高压输电线路故障测距算法综述

高压输电线路故障定位的准确性对电网的稳定运行有着非常重要的意义。文章对高压输电线路现有的各种测距方法进行了归纳总结和研究分析,并评述了各自的优点和不足。     

基于模糊综合评价法的市郊铁路客运站选址研究

本文针对其特点,应用层次分析法建立市郊铁路客运站站址比选的指标体系,确定各指标的权重,结合模糊综合评价原理建立相应的站址方案评价模型,并给出算例分析,为市郊铁路客运站站址方案的比选提供了一种更科学、更符合实际的方法。     

喷雾器喷头工艺优化模拟

本文利用moldflow软件优化喷雾器喷头,得到合理、可靠的注射工艺参素,优化模具结构。     

企业选址中的区位粘性问题

绝大多数企业并没有遵循区位理论的指引,将企业选址在具有明显区位优势的地区,这个基本事实表明区位理论对企业选址的解释存在缺陷。文章试图从区位粘性的角度弥补理论缺陷,增加区位理论对企业选址的解释力度。文章在综述区位理论的基础上,从空间经济学的角度定义了区位粘性,采用路径依赖理论和网络嵌入性理论对区位粘性的内涵进行了深入剖析,结合出生于小城市的中国企业区位选址的实践分析了区位粘性的构成因素。研究结果发现非理性决策因素、商业模式的地域关联性、社会资源优势、集聚效应、洼地效应以及政治资源优势等六种因素构成了区位粘性的基本内涵,并形成了企业原址对企业的强大粘着力,对企业选址决策具有强烈的影响和作用,只有在外在的冲击力强到足以打破区位粘性时,企业才会做出再选址决策。     

Hub location problems in transportation networks

In this paper we propose a 4-index formulation for the uncapacitated multiple allocation hub location problem tailored for urban transport and liner shipping network design. This formulation is very tight and most of the tractable instances for MIP solvers are optimally solvable at the root node. While the existing state-of-the-art MIP solvers fail to solve even small size instances of problem, our accelerated and efficient primal (Benders) decomposition solves larger ones. In addition, a very efficient greedy heuristic, proven to be capable of obtaining high quality solutions, is proposed. We also introduce fixed cost values for Australian Post (AP) dataset.     

Accommodating spatial correlation across choice alternatives in discrete choice models: an application to modeling residential location choice behavior

This paper presents a modeling methodology capable of accounting for spatial correlation across choice alternatives in discrete choice modeling applications. Many location choice (e.g., residential location, workplace location, destination location) modeling contexts involve choice sets where alternatives are spatially correlated with one another due to unobserved factors. In the presence of such spatial correlation, traditional discrete choice modeling methods that are often based on the assumption of independence among choice alternatives are not appropriate. In this paper, a Generalized Spatially Correlated Logit (GSCL) model that allows one to represent the degree of spatial correlation as a function of a multi-dimensional vector of attributes characterizing each pair of location choice alternatives is formulated and presented. The formulation of the GSCL model allows one to accommodate alternative correlation mechanisms rather than pre-imposing restrictive correlation assumptions on the location choice alternatives. The model is applied to the analysis of residential location choice behavior using a sample of households drawn from the 2000 San Francisco Bay Area Travel Survey (BATS) data set. Model estimation results obtained from the GSCL are compared against those obtained using the standard multinomial logit (MNL) model and the spatially correlated logit (SCL) model where only correlations across neighboring (or adjacent) alternatives are accommodated. Model findings suggest that there is significant spatial correlation across alternatives that do not share a common boundary, and that the GSCL offers the ability to more accurately capture spatial location choice behavior.     

区位商视角下的深圳优势产业实证分析

深圳经济特区成立30年以来,经济快速发展的同时也面临各种挑战。一方面,深圳内部面临着发展后劲不足、调控经济不力等多方面的问题;另一方面,外部经受着国内产业结构不断优化升级的考验。运用区位商对深圳的产业优势进行数量上的分析,可以为深圳产业结构的调整和转型提供科学指导,加速深圳的产业结构升级,以促使深圳的经济能够跃上新的台阶。     

Can farmers extend their cultivation areas in urban agriculture? A contribution from agronomic analysis of market gardening systems around Mahajanga (Madagascar)

The rapid urbanization in developing countries implies an increasing pressure on urban agriculture for production. As most perishable food products come from this agriculture in close proximity to population concentrations, we analysed from an agronomic point of view how market-garden farmers can meet this increasing urban demand. This work took place in the case of Mahajanga, a secondary city with high increasing demographic rate on the Northwest coast of Madagascar. Based on preliminary surveys to characterize the farming systems (on a sample of 91 farms), 11 market-garden farmers chosen in the three main agricultural zones of the urban area were surveyed during two years. Surveys aimed at understanding their decision rules in crop choices, crop allocation to land and resource management, and to estimate their room for manoeuvre to increase their leafy vegetable areas under cultivation. The wholesalers and retailers who buy the farmers’ produce were also surveyed. A previous model of decision rules regarding crop location on farm territory was used to analyse the on-farm surveys and cartographic methods (GIS and on-farm manual representations) were used to quantify the land use. We highlight the following major points. (1) The leafy vegetable production in the surveyed farms already intensively uses land: farmers have complex decision rules largely depending on the water dynamics in the two main environments (lowlands and lakesides) where leafy vegetables are cultivated during the dry season. (2) The scarcity of farmers’ resources (labour money and water) leads to very little internal room for manoeuvre to increase the leafy vegetable production in the farms. (3) At territorial level however, some land reserve exist in one of the lowlands, but not on lakesides. The water availability for agriculture must be better informed through specialized hydrologic studies, as one of the main constraints nowadays to extend the agricultural area. An extrapolation to other cases of urban agriculture is then discussed as well as the role of agronomy to help urban planners to consider the place of agriculture in the urban development.     

我国纺织服装业投资东盟的区位选择

纺织品配额取消以后,我国纺织服装出口反而遇到前所未有的挑战,纺织服装的低成本优势正在逐步丧失。为了化解出口压力,作为纺织服装出口大国,我国应该借助中国东盟自由贸易区(CAFTA)建设的机遇,把低端产品的生产转移到东盟。     

房地产营销定位新概念

从房地产营销定位的产生与发展入手 ,进而从理论上阐述了心理定位对房地产营销的意义 ,并从心理学角度讨论了心理定位对消费者的影响。还通过大量实例分析 ,进一步论述了心理定位的方法及策略