Preparation of modified polymer blend and electrical performance

In this study, a modified binary polymer blend made up of polycarbonate and polystyrene blend has been prepared by loading of aluminum oxide (Al₂O₃) as a dopant. The role of alumina with polymer blend system was addressed in view of interfacing criteria. The filler concentration of modified blend was taken as 5, 10, and 15%. The morphological, thermal, and electrical properties were characterized by various techniques. Optical microscopy confirms the homogenous dispersion of Al₂O₃ in blend. The presence of alumina was detected by subatomic level using atomic force microscope (both two and three dimensional approach). The differential scanning calorimetric thermographs demonstrate decreasing softing point as function of alumina loading. The dielectric properties such as dielectric constant, loss, and electrical modulus were studied under DC bias. The effect of DC bias exhibits significant changes at low amount of Al₂O₃. The dielectric polarization supports Maxwell Wagner (MW) theory due to low frequency response. 15% Al₂O₃ gives the highest dielectric constant (ε′) value (3.5?×?10⁵) at 10 Hz. The polymer modified blend with Al₂O₃ may be used as a one of the best dielectric medium.     

Li-defect interactions in electron-irradiated n-type silicon by EPR measurements

Single crystal silicon, both with and without oxygen, has been diffused with lithium to concentrations ～10¹⁷/cm², irradiated with 1 to 1.5 MeV electrons, and the ensuing defects studies by EPR measurements. The presence of oxygen strongly affects the properties of these defects. Measurements have indicated the presence of two new defects which involve Li-one in O-containing material and one in O-free material. The defects are observed in their electron-filled state, and indicate a net electron spinof ½. The defect spectra disappear (with time) at room temperature, and can be explained by the formation of other Li-involved defects which lie deeper in the energy bandgap and are not visible by EPR. Electron irradiation at 40 °K followed by annealing at higher temperatures show that both EPR defects described above begin to form at about 200 °K and begin to decrease at about 275 °K-just as does the 250 °K reverse annealing observed generally for n-type Si. Based on these data, and the work of others, it is suggested that both defects form as a result of the motion of Si interstitials which produce a (Li-O-interstitial) complex in O-containing Si, and a (Li-interstitial) complex in O-free Si.     

热-力-电耦合下天线罩电性能仿真及分析

在实际飞行工况下,热力载荷会改变高速飞行器天线罩原有的电磁特性,从而影响制导性能。提出了一种基于六面体网格划分的热-力-电耦合模型及仿真方法,可准确表征高速飞行工况下天线罩介电温漂和结构变形对电性能的影响。基于天线罩热-力-电共享网格模型,首先通过瞬态热仿真得到天线罩响应温度场,通过静力分析得到天线罩结构变形场。然后,将天线罩介电温漂和结构变形准确传递到其电磁仿真模型中,并采用三维射线跟踪法计算其电性能。最后通过一个典型算例对高速飞行工况下天线罩电性能的变化进行仿真和分析,结果表明电性能变化非常明显,也进一步说明了所提方法的可行性和研究的必要性。     

常压DBD二维流体模型的FCT方法数值模拟

根据常压介质阻挡放电流体模型的物理方程,采用固定网格有限差分算法,分别用四阶和六阶相位误差FCT方法模拟求解二维流体连续方程.在均匀的初始条件下研究放电雪崩过程中电子密度的时空演化,具体分析和比较两种算法的差异.FCT方法模拟求解得出的计算结果与气体放电理论吻合较好,是一种具有较好的准确性和高精度的算法.     

LD泵浦Nd:YVO4/LBO临界相位匹配腔内倍频瓦级绿光激光器

报道了一种光纤耦合LD泵浦Nd:YVO₄晶体、腔内Ⅰ类临界相位匹配(角度匹配)LBO倍频、瓦级输出的全固态绿光激光器的设计方法和实验结果.采用短三镜折叠腔结构,通过对热透镜焦距的估算及计算机优化设计选取合适的谐振腔参量,在8 W的泵浦功率下,获得了1.6 W绿光基模输出,光-光转换效率达20%.经测量,绿光的偏振比超过400:1,4 h功率稳定度为±1.6%.     

A new representation of permittivity versus temperature for alkanols of the same chain length

The alkanols of three carbon length have been studied by dielectric methods during many years and they do not obey any theoretical model. These substances have the same chain length and have one, two or three dipoles per molecule, so their ability to form hydrogen bridges changes from one substance to other, and one can obtain information by comparative studies. In previous works, we have measured the thermal dependence of permittivity of these substances and analysed the results with an empirical modification of the Onsager equation. Now we shall analyse and compare the results using a different representation. In this representation, the data shows straight lines, whose slopes depend on the quantity of dipoles of each molecule encouraging the high quality of the fittings obtained with the three substances, and also that they behave in the same dielectric way with the rise of temperature.     

ns脉冲激光对K9玻璃的破坏实验

 采用高速PIN光电探测器和高带宽的数字存储示波器，实时检测透射光脉冲和散射光脉冲的变化特征，并将之用作材料破坏的光学判据，测量得到K9玻璃在1.06μm纳秒脉冲激光作用下的能量损伤阈值约18mJ，相应的能量密度阈值为1.0kJ/cm²。通过分析透射光脉冲和散射光脉冲的特征，给出了材料的破坏时刻，并推断出K9玻璃所能承受的极限光强为10¹⁵W/m²。研究了能量透过率与泵浦能量的关系，并初步探讨了透明材料的破坏机理。结果表明：在多纵模激光的作用下，透明光学材料破坏是电离击穿与自聚焦效应综合作用的结果。     

沿面闪络流体模型电离参数粒子模拟确定方法

介绍了粒子模拟确定高功率微波介质沿面闪络击穿流体模型相关电离参数的方法.对粒子模拟方法 (包括带电粒子动力学方程、次级电子发射以及蒙特卡罗碰撞模型)和流体整体模型方法 (包括连续性方程和能量守恒方程)做了简介.基于自编的1D3V粒子模拟-蒙特卡罗碰撞程序给出了在高(低)气压、不同气体种类以及不同微波场强和微波频率下流体模型电离参数的粒子模拟结果,包括电离频率、击穿时间、平均电子能量、电子能量分布函数类型.研究结果表明:平均电子能量与电子能量分布函数类型关系不大;中低气压下,电子能量接近Maxwell分布,电子能量分布函数类型对电离参数几乎没有影响;中高气压下,电子能量分布函数类型对电离参数有重要影响,其依赖系数X趋于高阶形式.不同气体的电子能量分布函数类型不同,需要利用粒子模拟对电子能量分布函数类型进行标定.同时,电子能量分布函数依赖系数与微波场强和频率也有关系,其随微波场强增加而增大,随微波频率增加而减小.在给定考察范围(微波场强在7 MV/m以下,微波频率在40 GHz以内),中低气压下,平均电子能量随微波场强增加而迅速增大,电离频率随微波场强增加先增大后降低,平均电子能量随微波频率增加而降低,电离频率随微波频率增加先增加后降低;高气压下,平均电子能量随微波场强增加而缓慢增大,电离频率随微波场强增加而增大,微波频率对平均电子能量和电离频率影响不大.     

超六边形斑图的4种形成途径

为了减弱在斑图形成时实验条件的限制,获得同一斑图的多种形成途径,利用双水电极介质阻挡放电装置,在空气/氩气混合气体放电中,观察到了超六边形斑图的4种形成途径.在不同气压和氩气含量下,研究了4种斑图包括不规则六边形斑图、六边形斑图、四边形斑图和四六边形共存斑图到超六边形斑图的演化.实验发现随气压及氩气含量的变化,它们向超六边形斑图演化时的出现范围由大到小依次是六边形斑图、四六边形共存斑图、不规则六边形斑图和四边形斑图.     

具有4个传输零点的源-负载耦合滤波器

为了得到高选择性、小尺寸、低损耗和低成本的射频带通滤波器,提出了一种具有4个传输零点的源–负载耦合滤波器的设计方法.该滤波器采用二分之一波长T形多模谐振器,以减小滤波器尺寸和方便带宽设计.同时,根据信号的多路径传输产生零点原理,在滤波器的输入和输出端口之间加入可控耦合元件,为信号的传输提供多条路径,使得该滤波器可产生4个独立于带宽和中心频率的可控零点.文中最后设计和制作了一个带内最小测量插损为1.4dB、相对带宽为10%、具有4个传输零点的小型微带滤波器,并对其进行了测试,测试结果与仿真结果吻合良好,说明这种设计方法是有效的.