Search for: mathematical-formulation
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    Modern Production Data Analysis of Bottom Water Drive Reservoir

    , M.Sc. Thesis Sharif University of Technology Zardoshti, Mohammad Mehdi (Author) ; Masihi, Mohsen (Supervisor) ; Gerami, Shahab (Supervisor)
    Hydrocarbon reservoirs may be classified on the basis of their drive mechanisms. In the reservoirs adjoined by water aquifers, waterdrive may be the primary production mechanism. The invasion of reservoir rock by aquifer water may have a significant impact on reservoir performance. Therefore, water influx into hydrocarbon reservoirs must be predicted accurately as a function of time, pressure history at the reservoir/aquifer interface, reservoir/aquifer size ratio, and aquifer characteristics.To forecast the performance in a waterdrive reservoir, an aquifer model simulating the fluid flow in the aquifer and flow from the aquifer into the reservoir is needed. Robust techniques for analysis of... 

    Fast estimation of space-robots inertia parameters: A modular mathematical formulation

    , Article Acta Astronautica ; Volume 127 , 2016 , Pages 283-295 ; 00945765 (ISSN) Nabavi Chashmi, S. Y ; Malaek, S. M. B ; Sharif University of Technology
    Elsevier Ltd 
    This work aims to propose a new technique that considerably helps enhance time and precision needed to identify "Inertia Parameters (IPs)" of a typical Autonomous Space-Robot (ASR). Operations might include, capturing an unknown Target Space-Object (TSO), "active space-debris removal" or "automated in-orbit assemblies". In these operations generating precise successive commands are essential to the success of the mission. We show how a generalized, repeatable estimation-process could play an effective role to manage the operation. With the help of the well-known Force-Based approach, a new "modular formulation" has been developed to simultaneously identify IPs of an ASR while it captures a... 

    Innovative theory for the compliance computation in rotors

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1779-1788 ; 10263098 (ISSN) Ranjbaran, A ; Ranjbaran, M ; Sharif University of Technology
    The conventional energy release rate approach to the computation of the crack compliance in rotors is critically reviewed and its shortcoming is highlighted. The state functions and the generic compliance are introduced, defined, and verified. The proposed functions are defined based on the end states' conditions and are exact. The crack compliance of the shaft in torsion is explicitly defined as the function of the crack depth ratio and recommended as a good alternative to the classical procedure of the energy release rate method. The accuracy and efficiency of the work are verified by concise mathematical formulation and comparison of the results of the work with the others in four... 

    Generalized non-overlapping tooth coil winding method for variable reluctance resolvers

    , Article IEEE Transactions on Industrial Electronics ; 2021 ; 02780046 (ISSN) Saneie, H ; Nasiri Gheidari, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Variable Reluctance (VR) resolver is an angular position sensor that is commonly used in the automotive industry. In this paper, A general method for determining the winding configuration of VR resolvers is proposed, that eases the manufacturing process. At first, the operational principle of conventional winding has been presented using mathematical formulations. Following that, the non-overlapping tooth coil winding method, as the ideal winding option for VR resolver, has been extended that can be applied to the VR resolver with arbitrary poles and stator tooth numbers. The method of determining the reference and signal windings presented and used to determine the winding for a 2, 6, and 8... 

    A multistage stochastic programming approach in project selection and scheduling

    , Article International Journal of Advanced Manufacturing Technology ; Vol. 70, issue. 9-12 , 2014 , pp. 2125-2137 ; ISSN: 02683768 Rafiee, M ; Kianfar, F ; Farhadkhani, M ; Sharif University of Technology
    In this paper, the joint problem of project selection and project scheduling under uncertain environment is formulated, analyzed, and solved by multistage stochastic programs. First of all, a general mathematical formulation which can address several versions of the problem is presented. A multi-period project selection and scheduling problem is introduced and modeled by multistage stochastic programs, which are effective for solving long-term planning problems under uncertainty. A set of scenarios and corresponding probabilities is applied to model the multivariate random data process (costs or revenues, available budget, chance of success). Then, due to computational complexity, a scenario... 

    Manufacturing error compensation based on cutting tool location correction in machining processes

    , Article International Journal of Computer Integrated Manufacturing ; Vol. 27, Issue. 11 , 29 Oct , 2014 , pp. 969-978 ; ISSN: 0951192X Khodaygan, S ; Sharif University of Technology
    Inaccuracies in workpiece location lead to errors in position and orientation of machined features on the workpiece, and strongly affect the assemblability and the quality of the product. The accurate positioning of workpiece on a fixture is influenced by rigid body displacements and rotations of the workpiece due to several errors (e.g. geometric radial and position errors in locators and manufacturing tolerances of the workpiece). In this paper, an efficient approach is introduced for analysis and compensation errors in the workpiece-fixture-cutting tool system. A new mathematical formulation of workpiece-fixture modelling is proposed to establish the relationship between the locating... 

    Maximum clique-based resource allocation in device-to-device communications

    , Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 30 August 2015 through 2 September 2015 ; Volume 2015-December , Sept , 2015 , Pages 1195-1200 ; 9781467367820 (ISBN) Elhami, G ; Zehni, M ; Pakravan, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Device-to-Device communication (D2D) integrated in cellular networks emerges as a new trend in response to notable rise in traffic demand. Resource allocation is one of the important challenges in deployment of D2D networks. In this paper, we formulate an optimization problem for optimal resource allocation and then propose a novel algorithm namely maximum clique based resource allocation (MCRA) for improving the spectral reuse based on graph theoretic concept of maximum clique. Practical application of D2D communications requires each node to receive and transmit signals during the communication process. We have considered this issue in constructing the interference graph and mathematical... 

    3D simulation of propagation of hydraulically driven fractures in oil reservoirs using EFG mesh-less method considering coupled hydro-mechanical effects

    , Article Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014, 22 September 2014 through 25 September 2014, Kyoto ; September , 2015 , Pages 1675-1680 ; 9781138001480 (ISBN) Pak, A ; Samimi, S ; Sharif University of Technology
    Taylor and Francis - Balkema  2015
    Creating hydraulically induced fractures in oil/gas reservoirs is one of the methods for Enhanced Oil Recovery (EOR) that has been applied extensively in petroleum industry in recent years. Despite its popularity, the design process of Hydraulic Fracture treatment is mostly empirical based on the previous experiences gained in the oil-rich formation. The reason lies in the complexities involved in the Hydraulic Fracture process including interacting effects of fluid(s) flowand solid deformations, injection of non-Newtonian fluids in the porous media, leak-off of the injected fluid into the formation, complex geometry of the induced fracture in the intact or naturally fractured rock,... 

    Rational approximations in the simulation and implementation of fractional-order dynamics: A descriptor system approach

    , Article Automatica ; Volume 46, Issue 1 , 2010 , Pages 94-100 ; 00051098 (ISSN) Tavazoei, M. S ; Haeri, M ; Sharif University of Technology
    This paper deals with issues related to the use of rational approximations in the simulation of fractional-order systems and practical implementations of fractional-order dynamics and controllers. Based on the mathematical formulation of the problem, a descriptor model is found to describe the rational approximating model. This model is analyzed and compared with the original fractional-order system under the aspects which are important in their simulation and implementation. From the results achieved, one can determine in what applications the use of rational approximations would be unproblematic and in what applications it would lead to fallacious results. In order to clarify this point,... 

    An efficient method for workpiece locating error prediction in machining process

    , Article SAE 2016 World Congress and Exhibition, 12 April 2016 through 14 April 2016 ; Volume 2016-April , April , 2016 Khodaygan, S ; Sharif University of Technology
    SAE International 
    Fixtures play a key role in locating workpieces to manufacture high quality products within many processes of the product lifecycle. Inaccuracies in workpiece location lead to errors in position and orientation of machined features on the workpiece, and strongly affect the assemblability and the final quality of the product. The accurate positioning of workpiece on a fixture is influenced by rigid body displacements and rotations of the workpiece. In this paper, a systematic approach is introduced to investigate the located workpiece position errors. A new mathematical formulation of fixture locators modeling is proposed to establish the relationship between the workpiece position error and... 

    Mine blast harmony search: a new hybrid optimization method for improving exploration and exploitation capabilities

    , Article Applied Soft Computing Journal ; Volume 68 , July , 2018 , Pages 548-564 ; 15684946 (ISSN) Sadollah, A ; Sayyaadi, H ; Yoo, D. G ; Lee, H. M ; Kim, J. H ; Sharif University of Technology
    Elsevier Ltd  2018
    This paper proposes a hybrid optimization method that combines the power of the harmony search (HS) with the mine blast algorithm (MBA). The resulting mine blast harmony search (MBHS) uses MBA for exploration and HS for exploitation. The HS is inspired by the improvisation process of musicians, while the MBA is derived based on explosion of landmines. The HS used in the hybrid algorithm is an improved version, introducing a new concept for the harmony memory size, while the MBA is modified in terms of its mathematical formulation. Several numerical problems and benchmarks with many design variables and constraints are used to validate MBHS, and the optimization results are compared with... 

    Numerical investigation of flow pattern and hydrodynamic forces of submerged marine propellers using unsteady boundary element method

    , Article Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment ; Volume 233, Issue 1 , 2019 , Pages 67-79 ; 14750902 (ISSN) Najafi, S ; Abbaspoor, M ; Sharif University of Technology
    SAGE Publications Ltd  2019
    In this study, a numerical model of unsteady potential flow around submerged marine propellers has been developed. The boundary element approach in combination with time stepping method to model free wake dynamics has been implemented. An important feature of this method in the simulation of pressure-dominant problems is a proper balance between time and accuracy in the numerical process. Another advantage of time stepping method is that there is no need to define wake geometry before modeling. Due to inherent instability of boundary integral equations, a smoothing function to damp the effect of singularities is imposed to the solution. The main innovative idea of this work is that the... 

    Structural damage detection using principal component analysis of frequency response function data

    , Article Structural Control and Health Monitoring ; Volume 27, Issue 7 , 2020 Esfandiari, A ; Nabiyan, M. S ; Rahimzadeh Rofooei, F ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    In this paper, a new sensitivity-based model updating method is presented based on the changes of principal components (PCs) of frequency response function (FRF). Structural damage estimation, identification of damage location and severity, is conducted by an innovative sensitivity relation. The sensitivity relation is derived by incorporating PC analysis (PCA) data obtained from the incomplete measured structural responses in a mathematical formulation and is then solved by the least square method. In order to demonstrate the performance of the proposed method, it is applied to a truss and a frame model. The results prove the ability of the method as a robust damage detection algorithm in... 

    Thermomechanics of material growth and remodeling in uniform bodies based on the micromorphic theory

    , Article Journal of the Mechanics and Physics of Solids ; Volume 138 , 2020 Javadi, M ; Epstein, M ; Asghari, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Based on the micromorphic theory, a novel mathematical formulation for the mechanical modeling of material growth and remodeling processes in finite deformation is developed. These two processes have an important significance in evolution of living tissues. The presented formulation incorporates both the volumetric growth and mass flux phenomena into the modeling with the aid of the micromorphic theory's capability to include internal structures in materials. The balance equation of microinertia is presented which reveals the importance of rearrangement and alteration of microstructure in the micromorphic material growth. Within the framework of material uniformity, the evolution laws are... 

    Material growth and remodeling formulation based on the finite couple stress theory

    , Article International Journal of Non-Linear Mechanics ; Volume 121 , 2020 Javadi, M ; Asghari, M ; Sohrabpour, S ; Sharif University of Technology
    Elsevier Ltd  2020
    The mathematical formulation for material growth and remodeling processes in finite deformation is developed based on the couple stress theory. The generalized continuum mechanics of couple stress theory is capable of capturing small-scale cellular effects and of modeling mass flux in these processes. The frame-indifferent balance equations of mass, linear and angular momentums, as well as internal energy together with the entropy inequality are first introduced in the presence of the mass flux based on the finite couple-stress theory. Then, within the framework of material uniformity the Eshelby and Mandel stress tensors as driving or configurational forces for local rearrangement of the... 

    A comprehensive mathematical simulation of the composite size-dependent rotary 3D microsystem via two-dimensional generalized differential quadrature method

    , Article Engineering with Computers ; 2021 ; 01770667 (ISSN) Liu, H ; Zhao, Y ; Pishbin, M ; Habibi, M ; Bashir, M. O ; Issakhov, A ; Sharif University of Technology
    Springer Science and Business Media Deutschland GmbH  2021
    In this study, frequency simulation and critical angular velocity of a size-dependent laminated rotary microsystem using modified couple stress theory (MCST) as the higher-order elasticity model is undertaken. The centrifugal and Coriolis impacts due to the spinning are taken into account. The size-dependent thick annular microsystem's computational formulation, non-classical governing equations, and corresponding boundary conditions are obtained by using the higher-order stress tensors and symmetric rotation gradient to the strain energy. By using a single material length scale factor, the most recent non-classical approach captures the size-dependency in the annular laminated microsystem.... 

    Pricing and quality setting strategy in maritime transportation: Considering empty repositioning and demand uncertainty

    , Article International Journal of Production Economics ; Volume 240 , 2021 ; 09255273 (ISSN) Najafi, M ; Zolfagharinia, H ; Sharif University of Technology
    Elsevier B.V  2021
    Imbalanced international trade and the limited number of containers in the maritime transportation industry have resulted in considerable costs and decreased profits for shipping firms. To manage these issues, this study utilizes price management techniques to control empty container repositioning in a transportation system. In this system, there is a firm providing transportation services between two ports in both directions. Each direction has its own uncertain potential demand that can be affected by the prices and the quality set by the firm. We develop a mathematical formulation to set the quality and prices of the service in order to maximize the firm's profit. Due to demand... 

    Two tuned multi-objective meta-heuristic algorithms for solving a fuzzy multi-state redundancy allocation problem under discount strategies

    , Article Applied Mathematical Modelling ; 2015 ; 0307904X (ISSN) Mousavi, S. M ; Alikar, N ; Niaki, S. T. A ; Bahreininejad, A ; Sharif University of Technology
    Elsevier Inc  2015
    In this study, a bi-objective multi-state redundancy allocation problem of series-parallel systems consisting of some serial subsystems, each with non-repairable components in parallel, is investigated. Furthermore, due to uncertainty involved, both the performance rates and the availabilities of components are considered fuzzy. In addition, two strategies of all-unit and incremental-quantity discounts are used to purchase the components and that the fuzzy universal generating function (FUGF) is employed to evaluate the system availability. The aim is to find the optimal redundancy so as within limited budget and system weight the maximum system availability is obtained while the total cost... 

    Assessment of three preconditioning schemes for solution of the two-dimensional Euler equations at low Mach number flows

    , Article International Journal for Numerical Methods in Engineering ; Volume 89, Issue 1 , 2012 , Pages 20-52 ; 00295981 (ISSN) Hejranfar, K ; Kamali Moghadam, R ; Sharif University of Technology
    Three preconditioners proposed by Eriksson, Choi and Merkel, and Turkel are implemented in a 2D upwind Euler flow solver on unstructured meshes. The mathematical formulations of these preconditioning schemes for different sets of primitive variables are drawn, and their eigenvalues and eigenvectors are compared with each other. For this purpose, these preconditioning schemes are expressed in a unified formulation. A cell-centered finite volume Roe's method is used for the discretization of the preconditioned Euler equations. The accuracy and performance of these preconditioning schemes are examined by computing steady low Mach number flows over a NACA0012 airfoil and a two-element... 

    A comparative study of two preconditioners for solving 3D inviscid low speed flows

    , Article Applied Mechanics and Materials ; Volume 110-116 , 2012 , Pages 423-430 ; 16609336 (ISSN) ; 9783037852620 (ISBN) Hejranfar, K ; Moghadam, R. K ; Sharif University of Technology
    In the present study, two preconditioners proposed by Eriksson, and Choi and Merkel are implemented on a 3D upwind Euler flow solver on unstructured meshes. The mathematical formulations of these preconditioning schemes for the set of primitive variables Q→p 1=[ρ u v , w p] T are drawn and their eigenvalues and eigenvectors are compared with each others. A cell-centered finite volume Roe's method is used for discretization of the 3D preconditioned Euler equations. The accuracy and performance of these preconditioning schemes are examined by computing low Mach number flows over the ONERA M6 wing for different conditions