scholarly journals Discrimination between schools and submerged trees in reservoirs: A preliminary approach using narrowband and broadband acoustics

2021 ◽  
Author(s):  
Arthur Blanluet ◽  
Sven Gastauer ◽  
Franck Cattanéo ◽  
Chloé Goulon ◽  
David Grimardias ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Mode Frequency ◽  
Random Forest Algorithm ◽  
Good Discrimination ◽  
Fish Schools ◽  
Hydroelectric Energy ◽  
Discrimination Rate ◽  
Good Classification ◽  
Fisheries Acoustics ◽  
Gill Netting

With a growing demand for hydroelectric energy, the number of reservoirs is dramatically increasing worldwide. These new water bodies also present an opportunity for the development of fishing activities. However, these reservoirs are commonly impounded on uncut forests, resulting in many immersed trees. These trees hinder fish assessments by disrupting both gill netting and acoustic sampling. Immersed trees can easily be confused with fish schools on echograms. To overcome this issue, we developed a method to discriminate fish schools from immersed trees. A random forest algorithm was used to classify echo-traces at 120 and 200 kHz, recorded by an EK80 (SIMRAD) in narrowband (Continuous Wave) and in broadband mode (Frequency Modulated). We obtained a good discrimination rate between trees and schools, especially in broadband (90 % ratio of good classification). We demonstrate that it is possible to discriminate fish schools from immersed trees and thus facilitate the use of fisheries acoustics in reservoirs.

scholarly journals Bags-of-Features for fish school cluster characterization in pelagic ecosystems: application to the discrimination of juvenile and adult anchovy (Engraulis ringens) clusters off Peru

2012 ◽  
Vol 69 (8) ◽  
pp. 1329-1339 ◽  
Author(s):  
Ronan Fablet ◽  
Paul Gay ◽  
Salvador Peraltilla ◽  
Cecilia Peña ◽  
Ramiro Castillo ◽  
...  
Keyword(s):  
Data Sets ◽  
Correct Classification ◽  
Classification Rate ◽  
Fish Schools ◽  
Fish School ◽  
Acoustic Data ◽  
School Based ◽  
Engraulis Ringens ◽  
Fisheries Acoustics

Whereas fisheries acoustics data processing mainly focused on the detection, characterization, and recognition of individual fish schools, here we addressed the characterization and discrimination of fish school clusters. The proposed scheme relied on the application of the Bags-of-Features (BoF) approach to acoustic echograms. This approach is widely exploited for pattern recognition issues and naturally applies here, considering fish schools as the relevant elementary objects. It relies on the extraction and categorization of fish schools in fisheries acoustic data. Echogram descriptors were computed per unit echogram length as the numbers of schools in different school categories. We applied this approach to the discrimination of juvenile and adult anchovy ( Engraulis ringens ) off Peru. Whereas the discrimination of individual schools is low (below 70%), the proposed BoF scheme achieved between 89% and 92% of correct classification of juvenile and adult echograms for different survey data sets and significantly outperformed classical school-based echogram characteristics (about 10% of improvement of the correct classification rate). We further illustrate the potential of the proposed scheme for the estimation of the spatial distribution of juvenile and adult anchovy populations.

From two dimensions to three: the use of multibeam sonar for a new approach in fisheries acoustics

1999 ◽  
Vol 56 (1) ◽  
pp. 6-12 ◽  
Author(s):  
François Gerlotto ◽  
Marc Soria ◽  
Pierre Fréon
Keyword(s):  
Three Dimensional ◽  
Two Dimensions ◽  
School Structure ◽  
Fish Behaviour ◽  
New Approach ◽  
Multibeam Sonar ◽  
Fish Schools ◽  
Fisheries Acoustics ◽  
Working Frequency ◽  
School Classification

We present a methodology applying multibeam sonar for three-dimensional (3D) observation of fish schools that enhances the conventional use of vertical scientific echo sounders. The sonar we employ has 60 beams of 1.5° each. Its working frequency is 455 kHz. It is applied on a vertical plan normal to the vessel route, observing from the surface line to the bottom with a range set to 100 m. The sampled volume is 14 times larger than the volume observed with vertical echo sounding. The contribution of this new methodology to fisheries acoustics is detailed for school classification, internal school structure, spatial distribution of schools, fish behaviour, and biomass estimates. For each of these points, we present some preliminary results with the aim of defining the real progress in fisheries acoustics research as a result of 3D acoustics. Finally, we present a list of technical and methodological improvements that we are developing in order to make multibeam sonar fully adapted to fisheries acoustics.

Microstructures of Laser Processed Fe-Cr Surface Alloys

1981 ◽  
Vol 39 ◽  
pp. 328-329
Author(s):  
P. A. Molian ◽  
K. H. Khan ◽  
W. E. Wood
Keyword(s):  
Cooling Rate ◽  
Pure Iron ◽  
Continuous Wave ◽  
Laser Surface ◽  
Material Surface ◽  
Constitution Diagram ◽  
Incident Power ◽  
Surface Alloying ◽  
Laser Surface Alloying ◽  
Spot Diameter

In recent years, the effects of chromium on the transformation characteristics of pure iron and the structures produced thereby have been extensively studied as a function of cooling rate. In this paper, we present TEM observations made on specimens of Fe-10% Cr and Fe-20% Cr alloys produced through laser surface alloying process with an estimated cooling rate of 8.8 x 104°C/sec. These two chromium levels were selected in order to study their phase transformation characteristics which are dissimilar in the two cases as predicted by the constitution diagram. Pure iron (C<0.01%, Si<0.01%, Mn<0.01%, S=0.003%, P=0.008%) was electrodeposited with chromium to the thicknesses of 40 and 70μm and then vacuum degassed at 400°F to remove the hydrogen formed during electroplating. Laser surface alloying of chromium into the iron substrate was then performed employing a continuous wave CO2 laser operated at an incident power of 1200 watts. The laser beam, defocussed to a spot diameter of 0.25mm, scanned the material surface at a rate of 30mm/sec, (70 ipm).

1848: Revolix 70 Watt 2 Micron Continuous Wave Laser Vaporesection of the Prostate. Preliminary Results After a One Year Follow-Up

2007 ◽  
Vol 177 (4S) ◽  
pp. 614-614
Author(s):  
Thorsten Bach ◽  
Thomas R.W. Herrmann ◽  
Roman Ganzer ◽  
Andreas J. Gross
Keyword(s):  
Continuous Wave ◽  
Continuous Wave Laser ◽  
Preliminary Results ◽  
Wave Laser ◽  
One Year

Leitlinien zur peripheren Gefäßdiagnostik mit der direktionalen continuous-wave (CW) Doppler-Sonographie

Phlebologie ◽  
2000 ◽  
Vol 29 (05) ◽  
pp. 142-145
Author(s):  
T. Hertel ◽  
B. Kahle ◽  
H. G. Kluess ◽  
M. Marshall ◽  
E. Rabe ◽  
...  
Keyword(s):  
Continuous Wave

Investigating the Nonlinear Optical Response of Pepper Oil under Low Power Irradiation with Continuous Wave Visible Laser Beam

2020 ◽  
pp. 131-138
Keyword(s):  
Refractive Index ◽  
Nonlinear Refractive Index ◽  
Nonlinear Optical ◽  
Continuous Wave ◽  
Diffraction Integral ◽  
Visible Laser ◽  
Limiting Property ◽  
Kirchhoff Diffraction Integral ◽  
Theoretical Results ◽  
Good Agreement

The nonlinear optical properties of pepper oil are studied by diffraction ring patterns and Z-scan techniques with continuous wave beam from solid state laser at 473 nm wavelength. The nonlinear refractive index of the sample is calculated by both techniques. The sample show high nonlinear refractive index. Based on Fresnel-Kirchhoff diffraction integral, the far-field intensity distributions of ring patterns have been calculated. It is found that the experimental results are in good agreement with the theoretical results. Also the optical limiting property of pepper oil is reported. The results obtained in this study prove that the pepper oil has applications in nonlinear optical devices.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

Pump-Probe Measurements Using Silicon Nanocrystal Waveguides

2003 ◽  
Vol 770 ◽  
Author(s):  
Nathanael Smith ◽  
Max J. Lederer ◽  
Marek Samoc ◽  
Barry Luther-Davies ◽  
Robert G. Elliman
Keyword(s):  
Probe Beam ◽  
Time Resolution ◽  
Pump Beam ◽  
Silicon Nanocrystals ◽  
Continuous Wave ◽  
Optical Gain ◽  
Optical Pump ◽  
Time Resolved ◽  
Pump Probe ◽  
Probe Measurements

AbstractOptical pump-probe measurements were performed on planar slab waveguides containing silicon nanocrystals in an attempt to measure optical gain from photo-excited silicon nanocrystals. Two experiments were performed, one with a continuous-wave probe beam and a pulsed pump beam, giving a time resolution of approximately 25 ns, and the other with a pulsed pump and probe beam, giving a time resolution of approximately 10 ps. In both cases the intensity of the probe beam was found to be attenuated by the pump beam, with the attenuation increasing monotonically with increasing pump power. Time-resolved measurements using the first experimental arrangement showed that the probe signal recovered its initial intensity on a time scale of 45-70 μs, a value comparable to the exciton lifetime in Si nanocrystals. These data are shown to be consistent with an induced absorption process such as confined carrier absorption. No evidence for optical gain was observed.

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