SVPWM三相电压型逆变器的仿真研究

以三相电压型逆变器为基础,根据空间矢量脉宽调制（SVPWM）基本原理详细分析研究了电压矢量作用时间和扇区分配问题,以α-β坐标为基础,建立了互差π/3的x-y-z时间坐标系,提出了不同扇区矢量作用时间长短根据期望极值判断的原则。介绍了MATLAB中M文件编程的仿真方法,建立了MATLAB程序嵌入式主要功能模块,逆变器采用数字PID控制,利用Simulink对系统进行了综合仿真分析及试验,给出了仿真及实验波形,为实现SVPWM逆变器的数字控制提供参考。     

绥高#2线线路保护2动作分析

对高岭站2009年6月15日绥高#2线线路保护动作的原因进行深入分析,介绍处理措施。     

环境荷载联合作用下海上风电结构动力响应分析

为研究海上风电结构在复杂的海洋环境中承受环境荷载(风、波、冰、流)的联合作用时,结构产生的剧烈的动力响应问题。文章以三脚架基础海上风电结构为研究对象,采用ANSYS有限元软件建立其整体模型并进行荷载(风、波、流和风、冰、流)联合作用下的静力校核,通过对环境荷载联合作用下的三脚架基础海上风电结构进行瞬态分析,掌握其动力响应的特性及规律。结果表明:三脚架基础结构的一、二阶自振频率均为0.285Hz,在所选风机允许的频率范围内,可以保证整体结构不会与风机转动发生共振;风荷载在风、波、流荷载联合作用下主导控制结构响应的稳态波动,冰荷载在风、冰、流荷载联合作用下主导控制结构的稳态振动过程;塔筒顶端呈现的位移和加速度响应均远大于三脚架基础顶端;环境荷载联合作用下结构动力响应是环境荷载单独作用下动力响应叠加的结果。     

Multiperson interaction recognition in images: A body keypoint based feature image analysis

Most interaction recognition approaches have been limited to single‐person action classification in videos. However, for still images where motion information is not available, the task becomes more complex. Aiming to this point, we propose an approach for multiperson human interaction recognition in images with keypoint‐based feature image analysis. Proposed method is a three‐stage framework. In the first stage, we propose feature‐based neural network (FCNN) for action recognition trained with feature images. Feature images are body features, that is, effective distances between a set of body part pairs and angular relation between body part triplets, rearranged in 2D gray‐scale image to learn effective representation of complex actions. In the later stage, we propose a voting‐based method for direction encoding to anticipate probable motion in steady images. Finally, our multiperson interaction recognition algorithm identifies which human pairs are interacting with each other using an interaction parameter. We evaluate our approach on two real‐world data sets, that is, UT‐interaction and SBU kinect interaction. The empirical experiments show that results are better than the state‐of‐the‐art methods with recognition accuracy of 95.83% on UT‐I set 1, 92.5% on UT‐I set 2, and 94.28% on SBU clean data set.     

基于绿色证书交易机制的含风电场电力系统动态环境经济调度

为了促进风电消纳以及提高电力系统的经济性,构建基于绿色证书交易机制的含风电场电力系统多目标动态环境经济调度（DEED）模型,提出一种基于反向学习混沌搜索的OLCS-MOEA/D算法的DEED调度求解方法。首先,采用广义反向学习初始化种群提高种群多样性,并引入基于Logistic映射的混沌搜索算法以增强算法局部搜索能力。然后,为了验证算法的性能,采用标准测试函数F1—F7进行测试,同时将该算法对模型进行求解,获得了比其他算法范围更广和分布均匀的Pareto解集前沿。最后,对基于绿色证书交易机制的动态环境经济调度与传统动态环境经济调度进行结果对比分析,通过仿真算例验证该模型和算法的有效性和优越性。     

Cardioinotropic Effects in Subchronic Intoxication of Rats with Lead and/or Cadmium Oxide Nanoparticles

Subchronic intoxication was induced in outbred male rats by repeated intraperitoneal injections with lead oxide (PbO) and/or cadmium oxide (CdO) nanoparticles (NPs) 3 times a week during 6 weeks for the purpose of examining its effects on the contractile characteristics of isolated right ventricle trabeculae and papillary muscles in isometric and afterload contractions. Isolated and combined intoxication with these NPs was observed to reduce the mechanical work produced by both types of myocardial preparation. Using the in vitro motility assay, we showed that the sliding velocity of regulated thin filaments drops under both isolated and combined intoxication with CdO–NP and PbO–NP. These results correlate with a shift in the expression of myosin heavy chain (MHC) isoforms towards slowly cycling β–MHC. The type of CdO–NP + PbO–NP combined cardiotoxicity depends on the effect of the toxic impact, the extent of this effect, the ratio of toxicant doses, and the degree of stretching of cardiomyocytes and muscle type studied. Some indices of combined Pb–NP and CdO–NP cardiotoxicity and general toxicity (genotoxicity included) became fully or partly normalized if intoxication developed against background administration of a bioprotective complex.     

Dynamic “Molecular Portraits” of Biomembranes Drawn by Their Lateral Nanoscale Inhomogeneities

To date, it has been reliably shown that the lipid bilayer/water interface can be thoroughly characterized by a sophisticated so-called “dynamic molecular portrait”. The latter reflects a combination of time-dependent surface distributions of various physicochemical properties, inherent in both model lipid bilayers and natural multi-component cell membranes. One of the most important features of biomembranes is their mosaicity, which is expressed in the constant presence of lateral inhomogeneities, the sizes and lifetimes of which vary in a wide range—from 1 to 10³ nm and from 0.1 ns to milliseconds. In addition to the relatively well-studied macroscopic domains (so-called “rafts”), the analysis of micro- and nanoclusters (or domains) that form an instantaneous picture of the distribution of structural, dynamic, hydrophobic, electrical, etc., properties at the membrane-water interface is attracting increasing interest. This is because such nanodomains (NDs) have been proven to be crucial for the proper membrane functioning in cells. Therefore, an understanding with atomistic details the phenomena associated with NDs is required. The present mini-review describes the recent results of experimental and in silico studies of spontaneously formed NDs in lipid membranes. The main attention is paid to the methods of ND detection, characterization of their spatiotemporal parameters, the elucidation of the molecular mechanisms of their formation. Biological role of NDs in cell membranes is briefly discussed. Understanding such effects creates the basis for rational design of new prospective drugs, therapeutic approaches, and artificial membrane materials with specified properties.     

Observations on the role of oxide scales in high-temperature erosion-corrosion of alloys

The results are presented of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial high-temperature alloys. Analysis of the kinetic and morphological data suggested that the high-temperature oxidation behavior of a given alloy plays a very important role in determining its erosion-corrosion behavior under the conditions studied. In terms of relative behavior, alloys which are weak but ductile at temperature, and which form tenacious oxide scales, exhibited the highest resistance to high-temperature erosion-corrosion. Simple models were developed to describe the expected interaction between high-temperature oxidation and erosion.     

A1-Li合金的拉伸断裂过程研究

以2090 Ce合金为研究对象，对不同时效时间的室温拉伸断口进行了半定量分析，探讨了拉伸性能对断裂特征的响应关系，重点分析合金分层裂纹的形成过程。研究表明：2090 Ce合金的断裂方式以韧窝、分层开裂和沿亚晶界开裂3种为主，随时效时间的延长，韧窝、分层开裂逐渐减少，沿亚晶界开裂比例逐渐加大：分层开裂程度与时效程度有密切关系：分层开裂过程与试样内部受力状态、晶界状态有密切关系。分层最先发生在试样中心，随后在二分之一、四分之一……处反复发生，最终将试样分割成一系列平行的薄板。时效后期由于亚晶界的弱化，使裂纹倾向沿亚晶界扩展，从而抑制分层开裂的发生，同时导致合金强度，尤其是塑性的下降。