Search for: conductance
Total 735 records
Compact formulae for number of conduction channels in various types of graphene nanoribbons at various temperatures, Article Modern Physics Letters B ; Volume 26, Issue 1 , 2012 ; 02179849 (ISSN) ; Faez, R ; Moravvej Farshi, M. K ; Sharif University of Technology
We present two compact analytic formulae for calculating the channel number in graphene nanoribbons (GNRs), in terms of GNRs' width and Fermi energy. Numerical data obtained from these analytic formulae fit those obtained numerically from the exact formula, with accuracies within 1%. Using appropriate fit parameters, the compact formulae are valid for zigzag, armchair-metallic, and armchair-semiconducting GNRs, at room, liquid nitrogen, and liquid helium temperatures (i.e. 300, 77 and 4.2 K)
Investigating the effect of different conventional regularization methods on convergence in moving boundary inverse heat conduction problems, Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 104-113 ; 10263098 (ISSN) ; Farhanieh, B ; Sharif University of Technology
Sharif University of Technology 2004
In this paper, the temperature of a moving surface is determined with a moving, finite element-based inverse method. In order to overcome the ill-condition of moving inverse problems, three different conventional regularization methods are used: Levenberg, Marquardt and Modified Levenberg. The moving mesh is generated employing the transfinite mapping technique. The proposed algorithms are used in the estimation of surface temperature on a moving boundary in the burning process of a homogenous solid fuel. The measurements obtained inside the solid media are used to circumvent problems associated with the sensor and the receding surface. As the surface recedes, the sensors are swept over by...
Article Australian Journal of Basic and Applied Sciences ; Volume 4, Issue 8 , 2010 , Pages 3985-3997 ; 19918178 (ISSN) ; Sharifian, M ; Sharif University of Technology
In this study electrical conductivities of pure, distilled, municipal, industrial and river water liquids along with those of different electrolyte solutions are computed at room temperature (25 °C) and compared with the experimental results. For experiment, using a measuring module both R and C value of the water samples are measured by using two different cylindrical cells. The obtained RC product for the long and short cell probes are compared for different water samples. Obtained results give the relaxation time, which is the measure of the conduction relaxation and for a good conducting medium such a time is very short. The relaxation time for the salt solution is about 0.07044 ms...
Application GMDH artificial neural network for modeling of Al2O3/water and Al2O3/Ethylene glycol thermal conductivity, Article International Journal of Heat and Technology ; Volume 36, Issue 3 , 2018 , Pages 773-782 ; 03928764 (ISSN) ; Hajizadeh, F ; Rahimzadeh, M ; Shafii, M. B ; Chamkha, A. J ; Lorenzini, G ; Ghasempour, R ; Sharif University of Technology
International Information and Engineering Technology Association 2018
Thermal conductivity of nanofluids depends on several parameters including temperature, concentration, and size of nanoparticles. Most of the proposed models utilized concentration and temperature as influential factors in their modeling. In this study, group method of data handling (GMDH) artificial neural networks is applied in order to model the dependency of thermal conductivity on the mentioned factors. Firstly, temperature and concentration considered as inputs and a model is represented. Afterwards, the size of nanoparticles is added to the input variables and the results are compared. Based on obtained results, GMDH is an appropriate method to predict thermal conductivity of the...
Erratum: Circuit model in design of THZ transparent electrodes based on two-dimensional arrays of metallic square holes (IEEE transactions on terahertz science and technology (2014) 4:3 (383-390)), Article IEEE Transactions on Terahertz Science and Technology ; Volume 5, Issue 4 , June , 2015 , Pages 655-656 ; 2156342X (ISSN) ; Mehrany, K ; Shirmanesh, G. K ; Yarmoghaddam, E ; Sharif University of Technology
IEEE Microwave Theory and Techniques Society 2015
A circuit model has been proposed for two-dimensional metallic arrays of metallic square holes located on a homogeneous substrate. Although the proposed circuit model holds true, the surface admittance between the metallic hole array and the cover was erroneously calculated since the presence of the cross-polarization terms had been neglected. Furthermore, there have been mistakes in numerical simulation and in analytical calculations based on the presented formulas. The correct formulation is now given, and erroneous figures are replotted
Article Australian Journal of Basic and Applied Sciences ; Volume 4, Issue 11 , 2010 , Pages 5599-5613 ; 19918178 (ISSN) ; Golnabi, H ; Sharif University of Technology
Using two different capacitive cell probes; and monitoring capacitance and resistance values of the air and water liquids, the cell length and conductance effects of the water liquids are studied. Variations of the dielectric air capacitance and reactance capacitance parameter of liquids with cylinder length are investigated. In another study the probe length affects on the capacitance and resistance measurements for the liquid filling process are investigated. Different theories are also developed to calculate the capacitance values for the constructed probes. Capacitance per unit length from the Coulomb theory is different from the Gauss law that is a constant value. Measured air...
Preparation of polyaniline/graphene coated wearable thermoelectric fabric using ultrasonic-assisted dip-coating method, Article Materials for Renewable and Sustainable Energy ; Volume 9, Issue 4 , 2020 ; Ramazani Saadatabadi, A ; Siadati, M. H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH 2020
Abstract: The use of thermoelectric fabrics for powering wearable devices is expected to become widespread soon. A thermoelectric fabric was prepared by coating nanocomposite of polyaniline/graphene nanosheets (PANI/GNS) on a fabric. Four samples of the fabric containing different wt% of GNS (0.5, 2.5, 5, and 10) were prepared. To characterize the samples, Fourier transform infrared (FTIR) spectra, attenuated total reflectance-Fourier transform infrared (AT-FTIR) spectra, field-emission scanning electron microscopy (FE-SEM), electrical conductivity and Seebeck coefficient measurements were used. The electrical conductivity increased from 0.0188 to 0.277 S cm−1 (from 0.5 to 10 wt% of the GNS...
Article Superconductor Science and Technology ; Volume 21, Issue 9 , 4 July , 2008 ; 09532048 (ISSN) ; Mofakham, S ; Akhavan, M ; Sharif University of Technology
We have investigated the substitution of Ce and divalent Ca with a radius similar to Gd in Gd1-x-zCexCazBa 2Cu3O7-δ. We have prepared Gd 1-x-zCexCazBa2Cu3O 7-δ compounds with different concentrations of Ce and Ca by the standard solid-state reaction technique. X-ray diffraction (XRD) experiments are performed and the results are refined by the Rietveld method. XRD analysis shows a predominantly single-phase perovskite structure with orthorhombic Pmmm symmetry. In Gd1-x-zCexCazBa2Cu 3O7-δ compounds, induced suppression of T c due to Ce doping is compensated by hole doping with increasing Ca substitution for Gd. With the increase of Ca content, Tc increases up to an optimum value; thereafter...
Article Physical Review B - Condensed Matter and Materials Physics ; Volume 75, Issue 17 , 2007 ; 10980121 (ISSN) ; Langari, A ; Sharif University of Technology
The anisotropic Kondo necklace model in two and three dimensions is treated as a genuine model for magnetic to Kondo singlet quantum phase transitions in the heavy fermion compounds. The variation of the quantum critical point with anisotropy parameters has been investigated previously in the zero-field case. Here, we extend the treatment to finite fields using a generalized bond operator representation including all triplet states. The variation of critical tc with magnetic field and the associated phase diagram is derived. The influence of anisotropies and the different g factors for localized and itinerant spins on the field dependence of tc is also investigated. It is found that three...
Article Journal of Optics A: Pure and Applied Optics ; Volume 3, Issue 5 , 2001 , Pages 380-386 ; 14644258 (ISSN) ; Rashidian, B ; Sharif University of Technology
In this paper, the possibility of guided light propagation in dielectric slab waveguides in the presence of interface free charge layers is explored. It is shown that, under certain conditions, the interface charge layer can have no influence on the TM or TE polarized guided modes. The density, and therefore the conductivity, of the interface free charges can be controlled by a transverse dc voltage. It is concluded that the applied voltage across such a structure can be used for switching the light propagation on or off. This device finds numerous applications in integrated optics, as discussed here. A design example is also presented
Preparation of conductive polyaniline/graphene nanocomposites via in situ emulsion polymerization and product characterization, Article Synthetic Metals ; Vol. 196 , 2014 , pp. 199-205 ; Ramazani, S. A ; Mashayekhan, S ; Ghaderinezhad, F ; Sharif University of Technology
This work, which is a part of our ongoing studies on developing conductive scaffolds for nerve tissue engineering, reports synthesis of highly conductive binary-doped polyaniline nanoparticles and polyaniline/graphene nanocomposites. The samples were synthesized through chemical oxidation of aniline via in situ emulsion polymerization method in presence of hydrochloric acid and sodium dodecyl sulfate. Graphene nanosheets were also prepared via modified Hummer's method followed by chemical reduction using hydrazine monohydrate. Electrical conductivity measurements using a standard four-point probe technique with FTIR and UV-vis studies revealed that conductive binary-doped emeraldine salt...
Article Journal of Materials Science ; Volume 56, Issue 27 , 2021 , Pages 15151-15161 ; 00222461 (ISSN) ; Kazemi Ranjbar, S ; Sharif University of Technology
The development of polymer-based composites with thermal transport capability has now become essential in response to the efficient thermal management required in electronic and energy conversion devices. In this work, a novel hybrid filler consisting of graphene nanoplatelet (GNP) and boron nitride microparticles (micro-BN) is used to improve the thermal conductivity of epoxy composite. The GNPs with an average lateral size of 8 µm and an average thickness of 5 nm are in the same volume range with the 1 µm size micro-BN particles. According to the results, the thermal conductivity of the composites changes abruptly with increasing micro-BN loading at fixed GNP loading, which is attributed...
Article Applied Thermal Engineering ; Volume 61, Issue 2 , 2013 , Pages 228-235 ; 13594311 (ISSN) ; Alizadeh Abianeh, V ; Moezzinajafabadi, M ; Daneshi, M ; Sharif University of Technology
In engineering practice, the space occupied by high conductivity materials together with the cost are the two elements of major concern. Therefore, seeking for more efficient designs of high conductivity pathways ('inserts'), embedded into a heat generating body constitutes a formidable challenge. The main idea of this paper is to introduce new patterns for the highly conductive pathways, called 'fork-shaped' configurations. Essentially, two types of fork-shaped pathways, 'F1' and 'F2' are introduced. Numerical results demonstrate that, these two configurations of highly conductive pathways, remarkably surpass the latest configurations reported in the literature, with the same amount of high...
Article International Communications in Heat and Mass Transfer ; Volume 39, Issue 8 , 2012 , Pages 1265-1271 ; 07351933 (ISSN) ; Sharifi, F ; Salimpour, M. R ; Moosavi, A ; Sharif University of Technology
Conductive cooling of a rectangular chip heated from the bottom surface and connected to a heat sink is studied. Different configurations of a highly conductive material embedded in the chip are investigated and an optimal configuration for transferring heat to the heat sink is achieved. Our results indicate that the optimal configuration can be obtained by using side branches, parallel with the main channel, and also increasing the thickness of the main channel. Many complex configurations are checked and it is shown that these structures do not provide better performance
Article Energy ; Volume 32, Issue 9 , 2007 , Pages 1603-1616 ; 03605442 (ISSN) ; Montazeri, A ; Sharif University of Technology
Elsevier Ltd 2007
The performance of an MHD generator utilizing plasma as working fluid has been assessed from the viewpoint of the second law of thermodynamics. The plasma flow in the generator linear duct has been solved by dividing the channel cross-section to an inviscid core region and the viscous boundary layers in the vicinity of the walls. The Hall effect has been taken into account and equilibrium ionization has been assumed. The dependence of the plasma properties such as Hall parameter, the coefficients of thermal and electrical conductivity, and viscosity on the plasma state has also been considered. Using the information obtained on the plasma behaviour in the generator, the entropy generation...
Enhancing seebeck coefficient and electrical conductivity of polyaniline/carbon nanotube–coated thermoelectric fabric, Article Journal of Industrial Textiles ; 2021 ; 15280837 (ISSN) ; Ramazani Saadatabadi, A ; Pourjahanbakhsh, M ; Siadati, M. H ; Sharif University of Technology
SAGE Publications Ltd 2021
In this work, flexible thermoelectric fabrics, polyester/yarn fabrics coated with polyaniline/carbon nanotube (PANI/CNT) nanocomposite, were fabricated by sequential processing: (I) polyaniline/carbon nanotube nanocomposites preparation by a one-step in-situ polymerization and (II) dip coating of a mixture solution of CNT-doped PANI on a polyester/yarn fabric. Nanocomposites were synthesized with various CNT content (0.5, 2.5, 5, and 10 wt%) and characterized using different methods. The Seebeck coefficient and electrical conductivity measurements were used to determine their thermoelectric properties. The results revealed significant improvement in both electrical conductivity and the...
M.Sc. Thesis Sharif University of Technology ; Fardmanesh, Mahdi ; Hejazi, Mohammad Saeed
DNA is big protein molecule consisting of two strands intertwining each others. Recently DNA molecule has drawn attention of researchers to be used in electronic circuits and molecule electronic field. Therefore, many experiments have been carried out to measure DNA conductivity in different temperature in single molecule or bundle mode with varying size and shape. In this thesis, metallic bundle DNA at normal room temperature is studied and their resistance characteristic is obtained and compared. In order to improve DNA conductivity Metal Ions like zinc are adulterated to each of its structure period. DNAs with these metallic impurities are called metallic DNAs.
Thus, golden electrodes...
Thus, golden electrodes...
The temperature distribution eximer laser source (193 nm) within a human eye and review on some side-effects, Article Australian Journal of Basic and Applied Sciences ; Volume 4, Issue 5 , 2010 , Pages 724-730 ; 19918178 (ISSN) ; Khorvash, M ; Harun, S.W ; Ahmad, H ; Golnabi, H ; Sharif University of Technology
A mathematical model to predict the temperature distribution within the human eye when subjected to a laser source (193nm) is presented. In this paper the thermal effects of the laser radiation on different parameters of the eye and some side-effects are discussed. The influence of parameters such as the heat conductivity, diffusivity, the scattering and refraction coefficients are compared and the damage threshold conditions for temperature distribution are estimated. Other factors such as the color of eye, the ageing factor of the human eye and anxiety are also studied in this report. The interaction of the laser sources within the eye medium is described by employing the Penne's bioheat...
Thermal conductivity, viscosity, and electrical conductivity of iron oxide with a cloud fractal structure, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 53, Issue 4 , 2017 , Pages 1343-1354 ; 09477411 (ISSN) ; Pahlavanzadeh, H ; Kheradmand, A ; Sharif University of Technology
Springer Verlag 2017
In the present study, nanoscale iron oxide was synthesized using a hydrothermal method; XRD analysis revealed that all the produced crystals are iron oxide. FESEM microscopic imaging showed that particles are on the scale of nano and their morphology is cloud fractal. To study the laboratory properties of thermal conductivity, viscosity, and electrical conductivity of the nanoparticles, they were dispersed in ethylene glycol-based fluid and the nanofluid was in a two-step synthesis during this process. The experiments were carried out with a weight fraction between 0 and 2 % at temperatures between 25 and 45 °C. According to the results of the experiments, increasing the density of...
Surface electromagnetic waves supported by nano conducting layers with inhomogeneities in the conductivity profile, Article Optical and Quantum Electronics ; Volume 40, Issue 1 , 2008 , Pages 23-40 ; 03068919 (ISSN) ; Mehrany, K ; Sharif University of Technology
Conducting interfaces and nano conducting layers can support surface electromagnetic waves. Uniform charge layers of non-zero thickness and their asymptotic behavior toward conducting interfaces of infinitely small thicknesses, where the thin charge layer is modeled via a surface conductivity σ s , are already studied. Here, the possible effects of inhomogeneity in the conductivity profile of the thin conducting layers are investigated for the first time and a new approximate yet accurate enough analytical formulation for mode extraction in such structures is given. In order to rigorously analyze the structure and justify the proposed approximate formulation, the Galerkin's method with...