Loading...
Search for:
tavakoli-naeini--ashkan
0.099 seconds
Total 264 records
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...
Study and Preparation of Coated Drug by PEG Biopolymer (PEGylation) for Release Controlling
, M.Sc. Thesis Sharif University of Technology ; Vossoughi, Manoochehr (Supervisor) ; Sarbolouki, Mohammad Nabi (Supervisor)
Abstract
In the first part of this work, citric acid monomer was selected to produce dendrimer through the divergent method using logical conditions (for controlling its functional groups) on the base of poly (ethylene glycol) as the core. Triblock copolymers (ABA-type) of citric acid and poly (ethylene glycol) (PCA-PEG-PCA) as biocompatible compounds were synthesized in four different molecular weights and applied as nanocarriers. The structure definition of the molecules and nanoparticles were carried out using different spectroscopy methods. Diameter of the synthesized copolymers was investigated using dynamic light scattering (DLS) experiments and transmission electron microscopy (TEM) and it was...
Sustainable-Resilient Supplier Selection Through Fuzzy Multi-Criteria Decision Making Approaches
, M.Sc. Thesis Sharif University of Technology ; Akbari Jokar, Mohammad Resa (Supervisor) ; Memari, Ashkan (Co-Supervisor)
Abstract
Today, with the expansion of business relations at international levels, there are many organizations that operate in global supply chains. Activities at such levels face new types of challenges in various fields of "supply chain management" pillars, of which "supplier selection" is one of them. The possibility of unexpected events, the need to comply with environmental protection laws, as well as the need to take into account social considerations, are among the things that have increased by being in larger supply chains, making it challenging to provide the basic resources needed in such chains and forcing their managers to considering considerations other than what they have always...
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...
Organic halides and nanocone plastic structures enhance the energy conversion efficiency and self-cleaning ability of colloidal quantum dot photovoltaic devices
, Article Journal of Physical Chemistry C ; Volume 121, Issue 18 , 2017 , Pages 9757-9765 ; 19327447 (ISSN) ; Simchi, A ; Tavakoli, R ; Fan, Z ; Sharif University of Technology
American Chemical Society
2017
Abstract
This paper presents solid-state ligand exchange of spin-coated colloidal lead sulfide quantum dot (PbS QD) films by methylammonium iodide (MAI) and integration of them in depleted heterojunction solar (DHS) devices having an antireflecting (AR) nanocone plastic structure. Time-resolved photoluminescence measurements determine a shorter lifetime of the charge carries on a semiconductor (TiO2) electron transfer layer for the MAI-passivated QD films as compared with those with long-chain aliphatic or short thiol ligands. Consequently, the DHS device yields improved power conversion efficiency (>125%) relative to oleic-acid-passivated PbS QD films. Using anodized aluminum oxide templates, an...
Surface engineering of TiO2 ETL for highly efficient and hysteresis-less planar perovskite solar cell (21.4%) with enhanced open-circuit voltage and stability
, Article Advanced Energy Materials ; Volume 8, Issue 23 , 2018 ; 16146832 (ISSN) ; Yadav, P ; Tavakoli, R ; Kong, J ; Sharif University of Technology
Wiley-VCH Verlag
2018
Abstract
Interfacial studies and band alignment engineering on the electron transport layer (ETL) play a key role for fabrication of high-performance perovskite solar cells (PSCs). Here, an amorphous layer of SnO2 (a-SnO2) between the TiO2 ETL and the perovskite absorber is inserted and the charge transport properties of the device are studied. The double-layer structure of TiO2 compact layer (c-TiO2) and a-SnO2 ETL leads to modification of interface energetics, resulting in improved charge collection and decreased carrier recombination in PSCs. The optimized device based on a-SnO2/c-TiO2 ETL shows a maximum power conversion efficiency (PCE) of 21.4% as compared to 19.33% for c-TiO2 based device....
Efficient, hysteresis-free, and flexible inverted perovskite solar cells using all-vacuum processing.Efficient, hysteresis-free, and flexible inverted perovskite solar cells using all-vacuum processing
, Article Solar RRL ; 2020 ; Yadav, P ; Prochowicz, D ; Tavakoli, R ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
The fabrication of efficient perovskite solar cells (PSCs) using all-vacuum processing is still challenging due to the limitations in the vacuum deposition of the hole transporting layer (HTL). Herein, inverted PSCs using copper (II) phthalocyanine (CuPC) as an ideal alternative HTL for vacuum processing are fabricated. After proper optimization, a PSC with a power conversion efficiency (PCE) of 20.3% is achieved, which is much better than the PCEs (16.8%) of devices with solution-based CuPC. As it takes a long time to dissolve CuPC in the solution-based device, the evaporation approach has better advantage in terms of fast processing. In addition, the device with the evaporated CuPC HTL...
Efficient perovskite solar cells based on Cdse/Zns quantum dots electron transporting layer with superior UV stability
, Article Physica Status Solidi - Rapid Research Letters ; Volume 14, Issue 6 , 2020 ; Prochowicz, D ; Yadav, P ; Tavakoli, R ; Sharif University of Technology
Wiley-VCH Verlag
2020
Abstract
Stability is the main challenge in the field of perovskite solar cells (PSCs). Finding new strategies is required to protect the PSCs from deteriorating agents such as humidity, heating, and illumination. Herein, a new electron transporting layer (ETL), i.e., CdSe/ZnS quantum dots (QDs), is proposed for the fabrication of efficient and stable PSCs. CdSe/ZnS QDs layer not only works as an ETL but also has downshifting property, which can improve both efficiency and stability of the PSCs. Using CdSe/ZnS QDs ETL with green emission, a PSC with maximum power conversion efficiency (PCE) of 18% is achieved. More importantly, the device shows great UV stability, much better than the device with...
Optimization of Die Profile in Screw Extrusion Process for an Arbitrary Profile by Considering Viscoelastic Effects of the Material
, M.Sc. Thesis Sharif University of Technology ; Asghari, Mohsen (Supervisor)
Abstract
In this thesis, equations related to large deformation of a polymer were derived by considering viscoelastic effects. To express type of material behavior which includes elastoplastic and viscoelastic property at the same time, two-layer viscoplastic model was used. An axisymmetric model was used for modeling problem in finite element software. By derivation of parameters related to two layer model and entering them in finite element software and also entering other properties required to model the forming process, modeling was performed by special profile connecting input and output sections. Due to favorable properties of spline functions, profiles used in die geometry, were selected from...
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...
Timetable Optimization and Synchronization in an Urban Subway Network with Stop-Skip Strategy
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yousef (Supervisor)
Abstract
Stop-skipping and timetable synchronization in a transit network for subway operation are two effective strategies to reduce passengers' total travel time.Most of the current research on the topic does not consider stop-skipping strategy and timetable synchronization simultaneously. This paper proposes a mixed-integer programming model based on passenger smart-card data concerning the trains' capacity to minimize passengers' total waiting time and in-vehicle time and maximize the number of passengers who successfully reach their destination. Since increasing the number of trains, stations, or the study horizon, exponentially increase the size of the problem, seeking practical methods to...
Locating workstations in tandem automated guided vehicle systems
, Article International Journal of Advanced Manufacturing Technology ; Volume 52, Issue 1-4 , 2011 , Pages 321-328 ; 02683768 (ISSN) ; Kazemipoor, H ; Moslemi Naeini, L ; Sharif University of Technology
2011
Abstract
This paper presents a new solution framework to locate the workstations in the tandem automated guided vehicle (AGV) systems. So far, the research has focused on minimizing the total flow or minimizing the total AGV transitions in each zone. In this paper, we focus on minimizing total cumulative flow among workstations. This objective allocates workstations to an AGV route such that total waiting time of workstations to be supplied by the AGV is minimized. We develop a property which simplifies the available mathematical formulation of the problem. We also develop a heuristic algorithm for the problem. Computational results show that our heuristic could yield very high-quality solutions and...
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...
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...
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...
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
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,...
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...