The long and short of channel length

In this article, the powerful shift-and-ratio method proposed by Taur of IBM Corp. [1992] is used to accurately determine effective channel length and mobility of deep-submicron devices. We show that the extracted low field mobility of a short-channel device as a function of gate voltage is consistent with that of a long-channel device. Since in the BSIM3v3.2 industrial standard model a universal low field mobility is used for devices of various sizes, the shift-and-ratio method is particularly suitable for determining accurate effective channel length that leads to a consistent mobility value     

Gain-clamped fiber amplifier with a short length ofpreamplification fiber

Although gain-clamping an erbium-doped fiber amplifier (EDFA) by a counterpropagating ring resonator prevents oscillation light from being output, it degrades the amplifier's noise figure. The noise figure degradation can be reduced by using a length of EDF, that is short enough not to cause any gain saturation, for preamplification. Experiments confirm that the prestage EDFA reduces the noise figure degradation under constant gain operation     

Input impedance of arc antennas and short helical radiators

The problem of the input impedance of curved wire antennas is generally formulated in terms of an integral equation. A stationary formula is used in evaluating the input impedances of arc antennas and short helical radiators of which the cylindrical antenna is a special case. The computational results are presented in graphical form. The impedance characteristics of these curved antennas are discussed.     

Evaluation of short pulse and short time thermal transient measurements

Thermal transient recording and the time constant spectrum analysis are widely used methods in the thermal testing and qualification of IC packages. A limitation of these methods is that recording of the complete transient response requires long time. This limitation, however, can be overcome by sophisticated procedures. The first method is to apply short power pulse for excitation; the second one is the interruption of the transients long before the thermal equilibrium is reached. The paper offers algorithms to evaluate these short pulse and short time measurements. The presented methods are suitable if the extraction of the little time constants is needed. This is the case if the transient method is used e.g. for die attach quality checking.     

Experimental measurement of vacuum arc current chop

The rapidity of a current "chop," occurring when a vacuum arc spontaneously extinguishes, is measured for a low current tungsten arc. The time required for cessation of the arc is found to be 2-5 ns. An estimate of chopping current verifies the notion that a minimal current is necessary for the existence of an arc.     

A new Josephson junction with a very short barrier length and a very low capacitance

Josephson junctions of a new geometrical structure were fabricated and have turned out to be of good quality. They are almost-planar niobium-based bismuth-barrier Josephson junctions which have a barrier length of 75 nm and a capacitance of 0.04 pF. The amplitudes of the zero-voltage current and microwave-induced constant-voltage current steps periodically vanish several times as the power of the applied microwave radiation increases monotonically. The junctions suffer from no degradation due to interdiffusion of metals at room temperature. They are very resistant to unavoidable electrical pulses.     

Radiation from a short dipole or monopole near a thick conducting cylinder of resonant length

Using a theoretical-numerical technique involving the magnetic field integral equation, the radiation fields are determined for configurations comprised of a centrally located dipole and a thin quarter-wave monopole near conducting cylinders of finite lengths. Such configurations are important since they give measures of the radiation effects of fuselages of aircraft or other structures which the cylinders may model. The radiation fields are determined in the three principal planes for wavelengths passing through the resonant length of the cylinder, i.e.,L approx lambda. The radiation patterns for both the dipole and monopole sources when normalized with respect to one another are similar to within approximately 1 dB. The vertically polarized patterns in the horizontal plane (the plane orthogonal to the dipole axis and containing the cylinder axis) show small deviations from their near omnidirectional characteristics for cylinder electrical lengths of 0.5, 1.0, and1.5lambda. On the other hand, the cross polarized component (the horizontal component) in the same plane shows a substantial enhancement of the intensity of the lobe structure at resonance. The patterns are compared to those acquired experimentally in an anechoic chamber and close agreement is demonstrated.     

Modal interference in a short fiber section: Fiber length, spliceloss, cutoff, and wavelength dependences

When a short fiber section is inserted within a fiber link, it is known that modal interference can create periodic oscillations in the wavelength dependence of the insertion loss and, accordingly, the insertion loss can exceed the sum of the interconnection losses (in decibels). This modal interference phenomenon is a potential cause of noise in telecommunications transmission systems. Experimental and theoretical investigations were performed in order to better understand its dependences on relevant fiber parameters and to generate engineering guidelines to minimize it in a telecommunication link     

电弧炉电气系统的建模与谐波电流研究

电弧炉是一种不平衡、非线性、时变负载,给电网带来了严重的电能质量问题。基于电弧弧长随机特性和电弧炉电气系统实际运行环境,使用简化的电弧电流电压特性得到了交流电弧的等效电阻数学模型,应用Matlab/Simulink软件仿真验证了该模型的正确性。然后建立了三相非线性时变电弧炉电气系统的仿真模型,并且对电弧炉电气系统进行谐波分析,采用无源滤波器抑制谐波,仿真结果表明该模型能有效地减小谐波总失真率、改善电能质量。     

The current status and future prospects of kesterite solar cells: a brief review

Kesterite‐based solar cells are attracting considerable attention in recent years, owing to the reduced toxicity and greater abundance of their constituent elements. In this brief review, we discuss the current status of this important technology by focusing on three key aspects of the device: (i) the interface between the kesterite absorber and the Mo back contact, (ii) the kesterite absorber bulk defects and grain boundaries and (iii) the interface between the kesterite absorber and the buffer layer. By identifying key issues to be addressed, we provide suggestions for their potential improvement and future research. Copyright © 2016 John Wiley & Sons, Ltd.     

Reverberation-chamber research-then and now: a review of early workand comparison with current understanding

The heart of this paper is an English translation (from the original Italian) of an early (1976) paper. Interspersed with this translation is an original critical review (printed in normal text) of the paper. Much of the current theory, models, and analysis techniques associated with reverberation chambers can be directly traced to the original paper by Corona and Latmiral (1976). The paper also contained a number of interesting suggestions and applications that would make excellent research topics. The original paper is considered a classic, even though (prior to this publication), an English translation is difficult to locate and reference. Publication of this translation will help establish some of the origins of reverberation-chamber concepts that we now take for granted     

短时间测量实验装置的设计分析

本文主要对时间测量技术进行分析,主要采用游标法来进行短时间测量实验装置分析,并且结合振荡器振荡周期测试与其他测试内容,从而对短时间测量装置的进行分析,便于该装置能够应用于科学实验中.     

低边与高边电流检测

目前,电子系统的电源管理芯片通过有效的功率分配优化系统效率.这种管理方式的关键是电流检测,它不仅能帮助系统维持所需要的功率电平,还可通过伺服调整来维护电子系统的正常运行,防止电路失效和电池过放电. 电流检测有两个基本方法,可以测量载流导体的磁场,也可以在电流回路插入一个小电阻并测量其两端压降.第一种方法没有强行插入元件或引入插入损耗,但价格相对昂贵,而且容易导致非线性和温度系数误差.因此,磁场检测虽然避免了插入损耗,但由于其高成本,在具体应用中受到很大限制.     

高码率短码长两边类型LDPC码的设计

高码率LDPC（10w．densityparity-check）码的设计一直是当前纠错编码领域的难点,尤其在短码长情况下。近年被提出的两边类型LDPC（tow—edgetypeLDPC,TET-LDPC）码在高码率情况下具有比传统LDPC码更加优秀的纠错性能。基于对TET—LDPC码结构优势的分析,文中提出一种优化设计方法,该方法通过合理选取TET．LDPC码中删余变量节点的度以及优化校验节点和变量节点的连接关系,进一步提高了该码型的性能。仿真结果显示,在AWGN信道下,文中设计的高码率短码长TET—LDPC码,不仅好于传统LDPC码,而且也好于传统的TET-LDPC码,具有更低的误码平台。     

Suppression of transverse modes of a CW CO2laser by cavity length control

The described technique of transverse mode control makes use of the small transition linewidths of the CW CO2laser. The laser medium itself is used for spectral discrimination. The method was tested and found to be superior to the usual technique of using an intracavity iris.     

高码率短码长两边类型LDPC码的设计

高码率LDPC(low-density parity-check)码的设计一直是当前纠错编码领域的难点,尤其在短码长情况下。近年被提出的两边类型LDPC(tow-edge type LDPC,TET-LDPC)码在高码率情况下具有比传统LDPC码更加优秀的纠错性能。基于对TET-LDPC码结构优势的分析,文中提出一种优化设计方法,该方法通过合理选取TET-LDPC码中删余变量节点的度以及优化校验节点和变量节点的连接关系,进一步提高了该码型的性能。仿真结果显示,在AWGN信道下,文中设计的高码率短码长TET-LDPC码,不仅好于传统LDPC码,而且也好于传统的TET-LDPC码,具有更低的误码平台。     

Progress and feasibility for a unified standard for frequency, time, and length

The recent successful extension of frequency synthesis upward in the infrared to the 88-THz frequency of the very stable methane frequency standard has implications for expanded uses of frequency/time metrology and hence of frequency/time dissemination systems. After further refinements of the infrared frequency synthesis techniques, metrologists will have the opportunity to define a value for the speed of light and to use a particular frequency standard --the most accurate one--as a unified standard for frequency, time, and length.     

Stochastic behaviour of a two-unit cold standby system with three modes and allowed down time

This paper discusses the stochastic behaviour of a two-unit cold standby redundant system under two very general sets of conditions: (i) each unit of the system having three different modes of working—normal, partial failure and total failure; (ii) breakdown of the system occurring when with both the units in total failure mode, the system is not regarded as failed (the system fails only when the breakdown does not terminate within the allowed down time). Failure-time distributions of units are exponential, whereas repair time distributions are arbitrary. Several reliability characteristics of interest to system designers as well as operations managers have been evaluated.