scholarly journals Turbulence explains the accelerations of an eagle in natural flight

2021 ◽  
Vol 118 (23) ◽  
pp. e2102588118
Author(s):  
Kasey M. Laurent ◽  
Bob Fogg ◽  
Tobias Ginsburg ◽  
Casey Halverson ◽  
Michael J. Lanzone ◽  
...  
Keyword(s):  
Large Scale ◽  
Power Spectra ◽  
Life Forms ◽  
Flight Behavior ◽  
Avian Behavior ◽  
Avian Flight ◽  
Turbulent Environments ◽  
Wide Range ◽  
In The Wild ◽  
Atmospheric Phenomena

Turbulent winds and gusts fluctuate on a wide range of timescales from milliseconds to minutes and longer, a range that overlaps the timescales of avian flight behavior, yet the importance of turbulence to avian behavior is unclear. By combining wind speed data with the measured accelerations of a golden eagle (Aquila chrysaetos) flying in the wild, we find evidence in favor of a linear relationship between the eagle’s accelerations and atmospheric turbulence for timescales between about 1/2 and 10 s. These timescales are comparable to those of typical eagle behaviors, corresponding to between about 1 and 25 wingbeats, and to those of turbulent gusts both larger than the eagle’s wingspan and smaller than large-scale atmospheric phenomena such as convection cells. The eagle’s accelerations exhibit power spectra and intermittent activity characteristic of turbulence and increase in proportion to the turbulence intensity. Intermittency results in accelerations that are occasionally several times stronger than gravity, which the eagle works against to stay aloft. These imprints of turbulence on the bird’s movements need to be further explored to understand the energetics of birds and other volant life-forms, to improve our own methods of flying through ceaselessly turbulent environments, and to engage airborne wildlife as distributed probes of the changing conditions in the atmosphere.

scholarly journals Artist: fast radiative transfer for large-scale simulations of the epoch of reionization

2019 ◽  
Vol 489 (4) ◽  
pp. 5594-5611 ◽  
Author(s):  
Margherita Molaro ◽  
Romeel Davé ◽  
Sultan Hassan ◽  
Mario G Santos ◽  
Kristian Finlator
Keyword(s):  
Radiative Transfer ◽  
Large Scale ◽  
Power Spectra ◽  
Physical Parameters ◽  
Speed Of Light ◽  
Photon Propagation ◽  
Wide Range ◽  
Gas Ionization ◽  
Excursion Set ◽  
Large Scale Simulations

ABSTRACT We introduce the ‘Asymmetric Radiative Transfer In Shells Technique’ (artist), a new method for photon propagation on large scales that explicitly conserves photons, propagates photons at the speed of light, approximately accounts for photon directionality, and closely reproduces results of more detailed radiative transfer (RT) methods. Crucially, it is computationally fast enough to evolve the large cosmological volumes required to predict the 21cm power spectrum on scales that will be probed by future experiments targeting the epoch of reionization (EoR). Most seminumerical models aimed at predicting the EoR 21cm signal on these scales use an excursion set formalism (ESF) to model the gas ionization, which achieves computational viability by making a number of approximations. While artist is still roughly two orders of magnitude slower than ESF, it does allow to model the EoR without the need for such approximations. This is particularly important when considering a wide range of reionization scenarios for which artist would help limit the assumptions made. By implementing our RT method within the seminumerical code simfast21, we show that Artist predicts a significantly different evolution for the EoR ionization field compared to the code’s native ESF. In particular, artist predicts up to a factor of two difference in the power spectra, depending on the physical parameters assumed. Its application to large-scale EoR simulations will therefore allow more physically motivated constraints to be obtained for key EoR parameters. In particular, it will remove the need for the artificial rescaling of the escape fraction.

scholarly journals Profiles of Galaxy Clusters in Cosmological Scenarios

1987 ◽  
Vol 117 ◽  
pp. 287-287
Author(s):  
Michael J. West ◽  
Avishai Dekel ◽  
Augustus Oemler
Keyword(s):  
High Resolution ◽  
Galaxy Clusters ◽  
Hierarchical Clustering ◽  
Large Scale ◽  
Power Spectra ◽  
Clusters Of Galaxies ◽  
Spatial Symmetry ◽  
Abell Clusters ◽  
Wide Range ◽  
Large Scale Simulations

We have studied the properties of rich clusters of galaxies in various cosmological scenarios by comparing high resolution N-body simulations with observations of Abell clusters. The clusters have been simulated in two steps. First, protoclusters are identified in large-scale simulations which represent a wide range of cosmological scenarios (hierarchical clustering, pancake scenarios, and hybrids of the two, spanning a range of power spectra). Then the region around each protocluster is simulated with high resolution, the particles representing L* galaxies. The protoclusters have no spatial symmetry built into them initially. The final clusters are still dynamically young, and of moderate densities, which should be representative of Abell clusters of richness classes 1 and 2.

Evolution, theory of

2018 ◽  
Author(s):  
Elisabeth A. Lloyd
Keyword(s):  
Natural Selection ◽  
Evolutionary Theory ◽  
Life Forms ◽  
Genetic Mutation ◽  
Theory Of Evolution ◽  
Selection Processes ◽  
Wide Range ◽  
In The Wild ◽  
Forms Of Life ◽  
The Public Sphere

The biological theory of evolution advances the view that the variety and forms of life on earth are the result of descent with modification from the earliest forms of life. Evolutionary theory does not attempt to explain the origin of life itself, that is, how the earliest forms of life came to exist, nor does it apply to the history of changes of the non-biological parts of the universe, which are also often described as ’evolutionary’. The mechanisms of natural selection, mutation and speciation are used in evolutionary theory to explain the relations and characteristics of all life forms. Modern evolutionary theory explains a wide range of natural phenomena, including the deep resemblances among organisms, the diversity of life forms, organisms’ possession of vestigial organs and the good fit or ’adaptedness’ between organisms and their environment. Often summarized as ’survival of the fittest’, the mechanism of natural selection actually includes several distinct processes. There must be variation in traits among the members of a population; these traits must be passed on from parents to offspring; and the different traits must confer differential advantage for reproducing successfully in that environment. Because evidence for each of these processes can be gathered independently of the evolutionary claim, natural selection scenarios are robustly testable. When a trait in a population has arisen because it was directly selected in this fashion, it is called an adaptation. Genetic mutation is the originating source of variation, and selection processes shape that variation into adaptive forms; random genetic drift and various levels and forms of selection dynamic developed by geneticists have been integrated into a general theory of evolutionary change that encompasses natural selection and genetic mutation as complementary processes. Detailed ecological studies are used to provide evidence for selection scenarios involving the evolution of species in the wild. Evolutionary theory is supported by an unusually wide range of scientific evidence, gaining its support from fields as diverse as geology, embryology, molecular genetics, palaeontology, climatology and functional morphology. Because of tensions between an evolutionary view of homo sapiens and some religious beliefs, evolutionary theory has remained controversial in the public sphere far longer than no less well-supported scientific theories from other sciences.

scholarly journals Developing a unified pipeline for large-scale structure data analysis with angular power spectra – I. The importance of redshift-space distortions for galaxy number counts

2019 ◽  
Vol 489 (3) ◽  
pp. 3385-3402 ◽  
Author(s):  
Konstantinos Tanidis ◽  
Stefano Camera
Keyword(s):  
Parameter Estimation ◽  
Large Scale ◽  
Power Spectra ◽  
Computation Time ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Cosmological Parameter ◽  
Wide Range ◽  
Galaxy Bias ◽  
Number Counts

ABSTRACT We develop a cosmological parameter estimation code for (tomographic) angular power spectra analyses of galaxy number counts, for which we include, for the first time, redshift-space distortions (RSDs) in the Limber approximation. This allows for a speed-up in computation time, and we emphasize that only angular scales where the Limber approximation is valid are included in our analysis. Our main result shows that a correct modelling of RSD is crucial not to bias cosmological parameter estimation. This happens not only for spectroscopy-detected galaxies, but even in the case of galaxy surveys with photometric redshift estimates. Moreover, a correct implementation of RSD is especially valuable in alleviating the degeneracy between the amplitude of the underlying matter power spectrum and the galaxy bias. We argue that our findings are particularly relevant for present and planned observational campaigns, such as the Euclid satellite or the Square Kilometre Array, which aim at studying the cosmic large-scale structure and trace its growth over a wide range of redshifts and scales.

Random Excitation Forces in Tube Bundles Subjected to Two-Phase Cross-Flow

1996 ◽  
Vol 118 (3) ◽  
pp. 265-277 ◽  
Author(s):  
C. E. Taylor ◽  
M. J. Pettigrew ◽  
I. G. Currie
Keyword(s):  
Flow Regime ◽  
Void Fraction ◽  
Flow Rate ◽  
Large Scale ◽  
Power Spectra ◽  
Cross Flow ◽  
Random Excitation ◽  
Two Phase ◽  
Wide Range ◽  
Tube Bundles

Data from two experimental programs have been analyzed to determine the characteristics of the random excitation forces associated with two-phase cross-flow in tube bundles. Large-scale air-water flow loops in France and Canada were used to generate the data. Tests were carried out on cantilevered, clamped-pinned, and clamped-clamped tubes in normal-square, parallel-triangular, and normal-triangular configurations. Either strain gages or force transducers were used to measure the vibration response of a centrally located tube as the tube array was subjected to a wide range of void fractions and flow rates. Power spectra were analyzed to determine the effect of parameters such as tube diameter, frequency, flow rate, void fraction, and flow regime on the random excitation forces. Normalized expressions for the excitation force power spectra were found to be flow-regime dependent. In the churn flow regime, flow rate and void fraction had very little effect on the magnitude of the excitation forces. In the bubble-plug flow regime, the excitation forces increased rapidly with flow rate and void fraction.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

THE SOME QUESTIONS OF AUTONOMOUS MOTION AND MANAGEMENT OF LAND-MOBILE ROBOTIC COMPLEXES FOR UKRAINIAN GROUND FORCESE

2019 ◽  
pp. 53-58
Author(s):  
О. Кravchuk ◽  
V. Symonenkov ◽  
I. Symonenkova ◽  
O. Hryhorev
Keyword(s):  
Large Scale ◽  
Armed Forces ◽  
Distributed Information ◽  
Wide Range ◽  
Highly Effective ◽  
Information Management Systems ◽  
Robotic Devices ◽  
Principles And Standards ◽  
And Control ◽  
The Eu

Today, more than forty countries of the world are engaged in the development of military-purpose robots. A number of unique mobile robots with a wide range of capabilities are already being used by combat and intelligence units of the Armed forces of the developed world countries to conduct battlefield intelligence and support tactical groups. At present, the issue of using the latest information technology in the field of military robotics is thoroughly investigated, and the creation of highly effective information management systems in the land-mobile robotic complexes has acquired a new phase associated with the use of distributed information and sensory systems and consists in the transition from application of separate sensors and devices to the construction of modular information subsystems, which provide the availability of various data sources and complex methods of information processing. The purpose of the article is to investigate the ways to increase the autonomy of the land-mobile robotic complexes using in a non-deterministic conditions of modern combat. Relevance of researches is connected with the necessity of creation of highly effective information and control systems in the perspective robotic means for the needs of Land Forces of Ukraine. The development of the Armed Forces of Ukraine management system based on the criteria adopted by the EU and NATO member states is one of the main directions of increasing the effectiveness of the use of forces (forces), which involves achieving the principles and standards necessary for Ukraine to become a member of the EU and NATO. The inherent features of achieving these criteria will be the transition to a reduction of tasks of the combined-arms units and the large-scale use of high-precision weapons and land remote-controlled robotic devices. According to the views of the leading specialists in the field of robotics, the automation of information subsystems and components of the land-mobile robotic complexes can increase safety, reliability, error-tolerance and the effectiveness of the use of robotic means by standardizing the necessary actions with minimal human intervention, that is, a significant increase in the autonomy of the land-mobile robotic complexes for the needs of Land Forces of Ukraine.

Stirring and aeration system for the upgrading of small waste water treatment plants

1994 ◽  
Vol 29 (12) ◽  
pp. 149-156 ◽  
Author(s):  
Marcus Höfken ◽  
Katharina Zähringer ◽  
Franz Bischof
Keyword(s):  
Waste Water ◽  
Water Treatment ◽  
Large Scale ◽  
Waste Water Treatment ◽  
Water Treatment Plants ◽  
Waste Water Treatment Plants ◽  
Basic Fluid ◽  
Aeration System ◽  
Technical Realization ◽  
Wide Range

A novel agitating system has been developed which allows for individual or combined operation of stirring and aeration processes. Basic fluid mechanical considerations led to the innovative hyperboloid design of the stirrer body, which ensures high efficiencies in the stirring and the aeration mode, gentle circulation with low shear forces, excellent controllability, and a wide range of applications. This paper presents the basic considerations which led to the operating principle, the technical realization of the system and experimental results in a large-scale plant. The characteristics of the system and the differences to other stirring and aeration systems are illustrated. Details of the technical realization are shown, which conform to the specific demands of applications in the biological treatment of waste water. Special regard is given to applications in the upgrading of small compact waste water treatment plants.

Thin structure of heterogeneous and multiphase fluid flows

2012 ◽  
Vol 9 (1) ◽  
pp. 175-180
Author(s):  
Yu.D. Chashechkin
Keyword(s):  
Large Scale ◽  
Fundamental System ◽  
Fluid Flows ◽  
Regular Solutions ◽  
Flow Models ◽  
Group Methods ◽  
Wide Range ◽  
Thin Structure ◽  
Multiphase Fluid ◽  
Complete Solutions

According to the results of visualization of streams, the existence of structures in a wide range of scales is noted: from galactic to micron. The use of a fundamental system of equations is substantiated based on the results of comparing symmetries of various flow models with the usage of theoretical group methods. Complete solutions of the system are found by the methods of the singular perturbations theory with a condition of compatibility, which determines the characteristic equation. A comparison of complete solutions with experimental data shows that regular solutions characterize large-scale components of the flow, a rich family of singular solutions describes formation of the thin media structure. Examples of calculations and observations of stratified, rotating and multiphase media are given. The requirements for the technique of an adequate experiment are discussed.

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