Link choice proportions from trip distribution and assignment models: An overview and comparison

A number of estimation procedures have been suggested for the situation where a prior estimate of an origin-destination matrix is to be updated on the basis of recently-acquired traffic counts. These procedures assume that both the link flows and the proportionate usage of each link made by each origin-destination flow (referred to collectively as the link choice proportions) are known. This paper examines the possibility and methods for estimating the link choice proportions. Three methods are presented: (1) using ad hoc iteration between trip distribution and traffic assignment; (2) combining trip distribution and assignment in one step; (3) solving a new optimization problem in which the path flows are directly considered as variables and its optimal solution is governed by a logit type formula. The algorithms, covergencies and computational efficiencies of these methods are investigated. Results of testing the three methods on example networks are discussed.     

Optimum throughput and performance evaluation of marine terminals

The performance of marine terminals has generally been evaluated by comparing their actual throughputs with their optimum throughputs. The engineering approach that generally has been used to determine optimum throughputs may be appropriate when terminals have natural hinterlands. In a deregulated (competitive) environment in which the natural hinterlands of marine terminals have become diffused, the economic approach for determining optimum throughputs should be condiered. In such an environment, marine terminals are not only concerned with whether they can handle a given amount of cargo but also whether they can compete for such cargo.     

Shipper's councils: role and responsibility—a western view

Traditionally, liner markets have been seen as dominated by conferences on the seller side, facing small, unorganized shippers onn the buyers' side. This perceived asymmetry has greatly influenced conference legislation in North America (and more recently in the E.U.) and it has been deemed essential that government should regulate conference activities in order to curb any abuse of 'conference power'. In this view, shipowners and shippers are adversaries engaged in a zero-sum battle over transport costs rather than potential or actual partners in global distribution systems. This paper suggests that in today's global markets much can be achieved by cooperationn in the development of logistics systems and that shipowners and shippers may have much to gain from such cooperative alliances. A survey of shippers' councils in 1991-1992 demonstrates the diversity and increasing sophistication of many national shippers' councils, which devote themselves to the task of improving markets through education and the legislative process. The situation in the U.S.A. is different: for legal reasons, conventional shippers' councils do not exist. Instead, 'shippers' associations' play a commercial role in liner markets. It is suggested that European style shippers' councils can and should play an important role in the development and formulation of policies for internatinal liner markets. Such participation requires a cooperative industry environment quite different from the traditional adversarial approach, which is ill suited to global trade and logistics alliances.     

再生性原料在汽车上的应用

本文以联邦德国农业及经济状况为出发点，介绍了利用生物制品，主要是粮食，油料等农产品转化为发动机燃料的研究工作情况，并重点介绍了用菜籽油和酒精的试验研究情况。     

The role of the Federal Government in US marine transportation

The United States meets the world shipping crisis of the 1970s with a high-cost merchant fleet and a national maritime policy which needs clearer articulation. This paper examines the objectives, rationale and methods of implementation of the Us maritime programme with attention, finally, to the question of governmental reorganization.