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Investigation on Effects of Nanoparticles Presence on Hydrate Formation Characterization During Drilling
, M.Sc. Thesis Sharif University of Technology ; Mohammadi, Ali Asghar (Supervisor) ; Zarenezhad, Bahman (Co-Advisor) ; Ramazani, Ahmad (Co-Advisor)
Abstract
In past two decades, the direction of oil and gas exploration has moved towards deep water drilling. The pressure and temperature in these zones are ideal for gas hydrate formation that can cause serious and sometimes uncontrollable issues during drilling operations. Gas hydrate formation while drilling can cause problems such as occurrence of kick and blowout, plug chock and kill line, and change in rheology of drilling mud. On the other hand, nowadays, nanotechnology has created an evolution in engineering sciences and because of the wide range of this science, drilling industry is affected like other industries. In the meantime, because of high yield, high stability and various methods of...
Reliability Assessment, Allocation and Optimization for Launching Systems
, Ph.D. Dissertation Sharif University of Technology ; Pourtakdoost, Hossein (Supervisor)
Abstract
The subject of systemic reliability assessment, allocation and optimization as well as structural reliability (SR) of a two stage solid fuel launch vehicle (LV) is investigated. In this regards, first the LV reliability block diagram is broken-down into appropriate subsystems. Subsequently the total LV system reliability is determined assuming the subsystems reliability. In addition, using a hybrid GA-PSO algorithm optimal subsystems redundancy levels, reliabilities as well their type are determined to simultaneously maximize the total reliability while minimizing the LV cost (weight) as a constraint. While the reliability and cost of subsystems are not precisely known, the total LV...
Launch vehicle multi-objective reliability-redundancy optimization using a hybrid genetic algorithm-particle swarm optimization
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 10 , Nov , 2015 , Pages 1785-1797 ; 09544100 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
This paper focuses on multi-objective reliability optimization of a two-stage launch vehicle using a hybridized Genetic Algorithm-Particle Swarm Optimization with provisions of relative weighting between the objectives. In this respect, the launch vehicle key subsystems as well as their functions are initially introduced. Subsequently, the system reliability block diagram is constructed using the launch vehicle working order of the subsystems augmented with the requirements for a robust fault/failure tolerant design and performance. Next, based on the proposed reliability block diagram arrangement a bi-objective optimization is formulated to maximize the system reliability while minimizing...
Time-varying structural reliability of launch vehicle via extreme response approach
, Article Journal of Spacecraft and Rockets ; Volume 54, Issue 1 , 2017 , Pages 306-314 ; 00224650 (ISSN) ; Pourtakdoust, S. H ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2017
Abstract
Time-varying structural reliability of a multistage solid-propellant launch vehicle subjected to deterministic and stochastic loads is investigated. The study is of practical importance because the launch vehicle's structure is influenced by a combination of external aerodynamics as well as inertial and internal ballistic loads emanating from the solid rocket motors. In addition, as launch-vehicle flight conditions change during flight, the vehicle will be subjected to time-varying loads. In this sense, the environmental, aerodynamic, and internal pressure fluctuations can be interpreted as stochastic forces affecting the launch-vehicle structural reliability. To account for temporal...
Reliability and failure analysis of jet vane tvc system
, Article Journal of Failure Analysis and Prevention ; 2018 ; 15477029 (ISSN) ; Pourtakdoust, H ; Samiei Paghaleh, S ; Sharif University of Technology
Springer New York LLC
2018
Abstract
Structural and system reliability of a typical jet vane (JV) thrust vector control (TVC) subsystem subjected to stochastic loadings is investigated. Jet vane TVC (JVTVC) is used in many aerospace liquid and solid propulsion systems. For the purpose of this work, JVTVC structural reliability of a solid rocket propulsion system is computed using an explicit closed-form limit state function. The JV structure is influenced by the internal ballistic loads emanating out of the solid rocket propulsion internal ballistic, whose performance is modeled via a one-dimensional uniform flow assumption at the engine steady operating condition. Subsequently, JV structural reliability is predicted using the...
Reliability analysis of composite anisogrid lattice interstage structure
, Article Mechanics Based Design of Structures and Machines ; 2020 ; Davar, A ; Pourtakdoust, S. H ; Sharif University of Technology
Bellwether Publishing, Ltd
2020
Abstract
Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and...
Reliability analysis of composite anisogrid lattice interstage structure
, Article Mechanics Based Design of Structures and Machines ; Volume 50, Issue 9 , 2022 , Pages 3322-3330 ; 15397734 (ISSN) ; Davar, A ; Pourtakdoust, S. H ; Sharif University of Technology
Taylor and Francis Ltd
2022
Abstract
Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and...
Solving MEC and MEC/GI problem models, using information fusion and multiple classifiers
, Article Innovations'07: 4th International Conference on Innovations in Information Technology, IIT, Dubai, 18 November 2007 through 20 November 2007 ; 2007 , Pages 397-401 ; 9781424418411 (ISBN) ; Moeinzadeh, M. H ; Mohammadzadeht, J ; Ghazinezhad, A ; Habibi, J ; Najafi Ardabili, A ; Sharif University of Technology
IEEE Computer Society
2007
Abstract
Mutations in Single Nucleotide Polymorphisms (SNPs - different variant positions (1%) from human genomes) are responsible for some genetic diseases. As a consequence, obtaining all SNPs from human populations is one of the primary goals of recent studies in human genomics. Two sequences of mentioned SNPs in diploid human organisms are called haplotypes. In this paper, we study haplotype reconstruction from SNP-fragments with and without genotype information, problems. Designing serial and parallel classifiers was center of our research. Genetic algorithm and K-means were two components of our approaches. This combination helps us to cover the single classifier's weaknesses. ©2008 IEEE
Three heuristic clustering methods for haplotype reconstruction problem with genotype information
, Article Innovations'07: 4th International Conference on Innovations in Information Technology, IIT, Dubai, 18 November 2007 through 20 November 2007 ; 2007 , Pages 402-406 ; 9781424418411 (ISBN) ; Asgarian, E ; Najafi Ardabili, A ; Sharifian R, S ; Sheikhaei, M. S ; Mohammadzadeh, J ; Sharif University of Technology
IEEE Computer Society
2007
Abstract
Most positions of the human genome are typically invariant (99%) and only some positions (1%) are commonly variant which are associated with complex genetic diseases. Haplotype reconstruction is to divide aligned SNP fragments, which is the most frequent form of difference to address genetic diseases, into two classes, and thus inferring a pair of haplotypes from them. Minimum error correction (MEC) is an important model for this problem but only effective when the error rate of the fragments is low. MEC/GI as an extension to MEC employs the related genotype information besides the SNP fragments and so results in a more accurate inference. The haplotyping problem, due to its NP-hardness, may...
Structural reliability analysis of solid rocket motor with ellipsoidal cap
, Article Journal of Spacecraft and Rockets ; Volume 53, Issue 2 , 2016 , Pages 389-392 ; 00224650 (ISSN) ; Pourtakdoust, S. H ; Ashouri Amin Abadi, B ; Rajabi Ghanavieh, A ; Sharif Iniversity of Technology
American Institute of Aeronautics and Astronautics Inc
2016
Observations on using probabilistic c-means for solving a typical bioinformatics problem
, Article EMS 2008, European Modelling Symposium, 2nd UKSim European Symposium on Computer Modelling and Simulation, Liverpool, 8 September 2008 through 10 September 2008 ; 2008 , Pages 236-239 ; 9780769533254 (ISBN) ; Ghazinezhad, A ; Rasooli Valaghozi, A ; Nadi, A ; Asgarian, E ; Salmani, V ; Najafi Ardabili, A ; Moeinzadeh, M. H ; Sharif University of Technology
2008
Abstract
Recently, there has been great interest in Bio informatics among researches from various disciplines such as computer science, mathematics, statistics and artificial intelligence. Bioinformatics mainly deals with solving biological problems at molecular levels. One of the classic problems of bioinformatics which has gain a lot attention lately is Haplotyping, the goal of which is categorizing SNP-fragments into two clusters and deducing a haplotype for each. Since the problem is proved to be NP-hard, several computational and heuristic methods have addressed the problem seeking feasible answers. In this work it is shown that using PCM to solve Haplotyping problem in DALY dataset yields...
The isaac newton telescope monitoring survey of local group dwarf galaxies. iv. the star formation history of andromeda vii derived from long-period variable stars
, Article Astrophysical Journal ; Volume 910, Issue 2 , 2021 ; 0004637X (ISSN) ; Saremi, E ; Javadi, A ; Noori, M ; Van Loon, J. T ; Khosroshahi, H. G ; McDonald, I ; Alizadeh, M ; Danesh, A ; Gozaliasl, G ; Molaeinezhad, A ; Parto, T ; Raouf, M ; Sharif University of Technology
IOP Publishing Ltd
2021
Abstract
We have examined the star formation history (SFH) of Andromeda VII (And VII), the brightest and most massive dwarf spheroidal (dSph) satellite of the Andromeda galaxy (M31). Although M31 is surrounded by several dSph companions with old stellar populations and low metallicity, it has a metal-rich stellar halo with an age of 6-8 Gyr. This indicates that any evolutionary association between the stellar halo of M31 and its dSph system is frail. Therefore, the question is whether And VII (a high-metallicity dSph located ∼220 kpc from M31) can be associated with M31's young, metal-rich halo. Here we perform the first reconstruction of the SFH of And VII employing long-period variable (LPV) stars....