scholarly journals Simultaneous measurements of three-dimensional trajectories and wingbeat frequencies of birds in the field

2018 ◽  
Vol 15 (147) ◽  
pp. 20180653 ◽  
Author(s):  
Hangjian Ling ◽  
Guillam E. Mclvor ◽  
Geoff Nagy ◽  
Sepehr MohaimenianPour ◽  
Richard T. Vaughan ◽  
...  
Keyword(s):  
Stereo Matching ◽  
Imaging System ◽  
Three Dimensional ◽  
Bird Species ◽  
Three Dimensions ◽  
Natural Environments ◽  
Flight Performance ◽  
Stereo Imaging ◽  
Wingbeat Frequency ◽  
Wide Range

Tracking the movements of birds in three dimensions is integral to a wide range of problems in animal ecology, behaviour and cognition. Multi-camera stereo-imaging has been used to track the three-dimensional (3D) motion of birds in dense flocks, but precise localization of birds remains a challenge due to imaging resolution in the depth direction and optical occlusion. This paper introduces a portable stereo-imaging system with improved accuracy and a simple stereo-matching algorithm that can resolve optical occlusion. This system allows us to decouple body and wing motion, and thus measure not only velocities and accelerations but also wingbeat frequencies along the 3D trajectories of birds. We demonstrate these new methods by analysing six flocking events consisting of 50 to 360 jackdaws ( Corvus monedula ) and rooks ( Corvus frugilegus ) as well as 32 jackdaws and 6 rooks flying in isolated pairs or alone. Our method allows us to (i) measure flight speed and wingbeat frequency in different flying modes; (ii) characterize the U-shaped flight performance curve of birds in the wild, showing that wingbeat frequency reaches its minimum at moderate flight speeds; (iii) examine group effects on individual flight performance, showing that birds have a higher wingbeat frequency when flying in a group than when flying alone and when flying in dense regions than when flying in sparse regions; and (iv) provide a potential avenue for automated discrimination of bird species. We argue that the experimental method developed in this paper opens new opportunities for understanding flight kinematics and collective behaviour in natural environments.

scholarly journals Foraging in an unsteady world: bumblebee flight performance in field-realistic turbulence

2017 ◽  
Vol 7 (1) ◽  
pp. 20160086 ◽  
Author(s):  
J. D. Crall ◽  
J. J. Chang ◽  
R. L. Oppenheimer ◽  
S. A. Combes
Keyword(s):  
Field Experiments ◽  
Insect Flight ◽  
Energetic Cost ◽  
Natural Environments ◽  
Flight Performance ◽  
Wingbeat Frequency ◽  
Wind Speeds ◽  
Wide Range ◽  
Outdoor Environments ◽  
Stroke Amplitude

Natural environments are characterized by variable wind that can pose significant challenges for flying animals and robots. However, our understanding of the flow conditions that animals experience outdoors and how these impact flight performance remains limited. Here, we combine laboratory and field experiments to characterize wind conditions encountered by foraging bumblebees in outdoor environments and test the effects of these conditions on flight. We used radio-frequency tags to track foraging activity of uniquely identified bumblebee ( Bombus impatiens ) workers, while simultaneously recording local wind flows. Despite being subjected to a wide range of speeds and turbulence intensities, we find that bees do not avoid foraging in windy conditions. We then examined the impacts of turbulence on bumblebee flight in a wind tunnel. Rolling instabilities increased in turbulence, but only at higher wind speeds. Bees displayed higher mean wingbeat frequency and stroke amplitude in these conditions, as well as increased asymmetry in stroke amplitude—suggesting that bees employ an array of active responses to enable flight in turbulence, which may increase the energetic cost of flight. Our results provide the first direct evidence that moderate, environmentally relevant turbulence affects insect flight performance, and suggest that flying insects use diverse mechanisms to cope with these instabilities.

Turbulent three-dimensional dielectric electrohydrodynamic convection between two plates

2012 ◽  
Vol 696 ◽  
pp. 228-262 ◽  
Author(s):  
A. Kourmatzis ◽  
J. S. Shrimpton
Keyword(s):  
Spatial Data ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Energy Budgets ◽  
Turbulent Regime ◽  
Scalar Flux ◽  
Wide Range ◽  
Scalar Variance

AbstractThe fundamental mechanisms responsible for the creation of electrohydrodynamically driven roll structures in free electroconvection between two plates are analysed with reference to traditional Rayleigh–Bénard convection (RBC). Previously available knowledge limited to two dimensions is extended to three-dimensions, and a wide range of electric Reynolds numbers is analysed, extending into a fully inherently three-dimensional turbulent regime. Results reveal that structures appearing in three-dimensional electrohydrodynamics (EHD) are similar to those observed for RBC, and while two-dimensional EHD results bear some similarities with the three-dimensional results there are distinct differences. Analysis of two-point correlations and integral length scales show that full three-dimensional electroconvection is more chaotic than in two dimensions and this is also noted by qualitatively observing the roll structures that arise for both low (${\mathit{Re}}_{E} = 1$) and high electric Reynolds numbers (up to ${\mathit{Re}}_{E} = 120$). Furthermore, calculations of mean profiles and second-order moments along with energy budgets and spectra have examined the validity of neglecting the fluctuating electric field ${ E}_{i}^{\ensuremath{\prime} } $ in the Reynolds-averaged EHD equations and provide insight into the generation and transport mechanisms of turbulent EHD. Spectral and spatial data clearly indicate how fluctuating energy is transferred from electrical to hydrodynamic forms, on moving through the domain away from the charging electrode. It is shown that ${ E}_{i}^{\ensuremath{\prime} } $ is not negligible close to the walls and terms acting as sources and sinks in the turbulent kinetic energy, turbulent scalar flux and turbulent scalar variance equations are examined. Profiles of hydrodynamic terms in the budgets resemble those in the literature for RBC; however there are terms specific to EHD that are significant, indicating that the transfer of energy in EHD is also attributed to further electrodynamic terms and a strong coupling exists between the charge flux and variance, due to the ionic drift term.

scholarly journals The magnetorotational instability prefers three dimensions

2020 ◽  
Vol 476 (2233) ◽  
pp. 20190622
Author(s):  
Jeffrey S. Oishi ◽  
Geoffrey M. Vasil ◽  
Morgan Baxter ◽  
Andrew Swan ◽  
Keaton J. Burns ◽  
...  
Keyword(s):  
Shear Rate ◽  
Angular Velocity ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Linear Instability ◽  
Three Dimensions ◽  
Two Dimensional ◽  
Magnetorotational Instability ◽  
Dynamo Action ◽  
Wide Range

The magnetorotational instability (MRI) occurs when a weak magnetic field destabilizes a rotating, electrically conducting fluid with inwardly increasing angular velocity. The MRI is essential to astrophysical disc theory where the shear is typically Keplerian. Internal shear layers in stars may also be MRI-unstable, and they take a wide range of profiles, including near-critical. We show that the fastest growing modes of an ideal magnetofluid are three-dimensional provided the shear rate, S , is near the two-dimensional onset value, S c . For a Keplerian shear, three-dimensional modes are unstable above S  ≈ 0.10 S c , and dominate the two-dimensional modes until S  ≈ 2.05 S c . These three-dimensional modes dominate for shear profiles relevant to stars and at magnetic Prandtl numbers relevant to liquid-metal laboratory experiments. Significant numbers of rapidly growing three-dimensional modes remainy well past 2.05 S c . These finding are significant in three ways. First, weakly nonlinear theory suggests that the MRI saturates by pushing the shear rate to its critical value. This can happen for systems, such as stars and laboratory experiments, that can rearrange their angular velocity profiles. Second, the non-normal character and large transient growth of MRI modes should be important whenever three-dimensionality exists. Finally, three-dimensional growth suggests direct dynamo action driven from the linear instability.

scholarly journals Development of an X-ray real-time stereo imaging technique using synchrotron radiation

2011 ◽  
Vol 18 (4) ◽  
pp. 569-574 ◽  
Author(s):  
Masato Hoshino ◽  
Kentaro Uesugi ◽  
James Pearson ◽  
Takashi Sonobe ◽  
Mikiyasu Shirai ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Real Time ◽  
Imaging System ◽  
Silicon Crystal ◽  
Three Dimensional ◽  
Stereo Image ◽  
Large Field ◽  
Depth Information ◽  
Stereo Imaging ◽  
X Ray

An X-ray stereo imaging system with synchrotron radiation was developed at BL20B2, SPring-8. A portion of a wide X-ray beam was Bragg-reflected by a silicon crystal to produce an X-ray beam which intersects with the direct X-ray beam. Samples were placed at the intersection point of the two beam paths. X-ray stereo images were recorded simultaneously by a detector with a large field of view placed close to the sample. A three-dimensional wire-frame model of a sample was created from the depth information that was obtained from the lateral positions in the stereo image. X-ray stereo angiography of a mouse femoral region was performed as a demonstration of real-time stereo imaging. Three-dimensional arrangements of the femur and blood vessels were obtained.

scholarly journals Stereo Imaging Using Hardwired Self-Organizing Object Segmentation

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5833
Author(s):  
Ching-Han Chen ◽  
Guan-Wei Lan ◽  
Ching-Yi Chen ◽  
Yen-Hsiang Huang
Keyword(s):  
Neural Network ◽  
Stereo Vision ◽  
Stereo Matching ◽  
Imaging System ◽  
Object Segmentation ◽  
Hierarchical Architecture ◽  
Absolute Difference ◽  
Stereo Imaging ◽  
Som Neural Network ◽  
Self Organizing

Stereo vision utilizes two cameras to acquire two respective images, and then determines the depth map by calculating the disparity between two images. In general, object segmentation and stereo matching are some of the important technologies that are often used in establishing stereo vision systems. In this study, we implement a highly efficient self-organizing map (SOM) neural network hardware accelerator as unsupervised color segmentation for real-time stereo imaging. The stereo imaging system is established by pipelined, hierarchical architecture, which includes an SOM neural network module, a connected component labeling module, and a sum-of-absolute-difference-based stereo matching module. The experiment is conducted on a hardware resources-constrained embedded system. The performance of stereo imaging system is able to achieve 13.8 frames per second of 640 × 480 resolution color images.

Stereovision for three-dimensional measurements of fabric pilling

2011 ◽  
Vol 81 (20) ◽  
pp. 2168-2179 ◽  
Author(s):  
Bugao Xu ◽  
Wurong Yu ◽  
RongWu Wang
Keyword(s):  
Stereo Matching ◽  
Imaging System ◽  
Three Dimensional ◽  
Measurement Data ◽  
Objective Evaluation ◽  
Relevant Information ◽  
Digital Cameras ◽  
Dimensional Measurements ◽  
Fabric Structures ◽  
3D Surfaces

This paper introduces a three-dimensional (3D) imaging system designed for objective evaluation of fabric pilling. Thesystem was aimed at reconstructing high-fidelity 3D surfaces of fabric by using only two side-by-side images of a pilling fabric captured by a pair of regular digital cameras without special lighting. The robust calibration and stereo-matching algorithms were implemented to make the system insusceptible to fabric structures, colors, fiber contents and other factors. The depth data provide the most relevant information for pilling segmentation and measurements, because pilling is the protrusion of entangled fibers. 3D measurement data can be used for not only evaluating pilling appearance, but also for understanding pilling mechanisms in different abrasive treatments.

Aggregate Imaging System for Characterizing the Shape of Fine and Coarse Aggregates

2003 ◽  
Vol 1832 (1) ◽  
pp. 67-77 ◽  
Author(s):  
Thomas Fletcher ◽  
Chandan Chandan ◽  
Eyad Masad ◽  
Krishna Sivakumar
Keyword(s):  
Imaging System ◽  
Permanent Deformation ◽  
Image Resolution ◽  
Three Dimensions ◽  
Automated System ◽  
Coarse Aggregates ◽  
Wide Range ◽  
Aggregate Shape ◽  
Short Time ◽  
Tracking Devices

A unified computer-automated system was designed and developed for characterizing the shape of fine and coarse aggregates. The unique features of the system and the experimental design considerations are described. These considerations are related to the required image resolution, field of view, and lighting scheme. The unique features of the system include the ability to analyze fine and coarse aggregates and to quantify texture, angularity, and the three dimensions of form. The developed system is used to measure aggregate shape properties for a wide range of fine and coarse aggregates, and the results are compared with hot-mix asphalt laboratory performance. The analysis shows that the developed procedure yields detailed information on shape properties of aggregates in a short time. The measurements have very good correlation with the resistance of asphalt mixes to permanent deformation measured in the laboratory using different wheel-tracking devices.

scholarly journals Divergent excitation two photon microscopy for 3D random access mesoscale imaging at single cell resolution

2019 ◽  
Author(s):  
FK Janiak ◽  
P Bartel ◽  
MR Bale ◽  
T Yoshimatsu ◽  
E Komulainen ◽  
...  
Keyword(s):  
Single Cell ◽  
Neuronal Activity ◽  
Low Cost ◽  
Three Dimensional ◽  
Random Access ◽  
Field Of View ◽  
Three Dimensions ◽  
Two Photon ◽  
Wide Range ◽  
Effective Excitation

ABSTACTIn neuroscience, diffraction limited two-photon (2P) microscopy is a cornerstone technique that permits minimally invasive optical monitoring of neuronal activity. However, most conventional 2P microscopes impose significant constraints on the size of the imaging field-of-view and the specific shape of the effective excitation volume, thus limiting the scope of biological questions that can be addressed and the information obtainable. Here, employing ‘divergent beam optics’ (DBO), we present an ultra-low-cost, easily implemented and flexible solution to address these limitations, offering a several-fold expanded three-dimensional field of view that also maintains single-cell resolution. We show that this implementation increases both the space-bandwidth product and effective excitation power, and allows for straight-forward tailoring of the point-spread-function. Moreover, rapid laser-focus control via an electrically tunable lens now allows near-simultaneous imaging of remote regions separated in three dimensions and permits the bending of imaging planes to follow natural curvatures in biological structures. Crucially, our core design is readily implemented (and reversed) within a matter of hours, and fully compatible with a wide range of existing 2P customizations, making it highly suitable as a base platform for further development. We demonstrate the application of our system for imaging neuronal activity in a variety of examples in mice, zebrafish and fruit flies.

scholarly journals Parametric Study of Jet/Droplet Formation Process during LIFT Printing of Living Cell-Laden Bioink

Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1408
Author(s):  
Christina Kryou ◽  
Ioannis Theodorakos ◽  
Panagiotis Karakaidos ◽  
Apostolos Klinakis ◽  
Antonios Hatziapostolou ◽  
...  
Keyword(s):  
Formation Process ◽  
Imaging System ◽  
Three Dimensional ◽  
Droplet Formation ◽  
Layer By Layer ◽  
Time Resolved ◽  
Wide Range ◽  
Cell Concentrations ◽  
Living Tissues ◽  
Uniform Droplets

Bioprinting offers great potential for the fabrication of three-dimensional living tissues by the precise layer-by-layer printing of biological materials, including living cells and cell-laden hydrogels. The laser-induced forward transfer (LIFT) of cell-laden bioinks is one of the most promising laser-printing technologies enabling biofabrication. However, for it to be a viable bioprinting technology, bioink printability must be carefully examined. In this study, we used a time-resolved imaging system to study the cell-laden bioink droplet formation process in terms of the droplet size, velocity, and traveling distance. For this purpose, the bioinks were prepared using breast cancer cells with different cell concentrations to evaluate the effect of the cell concentration on the droplet formation process and the survival of the cells after printing. These bioinks were compared with cell-free bioinks under the same printing conditions to understand the effect of the particle physical properties on the droplet formation procedure. The morphology of the printed droplets indicated that it is possible to print uniform droplets for a wide range of cell concentrations. Overall, it is concluded that the laser fluence and the distance of the donor–receiver substrates play an important role in the printing impingement type; consequently, a careful adjustment of these parameters can lead to high-quality printing.

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