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  1. Academic Seminar

    July 16, 2019 by Ruan Die   Share:   RenRen   Print
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    Academic Seminar: On the Validity of Kirchhoff’s Law for Anisotropic Metamaterials

    Speaker: Prof. Zhuomin Zhang, Georgia Institute of Technology

    Time: Jul. 18th, 2019 (Thursday), 02:00 p.m.- 04:00 p.m.

    Location: Room 454, Long Bin Building, UM-SJTU Joint Institute, Shanghai Jiao Tong University

    Abstract

    It has been almost 160 years since Gustav Kirchhoff first conceptualized and cast the word blackbody and formulated the relationship between thermal emission and absorptance of a material. Kirchhoff’s law is often expressed as the equality of emittance and absorptance of a surface and has important applications to the determination of radiative properties. Due to the advancement of metamaterials, two-dimensional materials, and micro/nanoscale thermal radiation, Kirchhoff’s law has been revisited by several groups. Some studies also challenge the derivations and applicability of the statement of Kirchhoff’s law that appears in typical radiative heat transfer textbooks. This presentation will give a review of Kirchhoff’s law for isotropic objects and its validity for both hemispherical and directional properties. For anisotropic materials, including opaque media and semitransparent thin films, Kirchhoff’s law is formulated considering both co-polarization and cross-polarization. We show that for macroscopic objects, as long as the Helmholtz reciprocity can be established, conventional expressions of Kirchhoff’s law is applicable even with anisotropic media and metamaterials. On the other hand, for a magneto-optical material whose dielectric tensor is non-reciprocal, Kirchhoff’s law breaks down. Numerical examples based on a composite of bulk and anisotropic films will also presented.

    Biography

    Professor Zhuomin Zhang earned a Ph.D. degree from MIT and worked at NIST and University of Florida prior to joining Georgia Tech in 2002. He received his B.S. and M.S. degrees from the University of Science and Technology of China (Hefei). His research interests are in micro/nanoscale heat transfer especially nanoscale thermal radiation for energy conversion and temperature measurement. He has written a book on Nano/Microscale Heat Transfer (McGraw-Hill, 2007), co-authored over 190 journal papers, and given over 380 invited and contributed presentations. A number of his former students have established independent careers at major universities or industry in the United States, China (mainland and Taiwan) and South Korea. In addition, he has supervised many visiting scholars, postdoctoral fellows and undergraduate student researchers. Dr. Zhang currently serves as an associate editor of the Journal of Thermophysics & Heat Transfer and the Journal of Quantitative Spectroscopy & Radiative Transfer. He served as the Program Chair of the ASME 3rd Micro/Nanoscale Heat & Mass Transfer International Conference (Atlanta, March 2012), Chair of the 2nd International Workshop on Nano-Micro Thermal Radiation (Shanghai, June 2014), and General Chair for the ASME 5th Micro/Nanoscale Heat & Mass Transfer International Conference (Singapore, January 2016). Dr. Zhang is a Fellow of ASME, AAAS, and APS, and an Associate Fellow of AIAA. He was a recipient of the 1999 Presidential Early Career Award for Scientists and Engineers (PECASE) and the 2015 ASME Heat Transfer Memorial Award.