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    Reproducing Kernel particle method in plasticity of pressure-sensitive material with reference to powder forming process

    , Article Computational Mechanics ; Volume 39, Issue 3 , 2007 , Pages 247-270 ; 01787675 (ISSN) Khoei, A. R ; Samimi, M ; Azami, A. R ; Sharif University of Technology
    Springer Verlag  2007
    Abstract
    In this paper, an application of the reproducing kernel particle method (RKPM) is presented in plasticity behavior of pressure-sensitive material. The RKPM technique is implemented in large deformation analysis of powder compaction process. The RKPM shape function and its derivatives are constructed by imposing the consistency conditions. The essential boundary conditions are enforced by the use of the penalty approach. The support of the RKPM shape function covers the same set of particles during powder compaction, hence no instability is encountered in the large deformation computation. A double-surface plasticity model is developed in numerical simulation of pressure-sensitive material.... 

    A part-level learning strategy for JPEG image recompression detection

    , Article Multimedia Tools and Applications ; Volume 80, Issue 8 , 2021 , Pages 12235-12247 ; 13807501 (ISSN) Taimori, A ; Razzazi, F ; Behrad, A ; Ahmadi, A ; Babaie Zadeh, M ; Sharif University of Technology
    Springer  2021
    Abstract
    Recompression is a prevalent form of multimedia content manipulation. Different approaches have been developed to detect this kind of alteration for digital images of well-known JPEG format. However, they are either limited in performance or complex. These problems may arise from different quality level options of JPEG compression standard and their combinations after recompression. Inspired from semantic and perceptual analyses, in this paper, we suggest a part-level middle-out learning strategy to detect double compression via an architecturally efficient classifier. We first demonstrate that singly and doubly compressed data with different JPEG coder settings lie in a feature space... 

    Application of rkpm in numerical simulation of powder forming processes using cap plasticity model

    , Article 8th International Conference on Computational Plasticity: Fundamentals and Applications, COMPLAS VIII, Barcelona, 5 September 2005 through 7 September 2005 ; Issue PART 2 , 2005 , Pages 966-969 ; 849599979X (ISBN); 9788495999795 (ISBN) Samimi, M ; Khoei, A. R ; Sharif University of Technology
    2005
    Abstract
    In this paper, an application of the Reproducing Kernel Particle Method is presented in numerical simulation of powder forming processes using a cap plasticity model. A double-surface cap plasticity is developed within the framework of large deformation analysis in order to predict the non-uniform relative density distribution during powder die pressing. The RKPM technique is employed in the analysis of 2D compaction simulation. Numerical examples are presented to illustrate the applicability of the algorithm in modelling of powder forming processes  

    An Introduction to the Mathematical Theory of Generalized RKPM and Gradient RKPM

    , M.Sc. Thesis Sharif University of Technology Behzadan, Ali (Author) ; Mohammadi Shoja, Hossein (Supervisor)

    Modeling Material Discontinuities Via An Augmented RKPM and Performance of GRKPM in Fracture Mechanics

    , M.Sc. Thesis Sharif University of Technology Khezri, Mani (Author) ; Mohammadi Shodja, Hossein (Supervisor)
    Abstract
    During the past decade, element free methods have achieved great successes. One of these methods is the so called RKPM which has a suitable structure for use in fracture mechanics problems. Despite all characteristic abilities of element free methods; these methods due to their higher order continuous differentiable approximations fail to model discontinuous material properties of the subjected domains. In this study by improving the collocation method in RKPM treatment of such conditions have been achieved. Also in this study performance of a new meshfree method in fracture mechanics problems has been analyzed. GRKPM is one of these methods which its suitable accuracy and convergence has... 

    Electrochemical determination of atorvastatin on nano-scaled polypyrrole film

    , Article Bioelectrochemistry ; Vol. 98 , 2014 , pp. 1-10 ; ISSN: 15675394 Kamalzadeh, Z ; Shahrokhian, S ; Sharif University of Technology
    Abstract
    Pyrrole was electro-polymerized on the surface of the glassy carbon electrode (GCE) coated with a thin film of carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG) or graphite nanopowder (GNP). Morphology, thickness, stability and loading of the polypyrrole (PPY) film were significantly affected by the structure and morphology of the sub-layer of carbon nanomaterials. Electrochemical oxidation of atorvastatin (ATOR) was investigated. Under the optimized conditions, a significant increase in the peak current (compared to other modified electrodes and bare GCE) and a negative shift in the peak potential (compared to bare GCE) were... 

    Fully enriched weight functions in mesh-free methods for the analysis of linear elastic fracture mechanics problems

    , Article Engineering Analysis with Boundary Elements ; Vol. 43 , 2014 , pp. 1-8 Namakian, R ; Shodja, H. M ; Mashayekhi, M ; Sharif University of Technology
    Abstract
    The so-called enriched weight functions (EWFs) are utilized in mesh-free methods (MMs) to solve linear elastic fracture mechanics (LEFM) problems; the following issues are of concern: convergence behavior; sufficiency of EWFs to capture singular fields around the crack-tip; and the preservation of the J-integral path-independency. EWFs prove useful in conjunction with the moving least square reproducing kernel method (MLSRKM); for this purpose, both EWFs and MLSRKM are modified. Since EWFs are not truly representative of the near-tip solution, fully EWFs (FEWFs) are introduced. Finally, some descriptive examples address the aforementioned concerns and the accuracy and efficacy of the... 

    1H NMR based metabolic profiling in Crohn's disease by random forest methodology

    , Article Magnetic Resonance in Chemistry ; Vol. 52, issue. 7 , July , 2014 , p. 370-376 Fathi, F ; Majari-Kasmaee, L ; Mani-Varnosfaderani, A ; Kyani, A ; Rostami-Nejad, M ; Sohrabzadeh, K ; Naderi, N ; Zali, M. R ; Rezaei-Tavirani, M ; Tafazzoli, M ; Arefi-Oskouie, A ; Sharif University of Technology
    Abstract
    The present study was designed to search for metabolic biomarkers and their correlation with serum zinc in Crohn's disease patients. Crohn's disease (CD) is a form of inflammatory bowel disease that may affect any part of the gastrointestinal tract and can be difficult to diagnose using the clinical tests. Thus, introduction of a novel diagnostic method would be a major step towards CD treatment.Proton nuclear magnetic resonance spectroscopy ( 1H NMR) was employed for metabolic profiling to find out which metabolites in the serum have meaningful significance in the diagnosis of CD. CD and healthy subjects were correctly classified using random forest methodology. The classification model for... 

    Analysis of different material theories used in a FE model of a lumbar segment motion

    , Article Acta of Bioengineering and Biomechanics ; Volume 15, Issue 2 , 2013 , Pages 33-41 ; 1509409X (ISSN) Gohari, E ; Nikkhoo, M ; Haghpanahi, M ; Parnianpour, M ; Sharif University of Technology
    2013
    Abstract
    In this study, a nonlinear poroelastic model of intervertebral disc as an infrastructure was developed. Moreover, a new element was defined consisting a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. Using the new element, three different viscoelastic finite element models were prepared for lumbar motion segment (L4/L5). Prolonged loading (short-term and long-term creep) and cyclic loading were applied to the models and the results were compared with results of in vivo tests. Simplification of the models by using the new element leads to reduction of the runtime of the models in dynamic analyses to few minutes without losing the accuracy in the results  

    On the effect of hydrogen and Fe on reproducibility of tensile properties in cast Al-Si-Mg alloys

    , Article Materials Science and Engineering A ; Volume 565 , 2013 , Pages 278-284 ; 09215093 (ISSN) Eisaabadi B., G ; Davami, P ; Varahram, N ; Kim, S. K ; Sharif University of Technology
    2013
    Abstract
    Gas porosities and Fe-rich phases and entrapped double oxide films (hereafter: oxides) are known to be the most detrimental defects in cast Al-Si-Mg alloys. The effects of H (gas porosities) and Fe (Β-Al5FeSi phase) on reproducibility of tensile properties in Al-7Si-0.35Mg alloy have been investigated in this study. Four different casting conditions (Low H-Low Fe, Low H-High Fe, High H-Low Fe and High H-High Fe) were studied. In each case, 30 tensile test samples were prepared by casting in a metallic mold and machining (total of 120 tensile test samples). Results of tensile test were analyzed by Weibull three-parameter analyses. The microstructures of samples were studied by optical... 

    Effect of oxide films, inclusions and Fe on reproducibility of tensile properties in cast Al-Si-Mg alloys: Statistical and image analysis

    , Article Materials Science and Engineering A ; Volume 558 , 2012 , Pages 134-143 ; 09215093 (ISSN) Eisaabadi B, G ; Davami, P ; Kim, S. K ; Varahram, N ; Yoon, Y. O ; Yeom, G. Y ; Sharif University of Technology
    2012
    Abstract
    Double oxide films (hereafter: oxides), inclusions and Fe-rich phases are known to be the most detrimental defects in cast Al-Si-Mg alloys. The effects of these defects on reproducibility of tensile properties in Al-7Si-0.35Mg alloy have been investigated in this study. Four different casting conditions (low oxide-low Fe, high oxide-low Fe, low oxide-high Fe and high oxide-high Fe) were studied. In each case, 30 tensile test samples were prepared by casting in a metallic mold and machining (total of 120 tensile test samples). Results of tensile test were analyzed by Weibull three-parameter and mixture analyses. The microstructure and fracture surface of samples were studied by optical and... 

    RKPM approach to elastic-plastic fracture mechanics with notes on particles distribution and discontinuity criteria

    , Article CMES - Computer Modeling in Engineering and Sciences ; Volume 76, Issue 1 , 2011 , Pages 19-60 ; 15261492 (ISSN) Mashayekhi, M ; Shodja, H. M ; Namakian, R ; Sharif University of Technology
    2011
    Abstract
    A meshless method called reproducing kernel particle method (RKPM) is exploited to cope with elastic-plastic fracture mechanics (EPFM) problems. The idea of arithmetic progression is assumed to place particles within the refinement zone in the vicinity of the crack tip. A comparison between two conventional treatments, visibility and diffraction, to crack discontinuity is conducted. Also, a tracking to find the appropriate diffraction parameter is performed. To assess the suggestions made, two mode I numerical simulations, pure tension and pure bending tests, are executed. Results including J integral, crack mouth opening displacement (CMOD), and plastic zone size and shape are compared with... 

    RKPM with augmented corrected collocation method for treatment of material discontinuities

    , Article CMES - Computer Modeling in Engineering and Sciences ; Volume 62, Issue 2 , 2010 , Pages 171-204 ; 15261492 (ISSN) Shodja, H. M ; Khezri, M ; Hashemian, A ; Behzadan, A ; Sharif University of Technology
    2010
    Abstract
    An accurate numerical methodology for capturing the field quantities across the interfaces between material discontinuities, in the context of reproducing kernel particle method (RKPM), is of particular interest. For this purpose the innovative numerical technique, so-called augmented corrected collocation method is introduced; this technique is an extension of the corrected collocation method used for imposing essential boundary conditions (EBCs). The robustness of this methodology is shown by utilizing it to solve two benchmark problems of material discontinuities, namely the problem of circular inhomogeneity with uniform radial eigenstrain, and the problem of interaction between a crack... 

    A meshless approach for free transverse vibration of embedded single-walled nanotubes with arbitrary boundary conditions accounting for nonlocal effect

    , Article International Journal of Mechanical Sciences ; Volume 52, Issue 10 , 2010 , Pages 1343-1356 ; 00207403 (ISSN) Kiani, K ; Sharif University of Technology
    Abstract
    A single-walled nanotube structure embedded in an elastic matrix is simulated by the nonlocal EulerBernoulli, Timoshenko, and higher order beams. The beams are assumed to be elastically supported and attached to continuous lateral and rotational springs to take into account the effects of the surrounding matrix. The discrete equations of motion associated with free transverse vibration of each model are established in the context of the nonlocal continuum mechanics of Eringen using Hamilton's principle and an efficient meshless method. The effects of slenderness ratio of the nanotube, small scale effect parameter, initial axial force and the stiffness of the surrounding matrix on the natural... 

    Visual acuity classification using single trial visual evoked potentials

    , Article Proceedings of the 31st Annual International Conference of the IEEE Engineering in Medicine and Biology Society: Engineering the Future of Biomedicine, EMBC 2009 ; 2009 , Pages 982-985 ; 1557170X (ISSN) Hajipour, S ; Shamsollahi, M. B ; Abootalebi, V ; Sharif University of Technology
    Abstract
    Several researches have been done to identify visual system characteristics. Some of them are based on the processing of the brain signal recordings. Visual evoked potentials (VEPs) are electrical signals which are produced in response to the visual stimuli and recorded by means of electrodes placed on the head. These signals are usually characterized by the amplitude and latency of their peaks. Different types of visual stimuli and visual system characteristics can affect the shape and hence the characteristics of VEPs. In this paper, proper visual stimuli were used and VEPs were recorded in order to classify visual acuity. To achieve this goal, visual evoked potentials were recorded and... 

    The application of empirical mode decomposition for the enhancement of cardiotocograph signals

    , Article Physiological Measurement ; Volume 30, Issue 8 , 2009 , Pages 729-743 ; 09673334 (ISSN) Krupa, B. N ; Mohd Ali, M. A ; Zahedi, E ; Sharif University of Technology
    2009
    Abstract
    Cardiotocograph (CTG) is widely used in everyday clinical practice for fetal surveillance, where it is used to record fetal heart rate (FHR) and uterine activity (UA). These two biosignals can be used for antepartum and intrapartum fetal monitoring and are, in fact, nonlinear and non-stationary. CTG recordings are often corrupted by artifacts such as missing beats in FHR, high-frequency noise in FHR and UA signals. In this paper, an empirical mode decomposition (EMD) method is applied on CTG signals. A recursive algorithm is first utilized to eliminate missing beats. High-frequency noise is reduced using EMD followed by the partial reconstruction (PAR) method, where the noise order is... 

    Separation of phenolic glycolipids in mycobacterium bovis BCG by reversed-phase high performance liquid chromatography

    , Article Pakistan Journal of Pharmaceutical Sciences ; Volume 22, Issue 2 , 2009 , Pages 145-149 ; 1011601X (ISSN) Salimi, M ; Pourabdi, L ; Zakeri, M ; Abdipour, N ; Sharif University of Technology
    2009
    Abstract
    A crude phenolic glycolipid extract from Mycobacterium bovis BCG was fractionated by column chromatography. A reversed-phase high performance liquid chromatography (HPLC) method with UV detection at 275nm was developed for simultaneous detection and separation of phenolic glycolipids (PGLs) in Mycobacterium bovis BCG. This analysis provides a good resolution. Different solvent systems and columns for HPLC were compared. A system composed of acetonitrile-water in the ratio of 0→80% at a flow rate of 0.8 mL/min and C8 analytical column were found to be optimum for HPLC of the phenolic glycolipids. This simple method is therefore appropriate to purify these compounds present in M. bovis extract... 

    A multi-scale model for determining the effects of pathophysiology and metabolic disorders on tumor growth

    , Article Scientific Reports ; Volume 10, Issue 1 , 20 February , 2020 Nikmaneshi, M. R ; Firoozabadi, B ; Mozafari, A ; Munn, L. L ; Sharif University of Technology
    Nature Research  2020
    Abstract
    The search for efficient chemotherapy drugs and other anti-cancer treatments would benefit from a deeper understanding of the tumor microenvironment (TME) and its role in tumor progression. Because in vivo experimental methods are unable to isolate or control individual factors of the TME and in vitro models often do not include all the contributing factors, some questions are best addressed with systems biology mathematical models. In this work, we present a new fully-coupled, agent-based, multi-scale mathematical model of tumor growth, angiogenesis and metabolism that includes important aspects of the TME spanning subcellular-, cellular- and tissue-level scales. The mathematical model is... 

    Sensitivity analysis of the OWA operator

    , Article IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics ; Volume 38, Issue 2 , 2008 , Pages 547-552 ; 10834419 (ISSN) Zarghami, M ; Szidarovszky, F ; Ardakanian, R ; Sharif University of Technology
    2008
    Abstract
    The successful design and application of the ordered weighted averaging (OWA) method as a decision-making tool depend on the efficient computation of its order weights. The most popular methods for determining the order weights are the fuzzy linguistic quantifiers approach and the minimal variability method, which give different behavior patterns for the OWA. These two methods will be first analyzed in detail by using sensitivity analysis on the outputs of the OWA with respect to the optimism degree of the decision maker, and then the two methods will be compared. The fuzzy linguistic quantifiers approach gives more information about the behavior of the OWA outputs in comparison to the... 

    Images of finite sized spherical particles in confocal and conventional microscopes when illuminated with arbitrary polarization

    , Article Applied Optics ; Volume 47, Issue 3 , 2008 , Pages 453-458 ; 1559128X (ISSN) Alali, S ; Massoumian, F ; Sharif University of Technology
    OSA - The Optical Society  2008
    Abstract
    We investigate the form of the image of a finite sized spherical particle in confocal and conventional microscopes when the illuminating light has an arbitrary polarization. In particular, we take the cases of radial and azimuthal polarizations and use the Mie theory to find the scattered field from differently sized particles for these cases. We present numerical results for the changes in the detected intensity when subresolution and resolvable spherical particles are illuminated with particular wavelengths and polarizations. Further, we find the limiting size of a particle for which it can be considered a point scatterer for a particular wavelength. © 2008 Optical Society of America