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International Journal of Mathematics in Operational Research

 

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International Journal of Mathematics in Operational Research (80 papers in press)

 

Regular Issues

 

  • Passengers Queue Analysis in International Airports Terminals in Kerala Using Multiphase Queuing System   Order a copy of this article
    by Roshli Aniyeri, Ratnam Nadar 
    Abstract: Waiting period is a global problem that almost everyone has to face, which causes a great waste of time for everyone. It is well known that all these waiting line problems critically restrict the further development. The focus of this study is to deal with passengers Queue issues of the International airport terminals of Kerala. Queuing theory is a mathematical approach to the study of waiting period in queues. The dissect of queuing theory that evaluates the effectiveness of implementation of multi-server queuing model .The Multi Server approach of modeling was adopted in this cram to develop a mathematical model to solve problem of queuing of air transport passengers at the International Airports in Kerala. The airport in the aviation industry of the country faces problems of many passengers queuing for boarding, departure with different arrival rate due to non availability of state of the art logistics management mechanisms for predicting the nature and service demands of travelers. The passengers average wait time for reaching the gate area measures system performance. A mathematical queuing model was developed in this study.
    Keywords: Key words: Multi server Queuing model; Airport Passengers; queuing steady state condition; estimated queue length; Utilization factor,ANOVA.
    DOI: 10.1504/IJMOR.2018.10005038
     
  • Characterizations of the production possibility set in data envelopment analysis: an MOLP approach   Order a copy of this article
    by Seyyed Morteza Mirdehghan, Maryam Heydari 
    Abstract: The production possibility set in data envelopment analysis is a polyhedron and it is defined by the intersection of a finite number of half spaces which are constructed by their corresponding defining hyperplanes. Because of the importance of the characterizations of the production possibility sets in data envelopment analysis, we suggest two multi objective linear programming problems and then we identify some characterizations of the production possibility set by investigation of the relations among the suggested multi objective linear programming models and the input oriented envelopment and multiplier BCC models. In this paper, we use weighted sum and epsilon-constraint scalarization methods to present some mathematical properties for finding some relations among the efficient solutions of the proposed multi objective linear programming models and the characteristics of the production possibility set and data envelopment analysis models.
    Keywords: Data envelopment analysis; Multi-objective linear programming; Efficient weights.

  • An Optimal Inventory Control in Hybrid Manufacturing/Remanufacturing System with Deteriorating and Defective Items   Order a copy of this article
    by Ali Dhaiban, MD. Baten, Nazrina Aziz 
    Abstract: An optimal control model in a manufacturing/remanufacturing-inventory system, with defective, deteriorating, returned and disposed items was developed. In this model, the time of deterioration, and the percentages of defective, returned and disposed items were assumed random variables that follow the Gamma distribution, Beta rectangular, four-parameter generalized beta (FPGB) and Kumaraswamy distributions, respectively. The total of returned items from customers and defective items divided into the remanufacturing and disposed items. An optimality conditions were derived from the dynamic of the manufacturing/remanufacturing inventory level. The explicit solution under continuous-review policy was achieved by using the Pontryagin maximum principle. Also, simulation and sensitivity analysis results were illustrated numerically. The numerical results suggested that the model can help firms to maintain a balance between the manufacturing and remanufacturing rates to hedge demand and inventory levels. Also, the manufacturing rate was positively related to the disposal rate.
    Keywords: Optimal Control; Inventory System; Deteriorating Items; Defective Items; Pontryagin Maximum Principle; Demand Function.

  • A fuzzy robust programming approach to multi-objective portfolio optimization problem under uncertainty   Order a copy of this article
    by Hossein Khanjarpanah, Mir Saman Pishvaee 
    Abstract: Portfolio selection is one of the most important problems in financial markets. This paper proposes a novel robust flexible portfolio optimization model based on possibilistic mean and variance and flexible constraints, to cope with inherent uncertainty of such problem. The proposed model is extended by introducing a modified robust flexible approach. The developed models are evaluated and validated by using the real data of Tehran stock exchange. The obtained results show that in higher violation penalties, the proposed models outperform the deterministic model. In addition, experimental analyses are provided to compare the performance of the robust flexible portfolio optimization model to the modified version.
    Keywords: Fuzzy mathematical programming, robust optimization, portfolio problem, possibilistic mean and variance, flexible constraints.

  • Transient analysis of a discrete-time infinite server queue with system disasters   Order a copy of this article
    by Sebasthi Priya, Sudhesh R 
    Abstract: This paper studies a discrete-time in nite server queue subject to system disaster. The exact time-dependent probabilities of the number of customers present in the system are obtained using generating functions, continued fractions and confluent hypergeometric functions. Further, the results are extended to obtain closed form expression for busy period distribution and steady state system size probabilities. Numerical illustrations are provided to visualize the eff ect of system size probabilities, both in steady state and transient state, and busy period distribution for di erent parameter values.
    Keywords: Discrete Queue; Time-dependent probability; Busy period; Generating functions; Confluent hypergeometric functions;Continued fractions

  • Queuing Theory based Innovation Diffusion Modeling incorporating change in Adoption Rate   Order a copy of this article
    by Adarsh Anand, Mohini Agarwal, Deepti Aggrawal, Ompal Singh 
    Abstract: Adoption has always been an important process to discuss among marketers. Major work in the field of Innovation Adoption has been based on theory of first purchase by consumers. Of late attention has also been given to multi-stage nature of diffusion process. There are practitioners who have verified adoption as multi-stage process (depending on awareness and motivation). Researchers have lately also understood the value of change in marketing strategy and other factors that often lead to change in rate of adoption. In this paper, we have made use of this stage wise approach of market penetration along with change point concept, have developed a methodical approach based on Infinite Server Queuing Theory and predicted sales for consumer durables. Experimental results estimated on sales of two different consumer durables show that present proposal can depict the change in adoption rates and predict the behavior of the product in more accurate manner.
    Keywords: Change Points (CPs); Innovation Diffusion Model (IDM); Non-Homogeneous Poisson Process (NHPP); Queuing Theory

  • An EPQ Model for deteriorating items with variable demand rate and allowable shortages   Order a copy of this article
    by Shilpy Tayal, Deepa Khurana, S.R. Singh 
    Abstract: The fundamental assumption of an economic order quantity (EOQ) model is that 100% of items in an ordered lot are perfect. This assumption is not always pertinent for production processes because of process deterioration or other factors. This is an economic production quantity model for deteriorating items. To fulfill the market demands and expectations the production rate is taken as a function of demand rate. The demand and deterioration of the products are time dependent function. Shortages are allowed and partially backlogged. The backlogging phenomenon in the literature is often modeled using backordering and lost sale costs. The backlogging option gets used only when it is economic to do so. The inventory policy proposed here considers the optimal production run time, production quantity and shortage period such that the total average cost can be minimized. Numerical examples are provided to illustrate and sensitivity analyses of optimal solutions are given for the proposed inventory model.
    Keywords: Deterioration; Shortages; Variable production rate; Partial backlogging; EPQ

  • Pareto Optimal Solution for Multiobjective Stochastic Linear Programming Problems with Partial Uncertainty   Order a copy of this article
    by Abdulqader Hamadameen 
    Abstract: A study on Multiobjective Stochastic Linear Programming (MSLP) problems with partial information on probability distribution is conducted. A method is proposed to utilize the concept of dominated solution for the Multiobjective Linear Programming (MLP) problems, and find a Pareto Optimal Solution (POS) without converting the MLP problem into its unique Linear Programming (LP) problem. An algorithm is proposed along with a numerical example which illustrated the practicability of the proposed algorithm. Comparison of results with existing methods shows the efficiency of the proposed method based on the analysis of results performed.
    Keywords: Keywords Dominated solution, Fuzzy transformation, MSLP problems, POS, Stochastic transformation.

  • The Generalized Maximum Entropy Principle   Order a copy of this article
    by G. R. Mohtashami Borzadaran, M. Sanei Tabass 
    Abstract: Generalizations of Maximum entropy principle (MEP) and minimum discrimination information principle (MDIP) are described by Kapur and Kesavan (1989). In this paper we used generalized entropies and replaced Shannon entropy with Tsallis entropy when α = 2.The generalization has been achieved by the entropy maximization postulate and examining its consequences. The inverse principles which are inherent in the maximum α entropy and minimum discrimination α entropy are made in the new methodology.
    Keywords: Shannon entropy, Tsallis entropy, Tsallis divergence, Generalized Maximum Entropy Principle, Minimum discrimination.

  • An Alfa-cut approach for fuzzy product and its use in computing solutions of fully fuzzy linear systems   Order a copy of this article
    by Reza Hassanzadeh 
    Abstract: We propose an approach for computing the product of various fuzzy numbers using α-cuts. A regression model is used to obtain the membership function of the product. Then, we make use of the approach to compute solutions of fully fuzzy linear systems. We also show how to compute solutions of fully fuzzy linear systems with various fuzzy variables. Examples are worked out to illustrate the approach.
    Keywords: fuzzy numbers; α-cut; regression model; fuzzy product; fully fuzzy linear system (FFLS)

  • Unreliable Bulk Queueing Model with Optional services,Bernoulli vacation schedule and Balking.   Order a copy of this article
    by Binay Kumar 
    Abstract: This paper deals with queueing system in which arriving units join a single waiting line. Server provides the first essential service and one of the optional services among available optional services, to all arriving units. After completion of both phases of services of each unit the server may take optional vacation with probability . It is assumed that during any phase of service, server may stop working due to random failure and is sent for repair. Further it is assumed that arriving units may balk from the system when server is busy, vacation and under repair with probability . Using the probability generating functions we derive the queue size distribution at different time points as well as waiting time distribution. Finally numerical illustration is provided to analyses the sensitivity of different parameters on various performance measures.
    Keywords: Bulk arrival; Bernoulli vacation; Optional services; Balking; Random Breakdown; Supplementary Variable.

  • Algorithms for Solving Fuzzy Transportation Problem   Order a copy of this article
    by Pankaj Kumar Srivastava, Nirbhay Mathur, Ajit Paul 
    Abstract: The objective of this paper is a wide survey of recent optimization techniques in the field of fuzzy Transportation problems. The authors have reviewed here papers on various techniques to solve fuzzy transportation problems.Here we have considered the algorithms discussed in research papers within the last decade so as to knowhow of present scenario. A comparative study of methods with own critical comments as remarks has been included.
    Keywords: Fuzzy transportation problem,Linear programming method, Classical methods, Zero point method, zero suffices method, zero termination method.

  • Fuzzy methodology application for failure analysis of transmission system   Order a copy of this article
    by Dilbagh Panchal, Umesh Jamwal, Priyank Srivastava, Kushal Kamboj, Rohit Sharma 
    Abstract: The aim of this research work is to propose a fuzzy methodology based integrated framework for the failure analysis of the Transmission System of the TATA Company made heavy commercial vehicle. Under the failure analysis Failure Mode Effect Analysis (FMEA) approaches has been applied and the critical components of the considered system were identified on the basis of their Risk Priority Number (RPN). The identification of critical components on the basis of RPN score results in confusion to system analyst as it becomes difficult to allocate appropriate risk priorities under same RPN scores. Also, importance among the probability of occurrence of failure (Of), Severity (S), probability of non detection (Od) are assumed to be of same importance however in real practical application there exists relative importance among these three factors. Therefore, to overcome such types of limitations of FMEA approach a Fuzzy Decision Making System (FDMS) and Grey Relation Analysis (GRA) approaches were applied. The ranking results so obtained were compared for better and intelligent decision making of risky components and the results were further supplied to maintenance management/reliability engineer of the considered system for planning and implementing the suitable maintenance policy accordingly.
    Keywords: Transmission System, fuzzy methodology, Reliability, FMEA, Fuzzy Decision Making System, GRA

  • Symmetric duality for multiobjective second-order fractional programs   Order a copy of this article
    by Geeta Sachdev 
    Abstract: A pair of symmetric dual second-order multiobjective fractional programming programs is formulated. Various duality results are established for this pair which further helps to study minimax mixed integer programming problems. Symmetric duality theorem is established under pseudobonvexity and multiplicative separability assumptions on the functions involved.
    Keywords: Symmetric duality;rnFractional programming; Multiobjective programming; Minimax mixed integer programming.rn.

  • Cost Benefit Analysis of Three Configurations with Imperfect Coverage and Standby Switching Failures   Order a copy of this article
    by Kuo-Hsiung Wang 
    Abstract: Abstract: The cloud computing is an emerging new computing paradigm which provides high reliability, high availability, and QoS-guaranteed computing services. The reliability and stability of power supply is one of the most important factors in successful cloud computing. In this paper, we compare three different configurations with imperfect coverage and standby switching failures based on system reliability and availability. The time-to-repair and the time-to-failure for each of the primary and warm standby components are assumed to be exponentially distributed. We derive the explicit expressions for mean time-to-failure, MTTF, and steady-state availability, AT, for three configurations and perform a comparative analysis. Three configurations are ranked based on MTTF, , and cost/benefit where benefit is either MTTF or AT.
    Keywords: Keywords: Availability; comparisons; imperfect coverage; reliability,standby switching failures.

  • STOCHASTIC ANALYSIS OF A COMPLEX SYSTEM UNDER PREEMPTIVE RESUME REPAIR POLICY USING GUMBEL- HOUGAARD FAMILY COPULA   Order a copy of this article
    by Vijay Vir Singh, Hamisu Ismail Ayagi 
    Abstract: The present paper focuses on the study of complex system consisting of three units super priority, priority and ordinary unit under preemptive resume repair policy. Three units connected with an automatic changeover switch and human operator is handling the system. Together with the failure in super priority, priority and ordinary unit, the other important failures like deliberate failure and switch failure have been considered for study of mathematical model. All failure rates are assumed constant and follow exponential distribution however, the repair rate for partially failed state follow general distribution and complete failed states are repaired using Gumbel Hougaard family copula (a joint probability distribution of general distribution and negative exponential distribution). The system is analyzed using supplementary variable technique and Laplace transform. The various popular measures of reliability such as Availability, Reliability, Mean time to system failure (MTTF) and profit function has been calculated for particular values of failure and repair rates. Sensitivity analysis for different traditional measures has also been done. Computed results have been highlighted by tables and graphs.
    Keywords: Availability; Reliability; Human failure; Switch failure; Preemptive resume repair policy; Super priority unit; Priority unit and profit function.

  • An Exact Algorithm for MultiConstrained Minimum Spanning Tree Problem   Order a copy of this article
    by Singamsetty Purusotham, T. Jayanth Kumar 
    Abstract: This paper deals with a variant of minimum spanning tree problem with multiple constraints, which includes degree, weight and budgeting constraints simultaneously together. To model the problem, a zero-one programming is incorporated. An exact solution procedure called pattern recognition technique based lexi-search algorithm is developed. A suitable numerical illustration is given to check the applicability of the developed algorithm. Furthermore, the algorithm is programmed in C and tested with randomly generated hard instances, computational results are also reported. The overall results reveal that the proposed algorithm is fairly proficient in the sense of both acquiring the optimal solutions and computational time.
    Keywords: multi-constrained minimum spanning tree; lexi-search algorithm; pattern recognition technique; weight constraint; degree constraint; budgeting constraint.

  • An Order Level Inventory Model for Deteriorating Stock Product and Time Dependent Demand under Shortages   Order a copy of this article
    by Deepa Khurana, Rekha Rani Chaaudhary 
    Abstract: The objective of the present paper is to develop an inventory model for deteriorating products. In this paper the demand is a function of time and available stock level since the available stock level is an important tool to attract the customers. The shortages are allowed and partially backlogged. Depending on the rate of backlogging two different cases are developed. In first case, the rate of backlogging is constant and in another case the backlogging rate is time dependent. Numerical example is given to illustrate the model and its significant feature. Sensitivity analysis is also carried out to study the effect of different parameters on total average cost.
    Keywords: Deterioration; Shortages; Stock and time dependent demand; Partial backlogging.

  • A Production Inventory Model with Selling Price and Stock Sensitive Demand Under Partial Backlogging   Order a copy of this article
    by Deo Datta Aarya, Mukesh Kumar 
    Abstract: In the proposed paper we develop an inventory model for instantaneous deteriorating items with multi variate function of demand rate. Generally, we observe that the demand for any product depends on so many factors, out of which the available stock and selling price are the main factors. So in this paper we have assumed that the demand rate is a function of stock and selling price. The production rate is taken as a function of demand rate. The shortages are allowed and it is assumed that the occurring shortages will be backlogged for which the backlogging rate is a function of waiting time. The numerical example and sensitivity exploration with respect to various parameters are also cited to illustrate the study.
    Keywords: Inventory; Multi variate demand rate; Deterioration rate; Production; Shortages and Partial backlogging.

  • On duality of fuzzy multiobjective optimization problems : Application to a multiplicative search technique   Order a copy of this article
    by Mohamed Abd Allah El-hadidy, Mohamed Abd El-Hady Kassem 
    Abstract: In this paper, we present a new study to minimize the expected value of the first meeting time between one of the searcher and the randomly moving target in the space (case of the multiplicative search technique) from a viewpoint of computational optimization. We introduce the dual problem for the fuzzy multiobjective nonlinear programming problem (FMONLP) with inequality constraints which is obtained in El-Hadidy (International Journal of Computational Methods Vol. 13, No. 6 (2016) 1650038 (38 pages)). For this problem, we generalize the following classes of the vector-valued functions for fuzzy sets: weak strictly pseudo-quasi type I, strong pseudo-quasi type I, weak quasi strictly type I and weak strictly pseudo type I. We provide the fuzzy forms of Mond-Weir and general Mond-Weir duals for the involved problem and consequently various duality results are derived.
    Keywords: Multiplicative search technique; Convex fuzzy mappings; Invex fuzzy mappings; Multiobjective nonlinear programming; Weak strictly pseudo type I.

  • Optimal ordering policy for deteriorating items under down-stream trade credit dependent quadratic demand with full up-stream trade credit and partial down-stream trade credit   Order a copy of this article
    by Nita Shah, Mrudul Jani, Urmila Chaudhrai 
    Abstract: Now a days in use of, the offer of delay payment is very impressive tool to boost the market demand by attracting more customers. In this paper, we propose an inventory model in which, retailer receives a permissible delay on the entire purchase expanse from the manufacturer (i.e., an up-stream full trade credit). In comparison, retailer asks customers to pay some percent of purchasing cost at the time of receiving product to reduce default risk (i.e., a down-stream partial trade credit). We consider the product with maximum fixed-life time deterioration and to reduce deterioration of the product, seller spends capital on preservation technology to preserve the item. Here, down-stream trade credit dependent quadratic demand is debated which is suitable for the products whose demand increases initially and afterward it starts to decrease. The objective is to minimize the total relevant cost of retailer with respect to cycle time, down-stream trade credit and investment for preservation technology. The model is supported with numerical examples. Sensitivity analysis is done to derive insights for decision-maker. Graphical results, in three dimensions, are exhibited with supervisory decisions.
    Keywords: Inventory; deterioration; fixed-life time; quadratic demand; preservation investment; partial down-stream trade credit; full up-stream trade credit.

  • Simultaneous selection factories, assignment products to factories, lot-sizing and scheduling in distributed permutation flow shop   Order a copy of this article
    by Mohammad Mohammadi 
    Abstract: The simultaneous selection factorys problem has been recently proposed as a generalization in distributed permutation flow shop setting. In this paper, a new generalization of simultaneous lot-sizing and scheduling decisions in permutation flow shop problem to the distributed permutation flow shop has been studied. Under this generalization, it is not necessary to use all existing factories and each product cannot be produced in more than one factory. An exact formulation of the problem provided as a mixed integer program. In order to solve the problem, a heuristic procedure has been developed. To test the accuracy of heuristic, a lower bound is developed and compared against the optimal solution.
    Keywords: Distributed permutation flow shop; Lot-sizing and Scheduling; Sequence-dependent; Assignment products to factories.

  • An EOQ inventory model for deteriorating items with time-dependent deterioration rate, ramp type demand rate and shortages   Order a copy of this article
    by Trailokyanath Singh, Pandit Jagatananda Mishra, Hadibandhu Pattanayak 
    Abstract: This paper presents an economic order quantity (EOQ) model for deteriorating items having time proportional deterioration rate, time-dependent ramp-type demand rate and shortages. Shortages are allowed to occur in the inventory system and completely backlogged. The ramp-type demand rate is deterministic and varies with time up to a certain point and then becomes constant. The three-parameter Weibull distribution rate indicates the change in deterioration rate with respect to time and takes into account of the items which are already deteriorated while receiving into an inventory system as well as items those might start deteriorating in future. To start with, the model is developed for shortages, but is also valid for the seasonal items and newly launched high tech products like computers, laptops, mobile phones and automobiles etc. The purpose of this study is to develop an optimal policy, so that the average total cost is minimized by optimizing the procurement time point. Furthermore, the solution procedure and the numerical example are provided to illustrate the proposed model. Finally, sensitivity analysis of the various parameters on optimal solution is carried out.
    Keywords: Deteriorating items; EOQ; Ramp-type demand; Shortages; Time-dependent deterioration rate.
    DOI: 10.1504/IJMOR.2018.10008489
     
  • Bias-correction in DEA efficiency scores using simulated Beta samples: an alternative view of bootstrapping in DEA   Order a copy of this article
    by P. Sunil Dharmapala 
    Abstract: Bootstrapping of DEA efficiency scores came into being under the criticism that DEA input/output data may contain random error, and as a result the efficient frontier may be warped by statistical noise. Since the publication of the seminal paper by Simar and Wilson (1998), several researchers have carried out bootstrapping the DEA frontier, re-computing the efficiency scores after correcting the biases and developing confidence intervals for bias-corrected scores. We view bias-correction in DEA efficiency scores from a different perspective by randomizing the efficiency scores that follow underlying Beta distributions. In a step-by-step process, using the simulated Beta samples, we show how to correct the biases of individual scores, construct confidence intervals for the bias-corrected mean scores and derive some statistical results for the estimators used in the process. Finally, we demonstrate this method by applying it to a set of banks.
    Keywords: Data envelopment analysis (DEA); Assurance regions (AR); Order statistics; Beta distribution; Bias-correction; Simulation.

  • Duality for Non-Differentiable Multi-Objective Semi-Infinite Programming for Higher Order Invex Functions   Order a copy of this article
    by Promila Kumar, Jyoti  
    Abstract: Abstract: This paper deals with Non-Differentiable Multi-Objective Semi-Infinite Programming Problem. It is a problem of simultaneous minimization of finitely many scalar valued functions subject to an arbitrary (possibly infinite) set of constraints. Non-differentiability enters, due to the square root of a quadratic form which appears in the objective functional. Concept of efficiency of order m has been extended to the above stated problem. In order to study this new solution concept the notion of ρ-invexity of order m is also proposed which is utilized to establish sufficient optimality conditions for the non-differentiable multi-objective semi-infinite programming problem. Mond-Weir type of Dual is proposed for which Weak, Strong and Strict Converse duality theorems are established. .
    Keywords: Optimality; Duality; Semi-infinite programming; Non-differentiable programming; ρ-invexity of order m.

  • Testing the fractional integration parameter revisited: a Fractional Dickey-Fuller Test   Order a copy of this article
    by Ahmed Bensalma 
    Abstract: The main scope of this paper is to provide how to extend the standard Dickey-Fuller test (1979) by taking into account the fractional case. Such extension has already been discussed by Dolado et al. (2002). In this paper, we show, in the first step, that the fractional Dickey-Fuller test proposed by Dolado et al. is useless in practice. In the second step we show how to extend adequately the standard framework of Dickey-Fuller test to take into account the fractional case by using the usual test statistics and the usual asymptotic distributions (Phillips, 1987). Such extension can be very useful in practice. Through a simulation study, we show the good performance of the test in terms of size and power. Finally, in order to show how to use the new testing procedure, the test is applied to the well-known Nelson and Plosser data.
    Keywords: Fractional integration; Fractional unit root; Dickey-Fuller unit root test; Fractional Dickey-Fuller test.

  • Approximating Service--time Distributions by Phase--type Distributions in Single--server Queues: A~Strong Stability Approach   Order a copy of this article
    by Yasmina Djabali, Boualem Rabta, Djamil AÏSSANI 
    Abstract: Phasetype queueing systems are used to approximate queues with general servicetime distribtions. In this work, we provide by means of the strong stability method, the mathematical justification of the approximation method by phasetype distributions that is already used in several works. We consider the approximation of M=G=1 queueing system by a M=PH=1 system, where PH refers to a hyperexponential H2 or a hypoexponential HOE2 distribution depending on the value of the coefficient of variation of the original distribution. We prove the robustness of the underlying Markov chain in each case and estimate an upper bound of the deviation of the stationary vector, resulting from the perturbation of the servicetime distribution.We provide numerical examples and compare the perturbation bounds obtained in this paper with the estimates of the real deviation of the stationary vector obtained by simulation.
    Keywords: Queueing systems; phase-type distributions, Perturbation; Sensitivity analysis; Strong stability; Quantitative estimates; Perturbation bounds.
    DOI: 10.1504/IJMOR.2018.10005095
     
  • ALLOCATION PROBLEM IN PRESENCE OF NONRESPONSE: A MATHEMATICAL PROGRAMMING APPROACH   Order a copy of this article
    by Mushtaq Ahmad Lone, S.A. Mir, Imran Khan 
    Abstract: Survey nonresponse refers to the failure to get a useable response from the respondent selected for the sample. Nonresponse may occur due to several reasons. The randomized response technique (RRT) presented by warner (1965) used to estimate proportion of respondents to the sensitive questions without revealing his choice to the interviewer. In this article the problem of optimal allocation in stratified sampling where RRT is used in presence of nonresponse, is formulated as an Nonlinear Programming Problem (NLPP) .The formulated problem is solved using Branch and Bound method and the results are obtained through LINGO.
    Keywords: Stratified random sampling; optimum allocation; Randomized response technique; Nonresponse; Branch and Bound method; NLPP.
    DOI: 10.1504/IJMOR.2018.10004127
     
  • On logarithmic fixed-charge transportation problem   Order a copy of this article
    by Debiprasad Acharya, Manjusri Basu, Atanu Das 
    Abstract: The fixed charge transportation problem (FCTP) is still a challenging problem in the field of mathematical programming. In this paper, we consider fixed-charge transportation problem with logarithmic objective function. In the absence of any suitable algorithm to ob tain the solution of this type of non-linear transportation problem, we discuss the advantage of polynomial approximation. There exists a major difference between the two problems that the variables in the polynomial transportation problem have no upper bound but in the logarithmic transportation problem they are bounded. Using the expansion of loga rithm we show the resemblance between the structural behavior of linear and fixed charge transportation problems. We illustrate a numerical example in support of the developed method.
    Keywords: Transportation problem; fixed cost; logarithm modeling.

  • A Mathematical Investigation of Rao Diversity Coefficients Among the Communities According to Species Morphometry and Species Taxonomy   Order a copy of this article
    by Kenneth Barroga 
    Abstract: Although Rao Diversity Coefficient (Rao DIVC) is sensitive to the differences among species, a gap still remains in investigating how the communities are affected when the dissimilarity among the species are in terms of its morphometry and taxonomy. I studied the effect of using species taxonomic classification and species morphometrical traits in the computation of Rao DIVC in assessing diversity of ecological communities. I utlised the Mahalanobis distance for measuring the variation of species morphometry. As for species taxonomy, I employed the method by Warwick and Clarke (1995). When the calculated Rao DIVCs, Double Principal Coordinate Analysis and Co-inertia Analysis outputs were compared, I discovered that Rao DIVCs accounting species morphometry (Rsm) and species taxonomy (Rst) yielded different results and interpretation. Rsm clearly showed more the variation among communities but contributed less in the analysis, whereas Rst showed more clearly the clusters between the communities which make the interpretation easier.
    Keywords: double principal coordinate analysis; mahalanobis distance, rao diversity coefficient; co-inertia analysis.

  • Material Selection for multi tubular fixed bed reactor Fischer-Tropsch reactor (MFBR)   Order a copy of this article
    by Javier Martinez 
    Abstract: The future of the fossil fuel supply is uncertain. For this reason, the transition from a fossil energy-based scenario to a bioenergy-based one is necessary for achieving the greenhouse gas emissions reduction and climate change targets. In this regards, multi-tubular fixed-bed Fischer-Tropsch reactor (MFBR) appears has an essential technology to improve and to reduce operation costs. For designing a MFBR, many studies have drawn upon computational fluid dynamics (CFD) for detailed evaluation of reaction systems. However, engineers usually define certain materials based on previous experiences and related studies, yet they neglect any preliminary selection of this procedure. This research use Multi-criteria decision making methods (MCDM) for the material selection of a MFBR. This project focuses on the selection of a proper material which fulfills the technological requirements for building the vessel and piping of a MFBR while costs reduction is considered as part of the analysis. The MCMD methods implemented are complex proportional assessment of alternatives with gray relations (COPRAS-G), operational competitiveness rating analysis (OCRA), a new additive ratio assessment (ARAS) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) methods. The criteria weighting was performed by compromised weighting method, composed of analytic hierarchy process (AHP) and Entropy methods. The ranking results showed that ASME SA-106 and ASME SA-106 would be the best materials for the pipes and the vessel of a MFBR.
    Keywords: multi-criteria decision making methods; MCDM; material selection; multi tubular fixed bed reactor Fischer-Tropsch reactor; MFBR.

  • An O (pnL) interior-point algorithm for PL(q) horizontal linear complementarity problems   Order a copy of this article
    by Hossein Mansouri 
    Abstract: This paper presents a wide-neighborhood interior-point algorithm for\r\n $P_*(\\kappa)$ horizontal linear complementarity problem.\r\n The convergence analysis is shown for the introduced wide neighborhood of the central path by\r\n \\cite{Ai-Zhang} for monotone linear complementarity problem,\r\n and unifies the analysis for $\\m{N}_{\\infty}^-$ and $\\m{N}(\\tau,\\beta)$ wide neighborhoods.\r\n The Newton search directions are decomposed to the nonnegative and nonpositive parts,\r\n correspond to the parts of the right hand side.\r\n The achieved complexity bound is $O\\br{(1+4\\kappa)\\sqrt{n}\\log\\frac{n}{\\varepsilon}}$,\r\n which is the same as the best obtained bound for the monotone linear complementarity problems,\r\n except that it is multiplied by the factor $(1+4\\kappa)$, where $\\kappa$ is the handicap of the given problem.
    Keywords: Interior-point method; Horizontal linear complementarity problem; Wide neighborhood algorithm; Polynomial complexity.

  • A Hierarchical Cellular Manufacturing System   Order a copy of this article
    by Seyed Hojat Pakzad-Moghaddam, Farhad Salehian, Seyed Esa Hosseini, Hassan Mina 
    Abstract: Group technology proved to be advantageous in manufacturing a variety of products which have something in common. Cellular manufacturing is one of the most common and popular methods in order to take advantage of group technology. Cellular manufacturing helps the manufacturer to avoid surplus costs by bringing order to the whole manufacturing process. Of particular interest, applying Cellular Manufacturing Systems (CMSs) increases the efficiency of the applied transportation system by designing an efficient working floor. Controlling the amount of material handling, results in lower cost and energy required to transport materials/products. With this regard, hybrid cellular manufacturing systems are under consideration in the study at hand. Regarding a hybrid CMS, proper manufacturing systems such as (single machines, flow shops, job shops and open shops) are applied between and within cells to harmonize the whole manufacturing procedure. A special case of hybrid CMS, referred to as Hierarchical CMS (HCMS) is investigated in this paper. In a HCMS not only machines are placed in several interior cells, but also interior cells themselves must be located in exterior ones. Finally a Mixed Integer Non-Linear Programming (MINLP) mathematical model is presented and validated through numerical results. The aforementioned model is coded via GAMS IDE and solved by its well-known MINLP solver i.e. BARON.
    Keywords: Cellular manufacturing; Energy saving policy; Shop floor; Mathematical modeling.

  • A Two-Phase Heuristic for Set Covering   Order a copy of this article
    by Salim Haddadi, Meryem Cheraitia, Abdellah Salhi 
    Abstract: The set covering problem (SCP) is a well-known computationally intractable problem. We suggest here a two-phase heuristic to solve it. The first phase reduces substantially the size of the given SCP by removing some variables; the second phase applies a simple Lagrangian heuristic applied to the reduced problem. Construction and improvement heuristics are embedded in the Lagrangian solution approach. The construction heuristic provides good covers by solving small SCPs. The improvement heuristic inserts these covers into larger ones from which better covers are extracted, again by solving different but also small SCPs. The novelty lies in the reduction of the problem size by an effective variable-fixing heuristic, which, in practice, eliminates up to 95% of the variables of the problem without sacrificing the solution quality. Extensive computational and comparative results are presented.
    Keywords: Set Covering; Variable-fixing Heuristic; Greedy Heuristic with Regret; Lagrangian Heuristic.

  • New generalized mixed vector variational-like inequalities with semi-$eta$-pseudomonotonicity   Order a copy of this article
    by Prashanta Majee, Chandal Nahak 
    Abstract: In this paper, we introduce the concept of semi-$eta$-pseudomonotonicity for vector set-valued mappings. Using this concept, and utilizing KKM technique and Nadler's Lemma, we establish some existence results for the new generalized mixed vector variational-like inequality problem in reflexive Banach spaces. Our results are the extension and improvement of some of the results given by Plubtieng and Thammathiwat (J. Optim. Theory Appl. 162(2), 589-604, 2014). Few examples are given to justify our new findings.
    Keywords: New generalized mixed vector variational-like inequalities; semi-$eta$-pseudomonotonicity; Fan-KKM theorem; Nadler's result.

  • Comparison between Linear Programming and Integer Linear Programming: A Review   Order a copy of this article
    by Mei Lee Sam, Adi Saptari, Mohd Rizal Salleh, Effendi Mohamad 
    Abstract: This research discusses comparison of linear programming (LP) and integer linear programming (ILP). Both are used to seek for the optimal solution of a problem with the aim of minimizing cost or maximizing throughput with limited resources. LP allows having decimal solution, whereas ILP only allow integer. A review of literature of both programming was performed. LP and ILP have same formulation; it requires linear function for both objective and constraints. Two techniques to solve LP, simplex method and interior-point method were introduced. For ILP, available algorithms can be classified into exact algorithms and heuristic algorithms. Three criteria were used to evaluate the characteristics of LP and ILP techniques: time complexity, problem size and computational time. Simplex method is effective to solve small sized problems with less number of iteration while interior-point method was recommended for large sized problems due to its excellent performance and shorter computational time than simplex method. Exact algorithms is suitable for small sized problems and attain optimal solution in reasonable computational time. Meanwhile, heuristics outperform exact algorithms in solving large sized problem where it can obtain near optimal solution in an acceptable computational time. Heuristics are not guarantee obtain optimal solutions, compared to exact algorithms. Each technique has its own advantages.
    Keywords: linear programming;integer linear programming;computational time;problem’s size.

  • Multi-objective unbalanced assignment problem with restriction of jobs to agents via NSGA-II   Order a copy of this article
    by Amiya Biswas, Asoke Kumar Bhunia, Ali Akbar Shaikh 
    Abstract: In this paper, an approach based on genetic algorithm has beenproposed for solving multi-objective unbalanced assignment problems with restriction of job(s) to different agents which may arise due to the inability/ poor efficiency of performing certain jobs by some agents dealing with an additional constraint on the maximum number of jobs that can be performed by an agent. As the cost and time are considered as the most important factors for managerial decision in economic/ industrial establishments, so here the total cost of assignment of jobs to agents and the total time of completion of jobs by the agents are considered as the two prime objectives. This gives rise to an NP-hard 0-1 programming problem and to solve this problem, we have equipped NSGA-II with a newly developed crossover having the capability of repairing infeasible solution and two new mutation schemes. Also, for comparison of the results obtained from this algorithm, some other variants of this algorithm with existing crossover and mutation schemes have been considered.Finally, to illustrate the performance of proposed approach, a set of test problems have been solvedand the results have been analyzed for different variants of NSGA-IIand some potential future research directions has been discussed.
    Keywords: Multi-objective optimization,Unbalanced assignment problem; Genetic algorithm; Non-dominated sorting; Pareto-optimal solution.

  • Efficient Near-Optimal Procedures for Some Inventory Models with Backorders-Lost Sales Mixture and Controllable Lead Time, under Continuous or Periodic Review   Order a copy of this article
    by Marcello Braglia, Davide Castellano, Dongping Song 
    Abstract: This paper considers a number of inventory models with backorders-lost sales mixture, stockout costs, and controllable lead time. The lead time is a linear function of the lot size and includes a constant term that is made of several components. These lot-size-independent components are assumed to be controllable. Both single- and double-echelon inventory systems, under periodic or continuous review, are considered. To authors knowledge, these models have never been previously studied in literature. The purpose of this paper is to analyse and optimize these novel inventory models. The optimization is carried out by means of heuristics that work on an ad hoc approximation of the cost functions. This peculiarity permits to exploit closed-form expressions that make the optimization procedure simpler and more readily applicable in practice than standard approaches. Finally, numerical experiments investigate the efficiency of the proposed heuristics and the sensitivity of the developed models.
    Keywords: supply chain; inventory; logistics; lead time; stochastic; heuristics; optimization; joint economic lot size; stockout.

  • Evaluation of Reordering Time in a Manufacturing Inventory Division   Order a copy of this article
    by NANDAKUMAR C D, SRINIVASAN S, SATHIYAMOORTHI R 
    Abstract: In this paper, a production process is considered which requires two kinds of raw materials as inputs to make a product. The two kinds of raw materials are stored separately. During the time of crisis like non-availability of the raw materials due to scarcity or delayed delivery or for some other reasons, the reserve stocks are utilized to continue the production process, as a result; the level of reserve stocks would come down and finally may go void. This may result into production halt. To avoid this situation, a reorder is made to maintain the level of reserve inventory as soon as the reserve level touches a particular level called the threshold level. Using the shock model and cumulative damage process technique, a stochastic model is derived to find the threshold level or the time of reordering, which helps the production system to eliminate the holding cost on excessive raw materials and also the loss arising from the shortage of raw materials. Numerical illustrations are provided.
    Keywords: threshold level; reserve inventory; break down; random time points; depletion.

  • A model for continuously degrading systems with outsourcing maintenance service   Order a copy of this article
    by Allen Tai 
    Abstract: It is a common practice in industry that maintenance service is outsourced to external suppliers. In this paper, a model for a continuously degrading system is developed such that an optimal inspection-maintenance strategy can be derived. The model is capable of handling the situation when there is deferment of the maintenance services. Hence, the system manager can decide whether to stop system operation during the waiting time for the maintenance services. The system is subjected to two degradation sources: (i) the degradation due to the operation of the system and (ii) the degradation due to the operation environment. An optimal value of the inter-inspection time and an optimal maintenance threshold are then obtained by numerical methods such that the average availability of the system is maximized. Illustrative examples and some special cases are also provided.
    Keywords: Maintenance outsourcing; Degrading system; Periodic inspection; Availability.

  • Proposing a New Mathematical Model and a Meta-heuristic Algorithm for Scheduling and Allocating Automated Guided Vehicle   Order a copy of this article
    by Mohammad Mehdi Tavakoli, Seyed Mojtaba Sajadi, Seyed Ali Sadeghi Aghili 
    Abstract: One of the substantial things, which has been perceived more than ever by captains of industry in recent years is the necessity of earning competitive value. As a result, mechanization and enhancing the level of automation of the process has become one of the most fascinating issues to researchers. In this regard one of the most appealing systems to industries is flexible manufacturing systems which contribute to achievement of higher levels of automation in business environments. Since transportation plays an essential role in flexible production systems, Automated Guided Vehicle has been utilized to carry material in these systems in order to maintain the flexibility, increase the efficiency of production and distribution throughout the system. In this paper, a mathematical model for scheduling and allocating AVGs in the manufacturing process of a specific project is proposed and in the end, a heuristic algorithm is proposed and practiced to solve the model problem.
    Keywords: mathematical model; Automated Guided Vehicle (AGV); scheduling and allocation; NSGA II.

  • On the multiserver retrial queues with negative arrivals.   Order a copy of this article
    by Nesrine Zidani, Natalia Djellab 
    Abstract: The paper deals with an M/M/C/K retrial queue with exponential abandonments at which positive and negative customers arrive according to Poisson processes. This model is of practical interest: it can be used for analyzing the performance in call centers and e-mail contact systems. For model under investigation, we find the ergodicity conditions and also the approximate solution by using Finite Truncation and Value Extrapolation methods. We present some numerical results to examine the performance of Value Extrapolation method as well as the system performance.
    Keywords: abandonment; truncation; ergodicity condition; extrapolation; negative arrivals.
    DOI: 10.1504/IJMOR.2018.10005307
     
  • An imprecise-inventory model with PEND and SEND policy   Order a copy of this article
    by Barun Das, Dipak Barman 
    Abstract: A continuous review economic order quantity (EOQ) model (with shortage)is modelled here. The inventory cost parameters are imprecise in nature. The model is developed for Partially Enforced Delay (PEND) and Strictly Enforced Delay (SEND) policies with lead time crashing cost. Here demand of the item is a linear function of selling price and usable lead time. For each policy, a set-up cost reduction technique has been applied to the model. More-over a statistical t-test has been used to compare the policies. We also present some numerical examples, sensitivity analysis and their discussions to stabilize the model.
    Keywords: Continuous review inventory policy; imprecise cost; controllable lead time; set up cost reduction; Fisher’s t-test.

  • FINDING THE SHORTEST PATH BY ADHWARJEES ALGORITHM AND COMPARISON OF THIS POWERFUL METHOD WITH DIJKSTRA ALGORITHM   Order a copy of this article
    by DILIP KUMAR ADHWARJEE 
    Abstract: The author introduces an algorithm for finding the shortest path which is more powerful method over all the existing method like Dijkstras algorithm. ADHWARJEES ALGORITHM is introduced to the readers for finding the shortest path The author gives few steps to find the shortest path. This method takes less standard time over DIJKSTRAS ALGORITM. First the Dijkstras method is explained in brief which is readily available in books. We will concentrate the new method of finding the shortest path. Adhwarjees algorithm does need no table to compute. Simple addition , subtraction & finding minimum , maximum can be done mentally & posted in the network itself. In the network the reader can see the minimum distance or time which requires to be found out.
    Keywords: Origin; Destination; Vertex; Shortest Path; minimum.

  • On Optimization over the Integer Efficient Set in Fuzzy Linear Multicriteria Programming   Order a copy of this article
    by Ouiza Zerdani, Farida Achemine 
    Abstract: The problem of optimizing a linear function over the efficient set of a multiobjective linear programming problem is an important field of research and has some applications in multiple objective decision making. The main difficulty of this problem is that its feasible domain is nonconvex and not described explicitly. The main purpose of this paper is to describe an efficient and finite new algorithm which provides a global R-optimal solution of the problem of optimizing a fuzzy linear function over the efficient set of a Fuzzy Multiobjective Integer Linear Programming (FMOILP) problem without having to search all integer R-Efficient solutions. All the parameters of the considered problem are characterized by trapezoidal fuzzy numbers. The proposed approach is based first on the concept of comparison of fuzzy numbers by using ranking function and on an extension of Jorges algorithm onto fuzzy numbers. Finally a numerical illustration is included for illustration.
    Keywords: Integer programming; Global optimization; Optimization over the efficient set; Ranking function; Trapezoidal fuzzy numbers.
    DOI: 10.1504/IJMOR.2018.10004946
     
  • Partial Backlogging EOQ Model with Trade-Credit Facility and Inflationary Environment   Order a copy of this article
    by Rahul Goel 
    Abstract: In this article, an EOQ (economic order quantity) model for deteriorating items with trade-credit facility is presented. It is assumed that decay rate is two parameters Weibull distributed function of time. Demand rate of the products increases with time. Shortages are allowed and partially backlogged. The whole study is done in inflationary environment. A numerical assessment is done to exemplify the proposed model and sensitivity analysis with respect to the change in system parameters is also carried out.
    Keywords: EOQ; inventory; Weibull deterioration; shortages.

  • AN APPLICATION OF MULTI LAYERED FUZZY ATTRIBUTED ROUGH SET IN STUDYING ORGANIZATIONAL CULTURE SYSTEM   Order a copy of this article
    by Praba Bashayam, Gomathi Ganesan, Vijaya Mani, Vageesh Mohan 
    Abstract: In this paper, the concept of Rough set is introduced for an information system with multi layered weighted fuzzy attributes. The equivalence classes of the objects are formed using the fuzzy weight given to the objects in terms of these multi layered weighted fuzzy attributes. The weight of the Rough Set is also defined using the weight of its lower and upper approximations and also we defined an interval valued fuzzy set on the set of objects. This helps to study the behaviour of any system with complex attributes. These concepts are illustrated with a real time example.
    Keywords: Rough set; Information system; Lower Approximation; Upper Approximation; Equivalence classes.

  • Multi-objective optimization using genetic algorithm based clustering for multi- depot heterogeneous fleet vehicle routing problem with time windows   Order a copy of this article
    by Lahcene Guezouli, Samir Abdelhamid 
    Abstract: Efficient routing and scheduling of vehicles has significant economic implications for both the public and private sectors. To this purpose, we propose in this study a decision support system which aims to optimize the classical Capacitated Vehicle Routing Problem by considering the existence of different vehicle types (with distinct capacities and costs) and multiple available depots, that we call the Multi-Depot Heterogeneous Vehicle Routing Problem with Time Window (MDHVRPTW) by respecting a set of criteria including: schedules requests from clients, the heterogeneous capacity of vehicles..., and we solve this problem by proposing a new scheme based on the application of the bio-inspired genetic algorithm heuristics and by embedding a clustering algorithm within a VRPTW optimization frame work, that we will specify later. Computational experiments with the benchmark test instances confirm that our approach produces acceptable quality solutions compared with the best previous results in similar problems in terms of generated solutions and processing time. Experimental results prove that our proposed genetic algorithm is effective in solving the MDHVRPTW problem and hence has a great potential.
    Keywords: Multi-depot vehicle routing problem; clustering; routing; scheduling; genetic algorithm; heterogeneous vehicle routing problem.
    DOI: 10.1504/IJMOR.2018.10008290
     
  • Designing an open-loop supply chain network for recyclable products: A case study   Order a copy of this article
    by Shiva Zandkarimkhani, Mohammad Mahdi Nasiri, Jafar Heydari 
    Abstract: Recently because of the recycling policies and environmental issues, the combination of forward and reverse logistics have attracted lots of attention to itself. The current paper presents a designed open-loop supply chain network to reuse the returned goods. To this aim, a mixed integer linear model is proposed that minimizes the total cost. The proposed model determines the location of distribution centers, recycling centers, collection centers, disposal centers and also the quantity of the transferred product between levels. Finally, in order to investigate the effectiveness of the proposed model, it is implemented at one of Iranian Poly Ethylene Terephthalate (PET) product companies.
    Keywords: Supply chain management; Mathematical programming; Reverse logistics; open loop supply chain.

  • Generate random variates using a newly introduced approximation to cumulative density of lower truncated normal distribution for Simulation Applications   Order a copy of this article
    by Mohammad Hamasha 
    Abstract: The lower side truncated cumulative normal distribution and its inverse are approximated in simple functions, and random variates are explained how to be generated from the introduced approximation of the inverse. The introduced approximation is derived from Audaat and Alodat's model of approximating cumulative normal distribution. The accuracy of the introduced model and its inverse is investigated in term of maximum absolute error. The maximum absolute error of the introduced approximation is 0.003944 in the entire region. This level of maximum absolute error is the best comparing all other similar models to the best of authors knowledge.
    Keywords: Normal Distribution; Random Variate Generation; Cumulative Density Function; Upper and Lower Truncated Normal Distribution.

  • Equilibrium behavioral strategies in an M/M/1 queue   Order a copy of this article
    by Sofiane Ziani, Fazia RAHMOUNE, Mohammed Said RADJEF 
    Abstract: For an M/M/1 system, we analyze the strategic interactions of the social optimizer, the service provider and customers and their consequences on the system. The social optimizer chooses the type of information to make available to customers (make the system observable or unobservable), the service provider chooses the service rate with which he performs the service, and customers decide, according to the strategic choices of the first two agents, to use or not the system. As these agents are interacting in a common environment with respect to their objectives, we model the problem as a three-stage game between them. A resolution of the different stages will be made, which will give the overall solution to the considered problem, corresponding to the subgame perfect Nash equilibrium in behavioral strategies. A numerical analysis will be made where one can see the graphical solution of the game, comparisons and interpretationsrnwill be established.
    Keywords: Queueing; Reward-cost structure; Extensive form game; Behavioral strategy; Nash equilibrium.

  • N-Policy for Redundant Repairable System with Multiple Types of Warm Standbys with Switching Failure and Vacation   Order a copy of this article
    by Ritu Gupta, Madhu Jain 
    Abstract: This investigation is concerned with the reliability analysis of redundant repairable system which is supported by mixed standby and two repairmen who turn on according to a threshold N-policy failed. The first repairman never takes a vacation while the second repairman leaves for a vacation of random length when the number of failed components is less than N. The standby switching failure is taken into consideration to deal with real time redundant system. The concepts of degradation and common cause failure are incorporated. By developing Markov model, the transient queue size distribution and expressions for the system reliability, mean time to system failure and other performance measures are obtained. The sensitivity analysis is performed by taking numerical illustration. The model is also examined computationally by employing neuro-fuzzy technique based on adaptive network-based fuzzy interference system (ANFIS) to compute the system descriptors. Using supervised learning process, the comparison between approximate results and analytical results are made.
    Keywords: Reliability; N-policy; Standby switching failures; Server vacation; Neuro fuzzy technique.

  • Numerical approach to the uniqueness solution of Von-Karman evolution   Order a copy of this article
    by Oudaani Jaouad 
    Abstract: The purpose of this paper is to give some theoretical and numerical analysis approach, for local generalized and weakly uniqueness solution, to the models with interior dissipation and clamped boundary conditions of Von-Karman evolution, without rotational inertia and nonlinear internal dissipation. For approached the uniqueness solution we use the scheme of finite difference method.
    Keywords: Von-Karman evolution; Rotational inertia (α ≥ 0); finite difference method; Noncoupled method.

  • A Unified Approach for Optimal Release, Patching and Testing Time of a Software   Order a copy of this article
    by P.K. Kapur, Ompal Singh, A.K. Shrivastava 
    Abstract: The ever growing consumers expectations for innovative and reliable software products within no time have driven developers to reframe the whole development process accordingly. Rigorous testing is required before release to provide highly reliable software to the customer so that users face less failures during operational phase. Although, efficient testing ensures reliable software but costs a lot to developer in terms of higher testing and market opportunity cost. Also, due to stiff market competition and risk of delaying release, now a days software firms are releasing their product early and continue testing to fix the remaining number of bugs in the operational phase by providing patches. A Patch is a small program to fix the bugs. But continuing testing to provide patches for better product experience to users is also not economical from firms point of view. Hence it is important to determine the optimal time for releasing, patching and stop testing the software. In this paper we present a unified framework of optimal policy to determine optimal software release, patching time and testing stop time, to minimize overall testing cost. Proposed cost model is validated on a real life software failure data set of Tandem Computers.
    Keywords: Modeling; Patch; Release; Software Reliability; Software updating; Software testing; Unified Approach.

  • A model for supplier evaluation and selection based on integrated interval-valued intuitionistic fuzzy AHP-TOPSIS approach   Order a copy of this article
    by Hossein Sayyadi Tooranloo, Arezoo Sadat Ayatollah, Asiyeh Iranpour 
    Abstract: Todays, in the global market are confronted with short-lifecycle products or highly demanding customers that calls a lot of focus on supply chain. Among the activities of the supply chain, activities of effective purchasing are as most important activity to proper selection of suppliers. Since of Supplier evaluation and selection problem is a multi-criteria decision making problem that is along with high degree of ambiguity and uncertainty in the real world decision makings. Since of information of real world decision-makings are often imprecise and expressed with verbally terms therefore the fuzzy sets theory can be effectively used to solve such problems. This paper first provides an overview on the supplier evaluation and selection problem, and then presents a decision making model that is integrates interval-valued intuitionistic fuzzy AHP (IVIF- AHP) and interval-valued intuitionistic fuzzy TOPSIS (IVIF-TOPSIS) to solve such problems, and in the end, provides a numerical example to demonstrate the use of proposed approach.
    Keywords: supplier selection; AHP; TOPSIS; interval-valued intuitionistic fuzzy.

  • A Forward with Backward Inventory Policy Algorithm for Non-Linear Increasing Demand and Shortage Backorders   Order a copy of this article
    by Ririn Diar Astanti, Huynh Trungh Luong, Hui Ming Wee, The Jin Ai 
    Abstract: The traditional inventory policies have been developed for constant demand processes. In reality, demand is not always stable; it might have an increasing pattern. In this paper, a forward with backward inventory policy algorithm is developed to determine the operational parameters of an inventory system with a non-linear increasing demand rate, shortage backorders and a finite planning horizon. Numerical experiments are also conducted to compare the results with the existing techniques and to illustrate the applicability of the proposed technique.
    Keywords: Inventory; non-linear increasing demand pattern; shortage backorders; forward with backward inventory policy algorithm.

  • Measuring the Productivity Changes with Double Frontiers Data Envelopment Analysis for Two-stage processes   Order a copy of this article
    by Ali Mohtashami, Alireza Alinezhad, Mohammad Javad Nasiri Sadeghloo 
    Abstract: The purpose of this paper is to develop an output oriented methodology with constant return to scale (CRS) assumption for calculating productivity changes by using double frontier (optimistic and pessimistic) data envelopment analysis (DEA) simultaneously for two-stage processes. Measuring the productivity changes with Malmquist productivity index (MPI) via double frontiers DEA with single process has been defined by Wang and Lan (2011) as a geometrically average of optimistic and pessimistic point of views to generate an aggregate MPI. In order to develop and modify the previous studies, in this paper we have proposed a method to modify Wang and Lan (2011) aggregate MPI and also extend it to two-stage process which we refer to the double frontiers two-stage DEA (DFTDEA). It should be mentioned that the proposed model of this paper measures the MPIs distance functions for two individual stages and whole process for both DEA different points of view by the traditional DEA models and supposed relational models in output oriented CCR models, respectively. Therefore, the identified double frontiers two-stage DEA (DFTDEA-based MPI) is more realistic and comprehensive than the conventional optimistic or pessimistic DEA-based MPI individually. Subsequently, the proposed approach is examined to five Iranian commercial banks over the 5-years period (2009-2013).
    Keywords: Data envelopment analysis; Two-stage; Double Frontier; Malmquist productivity index.

  • Promotional effort and quality sensitive two echelon production inventory model with partial backlogging   Order a copy of this article
    by Brojeswar Pal 
    Abstract: This study deals with the modeling aspect of a two echelon imperfect production system in presence of the promotional effort of the retailer. The production cost of the system varies with both the ordering lot size and quality of product, and the demand of the product depends on the quality of the product. The inventory level for the manufacturer starts with shortages and new production and the inventory level for the retailer also begins with shortages and new product lot. The cycle ends for both the players with also backlogged inventory. The backlogging rate for each of the player is dependent on waiting time. The behavior of the model under integrated system is analyzed. In the decentralized structure, retailer Stackelberg model are also discussed. The sensitivity of the key parameters is examined to test feasibility of the model. Finally, a numerical example is provided to investigate the proposed model.
    Keywords: Imperfect production inventory model; promotional effort; quality; partially backlogging. 1 Introduction.

  • A New Short Term Energy Price Forecasting Method based on Wavelet Neural Network   Order a copy of this article
    by Farshid Keynia, Azim Heydari 
    Abstract: A Wavelet Neural Network (WNN) is proposed for Short-Term Price Forecasting (STPF) in electricity markets. Back propagation algorithm is used for training the Wavelet Neural Network for prediction. Weights in the back propagation algorithm are usually initialized with small random values. If the random initial weights happen to be far from a suitable solution or near a poor local optimum, training may take a long time or get trapped in the local optimum. In this paper, we show that WNN has acceptable prediction properties compared to other forecasting techniques. We investigated proper weight initializations of WNN, and proved that it attains a superior prediction performance. Finally, we used a two-step correlation analysis algorithm for feature selecting. This algorithm selects the best relevant and non-redundant input features for WNN. Our model is examined for MCP prediction of the Spanish market and LMP forecasting in PJM (Pennsylvania, New Jersey, and Maryland) market for the year 2002 and 2006 respectively.
    Keywords: Adaptive wavelet neural network; Electricity market; Location marginal price; Short term price forecasting.

  • Second Order Duality for Variational Problem Via Efficiency of Higher Order   Order a copy of this article
    by Promila Kumar, Bharti Sharma 
    Abstract: A mixed type second order dual of a multiobjective variational problem has been considered. Notion of generalized second order (F,ρ,θ,m)-invexity is introduced which is utilized to obtain duality results using efficiency of higher order as optimality criteria. Generalized second order (F,ρ,θ,m)-invexity assumptions broadens the domain of the problem, whereas efficiency of higher order leads to stronger results.
    Keywords: Second order duality; Variational problem; Efficiency of higher order.

  • Joint replenishment model of both-ways and one-way substitution among products in Fixed Time Horizon   Order a copy of this article
    by Raghu Nandan Giri, Shyamal Kumar Mondal, Manoranjan Maiti 
    Abstract: A general joint replenishment model (JRM) has been developed for two substitutable products with different demand structures depending on their prices and availabilities over the time cycle. When both products are available, the demand of a substitute product deceases against its own price and increases with the other's price. When one product is out of stock, a portion of demand of the stock-out product goes to the available product. The model is formulated to determine the optimal order quantities and total profits for different scenarios are determined using the classical optimization method and parametric study. The optimal criteria for maximum profit is outlined and the model is illustrated numerically. Some sensitivity analyses with different substitution ratios are performed and some interesting conclusions have been derived.
    Keywords: Joint replenishment model; Substitutable products; Degree of substitution; Fixed time horizon.

  • Developing an integrated decision making model in supply chain under demand uncertainty using genetic algorithm and network data envelopment analysis   Order a copy of this article
    by Sara Nakhjirkan, Farimah Mokhatab Rafiei, Ali Husseinzadeh Kashan 
    Abstract: Nowadays, organizations have recognized the importance of supply chain performance improvement and coordination and integration of supply, production, distribution and inventory operations. They have found out that achieving the competitive advantages requires more focus on supply chain integration (Mina et al., 2014). Since organizations are combined with each other as a network of supply and distribution, the ineffectiveness (such as less operation capacity) and inefficiencies (higher costs) have been more highlighted and the importance of integration has become more specific. This research describes a four echelon supply chain including supplier, producer, distribution and customer levels. Whole scheduling and decision makings are performed by producer. The considered problem is a location routing inventory problem (LIRP). Supply chain integration and demand uncertainty are considered to generate a proper model for the problem. An integrated mathematical model is presented and a set of problems are randomly generated and solved using GAMS software to validate the model. The results show that by increasing the dimensions of the problems the solution times increase exponentially; this represents the complexity of the problem. Therefore, a heuristic genetic algorithm base on network data envelopment analysis selection method is proposed. To evaluate the effectiveness of this proposed algorithm, a set of problems with various dimensions are solved by utilizing this method and three other selection methods. Obtained results are compared by Wilcoxon test which represents proposed algorithms effectiveness.
    Keywords: Supply chain network; Location-inventory-routing problem; Genetic Algorithm; NDEA.

  • A New Optimal Multi-product (Q, R, SS) Policy with Multivariate Markov Stochastic Demand Forecasting Model   Order a copy of this article
    by Jie Chen, Zhixiang Chen 
    Abstract: Multi-product inventory control is a challenging problem. Since its complexity in computation, many prior studies simplify the modeling conditions to assume that the demands are independent. In this paper, we consider a multi-product inventory system with stochastic demands which have multivariate Markov transition characteristics. We first study the demand transition process based on multivariate Markov theory, and construct a multivariate Markov demand model to forecast the stochastic demands of multiple products. Then, we propose a new optimization model of inventory decision for multi-product under the multivariate Markov demand transition pattern. By solving the optimal solution of the model, we propose an optimal (Q, R, SS) policy to decide the ordering quantity Q, ordering point R, and safety stock SS. At last, we use a numerical example to demonstrate the application feasibility and efficiency of the proposed method.
    Keywords: Demand forecasting; stochastic demand; multi-product inventory system; multivariate Markov model; optimal (Q; R; SS) policy.

  • Optimal Strategy for an Inventory Model Based on Agile Manufacturing under Imperfect Production Process   Order a copy of this article
    by Himani Dem, S.R. Singh, Leena Parasher 
    Abstract: This paper presents a production inventory model over infinite planning horizon with manufacturing process producing both perfect as well as imperfect items. Demand is stock dependent for perfect quality items and for imperfect items it depends on the reduction rate of selling price and the amount of imperfect production. The Production rate is a function of demand. Reliability of the manufacturing system is assumed to be exponentially decreasing function of time. The objective is to determine the optimal policy for production system which maximizes the total profit subject to some constraints under consideration. The results are discussed with a numerical example to illustrate the theory. The effects of important parameters on decision policy are also analysed through sensitivity analysis.
    Keywords: Imperfect production; Agile/ volume flexible manufacturing system; Stock dependent demand; Reduction rate.

  • A fuzzy rough integrated multi-stage supply chain inventory model with carbon emissions under inflation and time-value of money   Order a copy of this article
    by Soumita Kundu, Tripti Chakrabarti 
    Abstract: Growing consciousness about environment compel governments across nations to enact legislation to reduce the greenhouse gas emission from industries. Recently, many investigations have been done on supply chain model imposing carbon regulation policies. But the effect of inflation and time value of money are overlooked. Here, we extended our research by considering the concept of inflation and time value of money in fuzzy rough environment where the cost coefficient are taken as trapezoidal fuzzy rough variables. In order to obtain optimistic and pessimistic equivalent of fuzzy rough objective function we use fuzzy rough expectation operator based on trust measure theory. Optimal inventory replenishment policy is obtained by using interior point algorithm in MATLAB R2013a and sensitivity analysis is also presented to explore the effect of changes in carbon tax , net discount rate of inflation and optimistic -pessimistic parameter on the optimal solution.
    Keywords: Integrated supply chain; Shipment; Inflation; Greenhouse gas emission; Emissions tax;Fuzzy rough variable.

  • A two level supply chain model with trade credit and imperfect production process   Order a copy of this article
    by UDAYAKUMAR RAMASAMY, GEETHA KRITHIVASAN 
    Abstract: In this article, we discuss a production-distribution inventory model with a single-vendor and single buyer for defective items. The production process is imperfect and the items are inspected by a complete inspection process. Trade credit is offered by the supplier, who encourages the retailer to buy more products. The lead time is controllable. The lead time crashing cost is considered to be an exponential function of lead time. Two models are proposed in this article. In the first model, the lead time demand is allowed to follow a normal distribution and another model is framed with distribution free lead time demand. Also, the vendors setup cost is reduced by an added cost. The objective of this work is to frame the model under imperfect production process and delay in payment and to investigate the impact of product defective rate on the expected total cost of the integrated system. The optimal values of order quantity, lead time, setup cost and the number of shipments from vendor to the buyer are found such that the total expected cost of the system is minimized. Efficient computational algorithms for both the models are designed to find the optimal solution. Managerial insights are obtained with the help of numerical example and sensitivity analysis.
    Keywords: Supply chain; Setup cost; Controllable Lead time; Trade credit;.

  • Large deviations for the overflow level of G/G/1 queues in series.   Order a copy of this article
    by Karol Rosen 
    Abstract: We present a result characterizing the large deviations behavior of the total overflow level in a cycle starting with zero customers for a system of G/G/1 queues in series. We also present large deviations results for the total overflow level as seen by a random customer and in stationarity. We prove that the large deviations behavior of the total overflow level for all three distributions, in a cycle, as seen by a random customer and in stationarity, have the same decay rate. We find the most likely path to have overflow in the system. Based on those results we propose a state-independent importance sampling algorithm. We also give conditions under which that algorithm is asymptotically efficient. By means of numerical simulation, we provide evidence of the advantages of this algorithm.
    Keywords: Large deviations; G/G/1 queues in series; rare event simulation; importance sampling; exponential twist; Palm distribution; stationary distribution.

  • An M^[X]/G(a,b)/1 queueing system with Server breakdown and Repair, Stand-by server and Single vacation.   Order a copy of this article
    by Ayyappan G. Govindan, Karpagam S 
    Abstract: In this paper, we discuss a Non-Markovian batch arrival general bulk service single server queueing system with server breakdown and repair, single vacation and stand-by server. The main server may breakdown at any time during service with exponential rate alpha and in such a case the main server immediately goes for a repair which follows exponential distribution with rate eta and the service to the current batch of customers is interrupted. Such a batch of customers is transferred to the stand-by server who starts service to that batch of customers afresh. If the system size becomes less than a before main servers repair completion, then the stand-by server decides to stay in the system and starts service to the next batch only when the queue size reaches at least a. At the instant of repair completion, if the stand-by server is busy then the service to the batch of customers is interrupted and that batch of customers is transferred to the main server who starts service to that batch of customers afresh. Suppose at the instant of service completion if the queue length is less than a then the main server goes for a vacation. Otherwise, if he finds at least a customers waiting for service, say xi, then he serves a batch of size min (xi,b) customers, where b greater than or equal to a. Suppose at the instant of repair completion or at the instant of vacation completion if the system size is less than a then the main server stays in the system and waits for the next batch of arriving customers. The probability generating function of queue size at an arbitrary time and some performance measures of the system are derived. An extensive numerical result for a particular case of the model is illustrated.
    Keywords: General bulk service; Single vacation; Stand-by server; Non-Markovian queue; Breakdown and Repair.

  • Work planning optimization in ports. A simplex application   Order a copy of this article
    by Iñigo L. Ansorena 
    Abstract: This paper presents an optimization of the work plan at the gate of Barcelona Container Terminal (also known as TCB). The optimization problem is formulated in accordance with the average traffic flow as a Linear Programming (LP) problem. Constraints of the LP problem are based on the data collected at the gate of TCB. The LP problem is solved by simplex algorithm and the solution includes: First, the value of the objective function (that is the feasible solution that minimizes the number of clerks at the gate throughout a day); and second, the value, contribution to the objective, reduced cost, and range of optimality for each decision variable. Once the optimal solution has been achieved a sensitivity analysis is developed. The methodological procedure presented in this paper is general enough to be applied to any other container terminal.
    Keywords: Barcelona; container terminal; gate; linear programming; simplex.

  • Prioritizing Vulnerabilities using ANP and Evaluating their Optimal Discovery and Patch Release Time   Order a copy of this article
    by Yogita Kansal, P.K. Kapur, Uday Kumar, Deepak Kumar 
    Abstract: Risk assessment and management are the necessary actions performed by software developing organizations to ensure the continuity of the product in case of vulnerabilities. Clustering vulnerabilities on the basis of its behavior and properties is one of the approaches made by the experts as discussed in Common Weakness Enumeration that provides a hierarchy of vulnerabilities. Although vulnerability classification does not able to provide a solution as developers are still not able to decide which vulnerability class should be tackled first. Thus, a method for filtering and identifying a vulnerability class whose occurrence potential is high is needed by an organization to patch their software in timely manner. In this paper, our first step is to filter the most frequently observed vulnerability type/class through a multi-criteria decision making that involves dependency among various criteria and feedback from various alternatives, known as Analytic network process. We will also formulate a cost model so as to provide a solution to the developers facing high revenue debt because of the occurrence of highly exploited vulnerabilities belonging to the filtered group. The cost model involves the cost of identifying vulnerabilities, patching vulnerabilities, cost of testing the patches and cost of risk mitigation. The main aim of formulating the cost model is to evaluate the optimal discovery and patch release time such that the total developers cost could be minimized which is subject to risk constraints. To illustrate the proposed approach, reported vulnerabilities of Google chrome with high exploitability potential have been examined at its source level.
    Keywords: Vulnerability; Multi Criteria Decision Making; Analytic Network Process; Optimization; Patches.

  • Use of a Sine Cosine Algorithm Combined with Simpson Method for Numerical Integration   Order a copy of this article
    by Mohamed Abdelbaset, Yongquan Zhou, Ibrahim Mohamed 
    Abstract: The Sine Cosine Algorithm (SCA) is one of the most recent nature-inspired meta-heuristic optimization algorithm, which the mathematical model based on sine and cosine functions. SCA has validated excellent performance in solving continuous problems and engineering optimization problems. In this paper, we propose a new algorithm that encompasses the features of Sine Cosine Algorithm and Simpson method (SCA-SM). The proposed procedure consists of two phases: in the first phase, the of Sine cosine algorithm are used to find the optimal segmentation points on the integral interval of an integrand. In the second phase, the approximate integral value of the integrand is then calculated by a Simpson method. Numerical simulation results show that the algorithm offers an effective way to calculate numerical value of definite integrals, and it has a high convergence rate, high accuracy and robustness.
    Keywords: Sine cosine algorithm; meta-heuristics; optimization; Simpson method; numerical integration.

  • Robust and Stable flexible job shop scheduling with random machine breakdowns: Multi-objectives genetic Algorithm approach   Order a copy of this article
    by Seyed Mojtaba Sajadi, Azar Alizadeh, Mostafa Zandieh 
    Abstract: In this paper, robust and stable scheduling for a flexible job-shop problem with random machine breakdowns has been discussed. A two-stage genetic algorithm is used to generate the predictive schedule. The first stage optimizes the primary objective, which minimizes the makespan, where all data is considered to be deterministic with no expected disruptions. The second stage optimizes two objectives, makespan and stability, function in the presence of random machine breakdowns. For the second stage two different versions of multi-objective genetic algorithm, non-dominated sorting genetic algorithm II and non-dominated ranking genetic algorithm, is used. A simulator is proposed to simulate random machine breakdowns. An experimental study and analysis of variance is conducted to study the results of each multi-objective algorithm and breakdown simulator. The results of their comparison indicate that, non-dominated ranking genetic algorithm (NRGA) performs better and also shows a significant difference between various repair times in the proposed breakdown simulator.
    Keywords: Flexible job-shop scheduling problem; Machine breakdowns; Robustness; Stability.

  • Production Inventory Model of Deteriorating Items with Holding Cost, Stock, and Selling Price with Backlog   Order a copy of this article
    by Bani Mukherjee, Dharamender Singh 
    Abstract: This paper deals production inventory model with stock-dependent and selling price dependent demand. Demand rate is linearly increasing with stock and time, decreasing with a selling price of the item. Shortages are allowed and partially back ordered at the rate of decreasing waiting time of next replenishment. This model is classified as the deterioration rate is constant, and holding cost-based as constant. The model is solved numerically and analytically by minimizing the total inventory cost and maximizes the total profit at the last sensitivity analysis has been performed to show the nature of model in every parameter on the optimum solution. We have presented a solution-search procedure to find the preservation technology and optimal production time.
    Keywords: deterioration; inventory; preservation technology; production; shortage.

  • An EPQ model in the perspective of Carbon emission reduction.   Order a copy of this article
    by Sudipta Sinha, Nikunja Mohan Modak 
    Abstract: One of the major reasons behind the abnormal increase of temperature of the Earth is the uncontrollable emission of of the production houses. Industrialists are very much interested to enhance their profit only instead of greater interest of the society at large. The present paper devices to put in place an economic production quantity (EPQ) model reckoning the aspects of carbon emission and carbon trading. In the model production house or a firm house has to pay compulsory tax for carbon emission and in addition to that it incurs a penalty cost or carbon buying cost if the quantity of emitted carbon exceeds the permissible limit alloted to it. But, side by side, the manufacturer or producer is also able to earn revenue by the way of carbon trading (Cap & Trade policy) if it can control carbon emission within the permissible limit. Plantation of trees can effectively mitigate the effect of emission. Finally, some numerical examples are given to illustrate the validity and feasibility of the proposed model and comparison of result between with and without plantation are provided in tabular form. The problems are solved by the software Mathematica-7. Comprehensive sensitivity analysis of various parameters has also been carried out.
    Keywords: EPQ; Carbon emission; Carbon trading; Cap and trade; Penalty Tax; Plantation.

  • Steady state analysis of system size based balking in M/Mb/1 queue   Order a copy of this article
    by Gopal Gupta, Anuradha Banerjee 
    Abstract: In this paper we consider a single server Poisson queue where customers are served in batches of fixed size. The inter arrival time and the service time are considered to be exponentially distributed. The customers upon arrival may decide to join the system or not to join the system by observing the system length. They may join or balk the system with certain probability. Using probability generating function method we obtain the closed form expression for steady state queue length distribution, expected system (queue) length and expected waiting time of a customer in the system (queue). Finally, several numerical results are discussed in the form of table and graphs to explore the sensitivity of system parameters on key performance measures.
    Keywords: Balking; Bulk service queue; Fixed batch size; Probability generating function method; Steady state.

  • Single-vendor multi-buyer integrated inventory system for multi-item   Order a copy of this article
    by R. Uthayakumar, M. Ganesh Kumar 
    Abstract: In this paper, a single-vendor multi-buyer supply chain system is considered in which several products. The demand of this supply chain for each product is a stochastic variable and its assumed to follow a normal distribution. The lead time of receiving products from vendor to buyer is a variable which controllable by adding extra cost. During the consumption period, the shortages are allowed and they are completely backlogged in the next replenishment. The production process is assumed to be imperfect, i.e., all the finished products need not consumable, so the buyer implements a screening process to separate the defective and non-defective items and the vendor pay warranty cost for each defective item to the buyer. We investigated the Economic Order Quantity (EOQ), lead time and number of shipments such that total cost of the supply chain have been minimized. Numerical illustration and sensitivity analysis are given to show the applicability of the proposed methodology in real-world supply chain problems.
    Keywords: Controllable lead time; defective items; economic order quantity; inspection; integrated model; process quality.

  • An Inventory Model for Deteriorating Items with Time and Price Dependent Demand and Shortages Under the effect of Inflation.   Order a copy of this article
    by Sumit Saha, Nabendu Sen 
    Abstract: Variation of demand with time and price is one of the major concerns in any inventory system.. Several studies report situations where demand varies with time and price separately. A few researchers have considered the joint effect of demand with price and time on optimal solutions. Thus, a suitable inventory policy in this regard is always sought for. The paper presents an inventory model with selling price and time dependent demand, constant holding cost and time dependent deterioration. In this model, shortages are assumed to be partially backlogged. It is designed keeping in mind to optimize total inventory cost under the effect of inflation. For the solution of the model, an algorithm is proposed and illustrated with numerical values of system parameters. The optimal results are also presented graphically. Finally, sensitivity analysis is performed for different parametric values of system parameters.
    Keywords: Time and price dependent demand; Deterioration; Partial backlogging; Maximum life time of item; Inflation.

  • Ensure Optimum Profit using Linear Programming a Product-Mix of Textile Manufacturing Companies   Order a copy of this article
    by Gera Workie, Abebaw Bizuneh, Senait Asmelash 
    Abstract: An optimum profit is to be guaranteed for a rapidly changing manufacturing situation when the best product mix is produced. The product mix determination problem involves determining the optimal level of different products given a set of capacity limitations. This paper addresses a tool in operations research for determining the optimal allocation of limited resources in order to maximize profit. One of the methods widely used is linear programming, which has been proven to be a very powerful tool in making managerial decisions in a manufacturing plant about maximizing net profit. Fortunately, having well-formulated model, linear programming solution software packages help to determine the best combination of available resources. This paper considers a textile industrial unit in Ethiopia as a case study. In this company, held resources, product volumes, amount of resources required to produce single item and profit per unit of each manufactured goods have been collected. The data gathered was used to estimate the parameters of the linear programming model. The model was solved using Excel Solver software. The findings of the study show that the profit of the company can be improved by 11.8% (= (66850232.79-59793841.91/59793841.91)) if linear programing technique is used. This can be considered as a remarkable profit improvement. In addition, actual resource utilization can be significantly improved by adopting linear programing method.
    Keywords: Excel solver; Linear programming; Optimal profit; Product mix; Textile Manufacturing.

  • A Class of Always Pooling Shrinkage Testimators for the Weibull Model   Order a copy of this article
    by Zuhair Al-Hemyari 
    Abstract: Utilizing the prior information or additional information from the past in new estimation processes has been receiving considerable attention in the last few decades - as such appears from the list of the references of this paper. It may worth mentioning that the shrinkage testimators were developed orginally for the purpose of utilizing the prior information or additional prior information in new estimation problems. Most of the literature of the shrinkage testimators of the paramneters are either based on complete or censored data schemes and in single stage or double stage sampling.rnIn this paper, we have developed a general class of shrinkage testimator, and because it always uses the prior value, is called the always pooling shrinkage testimator (APST) for any parameter or distribution and two special cases, i.e. two testimators of the shape parameter of the Weibull model are studied. The expressions of bias, risk, risk ratio, relative efficiency, region and shrinkage weight function are derived.The simulation study has been developed and has revealed that the proposed cases have lower risk for the interval than the classical and existing testimators. The comparisons, recommendations, disscusions and limitations are provided in this paper.rn
    Keywords: always pooling; shrinkage; Weibull failure model; shape parameter; censored data;bias ratio; relative risk.

  • New model for improving discrimination power in DEA based on dispersion of weights   Order a copy of this article
    by Ali Ebrahimnejad, Shokrollah Ziari 
    Abstract: One of the difficulties of Data Envelopment Analysis(DEA) is the problem of deficiency discrimination among efficient Decision Making Units(DMUs) and hence, yielding large number of DMUs as efficient ones. The main purpose of this paper is to overcome this inability. One of the methods for ranking efficient DMUs is minimizing the Coefficient of Variation (CV) for inputs-outputs weights, which, was suggested by Bal et al.(2008). In this paper, we introduce a nonlinear model for ranking efficient DMUs based on modifying of the model suggested by Bal et al. and then we convert the nonlinear model proposed into a linear programming form. The motivation of this work is to linearize the existing nonlinear model which has the computational complexity.
    Keywords: Data Envelopment Analysis (DEA); Ranking; Extreme efficient; Dispersion of weights.