Paz Perez-Gonzalez

• Ph. D.
• University of Seville

Additive Manufacturing (AM) is a disruptive production technology that challenges many well-established, conventional practices in Operations and Supply Chain Management decisions. Consequently, new context-specific decision problems have appeared in this area, while existing decision problems must be adapted or extended to this context. In this ov...

In this paper we investigate how decentralised scheduling approaches can be used to improve manufacturing scheduling. In view of the potential shown by some of these novel decentralised approaches, we conduct a series of experiments on a set of job shop instances subject to different degrees of variability in their processing times, and compare the...

In this paper, we present a deterministic permutation flowshop scheduling problem with a new objective function, the total core idle time. The interest of this objective is related to reduce the energy consumption of the system, taking into account that the energy needed during the processing times is constant, and that machines are switched off du...

This paper addresses the 2-stage assembly scheduling problem to minimise makespan with availability constraints, where the machines are not always available due to periodic maintenance activities. To the best of our knowledge, the periodic maintenance constraint has never been considered for the problem under investigation. In the proposed model, t...

The assembly scheduling problem is a common layout with many applications in real manufacturing scenarios. Despite the high number of studies dealing with this problem, no benchmark has been proposed up-to-now in the literature generating neither hard nor balanced instances. In this paper we present two extensive sets of instances for two variants...

In static-deterministic flow shop scheduling, solution algorithms are often tested by problem instances with uniformly distributed processing times. However, there are scheduling problems where a certain structure, variability or distribution of processing times appear. While the influence of these aspects on common objectives, like makespan and to...

This paper focuses on two components of idle time and waiting time, namely core idle time, ∑CITi, and core waiting time, ∑CWTj. Both measures are relevant indicators of the efficiency of production systems, since they are directly related to machine utilization and to the flow of jobs, and they can be used as scheduling criteria if no-idle and no-w...

This paper addresses the permutation flowshop scheduling problem with availability constraints where the machines are not available cyclically and the starting and finishing times of the periodic unavailability intervals are known in advance. In our case, this constraint is due to the shift calendar in a company in the aerospace industry, where all...

In this paper, we address the two-stage multi-machine assembly scheduling problem, a layout consisting of several dedicated parallel machines in the first stage and identical parallel machines in the second stage. The objective considered is the minimisation of the total completion time. Despite its relevance in practice and its NP-hard nature, thi...

In this paper we address the classical hybrid flow shop scheduling problem with makespan objective. As this problem is known to be NP-hard and a very common layout in real-life manufacturing scenarios, many studies have been proposed in the literature to solve it. These contributions use different solution representations of the feasible schedules,...

In a time where detailed, instantaneous and accurate information on shop-floor status is becoming available in many manufacturing companies due to Information Technologies initiatives such as Smart Factory or Industry 4.0, a question arises regarding when and how this data can be used to improve scheduling decisions. While it is acknowledged that a...

This work considers a scheduling problem identified in a factory producing customised Heating, Ventilation and Air Conditioning (HVAC) equipment. More specifically, the metal folding section is modelled as unrelated parallel machines with machine eligibility and sequence-dependent setup times. The objective under consideration is the minimisation o...

In this paper we address the problem of scheduling jobs on a single machine with cyclical machine availability periods. In this problem, the scheduling horizon is composed of periods where the machine is available followed by other periods where no operation can be performed. In the literature, the problem is denoted as scheduling with periodic mai...

Many activities in industry and services require the scheduling of tasks that can be concurrently executed, the most clear example being perhaps the assembly of products carried out in manufacturing. Although numerous scientific contributions have been produced on this area over the last decades, the wide extension of the problems covered and the l...

In the last years, researchers are paying special attention to scheduling in distributed environments due to the increasing benefits of multi-factory manufacture. In this paper, we address the distributed permutation flowshop scheduling problem to minimise the total flowtime. Since, to the best of our knowledge, this problem has not been addressed...

The problem addressed in this paper belongs to the topic of order scheduling, in which customer orders - composed of different individual jobs - are scheduled so the objective sought refers to the completion times of the complete orders. Despite the practical and theoretical relevance of this problem, the literature on order scheduling is not very...

In this paper we address the 2-stage assembly scheduling problem where there are m machines in the first stage to manufacture the components of a product and one assembly station (machine) in the second stage. The objective considered is the minimisation of the total completion time. Since the NP-hard nature of this problem is well-established, mos...

In this paper, we study a customer order scheduling problem where a number of orders, composed of several product types, have to be scheduled on a set of parallel machines, each one capable to process a single product type. The objective is to minimise the sum of the completion times of the orders, which is related to the lead time perceived by the...

Interfering jobs problems (or multi agents scheduling problems) are an emergent topic in the scheduling literature. In these decision problems, two or more sets of jobs have to be scheduled, each one with its own criteria. More specifically, we focus on a problem in which jobs belonging to two sets have to be scheduled in a single machine in order...

Undoubtedly, Industrial and Systems engineers live challenging times: From the shift of paradigms in manufacturing, transportation and logistics, to the rapid advances in information technologies and communications, or from the need of real-time decisions to the ever decreasing life cycle of products and services -- just to mention a few--, nowaday...

We address the problem of scheduling jobs in a permutation flowshop when their processing times adopt a given distribution (stochastic flowshop scheduling problem) with the objective of minimization of the expected makespan. For this problem, optimal solutions exist only for very specific cases. Consequently, some heuristics have been proposed in t...

This paper focuses onto a situation arising in most real-life manufacturing environments when scheduling has to be performed periodically. In such a scenario, different scheduling policies can be adopted, being perhaps the most common to assume that, once a set of jobs has been scheduled, their schedule cannot be modified (‘frozen’ schedule). This...

Most classical scheduling research assumes that the objectives sought are common to all jobs to be scheduled. However, many real-life applications can be modeled by considering different sets of jobs, each one with its own objective(s), and an increasing number of papers addressing these problems has appeared over the last few years. Since so far t...

In a scenario where a vendor books its manufacturing capacity options to multiple retailers it is not unlikely that the vendor runs out of capacity and then it cannot serve more orders until future periods of time. This paper suggests that, once the vendor becomes a bottleneck for the network, it is possible to apply negotiation policies between th...

In this paper we study a due date setting problem in a flowshop layout. The problem consists of scheduling a set of jobs arriving to the system together with jobs already present (denoted as old jobs), in order to set a common due date for the new jobs. Since the old jobs have a common due date that must not be violated, our problem is a rescheduli...

A business process can be defined as a set of related tasks that are carried out within a business or organization in order to obtain certain output that should add value for the business client or organization (Gunasekaran & Kobu, 2002). An enterprise can be then analyzed and integrated through its business processes. Thus, business process modeli...

La resecuenciación es una de las principales consecuencias de la variabilidad en los talleres, ya que las interrupciones no hacen posible el seguimiento de la secuencia inicial. Este trabajo aborda un problema de resecuenciación en flujo regular donde un conjunto de trabajos llega al sistema, y son secuenciados junto con un conjunto de trabajos que...

In this paper, we address the problem of scheduling a set of jobs in a flowshop with makespan objective. In contrast to the usual assumption of machine availability presented in most research, we consider that machines may not be available at the beginning of the planning period, due to processing of previously scheduled jobs. We first formulate th...

CBPM software tools could provide these functionalities and make possible obtaining business process models developed in a collaborative manner. Hence, our study focuses specifically on CBPM tools. While there are many available tools for Enterprise Analysis and Business Process Management (particularly for the web environment) not all of them full...

Resumen Uno de los mecanismos de control de la producción más recientes son los sistemas de control de la producción a medida basados en tarjetas, los cuales han demostrado su efectividad en gran número de casos. La optimización de este tipo de sistemas puede ser formulada como un problema de optimización combinatoria. Por otra parte, el método cro...

Hospitals and health systems are trying to harmonise their information systems. However, most efforts have focused on data exchange, while little work has been carried out on the harmonisation of healthcare processes. Nonetheless, the latter may offer a number of advantages, such as the development of reference models containing best practices, and...

Resumen Los objetivos de UML (Unified Modeling Language – Lenguaje Unificado de Modelado) y de la EPC (Event-driven Process Chain-Cadena de Procesos guiada por Eventos), están bien diferenciados: mientras que UML se enfoca al diseño de sistemas de información (SI), las EPCs se emplean para el modelado de procesos de negocios (BPM) dentro de la meto...

This paper characterises the initial availability constraint problems in a permutation flowshop layout considering different objectives: makespan, total flowtime and idle time. The goal is to analyse the structure of solutions and to discuss the managerial implications of these three problems. Also, we intend to compare the cases with availability...

Resumen Presentamos un modelo de simulación basada en Eventos Discretos para manejar la incertidumbre en la duración real de la intervención y en la llegada de pacientes urgentes (grandes quemados) que dislocan la planificación de una unidad de Cirugía Plástica y Grandes Quemados. El modelo desarrollado se implementa en ARENA y se usa para evaluar...