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A trace-time framework for prediction of elevation angle over land mobile LEO satellites networks
, Article Wireless Personal Communications ; Volume 62, Issue 4 , February , 2012 , Pages 793-804 ; 09296212 (ISSN) ; Rahimi, F ; Sharif University of Technology
2012
Abstract
Elevation angle is one of the most significant parameters of land mobile satellite channels, subject to rapid variations in the case of Low Earth Orbit (LEO) satellite systems. In this paper a novel trace-based framework is proposed and analyzed which is capable of predicting elevation angle as a function of time during satellite visibility window. Trace-time based modeling makes the framework practical for real-time evaluation of elevation angle and its alteration incurred by communication links in LEO satellite systems. The proposed method is particularly suitable for development of communication channel models and services in mobile LEO satellite networks where path variability is of...
Erratum: A trace-time framework for prediction of elevation angle over land mobile LEO satellites networks (Wireless Personal Communications DOI 10.1007/s11277-010-0094-5)
, Article Wireless Personal Communications ; Volume 62, Issue 4 , February , 2012 , Pages 805-806 ; 09296212 (ISSN) ; Rahimi, F ; Sharif University of Technology
2012
Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si
, Article Sensors and Actuators, B: Chemical ; Volume 146, Issue 1 , 2010 , Pages 53-60 ; 09254005 (ISSN) ; Iraji-Zad, A ; Rahimi, F ; Sharif University of Technology
Abstract
We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I-V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal-interface-semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100-40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration...
Fourier transform infrared spectroscopy and scanning tunneling spectroscopy of porous silicon in the presence of methanol
, Article Sensors and Actuators, B: Chemical ; Volume 132, Issue 1 , 2008 , Pages 40-44 ; 09254005 (ISSN) ; Rahimi, F ; Iraji zad, A ; Sharif University of Technology
2008
Abstract
Porous silicon samples were obtained from p+- and n-type silicon wafers. Gas sensing measurements showed that the electrical conductivity of porous Si on p+- and n-type wafers increases strongly and decreases weakly in the presence of methanol gas, respectively. Scanning tunneling spectroscopy (STS) indicates that the adsorption of methanol on the surface of n-porous silicon decreases the average density of states especially in the band gap. Fourier transform infrared (FTIR) spectroscopy reveals that after methanol exposure partial surface oxidation occurs which produces electron traps as well as methanol adsorption on the porous surfaces. These observations imply that the number of...
Investigation of hydrogen sensing properties and aging effects of Schottky like Pd/porous Si
, Article Journal of Sensors and Actuators B: Chemical ; Volume 146, Issue 1 , 8 April , 2010 , PP. 53–60 ; Iraji Zad, A. (Azam) ; Rahimi, F. (Fereshteh) ; Sharif University of Technology
Abstract
We prepared porous silicon samples coated by continuous palladium layer in electroless process. Scanning electron microscopy (SEM) showed cauliflower-shape Pd clusters on the surface. I–V curves of Schottky like Pd/porous Si samples were measured in air and in hydrogen. These measurements showed a metal–interface–semiconductor configuration rather than an ideal Schottky diode. Variations of the electrical current in the presence of diluted hydrogen at room temperature revealed that the samples can sense hydrogen in a wide range of concentration (100–40,000 ppm) without any saturation behavior. Hydrogen sensing properties of these samples were investigated at room temperature for a duration...
Activated layered manganese oxides with deposited nano-sized gold or silver as an efficient catalyst for epoxidation of olefins
, Article RSC Advances ; Volume 3, Issue 46 , 2013 , Pages 24069-24074 ; ISSN: 20462069 ; Amini, M ; Sedigh, D. J ; Rahimi, F ; Bagherzadeh, M ; Sharif University of Technology
2013
Abstract
Activated layered manganese oxides with deposited nano-sized gold or silver were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, atomic absorption spectroscopy and energy-dispersive X-ray mapping. Here, we report that Au or Ag nanoparticles deposited on layered Mn oxides improve the catalytic activity of the Mn oxides toward the epoxidation of olefins in the presence of H2O2 and NaHCO3
Catalytic effect of copper oxide on H2S sensing properties of nanostructured WO3
, Article Sensor Letters ; Volume 11, Issue 11 , 2013 , Pages 2015-2020 ; 1546198X (ISSN) ; Razi, F ; Rahimi, F ; Zad, A. I ; Sharif University of Technology
American Scientific Publishers
2013
Abstract
Cuprous oxide powder was added to WO3 sol as a catalyst and the composite sol was deposited on alumina substrates by spin coating process and annealing at 500 °C for 1 hour. Sensing properties of the pure and doped tungsten oxide samples to H2S gas were analyzed. WO 3-Cu2O (1%) samples showed good sensitivity towards 250 ppb of the gas at 100 °C and 1 ppm at room temperature (25 °C). Crystal structure, morphology and chemical composition of the sample were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDAX) analyses and X-ray photoelectron spectroscopy (XPS). Based on these data, possible reaction mechanisms of hydrogen sulfide over WO...
A very simple method to synthesize nano-sized manganese oxide: An efficient catalyst for water oxidation and epoxidation of olefins
, Article Dalton Transactions ; Volume 41, Issue 36 , Jul , 2012 , Pages 11026-11031 ; 14779226 (ISSN) ; Rahimi, F ; Amini, M ; Nayeri, S ; Bagherzadeh, M ; Sharif University of Technology
RSC
2012
Abstract
Nano-sized particles of manganese oxides have been prepared by a very simple and cheap process using a decomposing aqueous solution of manganese nitrate at 100 °C. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction spectrometry have been used to characterize the phase and the morphology of the manganese oxide. The nano-sized manganese oxide shows efficient catalytic activity toward water oxidation and the epoxidation of olefins in the presence of cerium(iv) ammonium nitrate and hydrogen peroxide, respectively
Hydrogen sensing properties of multi-walled carbon nanotube films sputtered by Pd
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 9 , 2010 , Pages 4445-4449 ; 03603199 (ISSN) ; Mortazavi, S. Z ; Iraji zad, A ; Rahimi, F ; Sharif University of Technology
Abstract
Multi-Walled Carbon nanotube (MWCNTs) films were obtained by Thermal Chemical Vapor Deposition method and coated by palladium sputtering process. Raman spectroscopy was used to study alteration in quality of the carbon nanotubes after the sputtering process. Fourier Transform Infra Red (FTIR) spectroscopy showed that hydrogenation process can reduce the C{double bond, long}O to C-O and also produce O-H bond. Furthermore, the electrical resistance measurement for Pd/MWNTs films was performed in a chamber with 1% hydrogen gas in a constant dry air flow. Hydrogen sensing behavior of the films was investigated at 50 °C. Pd/MWCNTs films presented an irreversible gas response to hydrogen in the...
Pd doped WO3 films prepared by sol-gel process for hydrogen sensing
, Article International Journal of Hydrogen Energy ; Volume 35, Issue 2 , 2010 , Pages 854-860 ; 03603199 (ISSN) ; Iraji zad, A ; Rahimi, F ; Ghasempour, R ; Sharif University of Technology
Abstract
The sol gel method was employed to prepare peroxopolytungstic acid (P-PTA). Palladium chloride salt was dissolved in the sol with different Pd:W molar ratios and coated on Al2O3 substrates by spin coating method. XRD and XPS techniques were used to analyze the crystal structure and chemical composition of the films before and after heat treatment at 500 °C. We observed that Pd can modify the growth kinetic of tungsten trioxide nanoparticles by reducing the crystallite size and as a result can improve hydrogen sensitivity. Resistance-sensing measurements indicated sensitivity of about 2.5 × 104 at room temperature in hydrogen concentration of 0.1% in air. Considering all sensing parameters,...
Curcumin-loaded amine-functionalized mesoporous silica nanoparticles inhibit α-synuclein fibrillation and reduce its cytotoxicity-associated effects
, Article Langmuir ; Volume 32, Issue 50 , 2016 , Pages 13394-13402 ; 07437463 (ISSN) ; Morshedi, D ; Yaghmaei, S ; Aliakbari, F ; Rahimi, F ; Arpanaei, A ; Sharif University of Technology
American Chemical Society
2016
Abstract
This study aimed to develop a drug carrier based on amine-functionalized mesoporous silica nanoparticles (AAS-MSNPs) for a poorly water-soluble drug, curcumin (CUR), and to study its effects on α-synuclein (α-Syn) fibrillation and cytotoxicity. Here, we show that AAS-MSNPs possess high values of loading efficiency and capacity (33.5% and 0.45 mg drug/mg MSNPs, respectively) for CUR. It is also revealed that α-Syn species interact strongly with the CUR-loaded AAS-MSNPs, leading to a significant inhibition of the fibrillation process. Furthermore, these samples reduce the toxic effects of CUR. However, drug-loaded AAS-MSNPs do not affect the cytotoxic properties of the formed fibrils...
Characterization of porous poly-silicon as a gas sensor
, Article Sensors and Actuators, B: Chemical ; Volume 100, Issue 3 , 2004 , Pages 341-346 ; 09254005 (ISSN) ; Rahimi, F ; Chavoshi, M ; Ahadian, M. M ; Sharif University of Technology
2004
Abstract
Porous poly-silicon (PPS) is a cheaper alternative to single crystal porous silicon and is a favorable choice for making gas sensors. In this study, porous poly-silicon samples were prepared using different HF concentrations and the structural and gas-sensing properties were studied. The topography of the surface was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The variation of electrical conductivity of the samples in the presence of dry air-diluted acetone, ethanol and methanol showed that for a constant etching current, the sensitivity was highest for samples prepared in 13% HF solution. The structure of the films in the optimum HF...
Introducing a new intelligent adaptive learning content generation method
, Article 2010 2nd International Conference on E-Learning and E-Teaching, ICELET 2010, 1 December 2010 through 2 December 2010 ; December , 2010 , Pages 65-71 ; 9781424490110 (ISBN) ; Mazaheri, A ; Gholipour, A ; Tavakoli, M ; Zandi, N ; Narimani, H ; Rahimi, F ; Nouri, S ; Sharif University of Technology
2010
Abstract
E-learning environments are being used more efficiently by the rapid growth in internet and multimedia technologies. Adaptive learning is a kind of learning environment which provides individual learning. It can customize the learning style according to the individual's personality and characteristics. Although there are a lot of e-learning systems having adaptive learning feature, they do not satisfy all adaptive learning aspects. This paper proposes a new method which tries to help learners find educational contents adapted to their personalities in an efficient manner. Our proposed method has four essential parts: 1) It finds out learner's features by Bayesian networks. 2) Then It tries...