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Introduction
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August 2005 - May 2009
August 2009 - present
Publications
Publications (96)
The match rate of medical schools in the U.S. has been extensively studied from the perspective of applicants and influential factors. A method to objectively estimate the efficiency of a medical school’s match rate has not been described in the literature. Such a method constitutes a significant improvement opportunity for medical schools via benc...
This paper explores the characteristics of solutions when scheduling jobs in a shop with parallel machines. Three classical objective functions were considered: makespan, total completion time, and total tardiness. These three criteria were combined in pairs, resulting in three bi-objective formulations. These formulations were solved using the ε-c...
We propose a decision tree model that considers reverse and forward flows in a closed-loop supply chain (CLSC). Based on observations of three CLSCs, the model considers an environment where there is uncertainty in the quantity of returned used components (and new components from suppliers) with the decision being the incentive offered to each retu...
This research article utilizes a bootstrap DEA approach for assessing the operational efficiency of a single southwestern downtown hotel during the COVID-19 pandemic. The hotel’s performance is benchmarked throughout a 12-month period, which includes a two-month shutdown period due to COVID-19. The bias-corrected technical and scale efficiencies be...
It has become widely accepted that delivering diverse products to customers who have different needs by a “one-size-fits-all” supply chain results in lower profits and customer service. Therefore, there is a need to design supply chain systems that can effectively and profitably serve products and customers with diverse characteristics. This paper...
This paper addresses the two-machine permutation flowshop problem with deterioration. The objectives are minimizing the makespan and the average tardiness. Jobs have a baseline process time in each machine and have a due date. The actual time to process a job depends on the machine performance level at the start of each job, which is a function of...
This work studies a two-stage hybrid flowshop problem with secondary resources (workers). The goal is to minimise the average tardiness. The workers are assigned to the workstations by time buckets (work shifts), and the assignment changes during the planning horizon. Two versions of the problem are studied: (i) the case where the average efficienc...
Esta investigación propone un modelo de decisión para gestionar la compra de componentes nuevos y usados en un sistema de manufactura. Los componentes nuevos se adquieren de un proveedor el cual ofrece descuentos que dependen de la capacidad reservada. Los componentes usados provienen de varias fuentes, donde la cantidad que se recibirá de cada fue...
Given the high variability of both quantity and condition of the returns, closed-loop supply chains depend on a mix of remanufactured and new components. Effectively managing the combined flow of returned and new components is imperative to minimize total system costs. This paper proposes a model that helps manage the flow of returns by determining...
This note proposes and analyzes a posterior tight worst-case bound for the longest processing time (LPT) heuristic for scheduling independent jobs on identical parallel machines with the objective of minimizing the makespan. It makes natural remarks on the well-known posterior worst-case bounds, and shows that the proposed bound can complement the...
The inclusion of worker satisfaction in scheduling problems is of significant importance to many organizations and constitutes a current relevant research stream. This article contributes to the body of knowledge by studying the well-known identical parallel machine scheduling problem while considering workers’ satisfaction. Metrics of job preferen...
This chapter investigates the link between green supply chain management skills and performance outcomes in the logistics sector. Relationships between green supply chain management skills and two performance outcomes, environmental performance and innovation performance, are examined. Survey data were collected from the Finnish, Russian, Puerto Ri...
Esta investigación define ciertas características, accidentales o decididas, de un grupo de revistas académicas latinoamericanas en el campo de las ciencias administrativas que publican artículos mayormente en lenguaje castellano. Se caracterizan las revistas desde una perspectiva individual y luego como grupo. Desde el punto de vista individual, s...
Esta investigación define ciertas características, accidentales o decididas, de un grupo de revistas académicas latinoamericanas en el campo de las ciencias administrativas que publican artículos mayormente en español. Se caracterizan las revistas desde una perspectiva individual y luego como grupo. Desde el punto de vista individual, se clasifican...
This paper considers a parallel-machine scheduling problem with sequence dependent processing times and periodic maintenance. The time to complete jobs increases as the machines deteriorate and the machine deterioration depends on the particular job sequence assigned to a machine. The planned maintenance activity returns the machine to its optimal...
Responsive assemble-to-order supply chains demand efficient coordination between production and distribution functions. This paper investigates the case of customer orders assigned to configuration cells located in different geographical regions. Complete orders are directly shipped from the cells to customers located in distinct locations. The obj...
Purpose
The purpose of this paper is to study the relationships between the capabilities and performance characteristics of logistic service providers (LSPs) in the Caribbean region. The study considers the organization’s process improvement (PI) performance as it relates to their innovation capabilities, their efforts into information sharing and...
This research addresses the assignment of technicians to quality control tests in a pharmaceutical manufacturing environment. The problem is complex as it includes constraints related to the capabilities of the quality assurance technicians, as well as various criteria related to efficiency, customer service, and worker satisfaction. We consider se...
This research aims to evaluate the relationship between the operational and financial performance of logistic service providers (LSPs) and three relevant factors: The focus on long-term relationships with customers, the information technology capabilities, and the technology uncertainty of the LSPs' customers. The research aims to answer if there a...
This paper addresses the minimal makespan parallel machine problem where machines are subject to preventive maintenance events of a known deterministic duration. The processing time of a job depends on its predecessors since the machine’s last maintenance. The paper proposes some dominance criteria for sequences of jobs assigned to a machine, and u...
This article explores with extensive computational and statistical analyses the impact that correlation and data translation have, independently, on the average data envelopment analysis (DEA) efficiency score of a data set. The article explores three types of correlations, (a) between inputs and outputs, (b) among inputs only, and (c) among output...
Two important managerial objectives incorporated in production planning are the maximisation of the on-time delivery of orders and worker satisfaction. While the maximisation of on-time deliveries has frequently been considered in past production planning research, the component of maximising worker satisfaction has typically been ignored. The assi...
This note considers the longest processing time heuristic for scheduling n independent jobs on two uniform parallel machines to minimize the makespan. A posterior worst-case performance ratio, by depending on the index of the latest job inserted in the machine where the makespan takes place, is developed for this heuristic, and some examples demons...
The purpose of this study is to present a review of research on quality management in Latin-American and Spanish journals published between 2005 and 2013. The study considers managerial focused research written in Spanish or English. The classification of the research considers three elements: the research methodology, the type of application/busin...
A new polynomial algorithm is developed for the classical multiprocessor scheduling problem in which independent jobs are nonpreemptively scheduled on identical parallel machines with the objective of minimizing the makespan, i.e. the latest job finishing time. The algorithm at first generates and merges a set of partial solutions in order to obtai...
Effective production planning of manufacturing networks requires careful consideration of several factors, including capacity, production, yields, and resource failure costs. This is particularly critical in highly variable environments where multiple resource types are available during the planning and implementation processes. This paper presents...
La Gestión de la Cadena de Suministro (GCS) es un tema que ha recibido una
considerable atención por parte de investigadores, académicos y el mundo
empresarial. Esto se justifica por la importancia que una gestión eficiente y
efectiva de la GCS tiene en el éxito de una empresa. Las pequeñas y medianas
empresas (PyMEs) no son la excepción, es más, s...
We consider the optimal allocation of demand across a set of suppliers given the risk of supplier failures. We assume items sourced are used in multiple facilities and can be purchased from multiple suppliers with different cost and reliability characteristics. Suppliers have production flexibility that allows them to deliver a contingency quantity...
The globalization of production systems has led organizations to consider the supplier management function as a strategic decision. There is signifcant research work addressing decision making and supplier management. However, there is a lack of research in the case of multiple suppliers with different characteristics and attributes and able to sat...
This paper considers the problem of scheduling nonpreemptive jobs on identical parallel processors to minimize workload balancing criteria. While workload balancing is an important practical criterion given the need of production systems to efficiently use all of their resources, there is no established measure of performance in the scheduling lite...
Many researchers and economists have argued that competitiveness studies conducted by WEF and IMD, show limitations in small-economies, even more when they have different characteristics. The objective of this research is to study the competitiveness of three small-economies: Puerto Rico, Costa Rica and Singapore. The double-diamond model of compet...
This paper presents a model that captures the problem of supplier selection for textile recycling operations. Suppliers in this case are the agencies and organisations that collect used clothing through the year and sell the mostly unsorted garments to the recycler. The recycling organisation sorts the materials and sells the sorted and classified...
En ambientes de manufactura y de servicios es frecuente encontrar diferentes tareas que son realizadas en paralelo empleando recursos heterogéneos, los cuales tienen la característica de sufrir deterioro a medida que transcurre el tiempo. Ese deterioro tiene un impacto significativo en el desempeño de dichos recursos, lo que se puede medir de difer...
This article presents a ranking of business administration journals published in Spanish based on a survey completed via the Internet. A profile of participants is constructed based on the following criteria: country of origin, degree and academic ranking, number of peer reviewed publications, language and time devoted to research. Fifty five journ...
This paper considers the allocation of demand across a set of suppliers given supplier failures. The buyer can purchase a critical item from multiple suppliers and each supplier has unique reliability characteristics. The model assumes there is information about the suppliers' failure condition and the ability of those suppliers that do not fail to...
For organizations, security of information is eminent as threats of information security incidents that could impact the information continue to increase. Alarming facts within the literature support the current lack of adequate information security practices and prompt for identifying additional methods to help organizations in protecting their se...
We consider the multiprocessor scheduling problem in which independent jobs are scheduled on identical parallel machines, with the objective of minimizing the normalized sum of square for workload deviations (NSSWD) criterion in order to obtain workload balancing. NSSWD and other criteria for the related problem of number partitioning are presented...
In this paper, we consider the problem of scheduling multiple product types in parallel machines given variable demand across a multi-period planning horizon. Production is organised around a pre-defined lot size as frequently arises in the pharmaceutical industry. The problem class falls within the big bucket category with a single level of produc...
This paper proposes planning models that will assist a flower grower with the land and flower variety allocation decisions in such a way that the revenues (or profits) are maximised over a given planning period. In particular, this paper presents models where the mix of flowers is modified throughout the planning horizon to accommodate market fluct...
Supplier selection is a critical process in supply chain management and business competitiveness. This article presents a decision-making model that optimizes allocation of demand across a set of suppliers considering expected losses associated with delivery defaults, purchasing costs, unforeseen costs of non-delivered supplies, and supplier manage...
Supplier selection is a critical process in supply chain management and business competitiveness. This article presents a decision-making model that optimizes allocation of demand across a set of suppliers considering expected losses associated with delivery defaults, purchasing costs, unforeseen costs of non-delivered supplies, and supplier manage...
This article presents a review of the supply chain management literature focusing on Latin America and is based on articles written in English and Spanish. We characterize the literature in terms of topics addressed, results obtained, methodologies used, and analyze areas of congruence and provide directions for further research. The results sugges...
This research develops a fuzzy goal programming (FGP) model for personnel assignment decisions in skill-based environments. Although FGP has been applied to various areas within the management science and operations research literature, a FGP model has not been proposed within the skill-based personnel assignment literature. The paper develops a me...
This article presents a ranking of business administration journals published in Spanish based on a survey completed via the Internet. A profile of participants is constructed based on the following criteria: country of origin, degree and academic ranking, number of peer reviewed publications, language and time devoted to research. Fifty five journ...
Production environments where there are more tasks than workstations and any task can be assigned to any workstation are examples of operations flexibility. This paper investigates the benefits of operations flexibility in a flowshop when the goals are to minimize the makespan and workstation utilization. Furthermore, machine dominance principles a...
We study the problem of scheduling n jobs on two identical parallel processors or machines where an optimal schedule is defined as one with the shortest total
weighted flowtime (i.e., the sum of the weighted completion time of all jobs), among the set of schedules with minimum makespan
(i.e., the completion time of the last job finished). We presen...
This paper addresses a complex scheduling problem encountered in a major pharmaceutical industry setting. Specifically, the problem deals with assigning tasks to technicians as part of the quality control phase in order to minimise the total flowtime, and the number of jobs not meeting a required time window. The problem considers test batching, ov...
Supplier selection and allocation of demand across suppliers has become a critical activity for organisations. Safety stocks are necessary to protect against shortages caused by supplier delivery failures and to achieve reasonable customer service levels. We present a new supplier selection model that determines safety stocks based on the supplier...
This paper presents a model to minimise inventory and setup costs in a multi-product operation where production is organised in campaigns. A campaign is defined as a number of successive, equally sized lots of a same product. Major and minor sets are considered. The decision variables are the per product time between campaigns and number of lots pe...
In many production environments where demand and lead times are variable, significant levels of safety stock inventory are required to assure timely production and delivery of the final product. Traditional models to determine the appropriate safety stock level may result in more safety stocks at sub-assembly and finished goods levels than necessar...
This research considers a broad range of scheduling problems in the parallel machines environment. Schedules are evaluated according to two independent components of the objective function: (1) machine cost consisting of a fixed cost and a variable cost; and (2) a regular measure of performance. This study is only one of a few that take the selecti...
Purpose
The focus of this paper is on reliability and availability design goals. It aims to provide top‐level estimates of the safety and maintainability of future spacecraft systems.
Design/methodology/approach
The developed design tool uses basic reliability principles to estimate the probability of a safe mission and the need for repairs/replac...
In this paper, we propose a reformulation for the flowshop problem based on the concept of operation to workstation flexibility. While we assume a fixed sequence of operations in the reformulation, the “location” of each operation within the flow is not fixed. The proposed flowshop problem is important because the effective use of this flexibility...
The completion of reliable software products within their expected time frame represents a major problem for companies that develop software applications. Today, the software industry continues to struggle with delivering products in a timely manner. A major cause for delays is the training time required for engineers and other personnel to acquire...
In many organizations, it is desirable to distribute workload as equally as possible among a group of employees or machines. This paper proposes a performance measure, that we call the Normalized Sum of Square for Workload Deviations (NSSWD), and studies the problem of how to schedule a set of n jobs on m parallel identical processors in order to m...
The paper focuses on measuring the efficiency of 29 Mexican coastal ports using the data envelopment analysis (DEA) approach. Most of the ports perform cargo and cruise handling operations. We suggested combined and individual analysis of operations to perform an evaluation of port efficiency. The results of DEA showed 59% of the Mexican ports anal...
This simulation study investigates the performance of a number of multi-cell configurations generated by altering the cell size, worker flexibility and shop type, under a variety of experimental conditions. The experimental factors considered are product mix balance, due date tightness, and setup-to-processing-time ratio. The study is motivated by...
In this paper, we propose a heuristic for the well-known single-level un-capacitated dynamic lot-sizing problem. The proposed heuristic is based on the average period cost criterion introduced by the heuristic from Silver and Meal [18], also known as Least Period Cost (LPC). Two desirable features of the proposed heuristic are simplicity and the he...
Two important factors that affect outsourcing decisions are the production cost and the potential loss of customer goodwill due to late orders. This article deals with the problem of finding outsourcing strategies or solutions that consider trade-offs between outsourcing cost and average tardiness, an important measure of lost customer goodwill. As...
This paper considers a permutation flowshop problem with secondary resources with the objective of minimizing the number of tardy jobs. The number of secondary resources assigned to the machines (workcenters), as well as the allocation of resources among the various machines, will play a significant role in the time required to process each job by...
Outsourcing has been a very popular strategy in many industries to reduce production costs and allow companies to focus on their core competencies. Unfortunately, there are few models available in the literature that can aid management in the outsourcing decision. This paper presents a model that considers two critical characteristics relevant to t...
This research investigates the problem of scheduling jobs on a set of parallel machines where the speed of the machines depends on the allocation of a secondary resource. The secondary resource is fixed in quantity and is to be allocated to the machines at the start of the schedule. The scheduling objective is to minimize the number of tardy jobs....
Flexibility can counter the negative effects of the loss of pooling synergy in cellular systems. In this study we define flexibility as the ability of assembly cells to reallocate resources to accommodate changes in family assignments (i.e. shop flexibility) and the ability of workers to move between cells (i.e. worker flexibility). We investigate...
This paper utilizes the decision tree approach to determine the optimal number of suppliers in the presence of supplier failure risks. Previous proposed models have considered only two states of nature: all suppliers fail to deliver and not all suppliers fail to deliver. In practice, however, there is clearly a partial loss associated with the fail...
In this paper we consider the parallel machine scheduling problem with dual resource constraints with the objective of minimizing the maximum completion time. We develop heuristics that combine list-scheduling and bin-packing approaches with rules to iteratively modify the flexible resource allocation. A lower bound is presented and the previous an...
This paper proposes inventory models for an environment where the approval time of the production batches is an important problem variable. The model is motivated by industries, such as the Pharmaceutical, where a batch is produced and then withheld for a certain period pending release and disposition. The paper proposes a series of cost functions...
Achieving the goals of safe and cost effective space transportation systems requires the development of new methods and tools that allow leap-frog improvements in the conceptualization, design, development, production, and operation of these systems. This paper reports on a modeling methodology aimed at the knowledge based representation and operat...
The outsourcing of manufacturing operations continues to gain popularity, forcing companies to deal with the issue of scheduling orders in increasingly complex supply chains. This paper addresses a supply chain scheduling problem where both internal and external/outsourced parallel resources are available and the objectives are to minimize the numb...
This paper presents an approach to space transportation turnaround operations modeling using knowledge based complexity functions. This project is of significant relevance to the field of industrial engineering as it deals with knowledge based estimation of processing operations based on the design characteristics of an extremely complex product. T...
Supplier decision-making is a critical component of supply chain management given the recent increased reliance of many organizations on their suppliers. This paper presents a decision model that optimizes the allocation of demand across a set of suppliers by considering the expected losses due to supplier failure to deliver, the purchasing costs,...
This paper considers the problem of generating a set of efficient (non-dominated) schedules on identical parallel machines involving total flow-time and total number of tardy jobs. In view of the NP-hard nature of this problem, heuristic algorithms are proposed for its solution. Two evaluation methods that provide a scheme by which multiple non-dom...
The development of simulation models can be time consuming and highly dependant on system data being widely available. When using simulation modeling to analyze future systems, system data may not be available for the system under study and simulation results are often needed within a short time frame to support early system design efforts. This pa...
This paper describes a combination of simulation and knowledge based assessment models used in the operational analysis of future space transportation systems. The model uses knowledge based logic as estimating relationships combined with a process database to estimate the appropriate ground processes, their duration, and their variability. The dev...
We consider the problem of scheduling jobs on parallel machines when there are two criteria to optimize, namely, minimizing both the makespan and the number of tardy jobs. We propose four heuristics to find solutions to this problem, which we evaluate and compare using the Free Disposal Hull (FDH) formulation of Data Envelopment Analysis (DEA). Our...
We consider the problem of scheduling n jobs on m identical parallel machines. An optimal schedule to the proposed problem is defined as one that gives the smallest makespan (the completion time of the last job on any one of the parallel machines) among the set of all schedules with optimal total flowtime (the sum of the completion times of all job...
This paper considers the problems of scheduling jobs on parallel identical machines where an optimal schedule is defined as one that gives the smallest maximum tardiness (or the minimum number of tardy jobs) among the set of schedules with optimal total flow-time (the sum of the completion times of all jobs). We show that these problems are unary N...
This paper analyses whether differences in selective waste collection systems used commonly in Europe and America influence people's recycling habits and their opinions about the service they are offered. We study certain characteristics of the collection systems used in two specific areas-the Principality of Asturias (Northern Spain) and El Paso c...
This paper investigates algorithms that combine resource, family, and order assignment in a dynamic environment where orders from multiple families arrive over time and the number of families is larger than the number of production cells. A variety of production variables are considered including the size of setup between families, the ratio of fam...
This paper presents an approach to the operational analysis of future space transportation systems. The approach combines knowledge from government and industry space operation and design experts, with system analysis methodologies to predict operational characteristics of a future space transportation system. The model proposed under this approach...
This paper presents a new heuristic for minimizing makespan on identical parallel machines. The new heuristic, called LISTFIT, is based on bin-packing and list scheduling, two methods commonly used to solve this problem. Its worst case performance bound is no worse than that of the commonly used MULTIFIT heuristic. However, the average performance...
The growing emphasis on affordability for space transportation systems requires the assessment of new space vehicles for all life cycle activities, from design and development, through manufacturing and operations. This paper addresses the operational assessment of launch vehicles, focusing on modeling the ground support requirements of a vehicle a...
This research investigates the interaction of production scheduling and routing/transportation on a logistic network. Basic scheduling rules and existing routing /transportation alternatives were studied using a simulation model, with cost and customer service levels as measures of performance. The simulation model, including network configuration,...
Current studies indicate that buyers can improve lead-time performance and reduce total inventory-system costs by splitting orders between two suppliers. These studies, however, treat transportation only implicitly as an element of the cost of placing an order. This is an important limitation, because shipping costs increase disproportionately as t...
This paper presents the application of real-time simulation to assign due dates on logistic-manufacturing networks. Information from the manufacturing, transportation, and supplier elements was integrated into a simulation model of the system to help the assignment of reliable delivery dates. In addition, the system was used to generate multiple du...
This paper presents an approach to the operational analysis of future space transportation systems. The approach combines knowledge from government and industry space operation and design experts, with system analysis methodologies to predict operational characteristics of a future space transportation system. The model proposed under this approach...
This paper considers the identical parallel-machine scheduling problem of minimizing makespan subject to minimum total flow-time. In view of the NP-hard nature of the problem, lower bounds on the optimal makespan value and efficient heuristic algorithms for finding optimal schedules are described and empirically evaluated as to their effectiveness...
This paper presents the application of real-time simulation to assign due dates on logistic-manufacturing networks. Information from the manufacturing, transportation, and supplier elements was integrated into a simulation model of the system to help the assignment of reliable delive ry dates. In addition, the system was used to generate multiple d...
This paper presents the first part of a study of a scheduling problem where the objective is to minimize both the number of jobs late and the average flow-time. Unlike previous approaches, a weighted function of the two criteria is not utilized. Heuristics based on simulated annealing and neighborhood search are proposed with the objective of gener...
RESUMEN La administración de la cadena de suministro incluye una amplia variedad de áreas incluyendo la subcontratación de la producción. La decisión de producir o subcontratar está sujeta a factores endógenos, como la capacidad y los costos de los centros de producción internos de la empresa, y exógenos -ciertamente poco controlables-tales como la...
