MBE生长的跨导为186 mS/mm的AlGaN/GaN HEMT

用分子束外延(MBE)技术研制出了AlGaN/GaN高电子迁移率晶体管(HEMT)材料,其室温迁移率为1 035 cm2/Vs、二维电子气浓度为1.0×1013 cm-2;77 K迁移率为2 653 cm2/V*s、二维电子气浓度为9.6×1012 cm-2.用此材料研制了栅长为1 μm、栅宽为80 μm、源-漏间距为4 μm的AlGaN/GaN HEMT,其室温最大非本征跨导为186 mS/mm、最大漏极饱和电流密度为925 mA/mm、特征频率为18.8 GHz.另外,还研制了具有20个栅指(总栅宽为20×80 μm＝1.6 mm)的大尺寸器件,该器件的最大漏极饱和电流为1.33 A.

Search for signature inversion in the pi i(13/2) circle times upsilon i1(3/2) bands in Au-182,Au-184,Au-186

Search for low-spin signature inversion in the pi i(13/2) circle times nu i(13/2) bands in odd-odd Au-182,Au-184,Au-186 has been conducted through the standard in-beam gamma-spectroscopy techniques. The experiments for Au-182 and 186Au have been performed in the Japan Atomic Energy Agency (JAEA) via the Sm-152(Cl-35,5n)Au-182 and Yb-172(F-19,5n)Au-186 reactions, respectively. A study of Au-184 has been made using a multi-detector array GASP in LNL, Italy, via the Tb-159(Si-29,4n)Au-184 reaction. The pi i(13/2) circle times nu i(13/2) bands in these three nuclei have been identified and extended up to high-spin states. In particular, the inter-band connection between the pi i(13/2) nu i(13/2) band and the ground-state band in 184 Au has been established, leading to a firm spin-and-parity assignment for the pi i(13/2) circle times nu i(13/2) band. The low-spin signature inversion is found in the pi i(13/2) circle times nu i(13/2) bands in Au-182,Au-184,Au-186 according to our spin-assignment and the signature crossing observed at high-spin states.

Search for signature inversion in the pi i(13/2)circle times nu i(13/2) bands in Au-182,Au-184,Au-186

Search for low-spin signature inversion in the pi i(13/2) circle times nu i(13/2) bands in odd-odd Au-182,Au-184,Au-186 has been conducted through the standard in-beam gamma-spectroscopy techniques via the Sm-152(Cl-35,5n) Au-182, Yb-172(F-19,5n) (186)An, and Tb-159(Si-29,4n) (184)An reactions, respectively. The pi i(13/2) circle times nu i(13/2) bands in these three nuclei have been identified and extended up to high-spin states. In particular, the inter-band connection between the pi i(13/2) circle times nu i(13/2) band and the ground-state band in Au-184 has been established, leading to a firm spin-and-parity assignment for the pi i(13/2) circle times nu i(13/2) band. The low-spin signature inversion is found in the pi i(13/2) circle times nu i(13/2) bands according to our spin-assignment and-the signature crossing observed at high-spin states.

海底管线强度评估中的两个问题

海底管线是海上油气田生产设施的重要组成部分,它一旦发生破坏会在各方面引起重大损失.挖沟和提吊引起应力超标是海底管线两种重要的破坏形式.挖沟和提吊问题的难点是:1)二者都是动边界问题,悬空长度本身就是未知量;2)挖沟问题中应考虑台阶升高处土壤支持的弹性影响(这比刚性处理更准确,但这会使边界条件更复杂);3)提吊是一个几何非线性问题,求解难度较大.本文给出挖沟和提吊作业状态下,海底管线的强度分析方法.在挖沟分析中,采用线性梁理论,将台阶升高处的土壤支持处理为线性弹簧.在提吊问题中,将管线模型化为大位移梁,采用打靶法,将边值问题转变为初值问题求解.文中还给出有关的典型数值计算结果.

偶应力问题的非协调元分析

从偶应力弹性体势能泛函的驻值条件出发,得到了偶应力理论中非协调元体系的能量相容原理.基于其常应力(常偶应力)分片检验条件的强形式,对平面四结点单元的非协调试探内函数进行了优化,提出了一种稳定有效的非协调元方法.有限元列式中,微转动和宏观转动相等的约束条件通过罚因子的形式引入.分析了含中心圆孔的无限平板,在单轴拉伸以及纯剪状态时,偶应力的存在对孔周应力集中的影响.算例表明,该单元计算效率高,精度好,即使在材料本征长度很小时,仍然能够得到相当理想的结果.

Immunosensor Interface Based on Physical and Chemical Immunogylobulin G Adsorption onto Mixed Self-Assembled Monolayers

An immunosensor interface based on mixed hydrophobic self-assembled monolayers (SAMs) of methyl and carboxylic acid terminated thiols with covalently attached human Immunoglobulin G (hIgG), is investigated. The densely packed and organised SAMs were characterised by contact angle measurements and cyclic voltammetry. The effect of the non-ionic surfactant, Tween 20, in preventing nonspecific adsorption is addressed by ellipsometry during physical and covalent hIgG immobilization on pure and mixed SAMs, respectively. It is clearly demonstrated that nonspecific adsorption due to hydrophobic interactions of hIgG on methyl ended groups is totally inhibited, whereas electrostatic/hydrogen bonding interactions with the exposed carboxylic groups prevail in the presence of surfactant. Results of ellipsometry and Atomic Force Microscopy, reveal that the surface concentration of covalently immobilized hIgG is determined by the ratio of COOH/CH3-terminated thiols in SAM forming solution. Moreover, the ellipsometric data demonstrates that the ratio of bound anti-hIgG/hIgG depends on the density of hIgG on the surface and that the highest ratio is close to three. We also report the selectivity and high sensitivity achieved by chronoamperometry in the detection of adsorbed hIgG and the reaction with its antibody.

秦岭山脉对冷空气屏障的理论研究

利用二维大气中尺度数值模式，以１９７７年１月２０日－２２日的冷空气侵袭秦岭山区为例，从观测资料与数值计算两方面分析了由秦岭山脉的屏障作用而引起南北温差的主要原因。结果表明：这种屏障作用不仅体现在秦岭山脉对冷空气的阻挡作用上，而且还与秦岭南坡上的下坡风引起的绝热下沉增温有关。秦岭山脉对冷空气阻挡的动力原因除与秦岭山脉本身的拔海高度较高有关外，还与它的地形形状有关，尤其是位于秦岭北部的渭河河谷，它抑制冷空气入侵谷内，进而阻挡冷空气翻越秦岭山脉。

具有离散阻尼器的结构动力分析

本文论述了几种结合离散阻尼器于结构以增大其阻尼的方法。假设原结构是无阻尼的,用复数表示加在它的某些离散点上的阻尼器的刚度,推导出了一个对无阻尼结构的刚度阵作局部修改的运动方程,指出了用模态应变能法解决这个问题时的缺点,提出了用改进的直接频率响应积分法与模态综合法求解它。

研究快速现象的高速干涉摄影系统

我们研制了一种用于诊断TEACO_2脉冲激光与物质相互作用,以及其它流场中快速现象的高速干涉摄影系统;解决了这一技术中的时间同步、高速摄影机与激光平晶错位干涉仪的光学匹配;提出了逆程序运转方案,将连续输出的He-Ne激光改成了时间可控的脉冲光源;用这一技术拍出了一系列相互作用过程的微秒级高速干涉照片,以及超音速风洞中流场照片。这种技术也能广泛用于其它快速现象及流场显示领域中。

饱和水泥试样被爆炸激波损伤破碎的尺度研究

利用水中爆炸冲击波使水泥试样损伤破坏,模拟爆炸采油时激波使岩石损伤开裂的现象.实验获得了适合本实验条件的激波峰压衰减规律p_m≈8.2(~3√W/R~(1.46)),得知压碎区尺度为集中装药特征尺度的2～5倍、拉伸损伤区尺度为集中装药特征尺度的20～30倍,激波使水泥试样破碎、拉裂的能量占总能量的2%～7%.

矩形微槽道气体流动的速度分布

矩形微槽道的各个流向截面可以局部近似为平面Poiseuille流动，应用信息保存（IP）方法和直接模拟Monte Carlo（DSMC）方法计算了从连续介质区到自由分子流区的平面Poiseuille流动，利用其结果对Beskok-Karniadakis公式和质量流率动理论因子进行修正和重新拟合，给出在整个稀薄气体流动领域都适用的微槽道气体流动速度分布.

空间电动绳系推进中导电系绳动态特性分析

通过建立空间电动绳系系统动力学模型,研究了通有电流的导电系绳高速运动切割地球磁力线时系绳的振荡和变形特性。通过数值计算,分别给出了导电系绳在不同长度和不同主子星质量比下对系绳动态特性的影响,得到了一些规律性认识和结果。

微桥法镍膜的弹性模量和残余应力测量

利用MEMS技术制作了不同尺寸的镍(Ni)膜微桥结构样品.采用纳米压痕仪XP系统测量了微桥载荷与位移的关系,并结合微桥力学理论模型得到了两种不同尺寸的Ni膜的弹性模量和残余应力.结果表明,两种不同尺寸的Ni膜的弹性模量结果一致,为190 GPa左右,但是残余应力变化较大.与采用纳米压痕仪直接测得的带有硅(Si)基底的Ni膜弹性模量186.8±7.5 GPa相比较,两者符合较好.