A generalized Norde plot for reverse biased Schottky contacts

When a metal makes intimate contact with a semiconductor material, a Schottky barrier may be created. The Schottky contact has many important applications in the integrated circuit (IC) electronics field. The parameters of such contacts can be determined from their current-voltage (I-V) characteristics. The literature contains many proposals for extracting the contact parameters using graphical methods. However, such methods are generally applicable only to contacts with a forward bias, whereas many Schottky contacts actually operate under a reverse bias. Accordingly, the present study proposed a generalized reverse current-voltage (I-V) plot which enables the series resistance, barrier height, and ideality factor of a reverse biased Schottky contact to be extracted from a single set of I-V measurements. A theoretical derivation of the proposed approach was presented and a series of validation tests were then performed. The results show that the proposed method is capable of extracting reliable estimates of the contact parameters even in the presence of experimental noise.     

利用光纤光栅实现压力和温度同时测量

结合光纤光栅弹簧管压力传感器的结构特点 ,在悬臂梁的上下两面分别粘贴两个应力和温度灵敏系数基本相同的光纤光栅 ,通过分别测量光纤光栅对的波长位移 ,实现了压力和温度的同时测量 ,压力和温度测量的分辨率分别为 0 .1 4 MPa和 0 .5℃ .     

Forecasting time‐varying covariance with a robust Bayesian threshold model

This paper proposes a robust multivariate threshold vector autoregressive model with generalized autoregressive conditional heteroskedasticities and dynamic conditional correlations to describe conditional mean, volatility and correlation asymmetries in financial markets. In addition, the threshold variable for regime switching is formulated as a weighted average of endogenous variables to eliminate excessively subjective belief in the threshold variable decision and to serve as the proxy in deciding which market should be the price leader. The estimation is performed using Markov chain Monte Carlo methods. Furthermore, several meaningful criteria are introduced to assess the forecasting performance in the conditional covariance matrix. The proposed methodology is illustrated using daily S&P500 futures and spot prices. Copyright © 2010 John Wiley & Sons, Ltd.     

Multiple phosphoglucomutase alleles in two species ofMansonia mosquito

Summary Multiple phosphoglucomutase (E.C.2.7.5.1) alleles are found in the mosquitoesMansonia crassipes andM. uniformis. The present study reveals 4Pgm alleles, of whichPgm ^B andPgm ^C are common to both species whilePgm ^A is present only inM. crassipes andPgm ^D only inM. uniformis. The frequencies in both species accord well with Hardy-Weinberg expectations. The most frequent allele is that controlling a phenotype with an intermediate electrophoretic mobility, viz.Pgm ^B inM. crassipes andPgm ^C inM. uniformis.This work is supported in part by a University of Malaya research grant to the senior author.     

Cbl-b regulates the CD28 dependence of T-cell activation

Whereas co-stimulation of the T-cell antigen receptor (TCR) and CD28 triggers T-cell activation, stimulation of the TCR alone may result in an anergic state or T-cell deletion, both possible mechanisms of tolerance induction. Here we show that T cells that are deficient in the adaptor molecule Cbl-b (ref. 3) do not require CD28 engagement for interleukin-2 production, and that the Cbl-b-null mutation (Cbl-b(-/-)) fully restores T-cell-dependent antibody responses in CD28-/- mice. The main TCR signalling pathways, such as tyrosine kinases Zap-70 and Lck, Ras/mitogen-activated kinases, phospholipase Cgamma-1 and Ca2+ mobilization, were not affected in Cbl-b(-/-) T cells. In contrast, the activation of Vav, a guanine nucleotide exchange factor for Rac1/Rho/CDC42, was significantly enhanced. Our findings indicate that Cbl-b may influence the CD28 dependence of T-cell activation by selectively suppressing TCR-mediated Vav activation. Mice deficient in Cbl-b are highly susceptible to experimental autoimmune encephalomyelitis, suggesting that the dysregulation of signalling pathways modulated by Cbl-b may also contribute to human autoimmune diseases such as multiple sclerosis.     

Generation and detection of phase-coherent current-driven magnons in magnetic multilayers

The magnetic state of a ferromagnet can affect the electrical transport properties of the material; for example, the relative orientation of the magnetic moments in magnetic multilayers underlies the phenomenon of giant magnetoresistance. The inverse effect--in which a large electrical current density can perturb the magnetic state of a multilayer--has been predicted and observed experimentally with point contacts and lithographically patterned samples. Some of these observations were taken as indirect evidence for current-induced excitation of spin waves, or 'magnons'. Here we probe directly the high-frequency behaviour and partial phase coherence of such current-induced excitations, by externally irradiating a point contact with microwaves. We determine the magnon spectrum and investigate how the magnon frequency and amplitude vary with the exciting current. Our observations support the feasibility of a spin-wave maser' or 'SWASER' (spin-wave amplification by stimulated emission of radiation).     

Rayleigh backscattering: a method to highly compress laser linewidth

Ultra-narrow linewidth laser with several hun- dred hertz at room temperature has attracted a great deal of attention in recent years and played a critical role in both optical sensing and communication fields. In this paper, a new method based on Rayleigh backscattering to highly compress the laser linewidth was proposed and demon- strated theoretically and experimentally. By theoretical analysis and simulation, Rayleigh backscattering can be collected in any waveguide structure and all wave bands, which could have a revolutionary impact on the field of laser. A single-longitudinal mode fiber ring laser with 130-Hz linewidth was achieved with self-injection feed- back structure at normal atmospheric temperature. The linewidth compression based on Rayleigh backscattering lies in the fact that laser linewidth after scattering is narrower than that of incident light in high Rayleigh scattering structure. The self-rejection feedback method expanding free spectra range of laser cavity simultaneously was used to further suppress the mode-hopping and stabilizing output. Experimental results showed that the laser linewidth can be easily narrowed to hundreds of hertz with side-mode suppression up to 75 dB. This agrees with the theoretical analysis and simulation results qualitatively.     

An integration model for manpower forecasting

Manpower forecasting has made significant contributions to human resource management. Due to difficulties in collecting the required data for making appropriate analysis, most studies in the literature concentrate on forecasts of individual firms. This paper presents a regression model which utilizes the data of large firms to draw inferences to the demands of other firms. More specifically, a regression model showing the negative relationship between the rank of a firm and its associated demand is fitted to the data of a number of large manufacturing firms. The area under the regression line delineated by the y-axis is then an estimate of the total demand of the whole industry. Confidence intervals for the estimate can also be constructed. As an illustration, the demand for the industrial management manpower in Taiwan is forecasted by applying the proposed model.