基于直流电抗电压的柔性直流配电网故障测距方法

故障测距是柔性直流配电网发展所需的关键技术之一,传统的高压直流输电系统故障测距方法在直流配电系统中适应性不好。因此在考虑线路配置直流电抗器的情况下,提出一种基于直流电抗电压的直流配电网双端故障测距方法。该方法从直流故障的电容放电阶段进行研究,利用线路两端直流电抗电压构建包含故障距离和过渡电阻的两个未知参数的时域微分方程,并利用最小二乘法进行求解。PSCAD仿真结果表明该方法能够有效地进行故障定位,并且能够计算出故障点过渡电阻,可以满足直流配电网的故障测距要求。     

基于测后模拟原理的半波长输电线路暂态量纵联保护

针对特高压半波长超长的输电距离带来的继电保护难题,提出基于测后模拟原理的半波长输电线路暂态量纵联保护方法.特高压半波长交流输电具有传输距离远、输送容量大、全线无功自平衡等优点,可以作为未来清洁能源电力输送的一种可选方案.通过分析现有输电线路保护方法对于半波长交流输电线路的不适用性,对特高压半波长输电线路在区内外故障情况...     

The cortisol response to psychological stress in temporomandibular dysfunction

Recombinant antibody fragments can be produced in large quantities using bacterial expression systems and could potentially be useful for the generation of biofilters for the selective removal of viral particles from fluids. A human single chain-Fv antibody library, derived from synthetic repertoires of germ line VH-gene segments rearranged in vitro and paired to a single light chain (Nissim et al., 1994, EMBO J., 13, 692-698), has recently been used to isolate hundreds of different binding specificities by panning with antigen. Antibodies from this library typically have affinities in the 10(6)-10(7) M-1 range. Occasionally, better binders are isolated but at other times the affinities recovered are poor. In the latter situation binding cannot be detected with soluble antibodies, but only by high-avidity display of multiple copies of antibodies on phage. By panning with human cytomegalovirus (HCMV)-coated immunotubes, we have isolated a number of antibody clones from this library that bound to the antigen only if displayed on the filamentous phage, but not in soluble form. One of these clones was selected for an affinity maturation procedure, achieved by combinatorial mutagenesis of the complementarity determining region 3 (CDR3) of the antibody light chain, followed by selection of the resulting library for HCMV binding. By this means, we were able to isolate a number of binders, some of which exhibited specific HCMV binding in soluble form. The clone that gave the strongest ELISA signal was expressed in bacteria, purified in solution, characterised using a novel capture methodology with surface plasmon resonance detection on a BIAcore instrument and used for the production of an immunofilter for the removal of HCMV form human serum. The filter removed more than 99% of applied HCMV in 10 min circulation time, while the amount of HCMV retained non-specifically in a cartridge derivatised with a non-specific antibody was less than 10% under similar conditions.     

星用光纤通信系统中的发光二极管的总剂量效应研究

介绍了星用光纤通信系统中的发光二极管在 6 0 Co- γ射线辐照下的总剂量效应试验研究 ,通过对不同剂量辐照情况下发光二极管的发光光谱、伏安特性及 P- I曲线进行测试 ,给出了在不同剂量的 γ- 6 0 Co射线辐照下发光二极管的发光光谱、伏安特性及 P- I曲线     

航天轻型结构材料——铝锂合金的发展

概述了铝锂(Al-Li)合金的发展历史,总结了其发展趋势:(1)超强、超韧性方向发展;(2)超低密度化发展;(3)改善铝锂合金的焊接性能;(4)改善铝锂合金的各向异性;(5)改善铝锂合金的热稳定性.指出了提高铝锂合金性能的主要途径:(1)微合金化;(2)形变热处理;(3)纯净化;(4)再结晶、在不同方向上拉伸或冷轧、减小变形量等.介绍了铝锂合金的制造方法及其在航天方面的应用.     

氧化钒薄膜制备与特性研究

用磁控反应溅射法制备出具有红外敏感特性的氧化钒薄膜,进行了薄膜光电特性的测试.通过AFM和XRD对薄膜的结构和特性进行分析研究,并给出了沉积参数对薄膜性能的影响.     

ALC-OFDM系统中的ACMS新选择准则

针对新一代宽带卫星通信,建立了自适应低密度奇偶校验码(LDPC)编译码的正交频分复用(ALC-OFDM)传输系统结构与信道模型.在分析固定编码调制方式基础上,提出了一种加权信噪比(SNR)的自适应编码调制方案(ACMS)选择新准则,使每种编码调制方案对应着一个信道平均信噪比范围,可以有效找出使系统吞吐量最优的信噪比切换门限值.仿真结果表明:在系统的误比特率(BER)满足要求的情况下,对比各种加权准则,加权得到的SNR越大,采用该准则的系统吞吐量越大;当系统吞吐量都达到最大值时,采用3种加权方式的信噪比切换门限比传统准则至少降低了2 dB.     

收发频谱不一致条件下的变换域通信系统基函数设计

针对变换域通信系统收发频谱不一致条件下接收端基函数存在错误而导致系统性能下降的问题,提出了具有信噪比次优解的基函数设计方法。详细分析了系统的收发过程,在此基础上研究了系统误码率的最优化与接收端基函数组成的关系,在收发频谱不一致而无法获得最优基函数的情况下,采用类似等增益合并的方法设计了接收端基函数,从而以该基函数完成数据解调。仿真结果表明:在单用户和多用户环境下,当收发频谱不一致比例较高时,接收端采用类似等增益合并的基函数设计方法可以完成系统的次优接收。在单用户环境下,相比不一致比例为40%时,次优接收方法的信噪比增益可达4dB左右,并且发送端频谱可用率为80%时,相比最优接收法的信噪比损失在1.5dB以内。     

基于轮廓线局部描述符的三维人脸识别

提出了一种基于等测地轮廓线的局部描述符来识别三维人脸。首先对三维人脸数据进行预处理, 得到统一的人脸区域并进行姿态归一化; 然后根据测地距离提取到鼻尖点相同距离的点组成等测地轮廓线, 对轮廓线进行重采样, 并对轮廓线上每个采样点的邻域提取局部描述符; 最后在建立测试人脸和库集人脸的点对应关系后进行局部描述符的加权融合和比较, 给出最终识别结果。算法在FRGC(face recognition grand challenge)v2. 0数据库上进行测试, 实验结果表明该方法具有较好的识别性能。     

Microbiologic contamination during dental radiographic film processing

Arteriosclerotic intimal proliferation is one of the main long-term complications of organ transplantation. Low-molecular-weight, heparin-like molecules prevent myointimal proliferation in arterial wall injury and limit rejection in skin allografts. Cyclosporin limits rejection but has no major effect on intimal proliferation. Therefore, an experimental protocol was designed to test whether heparin-like molecules interacted with low doses of cyclosporin to prevent arterial wall immune system injury and response in a model of arterial graft rejection in normotensive and hypertensive rats. Aortic allografts were performed in spontaneously hypertensive rats (SHRs) and Wistar-Kyoto (WKY) normotensive control rats. Four groups of 10 allografted (SHR and WKY) rats were used: one group was treated with placebo, one with low doses of cyclosporin (2 mg/kg body wt per day), one with low-molecular-weight, heparin-like molecule (1 mg/kg body wt per hour), and one with low doses of cyclosporin plus low-molecular-weight, heparin-like molecule. Ten SHRs and 10 WKYs were isografted and served as the control groups. All rats were killed 8 weeks after aortic grafting. Structural parameters of the grafted segment were measured by morphometric analysis on formalin-fixed sections with specific stains. The classical signs of immune system injury and response were present in the untreated allografts in SHRs and WKYs: inflammatory infiltration of the adventitia, medial injury, and intimal proliferative response. Low doses of cyclosporin had a significant beneficial effect on immune medial injury by increasing medial thickness and the number of remaining smooth muscle cells and decreasing the extracellular matrix injury. Cyclosporin had no protective effect on intimal proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)