1,721,004 research outputs found
A tabu search algorithm for the cost-oriented multi-manned Assembly Line Balancing Problem
No full textPlants manufacturing large-sized high-volume products, such as automobiles and trucks, usually encounter Multi-manned Assembly Line Balancing Problems (MALBPs). In this paper, a cost-oriented version of MALBPs, namely CMALBP, is taken into account. These types of problems may arise in the final assembly lines of products in which the manufacturing process is pretty labor-intensive. Since CMALBP is NP-Hard, a heuristic approach based on a Tabu search algorithm is developed to solve the problem. The proposed algorithm uses two neighborhood generation mechanisms, namely swap and mutation, which effectively collaborate with each other to provide new feasible solutions. Moreover, two separate tabu lists (corresponding with the two mentioned generation mechanisms) are used to check whether or not moving to a new generated neighbor solution is forbidden. To examine the efficiency of the proposed algorithm, some experimental instances were collected from the literature and solved. The obtained results show the effectiveness of the proposed tabu search approach
Inequity evaluation for land use and transportation model on introduction of autonomous vehicles
No full textIn recent times, there have been rapid advancements in technologies that can bring about fully autonomous driving. This can potentially result in substantial changes in the road network and traffic operations. People previously not being able to travel frequently (e.g., the elderly and people with disabilities) will be able to commute themselves. Due to this intuitive property of autonomous vehicles, additional trip production may produce an impact on travel costs between some origin-destination pairs. These unwanted changes create both positive and negative impacts on the network users resulting in an inequity issue. It is necessary to evaluate the inequity caused to a whole society by providing benefits through autonomous driving to a certain group of people. In the above context, this paper uses a bi-level optimization model technique to find an optimal solution of a multi-objective function. The proposed model aims to evaluate the maximum growth of trips that a network can support without causing inequity to other network users. The upper level of the model maximizes the generation of trips constrained by the inequity parameters, whereas the lower level minimizes the travel equilibrium costs for all the users by assigning trips to the network following the multinomial logit principle. The solution to the proposed model is provided by a multi-objective genetic algorithm
A multi-objective optimization approach for disruption management in an intermodal freight transport network
No full textThe growing demand for freight transportation is leading to pay more attention to the management of intermodal freight transport network (IFTN). The optimization of IFTN management will have many benefits in terms of sustainability, reducing costs and pollution. Although many studies on the optimization of IFTN operations exist, the management of disruptions deserves a particular attention since disruptions may lead to a significant drop of performance in the entire network. In particular, seaport terminals are prone to disruptions because of their key role in connecting the land side and the sea-side operations. The availability and reliability of the entire network is directly affected by their disruptions. In this paper, a multi-objective linear programming model is developed to minimize congestion in an IFTN, which is originated from the occurrence of a disruption in a seaport terminal. The model aims to minimize cost and emissions, simultaneously. Computational results of a realistic case study, inspired by an Italian IFTN, shows the effectiveness of the developed model to improve the performance of the entire network
Towards the Physical Internet with Coloured Petri Nets
No full textColoured Petri Nets can be a valuable and powerful tool to design, analyse, and
control the subsystems composing the Physical Internet, as they are able to capture the
precedence relations and interactions among events which characterize the facilities and
infrastructures (multimodal logistics centres and hubs, transit centres, roads and railways)
through which p-containers are delivered. In this paper, the use of Coloured Petri Nets in the
field of the Physical Internet is discussed and an example of the application of such a modelling
tool to a multimodal hub in the PI is provided. The multimodal hub consists of four areas: a
port area at which vessels arrive and depart, a train terminal for rail transportation, a road
terminal for truck-to-X (and vice-versa) transhipment, and a storage area. The storage area
and the road terminal are considered in detail, and two nets representing a section of a pconveyor
and a p-sorter/p-composer are proposed to illustrate the applicability of the CPN
formalism to the Physical Internet paradigm
Joint coordination and routing of autonomous vehicles in road networks with machine learning-based travel time forecasting
No full textThis paper addresses the coordination and routing of autonomous vehicles in a traffic network populated only by connected and automated vehicles, by proposing a novel traffic management system (TMS) that jointly determines the optimal vehicle paths in the network, as well as the exact trajectories and speeds on each road and intersection. To this end, two optimization problems are considered and solved within the TMS: a scheduling and motion planning problem, and a routing problem; the latter is formalized in detail in this paper. In addition, a methodology for predicting accurate network travel times based on machine learning is proposed and included in the TMS so that vehicles are routed considering the most accurate information regarding the future expected network state, the exact intersection and road layouts, and the vehicle driving behavior. Different experiments are performed to validate the proposed TMS and provide evidence of its efficacy in reducing congestion and travel times while guaranteeing safety, comfort for passengers, and the feasibility of local vehicle maneuvers such as lane changes and overtaking. The proposed framework contributes to the need of managing the expected growing number of autonomous and connected vehicles within the transport sector, providing a tool to ensure that the expected automation benefits, together with commonly shared sustainable mobility goals, can be actually achieved
Optimization of public transport route assignment via travel time reliability
No full textBesides the impacts and importance in planning transportation networks, travel time reliability (TTR) is increasingly becoming a driving factor for commuting patterns. However, the implementation of TTR in route assignment is still not very common due to the discrete nature of scheduled services. Within day dynamics are usually modelled depending on various service characteristic factors such as regularity, frequency and information. However, in this research, frequency and regularity related factors were of prime focus to find the parameters and their values that can represent TTR in impedance functions to evaluate their impingements in public transport route assignment models. Perceived journey time (PJT) was optimized based on deterministic dynamic network model optimization for various TTR parameters based on data available for the city of Halle and later confirmed via simulative modelling in PTV Visum. Four different scenarios were generated in scenario management for each PJT value deduced from the Poisson parameter value in the optimization model. Comparison of these scenarios based on optimally decided penalties with the base scenario without TTR identified the most reliable lines. An appreciable change in journey times had been noticed depicting the strong effect of TTR in route assignment. Results obtained can pave way for developers to introduce a smart feature of choosing a reliable travel option in journey planners instead of the shortest one and for planners to evaluate large city models
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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