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Fabrication of SiC body by microwave sintering process
, Article Journal of Materials Science: Materials in Electronics ; Volume 28, Issue 7 , 2017 , Pages 5675-5685 ; 09574522 (ISSN) ; Khodaei, M ; Nemati, A ; Yaghobizadeh, O ; Sharif University of Technology
Springer New York LLC
2017
Abstract
In the present study, SiC samples with 3, 5, 7.5 and 10 wt% Al2O3–Y2O3 as additives were made by powder metallurgy method, then sintering was performed by microwave-assisted process. β–SiC samples sintering was performed for 100 min. The highest sintered relative density 91.06% was achieved at 10 wt% additives content. The maximum values of hardness and toughness were up to 23.3 GPa and 6.14 MPa.m− 1/2. α–SiC and α–SiC/β–SiC samples sintering was performed for 120 min. The maximum value of density and hardness were up to 96.38% T.D and 24.88 GPa in α–SiC with 7.5 wt% additives, whereas the highest toughness was achieved at 10 wt% additives content in β–SiC samples. The α–SiC samples...
Phase-noise measurement using two inter-injection-locked microwave oscillators
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 54, Issue 7 , 2006 , Pages 2993-3000 ; 00189480 (ISSN) ; Banai, A ; Farzaneh, F ; Sharif University of Technology
2006
Abstract
Phase noise in two mutually coupled oscillators is analyzed by the describing function method, and the after-lock phase noise of the oscillators is calculated in terms of their free-running phase noise. A new phase-noise measurement technique based on inter-injection locking of two similar oscillators is proposed. Experimental results are presented, which confirm the theory. It is shown that in the case of zero phase of coupling coefficient, the system is in the optimum state where the only required parameter for the measurement is the locking bandwidth. In this optimum state, as far as the locking bandwidth is measured correctly, imperfections such as the frequency drift, parameters...
Production of V2C MXene using a repetitive pattern of V2AlC MAX phase through microwave heating of Al-V2O5-C system
, Article Applied Surface Science ; Volume 542 , 2021 ; 01694332 (ISSN) ; Orooji, Y ; Azarniya, A ; Alizadeh, M ; Kazem-zad, M ; TouradjEbadzadeh ; Sharif University of Technology
Elsevier B.V
2021
Abstract
The present work focuses on the preparation of V2C MXene from Al-V2O5-C mixture heated in a microwave and etched under HF-based process. In the first stage of process, microwave heating caused the formation of an uncommon periodic pattern of V2AlC-Al2O3 MAX phase. In the second stage of process the aggressive leaching (temperature of 80 °C for 96 h) was performed in HF to remove the interlayer aluminum and Al2O3 particles as impurities. The leaching was not completed at room temperature even after 24 h. XRD and FESEM analyses confirmed the successful formation of V2C MXene and its distorted layer, respectively. HRTEM, XPS and Raman analyses also confirmed a perfect structure of V2C MXene. It...
Microwave Inspired Easy-to-Design Nano-Couplers for Hybrid Photonic-Plasmonic Waveguide Structures
, M.Sc. Thesis Sharif University of Technology ; Mehrany, Khashayar (Supervisor)
Abstract
Potential of plasmonic waveguide structures to confine light in sub-wavelength scales attracted many attentions in recent years. Among these structures planar metal-insulator-metal waveguide and plasmonic slot waveguide are more promising. That is because of their easy fabrication process along with their various reported applications. However, there are some obstacles in the path of developing plasmonic integrated circuits, among whichhigh propagation loss can be named as the most important. To solve this issue, photonic waveguides can be used as the lossless interconnections between small footprint plasmonic components on optical chips. Therefore, application of plasmonic slot waveguide...
Design and Implementation of Tunable Microwave Gain Equalizer
,
M.Sc. Thesis
Sharif University of Technology
;
Banai, Ali
(Supervisor)
Abstract
Modern broadband microwave and millimeter-wave systems often struggle with excessive pass band ripple and negative gain slopes due to the loss of transmission lines such as coaxial cables, or ripples in the gain characteristic of broadband amplifiers. The common solution for this problem is using a gain equalizer to compensate for the intrinsic pass band variation with some extra loss in the band of interest in return.Designed equalizers often have a constant slope in their bandwidth. However, having ripples in pass band or in other words slope changing in some parts of the band is one of the issues that designers should deal with. In this thesis, after reviewing the previous works on the...
Synthesis of N-Alkyl-1, 4 dihyroisoqinoline-3(2H)-one
, M.Sc. Thesis Sharif University of Technology ; Matlubi Moghaddam, Firoz (Supervisor)
Abstract
Isoquinolinonese are important structural compounds in plant alkaloids and useful synthetic intermediates for bio logically active compound some 3(2H)-isoquinolinone are known to exhibit biological effects such as antidepressant, cardiotonic, or analgesic activity. 3(2H)-isoquinolinone and its derivative are not so readily accessible. They have previously been synthesized by the reaction of o-acylphenyl acetic with ammonia, reaction of 3-isochromanon with amines this methods have problems like low yield and because of that we have developed practical and efficient route to synthesis 1٬4 dihydroisoquin-3(2H)-ones under microwave irradiation. We did this project with modified Pictet-Spengler...
Synthesis of Colloidal Silver Nanoparticles by Microwave Method and Study of its Antibacterial Activity
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
Silver nanoparticles are widely used in different industries because of their antibacterial effects. Many synthesis methods were used to obtain silver nanoparticles. In this study the microwave method is used to synthesize nanosilver. This method is easier and faster in comparison to other methods. The effect of precursors’ concentrations, using different solvents, different remaining time in microwave and microwave power were studied. By increasing the reaction time, microwave power and using different solvents, nanosilver particle size varies from 2 nm up to 300nm. The TEM images, size distribution, XRD patterns and UV-visible spectrum are shown. The obtained nanosilver was used to observe...
ChemInform abstract: microwave-assisted rapid ketalization/acetalization of aromatic aldehydes and ketones in aqueous media [electronic resource]
, Article Journal of Chemical Research ; September 1999, Volume -, Number 9; Page(s) 562 to 563 ; Mirjalili, Bibi Fatemeh ; Sharif University of Technology
Abstract
Aromatic aldehydes and ketones are readily acetalized or ketalized under microwave irradiation in the presence of water as a solvent
Noise figure of microwave photonic links operating under large-signal modulation and its application to optoelectronic oscillators
, Article Applied Optics ; Vol. 53, issue. 28 , Oct , 2014 , p. 6414-6421 ; Banai, A ; Sharif University of Technology
Abstract
The noise performance of intensity-modulation direct-detection microwave photonic links (MWPL) operating under large-signal conditions has been studied in this paper. A sinusoidal signal plus narrow-band white Gaussian noise is applied at the radio frequency input of the link, and the output spectrum is derived using a nonlinear analytical approach. We show that the output SNR can be severely affected by the interaction of signal and noise due to the nonlinearity of the MWPL combined with the large input modulating signal. It is shown that the large-signal noise figure (NF) of an MWPL depends on the input power, a dependence that is not readily apparent under small-signal conditions, due to...
Chemometrics-assisted gas chromatographic-mass spectrometric analysis of volatile components of olive leaf oil
, Article Journal of the Iranian Chemical Society ; Volume 10, Issue 1 , 2013 , Pages 169-179 ; 1735207X (ISSN) ; Abbasi, A ; Moazeni, R. S ; Parastar, H ; Jalali Heravi, M ; Sharif University of Technology
2013
Abstract
Iranian olive leaf essential oil components were extracted by microwave-assisted hydrodistillation and analyzed using gas chromatography-mass spectrometry. Ninety-seven components were identified by direct similarity searches for olive leaf essential oil. Chemometrics was used to find more components with the help of multivariate curve resolution methods. Eigenvalues-based methods and Malinowski functions were used for chemical rank determination of GC-MS data. Multivariate curve resolution-alternative least squares as an iterative method was used for resolving the overlapped and embedded peaks. With the use of this method the number of 97 components was extended to 127 components. Major...
Fully-Tunable microwave photonic filter with complex coefficients using tunable delay lines based on frequency-Time conversions
, Article Optics Express ; Volume 20, Issue 20 , 2012 , Pages 22728-22734 ; 10944087 (ISSN) ; Preuler, S ; Jamshidi, K ; Akbari, M ; Schneider, T ; Sharif University of Technology
Abstract
A fully electrically tunable microwave photonic filter is realized by the implementation of delay lines based on frequency-Time conversion. The frequency response and free spectral range (FSR) of the filter can be engineered by a simple electrical tuning of the delay lines. The method has the capability of being integrated on a silicon photonic platform. In the experiment, a 2-Tap tunable microwave photonic filter with a 3-dB bandwidth of 2.55 GHz, a FSR of 4.016 GHz, a FSR maximum tuning range from -354 MHz to 354 MHz and a full FSR translation range is achieved
Two building blocks of microwave photonics filters in the presence of group delay ripple: A comparative survey
, Article Optical and Quantum Electronics ; Volume 44, Issue 8-9 , 2012 , Pages 403-414 ; 03068919 (ISSN) ; Akbari, M ; Sharif University of Technology
Springer
2012
Abstract
We have developed an analytic approach to investigate the effect of group delay ripple of the dispersive devices on the performance of two major building blocks of microwave- photonic filters. Firstly, performance of PM-based block in the presence of an arbitrary group delay ripple (GDR) is analyzed and compared with the ripple-free case to reveal the destructive effects of added group delay ripple. In the next step, we repeat the proposed approach for the AM-based one; again, the performance is compared with the ripple-free case. Two distortion metrics are also introduced to quantify this distortion. Comparison of the performance of two building blocks in the presence of group delay ripple...
Transformer-feedback interstage bandwidth enhancement for MMIC multistage amplifiers
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 63, Issue 2 , 2015 , Pages 441-448 ; 00189480 (ISSN) ; Medi, A ; Sharif University of Technology
Abstract
The transformer-feedback (TRFB) interstage bandwidth enhancement technique for broadband multistage amplifiers is presented. Theory of the TRFB bandwidth enhancement and the design conditions for maximum bandwidth, maximally flat gain, and maximally flat group delay are provided. It is shown that the TRFB bandwidth enhancement can provide higher bandwidth compared to the conventional techniques based on reactive impedance matching networks. A three-stage low-noise amplifier (LNA) monolithic microwave integrated circuit with the TRFB between its consecutive stages is designed and implemented in a 0.1-μ m GaAs pHEMT process. The TRFB is realized by coupling between the drain bias lines of...
Microwave-assisted synthesis of narcis-like zinc oxide nanostructures
, Article Journal of Alloys and Compounds ; Volume 497, Issue 1-2 , May , 2010 , Pages 325-329 ; 09258388 (ISSN) ; Zanganeh, S ; Kajbafvala, E ; Zargar, H. R ; Bayati, M. R ; Sadrnezhaad, S. K ; Sharif University of Technology
2010
Abstract
Through a fast, simple, low cost, surfactant-free and convenient microwave-assisted route, narcis-like ZnO nanostructures (10-15 nm size) with flower diameters in the range of 1-2.5 μm were synthesized. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and room temperature photoluminescence (PL) measurements were used to characterize the produced ZnO nanostructures. The principle raw materials - ammonium hydroxide (NH4OH) and zinc acetate dihydrate [Zn(CH3COO)2·2H2O] - were both inexpensive. The method was fast, simple and surfactant-free capable of producing larger quantities of zinc oxide...
A broadband multistage LNA with bandwidth and linearity enhancement
, Article IEEE Microwave and Wireless Components Letters ; Volume PP, Issue 99 , 2016 ; 15311309 (ISSN) ; Yousefi, A ; Kalantari, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Design techniques to enhance bandwidth and linearity of broadband multistage low-noise amplifiers (LNAs) are presented. A feedback amplifier circuit is proposed to compensate for transistor gain roll-off with frequency in other amplifier stages and extend overall bandwidth. Moreover, a transistor width tapering in a multistage LNA is applied to improve linearity. These techniques are adopted in a three-stage monolithic microwave integrated circuit (MMIC) LNA implemented in a 0.1-μm GaAs pHEMT process. The LNA features 18-43 GHz bandwidth, 21.6 dB average gain, and 1.8-2.7 noise figure (NF). It exhibits output 1-dB compression point of 11.5 dBm at 30 GHz and consumes 70 mA bias current from a...
A broadband integrated class-J power amplifier in gaas pHEMT technology
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 64, Issue 6 , 2016 , Pages 1822-1830 ; 00189480 (ISSN) ; Medi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
This paper presents a design methodology for class-J monolithic microwave integrated circuit (MMIC) power amplifiers (PAs). Theoretical derivations of optimum load impedances, output power, efficiency, and maximum bandwidth are described in presence of nonlinear drain-source resistance of transistors (RDS). A procedure is developed for ideal transistor sizing where transistors are concurrently stabilized and sized to achieve the maximum power-added efficiency (PAE). A 3.5-7 GHz, 0.5-W class-J PA is implemented in a 0.1-μm AlGaAs-InGaAs pHEMT technology to check the accuracy of the proposed approach. With chip dimensions of 1.57 × 1.29 mm2, the PA achieves 56% average PAE over the frequency...
On Design of Wideband Compact-Size Ka/Q-Band High-Power Amplifiers
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 64, Issue 6 , 2016 , Pages 1831-1842 ; 00189480 (ISSN) ; Frounchi, M ; Medi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
This paper presents a methodology for the design of Ka/Q-band monolithic microwave integrated circuit (MMIC) high-power amplifiers (HPAs). Design techniques are introduced to reduce chip area and to improve bandwidth (BW). These techniques are applied to the design of a 31-39-GHz 5-W HPA implemented on a 0.1-μm AlGaAs-InGaAs pseudomorphic HEMT (pHEMT) technology. With chip dimensions of 3.35 × 3.2 mm2, the HPA achieves 24% average power-added efficiency (PAE) over the frequency band, while maintaining an average 22-dB small-signal gain. A balanced high-power amplifier (BPA) is also presented, which combines the power of two 5-W HPA cells to deliver peak 8.5-W output power (Pout) in the...
Distributed class-J power amplifiers
, Article IEEE Transactions on Microwave Theory and Techniques ; Volume 65, Issue 2 , 2017 , Pages 513-521 ; 00189480 (ISSN) ; Medi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper presents the design and implementation of a distributed class-J power amplifier (DJPA) in a 0.25-μm AlGaAs-InGaAs pHEMT technology. Class-J mode of operation is introduced in design of distributed power amplifiers (DPAs) to achieve high power added efficiencies (PAEs) over wide frequency ranges. Extensive load-pull (LP) and source-pull (SP) simulations are performed to show that class-J PAs are less sensitive to proper termination of higher order harmonics, and high PAE and output power can be obtained even if the second, third, fourth, and fifth harmonics comprise a real impedance. This is essential in DPAs as the higher order harmonics of the frequencies at lower side of the...
Novel microwave-assisted synthesis of porous g-C3N4/SnO2 nanocomposite for solar water-splitting
, Article Applied Surface Science ; Volume 440 , 15 May , 2018 , Pages 153-161 ; 01694332 (ISSN) ; Soleimani, F ; Naseri, N ; Soltaninejad, M ; Montazeri, S.M ; Sadrnezhaad, S.K ; Mohammadi, M.R ; Moghadam, H.A ; Forouzandeh, M ; Amin, M.H ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Highly porous nanocomposites of graphitic-carbon nitride and tin oxide (g-C3N4/SnO2) were prepared through simple pyrolysis of urea molecules under microwave irradiation. The initial amount of tin was varied in order to investigate the effect of SnO2 content on preparation and properties of the composites. The synthesized nanocomposites were well-characterized by XRD, FE-SEM, HR-TEM, BET, FTIR, XPS, DRS, and PL. A homogeneous distribution of SnO2 nanoparticles with the size of less than 10 nm on the porous C3N4 sheets could be obtained, suggesting that in-situ synthesis of SnO2 nanoparticles was responsible for the formation of g-C3N4. The process likely occurred by the aid of the large...
Microwave-assisted synthesis of 3-substituted coumarins using ZrOCl 2.8H2O as an effective catalyst
, Article Scientia Iranica ; Volume 16, Issue 1 C , 2009 , Pages 12-16 ; 10263098 (ISSN) ; Mirjafary, Z ; Saeidian, H ; Sharif University of Technology
2009
Abstract
An efficient route for the synthesis of 3-substituted coumarins via Knoevenagel condensation, using ZrOCl2.8H2O (10 mol %) as the. catalyst under microwave heating and solvent-free conditions, is described. This procedure offers several advantages, including the low loading of catalysts, high yields, clean reactions, short reaction times and the. use of various substrates, which make it a useful and attractive strategy for the. synthesis of 3-substituted coumarins. © Sharif University of Technology, June 2009