Reconfigurable Acoustic Arrays With Deployable Structure Based on a Hoberman–Miura System Synthesis

2020 ◽  
Vol 143 (6) ◽  
Author(s):  
Ningxiner Zhao ◽  
Ryan L. Harne
Keyword(s):  
Acoustic Waves ◽  
Shape Change ◽  
Near Field ◽  
Ring Structure ◽  
Wave Focusing ◽  
System Synthesis ◽  
Reconfigurable Mechanisms ◽  
Acoustic Arrays ◽  
Dimensional Shape ◽  
Low Dimensional

Abstract Curved surfaces are often used to radiate and focus acoustic waves. Yet, when tessellated into reconfigurable surfaces for sake of deployability needs, origami-inspired acoustic arrays may be challenging to hold into curved shape and may not retain flat foldability. On the other hand, deployable mechanisms such as the Hoberman ring are as low-dimensional as many origami tessellations and may maintain curved shape with ease due to ideal rigid bar compositions. This research explores an interface between a Hoberman ring and Miura-ori tessellation that maintain kinematic and geometric compatibility for sake of maintaining curved shapes for sound focusing. The Miura-ori facets are considered to vibrate like baffled pistons and generate acoustic waves that radiate from the ring structure. An analytical model is built to reveal the near field acoustic behavior of acoustic arrays resulting from a Hoberman–Miura system synthesis. Acoustic wave focusing capability is scrutinized and validated through proof-of-principle experiments. Studies reveal wave focusing phenomena distinct to this manifestation of the acoustic array and uncover design and operational influences on wave focusing effectiveness. The results encourage exploration of new interfaces between reconfigurable mechanisms and origami devices where low-dimensional shape change is desired.

scholarly journals Serial disparity in the carnivoran backbone unveils a complex adaptive role in metameric evolution

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Borja Figueirido ◽  
Alberto Martín-Serra ◽  
Alejandro Pérez-Ramos ◽  
David Velasco ◽  
Francisco J. Pastor ◽  
...  
Keyword(s):  
Evolutionary Constraint ◽  
Phenotypic Evolution ◽  
Quantitative Studies ◽  
Thoracolumbar Region ◽  
Complex Adaptive ◽  
Dimensional Shape ◽  
A Chain ◽  
Low Dimensional ◽  
Adaptive Role ◽  
Shape Changes

AbstractOrganisms comprise multiple interacting parts, but few quantitative studies have analysed multi-element systems, limiting understanding of phenotypic evolution. We investigate how disparity of vertebral morphology varies along the axial column of mammalian carnivores — a chain of 27 subunits — and the extent to which morphological variation have been structured by evolutionary constraints and locomotory adaptation. We find that lumbars and posterior thoracics exhibit high individual disparity but low serial differentiation. They are pervasively recruited into locomotory functions and exhibit relaxed evolutionary constraint. More anterior vertebrae also show signals of locomotory adaptation, but nevertheless have low individual disparity and constrained patterns of evolution, characterised by low-dimensional shape changes. Our findings demonstrate the importance of the thoracolumbar region as an innovation enabling evolutionary versatility of mammalian locomotion. Moreover, they underscore the complexity of phenotypic macroevolution of multi-element systems and that the strength of ecomorphological signal does not have a predictable influence on macroevolutionary outcomes.

The structure, and electronic and magnetic properties of MX (M=GA, IN; X=S, SE, TE) nanoribbons

2020 ◽  
Vol 34 (18) ◽  
pp. 2050168
Author(s):  
Fei Feng ◽  
Fengdong Lv ◽  
Gongping Zheng ◽  
Guangtao Wang
Keyword(s):  
Magnetic Properties ◽  
Quantum Confinement ◽  
Density Functional ◽  
Quantum Confinement Effect ◽  
Ring Structure ◽  
Functional Theory ◽  
Electronic And Magnetic Properties ◽  
Semiconductor Behavior ◽  
Low Dimensional ◽  
Edge Side

We used the first principle of density functional theory to perform detailed calculations regarding the structure, and the electronic and magnetic properties of MX (M[Formula: see text]=[Formula: see text]Ga, In; X[Formula: see text]=[Formula: see text]S, Se, Te) nanoribbons. The armchair nanoribbons (ARNs) are nonmagnetic semiconductors, which have even or odd oscillations of bandgaps. All small-sized zigzag nanoribbons (ZRNs) were found to break the six-membered ring structure and move to the center, thereby exhibiting nonmagnetic semiconductor behavior owing to the quantum confinement effect. However, among the large ZRNs, which are all metals, MTe ZRNs are nonmagnetic; this differs from the case of graphene, MoS2 and Ti2CO2 nanoribbons. MX (M[Formula: see text]=[Formula: see text]Ga, In; X[Formula: see text]=[Formula: see text]S, Se) ZRNs exhibited ferromagnetism owing to the presence of the unpaired electrons on the metal-edge side and the magnetic moment of each pair of molecules, which was controlled by the size of the nanoribbons. The results provided a theoretical reference that can be used in the future to produce MX materials for application in low-dimensional semiconductor devices, spin electron transport devices and new magnetoresistance devices.

Near field diffraction pattern of ion acoustic waves

1977 ◽  
Vol 20 (5) ◽  
pp. 840 ◽  
Author(s):  
Thomas Christensen ◽  
Noah Hershkowitz
Keyword(s):  
Diffraction Pattern ◽  
Acoustic Waves ◽  
Near Field ◽  
Ion Acoustic Waves ◽  
Ion Acoustic

scholarly journals Adaptive Shape Kernel-Based Mean Shift Tracker in Robot Vision System

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Chunmei Liu ◽  
Yirui Wang ◽  
Shangce Gao
Keyword(s):  
Manifold Learning ◽  
Vision System ◽  
Mean Shift ◽  
Robot Vision ◽  
Shape Space ◽  
Training Data ◽  
Learning Technique ◽  
Adaptive Kernel ◽  
Dimensional Shape ◽  
Low Dimensional

This paper proposes an adaptive shape kernel-based mean shift tracker using a single static camera for the robot vision system. The question that we address in this paper is how to construct such a kernel shape that is adaptive to the object shape. We perform nonlinear manifold learning technique to obtain the low-dimensional shape space which is trained by training data with the same view as the tracking video. The proposed kernel searches the shape in the low-dimensional shape space obtained by nonlinear manifold learning technique and constructs the adaptive kernel shape in the high-dimensional shape space. It can improve mean shift tracker performance to track object position and object contour and avoid the background clutter. In the experimental part, we take the walking human as example to validate that our method is accurate and robust to track human position and describe human contour.

Coherent Streamwise Vortex Structures in the Near-Field of the Three-Dimensional Wall Jet

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Lhendup Namgyal ◽  
Joseph W. Hall
Keyword(s):  
Velocity Field ◽  
Near Field ◽  
Three Dimensional ◽  
Vortex Pair ◽  
Streamwise Vortex ◽  
Vortex Structures ◽  
Stereoscopic Particle Image Velocimetry ◽  
Wall Jet ◽  
Streamwise Vorticity ◽  
Low Dimensional

A turbulent three-dimensional wall jet with an exit Reynolds number of 250,000 was investigated using stereoscopic particle image velocimetry (PIV) in the near-field region (x/D = 5). The proper orthogonal decomposition (POD) was applied to all three components of the velocity field to investigate the underlying coherent structures in the flow. A low-dimensional reconstruction of the turbulent velocity field using the first five POD modes showed the presence of coherent streamwise vortex structures formed in the outer shear-layers of the wall jet, not unlike those found in the near-field of free jets. The instantaneous streamwise vorticity reconstructed from the low-dimensional reconstructed velocity field indicates the presence of a persistent vortex pair close to the wall and on either side of the jet centerline that appear similar to the mean streamwise vorticity. These regions do not appear to be directly related to the positioning of the streamwise vortex structures in the outer shear-layer.

Self-generation of organized waves in an impinging turbulent jet at low Mach number

1982 ◽  
Vol 117 ◽  
pp. 425-441 ◽  
Author(s):  
Donald Rockwell ◽  
Andreas Schachenmann
Keyword(s):  
Mach Number ◽  
Phase Difference ◽  
Acoustic Waves ◽  
Near Field ◽  
Turbulent Jet ◽  
Maximum Pressure ◽  
Pressure Amplitude ◽  
Axisymmetric Cavity ◽  
Low Mach Number ◽  
Oscillation Frequencies

Self-generation of highly organized waves in a nominally turbulent jet at very low Mach number can arise from its impingement upon the downstream orifice of an axisymmetric cavity, having an impingement length much shorter than the corresponding acoustic wavelength. The oscillation frequencies are compatible with the resonant modes of a long pipe located upstream of the cavity and with jet-instability frequencies based on the column mode (0·3 [siml ] SD [siml ] 0·6), as well as the near-field shear layer mode (0·016 [siml ] Sθ0 [siml ] 0·03). Moreover, the frequency of the organized wave is constant from separation to impingement; consequently vortex pairing does not occur.Within the cavity, the pressure amplitude associated with the organized wave is directly related to the phase difference between the organized velocity fluctuations at separation and impingement. Maximum pressure amplitude occurs when this phase difference, measured along the cavity (i.e. jet) centre-line, is 2nπ. Streamwise amplitude and phase distributions of the organized wave cannot be explained from purely hydrodynamic considerations; however, they can be effectively modelled by superposing contributions from hydrodynamic and acoustic waves. This aspect has important consequences for externally excited jets as well.

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