Effect of photovoltage on current flow in metal-semiconductor schottky-barrier contacts

It is shown that changes in device characteristics and an increase in the light-to-electrical energy conversion efficiency in metal-semiconductor Schottky barrier contacts are associated with a peripheral electric field built into the contact. For contacts with longer perimeters, variations in device characteristics and the light-to-electrical energy conversion efficiency are significantly larger. Since the photovoltage and peripheral electric fields in the contact region are codirected with the intrinsic electric field of the space-charge region, contact illumination results in a larger increase in the “dead” zone in forward portions of current-voltage characteristics, a larger decrease in the effective Schottky barrier height, and an increase in the field electron emission. An increase in the reverse field emission under photovoltage leads to an increase in the recombination current in the space-charge region, which provides dc photocurrent flow in the circuit.     

基于2007-2013年COSMIC掩星数据的电离层振幅闪烁研究

利用2007-2013年的COSMIC掩星数据，分析了E区与F区电离层闪烁的变化特征.发现用闪烁出现频次、闪烁发生率以及闪烁强度来表征的电离层闪烁出现规律比较相似.E区电离层闪烁在夏季半球的中纬地区最强，其次是春秋季的低纬地区和冬季半球.就经度分布来说，春秋季E区电离层闪烁呈四波结构.对F区电离层闪烁来说:南美-大西洋扇区在12月至点最为显著；非洲和太平洋扇区在6月至点最为显著；大西洋扇区在春秋分季最为显著.极区也出现中等强度的闪烁，尤其在南半球的90°E~180°E扇区较为显著.高纬E区电离层闪烁强度随太阳活动的增强而增强，而低纬和南半球的中纬E区闪烁随太阳活动的增强而减弱.高纬和低纬F区闪烁随太阳活动的增强而增强，而中纬F区电离层闪烁对太阳活动无显著依赖关系.对于赤道区来说，北半球60°W~60°E经度区闪烁强度随太阳活动的变化最为显著，其次是南半球60°E~210°E附近；而对于高纬地区来说，F区闪烁强度随太阳活动的变化最为显著的区域在南半球60°E~210°E附近.     

Inventive payoff from R&D in Japanese industry: convergencewith the West

An attempt is made to determine if investment in R&D and the hiring of college-educated employees result in a higher rate of inventions. The relationship between the input of R&D and inventive output is studied in two samples of Japanese factories, 34 in 1982 and 44 in 1970. These results are compared with findings in a parallel American study. The correlations between R&D and inventive output are similar in Japan and America in the 1980s, despite some differences in the management of innovation in the two nations. Moreover, the most Westernized subsample of Japanese firms in the 1970s had correlations between R&D and invention similar to those observed in the American study. Thus, it is concluded that some degree of convergence may be taking place in R&D management strategies in the two nations     

Regulatory reform in the broadcasting industries of Brazil and Argentina in the 1990s

Regulatory reform has changed the organization of the broadcasting industry in Brazil and Argentina in the past decade. Although responding to a similar set of pressure, the pace, instruments, and character of reforms have been different in the 2 countries, resulting in media markets of diverse natures. This study argues that these different policy outcomes in the reform of broadcasting regulation in Brazil and Argentina reflect variations in three factors: the nature of the political system, the structure of the existing broadcasting industry, and the ideological legacy in the regulation of communication industries. The case of regulatory reform in the broadcasting industry illustrates different policy patterns in the restructuring of state-industry relations in communications and information technology industries in the 2 neighboring countries.     

重庆万盛采矿区内主要农作物的光谱测量和分析

矿山开采中产生的固体废弃物和废液会使矿区土壤中富集重金属元素,进而影响矿区内的农作物生长。选择重庆市万盛区矿区作为研究区,采集红薯和南瓜的实测高光谱数据和土壤样本的重金属含量数据。通过对土壤重金属含量和农作物的红边位置偏移进行相关分析,发现不同土壤重金属含量对研究区内主要农作物的影响是不同的。可以看出,在研究区内的两种主要农作物中,红薯对矿区土壤中的重金属Cr、Mn和Cd比较敏感,而南瓜则对以上三种土壤重金属具有一定的吸收和抵抗作用。该结果可以为万盛区矿区内农作物种植的选择提供理论依据。     

Growth of AlGaN epitaxial layers and AlGaN/GaN superlattices by metal-organic chemical vapor deposition

Special features of metal-organic chemical vapor deposition of AlGaN epitaxial layers and AlGaN/GaN superlattices either in an Epiquip VP-50 RP research and development reactor (for a single wafer 2 in. in diameter) or in an AIX2000HT production-scale reactor (for up to six wafers 2 in. in diameter) are stud-ied. It is found that the dependence of the aluminum content in the solid phase on the trimethylaluminum (TMA) flux in a reactor levels off; this effect hinders the growth of the layers with a high aluminum content in both types of reactors and is more pronounced in the larger reactor (AIX2000HT). Presumably, this effect is a consequence of spurious reactions in the vapor phase and depends on the partial pressure of TMA in the reactor. The aluminum content in the layers can be increased not only by reducing the total pressure in the reactor but also by increasing the total gas flow through the reactor and reducing the trimethylgallium flux. The approaches described above were used to grow layers with a mole fraction of AlN as large as 20% in the AIX2000HT production-scale reactor at a pressure of 400 mbar (this fraction was as large as 40% at 200 mbar). AlGaN layers with the entire range of composition were grown in the Epiquip VP-50 RP reactor.     

Fourth quarter 2009 IEEE communications surveys and tutorials

Welcome to the fourth issue of 2009 of the IEEE Communications Surveys and Tutorials. Paper in this issue survey the research effort in several areas such mobility in Wimax, mobility models in VANET, handoff in cellular networks, admission control in MANETS, physical impairments in optical networks, physical layer issues in the 802.11n standard as well as jamming in wireless sensor networks     

微视频在高校计算机操作性课程中的应用探究

微视频在学校各类教育中应用越来越普遍.依据微视频的教学特点,针对高校计算机操作性课程中存在的问题,本研究依据ADDIE模型和ARCS动机理论,探索构建微视频在高校计算机操作性课程中的教学应用模型,通过教学案例展示微视频在课堂应用中教与学的过程,利用微视频提高课堂教学质量.     

Lipid metabolic disorders in rats with a transplanted Pliss lymphosarcoma

Changes in biosynthesis of cholesterol and free fatty acids from 2-14C-acetate in the host liver and tumour tissue as well as concentrations of various classes of lipids in blood were determined in rats bearing the transplanted Pliss lymphosarcoma. The transplantation of the tumour stimulates cholesterol biosynthesis de novo in the liver, but produces no changes in the fatty acid synthesis. Tumour growth is accompanied by a progressive increase in the content of triglycerides and beta-lipoproteins with a parallel drop in the alpha-cholesterol level in the animal blood. The concentration of total cholesterol is of phasic character depending on the stage of tumour growth. The possible mechanisms determining such alterations in lipids metabolism are discussed.     

In situ off-axis electron holography of metal-oxide hetero-interfaces in oxygen atmosphere

Off-axis electron holography has been extended to in situ observations in gas atmospheres. The Yttria-stabilized zirconia (YSZ)-Pt hetero-interface was characterized by electron holography at high temperature in a vacuum and in an oxygen atmosphere. Analysis of the phase shift profiles revealed high mobility of anions in the oxide in the vicinity of the interface in the oxygen atmosphere. This would compensate for any increase in the number of oxygen vacancies in YSZ through the metal interface.     

Carrier heating in quantum wells under optical and current injection of electron-hole pairs

Carrier heating in GaAs/AlGaAs quantum wells (QWs) under optical interband pumping in the spontaneous-emission mode has been studied. The electron temperature was determined as a function of the pumping intensity. The effect of the electric field on the photoluminescence spectrum was examined. The change in the carrier concentration with the drive current in the spontaneous- and stimulated-emission modes in InGaAsSb/InAlGaAsSb QWs was determined from electroluminescence spectra. The rise in the temperature of hot carriers, which results in the increase in the carrier concentration with the drive current, was roughly estimated.     

微孔无铜原因分析与改善

文章主要分析了PCB制造过程中微孔出现孔无铜的各类原因以及改善预防措施,并且详细介绍了对于火山灰堵孔造成的微孔孔无铜的原因分析。     

Modulation of intersubband absorption in tunnel-coupled quantum wells in electric fields

Modulation of absorption of middle-infrared radiation in double tunneling-coupled quantum wells in longitudinal electric fields is studied. A specific feature of the quantum wells is the small separation in energy between the two lower levels. As a consequence, the levels may exhibit “anticrossing” even in low transverse electric fields. An interpretation of the change in intersubband absorption is suggested. The interpretation is based on the assumption that a transverse electric-field component may appear in the structure. The change in the absorption coefficient is calculated taking into account the redistribution of electrons between size-quantization subbands and the changes in the temperature of electrons in the subbands in the longitudinal electric field, as well as the changes in the optical matrix elements, the energies of transitions, and the concentrations of electrons in the subbands in the transverse electric field. The possibility of using the structure for the efficient modulation of middle-infrared light with the photon energy 136 meV is shown.     

氧含量对VO2-x晶格特性和结构相变影响的研究

采用沉淀法制备了氧含量不同的VO2-x纳米粉．对样品进行了差式扫描量热(DSC)、X-射线衍射(XRD)和透射电子显微镜(TEM)的测试，并结合第一性原理的计算结果，具体分析了氧含量对氧化钒纳米粉的晶格特性和结构相变造成的影响：缺氧样品中形成钒填隙，富氧样品中形成氧填隙，两种缺陷分别造成晶胞体积的膨胀；缺陷带来的各向异性造成晶粒形状的改变；同时，不同缺陷态造成的能带中电子状态的改变也可能成为影响氧化钒的结构相变特性的重要因素之一．     

Spectral quality of He-Zn II and He-Cd II hollow cathode metal vapor lasers in the magnetic fields

This paper reports the magnetic characteristics of the oscillation in the axial and transverse magnetic fields derived from the measurements for the oscillation spectra in the 492.4 nm He-Zn II, and in the simultaneously operating 537.8 and 636.0 nm He-Cd II hollow cathode lasers. The simultaneous oscillation in the He-Cd II lasers is compared to the monochromatic one in each wavelength. The experimental data in the magnetic fields are well explained by the theoretical treatment including not only Zeeman effects but also the plasma effects in which the excitation mechanisms are considered using the rate equations. The electron density in the laser plasma that depends on the magnetic fields plays an important role in the excitation mechanisms. This paper proposes that the magnetic characteristics will be used for the color control of a white light laser as well as for the improvement of the monochromaticity in the anomalously broadened lasers.     

Oxygen vacancy formation and the induced defect states in HfO2 and Hf-silicates – A first principles hybrid functional study

O vacancy formation and the associated electronic defect states in Hf-based oxides have been investigated over a wide range of compositions using first-principles hybrid density functional calculations. Based on the generated structure models, we have identified the most probable O coordination structures in amorphous HfO₂ and in Hf-silicates, respectively. Our calculations showed that the formation energies of O vacancy and the positions of the induced defect states in the band gap are largely dependent on the local structures of the vacancy site rather than on the compositions of Hf-silicates. Considering the measured valence band offset between Si and Hf-silicates, a considerable amount of O vacancies are likely to stay in the charge neutral state in Hf-silicates when the Fermi level lies in the band gap region of Si. Furthermore, the concentration of O vacancy in Hf-silicates was found to be much lower than that in HfO₂ when the Fermi level lies in/below the mid-gap region of Si. Consequently, the flat band voltage shift and the transient threshold voltage instability can be significantly reduced in Hf-silicates in comparison to that in HfO₂, indicating that the presence of a Hf-silicate layer in between the gate oxides and the Si substrate could be beneficial to the performance of the CMOS device.     

无人作战模拟仿真中的VV＆A

根据无人作战模拟研究、开发过程中分队级作战单位建模与仿真环节上所存在的VV&A问题,从军事建模的过程与军事工程技术的角度出发,将一般仿真过程中的VV&A技术与军事作战模拟的特点以及无人作战模拟的特殊性三者有机的结合在一起,深入的探讨了在无人作战模拟仿真过程中VV&A问题的解决办法以及实现过程。通过对无人作战模拟仿真中VV&A的研究与解决,为今后的作战模拟,特别是无人作战模拟中如何解决建模及仿真过程中所存在的类似问题提出了一套系统的、科学的实现办法,具有一定的理论及实践意义。对于我军无人作战研究的深入开展以及跨越式发展具有一定的参考价值。     

Analysis of the variation in the composition as a function of growth parameters in the MBE growth of indium doped Hg1−xCdxTe

Compositional changes induced in growing Hg_1−xCd_xTe layers as a function of the changes in temperature of the indium source in the MBE chamber have been analyzed in terms of the Hg-In alloy thermodynamics and changes in the activity of indium over the growing films as the Hg flux changes. Compositional changes induced by changes in the Te source temperature have been analyzed in terms of the changes in the activity of Cd over the growing layers. These analysis are helpful in understanding the compositional changes with variation of the growth parameters in the MBE chamber.     

扬声器单元TS参数偏差对系统频率响应曲线的影响

在闭箱、开口箱、被动辐射体箱和带通箱系统的设计中,人们已认识到单元的TS参数和箱体的声学参数有紧密的配合关系。一旦箱体的结构设计有所确定,安装在箱体上的扬声器单元的TS参数也必须确定,这样,系统的低音频特性就因此而定。但是在批量投产时,TS参数的偏差将对系统的低音频特性产生变化。以开口箱的系统频率响应曲线为分析目标,要观察TS参数的偏差所产生的变化。为此,采用LEAP5扬声器设计软件作相应的模拟,证明只要TS参数的偏差在一定的范围内,频率响应曲线的变化也可以维持在一个偏差带内。这样,可根据系统的技术指标来确定TS参数的偏差。     

A comparison of Japanese and US high-technology transfer practices

Some empirical results and observations are presented which describe the principal ways in which a sample of industrial researchers in Japan and in the US utilize certain technologies resulting from university research. The findings are from a survey conducted in Japan and the US between October 1986 and December 1987. These results indicate that personal communications and technical collaboration are the key factors in the rapid diffusion of research results in both countries, and that in Japan, government agencies and professional societies take a much more active role in organizing and energizing the civilian technology-transfer process than do counterpart organizations in the US