铁岭地区智能型坚强电网建设探讨

在简要分析铁岭地区农村电网发展现状的基础上,探讨在铁岭地区建设智能型坚强电网的必要性、基本思路和原则,提出铁岭地区建设智能型坚强电网的实用性建议,为实现农网与各级电网协调发展提供参考。     

柔性直流输电技术在风电场并网中的应用

为提高风电场电能的利用率和经济效率,针对风电场并网中存在的问题,以传统直流输电技术为对照,分析柔性直流输电技术的工作原理、控制策略和技术优势,探讨柔性直流输电技术在大规模风电场并网中的应用优势及广阔前景。     

Planning for success: Identifying effective and efficient survey designs for monitoring

Selecting a survey design to detect change through time in an ecological resource requires balancing the speed with which a given level of change can be detected against the cost of monitoring. Planning studies allow one to assess these tradeoffs and identify the optimal design choices for a specific scenario of change. However, such studies seldom are conducted. Even worse, they seem least likely to be undertaken when they offer the most insight – when survey methods and monitoring designs are complex and not well captured by simple statistical models. This may be due to limited technical capacity within management agencies. Without such planning, managers risk a potentially severe waste of monitoring resources on ineffective and inefficient monitoring, and institutions will remain ignorant of the true costs of information and the potential efficiency gains afforded by a moderate increase in technical capacity. We discuss the importance of planning studies, outline their main components, and illustrate the process through an investigation of competing designs for monitoring for declining brown bear (Ursus arctos) densities in southwestern Alaska. The results provide guidance on how long monitoring must be sustained before any change is likely to be detected (under a scenario of rather strong true decline), the optimal designs for detecting a change, and a tradeoff where accepting a delay of 2 years in detecting the change could reduce the monitoring cost by almost 50%. This report emphasizes the importance of planning studies for guiding monitoring decisions.     

一种适合配电网的电能质量监测系统结构设计

根据国家标准提出一种基于DSP和ARM的配电网电能质量监测装置的设计方案,说明其所具有的优点。试验证明：所研制的电能质量监测装置具有实时性好、性能高、体积小、成本低等优点,符合农村配电网络电能质量监测的要求。     

水田高茬秸秆旋耕埋覆装置功耗测试方法

为了检测水田高茬秸秆旋耕埋覆装置实时功耗,该文基于虚拟仪器技术和相位差原理,对适用于水田高茬秸秆翻埋装置作业功耗检测的测试系统进行了研究,分别使用相关法、FFT法、过零法3种数据处理方法编写了检测程序,并在试验台架上对测试系统进行了标定。结果显示：基于相关法的测试系统精度、稳定性和线性等指标均最高,对功耗的测量误差在4.5%以内,满足农业机械田间功耗检测要求。     

配电变压器无弧有载自动调容仿真分析

对配电变压器的有载自动调容技术进行了论述,提出了以电力电子开关为关键部件的无弧有载自动调容技术新方案,该方案以反并联大功率耐高压晶闸管作为调容开关,克服了机械式调容开关结构复杂、体积大、故障率高的缺点。探讨了配电变压器实现无弧有载自动调容的关键技术,利用电力系统仿真工具PSCAD/EMTDC建立了无弧有载调容方案的仿真模型,对电力电子开关实现自动调容进行了仿真分析,验证了所提方案的可行性。为农村和城市配电网配电变压器实施有效的季节性调容和峰谷调容提供了解决办法。     

Relationship between environmental factor and maximum daily stem shrinkage in apple tree in arid region of northwest China

After measuring maximum daily stem shrinkage (MDS) of irrigated apple tree using dendrometer during the year 2007–2010 in arid region of northwest China, we analyzed the respective relationships between MDS and single plant physiological index and environmental factors to investigate whether MDS can indicate the water status of apple tree and to establish empirical multiple regression equation among MDS and environmental factors. Results show that MDS increased at the beginning and then decreased gradually during whole growing stage. The close relationships between MDS and stem water potential, predawn water potential, stomatal conductance were found, showing that MDS can indicate the water status of mature apple tree. The relationships between MDS and single meteorological variable were significant at the other growth stages except at the bud development and flowering stage, because the canopy structure was not developed, and the order of determination coefficient (r²) over the whole growing stage was maximum vapour pressure deficit > maximum air temperature > net radiation. There were also significant correlations between MDS and soil volumetric water content and reference crop evapotranspiration over the whole growing stage. However, the determination coefficient among MDS and meteorological variables and soil volumetric water content at 0–120 cm depth was higher than those between MDS and single variable. Thus the multiple regression equation among MDS and meteorological variables and soil volumetric water content at 0–120 cm depth can be used to estimate MDS under fully irrigated apple orchard.     

补气活血对奶牛产后气虚血瘀证血液流变性的影响

从血液流变性变化角度研究补气活血方——归芪益母散防治产后气虚血瘀证的作用。试验分为 3组 :产后健康组 18例 ,气虚血瘀证组 9例 ,气虚血瘀证用药组 8例。用药组按 0 .8g/ kg体质量投喂归芪益母散 ,给药方法为产后 1、2、3、5、7d每日 1剂 ,共计 5剂。于产后 1、2、4、7、10 d按设计指标采血、化验分析。结果显示 :喂服归芪益母散可显著降低产后气虚血瘀证奶牛 1、2 d全血低切比粘度 (P<0 .0 5 ) ;显著降低 4、7、10 d血浆比粘度 (P<0 .0 1或 P<0 .0 5 ) ,归芪益母散有改善血液流变性的作用。补气活血可显著改善产后气虚血瘀证奶牛的血液流变性     

安塞纸坊沟流域草地资源利用空间结构及其畜牧业发展潜力

黄土丘陵沟壑区是黄土高原生态环境极其脆弱,经济发展十分落后的地区.随着国家退耕还林(草)政策的实施,给区域天然草地的恢复与重建以及人工草地的发展带来了契机.种草养畜以其环境亲和特点,以及稳定的生产和较高的产品商品率,在黄土丘陵沟壑区越来越受到重视.文章试以安塞纸坊沟流域为例,通过航片解译分析流域土地利用现状.结合流域地形特点、生态生产特征和流域社会经济调查,通过GIS空间分析,划分流域生态生产区.讨论其功能和资源利用特点,以此提出流域草地资源利用的空间结构.依据利用程度,将其划分为高效人工草地带,农草、林草间轮作草地带以及天然轮牧草地带三种利用模式.根据不同利用带生物产量,计算最大载畜量,以期为流域环境保护、未来畜牧业发展及区域治理提供可靠依据和具体参考.     

基于马尔科夫的城市道路行驶工况构建方法

将汽车行驶工况看作一个随时间变化的马尔科夫过程,利用最大似然估计法,将行驶工况分成6个不同状态,而每个行驶片段作为反映加速度变化的模型事件,更好地保持了车辆行驶过程中微小时间段内的速度变化特性.在此基础上提出了状态转移概率与相似性检验相结合的候选工况选择方法,建立了具有13个特征参数的评价准则.以合肥市典型道路为例进行了实际应用分析,并通过独立性检验,验证了马尔科夫方法应用于行驶工况的合理性.结果表明,在与试验数据进行模型事件加速度分布的K-S检验上,马尔科夫方法相似性水平为0.998、0.989和0.994,而传统方法的相似性水平则为0.788、0.036和0.992.因此其更符合实际道路的行驶工况.