地震时城市供水管网连通可靠性分析

在分析地震条件下管线功能函数及极限状态方程基础上,对城市供水管单元体进行震害预测。以供水管网系统作为边权的有向网络图,通过基于神经网络的Monte Carlo方法,模拟各管线运行状态及其破坏状态。结合图论理论,分析供水管网的管线连通可靠性。     

Pressure-Dependent Analysis of Water Supply Network Damaged by Earthquake Based on Emitter Model

When the water supply network suffered earthquake damages, pipeline leaks and bursts may occur. In the period in post-earthquake emergency rescue and repair, the network is supplying water with additional outflow of damages (leaks and breaks), which result in pressure deficient. According to the frictional head loss along the break pipeline, a model with additional emitter at the endpoint of the disconnect pipeline was proposed to simulate the break, which simplifies the modeling of breaks. The pressure-dependent demand relationship was adopted in the process of pressure-deficient hydraulic simulation to avoid node negative pressure. Meanwhile a backtracking and line search procedure was utilized to control the iteration step of pipeline network nonlinear equations, which ensure the global convergence of the hydraulic simulation. The effectiveness of the proposed method was verified by a case study.     

农业社会化服务供给博弈分析

农业社会化服务主体在农业社会化服务体系中扮演重要角色,各服务主体提供的服务能否为农户带来长远利益并最终被农户持续接受是农业社会化服务持续发展的关键问题。本文以博弈论为基础,通过分析公共服务机构及中间服务组织与农户之间的博弈过程发现：公共服务机构和中间服务组织为农户提供的社会化服务的质量及其自身的成本收益成为影响农业社会化服务持续发展的重要因素,农业社会化服务若要持续稳定的发展,离不开服务主体高水平的服务和农户的积极参与。只有适应市场需求,真正能够给农户带来实惠的服务才会最终被农户所接受。     

Comparison of Constant and Linear BEM Analysis for Small Viscous Fluid Sloshing

Linear boundary element method is used for the analysis of viscous fluid. The velocity components and the fluid mean pressure are taken as unknown functions. The comparison of linear BEM with constant BEM shows that the former presents much better precision and better convergence.     

北京产果品供应链整合运作模式探讨

探索供应链管理思想在农产品经营实践中的应用已逐渐受到关注。本文以北京出产的果品为研究对象,基于对果品供应链所涉及生产、经营和消费等环节的相关节点主体进行的实地调研资料,结合对果业发展间接资料的系统分析,探讨了北京出产果品在市场供求对接实践中,业已存在和未来可供选择的供应链整合运作模式,其中包括“产地主导的都市农业模式”、“核心主体拉动模式”和“基于信息网络平台的节点协同模式”。同时,针对不同模式又简要讨论了各自特点及其在实践中应用的适应条件。目的是为参与北京产果品供应链管理的各方面相关主体提供管理借鉴和参考。     

基于平衡膳食的中国农产品供需研究

促进农业增产,保障农产品供给一直是中国农业发展主要任务,但是中国的农业生产并没有同中国居民的膳食需求相结合制定合理的发展目标,生产存在一定的盲目性。依据中国营养学会制定的《中国居民膳食指南》中的膳食标准,计算出平衡膳食条件下中国各类农产品的需求量,通过与目前中国各类农产品的产量对比发现中国大部分农产品的产量已经超过了平衡膳食条件下中国居民的合理需求量,调整中国的农业生产结构,倡导平衡膳食,成为解决中国农产品供求平衡问题的一个重要途径。     

甘肃省“蛛网模型”马铃薯供求关系的分析

为了使马铃薯产业的供求机制及其价格变动成为甘肃省农民增收、工业发展的重要信息导向源,运用“蛛网模型”对甘肃省1999-2008年期间马铃薯价格的变化作深入的分析。并通过“蛛网模型”价格信号反应,分析了甘肃省马铃薯市场“蛛网模型”变迁路径与诱导因素,从而“管中窥豹”式的观察马铃薯市场,以便采取措施,规避市场风险。     

服务供应链视角下生鲜农产品品质不确定性因素研究

从服务供应链视角构建生鲜农产品服务供应链,将其作为农产品供应链的子链,利用系统分析的方法得出在服务供应链中影响生鲜农产品品质的不确定性因素,根据管理决策行为能否抑制不确定性因素对生鲜农产品的消极影响,将不确定性因素划分为可控不确定性因素和不可控不确定性因素。利用灰色关联分析得出影响生鲜农产品品质的关键可控不确定性因素,并从生鲜农产品流通渠道、冷链设施设备的投入、物流标准化、政府对质量的监管力度等方面提出控制策略,保障生鲜农产品质量安全。     

The Analysis of Abnormal State for Power Distribution Network Based on MATLAB

Along with the extensive use of power cable lines in power distribution system, the probability of fundamental frequency resonance has greatly increased. It may endanger the security operation and power supply reliability of the power system. On the basis of theoretical analysis and numerical calculations using MATLAB language combined with a real instance, it is indicated that the improper electrical parameter coordination caused by the abundance of power cable lines result in fundamental frequency current resonance, in addition, the countermeasures based on SVC to solve the problem are put forward. Further more, digital simulations have been carried out in detail based on the dynamic simulation model developed by the application of MATLAB/Simulink and its power system simulation software. Simulation results proves the effectiveness and practicability of the scheme presented.     

生鲜农产品温控供应链发展策略研究

近年来,人们越来越关注生鲜农产品品质,温控供应链是保障生鲜农产品品质的关键。通过梳理生鲜农产品温控供应链的概念,总结了温控供应链的特点,找出其中的不足并对生鲜农产品供应链体系建设发展提供了建议,以期加快生鲜农产品供应链体系建设进程,促进生鲜农产品温控供应链的健康发展。     

罗望子挥发油的超临界CO2萃取及其GC-MS分析

用超临界CO2流体萃取技术(SFE-CO2),对罗望子进行了的萃取,得到罗望子萃取物。考察了萃取压力、温度、时间、粒度、CO2流量对罗望子萃取收率的影响,得到最佳萃取工艺条件：压力25Mpa、温度40℃、时间4h、粒度40目和CO2流量25 L/h,在此工艺条件下超临界CO2法得到的罗望子萃取收率为4.08%。并利用气相色谱仪-质谱仪(GC-MS)对罗望子萃取物的化学组成进行了分析鉴定,并用面积归一化法测定了各种成分的质量分数,共鉴定了48种成分,占总质量分数为98.35%,其中主要成分为：5-甲基-2(3H)-呋喃酮、丁二酸二乙酯、糠醛、十六酸、亚麻酸、5-甲基糠醛、油酸、亚油酸等。     

The Research about Operating State of Enterprise in Exessive Indebtedness and the Boundary of Pressed for Funds

It analyzes the operating state of enterprise in exessive indebtedness by the methods of statistical and break even analysis; and it analyzes the boundary of pressed for funds by the methods of assets structure and business effective analysis.Submit the train of thought for scientific research in enterprise operating with debts.     

丽江山慈菇种子繁殖技术初报

丽江山慈菇是一种益辟坚属的小草本药用植物,鳞茎含有秋水仙碱,其野生资源远远不能满足医药生产的需求。对丽江山慈菇种子繁殖的适宜条件进行研究,表明丽江山慈菇种子的千粒重为0.3085g,种子活力为94%,其萌发的适宜光周期为18h,最适温度为25~28℃,适宜pH值为6.2~7.5,最佳浸种条件为50℃浸种12~18h,最佳低温处理条件为9℃处理5d,变温处理5d为最佳变温处理条件,最佳贮存时间为180d。     

超临界CO_2流体萃取分离高纯栀子甙的工艺研究

采用超临界CO2流体萃取分离技术,对栀子黄提取废液中的栀子甙进行分离精制。分别考察了分离温度和分离压力对栀子甙和栀子黄分离效果的影响,在此基础上对超临界CO2流体萃取的分离工艺进行了改进。实验结果表明,降低分离压力有利于对栀子甙和栀子黄的分离,分离温度低于40℃时,升高温度有利于栀子甙分离而不利于栀子黄分离;分离温度在高于40℃时,对二者分离均不利。改进后的"一萃两分"工艺最佳分离工艺参数为:分离压力均为8MPa,第1次分离温度为40℃,第2次分离温度为25℃。     

基于供应链视角的农产品质量安全研究

从介绍农产品供应链的结构入手,分析了我国农产品供应链的现状;结合质量安全的理念,提出了影响我国农产品供应链质量安全的制约要素;从供应链的角度探讨了保障农产品质量安全的5个关键点。     

Research on the Application of Moving Mesh Technology in Computational Fluid Dynamics Simulation

This paper applies moving mesh technology to the numerical simulation analysis of computational fluid dynamics（CFD） based on harmonic mapping theory.It deduces renewal process of the solving domain when moving mesh technolog deals with problems of large deformation,and the corresponding program flow diagram is given.It solves the problems of grid large deformation which the traditional fixed grid is unable to simulate.It uses the multi-physical coupling analysis software COMSOL Multiphysics 4.0a to couple the moving mesh equation with controlling differential equation,and simulates the movement of the oil inside the swaying tank. The numerical simulation show that moving mesh technology can simulate the situation of solving domain’s large deformation truly.In the process of simulation,the number of the nodes and grids in the fluid domain do not increase,it just changes the shape of the grids,so that,the moving mesh method dose not increase the spending of computer resources extra.     

不同保鲜模式对生鲜农产品供应链系统利润的影响分析

针对消费者对生鲜农产品保鲜要求高但企业保鲜意识不足的问题,研究了不同保鲜模式对生鲜农产品供应链系统利润的影响。采用迭代关系表示生鲜农产品新鲜度,依据成员是否保鲜将保鲜模式分为8类,构建不同保鲜模式下的生鲜农产品供应链系统利润模型,并求解不同保鲜模式下生鲜农产品供应链系统的最优决策参数和利润,分析影响供应链系统利润的因素,最后通过数值算例验证模型结论。研究表明,供应链系统三者(生产商、分销商、零售商)均保鲜时利润最大,降低成本或者降低运输时间均可使供应链系统的订货量和利润上升。