Simulation of turbulent effective wakes for propellers in off-design conditions by a correction factor approach

Journal of Marine Science and Technology - This paper presents a procedure for the estimation of propeller effective wakes in oblique flows. It shows how a recently developed method for controlling...     

Calculation of vaulted magnetic field above ship using equivalent surface magnetic charge北大核心CSCD

[目的]为了获得舰船上方不同高度平面磁场数据,解决舰船上方拱顶磁场推算到平面磁场的问题,提出用面磁荷法进行舰船上方的磁场推算。[方法]从等效源理论出发,利用拱顶磁场数据进行反演建模,将舰船磁场等效为面磁荷产生的磁场,用面磁荷正演舰船上方的磁场。将面磁荷法推算出的磁场与舰船实际磁场进行对比,验证面磁荷法的可行性。[结果]通过数值仿真计算,舰船磁场垂直分量推算的相对均方根误差为0.44%;利用磁性船模进行实验分析,磁场垂直分量推算的相对均方根误差为7.64%。[结论]仿真和船模实验分析表明,利用面磁荷法进行磁场推算,其推算值与测量值较为吻合,推算的相对均方根误差较小,具有较高的精度,可用于实际工程计算。     

Research and design of ship-shore integrated engine room intelligent operation and maintenance system based on data brain北大核心CSCD

[目的]为提升舰船机舱运维的智能化水平,针对机舱设备种类多、数量大、耦合关系复杂等特点,梳理机舱运维智能化应用的技术路线,开发船岸一体化机舱智能运维系统。[方法]首先,分析国内外机舱智能运维技术的发展趋势,融合利用健康管理、大数据挖掘、数字孪生、数据轻量化传输等技术优势;然后,设计符合舰船机舱特点的一体化智能运维系统。[结果]提出了一种基于数据大脑赋能的机舱智能运维系统功能框架、平台设计、运行体系、运行流程及关键技术应用。[结论]研究成果可为舰船机舱智能运维系统设计及应用实践提供参考。     

Study on J-integral with SENB specimensin a condenser material

A series of tests was performed with three-point single-edge-notched-bend (SENB) specimens in a condenser material (Titanium alloy). Results show that the J-integral values of welded joint and HAZ are obviously smaller than those of the base metal. It signifies that the welding process can result in a reduced toughness of Titanium alloy and the effect of crack orientation on toughness value is not negligible for engineering applications. Besides, the J-integral values of L-T direction specimens are much higher than those of LS ones. The J-integral values of rolled ring are: J_(C-R)>J_(C-L)>J_(L-R).     

Development and Evaluation of Vehicle Simulation Models for a 4WS Application

In the scope of the European Prometheus project a passenger car with active rear wheel steering was developed by TNO in cooperation with PSA. During development and engineering of the rear wheel steering system simulation tools have been used to reduce development costs. This paper describes the evaluation of different simulation models, from simple to complex, with results of full vehicle driving tests. The optimal balance for model complexity and accuracy was achieved with a 2-dimensional model with an added roll degree of freedom. The results show that validation using time responses can give ambiguous and inaccurate results, and that frequency response functions are much more usable in validation.     

Changing relationships in the financing of elderly and handicapped transportation services

This paper reports the results of a national survey of providers of specialized transportation services who are recipients of UMTA Section 5 or Section 9 funding and report owning demand responsive vehicles (Section 15 report). The study reports a variety of service measures, financial data, cost containment activities and related information for fiscal years 1980 and 1982. For a limited number of systems, financial data for fiscal year 1984 are also reported. Analysis of the data indicates a general but as yet uncertain trend towards declining UMTA participation in funding these systems, increased fares and increased usage of cost containment and cost reduction techniques by the responding systems. Should the reported trends continue, then the responding systems could be expected to have financial difficulty in complying with the currently proposed regulations for the enforcement of Section 504 of the Rehabilitation Act of 1973.     

Impact of high occupancy vehicle lanes on carpooling behavior

High occupancy vehicle lanes have become an integral part of regional transportation planning. Their purpose is to increase ridesharing by offering a travel time advantage to multiple occupant vehicles. This paper examines the extent to which an HOV facility increases ridesharing. Using data from the Route 55 HOV facility in Orange Country, California, changes in the carpooling rate on Route 55 are compared to that of a control group of freeway commuters. The analysis shows that the carpooling rate among peak period commuters, and particularly those who use the entire length of the facility, has increased. However, there has been no significant increase in ridesharing among the entire population of Route 55 commuters. Results suggest that barriers to increased ridesharing are formidable, that travel time savings must be large in order to attract new carpoolers, and that further increases in capooling will likely require development of extensive HOV lane systems.     

Application of time series techniques for forecasting truck traffic attracted by the Bombay metropolitan region

Knowledge of future traffic flow is an essential input in the planning, implementation and development of a transportation system. It also helps in its operation, management and control. Time series analysis techniques have been extensively adopted for this purpose in the fields of economics, social sciences and in other fields of technology. An attempt has been made in this study to apply the techniques of time series analysis to goods traffic, particularly truck traffic. Four predominant corridors, N.H.3, N.H.4, N.H.8 and Lal Bahadur Shastri Road (L.B. S. Rd.), accounting for majority of truck movement in the Bombay Metropolitan Region (BMR), have been considered for modeling. Raw data was processed initially, to obtain an insight into the structure of time series. Ten candidate models of the Auto-Regressive Moving Average (ARMA) and Auto-Regressive Integrated Moving Average (ARIMA) family are investigated to represent each of the four corridors. Models finally proposed, to represent each of the four corridors have been selected based on Minimum Mean Square Error (MMSE) and Maximum Likelihood Rule (MLR) criteria. Models ARIMA (2, 1, 0), ARMA (1.0), ARMA (1, 1) and ARIMA (1, 1, 0) are proposed for N.H.3, N.H.4, N.H.8 and L.B.S. Rd. respectively, based on significant weekly periodicity.     

Union rivalry and crew reform in shipping: A United States—Australia comparison

The national-flag fleets of most of the traditional martitime nations have, in virtually every case, been in decline in the 1980s and 1990s, despite the continued growth of ocean shipping. They have declined in terms of numbers of vessels and numbers of sea-going jobs, although not necessarily in terms of cargo carried. However, a number of those nations have responded to the changed technological and competitive conditions with some success by attempting to adjust crewing and work practices on vessels at sea. Neither the USA nor Australia has been in the forefront of such change. However, considerably more progress has been made in modernizing crewing practices and work rules in the Australian-flag fleet than in the US-flag fleet. There are a variety of reasons for this, inluding government policy. However, it is our argument that one of the principal reasons the US fleet lags behind the Australian fleet in the adoption of modern crewing practices and work rules is the much greater degree of union rivalry in the US shipping industry. In fact, while the degree of fragmentation and rivalry among unions in the Australian flag fleet has declined dramatically since 1980, their US cousins have continued, and in some ways expanded, their pattern of fratricidal behavior. First we shall discuss some of the technological and competitive imperatives that are driving human resource management practices in shipping and the crewing and industrial relations adjustments that are being made around the world to adjust to them. Then we shall indicate how the Australian and US fleets have responded to these challenges. This will be followed by a discussion of unionism in the Australian and US maritime industrics as it has devloped in the last two decades of the twentieth century. Finally, we shall draw conclusions about the impact of different patterns of unionization.     

An AI-based approach for transit route system planning and design

We present an AI-based solution approach to the transit network design problem (TNDP). Past approaches fall into three categories: optimization formulations of idealized situations, heuristic approaches, or practical guidelines and ad hoc procedures reflecting the professional judgement and practical experience of transit planners. We discuss the sources of complexity of the TNDP as well as the shortcomings of the previous approaches. This discussion motivates the need for AI search techniques that implement the existing designer's knowledge and expertise to achieve better solutions efficiently. Then we propose a hybrid solution approach that incorporates the knowledge and expertise of transit network planners and implements efficient search techniques using AI tools, algorithmic procedures developed by others, and modules for tools implemented in conventional languages. The three major components of the solution approach are presented, namely, the lisp-implemented route generation design algorithm (RGA), the analysis procedure TRUST (Transit Route Analyst), and the route improvement algorithm (RIA). An example illustration is included.