incident wave
Recently Published Documents


TOTAL DOCUMENTS

593
(FIVE YEARS 106)

H-INDEX

36
(FIVE YEARS 3)

2022 ◽  
Author(s):  
B.R. Julian ◽  
G.R. Foulger

ABSTRACT Seismic tomography methods that use waves originating outside the volume being studied are subject to bias caused by unknown structure outside this volume. The bias is of the same mathematical order and similar magnitude as the local-structure effects being studied; failure to account for it can significantly corrupt derived structural models. This bias can be eliminated by adding to the inverse problem three unknown parameters specifying the direction and time for each incident wave, a procedure analogous to solving for event locations in local-earthquake and whole-mantle tomography. The forward problem is particularly simple: The first-order change in the arrival time at an observation point resulting from a perturbation to the incident-wave direction and time equals the change in the time of the perturbed incident wave at the point where the unperturbed ray entered the study volume. This consequence of Fermat’s principle apparently has not previously been recognized. Published teleseismic tomography models probably contain significant artifacts and need to be recomputed using the more complete theory.


Author(s):  
A. V. Martynov ◽  
G. S. Nikonova ◽  
А. N. Kondratyev

The article presents the results of research and implementation of adaptive calibration systems used in setting up mass-produced products. The proposed method allows you to speed up the tuning of the HF transceiver. In the process of tuning, with the help of a neural network, an adaptive correction of the approximating function of the incident wave sensor is made according to the accumulated data, which makes it possible to reduce the time for tuning the transceiver. The introduction of the mathematical apparatus of neural networks can be applied in the process of mass production for other products.


Author(s):  
Pham Chi Vinh ◽  
Do Xuan Tung ◽  
Nguyen Thi Kieu

This paper deals with the reflection and transmission of P-waves at a very rough interface between two isotropic elastic solids. The interface is assumed to oscillate between two straight lines. By mean of homogenization, this problem is reduced to the reflection and transmission of P-waves through an inhomogeneous orthotropic elastic layer. It is shown that a P incident wave always creates two reflected waves (one P wave and one SV wave), however, there may exist two, one or no transmitted waves. Expressions in closed-form of the reflection and transmission coefficient have been derived using the transfer matrix of an orthotropic elastic layer. Some numerical examples are carried out to examine the reflection and transmission of P-waves at a very rough interface of tooth-comb type, tooth-saw type and sin type. It is found numerically that the reflection and transmission coefficients depend strongly on the incident angle, the incident wave frequency, the roughness and the type of interfaces.


2021 ◽  
Author(s):  
Vishal Sorathiya ◽  
shobhit patel

Abstract We present the comparative analysis of tunable graphene-based metasurface polarizer structure THz frequency range. This polarizer structures have been numerically investigated over the 10 THz to 25 THz of the frequency range. Reflectance co-efficient, phase variation, and phase difference parameters have been investigated to identify the behavior of polarization effect over the range of 10 THz to 25 THz of the frequency. The proposed polarizer has been also investigated for the different shapes of the top gold resonator structure. The proposed structure is tunable for the range of 0.1 eV to 0.9 eV of the graphene Fermi energy. The proposed structure also works on the wide range of the input incident wave of the X and Y polarization. This structure having small, compact tunable design and it can be used as a basic building block in the large THz circuits and structures.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Idban Alamzadeh ◽  
George C. Alexandropoulos ◽  
Nir Shlezinger ◽  
Mohammadreza F. Imani

AbstractReconfigurable reflective surfaces can alter the propagation environment to improve wireless communication and power transfer. Paramount to this operation—which has attracted much attention recently—is the assumption that the reflective surface has prior knowledge of the propagation environment, for example, the direction/location of the transmitter and the intended receiver(s). To address this need, we propose a reconfigurable reflective metasurface with integrated sensing capabilities. By modifying the tunable meta-atoms constituting the metasurface, we couple small portions of the incident wave to an array of sensing waveguides. As an illustrative example, we demonstrate the ability to use the sampled incident wave to detect its angle of arrival. In addition, we propose and numerically demonstrate the possibility to reduce the required sensors, i.e., the number of radio frequency (RF) chains needed to acquire the sensed signals, by leveraging the inherent metasurface’s tunable multiplexing capability. A reconfigurable reflective metasurface with integrated sensing capabilities can benefit wireless communications, wireless power transfer, RF sensing, and smart sensors.


2021 ◽  
Author(s):  
Hao Tian ◽  
Boyang Zhou ◽  
Zengmeng Zhang ◽  
Yongjun Gong

Abstract Heaving motion of ocean wave is a promising renewable energy source but challenging to capture with consistent conversion efficiencies. Main issue of the varying energy extraction efficiency of wave energy converters (WEC’s) is primarily caused by the variation of incident wave frequency and amplitude. Traditional design of the WEC has to account for the extreme sea conditions, leaving the WEC to work at suboptimal regions for most of the time. Due to the loss characteristics of the fluid power components, the performance and efficiency drop rapidly when moved away from the optimal working condition. In order to improve the efficiency of WEC, the buoy needs to operate at maximum amplitude most of the time. To do so, a new buoy structure based on actively controlled fluid-air ratio is proposed. Contrast to the traditional buoy for WEC’s, which has fixed density and weight, the proposed structure is capable of weight manipulation, resulting adjustable system natural frequency. MATLAB/Simulink simulation analysis is carried out to verify the feasibility of adjusting the gas-liquid ratio inside the buoy with a water hydraulic system. To resonate with the unknown incident wave, maximum power point tracking (MPPT) algorithm is proposed to control the buoy mass with trial steps for maximizing the resonating amplitude of the buoy. Initial simulation results have shown that the proposed system is capable of adjusting the natural frequency and the MPPT algorithm can increase the amplitude of the buoy motion.


2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhao Mi ◽  
Long Pengzhen ◽  
Wang Piguang ◽  
Zhang Chao ◽  
Du Xiuli

This paper presents an analytical method to investigate the multiple scattering problem within arrays of vertical bottom-mounted circular cylinders subjected to linear incident waves. Based on the Laplace equation and boundary conditions on the seabed and surface, a formulation of a two-dimensional multiple scattering problem is first obtained by using the variable separation method. Furthermore, the analytical solution of the wave forces on multiple circular cylinders is derived, which consists of the incident wave force due to the linear incident wave and the scattered wave forces considering multiple scattering waves. The presented analytical solution is validated by comparing its results with a numerical method, and the result shows that the analytical solution is in good agreement with the numerical one. Finally, the multiple scattering analysis is conducted on arrays of cylinders with different incident wave numbers, distances between cylinders, and quantities.


2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Mikko Salo ◽  
Henrik Shahgholian

AbstractWe study a question arising in inverse scattering theory: given a penetrable obstacle, does there exist an incident wave that does not scatter? We show that every penetrable obstacle with real-analytic boundary admits such an incident wave. At zero frequency, we use quadrature domains to show that there are also obstacles with inward cusps having this property. In the converse direction, under a nonvanishing condition for the incident wave, we show that there is a dichotomy for boundary points of any penetrable obstacle having this property: either the boundary is regular, or the complement of the obstacle has to be very thin near the point. These facts are proved by invoking results from the theory of free boundary problems.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chun-Hong Chen ◽  
Pei-Yang Wang ◽  
Jun Chen ◽  
Ting Xu

A single-layer capsule-shaped polarization conversion metasurface (PCM) is proposed in this paper. In the W-band, its polarization conversion rate (PCR) exceeds 97%, effectively changing the polarization direction of the incident wave. PCM is arranged in a chessboard array to achieve broadband RCS reduction. Placing the PCM array on a circularly polarized sequentially rotated slot antenna array, simulated results show that the radiation characteristics of the antenna array are hardly affected by the PCM array. The results of measurement demonstrate that the RCS of the antenna array with PCM array proposed is reduced by more than 10 dB from 40 to 119 GHz; the relative bandwidth (−10 dB) reaches 96.3%.


Sign in / Sign up

Export Citation Format

Share Document