熔融LiCl及其急冷非晶键取向序的分子动力学模拟研究

本文进一步讨论了我们新近提出的等近邻数键球谐函数方法,并通过分子动力学模拟研究了熔融LiCl及其急冷过程。对计算机模拟各时间步产生的瞬态构型进行平均,计算了不同温度下键序Q_l谱.将模拟Q_l谱与线性组合模型Q_l谱比较,观察到模拟Q_l谱与含90％局部正四面体结构的组合模型十分相似,表明熔融Licl及其急冷非晶中局部键取向序明显倾向于正四面体序。急冷过程中不同温度下局部键取向序可用同一线性组合模型描述,但模型方差随模拟温度明显变化。方差随温度而降低,且在发生玻璃态转变时有一显著下降。不同温度下的键角分布也作了计算,观察到键角分布在109°(正四面体局部结构键角)附近且分布峰随温度升高而展宽,与键序Q_l得到的结论一致。     

基于校园网的实验管理系统的设计

主要讨论了应用实验室管理系统的必要性,并从用户需求分析、系统总体设计、功能模块的设计等方面对B/S实验室管理系统的开发进行了详细的阐述。     

A method to collect an infrared spectrum in solution.

Herein we report a new method to collect a qualified infrared spectrum of a solute in solution by two solvent cells with different thickness during background single-beam spectrum scanning. By collecting the background spectrum with two cells (two stages), we successfully achieved accurate solvent compensation between a sample and a reference, namely, the solvent amounts in the sample and background measurements could become congruent. Therefore, the solvent bands were thoroughly suppressed in the infrared spectrum and a qualified spectrum of the solute was obtained.     

THERMAL AND THERMO-ELASTIC-PLASTIC RESPONSE OF CERAMIC-METAL FUNCTIONALLY GRADED MATERIALS—THERMAL SHOCK PROBLEM

The thermal and thermo-elastic-plastic response of newly developed ceramic-metalfunctionally graded materials under a thermal shock load is studied.The materials are heated at the ce-ramic surface with a sudden high-intensity heat flux input,and cooled at the metal surface with aflowing liquid nitrogen.Emphasis is placed on two aspects:(1)the influence of the graded composi-tion of the materials on the temperature and stress response;and(2)the optimum design of the gradedcomposition from a unified viewpoint of the heat insulation property and stress relaxation property.Moreover,a comparison between the thermoelastic stress and the thermo-elastic-plastic stress is alsomade to indicate the plasticity effect.     

三维随机Ising模型的亚稳态性(Ⅱ)

讨论三维格点环面上随机Ising模型当温度趋向零时的亚稳态性,确定从自旋全为-1的组态到自旋全为+1的组态的最大似然路径和临界组态,并计算出从自旋全为-1的组态出发首次到达自旋全为+1的组态的首达时间的渐近对数估计。证明利用一族带指数扰动的Markov链的大偏差估计。     

Reduction of Dislocations in GaN Epilayer Grown on Si （111） Substrates using a GaN Intermedial Layer

GaN intermedial layers grown under different pressures are inserted between GaN epilayers and AIN/Si（111） substrates. In situ optical reflectivity measurements show that a transition from the three-dimensional （3D） mode to the 2I） one occurs during the GaN epilayer growth when a higher growth pressure is used during the preceding GaN intermedial layer growth, and an improvement of the crystalline quality of GaN epilayer will be made. Combining the in situ reflectivity and transmission electron microscopy （TEM） measurements, it is suggested that the lateral growth at the transition of growth mode is favourable for bending of dislocation lines, thus reducing the density of threading dislocations in the epilayer.     

Scanning mirror on a vibrating membrane for dynamic optical trapping

A study of the variation of the spectral shape and the harmonic distribution of the high-order harmonics generated from silver plasma on the frequency chirp of the driving laser radiation (793 nm 48 fs) is reported. The results of the systematic study of the harmonic generation from the 21st order up to the 61st order (λ=13 nm) are presented. A tuning of the harmonic wavelength up to 0.8 nm can be accomplished by variation of the laser chirp. PACS 42.65.Ky; 42.79.Nv; 52.38.Mf     

具有六重穿插非中心对称金刚石网络结构的Cd(Ⅱ)和Zn(Ⅱ)的配位高聚物(英)

利用1，4-二-(4-羧基吡啶基)丁烷(L)合成了两个新的三维配位聚合物{(CdL₂)·4H₂O·2ClO₄}_n 1和{(ZnL₂)·4H₂O·2ClO₄}_n 2。单晶X-射线结构分析表明，1和2具有相同的计量式，但其晶体属于不同的空间群(1属于P4n2，2属于P4₂22)。两种配合物中，每个金属离子分别由配体与四个相邻的金属离子连接，从而形成具有六重穿插的金刚石网络结构，其网络中大的空腔被高氯酸根离子和(H₂O)₄分子簇所占据。     

铁羰基络合物制备的一氧化碳加氢催化剂的研究

本文采用Ｆｅ＿３（ＣＯ）＿（１２）制备担载型络合物催化剂。采用程序升温反应技术考察了这类催化剂（ＣＯ＋Ｈ＿２）的反应性能，井使用紫外漫反射光谱和穆斯堡尔谱对催化剂进行了表征。经２５０℃和１５０℃还原的Ｆｅ／γ－Ａｌ＿２Ｏ＿３催化剂不仅活性远远高于４５０℃还原的Ｆｅ／γ－Ａｌ＿２Ｏ＿３，而且前者在反应过程中有乙烯和乙烷生成，后者则只有甲烷生成。经２５０℃还原的Ｆｅ／分子筛催化剂的活性高于４５０℃还原的Ｆｅ／分子筛催化剂，而且前者在反应过程中有乙烯、乙烷和丙烯生成，后者则只有甲烷生成。紫外漫反射谱和穆斯堡尔谱结果表明：较温和条件下活化的催化剂上有金属于属键骨架的存在。