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    Refined microstructure of compo cast nanocomposites: the performance of combined neuro-computing, fuzzy logic and particle swarm techniques

    , Article Neural Computing and Applications ; 2014 ; ISSN: 09410643 Shabani, M. O ; Rahimipour, M. R ; Tofigh, A. A ; Davami, P ; Sharif University of Technology
    Abstract
    Aluminum metal matrix composites (MMCs) reinforced with nanoceramics are ideal materials for the manufacture of lightweight automotive and other commercial parts. Adaptive neuro-fuzzy inference system combined with particle swarm optimization method is implemented in this research study in order to optimize the parameters in processing of aluminum MMCs. In order to solve the problems associated with poor wettability, agglomeration and gravity segregation of nanoparticles in the melt, a mixture of alumina and aluminum particles was used as the reinforcement instead of raw nanoalumina. Microstructural characterization shows dendritic microstructure for the sand cast and non-dendritic... 

    Numerical finite element analysis of laterally loaded fin pile in sandy soil

    , Article Innovative Infrastructure Solutions ; Volume 4, Issue 1 , 2019 ; 23644176 (ISSN) Yaghobi, M. H ; Hanaei, F ; Fazel Mojtahedi, S. F ; Rezaee, M ; Sharif University of Technology
    Springer  2019
    Abstract
    In the present study, the behavior of fin pile under lateral loading was investigated by ABAQUS software. First, the generated model was verified against an available experimental small-scale test in the literature. Having conducted verification, a study was carried out on the fin pile dimensions under lateral loading. Different parameters, such as pile diameter, fin’s length, and width, were studied. Moreover, a study on the fin’s aspect ratio by setting fin’s area constant was conducted, and then, optimum fin’s ratio was obtained. The results indicated that both fin’s length and width could improve pile efficiency under lateral loading, yet fin’s length had a more critical impact, and... 

    Drill string instability reduction by optimum positioning of stabilizers

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Volume 224, Issue 3 , 2010 , Pages 647-653 ; 09544062 (ISSN) Mahyari, M. F ; Behzad, M ; Rashed, G. R ; Sharif University of Technology
    2010
    Abstract
    The main aim of this article is to find the optimum positions of the stabilizers that reduces the vibration and leads to the largest weight on bit (WOB) in drill strings. In this work, the potential energy of drill strings has been derived by considering the drill string weight and WOB. The potential energy of this continuous system is considered as a multi-degree-of-freedom system by the mode summation method. The equilibrium position of the system and its stability is determined by finding the roots of the first derivative and the sign of the second derivative of the potential energy, respectively. Using this formulation, the best positions of stabilizers that lead to the largest WOB can... 

    Optimum arrangement of layers in multi-layer compound cylinders

    , Article International Journal of Applied Mechanics ; Vol. 6, issue. 5 , 2014 Sharifi, M ; Arghavani, J ; Hematiyan, M. R ; Sharif University of Technology
    Abstract
    In this paper, using an analytical optimization method, optimum design of multi-layer compound cylinders with different materials in layers is investigated. For this purpose, considering Tresca criterion, maximum shear stress in each layer is minimized. At the optimum condition, the maximum shear stress at all layers occurs simultaneously. The general analytical relations for optimum dimension of layers, residual pressures and radial interferences are derived. The existence condition of the optimum solution is also investigated and the constraints for materials selection are derived too. It is shown that the allowable shear stress ratio of materials must be close to their geometric mean... 

    An analytical solution for optimum design of shrink-fit multi-layer compound cylinders

    , Article International Journal of Applied Mechanics ; Volume 4, Issue 4 , December , 2012 ; 17588251 (ISSN) Sharifi, M ; Arghavani, J ; Hematiyan, M. R ; Sharif University of Technology
    2012
    Abstract
    In this paper, employing an analytical method, optimum design of multi-layer compound cylinders is investigated. To this end, considering Tresca criterion, maximum shear stress in each layer is minimized. Analytical relations for optimum values of a layer dimension, residual pressures and radial interferences are derived. A technique for shrink-fitting of layers is also proposed and relationships for radial interferences, residual pressures and required temperature differences during the shrink-fitting process are derived. Three different examples are presented to show the effectiveness of the proposed method. It is shown that increasing the number of layers makes shear stress distribution... 

    New anti-ARM technique by using random phase and amplitude active decoys

    , Article Progress in Electromagnetics Research ; Volume 87 , 2008 , Pages 297-311 ; 10704698 (ISSN) Emadi, M ; Jafargholi, A ; Sargazi Moghadam, M. H ; Marvasti, F ; Sharif University of Technology
    Electromagnetics Academy  2008
    Abstract
    This paper presents a new method to counter Anti Radiation Missile (ARM) threats, which is effective against advanced ARM. By using random phase and amplitude active decoys in the specified optimum positions and network implementation we show that ARM threats will be removed profoundly. Also, iterative methods are presented to cancel the internal interference effects in the proposed structure  

    Efficient Methods for Transmission and Reception of Information in Molecular Communication Systems

    , M.Sc. Thesis Sharif University of Technology Mosayebi, Reza (Author) ; Nasiri-Kenari, Masoumeh (Supervisor) ; Gohari, Amin (Supervisor)
    Abstract
    This thesis studies on diffusion-based molecular communication channel between two nano-machines. The effect of the amount of memory on performance is characterized, and a simple memory-limited decoder is proposed and its performance is shown to be close to that of the best possible decoder (without any restrictions on the computational complexity or its functional form), using Genie-aided upper bounds. This effect is studied for the case of Molecular Concentration Shift Keying; it is shown that a four-bits memory achieves nearly the same performance as infinite memory. Then a general class of threshold decoders is considered and shown not to be optimal for a Poisson channel with memory,... 

    Optimization procedure to select an inherently safer design scheme

    , Article Process Safety and Environmental Protection ; Vol. 93 , 2014 , pp. 89-98 ; ISSN: 09575820 Eini, S ; Abdolhamidzadeh, B ; Reniers, G ; Rashtchian, D ; Sharif University of Technology
    Abstract
    There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this paper an optimization procedure is proposed which integrates both processing and accident costs for different design schemes. In this procedure, some of the design variables are chosen with regard... 

    Optimization procedure to select an inherently safer design scheme

    , Article Process Safety and Environmental Protection ; Volume 93 , Jan , 2015 , Pages 89-98 ; 09575820 (ISSN) Eini, S ; Abdolhamidzadeh, B ; Reniers, G ; Rashtchian, D ; Sharif University of Technology
    Institution of Chemical Engineers  2015
    Abstract
    There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this paper an optimization procedure is proposed which integrates both processing and accident costs for different design schemes. In this procedure, some of the design variables are chosen with regard... 

    Adaptive-passive structural vibration attenuation using distributed absorbers

    , Article Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics ; Volume 216, Issue 3 , 2002 , Pages 223-235 ; 14644193 (ISSN) Jalili, N ; Esmailzadeh, E ; Sharif University of Technology
    Professional Engineering Publishing  2002
    Abstract
    A distributed dynamic vibration absorber with adaptive capability is presented to improve vibration suppression characteristics of harmonically excited structures. A double-ended cantilever beam carrying intermediate lumped masses forms the absorber subsection. The adaptive capability is achieved through concurrent adjustment of the positions of the moving masses, along the beam, to comply with the desired optimal performance. The necessary and sufficient conditions for the existence of periodic oscillatory behaviour, along with some physical bounds placed on the absorber parameters, form a constrained optimization problem for the optimum tuning strategy. Through numerical simulations it is... 

    Semi-active control of forced oscillations in power transmission lines via optimum tuneable vibration absorbers: With review on linear dynamic aspects

    , Article International Journal of Mechanical Sciences ; Vol. 87, issue , 2014 , p. 163-178 Asmari Saadabad, N ; Moradi, H ; Vossoughi, G ; Sharif University of Technology
    Abstract
    Due to flexibility, relatively small weight and low energy-dissipative characteristics of cables, they are vulnerable to external excitations such as wind, wind-rain, earthquake and traffic loadings. Among them, galloping phenomenon is one of the most important sources of electrical/mechanical failures in power transmission lines. In this paper, tuneable vibration absorbers (TVAs) are used to suppress galloping forced vibrations (as a semi-active control approach). Using mode summation technique, mathematical model of the hybrid problem including the transmission line and an arbitrary number of absorbers is presented. Developing a sophisticated multi-loops optimization algorithm, best values... 

    Optimum design process of vibration absorber via imperialist competitive algorithm

    , Article International Journal of Structural Stability and Dynamics ; Volume 12, Issue 3 , 2012 ; 02194554 (ISSN) Hoseini, R ; Salehipoor, H ; Sharif University of Technology
    Abstract
    This paper deals with the optimum design of vibration absorbers utilized to reduce undesirable random vibrational effects that are originated in linear structures. Analytical expressions, for the case of nonstationary white-noise accelerations, are derived. The criterion is different from most conventional optimum design criteria, since it is based on minimizing the displacement or the acceleration variance of the main structure responses, without considering performances required against failure. In this study, in order to control the structural vibrations induced on a mechanical structure excited by nonstationary based acceleration random process, the MOO (multi-objective optimum) design... 

    Analytical power allocation for a full duplex decode-and-forward relay channel

    , Article 2013 Iran Workshop on Communication and Information Theory ; 2013 ; 9781467350235 (ISBN) Golami Davoodi, A ; Emadi, M. J ; Aref, M. R ; Sharif University of Technology
    Abstract
    For a Rayleigh fading full-duplex decode-and-forward relay channel, we analytically derive optimum power allocation schemes subject to individual power constraints for the source and the relay. The optimization problem is taken over the source power and the relay power. It is proven that the optimization problem is concave for this scenario, and optimum power allocations are derived in a closed-form. Finally, the implications of the theoretical results are discussed through the graphs  

    Cooperative abnormality detection via diffusive molecular communications

    , Article IEEE Transactions on Nanobioscience ; Volume 16, Issue 8 , 2017 , Pages 828-842 ; 15361241 (ISSN) Mosayebi, R ; Jamali, V ; Ghoroghchian, N ; Schober, R ; Nasiri-Kenari, M ; Mehrabi, M ; Sharif University of Technology
    Abstract
    In this paper, we consider abnormality detection via diffusive molecular communications (MCs) for a network consisting of several sensors and a fusion center (FC). If a sensor detects an abnormality, it injects a number of molecules into the medium which is proportional to its sensing output. Two transmission schemes for releasing molecules into the medium are considered. In the first scheme, each sensor releases a different type of molecule (DTM), whereas in the second scheme, all sensors release the same type of molecule (STM). The molecules released by the sensors propagate through the MC channel and some may reach the FC where the final decision regarding whether or not an abnormality... 

    Experimental and simulation investigation on separation of binary hydrocarbon mixture by thermogravitational column

    , Article Journal of Molecular Liquids ; Volume 268 , 2018 , Pages 791-806 ; 01677322 (ISSN) Hashemipour, N ; Karimi Sabet, J ; Motahari, K ; Mahruz Monfared, S ; Amini, Y ; Moosavian, M. A ; Sharif University of Technology
    Elsevier B.V  2018
    Abstract
    In this article, experimental and numerical investigations are performed to study a thermogravitational column (TGC) for the separation of toluene/n-heptane mixture. This research has tried to determine the main significant parameters and their effects on the performance of the process. In experimental examinations, the influence of the main parameters such as feed flow rate, cut and temperature gradient on the performance of the TGC efficiency is studied. In addition, computational fluid dynamics is used to simulate the separation process in this review. The response surface methodology (RSM) was also applied to minimize the number of runs and investigate the optimum operating conditions.... 

    A new biogas-fueled bi-evaporator electricity/cooling cogeneration system: Exergoeconomic optimization

    , Article Energy Conversion and Management ; Volume 196 , 2019 , Pages 1193-1207 ; 01968904 (ISSN) Gholizadeh, T ; Vajdi, M ; Rostamzadeh, H ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    An innovative bi-evaporator electricity/cooling cogeneration system fueled by biogas is introduced. The plausibility of the introduced integrated power plant is examined from thermodynamic and economic vantage points. Later, single- and multi-objective optimization of the reckoned system are achieved by selecting appropriate parameters as decision variables and thermal and exergy efficiencies and total unit product cost (TUPC) of the system as objective functions. Four optimum modes of thermal efficiency optimum design (TEOD), exergy efficiency optimum design (EEOD), cost optimum design (COD), and multi-objective optimum design (MOOD) are selected for optimization and the attained results... 

    Determining and optimizing power loss reduction in distribution feeders due to Distributed generation

    , Article 2006 IEEE PES Power Systems Conference and Exposition, PSCE 2006, Atlanta, GA, 29 October 2006 through 1 November 2006 ; 2006 , Pages 1914-1918 ; 142440178X (ISBN); 9781424401789 (ISBN) Honarvar Nazari, M ; Parniani, M ; Sharif University of Technology
    2006
    Abstract
    One of the beneficial impacts of Distributed generation (DG) units on electrical network is power loss reduction in the distribution feeder on which DG is located. In this paper the effect of DG on power losses of a distribution feeder with a combination of uniformly distributed and lumped loads is investigated, and a mathematical model of power loss reduction as a function of DG and the feeder parameters is extracted. Then, based on the derived formula, optimum conditions of utilizing and locating the DG units are obtained. © 2006 IEEE  

    Optimum Ground State for Quantum Spin Chains

    , M.Sc. Thesis Sharif University of Technology Heshami, Khabat (Author) ; Karimipour, Vahid (Supervisor)
    Abstract
    In this thesis, we have studied some exact solutions for low dimensional strongly correlated systems, especially spin chains. In the first chapter using simple AKLT model and introducing Valence Bond Solid States we have prepared good area to study Finitely Correlated States. In addition to presenting relation between these concepts, we have expressed Matrix Product States as a simpler formalism to deal with Finitely Correlated States. In the second chapter we have discussed the Optimum Ground State concept and we have studied a spin-32 with nearest neighbor interaction and a spin-1 model with next nearest neighbor interaction
    as example  

    Aerodynamic Analysis and Design of a Propeller for Light Flying Objects

    , M.Sc. Thesis Sharif University of Technology Sardari, Ali (Author) ; Farhanieh, Bijan (Supervisor)
    Abstract
    One of the major concerns in the use of light flying objects is propulsion for cruise and take off from land. Creating propulsion force is important in such way that no excessive weight is introduced, especially in case of UAVs. A common trend for propulsion in light flying objects is using propellers. Propellers are commonly driven by an external motive force and due to this force and their geometry, they convert energy from this motive force into the momentum of fluid in which they are immersed as a result a lift force is generated.In the present work, trend of propeller design with optimum performance is introduced with use of vortex theory, optimum energy loss condition or Betz condition... 

    Strategies for Iranian Natural Gas Resources by Economic Optimization Based on MCDM Analysis

    , Ph.D. Dissertation Sharif University of Technology Bakhteeyar, Halleh (Author) ; Maleki, Abbas (Supervisor)
    Abstract
    Due to rising demand of Natural gas in the global market and expected natural gas production soar in Iran which holds largest natural gas reserved in the world, addressing the optimal allocation of natural gas resources considering the role of Iran in global trade is of utmost importance to researchers as well as policy makers . The aim of this research is to develop a decision making tool which optimally allocate the natural gas resources. To develop this tool, qualitative and quantitative models of Multi-Criteria decision making considering energy security, economic and environment criteria are coupled to find the bests alternative options of natural gas exploration and the economic...