Search for: light
Total 783 records
Article 18th International Congress of Chemical and Process Engineering, CHISA 2008, Prague, 24 August 2008 through 28 August 2008 ; 2008 ; Gholamtamimi, M ; Hayati, R ; Sobati, M. A ; Sharif University of Technology
Gas-to-Liquid (GTL) is a multi-staged process in which natural gas is converted to liquid fuels. The stages of GTL process are discussed. A GTL plant with 10,000 bpd capacity and have similar specifications with the SASOL process was simulated using the Aspen-Plus software and the simulation results were compared with the SASOL process data. This is an abstract of a paper presented at the 18th International Congress of Chemical and Process Engineering (Prague, Czech Republic 8/24-28/2008)
Diffraction analysis of extraction efficiency for photonic crystal based white light emitting diodes, Article CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference ; 14-19 June , 2009 ; 21622701 (ISSN) ; 9781424440801 (ISBN) ; Sodagar, M ; Eftekharian, A ; Khorasani, S ; Sharif University of Technology
Optical Society of America 2009
Article Classical and Quantum Gravity ; Volume 32, Issue 21 , 2015 ; 02649381 (ISSN) ; Firouzjaee, J. T ; Mansouri, R ; Sharif University of Technology
Institute of Physics Publishing 2015
We have constructed a spherically symmetric structure model in a cosmological background filled with perfect fluid with non-vanishing pressure as an exact solution of the Einstein equations using the LemaѤtre solution. To study its local and quasi-local characteristics, including the novel features of its central black hole, we have suggested an algorithm to integrate the equations numerically. The result shows intriguing effects of the pressure inside the structure. The evolution of the central black hole within the FRW Universe, its decoupling from the expanding parts of the model, the structure of its space-like apparent horizon, the limiting case of the dynamical horizon tending to a...
Diffraction analysis of extraction efficiency for photonic crystal based white light emitting diodes, Article CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, Munich, 14 June 2009 through 19 June 2009 ; 2009 ; 9781424440801 (ISBN) ; Sodagar, M ; Eftekharian, A ; Khorasani, S ; Sharif University of Technology
Article International Journal of Environmental Analytical Chemistry ; 2020 ; Keshavarz Moraveji, M ; Mousavi, S ; Sharif University of Technology
Taylor and Francis Ltd 2020
This review paper is devoted to the intensification of processes for nitrate removal. First, the developments of microfluidic sensors for nitrate detection and analysis have addressed. Second, the process variables of photocatalytic nitrate removal have been categorized according to their relationship with activity, selectivity and stability of the catalyst. The objective of this classification is to generate guidelines toward the photocatalytic process optimization. Third, because of the fact that a single method for nitrate removal faces some challenges, hybrid methods have been presented, and the best choice for nitrate removal can be referred to as photocatalytic – reverse osmosis...
Nanodeposition and characterization of cobalt particles inside synthesized faujasitic support for preparing a catalyst for fischer-tropsch reaction, Article 18th International Congress of Chemical and Process Engineering, CHISA 2008, Prague, 24 August 2008 through 28 August 2008 ; 2008 ; Kazemian, H ; Kazemeini, M ; Sharif University of Technology
The importance of the gas-to-liquid process is increasing due to growing demand for a high quality, less expensive, and cleaner fuel. Faujasite zeolites, e.g,. zeolites type X and Y, are well-known catalysts in the petrochemical industry. Faujasitic supports (mainly X zeolites) were prepared via hydrothermal synthesis with different Si/Al ratios from pure chemical materials and fly ash as a source of silicon. A high quantity of cobalt oxides was deposited on supports by varying samples Si/Al ratios during the zeolite preparation procedure. Using fly ash in synthesizing the zeolitic support resulted in a A-X zeolite material with a very high cation exchange capability and final cobalt...
Article Applied Optics ; Volume 47, Issue 14 , 2008 , Pages 2680-2686 ; 1559128X (ISSN) ; Massoumian, F ; Sharif University of Technology
OSA - The Optical Society 2008
A new technique for coding and decoding of optical signals through the use of polarization is described. In this technique the concept of coding is translated to polarization. In other words, coding is done in such a way that each code represents a unique polarization. This is done by implementing a binary pattern on a spatial light modulator in such a way that the reflected light has the required polarization. Decoding is done by the detection of the received beam's polarization. By linking the concept of coding to polarization we can use each of these concepts in measuring the other one, attaining some gains. In this paper the construction of a simple point-to-point communication where...
Novel optical slow wave structure and surface electromagnetic wave coupler with conducting interfaces, Article Semiconductor Science and Technology ; Volume 19, Issue 7 , 2004 , Pages 890-896 ; 02681242 (ISSN) ; Rashidian, B ; Sharif University of Technology
Recently, a group of novel devices based on conducting interfaces has been proposed. These conducting interfaces can be implemented, for example, by using the inversion layer of MOS structures, trapped charges, or depletion layer charges. It has been shown that these structures can support surface electromagnetic waves. In this paper, the coupling of surface electromagnetic waves supported by conducting interfaces is first analysed. Next, by direct solution of Maxwell's equations and applying appropriate boundary conditions; exact analytical formulation of the dispersion equation has also been derived. Results driven by a coupled mode theory approach are justified by solving the exact...
Synergistic cobalt–nickel co-catalyst for enhanced visible light-induced photocatalytic water oxidation, Article Journal of Chemical Sciences ; Volume 132, Issue 1 , 2020 ; Nouri, O ; Rahman Setayesh, S ; Sharif University of Technology
Abstract: The loading of co-catalyst is an efficient way to increase the activity of synthesized carbon-based photocatalysts in the energy and environmental applications. Herein, Co and Ni decorated on g-C3N4 was synthesized as a visible light active photocatalyst and characterized with XRD, FT-IR, BET, DRS, TGA, FE-SEM, EDX, and EIS techniques. From the characterization results, it was demonstrated that cobalt and nickel which were present in the structure of the nanocatalyst, were in the metallic form. The decoration of Ni and Co reduced bandgap energy of g-C3N4 and made the synthesized nanocomposite active under visible light. The operating condition of O2 photocatalytic generation was...
Extended quantum yield: A dimensionless factor including characteristics of light source, photocatalyst surface, and reaction kinetics in photocatalytic systems, Article Industrial and Engineering Chemistry Research ; Vol. 53, issue. 30 , July , 2014 , pp. 11973-11978 ; ISSN: 08885885 ; Vossoughi, M ; Simchi, A. R ; Micklic, M ; Sharif University of Technology
Quantum yield relations were extended by adding effective conditional parameters in photodegradation of organic pollutants such as intensity of light, wavelength of light, average distance from light source, concentrations of dye/pollutant and photocatalyst, and volume of reactor. The geometry of light source and thin film and particulate photocatalytic systems were considered in analysis. Extended quantum yield that is a dimensionless factor is applicable in various types of dye and photocatalyst. This extended quantum yield allowed us to classify photodegradation as reported by scientific groups, performed in various operational conditions in order to identify the degree of similarity...
Ambient temperature effect on single-bubble sonoluminescence in different concentrations of sulfuric acid solutions, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 85, Issue 1 , January , 2012 ; 15393755 (ISSN) ; Bemani, F ; Silatani, M ; Sadighi Bonabi, R ; Sharif University of Technology
The effect of ambient temperature on the parameters of the single-bubble sonoluminescence in sulfuric acid (SA) diluted in water is studied. Using a hydrochemical model, three dominant instabilities of shape, Bjerknes, and diffusion are considered. The phase diagrams of the bubble in the (R 0 - P a) space are presented, and the parametric dependence of the light intensity is discussed. In contrast to water, the calculated thermal-bremsstrahlung mechanism of light emission at the fixed degassing condition of high SA concentrations shows that, with increasing the temperature of aqueous SA solutions, the light intensity increases. However, at diluted SA solutions similar to water, the light...
A Power-Law Relationship between Characteristics of Light Source and Quantum Yield in Photocatalytic Systems, Article Journal of Physical Chemistry C ; Volume 119, Issue 39 , July , 2015 , Pages 22425-22431 ; 19327447 (ISSN) ; Sharif University of Technology
American Chemical Society 2015
A new dimensionless parameter, Sh-factor, is introduced by using dimensional analysis and extending the quantum yield definition to show power-law relations among light intensity, light wavelength, distance from light source, concentrations of dye/pollutant and photocatalyst, time, and degradation percent. The Sh-factor has the same equation form for photoactivated remediation systems with particulate and thin-film photocatalysts, and it provides mathematical tools to predict degradation performance of a photocatalytic system. These power-law equations separate simply the operational parameters related to the lamp from semiconductor photocatalyst characteristics. The light scattering and...
Article New Journal of Chemistry ; Volume 44, Issue 46 , 2020 , Pages 20375-20386 ; Nguyen, D. T ; Diamanti, M. V ; Kaveh, R ; Asa, M ; Sakar, M ; Pedeferri, M ; Do, T. O ; Sharif University of Technology
Royal Society of Chemistry 2020
This study describes the synthesis of TiO2/WO3 composite systems with a varying concentration of WO3 by a glucose-template assisted method and demonstrates their round-the-clock photoactivity performance towards the degradation of methanol (MeOH) under illumination and dark conditions. XRD results indicated a biphasic anatase-rutile nature of TiO2, with tunable concentrations with respect to the WO3 loading. WO3 incorporation extended the light absorption of the system towards visible light, increasing the observed photoactivity. The obtained results were further validated using photo-electrochemical investigations such as photocurrent measurements and the impedance response of the systems....
Performance analysis of spectral-phase-encoded optical CDMA system using two-photon-absorption receiver structure for asynchronous and slot-level synchronous transmitters, Article Journal of Lightwave Technology ; Volume 25, Issue 6 , 2007 , Pages 1638-1645 ; 07338724 (ISSN) ; Salehi, J. A ; Sharif University of Technology
In this paper, we analyze the performance of a nonlinear two-photon-absorption (TPA) receiver and compare its performance with that of a single-photon-absorption (SPA) receiver in the context of spectral-phase-encoded optical code-division multiple access (CDMA) technique. The performances for the above systems are evaluated for two different transmission scenarios, namely, asynchronous and slot-level synchronous transmitters. Performance evaluation includes different sources of degradation such as multiple-access interference, noise due to optical amplification, shot noise, and thermal noise. In obtaining the performance, the mean and variance of the received signal in each of the above...
Modified differential-transfer-matrix method for solution of one-dimensional linear inhomogeneous optical structures, Article Journal of the Optical Society of America B: Optical Physics ; Volume 22, Issue 7 , 2005 , Pages 1521-1528 ; 07403224 (ISSN) ; Mehrany, K ; Rashidian, B ; Sharif University of Technology
Optical Society of American (OSA) 2005
A new formulation for the solution of wave propagation in inhomogeneous optical systems, based on the extension of conventional differential-transfer matrices into modified differential-transfer matrices, is given. In justification of our proposed method, several examples are presented, and the greater accuracy of our modified differential transfer matrices compared with that of conventional differential-transfer matrices is observed in several cases. It is also shown that the modified differential-transfer-matrix method is accurate enough even in those cases that the conventional differential-transfer-matrix method fails to yield acceptable results. © 2005 Optical Society of America
Extreme light absorption in a necking-free monolayer of resonant-size nanoparticles for photoelectrochemical cells, Article Journal of Optics (United Kingdom) ; Vol. 16, issue. 7 , 2014 ; ISSN: 20408978 ; Sharif University of Technology
Semiconductor photoelectrodes for water oxidation that absorb visible light usually have poor electronic transport properties and small optical absorption coefficients near their absorption edge. Therefore, innovative designs that lead to significant optical absorption in relatively thin layers of these compounds are highly desirable. Here, using full-field electromagnetic optical simulations, we demonstrate that a monolayer of resonant-size BiVO4 spheres can provide enhancement up to a factor of two in solar light absorption relative to dense planar layers. In this monolayer, BiVO4 spheres do not need to be interconnected; therefore, such monolayers are flexible and their fabrication...
Double-Layer TiO2 Electrodes with Controlled Phase Composition and Morphology for Efficient Light Management in Dye-Sensitized Solar Cells, Article Journal of Cluster Science ; Vol. 25, issue. 4 , 2014 , p. 1029-1045 ; Mohammadi, M. R ; Fray, D. J ; Sharif University of Technology
The light-scattering effect in the dye-sensitized solar cells (DSCs) was studied by controlling TiO2 phase composition and morphology by fabrication of double-layer cells with different arrangement modes. The starting material for preparation of TiO2 cells was synthesized by an aqueous sol-gel process. X-ray diffraction and field emission scanning electron microscopic analyses revealed that TiO2 nanoparticles had particle size ranging between 18 and 44 nm. The optical property and band gap energy of TiO2 nanoparticles were studied through UV-Vis absorption. The indirect optical band gap energy of anatase and rutile nanoparticles was found to be 3.47 and 3.41 eV, respectively. The...
Article Chemical Physics ; Volume 423 , September , 2013 , Pages 167-172 ; 03010104 (ISSN) ; Movahed, M. S ; Jafari, G. R ; Sharif University of Technology
The dynamical scattered light intensity and multiplicative cascade model was employed to characterize the anisotropic charged colloidal particles suspension during the so-called Sol-Gel transition. Generally we looked for finding a criterion to distinguish the properties of Sol and Gel states systematically. The probability density function (PDF) of the light scattering intensity shows an obvious change with proceeding of the sample aging process (during of gelation state). Our results confirmed that in the so-called Sol state, the value of non-Gaussian parameter, kW, as a function of time is larger than that of for weak-Gel or in coexistence Sol-Gel state. The number of cascades in the...
Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 31, Issue 1 , 2012 , Pages 81-87 ; 10219986 (ISSN) ; Safekordi, A. A ; Babazadeh Shareh, F ; Sharif University of Technology
The purpose of the present paper is to develop light beam method to measurement of interfacial area in a rectangular gas-liquid bubble column. Total interfacial area can be determined in bubble column filled by transparent liquid by light transmission method. According to pervious researches, the fraction of parallel light is function of interfacial area and optical path length that these two parameters imply Transmission Number or N T. The drop diameters were measured in the range of 2.2 to 5 mm, and in this range, the specific area is found to depend only upon the light transmission. Three different systems with various liquid phases have been used in this work. It had been proved that...
Article International Journal of Civil Engineering ; Volume 15, Issue 8 , 2017 , Pages 1107-1116 ; 17350522 (ISSN) ; Nassiri, H ; Sharif University of Technology
One of the frequent aspects of lawlessness at signalized intersections is red light violation (RLV). In addition to adverse effects on intersection safety, RLV can cause delay in the startup of the vehicles in the competing phase, defined as the green flow in this study. In this research, a video camera was used to collect the required data from intersections to investigate the adverse effect of RLV in the city of Esfahan, Iran. Then, by assigning a cellular network to the conflict points of the vehicles path in successive phases, the vehicles arrival times to these cells were measured and the imposed delays to the green flow were measured. The results of this study showed that the behavior...