Individual variability in sub-Arctic krill material properties, lipid composition, and other scattering model inputs affect acoustic estimates of their population

2021 ◽  
Author(s):  
Brandyn M Lucca ◽  
Patrick H Ressler ◽  
H Rodger Harvey ◽  
Joseph D Warren
Keyword(s):  
Lipid Composition ◽  
Material Properties ◽  
Acoustic Scattering ◽  
Gulf Of Alaska ◽  
Individual Variability ◽  
Target Strength ◽  
Frequency Independent ◽  
Lipid Mass ◽  
Order Of Magnitude

Abstract Target strength model inputs including morphometry, material properties, lipid composition, and in situ orientations were measured for sub-Arctic krill (Euphausia pacifica, Thysanoessa spinifera, T. inermis, and T. raschii) in the eastern Bering Sea (EBS, 2016) and Gulf of Alaska (GOA, 2017). Inter-species and -regional animal lengths were significantly different (F1,680 = 114.10, p < 0.01), while animal shape was consistent for all species measured. The polar lipid phosphatidycholine was the dominant lipid, comprising 86 ± 16% (mean ± SD) and 56 ± 22% of total lipid mass in GOA and EBS krill, respectively. Krill density contrasts varied by species and region rather than with morphometry, lipid composition, or local chla fluorescence. Mean in situ krill orientation was 1 ± 31°, with 25% of observed krill within ±5° of broadside incidence. Modelled target strength sensitivity was frequency independent for variations in material properties but was primarily sensitive to morphometry and orientation at lower (38 kHz) and higher (200 kHz) frequencies, respectively. Measured variability in material properties corresponded to an order of magnitude difference in acoustic estimates of biomass at 120 kHz. These results provide important inputs and constraints for acoustic scattering models of ecologically important sub-Arctic krill species.

Diagnostic tools for unbiased in situ target strength estimation

2001 ◽  
Vol 58 (11) ◽  
pp. 2149-2155 ◽  
Author(s):  
Stéphane Gauthier ◽  
George A Rose
Keyword(s):  
Large Scale ◽  
Sample Volume ◽  
Target Strength ◽  
Diagnostic Tools ◽  
Threshold Density ◽  
Measurement Scales ◽  
Order Of Magnitude ◽  
Unbiased Estimates ◽  
Optimal Measure

In situ target strength (TS) is theoretically the optimal measure to scale echo-integration values to fish density. In practice, in situ TS is often biased. The number of fish per sample volume (Nv) has been used to set a threshold density to reduce the bias attributable to multiple targets. However, order of magnitude differences in the Nv threshold have been reported within the theoretical range 0 < Nv [Formula: see text] 1. To investigate the use and scale-dependence of the Nv index, with the objective of achieving unbiased estimates of in situ TS, redfish (Sebastes spp.) aggregations were measured in Newfoundland waters. When averaged over large horizontal distances (large scale), TS was biased upwards if Nv exceeded 0.04. However, TS could be estimated at higher densities without bias using smaller measurement scales. To deal with these scale-dependent variations, we develop diagnostic tools based on Nv and an echo-count index (Tv), which enable unbiased estimates of the Nv threshold and in situ TS.

scholarly journals Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel

2009 ◽  
Vol 66 (6) ◽  
pp. 1169-1175 ◽  
Author(s):  
Tonje Lexau Nesse ◽  
Halvor Hobæk ◽  
Rolf J. Korneliussen
Keyword(s):  
Frequency Response ◽  
Acoustic Scattering ◽  
Ex Situ ◽  
Target Strength ◽  
Model Parameters ◽  
Acoustic Frequency ◽  
Atlantic Mackerel ◽  
Scattering Spectra ◽  
Laboratory Tank

Abstract Nesse, T. L., Hobæk, H., and Korneliussen, R. J. 2009. Measurements of acoustic-scattering spectra from the whole and parts of Atlantic mackerel. – ICES Journal of Marine Science, 66: 1169–1175. Atlantic mackerel (Scomber scombrus) are weak sound scatterers compared with fish that have swimbladders. Accurate acoustic estimates of mackerel abundance require estimates of target strength. Different parts of mackerel may dominate the backscattering spectra. Mackerel schools are acoustically recognized mainly by backscatter four times stronger at 200 kHz than at 38 kHz. Simulations have established that backscatter from only the flesh and the backbone could explain this frequency response, although there are uncertainties in the model parameters and simplifications. In this paper, experiments conducted in a laboratory tank to investigate the complexity of mackerel backscatter are discussed. Acoustic backscatter was measured over the frequency range 65–470 kHz from individual dead mackerel, and their backbones, heads, and skulls. Backscatter from the backbones was measured at several angles of incidence. Grating lobes (Bragg scattering) appeared at different angles, depending on the acoustic frequency and the spacing of the vertebrae. These lobes were evident in backbone backscatter after propagating through the flesh and can be used, in principle, to determine mackerel size acoustically. The frequency response of individual, ex situ Atlantic mackerel estimated from these measurements did not match that from the measurements of in situ mackerel schools. Further investigation is warranted.

Multiple-Frequency Acoustic Backscattering and Zooplankton Aggregations in the Inner Scotian Shelf Basins

1991 ◽  
Vol 48 (3) ◽  
pp. 340-355 ◽  
Author(s):  
N. A. Cochrane ◽  
D. Sameoto ◽  
A. W. Herman ◽  
J. Neilson
Keyword(s):  
Target Strength ◽  
Scotian Shelf ◽  
Migration Patterns ◽  
Acoustic Backscattering ◽  
Large Populations ◽  
Order Of Magnitude ◽  
Silver Hake ◽  
Merluccius Bilinearis ◽  
Domain Dependence

Acoustic backscatter observations at 12, 50, and 200 kHz in the inner Scotian Shelf basins reveal large populations of silver hake (Merluccius bilinearis) and its principal prey, the euphausiid Meganyctiphanes norvegica. Multichannel sonar colour imagery facilitates separation of fish from euphausiids and delineation of their separate diurnal migration patterns. Silver hake acoustic abundances are consistent with midwater trawl sampling. Acoustic column densities for mature M. norvegica of approximately 1000/m2 exceed net sampling column densities by over 1 order of magnitude indicating strong net avoidance. Numerical simulation of euphausiid backscattering using a fluid cylinder model and natural distribution of scatterer orientations yields an approximate 20 log L target strength length dependence and little frequency domain dependence in the "geometric" scattering regime. Quantitative interpretation of euphausiid scattering in situ must account for randomness in their orientations.

Quantitative Measurements of Euphausiids Using a 120-kHz Sounder and Their in situ Orientation

1980 ◽  
Vol 37 (4) ◽  
pp. 693-702 ◽  
Author(s):  
D. D. Sameoto
Keyword(s):  
Acoustic Scattering ◽  
Biological Data ◽  
Target Strength ◽  
Acoustic Data ◽  
Quantitative Measurements ◽  
Underwater Photography ◽  
Average Orientation ◽  
Opening And Closing ◽  
The Relationship

Biomass and density of euphausiids were estimated using a 120-kHz sounder during 2 y in the Gulf of St. Lawrence. Simultaneously, biological samples were taken with two types of multiple opening and closing nets: MOCNESS-type and BIONESS. Correlations for biomass and density estimates between the acoustic and biological data range from 0.391 to 0.791. Acoustic data showed that a high percentage of euphausiids avoided the MOCNESS-type net during the day. A comparison of the relationship between biological and acoustic data for both years showed that the BIONESS sampler captured euphausiids more efficiently during both day and night. Target strength of the euphausiids estimated from acoustic and biological data showed that it was lower than would be expected if the animals were oriented horizontally. Photographs taken from the BIONESS sampler at depths having acoustic scattering layers showed that the average orientation of euphausiids changed with time, the average orientation being closest to horizontal during daytime. Orientation changed from 27° from the horizontal at 14:00 to 51° during 02:00. The effect of orientation on target strength is discussed.Key words: euphausiids, acoustics, orientation, biomass, underwater photography, multiple net samplers, zooplankton

scholarly journals Time-Response-Histogram-Based Feature of Magnetic Barkhausen Noise for Material Characterization Considering Influences of Grain and Grain Boundary under In Situ Tensile Test

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2350
Author(s):  
Jia Liu ◽  
Guiyun Tian ◽  
Bin Gao ◽  
Kun Zeng ◽  
Yongbing Xu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Tensile Stress ◽  
Material Properties ◽  
Ferromagnetic Material ◽  
Silicon Steel ◽  
Time Response ◽  
Barkhausen Noise ◽  
Time Interval ◽  
Magnetic Barkhausen Noise

Stress is the crucial factor of ferromagnetic material failure origin. However, the nondestructive test methods to analyze the ferromagnetic material properties’ inhomogeneity on the microscopic scale with stress have not been obtained so far. In this study, magnetic Barkhausen noise (MBN) signals on different silicon steel sheet locations under in situ tensile tests were detected by a high-spatial-resolution magnetic probe. The domain-wall (DW) motion, grain, and grain boundary were detected using a magneto-optical Kerr (MOKE) image. The time characteristic of DW motion and MBN signals on different locations was varied during elastic deformation. Therefore, a time-response histogram is proposed in this work to show different DW motions inside the grain and around the grain boundary under low tensile stress. In order to separate the variation of magnetic properties affected by the grain and grain boundary under low tensile stress corresponding to MBN excitation, time-division was carried out to extract the root-mean-square (RMS), mean, and peak in the optimized time interval. The time-response histogram of MBN evaluated the silicon steel sheet’s inhomogeneous material properties, and provided a theoretical and experimental reference for ferromagnetic material properties under stress.

scholarly journals Identifying Spatial and Temporal Variations in Concrete Bridges with Ground Penetrating Radar Attributes

2021 ◽  
Vol 13 (9) ◽  
pp. 1846
Author(s):  
Vivek Kumar ◽  
Isabel M. Morris ◽  
Santiago A. Lopez ◽  
Branko Glisic
Keyword(s):  
Compressive Strength ◽  
Ground Penetrating Radar ◽  
Material Properties ◽  
Temporal Variations ◽  
Concrete Bridges ◽  
Spatial And Temporal Variation ◽  
Reflected Waves ◽  
Ground Penetrating ◽  
Over Time

Estimating variations in material properties over space and time is essential for the purposes of structural health monitoring (SHM), mandated inspection, and insurance of civil infrastructure. Properties such as compressive strength evolve over time and are reflective of the overall condition of the aging infrastructure. Concrete structures pose an additional challenge due to the inherent spatial variability of material properties over large length scales. In recent years, nondestructive approaches such as rebound hammer and ultrasonic velocity have been used to determine the in situ material properties of concrete with a focus on the compressive strength. However, these methods require personnel expertise, careful data collection, and high investment. This paper presents a novel approach using ground penetrating radar (GPR) to estimate the variability of in situ material properties over time and space for assessment of concrete bridges. The results show that attributes (or features) of the GPR data such as raw average amplitudes can be used to identify differences in compressive strength across the deck of a concrete bridge. Attributes such as instantaneous amplitudes and intensity of reflected waves are useful in predicting the material properties such as compressive strength, porosity, and density. For compressive strength, one alternative approach of the Maturity Index (MI) was used to estimate the present values and compare with GPR estimated values. The results show that GPR attributes could be successfully used for identifying spatial and temporal variation of concrete properties. Finally, discussions are presented regarding their suitability and limitations for field applications.

scholarly journals Tunable In Situ 3D-Printed PVDF-TrFE Piezoelectric Arrays

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5032
Author(s):  
Alec Ikei ◽  
James Wissman ◽  
Kaushik Sampath ◽  
Gregory Yesner ◽  
Syed N. Qadri
Keyword(s):  
3D Printing ◽  
Polyvinylidene Fluoride ◽  
Vinylidene Fluoride ◽  
Mechanical Strain ◽  
Pressure Sensors ◽  
Strain Ratio ◽  
Ex Situ ◽  
Order Of Magnitude ◽  
3D Printed

In the functional 3D-printing field, poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) has been shown to be a more promising choice of material over polyvinylidene fluoride (PVDF), due to its ability to be poled to a high level of piezoelectric performance without a large mechanical strain ratio. In this work, a novel presentation of in situ 3D printing and poling of PVDF-TrFE is shown with a d33 performance of up to 18 pC N−1, more than an order of magnitude larger than previously reported in situ poled polymer piezoelectrics. This finding paves the way forward for pressure sensors with much higher sensitivity and accuracy. In addition, the ability of in situ pole sensors to demonstrate different performance levels is shown in a fully 3D-printed five-element sensor array, accelerating and increasing the design space for complex sensing arrays. The in situ poled sample performance was compared to the performance of samples prepared through an ex situ corona poling process.

scholarly journals Magmatic flare-up causes crustal thickening at the transition from subduction to continental collision

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Carlos E. Ganade ◽  
Pierre Lanari ◽  
Daniela Rubatto ◽  
Joerg Hermann ◽  
Roberto F. Weinberg ◽  
...  
Keyword(s):  
Production Rate ◽  
Continental Margin ◽  
Subduction Zones ◽  
Continental Collision ◽  
Crustal Thickening ◽  
Time Intervals ◽  
West Gondwana ◽  
Continental Arc ◽  
Order Of Magnitude

AbstractAbove subduction zones, magma production rate and crustal generation can increase by an order of magnitude during narrow time intervals known as magmatic flare-ups. However, the consequences of these events in the deep arc environment remain poorly understood. Here we use petrological and in-situ zircon dating techniques to investigate the root of a continental arc within the collisional West Gondwana Orogen that is now exposed in the Kabyé Massif, Togo. We show that gabbros intruded 670 million years ago at 20–25 km depth were transformed to eclogites by 620 million years ago at 65–70 km depth. This was coeval with extensive magmatism at 20–40 km depth, indicative of a flare-up event which peaked just prior to the subduction of the continental margin. We propose that increased H2O flux from subduction of serpentinized mantle in the hyper-extended margin of the approaching continent was responsible for the increased magma productivity and crustal thickening.

Estimation and Scaling of the Near-Saturated Hydraulic Conductivity

1999 ◽  
Vol 30 (3) ◽  
pp. 177-190 ◽  
Author(s):  
Per Atle Olsen
Keyword(s):  
Hydraulic Conductivity ◽  
Saturated Hydraulic Conductivity ◽  
Scaling Analysis ◽  
Laboratory Measurements ◽  
Estimation Errors ◽  
Geometric Means ◽  
Top Soil ◽  
Structured Soils ◽  
Order Of Magnitude

The hydraulic conductivity in structured soils is known to increase drastically when approaching saturation. Tension infiltration allows in situ infiltration of water at predetermined matric potentials, thus allowing exploration of the hydraulic properties near saturation. In this study, the near saturated (ψ≥-0.15 m) hydraulic conductivity was estimated both in the top- and sub-soil of three Norwegian soils. A priory analysis of estimation errors due to measurement uncertainties was conducted. In order to facilitate the comparison between soils and depths, scaling analysis was applied. It was found that the increase in hydraulic conductivity with increasing matric potentials (increasing water content) was steeper in the sub-soil than in the top-soil. The estimated field saturated hydraulic conductivity was compared with laboratory measurements of the saturated hydraulic conductivity. The geometric means of the laboratory measurements was in the same order of magnitude as the field estimates. The variability of the field estimates of the hydraulic conductivity from one of the soils was also assessed. The variability of the field estimates was generally smaller than the laboratory measurements of the saturated hydraulic conductivity.

In situ target strength measurements of the scyphomedusa Chrysaora melanaster

2014 ◽  
Vol 153 ◽  
pp. 18-23 ◽  
Author(s):  
Alex De Robertis ◽  
Kevin Taylor
Keyword(s):  
Target Strength
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