Propagation of ultrasound through two- and three-dimensional strongly scattering media
2015.07.27 12:59
장소 | B501, Room Red, KI bldg. 5nd fl. |
---|---|
일시 | 2015/08/04, 11PM |
연사 | Dr. Eric Jin Ser Lee(Univ. of Manitoba, Canada) |
Propagation of ultrasound through two- and three-dimensional strongly scattering media
2015/08/04(TUE), 11PM, B501(Room Red, KI bldg. 5nd fl.)
Dr. Eric Jin Ser Lee, Department of Physics and Astronomy, Univ. of Manitoba, Canada
During my Ph. D study at the University of Manitoba, I have investigated the propagation of ultrasound through two- and three-dimensional strongly scattering media, with either random or ordered internal structures, through experiments and finite element simulations. All media investigated have strong scattering resonances, leading to novel transport behaviour.
The two-dimensional samples consist of nylon rods immersed in water. Nylon fishing lines under tension are used as two-dimensional scatterers. Note that since the rods are parallel and of uniform diameter, there is negligible scattering of waves out of the plane perpendicular to the rods, so that the system appears two-dimensional from the wave point of view for propagation in this plane. When nylon rods are surrounded by water, they exhibit strong scattering resonances. In such an environment, the nylon scattering resonance can couple with the propagating mode through water to create a bandgap. This is a called hybridization gap. When the nylon rods are arranged in a triangular lattice to form two-dimensional phononic crystals, very unusual dispersion properties are observed when the lattice constant is adjusted so that Bragg and hybridization gaps overlap in frequency. This behaviour is attributed to the competition between two co-existing propagating modes, leading to a new method for tuning bandgap properties and adjusting the transmission by orders of magnitude.
The three-dimensional media were fabricated by brazing aluminum beads together to form a disordered porous solid network with either vacuum in the pores. This system is of particular interest because it has been shown to exhibit Anderson localization of ultrasound. With such system, the density of states (DOS) was investigated. It is the number of vibrational states per unit frequency range per unit volume. The DOS is a fundamental property of any system and can influence not only wave transport but also the possibility of forming localized states. The DOS was measured by directly counting the modes in the frequency domain. At intermediate frequencies, the DOS was found to be approximately independent of frequency, while at higher frequencies, the frequency dependence was consistent with traditional DOS models. Furthermore, the level statistics, which describe the distribution of the separations between neighbour modes in frequency, of the modes was investigated to determine the conditions under which level repulsion occurs. As the sample becomes larger to have more modes, the modes start to overlap and repel each other so that level repulsion effects become important. Consequently, the level statistics were observed to become closer to GOE predictions as the sample size increased. For the last, as there is a transition from diffusive to localized regime around the lower bandgap edge, a transition from GOE to Poisson distribution is observed.
Contact: Prof. YongKeun Park, Physics Dept., (yk.park@kaist.ac.kr)
댓글 0
번호 | 일시 | 장소 | 연사 | 제목 |
---|---|---|---|---|
공지 | 2019/09/18 - 12/5 | Seminar Room #1323 | Prof. David Schuster and etc. | Fall 2019: Physics Seminar Serises |
공지 | 2019/09/02 - 12/09 | Seminar Room 1501 | 이호성 박사 (한국표준과학연구원) and etc. | Fall 2019: Physics Colloquium |
79 | Nov. 28 (Tue.), 4:00 PM | #1323 (E6-2. 1st fl.) | Samindranath Mitra, Editor at Physical Review Letters |
Physics after the lab and the desk: Your work in PRL
![]() |
78 | Nov. 29(Tue) 4p.m. | #1323(E6-2. 1st fl.) | Dr. SungBin Lee, KAIST | Symmetry Protected Kondo Metals and Their Phase Transitions |
77 | Nov. 3 (Fri.), 2:30 PM | #1323 (1st fl., E6-2.) | Dr. MinChul Lee(Department of Applied Physics, Kyung Hee Univ.) |
Quantum Resistor-Capacitor Circuit with Majorana Edge States
![]() |
76 | Nov. 3 (Fri.), 4:00 PM | #1323 (1st fl., E6-2.) | Dr. SungDae Ji (Max Planck POSTECH/Hshinchu Center (MPK)) |
Expedition to the Kitaev Quantum Spin Liquid: Hunting for Majorana fermions
![]() |
75 | Nov. 8 (Wed.), 1:00 PM | #5318 (E6-2. 5th fl.) | Prof. Y. Matsuda Department of Physics, Kyoto University |
“Emergent exotic quasiparticles in quantum spin liquids”
![]() |
74 | Nov. 9 (Fri.), 02:30 PM | E6-2. 1st fl. #1323 | Dr. Pilkyung Moon |
Moiré superlattices – from twisted bilayer graphene to quasicrystal
![]() |
73 | Nov. 9 (Fri.), 04:00 PM | E6-2. 1st fl. #1323 | Dr. Donghun Lee |
Quantum sensing and imaging with diamond defect centers for nano-scale spin physics
![]() |
72 | Nov.26(Thu), 04:00PM | Online(Zoom) | Myung-Ki Kim | 2020 가을학기 광학분야 특별세미나(Light Engineering Beyond the Diffraction Limit) |
71 | November 1 (Thu.), 16:00 PM | #1323, E6-2 | Dr. KyeoReh Lee |
Direct holography from a single snapshot
![]() |
70 | November 14 (Thu.), 16:00 PM | #1323, E6-2 | Prof. Ji-Hun Kang |
Semi-classical model of polariton propagation
![]() |
69 | November 20 (Wed.), 4:00 PM | #5302, E6-2 | Dr. Shigeyuki Ishida |
Correlation between superconducting transition temperature and critical current density in irradiated iron-based superconductors
![]() |
68 | November 21 (Wed.), 15:00 PM | #1323, E6-2 | Prof. Seongshik Oh |
Engineering topological quantum physics at the atomic scale
![]() |
67 | November 28 (Thu.), 16:00 PM | #1323, E6-2 | Prof. Kyung Taec Kim |
Generation of coherent EUV emissions using ultrashort laser pulses
![]() |
66 | November 29 (Thu.), 16:00 PM | #1323, E6-2 | Dr. Kee suk Hong |
양자 칸델라 실현을 위한 단일 광자 발생장치 개발
![]() |
65 | November 5 (Tue.), 4:00 PM | #1323, E6-2 | Dr. Shik Shin |
Study on nanomaterials by the development of ultrahigh resolution laser-photoelectron microscopy (PEEM)
![]() |
64 | November 7 (Thu.), 16:00 PM | #1323, E6-2 | Prof. Je-Hyung Kim |
Integrated quantum photonics with solid-state quantum emitters
![]() |
63 | November 8 (Thu.), 16:00 PM | #1323, E6-2 | 이종완 박사 |
Conformality lost
![]() |
62 | Oct 23 (Fri.), 14:00 PM | E6-2 #1323 | Prof. Ivan Savenko (University of Science and Technology & IBS PCS) |
Plasmon spectroscopy of low-dimensional superconductors in fluctuating regime
![]() |
61 | Oct 9 (Fri), 09:00 AM | https://kaist.zoom.us/j/85161896513?pwd=U3pwWFFZaWVRamxDZUR5REhNeVk0UT09 | Prof. Tim Hsieh (Perimeter Institute) |
Quantum Many-Body Simulation
![]() |
60 | Oct. 07 (Fri), 1:30 PM | E6-2. #1323(1st fl.) | Dr. Suk Bum Chung, IBS-CCES , Seoul National University | “Symmetry and topology in transition metal dichalcogenide?” |