Finite Element Simulation of Processes Involving Moving Heat Sources. Application to Welding and Surface Treatment

IntroductionAwiderangeofweldingorsurfacetreatmentprocessesinvolvetheuseofaheatsourcemovingataconstantspeedoverthesurfaceofthecomPonent.ThreedimensionalcomPutationofresidualstressesanddistortionsinducedbythiskindofprocesses,usingtheusualfiniteelementmethod,needsveryrefinedmeshesinordertocorrectlydescribethepropertiesandstressgradientsintheheataffCctCdzonealongthepathoftheheatsource.Inthispaper,wediscussthedifferentnumericalaPproaches,imPlementedinSYSWELD@software,whichcanbeusedtodorealisti…     

Linear probit models: Statistical properties and improved estimation methods

The multinomial probit model is a statistical tool that is well suited to analyze some transportation problems. Modal split, gap acceptance, and route choice are some examples of application contexts. This paper presents an in-depth analysis of its statistical properties and an estimation method for the trinomial case. In the statistical part of the paper it is shown that for multinomial probit models with specifications that are linear in the parameters, the global maximum of the log-likelihood function is consistent if the data do not exhibit multicollinearity as defined in the text. For the special case with three alternatives, lack of multicollinearity is also shown to guarantee asymptotic efficiency and normality, and the uniqueness of any root of the likelihood equations. In addition, it is also shown that for the trinomial probit model certain goodness-of-it measures and test statistics can be easily calculated. The methods part of the paper introduces an estimation process that solves the likelihood equations using a special purpose table of the bivariate normal distribution and analytical derivatives of the log-likelihood function. The method is very accurate, can be applied to nonlinear specifications, and is considerably faster than current computer programs. For linear specifications, the method can be mathematically proven to converge if the log-likelihood equations have a root.     

An analysis of elevator operation in moderate height buildings—II: Multiple elevators

Deterministic approximations for elevator trip times are applied to a system of m elevators. Comparisons of in-system time of passengers are made for elevators which are (a) physically separated, (b) ideally controlled, (c) zoned, or (d) uncontrolled. A more detailed study is then made of in-system passenger time for a pair of elevators subject to a minimum headway control at the lobby. Comparisons are made between rather primitive analytic estimates and simulation results.The main conclusion is that control of headways so as to prevent pairing is of doubtful value. At low traffic it is usually better to use no control; for higher traffic it is better to zone the building and have each elevator serve separate floors.     

Dynamic Interaction of Railway Systems with Large Bridges

In this paper have been described

- railway runability problems on large span bridges;

- the state-of-art of the methodologies adopted for a systematic analysis of the dynamic behaviour of railway vehicles running on a deformable structure, with particular reference to large span suspension bridges;

- some meaningful experimental and analytical results, related to railway runability of large span bridges.     

A GIS-Based approach for estimating truck flow patterns in urban settings

This paper describes how a Geographic Information System (GIS) is being used to help estimate multi-class truck flows in an urban setting. Emphasis is placed on the reasons why this approach is valuable, the specific GIS tools and techniques employed, the value added by employing a GIS-based approach, and the results being obtained. These findings are generalized to describe the benefits that might be expected in other situations where a similar modeling approach is used.     

Suburban congestion: Recommendations for transportation and land use responses

Transportation congestion is reaching intolerable levels in many urban and suburban areas in the US. Reliance upon traditional responses, such as transit and new highway capacity, is not working — especially in suburban areas. Although methods for dealing with suburban congestion are often different, there are a number of common features that must be considered in developing short term as well as more permanent and long lasting solutions. In proposing short term solutions, a Menu of Actions is described. It includes transportation actions (the traditional transit and transportation management options) where there are opportunities for getting more out of the existing systems; land use/growth management actions which will result in more rational land use-transportation interactions; financial incentives, to encourage or discourage appropriate actions; more comprehensive and systematic land use and transportation planning; and the organizational and institutional actions required to implement rational solutions.While the Manu of Actions provides a broad array of possible actions to provide relief in the short run, over time the growth in traffic is likely to outpace their effectiveness. Consequently, longer term and often more difficult solutions must be considered and implemented as appropriate. They could include changes in land use development and land use management policies; changes in lifestyle and business practices; improvements through technological innovation; changes in the traditional ways of providing transportation services; and greatly expanded research and development.     

Optimal Adaptive Active Suspensions for a Full Car Model

In order to present a useful method for designing active suspension of a vehicle, a linear full-car model is used in this investigation. In this model, the dampers of passive system are totally replaced by actuators. The actuators are controlled with optimal full state vector feedback. After determining feedback coefficients, the responses of active and passive systems were compared and it was found that performance of active system is much superior. It is desired that, changes in vehicle parameters would not affect the system's performance and hence should not violate its optimality. In other words, the system should behave adaptively using Model Reference Adaptive Control. The optimally controlled active suspension was used as a model for the active suspension of vehicle. In this way, the suspension of vehicle is controlled in such a way that its output approaches to that of the optimal active model. Thus the suspension should behave just like the optimal one.     

Formulating a methodology for modelling revealed preference discrete choice data-the selectively replicated logit estimation

There are a number of studies on modelling with Revealed Preference (RP) data. It is a traditional technique and it is based on actual market data. The method has been extensively used in transportation as a tool for predicting travel demand. Although the method constitutes a relevant analysis on the process of modelling, it suffers from limitations, mainly associated with the lack of control over the experiment, that sometimes overwhelm the model results. This work proposes and tests a methodology for estimating a more efficient binary RP sample set. The objective is to develop and test a methodology that identifies and eliminates potentially irrational choices made. Responses are evaluated according to the set of trade-offs in values of time. Having identified these individuals they are eliminated from the original sample and a new sample is created, the selectively replicated (SR) sample. Original and SR samples are then re-estimated in a tree nested logit structure.     

Modelling passenger demand for parkway rail stations

Interest in Parkway stations emerged in the 1980s. These act as convenient out-of-town stations for inter-urban rail journeys. There were 13 so-called Parkway stations in Great Britain in 1999 and two have subsequently been opened. This paper reports the development and application of a new Parkway forecasting model which was conducted for the Association of Train Operating Companies (ATOC), undertaken as part of an extensive update to the Passenger Demand Forecasting Handbook, which recommends demand forecasting frameworks and associated parameters that are widely used in the railway industry in Great Britain. The objective was to develop a model that had more desirable properties and was more straightforward to apply than the previously recommended procedure. The focus is entirely upon inter-urban journeys of over 80 km.The model forecasts the demand for Parkway stations based solely on rail ticket sales data and its properties are illustrated with two case study applications. The nature of Parkway stations forces consideration of competition, and it is demonstrated that the inclusion of a station choice component leads to a somewhat improved explanatory power and a more plausible generalised cost elasticity.In addition to the methodological developments, the model has provided generally reasonable elasticities and forecasts and shown that Parkway users have different preferences to rail travellers in general. In a test based around a newly opened Parkway station, its forecasts are more accurate than the procedure it replaces.