The validation of a microscopic simulation model: a methodological case study

The use of microscopic simulation models to assess the likely effects of new traffic management applications and changes in vehicle technology is becoming increasingly popular. However the validity of the models is a topic of increasing concern, as the quality of the presentation often exceeds the models ability to predict what is likely to happen.Traditionally, model validity has been ascertained through comparing outputs aggregated at a macroscopic level such as speed flow and lane use, against real data. Little microscopic comparison is generally possible and, where this is done there is often no separation of the calibration and validation process. This paper demonstrates how microscopic validation may be undertaken when suitable data is available, in this case time series data collected by an instrumented vehicle, and its use in the validation of the car following performance of a fuzzy logic based car following model. Good agreement has been attained between the simulated model and observed data, primarily using a root mean square error indicator. Lastly, a brief comparison of the new model with the performance of a number of existing formulations has also been undertaken.     

关于基础制动单元中牙式离合器结构零件的加工工艺分析及加工方法改进、应用

在列车基础制动产品中,包括盘形制动单元和踏面制动单元在内,都广泛使用了牙式离合器结构。现以城轨踏面制动单元中的典型零件吊耳为例进行工艺分析,制定加工方案、进行工装和专用刀具设计,确保加工精度、提高加工效率。     

Efficiency sensitivity analysis of a hydrostatic transmission for an off-road multiple axle vehicle

There is a large variety of multiple driven axle vehicles. Some of the most common are the 3-axle rigid vehicles and the 4-axle articulated vehicles, which can in some cases have different steering mechanisms, adaptive suspension, etc. This last kind of vehicles usually have very complex transmission configurations. Moreover, the required torques in each of the wheels can be very different, especially when the vehicle is working in rough terrains. The aim of this work is to study and model the driveline of this kind of vehicles, when using a hydrostatic transmission, from the performance and efficiency point of view, by analysing the influence of the operating conditions in the transmission efficiency. A global model is used to quantify the power flow in each of the transmission elements and the overall performance of the entire vehicle driveline, given the operating conditions thereof. A sensitivity analysis has also been done showing the influence of vehicle speed, rolling resistance, terrain slope and hydraulic motors displacement in the overall transmission efficiency. The interest of this work is also to make a contribution to the literature in the field of global modelling of drivelines under variable operating conditions and its application to ATVs. One important aspect is the influence of different actuation requirements that occur in different wheels at the same time. The results show that the overall performance of the transmission is highly dependent on operating conditions, on the selected transmission configuration and on the used components.     

A Fisherman's Co-operative: Open System Theory applied ☆

In this paper the effects on the economic output, income and employment relating to Shetland are considered using an input—output model. The results are presented on the basis of an individual industry and appropriate multipliers are derived.     

Unloading facilities at an iron-ore terminal

In this paper a project undertaken by the author is described to illustrate modifications which may be necessary to the type of analysis given in an earlier paper [1] when difficulties arise from various practical considerations. The problem examined deals with the installation of unloading facilities at a purpose-built iron ore terminal at a steelworks. However, some of the data quoted has been coded to preserve confidentiality. The project was bedevilled by an unusual number of uncertainties; to appreciate these it is necessary to view them in relation to the situation existing at that time.     

The design of shipboard organization: some experiences with a matrix-type of organization in Norway

This article describes an experimental project that was designed to meet the challenges of social and technological developments to the existing shipboard organization.     

On the practicality of the UNCTAD 40–40–20 Code for liner conferences

The potential effects of a rigid adherence to the UNCTAD Code are analysed for 26 developing countries. A brief commentary is given on the advantages of a more liberal application of the Code, including reciprocal sharing of liner tonnages by regions of developing countries with regions of developed market-economy countries.     

Emerging organizational values in shipping: Part 4. Decentralization—the redefinition of authority in shipping company organization

Decentralization is a major theme of organizational change in shipping. It is often seen as ‘putting power back aboard ship’. However, the authors argue that this view is too simple. Decentralization poses fundamental questions about the entire management structure of the shipping company. The redistribution of authority necessary for decentralization is discussed in terms of the company organization structure.