scholarly journals Teaching about Waves with Applications in Lenses

2020 ◽  
Vol 2 (3) ◽  
pp. p38
Author(s):  
Mihas Pavlos ◽  
Gemousakakis Triantafyllos
Keyword(s):  
Gradual Change ◽  
Two Dimensional ◽  
Refraction Angle ◽  
Wave Fronts ◽  
Perfect Lens ◽  
Speed Of Propagation

The paper examines ways of teaching wave pulses traveling on strings and wave fronts in two dimensional waves. The phenomena examined for pulses are: reflection, transmission and superposition. Two methods of finding the refracted wave fronts, the corresponding rays and the refraction angle are presented. Then the gradual change of the speed of propagation of a wave is presented. In the last part is examined the application of the concept of wave fronts in lenses and Huygens’ method of finding the shape of a perfect lens. The students’ difficulties with connection with all these subjects are presented.

scholarly journals Metamaterial Lensing Devices

Molecules ◽  
2019 ◽  
Vol 24 (13) ◽  
pp. 2460 ◽  
Author(s):  
Jiangtao Lv ◽  
Ming Zhou ◽  
Qiongchan Gu ◽  
Xiaoxiao Jiang ◽  
Yu Ying ◽  
...  
Keyword(s):  
Building Blocks ◽  
Biological Imaging ◽  
Transmission Mode ◽  
Two Dimensional ◽  
Optical Components ◽  
Practical Applications ◽  
Perfect Lens ◽  
Significant Potential ◽  
Integrated Optical

In recent years, the development of metamaterials and metasurfaces has drawn great attention, enabling many important practical applications. Focusing and lensing components are of extreme importance because of their significant potential practical applications in biological imaging, display, and nanolithography fabrication. Metafocusing devices using ultrathin structures (also known as metasurfaces) with superlensing performance are key building blocks for developing integrated optical components with ultrasmall dimensions. In this article, we review the metamaterial superlensing devices working in transmission mode from the perfect lens to two-dimensional metasurfaces and present their working principles. Then we summarize important practical applications of metasurfaces, such as plasmonic lithography, holography, and imaging. Different typical designs and their focusing performance are also discussed in detail.

Impact Resistance and Energy Absorption of Functionally Graded Cellular Structures

2011 ◽  
Vol 69 ◽  
pp. 73-78 ◽  
Author(s):  
Xiao Kai Wang ◽  
Zhi Jun Zheng ◽  
Ji Lin Yu ◽  
Chang Feng Wang
Keyword(s):  
Energy Absorption ◽  
Impact Resistance ◽  
Functionally Graded ◽  
Cellular Structures ◽  
Stress Wave Propagation ◽  
Initial Kinetic Energy ◽  
Gradual Change ◽  
Two Dimensional ◽  
The One ◽  
The Impact

The dynamic response of functionally graded cellular structures subjected to impact of a finite mass was investigated in this paper. Compared to a cellular structure with a uniform cell size, the one with gradually changing cell sizes may improve many properties. Based on the two-dimensional random Voronoi technique, a two-dimensional topological configuration of cellular structures with a linear density-gradient in one direction was constructed by changing the cell sizes. The finite element method using ABAQUS/Explicit code was employed to investigate the energy absorption and the influence of gradient on stress wave propagation. Results show that functionally graded cellular structures studied are superior in energy absorption to the equivalent uniform cellular structures under low initial kinetic energy impacts, and the performance of such structures can be significantly improved when the density difference is enlarged. The stress levels at the impact and support ends may be reduced by introducing a gradual change of density in cellular structures when the initial impact velocity is low.

scholarly journals Data-driven modeling of two-dimensional detonation wave fronts

Wave Motion ◽  
2022 ◽  
pp. 102879
Author(s):  
Ariana Mendible ◽  
Weston Lowrie ◽  
Steven L. Brunton ◽  
J. Nathan Kutz
Keyword(s):  
Detonation Wave ◽  
Data Driven ◽  
Two Dimensional ◽  
Wave Fronts ◽  
Data Driven Modeling

Real‐time visualization of acoustic wave fronts by using a two‐dimensional microphone array

1988 ◽  
Vol 84 (4) ◽  
pp. 1373-1377 ◽  
Author(s):  
Yukio Hiranaka ◽  
Osamu Nishii ◽  
Takayuki Genma ◽  
Hiro Yamasaki
Keyword(s):  
Acoustic Wave ◽  
Real Time ◽  
Microphone Array ◽  
Two Dimensional ◽  
Wave Fronts ◽  
Real Time Visualization

Wave Energy Focalization in a Plate With Imperfect Two-Dimensional Acoustic Black Hole Indentation

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Wei Huang ◽  
Hongli Ji ◽  
Jinhao Qiu ◽  
Li Cheng
Keyword(s):  
Black Hole ◽  
Power Law ◽  
Power Flow ◽  
Flexural Wave ◽  
Thickness Variation ◽  
Gradual Change ◽  
Two Dimensional ◽  
Practical Applications ◽  
Structural Problems ◽  
Thin Walled Structures

The acoustic black hole (ABH) phenomenon in thin-walled structures with a tailored power-law-profiled thickness allows for a gradual change of the phase velocity of flexural waves and energy focalization. However, ideal ABH structures are difficult to realize and suffer from potential structural problems for practical applications. It is therefore important to explore alternative configurations that can eventually alleviate the structural deficiency of the ideal ABH structures, while maintaining similar ability for wave manipulation. In this study, the so-called imperfect two-dimensional ABH indentation with different tailored power-law-profiled is proposed and investigated. It is shown that the new indentation profile also enables a drastic increase in the energy density around the tapered area. However, the energy focalization phenomena and the process are shown to be different from those of conventional ABH structure. With the new indentation profile, the stringent power-law thickness variation in ideal ABH structures can be relaxed, resulting in energy focalization similar to a lens. Different from an ideal ABH structure, the energy focalization point is offset from, and downstream of indentation center, depending on the structural geometry. Additional insight on energy focalization in the indentation is quantitatively analyzed by numerical simulations using structural power flow. Finally, the phenomenon of flexural wave focalization is verified by experiments using laser ultrasonic scanning technique.

Triangular Cellular Automata for Computing Two-Dimensional Elastodynamic Response on Arbitrary Domains

2010 ◽  
Vol 78 (2) ◽  
Author(s):  
Ryan K. Hopman ◽  
Michael J. Leamy
Keyword(s):  
Finite Element ◽  
Partial Differential Equations ◽  
Cellular Automata ◽  
Differential Equations ◽  
Numerical Experiments ◽  
Two Dimensional ◽  
Wave Fronts ◽  
Rule Set ◽  
Spurious Oscillations ◽  
Elastodynamic Response

This study extends a recently developed cellular automata (CA) modeling approach (Leamy, 2008, “Application of Cellular Automata Modeling to Seismic Elastodynamics,” Int. J. Solids Struct., 45(17), pp. 4835–4849) to arbitrary two-dimensional geometries via the development of a rule set governing triangular automata (cells). As in the previous rectangular CA method, each cell represents a state machine, which updates in a stepped manner using a local “bottom-up” rule set and state input from neighboring cells. Notably, the approach avoids the need to develop and solve partial differential equations and the complexity therein. The elastodynamic responses of several general geometries and loading cases (interior, Neumann, and Dirichlet) are computed with the method and then compared with results generated using the earlier rectangular CA and finite element approaches. Favorable results are reported in all cases with numerical experiments indicating that the extended CA method avoids, importantly, spurious oscillations at the front of sharp wave fronts.

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