Sharif Digital Repository

The major purpose of this research is increasing the photocatalytic activity of TiO2 nanotube arrays by doping with sodium and carbon for using in water splitting as photoanode. The synthesized TiO2 nanotubes (TNA) were characterized using FESEM (Field Emission Scanning Electron Microscope), XRD (X-ray Diffraction), DRS (Diffraction Reflection Spectroscopy) and XPS test (X-ray Photoelectron Spectroscopy) analyses. The results of FTIR and XPS confirmed the presence of sodium and carbon in the lattice of TNA as dopants. Moreover, the DRS test showed the decrease in the band gap energy of TNA from 3.20 to ∼2.88 eV; uv-visible test exhibited extension in the absorption edge of pure TiO2... 

The main purpose of this research work is to investigate the effect of nickel as metal dopant on the morphology and photocatalytic activity of TiO2 nanotube arrays synthesized in the organic electrolyte by anodizing process containing sodium carbonate as an additive (TNAS). In order to characterize the synthesized nanotubes, various analyses such as FESEM, XRD, FTIR, XPS, DRS, and EIS were applied. The results of XPS and FTIR tests evaluate the participation of sodium (Na), nickel (Ni), and carbon (C) in the lattice of nanotubes as dopants. According to the DRS and UV-visible tests results, the band gap energy of TiO2 nanotube arrays decreases from 3.20 to ~ 2.64 eV as well as the absorption... 

The main aim of this research is to improve the photocatalytic activity of TiO2 nanotubes by co-doping with copper and sodium for application in the water splitting process as a photoanode. The doping was performed simultaneously to the anodizing process through a single-step treatment. The synthesized TiO2 nanotube array (TNA) was characterized by applying FESEM (Field Emission Scanning Electron Microscopy), XRD (X-ray Diffraction), DRS (Diffraction Reflection Spectroscopy) and XPS (X-ray Photoelectron Spectroscopy) analyses. The results of XPS analysis proved the presence of copper with valence (2+) and carbon and sodium with valence (1+). Moreover, DRS tests showed a reduction in the band... 

Metropolitan areas consist of complicated systems of interconnected infrastructures that are highly interdependent. Disruption of one infrastructure may induce disruption in other interconnected ones. The results from analysis of one infrastructure as an independent system are not realistic without considering the behavior of other interconnected infrastructures. Consequently, the study of the interdependencies among critical infrastructures is important for addressing the cascading effects of a failed infrastructure on the entire network to properly model its performance and help the disaster management team in decision making. In this study, the extended Petri net and Markov chain have... 

Purpose: The purpose of this study is to present a comprehensive hydrothermal analysis on an inclined mini-channel using numerical and experimental techniques. The fin array acts as heat source within the channel, and a wavy wall located at the top of the channel is heat sink. The side walls are insulated with curved profiles. Also, the channel is inclined with four known inclination angles. To solve the governing equations, the dual-multi-relaxation-time lattice Boltzmann method with D2Q9 and D2Q5 lattice models for flow and temperature fields is used, respectively. Also, the channel is filled with SiO2-glycol nanofluid. Design/methodology/approach: Identifying the behavior of a thermal... 

Purpose: The nanofluid flow and heat transfer within a heat exchanger, with different thermal arrangements of internal active bodies, are investigated. Design/methodology/approach: For the numerical simulations, the lattice Boltzmann method is utilized. The KKL model is used to predict the dynamic viscosity of CuO-water nanofluid. Furthermore, the Brownian method is taken account using this model. The influence of shapes of nanoparticles on the heat transfer performance is considered. Findings: The results show that the platelet nanoparticles render higher average Nusselt number showing better heat transfer performance. In order to perform comprehensive analysis, the heatline visualization,... 

A new equation of state based on the Statistical Associating Fluid Theory (SAFT) is presented to study the phase behavior of associating and non-associating fluids. In the new equation of state, the hard sphere contribution to compressibility factor of the simplified version of the SAFT (SSAFT) is replaced with that proposed by Ghotbi and Vera. The Ghotbi-Vera SSAFT (GV-SSAFT) was also extended to study the phase behavior of associating and non-associating mixtures. The GV-SSAFT like the SSAFT equation of state has three adjustable segment parameters for non-associating fluids and five parameters for associating fluids. The experimental data of liquid densities and vapor pressures for pure... 

The present work aims to interpret the mass and heat transferal flow through Darcy Forchheimer porous medium involving, simultaneously, microorganisms and nanoparticles. The involvement of gyrotactic microorganisms in the flow of nanoparticles reinforces the thermal characteristics of several energy systems. The amalgamation of microorganisms (microbes) in the nanofluids not only enhances the thermal properties of the fluid but it also causes the stability in the flow. Some other prominent effects such as chemical reaction and heat generation have also been taken into account. The reduced form of the governing model equations is further simplified in order to obtain the algebraic system of... 

The numerical modeling of natural convection fluid flow and heat transfer in a quarter of gearwheel-shaped heat exchanger is carried out. The heat exchanger is included with internal active square bodies. These bodies have hot and cold temperatures with different thermal arrangements. Three different thermal arrangements are considered and showed with Case A, Case B and Case C. The CuO-water nanofluid is selected as operating fluid. The Koo-Kleinstreuer-Li (KKL) correlation is utilized to estimate the dynamic viscosity and thermal conductivity. In addition, the shapes of nanoparticles are taken account in the analysis. The Rayleigh number, nanoparticle concentration and thermal arrangements... 

In this work, in order to improve drawbacks of bare (pure) carbon graphite nitride (g-C3N4), phosphorus-selenium doped carbon nitride was synthesized to enhance light absorption in visible region. Then Ag nanoparticles loaded onto P-Se co-doped g-C3N4, as a result, the surface plasmonic resonance effect was created. In addition, the photocatalytic activity of samples was improved by suppression of charge carriers’ recombination. Synthesized photocatalyst was characterized by XRD, FT-IR, EDS, BET, XPS, FE-SEM, ICP, TEM, and DRS and PL analysis. All prepared samples were applied in the degradation of Rhodamine B as an azo dye under irradiation of visible light. According to the obtained... 

Secure routing is a major key to service maintenance in ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. As a result of the resource limitations in such networks nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a novel data redirection method to mitigate the impact of node misbehavior on network... 

This book focuses on a central question in the field of complex systems: Given a fluctuating (in time or space), uni- or multi-variant sequentially measured set of experimental data (even noisy data), how should one analyse non-parametrically the data, assess underlying trends, uncover characteristics of the fluctuations (including diffusion and jump contributions), and construct a stochastic evolution equation?
Here, the term "non-parametrically" exemplifies that all the functions and parameters of the constructed stochastic evolution equation can be determined directly from the measured data.
The book provides an overview of methods that have been developed for the analysis of... 

Consider the parameter Λ(G) = |E(G)| - |V(G)|(k - 1) + (k2) for a k-chromatic graph G, on the set of vertices V(G) and with the set of edges E(G). It is known that Λ(G)≥0 for any k-chromatic uniquely vertex-colourable graph G (k-UCG), and, S.J. Xu has conjectured that for any k-UCG, G, Λ(G) = 0 implies that cl(G) = k; in which cl(G) is the clique number of G. In this paper, first, we introduce the concept of the core of a k-UCG as an induced subgraph without any colour-class of size one, and without any vertex of degree k - 1. Considering (k, n)-cores as k-UCGs on n vertices, we show that edge-minimal (k, 2k)-cores do not exist when k ≥ 3, which shows that for any edge-minimal k-UCG on 2k...