scholarly journals Novel SNOM Probes Based on Nanofocusing in Asymmetric Structures

10.5772/50806 ◽  
2012 ◽  
Author(s):  
Valeria Lotito ◽  
Christian Hafner ◽  
Urs Sennhauser ◽  
Gian-Luca Bo
Keyword(s):  
Asymmetric Structures

scholarly journals Odd Willis coupling induced by broken time-reversal symmetry

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Li Quan ◽  
Simon Yves ◽  
Yugui Peng ◽  
Hussein Esfahlani ◽  
Andrea Alù
Keyword(s):  
Time Reversal ◽  
Time Reversal Symmetry ◽  
Acoustic Metamaterials ◽  
Asymmetric Structures ◽  
Sound Control ◽  
Wavefront Shaping ◽  
Scattering Response ◽  
Symmetric Structures ◽  
Signal Routing ◽  
Broad Interest

AbstractWhen sound interacts with geometrically asymmetric structures, it experiences coupling between pressure and particle velocity, known as Willis coupling. While in most instances this phenomenon is perturbative in nature, tailored asymmetries combined with resonances can largely enhance it, enabling exotic acoustic phenomena. In these systems, Willis coupling obeys reciprocity, imposing an even symmetry of the Willis coefficients with respect to time reversal and the impinging wave vector, which translates into stringent constraints on the overall scattering response. In this work, we introduce and experimentally observe a dual form of acoustic Willis coupling, arising in geometrically symmetric structures when time-reversal symmetry is broken, for which the pressure-velocity coupling is purely odd-symmetric. We derive the conditions to maximize this effect, we experimentally verify it in a symmetric subwavelength scatterer biased by angular momentum, and we demonstrate the opportunities for sound scattering enabled by odd Willis coupling. Our study opens directions for acoustic metamaterials, with direct implications for sound control, non-reciprocal scattering, wavefront shaping and signal routing, of broad interest also for nano-optics, photonics, elasto-dynamics, and mechanics.

scholarly journals Jet-torus connection in radio galaxies

2018 ◽  
Vol 609 ◽  
pp. A80 ◽  
Author(s):  
C. M. Fromm ◽  
M. Perucho ◽  
O. Porth ◽  
Z. Younsi ◽  
E. Ros ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Ambient Medium ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Asymmetric Structures ◽  
Long Baseline ◽  
Volume Method ◽  
Index Maps ◽  
Thermal Absorption ◽  
Core Shift

Context. High resolution very long baseline interferometry observations of active galactic nuclei have revealed asymmetric structures in the jets of radio galaxies. These asymmetric structures may be due to internal asymmetries in the jets or they may be induced by the different conditions in the surrounding ambient medium, including the obscuring torus, or a combination of the two. Aims. In this paper we investigate the influence of the ambient medium, including the obscuring torus, on the observed properties of jets from radio galaxies. Methods. We performed special-relativistic hydrodynamic (SRHD) simulations of over-pressured and pressure-matched jets using the special-relativistic hydrodynamics code Ratpenat, which is based on a second-order accurate finite-volume method and an approximate Riemann solver. Using a newly developed radiative transfer code to compute the electromagnetic radiation, we modelled several jets embedded in various ambient medium and torus configurations and subsequently computed the non-thermal emission produced by the jet and thermal absorption from the torus. To better compare the emission simulations with observations we produced synthetic radio maps, taking into account the properties of the observatory. Results. The detailed analysis of our simulations shows that the observed properties such as core shift could be used to distinguish between over-pressured and pressure matched jets. In addition to the properties of the jets, insights into the extent and density of the obscuring torus can be obtained from analyses of the single-dish spectrum and spectral index maps.

Insights into the velocity-dependent geometry and internal strain in accretionary wedges from analogue models

2017 ◽  
Vol 155 (5) ◽  
pp. 1089-1104 ◽  
Author(s):  
BIN DENG ◽  
LEI JIANG ◽  
GAOPING ZHAO ◽  
RUI HUANG ◽  
YUANBO WANG ◽  
...  
Keyword(s):  
Brittle Material ◽  
High Velocity ◽  
Frontal Zone ◽  
Volumetric Strain ◽  
Velocity Dependence ◽  
Shortening Velocity ◽  
Asymmetric Structures ◽  
Analogue Models ◽  
Velocity Of Shortening ◽  
Geometry And Kinematics

AbstractAlthough the brittle material in analogue models is characterized by a linear Navier-Coulomb behaviour and rate-independent deformation, the geometry and style of deformation in accretionary wedges is sensitive to shortening velocity. In this study we have constructed a series of analogue models with various shortening velocities in order to study the influence of shortening velocity on the geometry and kinematics of accretionary wedges. Model results illustrate how shortening velocity has an important influence on the geometry and kinematics of the resulting wedge. In general, for models having similar bulk shortening, the accretionary wedges with higher velocities of shortening are roughly steeper, higher and longer, as well as having larger critical wedge angles and height. It accommodates a number of foreland-vergent thrusts, larger fault spacing and displacement rates than those of low- to medium-velocity shortening, which indicates a weak velocity-dependence in geometry of the wedge. Moreover, models with a high velocity of shortening undergo larger amounts of volumetric strain and total layer-parallel shortening than models with low- to medium-velocity shortening. The former accommodate a greater development of back thrusts and asymmetric structures; a backwards-to-forwards style of wedge growth therefore occurs in the frontal zone under high-velocity shortening.

Subassemblage Technique for Asymmetric Structures

1973 ◽  
Vol 99 (11) ◽  
pp. 2259-2268
Author(s):  
William R. Hibbard ◽  
Peter F. Adams
Keyword(s):  
Asymmetric Structures

Composited structure of shallow cumulus clouds

2021 ◽  
Author(s):  
Chris Holloway ◽  
Jian-Feng Gu ◽  
Bob Plant ◽  
Todd Jones
Keyword(s):  
Kinetic Energy ◽  
Vertical Velocity ◽  
Inversion Layer ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Theoretical Models ◽  
Turbulence Kinetic Energy ◽  
Cloud Base ◽  
Asymmetric Structures ◽  
Negatively Buoyant

<div> <div> <div> <div> <p>The normalized distributions of thermodynamic and dynamical variables both within and outside shallow clouds are investigated through a composite algorithm using large eddy simulation of the BOMEX case. The normalized magnitude is maximum near cloud center and decreases outwards. While relative humidity (RH) and cloud liquid water (<em>q<sub>l </sub></em>) decrease smoothly to match the environment, the vertical velocity, virtual potential temperature (<em>θ<sub>v </sub></em>) and potential temperature (<em>θ</em>) perturbations have more complicated behaviour towards the cloud boundary. Below the inversion layer, <em>θ<sub>v</sub></em> becomes <span>negative before the vertical velocity has turned from updraft to subsiding shell outside the cloud, indicating the presence of a transition zone where the updraft is negatively buoyant. Due to the downdraft outside the cloud and the enhanced horizontal turbulent mixing across the edge, the normalized turbulence kinetic energy (TKE) and horizontal turbulence kinetic energy (HTKE) decrease more slowly from the cloud center outwards than the thermodynamic variables. The distributions all present asymmetric structures in response to the vertical wind shear, with more negatively buoyant air, stronger downdrafts and larger TKE on the downshear side. We discuss several implications of the distributions for theoretical models and parameterizations. Positive buoyancy near cloud base is mostly due to </span><span>the virtual effect of water vapor, emphasising the role of moisture in triggering. The mean vertical velocity is found </span><span>to be approximately half the maximum vertical velocity within each cloud, providing a constraint on some models. Finally, products of normalized distributions for different variables are shown to be able to well represent the vertical heat and moisture fluxes, but they underestimate fluxes in the inversion layer because they do not capture cloud top downdrafts.</span></p> </div> </div> </div> </div>

scholarly journals MODERN ARCHITECTURE AND VISUAL IMAGE OF THE CITY

2019 ◽  
pp. 102-104
Author(s):  
A. M. Tormakhova
Keyword(s):  
Urban Landscape ◽  
Residential Buildings ◽  
Visual Image ◽  
Cultural Analysis ◽  
Practical Significance ◽  
Modern City ◽  
Asymmetric Structures ◽  
The Status ◽  
Architectural Structures ◽  
The City

The aim of the article is to highlight the actual trends associated with architectural construction and identify ways of forming a visual image of a modern city. The solution to this goal involves not only the analysis of certain unique architectural structures, but also the outline of the existing visual practices in the city which correlate with the urban landscape. The research methodology is connected with the use of the method of synthe- sis, the use of tools of cultural analysis. The most extraordinary buildings are rarely residential buildings, much more often they are intended for public use. Their very essence is con- nected with publicity and attraction of a considerable quantity of visitors, tourists. These can be museums, libraries, concert halls, stadiums, shop- ping malls. In addition to these structures, extremely impressive structures are created in the field of transport – bridges, railway stations. The re- equipment of old objects and the creation of new ones becomes such that necessarily creates an occasion for communication, becoming a part of the media. In architecture there is a desire to circumvent the principle of statics that was inherent to it. Manifestations of this tendency in architecture were attempts to "revitalize" the building, giving them mobility through structures that visually convey the idea of fluidity (asymmetric structures, often deprived of straight angles with the prevalence of rounded parts). Creating the effect of architectural variability arises not only at the expense of innovative constructions, but also due to the equipment of the buildings by media facades, which perform as a purely aesthetic and advertising function, providing the opportunity to represent buildings in fundamentally different visual images. Scientific novelty consists in highlighting the specifics of architectural constructions claiming the status of "art" and visual practices that in- teract with them directly. The conclusion is made about the transformation of a modern city. The practical significance of the study is that features of the development of modern architectural constructions are presented and the factors influencing the formation of the visual image of the city are highlighted.

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