Distributed Power Flow Method Based on Ward Equivalent

With interconnecting and developing of power system, the problem of power flow computation on dispersed data resource need to be solved. A new distributed computation method of power flow based on Ward equivalent is presented. According to master-slaver splitting principle, multi-area interconnected power system is divided into master-slaver areas. Boundary buses in different areas are defined as different bus-types. Neighborhood areas are equivalent by Ward equivalent principle, and the equivalent injection power and equivalent impedance are worked out. Power flows from master area to slaver areas are solved by Newton method, and the equivalent injection power and equivalent impedance on the boundary are modified by their solutions. The process above repeats until to convergence. The proposed distributed power flow method takes full advantage of the information of power, voltage, network configuration in neighborhood areas, so it is better on convergence and quality of solution. The proposed algorithm is testified by IEEE 14-bus system and a practical 181-bus system.     

A FINITE ELEMENT ALGORITHM FOR PARALLEL PROCESSING OF MULTI-FRONTS

In this paper,a new algorithm for solving large-scale finite element system is presented, which utilizes the architecture of parallel processing. Firstly, the structure is partitioned into sub-regions. Then multi-fronts are used to assemble and eliminate concurrently in every sub-region. Thus the condensed interface stiffness matrices and load vectors are obtained. By serially assembling and solving global equation to get interface displacements and backing to every sub-region, the inter-nodal displacements and element stresses can be solved. The results of computation show that it can not only increase the speed of computation,but also save the memory space of computer effectively. This algorithm is an effective method for solving large-scale structural finite element systems.     

Nonlinear Finite Element Analysis of RC Deep Flexural Simply Supported Beams Using Disturbed Stress Field Model

A nonlinear finite element analysis of 4 RC deep flexural simply supported beams with the program VT2 is presented. Crack development and failure modes , longitudinal reinforcement strain distributions and load -deflection curves were compared as a result in order to evaluate the validity of the disturbed stress field model to analyse such deep simply supported beam.     

急、慢性冷应激对雏鸡腓肠肌及血清抗氧化功能的影响

【目的】探讨自由基在冷应激对禽类机体损伤中所起的作用,为探索促进动物冷适应的方法,提高动物的抗寒能力提供一定的理论依据;【方法】应用化学比色法检测了急、慢性冷应激对腓肠肌和血清中总抗氧化能力(T-AOC)、过氧化氢酶(CAT)活性、谷胱甘肽过氧化物酶(GSH-Px)活性、超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量的影响;【结果】急性应激时,随应激时间的延长,腓肠肌T-AOC与SOD活性均逐渐降低,GSH-Px活性、CAT活性及MDA含量均逐渐升高,血清T-AOC逐渐降低,GSH-Px活性、CAT活性、SOD活性及MDA含量均逐渐升高;慢性应激时,随应激时间的延长,腓肠肌T-AOC、GSH-Px活性、CAT活性及SOD活性均逐渐升高,MDA含量逐渐降低,血清T-AOC、GSH-Px活性、CAT活性及MDA含量均逐渐升高,SOD活性逐渐降低;【结论】表明急、慢性冷应激均可使机体的抗氧化功能发生改变,诱发氧化胁迫,导致机体内自由基增多,对机体造成损伤。     

棉花烂铃空间格局及抽样技术研究

本文通过聚集度指标（如：Ｃ、Ｋ、Ｃ＿Ａ、Ｉ、Ｉ＿δ、）测定，以及Ｉｗａｏ’线性回归、Ｔａｙｌｏｒ’ｓＳ￣２一回归和格局纹理分析，结果表明，棉花烂铃空间格而在一切密度下都呈聚集型，且聚集强度随烂铃密度的升高而增加，其空间格局的基本成分是疏松的个体群，其大小约为２～５株棉花，平均约含２．８４个烂铃个体，且个体群内的个体呈随机分布，经μ检验和方差分析，双对角线５点式、棋盘式和平行跳跃式等３种取样方法均适用于棉花烂铃田间调查，尤以双对角线５点式为佳，用双对角线５点式应样法调查的最适抽样数：一般病情普查至少１０个样方（每样方系５株棉花），系统测报和科研调查为２０～３０个样方。最后给出了棉花烂铃平均密度的零频率简易估计模型。     

联合收获机前进速度模糊控制系统多目标遗传优化

针对联合收获机前进速度模糊控制系统参数设计具有主观性,导致作业性能不理想的问题,以切纵流联合收获机样机为研究对象,构建联合收获机前进速度模糊控制系统仿真模型,并建立控制性能和收获性能的优化目标函数来衡量联合收获机的作业性能,利用多目标遗传算法对模糊控制系统的隶属函数和输送槽、割台螺旋输送器和切流滚筒对前进速度的影响因子进行优化。通过对优化前后模型仿真对比和两组田间试验数据分析,表明优化后的控制系统在受外界干扰情况下控制性能得到了较好的保持,收获性能在喂入量变化不大情况下,单位平均损失率分别由1.45%和1.26%降至1.12%和1.14%,联合收获机的总体作业性能得到改善。     

Effects of arrangement of surge-rootirrigation emitters on growth,yield andwater use efficiency of apple trees

Six-year old apple trees were selected for field experiment. The objective of this study was to obtain the reasonable arrangement of surge-root irrigation emitters in apple orchards. There were three factors: the buried depth H( 25,40,55 cm),the horizontal distance L( 30,40,60 cm) between the emitters and the trunk of the experimental tree,and the number of the irrigation emitters N( 1,2,4). The effect of the arrangement of surge-root irrigation emitters on the growth,yield and irrigation water use efficiency( IWUE) of apple trees were studied in Northern Shaanxi where the irrigation quota takes 60%-75% of the field water capacity. The results showed that the arrangement of emitters for surge-root irrigation had a significant effect on apple tree yield and IWUE,especially,the yield and IWUE reached 28 388. 17 kg/hm2 and 16. 83 kg/m3 in treatment T3,respectively. At the same L and N levels( T1,T2,and T3),the yield and IWUE in treatment T3 were the highest,and the yields in treatments T1 and T2 were decreased by 26.22% and 31.48%,while IWUE is reduced by14.02% and 18.12% compared with T3,respectively. At the same H and N levels( T3,T4,and T5),the yield and IWUE of apple trees were decreased with increasing L level. Especially,when L was 30 cm( T3),the yield and IWUE were the highest. The same L and H levels( T3,T6,and T7) could promote the growth of apple trees when N was 2( T3). Compared with treatment T3,it was found that the increment of new shoots was decreased by 8.07%-18.71%,and the fruit diameter was decreased by 5.41%-9.11%. Therefore,two emitters should be arranged symmetrically on both sides of an apple tree,each was buried at a 40 cm depth and 30 cm away from the trunk of the tree to effectively improve the yield and IWUE of the apple tree in mountainous areas in Northern Shaanxi.     

谷物收获超声波流量计的前期研究

以多普勒法的谷物收获超声波流量计为研究对象,进行谷物收获系统和超声波流量计的前期研究.超声波流量计是利用流体对超声波的影响来测量流量的仪表,传统的测量原理一般为时间差法,测量精度低,只能对液体或者气体进行流速测量;而采用多普勒测量法则可以达到更高的测量精度,并且尝试对谷物(固体)的流速进行测量.