Hot Deformation Behaviors in Ti-6Al-4V/(TiB + TiC) Composites

Thermal compression testing was investigated using the Gleeble 3800 thermal simulator,and thermal deformation behavior of particle-reinforced titanium matrix composites (TMCs) was studied under deformation temperatures of 750-900 ℃,strain rates of 0.001-1 s-1,and experimental deformation of 60％.According to obtained flow stress curves,the hot deformation characteristics were analyzed.Based on the Arrhenius hyperbolic sinusoidal model,the constitutive equation at high tempera-ture was established.Based on the theory of dynamic material models,a hot processing map of TMCs at high temperature was established,and the peak region of power dissipation rate and the instability region in the hot processing map were both determined.At the same time,the corresponding microstructures in the peak power dissipation rate and rheological instability regions were observed.The results showed that flow stress decreased with increasing deformation temperature and increased with increasing strain rate.The thermal deformation activation energy of titanium matrix composites was 301.8 kJ/mol.The Ti-6Al-4V/(TiB + TiC) composites possessed only one instability zone under high-temperature compression at a strain of 0.5,with corresponding temperatures at 750-840 ℃ and strain rates at 0.1-1 s-1.The optimal thermal deformation parameters included corresponding temperatures of 830-880 ℃ and strain rates of 0.001-0.05 s-1.The microstructures corresponding to optimal hot working parameters in processing maps were more homogeneous than the microstructures in the instability zone,including the distribution uniformity of reinforcement and the degree of dynamic recrystallization,and no instability phenomena including abnormal grain growth,microcracks or intensive fracture of reinforcements were found,indicating that the hot processing map had a positive guiding effect on the option of desirable material thermal-working parameters.     

低氧诱导因子-1α对脓毒症肠黏膜屏障的保护作用

目的：探讨低氧诱导因子-1α（HIF-1α）对脓毒症肠黏膜屏障的影响及机制。方法：SD大鼠随机分4组：假手术组、脓毒症组、脓毒症+HIF-1α刺激剂组（脓毒症+DMOG组）、脓毒症+HIF-1α抑制剂组（脓毒症+Bay87-2243组）,每组6只。采用盲肠结扎穿孔（cecal ligation and perforation, CLP）建立脓毒症模型。ELISA检测大鼠血浆炎性标记物IL-1β、IL-6、TNF-α,氧化应激标记物丙二醛（MDA）以及抗氧化因子超氧化物歧化酶（SOD）、过氧化氢酶（CAT）的水平。Western blot检测大鼠肠黏膜HIF-1α表达。HE染色检测肠黏膜病理学损伤。结果：与假手术组相比,脓毒症大鼠炎症因子、氧化应激因子以及HIF-1α显著上调（P<0.05）;给予腹腔注射DMOG明显降低脓毒症大鼠血浆IL-1β、IL-6、TNF-α、MDA水平（P<0.05）;增加血浆SOD、CAT水平（P<0.05）;HIF-1α表达上调（P<0.05）,肠黏膜病理损伤减轻,Chiu's评分显著降低（P<0.05）。口服灌胃Bay87-2243则得到相反的结果。 结论：HIF-1α对脓毒症肠黏膜损伤具有保护作用,其机制可能与缓解脓毒症炎性反应和抑制氧化应激水平有关。     

Stereo imaging quality evaluation in a full-color three-dimensional display system

To evaluate the light field display system with a liquid crystal display (LCD) and a holographic functional screen (HFS), the voxel theory based on the ray tracing is used. By analyzing the voxels defined by the cases of corresponding pixels overlapping completely and partially in the image space, the resolution characteristics of the system are discussed. The theoretical model is verified in the reconstruction experiment of a resolution target and compared with the calculation result of the presented system. Finally, we give an optimization method for the display image quality.     

基于肖特基二极管的太赫兹二倍频器设计

固态倍频器是太赫兹源应用中的关键器件,如何利用非线性器件提高太赫兹倍频器件的效率是设计太赫兹固态电路的关键。本文介绍了利用肖特基二极管非线性特性设计固态太赫兹二倍频器的2种方法,即采用直接阻抗匹配和传输模式匹配设计了2种不同拓扑结构的170 GHz二倍频器,针对设计的结构模型,分别进行三维有限元电磁仿真和非线性谐波平衡仿真。仿真结果表明,在17 dBm输入功率的驱动下,倍频器在160 GHz~180 GHz输出频率范围内,倍频效率在15%左右,输出功率大于7 mW。最后对2种方法设计的倍频器结构进行了简单对比和分析,为今后太赫兹倍频研究和设计提供仿真方法。     

一种Ka波段低相噪GaAs HBT压控振荡器

本文研究了一种采用GaAs HBT工艺实现的工作在Ka波段的压控振荡器。该振荡器采用共射级组态和对称式电容电感谐振腔结构以降低其相位噪声,采用π型反馈网络补偿180°相移。在片测试结果表明：偏离中心频率1 MHz处相位噪声为-96.47dBc/Hz,调谐范围为28.312到28.695GHz,在-6V电源电压下该振荡器直流功耗为18mA,振荡器芯片面积为0.7mm×0.7mm。     

Single event soft error in advanced integrated circuit

As technology feature sizes decrease, single event upset (SEU), and single event transient (SET) dominate the radiation response of microcircuits. Multiple bit upset (MBU) (or multi cell upset) effects, digital single event transient (DSET) and analogue single event transient (ASET) caused serious problems for advanced integrated circuits (ICs) applied in a radiation environment and have become a pressing issue. To face this challenge, a lot of work has been put into the single event soft error mechanism and mitigation schemes. This paper presents a review of SEU and SET, including: a brief historical overview, which summarizes the historical development of the SEU and SET study since their first observation in the 1970's; effects prominent in advanced technology, which reviews the effects such as MBU, MSET as well as SET broadening and quenching with the influence of temperature, device structure etc.; the present understanding of single event soft error mechanisms, which review the basic mechanism of single event generation including various component of charge collection; and a discussion of various SEU and SET mitigation schemes divided as circuit hardening and layout hardening that could help the designer meet his goals.     

基于TEV传感器与TOA算法的高压开关柜局部放电定位方法的研究

本文提出采用阈值法、能量法、AIC法、Gabor法提取局部放电脉冲波前时刻,基于时间差(TOA)实现局部放电点自动定位算法.采用上述算法首先在实验室进行高压开关柜的局部放电点定位,并对比上述方法的优劣.然后,在变电站现场对一面存在疑似放电的开关柜进行定位,通过查看时域波形波前时刻特征以及自动定位两种方法检测,检测结果表明,放电点位于该开关柜上部间隔的母线处,停电检修的结果印证了现场检测结论,证明了本文提出算法的有效性.     

基于全数字仿真系统对变压器和应涌流的影响因素及特性研究

利用全数字仿真系统建立了变压器和应涌流电磁暂态仿真模型,对并联和级联和应涌流的产生机理做了详细分析,研究了电网以及变压器中各种因素对变压器和应涌流幅值和产生速度的影响,得出系统阻抗中电阻是和应涌流产生的主要因素以及和应涌流中二次谐波含量较高且稳定的特点,为进一步研究和应涌流对变压器差动保护影响奠定了基础。     

波浪能转换装置中双浮子特性的数值研究

本文提出了以船形大浮子和陀螺形小浮子组合的双浮子波浪能发电试验平台,并针对陀螺形浮子展开了仿真研究。通过改变陀螺浮子的锥顶半径尺寸,建立了陀螺形浮子在波浪水平和竖直冲击作用下的受力和变形模型,分析了其对波浪的适应特性、功率特性以及效率特性,并对影响浮子受力和变形的关键参量进行了优化分析。仿真结果表明,陀螺形浮子作为漂浮式试验平台的波浪能捕获装置是合理的。     

大气压下不同气体的流注放电特性

大气压下气体放电通常表现为丝状放电形式。流注或先导放电是其气体击穿的起始阶段,相对于低气压下暗放电或辉光放电具有更复杂的演化特性。为了研究不同气体的流注传播特性,采用流体模型对1 cm平板电极中大气压下氮气、氧气,以及氮气混合20%、1%和0.01%氧气的双向流注传播过程进行了仿真计算。光电离作为源项加在流体模型中,在数值仿真时采用解多组Helmholtz方程代替Zheleznyak积分计算。仿真结果表明:氧气含量较低时,流注会出现分叉现象;氧气中流注发展速度较快;氧气中正流注通道半径较大。