基于改进蚁群算法的方向过电流保护整定优化

本文提出了基于蚁群优化算法的方向过电流保护整定配合的优化模型.首先说明了方向过电流保护的时间特性,然后建立了方向过电流整定优化模型.优化目标是所有主保护动作时间之和最小,考虑了主后备保护配合约束、保护动作时间约束、启动电流约束等.本文所提方向过电流保护为非线性优化问题,提出利用改进蚁群优化算法来求解该模型.最后本文利用...     

高速载运设施的无损检测技术应用和发展趋势

高速载运设施事关国家命脉,在其生产、布设、使用和维护各个环节,都需无损检测技术保驾护航。本文就高速载运设施无损检测的必要性,检测现状、检测技术的发展趋势（包括基于多物理原理的新型伤损检测技术,材料应力、微观结构、机械性能等状态检测,以及无损检测和结构健康监控及人工智能的结合）进行综述,旨在为高速载运设施的无损检测打下基础。     

Sanitizer efficacy in preventing cross-contamination during retail preparation of whole and fresh-cut cantaloupe

The objective of this study was to evaluate the efficacy of tap water (TW), commercial electrolyzed water (EW), and a commercial acid-based sanitizer (AS) in preventing cross-contamination of cantaloupe during processing in retail settings. A whole cantaloupe was dip-inoculated with a cocktail of Salmonella or L. monocytogenes to achieve approximately 5 log CFU/cm². One inoculated and two non-inoculated whole cantaloupes were treated in 76 L of TW, EW (free chlorine: 50–60 ppm), or AS (pH 2.8, combination of lactic acid and phosphoric acid) for 5 min. Subsequently, fresh-cut cantaloupe flesh from the inoculated and non-inoculated cantaloupes were soaked together in 76 L of TW, EW, or AS for 90 s. EW treatment resulted in an approximately 1.5 log reduction in both Salmonella and L. monocytogenes on the rind of whole cantaloupe, which was significantly greater than with the TW treatment (0.5 log reduction) (P < 0.05). Cross-contamination of non-inoculated whole cantaloupes occurred when washed with inoculated whole cantaloupe in TW (four of four cantaloupes positive for Salmonella and L. monocytogenes) or AS (four of four cantaloupes positive for Salmonella and two of four positive for L. monocytogenes). Cross-contamination did not occur when whole cantaloupes were washed in EW. Additional washing of mixed fresh-cut cantaloupe flesh from the inoculated and non-inoculated cantaloupes prepared after washing of whole cantaloupes demonstrated that the EW treatment reduced the likelihood of cross-contamination compared with TW and AS. No viable Salmonella or L. monocytogenes were detected from 100 mL sample of EW processing water, but were detected in TW and AS (L. monocytogenes only). The addition of a sanitizing agent to water used for the processing of whole and fresh-cut cantaloupe in a retail setting is recommended to prevent cross-contamination and reduce microbial load.     

技工学校模具专业课程设置探索

通过对当前技工学校模具专业教育存在问题的分析,以社会需求为导向,详细阐述了现代模具专业人才知识结构需求,提出了技工学校模具专业课程的设置方案。     

∏型接线滤波电容器组不平衡电流保护判据及定值

介绍了∏型接线的高压直流滤波电容器组不平衡保护原理和整定值计算方法。提出在部分电容器单元故障后,以滤波器的失谐度和剩余完好电容器单元上的过电压水平作为保护计算的依据。给出电容器单元或者元件故障后不平衡电流保护整定值计算公式。分别对内熔丝型电容器和无熔丝型电容器进行了分析,分析了部分不平衡电容器保护动作行为,并与计算结果进行了比较。     

螺旋锥齿轮数控磨齿机机床空间误差与机床调整参数的关系

为求得对各项机床调整参数影响较大的机床空间误差,分析螺旋锥齿轮加工过程中数控机床空间误差物理涵义,并建立七轴五联动数控磨齿机床空间误差模型.基于齐次变换矩阵方法建立机床空间误差与机床调整参数之间的几何等量关系,推导出两者间的关联函数并进行分析.通过实例分析,发现对机床刀位调整值影响较大的机床空间误差主要是三直线轴垂直度误差和x轴沿Z向垂直度误差;对机床轮位调整值影响较明显的机床空间误差为z轴、B轴沿x向直线度误差以及A轴的安装距误差.为机床调整参数优化及螺旋锥齿轮几何误差补偿提供了理论依据.     

山西中条山地区金矿成矿地质条件及找矿远景

研究对比了中条山、小秦岭地区的地层、岩浆岩、构造、成矿特征、地球物理场、地球化学场、成矿机理,确定了中条山地区最佳找矿类型,提出了中条山地区的成矿远景和勘查建议     

基于多代理系统的继电保护定值在线校核预警系统

基于多代理系统体系结构,研究并设计了继电保护定值在线校核预警系统.该系统利用代理的智能化特点,实现了对实时采集的电网信息的智能化分析,准确形成实时运行方式;利用多代理系统体系结构对分布式并行计算的良好支持,实现了校核计算的并行处理,提高了实时计算速度;利用公共对象请求代理体系结构软总线技术,以IEC 61970的公共信息模型和IEC 61850的保护功能逻辑节点相结合作为系统涉及的电力设备信息模型,提高了系统的可扩展性和开放性.实际应用表明,本系统利用代理实现多线程并行处理后,计算速度快,完全能满足在线运行需要,具有较高的实用价值.     

Thermostat settings in English houses: No evidence of change between 1984 and 2007

Rising demand temperatures are widely blamed for UK home energy use not declining over time despite the increased efficiency of dwelling envelopes and heating technologies. The hypothesis that thermostat settings have risen over time is tested using a repeated cross-sectional social survey of owners of centrally heated English houses. No statistical evidence for changes in reported thermostat settings between 1984 and 2007 is found.     

机床结构建模的研究与应用

本文探讨了一种考虑结合部动态特性的机床动力学模型的建立方法。该方法基于对结合部动态特性的研究,应用结合面通用动态数据获得结合部的物理参数,并利用设计图纸资料来建立机床结构的动力学模型。首先根据结合部的结合方式与结合条件,分析计算出结合部各结合面的压力分布,从而得到各结合面的等效物理参数,再由结合部的结构型式,导出结合部的物理参数。对机床结构中几种典型的结合部结构型式,分析了其结合部参数获取的途径和方法。作为实际应用,根据上述的建模方法,建立起昆明铣床厂生产的×8132万能工具铣床的整机动力学模型,将该机床简化为21个自由度的振动系统,利用FORTRAN语言编制的计算机程序,在CM—24微机上完成了固有特性与动态响应的计算,计算结果与激振试验数据在信号处理机7T17上分析得到的结论是相吻合的,所建立的动力学模型能够较好地模拟实际机床结构的动态特性,从而证明了本建模方法的正确性与实用性。