5 results
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2. A neural network based methodology to predict site-specific spectral acceleration values.
- Author
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Kamatchi, P., Rajasankar, J., Ramana, G. V., and Nagpal, A. K.
- Subjects
ARTIFICIAL neural networks ,SEISMIC networks ,METHODOLOGY ,ALGORITHMS ,RADIO wave propagation ,NUMERICAL analysis ,ACCELERATION (Mechanics) ,EARTHQUAKE zones - Abstract
general neural network based methodology that has the potential to replace the computationally-intensive site-specific seismic analysis of structures is proposed in this paper. The basic framework of the methodology consists of a feed forward back propagation neural network algorithm with one hidden layer to represent the seismic potential of a region and soil amplification effects. The methodology is implemented and verified with parameters corresponding to Delhi city in India. For this purpose, strong ground motions are generated at bedrock level for a chosen site in Delhi due to earthquakes considered to originate from the central seismic gap of the Himalayan belt using necessary geological as well as geotechnical data. Surface level ground motions and corresponding site-specific response spectra are obtained by using a one-dimensional equivalent linear wave propagation model. Spectral acceleration values are considered as a target parameter to verify the performance of the methodology. Numerical studies carried out to validate the proposed methodology show that the errors in predicted spectral acceleration values are within acceptable limits for design purposes. The methodology is general in the sense that it can be applied to other seismically vulnerable regions and also can be updated by including more parameters depending on the state-of-the-art in the subject. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
3. Numerical study of interaction between jet with rudders on slender body at hypersonic condition.
- Author
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Li, Long-Fei, Wang, Jiang-Feng, Zhao, Fa-Ming, and Wang, Yu-Han
- Subjects
- *
JETS (Fluid dynamics) , *NUMERICAL analysis , *COMPUTER simulation , *HYPERSONIC aerodynamics , *STEERING gear - Abstract
In this paper, a numerical study of the interaction between transverse cold jets on slender body in front of or between X-shape rudders with rudders in the oncoming free stream is presented. Firstly, the flow field at different jet conditions is simulated and analyzed. Then, the total force and moment amplification factors of the corresponding slender body with jet at different locations are analyzed and compared with those results of non-jet flow. Numerical results show that interactions take a great effect to the configuration of the flow field around rudders and the pressure distribution on slender surface. Moreover, the force and moment amplification changes regularly along with the location of jet nozzle. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
4. Convergence and Efficiency of Different Methods to Compute the Diffraction Integral for Gravitational Lensing of Gravitational Waves
- Author
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Youjun Lu and Xiao Guo
- Subjects
Physics ,Diffraction ,010308 nuclear & particles physics ,Gravitational wave ,Numerical analysis ,Mathematical analysis ,FOS: Physical sciences ,General Relativity and Quantum Cosmology (gr-qc) ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Amplification factor ,Physical optics ,01 natural sciences ,General Relativity and Quantum Cosmology ,Gravitational lens ,0103 physical sciences ,Convergence (routing) ,010306 general physics ,Asymptotic expansion ,Astrophysics - Instrumentation and Methods for Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) - Abstract
Wave optics may need to be considered when studying the lensed waveforms of gravitational waves (GWs). However, the computation of the diffraction integral (amplification factor) in wave optics is challenging and time-consuming. It is vital to develop an accurate and efficient method to calculate the amplification factor for detecting lensed GW systems. In this paper, we investigate the convergence of the diffraction integral for gravitational lensing of GWs and analyze the accuracy and efficiency of a number of numerical methods that can be used to calculate this integral, including the integral mean method, asymptotic expansion method, Levin's method, zero points integral method, etc. We further introduce a new method by combining the zero points integral and the asymptotic expansion methods to calculate the diffraction integral, which provides an efficient and accurate way to calculate the lensed waveform of GWs., 18 pages, 7 figures, accepted for publication in PRD
- Published
- 2020
5. Comparative study of coupling coefficients in Dirichlet–Robin procedure for fluid–structure aerothermal simulations
- Author
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Florent Duchaine, M.-P. Errera, ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), CERFACS [Toulouse], and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Mathematical optimization ,Physics and Astronomy (miscellaneous) ,Computation ,Context (language use) ,01 natural sciences ,Stability (probability) ,TRANSFERT CHALEUR CONJUGUE ,010305 fluids & plasmas ,STABILITE ,symbols.namesake ,0103 physical sciences ,Convergence (routing) ,CONVERGENCE ,COEFFICIENT OPTIMA ,Applied mathematics ,CONDITION ROBIN ,0101 mathematics ,Mathematics ,Coupling ,[SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph] ,Numerical Analysis ,Series (mathematics) ,Applied Mathematics ,Amplification factor ,Computer Science Applications ,IMPLICITE ,010101 applied mathematics ,Computational Mathematics ,Fourier transform ,Modeling and Simulation ,symbols - Abstract
International audience; This paper tests the performance of coupling coefficients of a Dirichlet–Robin transmission procedure in the context of steady conjugate heat transfer (CHT). Particular emphasis is put on the optimal coefficients highlighted recently in a theoretical study based on a normal mode stability analysis. This work can be seen as the logical continuation of that study in order to assess the relevance of the coefficients provided by the model problem in a realistic aerothermal computation. First, the numerical and physical CHT modeling methodologies are presented. Then, the optimal procedure applied to a Dirichlet–Robin algorithm (one-coefficient method) is briefly described. In order to gauge the ability of this model to predict the stability and convergence properties of a realistic case, it is compared on a heated cylinder in a flowfield test case. A series of five coupling coefficients and three Fourier numbers are considered. These parameters are introduced into the model problem as data to compute the amplification factor and the stability limits. The stability and convergence properties predicted by the model problem are then compared to those obtained in the CHT computation. This comparison shows an excellent overall agreement. Moreover, for all the Fourier numbers considered, the numerical solution is stable and oscillation-free when the optimal coefficient of the model problem is used. This would suggest that the one-dimensional normal mode analysis can provide relevant coefficients directly applicable to real CHT problems.
- Published
- 2016
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