Instability,intermixing and electronic structure at the epitaxial LaAlO3/SrTiO3(001) heterojunction

The question of stability against diffusional mixing at the prototypical LaAlO₃/SrTiO₃(001) interface is explored using a multi-faceted experimental and theoretical approach. We combine analytical methods with a range of sensitivities to elemental concentrations and spatial separations to investigate interfaces grown using on-axis pulsed laser deposition. We also employ computational modeling based on the density function theory as well as classical force fields to explore the energetic stability of a wide variety of intermixed atomic configurations relative to the idealized, atomically abrupt model. Statistical analysis of the calculated energies for the various configurations is used to elucidate the relative thermodynamic stability of intermixed and abrupt configurations. We find that on both experimental and theoretical fronts, the tendency toward intermixing is very strong. We have also measured and calculated key electronic properties such as potential energy gradients and valence band discontinuity at the interface. We find no measurable electric field in either the LaAlO₃ or SrTiO₃, and that the valence band offset is near zero, partitioning the band discontinuity almost entirely to the conduction band edge. Significantly, we find it is not possible to account for these electronic properties theoretically without including extensive intermixing in our physical model of the interface. The atomic configurations which give the greatest electrostatic stability are those that eliminate the interface dipole by intermixing, calling into question the conventional explanation for conductivity at this interface—electronic reconstruction. Rather, evidence is presented for La indiffusion and doping of the SrTiO₃ below the interface as being the cause of the observed conductivity.     

Chaotic dynamics of active optical fiber ring resonator with optical injection

We experimentally obtain the route from period doubling to chaos in an active optical fiber ring resonator （AOFRR） with optical injection. The results show that the AOFRR is sensitive to external optical injection and demonstrate various dynamic characteristics. Meanwhile, the change of the injection strength can cause the output of the AOFRR to become periodic or chaotic. It can be confirmed that all the dynamic characteristics of the system are due to the interaction of the semiconductor laser with the erbium-doped fiber amplifier （EDFA）.     

光互连中二元计算全息算法的研究

二元计算全息(BCGH)是光学信息处理中一个重要元件,其在动态光互连中被广泛使用.为了更好地在光互连中应用BCGH,本文设计改进了二元计算全息的选代算法,比较了几种内能函数下的迭代算法所设计的BCGH,对其象质的不同指标进行了分析.结果表明,用迭代搜索算法是光互连应用中设计BCGH的一种较理想算法.     

Bonding Interface Imaging and Shear Strength Prediction by Ultrasound

The propagation of a longitudinal ultrasonic wave normally incident upon an adhesively bonded structure is studied. The structure consists of adherend and adhesive layers with finite thickness. Interfaces between adherend and adhesive are regarded as distributed springs. Theoretical and experimental results show that resonant frequencies of the bonded structure vary sensitively with the interface stiffness constants and adhesive thickness, and these interface characteristics are inversed by the simulation annealing (SA) method. Furthermore, the distribution image of interface stiffnesses is compared with the state of fracture interface, and quantitative prediction of shear strength is achieved based on the distribution of interface stiffnesses and adhesive thicknesses by using a back-propagation neutral network. The average relative error of the shear strength from prediction to real value is 10.7%.     

New finite-gap solutions for the coupled Burgers equations engendered by the Neumann systems

On the tangent bundle TS^N-1 of the unit sphere S^N-1, this paper reduces the coupled Burgers equations to two Neumann systems by using the nonlinearization of the Lax pair, whose Liouville integrability is displayed in the scheme of the r-matrix technique. Based on the Lax matrix of the Neumann systems, the Abel--Jacobi coordinates are appropriately chosen to straighten out the restricted Neumann flows on the complex torus, from which the new finite-gap solutions expressed by Riemann theta functions for the coupled Burgers equations are given in view of the Jacobi inversion.     

弱吸收基底上弱吸收薄膜的光学常数计算方法

采用一种相对简单而又精确的光度法来计算弱吸收基底上弱吸收薄膜的光学常数,为低损耗紫外薄膜的设计与实现提供了理论基础。采用JGS1型熔融石英基底,制备了MgF2与LaF3材料的单层膜,获得了JGS1型熔融石英基底及MgF2与LaF3薄膜的光学常数色散曲线。结果显示:在200 nm左右处,JGS1型熔融石英基底的吸收已经比较明显,消光系数在10-8量级,因此,应考虑基底的弱吸收,以提高薄膜光学常数的计算精度。     

Thermal-induced nonlinear optical characteristics of ethanol solution doped with silver nanoparticles

The investigation of nonlinear optical characteristics of ethanol solution doped with is presented. A large thermal-induced third-order nonlinear refractive index up to silver nanoparticles 1.941× 10^-7 cm2/W is obtained from the mixed solution under 488-nm continue wave （CW） laser irradiation, which may result from surface plasmon resonance （SPR） enhancement effect of silver nanoparticles as well as high thermo-optic coefficient and low thermal conductivity of ethanol. Obvious spatial self-phase modulation and influence of thermal-induced negative lens effect are observed when a beam propagates through this solution, indicating promising applications such as optical limiting, beam flattening, and so on.     

基于ARM技术的嵌入式OCT成像系统研究

分析了光谱光学相干层成像的基本原理,并基于ARM9内核的嵌入式微处理器S3C2443和当前主流嵌入式的WINCE实时多任务操作系统,提出了一套用于检测人体胃肠道病变的光谱光学相干层内窥成像系统的研制方案。从硬件和软件两个方面,详细介绍了系统的搭建过程,给出了整个系统框架图和软件运行流程图,并通过旋转扫描实验获得三层盖玻片的实物图,实验结果表明该嵌入式光学相干层成像系统是可行的。     

Effect of cooling rate on microstructural formation and hardness of 30CrNi3Mo steel

The variation of microstructural formation and the hardness of the 30CrNi3Mo steel were systematically explored as a function of applied cooling rates in the range of 1–500°C/min. According to the measured Rockwell hardness results, four characteristic stages could be separated as different ranges of cooling rates, which corresponds well with the microstructural evolution observed. With the applied cooling rate increasing, the transformed structure evolves from granular bainite, lower bainite, self-tempered martensite, to finally martensite without self-tempering. Among them, the self-tempered martensite, obtained in the transformed specimens cooled with rates of 25–80°C/min, exhibits the highest hardness values due to the precipitation of fine carbides within it.