飞秒激光脉冲的谐波频率分辨光学开关法测量研究

建立了一台谐波频率分辨光学开关法(FROG)飞秒脉冲测量装置，利用该装置进行了掺钛蓝宝石飞秒激光脉冲的测量研究.在二次谐波自相关测得的时域和频域信号基础上，结合对信号光强度分布的计算机迭代处理，得到了有关飞秒激光电场、光谱及其相位的信息，所得脉宽与干涉测量的结果基本一致. 关键词： 频率分辨光学开关法(FROG) 迭代计算 飞秒激光 自相关     

ITER ���򳡴���֧��U �����Լк��ӷ����Ż�

利用试验及数值模拟技术研究了ITER 极向场磁体支撑U 型韧性夹的焊接变形规律,模拟和实际测量的比较验证了模拟的准确性,从而得到了U 型夹焊缝变形的基本规律,并改进现有夹具类型。基于验证好的热力边界条件以及优化的夹具,对三种焊接方案的U 型韧性夹的焊接变形进行了计算,从而提出了极向场磁体支撑制造的优化方案。优化后的焊接方案将焊接变形控制在0.6mm 以内。     

含缺陷的二维CuI光电性质的第一性原理计算

基于密度泛函理论计算了本征缺陷时二维CuI的光电特性,分析了能带结构以及复介电函数.本征2D CuI的带隙值为1.56 eV,为直接带隙半导体;I和Cu缺陷的引入使2D CuI的带隙值小,Cu缺陷的引入并未改变2D CuI的带隙方式,而I缺陷的引入使2D CuI变为间接带隙半导体.光学性质计算结果表明本征2D CuI的静介电函数为2.47, I缺陷的引入对2D CuI的静介电函数影响较小,但是在Cu缺陷时2D CuI的静介电函数急剧增大.     

The global dimensions of crossed products and crossed coproducts

In this paper, we show that if H is a finite-dimensional Hopf algebra such that H and H^＊ are semisimple, then gl.dim（A#σH）=gl.dim（A）, where a is a convolution invertible cocycle. We also discuss the relationship of global dimensions between the crossed product A^#σH and the algebra A, where A is coacted by H. Dually, we give a sufficient condition for a finite dimensional coalgebra C and a finite dimensional semisimple Hopf algebra H such that gl.dim（C α H）=gl.dim（C）.     

Carbon nitride with encapsulated nickel for semi-hydrogenation of acetylene: pyridinic nitrogen is responsible for hydrogen dissociative adsorption

A new mechanism of catalyst has been demonstrated in this article. With the interaction between carbon nitride (CN) and encapsulated nickel, the CN in the catalyst has been endowed with new active sites for the adsorption and activation of hydrogen while nickel itself is physically isolated from the contact with reactive molecules. For the selective hydrogenation of acetylene in large amount of ethylene, the catalyst shows excellent ethylene selectivity than the nickel catalyst itself, which is almost totally unselective. Meanwhile, the CN itself is inactive for the reaction. The results of characterization demonstrate that pyridinic nitrogen doped in the carbon matrix should be the active sites for hydrogen dissociative adsorption. The theoretical calculations further confirm the results and provide with the detail in the electron transfer between nickel and CN in the catalyst. The current results supply a new concept for design of high performance catalyst.     

Permanence of the nonautonomous competitive systems with infinite delay and feedback controls

We study the permanence of a class of nonautonomous two-species Lotka–Volterra competitive systems with infinite delay and feedback controls. New results on the permanence of solutions are obtained. The corresponding results given in [F. Chen, Z. Li, Y. Huang, Note on the permanence of a competitive system with infinite delay and feedback controls, Nonlinear Anal. RWA 8 (2007) 680–687] are improved and extended.     

Design and fabrication of subwavelength nanogratings based light-emitting diodes

Linearly polarized light from InGaN green light emitting diode grown on (0001) oriented sapphire is demonstrated by using subwavelength metallic nanogratings. Polarization ratio can reach 7:1 (∼88%), the highest ever reported from a single light emitting device. We discuss the design and fabrication of this device in detail.     

Polymorphism of Amino Acid‐Based Dendrons: From Organogels to Microcrystals

There is a delicate balance for a low‐weight molecule to behave as a gelator or crystal. The synthesis of two novel amino acid‐based naphthalene‐dendrons, Nap ‐ G1 and Nap ‐ G2 is described. Both dendrons display polymorphic properties in organic solvents. Nap ‐ G1 developed a fibrous network with β‐sheet architecture in cyclohexane but exhibited a spherulitic network in mixed solvents (chloroform/petroleum ether 1:5, v/v). On the other hand, Nap ‐ G2 acted as an efficient organogelator in chloroform but formed crystalline fibers in relatively high polarity solvents (such as acetone and methanol). Combinations of characterizations have been employed to study the polymorphism.