爆轰试验用新型射频连接器的结构设计

针对目前爆轰试验中使用的机械密封射频连接器存在的问题.设计了基于玻璃封接技术的新型密封射频连接器结构,并进行了射频反射补偿计算和强度分析.本项研究为爆轰条件下新型密封射频连接器的研制提供了设计依据.     

0.25μm CMOS千兆以太网发送器设计

分析了千兆以太网体系结构,给出了符合IEEE 802.3z标准中1000BASE-X规范的发送器电路结构,并采用TSMC 0.25 μm CMOS 混合信号工艺设计了符合该规范的高速复接电路和锁相环时钟倍频电路.芯片核心电路面积分别为(0.3×0.26)mm2和(0.22×0.12)mm2.工作电压2.5 V时,芯片核心电路功耗分别为120 mW和100 mW.时钟倍频电路的10倍频输出时钟信号频率为1.25 GHz,其偏离中心频率1MHz处的单边带相位噪声仅为-109.7 dBc/Hz.在驱动50 Ω输出负载的条件下,1.25 Gbit/s的高速输出数据信号摆幅可达到410 mV.     

基于嵌入式Linux的远程数据采集系统

以嵌入式微控制器为核心,将传感器网络收集来的数据通过无线电发射机发送到远程接收机,从而实现远程数据采集.系统的优势是充分利用了短波无线链路资源,适合于工作在无人区等场合.以ARM7为控制器,功耗小,性能稳定,维护方便;通信方式采用串口通信,连接线少,实现相对简单.系统设计主要应用嵌入式μCLinux系统设计、无线电发射、调制解调器等方面的知识,文中给出了调制解调器拨号协议、系统原理和软件流程等.     

大功率开关电源的设计与实现

介绍了开关电源设计中需要考虑的几个基本问题,包括频率的确定、最大占孔比Dm的确定、逆变变压器的设计和开关功率管的选择,并以一种1 kW的PWM大功率半桥式开关电源为例,详细介绍实际的开关电源设计方案,并给出了实验结果.     

A wavelet-based multisensor data fusion algorithm

This paper presents a wavelet transform-based data fusion algorithm for multisensor systems. With this algorithm, the optimum estimate of a measurand can be obtained in terms of minimum mean square error (MMSE). The variance of the optimum estimate is not only smaller than that of each observation sequence but also smaller than the arithmetic average estimate. To implement this algorithm, the variance of each observation sequence is estimated using the wavelet transform, and the optimum weighting factor to each observation is obtained accordingly. Since the variance of each observation sequence is estimated only from its most recent data of a predetermined length, the algorithm is self-adaptive. This algorithm is applicable to both static and dynamic systems including time-invariant and time-varying processes. The effectiveness of the algorithm is demonstrated using a piecewise-smooth signal and an actual time-varying flow signal.     

非编码MPSK-OFDM系统判决指导的相位估计研究

本文论及非编码MPSK-OFDM系统载波跟踪中的重要部件?判决指导的相位估计器(PED)的研究.多载波系统的相位估计可以表示为各子载波相位估计的加权和.文中在分析单载波的基础上考察了符号判决错误对多载波相位估计的影响,并提出了两种改进方案,一是给出一组新的加权系数,改善了PED在较低信噪比的性能;二是由导频子载波相位估计指导其它数据子载波相位估计,获得了(-(/)M (/)M)区间上的线性无偏估计器.文中对两种改进算法进行了分析比较和仿真验证.     

Mapping rule-based systems onto multicomputers using simulated annealing

In this paper, we present a static load balancing method for mapping production rules in an expert system onto processors of a message-passing multicomputer. The method uses simulated annealing to achieve a nearly optimal allocation of production rules onto processor nodes. The approach balances the initial rule distribution to avoid higher communication demand among processor nodes at run time. A formal mapping model is developed and a new cost function is defined for the annealing process. New heuristic swap functions and cooling policies are provided to ensure the quality of the annealing process. A software load balancing package, SIMAL, was implemented on a SUN workstation to carry out the benchmark experiments. The overhead associated with this mapping method is O(m In m), where m is the number of rules in the production system. Two benchmark production systems, Toru-waltz and Tourney, are mapped onto a hypercube computer with 32 nodes. Experimental benchmark results verify the effectiveness of the rule mapping method. The method can be applied for distributed artificial intelligence processing or for the parallel execution of cooperating expert systems on a message-passing multicomputer.     

掺Nd纳米ZnO薄膜特性研究

研究了用真空蒸发法在玻璃衬底上制备稀土掺杂纳米ZnO薄膜结构、导电性及光透射性能。结果显示 ,在 5 0 0℃氧化、热处理稀土元素Nd掺杂后能够明显改善纳米ZnO薄膜的结构特性 ,薄膜的晶粒尺寸随掺杂含量的增加而减小。掺Nd使ZnO薄膜的电性能有所改善但使纳米ZnO薄膜的光透射性有所降低。     

Dynamic external fixation for distal radius fractures

Thirty adult patients with closed comminuted and mostly intraarticular fractures of the distal radius were treated by closed reduction and immobilization with a dynamic external wrist fixator during a 2-year period. In 13 patients with severely comminuted and unstable fractures, additional Kirschner wires were used. After 10 to 14 days of rigid fixation in neutral position, the motion element was unlocked to allow up to 30 degrees flexion. Six weeks later, the fixator was removed. The patients then were observed for an average of 24 weeks. An excellent functional outcome was seen in 6 patients (20%), a good outcome in 20 patients (67%), and a fair outcome in 4 patients (13%). Anatomically, 15 patients (50%) had an excellent result, 14 (47%) a good outcome, and 1 (3%) a fair outcome. Only minimal loss of reduction averaging 1 degree palmar tilt was seen during mobilization. There were 2 major complications: 1 deep Kirschner wire tract infection and 1 index metacarpal fracture. Minor complications such as sensory disturbances and pin tenderness were present but recovered completely after removal of the fixator. This study provides promising data and offers an alternative method in the treatment of distal radius fractures with severe comminution. In cases with postreductive unstable fragments, additional Kirschner wires should be used to allow early mobilization of the wrist.     

一种新型陶瓷材料及其耐磨性

对新型Ａｌ２Ｏ３－ＴｉＣ－Ｃｏ陶瓷的磨粒磨损，冲蚀磨损及其在单颗粒作用下的摩擦磨损行为进行了研究。与ＡＴ３０（７０ｗｔ％Ａｌ２Ｏ３－３０ｗｔ％ＴｉＣ）陶瓷相比，Ａｌ２Ｏ３－ＴｉＣ－Ｃｏ陶瓷具有更为良好的耐磨性，金属钴的存在提高了基体的韧性，细化了晶粒，其综合力学性能得到了显著提高，ＡＴＣ陶瓷样品耐磨性与其强韧化水平和细致的组织结构有关。