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Design and Fabrication of Engineered Biomaterials for Tissue Engineering Applications such as Cardiovascular System
, M.Sc. Thesis Sharif University of Technology ; Shamlou, Amir (Supervisor)
Abstract
Cardiovascular diseases are the leading cause of death all over the world, even more common than cancers. The first reason of mortality in Iran according to statistics is the occlusion of coronary arteries. Unfortunately almost one third of patients doesn’t have enough blood vessels to be used in the bypass surgery and need artificial vessels. These artificial blood vessels with small diameters (less than 6 mm) will fail quickly. As a result there is an increasing demand for tissue engineered blood vessels which are capable of enduring high blood pressures. An artificial blood vessel should mimic both structure and mechanical properties of the real one. Blood vessels have layered structures,...
IF band width optimization of envelope detection system in presence of phase noise
, Article IET International Radar Conference 2009, Guilin, 20 April 2009 through 22 April 2009 ; Issue 551 CP , 2009 ; 9781849190107 (ISBN) ; Mirzaei, S ; Norouzi, Y ; Sharif University of Technology
2009
Abstract
In many radar and EW applications, after some processing, the envelope of the received pulse is calculated and is used for target detection. Most of the time only the effect of thermal noise is considered in such detectors, but in most of the practical applications, before envelope detection, the signal should be down converted from radio frequency (RF) to an intermediate frequency (IF). In this case, the phase noise of the local oscillator will affect the signal, too. Surprisingly, in contrast to thermal noise, the effect of phase noise on the envelope of signal becomes more considerable whenever the IF bandwidth is decreased. So there exists an optimum IF bandwidth for the receiver. In...
Optimization of energy consumption in the process of dehumidification of natural gas
, Article Biointerface Research in Applied Chemistry ; Volume 11, Issue 6 , 2021 , Pages 14634-14639 ; 20695837 (ISSN) ; Shiva, N ; Khajehpour, H ; Sharif University of Technology
AMG Transcend Association
2021
Abstract
In recent years, there has been a great tendency to optimize energy consumption in the oil and gas industry’s upstream and downstream equipment. One of the most energy-intensive processes in natural gas refineries is the condensate stabilization unit (gas condensate). The main bottlenecks of energy consumption in the old units are condensated stabilization (dehumidification with ethylene glycol), heater reboiler, and air coolers (air coolers). Therefore, much attention should be paid to these applications and electricity and steam consumption in this unit. In this study, a simulated model based on the Gachsaran gas refinery’s new layout has been developed. Optimization of this part of the...
The Minimum vulnerability problem
, Article Algorithmica ; Volume 70, Issue 4 , 2014 , pp 718-731 ; ISSN: 14320541 ; Emamjomeh-Zadeh, E ; Norouzi-Fard, A ; Yazdanbod, S ; Zarrabi-Zadeh, H ; Sharif University of Technology
2014
Abstract
We revisit the problem of finding (Formula presented.) paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the (Formula presented.) paths. We provide a (Formula presented.)-approximation algorithm for this problem, improving the best previous approximation factor of (Formula presented.). We also provide the first approximation algorithm for the problem with a sublinear approximation factor of (Formula presented.), where (Formula presented.) is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be...
VirSense: A novel haptic device with fixed-base motors and a gravity compensation system
, Article Industrial Robot ; Vol. 41, Issue. 1 , 2014 , pp. 37-49 ; ISSN: 0143991X ; Nahvi, A ; Yazdani, M ; Moghadam, M. M ; Arbabtafti, M ; Norouzi, M ; Sharif University of Technology
2014
Abstract
Purpose - This paper aims to present the design and implementation of VirSense, a novel six-DOF haptic interface system, with an emphasis on its gravity compensation and fixed-base motors. Design/methodology/approach - In this paper, the design and manufacture of the VirSense robot and its comparison with the existing haptic devices are presented. The kinematic analysis of the robot, design of the components, and manufacturing of the robot are explained as well. Findings - The proposed system is employed to generate a Virtual Sense (VirSense) with fixed-base motors and a spring compensation system for counterbalancing the torques generated by the weight of the links. The fixed bases of the...
The minimum vulnerability problem
, Article Algorithmica ; Volume 7676 LNCS , 2012 , Pages 382-391 ; 14320541(ISSN) ; 9783642352607 (ISBN) ; Emamjomeh Zadeh, E ; Norouzi Fard, A ; Yazdanbod, S ; Zarrabi Zadeh, H ; Sharif University of Technology
2012
Abstract
We revisit the problem of finding k paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the k paths. We provide a ⌊k/2⌋-approximation algorithm for this problem, improving the best previous approximation factor of k - 1. We also provide the first approximation algorithm for the problem with a sublinear approximation factor of O(n3/4), where n is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be improved to O(√n). While the problem is NP-hard, and even hard to approximate to within an O(log n)...
Approximating the distribution of flaws in magnetic materials using the generalized inverse
, Article 2011 IEEE International Conference on Imaging Systems and Techniques, IST 2011 - Proceedings, 17 May 2011 through 18 May 2011, Batu Ferringhi ; May , 2011 , Pages 137-141 ; 9781612848969 (ISBN) ; Abdollahi Jahdi, S ; Norouzi, E ; Sharif University of Technology
2011
Abstract
Non-destructive identification of voids in ferromagnetic materials is of great importance for industrial applications. Magnetic flux leakage technique is used here to examine the defected structure. To this end, an inverse problem should be solved in order to infer the location and depth of internal flaws from the measured leaked magnetic signals. Currently generalized inverse method and singular value decomposition are used for solving such inverse problem. Considering the cracks separation has significant effect on the absolute value of magnetic flux leakage signals, we study different distributions of cracks. In this paper, the magnetic dipole model is proposed to reconstruct the extent...
Feasibility Study and Design of Artificial Energy Island (in Persian Gulf Region)
, M.Sc. Thesis Sharif University of Technology ; Abbaspour Tehranifard, Majid (Supervisor)
Abstract
As it is obvious from the name of this study, the goal of doing this study is the feasibility study of southern shores of Iran for building an artificial energy island for and designing it. In this project by studying seven points coastwise of southern Iran and defining the criterions and scoring the points, the Chabahar was determined as the best place for erecting the artificial energy island. With respect to the environmental condition of the chosen point and modeling in software ANSYS, the structure of the artificial energy island has been studied and the type, geometric shape, area, trough, and the setting of the anchoring system has determined. As a result of these efforts, a hexagon...
Optimisation of binary integrators for decentralised detection
, Article IET Radar, Sonar and Navigation ; Volume 2, Issue 1 , 2008 , Pages 42-50 ; 17518784 (ISSN) ; Gini, F ; Nayebi, M. M ; Sharif University of Technology
2008
Abstract
Binary integrators are an important part of the receiver in many operating radar systems. The optimisation of a binary integrator is not a simple task, because it requires the solution of a (k×n)-dimensional nonlinear optimisation problem, where n is the number of integrated bits (or the number of sensors in a distributed radar or sensor network) and k is the number of the design parameters of the single-pulse detector. An algorithm that converts the multi-dimensional optimisation problem into a one-dimensional problem, so reducing considerably the computational complexity, is developed. This reduction in computational complexity makes the real-time optimisation possible and practical, so it...
Effects of geometrical and processing parameters on mechanical properties of auxetic polyurethane foams
, Article SN Applied Sciences ; Volume 4, Issue 6 , 2022 ; 25233971 (ISSN) ; Nourani, A ; Mohseni, M ; Hosseini, N ; Norouzi, S ; Bakhshayesh, P. R ; Sharif University of Technology
Springer Nature
2022
Abstract
This study aimed to investigate the influence of processing parameters on the mechanical properties of auxetic polyurethane foams including Poisson’s ratio and Young’s modulus. 12 different processing scenarios were considered using the method of Plackett–Burman in the design of experiments with three replicates for each one. Eventually, 36 foams were prepared with different densities and initial thicknesses, heating temperatures and times, applied compression ratios, and the rest times between two heating steps. The microstructures of the conventional and auxetic samples were observed by scanning electron microscopy (SEM). All samples were subjected to tensile loading in one direction with...
Design, Fabrication and Model-base Control of a Brachiation Robot with Flexible Support
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Gholamreza (Supervisor) ; Namvar, Mehrzad (Supervisor)
Abstract
Nowadays, many researches are inspired by nature and living creatures in order to build various scientific and industrial products such as robots, because of the highest level of creativity which is used in creating them along with their high level of efficiency in power consumption and designing parameters. Underactuated Robots are the type of robots which have more degrees of freedom comparing to the number of operators. As a result their optimum control has a lot of complications. Brachiating robots are designed and built based on an inspiration from long armed apes (Gibbons). This type of monkey is highly skilled in twisting in trees and traversing. This type of movement benefits from...
Molecular dynamics study on axial elastic modulus of carbon nanoropes
, Article Archives of Civil and Mechanical Engineering ; Volume 19, Issue 4 , 2019 , Pages 1127-1134 ; 16449665 (ISSN) ; Firouz Abadi, R. D ; Norouzi, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Carbon nanoropes (CNRs) are of interest for a wide variety of nanotechnological applications. Since little attention has been paid to mechanical properties of CNRs, their axial elastic modulus is explored herein. Molecular dynamics (MDs) simulations are adopted for analysis of Young's modulus of CNRs. It is also shown that increase in the initial helical angle decreases Young's modulus; however, by increase in the number of CNTs and strands, different influence on Young's modulus emerges. Therefore, the highest value of Young's modulus obtained at the lower value of initial helical angle and consequently, Young's modulus of bundle of straight CNTs is higher than CNRs with hierarchical...
Numerical Investigation of the Effects of Environmental Parameters on the Simulation of Spread of Fire in Grasslands
, M.Sc. Thesis Sharif University of Technology ; Farhanieh, Bijan (Supervisor) ; Afshin, Hossein (Co-Supervisor)
Abstract
Fire in Grasslands is one of the most dangerous natural disasters that is uncontrollable at the time of its occurrence and will continue until there is a fundamental change in the conditions of the fire. Fire in Grasslands due to the high density of vegetation can produce a large amount of heat energy in a short time and in a very large area, which alone can cause the spread of fire in Grasslands. Today, numerical studies of fire behaviour and propagation are given more attention than experimental studies due to their lower costs and limitations. In the present study, the numerical simulation of the fire spread with the influence of climate parameters such as humidity, rainfall during fire...
Diffusion brazing of Ti–6Al–4V and AISI 304: an EBSD study and mechanical properties
, Article Journal of Materials Science ; Volume 52, Issue 20 , 2017 , Pages 12467-12475 ; 00222461 (ISSN) ; Shamanian, M ; Atapour, M ; Khosravi, B ; Sharif University of Technology
2017
Abstract
Ti–6Al–4V and AISI 304 stainless steel were joined by diffusion brazing with a Cu interlayer at 900 °C for different bonding times. The influence of the bonding time on the joint width, microstructure, microhardness and shear strength was studied. Interfacial characterizations and the identification of phases were done by scanning electron microscopy and electron backscatter diffraction (EBSD). The results revealed that by increasing the bonding time, the thickness of the joint was first increased and then decreased. Microstructure examinations also showed that the joints consisted of several intermetallics such as TiCu, Ti2Cu, TiCu4, TiCu2, FeTi and Fe2Ti. On the other hand, EBSD results...
Heavy oil thermal conversion and refinement to the green petroleum: A petrochemical refinement plant using the sustainable formic acid for the process
, Article Biointerface Research in Applied Chemistry ; Volume 10, Issue 5 , 2020 , Pages 6088-6100 ; Talebi, S ; Fabi, M ; Khajehpour, H ; Sharif University of Technology
AMG Transcend Association
2020
Abstract
In this study, heat oil conversion experiments using steam and formic acid as a hydrogen carrier be carried out in a batch reactor at T = 380 degrees of Celsius and P = 165 bar. Material balance and product distribution were calculated after the process. Properties of crude oil before and after thermal conversion, including viscosity, API gravity, SARA measurement, and elemental analysis, were analyzed. It has been presented that the use of formic acid as a hydrogen carrier solvent reduces the formation of coke and gaseous products and enhances the performance of liquid products. Also, the viscosity of the refined oil decreased by 23.2% due to the addition of formic acid compared to the...
Exergy and exergoeconomic analysis of hydrogen and power cogeneration using an HTR plant
, Article Nuclear Engineering and Technology ; Volume 53, Issue 8 , 2021 , Pages 2753-2760 ; 17385733 (ISSN) ; Talebi, S ; Fani, M ; Khajehpour, H ; Sharif University of Technology
Korean Nuclear Society
2021
Abstract
This paper proposes using sodium-cooled fast reactor technologies for use in hydrogen vapor methane (SMR) modification. Using three independent energy rings in the Russian BN-600 fast reactor, steam is generated in one of the steam-generating cycles with a pressure of 13.1 MPa and a temperature of 505 °C. The reactor's second energy cycles can increase the gas-steam mixture's temperature to the required amount for efficient correction. The 620 ton/hr 540 °C steam generated in this cycle is sufficient to supply a high-temperature synthesis current source (700 °C), which raises the steam-gas mixture's temperature in the reactor. The proposed technology provides a high rate of hydrogen...
Developing an adaptive fractional model of a magnetic structure using evolutionary algorithm
, Article ICCC 2008 - IEEE 6th International Conference on Computational Cybernetics, Stara Lesna, 27 November 2008 through 29 November 2008 ; 2008 , Pages 189-192 ; 9781424428755 (ISBN) ; Hajihasani, M ; Farjami, Y ; Norouzi, E ; Sharif University of Technology
2008
Abstract
Magnetic flux leakage technique is used extensively to detect and characterize defects in natural gas and oil transmission pipelines. The amount of magnetic flux introduced into the test sample is an important factor in the resolution of flaw detection. It depends on the power of permanent magnets and the geometrical design of the magnetic yoke. Finite element method (FEM) is the most widely used method of analyzing magnetic yoke due to its power, accuracy and straightforwardness. On the other hand its calculations are so complicated and time consuming, and every single modification in the parameters of the problem requires a new run. In this paper, we present an innovative method to...
Linear Secret Sharing from the Optimality Point of View
, M.Sc. Thesis Sharif University of Technology ; Khazaei, Shahram (Supervisor)
Abstract
A secret sharing scheme is a way to share a secret between a group of people so that only authorized subsets can retrieve the original secret. Secret sharing schemes were first introduced by Shamir and Blakley for threshold access structures. In a threshold access structure, a subset of individuals is allowed if the number of members exceeds a predetermined threshold. After Shamir, the study of general access structures was considered, and Ito, Saito, and Nishizeki proposed a way to construct a secret sharing scheme for these structures. Reducing the length of party's share in secret-sharing schemes and finding the optimal scheme for access structures has long been the focus of researchers...
Performance evaluation of k out of n detector
, Article 14th European Signal Processing Conference, EUSIPCO 2006, Florence, 4 September 2006 through 8 September 2006 ; 2006 ; 22195491 (ISSN) ; Greco, M. S ; Nayebi, M. M ; Sharif University of Technology
2006
Abstract
In this paper the problem of k out of n detection, between sequence of M random bits is addressed. The main application of the result is in a radar system, when we want to detect a target (with unknown time of arrival (TOA)), using binary integration. Another application is in ESM systems, when the system wants to detect the existence of a swept jammer or a gated noise jammer. But as any other mathematical problem, it may have some other applications. In this paper some simple equations for P fa and P d calculation of a detector which detects the existence of sequence of n ones between M random bits, is derived. These equations are then used to find the optimal detector structure in some...
Evolving data stream clustering based on constant false clustering probability
, Article Information Sciences ; Volume 614 , 2022 , Pages 1-18 ; 00200255 (ISSN) ; Bagheri Shouraki, S ; Norouzi, Y ; Sharif University of Technology
Elsevier Inc
2022
Abstract
Today's world needs new methods to deal with and analyze the ever-increasingly generated data streams. Two of the most challenging aspects of data streams are (i) concept drift, i.e. evolution of data stream over time, which requires the ability to make timely decisions against the high speed of receiving new data; (ii) limited memory storage and the impracticality of using memory due to the large amount of data. Clustering is one of the common methods to process data streams. In this paper, we propose a novel, fully-online, density-based method for clustering evolving data streams. In recent years, a number of methods have been proposed, which also have the ability to cluster data streams....