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asgari--ehsannedin
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Deep Neural Models for Hierarchical Sequence Classification in Language Processing Applications
, M.Sc. Thesis Sharif University of Technology ; Asgari, Ehsannedin (Supervisor)
Abstract
Hierarchical text classification is an important challenge in machine learning and natural language processing, focusing on categorizing texts using a hierarchical label structure. This structure is often modeled as a directed acyclic graph (DAG) or a tree, illustrating the hypernym-hyponym relationships between classes. This research introduces a method to extract relevant labels from texts while utilizing hierarchical information, reviews current techniques, and evaluates them across various scenarios with different metrics, revealing the limitations of prior approaches. Hierarchical classification finds applications in areas like news classification, sentiment analysis, fake news...
Machine Learning Approaches for the Prediction of Pathogenicity in Genome Variations
, M.Sc. Thesis Sharif University of Technology ; Sharifi Zarchi, Ali (Supervisor) ; Asgari, Ehsannedin (Supervisor)
Abstract
Genome mutations whose effects are not specified pose one of the challenges in identifying genetic diseases. Utilizing wet lab tests to detect the pathogenicity of variants can be time-consuming and fiscally expensive. A rapid and cost-effective solution to this problem is the use of machine learning-based variant effect predictors, which have the ability to determine whether a mutation is pathogenic or not. The objective of this research is to predict the pathogenicity of genome variations. The proposed model exclusively utilizes the protein sequence as its input feature and does not have access to other protein features. The data used to construct the model comprises mutations with...
Correlations in a multisubband quasi-one-dimensional electron gas
, Article Physical Review B - Condensed Matter and Materials Physics ; Volume 62, Issue 23 , 2000 , Pages 16001-16017 ; 01631829 (ISSN) ; Nafari, N ; Asgari, R ; Asgari, R ; Sharif University of Technology
2000
Abstract
This paper is an extension of an earlier work on electron correlations in semiconducting GaAs-based quasi-one-dimensional quantum wires. The extension was twofold. First, we developed the Singwi, Tosi, Land, and Sölander (STLS) scheme for multisubband structures. Secondly, we developed the multisubband ladder approximation diagrammatic technique. By using the results obtained for the spin symmetric and spin antisymmetric interpolarization and intrapolarization potentials, we calculate the corresponding electron-electron effective potentials. Our results for a two-subband model show that these effective potentials have an attractive part implying the occurrence of s-wave and p-wave pairings,...
Age-hardening behavior and phase identification in solution-treated AEREX 350 superalloy
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 37, Issue 7 , 2006 , Pages 2051-2057 ; 10735623 (ISSN) ; Sharif University of Technology
2006
Abstract
This article presents results of an investigation on age-hardening behavior of superalloy AEREX 350. Microhardness testing was employed to evaluate the age-hardening response of the alloy while optical, scanning, and transmission electron microscopy techniques were used to characterize the major phases formed during the aging process. No significant hardening was found in solution-treated samples aged at temperatures up to about 680 °C. Aging at 700 °C up to 950 °C, however, caused a characteristic hardening response. This hardening was concurrent with the formation of γ', an ordered phase with L12 structure, as fine precipitate distributed throughout the fcc matrix. In the temperature range...
Anomalous plastic behavior of fine-grained MP35N alloy during room temperature tensile testing
, Article Journal of Materials Processing Technology ; Volume 155-156, Issue 1-3 , 2004 , Pages 1905-1911 ; 09240136 (ISSN) ; Sharif University of Technology
2004
Abstract
In this paper, results of an investigation on the strain hardening responses of superalloy MP35N with two average grain sizes of 38 and 1 μm, during room temperature tensile testing are reported. The microstructural evolution of the deformed samples was studied using optical and transmission electron microscopy (TEM) techniques. The strain hardening behavior of the 38 μm material was rather similar to that previously reported for low stacking fault energy (SFE) fee alloys. The plastic behavior of the fine grain material, however, was unexpected. In the strain range of 0.1-0.4, the work hardening rate of the fine grain size sample was evidently lower than that of the large grain size...
Ferromagnetic Single Electron Transistor
, M.Sc. Thesis Sharif University of Technology ; Faez, Rahim (Supervisor)
Abstract
This thesis completely introduses ferromagnetic single electron transistor while that identifies the application and types of the transistor.Master equation is used for simulationing of the transistor. This simulation is divided to two general sections.In the first section proposed thermal equilibrium the normal island and The two spin subsystems , however, are in thermal equilibrium and quantized nature of energy spectrum of a small central electrode and fluctuations in the spin accumulation were ignored , however, we simplify the problem and assume that the charging energy are independent of the electron distribution, and number of electrons in the normal island. ،hat tunnel rates can be...
Production of Nanostructured Composite Sheets of AA1100/St37 Using ARB Technique and Evaluation of Heat Treatment Effect on Grains Structure
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
In present work, nanostructured multilayer composites produced from AA1100 and St37 alloys and mechanical properties of resulted samples characterized using tension and micro hardness tests. Also dispersion pattern of second phase in matrix studied via optical microscopy. Thickness of second phase layers showed a little reduction after 2 ARB cycles; but their length decrease gradually. With increasing number of ARB cycles up to 6 cycles, sample's tensile strength first decrease rapidly and after that increased, but never reached initial value. In order to evaluation of heat treatment effects on samples grain structure, samples heat treated and tensile test carried on them. Annealing at 300...
The Effects of Stress-Assisted Heat Treatment on the Microstructure and Phase Transformation Behavior of Ni-Rich Ni-Ti Shape Memory Alloy
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Ni-Ti shape memory alloys have attracted most of the research in the field of shape memory alloys both because of their complicated and diverse phase transformation characteristics and their optimum properties for various applications which span such a properties as shape memory effect, pseudoelasticity, excellent mechanical properties and biocompatibility. The key properties of these alloys is generated through a thermoelastic martensitic transformation the occurrence of which is extremely sensitive to the metallurgical conditions of the alloy e.g. composition and microstructure. This has led to the development of various procedures implemented in either fabrication, processing or heat...
The Study of Microstructure and Phase Transformations in MP210 Superalloy
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
MP210 alloy is a member of multiphase family alloys, a class of wrought nickel-cobalt base alloys extensively used in high-quality applications including aerospace fasteners, gas turbine engines and petrochemical industry. Very limited information can be found in the literature about the microstructure and phase transformations of this alloy. The aim of this work is characterizing the aging response of the material and identifying the major strengthening phases precipitated in different range of temperatures and also studying the static recrystallization behavior of this alloy. The effect of age-hardening heat-treatment on the microstructure of MP210 superalloy was investigated using...
Linear Hardening in FCC Alloys
, Ph.D. Dissertation Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Previous observation and models on the origin of linear hardening behavior in FCC polycrystals are critically reviewed. To reveal the draw backs of the previous models, selected results of an investigation on the evolution of microstructure during simple compression testing of two FCC polycrystals, Inconel 625 superalloy and AISI 316L stainless steel are reported. It is found that while a number of FCC polycrystals show linear hardening behavior, the evolution of the underlying microstructure may be quite different. It is argued that, in contrast to the current belief, deformation twinning may not be the sole cause of linear hardening in low SFE FCC polycrystals. It is suggested that only...
Processing of Nanostructured Composite from Al1050 and Al2024 Via Aaccumulative Roll Bonding (ARB) and Study of Heattreatment Effects on its Microstructure and Mechanical Properties
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
In this study nanostructured composite from Al1050 and Al2024 were manufactured via accumulative roll bonding (ARB). Process was conducted in two different ways. In one approach the Al2024 sheets were annealed and in the other they were solution treated (ST). The sheets were degreased by acetone and wire-brushed, and then one Al2024 was placed between two sheets of Al1050, so three pieces of sheets were stacked to be 3 mm in thickness. The stacked sheets were rollbonded to produce the primary composite sandwich with thickness of 1 mm. Then, this sandwich was cut in the half and the two halves were degreased and wire-brushed and stacked to be 2 mm in thickness. Roll-bonding was conducted...
Lithium Iron Silicate Sol-Gel Synthesis and Electrochemical Investigation
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Recently lithium iron silicate (Li2FeSiO4) has been used as a new cathode material for lithium ion battery. Li2FeSiO4 has such benefits like low raw material price so lower production cost, lower environmental pollution, higher safety, electro chemical and cyclic stability and high theoretical capacity of 166 mAh/g against other cathode materials like LiMn2O4, LiBNiO2, LiCoO2 and LiFePO4. In this research Li2FeSiO4 was synthesized through sol gel synthesis method and effect of chelating agent concentration, calcination temperature and time has been investigated. To determine the appropriate calcination temperature range, TG/DTA was performed. Then the dried gel powder was calcined at each...
Coarsening Dynamics of Nanodroplets
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate....
Dispersion Modeling of Toxic Release (Chlorine) by CFD in Industrial and Urban Areas
,
M.Sc. Thesis
Sharif University of Technology
;
Rashtchian, Davood
(Supervisor)
Abstract
Chlorine is used in large quantities, in urban and industrial installations. Since chlorine is a toxic gas, its dispersion in such environments may have unpleasant consequences. On the point of Emergency Response Planning, it is important to know how such gases disperse. In this thesis, chlorine atmospheric dispersion is studied as an example of toxic dense gas dispersion. Chlorine accidental release from one of the storage tanks of Sohanak water refinery is selected for the case study. Laleh residential town is located in west of Sohanak refinery. According to the prevailing wind direction in Tehran (which is from the west to the east), the influence of the buildings of Laleh town on gas...
Colloidal Synthesis of CdSe Nanoparticles and the Influence of Processing Parameters on Growth kinetics
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
Over the past two decades, several studies have been investigated on synthesis and properties of semi-conductor quantum dots because of their applications in sensors, LEDs, detectors, solar cells, etc. One of challenging issues in synthesizing these nano-particles is their size distribution. In this study, Cadmium Selenide was synthesized by the method of colloidal synthesis. X-ray diffraction showed that the crystalline nano-particles have wurtzite structure. For obtaining a uniform size distribution, effect of various parameters such as molar ratio of components and reaction temperature on the growth kinetics of these particles, were studied. Results showed that molar ratio of Selenium to...
On-line SPE of Clodinafop Propargyl Traces from Aquatic Media Using Electrospun Polyamide Nanofibers Disks
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Habib (Supervisor)
Abstract
An on-line solid phase extraction (SPE) method coupled with high performance liquid chromatography (HPLC) was developed using electrospun polyamide (PA) nanofibers as the extractin medium for trace determination of clodinafop propargyl herbicide in environmental aqueous samples. The sufficient numbers of disc sheets were cut from the electrospun PA mat and used as packing material in a cartridge. The homogeneity and the porosity of the prepared PA sheet were studied using the scanning electron microscopy (SEM) and the observed nanofiber diameters and lengths proved that the prepared sorbent possess a high aspect ratio. Major parameters affecting the extraction efficiency were optimized. The...
Interaction of 3D dewetting nanodroplets on homogeneous and chemically heterogeneous substrates
, Article Journal of Physics Condensed Matter ; Vol. 26, Issue. 22 , 2014 ; ISSN: 09538984 ; Moosavi, A ; Sharif University of Technology
2014
Abstract
Long-time interaction of dewetting nanodroplets is investigated using a long-wave approximation method. Although three-dimensional (3D) droplets evolution dynamics exhibits qualitative behavior analogous to two-dimensional (2D) dynamics, there is an extensive quantitative difference between them. 3D dynamics is substantially faster than 2D dynamics. This can be related to the larger curvature and, as a consequence, the larger Laplace pressure difference between the droplets in 3D systems. The influence of various chemical heterogeneities on the behavior of droplets has also been studied. In the case of gradient surfaces, it is shown how the gradient direction could change the dynamics. For a...
Multiphase Simulation of Frost in High Pressure Air Flow Systems with Pressure Regulator
, M.Sc. Thesis Sharif University of Technology ; Darbandi, Masoud (Supervisor)
Abstract
In this study, our objective is to simulate the growth of frost for humid air passing through pressure regulators. The study is carried out in two main stages. First, we use an empirical method to model the formation of frost for a humid-air passing over a flat plate. The model is a semi-2D one and that it is limited to predict the frost growth at a particular station along the plate, considering the local flow heat transfer parameters. We show the validity of results comparing with available experimental data. Second, we numerically simulate the frost formation and growth for a humid air passing between two parallel plates. In this regard, the semi empirical method is suitably coupled with...
Late-stage evolution of thin liquid coating films over step topographies
, Article Advanced Materials Research ; Volume 569 , 2012 , Pages 560-563 ; 10226680 (ISSN) ; 9783037854808 (ISBN) ; Moosavi, A ; Sharif University of Technology
2012
Abstract
Mesoscopic hydrodynamic equations are solved to investigate late-stage evolution of thin liquid films over step topographies. Different geometrical parameters including step height and initial position and configuration of resultant masses of dewetting (droplets) are probed to find their effects on the mass evolution of the system. Our results indicate that increasing the step height and locating the droplets close to the step enhance the dynamics and accelerate smaller droplet collapse
The Effect of Heat Treatment on Microsructure, Hot Tensile Properties and Creep Bihavior of Nickel-based Superalloy CM88Y
, M.Sc. Thesis Sharif University of Technology ; Asgari, Sirous (Supervisor)
Abstract
The Ni-base superalloy CM88Y has good hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of gas turbine hot components. In most applications, heat treatment is required in order to achieve the desired mechanical properties and corrosion resistance of the working conditions; often three stages of heat treatment is designed for precipitation hardening nickel-base superalloy. In general, the effective parameters of heat treatment cycles includes temperature, time, heating rate and the cooling rate. In this study, the effect of cooling rate from partial solution temperature (second stage of heat treatment) on the...