Quasi-modes multiphase transmission line model

This article presents a new model to represent transmission lines including the frequency dependence of longitudinal parameters. The model uses the natural modes, for ideally transposed lines, and ‘quasi-modes’ for non-transposed lines, and is applied to lines that have a vertical symmetry plane. The line is represented through π-circuits, with one π-circuit for each mode. The transformation matrix is modeled using ideal transformers. The model is described for three-phase lines, dc lines, double three-phase lines and six phase lines. A 440 kV three-phase transmission line illustrates it and is compared with a frequency dependent EMTP line model, the Semlyen one.     

Load management in the Indian power sector using US experience

India has a scarcity of electric power during peak-use periods. Most Indian utilities resort to load shedding (LS) to manage the peak demand. A review of US experience with direct load control and interruptible or time-of-use (TOU) tariffs shows successful programs. Direct load control of agricultural pumps, commercial air conditioners and interruptible or TOU tariffs in the industrial sector are identified as useful options for India. Implementation strategies for these are suggested. Load management (LM) by Indian utilities may provide a better solution to the current peak power shortage than mandatory LS.     

初始应力状态对侧限条件黏土动态压缩过程和力学性能的影响

黏土的初始应力状态对其动力学性质有显著的影响。本文采用长时、分级、高压固结方式模拟了黏土的原始应力赋存环境,采用SHPB实验装置对侧限条件下的高压固结黏土进行应变率范围为200~800 s_^-1的冲击压缩实验,分析了黏土应力记忆效应、应变率效应和动态压缩过程。实验结果表明,黏土的应力历史影响了其动态压缩过程,试样依次经历压实段—线弹性加载段—线性卸载段,在动载下黏土压实段与线弹性加载段应力拐点的均值为3.8 MPa,与先期固结应力4.2 MPa具有相关性,并且压实段应变均值约为试样破坏应变的33%;采用200 mm和300 mm的短子弹进行冲击加载时,黏土试样未发生稳定的塑性变形,分析应力-应变率曲线发现,黏土的压实过程吸收了一部分动载能量,使其无法持续进行动态压缩行为,但进入动态压缩阶段后黏土受子弹长度影响较小;黏土试样动态加卸载段模量随应变率同步增加,但加卸载模量的比值稳定在0.45左右,表明更高的冲击速度没有造成试样进一步的损伤,这与冲击后的宏观破坏现象及塑性变形分析相互印证。实验结果也说明,针对软弱、松散颗粒体材料,高压固结方式为研究其动力学性质提供了一种思路。     

基于能量利用效率和耗能比的节能效果评估体系

本文提出了有效能量和无效能量的概念,并根据产生的原因或性质,对无效能量进行了较为详细的分类讨论.给出了能源利用效率(能效)和耗能比的定义,并介绍了其相互关系.在此基础上,建立了以能效和耗能比为主要指标的新型节能评估体系,并阐述了其重要意义:便于不同场合或者不同措施之间进行节能效果比较,利于有针对性地采取节能措施.     

基于柔性铰链结构的二维微动工作台研究

重点介绍了一种基于PZT驱动的双柔性平行四连杆结构二维微动工作台.推导了柔性铰链各尺寸对固有频率的影响公式,并用有限元参数化分析方法,找到对固有频率影响较大的参数.将有限元模态分析值和实验测试结果相比较,探讨影响微动工作台动态性能的综合因素,为微动台的设计提供理论和实验依据.     

Petroleum coke conversion behavior in catalyst-assisted chemical looping combustion

Efficiently using petroleum coke as fuel and reducing carbon emission meanwhile have become attractive in oil processing industry. The paper is focused on the application of Chemical Looping Combustion (CLC) with petroleum coke, with the purpose of investigating its combustion performance and effects of potassium. Some experiments were performed in a laboratory scale fluidized bed facility with a natural manganese-based oxygen carrier. Experimental results indicated that the coke conversion is very sensitive to reaction temperature. The present natural manganese-based oxygen carrier decorated by K has little effect on the improvement of coke conversion. XRD, SEM-EDX, and H₂-TPR were adopted to characterize the reacted oxygen carrier samples. After being decorated by K, the oxygen carrier's capacity of transferring oxygen was decreased. A calcination temperature above the melting point of K₂CO₃ (891 °C) shows better oxygen transfer reactivity in comparison to the one calcined at a lower temperature. The natural oxygen carrier used in the work has a high content of Si, which can easily react with K to form K(FeSi₂O₆). Further, irrespective of reaction temperature, the coke conversion can be significantly enhanced by decorating the coke with K, with a demonstration of remarkably shorter reaction time, faster average coke gasification rate and higher average carbon conversion rate.     

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．     

Exploring visual dictionaries: A model driven perspective

Good representative dictionaries is the most critical part of the BoVW: Bag of Visual Words scheme, used for such tasks as category identification. The paradigm of learning dictionaries from datasets is by far the most widely used approach and there exists a plethora of methods to this effect. Dictionary learning methods demand abundant data, and when the amount of training data is limited, the quality of dictionaries and consequently the performance of BoVW methods suffer. A much less explored path for creating visual dictionaries starts from the knowledge of primitives in appearance models and creates families of parametric shape models. In this work, we develop shape models starting from a small number of primitives and develop a visual dictionary using various nonlinear operations and nonlinear combinations. Compared with the existing model-driven schemes, our method is able to represent and characterize images in various image understanding applications with competitive, and often better performance.     

Study on selective hydrogen sulfide removal over carbon dioxide by catalytic oxidative absorption method with chelated iron as the catalyst

H₂S is a detrimental impurity that must be removed for upgrading biogas to biomethane. H₂S removal selectivity over CO₂ employing catalytic oxidative absorption method and its influence factors were studied in this work. The desulfurization experiments were performed in a laboratory apparatus using EDTA-Fe as the catalyst and metered mixture of 60% (v/v) CH₄, 33% (v/v) CO₂ and 2000–3000 ppmv H₂S balanced by N₂ as the simulated biogas. It was found that for a given catalytic oxidative desulfurization system, it exists a critical pH, at which desulfurization selectivity achieves the highest. It was also observed that desulfurization selectivity increased along with the increase of chelated iron concentration, gas flow rate, and ratio of gas flow rate to liquid flow rate (G/L). This demonstrated that high selectivity and high efficiency for biogas desulfurization could both be achieved through optimizing these parameters. Specific to the desulfurization system of this work, when the gas flow rate was set as 1.1 L/min, after optimizing the above mentioned parameters, i.e. EDTA-Fe concentration of 0.084 mol/L, absorption solution pH of 7.8, and G/L of 55, the desulfurization selectivity factor reached 142.1 with H₂S removal efficiency attained 96.7%.