故障信号小波检测方法的研究

分析小波变换用于故障检测的基本原理以及小波函数的选取原则,介绍利用不同小波函数进行信号噪声消除,奇异点检测及故障的定位等方法,通过测取电动机启动电流信号的小波变换,实现转子断条故障的在线诊断,说明该方法有效,并具有可操作性。     

小规模山体挖掘造成环境破坏值得重视

分析民房改扩建对环境的破坏因素,提出在特定的地质环境下应严禁进行山体切坡,以避免发生地质灾害.     

钨和钼的杂多化合物及其应用

本文介绍了钨和钼的杂多化合物的合成、结构、性质以及杂多化合物在固体化学、化学工业、临床化学和医学等方面的应用．     

Increased blood pressure later in life may be associated with perinatal n−3 fatty acid deficiency

Hypertension is a major risk factor for cardiovascular and cerebrovascular disease. Previous work in both animals and humans with high blood pressure has demonstrated the antihypertensive effects of n−3 polyunsaturated fatty acids (PUFA), although it is not known whether these nutrients are effective in preventing hypertension. The predominant n−3 PUFA in the mammalian nervous system, docosahexaenoic acid (DHA), is deposited into synaptic membranes at a high rate during the perinatal period, and recent observations indicate that the perinatal environment is important for the normal development of blood pressure control. This study investigated the importance of perinatal n−3 PUFA supply in the control of blood pressure in adult Sprague-Dawley rats. Pregnant rat dams were fed semisynthetic diets that were either deficient in (DEF) or supplemented with (CON) n−3 PUFA. Offspring were fed the same diets as their mothers until 9 wk; then, half of the rats from each group were crossed over to the opposite diet, creating four groups, i.e., CON-CON; CON-DEF; DEF-DEF, DEF-CON. Mean arterial blood pressures (MAP) were measured directly, at 33 wk of age, by cannulation of the femoral artery. The phospholipid fatty acid profile of the hypothalamic region was determined by capillary gas-liquid chromatography. The tissue phospholipid fatty acid profile reflected the diet that the rats were consuming at the time of testing. Both groups receiving DEF after 9 wk of age (i.e., DEF-DEF and CON-DEF) had similar profiles with a reduction in DHA levels of 30%, compared with rats receiving CON (i.e., CON-CON and DEF-CON). DEF-DEF rats had significantly raised MAP compared with all other groups, with differences as great as 17 mm Hg. DEF-CON rats had raised MAP compared with CON-CON rats, and DEF-DEF rats had higher MAP than CON-DEF rats, despite the fact that their respective fatty acid profiles were not different. These findings indicate that inadequate levels of DHA in the perinatal period are associated with altered blood pressure control in later life. The way in which these long-term effects are produced remains to be elucidated.     

220t/h煤粉锅炉臭氧氧化NOx超低排放试验研究

近年来,国家对于环境保护的要求愈发严苛,煤电行业节能减排任务愈加艰巨,燃煤电厂的超低排放改造工作迫在眉睫。笔者针对3台220 t/h煤粉锅炉NO_x进行臭氧脱硝改造和脱硝试验研究,采用烟气分析仪及电厂在线检测系统,探究了O_3/NO摩尔比及NO_x初始浓度等对脱硝效果的影响。试验结果表明,活性分子臭氧脱硝技术对该煤粉炉锅炉具有较好的脱硝效果,NO_x脱除效率可达90%以上。锅炉出口NO_x浓度随锅炉负荷波动较大,呈正相关关系,锅炉负荷升高,出口NO_x浓度升高;锅炉负荷降低,出口NO_x浓度随之降低。臭氧脱硝效率随O_3/NO摩尔比和臭氧投加量的增加而增大,但当O_3/NO摩尔比超过一定值后,其增大速率随臭氧量的增加而逐渐变缓。臭氧脱硝技术中脱硝效率受NO_x初始浓度的影响较小,O_3/NO摩尔比达到一定量时,可保证不同NO_x初始浓度波动下的脱硝效率。本试验获得的特性曲线为臭氧脱硝技术最佳臭氧喷射量的确定提供了依据,即在保证脱硝效率的前提下,如何选择最佳的O_3/NO摩尔比。应用臭氧脱硝技术后,该电厂顺利通过了168 h测试,烟气排放中NO_x浓度稳定在50 mg/Nm~3以下,满足国家超低排放要求,可见采用活性分子臭氧对烟气中的NO_x具有良好的脱除效果。     

2013年晶弘冰箱预计销售150万台

2013年9月,晶弘冰箱的新广告片在中央电视台播出,格力电器董事长董明珠以代言人的身份出现在该广告中,广告语为“晶弘冰箱,美食家的冰箱”。     

基于互高阶谱MUSIC法的间谐波检测

在电力系统中,准确有效地确定信号中的间谐波分量,对于改善电能质量有重要意义。研究了一种间谐波幅值和频率的估计算法--基于互高阶累积量的多信号分类法MUSIC(Multiple Signal Classification)方法,该方法可以有效地抑制非相关噪声和高斯噪声,在混合噪声和低信噪比的条件下,仍具有很高的谱分辨率和谱估计性能。为了证明其有效性,采用一具体的电力系统谐波模型进行仿真。仿真结果表明:在色噪声背景下,信噪比为-20dB时,且不需要对分析数据进行整周期采样,仍可以有效地估计出间谐波的频率和幅值,谱估计性能稳定,具有一定的工程应用前景。     

基于改进遗传模拟退火算法的PMU优化配置

分析了遗传算法和模拟退火算法的优缺点,将具有较好全局寻优性能的遗传算法和具有较强局部搜索能力的模拟退火算法结合,形成的遗传模拟退火MGASA算法用于解决以电力系统状态完全可观测和PMU配置数目最小为目标的PMU优化配置问题.在寻优过程中,先将每一代群体进行遗传操作,再对产生的新群体中各个体进行模拟退火操作,同时在选择、交叉、变异和复制操作过程中实施最优保留策略,复制策略采用Metropolis判别准则.通过采用IEEE14和IEEE39节点系统对该算法进行验证表明,MGASA算法在解决PMU优化配置问题上具有较高的寻优性能和搜索效率.