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.     

A Strategy for Broad-Band Network Introduction in Italy

Studies are being carried out in Italy concerning the strategy for the introduction in the 1990's of optical fiber systems in the distribution network, in order to supply customers with broad-band services (in particular with video services). This paper deals with some of the main choices that are being done, in particular in view of a field trial which is planned in Rome in 1988.     

Analysis of stacked rectangular patch antennas with nonalignedpatches or unequal patch sizes

Using the spectral domain technique, changes in the characteristics of electromagnetically coupled stacked rectangular patch antennas due to variations in the alignment of patches and patch sizes are investigated. Some of the observations can be used in the design of these antennas in order to equalize the input impedances at the resonances, shift the resonant frequencies, broaden the bandwidth, and estimate changes in the radiation patterns. It is specifically shown that a displacement in the top patch in the direction of resonance can broaden the beamwidth in the E-plane at the upper resonance at the expense of some distortion in the radiation pattern     

LIBS水下原位探测技术研究进展

作为一种分析技术,激光诱导击穿光谱(Laser induced breakdown spectroscopy, LIBS)近年来在各个领域有着快速的发展, 在水下的应用也逐渐受到关注。对LIBS水下研究从实验室模拟到现场试验、从机理研究到技术发展都进行了回顾,并以 中国海洋大学研制的深海LIBS原位探测系统LIBSea为例,给出了LIBS系统在海洋探测中获得的典型结果,最后对未 来5~10年LIBS水下研究方向进行了展望。     

Alkaline phosphatase activity in the osteoclasts induced by experimental tooth movement.

The localization of alkaline phosphatase (Alpase) activity in the osteoclasts was examined cytochemically. Alpase activity was located in the basolateral membrane in mature osteoclasts having ruffled borders and clear zones, and also in the basolateral membrane in the osteoclasts lacking a ruffled border or a clear zone on the bone surface. But in the preosteoclasts situated away from the bone surface the enzyme activity was noted in the whole plasma membrane. These results suggest that the localization of Alpase activity may be altered in relation to the changes in morphology associated with the functional activity of the osteoclasts.     

我国边缘群体科普公正问题研究

本文分析了我国流动人口、妇女、残疾人、农村人口、贫困人群等科普边缘群体的状况和成因,指出科普边缘群体低层次的科学素养和知识习得状况暴露了严重的科普公正问题,政府和社会在国家科普政策和关注重心、科普资源分配、具体的科普实践和科普实效三方面缺乏或者难以实现科普公正,最后提出了4条实现科普公正的建议。     

欧洲科学商店及其启示

科学商店是荷兰在20世纪70年代创造的,现在已扩展到欧洲许多国家。科学商店不是传统意义上的商店,而是一种科学传播的理念和服务。它运用双向互动的科学传播创新机制,支持科研人员深入社区、拓宽研究范围;为社区居民提供科学和研究服务;为大学学生创造实践和了解社会的机会。参与科学商店研究项目的工作人员、科研人员、市民和其他专业人员都可以从中受益。我国的科普工作可以借鉴欧洲科学商店的运作机制和成功经验,在建立全社会支持科普工作的机制和网络、创新社区科学传播活动和提高公众的科学素质和参与度等方面进行思考和探索。     

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.     

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.     

Some practical aspects of digital transmission

There are three worlds of digital transmission?digital transmission as an area of academic research, in which theoretical limitations and complicated schemes of modulation and encoding play the starring role; digital transmission in exotic space and military applications, in which it is, or may seem to be, worthwhile to search through the noise in a huge bandwidth in order to receive a few bits per second; and the digital transmission of everyday bulk communication. This article is concerned with that third area, in which apparatus must be economical and reliable; in which the FCC limits the bandwidth we may use in radio transmission; in which the increase in attenuation with frequency limits the bandwidth it is practical to use in cable transmission; in which error rates should be low enough that error correction is an expedient that need be resorted to only in special situations.     

Absorption loss at high temperatures in aluminum- and copper-coated optical fibers

Thermally induced variations in the optical loss of optical fibers with metal (copper and aluminum) coatings are studied. It is demonstrated that an increase in the loss related to the OH groups depends on the medium in which the annealing takes place (an increase in the loss related to the OH groups in argon is greater than the increase in air) and on the dopant (an increase in the loss in the core doped with GeO₂ + P₂O₅ is greater than the increase in GeO₂).     

A New Approach of Overlay Method for Cognitive SW HARQ System

The aim of this paper is to obtain communication resource based on the overlay method for the secondary user (SU) in the primary communication environment operating in the Stop-and-Wait Hybrid Automatic Repeat Request (SW-HARQ) protocol. Unlike the overlay Cognitive Radio applications in the literature, in this work communication resources have been obtained for the SU in the time period in which the primary user (PU) is active in the channel. Our performance results have shown that a significant amount of sources of communication can be achieved for the SU by evaluating the waiting times in the primary SW HARQ periods, even when the PU is continuously running in the SW HARQ protocol without emptying the channel.

     

单目视觉目标观瞄光点实时定位方法

针对目标跟踪仿真系统中观瞄光点在数字仿真图像中的实时定位问题,提出一种基于单目视觉的光点实时定位方法。首先,采用卡尔曼滤波的方法对光斑在采集图像中的粗略位置进行预测;然后,在以此粗略位置为中心的光斑区域内采用基于Hessian 矩阵的方法对光斑中心坐标精确提取;最后,在建立有摄像机像平面上点到数字仿真图像上对应点的定位模型基础上,由提取的光斑中心坐标经定位模型求解实现光点定位。实验结果表明:该方法对光点定位的误差为0.4 pixel,且每帧图像的光点定位时间为0.32 ms。该方法可实现目标跟踪仿真系统光点的高动态、高精度实时定位。     

Relaxation l.s.a. mode in InP

What are believed to be the first convincing observations of relaxation l.s.a.-mode operation in InP are reported. Devices fabricated from vapour-phase epitaxial material have shown the characteristic `signatures? of the mode in oscillators operated in S- and X-bands. So far, conversion efficiencies have not exceeded those for comparable samples in GaAs, almost certainly owing to remaining material limitations in the relatively thick active layers. The significance of the results lies, in practical terms, in the promise of high-peak-power sources with acceptable efficiencies, and, in diagnostic terms, in the derived information on the magnitude of the fundamental transferred-electron characteristic peak/valley ratio in InP and in achievable material quality factors for thick epitaxial layers.     

The activity of nuclear endonucleases and topoisomerases in the liver of rats and in diethylnitrosamine-induced tumors

The DNA endonuclease (Aendo) and DNA topoisomerase (Atopo) activities in liver nucleus extracts of normal rats, in DENA-induced hepatomas and in liver tissues around tumours were investigated. The profile of nuclear endonucleases measured in the presence of 2 mM CaCl2 + 5 mM MgCl2, or 5 mM MnCl2, or 5 mM MgCl2, or 2 mM CaCl2 (pH 7.4), or I mM EDTA (pH 5.0) was different in normal and tumour tissues. Mn2+-dependent endonuclease was the main endonuclease in the tumour tissue, whereas Ca2+, Mg2+-dependent endonuclease was the main one in the normal liver and in the tissue around the tumour. An increase in the Mn2+-dependent endonuclease activity correlated with a decrease in the hepatoma differentiation level. Atopo of types I and II increased in the tissue around the tumour. Aendo and Atopo of cellular nuclei decreased in animals given DENA without the liver tumour.     

Latch-up and image crosstalk suppression by internal gettering

Internal gettering can be used to reduce crosstalk in imagers and latch-up susceptibility in CMOS circuits. The internal gettering process forms defects in the bulk of the silicon wafers that are effective recombination sites for minority carriers in the substrate. Experimental and theoretical results are presented for the crosstalk reduction obtained in an area imager. Also, the current gain β of the parasitic lateral n-p-n transistors formed in the substrate in CMOS circuits was considerably lower for the internally gettered wafers. The trigger current needed to initiate latch-up in the n-p-n-p structures increased as 1/β, in accordance with the theory. A Monte Carlo method was developed to calculate the expected lateral transistor current gain. The calculated β's are in excellent agreement with the measured values.     

In vivo lysis of tumor cells of varying degrees of immune resistance

Mouse tumour cell immune resistance in vitro and in vivo is compared. Cell lysis in the cytotoxic test was estimated in the first case, while the dynamics of elimination of the labelled 125I cells from the organism--in the second case. The lysis of cells in vitro and in vivo was found to correspond to 10 out of 11 studied cell lines of mouse tumours. However in spite of the similarity these methods are not identical, since there were cases when differences between certain cell lines were revealed in vitro but not in vivo, and vice versa.     

Influence of water absorption by silicate glass on the strains in passivated Al conductor lines

X-ray diffraction strain measurements and elastic recoil detection analysis of aluminum conductor lines, passivated with silicon oxide, showed that the absorption of water molecules in the passivation layer directly influences the strain state in the lines. Volume changes of the passivation due to water absorption lead to unusual strain states, where the line is strained in compression in the width direction and in tension in the height and length direction, with the largest component in the height direction. The process of water absorption, as well as the rearrangement of the strain components in the lines, was found to be reversible.     

东海有机碳存量估算

海洋有机碳存量估算对研究碳循环过程和预估气候变化趋势有重要的作用。海洋有机碳存量可以通过遥感反射率、水体光学特性等参数反演得到。根据东海水域的水体特性,对比了多种有机碳反演算法,并结合东海有机碳垂直分布情况,得到一套完整的东海有机碳存量估算模型。利用2010年MODIS提供的遥感反射率数据和Argo提供的温盐数据,对中国东海区域的有机碳储量分季节进行计算分析。结果表明东海全水柱有机碳储量在1.530×1014 g到2.125×1014 g之间,真光层有机碳储量在4.119×1013 g到7.980×1013 g之间。全水柱有机碳储量整体呈现冬季高、春季低的特点,真光层有机碳储量整体呈现夏季高、冬季低的特点。从2006年至2015年,有机碳存量呈波动上升趋势。对东海有机碳存量进行了较为准确的估算,为今后我国海洋碳储量的评估提供了可供参考的思路。     

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.