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critical-parameter
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Idle time and gelation behavior in gelcasting process of PSZ in acrylamide system
, Article Ceramic Transactions, 31 May 2009 through 5 June 2009 ; Volume 212 , JUL , 2010 , Pages 105-113 ; 10421122 (ISSN) ; 9780470876466 (ISBN) ; Faghihi Sani, M. A ; Sharif University of Technology
2010
Abstract
Gelcasting is a novel forming method in fabricating complex three dimensional ceramic parts, and has many parameters and characteristics required to be specified. Up to now, few articles have been published on determination of the idle time of gelation precisely. In this work the chemorheology of gelation in aqueous solution of acrylamide and N, N′ methylenebisacrylamide monomer, and zirconia (PSZ) suspensions of this solution was investigated. As the viscosity of gel system increases abruptly in gelation point, idle time can be determined precisely by measurement of viscosity against time. Idle time can also be determined through temperature measurement against time since the reaction of...
Investigation of a nonlinear dynamic hydraulic system model through the energy analysis approach
, Article Journal of Mechanical Science and Technology ; Volume 23, Issue 11 , 2010 , Pages 2973-2979 ; 1738494X (ISSN) ; Ehramianpour, M ; Mohammadi, M ; Sharif University of Technology
Abstract
The dynamics of a pressure regulator valve have been studied using the through Bondgraph simulation technique. This valve consists of several elements that can transmit, transform, store, and consume hydraulic energy. The governing equations of the system have been derived from the dynamic model. In solving system equations numerically, various pressure-flow characteristics across the regulator ports and orifices have been taken into consideration. This simulation study identifies some critical parameters that have significant effects on the transient response of the system. The results have been obtained using the MATLAB-SIMULINK environment. The main advantage of the proposed methodology...
Key parameters in hydrothermal synthesis and characterization of low silicon content SAPO-34 molecular sieve
, Article Microporous and Mesoporous Materials ; Volume 126, Issue 1-2 , 2009 , Pages 1-7 ; 13871811 (ISSN) ; Farhadi, F ; Khorasheh, F ; Sahebdelfar, S ; Asadi, M ; Yan, Z. F ; Sharif University of Technology
2009
Abstract
Low silicon content SAPO-34 was successfully synthesized using the conventional hydrothermal crystallization in the static condition. Effects of different synthesis conditions including crystallization temperature and the silicon source were investigated through X-ray diffraction patterns. It was concluded that the silicon source had a significant effect on silicon incorporation into the alumino-phosphate building blocks in the course of crystallization. Using precipitated silica instead of silica sol resulted in the formation of impurities of alumino-phosphates phases whose crystalline structures collapse at the high temperature of calcination. For the low silicon SAPO-34 synthesis, the...
Electrochemical characterization of electrodeposited carbon nanotubes
, Article Thin Solid Films ; Volume 519, Issue 19 , July , 2011 , Pages 6230-6235 ; 00406090 (ISSN) ; Dolati, A ; Ghorbani, M ; Sharif University of Technology
2011
Abstract
Carbon nanotubes were electrodeposited in acetonitrile solution at room temperature using Cu, and Fe-Ni nanoparticles as nucleation sites on HF-etched Si(100) wafer substrate. The electrochemical behavior of the deposition was investigated by voltammetry and chronoamperometry techniques. In order to obtain the optimum growth condition, the deposition critical parameters including current density range, potential and time were studied and calculated. Carbon nanotubes with approximate external diameter of 40-100 nm were fabricated under potentiostatic condition and diffusion control at - 20 V in 4-6 h. The film crystallinity was investigated by means of X-ray diffraction and the tubes...
Dynamic behavior of pile foundations under cyclic loading in liquefiable soils
, Article Computers and Geotechnics ; Volume 40 , 2012 , Pages 114-126 ; 0266352X (ISSN) ; Pak, A ; Sharif University of Technology
Abstract
In this paper, a fully coupled three-dimensional dynamic analysis is carried out to investigate the dynamic behavior of pile foundations in liquefied ground. A critical state bounding surface plasticity model is used to model soil skeleton, while a fully coupled (u- P) formulation is employed to analyze soil displacements and pore water pressures. Furthermore, in this study, variation of permeability coefficient during liquefaction is taken into account; the permeability coefficient is related to excess pore water pressure ratio. Results of a centrifuge test on pile foundations are used to demonstrate the capability of the model for reliable analysis of piles under dynamic loading. Then, the...