南极菲尔德斯半岛六种藻类和地衣植物的X荧光分析

为了研究南极的植物与环境间的关系,探讨植物在南极环境监测中的作用。在无标样条件下,利用微束X荧光分析法对南极菲尔德斯半岛的6种藻类和地衣植物进行了元素分析．其中藻类植物有孔石莼(Ulva pertusa)、海膜（Halymenia sp.)和大型鞘丝藻（Lyngbya maijor),地衣植物有筛石蕊(Cladonia borealis)、喇叭石蕊（C.fimbriata)和松萝(Usnea sp.)．研究结果发现,不同的藻类植物对各种元素的吸收能力不同,在XRF（X射线荧光)谱中,孔石莼比海膜含有更多的元素,象As、Br和Rb,Cu和Zn的含量也较高。在大型鞘丝藻中,K比Ca少,Zn的含量较高．在3种地衣植物中,其XRF谱中的元素种类组成非常相似,只是Mn、Fe、Cu和Zn等元素的相对含量有些差异。     

谷氨酰胺结合蛋白的分子动力学模拟和自由能计算

谷氨酰胺结合蛋白(Glutamine-binding protein, GlnBp)是大肠杆菌透性酶系统中一个细胞外液底物专一性结合蛋白, 对于细胞外液中谷氨酰胺(Gln)的运输和传递至关重要. 本文运用分子动力学(Molecular dynamics, MD)模拟采样, 考察了GlnBp关键残基与底物Gln之间的相互作用和GlnBp两条铰链的功能差别; 并采用MM-PBSA方法计算了GlnBp与底物Gln的结合自由能. 结果表明: Ph13, Phe50, Thr118和Ile69与底物Gln的范德华相互作用和Arg75, Thr70, Asp157, Gly68, Lys115, Ala67, His156与底物Gln的静电相互作用是结合Gln的主要推动力; 复合物的铰链区85～89柔性大, 对构象开合提供了结构基础; 而铰链区181～185柔性小, 其作用更多是在功能上把底物Gln限制在口袋中; 自由能预测值与实验值吻合. 本研究很好地解释了GlnBp结构与功能的关系, 为进一步了解GlnBp的开合及转运Gln的机制提供了重要的结构信息.     

非等温TG- DTG法确定2,2'- 联吡啶- 对甲氧基苯甲酸铕(Ⅲ)热分解反应的机理函数和动力学参数

采用TG-DTG和DTA技术研究了2,2'-联吡啶-对甲氧基苯甲酸铕(Ⅲ)在静态空气中的非等温热分解过程及动力学,根据TG曲线确定了热分解过程中的中间产物及最终产物,运用微分法与积分法对非等温动力学数据进行分析,推断出第一步的动力学方程为dα/dt=Aexp(-E/RT)2(1-α)1/2.     

SIZE EFFECT AND GEOMETRICAL EFFECT OF SOLIDS IN MICRO—INDENTATION TEST

Micro-indentation tests at scales of the order of sub-micron show that the measured hardness increases strongly with decreasing indent depth or indent size,which is frequently referred to as the size effect.At the same time,at micron or sub-micron scale,another effect,which is referred to as the geometrical size effects such as crystal grain size effect,thin flim thickness effect,etc.,also influences the measured material hardness.However,the trends are at odds with the size-independence implied by the conventional elastic-plastic theory.In the present research,the strain gradient plasticity theory(Fleck and Hutchinson)is used to model the composition effects(size effect and geometrical effect) for polycrystal material and metal thin film/ceramic substrate systems when materials undergo micro-indenting.The phenomena of the “pile-up“ and “sink-in“ apeared in the indentation test for the polycrystal materials are also discussed.Meanwhile,the micro-indentation experiments for the polycrystal Al and for the Ti/Si3N4 thin film/substrate system are carried out.By comparing the theoretical predictions with experimental measuremtns.the values and the variation trends of the micro-scale parameter included in the strain gradient plasticity theory are predicted.     

Characterization of the nanopore structures of PAN-based carbon fiber precursors by small angle X-ray scattering

The nanopore structures in precursors are crucial to the performance of PAN-based carbon fibers. Four carbon-fiber precursors are prepared. They are bath-fed filaments (A), water-washing filaments (B), hot-stretching filaments (C) and drying-densification filaments (D). Synchrotron radiation small angle X-ray scattering is used to probe and compare the nanopore structures of the four fibers. The nanopore size, discrete volume distribution, nanopore orientation degree along the fiber axis and the porosity are obtained. The results demonstrate that the nanopores are mainly formed in the water-washing stage. During the processes of the subsequent production technologies, the slenderness ratio of nanopores and their orientation degree along the fiber axis increase further and simultaneously, the porosity decreases. These results are helpful for improving the performance of the final carbon fibers.     

时变切换时滞反馈镇定混沌系统不稳定周期轨线

为提高经典时滞反馈控制镇定不稳定周期轨线的效果, 扩大受控周期轨线的稳定区域, 本文基于时变切换策略对经典时滞反馈控制进行改进, 提出了时变切换时滞反馈控制. 时变切换时滞反馈控制的控制信号仅在特定的时段中存在, 而在其他时段上不存在控制信号, 这与经典时滞反馈控制中具有固定的控制信号是不同的. 通过实例分析, 研究了时变切换时滞反馈控制在镇定不稳定周期轨线中的具体性能. 以反馈增益系数为变量, 计算受控周期轨线的最大条件Lyapunov指数, 得到了受控周期轨线的稳定区域随切换频率变化的关系曲线. 结果表明, 随着切换频率增大, 受控周期轨线的稳定区域呈现非平滑地变化. 当选取恰当的切换频率时, 时变切换时滞反馈控制的稳定区域显著大于经典时滞反馈控制的稳定区域. 在混沌控制的工程实践中, 控制信号常常受到一定的限制. 要实现对目标周期轨线的稳定控制, 就需要受控周期轨线具有足够大的稳定区域. 因此, 与经典时滞反馈控制相比, 本文提出的时变切换时滞反馈控制具有更广泛的应用前景.      

Littlewood-Paley g_λ~*函数与局部Campanato函数生成的交换子在广义局部Morrey空间的有界性（英文）

本文主要研究了Littlewood-Paley g_λ~*函数及其与局部Campanato函数生成的交换子在广义局部Morrey空间LM_(p,φ)~({x_0})的有界性.     

正交型光热偏转光谱法及其差分构型研究

本工作设计了一种新的差分式光热偏转光路构型，光路的优点是只使用单一的位置传感器，可随意调节样品池和参考池的距离，电学补偿和差分光路装置简单，容易调整，可以有效地消除溶剂空白吸收的影响和泵浦激光功率起伏的影响。文章还讨论了该差分构型的原理，差分响应公式和基本实验参数。获得的结晶紫和钴的检测下限分别为８．０×１０＾－１０ｍｏｌ／Ｌ和６０ｍｇ／ｍｌ，对应的最小吸光度分别为１．２×１０＾－８和５．４×１０     

Superconductivity in LiTi2O4 Prepared by Hybrid Microwave Method

The well-known superconducting oxide LiTi2 04 has a structural phase transition from spinel to ramsdellite around 900℃. We have successfully obtained the superconducting spinel phase and the non-superconducting ramsdellitephase of LiTi2O4 using a hybrid microwave method. The samples are characterized by x-ray powder diffraction, scanning electron microscopy, and measurements of resistivity and magnetic susceptibility. The results show thatthe low-temperature spinel phase is a superconductor with Tc=13K, while the high-temperature ramsdellite phase is a semiconductor. By comparison between the crystal structures of the spinel and the ramsdellite phases, it is suggested that the geometrical frustration plays an important role in the superconductivity of the spinel LiTi2O4.     

求多项式展开式指定项系数的一个方法——逐次写通项法

本文在于给出形如(a_1x~(α_1)+a_2x~(α_2)+…+a_mx~(α_m))~n展开式中x~p系数的一个一般求法。其中 n·min(α_1,α_2,…, α_m)≤p≤n·max(α_1,α_2,…,α_m)