遗传算法的DV-Hop算法改进

DV-Hop算法中,平均每跳距离是影响定位精度的因素之一。针对平均每跳距离带来的定位误差,对锚节点和未知节点的平均每跳距离进行了改进和优化。首先引入遗传算法计算锚节点的平均每跳距离;然后利用跳数小于等于3的锚节点的平均每跳距离加权处理未知节点的平均每跳距离,减少平均每跳距离带来的误差。仿真结果表明,在不增加硬件开销的基础上,改进算法能够有效提高算法的定位精度,并且具有较好的稳定性。     

基于欧氏距离理论的农业可持续发展评价方法与实证研究

基于欧氏标准化距离理论,构建了农业可持续发展评价理论体系与评价指标框架,包括评价函数、评价等级、评级指标、佳态系统与原点系统等。选取甘肃镇原县、宁夏吴忠市和山东桓台县2000-2012年数据作为实证案例,并在评价指标框架下构建评价指标体系,对3个不同类型的农业系统进行了验证性评价。结果表明：甘肃镇原县ASDI(可持续发展指数)范围[0.70,0.83],呈上升趋势,处于中持续与高持续状态;宁夏吴忠市ASDI范围[0.40,0.77],呈波动较大,6年处于非持续、其余年份主要处于中持续状态;山东桓台县ASDI [0.53,0.71],大部分年份小于0.6,处于不可持续状态。欧氏距离法评价结果与农业系统实际情况接近,分别代表了3类农业生态系统。甘肃镇原在有机废弃物(秸秆与畜禽粪便)还田利用、人均粮食、高职教育、人均收入、饮用水安全、农药施用与基尼系数等方面接近佳态系统,仅在氮磷施用上稍微超标,属物质良性循环类型;宁夏吴忠由于在作物单产、有机废弃物还田与人均粮食等方面接近佳态,但在施肥量、水体污染与土壤有机质等方面远离佳态,因而ASDI有较大波动,属传统与集约化并存类型;山东桓台水肥药投入水平较高,农业面源污染负荷大,导致地表水、地下水氮磷超标引起ASDI较低,属典型的集约化类型。     

结球甘蓝产量性状的配合力与杂种优势分析

结球甘蓝全株重和叶球重是其产量性状的重要构成因素.研究其配合力和杂种优势表现,对甘蓝杂交育种和创制高产结球甘蓝杂交种具有重要意义.本研究通过6×7不完全双列杂交设计,对结球甘蓝产量性状的配合力效应和F,代杂种优势表现进行了分析,并基于SSR标记对13个亲本进行了聚类分析和遗传距离计算.结果表明,亲本880014、739...     

土地利用/植被覆盖动态变化及其预测——以河北省涉县为例

本文以河北省退耕还林典型县涉县为研究对象,根据1999年和2007年2期TM影像资料和其它辅助资料,分析了涉县土地利用变化、区域差异特征和各类型之间的转化情况,并利用马尔可夫模型对2015年土地利用动态变化趋势进行预测研究。结果表明：河北涉县1999-2007年,因为退耕还林工程的实施,林地和高覆盖草地的面积有较大幅度增加,分别增长了6.41%和5.61%;耕地和中覆盖草地面积有较大幅度降低,分别减少了7.68%和4.60%;可以看出林地,草地和耕地是本地区土地利用变化的主导类型,与其他土地利用类型间的相互转化分布较广。到2015年林地和高覆盖草地持续增加,分别增长了2.00%和1.23%;耕地面积持续降低,减少了3.74%;林地,草地和耕地始终为主要的转化类型,占据主导地位,因此,合理利用与保护该区的林地,草地和耕地资源,是该区生态环境建设的必要途径。     

发展现代农业远程教育-加快新农村建设

基于我国的国情考虑,积极发展现代农业远程教育已成为培养新型农民,加快社会主义新农村建设的有力措施,现代农业远程教育正在并将在社会主义新农村建设中发挥越来越大的作用。本文分析了现代农业远程教育的重要作用,存在的问题并提出了发展现代农业远程教的相关建议。     

Relationship between hybrid performance and AFLP based genetic distance in highland maize inbred lines

The objectives of this study were to determine the crossing performance of highland maize inbred lines for grain yield, days to silk and plant height; estimate genetic distance (GD) among the inbred lines and in association with tester parents, and to investigate the relationship of GD with hybrid performance and midparent heterosis (MPH). A total of 26 inbred lines were crossed with six (population and line) testers in a factorial-mating scheme. The F_1’s and the parents were evaluated at five locations in Ethiopia. Nine amplified fragment length polymorphism (AFLP) primer pairs were used to genotype all the parents. The F_1’s were found to vary widely for grain yield and other traits measured. Yield superiority of more than 30% over the best hybrid check was obtained for some testcross hybrids. Midparent heterosis on average was moderate for grain yield and, plant height. And for days to silking, MPH values were mostly negative. Mean GD values determined from the inbred lines by population tester (0.680) and line tester (0.661) combinations were not significantly different. Cluster analysis separated the tester parents from the corresponding inbred lines. AFLP grouping of the inbred lines was in agreement with their pedigree records. Genetic distances derived from the inbred lines × all testers and from the population testers’ sub-group were not positively correlated with hybrid performance and MPH for most traits. In contrast, correlations of GDs involving the line testers’ sub-group with F_1’s and MPH were significantly positive but with low magnitude to be of predictive value.     

微卫星座位数目对家禽遗传距离估测精确度的影响

以实际测定的29个微卫星座位的基因频率为基础,分析了4个中国地方家禽品种在5、10、15、20、25个微卫星座位情况下的遗传距离估测精确度,结果表明：随着微卫星数目的增多,遗传距离估测精确度精度也随着升高。对5个水平上的遗传距离标准差进行t检验,结果表明：25个座位水平对5、10、15、20个座位水平存在显著或极显著差异,初步得出在分析群体间遗传关系时应选用较多的座位     

Hierarchical control method of low voltage looped microgrid

The low voltage (LV) looped microgrid has high reliability of power supply and good accessibility of the DG. The medium voltage distribution network with single loop network and multi sectioned & multi linked is studied to analyze the wiring mode of the LV looped microgrid. A research on the two hierarchical control scheme of the looped microgrid is conducted, and the sub microgrid, which meets island operation requirements, is divided according to their segments. Then the incidence matrix is formed based on the connection relation of different segments and components, and the plan for switching the microgrid operation status is concluded from the reform of incidence matrix on the basis of the judgment of island and reconnection segments. A resynchronization strategy using microgrid central controller is proposed. The MATLAB/SIMULINK simulation software is used to analyze the dynamic characteristics of different operation status switching and synchronizing, and the results verify the effectiveness and correctness of the proposed control method.     

Experimental analysis of matrix shrinkage’s influence on mechanical permeability of gas filled coal

Based on the coal seam of Zhao zhuang coal mine and Si he coal mine belong to Jin cheng anthracite Mining Group in Shanxi province, by using the self developed three axial servo controlled seepage equipment for hot fluid solid coupling of coal containing methane, parallel experiments for permeability of helium and methane under different gas pressures are carried out to quantitatively study the influence of Klinkenberg effects on the permeability of coal. Meanwhile, the problem of permeability decreasing caused by fluid pressure decreasing and gas desorption is eliminated by controlling the effective stress. The results show thatthe Klinkenberg effect is obvious under low gas pressure. With the increase of gas pressure, the permeability of coal decreases at first and then increases. The inflection points of gas pressure for Klinkenberg effect are about 0.9 MPa both for coal samples in Zhao zhuang coal mine and Si he coal mine. When the effective stress is constant, with the increase of gas pressure, the permeability increment caused by Klinkenberg effect decreases, while permeability increment caused by coal matrix shrinkage increases. Coal matrix shrinkage has a close relationship with the mechanical properties of coal rock mass. For the coal sample with a poor mechanical property, coal matrix shrinkage is more obvious.     

周边干扰对煤气柜表面风压的影响

根据刚性模型风洞测压试验所得数据,研究了不同的周边干扰条件下柜体表面平均风压系数的变化规律,对比分析了不同柜体间距时干扰效应的变化情况。研究结果表明:干扰煤气柜位于柜体的正前方时,柜体迎风面平均风压系数显著减小;干扰煤气柜位于柜体的正后方时,柜体背风面平均风压系数会增大;两煤气柜相互平行时,柜体背风面平均风压系数会减小;柜体间距会对干扰效应产生影响,干扰效应随着柜体间距的变化而发生变化;在迎风面与侧风面,规范值有较高的安全储备;而在背风面,其安全储备略有不足。