连续可变偏振光注入垂直腔面发射激光器的偏振开关及双稳特性

基于垂直腔面发射激光器(VCSELs)的自旋反转模型(SFM),理论研究了连续可变偏振光注入VCSEL所产生的偏振开关及双稳特性。研究结果表明,在合适的注入参数设置下,通过连续正向扫描和反向扫描注入光偏振角,VCSEL的偏振分量可产生由偏振角度诱导产生的偏振开关(PS)及偏振双稳(PB)效应,且正反向PS点位置随扫描周期的变化而发生偏移,进而导致PB区域宽度发生改变。当注入强度一定时,正反向PS点位置随扫描周期的增大呈现相反的变化趋势,且更小的扫描周期和更大的频率失谐均有助于增加PB区域的宽度;对于频率失谐给定的情形,注入光强度的变化对PS和PB宽度也有着较大的影响,较小的注入强度及扫描周期更易于PB宽度的扩展。当给定注入强度和频率失谐时,正反向PS点所对应的偏振角度随偏置电流的增强均呈现近似增大的趋势,而PB区域宽度则表现出较大的起伏,且扫描周期越大,对应的PB宽度越小。此外,自旋反转速率也会影响VCSEL输出偏振分量的PS和PB特性,当注入参数一定时,较小的自旋反转速率更易于产生较大的PB宽度。     

Brightening single-photon emitters by combining an ultrathin metallic antenna and a silicon quasi-BIC antenna

Bright single-photon emitters(SPEs)are fundamental components in many quantum applications.However,it is difficult to simultaneously get large Purcell enhancements and quantum yields in metallic nanostructures because of the huge losses in the metallic nanostructures.Herein,we propose to combine an ultrathin metallic bowtie antenna with a silicon antenna above a metallic substrate to simultaneously get large Purcell enhancements,quantum yields,and collection efficiencies.As a result,the brightness of SPEs in the hybrid nanostructure is greatly increased.Due to the deep subwavelength field confinement(mode size<10 nm)of surface plasmons in the ultrathin metallic film(thickness<4 nm),the Purcell enhancement of the metallic bowtie antenna improves by more than 25 times when the metal thickness decreases from 20 nm to 2 nm.In the hybrid nanostructures by combining an ultrathin metallic bowtie antenna with a silicon antenna,the Purcell enhancement(Fp≈2.6×10⁶)in the hybrid nanostructures is 63 times greater than those(≤4.1×10⁴)in the previous metallic and hybrid nanostructures.Because of the reduced ratio of electromagnetic fields in the ultrathin metallic bowtie antenna when the high-index silicon antenna is under the quasi-BIC state,a high quantum yield(QY≈0.70)is obtained.Moreover,the good radiation directivity of the quasi-BIC(bound state in the continuum)mode of the silicon antenna and the reflection of the metallic substrate result in a high collection efficiency(CE≈0.71).Consequently,the overall enhancement factor of brightness of a SPE in the hybrid nanostructure is EF?≈Fp×QY×CE≈1.3×10⁶,which is 5.6×10² times greater than those(EF?≤2.2×103)in the previous metallic and hybrid nanostructures.     

Temperature dependence of the P-hit single event transient pulse width in a three-transistor inverter chain

A comparison of the temperature dependence of the P-hit single event transient (SET) in a two-transistor (2T) inverter with that in a three-transistor (3T) inverter is carried out based on a three-dimensional numerical simulation.Due to the significantly distinct mechanisms of the single event change collection in the 2T and the 3T inverters,the temperature plays different roles in the SET production and propagation.The SET pulse will be significantly broadened in the 2T inverter chain while will be compressed in the 3T inverter chain as temperature increases.The investigation provides a new insight into the SET mitigation under the extreme environment,where both the high temperature and the single event effects should be considered.The 3T inverter layout structure (or similar layout structures) will be a better solution for spaceborne integrated circuit design for extreme environments.     

Parasitic bipolar amplification in a single event transient and its temperature dependence

Using three-dimensional technology computer-aided design (TCAD) simulation, parasitic bipolar amplification in a single event transient (SET) current of a single transistor and its temperature dependence are studied. We quantify the contributions of different current components in a SET current pulse, and it is found that the proportion of parasitic bipolar amplification in total collected charge is about 30% in both 130-nm and 90-nm technologies. The temperature dependence of parasitic bipolar amplification and the mechanism of the SET pulse are also investigated and quantified. The results show that the proportion of charge induced by parasitic bipolar increases with rising temperature, which illustrates that the parasitic bipolar amplification plays an important role in the charge collection of a single transistor.     

具有区间参数的PCB组件随机振动响应

为降低具有区间参数印刷电路板的动力响应,建立了PCB组件的动力学区间分析模型,采用Block-Lanczos法求解固有频率,采用模态叠加法求解加速度功率谱激励下的区间动力响应.通过区间敏感度分析比较了影响目标变量的设计参数,对关键参数的取值区间进行了优化.算例表明,该方法可以获得此类区间问题的优化近似解.     

不确定结构动力区间分析方法研究

将结构中的不确定性参数用区间数来表示,建立了系统的区间动力特征方程和动力控制方程.通过将Monte Carlo方法引入到区间分析中来,并改进了一般Monte Carlo方法在区间模拟中存在的缺陷,对区间动力特征方程和动力控制方程进行了求解,得到了结构的固有频率、位移响应和应力响应的区间计算结果.算例表明改进的Monte Carlo方法求解简单,具有普适性,能够给出较高精度的响应区间.     

新型两亲性含糖嵌段聚合物的合成与自组装

以β-环糊精(β-CD)和2-乙基-2-噁唑啉(EtOz)为原料, 通过活性端基化学偶联法制备了乙酰麦芽七糖/聚(2-乙基-2-噁唑啉)两嵌段聚合物(AcMH-b-PEtOz), 借助核磁共振氢谱、红外光谱和凝胶渗透色谱等手段证实了产物的化学结构. 采用核磁共振氢谱、荧光光谱、透射电子显微镜、动态光散射及紫外-可见分光光度等方法探讨了产物在水溶液中的自组装行为. 结果表明, 所得嵌段聚合物直接溶于水后可通过自组装形成纳米球形“核-壳”结构胶束, 同时具有温度响应性. 所得聚合物的临界胶束浓度(cmc)为4~7 mg/L, 平均粒径(d)为83~115 nm, 临界相转变温度(LCST)为49~64 ℃, 并且均可通过PEtOz的链长进行调控.     

结构动力优化设计述评与展望

结构动力优化设计是当前工程结构设计研究领域中的前沿性课题。文中着重从结构动力特性优化、结构动力响应设计、结构动力灵敏度分析和基于可靠性的结构动力优化设计等四个专题方面对结构动力优化设计研究的发展与现状进行了述评,并粗略地展望了结构动力优化研究未来的发展趋势。      

模糊-区间参数连续体结构的拓扑优化设计

研究位移可靠性约束下的模糊-区间参数连续体结构的拓扑优化问题.利用3σ准则和信息熵分别将区间变量和模糊变量近似转换为随机变量,构建了随机参数平面连续体结构的拓扑优化模型,以结构的形状拓扑信息为设计变量,结构总质量均值极小化为目标函数.以满足位移可靠性为约束条件;利用代数综合法导出了位移响应的数字特征的计算表达式;通过单位虚载荷求得位移灵敏度然后采用双方向渐进结构优化方法求解.通过两个算例验证了文中模型的合理性和求解策略的有效性.     

嗜盐嗜碱芽孢杆菌NTT76启动子和信号肽序列的克隆及表达

利用启动子信号肽探测型质粒pGPB14,从嗜盐碱芽孢杆菌NTT76的总基因组中克隆具有启动子和信号肽功能的NDA片段,共得到41个转化子,其氨苄青霉素抗性水平在1000－12000mg/L之间,从3个不同抗性不平的转化子中提取重组质粒,酶切显示,外源插入片段在100－500bp之间,将重组粒质转化枯草芽孢杆菌,也同样使枯草芽孢杆菌具有分泌β－丙酰胺酶的功能,β－丙酰胺酶活力测定表明,大肠杆菌产生的酶主要积累在周质空间,而枯草芽孢杆菌产生的酶主要分泌在胞外,对外源插入片段进行定列测定发现,所有片段均含有启动子区、核糖体结合位点和信号肽编码区域。