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Anosov and expanding attractors

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Science China Mathematics 2020年第9期63卷 1929-1934页

作者： Robert f.Williams Department of Mathematics University of Texas at AustinAustinTX 78705USA Institute for Advanced Study PrincetonNJ 08540USA

An earlier conjecture is settled with an immersion of a 2-dimensional branched *** obstructions in linear algebra and tiling theory are studied rst.

关键词： Anosov expanding attractor Cantor set ber bundle

A review of landscape ecology experiments to understand ecological processes

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Ecological Processes 2022年第1期11卷 802-811页

作者： Yolanda f.Wiersma Department of Biology Memorial UniversitySt.John’sNL A1C 5S7Canada

Background:One way in which we make inferences about ecological processes is via *** ecological processes happen at landscape extents and it is at this extent that experimentation is more *** review explores the intersection between experimentation,ecological processes and landscape ***,this review seeks to discover how scientists design experiments to understand ecological processes at landscape ***:I found 87 papers where these three concepts intersected,and reviewed them in more depth to assess characteristics of scale(treatment and study area extent),replication,research question and experiment ***:The findings suggest that experimental approaches for understanding ecological processes are well established,and beginning to more readily accommodate spatial ***,there is room to integrate more spatially explicit,landscape-scale experiments into studies of ecological processes.

关键词： Inference Landscape ecology Manipulative experiment Observational experiment Scale

Photometric Investigation of Contact Binary DY Cet Based on TESS Data

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Research in Astronomy and Astrophysics 2022年第5期22卷 121-128页

作者： M.f.Yildirim Canakkale Onsekiz Mart University Astrophysics Research Center and Ulupinar Observatory17020CanakkaleTurkey Canakkale Onsekiz Mart University Department of Electricity and EnergyCan Vocational School17400CanakkaleTurkey

We present a photometric analysis of the Transiting Exoplanet Survey Satellite(TESS)light curve of contact binary system DY Cet and the behavior of its orbital period *** light curve and published radial velocity data analysis was performed using the Wilson-Devinney *** a result of simultaneous analysis of the light curve with radial velocity data,the masses and radii of the system’s components were determined as M_(1)=1.55±0.02 M_(⊙),M_(2)=0.55±0.01 M_(⊙) and R_(1)=1.51±0.02 R_(⊙),R_(2)=0.95±0.02 R_(⊙),*** degree of contact(f)and mass ratio(q)of the system were determined as 23%and 0.355±0.012,*** period analysis of DY Cet was conducted for the first time in this *** was observed that the orbital period has a sinusoidal change with decreasing *** explain the orbital period change,mass transfer between components is proposed with the assumption of conservative mass,and the transfer rate was calculated to be dM/dt=1.1×10^(-7) M_(⊙)yr^(-1).A possible third component is suggested for explaining the sinusoidal change,and the mass of the unseen component was determined as 0.13 M_(⊙).The age of the DY Cet system was estimated as 3.77 Gyr.

关键词： stars eclipsing binary stars-stars fundamental parameters of stars- stars individual (DY Cet)

MHD Equilibrium with Reversed Current Density and Magnetic Islands Revisited:the Vacuum Vector Potential Calculus

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Plasma Science and Technology 2013年第10期15卷 985-988页

作者： f.L.BRAGA Gleb-Wataghin Physics Institute Applied Physics DepartmentState University of Campinas federal Institute of Science and Technology of Espirito Santo

The solution of Grad-Shafranov equation determines the stationary behavior of fusion plasma inside a tokamak. To solve the equation it is necessary to know the toroidal current density profile. Recent works show that it is possible to determine a magnetohydrodynamic （MHD） equilibrium with reversed current density （RCD） profiles that presents magnetic islands. In this work we show analytical MHD equilibrium with a RCD profile and analyze the structure of the vacuum vector potential associated with these equilibria using the virtual casing principle.

关键词： magnetohydrodynamics vacuum vector potential reversed current density magnetic islands

Nanoscale displacement of the image of an atomic source of radiation

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Chinese Optics Letters 2009年第2期7卷 149-151页

作者： Henk f. Arnoldus Department of Physics and Astronomy Mississippi State University

Light emitted by an atomic source of radiation appears to travel along a straight line （ray） from the location of the source to the observer in the far field. However, when the energy flow pattern of the radiation is resolved with an accuracy better than an optical wavelength, it turns out that the field lines are usually curved. We consider electric dipole radiation, a prime example of which is the radiation emitted by an atom during an electronic transition, and we show that the field lines of energy flow are in general curves. Near the location of the dipole, the field lines exhibit a vortex structure, and in the far field they approach a straight line. The spatial extension of the vortex in the optical near field is of nanoscale dimension. Due to the rotation of the field lines near the source, the asymptotic limit of a field line is not exactly in the radially outward direction and as a consequence, the image in the far field is slightly shifted. This sub-wavelength displacement of the image of the source should be amenable to experimental observation with contemporary nanoscale-precision techniques.

关键词： Atoms Electric dipole moments flow patterns Nanotechnology Vortex flow

On the Indeterminacy in Hardness of Shape Memory Alloys

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Journal of Materials Science & Technology 2004年第6期20卷 700-702页

作者： f.T.Cheng DeDartment of Applied Phvsics

The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.

关键词： Hardness Elastic-plastic materials Elastic recovery Vickers microhardness test NiTi SMA

SPHERICAL MEANS, DISTRIBUTIONS AND CONVOLUTION OPERATORS IN CLIffORD ANALYSIS

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Chinese Annals of Mathematics,Series B 2003年第2期24卷 133-146页

作者： f.BRACKX R.DELANGHE f.SOMMEN Department of Mathematical Analysis Ghent UniversityB-9000 GentBelgium.Department of Mathematical AnalysisGhent UniversityB-9000 GentBelgium.Department of Mathematical AnalysisGhent UniversityB-9000 GentBelgium.

New higher dimensional distributions are introduced in the framework of Clifford *** complete the picture already established in previous work, offering unity and structuralclarity. Amongst them are the building block... 详细信息

关键词： Spherical means Distributions Convolution operators Clifford analysis

Cognition and the brain of brood parasitic cowbirds

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Integrative Zoology 2019年第2期14卷 145-157页

作者： David f.SHERRY Mélanie f.GUIGUENO Department of Psychology Western University LondonOntario Department of Natural Resource Sciences McGill UniversityMontrealQuebecCanada

Cowbirds are brood *** lay their eggs in the nests of other species,which then incubate the cowbird eggs and raise the young *** and returning to heterospecific nests presents cowbirds with several cognitive *** some species,such as brown-headed cowbirds(Molothrus ater),females but not males search for and remember the locations of potential host *** describe recent research on sex differences in cognition and the hippocampus associated with this sex difference in search for host *** brown-headed cowbirds perform better than males on some,but not all,tests of spatial memory and females show a pattern of adult hippocampal neurogenesis not found in males or in closely related non-parasitic *** of the apparent specialization of the hippocampus,brown-headed cowbirds may be a good model in which to examine spatial information processing in the avian hippocampus and we also describe recent research on the spatial response properties of brown-headed cowbird hippocampal neurons.

关键词： adult neurogenesis brood parasites cowbirds hippocampus sex differences spatial memory

flow-field Analysis of Anti-Kidney Vortex film Cooling

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Journal of Thermal Science 2012年第1期21卷 66-76页

作者： Lars Grf Leonhard Kleiser Institute of fluid Dynamics

film cooling is an important measure to enable an increase of the inlet temperature of a gas turbine and, thereby, to improve its overall efficiency. The coolant is ejected through spanwise rows of holes in the blades or endwalls to build up a film shielding the material. The holes often are inclined in the downstream direction and give rise to a kidney vortex. This is a counter-rotating vortex pair, with an upward flow direction between the two vortices, which tends to lift off the surface and to locally feed hot air towards the blade outside the pair. Reversing the rotational sense of the vortices reverses these two drawbacks into advantages. In the considered case, an anti-kidney vortex is generated using two subsequent rows of holes both inclined downstream and yawed spanwise with alternating angles. In a previous study, we performed large-eddy simulations (which focused on the fully turbulent boundary layer) of this anti-kidney vortex film-cooling and compared them to a corresponding physical experiment. The present work analyzes the simulated flow field in detail, beginning in the plenum (inside the blade or endwall) through the holes up to the mixture with the hot boundary layer. To identify the vortical structures found in the mean flow and in the instantaneous flow, we mostly use the λ 2 criterion and the line integral convolution (LIC) technique indicating sectional streamlines. The flow regions (coolant plenum, holes, and boundary layer) are studied subsequently and linked to each other. To track the anti-kidney vortex throughout the boundary layer, we propose two criteria which are based on vorticity and on LIC results. This enables us to associate the jet vortices with the cooling effectiveness at the wall, which is the key feature of film cooling.

关键词： film cooling anti-kidney vortex vortex identification trajectory tracking large-eddy simulation LES compound angle double row kidney vortex jet in cross-flow.