Numerical method for simulating tire rolling noise by the concept of periodically exciting contact force

For the numerical simulation of tire rolling noise, an important subject is the extraction of normal velocity data of the tire surface that are essential for the acoustic analysis. In the current study, a concept of periodically exciting contact force is introduced to effectively extract the tire normal velocity data. The ground contact pressure within contact patch that is obtained by the static tire contact analysis is periodically applied to the whole tread surface of stationary tire. The periodically exciting contact forces are sequentially applied with a time delay corresponding to the tire rolling speed. The tire vibration is analyzed by the mode superposition in the frequency domain, and the acoustic analysis is performed by commercial BEM code. The proposed method is illustrated through the numerical experiment of 3-D smooth tire model and verified from the comparison with experiment, and furthermore the acoustical responses are investigated to the tire rolling speed.     

Feasibility study for the application of air inflated membrane structure in China National Stadium

China National Stadium, also known as “Bird’s Nest”, is the main stadium of the 29th Olympic Games in Beijing in 2008, which has successfully held not only the Opening and the Closing ceremonies but also the track and field events. A new problem of rain preventing is brought out to improve the utilization of the Bird’s Nest after the Olympic Games. The scheme of installing an air inflated membrane at the opening of the steel structure is proposed in this paper to solve the rainproof problem of the Bird’s Nest. The form-finding and mechanical analyses of the air inflated membrane are carried out. Comparison between the mechanical performance and dynamical character before and after installing the air inflated membrane structure is given. To verify the analysis results, based on the practical structure of the Bird’s Nest, a test of a 1:20 model membrane is worked out.     

Exact and simplified estimations for elastic buckling pressures of structural pipe-in-pipe cross sections under external hydrostatic pressure

Structural pipe-in-pipe cross sections have significant potential for application in offshore oil and gas production systems because they combine thermal insulation performance with structural strength and self weight in an integrated way. Such cross sections comprise inner and outer thin-walled pipes with the annulus between them fully filled by a selectable filler material to impart an appropriate combination of properties. Structural pipe-in-pipe cross sections can exhibit several different collapse mechanisms, and the basis of the preferential occurrence of one over the others is of interest. This article presents an exact analysis for predicting the elastic buckling behaviours of a structural pipe-in-pipe cross section when subjected to external hydrostatic pressure. Simplified approximations are also investigated for elastic buckling pressure and mode when the outer pipe and its contact with the filler material is considered as a pipe on an elastic foundation. Results are presented to show the variation of elastic buckling pressure with the relative elastic modulus of the filler and pipe materials, the filler thickness, and the thicknesses of the inner and outer pipes. Case studies based on realistic application scenarios are used to show that the simplified approximations are sufficiently accurate for practical structural design purposes.     

Casualty analysis of large tankers

This article presents detailed results of a comprehensive analysis of recorded accidents of large oil tankers (deadweight greater than 80 000 tonnes) occurring between 1978 and 2003. The analysis encompasses a thorough review of available raw accident data and their postprocessing in a way to produce appropriate statistics useful for the implementation of risk-based assessment methodologies. The processing of the captured data led to the identification of significant qualitative historical trends of tanker accidents and of quantitative characteristics of large tanker accidents, such as overall accident rates per ship-year. Data were also analyzed for all major accident categories separately, taking into account tanker ship size/type, the degree of accident severity, and the oil spill tonne rates per ship-year; this led to the identification of heavily polluted worldwide geographical areas as a result of large tanker accidents.     

Phase change analysis of an underwater glider propelled by the ocean＇s thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.     

The ISM Code and the ISPS Code: A critical legal analysis of two SOLAS regimes

Within the comprehensive body of law encompassed by the International Convention on Safety of Life at Sea, 1974 (SOLAS), there are two regimes that are topical and outstanding in the current maritime milieu. These are the international safety management and the international ship and port facility regimes, both characterized by two codes serving as the centre of gravity of each, namely, the ISM Code and the ISPS Code, respectively. In this article the concept of the code as a legal instrument is perused following which a critical legal analysis is carried out of the two above-mentioned Codes, including their backgrounds, the evolutionary process culminating into the regimes and their interrelationships. Several anomalies and inadequacies in the two regimes are identified but in the final analysis it is concluded that both instruments are salutary additions to the body of convention law generated by the International Maritime Organization (IMO). They will undoubtedly influence the continuing development of international law in the field of maritime safety and security.     

Investigations of vehicle securing without lashings for Ro-Ro ships

To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will still need to be lashed. The limitations of the current investigations are also presented. The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine Technology, Chalmers University of Technology.     

Special issue: Importance of public transport

The transport demand in most major cities around the world can only be met with a high‐quality public transport system. The requirements on bus, rail, underground and tram systems are manifold with reliability and efficiency as the key factors. The service operating hours and the size of the network are often extended in order to serve the needs better. Further, most metropolitan areas are trying to provide more incentives for citizens to leave the car at home and use the local transit systems instead. The reasons are well known. Not only does a public transport system only make economical sense if it is well used, but most urban areas with a high car‐dependency face at least three major problems; safety, congestion, and pollution (noise and air pollution, land separation, etc.). It is generally recognised that to decrease car usage and to increase public transport usage a stick & carrot approach is needed. The London congestion‐charging scheme is an example since all revenues collected by the scheme are put into the improvement of bus and underground services.     

Quantifying uncertainty in high-resolution coupled hydrodynamic-ecosystem models

Marine ecosystem models are becoming increasingly complex and sophisticated, and are being used to estimate the effects of future changes in the earth system with a view to informing important policy decisions. Despite their potential importance, far too little attention has been, and is generally, paid to model errors and the extent to which model outputs actually relate to real-world processes. With the increasing complexity of the models themselves comes an increasing complexity among model results. If we are to develop useful modelling tools for the marine environment we need to be able to understand and quantify the uncertainties inherent in the simulations. Analysing errors within highly multivariate model outputs, and relating them to even more complex and multivariate observational data, are not trivial tasks. Here we describe the application of a series of techniques, including a 2-stage self-organising map (SOM), non-parametric multivariate analysis, and error statistics, to a complex spatio-temporal model run for the period 1988–1989 in the Southern North Sea, coinciding with the North Sea Project which collected a wealth of observational data. We use model output, large spatio-temporally resolved data sets and a combination of methodologies (SOM, MDS, uncertainty metrics) to simplify the problem and to provide tractable information on model performance. The use of a SOM as a clustering tool allows us to simplify the dimensions of the problem while the use of MDS on independent data grouped according to the SOM classification allows us to validate the SOM. The combination of classification and uncertainty metrics allows us to pinpoint the variables and associated processes which require attention in each region. We recommend the use of this combination of techniques for simplifying complex comparisons of model outputs with real data, and analysis of error distributions.     

谐波对牵引变压器损耗的影响

根据一个牵引变压器的损耗,提出了谐波对绕组电阻的影响.对同心式和饼式线圈的变压器进行了分析.使用二维有限元计算软件"Flux2D"进行了多种仿真,并且将其结果与实际变压器测量值进行对比,提出一个简单的定律,由此可确定2种不同类型变压器电阻随频率的变化规律.