The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
J D Achenbach - One of the best experts on this subject based on the ideXlab platform.
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application of the Reciprocity Theorem to scattering of surface waves by an inclined subsurface crack
International Journal of Solids and Structures, 2020Co-Authors: Oluwaseyi Balogun, Chuanyong Wang, J D AchenbachAbstract:Abstract In this paper the scattering of incident surface waves by an inclined subsurface crack in a homogenous, isotropic and linearly elastic half-space has been investigated in a two-dimensional plane strain configuration. The elastodynamic Reciprocity Theorem together with a virtual wave has been used to determine the amplitude of the scattered surface waves in the far field. It is found that the amplitude is in terms of the crack opening volume due to the incident surface waves. A special case of low frequency, for which the wavelength of the surface wave is sufficiently larger than the crack length, has been considered to illustrate the method. A specific expression of the amplitude has been obtained, which provides information on the angle, length and depth of the crack. It shows that the amplitude of the scattered surface wave increases first and then decreases as the crack angle changes from 0° to 90°. For the case of an inclined crack, the results of the numerical analysis together with the analytical solutions show excellent agreement when the crack length is much smaller than the wavelength. The results in this paper should be useful for the quantitative measurement of subsurface cracks.
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use of the Reciprocity Theorem for a closed form solution of scattering of the lowest axially symmetric torsional wave mode by a defect in a pipe
Ultrasonics, 2018Co-Authors: Jaesun Lee, J D Achenbach, Younho ChoAbstract:Abstract Guided waves can effectively be used for inspection of large scale structures. Surface corrosion is often found as major defect type in large scale structures such as pipelines. Guided wave interaction with surface corrosion can provide useful information for sizing and classification. In this paper, the elastodynamic Reciprocity Theorem is used to formulate and solve complicated scattering problems in a simple manner. The approach has already been applied to scattering of Rayleigh and Lamb waves by defects to produce closed form solutions of amplitude of scattered waves. In this paper, the scattering of the lowest axially symmetric torsional mode, which is widely used in commercial applications, is analyzed by the Reciprocity Theorem. In the present paper, the Theorem is used to determine the scattering of the lowest torsional mode by a tapered defect that was earlier considered experimentally and numerically by the finite element method. It is shown that by the presented method it is simple to obtain the ratio of amplitudes of scattered torsional modes for a tapered notch. The results show a good agreement with earlier numerical results. The wave field superposition technique in conjunction with the Reciprocity Theorem simplifies the solution of the scattering problem to yield a closed form solution which can play a significant role in quantitative signal interpretation.
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a study on closed form solution of guided waves scattering amplitude by the use of Reciprocity Theorem in the cylindrical coordinate
41st Annual Review of Progress in Quantitative Nondestructive Evaluation: Volume 34, 2015Co-Authors: Jaesun Lee, Younho Cho, J D AchenbachAbstract:The guided wave technique is well known for long range pipe inspection. Guided wave scattered signal analysis is difficult due to the complex geometry such as corrosion. Reciprocity relation is well established Theorem to convert complicate mathematical expression to simpler manner. Wave signal analysis is performed for half-space and plate problems with Reciprocity approach by earlier papers. The advantage of applying Reciprocity Theorem is providing closed form solution of scattered wave amplitude calculation. However, it is hard to find Reciprocity relation application on cylindrical coordinates. In this paper, Reciprocity Theorem is applied on cylindrical coordinate for wave propagation pattern analysis. The wave field is obtained in an elegant manner by using a superposition technique and the Reciprocity Theorem for three-dimensional elastodynamics. For the scattered field, there are two elastodynamic stages; actual wave field excited by time-harmonic loading, virtual wave. The amplitudes of the prop...
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verification of surface wave solutions obtained by the Reciprocity Theorem
Ultrasonics, 2014Co-Authors: Haidang Phan, Younho Cho, J D AchenbachAbstract:Surface wave motions generated by a time-harmonic point load applied at the surface of an isotropic linearly elastic half-space are conventionally solved by the use of integral transform techniques. The inverse transforms, are often complicated and will not always yield closed-form solutions. In this paper expressions for the displacements for surface wave motions radiated from point-load excitation are determined in a simple manner by the use of the elastodynamic Reciprocity Theorem. It is shown that the radiated amplitudes of the surface displacements obtained by the Reciprocity approach are identical to the corresponding results obtained by the use of Hankel transform and by Lamb in his classical paper.
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a new use of the elastodynamic Reciprocity Theorem
Mathematics and Mechanics of Solids, 2014Co-Authors: J D AchenbachAbstract:For an isotropic linearly elastic half-space whose elastic moduli and mass density depend on the distance from the free surface, the surface wave motion radiating from a time-harmonic point load applied normal to the surface of the half-space is considered in this paper. The surface wave velocity, which depends on the wave number, together with expressions for the displacements and stresses of free surface waves, are obtained in a high-frequency approximation. Application of the Reciprocity Theorem using general expressions for the surface wave radiated by the oscillating point load, together with a virtual free surface wave, yields relatively simple expressions for the amplitude factor of the radiated surface wave. For a few examples, results show the velocity of surface waves and the amplitude factor of the surface waves as a function of the wave number.
Chulsoon Hwang - One of the best experts on this subject based on the ideXlab platform.
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Reciprocity Theorem Based RFI Estimation for Heatsink Emission
2019 IEEE International Symposium on Electromagnetic Compatibility Signal & Power Integrity (EMC+SIPI), 2019Co-Authors: Qiaolei Huang, Yang Zhong, Ze Sun, Takashi Enomoto, Shingo Seto, Kenji Araki, Jun Fan, Chulsoon HwangAbstract:Heatsinks are widely used to dissipate heat in electronic devices. RF emission from heatsinks and ICs can cause radio frequency interference (RFI) issues. The existence of the heatsink affects the coupling from the noise source to the victim antenna. In this paper, the heatsink RFI problems are analyzed by two methods using Reciprocity Theorem. In the first method, the heatsink effect is combined with the antenna to derive the transfer function. In the second method, the heatsink can be characterized in both the source side and the antenna side on a closed 6-surface box. The physical insights and comparisons of the two RFI estimation methods based on Reciprocity Theorem will be investigated. The proposed methods will be utilized on a few numeric simulations for validations.
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radio frequency interference estimation by Reciprocity Theorem with noise source characterized by huygens s equivalent model
International Symposium on Electromagnetic Compatibility, 2016Co-Authors: Jingnan Pan, Chulsoon Hwang, Gyuyeong Cho, Harkbyeong Park, Yaojiang Zhang, Jun FanAbstract:Noise coupling from a working IC to the neighboring victim antenna is estimated by decomposition based Reciprocity Theorem. The overall problem is decomposed into two parts. In the first part, the IC is turned on and the victim antenna is turned off, which is defined as forward problem. The second part is called reverse problem in which case the victim antenna is excited while the IC is turned off. An imaginary Huygens's box is introduced above the victim antenna for evaluating the coupled power from noise source to the victim RF antenna. The noise source is characterized by Huygens's equivalent source in the forward problem, and the victim antenna is modeled in full-wave simulation tool. With tangential E and H fields obtained in both forward problem and reverse problem, the coupled power can be estimated by numerical calculation of Reciprocity Theorem. The method by using Huygens's equivalent source is first validated by simulation in the forward problem. Later a test board with an IC and patch antenna is further measured to validate the overall methodology.
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measurement validation for radio frequency interference estimation by Reciprocity Theorem
International Symposium on Electromagnetic Compatibility, 2015Co-Authors: Jingnan Pan, Chulsoon Hwang, Gyuyeong Cho, Harkbyeong Park, Yaojiang Zhang, Jun FanAbstract:This paper presents the measurement validation of Reciprocity Theorem method for near-field coupling estimation. The overall problem is decomposed into two parts, the first part is called forward problem, and the second part is called the reverse problem. For forward problem, the noise source IC is modelled by physics-based dipole moment model with data obtained from a near-field scanning plane, then the tangential E and H fields on a Huygens's box enclosing the victim antenna are calculated by analytical expression. In reverse problem, the victim RF antenna is modelled in full-wave simulation tool and the tangential E and H field are obtained by simulation. With tangential E and H field obtained in forward problem and reverse problem, the coupled noise power is then estimated by Reciprocity Theorem. The estimated noise coupling power is compared with measured power at the victim antenna port with IC excited. The difference is within 5dB which is acceptable for engineering practice.
S W Glunz - One of the best experts on this subject based on the ideXlab platform.
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investigation of electrical shading effects in back contacted back junction silicon solar cells using the two dimensional charge collection probability and the Reciprocity Theorem
Journal of Applied Physics, 2011Co-Authors: Christian Reichel, Filip Granek, M Hermle, S W GlunzAbstract:In this study, short-circuit current losses in high-efficiency n-type back-contacted back-junction silicon solar cells caused by the electrical shading effect have been investigated by two-dimensional simulations of the charge carrier collection probability. Based on the Reciprocity Theorem, the homogenous partial differential equation describing the probability of charge carriers being collected by the p-n junction on the rear side of the solar cell has been solved numerically using the finite element method implemented in the partial differential equation solver COMSOL Multiphysics. The method has been applied to study the impact of geometrical parameters of the solar cell, such as the pitch distance, as well as the emitter and back surface field width, on the local and global internal quantum efficiency and on the short-circuit current density. The influence of the rear surface recombination velocity of an undiffused gap and the effective rear surface recombination velocity of the back surface field re...
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analyzing the effects of front surface fields on back junction silicon solar cells using the charge collection probability and the Reciprocity Theorem
Journal of Applied Physics, 2008Co-Authors: Martin Hermle, Filip Granek, O Schultz, S W GlunzAbstract:In this work, a one-dimensional analytical model to calculate the quantum efficiency in back-junction solar cells with and without a high-low junction on the front side is presented. The analytical model, based on the Reciprocity Theorem for charge collection, is compared with numerical device simulations taking into account the influence of high-injection effects. Using the analytical model, the influence of base doping concentration and surface recombination velocity on the internal quantum efficiency of a n-type back-junction solar cell is analyzed.
Jun Fan - One of the best experts on this subject based on the ideXlab platform.
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Reciprocity Theorem Based RFI Estimation for Heatsink Emission
2019 IEEE International Symposium on Electromagnetic Compatibility Signal & Power Integrity (EMC+SIPI), 2019Co-Authors: Qiaolei Huang, Yang Zhong, Ze Sun, Takashi Enomoto, Shingo Seto, Kenji Araki, Jun Fan, Chulsoon HwangAbstract:Heatsinks are widely used to dissipate heat in electronic devices. RF emission from heatsinks and ICs can cause radio frequency interference (RFI) issues. The existence of the heatsink affects the coupling from the noise source to the victim antenna. In this paper, the heatsink RFI problems are analyzed by two methods using Reciprocity Theorem. In the first method, the heatsink effect is combined with the antenna to derive the transfer function. In the second method, the heatsink can be characterized in both the source side and the antenna side on a closed 6-surface box. The physical insights and comparisons of the two RFI estimation methods based on Reciprocity Theorem will be investigated. The proposed methods will be utilized on a few numeric simulations for validations.
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radio frequency interference estimation by Reciprocity Theorem with noise source characterized by huygens s equivalent model
International Symposium on Electromagnetic Compatibility, 2016Co-Authors: Jingnan Pan, Chulsoon Hwang, Gyuyeong Cho, Harkbyeong Park, Yaojiang Zhang, Jun FanAbstract:Noise coupling from a working IC to the neighboring victim antenna is estimated by decomposition based Reciprocity Theorem. The overall problem is decomposed into two parts. In the first part, the IC is turned on and the victim antenna is turned off, which is defined as forward problem. The second part is called reverse problem in which case the victim antenna is excited while the IC is turned off. An imaginary Huygens's box is introduced above the victim antenna for evaluating the coupled power from noise source to the victim RF antenna. The noise source is characterized by Huygens's equivalent source in the forward problem, and the victim antenna is modeled in full-wave simulation tool. With tangential E and H fields obtained in both forward problem and reverse problem, the coupled power can be estimated by numerical calculation of Reciprocity Theorem. The method by using Huygens's equivalent source is first validated by simulation in the forward problem. Later a test board with an IC and patch antenna is further measured to validate the overall methodology.
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measurement validation for radio frequency interference estimation by Reciprocity Theorem
International Symposium on Electromagnetic Compatibility, 2015Co-Authors: Jingnan Pan, Chulsoon Hwang, Gyuyeong Cho, Harkbyeong Park, Yaojiang Zhang, Jun FanAbstract:This paper presents the measurement validation of Reciprocity Theorem method for near-field coupling estimation. The overall problem is decomposed into two parts, the first part is called forward problem, and the second part is called the reverse problem. For forward problem, the noise source IC is modelled by physics-based dipole moment model with data obtained from a near-field scanning plane, then the tangential E and H fields on a Huygens's box enclosing the victim antenna are calculated by analytical expression. In reverse problem, the victim RF antenna is modelled in full-wave simulation tool and the tangential E and H field are obtained by simulation. With tangential E and H field obtained in forward problem and reverse problem, the coupled noise power is then estimated by Reciprocity Theorem. The estimated noise coupling power is compared with measured power at the victim antenna port with IC excited. The difference is within 5dB which is acceptable for engineering practice.
Hany H Sherief - One of the best experts on this subject based on the ideXlab platform.
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fractional order theory of thermoelasticity
International Journal of Solids and Structures, 2010Co-Authors: Hany H Sherief, A M A Elsayed, A Abd M EllatiefAbstract:In this work, a new theory of thermoelasticity is derived using the methodology of fractional calculus. The theories of coupled thermoelasticity and of generalized thermoelasticity with one relaxation time follow as limit cases. A uniqueness Theorem for this model is proved. A variational principle and a Reciprocity Theorem are derived.
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the theory of generalized thermoelastic diffusion
International Journal of Engineering Science, 2004Co-Authors: Hany H Sherief, Farid A Hamza, Heba A SalehAbstract:In this work, a derivation of the governing equations for generalized thermodiffusion in elastic solids is given. A variational Theorem is then obtained for the governing equations. Next, we prove the uniqueness of solution of these equations under suitable conditions. At last, we obtain a Reciprocity Theorem for these equations.
