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Peak load and energy absorption of DP600 advanced steel resistance spot welds
, Article Ironmaking and Steelmaking ; Volume 44, Issue 9 , 2017 , Pages 699-706 ; 03019233 (ISSN) ; Pouranvari, M ; Salim, R. K ; Hashim, F. A ; Marashi, S. P. H ; Sharif University of Technology
2017
Abstract
The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter...
Effect of zirconia nanotube coating on the hydrophilicity and mechanochemical behavior of zirconium for biomedical applications
, Article Surfaces and Interfaces ; Volume 28 , 2022 ; 24680230 (ISSN) ; Sarraf, M ; Musharavati, F ; Jaber, F ; Wang, J. I ; Hosseini, H. R. M ; Bae, S ; Chowdhury, M ; So, H ; Sukiman, N. L ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Zirconium has attracted considerable attention in the biomedical field owing to its biocompatibility and desirable tribological and mechanical properties. In this study, we anodized pure zirconium in an ammonium fluoride and ethylene glycol electrolyte, which produced a coating of ZrO2 nanotubes (NTs). The ZrO2 coated samples were annealed at different temperatures, and the morphology and structure of the coated substrates were studied using XPS, SEM, TEM, EDS, and SAED. The micro/nanomechanical properties and corrosion resistance of the samples were evaluated. Wear tests performed on bare and coated substrates revealed that the coated samples annealed at 400 °C had a significantly lower...
Peak load and energy absorption of DP600 advanced steel resistance spot welds
, Article Ironmaking and Steelmaking ; 2016 , Pages 1-8 ; 03019233 (ISSN) ; Pouranvari, M ; Salim, R. K ; Hashim, F. A ; Hoveida Marashi, S. P ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
The paper aims at investigating the microstructure, failure mode transition, peak load and energy absorption of DP600 dual phase steel during the tensile-shear test. It was found that the welding current has profound effect on the load–displacement characteristics. In the low welding current, welds failed in interfacial failure mode. Increasing welding current resulted in sufficient weld nugget growth to promote double-sided pullout failure mode with improved mechanical properties. Further increase in the welding current caused expulsion and failure mode was changed to single-sided pullout with reduced energy absorption capability. It was found that the fusion zone size is the key parameter...
Investigating the Effect of Operating Parameters on the Hold-Up and Slip Velocity in an L-Shaped Pulsed Sieve-Plate Extraction Column for Uranium Extraction using the Emulsion Liquid Membrane
,
M.Sc. Thesis
Sharif University of Technology
;
Samadfam, Mohammad
(Supervisor)
;
Safdari, Jaber
(Supervisor)
Abstract
In this research, for the first time, the emulsion liquid membrane method was used in a pulsed sieve plate column to separate uranium from uranyl nitrate solution. The L-shaped pulse extraction column was implemented on a semi-industrial scale at the Atomic Energy Organization. For the design and scale-up of these columns, it is necessary to measure hydrodynamic parameters and investigate the effects of operating parameters on them. The hydrodynamic parameters measured in this study include dispersed phase holdup and slip velocity under two conditions: without mass transfer and with mass transfer. Despite efforts, the operating conditions in the L-shaped column did not allow for the...
Investigation of Flow Rate and Cooling Water Temperature Effects on the Process Parameters in Centrifuge Machine
, M.Sc. Thesis Sharif University of Technology ; Otukesh, Mohammad (Supervisor) ; Safdari, Jaber (Supervisor)
Abstract
Centrifuge is a method in which great gravitational-like forces are used. Gravitational forces which cause molecules to move and are relevant to molecular weight; can cause isotope separation. The separation of light isotope from heavy one is done with a centrifugal field which produces a pressure gradient for the gas mixture. Pressure gradient is different for each of the isotopes due to the dependence of pressure gradient to the mass of the materials. But the separation in this way is very limited. The capacity of separation can be brought up by producing an additional axial flow in the rotor. This rotational flow can be produced with internal or external incitement. Rotational flow with...
Uranium Bioleaching from a Low Grade Ore
,
Ph.D. Dissertation
Sharif University of Technology
;
Roosta Azad, Reza
(Supervisor)
;
Safdari, Jaber
(Supervisor)
Abstract
In this work, bioleaching was used to extract valuable uranium from a low grade ore. Bioleaching experiments were carried out in batch cultures using a native strain of Acidithiobacillus ferrooxidans. Experiments were conducted to investigate the effects of rotation speed, initial redox potential, initially added Fe concentration, particle size, pH, temperature, pulp density, and culture type. In the shake flask systems, over 99% of the uranium was bioleached in 48 hours at some conditions. Uninoculated flasks gave only around 25% leaching. At each study, uranium and iron concentrations, solution oxidation– reduction potential and pH were measured. The results showed that 150 rpm, d80=100 ...
A Detailed Study on Extraction of Uranium from Mother Leach Liquor (of Uranium Mills) by TOA Extractant and Development of a Thermodynamical Model for it
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Safdari, Jaber (Supervisor) ; Mallah, Hassan (Co-Advisor)
Abstract
In many uranium mines such as gachin-bandarabbas, sulfuric acid is used for leaching operation on ore after crushing operation. This leach liquor, containing uranium, is extracted by specific solvent, including extractant like TOA. However, this operation, named Amex, have been used for many years, there is a vacancy for a detailed thermodynamical studying on uranium extraction from leach liquor.To have a thermodynamical model, we need information about the equilibrium concentration of all the components that may have effect on uranium extraction and also concentration of solvent, pH, phase ratio and activity coefficient alteration. This model must have the ability to predict the equilibrium...
Study of Effects of Operational Parameters on Flooding in Pertraction of Dysprosium in a Vertical Pulsed Packed Column
, M.Sc. Thesis Sharif University of Technology ; Bastani, Dariush (Supervisor) ; Safdari, Jaber (Supervisor) ; Raji, Maliheh (Co-Supervisor)
Abstract
Pulsed packed columns are among the most important devices used in liquid-liquid extraction, with wide application in petroleum and petrochemical industries, metal salt extraction, pharmaceutical industries, metallurgy, and other areas. Liquid-membrane technology is an alternative separation technique to the liquid-liquid extraction for the extraction and recovery of metal ions from aqueous solutions. There are three main types of liquid membranes: emulsion liquid membrane (ELM), Bulk Liquid Membrane (BLM), and Supported Liquid Membrane (SLM). Liquid emulsion membrane is one of the pertraction methods with phase dispersion. It is a three-phase dispersion system, consisting: external phase,...
Theoretical and Empirical Investigation on the Anticorrosion Performance of Smart Nano Composite Coating
, Ph.D. Dissertation Sharif University of Technology ; Shojaei, Akbar (Supervisor) ; Shariatpanahi, Homira (Supervisor) ; Neshati, Jaber (Co-Advisor)
Abstract
In the present study, smart anticorrosion coatings were successfully prepared based on epoxy ester (EPE) resin and conductive nano polyaniline particles (nES). Anticorrosion behaviors of these coatings were analyzed by electrochemical techniques. Generally, this thesis consists of two main parts: the theoretical studies (1st and 2nd Chaps.) and empirical investigations (3th to 8th Chaps.).The first Chap. expresses a basic introduction about the corrosion concepts and different types of anticorrosion coating. In the second Chap. main goals and stage works of the thesis about the smart anticorrosion coatings are introduced considering literature researches. The subject of the 3th Chap. is...
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Mallah, Mohammad Hassan (Supervisor) ; Safdari, Jaber (Supervisor)
Abstract
In many uranium mines such as gachin-bandarabbas, use sulfuric acid for leaching operation on ore. This leach liquor, containing uranium, is extracted by organic solvent, such as D2EHPA (dapex process ).althogh this process have being used for many years, there is a vacancy for detailed thermodynamical studying on uranium extraction of uranium from leach liquor. To have a thermodynamical model, we need information on equilibrium concentration of all component that may have effect on uranium extraction in addition we need concentration of solvent , pH, phase ratio and activity coefficient.such a model must have the ability to predict the equilibrium concentration in alloperation condition....
Bioleaching of Vanadium from Multimetal Ore of Saghand Mine
, M.Sc. Thesis Sharif University of Technology ; Roosta Azad, Reza (Supervisor) ; Safdari, Jaber (Supervisor) ; Firouzzare, Mohammad Ali (Co-Advisor)
Abstract
In this work bioleaching of vanadium has been done from Saghand Ore (Anomaly II). Leaching of vanadium was done in several stages. First, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxxidans were used for dissolution of pure vanadium pentoxide and it was observed that these bacteria are able to dissolve and reduce vanadium with high efficiency. After that these bacteria were employed to leaching of vanadium from ore; however there were no results by those experiments and no vanadium dissolved in liquor although bacterial activity was visible. In the second stage, oxalic acid 0.1 M as an organic acid and three inorganic acids, namely sulfuric, hydrochloridric and nitric acids, in...
A new control method of three-phase PMSG wind turbine connected to single-phase network through a Back-to-Back converter
, Article Asia-Pacific Power and Energy Engineering Conference, APPEEC ; 2011 ; 21574839 (ISSN) ; 9781424462551 (ISBN) ; Hojabri, H ; Mokhtari, H ; Chang, L ; Sharif University of Technology
2011
Abstract
In this paper, a new control strategy is proposed to improve the performance of a wind generator system composed of a three-phase PMSG and a Back-to-Back three-phase to single-phase converter. With the use of the large inductance of the synchronous generator, the control method minimizes the generator torque ripple when the system supplies a single-phase load. The problem arises from the fact that the instantaneous power of a single-phase load is pulsating at the double of the system frequency. This paper tries to minimize the effect of this pulsating power on the PMSG torque without using a large capacitor on the DC link. Simulation results show the effectiveness of the proposed method. ©...
Gas chromatography with atomic emission detection: A powerful technique
, Article TrAC - Trends in Analytical Chemistry ; Volume 21, Issue 9-10 , 2002 , Pages 618-626 ; 01659936 (ISSN) ; Brinkman, U. A.Th ; Bagheri, H ; Sharif University of Technology
Elsevier
2002
Abstract
Atomic emission detection (AED) is a sensitive as well as a selective detection technique for gas chromatography (GC) and provides element-specific information. A rapidly increasing number of applications in many different areas illustrates the versatility and analytical power of the technique - especially when complex samples have to be analysed. The complementary use of GC-AED and GC with mass-spectrometric detection often yields the most rewarding results. © 2002 Published by Elsevier Science B.V. All rights reserved
Evaluation the Effect of Molecular-Structural Properties of Asphaltene Fraction on Wettability Alteration and Crude Oil Dynamic Flow in Porous Media
, M.Sc. Thesis Sharif University of Technology ; Taghikhani, Vahid (Supervisor) ; Shahrabadi, Abbas (Co-Supervisor) ; Naderi, Hassan (Co-Supervisor) ; Taheri Shakib, Jaber (Co-Supervisor)
Abstract
In order to investigate the effect of molecular-structural properties of asphaltene fraction on changes in wettability and flow of crude oil in the porous medium, four crude oil samples from oil fields in southern Iran were tested ;To know the characteristics of crude oil, molecular-structural properties of asphaltene fraction and the effect of asphaltene fraction on the wettability properties of surface, Experiments such as crude oil density and viscosity measurement, crude oil hydrocarbon analysis, asphaltene extraction with standard IP-143 method, elemental analysis and metal content, gel permeation chromatography, nuclear magnetic resonance, interaction between rock and asphaltene....
QoS-aware water-filling for real-time transmission in OFDMA systems
, Article 2011 18th International Conference on Telecommunications, ICT 2011, 8 May 2011 through 11 May 2011, Ayia Napa ; 2011 , Pages 84-89 ; 9781457700248 (ISBN) ; Khalaj, B. H ; Froushani, M. H. L ; Sharif University of Technology
2011
Abstract
In this paper, we propose a distributed rate and power allocation algorithm for real time traffic by using second order statistics of the channel. Our method minimizes the average delay of transmission over the fading channel. We assume that each sub carrier relies on its own buffer, and a constant arrival rate from higher layer application arrives at input buffers of each sub-carrier. This constant rate is optimally distributed through individual sub-rates transmitted over each sub-channel. Optimum power coefficients are also derived to minimize the average delay of transmission. In addition, collision and buffer overflows are taken into account while achieving acceptable throughputs
Surface/interface effect on the scattered fields of an anti-plane shear wave in an infinite medium by a concentric multi-coated nanofiber/nanotube
, Article European Journal of Mechanics, A/Solids ; Volume 32 , 2012 , Pages 21-31 ; 09977538 (ISSN) ; Pahlevani, L ; Sharif University of Technology
2012
Abstract
In this paper, the scattering of anti-plane shear waves in an infinite matrix containing a multi-coated nanofiber/nanotube is studied. Based on the fact that the surface to volume ratio for nano-size objects increases, the usual classical theories which generally neglect the surface/interface effects fail to provide reasonable results. Therefore, to analyze the problem the wave-function expansion method is coupled with the surface/interface elasticity theory. In order to provide some quantitative results through consideration of several examples, the knowledge of the relevant surface and/or interface properties of the corresponding constituent materials are required. For this reason, part of...
Multicolored parallelisms of isomorphic spanning trees
, Article SIAM Journal on Discrete Mathematics ; Volume 20, Issue 3 , 2006 , Pages 564-567 ; 08954801 (ISSN) ; Alipour, A ; Fu, H. L ; Lo, Y. H ; Sharif University of Technology
2006
Abstract
A subgraph in an edge-colored graph is multicolored if all its edges receive distinct colors. In this paper, we prove that a complete graph on 2m (m ≠ 2) vertices K2m can be properly edge-colored with 2m - 1 colors in such a way that the edges of K2m can De partitioned into m multicolored isomorphic spanning trees. © 2006 Society for Industrial and Applied Mathematics
A generalized technique of modeling, analysis, and control of a matrix converter using SVD
, Article IEEE Transactions on Industrial Electronics ; Volume 58, Issue 3 , 2011 , Pages 949-959 ; 02780046 (ISSN) ; Mokhtari, H ; Chang, L ; Sharif University of Technology
2011
Abstract
In this paper, a new simple and complete technique of modeling and analysis of a matrix converter is presented based on the singular value decomposition (SVD) of modulation matrix. The proposed modeling method yields a new limitation between the matrix converter gain and its input power factor, which is more relaxed as compared to the limits reported so far in the literature. The SVD of the modulation matrix leads to a unified modulation technique which achieves the full capability of a matrix converter. It is shown that this approach is general and all other modulation methods established for a matrix converter are specific cases of this technique. The proposed modulation method can be used...
Reactive power control of permanent-magnet synchronous wind generator with matrix converter
, Article IEEE Transactions on Power Delivery ; Volume 28, Issue 2 , 2013 , Pages 575-584 ; 08858977 (ISSN) ; Mokhtari, H ; Chang, L ; Sharif University of Technology
2013
Abstract
In this paper, the reactive power control of a variable-speed permanent-magnet synchronous wind generator with a matrix converter at the grid side is improved. A generalized modulation technique based on singular value decomposition of the modulation matrix is used to model different modulation techniques and investigate their corresponding input reactive power capability. Based on this modulation technique, a new control method is proposed for the matrix converter which uses active and reactive parts of the generator current to increase the control capability of the grid-side reactive current compared to conventional modulation methods. A new control structure is also proposed which can...
Effect of the reactance term on the charge/discharge electrical measurements using cylindrical capacitive probes
, Article Journal of Applied Sciences ; Volume 11, Issue 18 , 2011 , Pages 3293-3300 ; 18125654 (ISSN) ; Fekri, L ; Golnabi, H ; Sharif University of Technology
2011
Abstract
In this study, operation of the contact Cylindrical Capacitive Sensor (CCS) for the reactance capacitance measurement of the water liquids by using the charge/discharge measurement module is investigated. The effect of geometric factor on the capacitance measurement of different liquid samples is also studied. The measured capacitances for the distilled, mineral, tap and salt water samples are reported by using two contact CCSs with the active length of 16 and 74 mm. The measured capacitances by small contact CCS for the saltwater is 1.76 uF and by big contact CCS is 47.8 uF, which shows a big difference for different probes. In another study, the effects of the liquid conductance on the...