Search results for "Operations"

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.

Navigating uncharted waters: Designing business models for virtual and augmented reality companies in the medical industry

2021

Abstract New technologies are at the heart of industry transformation. Virtual and augmented reality companies provide fundamentally new ways of communication, treatment, education, and specialist training within the medical industry. However, business models for new ventures that target the medical industry have received scant attention within academic research. Using a multiple case study approach, we analyze how virtual and augmented reality firms create value for their customers in the medical industry. In all, we have studied eight companies that offer different types of solutions for their target segments. The results of the analysis are four design elements consisting of twelve posit…

Bundle generation for last-mile delivery with occasional drivers

2022

In this paper, we present the vehicle routing problem (VRP) with occasional drivers (OD) and order bundles (OB). The problem VRP-OD-OB is an extension of the VRP-OD, where instead of assigning one customer per driver, drivers are assigned bundles of customers. To deal with the bundle-to-driver assignment, a bidding system is exploited, in which a company offers a set of bundles and the drivers raise their bids. These bids depend on features such as the drivers’ destination, flexibility in deviating from the shortest path, and willingness to offer service. To generate valuable bundles of customers, we propose two strategies: (i) an innovative approach based on the creation of corridors, and …

Modelling and forecasting mortality in Spain

2008

[EN] Experience shows that static life tables overestimate death probabilities. As a consequence of this overestimation the premiums for annuities, pensions and life insurance are not what they actually should be, with negative effects for insurance companies or policy-holders. The reason for this overestimation is that static life tables, through being computed for a specific period of time, cannot take into account the decreasing mortality trend over time. Dynamic life tables overcome this problem by incorporating the influence of the calendar when graduating mortality. Recent papers on the topic look for the development of new methods to deal with this dynamism. Most methods used in dyna…

Do Foreign Direct Investment (FDI) and Trade Openness Explain the Disparity in ICT Diffusion between Asia-Pacific and the Islamic Middle Eastern Coun…

2010

This study investigates the impact of FDI and trade openness on ICT diffusion in the Asia-Pacific and Middle East regions from 1996-2005. The results indicate that while dissimilarities exist between the economies included in this study in terms of their level of socio-economic and political development, education and the growth of GDP have had a positive impact on ICT diffusion in both regions. However, while FDI has generally had a positive and significant impact on ICT diffusion in Asia-Pacific economies, its impact on Middle Eastern economies has been detrimental. The results of this study also show that trade-openness has had, in general, a positive and significant impact on ICT diffus…

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…

A Framework for Assessing the Condition of Crowds Exposed to a Fire Hazard Using a Probabilistic Model

2014

Published version of an article in the journal: International Journal of Machine Learning and Computing. Also available from the publisher at: http://dx.doi.org/10.7763/IJMLC.2014.V4.379 open Access Allocating limited resources in an optimal manner when rescuing victims from a hazard is a complex and error prone task, because the involved hazards are typically evolving over time; stagnating, building up or diminishing. Typical error sources are: miscalculation of resource availability and the victims’ condition. Thus, there is a need for decision support when it comes to rapidly predicting where the human fatalities are likely to occur to ensure timely rescue. This paper proposes a probabil…

A framework for a network-level performance measurement system in SME networks

2008

The present study aims to present a theoretical framework for a network-level performance measurement system. The suggested framework for the performance measurement system is composed of the factors that enable and cause the productivity and profitability of the network form of organisation. The framework developed in this study can be divided into six subdimensions: (1) network culture, (2) resources and competences, (3) models of action, (4) internal processes, (5) customer perspective and (6) financial indicators of the network. We argue that this framework provides research opportunities to study the performance of the network form of organisation; but even more importantly, it provide…

2016

Increasing offensive or defensive efficiency? An analysis of Italian and Spanish football☆

2009

This paper analyses technical efficiency of Italian and Spanish football during three recent seasons, to shed light on the sport performance of professional football clubs. To achieve this we have used mathematical optimisation methods, particularly DEA models, which enable the calculation of the frontiers of efficient production. Some of the most interesting results are the following. Firstly, the Spanish league is clearly more homogeneous and competitive than the Italian league. Secondly, to obtain a better classification in the Italian league, it is much more important to improve defensive, rather than offensive, efficiency. The popular maxim holds in Italy: the best attack begins with a…