The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
K A Fathalah - One of the best experts on this subject based on the ideXlab platform.
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solar flux density distribution due to partially shaded blocked mirrors using the separation of variables Superposition Technique with polynomial and gaussian sunshapes
Journal of Solar Energy Engineering-transactions of The Asme, 1996Co-Authors: Moustafa M. Elsayed, K A FathalahAbstract:In a previous work (El Sayed et al., 1994), the separation of a variable/Superposition Technique was used to predict the flux density distribution on the receiver surfaces of solar central receiver plants. In this paper further developments of the Technique are given. A numerical Technique is derived to carry out the convolution of the sunshape and error density functions. Also, a simplified numerical procedure is presented to determine the basic flux density function on which the Technique depends. The Technique is used to predict the receiver solar flux distribution using two sunshapes, polynomial and Gaussian distributions. The results predicted with the Technique are validated by comparison with experimental results from mirrors both with and without partial shading/blocking of their surfaces.
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solar flux density distribution using a separation of variables Superposition Technique
Renewable Energy, 1994Co-Authors: Moustafa M. Elsayed, K A FathalahAbstract:A separation of variables/Superposition Technique is used to determine the flux density distribution Γ on the receiver plane of a central receiver system. This distribution is determined in terms of the flux density distribution F on the image plane. The distribution F is found in terms of the algebraic sum of several flux distribution functions. Each of these functions Fi is determined in terms of a basic dimensionless flux density function φ, transferred to have its origin of coordinates at one corner of the principal image of the heliostat. Using a special coordinate system, φ is found to depend only on the angle θ∗ between the sides of the principal image of the heliostat, for a given Sun shape and error function. Calculations of θ∗ and the lengths of the sides of the principal image are performed for a wide range of parameters, which include solar zenith and azimuth angles, radial distance of heliostat and its position azimuth angle, tower height, concentration and dimensions of the heliostat. For a given effective Sun shape, the basic dimensionless flux density distribution φ is calculated for several values of θ∗. This distribution is stored in a computer and used in an illustrative example to determine the flux density distribution on a receiver plane.
Moustafa M. Elsayed - One of the best experts on this subject based on the ideXlab platform.
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solar flux density distribution due to partially shaded blocked mirrors using the separation of variables Superposition Technique with polynomial and gaussian sunshapes
Journal of Solar Energy Engineering-transactions of The Asme, 1996Co-Authors: Moustafa M. Elsayed, K A FathalahAbstract:In a previous work (El Sayed et al., 1994), the separation of a variable/Superposition Technique was used to predict the flux density distribution on the receiver surfaces of solar central receiver plants. In this paper further developments of the Technique are given. A numerical Technique is derived to carry out the convolution of the sunshape and error density functions. Also, a simplified numerical procedure is presented to determine the basic flux density function on which the Technique depends. The Technique is used to predict the receiver solar flux distribution using two sunshapes, polynomial and Gaussian distributions. The results predicted with the Technique are validated by comparison with experimental results from mirrors both with and without partial shading/blocking of their surfaces.
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solar flux density distribution using a separation of variables Superposition Technique
Renewable Energy, 1994Co-Authors: Moustafa M. Elsayed, K A FathalahAbstract:A separation of variables/Superposition Technique is used to determine the flux density distribution Γ on the receiver plane of a central receiver system. This distribution is determined in terms of the flux density distribution F on the image plane. The distribution F is found in terms of the algebraic sum of several flux distribution functions. Each of these functions Fi is determined in terms of a basic dimensionless flux density function φ, transferred to have its origin of coordinates at one corner of the principal image of the heliostat. Using a special coordinate system, φ is found to depend only on the angle θ∗ between the sides of the principal image of the heliostat, for a given Sun shape and error function. Calculations of θ∗ and the lengths of the sides of the principal image are performed for a wide range of parameters, which include solar zenith and azimuth angles, radial distance of heliostat and its position azimuth angle, tower height, concentration and dimensions of the heliostat. For a given effective Sun shape, the basic dimensionless flux density distribution φ is calculated for several values of θ∗. This distribution is stored in a computer and used in an illustrative example to determine the flux density distribution on a receiver plane.
Martin Spies - One of the best experts on this subject based on the ideXlab platform.
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application and validation of the gaussian beam Superposition Technique to simulate the inspection of aero engine components
Review of Progress in Quantitative Nondestructive Evaluation, 2007Co-Authors: Martin Spies, W D FeistAbstract:Within the European research project VERDICT, the Gaussian beam Superposition Technique has been specifically refined to meet the simulation needs of aero engine manufacturers. Testing and validation of the refined method have been performed. A variety of simulation results, covering beam fields in water as well as C‐scans obtained on flat bottom holes in curved test specimens are shown in comparison with experimental data; excellent agreement has been obtained.
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analytical methods for modeling of ultrasonic nondestructive testing of anisotropic media
Ultrasonics, 2004Co-Authors: Martin SpiesAbstract:Many modern structural materials exhibit anisotropic elastic behavior leading to complicated wave propagation phenomena. To ensure the reliability of ultrasonic nondestructive testing Techniques, these material properties as well as the influence of microstructural inhomogeneities and the effects of interfaces on ultrasonic wave propagation have to be taken into account. In this respect, mathematical modeling provides an efficient method of assisting analysis. Two computationally efficient analytical approaches--a Gaussian beam and a point source Superposition Technique--are presented, which are well-suited for performing ultrasonic wave propagation and scattering simulations for anisotropic media. Results for homogeneous as well as inhomogeneous anisotropic media like composites and weld material are presented.
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modeling transient radiation of ultrasonic transducers in anisotropic materials including wave attenuation
Quantitative Nondestructive Evaluation, 2002Co-Authors: Martin SpiesAbstract:A point source Superposition Technique is applied to model transducer-radiated transient wavefields assuming anisotropic material and attenuation symmetry. For composite materials, viscoelasticity is taken into consideration thru a complex, frequency-dependent elastic tensor. The generation and propagation of quasi-shear vertical waves in transversely isotropic weld material and of quasi-longitudinal waves in an orthotropic composite are considered.
Matthew A Rice - One of the best experts on this subject based on the ideXlab platform.
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dynamic mechanical response of plasticizer laden acoustic polyurethanes extrapolated to higher frequencies using time temperature Superposition Technique
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Matthew A RiceAbstract:Acoustically transparent elastomers are the windows through which the US Navy views the ocean. For acoustic clarity and sensitivity, it is important that these elastomers operate well outside damping conditions as dictated by the temperatures and frequencies of interest. Damping behavior is characterized by a peak in the loss tangent and is associated with transitions in molecular mobility, such as the primary glass–rubber or alpha transition. However, the temperature and frequency location of this peak can shift in response to absorbed plasticizing fluids. This material characteristic is under investigation using dynamic mechanical analysis to assess its dependence on the plasticizer and polyurethane component chemistry. In this second stage of the research, the time–temperature Superposition Technique was employed to extrapolate storage modulus and loss factor to frequencies beyond the limits of the equipment. The Technique appears to be valid for plasticized primary transition behavior but becomes circumspect when applied to secondary transition behavior.
Carlos Friedrich Loeffler - One of the best experts on this subject based on the ideXlab platform.
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the direct interpolation boundary element method and the domain Superposition Technique applied to piecewise helmholtz s problems with internal heterogeneity
Engineering Analysis With Boundary Elements, 2021Co-Authors: Hercules De Melo Barcelos, Carlos Friedrich Loeffler, Luciano De Oliveira Castro LaraAbstract:Abstract This work presents the combination of the direct interpolation boundary element method (DIBEM) and the domain Superposition Technique (DST) to address piecewise inhomogeneous two dimensional Helmholtz problems, in which the internal constitutive property in each sector varies smoothly according to a known function. The domain integrals generated by the medium's heterogeneity are transformed into boundary integrals according to the DIBEM strategy where radial basis functions are used. The DST is applied to generate the influence coefficients related to the several sectors and compute them in the final matrix system. Thus, the proposed methodology preserves the main features and advantages of the Boundary Element Method. Concerning the evaluation of the numerical results, three different tests are performed, considering regular and irregular domains. For each example, benchmarks are generated by correlate simulations using the Finite Element Method.
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the domain Superposition Technique for solving three dimensional piecewise homogeneous laplace problems
International Journal of Solids and Structures, 2020Co-Authors: Luciano De Oliveira Castro Lara, Joao Paulo Barbosa, Carlos Friedrich LoefflerAbstract:Abstract Within the context of the Boundary Element Method, the Domain Superposition Technique is a novel alternative to the classical sub-regions approach for solving piecewise homogeneous problems. This new Technique was successful in two-dimensional piecewise cases governed by the Laplace Equation and for this reason it is applied in this work to similar three-dimensional problems. Unlike the two-dimensional problems, the modus operandi of the coordinates transformation, the numerical integration procedures and the treatment of singular integrals are not simple and are described herein a proper way. Flat triangular isoparametric elements with linear variation are used for discretization. Considering the absence of analytical solutions, the Finite Element Method was used to generate the reference solutions for adequate performance comparison.
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application of boundary element method Superposition Technique for solving natural frequencies in piecewise homogeneous domains
Computers & Mathematics With Applications, 2020Co-Authors: Joao Paulo Barbosa, Carlos Friedrich LoefflerAbstract:Abstract In this work, the domain Superposition Technique of the Boundary Element Method is coupled with the direct interpolation procedure to identifying the natural frequencies spectrum in two-dimensional piecewise domains with non-regular boundaries and internal inclusions. This problem can be addressed by well-established methods as Finite Element Method; however, the proposed methodology provides better results concerning the accuracy using a simple and expedite boundary element model. Solving the eigenvalue problem, the numerical quality of the matrix related to inertia can be evaluated more precisely, since it is approximated by radial basis functions. That is very important aiming future applications approaching wave propagation problems. A scalar acoustic and isotropic model is assumed, although the methodology can extend to the anisotropic materials. For better accuracy evaluation of the proposed methodology, the solution of some test problems is compared with those obtained with the Finite Element Method using fairly refined meshes.
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performance of bem Superposition Technique for solving sectorially heterogeneous laplace s problems with non regular geometry
Engineering Analysis With Boundary Elements, 2018Co-Authors: Carlos Friedrich Loeffler, Joao Paulo Barbosa, Hercules De Melo BarcelosAbstract:Abstract The Superposition Technique is a new BEM alternative for solving sectorially heterogeneous problems in which the complete domain is divided in a surrounding homogeneous domain and other complementary sub-domains with different constitutive properties. It is an alternative to the classic BEM sub-regions Technique. Results of preliminary simple problems governed by the Laplace's equation were successfully solved, using analytical solutions to performance evaluation. Thus, this paper examines the performance of the Superposition Technique to solve complex problems that present geometric irregularities on the boundary, such as grooves and notches, and internal inclusions. Considering the absence of analytical solutions, the Finite Element Method was used to generate the reference solutions for a suitable comparison.
