scholarly journals The analysis of echotrace obtained by a split-beam echosounder to observe the tilt-angle dependence of fish target strength in situ

2009 ◽  
Vol 67 (2) ◽  
pp. 215-230 ◽  
Author(s):  
Masahiko Furusawa ◽  
Kazuo Amakasu
Keyword(s):  
Theoretical Model ◽  
Tilt Angle ◽  
Three Dimensional ◽  
Prolate Spheroid ◽  
Target Strength ◽  
Accurate Information ◽  
Careful Selection ◽  
Angle Dependence ◽  
Selection Of

Abstract Furusawa, M., and Amakusu, K. 2010. The analysis of echotrace obtained by a split-beam echosounder to observe the tilt-angle dependence of fish target strength in situ. – ICES Journal of Marine Science, 67: 215–230. A method of echotrace analysis (ETA), proposed by Furusawa and Miyanohana in 1988 utilizes successive echodata from an individual fish to obtain the target-strength (TS) pattern as a function of fish tilt angle and behaviour. The method can be applied to data from an echosounder with any beam configuration, single-, dual-, and split-beam. However, the method has not been applied rigorously to split-beam sounder data, which provide most comprehensive and accurate information. The aim of this work is to establish an accurate and practical ETA method for split-beam echosounder data. Although the basic theory had already been developed, some theoretical and practical enhancement was needed; smoothing of an echotrack by linear and quadratic regressions, correction for transducer motion, and comparison of an observed TS pattern with a prolate-spheroid theoretical model. The analysis starts from careful selection of a single echotrace on an echogram and ends with a composite display of results including a three-dimensional fish track and a TS pattern as a function of the tilt angle of the fish. The method was applied to typical echotrace examples, and utility and practicality were confirmed. A means of increasing the number of applicable echotraces is discussed.

Three-Dimensional Oscillation Dynamics of the In Situ Piston Rod Transmission Between Buoy Line and the Double Hinge-Connected Translator in an Offshore Linear Wave Energy Converter

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Erland Strömstedt ◽  
Mats Leijon
Keyword(s):  
Tilt Angle ◽  
Lateral Displacement ◽  
Three Dimensional ◽  
Elastic Displacement ◽  
Direct Drive ◽  
Energy Converter ◽  
Oscillation Dynamics ◽  
Guiding System ◽  
Displacement Measurements

Force and displacement measurements have been performed in situ on the piston rod mechanical lead-through transmission in the direct drive of the second experimental wave energy converter (WEC) 3 km offshore at the Lysekil research site (LRS) during a 130-day continuous full-scale experiment in 2009. The direct drive consists of a buoy line and a piston rod transmission with a double-hinged link (DHL) at the lower end connecting the point absorbing surface-floating buoy to the translator of an encapsulated permanent magnet linear generator on the seabed. The buoy line is guided by a funnel in the buoy line guiding system 3.2 m above the generator capsule. The 3 m long piston rod reciprocates through a mechanical lead-through in the capsule wall, sealing off seawater from entering the generator capsule. A setup of laser triangulation sensors measures the relative lateral displacement of the piston rod. This paper introduces a method and a system of equations for calculating piston rod relative tilt angle and piston rod azimuth direction of tilting from the relative lateral displacement measurements. Correlation with piston rod axial displacement and forces enables evaluation of the three-dimensional (3D) oscillation dynamics. Results are presented from 2 weeks after launch and from 3 months after launch in altogether four cases representing two different stages of wear in two different sea states. Piston rod tilting from accumulated wear in the buoy line guiding system is separated from tilting due to elastic displacement. Structural mechanical finite element method (FEM) simulations verify the magnitude of elastic displacement and indicate negligible stress and strain at the mounting point of the laser sensor setup. The proposed theory for piston rod 3D motion is validated by the experiment. As the experiment progressed, wear in the buoy line guiding system accelerated due to splitting of the buoy line jacketing compound, thereby increasing the piston rod tilt angles. Over 94 days into the experiment, 21.8 mm of accumulated wear in the buoy line guiding system had altered the characteristics of the piston rod oscillations and increased the maximum piston rod relative tilt angle by 0.39 deg in the predominant azimuth direction of wave propagation. Further accumulated wear in the buoy line guiding system led to buoy line rupture 130 days after launch. The results presented in this paper have been used in assessments for improving the mechanical subsystems in subsequent experimental WECs based on the Uppsala concept.

scholarly journals Acoustic target strength (TS) of argentine anchovy (Engraulis anchoita): the nighttime scattering layer

2016 ◽  
Vol 74 (5) ◽  
pp. 1408-1420 ◽  
Author(s):  
Adrián Madirolas ◽  
Federico A. Membiela ◽  
Juan D. Gonzalez ◽  
Ariel G. Cabreira ◽  
Matías dell’Erba ◽  
...  
Keyword(s):  
Tilt Angle ◽  
Regression Line ◽  
Constant Term ◽  
Least Square ◽  
Target Strength ◽  
Data Series ◽  
Angle Distribution ◽  
Scattering Layer ◽  
Depth Dependence

Engraulis anchoita is a physostomous fish with a dual chambered swimbladder (sb). In situ target strength (TS) measurements on this species are only possible at night, when anchovies disperse forming a scattering layer near the sea surface. A survey data series comprising more than 50000 single target detections, recorded from 1995 to 2008, was analyzed in order to study the species specific TS at 38 kHz. A TS vs. fish total length (L) equation was obtained from the in situ measurements (TS = 31.9 log L – 82.4 dB; r2= 0.78). When the slope of the regression line was forced to 20 into the TS equation, the resulting value for the constant term (b20) was −68.6 dB. In any case, these results indicate an average difference of +3 dB (higher TS values) when compared with the general model suggested for clupeoid fish. The TS measurements obtained inside the nighttime sound scattering layer exhibited a negative trend with depth. An empirical depth dependence term for the anchovy TS equation was obtained through a three parameter least square fitting of the data [TS = 31.3 log L – 79.6 dB – 4.74 log (1 + z/10); r2 = 0.74]. Anatomical data obtained through high resolution X-Ray Computed Tomography was employed as input for a Prolate Spheroidal Model (PSM). Theoretical TS vs. tilt angle functions were obtained considering the compression of the sb at different depths and under the assumption of different contraction rates. The TS functions were then averaged over different fish tilt angle distributions and used to derive theoretical depth dependence curves of average fish TS. The implications of the adopted sb contraction rate and tilt angle distribution are discussed by comparing the modelled TS(z) curves against the empirical data.

scholarly journals The influence of beam position and swimming direction on fish target strength

2008 ◽  
Vol 65 (2) ◽  
pp. 226-237 ◽  
Author(s):  
M. J. Henderson ◽  
J. K. Horne ◽  
R. H. Towler
Keyword(s):  
Tilt Angle ◽  
Target Strength ◽  
Major Influence ◽  
Angle Distribution ◽  
Beam Position ◽  
Swimming Direction ◽  
Acoustic Transducer ◽  
Accurate Definition ◽  
Single Target

Abstract Henderson, M. J., Horne, J. K., and Towler, R. H. 2007. The influence of beam position and swimming direction on fish target strength. – ICES Journal of Marine Science, 65: 226–237. Fish orientation is consistently identified as a major influence on fish target strength (TS). Generally, orientation is defined as the tilt angle of the fish with respect to the acoustic transducer, whereas a more accurate definition includes tilt, roll, and yaw. Thus far, the influences of roll and yaw on fish TS have only been examined cursorily. We used in situ single-target data to create fish tracks, to estimate fish tilt and yaw, and correlated these estimates with TS. The results show that tilt, yaw, and beam position have a significant influence on fish TS. To investigate further how yaw and beam position affect TS, we calculated the expected backscatter from each fish within simulated fish aggregations using a backscatter model. The TS of individual fish at 38 and 120 kHz varied by as much as 11 and 19 dB with changes in yaw and beam position. Altering the fish’s tilt, yaw, and beam position resulted in TS differences of 14 and 26 dB at 38 and 120 kHz, respectively. Orientation had a minimal influence on an aggregation’s average TS if the aggregation had a variable tilt-angle distribution and was dispersed throughout the acoustic beam.

scholarly journals The average three-dimensional target strength of fish by spheroid model for sonar surveys

2009 ◽  
Vol 66 (6) ◽  
pp. 1176-1183 ◽  
Author(s):  
Yong Tang ◽  
Yasushi Nishimori ◽  
Masahiko Furusawa
Keyword(s):  
Three Dimensional ◽  
Prolate Spheroid ◽  
Target Strength ◽  
Fish Length ◽  
Fish Schools ◽  
Fluid Boundary ◽  
The Difference ◽  
Yaw Angle ◽  
The Relationship ◽  
Actual Orientation

Abstract Tang, Y., Nishimori, Y., and Furusawa, M. 2009. The average three-dimensional target strength of fish by spheroid model for sonar surveys. – ICES Journal of Marine Science, 66: 1176–1183. When surveying fish schools by sonar, the fish are insonified from various directions. Because the fish target strength (TS) has three-dimensional directivity, according to its orientation relative to the sonar beam, the TS must be appropriately averaged. By connecting the geometries of the sonar beam and the fish body, the relationship between the apparent orientation of fish, as viewed by the sonar, and the actual orientation in space is derived. Using this relationship, equations for calculating the three-dimensional-averaged TS (<TS>3D) are presented. A prolate-spheroid, modal-series, scattering model is then used to determine the characteristics of <TS>3D against various parameters, such as fish attitudes, fish length, sonar frequency, and method of beam scanning. The model is evaluated with two boundary conditions at the spheroid surface: a gas-fluid boundary relevant to fish with a swimbladder, and a fluid-fluid boundary relevant to fish without a swimbladder. The results reveal that <TS>3D varies greatly with the horizontal aspect (yaw angle), but only slightly with the vertical aspect (pitch angle) of the fish. The difference in <TS>3D between the side-on aspect and the end-on (head or tail) aspect increases with the ratio of the fish length to the acoustic wavelength.

Facilitation Strategies to Moderate Synchronous Virtual Discussion Groups in Teacher Training

2021 ◽  
pp. 96-117
Author(s):  
Kevin Oh ◽  
Natalie Nussli ◽  
Melisa Kaye ◽  
Nicole Michele Cuadro
Keyword(s):  
Second Life ◽  
Three Dimensional ◽  
Discussion Groups ◽  
Careful Selection ◽  
Group Discussions ◽  
Exploratory Case Study ◽  
Combination Strategies ◽  
Virtual Events ◽  
Selection Of

This chapter reports on an exploratory case study investigating strategies to facilitate group discussions in Second Life, a three-dimensional virtual world. The purpose was to identify best practices for discussion facilitation in-world from the perspective of a virtual host and a discussion facilitator. A host and a facilitator moderated four virtual group discussions with 16 in-service teachers enrolled in a graduate technology class. The chapter discusses several themes that emerged from the host's and the facilitator's debriefings. Key themes include the need for a careful selection of the communication modality (text or voice or a combination), strategies to promote interactivity among the participants, the critical need for at least one facilitator in addition to the host, the need for clear ground rules for the participants, and clear guidelines for the host and the facilitator. Several challenges experienced during the process of facilitating these virtual events are discussed and recommendations are made to address these difficulties. This chapter is of interest to educators who are planning to substitute in-class group discussions with synchronous group discussions in-world.

scholarly journals A Methodological Evaluation of Volumetric Measurement Techniques including Three-Dimensional Imaging in Breast Surgery

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
H. Hoeffelin ◽  
D. Jacquemin ◽  
V. Defaweux ◽  
J L. Nizet
Keyword(s):  
Breast Surgery ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Volumetric Measurement ◽  
A New Technique ◽  
Patient Stress ◽  
Methodological Evaluation ◽  
Selection Of

Breast surgery currently remains very subjective and each intervention depends on the ability and experience of the operator. To date, no objective measurement of this anatomical region can codify surgery. In this light, we wanted to compare and validate a new technique for 3D scanning (LifeViz 3D) and its clinical application. We tested the use of the 3D LifeViz system (Quantificare) to perform volumetric calculations in various settings (in situ in cadaveric dissection, of control prostheses, and in clinical patients) and we compared this system to other techniques (CT scanning and Archimedes’ principle) under the same conditions. We were able to identify the benefits (feasibility, safety, portability, and low patient stress) and limitations (underestimation of the in situ volume, subjectivity of contouring, and patient selection) of the LifeViz 3D system, concluding that the results are comparable with other measurement techniques. The prospects of this technology seem promising in numerous applications in clinical practice to limit the subjectivity of breast surgery.

A Sliding Microtubule Model Incorporating Axonemal Twist and Compatible with Three-dimensional Ciliary Bending

1979 ◽  
Vol 78 (1) ◽  
pp. 265-280
Author(s):  
M.J. E. HOLWILL ◽  
HOWARD J. COHEN ◽  
PETER SATIR
Keyword(s):  
Theoretical Model ◽  
Electron Micrographs ◽  
Twist Angle ◽  
Three Dimensional ◽  
Experimental Results ◽  
Central Pair ◽  
Metachronal Wave ◽  
Recovery Stroke ◽  
Selection Of

1. Equations are developed to calculate the relative displacements of the doublet microtubules at the tip of a cilium when the microtubules twist about the axis of the organelle. 2. Displacements measured from electron micrographs show asymmetry (or skew) which can be matched quantitatively by the theoretical model with the appropriate selection of twist angle and orientation of the axoneme with respect to the plane of beat. 3. For Elliptio cilia the experimental results are consistent with a planar effective stroke and a recovery stroke involving a three-dimensional bend. The plane of the effective stroke is not normal to a surface containing the central pair of microtubules but contains microtubule 2 to produce the observed skew. 4. This model for the beat also explains the range of orientations of axoneme observed in sections through the metachronal wave.

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

A High Angle, Double Tilting Cold Stage for the AEI EM7

1974 ◽  
Vol 32 ◽  
pp. 450-451
Author(s):  
P.R. Swann ◽  
A.E. Lloyd
Keyword(s):  
Habit Plane ◽  
Temperature Control ◽  
Tilt Angle ◽  
Cooling System ◽  
Thermal Drift ◽  
High Angle ◽  
Cold Stage ◽  
High Degree ◽  
Better Than

Figure 1 shows the design of a specimen stage used for the in situ observation of phase transformations in the temperature range between ambient and −160°C. The design has the following features a high degree of specimen stability during tilting linear tilt actuation about two orthogonal axes for accurate control of tilt angle read-out high angle tilt range for stereo work and habit plane determination simple, robust construction temperature control of better than ±0.5°C minimum thermal drift and transmission of vibration from the cooling system.

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