0000000000266206
AUTHOR
ÁNgeles Pérez
Integer Preemption Problems
A fundamental assumption in the basic RCPSP is that activities in progress are non-preemptable. Some papers reveal the potential benefits of allowing activity interruptions in the schedule when the objective is the makespan minimization. In this chapter we consider the Maxnint_PRCPSP in which it is assumed that activities can be interrupted at any integer time instant with no cost incurred, that each activity can be split into a maximum number of parts, and that each part has a minimum duration established. We show how some procedures developed for the RCPSP can be adapted to work with the Maxnint_PRCPSP and we introduce some procedures specifically designed for this problem. Furthermore, p…
Minimizing weighted tardiness of jobs with stochastic interruptions in parallel machines
Abstract In this paper, we address the problem of minimizing expected total weighted tardiness of jobs that have stochastic interruptions and that are processed on a set of parallel machines. Our research generalizes the problem of scheduling parallel machines to minimize total weighted tardiness. The proposed solution method is based on the scatter search methodology and implements an innovative structured combination procedure. Extensive computational testing with more than 400 problem instances shows the merit of the proposed solution method.
Heuristic algorithms for a storage location assignment problem in a chaotic warehouse
The extensive application of emerging technologies is revolutionizing warehouse management. These technologies facilitate working with complex and powerful warehouse management models in which products do not have assigned fixed locations (random storage). Random storage allows the utilization of the available space to be optimized. In this context, and motivated by a real problem, this article presents a model that looks for the optimal allocation of goods in order to maximize the storage space availability within the restrictions of the warehouse. For the proposed model a construction method, a local search algorithm and different metaheuristics have been developed. The introduced algorit…
Time and work generalised precedence relationships in project scheduling with pre-emption: An application to the management of Service Centres
Abstract In this paper we present an application of project scheduling concepts and solution procedures for the solution of a complex problem that comes up in the daily management of many company Service Centres. The real problem has been modelled as a multi-mode resource-constrained project scheduling problem with pre-emption, time and work generalised precedence relationships with minimal and maximal time lags between the tasks and due dates. We present a complete study of work GPRs which includes proper definitions, a new notation and all possible conversions amongst them. Computational results that show the efficiency of the proposed hybrid genetic algorithm and the advantages of allowi…
A multistage heuristic for storage and retrieval problems in a warehouse with random storage
The warehouse is one of the essential components of logistics and supply chains. The efficiency of the whole chain is affected by the performance of warehouse operations and, more particularly, the storage and retrieval of goods. This paper considers a storage and retrieval problem in a real warehouse with random storage and different types of forklifts, depending on the locations they can access. The problem deals with selecting locations to store/retrieve a predefined set of pallets, assigning an adequately skilled forklift to each operation and determining the order in which each forklift will perform its operations so that the total employed time is minimized. The problem is solved heur…
A multi-objective approach for a project scheduling problem with due dates and temporal constraints infeasibilities
In this paper, we study a multi-mode resource-constrained project scheduling problem (RCPSP) which considers time and work generalised precedence relationships with minimal and maximal time lags and due dates where each activity requires only one unit of resource (e.g. a worker, a machine, etc.). To find a feasible solution for this problem is NP-hard and therefore for instances where a feasible solution has not been found, an appropriate real-life approach would consist of providing the decision-maker with a collection of quality solutions with a trade-off between due dates and temporal constraints violations. We propose a multi-objective evolutionary algorithm for the generation of an app…
Project Scheduling with Stochastic Activity Interruptions
In this chapter we address the problem of scheduling the activities of a resource-constrained project, some of which may be interrupted by an uncertain amount of time. The resources may be, for example, machines in a jobshop, computers with specialized software packages (as those needed for engineering designs), or highly specialized technicians.
Static and dynamic policies with RFID for the scheduling of retrieval and storage warehouse operations
Warehouses are essential components of logistics and supply chains. The performance of warehouse operations significantly affects the efficiency of the whole chain it belongs to. Radio frequency identification (RFID) is an emerging technology capable of providing real-time information about the location and properties of tagged object(s), such as people, equipment or products. The objective of this article is threefold, to propose and compare different offline and online policies for the scheduling of warehouse operations, to design a tool that allows the decision maker to compare policies and environments without putting them into practice, and to study the benefits that can be obtained if…
A graph colouring model for assigning a heterogeneous workforce to a given schedule
Abstract We analyze a heterogeneous workforce assignment problem in which the minimum number of workers required to carry out a machine load plan is calculated. The problem is formulated as a restricted vertex colouring problem and a branch and bound algorithm is presented. The special characteristics of the graph to be coloured allow an efficient implementation of the branch and bound. Computational results show that the algorithm can solve problems of 50 activities, 5, 10 and 15 machines and between 2 to 15 different types of workers in just a few seconds.
Skilled workforce scheduling in Service Centres
Abstract The Skilled Workforce Project Scheduling Problem (SWPSP) is a complex problem of task scheduling and resource assignment that comes up in the daily management of many company Service Centres (SC). The SWPSP considers many real characteristics faced daily by the SC: client-company service quality agreements that establish maximum dates for the beginning and the end of tasks with penalties for delays, criticality levels indicating the client-priority in processing each task, generalized precedence relationships that can produce cycle structures, time period and percentage time lags and variable task durations depending on the worker executing the task. Furthermore, the SC workforce i…