Participation in online activities while travelling: an application of the MDCEV model in the context of rail travel

Transportation - Travel-based multitasking, i.e. using travel time to conduct enjoyable and/or productive activities, is the subject of an increasing number of theoretical and empirical studies....     

Multiple criteria optimization method for the vehicle assignment problem in a bus transportation company

A vehicle assignment problem (VAP) in a road, long‐haul, passenger transportation company with heterogeneous fleet of buses is considered in the paper. The mathematical model of the VAP is formulated in terms of multiobjective, combinatorial optimization. It has a strategic, long‐term character and takes into account four criteria that represent interests of both passengers and the company's management. The decision consists in the definition of weekly operating frequency (number of rides per week) of buses on international routes between Polish and Western European cities. The VAP is solved in a step‐wise procedure. In the first step a sample of efficient (Pareto‐optimal) solutions is generated using an original metaheuristic method called Pareto Memetic Algorithm (PMA). In the second step this sample is reviewed and evaluated by the Decision Maker (DM). In this phase an interactive, multiple criteria analysis method with graphical facilities, called Light Beam Search (LBS), is applied. The method helps the DM to define his/her preferences, direct the search process and select the most satisfactory solution.     

Application of the reverse 3D scanning method to evaluate the wear of forging tools divided on two selected areas

This study is focused on tools used in the industrial hot forging process of a front wheel forging (eventually–gear wheel) manufactured for the automotive industry. Four different variants were applied for the tools: 2 die inserts were coated with two different hybrid layers (GN + PVD type), i.e. AlCrTiN and AlCrTiSiN, one insert was only nitrided, and one was pad welded, to improve tool durability. The tool wear was analysed and represented by the material degradation on the working surface, based on the 3D scanning and the material growth of the periodically collected forgings. Additionally, the scanned tools were divided into two areas, in which it was found, based on the reliminary analysis, that various degradation mechanisms are predominant. Microstructural and hardness measurements of the analyzed tools were also performed. Based on the results, it was found that, in the central part of the die insert (area A), thermo-mechanical fatigue and wear occurred, while in the area of the bridge insert (area B), only abrasive wear could be observed. For these areas (A and B), the loss of material was determined separately. In area A for the inserts with hybrid layer GN+AlCrTiSiN and gas nitrided, an intensive increase of wear took place, which was not observed for the pad welded and GN+AlCrTiN layer insert, for which, together with the increase of the forging number, a proportional growth of the loss of material occurred. In area B the weakest results were obtained for the insert with GN+AlCrTiSiN layer, while wear of other die inserts grew similar and proportional.     

Multiple objective optimization of the fleet sizing problem for road freight transportation

A fleet sizing problem (FSP) in a road freight transportation company with heterogeneous fleet and its own technical back‐up facilities is considered in the paper. The mathematical model of the decision problem is formulated in terms of multiple objective mathematical programming based on queuing theory. Technical and economical criteria as well as interests of different stakeholders are taken into account in the problem formulation. The solution procedure is composed of two steps. In the first one a sample of Pareto‐optimal solutions is generated by an original program called MEGROS. In the second step this set is reviewed and evaluated, according to the Decision Maker's (DM's) model of preferences. The evaluation of solutions is carried out with an application of an interactive multiple criteria analysis method, called Light Beam Search (LBS). Finally, the DM selects the most desirable, compromise solution.     

Travel-based multitasking: review of the role of digital activities and connectivity

ABSTRACT

Travel-based multitasking, also referred to as travel time use, is now a well-established concept, whose existence is supported by the technological trajectories, with mobile information and communication technologies (ICT) and vehicle automation working together to allow travel time to be more productive and enjoyable. Despite existence of reviews of travel-time multitasking studies, the systematic overview of the role digital activities, i.e. those that necessarily require modern ICT equipment to participate, has been limited, often wrapped under the umbrella term “use of ICT”, potentially obscuring their complexity and sophistication. Similarly, the role of connectivity and its attributes, e.g. speed (bandwidth), reliability, price, ease of use, data allowance or security, deserves a more systematic overview given its key role in enabling digital online activities and hence the travel-based multitasking options. This paper provides a review of 77 empirical travel-based multitasking-studies that explored the role of digital activities or connectivity. In particular, the review discusses the existing typologies of digital activities, dividing them into hardware-centric, function-centric or a combination of both (mixed). Subsequently, key contributions are discussed with respect to the treatment of digital activities and connectivity and its attributes. Based on the review, it is possible to observe that the existing studies have looked only at a handful of rather restricted online activities that do not sufficiently capture the sophistication with which individuals interact with the virtual world nowadays. Furthermore, the role of connectivity, although deeply embedded in the “C” of the “ICT” concept, has not been looked at or modelled in any detail in studies related to travel time use or its quality. This existing shortcoming might have resulted in an insufficient understanding of the mechanisms driving travel time use, the associated experience indicators of customer satisfaction, productivity or the consequences for relative attractiveness of transport modes. All of these considerations remain, however, crucial for designing, appraising and operating transport infrastructure and services that are able to take the advantage of lifestyle digitisation to meet the increasing customer needs while also delivering broader economic, social benefits and possibly also environmental benefits.     

The methodology of multiple criteria decision making/aiding in public transportation

The paper presents methodological overview of the application of Multiple Criteria Decision Making/Aiding (MCDM/A) in public transportation. It explains why MCDM/A methodology is so important while dealing with different categories of decision problems that arise in mass transit systems. Major features and basic notions of MCDM/A methodology are presented. Different categories of MCDM/A methods are characterized and classified. Two case studies demonstrate possible applications of MCDM/A methodology in public transportation. In the first case study multiple objective evaluation of the mass transit system developments' scenarios is carried out. Four variants of the mass transit system are evaluated by a consistent family of criteria with an application of ELECTRE III method. The second case study refers to optimization of the crew size in the mass transit system operated by a public transportation company (PTC). Multiple objective mathematical programing problem is formulated and solved by a combination of an original, customized heuristic procedure implemented in a computer software PEOPLE and the Light Beam Search (LBS) method. Copyright © 2010 John Wiley & Sons, Ltd.     

Inverse discrete choice modelling: theoretical and practical considerations for imputing respondent attributes from the patterns of observed choices

ABSTRACT

The growing availability of geotagged big data has stimulated substantial discussion regarding their usability in detailed travel behaviour analysis. Whilst providing a large amount of spatio-temporal information about travel behaviour, these data typically lack semantic content characterising travellers and choice alternatives. The inverse discrete choice modelling (IDCM) approach presented in this paper proposes that discrete choice models (DCMs) can be statistically inverted and used to attach additional variables from observations of travel choices. Suitability of the approach for inferring socioeconomic attributes of travellers is explored using mode choice decisions observed in London Travel Demand Survey. Performance of the IDCM is investigated with respect to the type of variable, the explanatory power of the imputed variable, and the type of estimator used. This method is a significant contribution towards establishing the extent to which DCMs can be credibly applied for semantic enrichment of passively collected big data sets while preserving privacy.     

Biological properties of differently-aged human keratinocytes.population doubling time growth curve and cell cycle analysis

Objective To explore the biological properties of keratinocytes from differently-aged healthy human beings. Methods Keratinocytes from fetus, teenager and middle-aged groups were separated and cultured. The population doubling time (PDT) and cell growth curve in different cells were compared, and the cell cycles were analyzed by flow cytometry. Results ① In primary culture of keratinocytes, the adherence time in middle-aged group was longer than that in fetus and teenager groups. However, all cell morphology showed no obvioas differences. In subculture of kecatinocytes, with donator's age increasing, time of cell adherence prolonged, passage number decreused and differences in cell morphology were obrioas. ② The average PDT of keratinocytes was shorter in fetus group than in teenager and middle-aged groups. Bat difference in cell growth curve between different passages was not observed. ③ Keratinocytes showed G2/M period in fetus group but G0/G1 period in teenager and middle-aged groups mainly. Conclusion As age increases, the biological properties of keratinocytes change obviously.