Hamed Rafiei - Academia.edu (original) (raw)

Papers by Hamed Rafiei

European Journal of Operational Research, 1999

1. IntroductionManaging operations in today’s competitive marketplace poses signiﬁcant challenges... more 1. IntroductionManaging operations in today’s competitive marketplace poses signiﬁcant challenges. The traditionalthought was that there were so many conﬂicts in the multiple demands on the operations function thattrade-o•s were made in achieving excellence in one or more of these dimensions. Thus, for example, if aﬁrm competed on the dimensions of ﬂexibility and quality, cost was of secondary concern. This type ofthinking was motivated by the fact that customers requiring product variety and high quality were typicallywilling to pay a premium price. Similarly, if the competitive pressures required the supply of low costproducts (i.e., price was the major competitive force), then ﬂexibility in terms of new product variety wasnot necessarily a major priority for the ﬁrm and hence, was sacriﬁced. This type of analysis forced thetraditional operations manager to visualize the trade-o•s between competitive priorities were a way of life.However, the quality revolution and increased e†ciency of foreign manufacturers in the late 1970s andearly 1980s changed our thinking. Thus, for example, regardless of the type of product, ﬂawless quality wasrequired at extremely competitive prices. In fact, the competitive realities of the current marketplace andthe impact on the contemporary operations manager are aptly summarized below (Skinner, 1985):Make an increasing variety of products, on shorter lead times with smaller runs, and ﬂawless quality.Improve the ROI by automating and introducing new technology in processes and materials so thatprices can be reduced to meet local and foreign competition. Mechanize – but keep the schedules ﬂex-ible, inventories low, capital costs minimal, and the work force contented.From a strategic perspective, this indicates that the dimensions of cost, ﬂexibility, quality and delivery arenot to be traded-o• against one another but need to be simultaneously prioritized. In response to this,operations managers have focused their attention on a multitude of approaches. In our opinion, the adventof Total Quality Management (TQM) to achieve ﬂawless quality, Flexible Manufacturing Systems (FMS)

Advances in Industrial Engineering, Mar 20, 2016

Rairo-operations Research, Oct 1, 2017

In this paper, a novel model for dynamic pricing and inventory control of non-instantaneously det... more In this paper, a novel model for dynamic pricing and inventory control of non-instantaneously deteriorating items is proposed. To reflect the dynamic nature of the problem, the selling price is modeled as a time-dependent function of the initial selling price and the discount rate. To this end, the product is sold at the initial price value for a time period; then its price is exponentially discounted to boost customer demands. The demand rate is a function of dynamic price, advertisement and changes in price over time. The model seeks to maximize total profit of the system by determining the optimal replenishment cycle, initial price, discount rate, and frequency of advertisement. In order to characterize the optimal solution, some useful theoretical results are derived upon which an iterative solution algorithm is developed. To demonstrate validity of the proposed model and applicability of the developed algorithm, numerical results are provided that are accompanied by an efficient sensitivity analysis on the important parameters of the model.

Expert Systems With Applications, 2012

Prioritization or eliciting final weights from the pairwise comparison matrices might be a major ... more Prioritization or eliciting final weights from the pairwise comparison matrices might be a major part of some Multiple Criteria Decision Analysis (MCDA) methods which are based upon these matrices. However, in a fuzzy environment, two other issues, i.e., consistency and reciprocity, are also arisen in such matrices with at least one fuzzy component. In this paper, a single-decision-making optimization model along with two group-decision-making optimization models are developed towards prioritization in fuzzy pairwise comparison matrices. A comprehensive numerical analysis is performed to validate the proposed models. Finally, some conclusions are reported.

Journal of Industrial Engineering, International, Jul 1, 2016

Mixed-model assembly lines are increasingly accepted in many industrial environments to meet the ... more Mixed-model assembly lines are increasingly accepted in many industrial environments to meet the growing trend of greater product variability, diversification of customer demands, and shorter life cycles. In this research, a new mathematical model is presented considering balancing a mixed-model U-line and human-related issues, simultaneously. The objective function consists of two separate components. The first part of the objective function is related to balance problem. In this part, objective functions are minimizing the cycle time, minimizing the number of workstations, and maximizing the line efficiencies. The second part is related to human issues and consists of hiring cost, firing cost, training cost, and salary. To solve the presented model, two well-known multi-objective evolutionary algorithms, namely non-dominated sorting genetic algorithm and multi-objective particle swarm optimization, have been used. A simple solution representation is provided in this paper to encode the solutions. Finally, the computational results are compared and analyzed. Keywords Mixed-model assembly lines Á U-shaped assembly lines Á Learning and training effect Á Human-related issues Á Multi-objective & Masoud Rabbani

We examine the role of inventory in a hybrid Make-to-Stock (MTS)/Make-to-Order (MTO) production e... more We examine the role of inventory in a hybrid Make-to-Stock (MTS)/Make-to-Order (MTO) production environment, based on a case study performed in a fruit juice company. In this example, demands for Finished Good (FG) inventories follow normal distribution .We propose a model to calculate economic order quantity (EOQ) by obtaining demands for Raw Material (RM) inventories through Work-in-process (WIP) and FG inventories. For validity of our claim we illustrate some samples of production in different days and compare it with old method estimation of WIP and EOQ.

International Journal of Research, May 1, 2014

This article attempts to cope with one of the most vital strategic decisions in the supply chain ... more This article attempts to cope with one of the most vital strategic decisions in the supply chain design in terms of manufacturing context. The issue of finding the best position of Customer Order Decoupling Point (CODP) in a production line have been taken into consideration by many researchers in recent years, but locating CODP along a supply chain has not yet been completely investigated. Here we present a novel combined DEA/AHP method to tackle the problem of positioning CODP in a supply chain. Then in order to prove the applicability of the proposed structure in a real case, the model is implemented in a food processing supply chain.

World Academy of Science, Engineering and Technology, International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering, Oct 25, 2009

This paper proposes a new decision making structure to determine the appropriate product delivery... more This paper proposes a new decision making structure to determine the appropriate product delivery strategy for different products in a manufacturing system among make-to-stock, make-toorder, and hybrid strategy. Given product delivery strategies for all products in the manufacturing system, the position of the Order Penetrating Point (OPP) can be located regarding the delivery strategies among which location of OPP in hybrid strategy is a cumbersome task. In this regard, we employ analytic network process, because there are varieties of interrelated driving factors involved in choosing the right location. Moreover, the proposed structure is augmented with fuzzy sets theory in order to cope with the uncertainty of judgments. Finally, applicability of the proposed structure is proven in practice through a real industrial case company. The numerical results demonstrate the efficiency of the proposed decision making structure in order partitioning and OPP location. Keywords-Hybrid make-to-stock/make-to-order, Multi-attribute decision making, Order partitioning, Order penetration point. I. INTRODUCTION N the face of global competition, a manufacturing firm's survival increasingly depends on how best it can design, manage and restructure its production system to deal with product diversity, improve delivery reliability and also reduce system costs [1]. To cope with these issues, manufacturing companies often use different production systems. These production systems can be classified into two major categories: Make-To-Stock (MTS) and Make-To-Order (MTO) based on market demands' response policy [2]. The main advantage of MTS system is the short delivery time, since the final products are already in stock even before the customer order enters [1]. In an MTO system, an order is fulfilled only when it enters the system. This kind of production systems supplies a wide variety of products, usually in small quantities. Hence, ability to manufacture diverse orders and high production flexibility are the major advantages of this production system [2]. Recent years have shown a number of changes in

The mathematical model presented in this paper considers dynamic simultaneously and also takes in... more The mathematical model presented in this paper considers dynamic simultaneously and also takes into account motivati on, learning effect and rewards in cell formation p roblem’s human issues for the first time. In real world prob lems the available time of workers is not consta on different items therefore learning curve and mot ivation effects are noticed to indicate the real av ailable workers time. The model consists of two parts. First part i s machine handling cost, machine costs in the planning horizon and sec ond part is human training cost, overtime cost, reward cost and salar y. Finally a mathematical method and a hybrid solut ion approach based on simulated annealing (S A) and genetic algorithm (GA) is used in order to s olve the problem. Numerical examples are presented to demonstrate the model and compare both solution approaches.

International Journal of Services and Operations Management, 2012

In this paper, a new bi-objective fuzzy linear regression model is proposed in order to fill the ... more In this paper, a new bi-objective fuzzy linear regression model is proposed in order to fill the gap in the field of forecasting using possibilistic programming. Additionally, the proposed model is compared with three promising fuzzy linear regression models from literature in order to forecast the energy consumption in USA, Japan, Canada, and Australia during 2010 to 2015. In the fuzzy regression models, independent variables are population, cost of crude oil, gross domestic production (per capita), and annual energy production where dependent variable is energy consumption. In order to train the models and estimate their parameters, historical data from 1990 to 2005 are used for each country. Then, the models performance in energy consumption forecasting is tested using actual data from 2006 to 2009. Based on results of mean absolute percentage error (MAPE), the proposed model outperforms other models. Finally, the energy consumption in USA, Japan, Canada, and Australia is forecasted for 2010 to 2015 using the proposed model. The results show that the proposed model provides accurate solution for energy consumption problem.

international journal of management science and engineering management, Mar 3, 2015

This paper addresses a new product positioning problem, in which prices of the products are simul... more This paper addresses a new product positioning problem, in which prices of the products are simultaneously determined in order to maximize both customer satisfaction and seller’s net profit. In this regard, customer willingness is identified with respect to the products within a family, upon which prices of the products are optimized so as to attain two objective functions: 1) maximizing customer satisfaction and 2) maximizing seller’s net profit. Despite of the literature body which has taken this problem into account for a single product, the developed model in this paper considers the case of a multiple products for different customer segments. To do so, an algorithm is developed which the considered problem is divided into a number of sub-problems solved by using GAMS and Matlab. Finally, a numerical example is illustrated.

International Journal of Management Science and Engineering Management, 2012

Abstract Fuzzy Linear Regression (FLR) modeling and its application in different areas has been t... more Abstract Fuzzy Linear Regression (FLR) modeling and its application in different areas has been the focus of significant research in recent years. Because of the many different interpretations of fuzzy problems, diverse contributions have been made. However, they can be grouped under two categories: the least-square methods, and possibilistic approaches. In this paper, a new bi-objective goal programming model for a fuzzy linear regression problem is proposed. The proposed model considers the problem in two cases: (1) crisp independent variables, fuzzy parameters and fuzzy dependent variables, and (2) fuzzy independent variables, fuzzy parameters and fuzzy dependent variables. Then, an augmented -constraint method is applied to deal with a bi-objective optimization problem. Through comprehensive numerical examples, the proposed model is compared with state of art models from the research with respect to five performance criteria. The experimental results show the efficiency and efficacy of the model in both cases. Finally, some concluding remarks and future research directions are provided.

Computers & Industrial Engineering, 2016

This paper introduces human-related issues in the cell formation problem.This paper considers a b... more This paper introduces human-related issues in the cell formation problem.This paper considers a bi-objective dynamic mathematical model.The paper tackles uncertainty of the cell formation problem using stochastic programming. This paper addresses dynamic cell formation problem (DCFP) which has been explored vastly for several years. Although a considerable body of literature in this filed, two remarkable aspects have been significantly ignored so far, as uncertainty and human-related issues. In order to compensate such a shortage, this paper develops a bi-objective stochastic model. The first objective function of the developed model seeks to minimize total cost of machine procurement, machine relocation, inter-cell moves, overtime utilization, worker hiring/laying-off, and worker moves between cells; while the second objective function maximizes labor utilization of the cellular manufacturing system. In the developed model, labor utilization, worker overtime cost, worker hiring/laying off, and worker cell assignment are considered to tackle some of the most notable human-related issues in DCFP. Considering the complexity of the proposed model, a hybrid Tabu Search-Genetic Algorithm (TS-GA) is proposed whose strength is validated to obtain optimal and near optimal solutions through conducted experimental results.

International Journal of Advances in Management Science, Aug 1, 2013

Product bundle pricing is a pricing strategy in which several products, services, or any combinat... more Product bundle pricing is a pricing strategy in which several products, services, or any combinations of them are presented to the customers as a single package with a single price. This pricing strategy has attracted attention of academicians and practitioners in a growing manner. In this regard, this paper has reviewed the research papers published since 2000. To do so, body of literature is reviewed in three categories; marketing, optimization, and economic approach. Finally, discussion of the revised papers is presented upon six aspects; modeling approach, data, market structure, bundle components, problem dynamism, and objective function.

International Journal of Industrial and Systems Engineering, 2014

The International Journal of Advanced Manufacturing Technology, 2008

This paper investigates a novel multi-objective model for a permutation flow shop scheduling prob... more This paper investigates a novel multi-objective model for a permutation flow shop scheduling problem that minimizes both the weighted mean earliness and the weighted mean tardiness. Since a flow shop scheduling problem has been proved to be NP-hard in a strong sense, a new hybrid multi-objective algorithm based on shuffled frog-leaping algorithm (SFLA) and variable neighborhood search (VNS) is devised to find Pareto optimal solutions for the given problem. To validate the performance of the proposed hybrid multi-objective shuffled frog-leaping algorithm (HMOSFLA) in terms of solution quality and diversity level, various test problems are examined. Further, the efficiency of the proposed algorithm, based on various salient metrics, is compared against two well-known multiobjective genetic algorithms: NSGA-II and SPEA-II. Our computational results suggest that the proposed HMOSFLA outperforms the two foregoing algorithms, especially for large-sized problems.

Applied Mathematical Modelling, 2013

In this paper, a mathematical model is proposed using economic and environmental criteria for a t... more In this paper, a mathematical model is proposed using economic and environmental criteria for a type-2 fuzzy (T2F) cell formation (CF) problem emphasizing the effect of the man-machine relationship aspect. This model aims to show the use of this aspect in CF to minimize the costs of processing, material movement, energy loss, and tooling. For this purpose, a two-stage defuzzification procedure is used to convert the T2F variable into a crisp value. Due to NP-hardness of the model and problem, a genetic algorithm (GA) is used to derive the appropriate solutions. Furthermore, because there is no any existing benchmark to validate the performance of the proposed model, three tuned meta-heuristic algorithms, namely, differential evolution (DE), harmony search (HS) and particle swarm optimization (PSO), are proposed and used. The present research uses the Taguchi method to adjust the parameters in the four proposed algorithms. Furthermore, 15 examples are used to validate the presented model. The results show that PSO is the most appropriate algorithm for solving the model.

Waste collection is one of the important problems that can affect urban life. A multi-zone waste ... more Waste collection is one of the important problems that can affect urban life. A multi-zone waste coll ection routing problem is proposed in this paper consideri ng intermediate facilities, depot centers and bins as network’s nodes. In this model heterogeneous fleet vehicles a re considered to load wastes from bins from every z one and then unload them in disposal centers which belong to tha t zone and each zone can include just one depot cen ter. A mixed integer programming model is considered to solve th e problem with considering new assumptions. The objective function attempt to minimize the total operation co st of vehicles including fixed and variable costs a nd also minimizes the number of vehicles are used and last term of objective function is the absolute differen ce between the total number of unloading at each disposal center a nd the average number of unloading at all of the di sposal centers. Finally in order to show applicability of proposed model, two small large nume...

International Journal of Operational Research, 2020

Designing appropriate supply chain would provide numerous valuable feedbacks for the whole chain,... more Designing appropriate supply chain would provide numerous valuable feedbacks for the whole chain, since using returned products instead of reproducing them, is a more appropriate response to the environmental concerns on the one hand which provides benefit and financial savings for the chains on the other hand. Therefore, this paper presents a three-objective function mathematical model to maximise financial savings and quantities of returned products to the chain and minimise total costs in terms of uncertainty and risk that derives from reverse logistics nature. Finally, the developed model was solved by Monte Carlo simulation and genetic algorithm along with proper risk measures for risk-neutral and risk-seeking decision makers. The results indicated financial savings are one of the best objective functions in order to show superiority of reverse logistics network. As another result, it was pointed out that profitability of the chain increases because of delivering return products before their scrap-life.