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scaling-laws
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Finite-length scaling for polar codes
, Article IEEE Transactions on Information Theory ; Vol. 60, Issue. 10 , 2014 , Pages 5875-5898 ; ISSN: 00189448 ; Alishahi, K ; Urbanke, R. L ; Sharif University of Technology
Abstract
Consider a binary-input memoryless outputsymmetric channel W. Such a channel has a capacity, call it I (W), and for any R < I (W) and strictly positive constant Pewe know that we can construct a coding scheme that allows transmission at rate R with an error probability not exceeding Pe. Assume now that we let the rate R tend to I (W) and we ask how we have to scale the blocklength N in order to keep the error probability fixed to Pe. We refer to this as the finite-length scaling behavior. This question was addressed by Strassen as well as Polyanskiy, Poor, and Verdu, and the result is that N must grow at least as the square of the reciprocal of I (W)- R. Polar codes are optimal in the sense...
Investigating the Dynamic behavior of Fracture Networks using Percolation Theory
, M.Sc. Thesis Sharif University of Technology ; Masihi, Mohsen (Supervisor) ; Jamshidi, Saeed (Supervisor)
Abstract
Most of petroleum reservoirs of Iran are fractured reservoirs which has different properties, geometrical structure and drive mechanism in comparison with conventional reservoirs. The major difference is the existence of interaction between fractures and matrix respectively with a high and very low permeable (or imperable) medi. One simulation method for these fractures is discrete fracture network (DFN) modeling which is used in this study to investigate dynamic properties of these fractures. In this study, matrix is assumed as an impermeable media then dynamic properties like effective permeability of fracture network for different realization reservoirs are calculated and and evaluated by...
Statistical Mechanics of The Neocortex
, M.Sc. Thesis Sharif University of Technology ; Bahraini, Alireza (Supervisor)
Abstract
In this paper, the field theory tools will be used to study none-equilibrium statistical processes and eventually analyze the dynamic of the neocortex. Assuming the neocortex is Markovian, a model is proposed which contains fluctuations of the neuron activities as well as response to the stimulations. The experimental data shows that the fluctuation and correlation have a vital impact on the dynamics of the cortex, and many of its characteristics can only be justified by it.The paper will study the model that considers correlations and fluctuations to reach a more accurate evaluation of the cortex than the mean field approximation
Investigation of scaling effects on fiber metal laminates under tensile and flexural loading
, Article Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications ; Volume 229, Issue 3 , 2015 , Pages 189-201 ; 14644207 (ISSN) ; Sadighi, M ; Mohammadkhah, M ; Shahsavari Alavijeh, H ; Sharif University of Technology
SAGE Publications Ltd
2015
Abstract
In this study, scaling effects on fiber metal laminates under tensile and three-point bending tests were investigated numerically and experimentally. The fiber metal laminate specimens were made of aluminum 1050 and unidirectional glass-epoxy. Two scaled sizes of specimens were prepared based on A1n , 0n =90n s. Some specified mechanical properties of these samples were investigated and results showed that fiber metal laminates obey scaling law under quasi-static loading. Explicit finite element code LS-DYNA was utilized for numerical simulation. After validating numerical simulation with experiments, scaling law was studied numerically for four different...
Secrecy capacity scaling in large cooperative wireless networks
, Article IEEE Transactions on Information Theory ; Volume 63, Issue 3 , 2017 , Pages 1923-1939 ; 00189448 (ISSN) ; Papadimitratos, P. P ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
We investigate large wireless networks subject to security constraints. In contrast to point-to-point, interferencelimited communications considered in prior works, we propose active cooperative relaying-based schemes. We consider a network with nl legitimate nodes, ne eavesdroppers, and path loss exponent α ≥ 2. As long as n2e (log(ne))γ = o(nl ), for some positive γ , we show that one can obtain unbounded secure aggregate rate. This means zero-cost secure communication, given fixed total power constraint for the entire network. We achieve this result through: 1) the source using Wyner randomized encoder and a serial (multi-stage) block Markov scheme, to cooperate with the relays and 2) the...
Structural similitude in free vibration of orthogonally stiffened cylindrical shells
, Article Thin-Walled Structures ; Volume 47, Issue 11 , 2009 , Pages 1316-1330 ; 02638231 (ISSN) ; Navazi, H. M ; Jafari, A. A ; Bagheri, M ; Sharif University of Technology
2009
Abstract
In this paper, the necessary similarity conditions, or scaling laws, for free vibrations of orthogonally stiffened cylindrical shells are developed using the similitude theory. The Donnell-type nonlinear strain-displacement relations along with the smearing theory are used to model the structure. Then the principle of virtual work is used to analyze the free vibration of the stiffened shell. After non-dimensionalizing the derived formulations, the scaling laws are developed, using the similitude theory. Then, different examples are solved to validate the scaling laws numerically and experimentally. The obtained results show the effectiveness of the derived formulations. © 2009 Elsevier Ltd....
Scaled down models for free vibration analysis of orthogonally stiffened cylindrical shells using similitude theory
, Article 26th Congress of International Council of the Aeronautical Sciences 2008, ICAS 2008, Anchorage, AK, 14 September 2008 through 19 September 2008 ; Volume 2 , 2008 , Pages 3458-3469 ; 9781605607153 (ISBN) ; Jafari, A. A ; Navazi, H. M ; Sharif University of Technology
2008
Abstract
In this paper, the necessary similarity conditions, or scaling laws, for free vibrations of orthogonally stiffened cylindrical shells are developed using similitude theory. The Donnelltype nonlinear strain-displacement relations along with smearing theory are used to model the structure. Then the principle of virtual work is used to analyze the free vibration of the stiffened shell. After nondimensionalizing the derived formulations, the scaling laws are developed, using similitude theory. Then, different examples are solved to validate the scaling laws numerically and experimentally. The obtained results show the effectiveness of the derived formulations
Ferrofluid droplet breakup process and neck evolution under steady and pulse-width modulated magnetic fields
, Article Journal of Molecular Liquids ; Volume 343 , 2021 ; 01677322 (ISSN) ; Favakeh, A ; Mohammadi, K ; Akbari, A ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Numerous applications in engineering and biotechnology have attracted the attention of many researchers to the analysis of underlying physical phenomena during the droplet pinch-off. In this study, the neck evolution during the formation of a ferrofluid droplet from a capillary is investigated under two types of magnetic field for a drop-on-demand system. The two types are steady and Pulse-Width Modulated (PWM) magnetic fields. First, under steady magnetic field, the necking process is studied for different values of magnetic Bond number and various angles between magnetic coil centerline and gravity. Subsequently, self-similar behavior in the vicinity of the detachment moment is observed....