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Preparation of in-situ Cu/NbC nanocomposite and its functionally graded behavior for electrical contact applications
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 25, Issue 3 , 2015 , Pages 863-872 ; 10036326 (ISSN) ; Abachi, P ; Pourazarang, K ; Mohammadi Rahvard, M ; Sharif University of Technology
Nonferrous Metals Society of China
2015
Abstract
Abstract Cu-15%NbC (volume fraction) powder was synthesized using the starting powders of Cu, Nb and graphite in a high energy vibratory disc mill for 7 h of milling under argon atmosphere. A composite sample and a Cu/NbC functionally graded material (FGM) sample were produced by using the two-step press and sintering at 900 °C for 1 h under vacuum. The microstructure and physical and mechanical properties of the specimens were investigated. The field emission scanning electron microscopy, energy dispersive X-ray and X-ray diffraction analysis confirmed the synthesis of the nanostructure matrix of 18-27 nm with the nanoparticles reinforcement of 42 nm after sintering, verifying the thermal...
Production of in Situ Cu/NbC Nanocomposites Powders via Mechanical Alloying and Investigation the Mechanical (Wear Resistance) and Physical (Electrical Conductivity) Properties
, M.Sc. Thesis Sharif University of Technology ; Abachi, Parvin (Supervisor) ; Purazarang, Kazem (Supervisor)
Abstract
For application such as electrical contacts and spot welding electrodes, both high electrical conductivity and wear resistance are required. Additionally, such parts should have structural stability at evaluated temperature. Copper based composites containing carbides or oxides reinforcement can be the good choice for production of such parts. In present work, in-situ Cu/NbC composite via mechanical alloying with homogenous distribution of nano reinforcement particle has been produced. For this purpose, in first stage, copper powder was milled with 5, 8, 10 and 12 wt. % of niobium powder in two types of mills, i. e. vibratory dicky mill and planetary ball mill for 5 and 32 h respectively. At...
Modeling of photoplethysmography signal for quantitative analysis of endothelial cells during reactive hyperemia
, Article 2012 19th Iranian Conference of Biomedical Engineering, ICBME 2012 ; 2012 , Pages 174-178 ; 9781467331302 (ISBN) ; Firoozabadi, B ; Saidi, M. S ; Sharif University of Technology
2012
Abstract
In this study, at first the cardiovascular system is modeled based on the 1D method and then the simulation of the reactive hyperemia experiment has been applied on the model. In this simulation, by applying a cuff at the brachial artery, the flow downstream of the cuff is occluded. Then with releasing the cuff immediately, a large amount of shear stress, about 4 times the basal amount, is applied downstream of the cuff and consequently to the endothelial cells in a very short moment. Considering a reported experimental transfer function between shear stress and vasodilation, the increase of the artery diameter due to the sudden increase of the shear stress is obtained. Finally, the...
Multi independent latent component extension of naive bayes classifier
, Article Knowledge-Based Systems ; Volume 213 , 2021 ; 09507051 (ISSN) ; Hediehloo, A ; Shiri Harzevili, N ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Naive Bayes (NB) classifier ease of use along with its remarkable performance has led many researchers to extend the scope of its applications to real-world domains by relaxing the conditional independence assumption of features given the information about the class variable. However, fulfilling this objective, most of the generalizations, cut their own way through compromising the model's simplicity, make more complex classifiers with a substantial deviation from the original one. Multi Independent Latent Component Naive Bayes Classifier (MILC-NB) leverages a set of latent variables to preserve the overall structure of naive Bayes classifier while rectifying its major restriction. Each...
An exploratory study on application of various classification models to distinguish switchable-hydrophilicity solvents based on 3D-descriptors
, Article Separation Science and Technology (Philadelphia) ; 2020 ; Shiri, F ; Sharif University of Technology
Taylor and Francis Inc
2020
Abstract
A set of solvents were classified into the switchable-hydrophilicity solvents (SHSs) and non-switchable-hydrophilicity solvents based on forming or not forming a biphasic mixture with water. SHSs have been developed to make the reaction and product separation processes easier. Herein, three classifier algorithms and various feature selection techniques relay on 3D-molecular descriptors to characterize chemicals and forecast their classes were employed. Cfs-SVM method was employed to perform a classification study. The importance of this study helps to understand more about the presence of hydrophobic groups, their position, and their shape in the molecule. © 2020, © 2020 Taylor & Francis...
An exploratory study on application of various classification models to distinguish switchable-hydrophilicity solvents based on 3D-descriptors
, Article Separation Science and Technology (Philadelphia) ; Volume 56, Issue 5 , 2021 , Pages 961-969 ; 01496395 (ISSN) ; Shiri, F ; Sharif University of Technology
Bellwether Publishing, Ltd
2021
Abstract
A set of solvents were classified into the switchable-hydrophilicity solvents (SHSs) and non-switchable-hydrophilicity solvents based on forming or not forming a biphasic mixture with water. SHSs have been developed to make the reaction and product separation processes easier. Herein, three classifier algorithms and various feature selection techniques relay on 3D-molecular descriptors to characterize chemicals and forecast their classes were employed. Cfs-SVM method was employed to perform a classification study. The importance of this study helps to understand more about the presence of hydrophobic groups, their position, and their shape in the molecule. © 2020 Taylor & Francis Group, LLC
Improved Supply Chain Management Performance by Applying Hybrid Forecast Method
, M.Sc. Thesis Sharif University of Technology ; Hajji, Alireza (Supervisor)
Abstract
In today’s competitive world, using an efficient forecast method is necessity for companies. To now, many forecast methods have been developed, but many of them have not an expected efficiency. In this research, we develop a new hybrid forecast method with application of forecasting retails demand. The hybrid method is the combination of ARIMA method and neural networks. To test the efficiency of the method we use the 96 weeks data of plastic containers demand. We also comprise the hybrid method with other forecast methods including naïve method, ARIMA method and neural network method by applying root mean square error and mean absolute percentage error indexes. In the case of plastic...
Effect of superheat and solidified layer on achieving good metallic bond between A390/A356 alloys fabricated by cast-decant-cast process
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Vol. 24, issue. 3 , March , 2014 , p. 665-672 ; Tamizifar, M ; Boutorabi, M. A ; Shiri, S. G ; Sharif University of Technology
2014
Abstract
The cast-decant-cast is a new method for the preparation of the functionally graded components that has been developed in recent years. The functionally graded cylindrical shape component with a radial gradient, e.g. the first alloy (A390) with high wear resistance on the surface of the piece and toughness and the second alloy (A356) of low machining costs in the core of the piece can be produced via this melt process. The effect of the second alloy superheat at temperatures of 750, 820 and 860 °C as well as the effect of the first alloy solidified layer at 25, 35 and 45 s decanting time on achieving the perfect interface between the two alloys was investigated. The characterization of the...
The optimum combination of tool rotation rate and traveling speed for obtaining the preferable corrosion behavior and mechanical properties of friction stir welded AA5052 aluminum alloy
, Article Materials and Design ; Volume 50 , 2013 , Pages 620-634 ; 02613069 (ISSN) ; Gholami Shiri, S ; Yaghoubinezhad, Y ; Mohammadi Rahvard, M ; Sharif University of Technology
Elsevier Ltd
2013
Abstract
This study attempts to find an optimum combination of the welding tool rotation rate (ω) and traveling speed (υ), concerning the corrosion and mechanical properties of Friction Stir Welded (FSWed) AA5052 Aluminum alloy. The effect of the tool speeds on the FSWed AA5052 are investigated via potentiodynamic polarization, open circuit potential (OCP) monitoring, test of the susceptibility to intergranular corrosion, weight loss, tension and micro-hardness tests. Optical microscope and Scanning Electron Microscopy (SEM) were employed for studying the morphology and analyzing the probable intergranular attacks. It was found that by increasing υ up to 200. mm/min at ω=400 rpm, the microstructural...
Synthesis and Characterization of Electrospun N/S Doped ZnO and Investigation of their Applications in Dye Degradation
, M.Sc. Thesis Sharif University of Technology ; Poujavadi, Ali (Supervisor)
Abstract
In this research, the synthesis of the electrospum nano fiber doped zinc oxide and its photocatalyst usage was investigated. The band gap of the zinc oxide in the area of UV leads to deactivation of this material at the visible light. With due the attention to sunny weather in Iran and the fact that about 50 percentage of sunlight is visible light, producing and usage of catalyst materials actived at visible light is economical. Doping is one of the ways of activating ZnO at visible light, so in this research thiourea is used as the source of ZnO doping. The results of the expriments done at visible light and also spectrums of DRS, XPS and XRD prove that the doping is happened. Also, in this...
Prediction of crude oil refractive index through optimized support vector regression: a competition between optimization techniques
, Article Journal of Petroleum Exploration and Production Technology ; Volume 7, Issue 1 , 2017 , Pages 195-204 ; 21900558 (ISSN) ; Ansari, H. R ; Hosseini, S. S ; Sharif University of Technology
Springer Verlag
2017
Abstract
Refractive index (RI) provides valuable information about various reservoir engineering calculations, making it a key parameter for characterizing crude oils. Determination of this index through experiment is capital-intensive, time consuming, and also toil. Hence, it is essential to search for an efficient and accurate estimation of crude oil RI. In this study, an intelligent approach, based on optimized support vector regression (SVR), is introduced to find a quantitative correlation between crude oil RI and SARA (saturate, aromatic, resin, and asphaltene) fraction data. Optimization of SVR is implemented through three searching approaches, viz. hybrid of grid and pattern search (HGP),...
Analyzing symmetry in photonic band structure of gyro-magnetic photonic crystals
, Article Proceedings of SPIE - The International Society for Optical Engineering ; Volume 8096 , 2011 ; 0277786X (ISSN) ; 9780819487063 (ISBN) ; Khorasani, S ; Gholami, F ; Sharif University of Technology
2011
Abstract
In the band structure analysis of photonic crystals it is normally assumed that the full photonic gaps could be found by scanning high-symmetry paths along the edges of Irreducible Brillouin Zones (IBZ). We have recently shown [1] that this assumption is wrong in general for sufficiently symmetry breaking geometries, so that the IBZ is exactly half of the complete BZ. That minimal required symmetry arises from the requirement on time-reversal symmetry. In this paper we show that even that requirement might be broken by using gyro-magnetic materials in the composition of photonic structures we can observe that the IBZ extends fully to the boundaries of the complete BZ, that is IBZ must be as...
Modeling of DLL-based frequency multiplier in time and frequency domain with Matlab Simulink
, Article IEEE Asia-Pacific Conference on Circuits and Systems, Proceedings, APCCAS, 6 December 2010 through 9 December 2010 ; 2010 , Pages 1051-1054 ; 9781424474561 (ISBN) ; Sharifkhani, M ; Saeedi, S ; Sharif University of Technology
2010
Abstract
A systematic procedure of simulating charge pump based delay locked loops (DLLs) represents in this paper. The presented procedure is based on the systematic modeling of the DLL components in Matlab Simulink simulator. The system has been designed for 1Hz input clock signal that by changing the whole system scale, it can be used for every other input frequencies. The simulation results in Matlab and design considerations for DLL based frequency multiplier are presented
Process optimization and modeling of heavy metals extraction from a molybdenum rich spent catalyst by aspergillus niger using response surface methodology
, Article Journal of Industrial and Engineering Chemistry ; Volume 18, Issue 1 , January , 2012 , Pages 218-224 ; 1226086X (ISSN) ; Mousavi, S. M ; Borghei, S. M ; Sharif University of Technology
2012
Abstract
The present study examines the biorecovery of heavy metals from a spent refinery catalyst obtained from one of the oil refineries in Iran using Aspergillus niger. Bioleaching experiments were carried out in batch cultures using A. niger in the one-step process to mobilize Co, Mo and Ni from hazardous spent catalysts. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of pH, temperature, inoculum percentage, pulp density and rotation speed during the bioleaching of the metals. Experiments were designed as per the central composite design (CCD) technique. Three cubic mathematical models were derived for prediction of the responses....
Fungal leaching of hazardous heavy metals from a spent hydrotreating catalyst
, Article World Academy of Science, Engineering and Technology ; Volume 76 , 2011 , Pages 726-731 ; 2010376X (ISSN) ; Borghei, S. M ; Mousavi, S. M ; Sharif University of Technology
2011
Abstract
In this study, the ability of Aspergillus niger and Penicillium simplicissimum to extract heavy metals from a spent refinery catalyst was investigated. For the first step, a spent processing catalyst from one of the oil refineries in Iran was physically and chemically characterized. Aspergillus niger and Penicillium simplicissimum were used to mobilize Al/Co/Mo/Ni from hazardous spent catalysts. The fungi were adapted to the mixture of metals at 100-800 mg L -1 with increments in concentration of 100 mg L -1. Bioleaching experiments were carried out in batch cultures. To investigate the production of organic acids in sucrose medium, analyses of the culture medium by HPLC were performed at...
Bacterial leaching of a spent Mo-Co-Ni refinery catalyst using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans
, Article Hydrometallurgy ; Volume 106, Issue 1-2 , February , 2011 , Pages 26-31 ; 0304386X (ISSN) ; Borghei, S. M ; Mousavi, S. M ; Sharif University of Technology
2011
Abstract
A spent processing catalyst from an Iranian oil refinery was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize Al, Co, Mo and Ni from the spent catalysts under optimized conditions in batch cultures. The characteristics of the bioleach solution (pH, Eh, cell concentration and Fe(II)/Fe(III) concentration) were determined along with the concentration of metal values extracted from the catalyst. The results showed that after bioleaching using A. ferrooxidans in the presence of ferrous sulfate, maximum extractions of 63% Al, 96% Co, 84% Mo and 99% Ni were achieved after 30 days at pH 1.8-2.0. However, the...
Heavy metals recovery from spent catalyst using acidithiobacillus ferrooxidans and acidithiobacillus thiooxidans
, Article ICCCE 2010 - 2010 International Conference on Chemistry and Chemical Engineering, Proceedings, 1 August 2010 through 3 August 2010, Kyoto ; 2010 , Pages 331-335 ; 9781424477647 (ISBN) ; Borghei, S. M ; Mousavi, S. M ; Sharif University of Technology
2010
Abstract
In this investigation, a spent processing catalyst from one of the oil refineries in Iran was initially characterized physically and chemically. Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were used to mobilize aluminum, cobalt, molybdenum and nickel from hazardous spent catalysts. Bioleaching experiments were performed in batch cultures. The growth characteristics of the bacteria (pH, Eh, cell concentration and ferrous and ferric iron concentration) were determined during bioleaching along with the concentration of metal values extracted from the catalyst. The results obtained from Inductive coupled plasma-optical emission spectrometry (ICP-OES) showed that after the...
The effect of multiwalled carbon nanotubes and activated carbon on the morphology and photocatalytic activity of TiO2/C hybrid materials
, Article Catalysis Science and Technology ; Volume 1, Issue 2 , 2011 , Pages 279-284 ; 20444753 (ISSN) ; Ghasemi, S ; Gholami, M. R ; Sharif University of Technology
2011
Abstract
TiO2 nanoparticles supported on activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) were prepared by the sol-gel method using ultrasonic irradiation. All the prepared samples were calcined at different temperatures and characterized by X-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, transmission electron microscopy and diffuse reflectance spectroscopy. The effects of size and type of carbon on the morphology and photocatalytic activity of the resulting hybrid materials were investigated. The results showed that a decrease in the size of the carbon led to a decrease in size of TiO2 nanoparticles. Both AC and MWCNTs retarded the...
The impact of gas compositions on the intensity of positive coupling effect in gas condensate reservoirs
, Article 1st International Petroleum Conference and Exhibition ; 4-6 May , 2009 ; Hashemi, A ; Vaziri, S. M ; Sharif University of Technology
European Association of Geoscientists and Engineers, EAGE
2009
Abstract
The positive coupling effect decreases the condensate saturation as a result of very high flow rates in vicinity of the wellbore. The current work challenges the notion that the positive rate effect does not lead in falling trend of condensate saturation around the wellbore in the case of rich gas composition. According to the results obtained from this parameter case study, four distinct trends would appear in the condensate saturation profile of both lean and rich gas compositions. These quadruplet trends are consistent and their occurrence is mainly related to the considered base capillary number (Ncb) which is likely dependent to the composition of the fluid
Supported PtxPd1-x bimetallic nanoparticles on ionic liquid-functionalized SiO2@graphene oxide nanocomposite and its application as an effective multiphasic catalyst
, Article Applied Catalysis A: General ; Volume 579 , 2019 , Pages 30-43 ; 0926860X (ISSN) ; Giannakis, S ; Gholami, M. R ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In this work, PtxPd1-x (x = 0, 0.5, and 1)nanoparticles (NPs)were synthesized on the surface of SiO2@graphene oxide which covered by 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF6)ionic liquid (IL)layer. FT-IR spectroscopy, zeta potential, CHN elemental analysis, XRD, XPS, SEM, EDX, TEM, TGA, BET, and ICP-AES techniques were applied for the characterization of the multiphasic catalyst. The as-prepared nanocomposite was used as an effective heterogeneous catalyst for the oxidation of cyclohexene by molecular oxygen, as a green oxidant. Different experimental conditions such as oxygen pressure, reaction time, reaction temperature and amount of catalyst were investigated in this...