Numerical Studies and Potential Applications of the Vertical Array-Differential Target Antenna Coupling (DTAC) Method for Rapid Sensing and Imaging of Subsurface Targets

2015 ◽  
Vol 20 (2) ◽  
pp. 137-151 ◽  
Author(s):  
Ben K. Sternberg ◽  
Wanjie Feng ◽  
Steven L. Dvorak
Keyword(s):  
Vertical Array ◽  
Numerical Studies ◽  
Antenna Coupling ◽  
Potential Applications

scholarly journals Experimental and numerical study of helical auxetic yarns

2020 ◽  
pp. 004051752097719
Author(s):  
Yajie Gao ◽  
Xiaogang Chen ◽  
Rachel Studd
Keyword(s):  
Numerical Study ◽  
Structural Parameters ◽  
Tensile Modulus ◽  
Diameter Ratio ◽  
Element Analysis ◽  
Yarn Quality ◽  
Numerical Studies ◽  
Helical Angle ◽  
Potential Applications ◽  
New Finding

Auxetic materials, including textiles, exhibit a negative Poisson’s ratio (NPR), which is of interest for many applications. This research aims to optimize the structural parameters of helical auxetic yarns (HAYs) and to evaluate the auxetic performance of these yarns. The research reports on the improvement of auxetic yarn quality and the yarn auxeticity through studying the effect of helical angles, diameter ratio and tensile moduli of the two plies, as well as the binder filament feeding. The maximum NPR of the optimized auxetic yarns was experimentally achieved as low as –9.6, with the helical angle of around 14.0° on average using the optimal machine setting. The optimized yarn parameters enabled the making of high-quality auxetic yarns with a wider range of machine settings than before. In parallel, theoretical and numerical studies were carried out for the engineering design of auxetic yarns, which enabled comparisons among the experimental results, calculated results and results from finite element analysis. The comparison showed that a lower initial helical angle, higher tensile modulus of the wrap ply and lower tensile modulus of the core ply led to a higher auxetic effect. A new finding is reported in that a concave relationship between the diameter ratio and the NPR was discovered. The results of this study could assist researchers in producing HAYs, and this type of HAY could be used for many potential applications, such as filtration and impact protection.

An Experimental Investigation of Flow Phenomena in a Multi-Stage Micro Tesla Valve

2021 ◽  
Author(s):  
Jan Raffel ◽  
Shadi Ansari ◽  
David S. Nobes
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Flow Conditions ◽  
Numerical Studies ◽  
Multi Stage ◽  
Flow Phenomena ◽  
Potential Applications ◽  
Tesla Valve ◽  
Reynolds Number Flows ◽  
Unsteady Behavior

Abstract The Tesla-diode valve, with no moving parts, allows restricted flow in one direction. It has many potential applications in different industrial situations. Despite the application of the valve and the importance of the effect of flow phenomena on the Tesla valve's performance, very few studies have experimentally investigated the motion of flow within the Tesla valve. This study aims to contribute to this growing area of research on the performance of Tesla valves by demonstrating the flow phenomena and the flow conditions needed to be used in numerical studies. In this work, the effect of direction of the flow and Reynolds number on the flow phenomena generated in a Tesla-diode valve is studied. Particle shadowgraph velocimetry (PSV) is utilized to investigate and visualize the velocity field. The results of this study confirm some of the phenomena that has been observed using numerical simulations. It also highlights the flow phenomena leading to an increase in the diodicity by an increase in the number of Tesla loops in the valve. An important observation often ignored in numerical simulation is the presence of unsteady behavior and vortex shedding for higher Reynolds number flows.

Multi-band polarization independent cylindrical metamaterial absorber and sensor application

2016 ◽  
Vol 30 (08) ◽  
pp. 1650095 ◽  
Author(s):  
Furkan Dincer ◽  
Muharrem Karaaslan ◽  
Sule Colak ◽  
Erkan Tetik ◽  
Oguzhan Akgol ◽  
...  
Keyword(s):  
Rotational Symmetry ◽  
Microwave Frequency ◽  
Defense Industry ◽  
Metamaterial Absorber ◽  
Numerical Studies ◽  
Proposed Model ◽  
Potential Applications ◽  
Frequency Regime ◽  
Perfect Metamaterial Absorber ◽  
Multi Band

A multi-band perfect metamaterial absorber (MA) based on a cylindrical waveguide with polarization independency is numerically presented and investigated in detail. The proposed absorber has a very simple configuration, and it operates at flexible frequency ranges within the microwave frequency regime by simply tuning the dimensions of the structure. The maximum absorption values are obtained as 99.9%, 97.5%, 85.8%, 68.2% and 40.2% at the frequencies of 1.34 GHz, 2.15 GHz, 3.2 GHz, 4.31 GHz and 5.41 GHz, respectively. The numerical studies verify that the proposed model can provide multi-band perfect absorptions at wide polarization and incident angles due to its rotational symmetry feature. We have also realized sensor and parametric study applications in order to show additional features of the suggested model. The suggested MA enables myriad potential applications in medical technologies, sensors and in defense industry etc.

AN INDEX THEOREM FOR GRAPHENE

2007 ◽  
Vol 21 (30) ◽  
pp. 5113-5120 ◽  
Author(s):  
JIANNIS K. PACHOS ◽  
MICHAEL STONE
Keyword(s):  
Graphene Sheet ◽  
Good Description ◽  
Index Theorem ◽  
Continuous Limit ◽  
Zero Energy ◽  
Arbitrary Geometry ◽  
Numerical Studies ◽  
Topological Quantum ◽  
Potential Applications ◽  
Topological Quantum Computation

We consider a graphene sheet folded in an arbitrary geometry, compact or with nanotube-like open boundaries. In the continuous limit, the Hamiltonian takes the form of the Dirac operator, which provides a good description of the low energy spectrum of the lattice system. We derive an index theorem that relates the zero energy modes of the graphene sheet with the topology of the lattice. The result coincides with analytical and numerical studies for the known cases of fullerene molecules and carbon nanotubes, and it extends to more complicated molecules. Potential applications to topological quantum computation are discussed.

scholarly journals Wave scattering on lattice structures involving an array of cracks

2020 ◽  
Vol 476 (2236) ◽  
pp. 20190866
Author(s):  
Gaurav Maurya ◽  
Basant Lal Sharma
Keyword(s):  
Wave Scattering ◽  
Scattering Problem ◽  
Wave Mode ◽  
Atomic Scale ◽  
Square Lattice ◽  
Vertical Array ◽  
Single Crack ◽  
Discrete Green’S Function ◽  
Potential Applications ◽  
Limiting Case

Scattering of waves as a result of a vertical array of equally spaced cracks on a square lattice is studied. The convenience of Floquet periodicity reduces the study to that of scattering of a specific wave-mode from a single crack in a waveguide. The discrete Green’s function, for the waveguide, is used to obtain the semi-analytical solution for the scattering problem in the case of finite cracks whereas the limiting case of semi-infinite cracks is tackled by an application of the Wiener–Hopf technique. Reflectance and transmittance of such an array of cracks, in terms of incident wave parameters, is analysed. Potential applications include construction of tunable atomic-scale interfaces to control energy transmission at different frequencies.

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