永磁无刷直流电动机基于反电势的无传感器控制技术综述

无刷直流电动机的无位置传感器控制技术是业内近二十年来的一个重要研究方向。已经有多种技术见诸报道。文章对基于反电势的无传感器控制方法作一综合介绍和比较。     

在功率变化交叉闭锁振荡中对称故障的快速识别方法

在电力系统振荡期间,三相有功、无功的变化率分别是两侧系统功角的正弦和余弦函数,经过归一化后,理论上不可能同时低于0.7的门槛,而对称故障发生后,有功、无功的变化率都趋近于零。利用上述特征提出了基于功率变化率交叉闭锁振荡中对称故障的快速识别方法。通过修正后的2点采样值积算法,功率的计算不受频率变化的影响。作为一种积分型判据,其动作稳定性高。仿真结果表明:该方案具有较高的可靠性和速动性,最长动作延时为算法的数据窗长30ms。     

输电线路大跨越工程高塔组立施工技术探讨

介绍了输电线路大跨越工程高塔组立施工技术方案,吊装设备功能需求和安全保障措施;论述了高塔组立施工设备设计方案及原则、荷载计算及组合、有限元分析方法,提出了结构尺寸及重量估算的经验公式、设备基本参数;简要介绍了电视监控、超载保护、吊件位置检测系统、摇臂自动调位装置。     

合成试验回路的电流源电流零点预测

为能在合成试验中准确地控制延弧电路的投入时间，以保证试验成功，提出了一套以数字滤波技术为基础的移相方法，可根据用户需要预测出短路电流的零点，以考核断路器在第二半波和第三半波的开断能力；采用CPLD(Complex Programmable Logic Device)技术实现了短路电流的数字化测量和零点预测．仿真结果表明：所提出的方法具有精度高、费用低的特点．     

同位素分布式管理系统的设计与应用

文中设计了在Oracle环境下同位素管理系统分布式数据库的应用方案,重点研究了同位素管理系统的数据分布特点、分布式的数据库模型和拓扑结构、跨网域数据库访问技术、分布式查询与数据更新,并在同位素分布式管理系统中得到应用。     

正交法合成邻硝基苯酚最佳反应条件实验探讨

以苯酚硝酸钠和浓硫酸为原料，合成邻硝基苯酚和对硝基苯酚，产率一般很低，讨论了以硝酸钠和浓硫酸为原料，在醋酸介质下进行硝化反应合成邻硝基苯酚同时提取对硝基苯酚。通过正交法确定最佳反应条件，并对实验结果进行讨论。     

中马相迪电站工程混凝土配合比优化设计

采用试验优化设计的方法 ,确定了具体生产条件下考虑大量影响混凝土性能的因素的数学模型 ,其工艺计算准确 ,能在原始参数变化时进行配合比的必要修正 ,从而成功控制混凝土的质量     

Brief Introduction to High Tower Structure Design for Large Crossing

1.0verviewl.Sincel958,ECEPDIbegant0designthehighcrossingt0weracrosstheYangtzeRiver,on22OkV.Uptonow,therehavebeenapproximately20setsofhighcrossingtowersdesignedbyECEPDI,settinguponthebothsidesoftheYangtzeRiver,theHuaiheRiver,theHuangpuRiverandtheYongjiangRiver.Theselargecr0ssingprojectscarrylinesofthedesignedvoltagefrom22OkVto500kVhavingtheheightfromlO0mt0200m.l.llnconformitywithdifferenttechnicalrequirements,climate,terrainandgeol0gicconditions0fdifferentprojects,ECEPDIhasdesigned…     

勃利县中鲜渠首拦河闸施工特点

本工程在混凝土浇筑上采用新工艺并结合主体交叉作业方式，通过具体施工完善了设计。     

The influence of conformity and group identity on drink walking intentions: Comparing intentions to drink walk across risky pedestrian crossing scenarios

Despite the dangers associated with drink walking, limited research is currently available regarding the factors which influence individuals to engage in this risky behaviour. This study examined the influence of psychosocial factors upon individuals’ intentions to drink walk across four experimental scenarios (and a control condition). Specifically, a 2 × 2 repeated measures design was utilised in which all of the scenarios incorporated a risky pedestrian crossing situation (i.e., a pedestrian crossing against a red man signal) but differed according to the level of group identity (i.e., low/strangers and high/friends) and conformity (low and high). Individuals were assessed for their intentions to drink walk within each of these different scenarios. Undergraduate students (N = 151), aged 17–30 years, completed a questionnaire. Overall, most of the study's hypotheses were supported with individuals reporting the highest intentions to drink walk when in the presence of friends (i.e., high group identity) and their friends were said to be also crossing against the red man signal (i.e., high conformity). The findings may have significant implications for the design of countermeasures to reduce drink walking. For instance, the current findings would suggest that potentially effective strategies may be to promote resilience to peer influence as well as highlight the negative consequences associated with following the behaviour of other intoxicated pedestrians who are crossing against a red signal.