Growth and Characterization of A1GaN/A1N/GaN HEMT Structures with a Compositionally Step-Graded A1GaN Barrier Layer

A new A1GaN/A1N/GaN high electron mobility transistor （HEMT） structure using a compositionally step-graded A1GaN barrier layer is grown on sapphire by metalorganic chemical vapour deposition （MOCVD）. The structure demonstrates significant enhancement of two-dimensional electron gas （2DEG） mobility and smooth surface morphology compared with the conventional HEMT structure with high A1 composition A1GaN barrier. The high 2DEG mobility of 1806 cm2/Vs at room temperature and low rms surface roughness of 0.220 nm for a scan area of 5μm×5 μm are attributed to the improvement of interracial and crystal quality by employing the stepgraded barrier to accommodate the large lattice mismatch stress. The 2DEG sheet density is independent of the measurement temperature, showing the excellent 2DEG confinement of the step-graded structure. A low average sheet resistance of 314.5Ω/square, with a good resistance uniformity of 0.68%, is also obtained across the 50 mm epilayer wafer. HEMT devices are successfully fabricated using this material structure, which exhibits a maximum extrinsic transconductance of 218 mS/ram and a maximum drain current density of 800 mA/mm.     

用户专用键盘可测试性设计实现

针对用户专用键盘故障排查过程中的低效率问题,本文采用边界扫描法、内建自测试法等对其进行测试性设计改进,使得利用已有的边界扫描设备即可实现自动化故障诊断。并通过设置管脚短路和芯片功能异常两个故障实际验证了用户专用键盘可测试设计效果,实验结果表明,改进后的用户专用键盘可快速定位故障,并且具有较高的准确度和精度。本文对用户专用键盘进行测试性设计改进,以使其满足边界扫描设备测试要求,此种方法对其它单片机系统的测试性设计具有借鉴意义。     

带有记忆的热弹盘问题解的整体存在性(英文)

In this paper, we shall establish some global existence results for the higherdimensional nonhomogeneous, linear, semilinear and nonlinear Thermoelastic plates with memory respectively by using semigroup approach. The existence and decay of solutions of homogeneous linear problem has been solved by Romero [1] .     

对高维热粘弹方程组解的整体存在性的注记

In this paper, we obtain some global existence results for the higher-dimensional nonhomogeneous, linear, semilinear and nonlinear thermoviscoelastic systems by using semi-group approach.     

ABPXs的多刺激响应行为光谱研究

近年来,多刺激响应材料在基础研究和应用领域得到了广泛关注。Aminobenzopyranoxanthenes(ABPXs),作为一种常见的酸碱响应材料被熟知。研究结合吸收光谱及荧光光谱,针对四种具有顺反异构结构的ABPXs物质在光和力的刺激下的响应行为进行了深入研究与分析。该类材料在压力传感器、防伪等方面具有潜在应用。     

大沽河流域地下水溶解有机物的三维荧光光谱特征

利用三维荧光光谱研究了大沽河流域地下水中溶解有机物(DOM)的荧光组分类型及其空间分布与变化,并与地表河水进行了比较。基于平行因子分析模型在大沽河流域识别出2个类腐殖质组分及1个类蛋白质组分。研究区域上、下游地下水中各荧光组分的强度低,但中游区域呈现高值区,与人为污染的下渗输入以及为阻止海水入侵而修建的截渗墙对地下水循环模式的改变有关。地下水DOM以类腐殖质组分为主,类蛋白质组分平均只占15%,不及地表河水的一半,其新鲜度指数(β/α)也低于河水但荧光指数(FI)、腐殖化指数(HIX)高于河水,表明地下水DOM的腐殖化程度更高,与地下水停留时间长、微生物降解作用的贡献更为显著有关。本研究揭示,三维荧光指纹技术可区分天然背景及人为活动对地下水中DOM含量及性质的影响,是研究地下水环境中的碳循环过程及其影响因素的有用工具。