Showing papers in "Omega-international Journal of Management Science in 2007"

Global supplier development considering risk factors using fuzzy extended AHP-based approach

Abstract: Global supplier development is a multi-criterion decision problem which includes both qualitative and quantitative factors. The global supplier selection problem is more complex than domestic one and it needs more critical analysis. The aim of this paper is to identify and discuss some of the important and critical decision criteria including risk factors for the development of an efficient system for global supplier selection. Fuzzy extended analytic hierarchy process (FEAHP) based methodology will be discussed to tackle the different decision criteria like cost, quality, service performance and supplier's profile including the risk factors involved in the selection of global supplier in the current business scenario. FEAHP is an efficient tool to handle the fuzziness of the data involved in deciding the preferences of different decision variables. The linguistic level of comparisons produced by the customers and experts for each comparison are tapped in the form triangular fuzzy numbers to construct fuzzy pair-wise comparison matrices. The implementation of the system is demonstrated by a problem having four stages of hierarchy which contains different criteria and attributes at wider perspective. The proposed model can provide not only a framework for the organization to select the global supplier but also has the capability to deploy the organization's strategy to its supplier.

Selection of logistics service provider: An analytic network process (ANP) approach

Abstract: This article presents a comprehensive methodology for the selection of a logistic service provider. The proposed methodology consists of two parts: (i) preliminary screening of the available providers, and (ii) analytic network process (ANP)-based final selection. The criteria, which are relevant in the selection of a provider, have been identified and used to construct an ANP model. Thereafter, the application of ANP for the final selection of a provider has been demonstrated through an illustrative example. The results of this example indicate that compatibility between the user and the provider companies is the most important determinant, which influences the final selection process. This approach also enables the decision-makers to better understand the complex relationships of the relevant attributes in the decision-making, which may subsequently improve the reliability of the decision.

Supplier selection with multiple criteria in volume discount environments

Abstract: Supplier selection is a multi-criteria decision making problem which includes both qualitative and quantitative factors. In order to select the best suppliers it is necessary to make a trade-off between these tangible and intangible factors some of which may conflict. When business volume discounts exist, this problem becomes more complicated as, in these circumstances, buyer should decide about two problems: which suppliers are the best and how much should be purchased from each selected supplier. In this article an integrated approach of analytical hierarchy process improved by rough sets theory and multi-objective mixed integer programming is proposed to simultaneously determine the number of suppliers to employ and the order quantity allocated to these suppliers in the case of multiple sourcing, multiple products, with multiple criteria and with supplier's capacity constraints. In this context, suppliers offer price discounts on total business volume, not on the quantity or variety of products purchased from them. A solution methodology is presented to solve the multi-objective model, and the model is illustrated using two numerical examples.

Consumer trust in e-commerce in the United States, Singapore and China

Abstract: This study examines the antecedents and consequences of consumer trust in the United States, Singapore and China. The results show that reputation and system assurance of an Internet vendor and consumers’ propensity to trust are positively related to consumer trust. Consumers’ trust has a positive relationship with attitude and a negative relationship with perceived risk. Implications of the results are discussed. 2005 Elsevier Ltd. All rights reserved.

Adoption of the mobile Internet: An empirical study of multimedia message service (MMS)

Abstract: Multimedia message service (MMS) provides more multimedia communication with entertainment effects than current text-based short message service (SMS). While many reports indicate that the mobile Internet market will be huge, little is known about whether people will accept MMS. This study applies innovation diffusion theory to examine the factors that influence the adoption of MMS. The proposed model was empirically evaluated by using survey data collected from 207 users concerning their perceptions of MMS. The findings indicate that perceptions of use were different over innovation diffusion stages. Specifically, there was a significant difference between potential adopters and users. The results may provide further insights into MMS marketing strategies.

Microfinance institutions and efficiency

Abstract: Microfinance Institutions (MFIs) are special financial institutions. They have both a social nature and a for-profit nature. Their performance has been traditionally measured by means of financial ratios. The paper goes beyond simple financial ratios using a data envelopment analysis (DEA) approach to measure the efficiency of MFIs. Special care is taken in the specification of the DEA model. We take a methodological approach based on multivariate analysis. We rank DEA efficiencies under different models and specifications; e.g. particular sets of inputs and outputs. This serves to explore what is behind a DEA score. The results show that we can explain MFIs efficiency by means of four principal components of efficiency, and this way we are able to understand differences between DEA scores. It is shown that there are country effects on efficiency; and effects that depend on non-governmental organization (NGO)/non-NGO status of the MFI.

Optimal inventory model for items with imperfect quality and shortage backordering

Abstract: In this study, we develop an optimal inventory model for items with imperfect quality and shortage backordering. Such implicit assumption is reasonable in view of the fact that poor-quality items do exist during production. They are usually picked up during the screening process and are withdrawn from stock instantaneously. It is assumed that all customers are willing to wait for new supply when there is a shortage. The analysis shows that our model is a generalization of the models in current literatures. An algorithm and numerical analysis developed show that our model always results in better performance.

Applying consistent fuzzy preference relations to partnership selection

Abstract: Partnership selection has been important to the formation of a virtual enterprise. Based on the fuzzy preference programming (FPP) method proposed by Mikhailov [Fuzzy analytical approach to partnership selection in formation of virtual enterprises. Omega 2002;30:393–401], this investigation presents a consistent fuzzy preference relations method to select partners. Human thoughts are full of uncertainty, so the decision-makers cannot make exact pairwise comparisons. The FPP method solves this problem using an interval value instead of Saaty's 1–9 scale. In this study, the FPP method is reviewed, and then the consistent fuzzy preference relations method is elucidated. Finally, the presented method is applied to the example addressed by Mikhailov [Fuzzy analytical approach to partnership selection in formation of virtual enterprises. Omega 2002;30:393–401]. This study reveals that the proposed method yields consistent decision rankings from only n - 1 pairwise comparisons—the same number as in Mikhailov's research. Briefly, the presented consistent fuzzy preference relations method is an easy and practical way to provide rankings of partnership in making decision.

Multi-choice goal programming

Abstract: The situation of multi-choice aspiration levels (MCAL) may exist in many decision/management problems. However, the problem cannot be solved by current goal programming (GP) techniques. In order to improve the utility of GP and solve the MCAL problem, this paper proposes a new idea for programming the MCAL problem. The proposed method allows decision-makers (DMs) to set multiple aspiration levels for their problems in which “the more/higher is better” and “the less/lower is better” in the aspiration levels are addressed. In addition, illustrative examples are given to demonstrate the correctness of the proposed model.

A fuzzy set approach for R&D portfolio selection using a real options valuation model

Abstract: Making R&D portfolio decision is difficult, because long lead times of R&D and market and technology dynamics lead to unavailable and unreliable collected data for portfolio management. The objective of this research is to develop a fuzzy R&D portfolio selection model to hedge against the R&D uncertainty. Fuzzy set theory is applied to model uncertain and flexible project information. Since traditional project valuation methods often underestimate the risky project, a fuzzy compound-options model is used to evaluate the value of each R&D project. The R&D portfolio selection problem is formulated as a fuzzy zero–one integer programming model that can handle both uncertain and flexible parameters to determine the optimal project portfolio. A new transformation method based on qualitative possibility theory is developed to convert the fuzzy portfolio selection model into a crisp mathematical model from the risk-averse perspective. The transformed model can be solved by an optimization technique. An example is used to illustrate the proposed approach. We conclude that the proposed approach can assist decision makers in selecting suitable R&D portfolios, while there is a lack of reliable project information.

Revenue management for remanufactured products

Abstract: Revenue management for remanufactured products has not been addressed in literature so far. There could be more than one quality level of the recovered products, which would draw different prices in the secondary markets. In this paper, we develop a pricing model to maximize the expected revenue from the recovered products. Numerical examples are included for illustration.

Joint pricing and ordering policy for a deteriorating inventory with partial backlogging

Abstract: In this paper, a deterministic inventory model for deteriorating items with time-dependent backlogging rate is developed. The demand and deterioration rate are known, continuous, and differentiable function of price and time, respectively. Under these general assumptions, we first prove that the optimal replenishment schedule not only exists but is unique, for any given selling price. Next, we show that the total profit is a concave function of price when the replenishment schedule is given. We then provide a simple algorithm to find the optimal selling price and replenishment schedule for the proposed model. Finally, we use a numerical example to illustrate the algorithm.

Eco-efficiency analysis of paper mills along the Huai River: An extended DEA approach

Abstract: The objective of this paper is to estimate the ecological efficiency of paper mills along the Huai River in China. The main characteristic of the ecological efficiency evaluation problem is that an undesirable output of biochemical oxygen demand (BOD) and a non-discretionary input (BOD emission quota) should be considered simultaneously. By analyzing the impacts of the non-discretionary input on decision-making units’ (DMUs) desirable and undesirable outputs, a non-radial output-oriented DEA model is proposed. In the proposed model, we describe a new approach of defining reference set that requires reference units operate in a similar environment on average. We employ the model to provide efficient inputs/outputs targets for DMU managers to improve DMUs’ efficiencies. Based on the developed model, impacts of the non-discretionary input on DMUs’ returns are also analyzed. We illustrate the proposed model, using real data, for 32 paper mills along the Huai River in China.

The optimal number of suppliers considering the costs of individual supplier failures

Abstract: 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 failure of any individual supplier. We present models that allow a more realistic decision-making process by taking into consideration the independent risks of individual supplier failures when the probability of failure for each of the suppliers is equal as well as the case where the probability of failure from each of the suppliers is not equal. We also consider various levels of supplier failure probability and possible procurement or operating cost savings gained from using less reliable suppliers. The results indicate that when suppliers are highly reliable, sole sourcing is the lowest cost approach under all experimental conditions. However, as the suppliers become less reliable, additional suppliers may be required to obtain the lowest cost. Finally, it was shown that only in the extreme conditions of unreliable suppliers, high loss to operational cost per supplier, and low ability to mitigate the failure from a partial set of suppliers, having a large number of suppliers is an effective strategy.

Single-machine scheduling problems with the effects of learning and deterioration

Abstract: In this paper, we consider the single-machine scheduling problems with the effects of learning and deterioration. By the effects of learning and deterioration, we mean that job processing times are defined by functions of their starting times and positions in the sequence. It is shown that even with the introduction of learning effect and deteriorating jobs to job processing times, single-machine makespan and sum of completion times (square) minimization problems remain polynomially solvable, respectively. But for the following objective functions: the weighted sum of completion times and the maximum lateness, this paper proves that the WSPT rule and the EDD rule can construct the optimal sequence under some special cases, respectively.

Flight gate scheduling: State-of-the-art and recent developments

Abstract: This paper surveys a large variety of mathematical models and up-to-date solution techniques developed for solving a general flight gate scheduling problem that deals with assigning different aircraft activities (arrival, departure and intermediate parking) to distinct aircraft stands or gates. The aim of the work is both to present various models and solution techniques which are available in nowadays literature and to give a general idea about new open problems that arise in practise. We restrict the scope of the paper to flight gate management without touching scheduling of ground handling operations.

The permutation flow shop problem with blocking. A tabu search approach

Abstract: This paper develops a fast tabu search algorithm to minimize makespan in a flow shop problem with blocking. Some properties of the problem associated with the blocks of jobs have been presented and discussed. These properties allow us to propose a specific neighbourhood of algorithms. Also, the multimoves are used that consist in performing several moves simultaneously in a single iteration and guide the search process to more promising areas of the solutions space, where good solutions can be found. It allow us to accelerate the convergence of the algorithm. Besides, a dynamic tabu list is proposed that assists additionally to avoid being trapped at a local optimum. The proposed algorithms are empirically evaluated and found to be relatively more effective in finding better solutions than attained by the leading approaches in a much shorter time. The presented ideas can be applied in many local search procedures.

On the NEH heuristic for minimizing the makespan in permutation flow shops

Abstract: Over the last 20 years the NEH heuristic of Nawaz, Enscore, and Ham published in this journal has been commonly regarded as the best heuristic for minimizing the makespan in permutation flow shops In recent years some authors claimed to develop new heuristics that are competitive or outperform NEH Our study reveals that these claims are not justified We also address the issue of a fair comparison of the NEH results with those obtained by metaheuristics Finally we conduct a thorough analysis of NEH leading to its modification which secures the optimality in the two-machine case and improves the general performance

A hierarchical approach to multi-project planning under uncertainty

Abstract: We survey several viewpoints on the management of the planning complexity of multi-project organisations under uncertainty. Based on these viewpoints we propose a positioning framework to distinguish between different types of project-driven organisations. This framework is meant to aid project management in the choice between the various existing planning approaches. We also discuss the current state of the art of hierarchical planning approaches both for traditional manufacturing and for project environments. Next, we introduce a generic hierarchical project planning-and-control framework that serves to position planning methods for multi-project planning under uncertainty. We discuss various techniques for dealing with the uncertainty inherent to the different hierarchical stages in a multi-project organisation. In the last part of this paper we discuss two cases from practice and relate these to the positioning framework that is put forward in the paper.

A hybrid heuristic for the uncapacitated single allocation hub location problem

Abstract: The uncapacitated single allocation hub location problem (USAHLP), with the hub-and-spoke network structure, is a decision problem in regard to the number of hubs and location–allocation. In a pure hub-and-spoke network, all hubs, which act as switching points for internodal flows, are interconnected and none of the non-hubs (i.e., spokes) are directly connected. The key factors for designing a successful hub-and-spoke network are to determine the optimal number of hubs, to properly locate hubs, and to allocate the non-hubs to the hubs. In this paper two approaches to determine the upper bound for the number of hubs along with a hybrid heuristic based on the simulated annealing method, tabu list, and improvement procedures are proposed to resolve the USAHLP. Computational experiences indicate that by applying the derived upper bound for the number of hubs the proposed heuristic is capable of obtaining optimal solutions for all small-scaled problems very efficiently. Computational results also demonstrate that the proposed hybrid heuristic outperforms a genetic algorithm and a simulated annealing method in solving USAHLP.

The Fundamental Paradox in the Grief Literature: A Critical Reflection:

Abstract: A key theme in the bereavement literature is the recognition that every grief experience is unique and dependent on many variables, such as the circumstances of the death, characteristics of the bereaved individual, their relationship with the deceased, the provision and availability of support, and a myriad of sociocultural factors. Concurrently, there are corresponding efforts to define "normal" grief and delineate it from "complicated" grief experiences. The discord between these two potentially opposing statements remains a paradox evident within the three major tensions within the thanatological literature--the dominance of grief theories, the medicalization of grief, and the efficacy of grief interventions. Three recommendations for moving beyond the paradox are discussed--the provision of improved grief education for service providers, the bereaved, and the wider community; the conduct of research that emphasizes the context of grief and is relevant to service provision; and the examination of current grief interventions.

An effective decision making method for product acceptance

Abstract: Acceptance sampling plans are practical tools for quality assurance applications involving quality contract on product orders. The sampling plans provide the vendor and buyer decision rules for product acceptance to meet the preset product quality requirement. As the rapid advancement of manufacturing technology, suppliers require their products to be of high quality with very low fraction of defectives often measured in parts per million. Unfortunately, traditional methods for calculating fraction of defectives no longer work since any sample of reasonable size probably contains no defective product items. In this paper, we introduce an effective sampling plan based on process capability index C pk to deal with product acceptance determination for low fraction of defectives. The proposed new sampling plan is developed based on the exact sampling distribution rather than approximation. Practitioners can use the proposed method to determine the number of required inspection units, the critical acceptance value, and make reliable decisions in product acceptance.

Rough set-based approach to feature selection in customer relationship management

Abstract: In this paper, application of the rough set theory (RST) to feature selection in customer relationship management (CRM) is introduced. Compared to other methods, the RST approach has the advantage of combining both qualitative and quantitative information in the decision analysis, which is extremely important for CRM. To derive the decision rules from historical data for identifying features that contribute to CRM, both the mathematical formulation and the heuristic algorithm are developed in this paper. The proposed algorithm is comprised of both equal and unequal weight cases of the feature content with the limitation of the mathematical models. This algorithm is able to derive the rules and identify the most significant features simultaneously, which is unique and useful in solving CRM problems. A case study of a video game system purchase is validated by historical data, and the results showed the practical viability of the RST approach for predicting customer purchasing behavior. This paper forms the basis for solving many other similar problems that occur in the service industry.

Customer order scheduling to minimize total weighted completion time

Abstract: In this paper we study the scheduling problem in which each customer order consists of several jobs of different types, which are to be processed on m facilities. Each facility is dedicated to the processing of only one type of jobs. All jobs of an order have to be delivered to the customer at the same time. The objective is to schedule all the orders to minimize the total weighted order completion time. While the problem has been shown to be unary NP-hard, we develop a heuristics to tackle the problem and analyze its worst-case performance.

Combining decision tree and MAUT for selecting a country for a global manufacturing facility

Abstract: The paper presents a multi-phase approach for selecting a country in which to locate a global manufacturing facility. An influence diagram is used to frame the decision. A decision tree then analyzes uncertainties regarding cost and generates a risk profile. The risk profile becomes one of the measures in an MAUT model that incorporate a wide range of factors. This sequential approach of using the output from a decision tree as input to MAUT is demonstrated with an example involving an auto supplier locating a new plant in one of five countries. Three decision makers were interviewed to determine the weights and the shape of the individual utility curves. The paper identifies, clearly defines, and incorporates a variety of measures for which national data are readily available. This list is broader and less subjective when compared to other examples reported in the literature.

More-for-less algorithm for fixed-charge transportation problems

Abstract: The more-for-less (MFL) phenomenon in distribution problems occurs when it is possible to ship more total goods for less (or equal) total cost, while shipping the same quantity or more from each origin and to each destination. This paradox occurs often in fixed-charge transportation problems (FCTPs), and further analysis could bring significant reduction in costs. The MFL phenomenon for FCTPs has received minimal attention in the literature despite the fact that existing analytical algorithms, such as branch and bound, are limited to small problems due to excessive computational effort. In this paper, we develop a simple heuristic algorithm to identify the demand destinations and the supply points to ship MFL in FCTPs. The proposed method builds upon any existing basic feasible solution. It is easy to implement and can serve as an effective tool for managers for solving the more-for-less paradox for large distribution problems.

Aggregation of aggregating modes in MCDM: Synthesis of Type 2 and Level 2 fuzzy sets

Abstract: A new approach to MCDM in a fuzzy setting based on the aggregation of aggregating modes is proposed. The problem of appropriate common scale for representation of objective and subjective criteria is solved using the simple subsethood measure based on α-cut representation of fuzzy values. To elaborate an appropriate method for such aggregation, we use the synthesis of the tools of Type 2 and Level 2 fuzzy sets. As the result the final assessments of compared alternatives are presented in form of fuzzy-valued membership function defined on the support composed of considered alternatives. To compare obtained fuzzy assessments we use the probabilistic approach to fuzzy values comparison. Well known Tool Steel Material Selection problem is used as the test task.

Adolescent grief: relationship category and emotional closeness*

Abstract: Bereaved adolescents (N = 90) who had experienced relatively common death losses (e.g., grandparent, friend) completed the Texas Revised Inventory of Grief and the Emotional Closeness Scale and Continuum. Results indicated that present grief was significantly higher for friend than for grandparent death loss. A MANOVA revealed that those in the high closeness group reported significantly higher mean scores on past and present grief than those in the low closeness group. Finally, in a hierarchal multiple regression, after demographic variables were entered (e.g., age, present at death), emotional closeness added significant variance to the prediction of past and present grief. This research contributes to the understanding of grief intensity following adolescents' most common death losses and highlights the importance of counselors' intentionally and directly assessing bereaved adolescents' perceived emotional closeness to the deceased as part of grief-related counseling.

Tactical coordination in a multi-location and multi-stage operations structure: A model and a pharmaceutical company case☆

Abstract: In this paper, we look at the internal supply chain of an internationally operating firm characterized by a multi-location and multi-stage operations structure. We address problems at three levels, namely the strategic, tactical, and operational levels. Our approach goes beyond the operational literature, and focuses primarily on the tactical level. We specify a model and a case that capture strategic and tactical issues and relate the tactical issues to organizational issues. We simulate coordination in different organizational forms pertaining to the ‘tactical control’ of the firm. Our analysis suggests that a functionally organized multi-location and multi-stage operations structure using traditional planning will not work. The choice is between a strongly IT-based, centralized organization or a more decentralized organization using transfer prices as the coordination device.

Motor vehicle recalls: Trends, patterns and emerging issues

Abstract: This paper examines patterns and trends in motor vehicle safety recalls using a dataset based on 23.1 million vehicles registered in the UK between 1992 and 2002. A safety recall occurs when vehicle manufacturers call vehicles that have been sold and are in use back to their dealerships for safety-related remedial work. Safety recalls can be a strategic concern for car makers, having the potential to damage brand value, reduce stock price as well as resulting in significant direct costs. The data from this study show that the incidence of vehicle recalls is increasing—between 1998 and 2002 there was an average of over 120 recall incidents per annum in the UK, compared to less than 50 per annum between 1992 and 1994. Total numbers of vehicles recalled show no clear trend over time, but the absolute level of recalls year on year is very high: in the UK, 10.8 million vehicles were recalled during 1992–2002, representing 47% of all vehicle UK registrations in the period. Moreover, there are substantial differences in recall rates between different car manufacturers, suggesting that recall rates may be a useful indicator of process performance in the automotive design-and-production value chain. European and American producers have recall rates that are nearly three times greater than their East Asian counterparts. This paper concludes with some ideas that may explain these patterns and suggests an agenda for further research.