基于AlGaN/GaN共振隧穿二极管的退化现象的研究

文章研究了GaN基共振隧穿二极管 (RTD) 的退化现象. 通过向AlGaN/GaN/AlGaN量子阱中引入三个实测的深能级陷阱中心并自洽求解薛定谔方程和泊松方程, 计算并且讨论了陷阱中心对GaN基RTD的影响. 结果表明, GaN基RTD的退化现象是由陷阱中心的缺陷密度和激活能的共同作用引起. 由于陷阱中心的电离率和激活能的指数呈正相关关系, 因此具有高激活能的陷阱中心俘获更多电子, 对负微分电阻 (NDR) 特性的退化起主导作用. 关键词： 共振隧穿二极管 GaN 陷阱中心 电离率     

硝基漆品牌厂家红外光谱鉴别及预测模型建立

在法庭科学领域,硝基漆的检验鉴别是一项重要的工作。为提高检验工作效率,提高分析可靠性,提出一种基于中红外光谱结合化学计量学的硝基漆鉴别方法。实验采集并获取长颈鹿等6种品牌共计59个样本的红外光谱数据,借助主成分分析、K近邻模型和判别分析构建分类模型。结果表明,PCA模型和K近邻模型对59个样本的区分能力相对较弱,判别分析模型的区分能力较强,实现了96.6%的准确区分和归类,分类结果理想。该方法能够快速,准确,无损地鉴别硝基漆,可为其他物证的检验鉴别提供一定的借鉴和参考。     

考虑损伤界面的多相复合材料总体平均力学性能的预测

在广义自治有限元迭代法的基础上研究了损伤面对多相复合材料的总体平均横向力学性能的影响。给出了对于不同体分比和损伤界面性质的典型复合材料的数值结果。数值分析表明损伤界面的厚度及其损伤程度对复合材料总体平均横向平面应变体积模量和剪切模量有显著影响。本文还计算了损伤界面区域的局部应力场。     

GC–MS法同时测定聚氨酯塑胶跑道中16种多环芳烃

建立气相色谱–质谱法同时测定聚氨酯塑胶跑道中16种多环芳烃如萘、苊、二氢苊、芴、菲、蒽、荧蒽、苯并[b]荧蒽、芘、苯并[a]蒽、屈、苯并[k]荧蒽、苯并[a]芘、茚并[1,2,3-cd]芘、1-甲基奈、2-甲基萘的检测方法。样品采用甲苯为提取剂,经超声提取和硅胶柱净化后,用气相色谱–质谱法测定16种多环芳烃残留量。16种多环芳烃的质量浓度在0.2~10.0 mg/kg范围内与色谱峰面积呈良好的线性,线性相关系数r20.998,检出限为5.0~60.0μg/kg。回收率为72.4%~101.6%,测定结果的相对标准偏差为0.9%~7.2%(n=6)。该方法准确度高、精密度好,适用于聚氨酯塑胶跑道中多环芳烃多残留检测。     

含分层损伤复合材料层合板剩余压缩强度研究

准确预测含分层损伤层合板的剩余压缩强度,对复合材料具有十分重要 意义。本文基于层合板一阶剪切理论,建立了一种考虑复合材料多种损伤的含分层层合板刚度退化模型,通过数值算例分析了分层屈曲临界载荷与材料强度极限的关系以及刚度退化对含分层层合板前后屈曲行为的影响。     

含有分层损伤的复合材料加筋层合板的屈曲性态研究

基于Ｍｉｎｄｉｎ假定推导了考虑剪切的复合材料加筋层板的有限元列式,并在此基础上计算出筋间基板含嵌入分层以及筋与基板连接处含穿透分层的加筋层合板在受压缩载荷情况下的屈曲模式和临界力。本文所给出的有限元方法及结论对从事复合材料结构设计的工程人员具有参考价值。     

Numerical analysis of delamination growth for stiffened composite laminated plates

A study of postbuckling and delamination propagation behavior in delaminated stiffened composite plates was presented. A methodology was proposed for simulating the multi-failure responses, such as initial and postbuckling, delamination onset and propagation, etc. A finite element analysis was conducted on the basis of the Mindlin first order shear effect theory and the von-K6rm~n nonlinear deformation assumption. The total energy release rate used as the criteria of delamination growth was estimated with virtual crack closure technique (VCCT). A self-adaptive grid moving technology was adopted to model the delamination growth process. Moreover, the contact effect along delamination front was also considered during the numerical simulation process. By some numerical examples, the influence of distribution and location of stiffener, configuration and size of the delamination, boundary condition and contact effect upon the delamination growth behavior of the stiffened composite plates were investigated. The method and numerical conclusion provided should be of great value to engineers dealing with composite structures.     

ICP–AES法同时测定食品包装铝箔中锌、铅、镉、砷的溶出量

建立了ICP–AES法同时测定食品包装铝箔中锌、铅、镉、砷溶出量的方法。以4%乙酸溶液浸泡样品,室温放置24 h,分析线为Zn 213.856,Pb 220.353,Cd 226.502,As 193.759 nm。Zn,Pb,Cd,As的线性范围分别为0.3~5.0,0.1~2.0,0.01~0.2,0.03~0.5 mg/L,线性方程分别为Y=23 487.27X+769.79,Y=6 713.35X+38.46,Y=30 562.52X+362.02,Y=6 448.97X+13.57;相关系数分别为0.999 9,0.999 8,0.999 9,0.999 5;检出限分别为0.009 6,0.003 7,0.000 4,0.013 9mg/L;加标回收率为96.5%~100.5%;相对标准偏差为1.38%~3.06%(n=6)。该方法简便快速,测定结果准确。     

Impact of the distribution pattern of fast polarization scrambler on the performance of PMD mitigation with FEC for DQPSK optical system

The combination of fast polarization scrambler (FPS) and forward error correction (FEC) is one of the methods to mitigate the polarization mode dispersion (PMD) in high-speed optical fiber communication systems. The effect of the different distribution patterns of FPS on PMD mitigation with FEC is investigated. A comparison of the bit error rates (BERs) between two cases where the distributed FPS is absent and present along the fiber is carried out by simulation. A novel representation called the "ring chart" to assess the performance of different distribution patterns intuitively is proposed. The results show that the distribution pattern is an impact factor for this PMD mitigation scheme.