Sharif Digital Repository

This paper presents a novel video encoding method for cooperative educational dissemination systems. Taking into consideration the inherent characteristics of stereo cameras framework in our educational videos and the ability of determining objects in different depths in a scene, we have proposed a novel object-based video encoding based on "sprite coding" that supports the MPEG-4 Version 1 Main profile in order to transfer distance learning videos across narrow-band transmission links such as the Internet. This paper proposes a multi-layer video object layer generation scheme with foreground moving object extraction and background sprite generation using stereo camera property. The... 

A simple and mild procedure for the trimethylsilylation of a wide variety of phenols with hexamethyldisilazane (HMDS) on the surface of silica gel dispersed with NaHSO4 at r.t. in a few minutes with excellent yields under neutral conditions is reported. This procedure also allows an excellent selectivity for the silylation of phenols in the presence of amine and CO 2H groups  

In this paper, we present an efficient fractal method for detection and diagnosis of mass lesion in mammogram which is one of the abnormalities in mammographic images. We used 110 images that were carefully selected by a radiologist, and their abnormalities were also confirmed by biopsy. These images included circumscribed benign, ill-defined, and spiculated malignant masses. Firstly, we discriminated lesions automatically using new fractal dimensions. The results which were examined by different types of breast density showed that the proposed method was able to yield quite satisfactory detection results. Secondly, noting that contours of masses playing the most important role in diagnosis... 

In this work, the effects of rolling parameters, cooling media, and deformation path on mechanical properties and aging behavior of hot-rolled AA2017 were studied. First, hot-rolling experiments were conducted under different working conditions, and the rolled strips were then aged at room temperature for up to 57 days during which hardness and tensile tests were carried out to record the changes in the mechanical properties of the alloy. Furthermore, due to the importance of static recrystallization on subsequent aging behavior, the rate of recrystallization was also computed. To this end, a mathematical model was developed to predict thermomechanical responses during hot rolling using the... 

In the context of the care crisis in modern medicine, the existential needs of patients are not sufficiently satisfied. One idea to address the crisis is that physicians should be educated to be virtuous. This suggestion is inadequate because it does not take into account the role of (non-)human factors, including technologies. The paper focuses on online caring forums, arguing that they are technological factors that can play the role of “focal things”, in which the members gather together to do a care-related focal practice. We study empirically the online forums of Ninisite, a popular Persian website on pregnancy, childbirth, and parenting, and suggest that these forums shape focal... 

Cloud computing as a new technology can provide significant advantages in electronic banking services. Adoption of this technology in e-banking services requires consideration of several factors. The main objective of this study is to identify and rank the effective factors on adoption of cloud computing in e-banking. The factors were identified from literature review in four dimension based on TOE and HOT-fit models (technological, human, environmental and organisational factors). As a result of this study, 16 factors were identified in four dimensions. Using fuzzy group decision-making model and pairwise comparison between factors (by a survey of 63 experts, academics and practical persons... 

In this paper we use fractal method for detection and diagnosis of abnormalities in mammograms. We have used 168 images that were carefully selected by a radiologist and their abnormalities were also confirmed by biopsy. These images included asymmetric lesions, architectural distortion, normal tissue and mass lesion where in case of mass lesion they included circumscribed benign, ill-defined and spiculated malignant masses. At first, by using wavelet transform and piecewise linear coefficient mapping, image enhancement were done. Secondly detection of lesions was done by fractal method as a ROI. Since in investigation of breast cancer, it is important that fibroglandular tissues in both... 

In this paper a multi-scale image enhancement strategy using wavelets as applied to digital mammograms is presented. For multiresolution wavelet analysis redundant dyadic discrete wavelet transform is utilized to allow translation invariance and low resolution enhancement capability. Two alternative nonlinear gain adjustments, piecewise linear and Gaussian form of gain adjustment are used for coefficient modification for the enhancement of subtle details such as microcalcification and low resolution edges of different lesion types. The results of comparing these methods of gain adjustment are presented. This comparing has done by defining new parameters for measuring quality of image based... 

In this paper, a novel moving object modeling suitable for multicamera correspondence is introduced. Taking into consideration the color and motion features of foreground objects in each independent video stream, our method segments the existing moving objects and constructs a graph-based structure to maintain the relational information of each segment. Using such graph structures reduces our correspondence problem to a subgraph optimal isomorphism problem. The proposed method is robust against various resolutions and orientations of objects at each view. Our system uses the fuzzy logic to employ a human-like color perception in its decision making stage in order to handle color inconstancy... 

Based on the mathematical similarity of the Schrödinger and Helmholtz equations, the tight-binding method has been employed for solving optical waveguide problems, in a manner similar to the methods commonly used in solid-state physics. The solutions (TE mode electric field waveforms and propagation constants) of a single dielectric slab waveguide are considered to be known, and tight-binding is used to compute the propagation constants of several multi-waveguide structures. Analytical solutions are derived for linear and circular arrays of adjacent waveguides. The problem of two similar adjacent waveguides is treated in detail for two cases of similar and different propagation constants of... 

Heat exchangers are widely used to transfer heat between two or more fluids in so many industrial applications. In general, the thermal performance of any thermal unit, such as heat exchangers, highly depends on the thermal characteristics of its sub-components, e.g., tubes and tube bundles. In the other words, a more accurate prediction of tubes in a complex thermal unit such as the shell and tube heat exchangers can lead to a more correct prediction of the proposed heat exchanger. There are various methods and approaches to improve the thermal analysis and calculations of tubes, e.g., the artificial neural network (ANN) and the computational fluid dynamics (CFD). The main goal of the... 

A mathematical model was developed to assess thermomechanical behavior of work rolls during warm rolling processes. A combined finite element analysis-slab method was first developed to determine thermal and mechanical responses of the strip being rolled under steady-state conditions, and then, the calculated roll pressure and temperature field were utilized as the governing boundary conditions for the thermomechanical problem of the work roll. Finally, the thermomechanical stresses within the work rolls were predicted by a thermoelastic finite element approach. The results of the model indicate that, in warm strip rolling, thermal and mechanical stresses developed in the work rolls are... 

Thermal performance of a novel sintered wick heat pipe was investigated in this study. Two types of sintered wick heat pipes were fabricated and tested at different filling ratios of water, and their thermal resistances in different modes were compared. In the first type, wick was sintered annularly (conventional type), and in the other one (novel type of sintered wick) it was sintered only in one third of cross-section. Results showed that dry-out occurs at higher heat input by an increase in the filling ratio. Moreover, the best filling ratio is 20% for both heat pipes. Thermal resistances of the partly sintered wick heat pipe are approximately 28%, 17% and 47% lower than those of the... 

Heat pipes are important cooling devices that are widely used to transfer high heat loads with low temperature differences. In this paper, thermal performance of a novel type of sintered-wick heat pipe, namely, partly sintered-wick heat pipe, was investigated. The heat pipe was filled with degassed water and acetone, as working uids, and effects of filling ratio, orientation, and heat inputs were tested. Moreover, conditions at which dryout occurred were presented. The results showed that the best filling ratio for both working uids is about 20%. The heat pipe filled with water has better thermal performance than that filled with acetone; thus, the thermal resistances of the 20% water-filled... 

Hybrid-reinforced metals are novel composite materials in which nano-phases including nanoparticles and nanotubes/nanosheets are used simultaneously to reinforce metals or alloys to enhance physical, mechanical, wear and other properties. In this research, Cu/(CNT-SiC) hybrid nanocomposite was synthesized using flake powder metallurgy and spark plasma sintering method and the effects of hybrid reinforcements on microstructural, wear and corrosion properties of the developed material were investigated and compared with those of copper. Microstructural characterization showed reduction of average grain size from 419 to 307 nm and increase of low angle grain boundaries with the introduction and... 

A simple and green route to synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles is described. Two isomers can tautomerize to each other by the heat absorption. The tauto-isomerization process was studied by NMR technique. Acidity and stability of products were studied using B3LYP method. © 2009 Elsevier Ltd. All rights reserved  

This paper presents a novel and fast homography-based tracking method to segment and track the instructor placed in front of a class board using two synchronized views. In the proposed method we estimate the instructor as a planar object and track its planar parameters. At first, the homography of board and fundamental geometry of two views are extracted using six point correspondences. The homography transformation matrix of object is calculated by obtaining three point correspondences in parallax region introduced with homography of the board. The parameters to be tracked by Kalman filter are obtained frame by frame by object's homography decomposition. Our proposed method is robust... 

Using a model reduction method, a formula for the ideality factor of a pn junction as a function of the diffusion and generation terms of its reverse current is derived. Using this formula a method for separate computation of these two currents for a pn junction is presented. The validity of the method is investigated using computer simulations for an assumed diode with known ideality factor and total leakage current. Experimental results for two commercially available diodes validate the proposed technique  

Neurological diseases have different etiological causes. Contemporary, developing an ef-fective treatment for these diseases is an ongoing challenge. Cell therapy is recognized as one of the promising solutions for the treatment of these diseases. Amongst various types of stem cells, bone marrow-derived mesenchymal stem cells (BM-MSC) are known to be the most widely used stem cells. These cells are endowed with appealing properties such as the ability to differentiate into other cell types, including the muscle, liver, glial, and nerve cells. In this review study, we have systematically evaluated the ability of a variety of chemical compounds used in the last ten years to differentiate... 

Ethylene dichloride thermal cracking is one of the conventional methods for hydrogen chloride production. A critical issue concerned with this method is to provide thermal energy for cracking reaction, which is generally provided by the flammable gasses inside the furnace. Utilizing renewable energy sources can be an interesting topic in this case. Hence, in this paper, the thermal integration feasibility of an ethylene dichloride cracking unit with a hybrid renewable plant, based on geothermal and wind energies, is investigated, while the case study for wind turbines system (Alstom ECO 74/1670/ Class II model) is Meshkin Shahr, located in Iran. To utilize geothermal energy, a...