An EOQ Model at Random when Average Demand Is a Linear Increasing Function

For certain types of inventory, the ordering cycle and demand may be random variants, which satisfy certain types distribution. The classical EOQ model usually neglects the fact. Based on the constant demand, under the hypothesis that the ordering cycle is a random variant which satisfies exponent distribution, average demand is a linear increasing function, this paper considers the effects of the time-value of capital and inflation on replenishment strategy of inventory system. Loosening the condition of basic economic order quantity model under deterministic state, the total cost function of the model is provided. The optimum order quantity and cycle are obtained. The application range of EOQ model under the constant demand is widened. The theoretical evidence is provided for the inventory system to make management decision.     

Empirical Analysis of the Demand of Rail Freight Transport in China on Basis of VAR Model

With the rapid development of road and other transport modes in China, the railway freight transport is confronted with great challenge. So, the relations of rail freight transport, development of national economy and extension of railway become focuses. This paper makes a cointegreting VAR model according to the data from Chinese Statistical Year Book. On the basis of the model of the long-run and short-run equilibrium of rail freight demand are analyzed, The result shows that the rail freight transport in China has a stable and low elastic coefficient of income and a high but unstable elastic coefficient of supply in long-run. In short dynamics, the national economy is the first factor affecting rail freight demand and in the second term the innovation reaches a top point. Extension of railway has little effect on rail freight transport. The innovations from rail freight transport and railway extension has little impulse on national economy. Rail freight is the important factor affecting extension of rail-way with a third-term top, but GDP has a little impulse on it. Further analysis on the result and suggestion on policy are made.     

Preliminary Study on Eco-environmental Water Demand in Taohuajiang Valley, Guilin

Eco-environmental water demand in Taohuajiang Valley of Guilin is defined as the minimum water volume required by the valley to maintain the eco-environmental quality not to be degraded over time.By using the site survey data,the eco-environmental water demand in Taohuajiang valley is studied preliminarily.The results calculated indicate that: the out-stream eco-environmental water demand is about 14.9 million m3 per year,about 4 percent of annual runoff of the valley;and the in-stream eco-environmental water requirement is about 109.8 million m3 per year,about 30 percent of annual runoff.This study provides scientific basis for local sustainable water resources use and management as well as for eco-environmental water requirement study in similar regions in terms of Karst geological condition and climate.     

21世纪我国沿海地区城镇居民食品消费需求分析

利用2000~2004年12个省市面板数据构建消费需求Working模型,实证分析了21世纪我国沿海地区城镇居民食品需求情况。结果表明,沿海地区城镇居民食品消费结构发生了深刻变化,对外用餐、奶类和瓜果类需求会进一步扩大,而对其他食品的需求会减少,这对我国农业生产和餐饮服务业发展具有十分重要的意义。     

Design and Performance Analysis of Low Pressure Irrigation Distribution Systems

Low-pressure pipe distribution systems forsurface irrigation provide both off- andon-farm recognized environmental benefits.However, expected benefits can only beattained when adequacy, dependability andequity of systems are high enough tosupport appropriate conditions for wateruse on the farm. An innovative methodologyfor design and analysis is proposed anddescribed, which includes the generation ofthe demand at the scale of the distributionsystem and, consequently, the generation ofthe flow regimes expected during a givenperiod of time, generally the peak month.These flow regimes are utilized for theoptimization of pipe sizes using theiterative discontinuous method for severalflow regimes. The performance analysis isdeveloped through the system simulationwith several flow regimes, which allow thecomputation of the system adequacy,dependability and equity. An application toone sector of the Sorraia irrigation systemillustrates the usefulness of themethodology proposed.     

试论农业机械化在社会主义新农村建设中的作用

近几年,随着政策导向和资源配置通过市场杠杆促进农业机械化,使农村拥有的农业机械不断增加,农机化综合水平不断提高,推动了农业耕作制度的革新,加速了农业的产业化步伐和农村劳动力的转移,因此,农业机械化在社会主义新农村建设中发挥着愈来愈重要的作用。     

苹果果树渗灌试验研究

1989到1991年对10年生国光和金帅苹果品种的果树进行的渗灌试验结果如下:1,能节水并可防涝;2,可增加土壤孔隙度,提高土壤养分含量;3,增加吸收根数量,促进树体的生长发育。座果率和单株(或单位面积)产量均比漫灌(对照)区高;4,到1991年,果品质量有了明显的改善;5,多孔陶土管成本低;6,田间管理方便。     

用意杨压缩木替代传统木梳材料的研究

我国木梳素以小叶黄杨、楠木、枣木、梨木等树种为制梳材料。由于人口膨胀,木梳需求量巨增,制梳原材料渐已匮乏,绵延1 500多年的传统木梳手工艺文化正面临消亡的威胁。笔者选择速生树种——意杨为制梳材料,按木梳实用功能和产业经济的实际需求,对意杨压缩木进行一般物理特性试验,对其木梳制品进行实用和成本分析,最终确定50％左右的意杨压缩木完全能替代木梳传统原材料。     

木材纤维与回收聚丙烯的热压复合工艺研究

研究了热压时间、热压温度、聚丙烯和偶联剂加入量等工艺因子对木材纤维和回收聚丙烯复合材料性能的影响。确定了压制密度为0．80g／cm3、10mm厚的木塑复合材料的最佳工艺条件为:热压温度175℃、热压时间8min、塑料加入量40％、偶联剂的加入量4％。在此条件下压制的木塑复合板材,物理力学性能中的内结合强度和吸水厚度膨胀率与中密度板的国家标准相比达到优等水平,静曲强度和弹性模量基本满足中密度板的国家标准要求。     

生态系统服务权衡最新研究进展

生态系统服务权衡研究对协调生态环境保护和社会经济发展至关重要。为推动生态系统服务管理和提升人类福祉,本文以Web of Science核心合集(WOS)和中国科学引文数据库(CSCD)为数据源,运用文献计量分析法,系统梳理和总结生态系统服务权衡研究的学科知识基础、科学领域结构和热点变化等发展现状以及最新研究进展。研究表明:1)不同研究层面上,生态系统服务间的权衡关系受外部风险和人类需求、参数选取和服务提供者及区域差异性和不均衡性的影响。2)研究方法主要有基于关系识别和具体表征的权衡分析、权衡模拟和预测的模型量化分析和生态系统服务权衡管理优化的多准则分析3类。3)生态系统服务权衡关键驱动因子为城市化、生态工程和气候变化。基于此,我们认为把握生态系统服务权衡不同研究层面的关联特征、创新和优化生态系统服务权衡研究方法、准确甄别生态系统服务权衡关键驱动因子以及充分整合多维生态系统服务权衡资源搭建数据共享平台是未来研究的重点。