visual
visual

세미나

  • HOME
  • >
  • 소식
  • >
  • 세미나
날짜 2015-08-04 11:00 
연사  
장소 B501, Room Red, KI bldg. 5nd fl. 

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)

 

 

번호 날짜 연사 제목
공지 2025-04-29 10:00  Dr. Yeonju Go (Brookhaven National Laboratory)  Exploring the Hottest Matter in the Universe: Quark-Gluon Plasma through Hard Probes and Artificial Intelligence
공지 2025-05-01 16:00  Dr. Inwook Kim (Lawrence Livermore National Laboratory)  BSM Physics Search with Quantum Sensors
공지 2025-02-24 16:00    2025년 봄학기 콜로키움 안내
공지 2025-02-27 16:00    2025년 봄 물리학과 특별세미나 (광학/응집물리 분야)
606 2025-05-23 11:00  천상모 교수(한양대학교 물리학과)  Superconductivity in Topological Materials file
605 2025-05-22 16:00  Prof. Keun Su Kim (The Univ. of Yonsei)  Sublattice-interference model for Fermi arcs in cuprates file
604 2025-05-22 16:00  유현승 박사(삼성종합기술원)  Reconstructing Reality: Learning-based Methods for 3D Imaging and Graphics file
603 2025-05-15 16:00  노찬 박사(KAIST)  Generation of multimode Gaussian quantum states and their applications for quantum computing file
602 2025-05-13 16:00  Mr. Heonjoon Park(Univ. Washington, USA)  Fractional Quantum Anomalous Hall Effect file
601 2025-05-02 11:00  Prof. Joonho Jang  Anderson localization of electrons in a moire-of-moire lattice of helical twisted trilayer graphene file
600 2025-04-29 16:00  Dr. Tokuro Shimokawa (Okinawa Institute of Science and Technology)  Can experimentally-accessible measures of entanglement distinguish quantum spin liquid and random singlet phases? file
599 2025-04-28 16:00  지명국 (연세대 천문우주학과)  Galaxy Cluster Collisions as Cosmic Laboratories for Dark Matter file
598 2025-04-22 16:00  Dr. Nanse Esaki (The University of Tokyo)  Spin Nernst and thermal Hall effects of topological triplons in quantum dimer magnets on the maple-leaf and star lattices file
597 2025-04-22 13:30  Dr. Chaebin Kim (Georgia Institute of Technology)  Emulation of quantum correlations by classical dynamics in quantum magnets file
596 2025-04-21 16:00  Prof. Ambrose Sungseok Seo (Univ of Kentucky)  Condensed matter physics? All you gotta do is just meet me at the ... file
595 2025-04-16 13:00    오가노이드 사이언스(주) 여섯번째 세미나 시리즈 file
594 2025-04-11 11:00  옥종목 교수 (부산대학교 물리학과)  An Approach to Controlling Physical Properties:Defect-Engineered High-Quality Single Crystal Growth file
593 2025-04-11 11:00  조상연 박사(Wellman Center for Photomedicine)  Semiconductor Nanolaser Particles: The Building Blocks of Next-Generation, Highly Multiplexed Photonic Systems file
592 2025-04-04 12:00  조길영 교수(KAIST)  Theoretical Kaleidoscope of Quantum Material Research: From Quantum Field Theory and Quantum Information to Future Devices file
591 2025-04-03 16:00  윤홍 박사 (Corning Technology Center Korea)  Introduction of Corning Glass Innovation file
590 2025-03-28 11:00  명노준 교수 (조선대)  Quantum Transport in Strained-Engineered Graphene: Mesoscopic Perspective of Tunable Quantum Information Devices file
589 2025-03-27 16:00  김건우 교수 (중앙대)  Quantum dynamics in synthetic spaces file