Search results for " Logistics"
showing 10 items of 399 documents
The Hierarchical Mixed Rural Postman Problem: Polyhedral analysis and a branch-and-cut algorithm
2017
[EN] The Hierarchical Mixed Rural Postman Problem is defined on a mixed graph where arcs and edges that require a service are divided into clusters' that have to be serviced in a hierarchical order. The problem generalizes the Mixed Rural Postman Problem and thus is NP-hard. In this paper, we provide a polyhedral analysis of the problem and propose a branch-and-cut algorithm for its solution based on the introduced classes of valid inequalities. Extensive computational experiments are reported on benchmark instances. The exact approach allows to find the optimal solutions in less than 1 hour for instances with up to 999 vertices, 2678 links, and five clusters.
Optimizing the level of service quality of a bike-sharing system
2016
Public bike-sharing programs have been deployed in hundreds of cities worldwide, improving mobility in a socially equitable and environmentally sustainable way. However, the quality of the service is drastically affected by imbalances in the distribution of bicycles among stations. We address this problem in two stages. First, we estimate the unsatisfied demand (lack of free lockers or lack of bicycles) at each station for a given time period in the future and for each possible number of bicycles at the beginning of the period. In a second stage, we use these estimates to guide our redistribution algorithms. Computational results using real data from the bike-sharing system in Palma de Mall…
Understanding the Health Disaster: Research Design for the Response to the 2014 West African Ebola Outbreak
2015
International audience; The 2014 Ebola outbreak in West Africa is the largest ever in history, affecting multiple countries and to this date, the World Health Organization has registered more than 6,500 deaths attributed to Ebola. The challenges arising from this outbreak to responders worldwide do not follow the standard characterisation or response patterns of natural sudden onset vs. conflict disasters. Rather, it is a medical emergency, which is intertwined with multiple challenges in the sectors decision-making, coordination, logistics and information management. In this paper, we present our research framework, which is based on desk research and initial interviews with responders. Th…
Modelling pavement surface characteristics for noise prediction through Bailey-related indicators
2021
The aggregate gradation of bituminous mixtures (hot mix asphalts, HMA) is one of the major factors affecting their surface texture. In turn, this latter is a crucial factor and influences drivers and bystanders’ safety, comfort, and health. Despite this, the design of texture levels still lacks sound bases and dedicated algorithms and this negatively affects the acoustic design of bituminous mixtures. Consequently, the objectives of this study were confined into the derivation of relationships to be used in mix design to predict texture levels. Experimental data were analyzed, in the pursuit of setting up appropriate models and algorithms. Analyses involved the consideration of Bailey-relat…
Analysis of dust exposure during chainsaw forest operations
2017
Abstract: In 1999, the European Union proclaimed hardwood dust carcinogenic based on the classification of the International Agency for Research on Cancer (IARC) issued in 1995. The operational exposure limit (OEL) for inhalable wood dust has been set to 5 mg m-3 by EU directives, though in different countries the OEL ranges from 1 to 5 mg m-3. The objective of this study was to determine the exposure to wood dust of forest workers in chainsaw cutting and processing and suggest possible countermeasures. The study took into consideration different silvicultural treatments (coppice clear cut, conifer thinning, conifer pruning, and sanitary cut) and chainsaw fuel (normal two-stroke gasoline mi…
Pricing and infrastructure fees in shaping cooperation in a model of high-speed rail and airline competition
2020
Abstract This paper studies the effects of cooperation in a hub-and-spoke network with high-speed rail and airline competition. The distinctive elements of our analysis are the consideration of: (i) per-passenger airport and rail infrastructure fees; (ii) mixed bundling pricing by partners, and (iii) an airline duopoly in the international market. We show that partners fix the cheapest bundle price of the combined trip, that non-allied operators respond by decreasing the prices per link, and that connecting traffic increases. Per-passenger fees significantly affect the price differences following cooperation. An empirical application confirms that it is privately profitable and that welfare…
The 12th “Iter Mediterraneum” in Tunisia, 24 March – 4 April 2014
2015
The organization and logistics of the 12th OPTIMA Iter in Tunisia from 24 March to 4 April 2014 by OPTIMA and ATUTAX is here reported. The material used and the workflow are illustrated as reference for the organization of future similar collaborative botanical excursions.
Bio materials with reclaimed asphalt: from lab mixes properties to non-damaged full scale monitoring and mechanical simulation
2019
Three innovative environmentally friendly pavement materials, designed with 50% of Reclaimed Asphalt and three different biomaterials (2 bio-additivated bitumens and 1 bio-binder), were produced in an industrial plant. These mixes were tested in lab and also at full scale using an Accelerated Pavement Test facility. The asphalt mix viscoelastic properties were measured in lab and their intrinsic viscoelastic response were simulated. These rheological models are used to simulate the pavement mechanical response using both elastic and viscoelastic multilayer codes. Hence, full scale measurement performed during the full scale test at an early stage (without damages) can be compared with these…
Les leviers de contrôle de SIMONS : vers une compréhension des freins à l'équilibrage diagnostic / interactif
2015
Simons's researches in the mid-1990s offer an original framework for relations between control and strategy. The imprecision of the model, its vertical orientation focusing on top management were criticized and completed by additional researches. Adopting a transversal and vertical approach focused on middle managers, this research aims to analyze the development of diagnostics systems towards interactivity and brakes to such developments. The article analyzes the results of an intervention research conducted in a third-party logistics which has adopted a new measurement performance system, including its impact on diagnostic control systems used by middle managers.
QUALITATIVE RESEARCH IN TRAVEL BEHAVIOR STUDIES
2016
Qualitative methodology is extensively used in a wide range of scientific areas, such as Sociology and Psychology, and it is been used to study individual and household decision making processes. However, in the Transportation Planning and Engineering domain it is still infrequent to find in the travel behavior literature studies using qualitative techniques to explore activity-travel decisions. The aim of this paper is first, to provide an overview of the types of qualitative techniques available and to explore how to correctly implement them. Secondly, to highlight the special characteristics of qualitative methods that make them appropriate to study activity-travel decision processes. Fa…