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Synthesis and characterization of multi stimuli-responsive block copolymer-silica hybrid nanocomposite with core-shell structure via RAFT polymerization
, Article Composites Science and Technology ; Volume 188 , 2020 ; Rahemipoor, S ; Kohestanian, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
A novel multi stimuli-responsive silica nanocomposite with a core-shell structure is synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. The SiO2 nanoparticles are chemically modified via 3-(trimethoxylsilyl) propyl methacrylate (MPS) which they are used in the core of nanocomposite. The macro-RAFT agent is prepared by RAFT polymerization of N-isopropylacrylamide (NIPAM), spirooxazine acryloyl monomer (SOM), and 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT as a RAFT agent). Finally, the smart nanocomposite is prepared by reaction between the macro-RAFT agent and 2-(Dimethylamino) ethyl methacrylate (DMAEMA) as a monomer. SOM as a...
Polyacrylamide-grafted magnetic reduced graphene oxide nanocomposite: preparation and adsorption properties
, Article Colloid and Polymer Science ; 2019 ; 0303402X (ISSN) ; Nazari, M ; Kohestanian, M ; Hosseini, S. H ; Sharif University of Technology
Springer Verlag
2019
Abstract
Magnetic reduced graphene oxide/polymer nanocomposites were prepared by in situ polymerization and grafting of polyacrylamide on the surface of functionalized magnetic reduced graphene oxide (rGO). Graphene oxide nanosheets were decorated with Fe3O4 nanoparticles, reduced and functionalized with 3-(trimethoxysilyl)propyl methacrylate, and then grafted with polyacrylamide. Grafting of polyacrylamide makes magnetic rGO hydrophilic and highly water dispersible. The prepared material was used as adsorbent for removal of an anionic dye, Congo red, and a maximum adsorption capacity up to 166.7 mg g−1 was obtained. The kinetics and isotherm of adsorption and the effect of experimental condition on...
Synthesis and Characterization of Polymeric Nanocomposites Via Reversible Addition−Fragmentation Chain-Transfer (RAFT) Polymerization and Investigation of their Applications
, M.Sc. Thesis Sharif University of Technology ; Pourjavadi, Ali (Supervisor)
Abstract
In this thesis, nanocomposites based on magnetic graphene oxide and iron oxide nanoparticles coated with smart polymeric materials (by polymerization of monomers such as glycidyl methacrylate, acrylic acid, and N-isopropyl acrylamide) via Reversible Addition−Fragmentation Chain-Transfer (RAFT) polymerization were successfully synthesized. The combination of large surface area in nanoparticles and different functional groups in polymeric layers can give unique properties to nanocomposites. Therefore, we synthesized various smart nanocomposites with this perspective. After synthesizing these nanocomposites, smart magnetic nanoparticles were characterized by FT-IR, NMR, XPS, TGA, DLS, VSM, GPC,...
Preparation of poly (acrylic acid) microgels by alcohol type cross-linkers and a comparison with other cross-linking methods
, Article Polymer Bulletin ; 2021 ; 01700839 (ISSN) ; Bouhendi, H ; Keshavarzi, N ; Mahmoudi, M ; Pourjavadi, A ; Ghiass, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
Herein, poly (acrylic acid) (PAA) microgels were synthesized via alcohol type cross-linked by a free radical precipitation polymerization approach. At the first time, 1,6-hexanediol (1–6 diol), trimethylolpropane (TMP), and pentaerythritol (PEN) were selected as multifunctional cross- linking agent to synthesize cross-linked poly(acrylic acid) microgels. Alcohol type cross-linking agents can connect the PAA chains. The cross-linking reaction takes place due to reaction between hydroxyl groups of various cross-linkers and carboxyl groups of PAA chains. All of the hydroxyl groups do not participate in the reaction with acid groups of polymer chains through the polymerization stage; therefore,...
Cobalt -mediated radical polymerization of vinyl acetate in a packed column system: simultaneous effective control of molecular weight, separation, and purification
, Article Journal of Polymer Research ; Volume 29, Issue 12 , 2022 ; 10229760 (ISSN) ; Dadkhah, A. S ; Kohestanian, M ; Mahdieh, A ; Semsarzadeh, M. A ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
The simultaneous control of the molecular weight, separation, and purification of polyvinyl acetate was achieved using a cobalt-mediated radical polymerization (CMRP) in a packed column with silica gel particles (PC-CMRP). The controlled radical polymerization of VAc in the packed columns was evaluated from the linear time dependence of Ln[M]0/[M], linear increase of molecular weight with the increase in conversion, and narrow molecular weight distribution. PC-CMRP method was used to produce high-purity polymers with controlled molecular weight and narrow molecular weight distribution without requiring additional purification steps. The high ability of silica gel particles to adsorb free...
Preparation of poly (acrylic acid) microgels by alcohol type cross-linkers and a comparison with other cross-linking methods
, Article Polymer Bulletin ; Volume 79, Issue 9 , 2022 , Pages 7775-7794 ; 01700839 (ISSN) ; Bouhendi, H ; Keshavarzi, N ; Mahmoudi, M ; Pourjavadi, A ; Ghiass, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Herein, poly (acrylic acid) (PAA) microgels were synthesized via alcohol type cross-linked by a free radical precipitation polymerization approach. At the first time, 1,6-hexanediol (1–6 diol), trimethylolpropane (TMP), and pentaerythritol (PEN) were selected as multifunctional cross- linking agent to synthesize cross-linked poly(acrylic acid) microgels. Alcohol type cross-linking agents can connect the PAA chains. The cross-linking reaction takes place due to reaction between hydroxyl groups of various cross-linkers and carboxyl groups of PAA chains. All of the hydroxyl groups do not participate in the reaction with acid groups of polymer chains through the polymerization stage; therefore,...
Facile and tunable method for polymeric surface modification of magnetic nanoparticles via RAFT polymerization: Preparation, characterization, and drug release properties
, Article European Polymer Journal ; Volume 167 , 2022 ; 00143057 (ISSN) ; Pourjavadi, A ; Keshavarzi, N ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Herein, the facile and tunable technique for the preparation of novel multi-stimuli-responsive nanocomposites via RAFT polymerization for DOX delivery is reported. The influence of the molecular weight of pH- and thermo-sensitive poly (acrylic acid-co-NIPAM) (PNAx), as a macro-RAFT agent, on the nanocomposites size and drug release rate was investigated. The outcome of this study reveals that macro-RAFT agent with lower molecular weight can be attached to the surface of magnetic nanoparticles with higher content of polymeric layer than can macro-RAFT agent with higher molecular weight. Also, it was observed that the particle size, polymer grafting density, DOX loading capacity, and DOX...
Probability of missed detection as a criterion for receiver placement in MIMO PCL
, Article IEEE National Radar Conference - Proceedings, 7 May 2012 through 11 May 2012, Atlanta, GA ; 2012 , Pages 0924-0927 ; 10975659 (ISSN) ; 9781467306584 (ISBN) ; Chitgarha, M. M ; Radmard, M ; Nayebi, M. M ; Sharif University of Technology
IEEE
2012
Abstract
Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar
An efficient method for the ring opening of epoxides with aromatic amines by Sb(III) chloride under microwave irradiation
, Article Journal of Chemical Research ; Issue 4 , 2008 , Pages 220-221 ; 03082342 (ISSN) ; Hashemi, M. M ; Mottaghi, M. M ; Foroughi, M. M ; Sharif University of Technology
2008
Abstract
SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity
MIMO radar signal design to improve the MIMO ambiguity function via maximizing its peak
, Article Signal Processing ; Volume 118 , 2016 , Pages 139-152 ; 01651684 (ISSN) ; Radmard, M ; Nazari Majd, M ; Karbasi, S. M ; Nayebi, M. M ; Sharif University of Technology
Elsevier
2016
Abstract
One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function...
Detection-localization tradeoff in MIMO radars
, Article Radioengineering ; Volume 26, Issue 2 , 2017 , Pages 581-587 ; 12102512 (ISSN) ; Radmard, M ; Chitgarha, M. M ; Bastani, M. H ; Nayebi, M. M ; Sharif University of Technology
2017
Abstract
Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance...
Antenna placement and power allocation optimization in MIMO detection
, Article IEEE Transactions on Aerospace and Electronic Systems ; Vol. 50, Issue 2 , April , 2014 , pp. 1468-1478 ; Chitgarha, M. M ; Majd, M. N ; Nayebi, M. M ; Sharif University of Technology
2014
Abstract
It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive...
Ambiguity function of MIMO radar with widely separated antennas
, Article Proceedings International Radar Symposium ; 16 -18 June , 2014 ; ISSN: 21555753 ; Chitgarha, M. M ; Nazari Majd, M ; Nayebi, M. M ; Sharif University of Technology
2014
Abstract
There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas
Choosing the position of the receiver in a MISO passive radar system
, Article European Microwave Week 2012: "Space for Microwaves", EuMW 2012, Conference Proceedings - 9th European Radar Conference, EuRAD 2012 ; 2012 , Pages 318-321 ; 9782874870293 (ISBN) ; Majd, M. N ; Radmard, M ; Nayebi, M. M ; Sharif University of Technology
2012
Abstract
By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only...
Adaptive filtering techniques in passive radar
, Article Proceedings International Radar Symposium, Dresden ; Volume 2 , June , 2013 , Pages 1067-1078 ; 21555753 (ISSN) ; 9783954042234 (ISBN) ; Radmard, M ; Majd, M. N ; Nayebi, M. M ; Sharif University of Technology
2013
Abstract
One of the most important obstacles in passive radar applications is removing the direct signal from the target channel. Otherwise, week echoes from the targets in the target channel would be ignored due to the limited dynamic range of the system. One of the most effective techniques in this field is using adaptive filters. In this paper various adaptive filters are introduced and their performances are shown and compared
Ambiguity function based receiver placement in multi-site radar
, Article 2016 CIE International Conference on Radar, RADAR 2016, 10 October 2016 through 13 October 2016 ; 2017 ; 9781509048281 (ISBN) ; Chitgarha, M. M ; Nazari Majd, M ; Nayebi, M. M ; Sharif University of Technology
2017
Abstract
It has been shown that using multiple antennas in a radar system improves the performance considerably, since multiple target echoes are received from different aspect angles of the target. In this way, the target detection is improved. However, when using multiple antennas, some problems, such as designing the transmit signals, synchronization, etc. emerge that should be solved. One of such problems is the receiver placement. Receiver placement deals with choosing a proper position for the receive antenna in order to optimize the whole system's performance. In this paper, a receiver placement procedure based on improving the radar ambiguity function is proposed for the case of a multisite...
Improving MIMO radar's performance through receivers' positioning
, Article IET Signal Processing ; Volume 11, Issue 5 , 2017 , Pages 622-630 ; 17519675 (ISSN) ; Radmard, M ; Nazari Majd, M ; Nayebi, M. M ; Sharif University of Technology
Institution of Engineering and Technology
2017
Abstract
By employing the MIMO (multiple-input-multiple-output) technology in radar, some new problems emerged, that, in order to benefit the MIMO gains in radar, it was necessary to solve them suitably. One of such obstacles is determining the positions of receive antennas in a MIMO radar system with widely separated antennas (WS MIMO radar), since it is shown that the antennas' positions affect the whole system's performance considerably. In this study, a proper receivers' positioning procedure is proposed. To do this end, four criteria are developed based on the proposed MIMO detector and the MIMO ambiguity function. The simulations verify that the proposed positioning procedure improves the...
Silylation of hydroxy groups with HMDS under microwave irradiation and solvent-free conditions
, Article Phosphorus, Sulfur and Silicon and Related Elements ; Volume 177, Issue 2 , 2002 , Pages 289-292 ; 10426507 (ISSN) ; Saidi, M. R ; Bolourtchian, M ; Heravi, M. M ; Sharif University of Technology
2002
Abstract
Phenols and alcohols are silylated with hexamethyldisilazane (HMDS) under microwave irradiation in solvent-free condition in good to excellent yields
Dynamic analysis of carbon nanotubes under electrostatic actuation using modified couple stress theory
, Article Acta Mechanica ; Vol. 225, Issue 6 , June , 2014 , pp. 1523-1535 ; Online ISSN: 1619-6937 ; Rastgoo, A ; Ahmadian, M. T ; Mashhadi, M. M ; Sharif University of Technology
2014
Abstract
Modified couple stress theory is a size-dependent theorem capturing the micro/nanoscale effects influencing the mechanical behaviors of the micro- and nanostructures. In this paper, it is applied to investigate the nonlinear vibration of carbon nanotubes under step DC voltage. The vibration, natural frequencies and dynamic pull-in characteristics of the carbon nanotubes are studied in detail. Moreover, the effects of various boundary conditions and geometries are scrutinized on the dynamic characteristics. The results reveal that application of this theory leads to the higher values of the natural frequencies and dynamic pull-in voltages
White space regions
, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 22 January 2011 through 28 January 2011, Novy Smokovec ; Volume 6543 LNCS , 2011 , Pages 226-237 ; 03029743 (ISSN) ; 9783642183805 (ISBN) ; Fazli, M ; Ghodsi, M ; Safari, M ; Saghafian, M ; Tavakkoli, M ; Sharif University of Technology
2011
Abstract
We study a classical problem in communication and wireless networks called Finding White Space Regions. In this problem, we are given a set of antennas (points) some of which are noisy (black) and the rest are working fine (white). The goal is to find a set of convex hulls with maximum total area that cover all white points and exclude all black points. In other words, these convex hulls make it safe for white antennas to communicate with each other without any interference with black antennas. We study the problem on three different settings (based on overlapping between different convex hulls) and find hardness results and good approximation algorithms