天线罩相关参数的改变对天线方向图影响

天线罩在保护雷达天线不受环境影响的同时,又会对天线的电磁辐射产生某些干扰,改变天线的电气性能。利用电磁场数值计算方法研究了在因气动、机械强度和耐热性等因素而需改变天线罩的厚度或材料的介电常数等相关参数时对天线方向图的影响,作为天线和天线罩的电磁相容性研究的参考。     

装甲车辆1553B总线系统试验方法

装甲车辆1553B总线系统的试验.其硬件检测含数据总线特性、输入输出特性、余度数据.软件检测项目包括正常传输及故障.总线系统性能参教测试包括:总线负载、总线使用效率、总线利用率、延迟时间、平均等待时间、可靠性及信息传输准确性.试验方法直接通过综合电子系统采集数据,测试设备以总线监视器模式接入综合电子系统.     

塑炼1,2-聚丁二烯的无扰尺寸

利用测得(?)和[η]数据,由Stockmayer-Fixman-Burchard、Stockmayer-Kurata-Roig和Inagaki-Suzuki-Kurata方程外推,估算了塑炼过程中不同1,2-链节含量的1,2-聚丁二烯(1,2-PB)的无扰尺寸变化规律。1,2-链节含量分别为40％和87.2％时,随薄通次数的增加,无扰尺寸降低;但前者薄通50次后变化很小,后者薄通100次后仍有波动。1,2-链节含量为87.2％的1,2-PB,薄通后放置30d,其无扰尺寸随薄通次数的增加而降低的程度,均大于当日测定的结果。     

Microstructure and mechanical properties of ZrO2-2 mol% Y2O3 ceramics

The microstructure and mechanical properties of ZrO₂-2 mol% Y₂O₃ ceramics were studied on samples prepared by cold isostatic pressing and pressureless sintering. It was shown that the density of the alloy increases with increasing sintering temperature. The Vickers hardness decreases with the appearance of the monoclinic phase and increasing its content. Compared with the single tetragonal phase, the (t + m) dual-phase structure with microcracks has a much higher fracture toughness (16·5 MPa√m) because of a complex mechanism of toughening (transformation, microcracks and residual stresses).     

Crystal structure of poly(tetrafluoroethylene) homo- and copolymers in the high pressure phase

X-ray diffraction measurements are reported for 27°C, pressures to 5.2 GPa and concentrations of CF₃ units to 0.049 CF₃/CF₂. These show both orthorhombic and monoclinic structures to exist under high hydrostatic pressure. It is proposed that shear stresses generated at elastic inhomogeneities in the sample lead to the monoclinic phase. Energy calculations are consistent with this concept. They also indicate that conformational and rotational disorders raise the entropy of the high pressure phase III. Perfluoromethyl branches increase the volume/CF₂ of phase III more than that of the low pressure phase I. At high CF₃ concentrations and pressures, both phases become metrically hexagonal. The volume of transition becomes zero at a concentration near 0.05 CF₃/CF₂ and no transition is observed to a pressure of 5.2 GPa. There appears to be a critical point near 27°C, a CF₃ concentration of 0.05 and a pressure of 3.5 to 5 GPa.     

破伤风毒素的提纯及形成离子通道的特性

应用硫酸铵分段沉淀和 Ultrogei AcA_(34)凝胶过滤对破伤风毒进行了提纯,并对形成的离子通道在中毒作用中的功能进行了讨论。提纯的毒素与抗粗制毒素血清形成一条沉淀线,于聚丙烯酰胺凝胶电泳中形成单一的蛋白带,分子量为15万,等电点为5.95,毒力为1～3×10~4MLD/μg 蛋白。给小鼠注射低剂量毒素引起迟发性强直性痉挛;注射高剂量毒素引起快速的类肉毒毒素的松弛性麻痹,直至死亡。应用 Patch clamp 技术,破伤风毒素于人工磷脂膜上形成离子通道。只有当膜两侧存有 pH 梯度时毒素才形成离子通道,因此是 pH 依赖的。通道的电导系数为9 PS。     

基于RTP的流媒体传输系统的设计与实现

旨在解决流媒体实时传输的效率和系统的可拓展性问题。介绍了流媒体传输的基本协议RTP,并针对实时传输过程中的特殊要求,设计出了一种流媒体传输的结构模型,在流量控制、组包算法和缓存管理等方面进行研究,给出了详细的实现过程。