Search results for "Operations Research"
showing 10 items of 1297 documents
Branch-and-Price-and-Cut for the Active-Passive Vehicle-Routing Problem
2018
This paper presents a branch-and-price-and-cut algorithm for the exact solution of the active-passive vehicle-routing problem (APVRP). The APVRP covers a range of logistics applications where pickup-and-delivery requests necessitate a joint operation of active vehicles (e.g., trucks) and passive vehicles (e.g., loading devices such as containers or swap bodies). The objective is to minimize a weighted sum of the total distance traveled, the total completion time of the routes, and the number of unserved requests. To this end, the problem supports a flexible coupling and decoupling of active and passive vehicles at customer locations. Accordingly, the operations of the vehicles have to be s…
Simultaneous Vehicle and Crew Routing and Scheduling for Partial- and Full-Load Long-Distance Road Transport
2013
AbstractThis paper studies a simultaneous vehicle and crew routing and scheduling problem arising in long-distance road transport in Europe: Pickup-and-delivery requests have to be fulfilled over a multi-period planning horizon by a heterogeneous fleet of trucks and drivers. Typically, in the vehicle routing literature, a fixed assignment of a driver to a truck is assumed. In our approach, we abandon this assumption and allow truck/driver changes at geographically dispersed relay stations. This offers greater planning flexibility and allows a better utilization of trucks, but also creates intricate interdependencies between trucks and drivers and requires the synchronization of their routes…
Mathematical models for Multi Container Loading Problems with practical constraints
2019
Abstract We address the multi container loading problem of a company that serves its customers’ orders by building pallets with the required products and loading them into trucks. The problem is solved by using integer linear models. To be useful in practice, our models consider three types of constraints: geometric constraints, so that pallets lie completely inside the trucks and do not overlap; weight constraints, defining the maximum weights supported by a truck and by each axle, as well as the position of the centre of gravity of the cargo; and dynamic stability constraints. These last constraints forbid empty spaces between pallets to avoid cargo displacement when the truck is moving, …
The Multi-period Multi-trip Container Drayage Problem with Release and Due Dates
2021
Abstract The Container Drayage Problem (CDP) aims at routing a fleet of trucks, based at a common terminal, to serve customers while minimizing the total travel distance. Each trip starts from and ends at the terminal, and handles a subset of customers. Each customer requires either that a container is picked up or delivered. We introduce a more realistic variant, i.e., the Multi-trip Multi-period CDP with Release and Due Dates (MM-CDP-RDD), in which the planning horizon is composed of several periods (days). On each day, each truck may perform more than one trip respecting the Release and Due Dates (RDD) associated with customer services, corresponding to the first and the last day on whic…
Singular Neumann (p, q)-equations
2019
We consider a nonlinear parametric Neumann problem driven by the sum of a p-Laplacian and of a q-Laplacian and exhibiting in the reaction the competing effects of a singular term and of a resonant term. Using variational methods together with suitable truncation and comparison techniques, we show that for small values of the parameter the problem has at least two positive smooth solutions.
Resistance to change: a literature review and empirical study
2003
This paper examines organizational change, focusing on the distinction of changes according to their scope and presenting a typology of evolutionary and strategic changes. It also offers an in‐depth study of resistance to change. Through empirical research, the paper analyzes the importance of the sources of resistance to change defined theoretically, and considers both types of changes. The article shows which sources of resistance differ most, according to the scope of change, offering hints about where organizations should pay special attention when initiating a change process.
Diagnosis in track and field performances past the 1988 Ben Johnson doping scandal
1999
Beginning with the early 1960s, a lot of performance supporting effects have been integrated in the structure of track and field training, such as technical progress, theoretical knowledge of the training process, development of societies and medical steps, which among others include the forbidden use of steroids or other doping ‘techniques’. Since the integration of those effects took place quite fast, a logistic growth of world class performances concerning the years 1960–1988 can be observed in many disciplines especially if they were not far developed at the beginning of this period. Eight years (1989–1996) later, doping tests of world class athletes have spread (or should have spread) …
La investigación en docencia en dirección de operaciones: Tendencias y retos
2011
[EN] Purpose: The objective is to analyse research in Operations Management (OM) teaching published in high impact journals in the area in order to examine trends and set future challenges. Design/methodology/approach: A bibliometric study was carried out of 45 of the main JCR OM and Management journals for the 1995-2010 period. The 129 articles identified on research in OM teaching were analysed. Findings: There is a dearth of articles on teaching in the main OM and Management journals. Sixty-two point two percent of the journals analysed have not published any and the remainder (17) have devoted only 0.4% of all their publications to this subject area. Descriptive and theoretical/conceptu…
A reconsideration of the link between vertical externality and managerial incentives
2018
Previous research revealed that the strategic role of delegation contracts disappears if two quantity†setting firms outsource input production to a monopolistic supplier. I show that this role is restored if the assumption of a downstream duopoly is relaxed. Thus, delegation contracts allow downstream profit†maximizing owners to commit their firms to a behavior that differs from their preferences. This behavior varies nonmonotonically with the number of firms in the downstream market. Corresponding deviations from profit maximization are larger if the upstream monopolist makes a price precommitment. But little to no deviation occurs if the number of firms is large.
Latent Class Approach to Estimate the Willingness to Pay for Transit User Information
2012
The aim of analysis is to understand how unreliable information influences user behaviour and how much it discourages public transport use. For this purpose, a Stated Preference Survey was carried out in order to know the preferences of public transport users relating to information needs and uncertainty on the information provided by Advanced Traveller Information System (ATIS). The perceived uncertainty is defined as information inaccuracy. In our study, we consider- ed the difference between forecasted or scheduled waiting time at the bus stop and/or metro station provided by ATIS, and that experienced by user, to catch the bus and/or metro. A questionnaire was submitted to an appropriat…