Soft switching based on analysis of transient and steady-state characteristics: Application to a single-ended high-frequency inverter

A single-ended resonant-type high-frequency inverter using a static induction transistor (SIT) described in this paper can be performed as a zero current switching (ZCS) operation without dc reactor. The SIT high-frequency inverter is a low-cost one which has no transformer and it would be developed for a high-intensity ultrasonic power supply and dc-dc converter. The circuit operation regions, not only ZCS but also ZCS-ZVS (zero current switching and zero voltage switching), were elucidated in the normalized plane. The characteristics of the inverter including the power control by frequency regulation were discussed. Furthermore, the switching characteristics in the transient-state were investigated. These characteristics were substantiated on the basis of the numerical analysis and experimental results.     

Bioleaching and chemical leaching as an integrated process in the zinc industry

This work sought to integrate bioleaching and chemical leaching as a cost-effective process to treat zinc sulphides. The continuous bioleaching of a sphalerite concentrate, assaying 51.4% Zn, 1.9% Pb, 31.8% S and 9.0% Fe with mesophile iron and sulphur-oxidizing bacteria followed by chemical leaching of the bioleaching residue were assessed. In the bioleaching step, the first reactor was used to produce Fe(III) concentrations as high as 20 g/L. This solution was fed to the subsequent bioleaching reactors to oxidize sphalerite. It was possible to achieve 30% zinc extraction for 70 h residence time. In chemical leaching experiments, carried out with the residue of the bioleaching step, the effects Fe_total and acidity on zinc extraction were studied. It was noticed that Fe(III) concentrations over 12 g/L did not affect zinc recoveries. Furthermore, the higher the acidity, the larger the zinc recovery, for experiments carried out up to 181 g/L sulphuric acid. The results have demonstrated that it is possible to devise a new process capable of achieving 96% zinc extraction, similarly to the conventional roasting–leaching–electrolysis process.     

基于非线性系统的高增益自适应λ跟踪控制研究

针对多变量、相对阶为一、全局最小相位非线性系统,对已有的高增益自适应控制策略进行改造,结合跟踪方法构造了一种高增益自适应跟踪控制策略.应用Matlab 7.0对三容水箱的仿真证明该控制方法是有效的.     

Eco-economic excavator configuration method

Excavating processes performed frequently in building, civil and infrastructure projects are critical and costly. To define a cost-effective excavator configuration, an earthwork planner depends mostly on experience and intuition. This intuitive reasoning is often error-prone, and highly experience based. This paper presents a computational method called the Eco-Economic Excavator Configuration (E3C), which selects the most favorable configuration of a heavy duty excavator according to the earthwork package and its job conditions. E3C obtains the input data from external databases, derives the formulae involved in computing the process performance (e.g., production rate, process completion time, and profit), and instructs the earthwork manager in the best-fit excavator configuration (e.g., maximum digging depth, engine size in HP, and bucket size) for profitable operation by considering the implicit constraints and conditions exhaustively. The method identifies the best-fit PDFs of the process completion time and that of the total profit, given an excavator configuration. A test case, which was performed at a building basement excavating project, confirmed the usability and validity of the method.     

Review of ICT Implementations for Facilitating Information Flow between Virtual Models and Construction Project Sites

Information and communications technology (ICT) has had major effects on the architecture, engineering, and construction (AEC) research fields in recent decades, but a comprehensive and in-depth review of how ICT has been used to enable different modes of information flow on project sites is missing from the current literature. To fill this gap, this paper defines a systematic approach for classifying information flow modes and uses this method to determine trends in information communication modes reported in recent publications. These trends were determined through the identification and analysis of 119 journal articles published between 2005 and 2015 in order to determine the mode of information flow reported. The results show that the majority of papers (70.6%) report a unidirectional flow of information, while a much smaller portion report one of two bidirectional information flow modes (26.9% non-automated, and 2.5% automated). The contribution of this work is in systematically defining current trends in ICT publications related to information flow and also in the identification of the typical technologies used to enable these communication modes.     

记忆功放的BP神经网络分离预失真方法

针对OFDM无线通信系统中的记忆非线性功率放大器预失真困难以及预失真精度不高的问题,充分考虑了记忆非线性功率放大器的失真特性及其结构特点,提出了神经网络分离预失真方法,并给出了该方法的原理、实现结构和自适应算法．该方法把记忆非线性功率放大器的预失真分为3个模块来实施,即抵消记忆效应模块、AM/AM失真矫正模块和AM/PM失真矫正模块,并基于神经网络预失真器非直接学习结构,利用Levenberg-Marquardt BP算法确定各个神经网络预失真器．仿真结果表明该方法可降低邻信道互调功率约30dB．     

Post-earthquake recoverability of existing RC bridge piers retrofitted with FRP composites

The novel concept of this paper is to investigate the required recoverability of existing important reinforced concrete (RC) bridges retrofitted with fiber-reinforced polymers (FRP) to restore their original functions after a moderate or strong earthquake. Hence, this paper presents an up-to-date literature search on the inelastic performance of 109 FRP-retrofitted columns with lap-splice deficiency, flexural deficiency, or shear deficiency. The study is conducted in the following steps: using post-yield stiffness as a seismic index, the effectiveness of FRP jackets in enhancing the inelastic stage performance of non-ductile reinforced concrete columns is scrutinized for the available database; the performance of columns which successfully achieved post-yield stiffness is categorized in accordance with the required recoverability after an earthquake; and according to the definition of a controllable recoverable structure, the appropriate composite jacket thickness is calculated. In the view of a proposed mechanical model of an FRP–RC damage-controllable structure, 61 columns of the available database exhibited idealized lateral performance with stable post-yield stiffness, or secondary stiffness. Lateral drift at the end of the recoverable state is defined from the hysteretic responses of 39 columns and is visualized as a ratio of column lateral drift by the end of the post-yield stiffness with explicit consideration for the effect of both column cross-section shape and deficiency. Finally, suitable FRP design assumptions and concepts certifying the reality of post-yield stiffness are given. Furthermore, in the light of Seismic Design Specifications of Highway Bridges in Japan, a FRP strengthening design guideline that considers and evaluates structural recoverability is proposed.     

基于甚宽带脉冲电流法的局部放电检测系统

局部放电的检测与分析是评价电力设备绝缘状况,发现早期故障的一种有效方法.与传统的脉冲电流法相比,甚宽带测量方法可以获取更多的局部放电信息,有助于提高测量的灵敏度和抗干扰能力.本文介绍了基于甚宽带脉冲电流法的局部放电检测系统,研究了传感器特性、脉冲分离技术和定量方法.并在实验室和现场对该系统的性能进行了测试,结果表明该系统具有灵敏度高和抗干扰能力强等优点,可以有效地应用于局部放电的现场检测和在线监测.     

Canada to move out of Kyoto agreement…

The Canadian government, under pressure from energy producers worried about the costs of the Kyoto climate change protocol, has given a clear sign that it might not ratify the Kyoto treaty.     

Hazard and operability (HAZOP) analysis. A literature review

Hazard and operability (HAZOP) methodology is a Process Hazard Analysis (PHA) technique used worldwide for studying not only the hazards of a system, but also its operability problems, by exploring the effects of any deviations from design conditions. Our paper is the first HAZOP review intended to gather HAZOP-related literature from books, guidelines, standards, major journals, and conference proceedings, with the purpose of classifying the research conducted over the years and define the HAZOP state-of-the-art.