Decision threshold adjustment in class prediction

Standard classification algorithms are generally designed to maximize the number of correct predictions (concordance). The criterion of maximizing the concordance may not be appropriate in certain applications. In practice, some applications may emphasize high sensitivity (e.g., clinical diagnostic tests) and others may emphasize high specificity (e.g., epidemiology screening studies). This paper considers effects of the decision threshold on sensitivity, specificity, and concordance for four classification methods: logistic regression, classification tree, Fisher's linear discriminant analysis, and a weighted k-nearest neighbor. We investigated the use of decision threshold adjustment to improve performance of either sensitivity or specificity of a classifier under specific conditions. We conducted a Monte Carlo simulation showing that as the decision threshold increases, the sensitivity decreases and the specificity increases; but, the concordance values in an interval around the maximum concordance are similar. For specified sensitivity and specificity levels, an optimal decision threshold might be determined in an interval around the maximum concordance that meets the specified requirement. Three example data sets were analyzed for illustrations.     

放大器静态工作点的正确测量

分析并纠正了放大器静态工作点测量中存在的问题     

PCB材料相关温度及其测试的释疑

随着电子产品的功率增加、密度提高和可靠性要求的提高,PCB基材的热特性也日益被关注。在此,我们对于几个与温度相关的术语及其测试方法作出了较为详细的解释,希望能对大家正确选用板材有所帮助。     

3G时代运营商攻守结合的全业务竞争策略

本文以产业大融合的趋势为出发点,结合英国电信、Vodafone、法国电信、软银等国际先进运营商成功经验,深入分析3G时代运营商为适应来自产业内外的竞争压力,如何实施攻守结合的全业务竞争策略.     

Multi-layer protruded electrodes for reducing the operating voltage and gamma shift of fringe-field switching LCDs

ABSTRACT

To reduce the operating voltage and gamma shift of the nematic liquid crystal display (LCD), a single-domain-protruded fringe-field switching (PFFS) electrode structure is designed. In this work, a kind of nematic liquid crystal (NLC) is introduced firstly. Then, the operating voltage and gamma shift of the proposed PFFS LCD are investigated under various electrodes’ parameters. Besides, its light leakage and contrast ratio are also discussed. The results show that the operating voltage of the PFFS LCD is only 1.40 V, here the electrodes’ width is 2 μm and electrodes’ gap is 4 μm. The gamma shift of the PFFS LCD can be reduced to the indistinguishable level under various electrodes’ sizes, if the height of the insulation layer is proper. For contrast ratio, it is larger than 200:1 at full viewing-angle, and the zone of 500:1 covers 60° polar angle.     

Experimental investigation of impact of environmental temperature and optimal baseline for thermal attenuation in structural health monitoring based on ultrasonic guided waves

Structural health monitoring (SHM) of any mechanical component is compulsory for its efficient and long-term performance. One of the major challenges to apply SHM technique in real-time inspections is variation in environmental and operating conditions (EOCs). Sometimes the effect of this variation in EOCs is so severe that it influences the SHM system’s response and reduces the accuracy of the inspection process. The goal of current research is to investigate experimentally the impact of environmental temperature on the ultrasonic guided wave signal during damage detection. According to the characteristic of breathing phenomenon of fatigue crack caused by the applied temperature (30 °C–180 °C) under operation condition, behavior of reflection and transmission signal is analyzed in terms of amplitude and group velocity. Based on experiment findings, a wave velocity function has been generated in the Matlab® environment to compute the velocity of acquired signal considering the effect of both temperature and excitation frequency. A corresponding sequence curve is drawn which illustrates that the proposed function is valid when the operating temperature is less than 130 °C because sensor bonding’s characteristics are affected by the further increment in temperature and consequently it would become difficult to illuminate the sole impact of temperature on damage detection results. Impact of temperature on examined material properties and sensor’s bonding strength is also observed in the current study. Analysis of dispersion curves is performed to examine the individual behavior of S0 and A0 wave modes with temperature and to determine the temperature invariant points to reduce the influence of environmental temperature in SHM. Hence current study not only evaluates the impact of temperature on damage detection but also provides an optimal baseline for thermal attenuation in real-time ultrasonic guided wave inspections.     

中小企业信息化现状及电信运营商的对策探讨

通过对无锡市中小企业的信息化现状进行调查分析,指出了信息化建设中存在的问题,并探讨了电信运营商介入中小企业信息化市场促企业转型的相关对策。     

通信电源系统在移动基站中的常见问题及处理办法

通信电源系统是移动通信基站中的一个重要组成部分,本文将通信电源系统在作者平时的工作过程中一些常见的问题及处理方法进行阐述.     

电信行业能否拯救地球？

近年来，有关全球变暖的原因开始显得越发明显，特别是对温室效应来说。四大商业因素——建筑，履行，交通，以及食物（肉制品极其重要）——占据了全球能源消耗以及二氧化碳排放的四分之三。通讯技术无力独自改变现状，但ICT却是未来低碳世界的一个关键。就中短期而言，我们相信ICT可以提供5％-20％的削减量。最近的研究表明，在全球变暖中，ICT的直接二氧化碳排放量大概占据2％的份额。其中移动通讯占了0．2％，而固定电话（包括宽带）则是0．3％。就全球变暖而言，ICT领域中，电脑以及互联网（特别是数据中心）才是最大最重要的肇事者。     

江苏电信BSS1.0系统软件体系结构

本文介绍了中国电信业务支撑系统的产生由来以及老“97”系统所具有的缺陷。着重阐述了BSs的整体框架，并从客户层、接入层、表示层、业务逻辑层、数据层等五个层面结合图示进行论述。此外从技术角度分析了J2EE多层体系结构在承载电信业务方面所具有的优势。