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#### Evaluating Availability of Data Storage Systems and Its Impact on Total Cost of Ownership

, Ph.D. Dissertation Sharif University of Technology ; Asadi, Hossein (Supervisor)
Abstract

From small businesses to large organizations and corporations, data is the most valuable and most vulnerable asset. The exponential explosion of digital data, known as Big Data, has evolved data storage industry and mandates new solutions for handling dependability and performance demands. Now Exa-scale datacenters employ millions of storage media that translates to multiple failures per hour. The storage design problem gets more dimensions by the emerge of Non-Volatile Memories (NVMs) and Solid-State Drives (SSDs) that have limited endurance. Both industry and academy continuously struggle to evaluate and improve the dependability of data storage systems and minimize the chance of data...

#### The Application of Acceptance Sampling Plans on the Reliability of k-out-of-m Systems

, M.Sc. Thesis Sharif University of Technology ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
Abstract

Modern engineered products from individual parts to large systems shall be designed and produced to meet the required reliability at the time of the mission. A well-known type of systems in reliability issues is called k-out-of-m system. There are two common ways to enhance the reliability of these systems. These are: (1) increasing component reliability through more stringent acceptance sampling, and (2) improving system reliability through increases in component redundancy. The objective of this study is to determine the optimal plan in k-out-of-m systems. In fact, we seek to find an optimal plan for a decision maker considering his or her limitations such as cost and reliability. An...

#### One-for-one period policy and a series of suppliers

, Article 2009 International Conference on Computers and Industrial Engineering, CIE 2009, 6 July 2009 through 9 July 2009, Troyes ; 2009 , Pages 902-906 ; 9781424441365 (ISBN) ; Pirayesh Neghab, M ; Haji, A ; Sharif University of Technology
Abstract

The purpose of this paper is to adopt and analyze a new ordering policycalled one-for-one-period policy in a multi-echelon supply chain consisting ofone retailer and a series of TV suppliers. The main advantage of adopting theone-for-one-period (7,7) ordering policy for retailers is the elimination ofuncertainty for supplier which leads to total elimination of the safety stocksat all suppliers. This in turn leads to the reduction of the total system costsand in case any supplier's ordering cost is negligible it can even eliminate theneed for him to carry any inventory. In addition to this advantage, thenumerical results show that the application of this new policy for the retailerleads to...

#### Optimal batch production with minimum rework cycles and constraint on accumulated defective units

, Article 2009 IEEE/INFORMS International Conference on Service Operations, Logistics and Informatics, SOLI 2009, Chicago, IL, 22 July 2009 through 24 July 2009 ; 2009 , Pages 633-638 ; 9781424435418 (ISBN) ; Haji, A. R ; Haji, R ; Sharif University of Technology
2009

Abstract

This paper deals with the issue of economic batch quantity (EBQ) in a single machine system in which defective items are produced in each cycle of production. The accumulated defective items produced in a period, consisting of several equal cycles, are all reworked in the last cycle of this period called the rework cycle. At the end of each period the whole process will start all over again. We assume that there is a limitation on the total defective items. We also do not adopt the restriction that the rework process rate be equal to the normal production rate. In addition we assume that there is a set up time for rework process. Further we assume that the number of rework cycles be as small...

#### Developing a coordinated vendor-buyer model in two-stage supply chains with stochastic lead-times

, Article Computers and Operations Research ; Volume 36, Issue 8 , 2009 , Pages 2484-2489 ; 03050548 (ISSN) ; AkbariJokar, M. R ; Modarres, M ; Sharif University of Technology
2009

Abstract

This paper develops an approach to determine the optimal production and shipment policy for an integrated vendor-buyer problem. The vendor manufactures the product in batches at a finite rate and ships the output to the buyer. All shipments to the buyer are equal-sized batches. Despite previous papers in the literature, we assume that the supply lead-time between vendor and buyer is stochastic and shortage is also allowed. The objective is to minimize the expected total cost of both buyer and vendor. We derive the expected annual integrated total cost function and propose an analytic solution procedure to determine the optimal policy. To illustrate the significance of cost-reduction of the...

#### Random rework rate: Obtaining economic batch quantity

, Article 38th International Conference on Computers and Industrial Engineering 2008 ; Volume 3 , 2008 , Pages 3030-3033 ; 9781627486828 (ISBN) ; Haji, A ; Sharif University of Technology
2008

Abstract

In this paper we intend to obtain the economic batch quantity (EBQ) for an imperfect production system in which defective items are produced in each cycle of production. In the litrature of inventory control when the rework is done on defective items it is assumed that the production rate of the rework process is constant and the setup time for rework is ignored. Here we assume that due to the nature of the rework process its production rate is different from the normal production rate and is stochastic. We also assume that after each production run the rework process starts immediately after a non-zero setup time for the rework. Further we assume that the inspection costs during the normal...

#### Economic batch quantity with rework and storage capacity constraint

, Article 38th International Conference on Computers and Industrial Engineering 2008 ; Volume 3 , January , 2008 , Pages 3034-3038 ; 9781627486828 (ISBN) ; Haji, A ; Paseban, M ; Sharif University of Technology
2008

Abstract

In this paper we consider a single stage production system in which defective items are produced in each cycle of production. In the litrature of inventory control when the rework is done on defective items it is assumed that the storage space is unlimited and the setup time for rework is ignored. Here we assume that the storage space is limited and due to the nature of the rework process its production rate is different from the normal production rate. We also assume that after each production run the rework process starts immediately after a non-zero setup time for the rework. Further we assume that the unit operation processing cost during the normal production and rework proccessing...

#### Cost derivation of a dyadic supply chain with time lag information sharing

, Article 37th International Conference on Computers and Industrial Engineering 2007, Alexandria, 20 October 2007 through 23 October 2007 ; Volume 3 , 2007 , Pages 1709-1714 ; 9781627486811 (ISBN) ; Haji, R ; Shenas, N. Y ; Sharif University of Technology
2007

Abstract

In this paper we consider a dyadic supply chain consisting of one warehouse and one retailer with information exchange. We assume that the demand process to the retailer is a Poisson process and transportation times are constant. The retailer applies continuous review (R,Q)-policy. When the retailer's inventory position reaches R+s she sends information about her customer demand and inventory activities to the supplier. The supplier receives this information after a constant time lag. The supplier starts with m initial batches (of size Q), and places an order in a batch of size Q to an outside source immediately after receiving the information from the retailer. In this paper using the idea...

#### Temperature-aware Power Dissipation Analysis in Hyperscale Data Centers

, Ph.D. Dissertation Sharif University of Technology ; Sarbazi-Azad, Hamid (Supervisor)
Abstract

Hyperscale cloud data center (HCDC) (a.k.a., hyperscale data center) is the backbone of a wide variety of Internet services such as web-hosting, ecommerce, social networking, software as a service (SaaS), platform as a service (PaaS), application as a service (AaaS), and cloud computing.HCDC platforms consist of massive parallel processing, high utilization rate, and high volume storage that cost hundreds of million dollars.The increased demand for various Internet services and the subsequent dramatic growth in HCDC platforms, have caused an exponential increase in utilization of energy. With energy costs on the rise and global attention focused on carbon footprints, organizations are...

#### Due date assignment in single machine with stochastic processing times

, Article International Journal of Production Research ; Volume 51, Issue 8 , 2013 , Pages 2352-2362 ; 00207543 (ISSN) ; Salmasi, N ; Sharif University of Technology
2013

Abstract

This paper considers two different due date assignment and sequencing problems in single machine where the processing times of jobs are random variables. The first problem is to minimise the maximum due date so that all jobs are stochastically on time. It is shown that sequencing the jobs in decreasing service level (DSL) order optimally solves the problem. The results are then extended for two special cases of flow shop problem. The other problem is to minimise a total cost function which is a linear combination of three penalties: penalty on job earliness, penalty on job tardiness, and penalty associated with long due date assignment. The assignment of a common due date and distinct due...

#### 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...

#### Cooperative supply chain management using a grid-based optimizer

, Article Proceedings - 2010 IEEE 17th International Conference on Industrial Engineering and Engineering Management, IE and EM2010, 29 October 2010 through 31 October 2010 ; October , 2010 , Pages 1300-1305 ; 9781424464814 (ISBN) ; Najmi, M ; Fayazbakhsh, K ; Sharif University of Technology
2010

Abstract

A cooperative supply chain seeks to coordinate its members to produce and distribute products along the chain, for minimum overall costs to satisfy customer demand. An integrated multi-period, multiple product and multiple stage supply chain is formulated using a flow networks framework. A Cooperative Supply Chain Optimizer (CSCO), as a central software entity taking advantage of Grid technology, connects and gathers necessary operational information from members of the corporate supply chain. The CSCO then guides supply chain members on ordering decisions, for a minimum overall cost of the entire supply chain, while continuously re-directing the members as new data becomes available. The...

#### A method for optimal coordinated insulation design of transmission line

, Article Australian Journal of Electrical and Electronics Engineering ; Volume 7, Issue 3 , 2010 , Pages 211-223 ; 1448837X (ISSN) ; Vakilian, M ; Blackburn, T. R ; Sharif University of Technology
Abstract

The first step in the accepted methods of overhead transmission line insulation coordination is to specify a reliability criterion, and then based on this constraint the most economic insulation design is sought. While the objective of an optimal insulation design method is to find an insulation design that minimises the total cost (the sum of the installation cost, operational cost and cost of failure), each of the cost components can be determined on a per-year basis taking into account the equipment's lifetimes. In this paper, through application of ATP software and realising the total cost of different transmission line designs, a set of alternative insulation designs using various surge...

#### A Corporate Supply Optimizer with flow network

, Article Scientia Iranica ; Volume 17, Issue 1 E , June , 2010 , Pages 70-83 ; 10263098 (ISSN) ; Fayazbakhsh, K ; Ghasemzadeh, F ; Sharif University of Technology
2010

Abstract

A holding or a multi-business corporate seeks to coordinate its supply for minimum overall costs. A Corporate Supply Optimizer (CSO), as a central entity taking advantage, of the notion of flow networks, gathers necessary operational information from members of the corporate supply chain. The CSO then guides supply chain members on ordering decisions for a minimum overall cost for the entire supply chain. Its computational engine models the entire supply chain with multiple members in four stages to satisfy customer demand. The CSO seeks a solution with minimum total costs, unlike noncooperative supply chains where individual members compete, to optimize, their local costs. The existing...

#### Optimal batch production with rework and non-zero setup cost for rework

, Article 2009 International Conference on Computers and Industrial Engineering, 6 July 2009 through 9 July 2009 ; 2009 , Pages 857-862 ; 9781424441365 (ISBN) ; Haji, R ; Haji, A ; Sharif University of Technology
Abstract

This paper attempts to develop the optimal solution for an inventoryproblem consisting of a single machine which produces items some of which may bedefective. We assume that no shortages are allowed and all defective items areto be reworked. Setup cost for rework and waiting time of defectives areconsidered. We consider two different policies where in the first policy in eachcycle after the regular production the machine is setup for the rework ofdefectives of the same cycle. In the second policy several cycles constitute aperiod. All the defectives produced in the period are reworked in the last cycleof that period. At the end of the rework cycle the whole process starts allover again. One...

#### One-for-one period policy in a two-echelon inventory system with commoncycle and poisson demand rate for retailers

, Article 2009 International Conference on Computers and Industrial Engineering, CIE 2009 ; 2009 , Pages 831-834 ; 9781424441365 (ISBN) ; Tayebi, H ; Haji, B ; Sharif University of Technology
Abstract

This paper deals with a two-echelon inventory system consisting of onesupplier and N retailers. Each retailer faces an independent Poisson demand withthe same rate and applies a new ordering policy called one-for-one- periodordering policy for its inventory control. In this ordering policy the ordersize is equal to one and the time interval between any two consecutive ordersforms a common fixed cycle. Thus, the supplier faces a deterministic demand andadopts a deterministic inventory policy. At each cycle he orders a batch of sizeN to his own supplier. Upon receipt of each batch he sends 1 unit of theproduct to each retailer with a transportation cost. In this paper, for theabove system we...

#### Concurrent project scheduling and material planning: a genetic algorithm approach

, Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 91-99 ; 10263098 (ISSN) ; Shadrokh, S ; Hassanzadeh, F ; Sharif University of Technology
Abstract

Scheduling projects incorporated with materials ordering results in a more realistic problem. This paper deals with the combined problem of project scheduling and material ordering. The purpose of this paper is to minimize the total cost of this problem by determining the optimal values of activity duration, activity finish time and the material ordering schedule subject to constraints. We employ a genetic algorithm approach to solve it. Elements of the algorithm, such as chromosome structure, unfitness function, crossover, mutation and local search operations are explained. The results of the experimentation are quite satisfactory

#### 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....

#### One-for-one period policy in a two-echelon inventory system with poisson demand and constraint on total lost sales

, Article 2009 IEEE/INFORMS International Conference on Service Operations, Logistics and Informatics, SOLI 2009, Chicago, IL, 22 July 2009 through 24 July 2009 ; 2009 , Pages 74-77 ; 9781424435418 (ISBN) ; Haji, B ; Sharif University of Technology
2009

Abstract

In this paper we consider a two- echelon inventory system consisting of one supplier and a number of retailers with independent Poisson demand. Unsatisfied demands in retailers are lost and it is assumed that there is a constraint on total lost sales for the system. Each retailer applies a new ordering policy called one-fer-one-peried ordering policy for its inventory control. In this ordering policy the order size is equal to one and the time interval between any two consecutive orders is fixed. Thus, the supplier faces a uniform and deterministic demand originated from each retailer and applies one for one ordering policy in response to orders received from all retailers. For this system...

#### A queuing approach for making decisions about order penetration point in multiechelon supply chains

, Article International Journal of Advanced Manufacturing Technology ; Volume 63, Issue 1-4 , 2012 , Pages 359-371 ; 02683768 (ISSN) ; Modarres, M ; Khondabi, I. G ; Fathi, M ; Sharif University of Technology
2012

Abstract

This study is dedicated to order penetration point (OPP) strategic decision making which is the boundary between make-to-order (MTO) and make-to-stock (MTS) policies. A multiproduct multiechelon production supply chain is considered where the first production stage manufactures semifinished products based on an MTS policy to supply the second production stage which operates on the MTO policy. The producer desires to find the optimal fraction of processing time fulfilled by supplier and optimal semifinished products buffer capacity in OPP. To calculate system performance indexes, the matrix geometric method is employed. Afterward, optimal solutions are obtained by enumeration and direct...