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    A counterexample to polynomially bounded realizability of basic arithmetic

    , Article Notre Dame Journal of Formal Logic ; Volume 60, Issue 3 , 2019 , Pages 481-489 ; 00294527 (ISSN) Ardeshir, M ; Khaniki, E ; Shahriari, M ; Sharif University of Technology
    Duke University Press  2019
    Abstract
    We give a counterexample to the claim that every provably total function of Basic Arithmetic is a polynomially bounded primitive recursive function. © 2019 by University of Notre Dame  

    A counterexample to polynomially bounded realizability of basic arithmetic

    , Article Notre Dame Journal of Formal Logic ; Volume 60, Issue 3 , 2019 , Pages 481-489 ; 00294527 (ISSN) Ardeshir, M ; Khaniki, E ; Shahriari, M ; Sharif University of Technology
    Duke University Press  2019
    Abstract
    We give a counterexample to the claim that every provably total function of Basic Arithmetic is a polynomially bounded primitive recursive function. © 2019 by University of Notre Dame  

    Notes on the state space realizations of rational order transfer functions

    , Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 58, Issue 5 , 2011 , Pages 1099-1108 ; 15498328 (ISSN) Tavakoli-Kakhki, M ; Haeri, M ; Tavazoei, M. S ; Sharif University of Technology
    2011
    Abstract
    In this paper, the concept of minimal state space realization for a fractional order system is defined from the inner dimension point of view. Some basic differences of the minimal realization concept in the fractional and integer order systems are discussed. Five lower bounds are obtained for the inner dimension of a minimal state space realization of a fractional order transfer function. Also, the concept of optimal realization, which can be a helpful concept in practice, is introduced for transfer functions having rational orders. An algorithm is suggested to obtain the optimal realizations of rational order transfer functions. The introduced concept might be used to get minimal... 

    Minimal realizations for some classes of fractional order transfer functions

    , Article IEEE Journal on Emerging and Selected Topics in Circuits and Systems ; Volume 3, Issue 3 , 2013 , Pages 313-321 ; 21563357 (ISSN) Tavazoei, M. S ; Tavakoli Kakhki, M ; Sharif University of Technology
    2013
    Abstract
    It has been known that finding a minimal pseudo state space realization for a fractional order transfer function is helpful in circuitry implementation of such a transfer function with the minimum number of fractional capacitors. Considering this importance, the present paper deals with finding minimal realizations for some classes of fractional order transfer functions. To this end, at first some upper bounds are obtained for the minimal inner dimension of a fractional order transfer function. By considering these upper bounds and also the lower bounds, previously presented in literature, the minimal inner dimension is exactly found for some classes of fractional order transfer functions.... 

    Passively realizable approximations of non-realizable fractional order impedance functions

    , Article Journal of the Franklin Institute ; Volume 357, Issue 11 , 2020 , Pages 7037-7053 Tavazoei, M. S ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    Approximating the fractional order differentiation and integration operators is a common approach in implementation of fractional order dynamics. This paper aims to investigate how the procedure of approximating the fractional order operators influences on the realizability of a fractional order impedance function by passive networks. To this aim, conditions for the possibility of passive realization of the approximations of the fractional order impedance functions by using RLC components are obtained. More precisely, considering two general forms for the filters approximating the fractional order operators, the open mapping theorem in complex analysis is applied to obtain the realizability... 

    Ranking Realizations of Reservoir Model by Using Well Test Data

    , M.Sc. Thesis Sharif University of Technology Tahmasbi, Mehran (Author) ; Masihi, Mohsen (Supervisor) ; Shad, Saeed (Co-Advisor)
    Abstract
    Characteristic of the reservoir, including the important discussion in the oil industry, is widely practiced in the modeling, simulation and EOR. One of the methods fordetermining the specifications of the reservoir is geostatistical technique. This means that a large number of realizations of the reservoir model to assess the uncertainty in reservoir descriptions of performance predictions should be made.However flow simulation of all these realizations is very difficult due to cost and time calculations.To mend the problem, we use ranking realization that finally a minor number of realizations are selected and flow simulation is used to them.In this project, we use streamline simulation to... 

    Realizability and dynamic reconfiguration of chor specifications

    , Article Informatica (Ljubljana) ; Volume 35, Issue 1 , 2011 , Pages 39-49 ; 03505596 (ISSN) Roohi, N ; Salaun, G ; Sharif University of Technology
    Abstract
    Choreography description languages aim at specifying from a global point of view interactions among a set of services involved in a new system. From this specification, local implementations or peers can be automatically generated. Generation of peers that precisely implement the choreography specification is not always possible: This problem is known as realizability. When peers corresponding to this specification are being executed we may want to modify the choreography specification and reconfigure dynamically the system. This is the case for instance if we add or remove interactions due to the addition of functionalities to the system at hand or the loss of a service. In this article, we... 

    A new approach to reduce the dynamic order of induction generators

    , Article International Journal of Power and Energy Systems ; Volume 27, Issue 4 , 2007 , Pages 315-319 ; 10783466 (ISSN) Varahram, M. H ; Behzadi Rafi, S ; Sharif University of Technology
    Acta Press  2007
    Abstract
    Various attempts have been made to derive linearized, reduced order models of induction generators. Due to the fact that there is usually numerous number of these machines in wind power plants, these models provide great facilities in calculations, and therefore are used widely in power system transient stability studies. In this paper, some of these methods are discussed and compared and then a method known as "balanced realizations" is used to reduce the dynamic order of the machine. Computer simulation shows that the last method markedly improves the accuracy of the resulting reduced order model. The improvement is demonstrated by comparing the response characteristics predicted by each... 

    Thermal entanglement of spins in an inhomogeneous magnetic field

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 71, Issue 2 , 2005 ; 10502947 (ISSN) Asoudeh, M ; Karimipour, V ; Sharif University of Technology
    American Physical Society  2005
    Abstract
    We study the effect of inhomogeneities in the magnetic field on the thermal entanglement of a two-spin system. We show that in the ferromagnetic case a very small inhomogeneity is capable of producing large values of thermal entanglement. This shows that the absence of entanglement in the ferromagnetic Heisenberg system is highly unstable against inhomogeneity of magnetic fields, which is inevitably present in any solid state realization of qubits. © 2005 The American Physical Society  

    Evaluation of Caviar Models Incorporated with Intraday Information ,the Case Study:Estimation Value at Risk of Gold

    , M.Sc. Thesis Sharif University of Technology Karimi, Parvane (Author) ; Barakchian, Mahdi (Supervisor)
    Abstract
    Value at risk (VaR) is the maximum loss of the asset portfolio at the specified confidence level and certain time horizon. This tool is used to measure market risk and also used as a basis in determining financial standards for international financial instituation. Conditional Autoregressive Value at Risk models or CAViaR models introduced by Engle and Manganelli (2004). This models calculate VaR base on quantile regession approach and show some promising performance properties.
    In order to propose a more accurate model for calcutating VaR , we develop CAViaR models by incorporating them with intraday information then we calculate VaR with this kind of models and CAViaR... 

    Development of Low-order Model/controllers for Oil Reservoir Smart Wells

    , M.Sc. Thesis Sharif University of Technology Hemmati, Sahar (Author) ; Pishvaie, Mahmoud Reza (Supervisor)
    Abstract
    Upstream oil industry operators have turned to optimal production methods for further recoveries, such as smart wells. Control algorithms for smart wells must be equipped with online measurements, in other words, reflected in the feedback philosophy. On the other hand, after discretization, an oil reservoir's dynamic and control-driven model becomes a realization or a large-scale and sparse state space. One way to deal with this problem and provide an appropriate model for the design of smart well controllers is to use appropriate reservoir dimensional reduction methods. Therefore, to design low-order controllers, a study must first be performed at the level of the reservoir model and its... 

    Passive realization of fractional-order impedances by a fractional element and rlc components: conditions and procedure

    , Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 64, Issue 3 , 2017 , Pages 585-595 ; 15498328 (ISSN) Sarafraz, M. S ; Tavazoei, M. S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2017
    Abstract
    In this paper, conditions for checking the realizability of fractional-order impedance functions by passive networks composed of a fractional element (either a fractional capacitor or a fractional inductor) and some RLC components are derived. To this end, at first the newly obtained conditions for realizability of fractional-order impedance functions by a passive network composed of a fractional capacitor and some RLC components are extended to include the case that the polynomials involving in the impedance function can have roots on the imaginary axis. Then, the necessary and sufficient conditions are found on a fractional-order impedance function to be realized by a passive network... 

    Color PCA eigenimages and their application to compression and watermarking

    , Article Image and Vision Computing ; Volume 26, Issue 7 , 2008 , Pages 878-890 ; 02628856 (ISSN) Abadpour, A ; Kasaei, S ; Sharif University of Technology
    Elsevier Ltd  2008
    Abstract
    From the birth of multi-spectral imaging techniques, there has been a tendency to consider and process this new type of data as a set of parallel gray-scale images, instead of an ensemble of an n-D realization. However, it has been proved that using vector-based tools leads to a more appropriate understanding of color images and thus more efficient algorithms for processing them. Such tools are able to take into consideration the high correlation of the color components and thus to successfully carry out energy compaction. In this paper, a novel method is proposed to utilize the principal component analysis in the neighborhoods of an image in order to extract the corresponding eigenimages.... 

    Fractional Simplification of Linear Fractional Order Models

    , Ph.D. Dissertation Sharif University of Technology Tavakoli-Kakhki, Mahsan (Author) ; Haeri, Mohammad (Supervisor)
    Abstract
    In recent years, increasing attention has been paid to the fractional calculus as a powerful tool for more precise modeling of real world phenomena. Also, it has been shown that using this tool in designing control systems results in controllers that are more efficient in comparison with their traditional integer order counterparts. In spite of the advantages of fractional order models, the difficulties in the implementation of this type of models are still the main concern of the control system community. Clearly, as a model becomes simpler, its implementation becomes more convenient. Therefore, one way to rectify the implementation problems is to model the intended system as simple as... 

    Random walk-percolation-based modeling of two-phase flow in porous media: Breakthrough time and net to gross ratio estimation

    , Article Physica A: Statistical Mechanics and its Applications ; Vol. 406, issue , July , 2014 , p. 214-221 ; ISSN: 03784371 Ganjeh-Ghazvini, M ; Masihi, M ; Ghaedi, M ; Sharif University of Technology
    Abstract
    Fluid flow modeling in porous media has many applications in waste treatment, hydrology and petroleum engineering. In any geological model, flow behavior is controlled by multiple properties. These properties must be known in advance of common flow simulations. When uncertainties are present, deterministic modeling often produces poor results. Percolation and Random Walk (RW) methods have recently been used in flow modeling. Their stochastic basis is useful in dealing with uncertainty problems. They are also useful in finding the relationship between porous media descriptions and flow behavior. This paper employs a simple methodology based on random walk and percolation techniques. The... 

    Realizability of choreographies using Process algebra encodings

    , Article IEEE Transactions on Services Computing ; Volume 5, Issue 3 , 2012 , Pages 290-304 ; 19391374 (ISSN) Salaün, G ; Bultan, T ; Roohi, N ; Sharif University of Technology
    IEEE  2012
    Abstract
    Service-oriented computing has emerged as a new software development paradigm that enables implementation of Web accessible software systems that are composed of distributed services which interact with each other via exchanging messages. Modeling and analysis of interactions among services is a crucial problem in this domain. Interactions among a set of services that participate in a service composition can be described from a global point of view as a choreography. Choreographies can be specified using specification languages such as Web Services Choreography Description Language (WS-CDL) and visualized using graphical formalisms such as collaboration diagrams. In this paper, we present an... 

    The minimal state space realization for a class of fractional order transfer functions

    , Article SIAM Journal on Control and Optimization ; Volume 48, Issue 7 , 2010 , Pages 4317-4326 ; 03630129 (ISSN) Tavakoli Kakhki, M ; Haeri, M ; Sharif University of Technology
    2010
    Abstract
    In this paper, the minimal state space realization of a fractional order transfer function is investigated in the sense of inner dimension both for commensurate and incommensurate cases. It is shown that while the traditional tools are applicable to check the minimality of a commensurate realization, there is no specific procedure to be certain about the minimality of incommensurate realizations. In this regard, the necessary and sufficient conditions are obtained for a specific class of fractional order transfer functions by which one can verify the existence of minimal realizations with inner dimension 2. Furthermore, a transformation is introduced through which all these realizations can... 

    Analyzing chor specifications by translation into FSP

    , Article Electronic Notes in Theoretical Computer Science ; Volume 255 , 2009 , Pages 159-176 ; 15710661 (ISSN) Roohi, N ; Salaun, G ; Mirian, H ; Sharif University of Technology
    2009
    Abstract
    A choreography specifies activities and interactions among a set of services from a global point of view. From this specification, local implementations or peers can be automatically generated. Generation of peers that precisely implement the choreography specification is not always possible: this problem is known as realizability. This paper presents an encoding of the Chor choreography calculus into the FSP process algebra. This encoding allows to: (i) validate and verify Chor specifications using the FSP toolbox (LTSA), (ii) generate peer protocols from its choreography specified in Chor, (iii) test for realizability of the Chor specification, and (iv) generate Java code from FSP for... 

    Circuit realization of a tilted Dirac cone: Platform for fabrication of curved spacetime geometry on a chip

    , Article Physical Review B ; Volume 104, Issue 24 , 2021 ; 24699950 (ISSN) Motavassal, A ; Jafari, S. A ; Sharif University of Technology
    American Physical Society  2021
    Abstract
    We present an LC circuit model that supports a tilted “Dirac cone” in its spectrum. The tilt of the Dirac cone is specified by the parameters of the model consisting of mutual inductance between the neighboring sites and a capacitance C0 at every lattice site. These parameters can be completely measured by impedance spectroscopy. Given that a tilted Dirac cone can be described by a background spacetime metric, the impedance spectroscopy can perfectly provide (local) information about the metric of the spacetime. Nonuniform spatial dependence of the mutual inductance or capacitance induces a nontrivial geometrical structure on the emergent spacetime. Our work extends the range of usefulness...