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Optimal Retrieval Trajectory of Tethered System of Space Debris for Maximize the Aerodynamic Heating
, M.Sc. Thesis Sharif University of Technology ; Malaek, Mohammad Bagher (Supervisor)
Abstract
In this study, a model for the optimal routes for the recovery of space debris is expressed. The dynamic model using a binary system consisting of satellites and orbital debris containment space is extracted. Trastrhay available on satellite and aerodynamic drag on the system circuit changes the whole system and the entry of debris into the thick atmosphere began to burn.This circuit must be optimized. The thrusters are assumed as variable optimization problem. After simulation of optimization, it follows that by changing the initial value thrusters, Trastrhay the optimal cost function changes. Also, indicating the final height of system affects on parameters, thrusters and the cost...
Study of the triple-mass tethered satellite system under aerodynamic drag and J2 perturbations
, Article Advances in Space Research ; Volume 56, Issue 10 , November , 2015 , Pages 2141-2150 ; 02731177 (ISSN) ; Assadian, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
The dynamics of multi-tethered satellite formations consisting of three masses are studied in this paper. The triple-mass triple-tethered satellite system is modeled under the low Earth orbit perturbations of drag and Earth's oblateness and its equilibrium conditions are derived. It is modeled as three equal end-masses connected by a uniform-mass straight tether. The lengths of tethers are supposed to be constant and in this manner the angles of the plane consisting the masses are taken as the state variables of the system. The governing equations of motion are derived using Lagrangian approach. The aerodynamic drag perturbation is expressed as an external nonconservative force and the Earth...
Transport Properties in Heterostructures of 2D Layers of Graphene with WS2 and hBN Quantum Dots
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
Graphene based photodetectors which are modified with quantum dots, are the new generation of detectors. In these supplies an integration of graphene’s unique characteristics like high conductivity and mobility and the high light absorption of quantum dots, are used.In this research graphene by chemical vapor deposition in centimetric large scales, tungsten disulfide quantum dots, boron nitride and graphene quantum dots and 2D tungsten disulfide have been synthesized. In the next step each of them were characterized to modify the quality of used layers in heterostructure.Based on the characteristic tests, quantum dots aspect ratios were 1 to 5 nanometers. Also tungsten disulfide was obtained...
Brandom’s Conception of Trust
, M.Sc. Thesis Sharif University of Technology ; Abazari, Arash (Supervisor)
Abstract
A Spirit of Trust results from Brandom's thirty-year effort to give a pragmatistic reading of Hegel's Phenomenology of Spirit. In A Spirit of Trust, Brandom reformulates Hegel's arguments in the language of contemporary Analytical Philosophy and gives a unique interpretation of Hegel's key concepts. In this Thesis, we will examine one of its key concepts, namely, Trust; We will pursue the following questions: First, What is Trust? And what is its connection to other aspects of Brandom's philosophy? Second, How does Trust help us in overcoming Alienation? Third, Are Confession and Forgiveness, which are the constitutive concepts of Trust, psychologistic or normative? Fourth, What is the...
Combustible organic materials : determination and prediction of combustion properties
, Book
De Gruyter
2018
Linear decoupled space-time codes
, Article 14th IEEE 2003 International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC2003, Beijing, 7 September 2003 through 10 September 2003 ; Volume 3 , 2003 , Pages 2862-2867 ; 0780378229 (ISBN); 9780780378223 (ISBN) ; Khalaj, B. H ; Sharif University of Technology
2003
Abstract
In this paper, we will introduce a new constraint on linear space-time block codes that will result in a novel decoupled symbol-by-symbol detection scheme. Based on the new framework, a quasi-decoupled space-time code that is applicable to any number of transmit and receive antennas will be proposed. We will also solve a more general case and show that all other known solutions to this problem such as orthogonal designs and Clifford algebra representations, represent special cases of such general solution which will provide an easier framework, to deal with such codes. It is noticeable that the new framework not only provides better understanding of earlier solutions but may also help in...
Improve the Structure of Membrane Bioreactor to Reduce Fouling for Industrial Waste Water Purification
, M.Sc. Thesis Sharif University of Technology ; Seifkordi, Ali Akbar (Supervisor) ; Hemati, Mahmood (Co-Advisor)
Abstract
In the presence project by using of hydrophilic polymer, Cellulose acetate (CA), we tried to modify the membrane made of Polyvinylidine fluoride (PVDF). The membranes were made by phase inversion method. In five levels, at least 10% and at most 30%, CA was added to casting solution. The hydrophilicity of membranes’ surface and pore size was increased. The permeation of the neat membrane of PVDF was less than 10 , on the other hand the permeation of the membranes, which were made by adding CA, was increased up to 500 . The increment of CA more than 20% reduced the porosity of membrane. In the next step to reduce the irreversibility fouling tried to reduce the pore size by adding some...
The Study of Eliminating Gender Gap in Iran Labor Market on Participation Rate of Married Urban Women
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor) ; Joshaghani, Hossein (Supervisor)
Abstract
The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's...
Cross-cultural Perceptions of Impoliteness by Native English Speakers and EFL Learners: The Case of Apology Speech Act
, Article Journal of Intercultural Communication Research ; Vol. 43, issue. 4 , Sep , 2014 , pp. 304-326 ; ISSN: 17475759 ; Alemi, M ; Razzaghi, S ; Sharif University of Technology
2014
Abstract
This study investigated native English speakers’ and English as a foreign language (EFL) learners’ perception of (im)politeness. Seventy-five native speakers and 177 EFL learners were administered a discourse completion task for the speech act of apology accompanied by responses violating politeness by various degrees. Participants were asked to assess the degree of (im)politeness embedded in each response and to write down their assessment comments. Content analysis of respondents’ comments indicated that both groups mentioned similar (im)politeness criteria. However, the analysis of frequency counts displayed significant differences between the two groups in their degree of preference for...
Crack Detection in a Rotor using Traditional Mode Shape Based Modal Analysis Methods and Experimental Evaluation
, M.Sc. Thesis Sharif University of Technology ; Mohammad Navazi, Hossein (Supervisor)
Abstract
Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have...
The Effect of Increasing The Value of Natural Gas Production on Property Value, Wages, Unemployment Rate and Birth Rate in The United States of America (2000-2011)
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
In the present study, the effects of increasing the value of shale gas production, either due to increased production or price increases, have been studied on economic variables such as employment, wage, property value and the number of births. In this regard, the data for each of these variables was used at the county level in the United States of America between 2000 and 2011. In order to estimate the desired effects, counties are divided into two types of boom and non-boom counties. The findings indicate that increasing natural gas production will lead to more employment and wage growth in boom counties than non-boom counties. Also, during the period of increasing production, the value of...
Investigating and Analyzing the Optimal Method for Construction of Keshavarz Metro Station on Line Three of Esfahan Urban Railway
, M.Sc. Thesis Sharif University of Technology ; Sadaghiani, Mohammad Hossein (Supervisor)
Abstract
It is important to provide an appropriate and economically method with technical and engineering considerations to stabilize excavated underground spaces. The necessity of this, especially for the construction of underground metro stations located in the cities which faces many problems, is more evident. In this research, it has been tried to introduce an optimal method according to the type of area for the construction of the underground station. In order to obtain stress and strain condition in structural elements and surface deformations due to different stages of excavating, numerical modeling in FLAC3D has been used. By examining the parameters that affect the sustainability of this...
Learning Interpretable Representation of Drugs based on Microscopy Images
, M.Sc. Thesis Sharif University of Technology ; Rohban, Mohammad Hossein (Supervisor)
Abstract
In this study, we aim to learn representations from microscopic cell images that effectively capture the features of drugs affecting the cells, allowing us to identify effective drugs for treating a disease. We employ two parallel learning paths using predictive and generative models. Specifically, we have achieved a predictive model on the RxRx19a dataset that, unlike previous models, is interpretable, optimized, and robust to dras- tic changes in drug properties. Additionally, we have developed the first generative model on this dataset, which not only generates high-quality images but also discovers a meaningful latent space. This latent space divides the representation into relevant...
Inflationary Permanent and Long-Term Positive Interest Rate Shocks
, M.Sc. Thesis Sharif University of Technology ; Rahmati, Mohammad Hossein (Supervisor)
Abstract
Co-movement between inflation and nominal interest in response to an interest rate shock, dubbed neo-fisherianism, has been the subject of contentious debate since the advent of non-inflationary ZLB environment. We design an economic model rich with banking features to understand the economic responses to permanent and long-term interest rate shocks. We find that responses to a permanent positive interest rate shock depend on the monetary authorities’ speculation of the new long-term inflation rate, with the most probable outcome being a permanent increase in inflation. Responses to a long-term positive interest rate shock depict an increase and then decrease in inflation. We also discover...
A new model for robust facility layout problem [electronic resource]
, Article Information Sciences, Elsevier ; Volume 278, 10 September 2014, Pages 498–509 ; Eshghi, Kourosh ; Salmani, Mohammad Hassan ; Sharif University of Technology
Abstract
The Facility Layout Problem (FLP) is the problem of locating each department in a long plant floor without any overlap between departments in order to minimize the material handling cost. The main purpose of this study is to show the effectiveness of a robust approach to solve FLP. In this study, it is assumed that the departments’ length and width are not predetermined. For modeling this kind of uncertainty, the size of each department is considered as a bounded variable and two new parameters are also introduced to implement a robust approach. Moreover, a new adaptive algorithm is designed to determine the robust layout with respect to the decision makers’ requirements. Furthermore, the...
Interaction of Parallel Tunnels; Case Study: Interaction of Towhid Tunnel and Tehran Metro line 7 Tunnel
, M.Sc. Thesis Sharif University of Technology ; Sadaghiani, Mohammad Hossein (Supervisor)
Abstract
Influence of excavating the Tehran metro line 7 tunnel on surface settlement, stresses and deformations induced in Towhid tunnel is investigated using numerical modeling. Construction of Metro tunnel as the new one must be carried out without imposing any damage to the Towhid tunnel as the existing tunnel. Towhid tunnel is a set of twin tunnels along the Chamran highway in Tehran. The tunnels were constructed using sequential excavation method and lined with cast in place reinforced concrete; on the other side metro line 7 is being constructed using 2 EPB tunnel boring machines and lined with reinforced concrete segments. This research consists of the study of the effects of pillar width,...
Pore-Scale Experimental Study of Foam/Nano-Foam Flooding to Heavy oil in Heterogeneous Five-Spot System: Stability Analysis and Displacement Mechanisms
,
M.Sc. Thesis
Sharif University of Technology
;
Ghazanfari, Mohammad Hossein
(Supervisor)
Abstract
Foam injection for enhanced oil recovery is concerned by petroleum engineers because it decreases adverse effects of fingering and gravity segregation caused by the injected fluid .Obviously foam stability is an important factor in the efficiency of this process. So investigating it is an imperative. One of the ways that less studied and can improve foam stability is using of nanoparticles. In this project effect of nanoparticles on foam stability and displacement mechanism during foam flooding has been discussed.
Study consisted of two sets of experiments. In the first part, the static foam stability in the presence of silica nanoparticles has been investigated. Also influence of...
Study consisted of two sets of experiments. In the first part, the static foam stability in the presence of silica nanoparticles has been investigated. Also influence of...
Modeling and Simulation of Miscible Flow through Fractured Porous Media Using Random Walk Method
, M.Sc. Thesis Sharif University of Technology ; Ghazanfari, Mohammad Hossein (Supervisor)
Abstract
Miscible displacement in fluid flowing through a porous medium plays an important role in many environmental and industrial applications; for instance, miscible displacements in enhanced oil recovery processes and pollutant spreading in groundwater. A large number of numerical approaches have been developed to solve the advection-dispersion equation that describes the behavior of miscible displacement in porous media. Most of these numerical models suffer from numerical dispersion. Random walk seems to be an effective method to overcome this problem especially in heterogeneous media. Here, a random walk model was developed and used for simulating miscible displacement in heterogeneous porous...
Non-stationary Vibration of a Rotor with Foil Gas Bearings Passing Through Critical Speeds
, M.Sc. Thesis Sharif University of Technology ; Mohammad Navazi, Hossein (Supervisor)
Abstract
The use of air bearings was began the last decade. Oil-free air bearing technology is implemented in rotating machines such as turbines, Micro gas turbines and turbocharged, this technology has improved the efficiency of rotating systems. In rotating machines, at high speeds, passing through the critical speed happens. As a result, the natural frequency of the system is crossing the critical speed, which causes system instability and lack of system amplitude control. Instability causes damage to the system. The aim of this thesis is to investigate the nonstationary vibrations of a flexible rotor with air bearings in the passing critical speeds. Behavior of air bearings is also considered to...
Spherical Graphite Cast iron Production from Sponge Iron
, M.Sc. Thesis Sharif University of Technology ; Ashuri, Hossein (Supervisor)
Abstract
Due to the increasing spread of metal industries and the need for raw material as feed for electric furnaces in order to produce cast iron and steel, as well as scrap deficiency and rising prices, the use of sponge iron as a substitute for scrap was considered in this project Therefore, in order to achieve the chemical analysis of the sorel ingot that is special for spherical graphite cast iron production with low manganese and chromium content, the direct reduction process was carried out using tunnel kiln method on low-manganese iron ore concentrate.After the investigation on direct reduction parameters including the saggers and coal grading,the produced sponge iron has melted in...