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General bounds for the optimal value of retailers' reorder point in a two-level inventory control system with and without information sharing
, Article International Journal of Advanced Manufacturing Technology ; Volume 48, Issue 1-4 , April , 2010 , Pages 383-393 ; 02683768 (ISSN) ; Eshragh Jahromi, A ; Akhavan Niaki, S ; Sharif University of Technology
2010
Abstract
In this study, an inventory system consisting of a single product, one supplier, and multiple identical retailers is considered. Each retailer replenishes inventory from the supplier according to the well known (R,Q) policy. Transit times are constant and retailers face independent Poisson demand. The supplier utilizing the retailers' information in decision making for replenishment policy with a given order size starts with m initial batches (of size Q) and places an order in a batch of size Q to an outside source when a new order is placed. In this inventory system, excess demand is backordered, delayed orders are satisfied on a first-come first-serve basis, and no partial shipment is...
An efficient procedure for computing an optimal (R, Q) policy in continuous review systems with poisson demands and constant lead time
, Article Scientia Iranica ; Volume 16, Issue 2 E , 2009 , Pages 128-137 ; 10263098 (ISSN) ; Eshraghnia Jahromi, A ; Modarres Yazdi, M ; Sharif University of Technology
2009
Abstract
In this paper, a continuous review inventory system is considered in which an order in a batch of size Q is placed immediately after the inventory position reaches R. Transportation time is constant and demands are assumed to be generated by a stationary Poisson process with one unit demand at a time. Demands not covered immediately from the inventory are backordered. In a recent paper, the exact evaluation of batch-ordering policies for two-level inventory systems was derived. This evaluation is based on a recursive procedure for determining the exact policy costs in case of one-for-one replenishment policies. In this paper, we show how this result can be applied to find the optimal...
Determination of the Optimal Policy in a Two Level Inventory System, Using Information Sharing, with a Different Order Size
, Ph.D. Dissertation Sharif University of Technology ; Eshraghniaye Jahromi, Abdolhamid (Supervisor)
Abstract
To coordinate between different echelons in supply chains, it is necessary to analyze the multi-echelon inventory systems. Access to advanced technologies in Information Technology make some changes in the inventory management in these systems. Theses technologies that were gradually got inexpensive are attractive for researchers of the multi-echelon inventory systems. Using theses technologies, the information that leads to costs reduction in a supply chain is accessible economically. In this thesis, first efficient solutions for Base Stock and Reorder point, Quantity of order policies will be derived. Then, a serial two-level supply chain comprised of one retailer and one supplier will be...
A new approach to find the optimal solution for base stock policies
, Article Journal of Applied Sciences ; Volume 9, Issue 4 , 2009 , Pages 789-793 ; 18125654 (ISSN) ; Eshraghniaye Jahromi, A ; Modarres, M ; Sharif University of Technology
2009
Abstract
In this study, the cost function of the defined system is derived first. Then, we prove this function is convex in the system's base stock level. Finally, based on the convexity of the cost function, the optimal solution for the base stock model is determined. For demonstrating the applicability of the proposed method, we resort to solving an example. © 2009 Asian Network for Scientific Information
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...
Study of Melting and Rapid Solidification of TiAl alloy and Formation of its Diffusion Bonded Structure using Molecular Dynamics Simulation
, M.Sc. Thesis Sharif University of Technology ; Aashuri, Hossin (Supervisor) ; Simchi, Abdolreza (Co-Advisor)
Abstract
The rapid pace of development of nanoscience and nanotechnology and their applications in various fields have made the study of materials in smaller scales more important than any time ever. Having an insight of materials’ microstructure and the mechanism of different phenomena in the atomic scale will be very beneficent in designing new and advanced materials or modifying the current manufacturing processes. Since molecular dynamics (MD) method has been well known as a mean of studying materials in atomic scale, it has been used in this study to investigate two different phenomena. The selection of the appropriate interatomic potential is of great importance in MD; Embedded Atom Method...
An adaptive filter for noise cancelling in mammography images based on Cellular Automata
, Article International Review on Modelling and Simulations ; Volume 5, Issue 3 , June , 2012 , Pages 1322-1326 ; 19749821 (ISSN) ; Masoumzadeh Tork, A ; Yazdan Talab, E ; Ramezanpour, H ; Darmani, G ; Sharif University of Technology
2012
Abstract
In recent years, several techniques based on repetition of the image are used to remove noise. In this paper a new method based on Cellular Automata for image noise removal in mammography images is recommended. We present a new formulation that makes improvements. The formulation uses a neighborhood with sizes and format adapted to the features of the image on reconstruction. We demonstrated through experiments and comparison with other common used techniques that this procedure produces excellent results for the problem of restoring true color images
Fabrication of Nano Sensor for Detecting H2S
, M.Sc. Thesis Sharif University of Technology ; Soltanieh, Mohammad (Supervisor) ; Rashidi, Alimorad (Supervisor) ; Izadi Yazdan Abadi, Nosrat (Co-Advisor)
Abstract
Due production and use of large amount of chemical and emissions of pollutants in air, detection and control of these compounds are necessary. One of the common methods to detect these pollutants in the ambient is using metal oxide semiconductor sensors. However, these types of sensors suffer from low selectivity toward a certain compound in the mixture of different gas components. In this study, the object was to investigate the effect of different amount of CNTs on performance of tin oxide to improve their selectivity for detection of 50 ppm of hydrogen sulfide at low temperature. To perform the study, nanoparticles of pure tin oxide and SnO2 base hybrids containing 0.25wt%, 0.5wt%, 2.5wt%...
Recent activities in science and technology and the progress of women in physics in the last three years in Iran
, Article AIP Conference Proceedings, Stellenbosch ; Volume 1517 , 2013 , Pages 108-109 ; 0094243X (ISSN); 9780735411388 (ISBN) ; Azad, M. T ; Mahmoudi, N ; Izadipanah, N ; Eshghi, N ; Sharif University of Technology
2013
Abstract
For the 4th IUPAP International Conference of Women in Physics, we report on activities in science and engineering in Iran, and conditions for women in physics, in the three years since the 3rd IUPAP International Conference of Women in Physics was held in 2008. Iran has made prominent advancements and astonishing progress in laser technology, biotechnology, nanotechnology, genetics, computer software and hardware, and robotics. Iranian scientists have been very productive in several experimental fields, such as pharmaceutical, organic, and polymer chemistry. Conditions for women in physics have improved greatly in recent years. A project to improve the environment for learning physics, and...
Lead-free MAGeI3 as a suitable alternative for MAPbI3 in nanostructured perovskite solar cells: a simulation study
, Article Environmental Science and Pollution Research ; Volume 30, Issue 19 , 2023 , Pages 57032-57040 ; 09441344 (ISSN) ; Akhavan, O ; Rabiee, N ; Afshar, E. N ; Zare, E. N ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2023
Abstract
The lead is a heavy metal with hazardous impacts on environment and human life. Lead-free perovskite solar cells have attracted much attention in recent years, due to eco-friendly characteristics. Meanwhile, Pb-containing cells showed the highest efficiencies among the various types of cells. Hence, designing novel Pb-free solar cells with comparable or better performance than the Pb-containing ones is highly required. In this work, a lead-free methyl-ammonium-germanium-iodide (MAGeI3)-based perovskite solar cell with ITO/TiO2/MAGeI3/Spiro-OMeTAD/Ag multilayer nanostructure has been proposed and its main characteristics including open-circuit voltage (VOC) and power conversion efficiency (η)...
Ab initio study of electronic effects in the ZnO/TiO2 core/shell interface: Application in dye sensitized solar cells
, Article RSC Advances ; Vol. 4, issue. 1 , April , 2014 , p. 301-307 ; Nafari, N ; Taghavinia, N ; Sharif University of Technology
2014
Abstract
Core/shell structure of ZnO nanowires coated with a monolayer of TiO 2 is investigated using Density Functional Theory (DFT). The electronic states of the semiconductor is calculated and compared before and after coating of the TiO2 monolayer on a ZnO [101 0] surface. The effect of TiO2 coating induce surface states changes and shifts the conduction and valence band edges to higher energies. Our results, in qualitative agreement with the experimental work of Matt Law et al. (J. Phys. Chem. B, 110, 22652), show an increase in open circuit voltage and a decrease in short circuit current in ZnO/TiO2 core shell dye sensitized solar cells. Regarding the semiconductor density of states (DOS), TiO2...
Analyzing factors effective on the development of relationship commitment
, Article Proceedings of the 2012 International Conference on Artificial Intelligence, ICAI 2012, 16 July 2012 through 19 July 2012 ; Volume 1 , July , 2012 , Pages 398-404 ; 1601322186 (ISBN) ; 9781601322180 (ISBN) ; Lotfi, N ; Karami, N ; Sharif University of Technology
2012
Abstract
Due to the important role of commitment and trust in the relationship marketing, the factors which can directly result in a committed relationship along with the factors which can influence the commitment through influencing trust, according to the model of commitment and trust by (Morgan & Hunt, 1994) have been introduced and their level of importance has been investigated here. The article uses fuzzy cognitive maps (FCMs) in the proposed model to find the most important paths leading to relationship commitment. The FCM analyzes the responses of a group of 30 people including general practitioners in dentistry, managers of dental departments in some of the public clinics and hospitals who...
Morphological dependence of light backscattering from metallic back reflector films: Application in dye-sensitized solar cells
, Article Physica Status Solidi (A) Applications and Materials Science ; Volume 212, Issue 4 , January , 2015 , Pages 785-790 ; 18626300 (ISSN) ; Ghazyani, N ; Taghavinia, N ; Sharif University of Technology
Wiley-VCH Verlag
2015
Abstract
Conventionally, a film of TiO2 particles of 300 nm size is employed in Dye-sensitized solar cells (DSCs) as the back reflector film to enhance the light harvesting. Perfect reflectance of silver in visible and near infrared motivates to investigate its potential as the material for the light back reflector film in DSCs. In this study, light back reflector films consisting of 300 nm-sized silver particles, as well as vacuum evaporated silver flat film, were fabricated and compared to 300 nm-sized rutile-type TiO2 particulate reflector film to study their optical aspects. Conventional TiO2 rutile-type particulate film demonstrates slightly lower performance...
Monolithic dye sensitized solar cell with metal foil counter electrode
, Article Organic Electronics ; Volume 57 , June , 2018 , Pages 194-200 ; 15661199 (ISSN) ; Taghavinia, N ; Ghazyani, N ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2...
A compact versatile microbial fuel cell from paper
, Article ASME 2013 11th Int. Conf. on Fuel Cell Science, Eng. and Technology Collocated with the ASME 2013 Heat Transfer Summer Conf. and the ASME 2013 7th Int. Conf. on Energy Sustainability, FUELCELL 2013 ; 2013 ; 9780791855522 (ISBN) ; Hashemi, N ; Hashemi, N ; Sharif University of Technology
2013
Abstract
Microbial fuel cells (MFCs) have been a potential green energy source for a long time but one of the problems is that either the technology must be used on a large scale or special equipment have been necessary to keep the fuel cells running such as syringe pumps. Paper-based microbial fuel cells do not need to have a syringe pump to run and can run entirely by themselves when placed in contact with the fluids that are necessary for it to run. Paper-based microbial fuel cells are also more compact than traditional MFCs since the device doesn't need any external equipment to run. The goal of this paper is to develop a microbial fuel cell that does not require a syringe pump to function. This...
Decentralized model predictive voltage control of islanded DC microgrids
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Mahdian Dehkordi, N ; Sadati, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
This paper proposes a novel decentralized control approach for islanded direct-current (DC) microgrids (MGs) based on model predictive control (MPC) to regulate the distributed generation unit (DGU) output voltages, i.e. the voltages of the point of common coupling (PCC). A local controller is designed for each DGU, in the presence of uncertainties, disturbances, and unmodeled dynamics. First, a discrete-time state-space model of an MG is derived. Afterward, an MPC algorithm is designed to perform the PCC voltage control. The proposed MPC scheme ensures that the PCC voltages remain within an acceptable range. Several simulation studies have been conducted to illustrate the effectiveness of...
Intelligent optimal feed-back torque control of a 6DOF surgical rotary robot
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Ebrahimi Toulkani, N ; Zhilakzadeh, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine, and restrict their workspace, while controlling and validating the robots are complicated regarding to their complex dynamic. To this end, in this paper, a 6-DOF robot, with rotary manipulators, is designed and controlled. Addressing nonlinearity of parallel robots, an innovative methodology is formulated to robustly penalize the error of...
Semi-Real evaluation, and adaptive control of a 6DOF surgical robot
, Article 11th Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2020, 4 February 2020 through 6 February 2020 ; 2020 ; Ebrahimi Toulkani, N ; Zhilakzadeh, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Sophisticated surgeons are widely indicating the use of surgical robots in order to reject human error, increase precision, and speed. Among well-known robotic mechanisms, parallel robots are broadly more investigated regarding their special characters as higher acceleration, speed, and accuracy, and less weight. Specific surgical procedures confine and restrict their workspace, while controlling and validating the robots are complicated based on their complex dynamic. To this end, in this paper, a 6-DOF robot, with linear manipulators, is designed and controlled. Addressing the inherent nonlinearity of the robot mechanism, an adaptive PID manipulator is employed and validated with nonlinear...
Modeling superconductive fault current limiter using constructive neural networks
, Article 2007 IEEE International Symposium on Industrial Electronics, ISIE 2007, Caixanova - Vigo, 4 June 2007 through 7 June 2007 ; 2007 , Pages 2859-2863 ; 1424407559 (ISBN); 9781424407552 (ISBN) ; Sadati, N ; Hosseini, M. N ; Sharif University of Technology
2007
Abstract
Although so many advances have been proposed in the field of artificial intelligence and superconductivity, there are few reports on their combination. On the other hand, because of the nonlinear and multivariable characteristics of the superconductive elements and capabilities of neural networks in this field, it seems useful to apply the neural networks to model and control the superconductive phenomena or devices. In this paper, a new constructive neural network (CNN) trained by two different optimization algorithms; back-propagation and genetic algorithm, is proposed which models the behavior of the superconductive fault current limiters (SFCLs). Simulation results show that the proposed...
Satellite attitude tracking using optimal neuro-controller
, Article 2003 IEEE Aerospace Conference, Big Sky, MT, 8 March 2003 through 15 March 2003 ; Volume 6 , 2003 , Pages 2663-2669 ; 1095323X (ISSN); 078037651X (ISBN); 9780780376519 (ISBN) ; Sadati, N ; Tehrani, N. D ; Sharif University of Technology
2003
Abstract
In this paper, a new control strategy for optimal attitude tracking control of a multivariable satellite system has been presented. The approach is based on a Multilayer Perceptron Neural Network (MLPNN) and a classical PD Controller for its initial stabilization. It is shown how the network can be employed as a multivariable self-organizing and self-learning controller in conjunction with a PD controller for attitude control of a satellite. By using three thrusters and quaternion for kinematics representation, the attitude dynamics of the satellite has been presented. In contrast to the previous classical approaches, it is shown how this controller can be carried out in an on-line manner...