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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,...
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...
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,...
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...
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...
The Study of the Behaviour and Performance of a New Elevated Tank
, M.Sc. Thesis Sharif University of Technology ; Khansari, Vahid (Supervisor)
Abstract
Various types of tanks are used to store a variety of liquids, drinking water, chemicals, petrochemicals, and liquefied natural gas. Of these, one type is ‘elevated tank’ which is used to provide the required pressure for the water distribution systems rather than satisfying the water demand. Satisfactory performance of tanks during strong ground motions is crucial for modern facilities. Theoritical and experimental investigations of the dynamic behaviour of liquid storage tanks are conducted to seek possible improvments in the design of such tanks to resist earthquakes. The behaviour and performance of a new elevated tank was studied in this work. It was carried out through finite elements...
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...
Experimental and Numerical Study of the Use of Phase Change Materials on the Performance of Compression Refrigeration Systems
, M.Sc. Thesis Sharif University of Technology ; Shafii, Mohammad Behshad (Supervisor)
Abstract
In this study, a vapor-compression cooling system utilizing different PCMs has been studied whereby the electricity consumption peak load is shifted. More specifically, the dynamic performance of cooling systems with and without using PCM is evaluated for the hottest day of the year. The proposed system uses the cooling energy to freeze, or “discharge” the PCM during nighttime when the cooling load is minimally needed and uses the stored thermal energy during the peak load hours by melting, or “charging” the PCM. This leads to better performance during peak load hours when higher cooling loads are needed. Different PCMs including Oleic acid, SP224A, CL, CaCl2.6H2O have been investigated. The...
Scalable fabrication of tunable titanium nanotubes via sonoelectrochemical process for biomedical applications
, Article Ultrasonics Sonochemistry ; Volume 64 , June , 2020 ; Khataee, A ; Riahi, Z ; Shahin, K ; Asadnia, M ; Razmjou, A ; Hojjati Najafabadi, A ; Mei, C ; Orooji, Y ; Li, D ; Sharif University of Technology
Elsevier B. V
2020
Abstract
Titanium does not react well with the human tissues and due to its bio-inert nature the surface modification has yet to be well-studied. In this study, the sonoelectrochemical process has been carried out to generate TiO2 nanotube arrays on implantable Ti 6–4. All the prepared nanotubes fill with the vancomycin by immersion and electrophoresis method. Drug-releasing properties, antibacterial behavior, protein adsorption and cell attachment of drug-modified nanotubes are examined by UV–vis, flow cytometry, modified disc diffusion, BSA adsorption, and FESEM, respectively. The most uniform morphology, appropriate drug release, cell viability behavior and antibacterial properties can be achieved...
Finite element modeling of incremental bridge launching and study on behavior of the bridge during construction stages
, Article International Journal of Civil Engineering ; Volume 13, Issue 1 , 2015 , Pages 112-125 ; 17350522 (ISSN) ; Tajmir Riahi, H ; Hirmand, M ; Sharif University of Technology
Iran University of Science and Technology
2015
Abstract
Incremental launching is a widespread bridge erection technique which may offer many advantages for bridge designers. Since internal forces of deck vary perpetually during construction stages, simulation and modeling of the bridge behavior, for each step of launching, are tedious and time consuming tasks. The problem becomes much more complicated in construction progression. Considering other load cases such as support settlements or temperature effects makes the problem more intricate. Therefore, modeling of construction stages entails a reliable, simple, economical and fast algorithmic solution. In this paper, a new Finite Element (FE) model for study on static behavior of bridges during...
Study of Endurance Time Analysis Method in Seismic Evaluation of Steel Moment Resisting Frames
, Ph.D. Dissertation Sharif University of Technology ; Esmaeil Pourestekanchi, Homayun (Supervisor)
Abstract
In this research the capability of a new method named Endurance Time analysis in seismic assessment of single and multi degree of freedom structures in nonlinear range is investigated. Endurance Time analysis is based on time history analysis but in this method structure is subjected to an intensifying acceleration function and different damage indices of the structure are evaluated through analysis time. This method can be a useful tool for executing Performance Based Design of structures. Firstly the Endurance Time criterion is defined and the progress of the generation of Endurance Time acceleration functions is described. Also the optimization procedure used for the generation of...
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...
A study to find influential parameters on a Farsi-English statistical machine translation system
, Article 2010 5th International Symposium on Telecommunications, IST 2010, 4 December 2010 through 6 December 2010 ; 2010 , Pages 985-991 ; 9781424481835 (ISBN) ; Khadivi, S ; Riahi, N ; Sameti, H ; Sharif University of Technology
2010
Abstract
The aim of this paper is to analyze the Farsi-English statistical machine translation systems as a useful communication tool. Improvement of the nation's communication increases the need of easier way of translating between different languages in front of expensive human translators. In this work, a statistical phrase-based system is run on Farsi - English pair languages and the effect of its parameters on the translation quality has been deeply studied. Using BLEU as a metric of translation accuracy, the system achieves an improvement of 1.84%, relative to the baseline accuracy, which is increment from 16.97% to 18.81% in the best case
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...
Electrophoretic encapsulation for slow release of vancomycin from perpendicular TiO2 nanotubes grown on Ti6Al4V electrodes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; https://iopscience.iop.org/article/10.1088/2053-1591/ab6c98 ; Ahmadi Seyedkhani, S ; Sadrnezhaad, S. K ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
Ordered perpendicular TiO2 nanotubes (TNT) with 405 to 952 nm length and 60 to 90 nm diameter were grown via 40 to 120 min anodization of Ti6Al4V flat substrates. The samples were called TNT-40, -60, -80, -100, and -120. Vancomycin was loaded on the bare and anodized electrodes by separate immersion and electrophoretic (EP) deposition procedures. EP loading resulted in storage capacity of 5221.86 μg cm-2 for TNT-80 which was much higher than 1036.75 μg cm-2 of immersed sample. Drug release comprised of three stages: (i) burst release (78% for the bare, and 23% for the TNT-80 sample), (ii) gradual transport (21% for the bare, and 64% for the TNT-80 sample), and (iii) equilibrium. Transfer...
Electrophoretic encapsulation for slow release of vancomycin from perpendicular TiO2 nanotubes grown on Ti6Al4V electrodes
, Article Materials Research Express ; Volume 6, Issue 12 , 2019 ; 20531591 (ISSN) ; Ahmadi Seyedkhani, S ; Sadrnezhaad, S. K ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
Ordered perpendicular TiO2 nanotubes (TNT) with 405 to 952 nm length and 60 to 90 nm diameter were grown via 40 to 120 min anodization of Ti6Al4V flat substrates. The samples were called TNT-40, -60, -80, -100, and -120. Vancomycin was loaded on the bare and anodized electrodes by separate immersion and electrophoretic (EP) deposition procedures. EP loading resulted in storage capacity of 5221.86 μg cm-2 for TNT-80 which was much higher than 1036.75 μg cm-2 of immersed sample. Drug release comprised of three stages: (i) burst release (78% for the bare, and 23% for the TNT-80 sample), (ii) gradual transport (21% for the bare, and 64% for the TNT-80 sample), and (iii) equilibrium. Transfer...
Application of endurance time method in nonlinear seismic analysis of steel frames
, Article Procedia Engineering ; Volume 14 , 2011 , Pages 3237-3244 ; 18777058 (ISSN) ; Estekanchi, H. E ; Seyedain Boroujeni, S ; Sharif University of Technology
2011
Abstract
In Endurance Time (ET) method gradually intensifying acceleration functions are created in a manner that the linear and nonlinear response spectra of them, while being proportional to average of real earthquakes spectra, intensifies in a uniform manner with time. These functions are used as input functions for nonlinear time history analysis of structures and performance of structures is assessed based on the maximum time duration that they can meet the specified performance objectives. In this paper, application of the ET method in nonlinear seismic analysis of structures has been investigated. Numerical procedures and optimization techniques that are used for the production of acceleration...
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...