量动力分析,并采用核密度估计法获得了拼装桥墩和同尺寸现浇桥墩的地震易损性曲线.结果表明,相较于现浇桥墩,拼装桥墩各级损伤状态的超越概率更大.当混凝土强度在C30～C4...     

以群组方式实现互动手机电视

为以更高的效率提供互动式手机电视业务,基于诺基亚的IP数据广播结构,提出了一种使用DVB-H网和蜂窝网相结合的群组式方案.该方案使用蜂窝网作为回程信道,搜集点播选择信息,将点播同一内容的若干用户划为一组,点播内容通过DVB-H网递送.仿真结果表明,相对于一对一的流媒体提供方式,该方案可获得高得多的网络容量和小得多的用户平均等待时间,并具有价格优势.     

A new method for uniform local heating deep in body using ultrasound phased-array system

A new method for targeted heating of deep tissue was developed by using an ultrasound phased-array system which can generate various multiple foci patterns by electronically changing its amplitude or phase pattern. This method involves using a technique of combining switching and rotating of multiple foci patterns to create a uniform temperature over tissue volumes in various size. Using this method, the target tissue deep in the body can be heated to a specified temperature, which gives conditions for thermo-sensitive liposomes release. A simulation study for a 108-element, spherically sectioned array was performed to determine an optimal heating scheme from a set of multiple focus fields which were produced by inputting different combinations of phases and amplitudes. Comparisons of a static multiple foci field, the switched fields and the switched-rotated fields indicated that the technique of combining switching and rotating of multiple foci patterns has advantages of both lowering the peak temperature and evening the temperature distribution. The simulation results also show that the therapeutic heating zones in various size employing the combined method. These results offer significant data for designing thermotherapy equipment for tumor-specific drug release with thermo-sensitive liposomes.     

Multi-user performance analysis of differential frequency hopping system over Rayleigh-fading channel

A novel non-coherent detection scheme for differential frequency hopping （DFH） system is proposed in asynchronous multi-user environments over Rayleigh-fading channels. The synchronous and asyn- chronous multi-user performances of DFH with the conventional detection scheme and this novel detection scheme are analyzed, respectively. The performance results are validated with simulation. The results of analyses and simulations prove two conclusions. Firstly, the performance of asynchronous multi-user DFH system overcomes that of synchronous multi-user DFH system over Rayleigh-fading channel. Secondly, the novel detection scheme can achieve better performance than the conventional non-coherent detection scheme in asynchronous multi-user environments.     

碳化硼颗粒表面化学镀镍

对非金属B4CP表面化学镀镍前的活化工艺进行了研究,提出了NaCl活化工艺,在B4CP表面制备了镀镍层.镀层能谱分析及扫描电镜图片表明:在B4CP表面上得到了均匀、致密的镍包覆层,镀覆层含镍和磷元素.