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Modeling the acoustic effects on droplet vaporization in a laboratory pulse combustor
, Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED ; Volume 253 , 2000 , Pages 1077-1084 ; 08888116 (ISSN) ; Akbari, P ; Ghafourian, A ; Sharif University of Technology
2000
Abstract
Both theoretical and experimental analysis of acoustics fields effects on droplet vaporization are presented. Theoretical investigation is based on droplet vaporization without combustion in both steady and longitudinal acoustic fields with variable properties in one dimension. An axisymmetric pulse combustor is developed for simulating the longitudinal acoustic field. A spray system is used for producing water droplets. Controllable parameters of the system are the hot air and liquid injection velocities, direction of injection and frequency of acoustic oscillation. The theoretical results indicate that the evaporation time decreases up to 30 percent in an acoustic field in comparison to...
Design Optimization of Linear Variable-Reluctance Resolver for Higher Accuracy and Smaller Size
, Article IEEE Sensors Journal ; Volume 23, Issue 15 , 2023 , Pages 16764-16771 ; 1530437X (ISSN) ; Nasiri Gheidari, Z ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2023
Abstract
Linear variable reluctance (VR) resolvers offer robustness and affordability in comparison with wound mover sensors. However, the accuracy of linear sensors is influenced by geometrical dimensions and the longitudinal end effect. In this article, the end effect was compensated by altering the teeth's shape using the tooth-pairing method. This altered shape could achieve much better accuracy. Furthermore, the influence of many different geometrical dimensions and shapes of teeth and yoke were examined using finite-element analysis (FEA). In addition, the results of this analysis show a trade-off between the accuracy and weight of the resolver in some cases. To verify the correctness of the...
Provide a Model for the Sitting of Hydroelectric Power Plants Using GIS and Multiple Criteria Decision FTOPSIS: A Case From Kelas Basin
, M.Sc. Thesis Sharif University of Technology ; Shamsai, Abolfazl (Supervisor)
Abstract
Nowadays due to increasing environmental considerations and effort to reducing of the fossil fuels consumption, the necessity of hydroelectric power plants development is emerged. The purpose of this study is to suggest a method of spatial analysis for finding sites with appropriate potential for construction of these power plants, using TOPSIS and GIS. In this research, using the Python programming language, in software environment of Arc GIS version 9.3, local hydrological model was generated using the DEM layer and using of streams ordering methods, the overall situation along the river were processed. In the next step, with using of fuzzy TOPSIS algorithm implementation in software...
Steganography Based on Sparse Decomposition
, Ph.D. Dissertation Sharif University of Technology ; Ghaem Maghami, Shahrokh (Supervisor)
Abstract
The goal of this thesis is using sparse decomposition to design secure steganography algorithms to insert secret data into the different cover signals. We propose data embedding in higher semantic levels of the cover signal to reach this goal. Sparse decomposition represents a signal as a linear combination of its structural elements. Data insertion into the sparse coefficients slightly changes the effect of structural elements in the signal representation. So, quality of the stego signal is preserved and such a steganography method leads to higher imperceptibility. In addition, data insertion into the higher semantic levels leads to the higher undetectability. Steganalyzers use statistical...
Speech Enhancement Using Deep Neural Networks in Non-stationary Noise Environment
, M.Sc. Thesis Sharif University of Technology ; Ghaem Maghami, Shahrokh (Supervisor)
Abstract
Before performing any operation on a speech signal, it is necessary to properly remove the environmental noise existing on it. Noise Canceling Operation on Speech Signal is called speech enhancement. Up to now, many studies have been conducted on various ways to enhance the speech signal. Among the existing methods, statistical methods have proven to be superior to others. In all noise removal methods, the main challenge is that most noises are non-stationary. Since most of the noises in the environment are non-stationary, we are still looking for the better ways to remove them. With the advent of deep neural networks and their successful results in areas such as machine learning, a method...
Development of a Control Algorithm for Functional Electrical Stimulation to Achieve Smooth Motion
, M.Sc. Thesis Sharif University of Technology ; Behzadipour, Saeed (Supervisor)
Abstract
The use of functional electrical stimulation after spinal cord injury is one of the most effective ways to prevent muscle atrophy.” Enzymes construction set, torque output increases and improved fatigue resistance”.
Functional electrical stimulation devices help in the operation of a muscle by applying a weak electrical current. This stimulation causes muscle contraction. In other words, it replaces the neural signals required to move the limb that cannot be produced due to causes such as spinal cord injury (SCI) orsecondary problems that arise after SCI.
One of the drawbacks of using FES is jerky motions in the muscles and limps. Such movements are not only harmful, but results in...
Functional electrical stimulation devices help in the operation of a muscle by applying a weak electrical current. This stimulation causes muscle contraction. In other words, it replaces the neural signals required to move the limb that cannot be produced due to causes such as spinal cord injury (SCI) orsecondary problems that arise after SCI.
One of the drawbacks of using FES is jerky motions in the muscles and limps. Such movements are not only harmful, but results in...
A catalyzed method to remove polychlorinated biphenyls from contaminated transformer oil
, Article Environmental Science and Pollution Research ; 2021 ; 09441344 (ISSN) ; Gholipour Zanjani, N ; Khorasheh, F ; Arjmand, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
The disposal of polychlorinated biphenyls (PCBs) as persistent organic pollutants from the environment has been normally performed by isolation from soil or water because of their biological activity and toxic potential. In the present investigation, catalytic hydrodehalogenation was used to detoxify PCBs-contaminated transformer oil. All reactions were directed on an oil containing 11.09 wt% of PCBs utilizing palladium supported on multi-walled carbon nanotubes (Pd/MWCNTs). The amount of hexa-chlorine homologues reduced considerably from 5.07% to less than 800 ppm utilizing HDC at the atmosphere of argon. Moreover, the amounts of long half-lives and bioaccumulative congener of PCB 153...
A catalyzed method to remove polychlorinated biphenyls from contaminated transformer oil
, Article Environmental Science and Pollution Research ; Volume 29, Issue 9 , 2022 , Pages 13253-13267 ; 09441344 (ISSN) ; Gholipour Zanjani, N ; Khorasheh, F ; Arjmand, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
The disposal of polychlorinated biphenyls (PCBs) as persistent organic pollutants from the environment has been normally performed by isolation from soil or water because of their biological activity and toxic potential. In the present investigation, catalytic hydrodehalogenation was used to detoxify PCBs-contaminated transformer oil. All reactions were directed on an oil containing 11.09 wt% of PCBs utilizing palladium supported on multi-walled carbon nanotubes (Pd/MWCNTs). The amount of hexa-chlorine homologues reduced considerably from 5.07% to less than 800 ppm utilizing HDC at the atmosphere of argon. Moreover, the amounts of long half-lives and bioaccumulative congener of PCB 153...
Audio-visual Speaker Verification Using Identity Based Articulatory Features
, M.Sc. Thesis Sharif University of Technology ; Ghaem Maghami, Shahrokh (Supervisor)
Abstract
Many companies feel the need of automatic person identification for tracking entrance and exit of their employers. This system will help the company in reducing security costs, waste of time and increasing security. In this thesis a novel idea for 3d convolutional neural network text independent speaker verification system will introduced. Since many scenarios visionary data like lip motion, besides speech data, is available, in this thesis both of these data streams are used for developing designed speaker verification system. Multimodalily helps the verification system to be more robust to the noise and attacks. One of the main challenges in designing multimodal neural network speaker...
Application of an optimized SLW model to calculation of non-gray radiation heat transfer in a furnace
, Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 13 November 2015 through 19 November 2015 ; Volume 8B-2015 , 2015 ; 9780791857502 (ISBN) ; Abrar, B ; Schneider, G. E
2015
Abstract
The spectral line based weighted sum of gray gases (SLW) model is considered as an advanced model, which can solve the radiative transfer equation (RTE) in non-gray participating media by dividing the absorption cross section spectrum into a limited number of intervals. Each interval is then treated as a gray gas medium, in which the attributed RTE should be solved separately. Therefore, the SLW model would be computationally more efficient than the other non-gray participating media solvers because it is faced with a small number of RTE solutions. In this work, we present a novel optimized SLW model and applied it to radiation heat transfer calculation in a model furnace. The current...
The effect of soot nano-particles injection on two-phase smoke aerosol formation in a kerosene-fired burner
, Article 54th AIAA Aerospace Sciences Meeting, 2016, 4 January 2016 through 8 January 2016 ; 2016 ; 9781624103933 (ISBN) ; Ghafourizadeh, M ; Schneider, G. E
American Institute of Aeronautics and Astronautics Inc, AIAA
2016
Abstract
Feeding a laboratory furnace with the gaseous kerosene, the resulting two-phase turbulent flame is simulated to study the effects of injecting soot nano-particles into the inflow air on the emissions of smoke aerosol, CO, and CO2species pollutants, and the resulting radiation heat transfer. We use our past experiences in aerosol modeling of soot nano/micro particles in turbulent nonpremixed flames burning simple hydrocarbon fuels and extend them to study the effects of injecting gaseous kerosene on the aforementioned parameters. To model the evolutionary process of soot nanoparticle formation, i.e., the nucleation, coagulation, surface growth, and oxidation, we employ a two-equation soot...
Application of a dual functional luminescent layer to enhance the light harvesting efficiency of dye sensitized solar cell
, Article Materials Letters ; 2016 ; 0167577X (ISSN) ; Taghavinia, N ; Diau, E. W. G
Elsevier B.V
2016
Abstract
A luminescent coating of CaAlSiN3:Eu2+ particles applied on photoanode (TiO2) layer of SQ1 sensitized solar cell by doctor blading the paste of phosphor particles. The luminescent layer acted as a dual functional layer and enhanced the short circuit current density (JSC) by 64% via both scattering effect and downshifting of the photons in 400-600nm spectral range to photons in 600-800nm spectral range. Considerable relative enhancement in incident photon to current conversion efficiency (IPCE) up to 350% in 400-600nm spectral range proves the down shifting effect as the dominant factor for the improved performance of dye sensitized solar cell (DSSC). © 2016 Elsevier B.V
CFD-aided simulation of frost growth inside a narrow duct with uniform wall temperature variation
, Article ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM 2014, Collocated with the ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting ; 2014 ; ISBN: 9780791846278 ; Asgari, E ; Hajikaram, M ; Schneider, G. E ; Sharif University of Technology
2014
Abstract
In this paper, we study the frost formation and growth at the walls of a duct with uniform wall temperature variation. The simulation is performed for laminar flow regime considering suitable semi-empirical models incorporated with computational fluid dynamics (CFD) method. The frost growth is considered to be normal to the duct surface. Since the duct aspect ratio is high, we perform our simulations in two-dimensional zones. To simulate the frost layer properly, we solve both the energy and mass balance equations implementing some semi-empirical correlations on the frost side. At this stage, we suitably predict the required heat flux value at the solid boundary and the heat transfer...
Using the direct simulation Monte Carlo method to study the effect of wall temperature variation on gas mixing evolution through micro T-mixers
, Article 11th International Energy Conversion Engineering Conference ; 2013 ; Sabouri, M ; Lekzian, E ; Schneider, G. E ; Sharif University of Technology
2013
Abstract
In this work, we study the gas mixing behavior in a micro T-mixer using the direct simulation Monte Carlo (DSMC) method. The gas mixing process is monitored through a T-mixer, which is fed by two different CO and N2 gases; flowing into the T-mixer through the upper and lower inlets. We investigate the effects of axial and lateral wall temperature gradients on the mixing evolution at different rarefaction levels. The achieved results show that any temperature difference between the channel walls would result in an increase in mixing length for the chosen wall temperature gradient ranges and the studies pressure cases. Our observations show that a positive temperature gradient toward the...
Toward electrically tunable, lithography-free, ultra-thin color filters covering the whole visible spectrum
, Article Scientific Reports ; Volume 8, Issue 1 , 2018 ; 20452322 (ISSN) ; Serebryannikov, A. E ; Khavasi, A ; Vandenbosch, G. A. E ; Ozbay, E ; Sharif University of Technology
Nature Publishing Group
2018
Abstract
The possibility of real-time tuning of optical devices has attracted a lot of interest over the last decade. At the same time, coming up with simple lithography-free structures has always been a challenge in the design of large-area compatible devices. In this work, we present the concept and the sample design of an electrically tunable, lithography-free, ultra-thin transmission-mode color filter, the spectrum of which continuously covers the whole visible region. A simple Metal-Insulator-Metal (MIM) cavity configuration is used. It is shown that using the electro-optic dielectric material of 4-dimethyl-amino-N-methyl-4-stilbazoliumtosylate (DAST) as the dielectric layer in this...
Thermobuoyancy treatment for electronic packaging using an improved advection scheme
, Article Journal of Electronic Packaging, Transactions of the ASME ; Volume 125, Issue 2 SPEC , 2003 , Pages 244-250 ; 10437398 (ISSN) ; Schneider, G. E ; Sharif University of Technology
2003
Abstract
The complex nature of the convective terms in the fluid flow governing equations has caused many researchers to work on estimating more accurate advection term magnitudes by employing better approximate expressions. The trend of progress has been to include more physics of flow in the approximations. However, there is no archival evidence that reports the direct implementation of buoyancy as a physical influence in the advection term modeling. In this work, the influence of buoyancy in an efficient advection term expression is investigated in a control volume context with a collocated grid arrangement. The accuracy of the results obtained by both excluding and including the buoyancy term is...
Extension of a control volume incompressible approach to compressible flow solutions
, Article 34th Thermophysics Conference 2000, Denver, CO, 19 June 2000 through 22 June 2000 ; 2000 ; Schneider, G. E ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2000
Abstract
The main purpose of the present research is to use a developed analogy between compressible and incompressible governing equations in order to extend incompress¬ible procedures to solve compressible flows. The investigation is performed for different pressure-based incompressible approaches mainly control-volume-based. The chosen in¬compressible methods are a multi-grid procedure on a collocated grid distribution, a SIMPLE-based method on a non-staggered grid, and a SIMPLE-based approach on a staggered grid arrangement. The final results for the developed compressible procedure are presented for one of the preceding incompressible methods based on the best incom¬pressible performance...
Performance of an analogy-based all-speed procedure without any explicit damping
, Article Computational Mechanics ; Volume 26, Issue 5 , 2000 , Pages 459-469 ; 01787675 (ISSN) ; Schneider, G. E ; Sharif University of Technology
Springer Verlag
2000
Abstract
The performance of a numerical method which solves flow at all speeds, and does not use any explicit artificial viscosity or damping mechanism whatsoever, is investigated by testing a number of selected cases in compressible and incompressible flows. Contrary to existing methods, the momentum components are chosen as the dependent variables instead of the velocity components in order to provide a number of advantages. Among the motivations for this change is a flow analogy which permits incompressible methods to be used to solve compressible flows. The method is formulated within a control-volume-based finite-element approach using a collocated grid arrangement. The definition of two types...
Residual stress analysis of the autofrettaged thick-walled tube using nonlinear kinematic hardening
, Article Journal of Pressure Vessel Technology, Transactions of the ASME ; Volume 135, Issue 2 , 2013 ; 00949930 (ISSN) ; Voyiadjis, G ; Hoseini, S. H ; Hosseinian, E ; Sharif University of Technology
2013
Abstract
Recent research indicates that accurate material behavior modeling plays an important role in the estimation of residual stresses in the bore of autofrettaged tubes. In this paper, the material behavior under plastic deformation is considered to be a function of the first stress invariant in addition to the second and the third invariants of the deviatoric stress tensor. The yield surface is assumed to depend on the first stress invariant and the Lode angle parameter which is defined as a function of the second and the third invariants of the deviatoric stress tensor. Furthermore for estimating the unloading behavior, the Chaboche's hardening evolution equation is modified. These...
Residual stress analyses of re-autofrettaged thick-walled tubes
, Article International Journal of Pressure Vessels and Piping ; Volume 98 , 2012 , Pages 57-64 ; 03080161 (ISSN) ; Voyiadjis, G. Z ; Hoseini, S. H ; Hosseinian, E ; Sharif University of Technology
Elsevier
2012
Abstract
In this paper the effect of the re-autofrettage process on the residual stress distribution at the wall of a thick-walled tube is considered. For accurate material behavior modeling, it is assumed that the yield surface is a function of all the stress invariants. Also for estimating the behavior of the material under loading-unloading process, a modified Chaboche's hardening model is applied. For evaluation of this unloading behavior model a series of loading-unloading tests are conducted on specimens that are made of the high strength steel, DIN1.6959. In addition the finite element simulations are implemented to simulate the re-autofrettage process and to estimate the residual stresses....