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    A swarm based method for solving transit network design problem

    , Article Australasian Transport Research Forum, ATRF 2013 - Proceedings ; 2013 Bagherian, M ; Massah, S ; Kermanshahi, S ; Sharif University of Technology
    Australasian Transport Research Forum  2013
    In this study, a Discrete Particle Swarm Optimization (DPSO) algorithm is assimilated to solve the Transit Network Design Problem (TNDP). First, A Mixed Integer Model is developed for the TNDP. The solution methodology utilized here is made of two major elements. A route generation module is firstly developed to generate all the feasible transit lines. Through the second part, a DPSO algorithm is utilized to select the optimal set of lines from the constructed ones. The objective function is to maximize coverage index while satisfying the operator cost upper level constraints. The efficacy and accuracy of the implemented algorithms is compared with ones obtained by an enumeration process as... 

    KNNDIST: A non-parametric distance measure for speaker segmentation

    , Article 13th Annual Conference of the International Speech Communication Association 2012, INTERSPEECH 2012 ; Volume 3 , 2012 , Pages 2279-2282 ; 9781622767595 (ISBN) Mohammadi, S. H ; Sameti, H ; Langarani, M. S. E ; Tavanaei, A ; Sharif University of Technology
    A novel distance measure for distance-based speaker segmentation is proposed. This distance measure is nonparametric, in contrast to common distance measures used in speaker segmentation systems, which often assume a Gaussian distribution when measuring the distance between two audio segments. This distance measure is essentially a k-nearest-neighbor distance measure. Non-vowel segment removal in preprocessing stage is also proposed. Speaker segmentation performance is tested on artificially created conversations from the TIMIT database and two AMI conversations. For short window lengths, Missed Detection Rated is decreased significantly. For moderate window lengths, a decrease in both... 

    Design and application of a new tapered superelement for analysis of revolving geometries

    , Article Finite Elements in Analysis and Design ; Volume 47, Issue 11 , November , 2011 , Pages 1242-1252 ; 0168874X (ISSN) Ahmadian, M. T ; Movahhedy, M. R ; Rezaei, M. M ; Sharif University of Technology
    Structures of tapered geometry are customarily used in a variety of applications. The analysis of such structures is usually made through finite element method using traditional beam, shell or brick elements. In this paper, a new tapered superelement is presented that lends itself to modeling revolving geometries under lateral, axial and torsional loads. The presented tapered superelement has 16 nodes. The performance of this element under static and dynamic loading and in rotating condition is examined. It is shown that this element yields accurate results with higher computational efficiency compared to conventional elements. Furthermore, it is verified that a single tapered superelement... 

    Finite element simulation of shot peening coverage with the special attention on surface nanocrystallization

    , Article Procedia Engineering, 5 June 2011 through 9 June 2011 ; Volume 10 , 2011 , Pages 2464-2471 ; 18777058 (ISSN) Hassani Gangaraj, S. M ; Guagliano, M ; Farrahi, G. H ; Sharif University of Technology
    The present study aims to challenge the existing finite element models in terms of one of the most important practical parameters, i.e. coverage. Important models from the literature are re-simulated and their resulted treated surfaces are carefully examined. Result of this study shows that existing finite element models could not reflect the realistic coverage. A variable dimension symmetry cell is developed in order to acquire full coverage and at the same time not increasing the computational cost. This model can successfully simulate the surface nanocrystallization by severe shot peening in which the amount of coverage is much higher than conventional shot peening  

    Functional observer design with application to pre-compensated multi-variable systems

    , Article 2015 IEEE Conference on Control and Applications, CCA 2015 - Proceedings, 21 September 2015 through 23 September 2015 ; 2015 , Pages 620-625 ; 9781479977871 (ISBN) Nazmi, S ; Mohajerpoor, R ; Abdi, H ; Nahavandi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Partial state estimation of dynamical systems provides significant advantages in practical applications. Likewise, pre-compensator design for multi variable systems invokes considerable increase in the order of the original system. Hence, applying functional observer to pre-compensated systems can result in lower computational costs and more practicability in some applications such as fault diagnosis and output feedback control of these systems. In this note, functional observer design is investigated for pre-compensated systems. A lower order pre-compensator is designed based on a H2 norm optimization that is designed as the solution of a set of linear matrix inequalities (LMIs). Next, a... 

    Detection of top-K central nodes in social networks: A compressive sensing approach

    , Article Proceedings of the 2015 IEEE/ACM International Conference on Advances in Social Networks Analysis and Mining, ASONAM 2015, 25 August 2015 through 28 August 2015 ; 2015 , Pages 902-909 ; 9781450338547 (ISBN) Mahyar, H ; Pei, J ; Tang, J ; Silvestri, F ; Sharif University of Technology
    Association for Computing Machinery, Inc  2015
    In analysing the structural organization of a social network, identifying important nodes has been a fundamental problem. The concept of network centrality deals with the assessment of the relative importance of a particular node within the network. Most of the traditional network centrality definitions have a high computational cost and require full knowledge of network topological structure. On the one hand, in many applications we are only interested in detecting the top-k central nodes of the network with the largest values considering a specific centrality metric. On the other hand, it is not feasible to efficiently identify central nodes in a large real-world social network via... 

    Development of thermo-elastic tapered and spherical superelements

    , Article Applied Mathematics and Computation ; Volume 265 , 2015 , Pages 380-399 ; 00963003 (ISSN) Shamloofard, M ; Movahhedy, M. R ; Sharif University of Technology
    Elsevier Inc  2015
    Special superelements are often used to improve the computational efficiency and improve accuracy of finite element modeling. Structures with tapered and spherical geometry exist in many engineering problems. In this work, special tapered and spherical superelements are presented that can be used for modeling of tapered and spherical bodies in thermo mechanical analyses with computational efficiency. The performance of these superelements under thermal and structural loads is demonstrated by presenting several examples and comparing the results with those from conventional 3D brick elements, which shows high accuracy at reduced computational cost  

    Assessment of cell-centered and cell-vertex finite volume approaches for computation of 2d structural dynamics on arbitrary quadrilateral grids

    , Article CMES - Computer Modeling in Engineering and Sciences ; Volume 106, Issue 6 , 2015 , Pages 395-439 ; 15261492 (ISSN) Hejranfar, K ; Azampour, M. H ; Sharif University of Technology
    Tech Science Press  2015
    In this study, cell-centered (CC) and cell-vertex (CV) finite volume (FV) approaches are applied and assessed for the simulation of two-dimensional structural dynamics on arbitrary quadrilateral grids. For the calculation of boundary nodes displacement in the CC FV approach, three methods are employed. The first method is a simple linear regression of displacement of boundary nodes from the displacement of interior cell centers. In the second method, an extrapolation technique is applied for this purpose and, in the third method; the line boundary cell technique is incorporated into the solution algorithm in an explicit manner. To study the effects of grid irregularity on the results of CC... 

    Optimal capacity allocation for executing mapreduce jobs in cloud systems

    , Article Proceedings - 16th International Symposium on Symbolic and Numeric Algorithms for Scientific Computing, SYNASC 2014, 22 September 2014 through 25 September 2014 ; Sept , 2015 , Pages 385-392 ; 9781479984480 (ISBN) Malekimajd, M ; Rizzi, A. M ; Ardagna, D ; Ciavotta, M ; Passacantando, M ; Movaghar, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Nowadays, analyzing large amount of data is of paramount importance for many companies. Big data and business intelligence applications are facilitated by the MapReduce programming model while, at infrastructural layer, cloud computing provides flexible and cost effective solutions for allocating on demand large clusters. Capacity allocation in such systems is a key challenge to providing performance for MapReduce jobs and minimize cloud resource cost. The contribution of this paper is twofold: (i) we formulate a linear programming model able to minimize cloud resources cost and job rejection penalties for the execution of jobs of multiple classes with (soft) deadline guarantees, (ii) we... 

    Dissipative particle dynamics simulation of electroosmotic flow in nanoscale channels

    , Article 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando, FL, 4 January 2010 through 7 January 2010 ; 2010 ; 9781600867392 (ISBN) Darbandi, M ; Zakeri, R ; Schneider, G. E ; Sharif University of Technology
    This Paper presents the simulation of electroosmotic flow in nanochannels using the dissipative particle dynamics (DPD) method. Most of the past electroosmotic phenomenon studies have been carried out using the continuum flow assumptions. However, there are many electroosmotic applications in nanoscales NEMS and microscales MEMS, which need to be treated using non-continuum flow assumptions. We simulate the electroosmotic flow within the mesoscopic scale using the DPD method. Contrary to the ordinary molecular dynamics method, the DPD method provides less computational costs. We will show that the current DPD results are in very good agreement with other available non-DPD results. To expand... 

    Dimension reduction of remote sensing images by incorporating spatial and spectral properties

    , Article AEU - International Journal of Electronics and Communications ; Volume 64, Issue 8 , 2010 , Pages 729-732 ; 14348411 (ISSN) Dianat, R ; Kasaei, S ; Sharif University of Technology
    A new and efficient dimension reduction method is introduced in this paper. The proposed method, almost the same as the well-known principal component analysis (PCA) method, enjoys the properties of uncorrelatedness of resulting components and orthogonality of transform coefficients. In addition, by incorporating spatial and spectral properties among image pixels, the method obtains more accurate classification results with less computational cost  

    Persian text classification based on topic models

    , Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 86-91 ; 9781467387897 (ISBN) Ahmadi, P ; Tabandeh, M ; Gholampour, I ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    With the extensive growth in information, text classification as one of the text mining methods, plays a vital role in organizing and management information. Most text classification methods represent a documents collection as a Bag of Words (BOW) model and then use the histogram of words as the classification features. But in this way, the number of features is very large; therefore performing text classification faces serious computational cost problems. Moreover, the BOW representation is unable to recognize semantic relations between words. Recently, topic-model approaches have been successfully applied for text classification to overcome the problems of BOW. Our main goal in this paper... 

    Evaluation of the EDR performance in seismic control of steel structures using endurance time method

    , Article Scientia Iranica ; Volume 23, Issue 3 , 2016 , Pages 827-841 ; 10263098 (ISSN) Foyouzat, M. A ; Estekanchi, H. E ; Sharif University of Technology
    Sharif University of Technology 
    The Energy Dissipating Restraint (EDR) is a friction device which can be used to dissipate the energy introduced to a structure by a seismic event. In this paper, the performance of the structures which are equipped with the EDR is investigated in several intensity levels by using a novel seismic analysis method, namely the Endurance Time (ET) method. By reasonably estimating the response of structures over the entire range of the desired intensity levels through each time-history analysis, this method can effectively reduce the computational cost, offering an appropriate procedure for performance-based design of structures. The EDR performance in the seismic control of steel frames is... 

    On the coupled continuous knapsack problems: projection onto the volume constrained Gibbs N-simplex

    , Article Optimization Letters ; Volume 10, Issue 1 , 2016 , Pages 137-158 ; 18624472 (ISSN) Tavakoli, R ; Sharif University of Technology
    Springer Verlag  2016
    Coupled continuous quadratic knapsack problems (CCK) are introduced in the present study. The solution of a CCK problem is equivalent to the projection of an arbitrary point onto the volume constrained Gibbs N-simplex, which has a wide range of applications in computational science and engineering. Three algorithms have been developed in the present study to solve large scale CCK problems. According to the numerical experiments of this study, the computational costs of presented algorithms scale linearly with the problem size, when it is sufficiently large. Moreover, they show competitive or even superior computational performance compared to the advanced QP solvers. The ease of... 

    Numerical study of pollutant emissions in a Jet stirred reactor under elevated pressure Lean premixed conditions

    , Article Mathematical Problems in Engineering ; Volume 2016 , 2016 ; 1024123X (ISSN) Mazaheri, K ; Shakeri, A ; Sharif University of Technology
    Hindawi Publishing Corporation  2016
    Numerical study of pollutant emissions (NO and CO) in a Jet Stirred Reactor (JSR) combustor for methane oxidation under Elevated Pressure Lean Premixed (EPLP) conditions is presented. A Detailed Flow-field Simplified Chemistry (DFSC) method, a low computational cost method, is employed for predicting NO and CO concentrations. Reynolds Averaged Navier Stokes (RANS) equations with species transport equations are solved. Improved-coefficient five-step global mechanisms derived from a new evolutionary-based approach were taken as combustion kinetics. For modeling turbulent flow field, Reynolds Stress Model (RSM), and for turbulence chemistry interactions, finite rate-Eddy dissipation model are... 

    Molecular dynamics study of bio-manipulation in aqueous media

    , Article Micro and Nano Letters ; Volume 11, Issue 1 , 2016 , Pages 9-14 ; 17500443 (ISSN) Kheirodin, M ; Pishkenari, H. N ; Mahboobi, S. H ; Sharif University of Technology
    Institution of Engineering and Technology  2016
    Nano-manipulation is one of the most important aspects of nano-robotics and nano-assembly. The positioning process is considered by many researches to be one of the most important parts of nano-assembly, but has been poorly investigated, particularly for biologic samples. This Letter is devoted to modelling the process of positioning a biomolecule with atomic force microscopy (AFM) in an aqueous media using molecular dynamics simulations. Carbon nanotube (CNT) and graphite sheet are selected as AFM tip and substrate, respectively. To consider the effects of the medium on the manipulation, several models for decreasing the calculations including implicit, coarse grained, and all-atom methods... 

    A meshless method to simulate interactions between large soft tissue and a surgical grasper

    , Article Scientia Iranica ; Volume 23, Issue 1 , 2016 , Pages 295-300 ; 10263098 (ISSN) Saghaei Nooshabadi, Z ; Abdi, E ; Farahmand, F ; Narimani, R ; Chizari, M ; Sharif University of Technology
    Sharif University of Technology  2016
    Realistic simulation of tool-tissue interactions can help to develop more effective surgical training systems and simulators. This study uses a finite element and meshless modeling approach to simulate the grasping procedure of a large intra-abdominal organ, i.e. a kidney, during laparoscopic surgery. Results indicate that the accuracy of the meshless method is comparable with that of the finite element method, with root mean square errors in the range of 0.8 to 2.3 mm in different directions. For the model presented in this study, the computational cost of the meshless method was much less than that of the finite element model  

    A consistent incompressible SPH method for internal flows with fixed and moving boundaries

    , Article International Journal for Numerical Methods in Fluids ; Volume 81, Issue 10 , 2016 , Pages 589-610 ; 02712091 (ISSN) Jahangiri Mamouri, S ; Fatehi, R ; Taghizadeh Manzari, M ; Sharif University of Technology
    John Wiley and Sons Ltd 
    An improved incompressible smoothed particle hydrodynamics (ISPH) method is presented, which employs first-order consistent discretization schemes both for the first-order and second-order spatial derivatives. A recently introduced wall boundary condition is implemented in the context of ISPH method, which does not rely on using dummy particles and, as a result, can be applied more efficiently and with less computational complexity. To assess the accuracy and computational efficiency of this improved ISPH method, a number of two-dimensional incompressible laminar internal flow benchmark problems are solved and the results are compared with available analytical solutions and numerical data.... 

    Highly accurate and east convergent diffractive interface theory for fast analysis of metasurfaces

    , Article IEEE Journal of Quantum Electronics ; Volume 52, Issue 7 , 2016 ; 00189197 (ISSN) Nekuee, S. A. H ; Khavasi, A ; Akbari, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    Recently, an approximate formalism [Opt. Express 23, 2764, (2015)] called diffractive interface theory has been reported for the fast analysis of the optical response of metasurfaces, subwavelength two-dimensional periodic arrays. In this method, the electromagnetic boundary conditions are derived using the susceptibility distribution of the metasurface, such that the analysis of metasurface is possible without solving any eigenvalue equation inside the grating layer. In this paper, we modify the boundary conditions to achieve more accurate results. In addition, in this paper, correct Fourier factorization rules are also applied leading to faster convergence rate. The obtained results are... 

    Using sensitivity analysis and gradual evaluation of ignition delay error to produce accurate low-cost skeletal mechanisms for oxidation of hydrocarbon fuels under high-temperature conditions

    , Article Energy and Fuels ; Volume 31, Issue 10 , 2017 , Pages 11234-11252 ; 08870624 (ISSN) Shakeri, A ; Mazaheri, K ; Owliya, M ; Sharif University of Technology
    Three-dimensional thermo-hydrodynamic analysis of gas turbine combustion chambers is of great importance in the power generation industry to achieve higher efficiency and reduced emissions. However, it is prohibitive to use a comprehensive full-detailed mechanism in their simulation algorithms because of the huge CPU time and memory space requirements. Many reduction approaches are available in the literature to remedy this problem. Here a new approach is presented to reduce large detailed or skeletal mechanisms of oxidation of hydrocarbon fuels to a low-cost skeletal mechanism. The method involves an integrated procedure including a Sensitivity Analysis (SA) and a procedure of Gradual...