Documents disponibles écrits par cet auteur

Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures / L. P. Wang in Journal of heat transfer, Vol. 133 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [072701/1-7] Titre : Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures Type de document : texte imprimé Auteurs : L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur Année de publication : 2011 Article en page(s) : pp. [072701/1-7] Note générale : Physique Langues : Anglais (eng) Mots-clés : Generalizes  Kirchhoff's  law  Thermal  emission  Fluctuational  electrodynamics  Multilayers Index. décimale : 536 Chaleur. Thermodynamique Résumé : The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the “indirect” and “direct” methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff's law. On the other hand, a few studies have used a combination of Maxwell's equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating the far-field thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry–Pérot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...] [article] Direct and indirect methods for calculating thermal emission from layered structures with nonuniform temperatures [texte imprimé] / L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur . - 2011 . - pp. [072701/1-7]. Physique Langues : Anglais (eng) in Journal of heat transfer > Vol. 133 N° 7 (Juillet 2011) . - pp. [072701/1-7] Mots-clés : Generalizes  Kirchhoff's  law  Thermal  emission  Fluctuational  electrodynamics  Multilayers Index. décimale : 536 Chaleur. Thermodynamique Résumé : The determination of emissivity of layered structures is critical in many applications, such as radiation thermometry, microelectronics, radiative cooling, and energy harvesting. Two different approaches, i.e., the “indirect” and “direct” methods, are commonly used for computing the emissivity of an object. For an opaque surface at a uniform temperature, the indirect method involves calculating the spectral directional-hemispherical reflectance to deduce the spectral directional emissivity based on Kirchhoff's law. On the other hand, a few studies have used a combination of Maxwell's equations with the fluctuation-dissipation theorem to directly calculate the emissivity. The present study aims at unifying the direct and indirect methods for calculating the far-field thermal emission from layered structures with a nonuniform temperature distribution. Formulations for both methods are given to illustrate the equivalence between the indirect and the direct methods. Thermal emission from an asymmetric Fabry–Pérot resonance cavity with a nonuniform temperature distribution is taken as an example to show how to predict the intensity, emissivity, and the brightness temperature. The local density of states, however, can only be calculated using the direct method. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO00013300 [...]

Direct measurement of thermal emission from a fabry–perot cavity resonator / L. P. Wang in Journal of heat transfer, Vol. 134 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of heat transfer > Vol. 134 N° 7 (Juillet 2012) . - 09 p. Titre : Direct measurement of thermal emission from a fabry–perot cavity resonator Type de document : texte imprimé Auteurs : L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur Année de publication : 2012 Article en page(s) : 09 p. Note générale : heat transfer Langues : Anglais (eng) Mots-clés : high  temperature;  thermal  emission;  thin  films;  wave  interference Index. décimale : 536 Chaleur. Thermodynamique Résumé : There have been growing interests in selective control of thermal emission by using micro/nanostructures. The present study describes direct measurements of infrared thermal emission at elevated temperatures of an asymmetric Fabry–Perot resonator at variable angles for each polarization. The multilayered structure mainly contains a SiO2 optical cavity sandwiched between a thick (opaque) Au film and a thin Au film. Metallic adhesive and diffusion-barrier layers were deposited on a Si substrate before depositing the thick Au film. A dielectric protection layer was deposited atop the thin Au film to prevent oxidation at high temperatures. A SiC wafer was used as the reference to test the emittance measurement facility, which includes a heated sample holder, a blackbody source, mirror assembly, a polarizer, and a Fourier-transform infrared spectrometer with different detectors. The measured emittance spectra of the Fabry–Perot structure exhibit peak broadening and shifting as temperature increases; the mechanisms are elucidated by comparison with theoretical modeling. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000007 [...] [article] Direct measurement of thermal emission from a fabry–perot cavity resonator [texte imprimé] / L. P. Wang, Auteur ; S. Basu, Auteur ; Z. M. Zhang, Auteur . - 2012 . - 09 p. heat transfer Langues : Anglais (eng) in Journal of heat transfer > Vol. 134 N° 7 (Juillet 2012) . - 09 p. Mots-clés : high  temperature;  thermal  emission;  thin  films;  wave  interference Index. décimale : 536 Chaleur. Thermodynamique Résumé : There have been growing interests in selective control of thermal emission by using micro/nanostructures. The present study describes direct measurements of infrared thermal emission at elevated temperatures of an asymmetric Fabry–Perot resonator at variable angles for each polarization. The multilayered structure mainly contains a SiO2 optical cavity sandwiched between a thick (opaque) Au film and a thin Au film. Metallic adhesive and diffusion-barrier layers were deposited on a Si substrate before depositing the thick Au film. A dielectric protection layer was deposited atop the thin Au film to prevent oxidation at high temperatures. A SiC wafer was used as the reference to test the emittance measurement facility, which includes a heated sample holder, a blackbody source, mirror assembly, a polarizer, and a Fourier-transform infrared spectrometer with different detectors. The measured emittance spectra of the Fabry–Perot structure exhibit peak broadening and shifting as temperature increases; the mechanisms are elucidated by comparison with theoretical modeling. DEWEY : 536 ISSN : 0022-1481 En ligne : http://asmedl.org/getabs/servlet/GetabsServlet?prog=normal&id=JHTRAO000134000007 [...]