基于光折变光栅的可调谐滤波方案及特性分析

在LiNbO3单模波导上利用双光束干涉可形成光折变波导光栅,针对粗波分复用系统提出了通过实时改变双光束之间的夹角进而改变光栅间距,实现可调谐滤波的方案.利用光折变动力学理论,得到光栅调谐时间在毫秒数量级.研究发现,适当提高光强和增加杂质掺杂浓度可提高衍射效率、减少光栅初次建立时间.基于耦合波理论的数值模拟结果表明,增大光栅长度能使衍射效率提高且带宽变小,而增加折射率调制度使衍射效率提高但同时带宽变宽.在折射率调制度为8×10-5,光栅长度大于12mm时,可获得91％以上的衍射效率和小于0.08 nm的带宽.     

The TRAIL to selective tumor death

BACKGROUND: The aim of this study was to assess the cost effectiveness of routine preoperative blood type and screen testing before laparoscopic cholecystectomy. METHODS: All 2,589 laparoscopic cholecystectomies and 603 open cholecystectomies performed at our institution between January 1990 and December 1996 were retrospectively reviewed to identify the incidence and causes of blood transfusions. With the use of ICD-9-CM coding, a computerized retrospective research was done to match the corresponding codes for the aforementioned operations and blood transfusion. Individual charts were reviewed to identify the indications for blood transfusion. RESULTS: Of the 2,589 laparoscopic cholecystectomies performed, 12 patients required blood transfusion, and of the 603 open cholecystectomies, 33 patients required blood transfusion. The incidence of blood transfusions was 0.46% for laparoscopic cholecystectomy and 5.47% for open cholecystectomy. Two of the blood transfusions given intraoperatively were due to major vascular injury in the laparoscopic cholecystectomy group. The remaining blood transfusions were found to be the result of preexisting medical conditions including sickle-cell anemia, end-stage renal disease, and chronic iron deficiency anemia. CONCLUSIONS: Laparoscopic cholecystectomy has become a widely used therapeutic modality in general surgery. The procedure is safe, effective, and well tolerated by the patient. In the era of managed healthcare, the cost effectiveness of commonly ordered tests is frequently questioned. In the absence of preoperative indications, routine preoperative blood type and screen testing should be eliminated for laparoscopic cholecystectomy. The elimination of routine preoperative blood type and screen testing could have saved our institution $79,800 during a 6-year period.     

Crack growth predictions in a complex helicopter component under spectrum loading

Fatigue crack growth predictions have been made on a helicopter round‐robin crack configuration. The crack configuration was a small corner defect at the edge of a large central hole in a flanged plate made of 7010 aluminium alloy and the component was subjected to a simulated helicopter spectrum loading. The crack growth rate data and the stress‐intensity factor (K) solution for the crack configuration were provided in the round‐robin. The FASTRAN life‐prediction code was used to predict fatigue crack growth under various load histories on the aluminium alloy, such as Rotorix and Asterix, on both compact tension C(T) specimens and the complex crack configuration. A BEASY three‐dimensional stress‐intensity factor solution for the round‐robin problem was also provided for this paper and is compared with the original K solution. Comparisons are made between measured and predicted fatigue crack growth lives for both crack configurations. The predicted lives for the C(T) specimens were 15–30% longer than the measured lives; and crack growth in the round‐robin configuration agreed very well in the early stages of crack growth, but the life was 30% short of the test results at the final crack length.     

自适应回声消除算法的仿真研究

介绍几种自适应回声消除算法:NLMS,PNLMS,PNLMSDU,IPNLMS,MPNLMS,并在Matlab环境下进行了仿真比较.采用高斯噪声作为输入,分别在回声路径稀疏、回声路径中等稀疏、回声路径完全非稀疏的条件下进行仿真.仿真结果表明,PNLMS算法是针对稀疏回声路径的有效快速算法,MPNLMS算法做了进一步的优化.IPNLMS算法和PNLMSDU算法融合了NLMS算法和PNLMS算法的优点,既保证有较快的初始收敛速度,又保证后阶段收敛速度不明显下降.     

基于USB接口的Multi-sniffer无线传感器网络测试平台

作为一种新颖的无线传感器网路测试平台SNUMP,实现了基于CC 2531 USB Dongle对IEEE802.15.4协议数据帧的监测,提供了详细的网络组建测试、网络稳定性分析以及网络通信拓扑结构。SNUMP用USB接口代替串口,解决了无线传感器网络传输速度快,数据量大的问题,自主创新强,成本低,具有很强的通用性和实用性。     

基于FPGA的PCI接口的设计与实现

针对PCI接口使用的广泛性,分析了现阶段实现PCI接口各种方案的优缺点,提出了一种使用FPGA实现PCI接口的设计方案,首先详细论述了该设计的PCI接口信号,重点叙述了PCI接口功能模块划分以及PCI接口的核心状态机设计原理、结构和工作过程,并对设计的PCI接口进行了仿真测试,经验证后满足PCI规范的时序要求,并在身份智能认证卡中得到了很好的应用。     

原发性肝癌患者手术前后血浆HGF水平变化及其临床意义

目的:探讨HGF与肝癌之间的关系.方法:选择肝细胞性肝癌、肝硬化门静脉高压症及慢性乙型肝炎病人进行调查,并且设立正常对照组,用酶联免疫吸附法检测其血浆HGF水平;同时检测肝功能、AFP、血小板等项指标.结果HCC病人的HGF水平明显高于肝硬化、慢性肝炎患者.正常人群HGF不易测得.HCC患者与其它各组有显著差异(P＜0.01).肝癌患者手术前与手术后3天血清HGF无明显差异(P0.05);而与手术后7到10天的血清HCF有显著差异(P＜0.01).HGF与AFP水平的相关性r=0.162,P0.05;与ALT的相关性r=0.001,P0.05.结论:血清HCF水平与肝癌有密切关系,检测血清HGF水平可以作为HCC诊断或治疗后随访的肿瘤标志物之一.     

清洁技术在触摸屏工艺中的研究与应用

文章介绍了清洁机构的概念、原理、功能,对关键结构部分进行了分析,并分析对比了清洁前与调整参数清洁后的实际清洁效果。     

半导体温差发电器的工作性能优化

应用有限时间热力学理论分析了半导体温差发电器的工作性能.推导了在内外均不可逆情况下发电器的输出功率和效率的表达式,并在此基础上重点讨论了发电器在外部条件变化时的性能,获得了一些有意义的结果.