Trip distribution for limited destinations: a case study for grocery shopping trips in the Netherlands

In this paper, we introduce a new trip distribution model for destinations that are not homogeneously distributed. The model is a gravity model in which the spatial configuration of destinations is incorporated in the modeling process. The performance was tested on a survey with reported grocery shopping trips in the Dutch city of Almelo. The results show that the new model outperforms the traditional gravity model. It is also superior to the intervening opportunities model, because the distribution can be described as a function of travel costs, without increasing the computational time. In this study, the distribution was described by a simple function of Euclidean distance, which provides a good fit to the survey data. The slope of the distribution is quite steep. This shows that most trips are made to nearby supermarkets. However, a significant fraction of trips, mainly made by car, still goes to supermarkets further away. We argue that modeling of these trips by the new method will improve traffic flow predictions.     

Optimal resource allocation among transit agencies for fleet management

Most transit agencies require government support for the replacement of their aging fleet. A procedure for equitable resource allocation among competing transit agencies for the purpose of transit fleet management is presented in this study. The proposed procedure is a 3-dimensional model that includes the choice of a fleet improvement program, agencies that may receive them, and the timing of investments. Earlier efforts to solve this problem involved the application of 1- or 2-dimensional models for each year of the planning period. These may have resulted in suboptimal solution as the models are blind to the impact of the fleet management program of the subsequent years. Therefore, a new model to address a long-term planning horizon is proposed. The model is formulated as a non-linear optimization problem of maximizing the total weighted average remaining life of the fleet subjected to improvement program and budgetary constraints. Two variants of the problem, one with an annual budget constraint and the other with a single budget constraint for the entire planning period, are formulated. Two independent approaches, namely, branch and bound algorithm and genetic algorithm are used to obtain the solution. An example problem is solved and results are discussed in details. Finally, the model is applied to a large scale real-world problem and a detailed analysis of the results is presented.     

菲奥娜·班纳 直入云霄

两架战斗机被摆放在了伦敦杜英画廊的古典艺术品展厅里,菲奥娜·班纳受到英国泰特美术馆的邀请,设计了上述项目。班纳是"英国年轻艺术家"一代中的创始成员,她的这项最新的艺术展品的主角是两架来自皇家英国空军的退役战斗机:一架是"美洲虎"超音速战斗机,一架是可以垂直起落的"鹞"式战斗机。这两架飞机解体后,被运入这家圆形的新古典主义画廊,重新拼装后,被摆成了怪异的状态,并进行了巧妙的改装。     

The implications of MARPOL Annex V on the management of ports and coastal communities

Abstract

The passage of the Marine Plastics Pollution Research and Control Act of 1987 (MPPRCA), which codified Annex V of the International Convention for the Prevention of Pollution from Ships (MARPOL), has encompassed every commercial and recreational shipping and boating facility in the United States. As a group, these ports, harbors, and marinas form a significant, although proportionately small, portion of the coastline of the country. More important, the economic benefits derived from the complex shoreside infrastructures required for international ocean trade, commercial and recreational fishing, and pleasure boating indicate just how critical it is for these facilities to be in conformance with effective and prudent coastal zone and environmental management practices.     

The place of the ISPS Code in the legal international regime

The adoption of the International Ship and Port Facility Security Code (ISPS Code) is the latest response of the international shipping community to the increasing threat posed by acts of terrorism at sea. The ACHILLE LAURO incident of 1985 showed that the traditional law against piracy was not adequate to deal with new types of unlawful acts against international shipping, especially those involving acts of terrorism. The 1988 Convention for the Suppression of Unlawful Acts against the Safety of Maritime Navigation (SUA Convention) and the technical and administrative measures adopted by the Maritime Safety Committee of IMO in 1986 and 1996 attempted to develop a broader regime to deal with unlawful acts against international shipping.However, the events of September 11, 2001 showed that additional measures were still needed to prevent terrorist attacks against ships.     

Adapting interactive stated response techniques to a self-completion survey

We report here on how we adapted Interactive Stated Response Methods to use in a self-completion survey of 454 California households to measure the market for electric vehicles in California. Electric vehicles are a novel product and have many features unfamiliar to consumers, in particular their home recharging capability and limited range. Reflexive techniques were designed to draw households into a deeper exploration of the lifestyle implications of electric vehicles than can be done in more typical self-completion surveys, and to stimulate key decision processes previously observed in detailed gaming interviews with 51 households. Reflexive self-completion techniques provide a middle course between typical large sample quantitative surveys and small sample, detailed gaming interviews. One of the benefits of the more intensive techniques was that participants reported finding the surveys interesting and return rates were high for a self-completion approach – over sixty percent. We review previous transportation and sociological methods which inspired our design, describe the design goals and features of our research, and summarize research results pertinent to testing the validity of our approach.     

An evaluation of vehicle deceleration profiles

Vehicles stopping at signalized intersections were examined for the purpose of evaluating the validity of the common assumption of constant and uniform deceleration rates. The data set consisted of the first vehicles to stop upon the onset of the yellow signal interval with measurements of the initial approach speed, deceleration time, and deceleration distance. The deceleration rate may be computed using only two of the three measured values; thus the rate for each vehicle can be determined by three different equations. With nonuniform deceleration profiles, the equations will produce different values; and the degree of nonuniformity can be determined by comparing the differences in the computed deceleration rates. The analysis of the field observations indicated that 69 percent of the vehicles demonstrated deceleration profiles associated with nonuniform deceleration rates. Furthermore, the deceleration profile and the degree of nonuniformity were found to be a function of the initial approach speed.     

Finding a balance: companies, seafarers and family life

Separation from partner and family has been found to be one of the most significant causes of stress for seafarers, with separation from the family one of the most important 'stress' factors influencing a decision to reduce planned sea service. Drawing on in-depth interviews with seafarers' partners in the UK, China and India, this paper focuses on the impact of seafaring on family life, with particular attention given to the effects of differing conditions of service and the range of company support available to seafarers and their partners. The paper concludes that the negative consequences of seafaring can be minimized by such policies as shorter trips, continuous employment (rather than employment by voyage) and opportunities for partners and families to sail. Whilst these measures may have financial costs, these can be off-set by improved retention of seafarers and the avoidance of stress-related illnesses. Indeed, at a time when there is a projected shortfall of well-trained seafarers, such steps may be sound company policy     

A probabilistic damage tolerance concept for welded joints Part 2: a supplement to the rule based S–N approach

The first part of this paper presented the required statistics and stochastic models for reliability analysis of the fatigue fracture of welded plate joints. This present Part 2 suggests a probabilistic damage tolerance supplement to the design S–N curves for welded joints. The goal is to provide the practising engineer with simple tools that predict the reliability against fatigue fracture during service life. The impact of the chosen fatigue design factors (FDF) and the uncertainty in the applied stresses is revealed. The effect of an in-service inspection programme is also predicted. The results are presented as dimensionless matrices and suggested for use in support of decision-making at the design stage, without any advanced fracture mechanics modelling and stochastic simulation. One important advantage of this format is that the probability levels are presented regardless of actual weld class and target service life (TSL). This is obtained by introducing the FDF as a key parameter to the results. This parameter is defined as the ratio of predicted fatigue life over TSL. FDF is always calculated in the S–N approach which is mandatory in fatigue life prediction. Various welded details (classes) will have the same reliability level for the same FDF. This is true at the end of TSL and at earlier stages, i.e. fractions of TSL. The absolute value of TSL is immaterial for a given FDF. In the case of in-service inspection, the inspection interval is also given without dimensions as a fraction of TSL.

Only the influence of future scheduled inspections is treated. Updating based on actual inspection results is not included as the scope of work is inspection planning at the design stage. Results for some frequent cases occurring in practice are readily derived and presented.