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Modulation Mechanism of Acoustic Scattering in Underwater Corner Reflectors with Acoustic Metasurfaces

Du Jiaman, Peng Zilong, Ge Lili, Lyu Shijin, Zhou Fulin, Liu Yan

Archives of Acoustics

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2023

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Vol. 48, No. 4

465--473

EN

Using the tunderwater corner reflector (CR) to simulate the acoustic scattering characteristics of the military target is a new technology to counter active sonar detection. Existing underwater CRs only have the ability to interfere with the acoustic field, but have limitations in acoustic wave modulation. Therefore, acoustic metasurfaces applied on CRs to enhance the ability of acoustic wave modulation has a great application prospect. A fast prediction method based on the Kirchhoff approximation (KA) and the ray tracing theory is proposed to calculate the acoustic scattering characteristics of CR with acoustic metasurfaces in grooves array type. The accuracy of the method is verified by the finite element method (FEM) simulation. The modulation effect of CR with grooves array in different gradient combinations on the structural scattering acoustic field is analyzed. The research shows that the CR with different combinations of the acoustic metasurface has an obvious modulation effect on the amplitude of the acoustic waves and the deflection of acoustic field. In particular, the grooves array in combination with positive and negative gradients has an obvious deflection impact on the scattering acoustic field.

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Monitoring dynamiki ruchów powierzchni osuwisk w warunkach zmiennego poziomu wód gruntowych z wykorzystaniem reflektorów radarowych

Perski Zbigniew, Wojciechowski Tomasz

Przegląd Geologiczny

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2022

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Vol. 70, nr 9

661--670

EN

The main objective of the presented analysis was to investigate to what extent even minor changes in the hydrological and hydrogeological environment affect the changes in the dynamics of landslide surface displacement. The research was carried out for selected monitored landslides, which, in addition to the in-depth monitoring devices, were equipped with corner reflectors suitable for satellite radar interferometry measurements. The high temporal resolution of the interferometric data allowed demonstrating the existence of a relationship between the speed of surface movements and slight changes in the depth to the groundwater table. The analyses were performed for five landslides, which also showed a high dependence of these compounds on the geological structure of the landslide and its substrate.

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Zaawansowane techniki InSAR w monitorowaniu osuwisk

Perski Zbigniew

Przegląd Geologiczny

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2019

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Vol. 67, nr 5

351--359

EN

In recent years, there has been a rapid development of SAR acquisition techniques and all new satellite radar missions are equipped with SAR devices allowing beam steering. This paper presents results of experimental application of TerraSAR-X in ultra-high resolution SpotLight and Staring SpotLight modes for the area of the Just landslide in the Rożnow lake area. Another analyzed example was to use data of the medium resolution Sentinel-1 data acquired in the TOPS mode for the Huciska and Zapadle landslides in Szymbark. In this case, a network of 12 radar reflectors (corner reflectors) was installed to make the results independent of vegetation conditions on landslides. This study presents preliminary results of measurements and discusses the potential of applications and directions of further work.