A new modified centroid classifier approach for automatic text classification

To enhance the automatic text classification task, this paper proposes a novel approach for treating the problem of inductive bias incurred by the centroid classifier assumption. This approach is a trainable classifier, which takes into account tfidf as a text feature. The main goal of the proposed approach is to take advantage of the most similar training errors in the classification model for successively updating that model based on a certain threshold. The proposed approach is practical and flexible to implement. The complete performance of the proposed approach is measured at several threshold values on the Reuters‐21578 text categorization collection. Experimental results show that the proposed approach can improve the performance of the centroid classifier better than traditional approaches (traditional centroid classifier, support vector machines, decision trees, Bayes nets, and N Bayes) by 1, 1.2, 4.1, 7.5, and 11%, respectively. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Perkins:发电设备市场的全方位供应商

Perkins一向致力提供最优质的发电用动力系统,多年来Perkins已成为低油耗、高功率发动机的同义词.4016-61TRG柴油发动机提供卓越的功率密度和紧凑尺寸,开发的目标是提供高性价比的常用及备用发电机的动力系统.     

A modified approach to transient stability enhancement with fast valving and braking resistor applications

Fast valving and braking resistor are two important members of the family of the discrete supplementary controllers (DISCOS). Both of these are very effective and economic means of transient stability enhancement under extreme contingencies. Being stationed at the similar end of a power system the two schemes carry a very good potential of an effective coordination. Such a coordinated control is helpful not only in obtaining an improved gain in stability, but also in overcoming the limitations and avoiding excessive duty on the part of an individual controller. In this work, a detailed study has been carried out to evaluate the scope and limitations of fast valving and dynamic braking resistor controls in enhancing the transient stability of power systems. Improvements have been suggested over the conventional schemes of control so as to improve their adaptability under different conditions of fault and loading or with different types of generating units.     

Silicone rubber dielectrics modified by inorganic fillers for outdoor high voltage insulation applications

The paper discusses the mechanisms by which inorganic fillers in silicone rubber dielectrics enhance the properties of thermal conductivity, relative permittivity, and electrical conductivity making them useful in outdoor high voltage insulation applications. The addition of alumina trihydrate or silica fillers to silicone elastomers, forming binary composites with enhanced thermal conductivity, is discussed in relation to filler type, particle size, shape, and concentration, and its use as a housing material for non-ceramic insulators to minimize material erosion at dry band arcing sites by lowering hot spot temperature. Also discussed is the enhanced relative permittivity of silicone dielectrics that is obtained through the addition of barium titanate powder which can be further increased with the addition of aluminium powder forming a tertiary composite, resulting in a significant grading of the surface electric field when applied as a housing material to high voltage bushings. Controlled electrical conductivity of silicone dielectrics is discussed through the use of antimony-doped tin oxide filler binary composites and when applied as a housing material to outdoor bushings, the pollution performance is greatly enhanced.     

Dielectric windows for UHF partial discharge detection

Increasing the permittivity of the propagation medium inside a hollow tube lowers its cut-off frequency, allowing it to transmit a wider range of signal frequencies. This principle is applied to the design of dielectric windows that can be used to facilitate partial discharge (PD) detection at ultra high frequency (UHF) in a HV metalclad plant such as gas-insulated substation (GIS), power transformers and circuit breakers. External UHF couplers mounted on such windows can be removed or replaced without compromising the integrity of the insulation system. By increasing the signal power level incident on a window-mounted external UHF coupler, higher sensitivity to PD can be achieved. The problem is analyzed using waveguide theory and, using GIS as an example, improvements of ≈6 dB are demonstrated by means of coupler sensitivity measurements and experiments using PD sources     

A robust algorithm for text region detection in natural scene images

In this paper, a new method for detecting text regions in natural scene images is presented. The proposed algorithm is based on the segmentation of objects in a scene, followed by the identification of text objects by a support vector machine (SVM). First, to segment objects in the scene, the input image is separated into chromatic and achromatic regions according to the distribution of red, green and blue (RGB) elements, and different clustering algorithms are applied. Second, each object is transformed into the wavelet domain for multi-resolution analysis, and moment features of the wavelet coefficients are used in the SVM for the classification of text objects. The proposed approach provides robustness to non-uniform illumination by using different clustering algorithms according to the characteristics of the colour components in the segmentation. Also, moment features, used for classification, are invariant to the size, direction, shape and other properties of texts. Experimental results demonstrate the effectiveness of this approach.     

一种改进的定时恢复方法

定时恢复是全数字接收机中的一项关键技术,以传统的Gardner定时恢复理论为基础研究了一种改进的定时恢复方法。该方法去掉环路滤波,改插值滤波器为多相滤波器,并对NCO和定时误差提取方法进行了改进。以16QAM为例对整个环路进行了仿真验证,该方法对载波相位不敏感,并且较传统Gardner插值算法简单易行。在满足准确性和速度的前提下,由于采用连续可变分数倍抽取技术,该方法在工程应用中可适用于每个符号非整数个采样点的信号的定时恢复,同时能有效避免多电平信号在采用Gardner算法估算定时误差时出现的局部抖动现象,适用于PSK、QAM信号的定时恢复。     

二进时间窗FFT谐波检测

电力系统中存在着各种频率的谐波,有工频整数倍的普通谐波,也有非工频整数倍的间谐波,要把电力系统中所有的谐波分量准确地测量出来有一定的困难,为提高谐波分析精度的同时提高谐波最小分辨率,基于传统的FFT谐波分析法,提出二进时间窗的FFT谐波检测算法,该方法充分考虑了计算时间及计算精度.实验结果表明,该方法可以在不明显增加硬件水平的条件下用最短的时间进行分析计算,即能保证谐波测量的精度,又能提高谐波测量的分辨率,对抑制电力系统中日益复杂严重的谐波污染,有一定的推广价值.     

A modified C-dump converter for variable-reluctance machines

A new type of converter for variable-reluctance-machine (VRM) drives is described. In this converter topology, the energy extracted from an ongoing phase is stored in a dump capacitor. The energy stored is consequently used either to quickly turn on the next ongoing phase or to energize the conducting phase frequently during the conduction interval instead of being returned to the supply as for a conventional C-dump circuit. Since, the additional switch used to pass the energy to the C-dump capacitor is switched under a relatively-low-voltage condition and its switching frequency is relatively low, the rating of the additional switch is modest. The major advantage os this converter is that it uses a low-switching device/phase ratio while achieving better performance characteristics than the other topologies     

A high-density heat-sink-mounted inductor for automotive applications

Passive components, and inductors, in particular, contribute greatly to the overall volume of power electronic converters. These components are normally packaged individually with little concern for the overall system. For high-density switching power supplies it is imperative to minimize the volume to as great an extent as possible which implies that the passive component volume usage needs to be improved. This can be accomplished by applying suitable packaging and cooling techniques to these components. In this paper, two inductor structures finding application in a 2.1-kW synchronous automotive converter are described. The air-gap placement, losses, cooling methods, and thermal profiles are analyzed and verified experimentally with an inductor designed for operation at 85/spl deg/C ambient.     

A modified sensitivity measure for linear digital systems

In this paper a new sensitivity measure for state space systems is proposed. This new measure is a modified form of Tavsanoglu and Thiele's measure but has three advantages: (1) it is more precise than Tavsanoglu and Thiele's measure when the parameters of the state space realizations contain 0 and ±1; (2) it can be used to explain why the sparse Schur and Hessenberg realizations can give better actual sensitivity performance than the corresponding fully parametrized optimal realizations; (3) it is identical with the global round-off noise gain G = tr(QW) + y obtained by Hwang under a dynamic constraint.     

A family of Wien-type oscillators modified for chaos

A family consisting of four Wien-type oscillator circuits are modified for chaos by direct replacement of one of the linear resistors with an asymmetrical-type non-linearity introduced by a junction field effect transistor (JFET) operating in its triode region and the addition of a single capacitor. The internal op amp dominant pole is found to play a major role in understanding the chaotic behaviour of the proposed circuits. Mathematical models that describe the observed behaviours are derived. The well known Wien bridge oscillator design equations are shown to be useful as a starting point for chaos modification. Experimental laboratory results, PSpice simulations and numerical simulations of the mathematical models are provided for this family of autonomous RC chaos generators. © 1997 John Wiley & Sons, Ltd.     

A lossless switching technique for smart grid applications

Smart grid is an upgrade of the existing electricity infrastructure in which integration of non conventional energy sources are an integral part. This leads to the introduction of harmonics and increased switching losses in the system. Thus there is a need of loss less switching techniques for smart grid applications. Switched mode power supplies (SMPSs) are being extensively used in most power processes [1]. Developments were carried out centered on hard switched converters, where switching frequency is limited to 10 s of kHz [2]. The uses of soft switching techniques, [3], [4], [5], [6] zero voltage switching (ZVS) or zero current switching (ZCS), is an attempt to substantially reduce the switching losses and hence attain high efficiency at increased switching frequency. The soft-switching topologies belong to families namely resonant load converters [3], resonant switch converters [2], [4], resonant transition converters [5], [6], and most recently active clamped PWM converters [7], [8], [9]. The active clamp topology adds an active clamp network, consisting of a small auxiliary switch in series with a capacitance plus the associated drive circuitry to the traditional hard switch converters. The proposed paper basically deals with the design, modeling and simulation of a ZVS–PWM active clamp/reset forward converter having features like zero switching power losses, constant frequency and PWM operation, Soft-switching for all devices and Low voltage stresses on active devices due to clamping action.     

基于改进的逆序排序法的机组组合优化算法

文章提出了改进的逆序排序法来求解机组组合优化问题.该算法从可用机组全投入运行这一可行解出发,在每次迭代过程中优化一台机组在整个调度周期内的开停状况,以最小化总生产成本或总购电成本,直到连续两次迭代的目标函数值不再减小为止.该方法的显著优点在于计算不会振荡,迭代不会发散,且每次迭代的结果均为可行解.该算法在单机组优化过程中,以机组的最小启停区间而不是单个时段为研究调度对象,缓解了组合爆炸问题,明显地加快了计算速度.     

A .NET solution for distributed computing applications

Distributed computing is used to solve computational complexity problems. This paper explores the suitability of the .NET platform and XML Web services for distributed computing applications. This study demonstrates the practical feasibility of a .NET Web-services application in distributed computing and it also exposes APIs on the Internet. Thus from the experimental results, the speed of the algorithm introduced by Web services are determined and the cluster performance is achieved by scheduling algorithm, which properly selects the size of the work slice for each client to assign.     

A signal processing module for power system applications

This paper presents a unified power signal processor (PSP) for use in various applications in power systems. The introduced PSP is capable of providing a large number of signals and pieces of information which are frequently required for control, protection, status evaluation, and power quality monitoring of power systems. The PSP receives a set of locally measured three-phase voltage and current signals and provides their fundamental components, amplitudes, phase angles, frequency, harmonics, instantaneous and stationary symmetrical components, active and reactive currents and powers, power factor, and the total harmonic distortion. Simplicity and integrity of its structure as well as its robustness with respect to internal parameters and external disturbances and noise render the proposed scheme very attractive for practical implementations.     

A new hybrid current sensor for high-voltage applications

This article presents a new hybrid electro-optic/inductive current sensor for metering and protective relaying applications. The sensor combines a Rogowski coil with a passive integrator located in the high-voltage environment. An integrated-optic Pockels cell (IOPC) having integrated electrodes provides optical isolation. Test results from 30 A to 30 kA show the sensor to be highly linear, exceeding 0.2% linearity standards. Temperature cycling tests show the ratio error to have a maximum value of 0.3% over the -30 to +70/spl deg/C range.     

A miniaturized slotted multiband antenna for wireless applications

A novel miniaturized slotted multiband antenna is presented in this article. The antenna consists of a kite-shaped slot in the radiating patch to obtain miniaturization, C- and G-shaped slots in the ground plane to incorporate multiband operation and a microstrip feedline to obtain an impedance matching. The aforementioned miniaturization method results in about 50% reduction in active patch area and about 36% reduction in volume of the proposed design, as compared to the conventional antenna. G-shaped slot is used to obtain operations at 3.6 and 5.8 GHz, while C-Shaped slot is used to obtain operations at 6.9 and 9.5 GHz. The antenna has an active patch area of only 384 \(\hbox {mm}^{2} (24\times 16\,\hbox {mm}^{2})\), and the entire performance analysis of the antenna are carried out using HFSS v.13.0 simulation software. The proposed design operates at about 3.58 (WiMAX), 5.9 (WLAN), 6.72 (Satellite TV), 8.51 and 9.76 GHz (X-band) with \({S}_{11}<-\,10\,\hbox {dB}\) bandwidth of about 1.95% (3.54–3.61 GHz), 3.5% (5.88–6.09 GHz), 1.7% (6.68–6.80 GHz), 4.4% (8.36–8.74 GHz) and 3.96% (9.4–9.78 GHz), respectively. The proposed structure is compact in size, simple in construction, low profile, easy to fabricate, exhibits good impedance matching, moderate gain and stable radiation characteristics across the operational bandwidths.     

A novel uninterruptible DC-DC converter for UPS applications

The authors describes a novel DC-DC converter that integrates a Cuk converter and a buck converter to deliver uninterruptible DC output power. This converter has the desirable features of a simple circuit and high efficiency compared with a standalone uninterruptible power supply (UPS). The circuit operation and analysis of the converter, together with experimental results from a prototype circuit, are presented