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    Evaluation of desiccant wheel and prime mover as combined cooling, heating, and power system

    , Article International Journal of Green Energy ; Volume 16, Issue 3 , 2019 , Pages 256-268 ; 15435075 (ISSN) Mohammadian Korouyeh, M ; Saidi, M. H ; Najafi, M ; Aghanajafi, C ; Sharif University of Technology
    Taylor and Francis Inc  2019
    Abstract
    In this research heating, cooling and electrical demands of a residential tower are evaluated for Iran various weather conditions. For this purpose, several cities are selected as the representative of the specific weather conditions. To meet the cooling demand, desiccant cooling system plus alternative systems are applied. To analyze desiccant wheel, outlet humidity and temperature have been modeled. Also, the effect of rotational speed and regeneration temperature on entropy generation of the desiccant wheel has been studied based on the obtained results. It is deduced that the entropy generation may be increased by increasing the regeneration temperature and the rotational speed. To... 

    Selection of prime mover to meet heating demand of a single effect absorption chiller based on laws of thermodynamics

    , Article SN Applied Sciences ; Volume 3, Issue 1 , 2021 ; 25233971 (ISSN) Mohammadian Korouyeh, M ; Saidi, M. H ; Najafi, M ; Aghanajafi, C ; Sharif University of Technology
    Springer Nature  2021
    Abstract
    In this study the first and the second laws of thermodynamics are evaluated for a single effect absorption chiller. Entropy generation and COP are selected as the objective functions and their variations are studied by varying the generator temperature for various condensing temperatures. For this purpose, the enthalpy and the entropy data of the super-heated steam, saturated steam and the saturated water are formulated in the mathematical equations. Also to provide the required steam of generator, prime mover in the form of internal combustion engine is applied and its partial load conditions are analyzed. A residential tower is considered as the case study for selecting the proper prime... 

    A simplified analytical model for predicting the heating performance of single U-tube underground heat exchangers

    , Article Scientia Iranica ; Volume 28, Issue 2 B , 2021 , Pages 847-859 ; 10263098 (ISSN) Mohammadian Korouyeh, M ; Saidi, M. H ; Naja, M ; Aghanaja, C ; Sharif University of Technology
    Sharif University of Technology  2021
    Abstract
    To ensure an optimized borehole in terms of heat capacity and cost-effectiveness, it is necessary to predict the heating performance of underground U-tube heat exchangers (boreholes) so that proper parameters such as length, diameter, material, etc. can be designed and selected. To this end, employing reliable equations is essential to predicting the heating performance of a borehole and also, to resolving the design issues. In this study, a single vertical U-tube borehole with a constant wall temperature is considered and analytical equations for temperature distribution in the surrounding ground around the borehole are evaluated based on one- and two-dimensional heat conduction,... 

    Analysis of dehumidification effects on cooling capacity of an evaporative cooler

    , Article Journal of Thermal Science and Technology ; Volume 5, Issue 1 , 2010 , Pages 151-164 ; 18805566 (ISSN) Saidi, M. H ; Aghanajafi, C ; Mohammadian, M ; Sharif University of Technology
    2010
    Abstract
    In this study, effect of desiccant wheel, heat exchanger and cooling coil will be evaluated on decreasing the wet bulb temperature of entering air to cooling tower and decreasing the outlet cold water temperature. For this purpose, change effect of desiccant wheel parameters will be investigated on wet bulb temperature of outlet air from heat exchanger. After that, optimum parameters and minimum wet bulb temperature will be selected. Then, outlet cold water temperature will be achieved for various cooling coil surface temperature with definition of by pass factor and also by using optimum desiccant wheel parameters and entrance air wet bulb temperature to tower related to cooling coil... 

    Simulation of startup operation of an industrial twin-shaft gas turbine based on geometry and control logic

    , Article Energy ; Volume 183 , 2019 , Pages 1295-1313 ; 03605442 (ISSN) Keshavarz Mohammadian, P ; Saidi, M. H ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    In this paper, a transient model is developed to simulate the start-up operation of an industrial twin-shaft gas turbine based on real geometry and control logic. The components’ characteristic curves of the studied gas turbine were generated with the aid of CFD simulation tools and according to the real geometry of each component. The control logic of the studied gas turbine was simplified and coupled with the developed engine performance model. Also, the gas turbine actuators including variable inlet guide vanes, compressor bleed valves, and fuel valves were simulated so that their concurrent effects on the gas turbine transient behavior can be captured precisely. Moreover, the air-cooled... 

    On commuting graphs of semisimple rings

    , Article Linear Algebra and Its Applications ; Volume 390, Issue 1-3 , 2004 , Pages 345-355 ; 00243795 (ISSN) Akbari, S ; Ghandehari, M ; Hadian, M ; Mohammadian, A ; Sharif University of Technology
    2004
    Abstract
    Let R be a non-commutative ring. The commuting graph of R denoted by Λ (R), is a graph with vertex set R Z(R), and two distinct vertices a and b are adjacent if ab = ba. In this paper we investigate some properties of Λ(R), whenever R is a finite semisimple ring. For any finite field F, we obtain minimum degree, maximum degree and clique number of Λ(M n (F)). Also it is shown that for any two finite semisimple rings R and S, if Λ(R) ≃ Λ(S), then there are commutative semisimple rings R1 and S1 and semisimple ring T such that R ≃T × R1, S ≃ T × S1 and |R1| = |S1|. © 2004 Elsevier Inc. All rights reserved  

    Optimization of solar collector surface in solar desiccant wheel cycle

    , Article Energy and Buildings ; Volume 45 , February , 2012 , Pages 197-201 ; 03787788 (ISSN) Hatami, Z ; Saidi, M. H ; Mohammadian, M ; Aghanajafi, C ; Sharif University of Technology
    2012
    Abstract
    This work presents the optimization of a solar collector surface in solar desiccant wheel cycle which for cooling process with typical configuration naming desiccant wheel, heat exchanger and water spray evaporative cooler. In this cooling cycle the thermal solar energy has used to heat the regeneration air of desiccant wheel cycle. The optimum solar collector surface has determined by taking into account of design parameters such as velocity of air, wheel speed, thickness of the desiccant and hydraulic diameter of the desiccant wheel and also operating conditions such as outside temperature, outside relative humidity, regeneration air temperature and total solar irradiance. For this... 

    A conservative extension of the method of characteristics for 1-D shallow flows

    , Article Applied Mathematical Modelling ; Volume 31, Issue 2 , 2007 , Pages 332-348 ; 0307904X (ISSN) Mohammadian, A ; Le Roux, D. Y ; Tajrishi, M ; Sharif University of Technology
    2007
    Abstract
    The method of characteristics (MOC) has been used for a long time in open channels and pipes flows. It is based on non-conservative equations, and hence it cannot be used directly for solving discontinuous shallow flows. In this paper we develop a conservative version of the MOC scheme for 1-D shallow flows by imposing the conservation law at the interpolation step. The conservation property of the scheme ensures the production of an accurate shock modeling and enables the MOC scheme to simulate dam-break type flows. By using a proper interpolation function, the proposed method can also produce quite accurate low-oscillatory results. A number of challenging test cases show considerable... 

    Fast maximum power point tracking for PV arrays under partial shaded conditions

    , Article 2016 18th European Conference on Power Electronics and Applications, EPE 2016 ECCE Europe25 October 2016, Article number 7695463 ; 2016 ; 9789075815245 (ISBN) Ghasemi, M. A ; Parniani, M ; Zarei, S. F ; Mohammadian Foroushani, H ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    P-V characteristic of photovoltaic (PV) arrays under partially shaded conditions (PSC) has multiple peaks, and conventional maximum power point tracking (MPPT) algorithms may fail to track the global maximum power point (GMPP) because of their insufficient intelligence in discriminating the local and global peaks. This paper proposes a novel fast MPPT method to achieve GMPP of PV array under all PSCs. The proposed method reduces the number of required samples and increases the speed of GMPP tracking based on comprehensive study of I-V and P-V characteristics of PV array. Performance of the proposed method has been evaluated in simulations of different PSCs. Also, its performance has been... 

    Compressive Behavior of Confined Concrete Column with FRP Layers

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Armita (Author) ; Khaloo, Alireza (Supervisor)
    Abstract
    In recent years, the use of fiber reinforced polymer (FRP) jackets, as an external lateral confinement has found considerable attention in retrofitting and strengthening existing reinforced concrete (RC) columns in earthquake prone areas. The FRP composites have numerous advantages such as ease in application, high strength and stiffness-weight ratio, no corrosion and negligible changes in the member dimension. Most of previous studies have concentrated on evaluation of the effect of confinement with spiral bars or FRP composites, separately. However, in practice both types of confinements exist in strengthening RC columns.
    This paper presents the results of a computational modeling to... 

    Performance Improvement of Maximum Power Point Tracker in Grid-Connected Photovoltaic Systems

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Hossein (Author) ; Parniani, Mostafa (Supervisor)
    Abstract
    Increase in growing concerns over environmental pollution and depletion of fossil fuel resources motivate the need for cleaner energy technologies and stimulate research in facilitating renewable energy systems. In recent years, photovoltaic systems have attracted great attention since they remove the need for energy storage systems and intermediate processess for energy conversion. However, high capital cost, low efficiency and low energy density per area of these systems, as compared with other technologies hinder its industrial use. To surmount these bottlenecks and improve technical performance of PV systems, it is crucial to optimize configuration of convertor connection and to improve... 

    An Approach to Improve the Security of Big Data

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Esmaeil (Author) ; Jalili, Rasool (Supervisor)
    Abstract
    Different data sources are creating a huge amount of data at increasing speeds that require real-time processing. Such data is called “Big data stream". Although, mining and analysis this type of data is so useful for companies, but it also may cause many privacy breaches. The principle issues for big data stream’ anonymization are real time processing and information loss. There are some works that are proposed for data streams, but they have some drawbacks such as inefficient anonymization of big data stream and also not consider time expiration of tuples that lead to increase the information loss and cost of the data publishing. In this thesis, in order to speed up the ability of big data... 

    Hybrid Approach based on QFD for Improving the Selection of Product Suppliers

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Aidin (Author) ; Mostafavi, Mostafa (Supervisor)
    Abstract
    Multi-Criteria Decision-Making models have been considered by many researchers in recent years. In this study, considering the transition matrix, the probability of changing in the priories of the customers in the framework of a hybrid QFD-ANP has been proposed. The developed methodology is implemented to solve the supplier selection problem, one of the most important problems in the supply chain management, in a dairy manufacturer in Iran. The company is one of the most prominent companies that has a big segment of the dairy market. The results show the efficiency of the proposed methodology for multi-criteria decision-making problems.• Chapter 1) General research reasons for the purpose... 

    Fuzzy Fractional Order PID Design

    , M.Sc. Thesis Sharif University of Technology Mohammadian Roshan, Yaser (Author) ; Sadati, Naser (Supervisor)
    Abstract
    In this thesis a novel Fuzzy Fractional Order Controller (FFOPID) is presented. This controller is designed by the means of the combination of a fuzzy system and a fractional order PID. Fractional controllers, especially fractional PIDs, shows their performance in control systems after the advent of fractional calculus. Fractional PID has better flexibility according to the classic PID. As the real control systems are nonlinear actually, so solving the control problem needs a nonlinear controller. Therefore, a fuzzy system is used in this thesis, in order to adapt the controller parameters with different operating points of the system. Fuzzy system design needs the optimal values for... 

    Lattice Approximation for Stochastic Partial Differential Equations

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Sogol (Author) ; Zohuri Zangeneh, Bijan (Supervisor)

    A behavioral analysis of freight mode choice decisions

    , Article Transportation Planning and Technology ; Volume 34, Issue 8 , 2011 , Pages 857-869 ; 03081060 (ISSN) Samimi, A ; Kawamura, K ; Mohammadian, A ; Sharif University of Technology
    2011
    Abstract
    This paper develops a behavioral analysis of freight mode choice decisions that could provide a basis for an acceptable analytical tool for policy assessment. The paper specifically examines the way that truck and rail compete for commodity movement in the US. Two binary mode choice models are introduced in which some shipment-specific variables (e.g. distance, weight and value) and mode-specific variables (e.g. haul time and cost) are found to be determinants. The specifications of the non-selected choice are imputed in a machine learning module. Shipping cost is found to be a central factor for rail shipments, while road shipments are found to be more sensitive to haul time. Sensitivity of... 

    Studying and Modeling Climatic and Terrestrial Factors Effect the Occurrence of Dust Phenomena, and Determining the Origin of Dust Storms in IRAN

    , M.Sc. Thesis Sharif University of Technology Mohammadian Bishe, Esmaeil (Author) ; Farhanieh, Bijan (Supervisor)
    Abstract
    Particulate matter is an important source of air pollution. Particulate matters have an Undesirable effect on the environment, economic, and the health of Tehran Citizens. Annually, more than 8 thousands of tons of mineral dust from Internal and external resources deposit in Tehran city. In this project, the increase in the level of PM10 concentration during June, 12th to 14th, 2015 have been considered. The intrusion and dispersion of mineral dust during June, 11th to 15h, 2015 have been simulated with the HYSPLIT Model. Also, the Trajectory of particle end in Tehran during the mentioned days simulated and plotted with the HYSPLIT. The results show that more than 85% of PM10 reported by Air... 

    Commutativity of the adjacency matrices of graphs

    , Article Discrete Mathematics ; Volume 309, Issue 3 , 2009 , Pages 595-600 ; 0012365X (ISSN) Akbari, S ; Moazami, F ; Mohammadian, A ; Sharif University of Technology
    2009
    Abstract
    We say that two graphs G1 and G2 with the same vertex set commute if their adjacency matrices commute. In this paper, we find all integers n such that the complete bipartite graph Kn, n is decomposable into commuting perfect matchings or commuting Hamilton cycles. We show that there are at most n - 1 linearly independent commuting adjacency matrices of size n; and if this bound occurs, then there exists a Hadamard matrix of order n. Finally, we determine the centralizers of some families of graphs. © 2008 Elsevier B.V. All rights reserved  

    A Novel Model for Mutual Module and Operation Assignment in a RMS

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Noushin (Author) ; Fatahi Valilai, Omid (Supervisor)
    Abstract
    Reconfigurable Manufacturing system (RMS) is used to surge the speed of production and its flexibility of it which is restricted to limited extent. Its flexibility confined to at most that is essential to fabricate the members of a part family. This thesis proposes a novel model for RMS, that, that is a manufacturing framework that is cost-effectively and at the minimum time responses to changesto changes and can fulfill thefulfill marketthe demandmarket demands rapidly. In many researches the minimization of timeof time and cost is the main factors that is making anmake impressionan onimpression projecton the performance of the performanceproject. In the frame offrame theof... 

    Commuting graphs of matrix algebras

    , Article Communications in Algebra ; Volume 36, Issue 11 , 2008 , Pages 4020-4031 ; 00927872 (ISSN) Akbari, S ; Bidkhori, H ; Mohammadian, A ; Sharif University of Technology
    2008
    Abstract
    The commuting graph of a ring R, denoted by Γ(R), is a graph whose vertices are all noncentral elements of R, and two distinct vertices x and y are adjacent if and only if xy = yx. The commuting graph of a group G, denoted by Γ(G), is similarly defined. In this article we investigate some graph-theoretic properties of Γ(Mn(F)), where F is a field and n ≥ 2. Also we study the commuting graphs of some classical groups such as GLn(F) and SLn(F). We show that Γ(Mn(F)) is a connected graph if and only if every field extension of F of degree n contains a proper intermediate field. We prove that apart from finitely many fields, a similar result is true for Γ(GLn(F)) and Γ(SL n(F)). Also we show...