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Synthesis of composite coating containing tio2 and ha nanoparticles on titanium substrate by ac plasma electrolytic oxidation
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 50, Issue 7 , 2019 , Pages 3310-3319 ; 10735623 (ISSN) ; Ghorbani, M ; Chambari, E ; Sharif University of Technology
Springer Boston
2019
Abstract
In this study, biocompatible ceramic layers containing TiO2 and hydroxyapatite (HA) nanoparticles (TiO2/HA) were deposited on pure commercial titanium (Grade 2) by using plasma electrolytic oxidation and AC power supply. The coating process was carried out in five different solutions for various times at a current density of 500 mA cm−2. To achieve the optimum conditions for thickness and microstructure, the coating process was conducted in solutions with a 3 g L−1 concentration of HA nanoparticles. FESEM, XRD, and FTIR results showed that HA nanoparticles were successfully incorporated into the pores of the layer. Furthermore, the corrosion behavior of the coating layers in the simulated...
Synthesis of Composite Coating with HA Nanoparticles on Ti by AC Plasma Electrolyte Oxidation
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
In this project, a ceramic biocompatible coating was applied on Titanium which is included Hydroxyapatite by AC Plasma Electrolyte Oxidation method. First, coating was performed in 5 different solutions and various duration in 500mA/Cm2 as a current density. Then, by microscopic and macroscopic images and size of porosity and also thickness of coat, 3 solutions were chosen for adding nanoparticles: Solution 1 which includes NaH2PO4 and Ca(CH3COO)2 , Solution 3 which includes Ca(CH3COO)2 and Na-Beta G and Solution 4 which includes Ca(H2PO4)2, HMP, NA2(EDTA) and Ca(CH3COO)2 . Also the time 10 minutes was chose as a appropriate time. The average of the porosities size in solution 1 was about...
Using Deep Neural Networks in Reinforcement Learning
, M.Sc. Thesis Sharif University of Technology ; Soleymani Baghshah, Mahdieh (Supervisor) ; Rabiei, Hamidreza (Supervisor)
Abstract
Reinforcement learning is a field of machine learning which is more similar to human training procedures.It uses reward signals to train an agent designed to act in that environment. Deep neural networks enhance the agent’s ability to determine and act better in its complex environment. Most previous works have addressed model-free agents, which ignore modeling details of the environment that in turn can be used to achieve better results. On the other hand, humans utilize a model-based approach in their decision-making process. They use their knowledge to predict the future and choose the action that leads them to a better state. To combine the benefits of model-based and model-free designs,...
Investigations of thermal behavior of Fe3Si2O5(OH)4·Sb3O6(OH)·Sb2O3 in air atmosphere: a study of acidic leaching process of Sb mineral
, Article Journal of Thermal Analysis and Calorimetry ; Volume 148, Issue 9 , 2023 , Pages 3295-3300 ; 13886150 (ISSN) ; Sadeghi Naeini, M ; Sharif University of Technology
Springer Science and Business Media B.V
2023
Abstract
The thermal behavior of Fe3Si2O5(OH)4·Sb3O6(OH)·Sb2O3 (a sample of antimony from Sefidabe mine in Zahedan) was investigated by the technique of thermogravimetry under air atmosphere from 25 to 1200 °C. The obtained results from TGA were reported. This study reports comprehensive information about these minerals. XRD and XRF techniques, UV/visible and elemental analysis such as ICP are used to identify the products at different decomposition steps. The acidic leaching of this mineral Fe3Si2O5(OH)4·Sb3O6(OH)·Sb2O3 is carried out, and the obtained results are reported. In total, the recovery was achieved by leaching with hydrochloric acid was 85% at D80 granulation below 45 microns. In leaching...
Simultaneously synthesis and encapsulation of metallic nanoparticles using linear-dendritic block copolymers of poly (ethylene glycol)-poly (citric acid)
, Article Key Engineering Materials, 8 July 2010 through 9 July 2010 ; Volume 478 , July , 2011 , Pages 7-12 ; 10139826 (ISSN) ; 9783037851357 (ISBN) ; Vossoughi, M ; Adeli, M ; Sharif University of Technology
2011
Abstract
Linear-dendritic triblock copolymers of linear poly(ethylene glycol) and hyperbranched poly(citric acid) (PCA-PEG-PCA) were used as the reducing and capping agents to encapsulate gold and silver nanoparticles (AuNPs and AgNPs). PCA-PEG-PCA copolymers in four different molecular weights were synthesized using 2, 5, 10 and 20 citric acid/PEG molar ratios and were called A 1, A 2, A 3 and A 4, respectively. Nanoparticles were encapsulated simultaneously during the preparation process. AuNPs were simply synthesized and encapsulated by addition a boiling aqueous solution of HAuCl 4 to aqueous solutions of A 1, A 2, A 3 and A 4. In the case of silver, an aqueous solution of AgNO 3 was reduced...
Poly(citric acid)-block-poly(ethylene glycol) copolymers-new biocompatible hybrid materials for nanomedicine
, Article Nanomedicine: Nanotechnology, Biology, and Medicine ; Volume 6, Issue 4 , Aug , 2010 , Pages 556-562 ; 15499634 (ISSN) ; Adeli, M ; Vossoughi, M ; Sharif University of Technology
2010
Abstract
Linear-dendritic ABA triblock copolymers containing poly(ethylene glycol) (PEG) as B block and hyperbranched poly(citric acid) (PCA) as A blocks were synthesized through polycondensation. The molecular self-assembly of synthesized PCA-PEG-PCA copolymers in water led to formation of nanoparticles and fibers in different sizes and shapes depending on the time and size of PCA blocks. Ten days after dissolving PCA-PEG-PCA copolymers in water, the size of fibers had reached several millimeters. Mixing a water solution of fluorescein as a small guest molecule and PCA-PEG-PCA copolymers led to the encapsulation of fluorescein by products of molecular self-assembly. To investigate their potential...
Synthesis of gold nanoparticle necklaces using linear-dendritic copolymers
, Article European Polymer Journal ; Volume 46, Issue 2 , 2010 , Pages 165-170 ; 00143057 (ISSN) ; Adeli, M ; Vossoughi, M ; Sharif University of Technology
2010
Abstract
Linear-dendritic copolymers containing hyperbranched poly(citric acid) and linear poly(ethylene glycol) blocks (PCA-PEG-PCA) were used as reducing and capping agents to synthesize and support gold nanoparticles (AuNPs). PCA-PEG-PCA copolymers with 1758, 1889 and 3446 molecular weights, called A1, A2 and A3 through this work, respectively, were synthesized using 2, 5, and 10 citric acid/PEG molar ratios. The diameter of A1, A2 and A3 in a fresh water solution was investigated using dynamic light scattering (DLS) and it was between 1.8 and 2.8 nm. AuNPs were simply synthesized and supported by addition a boiling aqueous solution of HAuCl4 to aqueous solutions of A1, A2 and A3. Supported AuNPs...
Coupling reduction of printed yagi antenna arrays for millimeter-wave imaging applications
, Article 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019, 7 July 2019 through 12 July 2019 ; 2019 , Pages 1767-1768 ; 9781728106922 (ISBN) ; Fakharzadeh, M ; Ranjbar Naeini, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, methods for reduction of coupling between receiving and transmitting antenna arrays are proposed and tested. Coupling between RX and TX causes saturation and a higher noise level in IF. So, coupling reduction improves image quality of system. Antenna element of arrays are printed antipodal Yagi-Uda antenna with greater than 8 dBi gain and higher than 4 GHz bandwidth. Frequency bandwidth of this imaging system is 27 to 30.5 GHz. Half power beamwidth of this antenna element is larger than 90 dB. Front to back ratio of this antenna is improved in this paper to 30 dB at 29 GHz. © 2019 IEEE
Young’s modulus of metal foams based on resonance frequencies
, Article Materials Performance and Characterization ; Volume 12, Issue 1 , 2023 , Pages 170-178 ; 21653992 (ISSN) ; Ahmadian, M. T ; Sharif University of Technology
ASTM International
2023
Abstract
Estimating the mechanical properties of metal foams is becoming important in developing new materials and advancing new manufacturing processes. Among various mechanical properties, effective Young’s modulus as one of the key properties may be evaluated through several measurement methods, but because of some limitations, merely a few techniques can be used in each application. Metal foam as a novel conventional material is one of the significant materials with limited methods for effective Young’s modulus measurement. Recently, several empirical relationships have been developed between effective Young’s modulus and metal foam’s porosity to estimate its elasticity based on the material’s...
A comprehensive dynamic model and configuration control of a free-floating soft manipulator-spacecraft system
, Article Acta Astronautica ; Volume 222 , 2024 , Pages 325-345 ; 00945765 (ISSN) ; Kiani, M ; Sharif University of Technology
2024
Abstract
Space robots are inseparable components of many space missions. However, capabilities of space robots with rigid manipulators are restricted in confronting with unknown and confined environments and situations require high safety. To overcome these defects, the potential of bio-inspired soft robots for space applications has recently been addressed in the literature. Dynamic modeling and control of soft manipulators are challenging due to their infinite degrees of freedom. In this paper, a general comprehensive three-dimensional dynamic modeling framework is developed for a floating soft manipulator-spacecraft system employing the Euler-Lagrange method. This framework derives the coupled...
Planar soft space robotic manipulators: Dynamic modeling and control
, Article Advances in Space Research ; Volume 74, Issue 1 , 2024 , Pages 384-402 ; 02731177 (ISSN) ; Kiani, M ; Sharif University of Technology
2024
Abstract
Space robots have proven their ability to accomplish many space missions impossible or dangerous for the human. However, the conventional space robots suffer from the low adaptability, heavy structures, and the low safety. In this regard, the bio-inspired soft robots, composed of the soft material, have been emerged to overcome these shortcomings and to expand the space missions’ diversity. The potential of soft robots for space applications has recently been investigated in the literature. Although the dynamic modeling and control of soft robotic arms are complicated due to their infinite degrees of freedom, soft manipulators are anticipated to provide the adaptive capture of targets,...
A figure of merit in a time-modulated array
, Article IEEE Antennas and Wireless Propagation Letters ; Volume 18, Issue 10 , 2019 , Pages 2086-2089 ; 15361225 (ISSN) ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this letter, we use G/T as a figure of merit to evaluate the performance of time-modulated arrays (TMA). The noise performance of a receiver, which is periodically switched on and off, is quite different from that of a conventional receiver. We analytically investigate the noise performance of a TMA. Based on this analysis, the figure of merit, G/T, of the TMA structure is investigated, including the details of the receiver hardware. Moreover, the G/T of the TMA is compared with that of a phased array. The comparison indicates that the TMA structure provides the same or even better performance compared to a phased array system, which demonstrates the capability of TMA in providing...
A time modulated array with polarization diversity capability
, Article IEEE Access ; Volume 9 , 2021 , Pages 53735-53744 ; 21693536 (ISSN) ; Fakharzadeh, M ; Akbari, M ; Safavi Naeini, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
The Time Modulated Array (TMA) provides multiple radiation beams at different frequencies, by turning the radiating elements on and off. In this paper, we propose to add polarization diversity to a wireless communication link by leveraging the capabilities of the TMA. The proposed architecture switches between two orthogonal polarizations, instead of turning the antenna off, providing polarization diversity for the receivers. We show that the beams of each polarization at the sidebandsare exactly the same. However, the switching sequence should be optimized for the fundamental frequency to provide the same radiation level at each sideband. Two different switching sequences are proposed,...
Travelling-wave Ka-band frequency scanning Antennas for millimeter-wave imaging applications
, Article 2016 8th International Symposium on Telecommunications, IST 2016, 27 September 2016 through 29 September 2016 ; 2017 , Pages 591-595 ; 9781509034345 (ISBN) ; Fakharzadeh, M ; Farzaneh, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper, a novel travelling-wave printed Frequency Scanning Antenna (FSA), which can be used for imaging purposes, is proposed. All sample designs scan the space symmetrically about the broadside direction. For different scanning ranges, two low profile antennas are designed on a 6.6 mils thick Rogers 4350 board substrate layer. Impedance bandwidth of the first one covers 6.5GHz, from 29.5GHz to 36GHz, and this antenna scans 56° in angular space. The second antenna has 5.6GHz bandwidth from 30.6GHz to 36.2GHz, and scans 98° in angular space by means of switching the input port. The average gain and the Side-lobe level (SLL) of the first and the second antennas are 11.46dBi, 12.8dB, and...
Ka-band frequency scanning antenna with wide-angle span
, Article Journal of Infrared, Millimeter, and Terahertz Waves ; Volume 40, Issue 2 , 2019 , Pages 231-246 ; 18666892 (ISSN) ; Fakharzadeh, M ; Farzaneh, F ; Sharif University of Technology
Springer New York LLC
2019
Abstract
This paper describes the design procedure and measurement results of a single-layer low-cost, and wideband frequency scanning antenna, which exhibits a nearly symmetrical beam-steering around broadside direction. The measured antenna bandwidth ranges from 27.5 to 40 GHz, which covers most of the Ka-band. In addition, the antenna main beam scans from − 52° to + 42° as the frequency sweeps from 27.5 to 36.5 GHz, showing 94° beam-steering range. At the center frequency of 32 GHz, the beam points to the broadside direction. The measured radiation patterns verify that the beam-pointing error is less than 2° over the scanning range. Furthermore, the measured gain for a 10-cell structure with 6-cm...
Optimizing and synchronizing timetable in an urban subway network with stop-skip strategy
, Article Journal of Rail Transport Planning and Management ; Volume 22 , 2022 ; 22109706 (ISSN) ; Shafahi, Y ; SafariTaherkhani, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Stop-skipping and timetable synchronization are two effective strategies to reduce total passengers’ travel time in a transit network for subway operation. However, the majority of studies conducted on the topic do not consider stop-skipping strategy and timetable synchronization simultaneously. Thus, this article proposes a mixed-integer programming model considering both strategies simultaneously. The model is based on passenger smart-card data concerning the trains’ capacity to minimize total passengers’ waiting time and in-vehicle time and maximize the number of passengers who successfully reach their destination in a specific study horizon. Since increasing the number of trains,...
A novel approach to persian online hand writing recognition
, Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 232-236 ; 9759845857 (ISBN) ; Jamzad, M ; Soleymani, M ; Sharif University of Technology
2005
Abstract
Persian (Farsi) script is totally cursive and each character is written in several different forms depending on its former and later characters in the word. These complexities make automatic handwriting recognition of Persian a very hard problem and there are few contributions trying to work it out. This paper presents a novel practical approach to online recognition of Persian handwriting which is based on representation of inputs and patterns with very simple visual features and comparison of these simple terms. This recognition approach is tested over a set of Persian words and the results have been quite acceptable when the possible words where unknown and they were almost all correct in...
A low-cost and low-power single Bit phased array at Ka-Band for 5G applications
, Article 49th European Microwave Conference, EuMC 2019, 1 October 2019 through 3 October 2019 ; 2019 , Pages 622-625 ; 9782874870552 (ISBN) ; Vafaeinezhad, M ; Alizadeh, M ; Fakharzadeh, M ; Safavi Naeini, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
In this paper, we develop a phase inverting technique to improve the received power of an antenna array, with an emphasis on the simplicity of the receiver hardware and reducing the power consumption. The goal is to propose a simple array architecture to develop intelligent algorithms to enhance the received power of the array. A test set-up with 8-element switched array antenna at 28 GHz has been developed to implement the proposed algorithms. The measured results reveal that in a high scattering environment, the phase inverting technique provides about 13 dB enhancement in the received power compared to a fixed array. This significant enhancement plays a major role in establishing a robust...
High cycle fatigue behavior and thermal properties of PLA/PCL blends produced by fused deposition modeling
, Article Journal of Polymer Research ; Volume 30, Issue 7 , 2023 ; 10229760 (ISSN) ; Sedighi, M ; Kasaeian Naeini, M ; Jabbari, A. H ; Sharif University of Technology
Springer Science and Business Media B.V
2023
Abstract
In this paper, high cycle fatigue behavior and thermal properties of blend specimens made of polylactic acid (PLA) and polycaprolactone (PCL) were studied and the influence of crystallization was investigated on the fatigue behavior. In this regard, fused deposition modeling method was employed to manufacture neat-PLA, neat-PCL, PLA/10wt.% PCL (90/10), and PLA/20wt.% PCL (80/20) specimens. The results show that the addition of 10wt.% and 20wt.% of PCL to the neat-PLA increases the elongation of the specimens by 32% and 284%, respectively, compared to that of the neat-PLA. However, Young’s modulus respectively decreases by 22% and 34%. According to the differential scanning calorimetry (DSC)...
Effect of dip-coating on tensile and high cycle fatigue behavior of 3D printed bio-polymer blends
, Article 2023 30th National and 8th International Iranian Conference on Biomedical Engineering, ICBME 2023 ; 2023 , Pages 232-236 ; 979-835035973-2 (ISBN) ; Sedighi, M ; Kasaeian Naeini, M ; Mostahsan, A. J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Considering the desirable biodegradable properties and mechanical characteristics of poly lactic acid (PLA) and poly caprolactone (PCL), these polymers are recently widely utilized in medical applications including the fabrication of body-compatible implants. One of the most efficient manufacturing methods to fabricate polymer-based implants is 3D printing, due to its ability to rapidly produce parts with complex geometries. In this study, an effort has been made to study the impact of the dip-coating process on tensile and high cycle fatigue behavior of 3D printed PLA/PCL blends, using PCL/chloroform solution. The results demonstrate that after applying the PCL coating on the surface of the...