Properties of self-assembled InAs quantum dots grown by various growth techniques

The properties of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy on GaAs substrates were investigated. The surface properties of samples were monitored by reflection high-energy electron diffraction to determine growth. Photoluminescence (PL) and transmission electron microscope (TEM) were then used to observe optical properties and the shapes of the InAs-QDs. Attempts were made to grow InAs-QDs using a variety of growth techniques, including insertion of the InGaAs strained-reducing layer (SRL) and the interruption of In flux during QD growth. The emission wavelength of InAs-QDs embedded in a pure GaAs matrix without interruption of In flux was about 1.21 μm and the aspect ratio was about 0.21. By the insertion InGaAs SRL and interruption of In flux, the emission wavelength of InAs-QDs was red shifted to 1.37 μm and the aspect ratio was 0.37. From the PL and TEM analysis, the properties of QDs were improved, particularly when interruption techniques were used.     

Properties of InGaN/GaN quantum wells and blue light emitting diodes

We have reported the effects of growth interruption time on the optical and structural properties of high indium content In_xGa_1−xN/GaN (x>0.2) multilayer quantum wells (QWs). The InGaN/GaN QWs were grown on c-plane sapphire by metal organic chemical vapor deposition. The interruption was carried out by closing the group-III metal organic sources before and after the growth of the InGaN QW layers. The transmission electron microscopy (TEM) images show that with increasing interruption time, the quantum-dot-like region and well thickness decreases due to indium reevaporation or the thermal etching effect. As a result the photoluminescence (PL) peak position was blue-shifted and the intensity was reduced. The sizes and number of V-defects did not differ with the interruption time. The interruption time is not directly related to the formation of defects. The V-defect originates at threading dislocations and inversion domain boundaries due to higher misfit strain. Temperature dependent PL spectra support the results of TEM measurements. Also, the electroluminescence spectra of light-emitting diode show that dominant mechanism in InGaN/GaN QWs is a localized effect in the quantum-dot-like regions.     

供应中断下具有随机需求的闭环供应链最优差别定价模型

研究了在供应中断下具有随机需求的闭环供应链系统的最优差别定价模型.基于博弈论的理论和方法分别在集中式和分散式决策情形下,确定了最优批发价、最优销售价、最优订购量及系统利润.最后通过数值例子对最优差别定价模型进行了实证分析.     

Hardware and a Memory Resident Program for Simultaneous Control and Switching of Pulsed Field Gel Electrophoresis

Abstract

We describe here the automatic switching of the electric field for PFGE systems to simultaneously control at least two PFGE experiments. For this purpose an IBM interface card was designed, that demands the execution of a specially programmed service routine based on the interruption technique. The interface card is commanded by a software program that contains a memory resident module to report the status of the electrophoresis. The approach also allows the construction of simpler switching units than those currently used. The system facilitates the study of DNA migration under different electrode geometries without disturbing the computer routine tasks. The system was validated by running simultaneously Saccharomyces cerevisiae chromosomes and λ Hind III restriction fragments in CHEF and TAFE systems.

     

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提出一种基于双缓冲的中断式数据采集、文件分割式存储以及文件合并式数据显示方法,解决了EAST低杂波系统数据量大幅增加后数据采集、储存和显示的问题。此方法在首次EAST低杂波放电中的应用令人满意。     

The Electroluminescence Characterization of Poly(p-phenyleneethynylene)——The π-conjugated Backbone Interrupted by a Butylene Unit

IntroductionSince the firstreport in1 990 of the electro- lu-minescence of the conjugated polymers in the filmof poly(p- phenylenevinylene) sandwiched betweenan anode and a cathode of appropriate work func-tions[1] ,enormous efforts have been devoted to thesynthesis of light emitting polymers[2— 4 ] .Owing toconjugated polymers′ photoluminescence and elec-troluminescence having been found out,their im-portant properties,polymer processability,bandgap tunability and mechanical flexibility mak…