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    , M.Sc. Thesis Sharif University of Technology Behravesh, Mahmood (Author) ; Hajji, Alireza (Supervisor)
    Abstract
    In this research, effect process TOC in MRP system have been studied,therefore, first the hypothesis in TOC process and MRP system have been studied and generated. Afterward, whit the use of library and sydies the research guestions have been compiled. The society under studyis an aluminium oasts manufacturing daycust tabriz company. For surveying the memtioned company, samed documents hase been studied. After gathering all information and documents, and analyzing them, the result has been revealed. Therefore the effect of TOC and MRP process an production system has been comeout. At present situation, the mast crucial factors for suruival and compdtetion are ones couse the reduction of the... 

    A theoretical game approach for two- echelon stochastic inventory system

    , Article Acta Polytechnica Hungarica ; Volume 12, Issue 4 , 2015 , Pages 221-239 ; 17858860 (ISSN) Alaei, S ; Hajji, A ; Alaei, R ; Behravesh, M ; Sharif University of Technology
    Budapest Tech Polytechnical Institution  2015
    Abstract
    In this paper, we study the differences between the Centralized and Decentralized approaches in a two-echelon stochastic inventory system under the lost sale policy. We formulate the condition in which the retailer applies (r, Q) inventory policy, and his relation with the upper echelon who acts as a manufacturer. This situation has not been considered in the literature before. The Centralized approach results in optimal solution of the system and the Decentralized one is based on Stackelberg game in which the manufacturer is the leader. The demand arrives according to the stationary Poisson process. We drive the long-run average cost functions, then a set of computational steps are... 

    Two-way information exchange in two-level supply chain

    , Article 2012 3rd International Conference on System Science, Engineering Design and Manufacturing Informatization, ICSEM 2012 ; Volume 2 , 2012 , Pages 92-95 ; 9781467309141 (ISBN) Dodd, O ; Haji, A ; Zare, A. G ; Behravesh, M ; Sharif University of Technology
    2012
    Abstract
    The objective of the present study is to model and analyzing a two-level supply chain with reverse information exchange in which the manufacturer and the retailer are aware of the status of each other's stocks. To take advantages of this method of information exchange, manufacturers and retailers change their stock policies from traditional base-stock policy to a state-dependent two-level base-stock policy. Then, they change their ordering policy according to the other side's stock availability. Applying the mentioned method reduces the total cost of system as well as decreasing the average amount of manufacturer's inventory and improving the waiting time of walk-in customers  

    Examining the level and strength of technology in the industries of the country iran by using escap model and introducing solutions for developing technology

    , Article Australian Journal of Basic and Applied Sciences ; Volume 4, Issue 10 , October , 2010 , Pages 4638-4649 ; 19918178 (ISSN) Rahmani, K ; Behravesh, M ; Behravesh, M ; Karegar, N ; Fereidooni, A ; Sharif University of Technology
    2010
    Abstract
    The economic growth or asset of country basically depends on the amount of goods which can be produced by the combination of land, capital, manpower and natural resources. Therefore, changing natural resources into production is the new process of economical development, and technology is the brain of this type of transformational activities. This tool not only makes the changing operation possible but also, in the world economy makes the survival and growth foundation of business enterprises. The Development of today's technology has caused some change in the productivity and costs, and because of this, the global and national structure in the areas of production, business and employment... 

    Improving Efficiency of Labyrinth Side Weirs Using Asymmetric Geometry

    , M.Sc. Thesis Sharif University of Technology Parvaneh, Ali (Author) ; Borghei, Mahmood (Supervisor)
    Abstract
    One of the most important methods of controlling discharge in water industry which is widely used in irrigation, water distribution, waste-water engineering, drainage, flood control and other water related projects, is side weir. The hydraulic behavior of flow over side weir is spatially varied flow with decreasing discharge. Various investigators have related the weir discharge coefficient as a function of main channel upstream Froude number and the fraction of weir height to upstream depth . Performance of sharp crested side weirs with extended length (as labyrinth side weir with asymmetric geometry) has been studied in this thesis. The variables for this study are height of weir ,... 

    Experimental Study of Pressure Fluctuation in Two Phase Slug Flow In a Tunnel with Rectangular Cross Section with an Expansion Transition and Horizontal Slope

    , M.Sc. Thesis Sharif University of Technology Jalilvand, Ehsan (Author) ; Borghie, Mahmood (Supervisor)
    Abstract
    Air enterance in to flowing water is something that is commonly seen in the water conveyance systems. The mixture of Air and water that flow together create a kind of flow that is called two phase flow. This kind of flow is often seen in culverts and water conveyance systems. There are different flow patterns in two phase flow. Considering pressure fluctuation, pressure drop and pressure recovery, slug flow pattern is the most complicated pattern among all.
    Sometimes a singularity is used in a tunnel; one of the singularities that are frequently used in water conveyance system is expansion transition. In this study an experimental setup is used to model two phase slug flow, which passes... 

    Controlling Local Scour Due to Hydraulic Jump Using Oblique Buried Plates

    , M.Sc. Thesis Sharif University of Technology Borhani, Sanaz (Author) ; Borghei, Mahmood (Supervisor)
    Abstract
    Local scouring at the downstream of sluice gates in the erosive beds is one of the main concerns of hydraulic engineers because of the significant damage that it can cause to the hydraulic structures. It is important to control the local scour depth at downstream of hydraulic structures to ensure safety operation of these systems. Many researchers have conducted various studies to predict the maximum depth and diameter of scour hole and develop new methods in order to control this phenomenon. One way to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron length or decrease the effect of the... 

    Performance Analysis and Optimization of Optically Steered Arrayed Antennas with Gratings

    , Ph.D. Dissertation Sharif University of Technology Shabani, Mostafa (Author) ; Akbari, Mahmood (Supervisor)
    Abstract
    It is well known that arrays of antennas make it possible to steer the radiation pattern without steering a physical structure. For the past few decades this has been considered for many civil and military communication systems. Recently, ultra-short pulses are considered for high resolution radars and ultra-wideband communication systems. Systems with short pulses and large antenna arrays may benefit from high resolution in both temporal and spatial domains. But the implementation of the ultra-wideband feeding circuits for such antenna arrays is a hard job even with state of the art electronics. Optical technology has been applied, successfully, to a number of radio applications such as... 

    Laboratory Investigation For Unsymmetric Rectangular Weir

    , M.Sc. Thesis Sharif University of Technology Aghazadeh, Pooya (Author) ; Borghei, Mahmood (Supervisor)
    Abstract
    Sharp crested weirs are one of the main and oldest means of measuring discharge in water conveyance systems. Many studies have been done on sharp rectangular weirs and have provided many relationships regarding the effect of geometric parameters and various factors on discharge coefficient of the weirs.In some places, due to existence of obstacles or barriers in the channel, it is impossible to create a symmetrical continuous weir some other cases,multiple or asymmetric weirs should be used, which is the main concept of this project.Since it seems unlikely that a purely mathematical model can review the impact of the multiplicity and asymmetry of these weirs without using empirical... 

    Analysis and Simulation of Micrometre-scale Silicon Electro-optic Modulators Based on Ring Resonators

    , M.Sc. Thesis Sharif University of Technology Jafari, Omid (Author) ; Akbari, Mahmood (Supervisor)

    Optimization of Maximum Frequency and Power, Extraction of Parameter Data and Final Publication Design of High Power Microwave Pulse Generation Using nonlinear Transmission Line with the Periodic Structure of the Gas Switch

    , M.Sc. Thesis Sharif University of Technology Komeylian, Saeed (Author) ; Akbari, Mahmood (Supervisor)
    Abstract
    High-power (108 – 109 W) RF pulses with a carrier frequency of C band and a duration of several oscillation periods can be produced through direct energy conversion of a travelling high-voltage pulse with the use of nonlinear elements.
    Nonlinear transmission lines consist either of lumped nonlinear elements and provide spatial dispersion of excited oscillations or of elements uniformly distributed on a certain line segment. The first type of NLTL’s can be referred to NLTL’s with spatial dispersion. The second type of NLTL’s is ensemble of nonlinear oscillators with a characteristic natural frequency and temporal dispersion. In the first case, the duration of electromagnetic pulses is... 

    An Estimation Model for Computation and Control of Trajectory Coverage Error in Additive Manufacturing

    , M.Sc. Thesis Sharif University of Technology Zargar, Farinaz (Author) ; Houshmand, Mahmood (Supervisor)
    Abstract
    During 1980s Additive Manufacturing technologies for the purpose of prototyping with fast and less expensive, under the name of Rapid Prototyping was invented. But nowadays under the vast progress made in this field, it possesses a notable place in different industries such as automobile manufacturing, aerospace, architecture, medicine and so on for part manufacturing. In all AM machines, the CAD model design part is manufactured by adding layered to each other. In this research, at first by explaining manufacturing process and current different technologies, the place of this manufacturing process in today and future industry, is analyzed. For discussing replacement of this method instead... 

    Analysis and Design of Nanoantenna Arrays

    , M.Sc. Thesis Sharif University of Technology Dehmollaian, Ayyoub (Author) ; Akbari, Mahmood (Supervisor)
    Abstract
    If the size of the conventional telecommunication antennas -that are widely used in transmitting broadcasted radio and TV messages- is reduced by a nanometer size these antennas can be used at optical frequencies. Dimensions of these optical nanoantennas -that made of nanoparticles with highly permittivity- can be smaller than half of the wavelength. Based on this capability, optical nanoantennas have some important applications such as optical communication, photovoltaic devices, non-classical light, and optical sensing. After studying on optical nanoantennas and their features, in this project, we present distinctions between optical NAs and MW antennas and then investigate about different... 

    Optimized Design of Switch Circuit and Receiver Antenna in the Field of Fifth Generation Telecommunications to Reduce the Fading Effect

    , M.Sc. Thesis Sharif University of Technology Bakhshi, Mehran (Author) ; Akbari, Mahmood (Supervisor)
    Abstract
    The Deep Fading Effect is a destructive factor in communication systems, one of the solutions to eliminate it is the use of Diversity, and there are two types of indicators of Diversity, Spatial Diversity and Polarization Diversity. Spatial Diversity is a common method to reduce the Fading Effect while increasing the cost and increasing the volume of the communication station, which to optimize the cost and reduce the volume of the communication station, the Polarization Diversity Structure is added to the telecommunication system. To apply Spatial Diversity, several Antennas with different Polarizations are used, which The most common method in mobile telecommunication station systems is... 

    Designing a New System for Proposing a Suitable Computer System for Customers Using Cloud Computing and Service Composition

    , M.Sc. Thesis Sharif University of Technology Mousavi, Danial (Author) ; Hushmand, Mahmood (Supervisor)
    Abstract
    Cloud computing has brought about many changes in the new business arena. These changes do not only include technological changes, but have penetrated the business models of many companies. For example, in recent years, many companies have migrated from their former systems to cloud computing for reasons such as easy and low-cost access to high-performance hardware and software systems, and to avoid maintenance and repair costs and security costs.Due to the economic conditions in recent years and the high cost of electronic items, the criterion of purchase price has become much more important than in the past among people when buying such goods. Now in the Iranian electronics market,... 

    Assessment of fiber-reinforcement and foam-filling in the directional energy absorption performance of a 3D printed accordion cellular structure

    , Article Composite Structures ; Volume 297 , 2022 ; 02638223 (ISSN) Farrokhabadi, A ; Mahdi Ashrafian, M ; Behravesh, A. H ; Kaveh Hedayati, S ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson's ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The... 

    Design and Implementation of an Audio Steganography System on FPGA

    , M.Sc. Thesis Sharif University of Technology Ebrahimabadi, Mohammad (Author) ; Tabandeh, Mahmood (Supervisor)
    Abstract
    In recent years, along with development of technology and decrease in size of digital devices, copying and editing of digital multimedia products has become easier. Also, broadband technology caused simpler distribution of data. Considering above mentioned problems, we can use watermarking. Nowadays, watermarking has many applications such as secure transmission of data, owner identification, proof of ownership, authentication, broadcast monitoring etc. Watermarking is the process of hiding information in a secure host, in a way that it does not change the quality of signal. Watermarking is the science and art of hiding secret information in which neither the sender nor the receiver would... 

    Analysis of Wave Propagation Eigenproblem in Periodic Structures

    , Ph.D. Dissertation Sharif University of Technology Faghihifar, Ehsan (Author) ; Akbari, Mahmood (Supervisor)
    Abstract
    The Fourier modal method is one of the most important methods in the analysis of flat periodic structures (gratings). Using this method, the problem of wave propagation in the periodic medium leads to an eigenproblem, in which eigenvalues represent the propagation constants and eigenvector or eigenfunctions determine the filed distribution of the modes. On the other side, considering all the generalizations and modifications reported so far, the Fourier modal method still faces two fundamental problems. First, for problems involving large dielectric constants or high contrasts, the matrix form of the eigenproblem (the modal matrix) can be large, dense, and require a high computational cost.... 

    Simulation and plant wide Control of Combined Pervaporation/Distillation Process for MTBE Production

    , M.Sc. Thesis Sharif University of Technology mozegar, Mostafa (Author) ; Pishvaei, Mahmood Reza (Supervisor)
    Abstract
    In this thesis we are about to simulate and control an MTBE production unit which use membrane instead of azeotropic distillation tower. At first an MTBE Production Unit with two distillation towers in separation part is simulated whit traditional method. One of these distillation towers is azeotropic. Then azeotropic distillation tower is replaced with membrane.After simulation the unit with best process indicators is selected. The goal is minimization of fixed and operating costs.In the next stage the best control loops in each unit is selected. The unit with best control indicators is determined. Control indicators are load rejection and set point tracking. All units have been simulated... 

    A Nonlinear Viscoelastic Plate Equation with P-laplacian Operator

    , M.Sc. Thesis Sharif University of Technology Karimloo Feiz, Alireza (Author) ; Hesaraki, Mahmood (Supervisor)
    Abstract
    This work is concerned with a class of plate equations with memory and p-laplacian operator with simply supported boundary condition, where Ω is a bounded domain
    of RN; g > 0 is a memory kernel that decays exponentially and f(u) is a nonlinear perturbation. This kind of problem without the memory term models elastoplastic flows