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In generating a digital elevation map from an interferogram obtained by interferometric synthetic aperture radar, the filtering process is as important as the phase unwrapping process. Before unwrapping, we usually have to restore the data image by reducing so-called singular points (SPs) by filtering process without destroying or smearing delicate fringes. Previously, an effective SP restoration method was proposed based on the complex-valued Markov random field (CMRF) model. However, there is still room for improvement in the definition of SPs and in the formulation of CMRF parameter estimation. In this letter, we propose a novel scheme by introducing a new concept, namely, the ldquosingular unit.rdquo We also estimate CMRF parameters locally as a weighted sum by taking the distance and SP numbers in sample sites into account. By using this restoration method, we demonstrate a high-performance removal of SPs. We also find that delicate landscape features, which are often lost in conventional filtering, are preserved appropriately. We confirm the quality in higher signal-to-noise ratios obtained against actual height data. 相似文献
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Experimental studies have been carried out on the dynamic stability of a cantilever cylindrical shell partially filled with liquid, under vertical excitation. Two polyester test cylinders with radius 100 mm, thickness 0.25 mm, and lengths 113 and 227 mm were used. The test cylinder was harmonically excited with constant acceleration- or displacement-amplitude. It was found that not only the parametric principal instability resonance but also the parametric combination involving two natural vibrations, each of which has the same circumferential wave number but different axial mode numbers, could occur. The latter type of vibration apparently has not been previously studied. By varying the dimensionless water height from 0.25 to 1.0 stepwise by 0.25 increments, the instability regions and vibration modes were determined for the two test cylinders. The response waves of shell wall and liquid free surface, and axial and circumferential vibration modes were also observed. 相似文献
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Koichi Ara Koh Yamaki Keisuke Wada Satoshi Fukuyama Takeshi Okutsu Sadao Nagasaka Akihiro Shiomoto Juro Hiromi 《Journal of Oceanography》2011,67(1):87-111
Seasonal and interannual variations in physicochemical properties (i.e., temperature, salinity, dissolved oxygen and dissolved
inorganic nutrients), chlorophyll a (Chl-a), particulate carbon and nitrogen (PC and PN, respectively), and primary production were investigated in the neritic area
of Sagami Bay, Kanagawa, Japan, from January 2002 to December 2008. These abiotic/biotic variables, except for NH4
+–N, repeated similar seasonal variations for all 7 years. On the basis of the analysis of data obtained on 167 sampling dates,
depth-integrated primary production in this water can be easily estimated from Chl-a at the surface using the regression equations obtained in the present study. Intermittently high values of dissolved inorganic
nutrients, Chl-a, PC, PN and primary productivity at the surface during the summer stratified period were induced by high freshwater discharge
from the rivers after rainfalls and by the expansion of nutrient-rich Tokyo Bay Water. Temperature, salinity and dissolved
inorganic nutrients showed drastic variations within a scale of a few days and/or weeks, and these variations were related
to sea levels that represent the intrusion of the Kuroshio Water, Intermediate Oyashio Water or deep water from the continental
slope. However, there was no consistent trend in the variations in Chl-a, PC, PN and primary production due to the complex effects of these waters. 相似文献
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