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