Dr. Yun Lai

Research Associate @ Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong

Office number: 4448     Phone: (852) 2358-7492       email: laiyun@ust.hk

Brief Biography (CV)

I am currently a Research Associate in the Physics Department at Hong Kong University of Science and Technology. I received my B.Sc. degree in Physics from Nanjing University in 1999, and my Ph.D. degree in Physics from Hong Kong University of Science and Technology in 2005. My thesis advisor is Prof. Zhang Zhao-Qing. Before my undergraduate study, I received my high school education in High School Affiliated to Nanjing Normal University from 1992 to 1995.

Research Interests

Waves propagation and localization in periodic, quasiperiodic and random media, which include many interesting topics such as

My current research focus is on the wave propagation in quasiperiodic structures. Due to the absence of Bloch theorem, the research is much more difficult than in periodic structures. Especially, we are interested in the quasiperiodic long-range order effects instead of the short-range order effects. The short-range order may be responsible for the formation of band gaps, as has been discussed in previous literature. However, it is the long-range order that introduces the unsmooth, critical, and self-similar behavior into quasiperiodic systems and makes them fundamentally different from periodic systems. To investigate the long-range order effects, large scale calculations of large-sized samples are inevitable.

Based on the MST (multiple scattering theory) method, after making an improvement by using the SMCG (sparse-matrix canonical-grid) method developed by Prof. C. H. Chan and Prof. L. Tsang, we successfully reduce the operation cost to O(NlogN) (N is the scatterer number) and the memory cost to O(N). With this improved method and parallel computation techniques, we have performed large-scale calculations with tens of thousands of cylinders in 2D. Many interesting and unique phenomena have been found, such as an unsmooth, self-similar-like evolution of gap structures, self-similar states with a power-law decay, large-sized localized states, etc.

Publications

Y Lai, SK Cheung and ZQ Zhang Wave transport in two-dimensional random media: The ballistic to diffusive transition and the extrapolation length PHYSICAL REVIEW E 72 (3): 036606 SEP 2005

Y Lai and ZQ Zhang Large enhancement of phononic gap in periodic and quasiperiodic elastic composites by using air inclusions ZEITSCHRIFT FUR KRISTALLOGRAPHIE 220 (9-10): 877-883 2005

Y Lai and ZQ Zhang Large band gaps in elastic phononic crystals with air inclusions APPLIED PHYSICS LETTERS 83 (19): 3900-3902 NOV 10 2003

Y Lai, XD Zhang and ZQ Zhang Large sonic band gaps in 12-fold quasicrystals JOURNAL OF APPLIED PHYSICS 91 (9): 6191-6193 MAY 1 2002

Y Lai, XD Zhang and ZQ Zhang Engineering acoustic band gaps APPLIED PHYSICS LETTERS 79 (20): 3224-3226 NOV 12 2001

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