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conductivity
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Analytical results on coherent conductance in a general periodic quantum dot: Transfer matrix method
, Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 28, Issue 2 , 2005 , Pages 150-161 ; 13869477 (ISSN) ; Shokri, A. A ; Esfarjani, K ; Sharif University of Technology
2005
Abstract
In this work, we study the conductance of a general periodic quantum dot (QD) attached to ideal semi-infinite uniform metallic leads (nanocrystals), fully analytically. We propose a new general formula which relates conductance to transfer matrix (TM) for an isolated cell in the periodic dot. The equation describes exactly the dependence of the transmission coefficient (TC) on Fermi energy, dot-size, dot-lead coupling, and gate voltage for an arbitrary periodic dot. Then, we derive a nonlinear equation which gives the resonance, bound, and surface state energies. Finally, the TC has been calculated for gapless, single, and double gap models exactly. Moreover, we have also calculated the...
Pragmatic Semantics
, M.Sc. Thesis Sharif University of Technology ; Izadi, Mohammad (Supervisor)
Abstract
Three distinct areas in linguistic studies are typically considered, namely, syntax, semantics and pragmatics. Each category has a specific realm and deals with special linguistic phenomena. Presenting exact definition and clarification of the corresponding boundaries of each area is considered in both linguistics and philosophy of language. In order to explain the “meaning” for sentences of a language, this issue turns out to be vital. Representing the definition and evaluating the domain of each area, is the objective of the first chapter. In chapter two, some important semantic theories have been investigated. Since at first one semantic theory ought to clear its position about reference,...
Impedance analysis of growth and morphology of electropolymerized polypyrrole nanocomposites [electronic resource]
, Article Journal of New Materials for Electrochemical Systems ; 2014, Volume 17, Number 2 ; Sadrnezhaad, S. K ; Sharif University of Technology
Abstract
Pure polypyrrole (PPy), PPy/Al2O3 and PPy/SiO2 nanocomposites synthesized galvanostatically using different polymerization charges. Electrochemical impedance measurements of pure polypyrrole revealed that the film thickness affected the impedance responses. The characteristic frequencies vs. film thickness that obtained using Cole-Cole plots showed that electrodeposition mechanism changed from 3D to 1D after nuclei overlapping for pure PPy. Analysis of the nanocomposites impedance spectrums revealed no changes during the film growth, i.e. deposition continues 3D even after nuclei overlapping. Scanning electron microscopy (SEM) confirmed the impedance results and showed that the morphology of...
Experimental and theoretical investigation of drying of Green Peas in a Fluidized Bed Dryer of inert particles assisted by Infrared heat source
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 32, Issue 1 , 2013 , Pages 83-94 ; 10219986 (ISSN) ; Mowla, D ; Safekordi, A. A ; Sharif University of Technology
2013
Abstract
Drying of green peas in a Fluidized Bed Dryer (FBD) with inert particle, heated by combined sources of hot air and InfraRed (IR) radiation, has been experimentally and theoretically studied. For this purpose, an experimental set up was constructed. This setup was composed of a cylindrical bed dryer containing some inert particles which are fluidized by hot air. Some infrared lamps were also placed around the bed for heating assistance. A sample of green pea was hung in the fluidized bed and its moisture content, surface and central temperature were measured with time. A mathematical model, based on the two layers concept of penetration and conduction was also proposed for this process. The...
Conductive polymer-based microextraction methods: A review
, Article Analytica Chimica Acta ; Volume 767, Issue 1 , March , 2013 , Pages 1-13 ; 00032670 (ISSN) ; Ayazi, Z ; Naderi, M ; Sharif University of Technology
2013
Abstract
Conductive polymers (CPs) are classified as materials which exhibit highly reversible redox behavior and the unusual combined properties of metal and plastics. CPs, due to their multifunctionality, ease of synthesis and their stability, have attracted more attentions in different fields of research, including sample preparation. CPs along with several commercial hydrophilic sorbents, are alternative to the commercially available hydrophobic sorbents which despite their high specific surface areas, have poor interactions and retentions in the extraction of polar compounds. This review covers a general overview regarding the recent progress and new applications of CPs toward their synthesis...
Effect of water-cement ratio on abrasive strength, porosity and permeability of nano-silica concrete
, Article World Applied Sciences Journal ; Volume 17, Issue 8 , 2012 , Pages 929-933 ; 18184952 (ISSN) ; Peroti, S ; Rahmani, K ; Rahemi, L ; Sharif University of Technology
2012
Abstract
Today, due to rapid development of construction of hydraulic structures like dams, the constituent material used in concrete and its durability in these kinds of structures has gained dominant interests and importance. One of the important factors of concrete durability in these structures is its resistance against abrasion due to crash of particles carried out as hydrated crystalline particulate matter. To enhance the abrasion resistance of concrete, different methods have been offered and investigated by many research3ers/ The aim of present article is to investigate the important parameter i.e. water-cement ratio on abrasive strength, porosity and the coefficient of hydraulic conductivity...
Investigation and modeling of the thermal conductivity of PP/clay nanocomposites and PP/MWCNT nanocomposites
, Article E-Polymers ; Dec , 2010 ; 16187229 (ISSN) ; Golzary, A ; Sharif University of Technology
2010
Abstract
In this study, polypropylene/clay nanocomposites were prepared by melt blending method and their thermal conductivity and the thermal conductivity of polypropylene/multi-wall carbon nanotube (MWCNT) nanocomposites were investigated and modeled. It is found that the thermal conductivity of the PP/Clay and PP/MWCNT nanocomposites is increased with increasing temperature. The thermal conductivity of the nanocomposites is improved due to incorporation of nanoclay and MWCNT compared with pure PP matrix
Numerical analysis of heat conduction treated with highly conductive copper oxide nanoparticles In porous media
, Article Special Topics and Reviews in Porous Media ; Volume 7, Issue 2 , 2016 , Pages 149-160 ; 21514798 (ISSN) ; Rabbani, A ; Ayatollahi, S ; Taghikhani, V ; Sharif University of Technology
Begell House Inc
2016
Abstract
In this paper, the effect of highly conductive copper oxide nanoparticles on the effective thermal conductivity (ETC) of rock samples was mathematically investigated. To solve the governing conservation equations for the ETC a commercial finite element package (COMSOL Multiphysics) was used. It should be stressed that the single-phase approach was employed to mathematically model the effect of nanofluid on the heat transfer improvement. The computational geometry of the rock samples was obtained by analyzing the microscopic images of the limestone rock samples. The results obtained from the mathematical modeling of the rock samples showed that the conductive heat transfer through porous...
Copper oxide nano-fluid stabilized by ionic liquid for enhancing thermal conductivity of reservoir formation: Applicable for thermal enhanced oil recovery processes
, Article Chemical Industry and Chemical Engineering Quarterly ; Volume 22, Issue 2 , 2016 , Pages 211-225 ; 14519372 (ISSN) ; Hezave, A. Z ; Sabbaghi, S ; Ayatollahi, S ; Sharif University of Technology
CI and CEQ
2016
Abstract
Since oil reservoirs are limited and energy demand is increasing, seeking for high efficient EOR processes or enhancing the efficiency of current proposed EOR methods for producing trapped oil from reservoirs are highly investigated. As a way out, it is possible to couple the EOR and nanotechnology to utilize the efficiency of both methods together. Regarding this possibility, in the present study, in the first stage of investigation stable and uniform water-based solution of nano-sized particles of copper oxide with different concentrations (0.01–0.05 M) were prepared and then injected into the core samples. In the first stage, the effects of different surfactants with respect to their...
Nitrogen-doped carbon nanotubes for heat transfer applications: Enhancement of conduction and convection properties of water/N-CNT nanofluid
, Article Journal of Thermal Analysis and Calorimetry ; Volume 138, Issue 1 , 2019 , Pages 69-79 ; 13886150 (ISSN) ; Askari, S ; Ghasemy, E ; Rashidi, A ; Ettefaghi, E ; Sharif University of Technology
Springer Netherlands
2019
Abstract
In this research, it is aimed to enhance the heat transfer properties of the carbon nanotubes through nitrogen doping. To this end, nitrogen-doped multiwall carbon nanotubes (N-CNTs) were synthesized via chemical vapor deposition method. For supplying carbon and nitrogen during the synthesis of N-CNTs, camphor and urea were used, respectively, at 1000 °C over Co–Mo/MgO nanocatalyst in a hydrogen atmosphere. N-CNTs with three different nitrogen loadings of 0.56, 0.98, and 1.38 mass% were synthesized, after which, water/N-CNT nanofluids of these three samples with concentrations of 0.1, 0.2, and 0.5 mass% were prepared. To obtain a stable nanofluid, N-CNTs were functionalized by nitric acid...
Analytical modeling of phosphorene-based NO2 gas sensor
, Article International Journal of Modern Physics B ; Volume 33, Issue 14 , 2019 ; 02179792 (ISSN) ; Karamdel, J ; Ahmadi, M. T ; Berahman, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2019
Abstract
Phosphorene is a new two-dimensional material that has great potentials in Nano electronic application, so it has attracted more researchers' attention nowadays. Indeed, phosphorene is an interesting material in gas sensing, due to its high surface-to-volume ratio and its carrier mobility. Many studies have been reported on phosphorene gas sensing, but there is not enough study on analytical modeling of phosphorene gas sensing properties. In this research, by adopting data from experimental NO2-based gas sensor, an analytical model of the phosphorene gas sensing behavior is presented. Then, the experimental results of NO2 gas sensing are compared with the proposed model and acceptable...
Obtaining the effect of sewage network on groundwater quality using MT3DMS code: Case study on Bojnourd plain
, Article Groundwater for Sustainable Development ; Volume 11 , October , 2020 ; Rahimi, H ; Kamaliardakani, M ; Salim, R ; Sharif University of Technology
Elsevier B. V
2020
Abstract
Groundwater contamination is a significant problem related strongly to both the protection of the environment and the need for water. In the present study, groundwater quality was investigated in the Bojnourd watershed. The Bojnourd watershed is located in the northeast of Iran, which covers 65.5 km2 of the North Khorasan province area. There are 11 extracting wells in the region. Annual water extraction from the alluvial aquifer in the area is used for agriculture, drinking, sanitary and industrial consumptions. In this research, groundwater quantity modeling, including calibration and verification by GMS software, had been performed. In the quality modeling stage, pollution contours for...
Analysis of the effect of kevlar fibers on abrasion resistance, flexural strength and hydraulic conductivity coefficient of silica fume concretes
, Article Iranian Journal of Science and Technology - Transactions of Civil Engineering ; Volume 44, Issue 2 , 2020 , Pages 669-674 ; Piroti, S ; Ghameian, M ; Sharif University of Technology
Springer
2020
Abstract
Reinforcing fiber and silica fume of concrete can be considered as one of the most widely used additives. In this study, with a review of the history and advantages of using silica fume and polypropylene fibers in concrete, 380 concrete laboratory samples were constructed, of which 25 mixing designs with water–cement ratio of 0.35 and fiber content of 0.2, 0.3, 0.4 and 0.5 of concrete volume and 7% silica fume were prepared according to the ACI standard in their manufacturing. In the present research, samples of Kevlar fiber containing silica fume were tested under flexural strength, abrasion resistance and hydraulic conductivity coefficient. According to achieved results, the optimum amount...
Efficient carrier utilization induced by conductive polypyrrole additives in organic-inorganic halide perovskite solar cells
, Article Solar Energy ; Volume 207 , 2020 , Pages 1300-1307 ; Balkan, T ; Solati, N ; Halali, M ; Askari, M ; Kaya, S ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The morphology of the perovskite layer, the effective extraction of the charge carriers, and their transport are the main factors determining the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). In this work, we demonstrated that the geometric and electronic structures of the PSCs could be modified by using a conductive polymer additive in the lead (Pb) halide layer prepared by a two-step deposition method. Polypyrrole (PPy) as a conductive polymer is used in the perovskite layers which could increase the PCE of CH3NH3PbI3-xClx mixed-halide PSCs. By adding an optimized amount of PPy, PCE has been raised from 10.4 to 13.2%. PPy acts as a conductive channel facilitating...
Plasmonic propagation modes of a structured two-dimensional conducting interface
, Article Journal of Optics A: Pure and Applied Optics ; Volume 10, Issue 2 , 2008 ; 14644258 (ISSN) ; Khorasani, S ; Hosseini, A ; Mehrany, K ; Rashidian, B ; Adibi, A ; Sharif University of Technology
2008
Abstract
In this paper, we present a detailed analysis of a two-dimensional lossless and non-dispersive structured conducting interface, which is approximated by a two-dimensional ideal one-component plasma-like conducting sheet enclosed by two isotropic dielectrics. We present a Green's function formalism to analyze the propagation of surface plasmons and find new expressions. We also present analytical extensions of the approach to include loss, and discuss the results and applications of the theory. We study the symmetry properties of eigenmodes and show that the symmetries of the eigenmodes at high-symmetry points of the Brillouin zone are similar to those of the E-polarization eigenmodes of a...
The effect of local thermal non-equilibrium on impulsive conduction in porous media
, Article International Journal of Heat and Mass Transfer ; Volume 50, Issue 15-16 , 2007 , Pages 3244-3249 ; 00179310 (ISSN) ; Noghrehabadi, A. R ; Rees, D. A. S ; Sharif University of Technology
2007
Abstract
We examine the effect of local thermal non-equilibrium on the evolution of the stagnant temperature field in a semi-infinite porous medium. When local thermal equilibrium pertains, the temperature field which is induced by a step change in the temperature of a plane boundary is given by the classical conduction solution involving the complementary error function. When thermal local equilibrium does not apply, then conduction takes place more rapidly in one phase than in the other, although local thermal equilibrium is always approached as time increases. This note examines the evolution of the temperature field in each phase in detail using numerical methods, and the numerical solutions are...
Investigation of a new mean temperature-dependent potential energy function for methane and its use for the prediction of transport properties
, Article Molecular Physics ; Volume 105, Issue 10 , 2007 , Pages 1453-1463 ; 00268976 (ISSN) ; Parsafar, G. A ; Goharshadi, E. K ; Sharif University of Technology
2007
Abstract
In this work an improved mean potential energy function for the interaction of an isolated pair of methane is obtained, from which the non-equilibrium properties of methane at zero pressure limit are calculated, accurately. The potential energy function of 21 different fixed orientations of (CH4)2 dimer has been obtained via the coupled cluster method. In order to obtain a mean potential energy function, the Boltzmann-average of the obtained potentials of the selected fixed orientations has been used. Unlike the full potential energy surface with the angle-dependent, the parameters of the mean potential are found to be temperature-dependent. The mean potential energy function is fitted well...
The role of powder preparation route on physical and mechanical properties of Cu-rGO bulk nanocomposites
, Article Materials Today Communications ; Volume 28 , 2021 ; 23524928 (ISSN) ; Abachi, P ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
To study the effect of the production method on physical and mechanical properties of Cu-rGO nanocomposites, nanocomposite powder samples with rGO content of 0.25–1 wt.% were prepared via combined routes of molecular-level mixing (MLM) and powder metallurgy (PM). Spark plasma sintering (SPS) was applied to consolidate nanocomposite powders with better control on the grain size. According to the specific electrical resistivity measurements, microhardness, and pin-on-disk wear tests, the sample with 0.5 wt.% rGO comprised the best overall properties. For assessment, samples containing 0.5 wt.% rGO were also produced via PM and MLM routes, separately. The physical and mechanical properties of...
Electrocatalytic hydrogen evolution reaction on graphene supported transition metal-organic frameworks
, Article Inorganic Chemistry Communications ; Volume 127 , May , 2021 ; 13877003 (ISSN) ; Hasanzadeh, M ; Simchi, A ; Sharif University of Technology
Elsevier B. V
2021
Abstract
A highly efficient, cost-effective, and durable electrocatalysts based on CoNi metal–organic framework (MOF) nanosheets on highly porous conductive graphene (PCG) is introduced for the hydrogen evolution reaction (HER). The electrocatalyst was fabricated by template-assisted chemical vapor deposition of graphene followed by solvothermal growth of CoNi-MOF nanosheets. Highly porous 3D structure of PCG with open channels of 200–500 nm sizes provided high active surface area and facilitates gas evolution. In a highly alkaline solution, the electrocatalyst exhibits superior figures of merits, e.g. overpotential of 265 mV at −10 mA cm−2 and Tafel slope of 44.5 mV dec-1, to existing hydrogen...
Corrigendum: partial replacement of copper slag with treated crumb rubber aggregates in alkali-activated slag mortar” (construction and building materials (2020) 256, (S0950061820314732), (10.1016/j.conbuildmat.2020.119468))
, Article Construction and Building Materials ; Volume 283 , 2021 ; 09500618 (ISSN) ; Shoaei, P ; Reza Musaeei, H ; Zareei, A. R ; Chee Ban, C ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The authors regret that there was an error in the SEM image presented in Fig. 4(c) of the previously print version of the article. Please refer to the corrected SEM image as presented here. It is noteworthy that this change does not affect any of the conclusions. The authors would like to apologise for any inconvenience caused. © 2021 Elsevier Ltd