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inventory-modeling
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Inventory Management in Two-Echelon Chain with Shortage
, M.Sc. Thesis Sharif University of Technology ; Haji, Alireza (Supervisor)
Abstract
The thesis has considered a two-echelon supply chain which consists of one central warehouse and multiple retailers. Assume all retailers and the warehouse follow a continuous review inventory model. The costumer’s demand comes to retailers in a Poisson process. The retailers replenish their stocks from the warehouse in an (S-1, S) inventory control policy and the warehouse replenishes its stocks in an (r, Q) inventory control policy from an external supplier with an infinite capacity. It may be more representative to model stockouts as lost sales when the retailers are in a competitive market or in monopoly markets all demand will be backorder. Therefore, if the market situation goes...
Analysis of a Two-Echelon Queuing-Inventory System with M/M/c Product System
, M.Sc. Thesis Sharif University of Technology ; Hajji, Alireza (Supervisor)
Abstract
The subject of this thesis is a two-echelon inventory system with a manufacturer and multiple distribution centers (DCs) that satisfy the demand originating from multiple sources. Demand from each source follows an independent Poisson process. The transportation times between the manufacturer and the DCs are assumed to be positive which may require keeping inventory at both the warehouse and the DCs. Inventory in both echelons is managed using the base-stock policy. The manufacturer works with
M/M/c product system. The cost of demand fulfillment for each DC consists of inventory holding and backlog costs. The objective is to determine the optimal base-stock levels at the DC
M/M/c product system. The cost of demand fulfillment for each DC consists of inventory holding and backlog costs. The objective is to determine the optimal base-stock levels at the DC
Developing Inventory Control Policies with No Ordering Costs in Two-Echelon Supply Chains
, Ph.D. Dissertation Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
This dissertation attempts to develop four inventory control models for two-echelon supply chains. For the all models, the retailers face Poisson demand and lost sales during a stockout. There is also a time-dependent holding cost and a cost per unit of lost sales. However, there is no (or negligible) cost associated with placing an order.
For the first model, we consider a two-echelon inventory system with one central warehouse and a number of retailers. The central warehouse applies (R, Q) policy and retailers apply base stock policy. In this model, we approximate the arrival process of the central warehouse and obtain the total cost of the system, as well as the optimal solution....
For the first model, we consider a two-echelon inventory system with one central warehouse and a number of retailers. The central warehouse applies (R, Q) policy and retailers apply base stock policy. In this model, we approximate the arrival process of the central warehouse and obtain the total cost of the system, as well as the optimal solution....
Analysis of a Two-Echelon Inventory Model with Lost Sales and Stochastic Demand using Continuous-Time Markov Chain
, M.Sc. Thesis Sharif University of Technology ; Haji, Rasoul (Supervisor)
Abstract
In this paper, we studied a two-echelon inventory system which consists of one central warehouse and one retailer. All installations follow base stock inventory management policy. The customers arrive at retailer according to Poisson distribution. The demand is satisfied when both central warehouse and retailer have positive on-hand inventory. Otherwise, the demand is lost. The lead time of central warehouse and the time needed to replenish orders of retailer are assumed to be exponentially distributed. The purpose of this study is to minimize the expected long-run total cost of the system per unit time. Total cost of the system includes holding costs of central warehouse and retailer, cost...
, M.Sc. Thesis Sharif University of Technology ; Shavandi, Hassan (Supervisor)
Abstract
In this research, the location-inventory problem is developed in order to design a distribution center considering customers behavior. We consider two groups of customers who have different behavior on purchase. The customers may order the product via internet and receive it at their location or go to the nearest store and buy the product at the store center. We model the problem as a multi-objective programming model. The objectives are maximizing the profit as well as maximizing the market share. The model locates the distribution centers (DC) and allocates the customers to DCs. Two heuristic algorithms developed to solve the model: non- dominated Sorting Genetic Algorithm (NSGA-II) and...
Development of Location-Inventory Model in Dual Channel Supply Chain and Solving the Model by Tabu Search Algorithm
,
M.Sc. Thesis
Sharif University of Technology
;
Hajji, Rasool
(Supervisor)
Abstract
This thesis presents a location- inventory model for dual-channel supply chains .Dual-channel supply chains have two channels for sale the traditional in-store (retail) channel and the online (retail) channel.The model assigns online demands to the capacitated stores currently serving in-store demands. Keeping the delivery network of the in-store demands unchanged, the model aims at minimizing the summation of transportation cost, inventory cost, and fixed handling cost in the system while assigning the online demands. We assume that at the beginning of each period a distribution center which just distributes products to the stores, follows an order-up-to policy which increases the total...
On competence of vendor managed inventory in supply chains using basic mathematical inventory models
, Article Scientia Iranica ; Vol. 21, issue. 3 , 2014 , p. 1061-1071 ; Haji, A ; Gharibi, M ; Sharif University of Technology
Abstract
In this study, a two-echelon single-vendor supply chain is selected to do a cost-based comparison between short-term performances of a Vendor Managed Inventory (VMI) and a Retailer Managed Inventory (RMI). While the inventory costs include ordering and storing expenses, the rate of consumption and the price of goods are constant, the rate of production and pace of transportation are infinite and shortage is not allowed. This paper, after a comprehensive literature review, is followed by three cases of single retailer, n-retailer and two-retailer chains. Unlike the second case, in the first case, VMI shows an absolute superiority to RMI, and this is the reason for devising the third case in...
Optimizing a multi-vendor multi-retailer vendor managed inventory problem: Two tuned meta-heuristic algorithms
, Article Knowledge Based Systems ; Volume 50 , September , 2013 , Pages 159-170 ; 09507051 (ISSN) ; Mousavi, S. M ; Niaki, S. T. A ; Sadeghi, S ; Sharif University of Technology
2013
Abstract
The vendor-managed inventory (VMI) is a common policy in supply chain management (SCM) to reduce bullwhip effects. Although different applications of VMI have been proposed in the literature, the multi-vendor multi-retailer single-warehouse (MV-MR-SW) case has not been investigated yet. This paper develops a constrained MV-MR-SW supply chain, in which both the space and the annual number of orders of the central warehouse are limited. The goal is to find the order quantities along with the number of shipments received by retailers and vendors such that the total inventory cost of the chain is minimized. Since the problem is formulated into an integer nonlinear programming model, the...
A replenishment policy for perishable products with non-linear holding cost under stochastic supply lead time
, Article International Journal of Advanced Manufacturing Technology ; Volume 64, Issue 5-8 , 2013 , Pages 1087-1098 ; 02683768 (ISSN) ; Baboli, A ; Akbari Jokar, M. R ; Sharif University of Technology
2013
Abstract
The development and application of inventory models for deteriorating items is one of the main concerns of subject matter experts. The inventory models developed in this field have focused mainly on supply chains under the assumption of constant lead time. In this study, we develop an inventory model for a main class of deteriorating items, namely perishable products, under stochastic lead time assumption. The inventory system is modeled as a continuous review system (r, Q). Demand rate per unit time is assumed to be constant over an infinite planning horizon and the shortages could be backordered completely. For modeling the deterioration process, a non-linear holding cost is considered....
An integrated vendor-buyer inventory model with partial backordering
, Article Journal of Manufacturing Technology Management ; Volume 23, Issue 7 , 2012 , Pages 869-884 ; 1741038X (ISSN) ; Jokar, M. R. A ; Sharif University of Technology
2012
Abstract
Purpose - The purpose of this paper is to analyze the effects of supply chain coordination on inventory management while the retailer inventory cycle consists of a shortage period and the backorder rate linearly decreases as a function of shortage duration. It is intended to consider how on-hand inventory and shortage durations are altered when the decisions are centralized. Design/methodology/approach - Mathematical modelling of inventory costs for the retailer and the vendor is used to formulate objective functions. The vendor sets his inventory period as an integer multiple (n) of the retailer inventory cycle in which the integer multiple is a decision variable. Solution spaces of models...
Centralized replenishment policy for deteriorating items in a three echelon supply chain under stochastic lead time
, Article IFAC Proceedings Volumes (IFAC-PapersOnline) ; Volume 14, Issue PART 1 , 2012 , Pages 493-498 ; 14746670 (ISSN) ; 9783902661982 (ISBN) ; Akbari Jokar, M ; Baboli, A ; Campagne, J. P ; Sharif University of Technology
2012
Abstract
One of the significant problems faced in inventory management is how to control and maintain the inventories of deteriorating items. Most of studies developed in this field, assumed supply lead time is fixed while that is hard to be exactly determined in the majority procurement systems. Also, most of integration inventory models for supply chains with a deterioration item have been developed for two-echelon supply chains. In this paper, in order to fill these gaps, we focus on optimally determining replenishment policy for deteriorating items among all the partners in a three echelon supply chain with stochastic supply lead time for the buyer. For modeling the deterioration process, a...
A constrained multi-product pricing and inventory control problem
, Article Applied Soft Computing Journal ; Volume 12, Issue 8 , 2012 , Pages 2454-2461 ; 15684946 (ISSN) ; Mahlooji, H ; Nosratian, N. E ; Sharif University of Technology
Elsevier
2012
Abstract
The aim of this article is presenting a new constrained multi-product pricing and inventory model in which perishable products are put into three categories: substitute, complementary and independent. The general demand is found by considering the relations of different products and the impact of their prices. The goal of the model is deciding on the prices as well as the inventory and production decisions in order to maximize the total profit. The derived model is a non-linear programming model and a genetic algorithm is developed for its solution. To enhance the performance of our genetic algorithm, we apply the Taguchi experimental design method to tune the parameters of the algorithm....
One for one period policy for perishable inventory
, Article Computers and Industrial Engineering ; Volume 79 , January , 2015 , Pages 10-17 ; 03608352 (ISSN) ; Haji, A ; Haji, R ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Recently, for zero ordering cost a new ordering policy named (1, T), in which the time interval between two consecutive orders and the value of the order size are both constant, have been developed for nonperishable products. In this paper, the (1, T) policy is developed for perishable products. Using an analogy among this inventory model, a queueing model with impatient customers, and a finite dam model, the long-run average total cost function of the inventory system is derived. It is observed that the total cost rate is independent from the lead time as is for nonperishable products. Since analyzing the convexity of the model is extremely complicated, a proposition is proved to define a...
A multi-product pricing-inventory model with stochastic demand and products interdependency
, Article Proceedings - 3rd International Conference on Information Management, Innovation Management and Industrial Engineering, ICIII 2010, 26 November 2010 through 28 November 2010 ; Volume 2 , Nov , 2010 , Pages 227-231 ; 9780769542799 (ISBN) ; Shavandi, H ; Sharif University of Technology
2010
Abstract
In this paper, we study a pricing-inventory model with multiple interdependent products and stochastic demand. In the relevant literature, there are many researches that try to optimize the inventory or price independently and also optimizing joint inventory and pricing problems for single product. But joint optimization of inventory and pricing for multiple interdependent products is relatively new and still there are many potential research gaps in this area. We show that the multiplicative demand form problem, that we develop, is a convex nonlinear programming (NLP) model or is convertible to it. We also provide upper and lower bounds for the additive demand form model
Optimizing a joint economic lot sizing problem with price-sensitive demand
, Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 159-164 ; 10263098 (ISSN) ; Sheikh Sajadieh, M ; Sharif University of Technology
Abstract
This paper considers the problem of a vendor-buyer integrated production-inventory model. The vendor manufactures the item at a finite rate and delivers the final goods at a lot-for-lot shipment policy to the buyer. We relax the assumption of uniform demand in the hitherto existing joint economic lot sizing models and analyze the problem where the end customer demand is price-sensitive. The relation between demand and price is considered to be linear. The model proposed, based on the integrated expected total relevant profits of both buyer and vendor, finds out the optimal values of order quantity and mark-up percentage, using an analytical approach. Some numerical examples are also used to...
Optimal integrated inventory model with lost sale and backordering
, Article 2009 International Conference on Computers and Industrial Engineering, CIE 2009, 6 July 2009 through 9 July 2009, Troyes ; 2009 , Pages 825-830 ; 9781424441365 (ISBN) ; Amiri Elyasi, K ; Save Shemshaki, A ; Sharif University of Technology
Abstract
Rapid market changes, explosion of product varieties and short life cycleshave increased competition in today's global markets. It is obvious that intoday's competitive markets, collaboration between the vendor and the buyer isnecessary to reduce the joint inventory cost and the response time of thevendor-buyer system. Joint Economic Lot sizing Problem has been extended in manydifferent directions. Shortage is not allowed in the most of the previousresearches. A few of them considered shortage backordering as a result ofimperfect quality. The purpose of this paper is to recast the Joint economic lotsizing model to be more relevant to current situations, where lost sales and/orbackorders are...
A location-inventory model considering a strategy to mitigate disruption risk in supply chain by substitutable products
, Article Computers and Industrial Engineering ; Volume 108 , 2017 , Pages 213-224 ; 03608352 (ISSN) ; Shavandi, H ; Rahmani, D ; Sharif University of Technology
Abstract
In this paper we consider a multiple products inventory location problem with disruption. Disruptions may occur in any supply chain due to several reasons such as earthquakes, floods, fires, labor strikes, terrorist attacks, equipment breakdowns and economic crises. We develop a model by assuming that facilities may fail partially in case of disruption and considering substitutable products as a strategy to mitigate the risk of disruption. The developed model is a non-linear integer programming model and NP-Hard. To solve the model, a hybrid algorithm including Tabu Search (TS) and Variable Neighborhood Search (VNS) is proposed. Numerical results show reasonable performance of the algorithm...
An optimal integrated lot sizing policy of inventory in a bi-objective multi-level supply chain with stochastic constraints and imperfect products
, Article Journal of Industrial and Production Engineering ; Volume 35, Issue 1 , 2018 , Pages 6-20 ; 21681015 (ISSN) ; Pasandideh, S. H. R ; Akhavan Niaki, S. T ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
This paper provides a developed mathematical model to derive the optimal integrated lot sizing in a multi-level supply chain with imperfect quality products. The developed mathematical model has a bi-objective function, with conflicting goals, minimizing the chain inventory costs and maximizing the chain total profit aided to find optimum policy for integrated lot sizing. We further actualize the problem by assuming multiple stochastic constraints. The mathematical formulation of the problem is stochastic, nonlinear, and large. In this regard, the interior point algorithm that is developed as more effective algorithm with less iteration is used for solving the recent convex nonlinear model....
An integrated vendor-buyer cooperative model under stochastic supply lead-time
, Article International Journal of Advanced Manufacturing Technology ; Volume 41, Issue 9-10 , 2009 , Pages 1043-1050 ; 02683768 (ISSN) ; Akbari Jokar, M. R ; Sharif University of Technology
2009
Abstract
This paper presents a single-vendor, single-buyer integrated inventory model. We relax the assumption of deterministic lead-time in the hitherto existing joint economic lot sizing (JELS) models and analyze the problem where the buyer lead-time is a stochastic variable. Moreover, we consider the situation in which shortage is allowed. The vendor produces the product in batches and periodically delivers final goods at a fixed lot size to the customer, who has a constant demand rate. The proposed model, based on the integrated expected total relevant costs of both buyer and vendor finds out optimal values of reorder point, order quantity, and number of shipments, using a solution procedure....
Developing a partial backlogging deteriorating inventory model with selling price dependant demand rate and cycle length dependant selling price
, Article 2008 IEEE International Conference on Industrial Engineering and Engineering Management, IEEM 2008, Singapore, 8 December 2008 through 11 December 2008 ; January , 2008 , Pages 198-202 ; 9781424426300 (ISBN) ; Sabahno, H ; Haji, R ; Sharif University of Technology
2008
Abstract
In this paper, we develop an inventory model with price dependant demand rate, under time value of money and inflation, finite time horizon, exponential backlogging rate and exponential deterioration rate with the objective of maximizing the present worth of the total system profit. Using a dynamic programming based solution algorithm, we are able to find the optimal sequence of the cycles and also to obtain different optimal selling prices and optimal order quantities for the cycles with unequal lengths, which have never been done before for our model. We also use a proper numerical example to show accuracy of the solution procedure. © 2008 IEEE