新技术改善光纤通讯质量

新一期的《自然一光子学》报道了一种新技术可改善光纤通讯系统中的数据传输速率和发射距离。该技术可减少光纤长距离连接传输中的光学数据信号失真损失量，进而改善在此基础上的全球网络和声音数据的传输质量。与以往利用单个光束编码数据不同，XiangLiu等人采用了两种特制的“相位共轭”光束，这两种光束能有效地起到相互镜像的作用。因为任何失真在这两束光中将表现出相反的形式，     

Searching for Flavor-Changing Neutral-Current Signals via e＋e-（γγ） →tcht0 in Topcolor-Assisted Technicolor Model

In the context of the top-color-assisted technicolor （TC2） model, the flavor-changing neutral-current （FCNC） interaction induced by the top-higgs （hOt） are predicted at tree level. We study the relevant processes of e＋e-（γγ）→tcht0 at the International Linear Collider （ILC）. It is found that these rare processes production rates can be enhanced significantly in the TC2 model. Especially for the process γγ→tcht0, the total cross section will reach a few fb in the reasonable parameter space. We also calculate the distributions of transverse momenta, pseudo-rapid and invariant mass of the top-higgs. In view of the main decay modes of top-higgs for mho 〈 2mr, we find that there will be several hundreds FCNC events produced at the ILC with annually integral luminosity of 500 fb-1. Due to the clean background, such FCNC signals can possibly be detected at the ILC.     

Negative Resistance in a Two-Dimensional System with Entropic Barrier

A phenomenon of negative resistance is found in two-dimensional bistable and periodic potentials via Langevin simulation, where output quantities for noise and signal driven system, such as the power-spectrum density modulus and the signal power amplification, can become minima at finite temperatures. In such a system, the curvature of the potential along non-transport degree of freedom at the barrier is larger than that at the local minima. The temperature-dependent effective barrier, i.e. entropic barrier, is introduced via integration over the non-transport variables. The system shows the negative resistance because of the competence between the signal and the entropic barrier.     

微弱信号检测讲座：第五讲 超导电子器件在微弱电磁信号检测中的应用

超导电子器件是一种低温电子器件,它是基干约瑟夫森(Josephson)效应而研制成功的一种新型电子器件.它的基本结构如图1中的插图那样,是一个具有三层结构的二端器件,其中S1和S2是两块超导体。中间由一薄层绝缘体隔开,这层绝缘体的厚度只有几nm. 一、超导电子器件的特性 1.它的直流 I-V 曲线如图1中的曲a　所示.如果逐渐增大通过此二端器件的电流,那么在开始时,器件两端电压为零;当通过的电流达到Ic时,电压从零跳到Vg;当电流继续增大时,电压沿着一条二次曲线上升.如果在此二端器件上加一个直流磁场,则 Ie会减小;当磁场从零增加到某个值Hl时…     

ZJ-1型桩基质量检测仪

由中国科学院武汉岩土力学所-室断裂力学组和中国科学院声学所十一室地声组联合开发的ZJ-1型桩基质量检测仪,具有完备的检测功能和先进的分析处理软件、能对桩基质量进行现场检验并即刻给出检验结果。现将仪器的主要性能等指标简述于下。     

Cr（V）与H2络合物的EPR信号

Cr交换丝光沸石在氢气氛中强烈还原并冷却后,出现了一个各向同性的EPR信号,g值2.003,△H_PP 13.4 gauss.采用EHMO方法计算了各种可能模型化合物的g值,结果建议这一信号对应Cr(V)与H₂分子形成的络合物。     

加性信号调制下指数形式关联噪声驱动的单模激光的光强关联时间

采用线性化近似,计算了加性信号调制下的由具有指数关联的两白噪声驱动的单模激光增益模型的光强关联时间.发现两噪声间关联程度对光强关联时间随噪声强度的变化曲线有很大的影响,两噪声间关联程度取不同值时,光强关联时间随噪声强度的变化曲线中将出现极大值(即出现共振) 或极小值(即出现抑制) .     

磁场对光抽运信号的影响

在做光泵磁共振实验时,分别研究了竖直线圈和水平线圈产生的磁场对光抽运信号的影响,并做出了它们之间的关系曲线.由此曲线计算了北京地磁场的垂直分量为(0.0881±0.0015)×10-4T,估算出北京地磁场的水平分量约为0.425×10-4T.同时,这项工作对于区分光抽运信号和磁共振吸收信号也有一定的帮助.     

Stochastic Resonance in an Asymmetric Bistable System Subject to Frequency Mixing Periodic Force and Noise

The phenomenon of stochastic resonance (SR) in an asymmetric bistable system subject to the multiplicative and additive white noises and two periodic fields is investigated. Using the two-state theory, analytic expressions of the signal-to-noise ratio (SNR) for fundamental harmonics and higher harmonics are derived. It is found that SR appears at both fundamental harmonics and mixed harmonics (of second- and third-order approximation).Moreover, the higher the order of mixed harmonics is, the larger the SNR values are. The effects of static asymmetry on the SNR (of second- and third-order approximation) are different, and the noise intensity ratio can enhance the SNR for higher harmonics.