微脉冲激光雷达测量大气水平能见度

为了改进乃至革新大气能见度的探测技术,探索新型、快速、准确测量大气能见度的方法,采用自行研制的能见度微脉冲激光雷达,进行了水平大气能见度测量实验,并同已经商品化的能见度仪NQ-1进行了同步对比测量。实验结果表明,在水平能见度较差时,微脉冲激光雷达和能见度仪具有很高的相关性,相关系数达到了0.88;在水平能见度较好的时候,相关系数保持在0.73以上。说明能见度微脉冲激光雷达系统可以应用于大气能见度的探测。     

Progress in CdZnTe substrate producibility and critical drivers of IRFPA yield originating with CdZnTe substrates

With the goal of maximizing the yield of infrared focal plane arrays (IRFPAs), Santa Barbara Research Center’s (SBRC) Infrared Materials Producibility Program (IRMP) has focused on assessing and improving the quality, yield, and throughput of CdZnTe substrates. A baseline detector lot was fabricated to identify the critical drivers of IRFPA yield coming from the substrates and to evaluate the quality and yield of the current vendor base for CdZnTe substrates. Substrate induced defects and impurities that can potentially affect device performance and operability were carefully mapped out in detail on 44 × 67 mm² size substrates, received from IRMP substrate vendors as well as SBRC. This paper will report on the correlations found between this substrate characterization data base and the IRFPA level defect distributions. Key results from these correlation studies are: (1) extended defects found on the substrates with the Nakagawa etch correlated well with responsivity reduction in the final IRFPA; (2) cross-hatch patterns that were evident in the responsivity map correlated well with similar features seen by x-ray topography on LPE double layers; and (3) a possible correlation of device performance (leakage current at 78K) with copper and lithium impurities in the substrate. Recent initiatives toward improving the quality and yield of the substrate growth process have focused on improving purity in the pre-growth charge preparation, modification of growth parameters to reduce defects and scaling up of the vertical Bridgman growth process from its current 67 mm diameter boule size to 92 mm diameter boules. Promising initial results from the large diameter boule growth process will be shown. The 92 mm diameter CdZnTe boule (6 kg charge) shows two predominant single crystal grains encompassing 75% of boule volume. Defect characterization of boules grown under baseline and modified conditions is discussed.     

水轮机导叶分段关闭的灰色决策

本文对灰色局势决策作点滴引伸，结合正交设计对水轮机导叶分段关闭作寻优分析，与一般加权法比较说明，灰色决策法具有算法直观简便，概念清楚和准确度高等特点。     

基于多Agent导弹编队图像融合研究

导弹编队协同作战的目的是通过导弹之间的协作与通信,最大限度提高目标命中率。丈中针对复杂环境下导弹协同作战中存在图像融合的问题,提出了基于多Agent黑板协作模型,在编队内部不同任务和功能的导弹之间建立公共信息平台,实现多种传感器的图像融合,从而提高攻击目标的命中率,并通过一个仿真实例说明了该方法的可行性。     

基于整数运算的LDPC码最小和译码算法

对低密度奇偶校验码(LDPC)在高斯信道下的译码算法进行了深入研究,提出了一种基于整数运算的最小和译码算法.在该算法中所有变量都用固定长度的整数表示,因此非常便于硬件实现,其性能在信噪比大于3dB时,与高精度浮点数的和积译码算法相当;同时对最小和算法提出了一个修正因子,加上修正因子,其译码性能有进一步的提高,特别是在低信噪比下改善较大;另外还发现在高信噪比下,该算法具有更低的错误平层.     

用C++ Builder实现组态王实时监控艾默生变频器

本文介绍了工业自动化通用组态软件——组态王,提出了一种用C++Builder作为后台实现组态王软件实时监控艾默生变频器的方法,并简单介绍了另一种用BCB制作控件嵌入组态王实现控制变频器的方法,相关方法已在砖窑监控系统中得到了具体应用。     

基于ModBus通信协议的变频控制系统设计

由于变频控制系统多工作于高电压、高温度的环境中,对变频装置的稳定性和抗干扰性都要有很高的要求。鉴于ModBus总线可靠的数据传输、快速的响应和强大的抗干扰能力,文中主要介绍了ModBus协议RTU传输模式的基本内容,设计了基于ModBus RTU的变频控制系统,替代继电器组成的控制回路。通信采用RS485总线标准,串口通信采用查询方式接收和发送数据.开发控制器和变频器之间通信连接程序.从而提高变频器抗干扰性和稳定性。     

A call admission and control scheme for quality‐of‐service (QoS) provisioning in next generation wireless networks

We propose a framework for quality‐of‐service (QoS) provisioning for multimedia services in next generation wireless access networks. This framework aims at providing a differentiated treatment to multimedia traffic flows at the link layer, which can be broadly classified as real‐time (or delay‐sensitive) and non‐real‐time (or delay‐tolerant). Various novel schemes are proposed to support the differential treatment and guarantee QoS. These schemes include bandwidth compaction, channel reservation and degradation, with the help of which a call admission and control algorithm is developed. The performance of the proposed framework is captured through analytical modeling and simulation experiments. Analytically, the average carried traffic and the worst case buffer requirements for real‐time and non‐real‐time calls are estimated. Simulation results show up to 21% improvement in the admission probability of real‐time calls and up to 17% improvement in the admission probability of non‐real‐time calls, when various call control techniques like bandwidth compaction are employed. Using our channel reservation technique, we observe a 12% improvement in the call admission probability compared to another scheme proposed in the literature. This revised version was published online in August 2006 with corrections to the Cover Date.     

弹道导弹中段红外辐射特性数学建模与仿真

针对TBM中段的弹道特性,根据热平衡理论建立了TBM在中段的温度计算模型,然后根据普朗克定律建立了目标红外辐射计算模型;在红外辐射的大气传输理论基础上,综合考虑大气吸收、散射及气象条件等各种因素,分析了大气衰减对红外辐射的影响建立了大气透过率的计算模型,得到了大气衰减作用下的目标辐射模型;最后,在假定的仿真条件下,利用模型计算了两种波段下目标红外辐射强度、大气光谱透过率以及经过大气衰减后的红外辐射强度,并对计算结果进行了分析,结果表明,这是一种计算TBM中段红外辐射的有效方法.     

Low-thermal-budget Au-free ohmic contact to an ultrathin barrier AlGaN/GaN heterostructure utilizing a micro-patterned ohmic recess

A pre-ohmic micro-patterned recess process,is utilized to fabricate Ti/Al/Ti/TiN ohmic contact to an ultrathin-barrier(UTB) AlGaN/GaN heterostructure,featuring a significantly reduced ohmic contact resistivity of 0.56 Ω.mm at an alloy temperat-ure of 550 ℃.The sheet resistances increase with the temperature following a power law with the index of +2.58,while the spe-cific contact resistivity decreases with the temperature.The contact mechanism can be well described by thermionic field emis-sion (TFE).The extracted Schottky barrier height and electron concentration are 0.31 eV and 5.52 × 1018 cm-3,which suggests an intimate contact between ohmic metal and the UTB-AlGaN as well as GaN buffer.A good correlation between ohmic trans-fer length and the micro-pattern size is revealed,though in-depth investigation is needed.A preliminary CMOS-process-compat-ible metal-insulator-semiconductor high-mobility transistor (MIS-HEMT) was fabricated with the proposed Au-free ohmic con-tact technique.