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The study of prepration of blue V zircon pigment by using zircon and sulphuric acid
, Article Innovative Processing and Manufacturing of Advanced Ceramics and Composites - 8th Pacific Rim Conference on Ceramic and Glass Technology, PACRIM 8, Vancouver, BC, 31 May 2009 through 5 June 2009 ; Volume 212 , JUL , 2010 , Pages 197-206 ; 10421122 (ISSN); 9780470876466 (ISBN) ; Faghihi Sani, M. A ; Sharif University of Technology
2010
Abstract
Depending on the type of dopant metal, many kinds of zircon based pigments are produced and blue vanadium pigment is the most important one of them. In this study, blue zircon ceramic pigments were synthesized from intermediate product, resulting from decomposition of zircon sand with NaOH. In this regard, various amounts of sulfuric acid, water, NH4VO3 as colorant, NaF as mineralizer and extra quartz were added to the prepared Na 2ZrSiO5. Role of quartz was to omit the repercussions of presence of free zirconia in the composition. The main objective of this work is to assess various reactions at different temperatures during blue pigment synthesis. Phase analysis was done by X ray...
The effect of mixing molar ratios and sand particles on microstructure and mechanical properties of metakaolin-based geopolymers
, Article Materials Chemistry and Physics ; Volume 240 , 2020 ; Nemati, A ; Khodabandeh, A. R ; Baghshahi, S ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this study the influence of the molar ratios such as SiO2:Al2O3:Na2O:H2O, as well as the sand particles on the mechanical performance, shrinkage and microstructure of metakaolin based geopolymers was studied. Considering different content of the reactive silica and alumina in metakaolin, forty eight different compositions were prepared. The proper condition for achieving the highest mechanical performance as well as less structural defects by tailoring the curing condition, molar ratios and addition of sand particles are presented. Special attention was paid to the incorporation of sand particles up to 70 wt% on the microstructure, shrinkage and mechanical properties of metakaolin based...
Investigation of interfacial and mechanical properties of alumina-coated steel fiber reinforced geopolymer composites
, Article Construction and Building Materials ; Volume 288 , 2021 ; 09500618 (ISSN) ; Nemati, A ; Khodabandeh, A. R ; Baghshahi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this study, alumina coated steel reinforced geopolymer composites were successfully fabricated and their interfacial and mechanical properties were investigated. The fiber–matrix interface characteristics were assessed using single-fiber push-out and water contact angle experiments as well as SEM-EDS analysis. Finally, the role of alumina coating on the compressive, flexural and toughness of the geopolymer composites was investigated. The morphological studies revealed that alumina coating on steel can chemically bonded and microstructurally integrated with the surrounding matrix. The push-out test showed that the interfacial shear strength was increased approximately 150% in composites...
Error estimation, adaptivity and data transfer in enriched plasticity continua to analysis of shear band localization
, Article Applied Mathematical Modelling ; Volume 31, Issue 6 , 2007 , Pages 983-1000 ; 0307904X (ISSN) ; Asil Gharebaghi, S ; Tabarraie, A. R ; Riahi, A ; Sharif University of Technology
2007
Abstract
In this paper, an adaptive FE analysis is presented based on error estimation, adaptive mesh refinement and data transfer for enriched plasticity continua in the modelling of strain localization. As the classical continuum models suffer from pathological mesh-dependence in the strain softening models, the governing equations are regularized by adding rotational degrees-of-freedom to the conventional degrees-of-freedom. Adaptive strategy using element elongation is applied to compute the distribution of required element size using the estimated error distribution. Once a new mesh is generated, state variables and history-dependent variables are mapped from the old finite element mesh to the...
Obtaining optimal performance with ring stiffeners on strength for submarine pipeline
, Article World Applied Sciences Journal ; Volume 15, Issue 11 , 2011 , Pages 1494-1502 ; 18184952 (ISSN) ; Shamsai, A ; Rahmani, K ; Showkati, H ; Sharif University of Technology
2011
Abstract
Submarine pipelines as the principal structural components are prone to fail by circumferential buckling under the effect of hydrostatic external pressure. Basically, the buckling capacity of a thin-walled pipe is dependent on "radius to thickness" ratio. At least two modes of local and overall buckling are possible in any pipeline system, which could be developed in pipe wall. A method of strengthening of pipes is developed in this paper to stop the failure. A total of 21 stiffened models are generated and analyzed using the well-known finite element program ABAQUS. In this study, the buckling and post-buckling behaviour of stiffened pipes are investigated by carrying out linear and...
Estimates of average inelastic deformation demands for regular steel frames by the Endurance Time method
, Article Scientia Iranica ; Volume 16, Issue 5 A , 2009 , Pages 388-402 ; 10263098 (ISSN) ; Estekanchi, H. E ; Vafai, A ; Sharif University of Technology
2009
Abstract
The Endurance Time (ET) method is a new dynamic pushover procedure in which structures are subjected to gradually intensifying acceleration functions and their performance is assessed based on the length of the time interval that they can satisfy required performance objectives. In this paper, the accuracy of the Endurance Time method in estimating average deformation demands of low and medium rise steel frames using ETASOf series of ET acceleration functions has been investigated. The precision of the ET method in predicting the response of steel frames in nonlinear analysis is investigated by considering a simple set of moment-resisting frames. An elastic-perfectly-plastic material model...
Endurance time method: Exercise test applied to structures
, Article Asian Journal of Civil Engineering ; Volume 10, Issue 5 , 2009 , Pages 559-577 ; 15630854 (ISSN) ; Tajmir Riahi, H ; Vafai, A ; Sharif University of Technology
Building and Housing Research Center (BHRC)
2009
Abstract
Endurance Time (ET) method is a new dynamic analysis procedure that aims at estimating seismic performance of structures by subjecting them to predesigned intensifying acceleration. These acceleration functions are designed in a way that they approximately simulate earthquakes with different intensities through their duration. Performance of the structure is judged based on its behavior for different intensity measures through time. A set of three acceleration functions have been produced using the ET concept by applying optimization techniques. These acceleration functions are designed in such a way that their response spectrum, while complying with typical code design spectra, intensify...
Endurance time method-application in nonlinear seismic analysis of single degree of freedom systems
, Article Journal of Applied Sciences ; Volume 9, Issue 10 , 2009 , Pages 1817-1832 ; 18125654 (ISSN) ; Ismail pour Estekanchi, H ; Vafai, A ; Sharif University of Technology
2009
Abstract
Endurance Time (ET) method has been introduced as a lime-history based dynamic analysis procedure. In this method, structures are subjected to a gradually intensifying acceleration function. Performance of the structures is assessed based on the length of the time interval that they can satisfy required performance objectives. In this study, some fundamental concepts of ET method are explained and the potentials and limitations of this procedure in nonlinear seismic analysis of SDOF structures are investigated. A numerical optimization procedure for generating ET acceleration functions that are compatible with ground motions are explained. Results of ET analysis for inelastic SDOF systems...
Design and construction of a charge controller for stand-alone PV/battery hybrid system by using a new control strategy and power management
, Article Solar Energy ; Volume 149 , 2017 , Pages 132-144 ; 0038092X (ISSN) ; Forooghi, M ; Ghadimi, A. A ; Abolmasoumi, A. H ; Riahi, M. R ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
In this paper, a new control strategy and power management for a stand-alone PV/battery hybrid power system has been suggested. The solar cell arrays provide energy in the steady-state and the battery provides energy in transient states. Here, a charge controller system based on the MPP tracking technology, suitable for using in the islanded micro grid that contains a solar panel and a battery is designed. The charge controller includes a unidirectional DC-DC converter as an interface circuit between the solar panel and the DC bus, a bidirectional DC-DC converter as an interface circuit between the battery and the DC bus with a control system and power management in different states of...
Influence of polyaniline synthesis conditions on its capability for removal and recovery of chromium from aqueous solution
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 30, Issue 3 , 2011 , Pages 97-100 ; 10219986 (ISSN) ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
2011
Abstract
Absorptive characteristics of polyaniline synthesized in different solvents were studied. Water and mixture of water with other solvents were implemented for polyaniline synthesis. Synthesized polyanilines in powder shape is used as an adsorbent to remove toxic hexavalent chromium from aqueous solutions. Experiments were conducted in batch mode. Removal mechanism involving polyaniline is the combination of surface adsorption and reduction. The kind of solvent used at synthesizing stage can affect the capacity of produced polyanilines for removal of heavy metals including chromium. Synthesized polyaniline in water had the maximum chromium removal efficiency. The morphology study of...
Removal of chromium from aqueous solution using two kinds of polyaniline
, Article Journal of Environmental Studies ; Volume 36, Issue 55 , 2010 , Pages 91-98 ; 10258620 (ISSN) ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
2010
Removal of chromium from aqueous solution using polyaniline - Poly ethylene glycol composite
, Article Journal of Hazardous Materials ; Volume 184, Issue 1-3 , December , 2010 , Pages 248-254 ; 03043894 (ISSN) ; Borghei, S. M ; Olad, A ; Chaichi, M. J ; Sharif University of Technology
2010
Abstract
The adsorption of chromium compounds from solutions by a composite of polyaniline/poly ethylene glycol (PANi/PEG) was investigated in this study. Experiments were conducted in batch mode under various operational conditions including agitation time, solution pH, PANi/PEG dose and initial concentration of chromium salts. Results showed that concentration of PEG at synthesizing stage has a significant effect on the capacity of produced composite for removal of chromium. Morphologically, PANi/PEG composite is closely dependent on the concentration of PEG. Maximum removal of hexavalent chromium was experienced when 2. g/L of PEG was used in synthesis of PANi/PEG. Removal of hexavalent chromium...
Effects of geometric imperfections on the performance of Sahand cooling tower
, Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 5 , 2006 , Pages 331-338 ; 9748257207 (ISBN); 9789748257204 (ISBN) ; Haghighi, B ; Sharif University of Technology
School of Engineering and Technology
2006
Abstract
During construction of one of the Sahand cooling towers due to slip forming performance some imperfections were raised mostly between elevation of +30 and +40 meter. It was evaluated that some points of the shell should be repaired. In constructing the cooling tower from elevation +40 to +60 meter these imperfections were removed and the cooling tower was constructed with no problem until the elevation +130 meter. In this paper reasons of generation of geometric imperfections in Sahand cooling tower are clearly shown and possible ways for preventing them are discussed. Applied repairing method for Sahand cooling tower is explained in detail. Geometrical imperfections of the constructed...
Parametric study of a vapor compression refrigeration system integrated with a PCM storage tank for increasing condenser sub-cooled temperature
, Article Case Studies in Thermal Engineering ; Volume 47 , 2023 ; 2214157X (ISSN) ; Shafii, M. B ; Sharif University of Technology
Elsevier Ltd
2023
Abstract
In this work, the parametric study of a vapor compression refrigeration system integrated with a PCM storage tank for increasing the condenser sub-cooled temperature has been conducted based on the hottest day in Tehran city. The effects of various parameters such as comfort zone temperature, condenser and evaporator temperatures, and changes in heat transfer coefficient relative to the thickness of the ice formation in the PCM tank have been considered for simulating the desired system in the EES software. The focus of this study is to figure out the system's performance according to the changes in the effective parameters of the PCM storage tank. The results indicate that adding the PCM...
Experimental evaluation of a vapor compression cycle integrated with a phase change material storage tank for peak load shaving
, Article Engineered Science ; Volume 23 , 2023 ; 2576988X (ISSN) ; Shafii, M. B ; Sharif University of Technology
Engineered Science Publisher
2023
Abstract
In this study, the combination of a vapor compression cycle with a phase change material (PCM) storage tank has been assessed experimentally during the hottest day based on Tehran city climatic conditions. The temperature conditions for outdoor (condenser, compressor, etc.) and indoor (evaporator) air conditioning (AC) units are provided with the help of two separate test chambers and a controller system. The desired system has been surveyed based on two scenarios. In each scenario, the system is evaluated for the conventional AC system (with no PCM involved) and the AC plus PCM unit (conventional AC + PCM storage tank). Based on scenario 1 operating strategy, the results show that adding...
Surface Modification of Metallic Implants and Improvement of their Biological Properties in Presence of Bioactive Ceramic Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; Sadrnezhad, Khatiboleslam (Supervisor)
Abstract
By consideration of increasing demands to use implants and efforts to get technical knowledge and localization of this implants, considerable research in this field is needed. Therefore, presentation of a coating which is able to provide parameters needed for an acceptable implant is the aim of this study. In this direction, modification of surface of metallic implants in order to achieve nanotubes of titanium oxide, with the purpose of providing biocompatibility was done. On the other hand, because chronic infection of the implant’s surrounding is one of the main important reasons in rejection of implants, 〖TiO〗_2 nanotubes as a drug carrier were used in order to solve this problem. So,...
Seismic assessment of steel frames with the endurance time method
, Article Journal of Constructional Steel Research ; Volume 66, Issue 6 , 2010 , Pages 780-792 ; 0143974X (ISSN) ; Estekanchi, H. E ; Sharif University of Technology
2010
Abstract
In the endurance time (ET) method, structures are subjected to a specially designed intensifying ground acceleration function and their performance is judged based on their response at various excitation levels. A range of equivalent intensities can be covered in a single numerical or experimental simulation, thus significantly reducing the computational demand as compared to full nonlinear response-history analyses. The applied excitation intensity at various times has been correlated with those of the scaled ground motions. Response spectra of seven ground motions on stiff soil were used to produce intensifying acceleration functions that at each time window produce a response spectrum...
Experimental and numerical investigation of fluid dynamics of the bounded and unbounded triangular jets
, Article Proceedings of the ASME Turbo Expo, 9 June 2008 through 13 June 2008, Berlin ; Volume 5, Issue PART A , 2008 , Pages 41-47 ; 9780791843154 (ISBN) ; Bagheri, F ; Farhanieh, B ; Sharif University of Technology
2008
Abstract
In the present study, the fluid characteristics of triangular turbulent jet flow are considered experimentally and numericafly. The results of spatially developed three- dimensional jet, issued from an equilateral triangular nozzle are presented. The jet is discharged to both bounded and unbounded domains. Because of the wind tunnel set up restrictions, the experimental study has done just for the bounded domain. The hot-wire anemometry is used for experimental study. A numerical method employing control volume approach with collocated grid arrangement which couples the velocity and pressure fields with SIMPLEC algorithm is introduced to discrete the governing equations of fluid flow. The...
Speed Control of Permanent Magnet Synchronous Motor with Flexible Coupling Using Load Torque Observer
, M.Sc. Thesis Sharif University of Technology ; Tahami, Farzad (Supervisor)
Abstract
Elastic joints in 2-mass drive systems, because of their limited stiffness, can decrease the performance of the control system and lead to motor and load speed oscillation. Shaft torque ignoring can also stress both mechanical and electrical drive components. Because of low degree of freedom, conventional controllers, such as the PI controllers, cannot improve the performance of the system and keep the system stable at the same time. In this thesis, the dynamic response and stability of the 2-mass systems is improved using state controller. State estimation of 2-mass system is required for state space controller . In the thesis, different state observer is analyzed and compared with each...
Nano Ethics: Reviewing and Criticizing the Approaches to Solve the Ethical Problems in Nanotechnology
, M.Sc. Thesis Sharif University of Technology ; Taghavi, Mostafa (Supervisor)
Abstract
Nanotechnology is an emerging field in technology that exploits the chemical and physical properties created by careful manipulation of materials at atomic and molecular levels. These properties lead to abilities created by this technology, which many scientists regard as the next industrial revolution. Although Nanotechnology promises bright future, today, researchers having learned from the history of technology are trying to predict its unwanted aspects and negative effects to decrease its potential issues. Researchers of Nano-ethics are trying to enable us to encounter Nanotechnology’s achievements in a reasonable way, by studying its ethical and social obligations. Since in our country,...