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diffusion-reflection
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Expanding Visibility Polygons by Mirrors
, M.Sc. Thesis Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
We consider extending the visibility polygon of a given point q inside a simple polygon by converting one or some of the edges to mirrors. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm that checks whether a given segment inside a simple polygon is visible by a given point q via a mirror-edge, and finds all such edges. And we prove that finding edges to add exactly k unit squares to the visibility polygon of a query point q in most cases is NP-complete and its minimization is NP-hard. These cases contain single and muliple, either with secular or difuse reflections. Moreover,...
Visibility Via Reflection
, Ph.D. Dissertation Sharif University of Technology ; Ghodsi, Mohammad (Supervisor)
Abstract
This document deals with the following results in details:Given a simple polygon P with $n$ vertices, the visibility polygon (VP) of a point q, or a segment pq inside P can be computed in linear time. It is known that the visibility polygon of a point inside a polygon in the presence of a mirror can be computed in linear time. We propose a linear time algorithm to extend the VP of a viewer (point or segment) by converting some edges of P into mirrors (reflecting-edges with specular type of reflection), such that a given non-visible segment uw can also be seen from the viewer.Various definitions for the visibility of a segment, such as weak, strong, or complete visibility, are considered. Our...
Highly efficient of molybdenum trioxide-cadmium titanate nanocomposites for ultraviolet light photocatalytic and antimicrobial application: Influence of reactive oxygen species
, Article Journal of Photochemistry and Photobiology B: Biology ; Volume 191 , 2019 , Pages 75-82 ; 10111344 (ISSN) ; Hosseini, M ; Fakhri, A ; Salari Rad, S ; Hadadi, T ; Nobakht, N ; Sharif University of Technology
Elsevier B.V
2019
Abstract
In the present work we report the enhanced UV light photocatalytic performance of cadmium titanate photocatalyst by MoO 3 for Drug pollutant degradation. The nano photocatalyst sample was synthesized employing the Pechini-ultrasonic-hydrothermal route. Therefore, the nano photocatalyst were characterized by various analytical devices. The wide scan X-ray photoelectron spectral study confirmed the MoO 3 in the CdTiO 3 matrix. The crystallite size calculated with the Debye-Scherrer equation (55.4, 57.0, 61.2 and 63.1 nm for pure CdTiO 3 , MoCdTi-0, MoCdTi-1, and MoCdTi-2 nanocomposites, respectively). SEM micrographs revealed nanowire morphology indicated the crystalline nature of the sample....
The effect of multiwalled carbon nanotubes and activated carbon on the morphology and photocatalytic activity of TiO2/C hybrid materials
, Article Catalysis Science and Technology ; Volume 1, Issue 2 , 2011 , Pages 279-284 ; 20444753 (ISSN) ; Ghasemi, S ; Gholami, M. R ; Sharif University of Technology
2011
Abstract
TiO2 nanoparticles supported on activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) were prepared by the sol-gel method using ultrasonic irradiation. All the prepared samples were calcined at different temperatures and characterized by X-ray diffraction, nitrogen adsorption/desorption isotherms, scanning electron microscopy, transmission electron microscopy and diffuse reflectance spectroscopy. The effects of size and type of carbon on the morphology and photocatalytic activity of the resulting hybrid materials were investigated. The results showed that a decrease in the size of the carbon led to a decrease in size of TiO2 nanoparticles. Both AC and MWCNTs retarded the...
Impact of chromium doping on physical, optical, electronic and photovoltaic properties of nanoparticle TiO2 photoanodes in dye-sensitized solar cells
, Article New Journal of Chemistry ; Volume 41, Issue 23 , 2017 , Pages 14516-14527 ; 11440546 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
Royal Society of Chemistry
2017
Abstract
Herein, we report the impact of chromium doping on the physical properties, electronic band structure and photovoltaic characteristics of their corresponding devices based on dye-sensitized solar cells (DSCs). Different DSCs with various compositions of the photoanode electrodes are fabricated to study their optical, structural, conduction band edge, donor density, depth of trap states and photoelectrochemical properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), Mott-Schottky capacitance analysis, chemical capacitance and electrochemical impedance spectroscopy (EIS) measurements. For such studies, the Cr-doped...
Photocatalytic activity of CuO nanoparticles incorporated in mesoporous structure prepared from bis(2-aminonicotinato) copper(II) microflakes
, Article Transactions of Nonferrous Metals Society of China (English Edition) ; Volume 25, Issue 11 , November , 2015 , Pages 3634-3642 ; 10036326 (ISSN) ; Akhavan, O ; Bijanzad, K ; Sharif University of Technology
Nonferrous Metals Society of China
2015
Abstract
An easy method for preparing CuO nanoparticles incorporated in a mesoporous structure was presented based on the thermal decomposition of a copper complex. The novel copper coordination compound of [Cu(anic)2]·0.75H2O (anic= 2-aminonicotinate) with the microflake morphology was synthesized through the reaction of 2-aminonicotinic acid (Hanic) and copper(II) nitrate. Using elemental analysis and Fourier transform infrared (FTIR) spectroscopy, the chemical composition of CuC12H11.5N4O4.75 was proposed. Calcination process at 550 °C for 4 h transformed the microflakes into CuO nanoparticles incorporated in a mesoporous structure. The FTIR peaks assigned to 2-aminonicotinate were completely...
Efficient dye-sensitized solar cells based on carbon-doped TiO2 hollow spheres and nanoparticles
, Article Journal of Materials Science: Materials in Electronics ; Volume 26, Issue 11 , 2015 , Pages 8863-8876 ; 09574522 (ISSN) ; Mohammadi, M. R ; Sharif University of Technology
Springer New York LLC
2015
Abstract
Different structures of TiO2 photoelectrodes are fabricated with various arrangement modes of the layers. TiO2 nanoparticles, synthesized by stabilizing agent free non-hydrolytic sol–gel method, are employed as the under layer, whereas carbon-doped TiO2 hollow spheres, prepared by hydrothermally grown carbon template, are used as the scattering layer of solar cells. The nanoparticles (22 nm) have anatase structure, while 300–700 nm hollow spheres show mixtures of anatase and rutile phases. X-ray photoelectron spectroscopy confirms that carbon is doped into TiO2 hollow spheres, resulting in a decrease in band gap energy in the range 2.96–3.13 eV compared with 3.04 eV band gap energy for the...
Preparation and characterization of visible light sensitive nano titanium dioxide photocatalyst
, Article Scientia Iranica ; Volume 19, Issue 6 , December , 2012 , Pages 1626-1631 ; 10263098 (ISSN) ; Kazemeini, M ; Fattahi, M ; Sharif University of Technology
2012
Abstract
Dye sensitizers loaded on TiO2 decrease the electron excitation energy, thereby improving the photocatalytic performance by causing an increase in sensitivity under visible light irradiation. Three dye sensitizer precursors, Mordant Orange 1, N3 (red dye) and Cobalt (II) Phthalocyanine Tetrasulfonate (CoPcTs), were utilized to load the photocatalyst. The rate of the electron trapping process on platinum is clearly compatible with the migration rate of boundary electrons. Consequently, the migration of boundary electrons from the conduction band towards electron acceptors is increased by loading platinum onto the titanium dioxide. In this research, TiO2 was synthesized from a titanium...
Nitrogen-doped submicron-size TiO2 particles as bifunctional light scatterers in dye-sensitized solar cells
, Article Applied Physics A: Materials Science and Processing ; Volume 119, Issue 4 , 2015 , Pages 1283-1290 ; 09478396 (ISSN) ; Mohammadpour, R ; Iraji zad, A ; Taghavinia, N ; Sharif University of Technology
Springer Verlag
2015
Abstract
The structural, electrical, optical, and photovoltaic properties of aggregated submicron nitrogen-doped TiO2 particles (NTiO2) and the influence of utilizing them, in comparison with undoped ones, as the light-scattering layer of dye-sensitized solar cells were investigated. Field emission scanning electron microscope, X-ray diffraction, and diffuse reflectance spectra showed that both type samples have similar morphology, crystal phase, and scattering feature. Moreover, photoluminescence, Mott–Schottkey, and photovoltaic characteristics such as IMPS/IMVS and charge extraction analysis indicated that the NTiO2 layer is an efficient scatterer in two aspects: enhancement of light-harvesting...
Silver nano-islands on glass fibers using heat segregation method
, Article Materials Chemistry and Physics ; Volume 113, Issue 1 , 2009 , Pages 63-66 ; 02540584 (ISSN) ; Taghavinia, N ; Sharif University of Technology
2009
Abstract
A new method for fabrication of silver nano-islands on glass fibers using a top-down process is introduced. A thin layer of silver chemically coated on the surface of the glass fibers evolves into silver islands by heat treatment. The effect of the concentration of the initial solution and the temperature were investigated. Segregation was more clearly observed for lower solution concentrations and higher temperatures. The temperature of 500 °C was found optimum where separated islands form. At higher temperatures, the coagulation and burial of silver islands occur. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and diffused reflectance spectroscopy (DRS) were...
Simply synthesized TiO2 nanorods as an effective scattering layer for quantum dot sensitized solar cells
, Article Chinese Physics B ; Vol. 23, issue. 4 , 2014 ; Zad, A. I ; Molaei, M ; Sharif University of Technology
Abstract
TiO2 nanorod layers are synthesized by simple chemical oxidation of Ti substrates. Diffuse reflectance spectroscopy measurements show effective light scattering properties originating from nanorods with length scales on the order of one micron. The films are sensitized with CdSe quantum dots (QDs) by successive ionic layer adsorption and reaction (SILAR) and integrated as a photoanode in quantum dot sensitized solar cells (QDSCs). Incorporating nanorods in photoanode structures provided 4- to 8-fold enhancement in light scattering, which leads to a high power conversion efficiency, 3.03% (Voc = 497 mV, Jsc = 11.32 mA/cm2, FF = 0.54), in optimized structures. High efficiency can be obtained...
Role of CdO addition on the growth and photocatalytic activity of electrospun ZnO nanofibers: UV vs. visible light
, Article Applied Surface Science ; Vol. 298, issue , April , 2014 , pp. 147-154 ; ISSN: 01694332 ; Pourjavadi, A ; Moshfegh, A. Z ; Sharif University of Technology
Abstract
(ZnO)1-x(CdO)x nanofibers were fabricated via electrospinning of polymer precursor by subsequent annealing in air. Field emission scanning electron microscopy (FESEM) showed the smooth and beadless nanofibers and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed the ZnO hexagonal and the CdO cubic structure. Diffuse reflectance spectroscopy (DRS) showed the band gap energy reduction by increasing the amount of CdO in (ZnO)1-x(CdO)x nanofibers that resulted in the photocatalytic activity under the visible light for dye degradation. Under the UV light CdO acted as both electron and hole sink in the (ZnO) 1-x(CdO)x nanofibers and a possible photocatalytic activity...
Synergism of oxygen vacancy and carbonaceous species on enhanced photocatalytic activity of electrospun ZnO-carbon nanofibers: Charge carrier scavengers mechanism
, Article Applied Catalysis A: General ; Volume 466 , September , 2013 , Pages 153-160 ; 0926860X (ISSN) ; Shivaee, H. A ; Pourjavadi, A ; Moshfegh, A. Z ; Sharif University of Technology
2013
Abstract
Novel ZnO-carbon and ZnO nanofibers were fabricated by electrospinning of polymer precursor followed by subsequent annealing in nitrogen and air, respectively. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) indicated the smooth and beadless nanofibers with wurtzite crystal structure. X-ray photoelectron spectroscopy (XPS) showed the presence of oxygen vacancies (VO) and chemisorbed O2 on the surface of the samples. Band gap narrowing of the ZnO-carbon nanofibers in comparison to ZnO were measured by diffuse reflectance spectroscopy (DRS). Photo-degradation of azo dye under the UV and visible light was evaluated and ZnO-carbon showed an enhancement in...
Photocatalytic TiO2@MIL-88A (Fe)/polyacrylonitrile mixed matrix membranes: Characterization, anti-fouling properties, and performance on the removal of natural organic matter
, Article Chemosphere ; Volume 302 , 2022 ; 00456535 (ISSN) ; Mehdipour, M. H ; Fotovat, F ; Mousavi, S. A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Photocatalytic membrane reactors (PMRs), coupling photocatalysts and membranes in a single system, have shown a considerable potential to reduce membrane fouling, which is one of the major drawbacks of using membranes to treat water and wastewater. In this study, the visible light-activated photocatalysts were incorporated into the polyacrylonitrile (PAN) casting solution to synthesize the photocatalytic composite membranes. The physicochemical properties and the morphology of the membranes and photocatalysts were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction analysis (XRD), ultraviolet–visible diffuse reflectance...
Permeability correlation with porosity and Knudsen number for rarefied gas flow in Sierpinski carpets
, Article Journal of Natural Gas Science and Engineering ; Volume 56 , 2018 , Pages 549-567 ; 18755100 (ISSN) ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In recent years, application of porous media is highlighted among researchers due to their wide range of usability in micro-scale problems, such as gas reservoirs, micro-filtering, heat exchangers, etc. With this respect, the accurate description of flow behavior using governing equations based on the continuum assumption is not valid since the mean free path is comparable to the characteristics length of the problem. For this purpose, a simple methodology for diffusion reflection boundary condition is developed and validated for two valuable benchmarks, namely micro-channel flow and fractal porous media, where the results were in good agreement with literature. Then, pore-scale simulation...
Pore-scale modeling of rarefied gas flow in fractal micro-porous media, using lattice Boltzmann method (LBM)
, Article Journal of Thermal Analysis and Calorimetry ; 2019 , Pages 1-12 ; 13886150 (ISSN) ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
Springer Netherlands
2019
Abstract
Due to the widespread use of rarefied gas flow in micro-porous media in industrial and engineering problems, a pore-scale modeling of rarefied gas flow through two micro-porous media with fractal geometries is presented, using lattice Boltzmann method. For this purpose, square- and circular-based Sierpinski carpets with fractal geometries are selected due to their inherent behavior for real porous media. Diffusive reflection slip model is used and developed for these porous media through this study. With this respect, the planar Poiseuille flow is selected as a benchmark and validated with the literature. The effect of Knudsen number (Kn) on the permeability is investigated and compared in...
Pore-scale modeling of rarefied gas flow in fractal micro-porous media, using lattice Boltzmann method (LBM)
, Article Journal of Thermal Analysis and Calorimetry ; Volume 135, Issue 3 , 2019 , Pages 1931-1942 ; 13886150 (ISSN) ; Salimi, M. R ; Taeibi Rahni, M ; Sharif University of Technology
Springer Netherlands
2019
Abstract
Due to the widespread use of rarefied gas flow in micro-porous media in industrial and engineering problems, a pore-scale modeling of rarefied gas flow through two micro-porous media with fractal geometries is presented, using lattice Boltzmann method. For this purpose, square- and circular-based Sierpinski carpets with fractal geometries are selected due to their inherent behavior for real porous media. Diffusive reflection slip model is used and developed for these porous media through this study. With this respect, the planar Poiseuille flow is selected as a benchmark and validated with the literature. The effect of Knudsen number (Kn) on the permeability is investigated and compared in...
Characterisation of nanocrystalline sulfated titania modified with transition metals and aluminum as solid acids for esterification
, Article Progress in Reaction Kinetics and Mechanism ; Volume 41, Issue 1 , 2016 , Pages 57-66 ; 14686783 (ISSN) ; Abolhasani, E ; Ghasemi, S ; Sharif University of Technology
Science Reviews 2000 Ltd
2016
Abstract
TiO2, transition metal (Cr, Mn, Fe, Co, Ni, Cu, and Zn)- and aluminum-doped TiO2 nanoparticles were prepared by the sol-gel technique. The sulfated catalysts were prepared by the impregnation method with H2SO4 solution. The catalysts were characterised by X-ray diffraction (XRD), BET surface area measurement, diffuse reflectance spectroscopy (DRS), and Fourier transform infrared (FTIR) techniques. The sulfate content of the metal-incorporated samples was considerably higher than for SO4 2-/TiO2. The metal doping brought about a considerable reduction in the extent of sulfate loss from the catalyst surface due to the wide dispersion on the surface. The SO4 2-/TiO2 and SO4 2-/M/TiO2...
Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks for efficient photodegradation of the environmental pollutants and pathogenic bacteria
, Article Journal of Inorganic and Organometallic Polymers and Materials ; Volume 29, Issue 4 , 2019 , Pages 1314-1323 ; 15741443 (ISSN) ; Asgarpour, F ; Akbari, A ; Eftekhari Sis, B ; Lammel, G ; Sharif University of Technology
Springer New York LLC
2019
Abstract
Hexagonal core–shell SiO2[–MOYI]Cl–]Ag nanoframeworks were synthesized via surface modification of hexagonal silica nanoparticles prepared from perlite (EP) as a cheap and abundant raw material. The prepared samples were well characterized by X-ray diffraction powder (XRD), energy dispersive X-ray (EDX), diffuse reflectance spectroscopy (DRS), Brunauer–Emmett–Teller (BET) specific surface area analysis, fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The XRD patterns confirmed that Ag and AgCl crystalline phases were successfully loaded on the surface. The TEM images were also implied that the...
Free radical graft polymerization of 2-hydroxyethyl methacrylate and acrylic acid on the polysulfone membrane surface through circulation of reaction media to improve its performance and hemocompatibility properties
, Article Journal of Membrane Science ; Volume 564 , 2018 , Pages 762-772 ; 03767388 (ISSN) ; Mousavi, S. A ; Abdekhodaie, M. J ; Sadeghi, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this study, a new facile and cost effective method is used to modify polysulfone membrane surface in order to improve the hydrophilicity, antifouling, and blood compatibility. This modification was performed by adding two functional monomers on the dialysis membrane. Polysulfone (PSF) membranes containing polyvinylpyrrolidone were prepared via phase inversion technique. In the next step, free radical polymerization combined with surface polymerization was used to introduce acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) onto the polysulfone membrane surface via circulation of initiator and monomer solutions across the membrane surface, respectively. Various monomer concentrations...