Simulation based performance analysis of an end-of-Aisle automated storage and retrieval system

This paper presents and discusses simulation of an End-of-Aisle automated storage and retrieval system, using FLEXSIM 6. The objective of the simulation model is to analyze and compare results of different control policies and physical designs. The performance measures considered for the evaluation of each control policy and layout combination are the total travel time of the crane and the number of storage and retrieval operations performed. The experiments set up and the corresponding results are discussed

Optimizing operations of large-scale water supply networks: a case study

In this paper we propose a mathematical programming model for a large drinking water supply network and discuss some possible extensions. The proposed optimization model is of a real water distribution network, the largest water supply network in Flanders. The problem is nonlinear, nonconvex and involves some binary variables, making it belong to the class of NP-hard problems. We discuss a way to convexify the nonconvex term and show some results on two case instances of the actual network

HPC for sensitivity studies: simulations with TOMAWAC and TELEMAC-3D

Water Qualit

Influence of relative traffic distribution in nodes with blocking: an analytical model

In nodes where the arriving packets are stored in one common buffer, packets with a given destination may have to wait for the transmission of packets with other destinations, even when the corresponding output channel is free. Although this so-called blocking effect has attracted considerable attention in literature, the influence of the relative distribution of the traffic according to destination has been largely overlooked. We therefore develop and analyze an appropriate discrete-time queueing model for a node whereby all arriving packets are accommodated in one common buffer and with two output channels that lead to distinct destinations. We study the stability of and the number of packets in the node. We then compare these results with those obtained for an analogous node with individual buffers for the distinct output channels. We demonstrate that the relative distribution of the traffic according to destination can have a major impact on the blocking effect and hence on the overall performance of the node

Assessment of Relative Technical Efficiency of Small Mental Health Areas in Bizkaia (Basque Country, Spain)

Mental disorders cause an enormous burden to society. Considering the current economic context, an efficient use of scarce inputs, with an appropriate outcome production, is crucial. This situation defines a classical Relative Technical Efficiency (RTE) problem. A well-known methodology to assess RTE is the Data Envelopment Analysis, although it presents some limitations. These may be overcome through a hybrid strategy that integrates Monte-Carlo simulation and artificial intelligence. This study aims to (1) design of a Decision Support System for the assessment of RTE of Small Mental Health Areas based on DEA; and (2) analyse 19 mental health areas of the Bizkaian Healthcare System (Spain) to classify them and to identify potential management improvements. The results have showed higher global RTE in the output-oriented orientation than in the input-oriented one. This suggests that a decision strategy based on improving the input management, within the ranges of the expert-driven model of community healthcare, could be appropriate. A future research line will focus our attention on the validation process through the analysis of micromanagement interventions and their potential impacts in the real system

Double ant colony system to improve accessibility after a disaster

We propose a novel double ant colony system to deal with accessibility issues after a natural or man-made disaster. The aim is to maximize the number of survivors that reach the nearest regional center (center of economic and social activity in the region) in a minimum time by planning which rural roads damaged by the disaster should be repaired given the available financial and human resources. The proposed algorithm is illustrated by means of a large instance based on the Haiti natural disasters in August-September 2008

Solving the Multi-activity Shift Scheduling Problem using Variable Neighbourhood Search

This paper presents a set of benchmarks instances for the multi-activity shift scheduling problem and the results produced using a variable neighbourhood search method. The data set is intended as a resource to generate and verify novel research on an important and practical but challenging problem. The variable neighbourhood search uses four different neighbourhood operators and can produce feasible solutions within short computation times

A cooperative game approach to a production planning problem

This paper deals with a production planning problem formulated as a Mixed Integer Linear Programming (MILP) model that has a competition component, given that the manufacturers are willing to produce as much products as they can in order to fulfil the market’s needs. This corresponds to a typical game theoretic problem applied to the productive sector, where a global optimization problem involves production planning in order to maximize the utilities for the different firms that manufacture the same type of products and compete in the market. This problem has been approached as a cooperative game, which involves a possible cooperation scheme among the manufacturers. The general problem was approached by Owen (1995) as the “production game” and the core was considered. This paper identifies the cooperative game theoretic model for the production planning MILP optimization problem and Shapley Value was chosen as the solution approach. The results obtained indicate the importance of cooperating among competitors. Moreover, this leads to economic strategies for small manufacturing companies that wish to survive in a competitive environment