Imma Ribas - Academia.edu (original) (raw)
Papers by Imma Ribas
Ramon Companys & Imma Ribas DOE-ETSEIB-UPC Este es el primero de tres trabajos dedicados a proced... more Ramon Companys & Imma Ribas DOE-ETSEIB-UPC Este es el primero de tres trabajos dedicados a procedimientos de resolución de los problemas flowshop con criterio minimización del makespan, basados en la clásica heurística de Nawaz, Enscore y Ham. Consideramos dos casos el FmprmuC max y el FmblockC max. En el presente trabajo analizamos los procedimientos de desempate en la intercalación del segundo paso del NEH. Basamos las conclusiones en los experimentos realizados tomando como base los 120 ejemplares de las colecciones de Taillard. Son suficientemente conocidos y ejercen cierta fascinación sobre los investigadores. En anexo recogemos resultados sobre otras colecciones, más numerosas, generadas siguiendo los principios establecidos por Taillard. Al no disponer de personal auxiliar para realizar los experimentos computacionales, dicho anexo se irá completando en la medida de lo posible. El segundo trabajo estará dedicado a analizar el efecto de diferentes procedimientos de ordenación en el paso 1, algunos propuestos por otros autores, otros originales. El tercer trabajo se dedicará al efecto de los procedimientos de mejora de las soluciones obtenidas en el paso 1 y el paso 2. De esta forma dispondremos de manera ordenada un material muy considerable que hemos ido elaborando durante los últimos años, algunas veces siguiendo senderos tortuosos a los que nos condujeron los comentarios de algunos revisores, supuestamente bien intencionados.
English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not i... more English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best one. Resumen (Castellano) En este trabajo se muestra que el procedimiento de inserción de la heurística NEH no siempre mejora la calidad de la secuencia. Este hecho se da especialmente en los procedimientos propuestos en la literatura para el flow shop con bloqueo y, como resultado de este trabajo, se recomienda evaluar siempre la secuencia antes y después del procedimiento de inserción con el fin de quedarse con la mejor.
Ronconi instances, Fm|block|ΣT (I) scenario 1 scenario 2 scenario 3 scenario 4 # BEST # BEST # BE... more Ronconi instances, Fm|block|ΣT (I) scenario 1 scenario 2 scenario 3 scenario 4 # BEST # BEST # BEST #
... Alternative NEH was served for traditional reasons, MME for to be consistent with our conclus... more ... Alternative NEH was served for traditional reasons, MME for to be consistent with our conclusions about its effectiveness, RAE for its superior variability. ... She uses a new bound (time limit 3600 seconds on a Pentium IV with 1.4 GHz PC). 3. J. Grabowski and J. Pempera (2007). ...
The distributed blocking flow shop scheduling problem (DBFSP) allows modeling the scheduling proc... more The distributed blocking flow shop scheduling problem (DBFSP) allows modeling the scheduling process in companies with more than one factory. It configures production systems as flow shop lines where the blocking constraint must be considered. To the best of our knowledge, this variant of the distributed permutation flow shop scheduling problem has not been studied. In this working paper, we show the best solutions found during our research for the Taillard's instances adapted to this problem.
English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not i... more English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best one. Resumen (Castellano) En este trabajo se muestra que el procedimiento de inserción de la heurística NEH no siempre mejora la calidad de la secuencia. Este hecho se da especialmente en los procedimientos propuestos en la literatura para el flow shop con bloqueo y, como resultado de este trabajo, se recomienda evaluar siempre la secuencia antes y después del procedimiento de inserción con el fin de quedarse con la mejor.
Taillard instances, FmblockC max # BEST source # BEST source # BEST source
This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorith... more This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorithm, which are both combined with a variable neighbourhood search (VNS), for dealing with the flow shop problem with blocking, in order to minimize the total tardiness of jobs. The structure of both algorithms is very similar, but they differ in the way that the search is diversified in the space of solutions. In the ILS algorithm, the diversification is performed by a perturbation mechanism that takes into account some characteristics of the problem; whereas the perturbation in the IG is performed through a deconstruction and construction phase proposed in the literature that has been proven to be very effective in dealing also with the makespan criterion. Moreover, the algorithms have been tested with three initial solution procedures. The computation of these algorithms when evaluated against an algorithm from the literature has shown their good performance.
Towards a new future in engineering education, new scenarios that european alliances of tech universities open up
Modern higher education needs to provide skills needed in working life, such as entrepreneurship,... more Modern higher education needs to provide skills needed in working life, such as entrepreneurship, besides the more traditional technological competence. The Boost I&E Project2 was developed in 2020 and 2021 with the aim of generating a set of guidelines for innovation and entrepreneurship challenge-driven projects for master's programmes. The added value was created by collaborating and exchanging best practices among higher education institutions in seven different countries, with the aim of developing students' skills with an international perspective and exposure to the knowledge triangle. The implementation of Boost I&E would allow learning about the advantages and disadvantages of different approaches in a practical way, while courses on urban mobility were provided. The activities involved more than 100 students over two years. The experience concluded with the adoption of a set of guidelines based on best practices, covering several aspects. Most emphasis was placed o...
Lecture Notes in Management and Industrial Engineering, 2014
This paper deals with the blocking flow shop problem and proposes new constructive procedures for... more This paper deals with the blocking flow shop problem and proposes new constructive procedures for the total tardiness minimization of jobs. The heuristic has three-phases to build the sequence; the first phase selects the first job to be scheduled, the second phase arranges the remaining jobs and the third phase uses the insertion procedure of NEH to improve the sequence. The proposed procedures evaluate the tardiness associated to the sequence obtained before and after the third phase in order to keep the best of both because the insertion phase can worsen the result. The computational evaluation of these procedures against the benchmark constructive procedures from the literature reveals their good performance.
A configuration of reverse logistics network for end-of-use products is considered in order to es... more A configuration of reverse logistics network for end-of-use products is considered in order to establish a decision model that can help to design the network according to the characteristics of the product to be recovered. The proposed model comes from an extensive review of the literature, which proposes to consider the combination of product residual value and marginal value time of the product with the type of recovery option to design the structure. Resumen Se considera el problema del diseño de las redes de suministro inversa para la recuperación de productos usados, con el objetivo de establecer un modelo que permita configurar la red en función las características del producto a recuperar. El modelo propuesto es el resultado de una extensa revisión de la literatura y propone el diseño de la red en función del valor residual del producto, de su "depreciación" durante el periodo de recuperación y del proceso de recuperación económica requerida (reutilización, reciclaje, refabricación).
This paper analyses the behaviour of the insertion procedure of the NEH heuristics due to in some... more This paper analyses the behaviour of the insertion procedure of the NEH heuristics due to in some cases the procedure does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best of both.
Omega, 2011
This paper proposes an iterated greedy algorithm for solving the blocking flowshop scheduling pro... more This paper proposes an iterated greedy algorithm for solving the blocking flowshop scheduling problem for makespan minimization. Moreover, it presents an improved NEH-based heuristic, which is used as the initial solution procedure for the iterated greedy algorithm. The effectiveness of both procedures was tested on some of Taillard's benchmark instances that are considered to be blocking flowshop instances. The experimental evaluation showed the efficiency of the proposed algorithm, in spite of its simple structure, in comparison with a state-of-the-art algorithm. In addition, new best solutions for Taillard's instances are reported for this problem, which can be used as a basis of comparison in future studies.
Journal of Industrial Engineering and Management
Purpose: This paper, devoted to the selection of strategic sourcing options as a part of the supp... more Purpose: This paper, devoted to the selection of strategic sourcing options as a part of the supply chain design, aims to provide supply chain designers with guidelines for selecting the best strategic sourcing option for each item (i.e., products, modules, parts and services).Design/methodology/approach: The study is based on a review of the literature on sourcing options, buyer-supplier relationships, factors and criteria to select a sourcing strategy as well as the authors experience in this field.Findings: We propose a multi-step process by considering the three dimensions of the strategic sourcing options (who and how many will make the item; in cases of outsourcing, the kind of relationship between buyer and supplier(s); and where the item is to be made) together with the characteristics of the context, demand and product, and the relevant criteria to evaluate them.Originality/value: The main contributions are the review of the factors and criteria for selecting the best strat...
A scheduling problem in a production system with different parallel machines is solved. Each orde... more A scheduling problem in a production system with different parallel machines is solved. Each order consists of multiple batches of products, with their amounts, and a due date. For each type of product, each machine has a setup sequence-dependent time and a processing time. The problem is to assign and schedule each batch of the orders to one machine, tr ying to minimize a bicriteria objective function, which considers the mean tardiness and the mean completion time.The proposed procedure is a GRASP, which proposes three rules for the initial solution.
Purpose: Since the emergence of Lean Manufacturing many organizations strived to implement it. No... more Purpose: Since the emergence of Lean Manufacturing many organizations strived to implement it. Nonetheless, sustainable Lean transformation is not as easy as to be simply achieved. Several aspects need to be taken into account before Lean implementation which national and organizational culture are important. By considering influences of national culture on the organizational culture, this paper aims at proposing an evaluation model to determine the cultural weaknesses of an organization and give some recommendations to manage people before implementing Lean. Design/methodology/approach: This research has been conducted based on literature review survey and semi-structured interviews. Research papers, conference proceedings, books, and official websites regarding Lean philosophy were reviewed to find the influence of national culture in Lean implementation. Different databases were scrutinized, from 2015 to 2017, containing Scopus and Web of Science with the time period of 1996-2016...
Ramon Companys & Imma Ribas DOE-ETSEIB-UPC Este es el primero de tres trabajos dedicados a proced... more Ramon Companys & Imma Ribas DOE-ETSEIB-UPC Este es el primero de tres trabajos dedicados a procedimientos de resolución de los problemas flowshop con criterio minimización del makespan, basados en la clásica heurística de Nawaz, Enscore y Ham. Consideramos dos casos el FmprmuC max y el FmblockC max. En el presente trabajo analizamos los procedimientos de desempate en la intercalación del segundo paso del NEH. Basamos las conclusiones en los experimentos realizados tomando como base los 120 ejemplares de las colecciones de Taillard. Son suficientemente conocidos y ejercen cierta fascinación sobre los investigadores. En anexo recogemos resultados sobre otras colecciones, más numerosas, generadas siguiendo los principios establecidos por Taillard. Al no disponer de personal auxiliar para realizar los experimentos computacionales, dicho anexo se irá completando en la medida de lo posible. El segundo trabajo estará dedicado a analizar el efecto de diferentes procedimientos de ordenación en el paso 1, algunos propuestos por otros autores, otros originales. El tercer trabajo se dedicará al efecto de los procedimientos de mejora de las soluciones obtenidas en el paso 1 y el paso 2. De esta forma dispondremos de manera ordenada un material muy considerable que hemos ido elaborando durante los últimos años, algunas veces siguiendo senderos tortuosos a los que nos condujeron los comentarios de algunos revisores, supuestamente bien intencionados.
English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not i... more English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best one. Resumen (Castellano) En este trabajo se muestra que el procedimiento de inserción de la heurística NEH no siempre mejora la calidad de la secuencia. Este hecho se da especialmente en los procedimientos propuestos en la literatura para el flow shop con bloqueo y, como resultado de este trabajo, se recomienda evaluar siempre la secuencia antes y después del procedimiento de inserción con el fin de quedarse con la mejor.
Ronconi instances, Fm|block|ΣT (I) scenario 1 scenario 2 scenario 3 scenario 4 # BEST # BEST # BE... more Ronconi instances, Fm|block|ΣT (I) scenario 1 scenario 2 scenario 3 scenario 4 # BEST # BEST # BEST #
... Alternative NEH was served for traditional reasons, MME for to be consistent with our conclus... more ... Alternative NEH was served for traditional reasons, MME for to be consistent with our conclusions about its effectiveness, RAE for its superior variability. ... She uses a new bound (time limit 3600 seconds on a Pentium IV with 1.4 GHz PC). 3. J. Grabowski and J. Pempera (2007). ...
The distributed blocking flow shop scheduling problem (DBFSP) allows modeling the scheduling proc... more The distributed blocking flow shop scheduling problem (DBFSP) allows modeling the scheduling process in companies with more than one factory. It configures production systems as flow shop lines where the blocking constraint must be considered. To the best of our knowledge, this variant of the distributed permutation flow shop scheduling problem has not been studied. In this working paper, we show the best solutions found during our research for the Taillard's instances adapted to this problem.
English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not i... more English) In this paper it is shown that, in some cases, the insertion procedure of NEH does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best one. Resumen (Castellano) En este trabajo se muestra que el procedimiento de inserción de la heurística NEH no siempre mejora la calidad de la secuencia. Este hecho se da especialmente en los procedimientos propuestos en la literatura para el flow shop con bloqueo y, como resultado de este trabajo, se recomienda evaluar siempre la secuencia antes y después del procedimiento de inserción con el fin de quedarse con la mejor.
Taillard instances, FmblockC max # BEST source # BEST source # BEST source
This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorith... more This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorithm, which are both combined with a variable neighbourhood search (VNS), for dealing with the flow shop problem with blocking, in order to minimize the total tardiness of jobs. The structure of both algorithms is very similar, but they differ in the way that the search is diversified in the space of solutions. In the ILS algorithm, the diversification is performed by a perturbation mechanism that takes into account some characteristics of the problem; whereas the perturbation in the IG is performed through a deconstruction and construction phase proposed in the literature that has been proven to be very effective in dealing also with the makespan criterion. Moreover, the algorithms have been tested with three initial solution procedures. The computation of these algorithms when evaluated against an algorithm from the literature has shown their good performance.
Towards a new future in engineering education, new scenarios that european alliances of tech universities open up
Modern higher education needs to provide skills needed in working life, such as entrepreneurship,... more Modern higher education needs to provide skills needed in working life, such as entrepreneurship, besides the more traditional technological competence. The Boost I&E Project2 was developed in 2020 and 2021 with the aim of generating a set of guidelines for innovation and entrepreneurship challenge-driven projects for master's programmes. The added value was created by collaborating and exchanging best practices among higher education institutions in seven different countries, with the aim of developing students' skills with an international perspective and exposure to the knowledge triangle. The implementation of Boost I&E would allow learning about the advantages and disadvantages of different approaches in a practical way, while courses on urban mobility were provided. The activities involved more than 100 students over two years. The experience concluded with the adoption of a set of guidelines based on best practices, covering several aspects. Most emphasis was placed o...
Lecture Notes in Management and Industrial Engineering, 2014
This paper deals with the blocking flow shop problem and proposes new constructive procedures for... more This paper deals with the blocking flow shop problem and proposes new constructive procedures for the total tardiness minimization of jobs. The heuristic has three-phases to build the sequence; the first phase selects the first job to be scheduled, the second phase arranges the remaining jobs and the third phase uses the insertion procedure of NEH to improve the sequence. The proposed procedures evaluate the tardiness associated to the sequence obtained before and after the third phase in order to keep the best of both because the insertion phase can worsen the result. The computational evaluation of these procedures against the benchmark constructive procedures from the literature reveals their good performance.
A configuration of reverse logistics network for end-of-use products is considered in order to es... more A configuration of reverse logistics network for end-of-use products is considered in order to establish a decision model that can help to design the network according to the characteristics of the product to be recovered. The proposed model comes from an extensive review of the literature, which proposes to consider the combination of product residual value and marginal value time of the product with the type of recovery option to design the structure. Resumen Se considera el problema del diseño de las redes de suministro inversa para la recuperación de productos usados, con el objetivo de establecer un modelo que permita configurar la red en función las características del producto a recuperar. El modelo propuesto es el resultado de una extensa revisión de la literatura y propone el diseño de la red en función del valor residual del producto, de su "depreciación" durante el periodo de recuperación y del proceso de recuperación económica requerida (reutilización, reciclaje, refabricación).
This paper analyses the behaviour of the insertion procedure of the NEH heuristics due to in some... more This paper analyses the behaviour of the insertion procedure of the NEH heuristics due to in some cases the procedure does not improve the solution quality. This fact is observed specially in the NEH-based heuristics that have been proposed in the literature of the blocking flow shop problem. As a result of this work, we recommend to evaluate the sequence before and after the insertion phase in order to retain the best of both.
Omega, 2011
This paper proposes an iterated greedy algorithm for solving the blocking flowshop scheduling pro... more This paper proposes an iterated greedy algorithm for solving the blocking flowshop scheduling problem for makespan minimization. Moreover, it presents an improved NEH-based heuristic, which is used as the initial solution procedure for the iterated greedy algorithm. The effectiveness of both procedures was tested on some of Taillard's benchmark instances that are considered to be blocking flowshop instances. The experimental evaluation showed the efficiency of the proposed algorithm, in spite of its simple structure, in comparison with a state-of-the-art algorithm. In addition, new best solutions for Taillard's instances are reported for this problem, which can be used as a basis of comparison in future studies.
Journal of Industrial Engineering and Management
Purpose: This paper, devoted to the selection of strategic sourcing options as a part of the supp... more Purpose: This paper, devoted to the selection of strategic sourcing options as a part of the supply chain design, aims to provide supply chain designers with guidelines for selecting the best strategic sourcing option for each item (i.e., products, modules, parts and services).Design/methodology/approach: The study is based on a review of the literature on sourcing options, buyer-supplier relationships, factors and criteria to select a sourcing strategy as well as the authors experience in this field.Findings: We propose a multi-step process by considering the three dimensions of the strategic sourcing options (who and how many will make the item; in cases of outsourcing, the kind of relationship between buyer and supplier(s); and where the item is to be made) together with the characteristics of the context, demand and product, and the relevant criteria to evaluate them.Originality/value: The main contributions are the review of the factors and criteria for selecting the best strat...
A scheduling problem in a production system with different parallel machines is solved. Each orde... more A scheduling problem in a production system with different parallel machines is solved. Each order consists of multiple batches of products, with their amounts, and a due date. For each type of product, each machine has a setup sequence-dependent time and a processing time. The problem is to assign and schedule each batch of the orders to one machine, tr ying to minimize a bicriteria objective function, which considers the mean tardiness and the mean completion time.The proposed procedure is a GRASP, which proposes three rules for the initial solution.
Purpose: Since the emergence of Lean Manufacturing many organizations strived to implement it. No... more Purpose: Since the emergence of Lean Manufacturing many organizations strived to implement it. Nonetheless, sustainable Lean transformation is not as easy as to be simply achieved. Several aspects need to be taken into account before Lean implementation which national and organizational culture are important. By considering influences of national culture on the organizational culture, this paper aims at proposing an evaluation model to determine the cultural weaknesses of an organization and give some recommendations to manage people before implementing Lean. Design/methodology/approach: This research has been conducted based on literature review survey and semi-structured interviews. Research papers, conference proceedings, books, and official websites regarding Lean philosophy were reviewed to find the influence of national culture in Lean implementation. Different databases were scrutinized, from 2015 to 2017, containing Scopus and Web of Science with the time period of 1996-2016...