37 research outputs found
Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A
Local bathymetric quasi-periodic patterns of oscillation are identified from
monthly profile surveys taken at two shore-perpendicular transects at the USACE
field research facility in Duck, North Carolina, USA, spanning 24.5 years and
covering the swash and surf zones. The chosen transects are the two furthest
(north and south) from the pier located at the study site. Research at Duck has
traditionally focused on one or more of these transects as the effects of the
pier are least at these locations. The patterns are identified using singular
spectrum analysis (SSA). Possible correlations with potential forcing
mechanisms are discussed by 1) doing an SSA with same parameter settings to
independently identify the quasi-periodic cycles embedded within three
potentially linked sequences: monthly wave heights (MWH), monthly mean water
levels (MWL) and the large scale atmospheric index known as the North Atlantic
Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the
local bathymetric patterns. The results agree well with previous patterns
identified using wavelets and confirm the highly nonstationary behaviour of
beach levels at Duck; the discussion of potential correlations with
hydrodynamic and atmospheric phenomena is a new contribution. The study is then
extended to all measured bathymetric profiles, covering an area of 1100m
(alongshore) by 440m (cross-shore), to 1) analyse linear correlations between
the bathymetry and the potential forcings using multivariate empirical
orthogonal functions (MEOF) and linear correlation analysis and 2) identify
which collective quasi-periodic bathymetric patterns are correlated with those
within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum
analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure
Spatio-temporal video error concealm entusing priority-ranked region-matching
When transmitted over error-prone networks, compressed video sequences may be received with errors. In this paper we propose a priority-ranked region-mathing algorithm to recover the "lost" area of the decoded frames, in which both temporal and spatial correlations of the video sequence are exploited. In the proposed scheme, we first calculate the priorities of alledge pixels of the "lost" area and generate a priority-ranked region group. Then according to their priorities, the regions in the group will search their best matching regions ten porally and spatially. Finally, the "lost" area is recovered progressively by the corresponding pixels in the matching regions. Experimental results show that the proposed scheme achieves higher PSNR as well as better video quality in comparison with the method adopted in H 264. © 2005 IEEE.link_to_subscribed_fulltex