Improving properties of ceramic silicone rubber composites using high vinyl silicone oil

Reactive high vinyl silicone oil (HVSO) was selected to prepare the ceramic silicone rubber composites. The effects of HVSO on the mechanical properties and thermal stabilities of ceramic silicone rubber composites were investigated. The structures of the cross‐linked network of silicone rubber with or without HVSO were studied. The intermolecular space of silicone rubber was enlarged, and the cross‐linked point was concentrated by addition of HVSO, which was demonstrated by cross‐linking densities, scanning electron microscope (SEM) images, and dynamic mechanical analysis (DMA). The cross‐linked network model was formed with the slipping of the cross‐linked points along with the silicone rubber chain. Mechanical properties of composites were enhanced by the formation of this cross‐linked network. The tear strength, tensile strength, and elongation at break of the composites were increased by 18.5%, 13.2%, and 37.4% by the adding of 2 phr HVSO, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41864.     

Convective Drying of Agitated Silica Gel and Beech Wood Particle Beds—Experiments and Transient DEM-CFD Simulations

With coupled discrete element (DEM)–computational fluid dynamics (CFD) simulations, drying processes can be simultaneously described on the system scale while resolving detailed subprocesses on the particle scale. In this contribution, DEM-CFD simulations are used to analyze the transient heat and mass transfer in mechanically agitated particle beds during drying. Results are compared to convective batch-drying experiments with silica gel and beech wood spheres and mixing effects are studied in detail. A good agreement with the measurements of both single-particle and particle bed drying is achieved by resolving heat and moisture transport three-dimensionally inside each particle.     

计算传输线平均耦合截面积的一种高效全波方法

在功率平衡法的网络化公式应用中,精确预知腔内装载物的耦合截面积是关键,这通常依赖于混响室的实验测定.文中使用平面波角谱概念和蒙特卡罗方法来数值模拟混响室中的电磁环境,在此基础上,首次应用基于互易定理的快速全波分析方法提取了理想混响室内靠近理想导电地平面的多导体传输线的平均耦合截面积,验证了方法的正确性,并计算了单根裸线传输线、带包层传输线、双绞传输线、传输线附近有导体挡板以及多导体传输线端口的平均耦合截面积.该方法具有计算精度高、仿真速度快、适用范围广的特点.     

双时间步时域有限体积方法计算时变电磁场

双时间步被引入到时域有限体积解算器这一直接求解麦克斯韦方程组的高精度数值方法中.双时间步方法作为非定常时间推进技巧,时间精度由物理时间步长决定,稳定性要求由定常子迭代时间步长所满足,从而放松了通常显式时间格式和网格对物理时间步长的限制,达到节约计算量的目的.典型目标电磁散射计算表明:通过对物理时间步长、最大子迭代步数、子迭代收敛判据的合理选取,双时间步方法在保证计算精度的同时,能提高计算效率.     

受主型杂质对p型单晶硅中少子衰减过程的影响

少子寿命测试技术是监控单晶硅中杂质和缺陷的数量及性质的重要技术手段.基于常规光电导少子寿命测试的基本参数,研究了不同性质的受主型杂质缺陷对太阳电池用p型单晶硅中少子衰减过程的影响,并重点分析了仅存在受主型电子陷阱或复合中心时,少子衰减过程的变化规律;受主型电子陷阱和复合中心并存时,少子衰减过程的变化规律.研究表明:p型单晶硅中仅存在电子陷阱或复合中心时,二者的密度和俘获截面越小,少子寿命越长,且二者均存在一个最小阈值;当二者并存时,少子电子的衰减过程可根据少子寿命值的不同分成不同的衰减区域.     

一个紧凑的梯形领结无芯RFID标签的设计

提出了一种紧凑、低成本、可完全印制的缝隙加载领结型无芯射频识别标签的设计。标签由2个梯形金属贴片组成,2组谐振频率邻近的缝隙谐振器分别加载在2个贴片上。在不增加缝隙间相互耦合的前提下,标签在超宽带频段内容纳的数据位数提高了1倍,在35mm×33mm的合理尺寸内,12个缝隙谐振器对应12位数据。仿真给出了标签的雷达散射截面积曲线,实测是在双站天线配置下进行,在频域内测出了传输系数s21。实测和仿真结果一致,验证了本设计的合理性。该标签具有高数据位数和低成本,因其只需1个导电层,所以能被直接印刷在ID卡甚至纸张上。     

多层印制板叠层设计对信号完整性的影响研究

基于优化多层印制板叠层设计改进信号完整性的目的,提出了通过叠层设计中调整印制板各层导线宽度、基板厚度、填充层厚度和绝缘材料厚度4个参数值,以改变各层信号传输路径特性阻抗的方法,结合工程实例,通过在特性阻抗连续和阻抗不连续两种情况下仿真的对比试验,验证了叠层设计优化方法的有效性.     

Shape‐Shifting 3D Protein Microstructures with Programmable Directionality via Quantitative Nanoscale Stiffness Modulation

The ability to shape‐shift in response to a stimulus increases an organism's survivability in nature. Similarly, man‐made dynamic and responsive “smart” microtechnology is crucial for the advancement of human technology. Here, 10–30 μm shape‐changing 3D BSA protein hydrogel microstructures are fabricated with dynamic, quantitative, directional, and angle‐resolved bending via two‐photon photolithography. The controlled directional responsiveness is achieved by spatially controlling the cross‐linking density of BSA at a nanometer lengthscale. Atomic force microscopy measurements of Young's moduli of structures indicate that increasing the laser writing distance at the z‐axis from 100–500 nm decreases the modulus of the structure. Hence, through nanoscale modulation of the laser writing z‐layer distance at the nanoscale, control over the cross‐linking density is possible, allowing for the swelling extent of the microstructures to be quantified and controlled with high precision. This method of segmented moduli is applied within a single microstructure for the design of shape‐shifting microstructures that exhibit stimulus‐induced chirality, as well as for the fabrication of a free‐standing 3D microtrap which is able to open and close in response to a pH change.     

单粒子翻转敏感区定位的脉冲激光试验研究

利用脉冲激光单粒子翻转敏感区定位成像系统,对静态随机存储器件IDT71256开展了单粒子翻转敏感区定位的试验研究。为避开器件正面金属层对激光的阻挡,试验采用背面辐照方式进行测试。试验结果表明,存储单元中存储数据类型对器件单粒子翻转的敏感性有较大影响,由测得的单粒子翻转敏感区分布图经处理得到单粒子翻转截面,结果与重离子试验测得的翻转截面数据一致。     

某型号十字轴精密成形工艺分析

目的研究十字轴闭塞式单向温挤压成形的可行性。方法根据十字轴的结构特点,确定了成形方案,并利用有限元技术对成形过程进行了数值模拟分析,然后结合物理实验对工艺可行性进行了验证。结果有限元分析和试验结果相吻合,锻件成形效果较好,没有出现充不满、折叠缺陷。结论采用闭塞式单向温挤压成形工艺,获得了满足尺寸要求的十字轴锻件,成形过程稳定可靠,成形工艺可行。