Human Control of Road Vehicles

This paper reviews the present state of knowledge of human control of road vehicles. Lateral and longitudinal control of motorcycles and automobiles are discussed, whenever information is available. Although knowledge has increased greatly in the last decade, the major part of this concerns lateral control and most is of an ad hoc nature. Adequate mathematical models for longitudinal motion of the vehicle are yet to be developed. Their development is a necessary step in the attainment of a complete understanding of longitudinal control.     

On the role played by turbulence closures in hull shape optimization at model and full scale

 The practical use of automated computational fluid dynamics (CFD)-based design tools in the ship-building industry requires powerful flow solvers which are able to take into account realistic geometries as well as complex physical phenomena, such as turbulence. A shape optimization tool is developed in this framework. A derivative-free optimizer, yielding both flexibility and robustness, is preferred to the classical gradient-based method, which is more difficult to implement and is still limited to only moderately complex problems. The flow solver included in the design procedure solves the incompressible Reynolds-averaged Navier–Stokes equations on unstructured grids using a finite-volume formulation involving several near-wall low-Reynolds-number turbulence models. The design tool is used to optimize the stern of a modern hull shape at model and full scale, with different purposes being considered. More precisely, the drag reduction and the homogenization of the flow in the wake are expected by controlling the longitudinal vortex generated. Our interest is particularly focused on the influence of turbulence modeling in the design process. The effects of a two-equation model based on the eddy-viscosity assumption and a second-order closure relying on the Reynolds stress transport equations are compared. Received: September 24, 2002 / Accepted: April 14, 2003 RID="*" Acknowledgment. The authors thank the scientific committee of CINES (project dmn2050) for the attribution of CPU time.     

Modeling oil spills in a river—lake system

A general model shell, ROSS3, is developed for simulating oil spills in complex river systems using techniques which have not been previously exploited in oil spill models. ROSS3's new approach has several advantages over the approach to model oil spills in the past: (a) The use of a time-varying boundary-fitted coordinate system that allows accurate accounting for complex river/lake boundary as well as the river boundary changes as its water levels fluctuate; (b) The ability to confine two-dimensional hydrodynamic computations to a limited river reach; (c) The ability to interactively layout the channel networks for setting up the model, define extra cross sections to increase the accuracy if needed, in addition to the traditional data entry and visualization interfaces.ROSS3 is a two-layer two-dimensional oip spill model that can simulate the mechanism of advection, horizontal diffusion, mechanical spreading, shoreline deposition, evaporation, dissolution, vertical mixing, resurfacing and sinking. In ROSS3 spilled oil may be a surface slick or suspended oil droplets, or a combination of both. Both free surface and ice cover conditions can be simulated. The flow of conditions can be varied and the unsteady flow model can be run within ROSS3 to simulate the flow conditions in both the river and the lake. The ice conditions can be added or removed from the model input using easy interactive procedures.     

作为竞争因素的现代化动车组--以市郊铁路客运为例

铁路改革的核心目的之一,是在改善市郊铁路客运(SPNV)经济性的同时增加铁路对旅客的吸引力.决策者希望通过已知的乃至未知的竞争来实现这一点.德国铁路公司(DB AG)自成立后对这种新形势的反应是,对其机车车辆实施了较大范围的现代化改造和空前的采购计划.文章以城市高速铁路和区间铁路动车组为例,扼要介绍了近年来新购车辆以及新框架条件的影响.     

Job satisfaction and personality of Merchant Navy officers

Until recently little research had been carried out into job satisfaction of seafarers. Wastage in the shipping industry is higher than most other industries and although some improvements have been made to working conditions and facilities the wastage is still very high.

During the last two decades shipping technology has changed drastically, necessitated by changing economic factors, resulting in the need for highly trained personnel. Training costs are high, particularly for officers, and could be reduced if efficient selection processes were employed.

The project is designed to study perceived and implied (calculated) job satisfaction of officers who have served in the Merchant Navy for five years or more. Gone are the days of high port-time/sea-time ratios due to increased port and labour costs. Consequently seafarers may be confined together for longer periods at sea such that a different type of personality may be required to survive the stresses and strains of such a way of life. The project also attempted to discover whether the personalitics of the seafaring officers differ from those of the shoreside population and whether personality is related to job satisfaction at sea.

The project took the form of a survey by applying a questionnaire to Merchant Navy deck, engineer and radio officers at nautical educational establishments between September and October 1978.

The results showed that the majority of officers have a moderately high level of perceived job satisfaction whereas implied satisfaction was comparatively low. The personality of officers was found to be significantly different from that of the shoreside population in almost 50% of the 31 personality scales measured. There were also found to be differences between the personalities of deck and engineer officers.

A correlational study indicated that the personality of the Merchant Navy officer is related to overall job satisfaction.     

Validation of Railway Vehicle Lateral Dynamics Models

The general form of the railway vehicle lateral dynamic predictions seems to have been proven. If wheels are coned, rails are of uniform cross-section, and suspensions are linear, then good predictions can be obtained. If wheels are not coned, and rail sections vary, but the suspension is relatively linear, as in modern vehicles, it is still possible to obtain good predictions of critical speed for flexible suspensions. The situation with “stiff” vehicles remains unproven. In each case dynamic response calculations will be only as good as the knowledge of the track input including the rolling line term. The validity of making calculations to predict critical speeds of very non-linear vehicles has not yet been convincingly demonstrated. Validation experiments for the more difficult case of time history representation suggest the possibility of correct prediction for easily comprehensible vehicles, but even this requires an enormous amount of supportive experimental work.