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ghasemi-fard--ali
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Investigation of Microstructural Evolutions During Dissimilar TLP Bonding of IN792 and Hastelloy X Nickel Based Superalloys
, M.Sc. Thesis Sharif University of Technology ; Pouranvari, Majid (Supervisor)
Abstract
In this thesis, macrostructural evolutions in dissimilar TLP bonding of as-cast nickel based supperalloy IN792 to wrought HX was investigated. In the first step of this study solidification behavior of Ni-Cr-Fe-Si-B (MBF-15) interlayer in presence of HX as base metal at 1120 °C was surveyed. In second step, bonding of HX/HX, IN792/IN792 and HX/IN792 systems with MBF-15 interlayer at 1120 °C and different times were studied and isothermal solidification time and factors that affect this stage were discussed. In third step, synchronization of dissimilar bonding with standard heat treatment cycle of IN792 was investigated and effect of this cycle on aging response of different zones, isothermal...
Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal
, Article Science and Technology of Welding and Joining ; 2017 , Pages 1-7 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
2017
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) filler metal. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone, borides/silicide formation during eutectic-type solidification in an athermal solidification zone, on-cooling precipitation of fine nickel silicides in the joint centerline, in situ precipitation of Mo–Cr-rich borides in the diffusion affected zone and grain growth in the heat affected zone. The implication of the phase transformations on the joint properties is discussed. It is shown...
Investigating Different Methods of Coating the Polyaniline on Anode Electrode and its Effect on Microbial Fuel Cell Performance
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheila (Supervisor)
Abstract
In this research, different methods of coating polyaniline on the anode electrode and its performance in a microbial fuel cell, and a chemical method for making polyaniline / graphene catalyst on a cathode electrode and its performance in microbial electrolysis cell electrode were investigated. There are two main goals in this study. First, the production of polyaniline and the comparison of the surface morphology of this fiber with other forms of polyaniline on the surface of the electrode and its effect on the performance of the microbial fuel cell and the second, the production of polyaniline / graphene catalyst in the cathode electrode and its comparison with the platinum catalyst in the...
Dynamic Pricing by Considering Reference Price Effects in Competitive Environment
, M.Sc. Thesis Sharif University of Technology ; Modarres, Mohammad (Supervisor)
Abstract
Taking into account the impact of advertising on the reference price, we propose an optimal pricing strategy for supply chains in competitive industries subject to reference price effect. Most of researches do not consider the competition among supply chains. An industry with two competing supply chains is considered. Each supply chain includes a manufacturer who sells his/her product via a retailer. There are two types of structures: integrated and decentralized (it is assumed that the relation in a chain is Manufacturer– Stackelberg). Each manufacturer offers wholesale price to his/her retailer anticipating the retailer’s order quantity. In addition, the retailers choose their retail...
Planar Motion Control and Path Following of a Biomimetic Helical Swimmer Robot in Low Reynolds Condition
, M.Sc. Thesis Sharif University of Technology ; Sayadi, Hassan (Supervisor)
Abstract
Today, the use of controllable swimmer micro-robots has expanded from micro to macro-scale dimensions due to their many applications. These robots, as a result of their small size and dimensions, have the ability to access limited and complex environments. Considering the various applications of such swimmers, it can be said that in addition to the necessity of well designing and implementation, their maneuverability and controllability are among the most important research areas on these swimmers. Regarding the dimensions and technologies needed for these robots, various methods for designing and implementing them are suggested, which are mostly inspired by the nature of microorganisms. In...
A quantum mechanical approach towards the calculation of transition probabilities between DNA codons
, Article BioSystems ; Volume 184 , 2019 ; 03032647 (ISSN) ; Shafiee, A ; Sharif University of Technology
Elsevier Ireland Ltd
2019
Abstract
The role of quantum tunneling in altering the structure of nucleotides to each other and causing a mutational event in DNA has been a topic of debate for years. Here, we introduce a new quantum mechanical approach for analyzing a typical point-mutation in DNA strands. Assuming each codon as a base state, a superposition of codon states could provide a physical description for a set of codons encoding the same amino acid and there are transition amplitudes between them. We choose the amino acids Phe and Ile as our understudy bio-systems which are encoded by two and three codons, respectively. We treat them as large quantum systems and use double- and triple-well potential models to study the...
Efficient Implementation of Classification of Air-Polluting Cars in Apache Storm
, M.Sc. Thesis Sharif University of Technology ; Goudarzi, Maziar (Supervisor)
Abstract
Today, due to the increasing use of fossil fuel-powered vehicles, attention has been paid to advanced societies by the amount of pollutants emitted by these vehicles and the need to control and reduce them. As the number of cars increases, the volume of data for processing increases, which increases the need for data centers and processing infrastructure with more computing power. Therefore, in this research, we intend to implement a program that continuously categorizes cars according to specific criteria in terms of emission levels. For this purpose we used Apache Storm, a data stream processing framework, to implement the program.In this research, we develop a simulation for cars with the...
A new approach to study the Zeno effect for a macroscopic quantum system under frequent interactions with a harmonic environment
, Article Scientific Reports ; Volume 9, Issue 1 , 2019 ; 20452322 (ISSN) ; Shafiee, A ; Sharif University of Technology
Nature Publishing Group
2019
Abstract
Quantum Zeno and anti-Zeno behaviors of a two-level macroscopic quantum system in interaction with a harmonic environment are studied using the perturbation theory. The system-environment interactions are applied in a successive and step-by-step way. A new expression for the probability of surviving the macrosystem in its initial state, after the Nth interaction step, is derived through a different method of calculation. It is shown that multiple transitions between Zeno and anti-Zeno behaviors can be found in our approach. We have shown that in addition to the environmental parameters like the Ohmicity, the macroscopic trait of the system also has a notable effect on the decay rate Γ(τ)....
Thermal processing strategies enabling boride dissolution and gamma prime precipitation in dissimilar nickel-based superalloys transient liquid phase bond
, Article Materials and Design ; Volume 182 , 2019 ; 02641275 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The microstructure of dissimilar transient liquid phase bond between Hastelloy X and IN792 nickel-based superalloys is featured by lack of sufficient formation of γ′ precipitates in the bond-centerline and extensive in-situ precipitation of boride second phases in the diffusion affected zones (DAZ). This paper investigates the impact of two thermal processing strategies, using standard solution treatment and aging of IN792 (STA strategy) and using solution treatment of IN792 followed by a post-bond heat treatment utilizing solution treatment of Hastelloy X and aging treatment of IN792 (SPTA strategy) on the joint microstructure and mechanical properties. The boride precipitates in the DAZ of...
Fast isothermal solidification during transient liquid phase bonding of a nickel alloy using pure copper filler metal: solubility vs diffusivity
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 50, Issue 5 , 2019 , Pages 2235-2245 ; 10735623 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Springer Boston
2019
Abstract
This investigation aims at understanding the underlying fundamentals of the isothermal solidification phenomenon during the transient liquid phase (TLP) bonding process. The isothermal solidification is governed by solid-state diffusion of the melting point depressant (MPD) into the base material, which, in turn, is controlled by both kinetic and thermodynamic parameters; however, the latter factor is generally ignored. In this work, the competition between kinetics and thermodynamics of diffusion were considered in TLP bonding of a nickel alloy, Monel 400, using two distinct filler metals including pure copper (Cu) and Ni-Si-B filler metal. The joint generated by Ni-Si-B filler metal...
Intermetallic phase formation during brazing of a nickel alloy using a Ni–Cr–Si–Fe–B quinary filler alloy
, Article Science and Technology of Welding and Joining ; Volume 24, Issue 4 , 2019 , Pages 342-351 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Fundamental understanding of the intermetallic phase formation is the key for enhancing the robustness and reliability of the brazed joints. The paper addresses the phase transformations during brazing of the Hastelloy X nickel-base superalloy using the quinary Ni–13Cr–4.5Si–4.2Fe–2.8B (wt-%) braze alloy. The mechanisms of intermetallic formation via solidification and solid-state precipitation are discussed. The athermal solidification zone (ASZ) is featured by the formation of brittle and hard borides and boro-silicides that are formed via eutectic reactions. However, in contrast to other commercial B-bearing Ni-based filler alloys, it was identified that the presence of a high-volume...
Calculation of Quantum Transition Probabilities between Codons and Concept of Biological Information
, Ph.D. Dissertation Sharif University of Technology ; Shafiee, Afshin (Supervisor)
Abstract
It has been about a century since the introduction of the theory of quantum mechanics. This theory is a branch of physics that describes the behavior of nature in very small scales and microscopic systems . Since no quantum system is entirely isolated from its surroundings , it is necessary to study their interactions with the environment to understand them accurately. The theory of open quantum systems provides the theoretical and conceptual framework needed to consider these interactions. Then using the appropriate quantum operations , the evolution of the combined system can be investigated. Moreover , considering the environmental effects, some quantum features such as dissipation...
An investigation into the energy transfer efficiency of a two-pigment photosynthetic system using a macroscopic quantum model
, Article BioSystems ; Volume 197 , 2020 ; Shafiee, A ; Sharif University of Technology
Elsevier Ireland Ltd
2020
Abstract
Despite several different measures of efficiency that are applicable to the photosynthetic systems, a precise degree of efficiency of these systems is not completely determined. Introducing an efficient model for the dynamics of light-harvesting complexes in biological environments is a major purpose in investigating such systems. Here, we investigate the effect of macroscopic quantum behavior of a system of two pigments on the transport phenomena in this system model which interacts with an oscillating environment. We use the second-order perturbation theory to calculate the time-dependent population of excitonic states of a two-dimensional Hamiltonian using a non-master equation approach....
Microstructural evolution mechanism during brazing of Hastelloy X superalloy using Ni–Si–B filler metal
, Article Science and Technology of Welding and Joining ; Volume 23, Issue 5 , 2018 , Pages 441-448 ; 13621718 (ISSN) ; Pouranvari, M ; Sharif University of Technology
Taylor and Francis Ltd
2018
Abstract
The paper aims at understanding solidification phenomena and solid state precipitations during diffusion brazing of Hastelloy X nickel base superalloy using a ternary Ni–4.5Si–3.2 B (in wt-%) filler metal. The joint is featured by the formation of Ni-rich solid solution in an isothermal solidification zone, borides/silicide formation during eutectic-type solidification in an athermal solidification zone, on-cooling precipitation of fine nickel silicides in the joint centerline, in situ precipitation of Mo–Cr-rich borides in the diffusion affected zone and grain growth in the heat affected zone. The implication of the phase transformations on the joint properties is discussed. It is shown...
Spinal segment ranges of motion, movement coordination, and three-dimensional kinematics during occupational activities in normal-weight and obese individuals
, Article Journal of Biomechanics ; Volume 123 , 2021 ; 00219290 (ISSN) ; Arjmand, N ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Measurements of spinal segment ranges of motion (RoMs), movement coordination, and three-dimensional kinematics during occupational activities have implications in occupational/clinical biomechanics. Due to the large amount of adipose tissues, obese individuals may have different RoMs, lumbopelvic coordination, and kinematics than normal-weight ones. We aimed to measure/compare trunk, lumbar, and pelvis primary RoMs in all anatomical planes/directions, lumbopelvic ratios (lumbar to pelvis rotations at different trunk angles) in all anatomical planes/directions and three-dimensional spine kinematics during twelve symmetric/asymmetric statics load-handling activities in healthy normal-weight...
Mining the Tenant Experience: Uncovering the Determinants of Residential Satisfaction through Topic Modelling of Online Rental Apartment Reviews
, M.Sc. Thesis Sharif University of Technology ; Aslani, Shirin (Supervisor)
Abstract
Residential satisfaction plays a pivotal role in shaping liveable cities, profoundly influencing individuals' health and well-being. In contrast, dissatisfaction in living environments often triggers relocation intentions, leading to significant vacancy costs for landlords and property managers. While previous studies predominantly relied on traditional methods like surveys and interviews, our research adopts a novel, bottom-up approach, analysing this phenomenon through the lens of residents themselves. Leveraging a custom-developed Python-based web scraper, we meticulously gathered 195,000 online reviews from apartments.com. This comprehensive dataset spans the most populous cities and...
Author Correction: Environment assisted quantum model for studying RNA-DNA-error correlation created due to the base tautomery (Scientific Reports, (2023), 13, 1, (10788), 10.1038/s41598-023-38019-7)
, Article Scientific Reports ; Volume 13, Issue 1 , 2023 ; 20452322 (ISSN) ; Tirandaz, A ; Sharif University of Technology
Nature Research
2023
Abstract
Correction to: Scientific Reports, published online 04 July 2023 In the original version of this Article, author Arash Tirandaz was omitted as a corresponding author. Correspondence and requests for materials should also be addressed to a.tirandaz@basu.ac.ir. The original Article has been corrected. © 2023, The Author(s)
Implementation and Analysis of Optical Isolation using Reciprocal and Nonreciprocal Elements
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor)
Abstract
In this thesis we study the possibility of unidirectional transmission of light using reciprocal and nonreciprocal elements. Unidirectional transmission will allow us to separate the coupling of light into and out of resonators and design unidirectional waveguides. We start by studying the effects of one-sided modulations of dielectric constant of reciprocal structures. One-sided modulation will satisfy the phase matching condition for the coupling of two waves only in one direction. Using coupled mode theory, we study one sided modulation in layered media. Next, we find the exact solution to such strucures using transfer matrix method and analyze one-sided modulation in waveguide...
Theoretical investigation on the structural and electronic properties of complexes formed by thymine and 2'-deoxythymidine with different anions
, Article Structural Chemistry ; Volume 23, Issue 1 , July , 2012 , Pages 17-28 ; 10400400 (ISSN) ; Fattahi, A ; Sharif University of Technology
2012
Abstract
Hydrogen bonding interactions between thymine nucleobase and 2'-deoxythymidine nucleoside (dT) with some biological anions such as F - (fluoride), Cl - (chloride), OH - (hydroxide), and NO 3 - (nitrate) have been explored theoretically. In this study, complexes have been studied by density functional theory (B3LYP method and 6-311++G (d,p) basis set). The relevant geometries, energies, and characteristics of hydrogen bonds (H-bonds) have been systematically investigated. There is a correlation between interaction energy and proton affinity for complexes of thymine nucleobase. The nature of all the interactions has been analyzed by means of the natural bonding orbital (NBO) and quantum theory...
Influence of cation-heteroatom (Li+, Na+, and K +) interaction on the structural and thermochemical properties of 2′-deoxythymidine nucleoside: Qtaim and NBO analyzes
, Article Journal of Theoretical and Computational Chemistry ; Volume 12, Issue 2 , December , 2013 ; 02196336 (ISSN) ; Fattahi, A ; Sharif University of Technology
2013
Abstract
Density functional theory (DFT) method and B3LYP/6-311++G(d,p) basis set were used to determine coordination geometries, binding strength, and metal ion affinity (MIA) for interaction of 2′-deoxythymidine (dT) with alkali metal cations including Li+, Na+, and K+. Calculations demonstrated that the interaction of dT with these cations is tri-coordinated η (O2, O4′, O5′). Among these cations, Li + cation exhibited the most tendency for interaction with dT. Cations via their interaction with dT can affect the N-glycosidic bond length, the values of pseudorotation of the sugar ring, the orientation of base unit with respect to sugar ring and the acidity of O5′H, O3′H, and N3H groups in 2′-dT...