Sharif Digital Repository

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... 

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  

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... 

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... 

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... 

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  

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... 

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... 

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... 

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 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... 

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... 

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... 

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... 

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... 

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... 

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  

This paper introduces a wavelet packet algorithm based on a new wavelet like filter created by a neural mass model in place of wavelet. The hypothesis is that the performance of an ERP based BCI system can be improved by choosing an optimal wavelet derived from underlying mechanism of ERPs. The wavelet packet transform has been chosen for its generalization in comparison to wavelet. We compared the performance of proposed algorithm with existing standard wavelets as Db4, Bior4.4 and Coif3 in wavelet packet platform. The results showed a lowest cross validation error for the new filter in classification of two different kinds of ERP datasets via a SVM classifier. © 2007 IEEE