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Optimizing shipment, ordering and pricing policies in a two-stage supply chain with price-sensitive demand
, Article Transportation Research Part E: Logistics and Transportation Review ; Volume 45, Issue 4 , 2009 , Pages 564-571 ; 13665545 (ISSN) ; Akbari Jokar, M. R ; Sharif University of Technology
Elsevier Ltd
2009
Abstract
In this paper we focus on a two-stage supply chain consisting of one vendor and one buyer. We develop an integrated production-inventory-marketing model to determine the relevant profit-maximizing decision variable values. The model proposed is based on the joint total profit of both the vendor and the buyer, and it finds out the optimal ordering, shipment and pricing policies. We are able to ascertain the optimal decision variable values employing an analytical solution procedure. The numerical evidence suggests that it is more beneficial for the buyer and the vendor to cooperate with each other when the demand is more price sensitive. © 2008 Elsevier Ltd. All rights reserved
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 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...
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
2009
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
Developing a Joint Economic Lot Sizing (JELS) Model in Multi-Stage Supply Chains
, Ph.D. Dissertation Sharif University of Technology ; Akbari Jokar, Mohammad Reza (Supervisor)
Abstract
In this thesis, we develop seven integrated production-inventory models for two or three-stage supply chains under stochastic and/or dependent parameters. The problem is called Joint Economic Lot Sizing (JELS) and can be considered as the building block for wider supply chain systems. The first and the second researches deal with the problem in which the supply lead time between the vendor and the buyer is stochastic with uniform and exponential distribution, respectively. The numerical analyses shows that the cooperation between two partners is more critical in unpredictable purchasing environments in terms of stochastic lead-times. In the third research, we investigate four sourcing models...
Coordination in supply chain management
, Article Supply Chain Sustainability and Raw Material Management: Concepts and Processes ; 2011 , Pages 52-74 ; 9781613505045 (ISBN) ; Bolooriarabani, A ; Sharif University of Technology
2011
Abstract
The aim of this chapter is to review various perspectives on supply chain (SC) coordination issues and appreciate a range of coordination categories and mechanisms. The application of information technology in supply chain coordination (SCC) and the related cases are also studied in this chapter
Sole versus dual sourcing under order dependent lead times and prices
, Article Computers and Operations Research ; Volume 36, Issue 12 , 2009 , Pages 3272-3280 ; 03050548 (ISSN) ; Eshghi, K ; Sharif University of Technology
2009
Abstract
In this paper, we consider a dual-sourcing model with constant demand and stochastic lead times. Two suppliers may be different in terms of purchasing prices and lead-time parameters. The ordering takes place when the inventory level depletes to a reorder level, and the order is split among two suppliers. Unlike previous works in the order splitting literature, the supply lead time between vendor and buyer as well as unit purchasing prices is considered to be order quantity dependent. The proposed model finds out the optimal reorder point, order quantity and splitting proportion, using a solution procedure. Numerical results show that neglecting the relationship between ordering batch size...
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
2009
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...
Analyzing the supply chain using SCOR model in a steel producing company
, Article 40th International Conference on Computers and Industrial Engineering, 25 July 2010 through 28 July 2010 ; 2010 ; 9781424472956 (ISBN) ; Akbari, M. R ; Ssheikh Sajadieh, M ; Sharif University of Technology
2010
Abstract
Supply Chain Operations Reference (SCOR) model is developed and maintained by the Supply Chain Council (SCC). The model is a reference model which can be used to map, benchmark and improve the supply chain operations. SCOR model provides companies with a basic process modeling tool, an extensive benchmark database and defines a set of supply chain metrics. Mobarakeh Steel Company (located in Isfahan, Iran) initiated the project of studying and analyzing its supply chain performance based on the SCOR model. This paper explains the steps and the results of the project. Interviews with the managers and considering the documents on the four major subjects of planning, logistics, information flow...
An integrated vendor-buyer model with stock-dependent demand
, Article Transportation Research Part E: Logistics and Transportation Review ; Volume 46, Issue 6 , November , 2010 , Pages 963-974 ; 13665545 (ISSN) ; Thorstenson, A ; Akbari Jokar, M. R ; Sharif University of Technology
2010
Abstract
We develop an integrated vendor-buyer model for a two-stage supply chain. The vendor manufactures the product and delivers it in a number of equal-sized batches to the buyer. The items delivered are presented to the end customers in a display area. Demand is assumed to be positively dependent on the amount of items displayed. The objective is to maximize total supply chain profit. The numerical analysis shows that buyer-vendor coordination is more profitable in situations when demand is more stock dependent. It also shows that the effect of double marginalization provides a link between the non-coordinated and the coordinated case
Classification of all 1/2 BPS solutions of the tiny graviton matrix theory
, Article Journal of High Energy Physics ; Issue 4 , 2005 , Pages 1-35 ; 10298479 (ISSN) ; Torabian, M ; Sharif University of Technology
2005
Abstract
The tiny graviton Matrix theory [1] is proposed to describe DLCQ of type IIB string theory on the maximally supersymmetric plane-wave or AdS5 × S5 background. In this paper we provide further evidence in support of the tiny graviton conjecture by focusing on the zero energy, half BPS configurations of this matrix theory and classify all of them. These vacua are generically of the form of various three sphere giant gravitons. We clarify the connection between our solutions and the half BPS configuration in script N sign = 4 SYM theory and their gravity duals. Moreover, using our half BPS solutions, we show how the tiny graviton Matrix theory and the mass deformed D = 3,script N sign = 8...
A Survey on Searchable Symmetric Encryption Schemes
, M.Sc. Thesis Sharif University of Technology ; Khazaei, Shahram (Supervisor)
Abstract
Using “Searchable Encryption” enables us to encrypt the data, while preserving the possibility of running search queries. One of the most important applications of the mentioned is in Cloud Storage. As users do not trust the Cloud space, they are not inclined to store their data on the Could. The solution to this problem is of course, Cryptography. However, ordinary Cryptography methods, eliminate the data’s searchability. Hence, we need encryption schemes that code the data while retaining their searchability. So far, various schemes has been proposed that differ in their performance, security level, and usage. In this thesis, we aim to discuss and analyze these methods
NHEG mechanics: Laws of near horizon extremal geometry (thermo)dynamics
, Article Journal of High Energy Physics ; Vol. 2014, issue. 3 , 2014 ; ISSN: 11266708 ; Seraj, A ; Sheikh-Jabbari, M. M ; Sharif University of Technology
2014
Abstract
Near Horizon Extremal Geometries (NHEG) are solutions to gravity theories with SL(2, ℝ) × U(1) N (for some N) symmetry, are smooth geometries and have no event horizon, unlike black holes. Following the ideas by R. M. Wald, we derive laws of NHEG dynamics, the analogs of laws of black hole dynamics for the NHEG. Despite the absence of horizon in the NHEG, one may associate an entropy to the NHEG, as a Noether-Wald conserved charge. We work out "entropy" and "entropy perturbation" laws, which are respectively universal relations between conserved Noether charges corresponding to the NHEG and a system probing the NHEG. Our entropy law is closely related to Sen's entropy function. We also...
Dirac quantization of open strings and noncommutativity in branes
, Article Nuclear Physics B ; Volume 576, Issue 1-3 , 2000 , Pages 578-596 ; 05503213 (ISSN) ; Arfaei, H ; Sheikh-Jabbari, M. M ; Sharif University of Technology
Elsevier
2000
Abstract
We apply the Dirac bracket quantization to open strings attached to branes in the presence of background antisymmetric field and recover an inherent noncommutativity in the internal coordinates of the brane. © 2000 Elsevier Science B.V. All rights reserved
Tachyonic resonance preheating in an expanding universe
, Article Physical Review D - Particles, Fields, Gravitation and Cosmology ; Volume 81, Issue 4 , 2010 ; 15507998 (ISSN) ; Firouzjahi, H ; Sheikh Jabbari, M. M ; Sharif University of Technology
2010
Abstract
In this paper the tachyonic resonance preheating generated from the bosonic trilinear χ2 interactions in an expanding universe is studied. In λ 4/4 inflationary model the trilinear interaction, in contrast to the four-legs 2χ2, breaks the conformal symmetry explicitly and the resonant source term becomes nonperiodic, making the Floquet theorem inapplicable. We find that the occupation number of the produced χ particles has a nonlinear exponential growth with exponent ∼x3/2, where x is the conformal time. This should be contrasted with preheating from a periodic resonant source arising, for example, from the four-legs 2χ2 interaction, where the occupation number has a linear exponential...
A novel dual and triple shifted RSVP paradigm for P300 speller
, Article Journal of Neuroscience Methods ; Volume 328 , 2019 ; 01650270 (ISSN) ; Shamsollahi, M. B ; Sheikh Hassani, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Background: A speller system enables disabled people, specifically those with spinal cord injuries, to visually select and spell characters. A problem of primary speller systems is that they are gaze shift dependent. To overcome this problem, a single Rapid Serial Visual Presentation (RSVP) paradigm was initially introduced in which characters are displayed one-by-one at the center of a screen. New method: Two new protocols, Dual and Triple shifted RSVP paradigms, are introduced and compared against the single paradigm. In the Dual and Triple paradigms, two and three characters are displayed at the center of the screen simultaneously, holding the advantage of displaying the target character...
Work hardening of Duratherm 600 cobalt superalloy using repetitive corrugation and straightening process
, Article Russian Journal of Non-Ferrous Metals ; Volume 51, Issue 1 , February , 2010 , Pages 59-61 ; 10678212 (ISSN) ; Paimozd, E ; Hashemi, S. M ; Sharif University of Technology
2010
Abstract
In this paper, the effect of repetitive corrugation and straightening (RCS) process on hardness of Duratherm 600 superalloy has been investigated. To do so, the RCS was carried out until 25 cycles using multiple teeth corrugative setup that the rotation of sample with 90° between cycles was utilized. The results show that the increasing of cycle number enhances the value of hardness. Also, the microstructures of samples are an evidence of slipbands formation during RCS showing the applied strain on the material. As a result, the increasing of hardness can be attributed to formation of subgrains, LAGBs and hcp martensitic plates at large strains
Local excitation of a perfectly conducting slab with finite or infinite number of slits and the role of proper complex waves
, Article IEEE Transactions on Antennas and Propagation ; Volume 68, Issue 8 , 2020 , Pages 6154-6161 ; Rejaei, B ; Memarian, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The physics and modes of radiation in structures exhibiting extraordinary transmission (ET) can be best studied using Green's function formalism. In this article, we find the electromagnetic response to local excitation of a canonical structure exhibiting ET, and investigate the role of complex waves. The structure is a perfectly conducting slab having a finite or infinite number of through-slits. The solution breaks up the field into even and odd modes, and solves for the fields of the structure with a finite number of slits, by setting up an integral equation. The solution is then extended to find Greens' function of the infinitely periodic structure. The dispersion relations of the...
Investigation into characteristics of Portevin-Le Chatelier effect of an Al-Mg Alloy
, Article Journal of Materials Engineering and Performance ; Volume 19, Issue 9 , 2010 , Pages 1264-1267 ; 10599495 (ISSN) ; Sharif University of Technology
2010
Abstract
In this study, the plastic instabilities associated with the Portevin-Le Chatelier (PLC) and their effects on the mechanical properties and the fracture surfaces have been investigated for AA 5083. Tensile tests were performed at various temperatures and strain rates in order to do so. Then, serrated and smooth yielding domains were determined in Ln ε̇-1/T diagram. The stress-strain curves related to the serrated domain show the values of flow stress decreases by increasing the strain rate at a constant temperature. In addition, the plot of critical strain versus imposed strain rate indicates an inverse manner at very low strain rates. It is confirmed that the type of PLC bands alters the...
Extremal rotating black holes in the near-horizon limit: Phase space and symmetry algebra
, Article Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics ; Volume 749 , October , 2015 , Pages 443-447 ; 03702693 (ISSN) ; Hajian, K ; Seraj, A ; Sheikh Jabbari, M. M ; Sharif University of Technology
Elsevier
2015
Abstract
We construct the NHEG phase space, the classical phase space of Near-Horizon Extremal Geometries with fixed angular momenta and entropy, and with the largest symmetry algebra. We focus on vacuum solutions to d dimensional Einstein gravity. Each element in the phase space is a geometry with SL(2,R)×U(1)d-3 isometries which has vanishing SL(2,R) and constant U(1) charges. We construct an on-shell vanishing symplectic structure, which leads to an infinite set of symplectic symmetries. In four spacetime dimensions, the phase space is unique and the symmetry algebra consists of the familiar Virasoro algebra, while in d> 4 dimensions the symmetry algebra, the NHEG algebra, contains infinitely many...