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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...
Reducing part Warpage by Optimizing Process Parameters in Selective Laser Sintering
, M.Sc. Thesis Sharif University of Technology ; Movahhedy, Mohammad Reza (Supervisor) ; Akbari, Javad (Supervisor)
Abstract
One of the newest methods of rapid prototyping is SLS . In this day, SLS is more common in compare others methods, because it uses little time and man does not nearly interfere in the producing stages of part which is made by SLS method. Also, sophisticated parts, which cannot be built by other methods, can be produced by SLS method. One of the disadvantages of SLS method is low dimensions accuracy of parts produced in this way. This problem has two major reasons: Shrinkage and Warpage. These two phenomena are created because of ununiformed temperature distribution. Others features which have effect on dimensions accuracy are residual stress, porosity and removing space of between powder...
Manipulation of Two-Dimensional Nanosheets Tin Sulfide by Solvothermal Process
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor) ; Mohammadi, Mohammad Reza (Supervisor)
Abstract
Tin sulfide with an energy gap of about 1.1 ev is a semiconductor suitable for applications such as solar cells, lithium-ion batteries, photocatalysts and other semiconductor-based devices. There are several methods for synthesizing this semiconductor at the nanometer scale, among which the solvothermal method is an efficient, controllable and inexpensive method. By precisely controlling the parameters of this process, two-dimensional tin sulfide nanosheets with high purity and desirable morphology can be produced. In this research, tin sulfide has been synthesized by solvothermal / hydrothermal chemical method and its metallurgical properties have been studied. Effect of solvothermal...
The Investigation of Effective Parameters in Coating on Aluminized Steel by Plasma Electrolytic Oxidation Process
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Plasma electrolytic oxidation process (PEO) is now recognized as a relatively new method in surface engineering. In this process, formation of micro arcs resulted from electric discharges on the surface of the specimen in the appropriate electrolyte, is used to ionize the gas layer which has enshrouded the specimen. In the present study, ceramic coating on aluminized steel was produced by PEO process and the effects of the influential parameters were comprehensively investigated. For this purpose, coating on the aluminized steel with dimension of 25×30 mm² was produced under different condition of processing time from 1 to 15 minutes, current density from 10 to 20 A/dm², frequency from 50 to...
Numerical study of the effects of process parameters on tool life in a cold radial forging process
, Article Scientia Iranica ; Vol. 21, issue. 2 , 2014 , p. 339-346 ; Movahhedy, M. R ; Sharif University of Technology
Abstract
Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axles, and for creating internal profiles in tubes. Due to very large forging loads, the tool should withstand high stress and wear. Therefore, the success of the forging process depends upon recognition of the die failure factors and optimization of the tool working conditions that enhance tool life. In this study, the effect of process parameters on tool life in the cold radial forging process is investigated using nonlinear three dimensional finite element modeling. Wear and mechanical fatigue are considered as the main modes of tool failure, and a parametric study on the...
Optimization of sputtering parameters for the deposition of low resistivity indium tin oxide thin films
, Article Acta Metallurgica Sinica (English Letters) ; Vol. 27, issue. 2 , Apr , 2014 , p. 324-330 ; Bagheri, B ; Yazdanfar, P ; Rashidian, B ; Sasanpour, P ; Sharif University of Technology
Abstract
Indium tin oxide (ITO) thin films have been deposited using RF sputtering technique at different pressures, RF powers, and substrate temperatures. Variations in surface morphology, optical properties, and film resistances were measured and analyzed. It is shown that a very low value of sheet resistance (1.96 ω/sq.) can be achieved with suitable arrangement of the deposition experiments. First, at constant RF power, deposition at different pressure values is done, and the condition for achieving minimum sheet resistance (26.43 ω/sq.) is found. In the next step, different values of RF powers are tried, while keeping the pressure fixed on the previously found minimum point (1-2 Pa). Finally,...
Leak-Gauge: A late-mode variability-aware leakage power estimation framework
, Article Microprocessors and Microsystems ; Volume 37, Issue 8 PARTA , 2013 , Pages 801-810 ; 01419331 (ISSN) ; Momtazpour, M ; Goudarzi, M ; Sharif University of Technology
2013
Abstract
Leakage power has already become the major contributor to the total on-chip power consumption, rendering its estimation a necessary step in the IC design flow. The problem is further exacerbated with the increasing uncertainty in the manufacturing process known as process variability. We develop a method to estimate the variation of leakage power in the presence of both intra-die and inter-die process variability. Various complicating issues of leakage prediction such as spatial correlation of process parameters, the effect of different input states of gates on the leakage, and DIBL and stack effects are taken into account while we model the simultaneous variability of the two most critical...
Evaluation of the effects of process parameters on granule mean size in a conical high shear granulator using response surface methodology
, Article Powder Technology ; Volume 237 , 2013 , Pages 186-190 ; 00325910 (ISSN) ; Farhadi, F ; Sharif University of Technology
2013
Abstract
Response surface methodology was used to investigate the effects of operating parameters such as impeller speed, binder mass and granulation time on the average size of granules produced in a lab scale conical high shear granulator. Two quadratic models were proposed to express granule mean size as a function of impeller speed and binder mass as well as impeller speed and granulation time. It was found out that in the studied domain, the influence of each parameter on granule size differs from one another. While increasing binder mass at constant quantity of powder increased the average size linearly, increasing impeller speed changed the mean size in accordance with quadratic trend. The...
Accurate estimation of leakage power variability in sub-micrometer CMOS circuits
, Article Proceedings - 15th Euromicro Conference on Digital System Design, DSD 2012 ; 2012 , Pages 18-25 ; 9780769547985 (ISBN) ; Momtazpour, M ; Goudarzi, M ; Sharif University of Technology
2012
Abstract
Leakage power has already become the major contributor to the total on-chip power consumption, rendering its estimation a necessary step in the IC design flow. The problem is further exacerbated with the increasing uncertainty in the manufacturing process known as process variability. We develop a method to estimate the variation of leakage power in the presence of both intra-die and inter-die process variability. Various complicating issues of leakage prediction such as spatial correlation of process parameters, the effect of different input states of gates on the leakage, and DIBL and stack effects are taken into account while we model the simultaneous variability of the two most critical...
MAO-derived hydroxyapatite-TiO 2 nanostructured bio-ceramic films on titanium
, Article Materials Research Bulletin ; Volume 47, Issue 11 , 2012 , Pages 3407-3412 ; 00255408 (ISSN) ; Golestani Fard, F ; Rezaie, H. R ; Mirhosseini, S. M. M ; Ziaee, A ; Sharif University of Technology
2012
Abstract
Micro Arc Oxidation (MAO) process was utilized to fabricate nano bioceramic TiO 2-hydroxyapatite coatings on titanium substrates. Samples were produced in electrolytes contained 1 g/l β-glycerophosphate and 5, 10 and 15 g/l calcium acetate for 3, 6 and 10 min at 350 V. The techniques including XRD, XPS, SEM, FESEM and EDX were employed to study the effect of processing parameters. Hydroxyapatite, anatase, α-tri calcium phosphate and calcium titanate phases as well as 30-60 nm-size crystals were detected in the coating layer. It was also observed that the pore volume would increase by increasing the electrolyte concentration. The growth time was also found to influence the total pore volume....
Tailoring of morphology and crystal structure of nanomaterials in MgO-TiO 2 system by controlling Mg:Ti molar ratio
, Article Journal of Sol-Gel Science and Technology ; Volume 64, Issue 1 , October , 2012 , Pages 135-144 ; 09280707 (ISSN) ; Fray, D. J ; Sharif University of Technology
Springer
2012
Abstract
The morphological manipulation and structural characterisation of TiO 2-MgO binary system by an aqueous particulate sol-gel route were reported. Different crystal structures including pure MgTiO 3, mixtures of MgTiO 3 and TiO 2 and mixtures of MgTiO 3 and Mg 2TiO 4 were tailored by controlling Mg:Ti molar ratio and annealing temperatures as the processing parameters. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) revealed that all compounds crystallised at the low temperature of 500 °C. Furthermore, it was found that the average crystallite size of the compounds depends upon the Mg:Ti molar ratio as well as the annealing temperature, being in the range 3-5 nm at...
Influence of key parameters on crude oil desalting: An experimental and theoretical study
, Article Journal of Petroleum Science and Engineering ; Volume 90-91 , July , 2012 , Pages 107-111 ; 09204105 (ISSN) ; Ganjian, K ; Fattahi, M ; Sharif University of Technology
2012
Abstract
Desalting plants are often installed in crude oil production units in order to remove water-soluble salts from an oil stream. Experiments in both the laboratory and field have shown the desalting process parameters to be very complicated. This research reflects the results of a study conducted regarding the impact of operational desalting parameters, including the effects of temperature, injected chemicals and the pH of the crude oil associated water, on an electrostatic desalter on one of the oil platforms owned by the Iranian Oil Offshore Company in the Persian Gulf. The temperature range applied was between 98 to 133 °C, at which the effects on water and oil density as well as salt...
Application of response surface methodology for optimization of paracetamol particles formation by RESS method
, Article Journal of Nanomaterials ; Volume 2012 , 2012 ; 16874110 (ISSN) ; Ghotbi, C ; Dorkoosh, F ; Sharif University of Technology
2012
Abstract
Ultrafine particles of paracetamol were produced by Rapid Expansion of Supercritical Solution (RESS). The experiments were conducted to investigate the effects of extraction temperature (313353K), extraction pressure (1018MPa), preexpansion temperature (363403K), and postexpansion temperature (273323 K) on particles size and morphology of paracetamol particles. The characterization of the particles was determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Liquid Chromatography/Mass Spectrometry (LC-MS) analysis. The average particle size of the original paracetamol was 20.8m, while the average particle size of paracetamol after nanonization via the...
The modeling and process analysis of resistance spot welding on galvanized steel sheets used in car body manufacturing
, Article Materials and Design ; Volume 34 , February , 2012 , Pages 759-767 ; 02641275 (ISSN) ; Kolahan, F ; Kokabi, A. H ; Sharif University of Technology
Abstract
In this study, the resistance spot welding (RSW) process of the galvanized interstitial free (IF) steel sheets and galvanized bake hardenable (BH) steel sheets, used in the manufacturing of car bodies, has been modeled and optimized. The quality measure of a resistance spot welding joint is estimated from the tensile-shear strength. Furthermore, four important process parameters, namely welding current (WC), welding time (WT), electrode force (EF), and holding time (HT) are considered as the factors influencing the quality of the joints. In order to develop an accurate relationship between the process inputs (4-component vectors) and the response output (tensile-shears strength) at first a...
Prediction of temperature distribution in dissimilar arc welding of stainless steel to carbon steel
, Article Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture ; Volume 226, Issue 1 , October , 2012 , Pages 117-125 ; 09544054 (ISSN) ; Serajzadeh, S ; Kokabi, A. H ; Fischer, A ; Sharif University of Technology
Abstract
In this work, a three-dimensional model has been proposed to predict temperature distribution and weld-pool shape during dissimilar arc welding of low-carbon steel (CK4) and ferritic stainless steel (AISI 409). The model has been developed using the finite-element software ANSYS, while in the analysis, the effects of process parameters, as well as dilution, in the weld pool have been considered. To verify the predictions, welding experiments were conducted under different welding conditions, and the model results were then compared with the measured weld-pool geometry; a reasonable consistency was observed
A coupled stream function-finite element analysis for wire drawing processes
, Article International Journal of Advanced Manufacturing Technology ; Volume 57, Issue 9-12 , 2011 , Pages 917-926 ; 02683768 (ISSN) ; Serajzadeh, S ; Sharif University of Technology
Abstract
A numerical approach has been developed based on the stream function technique and the finite element analysis to predict required power and temperature rise in wire drawing processes. An admissible velocity field is first proposed using a stream function and then power consumption in the wire drawing is optimized to achieve sensible and unique deformation geometry. In addition, the finite element method together with axi-symmetric Petrov-Galerkin algorithm is coupled with the deformation model to assess the temperature distribution in both the deforming wire and the die during the process. The work hardening effects are also considered in the model both in the deformation zone and on the...
Adsorption of hydrocarbons on modified nanoclays
, Article IOP Conference Series: Materials Science and Engineering, 14 November 2010 through 18 November 2010, Osaka ; Volume 18, Issue SYMPOSIUM 12 , 2011 ; 17578981 (ISSN) ; Bazgir, S ; Tamizifar, M ; Nemati, A ; Sharif University of Technology
2011
Abstract
In this study organically modified nanoclay were prepared by exchanging of the cetyltrimethylammonium (CTAB), with inorganic/metal ions/cations in montmorillonite structure. To investigate the influence of the amount of modifier on basal spacing and subsequent removal efficiency of hydrocarbon, different amount of modifier was used. The modified and unmodified nanoclays characterized by XRD, CHN and FTIR techniques. The X-ray diffraction results showed that the interlayer spacing of CTAB-modified clays increased from 12 to 22Å. The effectiveness of the sorbent materials for sorption of a range of products was investigated using crude oil, kerosene, gasoline and toluene. The process...
Controlling morphology and structure of nanocrystallineVcadmium sulfide (CdS) by tailoring solvothermal processing parameters
, Article Journal of Nanoparticle Research ; Volume 13, Issue 7 , 2011 , Pages 3011-3018 ; 13880764 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
2011
Abstract
Cadmium sulfide (CdS) with different morphologies was successfully prepared by solvothermal process by controlling the processing parameters, including nature of precursor and solvent, reaction temperature and process time. X-ray diffraction patterns revealed that, in all cases highly pure and crystallized CdS with hexagonal structure were obtained. In addition, it was found that the processing parameters influence on preferable growth direction of CdS nanostructures. Field emission scanning electron microscope analysis showed that CdS nanowires with different aspect ratios were obtained (depending upon the reaction temperature and process time) in presence of sulfur powder and...
Development of an aqueous TiO2 paste in terms of morphological manipulation of nanostructured photoanode electrode of dye-sensitized solar cells
,
Article
Journal of Sol-Gel Science and Technology
;
Volume 75, Issue 2
,
August
,
2015
,
Pages 447-459
;
09280707 (ISSN)
; Mohammadi, M. R
;
Sharif University of Technology
Kluwer Academic Publishers
2015
Abstract
Abstract: A novel simple synthetic procedure for improving cell efficiency and reducing the production cost of TiO2 dye-sensitized solar cells (DSSCs) by modification and optimization of homemade formulated paste is reported. This is achieved in terms of morphological manipulation of deposited monolayer TiO2 films by controlling three processing parameters of paste formulation. These parameters are tailored to obtain a paste with proper viscosity suitable for spin-coating technique and to achieve uniform, homogeneous, and crack-free films with good connections between TiO2 grains and porous structure. Photovoltaic measurements show that TiO2 ...
The improvement of light scattering of dye-sensitized solar cells aided by a new dandelion-like TiO2 nanostructures
, Article Solar Energy Materials and Solar Cells ; Volume 137 , 2015 , Pages 113-123 ; 09270248 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
Elsevier
2015
Abstract
We present a new dandelion-like TiO2 spheres by a modified hydrothermal method for manufacture of dye-sensitized solar cells (DSSCs). This construct is composed of numerous nanowires for employment as the scattering layer of DSSCs. Such morphology is produced by nucleation-growth-assembly mechanism. The size of the dandelion-like spheres and their morphology can be tailored by controlling the processing parameters of the modified hydrothermal process. TiO2 nanoparticles with narrow size distribution are also synthesized by hydrothermal route for the active layer of DSSCs. The nanoparticles show pure anatase phase with average size of 40 nm, whereas the dandelion-like TiO2 spheres are pure...