Experimental Study on Forward Acoustic Scattering in Stratified Water Turbulence

Target acoustic scattering is the primary characteristic of target echo stealth performance, and it is an important sign of the viability of large-scale complex targets underwater. In a test band, owing to the superposition of scattered waves and the elastic echo produced by shells, liquid tanks, partition plates, ribs, etc., a target exhibits an extremely complex echo phenomenon. Accurate measurement and evaluation of the acoustic scattering characteristics of underwater complex targets can be achieved via experimental research on the echo characteristics of large-scale scaled models. In this study, the contribution and regularity of the strong reflection source of underwater complex targets in various azimuths, structures, and locations were analyzed quantitatively as a basis for in-depth research and understanding of the echo characteristics of underwater complex targets.

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An experimental study of water dispersal in Polygonum spp.

Canadian Journal of Botany ◽

10.1139/b76-278 ◽

1976 ◽

Vol 54 (22) ◽

pp. 2587-2596 ◽

Cited By ~ 41

Author(s):

R. J. Staniforth ◽

P. B. Cavers

Keyword(s):

Experimental Study ◽

Water Transport ◽

Environmental Conditions ◽

Physical Disturbance ◽

Flood Water ◽

Alluvial River ◽

Water Dispersal ◽

Polygonum Lapathifolium ◽

Water Turbulence

The annual smartweeds Polygonum lapathifolium L., P. pensylvanicum L., and P. persicaria L. grow on alluvial river bars during the summer and autumn when their substrate is free of flood waters and physical disturbance. They are dependent upon dispersal for the annual recolonization of this habitat. Achenes are the only diaspores (dispersal units), and hydrochory (water dispersal) appears to be a major dispersal method.An experimental study of water dispersal of these species revealed several adaptive features. The coordination of fruit fall with the availability of the agent (flood water) ensures that the achenes are picked up. The duration of buoyancy is adequate for successful transport downstream. The presence and condition of the perianth, degree of water turbulence, and achene size are factors which determine the duration of buoyancy. Alteration of the degree of dormancy but no loss of viability occurs as a result of water transport. After deposition the achenes may remain dormant or germinate rapidly depending on environmental conditions. The deposition stage (and therefore, hydrochory) is unsuccessful for most achenes of P. persicaria, which rapidly lose viability in sites where deposition is likely to occur. The presence of this species on alluvial bars must be due to other means of dispersal.

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Theoretical and experimental study of acoustic scattering in turbulent water

The Journal of the Acoustical Society of America ◽

10.1121/1.2017841 ◽

1979 ◽

Vol 66 (S1) ◽

pp. S58-S58

Author(s):

T. J. Eisler ◽

J. A. Clark

Keyword(s):

Experimental Study ◽

Acoustic Scattering ◽

Turbulent Water

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Acoustic scattering by a three‐cylinder scatterer: Theoretical and experimental study of resonances

The Journal of the Acoustical Society of America ◽

10.1121/1.421983 ◽

1998 ◽

Vol 103 (5) ◽

pp. 2851-2851

Author(s):

Paul Gabrielli ◽

Yves Decanini ◽

Antoine Folacci ◽

Elisabeth Fournier

Keyword(s):

Experimental Study ◽

Acoustic Scattering

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Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013955x ◽

1995 ◽

Vol 53 ◽

pp. 636-637

Author(s):

Norio Baba ◽

Norihiko Ichise ◽

Syunya Watanabe

Keyword(s):

Experimental Study ◽

Spherical Aberration ◽

Incident Beam ◽

Optical Parameters ◽

Beam Tilting ◽

Illumination Method ◽

Restoration Method ◽

Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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