Digital measuring scheme for half-wave voltage of Y-tap multiple integrated optical circuit

A high-precision digital measuring scheme for half-wave voltage of Y-tap multiple integrated optical circuits is proposed. This scheme is based on Sagnac interferometer modulated with digital step waveform whose frequency is half of eigen frequency of the interferometer. The technology and measuring precision are discussed. An experimental setup is made and the temperature-dependences of half-wave voltage of two samples are studied. Analysis and experimental study prove that this scheme is convenient and accurate.     

Nonlinear dynamics study of an open resonant Λ-type system

Quantum coherence and interference in atomic systemshave a number of important consequences, includinglasing without inversion (LWI), the electromagneticallyinduced transparency, coherent population trapping, thesubrecoil cooling of atoms, potentiality for sensitive mea-surements of magnetic fields, and so on. In particular,LWI has attracted much more attention[1-12] and havebeen studied in the past few decades. The open Λ-typethree-level system for LWI is proposed[13-14]. From thenonline…     

LT-GaAs飞秒光电导之电场响应特性

利用飞秒光电导自相关技术研究了LT GaAs飞秒光电导开关时间随外加偏置电场的变化规律 .实验结果显示当外加偏置电场从0.5×10⁴ V/cm 上升到9.5×10⁴ V/cm 时，光电导 开关时间开始在200fs附近缓慢变化再迅速增加到750fs.这是由于随着外加电场增加，Fren kel-Poole效应导致的EL2缺陷中心库仑吸引势垒降低和电场增强的碰撞电离效应显著增强 ，导致载流子俘获截面减小，载流子寿命增加之故. 关键词： 光电导自相关技术 载流子俘获时间 Frenkel-Poole效应 电子碰撞电离效应     

Twin—layer films of copper phthalocyanine and amorphous titanyl or vanadyl phthalocyanine

Metallophthalocyanine (MPc) twin-layer thin films on glass substrates, consisting of copper phthalocyanine (CuPc) overlayer and amorphous vanadyl phthalocyanine (VOPc) as well as titanyl phthalocyanine (TiOPc) buffers, were found to have different gas sensing characteristics. These twin-layer thin films were studied using x-ray photoemission spectroscopy. Photoelectrons of either V or Ti core levels were found to be present at the surface, indicating the existence of possible molecular migrations. The stability of the twin-layers under thermal annealing up to a maximum temperature of 250℃ and low-energy Ar ion bombardment was also examined and compared with that of CuPc directly grown on the substrates. We concluded that the twin-layer structures were thermally fairly stable. Ar ion bombardment, however, caused substantial damage to the Pc ligands and a reduction of the valence state of the central Cu atoms.     

Y203：Eu^3＋纳米线阵列的制备与表征

Y203：Eu^3 红色荧光粉由于色纯度高、化学性质稳定和量子效率接近100％而广泛用于荧光灯和投影电视等方面．近年来，Y203：Eu^3 的大量研究工作主要集中于纳米粉末的制备方法及其与体相材料不同的发光特性．最近，有关Y203：Eu^3 及其稀土化合物的纳米管、纳米线和纳米带一维材料     

钾改性对Au/ZSM-5催化剂上正丁烷裂解性能的影响

采用负压沉积沉淀法制备了负载型Au/HZSM-5催化剂,采用X射线衍射（XRD）、透射电镜（TEM）、Ｘ射线光电子能谱（XPS）、NH3-TPD、紫外可见漫反射（UV-vis）等技术对催化剂进行了表征分析,并考察了催化剂对正丁烷裂解性能的影响。结果表明,Au金属成功负载到HZSM-5催化剂上,并且金颗粒的尺寸受负载量的影响,其中1.0%Au/HZSM-5催化剂中的金颗粒粒径最小,约为5～10nm。钾离子作为一种碱性离子可以调节载体酸性,随着K离子的引入xK-Au/HZSM-5催化剂的酸性逐渐降低,使Au0的电子结合能更高。相对于HZSM-5,2.0Au/HZSM-5催化剂对于正丁烷的转化率从13.1%提升到了37.5%,对丙烯的选择性从17.2%提升到了52.5%。随着K离子的引入,催化剂对于丁烯以及异丁烷的选择性有所提高,当K离子负荷为0.08%时,对丁烯的选择性从3.8%提高到36.9%,负荷为0.1%时,对异丁烷的选择性由2.8%提升到51.8%。但原料转化率低于2.0Au/HZSM-5,这可能与K的加入降低催化剂酸改性有关。此外通过研究Au/HZSM-5用K+修饰得知Au+离子是Au/HZSM-5催化剂转化正丁烷主要活性中心。     

甲醇为氢源的连续化催化转移加氢合成芳胺

开发了一种温和高效的以甲醇为氢源，以Ru-Fe双金属为催化剂的硝基芳烃连续化转移加氢方法。采用浸渍法制备Ru-Fe双金属催化剂，通过电感耦合等离子体-质谱(ICP-MS)、透射电子显微镜(TEM)、X射线衍射(XRD）、氢气程序升温还原(H₂-TPR)对催化剂进行表征。结果表明催化剂具有较小的粒径和较好的分散性。在Ru-Fe双金属催化剂上，成功实现了硝基芳烃与甲醇在无外加氢源条件下的连续化转移加氢合成芳胺。通过对反应条件的调控，成功得到了一系列产率较高的胺类化合物。特别地，该方法对不饱和基团(醛基、羰基或炔基)取代的硝基芳烃的加氢表现出优异的选择性和转化率。     

Elastic behaviour of a wedge sharp crack emanating from a disclination dipole near a semi-elliptical blunt crack

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.     

Shielding Effect and Emission Criterion of a Screw Dislocation Near an Interfacial

Shielding effect and emission criterion of a screw dislocation near an interracial crisscross crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial crisscross crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the crisscross crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interracial crisscross crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle and the distance between the dislocation and the crack tip. The critical loads at infinity for dislocation emission increases with the increase of emission angle and the vertical length of the crisscross crack, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.     

NUMERICAL ANALYSIS OF THE LARGE DEFLECTION OF AN ELASTIC-PLASTIC BEAM

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