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Diffusional release of a solute from a spherical reservoir into a finite external volume
, Article Journal of Pharmaceutical Sciences ; Volume 91, Issue 8 , 2002 , Pages 1803-1809 ; 00223549 (ISSN) ; Sharif University of Technology
John Wiley and Sons Inc
2002
Abstract
An exact solution has been obtained for the release kinetics of a solute from a spherical reservoir with the burst effect initial condition into a finite external volume. The exact solution is derived based on the time Laplace transform method. The results presented here indicate that as the external fluid volume increases, the cumulative release at any time and the releasable amount of the solute at infinite time increase. In addition, for a given external volume, as the polymeric coat thickness increases the fractional release at any time decreases, Experimentally, cumulative release profiles of theophylline microspheres coated with ethylene vinyl acetate copolymer into different external...
A validated numerical-experimental design methodology for a movable supersonic ejector compressor for waste-heat recovery
, Article Journal of Thermal Science and Engineering Applications ; Volume 6, Issue 2 , Oct , 2014 ; 19485085 (ISSN) ; Persoons, T ; Murray, D. B ; Tehrani, M. S ; Farhanieh, B ; Koehler, J ; Sharif University of Technology
Web Portal ASME (American Society of Mechanical Engineers)
2014
Abstract
The aim of this paper is to develop the technical knowledge, especially the optimum geometries, for the design and manufacturing of a supersonic gas-gas ejector for a wasteheat driven vehicle cooling system. Although several studies have been performed to investigate the effects of geometrical configurations of gas-gas ejectors, a progressive design methodology of an ejector compressor for application to a vehicle cooling system has not yet been described. First, an analytical model for calculation of the ejector optimum geometry for a wide range of operating conditions is developed, using R134a as the working fluid with a rated cooling capacity of 2.5 kW. The maximum values of entrainment...
Numerical modeling and experimental validation of microstructure in gray cast iron
, Article International Journal of Minerals, Metallurgy and Materials ; Volume 19, Issue 10 , 2012 , Pages 908-914 ; 16744799 (ISSN) ; Davami, P ; Varahram, N ; Sharif University of Technology
Springer
2012
Abstract
To predict the amount of different phases in gray cast iron by a finite difference model (FDM) on the basis of cooling rate (R), the volume fractions of total γphase, graphite, and cementite were calculated. The results of phase composition were evaluated to find a proper correlation with cooling rate. More trials were carried out to find a good correlation between the hardness and phase composition. New proposed formulas show that the hardness of gray cast iron decreases as the amount of graphite phase increases, and increases as the amount of cementite increases. These formulas are developed to correlate the phase volume fraction to hardness. The results are compared with experimental data...
Experimental validation of a novel radiation based model for spacecraft attitude estimation
, Article Sensors and Actuators, A: Physical ; Volume 250 , 2016 , Pages 114-122 ; 09244247 (ISSN) ; Pourtakdoust, S. H ; Kiani, M ; Sheikhi, A. A ; Alikhani, A ; Sharif University of Technology
Elsevier
Abstract
Attitude Determination (AD) is one of the key requirements of many current and emerging remote sensing missions. As such AD has been traditionally accomplished through a variety of algorithms and measurement models pertinent to sensing mechanisms. The current paper addresses conceptual validation and utility of a novel radiation based heat (measurement) model for space application. The proposed new Heat Attitude (HA) model utilizes temperature data to relate the Satellite Surfaces’ (SS) Net Heat Flux (NHF) to attitude assuming that the satellite navigational data are available. As Sun and the Earth are considered the main external sources of radiation, their effects are modeled for the SS...
A wavelet-based scheme for impact identification of framed structures using combined genetic and water cycle algorithms
, Article Journal of Sound and Vibration ; Volume 443 , 2019 , Pages 25-46 ; 0022460X (ISSN) ; Rofooei, F. R ; Sadollah, A ; Xu, C ; Sharif University of Technology
Academic Press
2019
Abstract
This paper presents a synthesis strategy for impact force localization and identification of framed structures in time-domain using a two-step wavelet-based fitness evaluation scheme in conjunction with genetic and water cycle algorithms. For this purpose, a straightforward approach is developed for sensitivity analysis of accelerations and spatial signal connecting the peak values. The proposed scheme is capable of using diverse scales of wavelet functions at considerably small sampling rates. A decimal genetic algorithm (GA) coding system and a recently developed water cycle algorithm (WCA) are improved to be used for impact localization and identification, respectively. The fitness...
Damage detection of L-shaped beam structure with a crack by electromechanical impedance response: analytical approach and experimental validation
, Article Journal of Nondestructive Evaluation ; Volume 39, Issue 2 , 2020 ; Barzegar, M ; Mohsenzadeh, M ; Sharif University of Technology
Springer
2020
Abstract
Damage detection and structural health monitoring using the electromechanical impedance method has been accepted as an effective technique between various approaches of nondestructive evaluation. Many efforts have been made on experimental methods for obtaining the impedance of structures. However, expensive experimental methods encourage researchers to develop theoretical models. In this paper, a new theoretical model is developed for damage detection of L-shaped beams, which are basic components in frame structures, with an embedded piezoelectric wafer active sensor. For this purpose, a chirp signal of voltage is used to activate a piezoelectric patch for inducing local strains that lead...
Dual-diffusivity stochastic model for macromolecule release from a hydrogel
, Article ACS Applied Bio Materials ; Volume 3, Issue 7 , 2020 , Pages 4208-4219 ; Lau, C. M. L ; Abdekhodaie, M. J ; Chau, Y ; Sharif University of Technology
American Chemical Society
2020
Abstract
A three-dimensional model has been developed to describe the multiphase release of macromolecular drugs encapsulated in a hydrogel. The heterogeneity of network mesh size was considered by assigning varying diffusion coefficients to the network lattices randomly. Using a stochastic approach, the random nature of diffusion of drug molecules was captured within the network. The simplest form of distribution containing two diffusion coefficients was tested. To generate the drug release profiles for experimental validation under the limitation of computational cost, a simple scaling relationship was employed. Unlike the single-diffusivity model, the dual-diffusivity model showed good agreement...
3D finite element analysis and experimental validation of constrained groove pressing-cross route as an SPD process for sheet form metals
, Article International Journal of Advanced Manufacturing Technology ; Volume 73, Issue 9-12 , August , 2014 , Pages 1291-1305 ; ISSN: 02683768 ; Abbaszadeh, M ; Mohebpour, S. R ; Eskandari, H ; Sharif University of Technology
Abstract
A new modification of constrained groove pressing (CGP) process named as constrained groove pressing-cross route (CGP-CR) was suggested for severe plastic deformation (SPD) of sheet form metals with great potential for fabricating high strength nanostructured sheets. This process is based on the conventional CGP process including some modifications. One pass of this process includes eight stages (four corrugation and four flattening) and involves 90° cross-rotation between each two stages. As a result of each CGP-CR pass, a strain magnitude of ∼2.32 is imparted to the sample. To simulate the process, finite element modeling (FEM) was carried out using three-dimensional finite element...
Effects of catalyst loading gradient in catalyst layers on performance of polymer electrolyte membrane fuel cells
, Article Renewable Energy ; Volume 50 , February , 2013 , Pages 921-931 ; 09601481 (ISSN) ; Ahmadi, F ; Sharif University of Technology
2013
Abstract
In this paper, numerical and analytical approaches are presented to evaluate the effect of catalyst loading gradient in the catalyst layer (CL) of a polymer electrolyte membrane (PEM) fuel cell. The model is developed based on agglomerate catalyst and accounts for reactant spices and charge (ion and electron) transport in the cathode side of a PEM fuel cell. The special variation of catalyst loading is considered in two direction, "across the layer" from membrane/CL interface to gas diffusion layer (GDL) and "in catalyst plane" under the channels and land areas in the channel direction. A fuel cell test stand is designed and built to facilitate experimental validation of the model. The...
Development of inverse receptance coupling method for prediction of milling dynamics
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010, Istanbul ; Volume 5 , 2010 , Pages 339-346 ; 9780791849194 (ISBN) ; Movahhedy, M. R ; Ahmadian, M. T ; Moradi, H ; Sharif University of Technology
2010
Abstract
Receptance coupling substructure analysis (RCSA) is extensively used to determine the dynamic response of milling tool at its tip for the purpose of prediction of machining stability. A major challenge in using this approach is the proper modelling of the joint between the substructures and determination of its parameters. In this paper, an inverse RCSA is developed for experimental extraction of tool-holder frequency response function (FRF) including joint parameters. The accuracy and efficiency of this method is evaluated through an analytical investigation. It is shown that the extracted holder FRF can provide a highly accurate prediction of the tool tip FRF. The developed method is used...
Modeling, design and fabrication of non-uniform catalyst layers for PEM fuel cells
, Article ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2010, 14 June 2010 through 16 June 2010 ; Volume 1 , 2010 , Pages 697-705 ; 9780791844045 (ISBN) ; Advanced Energy Systems Division ; Sharif University of Technology
Abstract
Catalyst layers are one of the most important parts of the PEM fuel cells and the cell performance is highly related to its structure. Catalyst layers are generally made by uniform distribution of catalyst on carbon cloth or carbon papers to form electrodes. In this paper, the idea of using non-uniform catalyst layer instead of common uniform catalyst layers is presented and simulated by a two-dimensional steady-state computational model. The model accounts for species transport, electrochemical kinetics, charge transport and current density distribution. A fuel cell test stand is designed and built to facilitate experimental validation of the model. Modeling results show that electrical...
An analytical model of a gas turbine components performance and its experimental validation
, Article Proceedings of the ASME Turbo Expo, 14 June 2010 through 18 June 2010, Glasgow ; Volume 1 , 2010 , Pages 335-340 ; 9780791843963 (ISBN) ; Hajilouy Benisi, A ; Farshchi, M ; Sharif University of Technology
2010
Abstract
Gas turbine has broad applications in variety of industries. The developing gas turbine efficiency is of great engineering concern. This appeals to more precise modeling as somewhat inevitable. Modeling plays a decisive and essential role not only in all design phases, but also in development and manufacturing process to investigate performance of an engine. In this research, components of a gas turbine including air intake, axial and centrifugal compressors, combustion chamber and axial turbine are investigated. A novel dimensionless modeling approach is introduced and then, the engine performance parameters are predicted. Setting up a systematic series of experiments on the existing engine...
Development and experimental validation of a correlation monitor tool based on the endogenous pulsed neutron source technique
, Article Metrology and Measurement Systems ; Volume 24, Issue 3 , 2017 , Pages 441-461 ; 20809050 (ISSN) ; Khalafi, H ; Vosoughi, N ; Khakshournia, S ; Sharif University of Technology
Abstract
A correlation measuring tool for an endogenous pulsed neutron source experiment is developed in this work. Paroxysmal pulses generated by a bursts of neutron chains are detected by a 10-kbit embedded shift register with a time resolution of 100 ns. The system is implemented on a single reprogrammable device making it a compact, cost-effective instrument, easily adaptable for any case study. The system was verified experimentally in the Esfahan heavy-water zero power reactor (EHWZPR). The results obtained by the measuring tool are validated by the Feynman-α experiment, and a good agreement is seen within the boundaries of statistical uncertainties. The theory of the methods is briefly...
Class-J2 Power Amplifiers
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 64, Issue 8 , 2017 , Pages 1989-2002 ; 15498328 (ISSN) ; Yaghoobi, M ; Medi, A ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper presents the theoretical introduction and experimental validation of the "Class-J2 Mode Power Amplifier," which provides higher efficiency and output power compared with conventional class-J mode counterpart. This mode of operation is realized by injection of the second-harmonic current to drain node of a class-J power amplifier (PA) to reduce the 45° phase shift between drain current and voltage signals. Similar to class-J PAs, the second-harmonic impedance of class-J2 PAs is purely reactive to simplify the design of the output matching network. The auxiliary second-harmonic injection circuit comprises a transistor biased in class-B mode followed by a class-C biased amplifier to...
Comprehensive electric arc furnace model for simulation purposes and model-based control
, Article Steel Research International ; Volume 88, Issue 3 , 2017 ; 16113683 (ISSN) ; Saboohi, Y ; Škrjanc, I ; Logar, V ; Sharif University of Technology
Wiley-VCH Verlag
2017
Abstract
The paper presents a comprehensive electric arc furnace (EAF) model, developed for simulation and model-based control of the EAF processes. The model consists of three sub models, i.e., (i) arc model; (ii) chemical and slag model; and (iii) heat-transfer model. Arc model predicts the amount of energy dissipated from the arcs using arc currents and arc lengths; chemical and slag model calculates chemical energy and changes of elements/compounds, slag height and slag quality; while the heat-transfer model uses calculations of the other two models in order to establish a reference energy system (RES) for each zone in the EAF due to the variations in arc length, slag height, and bath height. The...
Experimental validation of frequency response of an CVT for EHV harmonic measurements
, Article 16th International Conference on Protection and Automation of Power Systems, IPAPS 2022, 19 January 2022 through 20 January 2022 ; 2022 ; 9781665484374 (ISBN) ; Mokhtari, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
A capacitive voltage transformer (CVT) operating at extra high voltage (EHV) is examined for measuring power system harmonics in this paper. With the capacitor connections rearranged in the divider, the internal components can be energized with their nominal values by applying an intermediate voltage. Through this procedure, the effect of different burdens on frequency response is tested. The linearity of CVT circuits is also evaluated with respect to applied voltage level. In addition, an examination of the effects of amplitude and phase differences between harmonic components and the fundamental component is conducted. The practical test results are subsequently discussed. © 2022 IEEE
Optical flow-based motion estimation of ultrasonic images for force estimation in percutaneous procedures: Theory and experimental validation
, Article IECON Proceedings (Industrial Electronics Conference), 25 October 2012 through 28 October 2012 ; October , 2012 , Pages 1557-1560 ; 9781467324212 (ISBN) ; Jahed, M ; Sharif University of Technology
2012
Abstract
In recent years, there hass been a pronounced emphasis on percutaneous needle steering with the aid of advanced soft tissue modeling techniques. In this work an optical flow based motion estimation method is used to estimate the force applied to the needle by the soft tissue during percutaneous applications. The study considers Finite Element Model (FEM) of the tissue evaluated by the deformation data acquired through the optical flow method. To represent the soft tissue behavior, dynamic FEM with Rayleigh damping and viscoelastic models are used. The method is validated experimentally through offline evaluation of the ultrasonic images of the chicken breast punctured by a needle. The force...
Improvement and experimental validation of a multi-zone model for combustion and NO emissions in CNG fueled spark ignition engine
, Article Journal of Mechanical Science and Technology ; Volume 26, Issue 4 , 2012 , Pages 1205-1212 ; 1738494X (ISSN) ; Hannani, S. K ; Ebrahimi, R ; Sharif University of Technology
2012
Abstract
This article reports the experimental and theoretical results for a spark ignition engine working with compressed natural gas as a fuel. The theoretical part of this work uses a zero-dimensional, multi-zone combustion model in order to predict nitric oxide (NO) emission in a spark ignition (SI) engine. The basic concept of the model is the division of the burned gas into several distinct zones for taking into account the temperature stratification of the burned mixture during combustion. This is especially important for accurate NO emissions predictions, since NO formation is strongly temperature dependent. During combustion, 12 products are obtained by chemical equilibrium via Gibbs energy...