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khalighi--sadaf
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The Effect of Different Stresses in the Three Principal Directions on a Formation with 30 Degree Fractured
, M.Sc. Thesis Sharif University of Technology ; Goodarznia, Iraj (Supervisor)
Abstract
In this study we investigated the stress effects on the fractured block in formation and its impact on flow through the matrix. At first the effect of various stresses on reduction of sample's pore volume and thereby reduction the permeability have been studied. The equations used to describe the elasticity relations in saturated matrix block is provided by Bayot theory. In this theory, the system of related equations to stress and strain changes have been developed in matrix. We have used finite element method in COMSOL software to solve the equation system created by elasticity relations in formation. After solving the equations, volume and volumetric strain changes which are caused by the...
Fabrication of Thick Scaffold with Microfluidic Channels by Bioprinter
, M.Sc. Thesis Sharif University of Technology ; Saadatmand, Maryam (Supervisor)
Abstract
Cardiovascular diseases are among the leading causes of death worldwide. For instance, in 2015, almost 31% of the world’s mortality rate was due to these causes. One of these diseases is cardiac coronary vessels’ occlusion which leads to the insufficient blood supply to the heart tissue and cardiomyocytes death after Myocardial Infarction (MI). After MI, a hierarchy of events in the heart tissue changes heart muscle and forms cardiac fibrosis. This fibrotic tissue does not have the native one’s properties and function, so it will cause cardiac arrest and patient death. Therefore, it is obvious that vascular network plays a crucial role in the heart function. The importance of cardiac...
Bioprinting a thick and cell-laden partially oxidized alginate-gelatin scaffold with embedded micro-channels as future soft tissue platform
, Article International Journal of Biological Macromolecules ; Volume 193 , 2021 , Pages 2153-2164 ; 01418130 (ISSN) ; Saadatmand, M ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Despite all the advancements in tissue engineering, one of the unsolved challenges is the mass transfer limitation. Therefore, the subject of pre-vascularization in the engineered tissues gets more attention to avoid necrotic core formation. In this study, we considered a design for interconnected channels with a muscle tissue-like structure, in silico and in vitro. A sequence of simple steps make it possible for us to use the same material, gelatin, as both a sacrificial material and one of the main components of the scaffold simultaneously. We defined a new approach to quantify the repeatability of a new combination of hydrogels (Partially Oxidized Alginate + Gelatin) for extrusion-based...
CFAR adaptive threshold for ESM receiver with logarithmic amplification
, Article Signal Processing ; Volume 84, Issue 1 , 2004 , Pages 41-53 ; 01651684 (ISSN) ; Nayebi, M. M ; Sharif University of Technology
2004
Abstract
An adaptive threshold with constant false alarm rate (CFAR) property is proposed to be used in a channelized electronic support measures (ESM) system with logarithmic video amplification. For this purpose, two CFAR processors are designed which are in fact modified excision (MEx) and adaptive MEx (AMEx) processors, previously presented by authors, but modified for the logarithmic amplification case. In the case of relatively small variations in the noise power, MEx-LOG/CFAR is proposed. This processor exhibits a good robustness against interfering pulses, which cause the major difficulty in the estimation of noise statistics. In the case of relatively large variations in the noise power,...
CFAR processor for ESM systems applications
, Article IEE Proceedings: Radar, Sonar and Navigation, Stevenage, United Kingdom ; Volume 147, Issue 2 , 2000 , Pages 86-92 ; 13502395 (ISSN) ; Nayebi, M. M ; Sharif University of Technology
IEE
2000
Abstract
The authors consider the design of a CFAR processor for the adaptive thresholding system of an ESM receiver. For this purpose, the important specifications of ESM systems are the reception of pulses with various widths and rates, and vulnerability to noise jammers. The major difficulty in determining the statistics of the background noise is the problem of interfering signals. In situations of tolerable variations in background noise power, an MEx-CFAR processor is proposed, which exhibits good robustness against interfering pulses. When large variations in noise power are possible, an AMEx-CFAR processor is proposed. The feedback loop used in the structure of the AMEx processor permits it...
A contourlet-based image watermarking scheme with high resistance to removal and geometrical attacks
, Article Eurasip Journal on Advances in Signal Processing ; Volume 2010 , June , 2010 ; 16876172 (ISSN) ; Tirdad, P ; Rabiee, H. R ; Sharif University of Technology
2010
Abstract
We propose a new nonblind multiresolution watermarking method for still images based on the contourlet transform (CT). In our approach, the watermark is a grayscale image which is embedded into the highest frequency subband of the host image in its contourlet domain. We demonstrate that in comparison to other methods, this method enables us to embed more amounts of data into the directional subbands of the host image without degrading its perceptibility. The experimental results show robustness against several common watermarking attacks such as compression, adding noise, filtering, and geometrical transformations. Since the proposed approach can embed considerable payload, while providing...
A new robust non-blind digital watermarking scheme in contourlet domain
, Article IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2009, 14 December 2009 through 16 December 2009, Ajman ; 2009 , Pages 20-25 ; 9781424459506 (ISBN) ; Tirdad, P ; Rabiee, H. R ; Sharif University of Technology
2009
Abstract
In this paper, we propose a new multiresolution watermarking method for still images based on the Contourlet Transform (CT). In our algorithm, the watermark is a grayscale image which is embedded into the host image in its contourlet domain. We demonstrate that in comparison with other methods, the proposed method enables us to embed more amount of data into the host image without degrading its perceptual quality. The experimental results show robustness against several common watermarking attacks such as compression, adding noise, and filtering. ©2009 IEEE
A novel OCR system for calculating handwritten persian arithmetic expressions
, Article IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2009, 14 December 2009 through 16 December 2009 ; 2009 , Pages 277-282 ; 9781424459506 (ISBN) ; Tirdad, P ; Rabiee, H. R ; Parviz, M ; Sharif University of Technology
2009
Abstract
In this paper we propose a novel OCR system which can recognize and calculate handwritten Persian arithmetic expressions without using a keyboard or a memory to store the intermediate results. Our research is composed of two major phases: character recognition and calculation. The recognition phase is based on a new approach for feature extraction. Fuzzy Support Vector Machines (FSVMs) are employed as the classifier. In calculation phase a simple algorithm is used for calculating the recognized arithmetic expression. The performance of the system is evaluated on a database consisting of 3400 digits and symbols written by 20 different people. 92 percent accuracy in recognition proves the good...
A novel OCR system for calculating handwritten Persian arithmetic expressions
, Article 8th International Conference on Machine Learning and Applications, ICMLA 2009, 13 December 2009 through 15 December 2009 ; 2009 , Pages 755-758 ; 9780769539263 (ISBN) ; Tirdad, P ; Rabiee, H. R ; Parviz, M ; Sharif University of Technology
2009
Abstract
In this paper, we propose a novel OCR system which can recognize and calculate handwritten Persian arithmetic expressions without using a keyboard or a memory to store the intermediate results. Our system is composed of two major phases: character recognition and calculation. The recognition phase is based on a new approach for feature extraction followed by a Fuzzy Support Vector Machines (FSVMs) as the classifier. In calculation phase a simple algorithm is used for calculating the recognized arithmetic expressions. The performance of the system was evaluated on a database consisting of 3400 digits and symbols written by 20 different people. 92 percent accuracy in recognition proves the...
Electrical Impedance Tomography
, M.Sc. Thesis Sharif University of Technology ; Vosoughi Vahdat, Bijan (Supervisor) ; Mortazavi, Mohammad (Supervisor)
Abstract
Electrical Impedance Tomography, (EIT), is one of the medical imaging technologies, similar to CT-Scan or X-Ray. It can also be used in industrial process monitoring. In this technique a reconstructed image of the inner part of a conductive subject can be made with an array of external electrodes which are connected to the boundary of the subject (e.g., body). It is inexpensive, fast, small and portable. In this imaging method, the image of electrical conductivity (or impedance) distribution of the internal part of a typical subject is reconstructed. The Image reconstruction process is done by injecting an accurate current into the boundary of the subject, measuring voltages around the...
Maneuverability improvement for an ultra eight airplane model using variable shape wing
, Article Collection of Technical Papers - AIAA Atmospheric Flight Mechanics Conference, Providence, RI, 16 August 2004 through 19 August 2004 ; Volume 1 , 2004 , Pages 467-476 ; 1563477009 (ISBN) ; Alemohammad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
2004
Abstract
One of the significant methods to design airplanes with high capabilities is taking advantage of variable shape structures to improve flight efficiency. In present article the effect of a variable shape wing on an ultra light flyer has been considered. Very low weight of this kind of airplane limits the applicability of control surfaces to attain appropriate maneuvers. To overcome this problem, implementation of a variable shape structure using SMA actuators has been proposed. For simulation, deformed shape of wings has been calculated with finite element method; this data has been used to determine aerodynamic coefficients using computational fluid dynamic (CFD) and finally leads to flight...
Modeling and analysis of AN ultra light slow flyer with variable shape control surfaces using shape memory alloy actuators
, Article Proceedings of the 7th Biennial Conference on Engineering Systems Design and Analysis - 2004, Manchester, 19 July 2004 through 22 July 2004 ; Volume 2 , 2004 , Pages 153-162 ; 0791841731 (ISBN); 9780791841730 (ISBN) ; Alemohamad, S. H ; Khiabani, R. H ; Khalighi, Y ; Sharif University of Technology
American Society of Mechanical Engineers
2004
Abstract
Applying flexible variable shape control surfaces (wing and elevator) structures is a way to increase efficiency and maneuverability of the planes, which is recently under research. In this paper, modeling of the flight of an unmanned ultra light plane is discussed. The modeling is done based on a real ultra light plane presented recently. To increase maneuverability of the plane, flexible variable shape structures are designed for the wing and the elevator. In design procedure, having an ultra light plane is considered. The elevator and the wing are used as control surfaces for longitudinal and lateral maneuvers respectively. Shape memory alloys (SMA) are used for reshaping the flexible...
Practical design of low-cost instrumentation for industrial electrical impedance tomography (EIT)
, Article ; 2012 IEEE I2MTC - International Instrumentation and Measurement Technology Conference, Proceedings, 13 May 2012 through 16 May 2012, Graz , 2012 , Pages 1259-1263 ; 9781457717710 (ISBN) ; Vosoughi Vahdat, B ; Mortazavi, M ; Hy, W ; Soleimani, M ; Sharif University of Technology
IEEE
2012
Abstract
Electrical Impedance Tomography (EIT), is one of the medical imaging technologies. It can also be used in industrial process monitoring. In this method, the image of the electrical conductivity distribution of the inner part of a conductive subject can be reconstructed. The image reconstruction process is done by injecting an accurate current into the boundary of a conductive subject (e.g. body), measuring the voltages around the boundary and transmitting them to a computer, and processing on acquired data with a software (e.g., MATLAB). The images are obtained from the peripheral data by using an algorithm. Precise EIT instrumentation plays an important role in the final images quality. In...