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Localized Multiple Kernel Learning for Image Classification
, Ph.D. Dissertation Sharif University of Technology ; Jamzad, Mansour (Supervisor)
Abstract
It is not possible to compute a linear classifier to classify real world images, which are the focus of this thesis. Therefore, the space of such images is considered as a complex. In such cases, kernel trick in which data samples are implicitly mapped to a higher dimension space, leads to a more accurate classifier in such spaces. In kernel learning methods, the best kernel is trained for the classification problem in hand. Multiple Kernel Learning is a framework which uses weighted sum of multiple kernels. This framework achieves good accuracy in image classification since it allows describing images via various features. In the image input space which is composed of different extracted...
Evaluation of the Hydrodynamic Performance of A Special Submarine Rescue System
, M.Sc. Thesis Sharif University of Technology ; Abbaspour, Madjid (Supervisor)
Abstract
The increasing growth of marine tourism has strengthened the activities related to this industry. One of the most profitable of these activities is recreational submarines. A traction recreational submarine is an idea in this field, in order to reduce costs, the propulsion force is removed and the submarine is towed by the mother ship. The most important reason for using the traction system and removing the independent drive is to prevent vibration and noise caused by the rotation of the propeller to prevent the escape of aquatic animals and to create a beautiful view from under the sea to watch underwater wonders. Searching for safety and saving people's lives in emergency situations is an...
Design and Fabrication of Weigh in Motion System for Railway Vehicles
, M.Sc. Thesis Sharif University of Technology ; Saadat Foumani, Mahmud (Supervisor)
Abstract
Railroads should be well maintained for safe and efficient operation. The most important reason for the failure of railways is overload and asymmetric load on them. Also, the proper interval for repairs should be adjusted to fit the load crossed over. In order to carry out all these tasks, a constant observation of the weight on the rails must take place. Current dynamic weighing systems are costly. In addition, the installation of these systems is time-consuming and causes permanent damage to the rails. On the other hand, some of the cheaper models of weighing systems require full stop and static weighing, which practically does not work at all, especially on busy rails due to delays. The...
Studying the Effect of Zirconia & GNP on Mechanical, Tribological & Biological Properties of UHMWPE-HAp Nanocomposites used in Total Hip Joint Replacement
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor) ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Medical engineering advances in total joint replacements and society’s rising demand for long lasting materials, have proven it essential to manufacture materials that are more similar to the original tissue in the fields of mechanical, tribological and biological properties. Ultra High Molecular Weight Polyethylene(UHMWPE), is a polymer widely used in arthroplasty applications due to its biocompatibility, chemical stability and proper mechanical properties. In this study, UHMWPE-HAp nanocomposites reinforced with Zirconia and Graphene were manufactured aiming to reach a structure that is more compatible with bone tissue and also to improve overall properties. First, using ultrasonication...
Preparation and Investigation of Ziegler-natta Catalyst with Nano MoS2 Support in UHMWPE Synthesis
, M.Sc. Thesis Sharif University of Technology ; Ramazani Saadat Abad, Ahmad (Supervisor)
Abstract
Ultra high molecular weight polyethylene has attracted the attention of numerous researchers and industries. This polymer due to its strong properties can be used in advanced military industries, medical engineering and cases in which high strength and high abrasion resistance is required. Present study aims to fabricate UHMWPE/Molybdenum disulfide composites, using in-situ polymerization. Before carrying out the polymerization process, nanoparticles of molybdenum disulfide underwent various processes such as oxidation, pickling, ultrasonic and thermal shock, in order to increase the interlayer distance and creating functional groups on the surface, then various analyzes, such as XRD, FESEM,...
Experimental Investigation of Biodiesel Production from Oils by Transesterification Method Catalyzed by Nano-heterogeneous Catalysts
, M.Sc. Thesis Sharif University of Technology ;
Abstract
Today polyolefin definitely is one of the most applicable polymers in the world. One of these polymers is ultra-high molecular weight polyethylene. Being applicable in a number of high-tech industries such as military service, battery separators, and other areas, expands the usage of these polymers. Electrospinning is one of the molding methods in order to synthesize fiber polymers. Using this method, a great deal of polymer fibers have been prepared. It is worth noting that the device used for olefins should have temperature control and temperature increase ability. The electrospinning device with the temperature control has not been built in the country; therefore, this device has been...
Preparation and Investigation the Properties of UHMWPE/Graphene Nanocomposites Via in Situ Polymerization Using Ziegler Natta Catalyst
, Ph.D. Dissertation Sharif University of Technology ; Ramezani Saadat Abadi, Ahmad (Supervisor)
Abstract
The main object of the presented thesis is manufacturing ultra high molecular weight polyethylene(UHMWPE)/Graphene nanocomposites by insitu polymerization using Ziegler Natta catalysts. In this study, three types of Ziegler Natta Catalysts such as Magnesium ethoxide supported, single-supported and bi-supported have been studied. Experimental conditions are optimized (from point of productivity and molecular weight) by Design expert software with response surface methodology (Box-Behnken design). Effect of process parameters like temperature, pressure and [Al]/[Ti] molar ratio on productivity and Molecular weight are investigated. Also, the effect of hydrogen presence and type of cocatalyst...
The effect of multiple surface treatments on biological properties of Ti-6Al-4V alloy
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Vol. 45, issue. 10 , 2014 , p. 4588-4593 ; Amini, P ; Asgari, S ; Sharif University of Technology
Abstract
In this research, the effect of various surface treatments including laser processing, grit blasting and anodizing on chemical structure, surface topography, and bioactivity of Ti-6Al-4V was investigated. Six groups of samples were prepared by a combination of two alternative laser processes, grit blasting and anodizing. Selected samples were first evaluated using microanalysis techniques and contact roughness testing and were then exposed to in vitro environment. Scanning electron microscopy was used to characterize the corresponding final surface morphologies. Weight measurement and atomic absorption tests were employed for determination of bioactivity limits of different surface...
Detecting matrices for random CDMA systems
, Article 2013 20th International Conference on Telecommunications, ICT 2013 ; 2013 ; Bateni, F ; Marvasti, F ; Sharif University of Technology
IEEE Computer Society
2013
Abstract
This paper studies detecting matrices in random dense and sparse Code Division Multiple Access (CDMA) systems. Detecting matrices were originally introduced in the coin weighing problem. Such matrices can be used in CDMA systems in over-loaded scheme where the number of users is greater than the number of chips. We drive some conditions in the large system limit for binary and bipolar random CDMA systems to ensure that any random matrix is a detecting matrix. Furthermore, we extend our results to sparse random ternary matrices that have been using in the sparse CDMA literature. Finally, a construction method for the sparse detecting matrices is introduced
An optimal path in a bi-criteria AGV-based flexible jobshop manufacturing system having uncertain parameters
, Article International Journal of Industrial and Systems Engineering ; Volume 13, Issue 1 , 2013 , Pages 27-55 ; 17485037 (ISSN) ; Mahdavi Amiri, N ; Sharif University of Technology
2013
Abstract
We propose an approach for finding an optimal path in a flexible jobshop manufacturing system considering two criteria of time and cost. With rise in demands, advancement in technology and increase in production capacity, the need for more shops persists. Therefore, a flexible jobshop system has more than one shop with the same duty. The difference among shops with the same duty is in their machines with various specifications. A network is configured in which the nodes are considered to be the shops with arcs representing the paths among the shops. An automated guided vehicle functions as a material handling device through the manufacturing network. To account for uncertainty, we consider...
A robust keypoint extraction and matching algorithm based on wavelet transform and information theory for point-based registration in endoscopic sinus cavity data
, Article Signal, Image and Video Processing ; 2015 , Pages 1-9 ; 18631703 (ISSN) ; Ahmadian, A ; Kasaei, S ; Sadrehosseini, S. M ; Farnia, P ; Sharif University of Technology
Springer-Verlag London Ltd
2015
Abstract
Feature extraction is one of the most important steps in processing endoscopic data. The extracted features should be invariant to image scale and rotation to provide a robust matching across a substantial range of affine distortions and changes in 3D space. In this study, a method is proposed on the basis of the dual-tree complex wavelet transform. First, a map is estimated for each scale, and then a Gaussian weighted additive function (GWAF) is determined. Keypoints are selected from local peaks of GWAF. The matching and registration are performed by applying normalized mutual information and our modified iterative closest point. Results are reported in terms of robustness to rotation,...
On optimum asymptotic multiuser efficiency of randomly spread CDMA
, Article IEEE Transactions on Information Theory ; Volume 61, Issue 12 , 2015 , Pages 6635-6642 ; 00189448 (ISSN) ; Müller, R. R ; Marvasti, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2015
Abstract
We extend the result by Tse and Verdú on the optimum asymptotic multiuser efficiency of randomly spread code division multiple access (CDMA) with binary phase shift keying input. Random Gaussian and random binary antipodal spreading are considered. We obtain the optimum asymptotic multiuser efficiency of a K-user system with spreading gain N when K and N → ∞ and the loading factor, (K/N) , grows logarithmically with K under some conditions. It is shown that the optimum detector in a Gaussian randomly spread CDMA system has a performance close to the single user system at high signal-to-noise ratio when K and N → ∞ and the loading factor, (K/N), is kept less than (log3 K/2). Random binary...
A bi-criteria AGV-based flexible jobshop manufacturing network having uncertain parametersd
, Article 2010 2nd International Conference on Engineering System Management and Applications, ICESMA 2010, 30 March 2010 through 1 April 2010 ; March-April , 2010 ; 9781424465200 (ISBN) ; Mahdavi Amiri, N ; Sharif University of Technology
2010
Abstract
We propose an approach for finding an optimal path in a flexible jobshop manufacturing system considering two criteria of time and cost. With rise in demands, advancement in technology, and increase in production capacity, the need for more shops persists. Therefore, a flexible jobshop system has more than one shop with the same duty. The difference among shops with the same duty is in their machines with various specifications. A network is configured in which the nodes are considered to be the shops with arcs representing the paths among the shops. An Automated Guided Vehicle (AGV) functions as a material handling device through the manufacturing network. To account for uncertainty, we...
The impact of CO2 injection and pressure changes on asphaltene molecular weight distribution in a heavy crude oil: An experimental study
, Article Petroleum Science and Technology ; Volume 28, Issue 17 , 2010 , Pages 1728-1739 ; 10916466 (ISSN) ; Firoozinia, H ; Kharrat, R ; Ghazanfari, M. H ; Sharif University of Technology
Abstract
This work concerns observing the pressure as well as CO2 mole percentage effects on asphaltene molecular weight distributions at reservoir conditions. A high-pressure, high-temperature asphaltene measurement setup was applied, and the amount of precipitated asphaltene at different pressures as well as CO2 mole percentage in an Iranian heavy crude oil was measured. Moreover, the asphaltene molecular weight distributions during titration of crude oil with different n-alkanes were investigated. The gel permeation chromatography (GPC) apparatus was used for characterization of asphaltene molecular weight under different conditions. It has been observed that some thermodynamic changes such as...
A robust keypoint extraction and matching algorithm based on wavelet transform and information theory for point-based registration in endoscopic sinus cavity data
, Article Signal, Image and Video Processing ; Volume 10, Issue 5 , 2016 , Pages 983-991 ; 18631703 (ISSN) ; Ahmadian, A ; Kasaei, S ; Sadrehosseini, S. M ; Farnia, P ; Sharif University of Technology
Springer-Verlag London Ltd
2016
Abstract
Feature extraction is one of the most important steps in processing endoscopic data. The extracted features should be invariant to image scale and rotation to provide a robust matching across a substantial range of affine distortions and changes in 3D space. In this study, a method is proposed on the basis of the dual-tree complex wavelet transform. First, a map is estimated for each scale, and then a Gaussian weighted additive function (GWAF) is determined. Keypoints are selected from local peaks of GWAF. The matching and registration are performed by applying normalized mutual information and our modified iterative closest point. Results are reported in terms of robustness to rotation,...
HTS transformer windings design using distributive ratios for minimization of short circuit forces
, Article Journal of Superconductivity and Novel Magnetism ; 2018 ; 15571939 (ISSN) ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Springer New York LLC
2018
Abstract
High-temperature superconducting (HTS) transformers have a promising feature in reduction of total weight, total size, and the losses of large-scale distribution transformers. However, the lower leakage reactance of HTS transformers results in a higher short-circuit fault currents and electromagnetic forces. Therefore, optimization of short-circuit electromagnetic forces is one of the crucial aspects in the design of HTS transformers. In this paper, a novel analytical method is proposed for determination of optimum distributive ratios resulting in minimization of these forces for asymmetrical multi-segment windings of an HTS transformer. Employing these distributive ratios, radial and axial...
Multirate, differentiated-qoS, and multilevel fiber-optic CDMA system via optical logic gate elements
, Article Journal of Lightwave Technology ; Volume 27, Issue 19 , 2009 , Pages 4348-4359 ; 07338724 (ISSN) ; Ghaffari, B. M ; Salehi, J. A ; Sharif University of Technology
2009
Abstract
In this paper, we present a novel multirate, differentiated quality of service (QoS) optical CDMA (OCDMA) system using multilevel signaling technique. The emphasis is on OCDMA systems employing multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequence. We begin by presenting a two-class variable-weight OCDMA system in which all users have the same energy level in one bit duration. As a consequence, high weight users transmit their corresponding optical pulses at a lower power while low weight users transmit their corresponding optical pulses at a higher power level. We show that using this multilevel signaling technique, while employing the well known optical AND...
Two-dimensional clustering of nanoparticles on the surface of cellulose fibers
, Article Journal of Physical Chemistry C ; Volume 113, Issue 28 , 2009 , Pages 12022-12027 ; 19327447 (ISSN) ; Taghavinia, N ; Irajizad, A ; Mahdavi, M ; Ye, J ; Chavoshi, M ; Vashaei, Z ; Sharif University of Technology
2009
Abstract
Density of surface charges of cellulose fibers and -potential of TiO2 nanoparticles in the solution were measured and controlled by pH. The adsorption and clustering of TiO2 nanoparticles on the surface of cellulose fibers were studied using scanning electron microscopy (SEM) and a scale in different situations of repulsion and attraction between the particles and surface. The experiments show formation of two-dimensional clusters of nanoparticles on the surface. Weight measurement of the adsorbed particles and clusters via the adsorption time results in that there are three stages containing nucleation, two-dimensional growth and saturation for clustering of nanoparticles on the surface....
Buckling and frequency responses of a graphene nanoplatelet reinforced composite microdisk
, Article International Journal of Applied Mechanics ; Volume 11, Issue 10 , 2019 ; 17588251 (ISSN) ; Habibi, M ; Safarpour, H ; Safarpour, M ; Foong, L. K ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
This is the first research on the vibration and buckling analysis of a graphene nanoplatelet composite (GPLRC) microdisk in the framework of a numerical based generalized differential quadrature method (GDQM). The stresses and strains are obtained using the higher-order shear deformable theory (HOSDT). Rule of the mixture is employed to obtain varying mass density, thermal expansion, and Poisson's ratio, while the module of elasticity is computed by modified Halpin-Tsai model. Governing equations and boundary conditions of the GPLRC microdisk are obtained by implementing Extended Hamilton's principle. The results show that outer to inner ratios of the radius (Ro/Ri), ratios of length scale...
Using approximate similitude to design dynamic similar models
, Article Aerospace Science and Technology ; Volume 94 , 2019 ; 12709638 (ISSN) ; Hajipouzadeh, P ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
This research deals with the analysis of approximate similitude between the dynamic similar models and the full-scale prototype of an aircraft. Due to physical and technical constraints, a full dynamic similarity is not practically possible and previous works have all neglected one or two similarity criteria like Mach or Reynolds numbers for the sake of Froude number similarity. In this work, it is shown that Mach number has an important effect on aerodynamic characteristics and dynamic response of an aircraft and that neglecting it makes the generalization of the scale-model test data invalid for the full-scale prototype. In order to address this problem, a measurable quantity named...