4D技术在工程项目管理中的应用和发展趋势

现代建设工程日趋复杂，传统的工程项目管理思想和手段已经无法满足项目业主越来越高的要求，进度、成本和质量管理彼此独立的传统模式导致许多弊端，主要表现在各专业生成的软件信息不能共享、项目参与各方所拥有的知识和经验不能很好地提供项目决策支持。随着管理思想、管理理论、IT技术的飞速发展，运用产品数据建模、软件集成(3D 成本／进度)的思想和方法，对传统管理工具进行变革成为可能。本文引进工程项目集成化管理思想，分析国内外4D技术研究的情况，提出4D建模技术辅助工程项目管理的发展方向和趋势。     

4G通信的网络结构与关键技术解析

随着3G网络的普及,加深了人们对于更快更好的通信网络需求,4G移动通信的发展迫在眉睫,本文就4G移动通信的发展前景及其特点做出简要介绍。     

结合CET4促进大学英语听力日常训练

本文从CET4对于学生听力的要求入手,结合具体的课堂,从知识面、听说习惯、记忆能力,心理素质四个方面,详尽探讨了日常训练听力的方法,目的在于帮助学生克服考前听力复习的仓促局面,同时又能有效地提高他们自身的听力水平。     

汽车4S店构建信息流与运营提升

汽车4S店是目前汽车厂商采取的主要营销模式,在经营管理过程中会产生大量的信息,这些信息如果能够被系统地收集、分析、整理和传递,必将对4S店的运营提升有着很大的推进作用。文章从信息流对4S店运营提升的作用出发,归纳目前4S店信息流现状,探讨如何构建完善的信息流体系。     

Spatial analysis of the U.S. lodging industry, 1963–1977

Data from the U.S. Department of Commerce Census of Business in 1963, 1972, and 1977 were compared on a state by state basis and by standard metropolitan statistical areas in order to analyze the spatial growth points of the U.S. lodging industry. The results point to major lodging growth areas in the Sunbelt states with central Florida, Las Vegas, Nevada and Hawaii as outstanding nodes of development. Metropolitan lodging growth has taken place in the Sunbelt cities with populations of 100,000 to one million, with above average growth in those cities located in the coastal zone.     

Spatial price mimicking on Airbnb: Multi-host vs single-host

This paper studies the existence of two different supply operators in the peer-to-peer accommodation rental market for the city of Madrid. We specifically analyse spatial dependencies in price formation and whether the so-called professional hosts (i.e. those who have several Airbnb listings) set prices differently from single-property hosts. To this end, hedonic price models are estimated with and without spatial price dependence. Listings’ structural characteristics and accessibility measures to transportation hubs and sightseeing spots are considered in the regressions. Results provide clear evidence that price mimicking is higher among non-professional hosts whereas professional hosts set prices more independently.     

4PL模式下基于时间资源调度的供应成本优化研究

订单时间是影响供应成本的主要因素,合理的进行时间资源调度更是供应成本优化的关键所在。现有的第四方物流(Fourth Party Logistics,4PL)路径优化研究只关注物流环节的时间和成本因素,没有与物流上一环节的整合。本文提出将4PL服务拓展到客户的生产环节,在供应商的生产时间窗约束下,构建模型得到生产时间与物流时间的最优组合方案使供应商供应成本最低。最后基于一个实例的分析,验证了该模型能有效帮助4PL为客户提供最优供应方案。     

Price relationships between qualitatively differentiated agricultural products: organic and conventional wheat in Germany

Organic agriculture, which produces commodities that can be qualitatively differentiated from conventional food products, has grown into an important market in many countries. The dynamics of commodity prices in both sectors are partly interdependent, but are also shaped by independent determinants and have rarely been studied. We analyze organic food markets and their interdependencies with conventional markets in the context of wheat markets in Germany, which have been subject to a number of fundamental changes during the last two decades. Based on institutional market characteristics, we suggest a flexible Markov‐switching asymmetric time series model. We find a pronounced temporal sequence of market phases that differ in their asymmetric dynamics and the extent to which the organic price is influenced by the conventional price. Organic wheat prices tend to be increasingly connected to prices of conventional wheat.     

微波常压法浓硫酸催化合成对叔丁基苯乙酸甲酯

对叔丁基苯乙酸在浓硫酸催化下，采用微波常压法与甲醇合成对叔丁基苯乙酸甲酯。结果表明：当对叔丁基苯乙酸：甲醇：浓硫酸=2：20：0．75(摩尔比)，采用600w微波辐射20min时，对叔丁基苯乙酸甲酯的产率达93．6％，反应速率是常规方法的12倍。