A numerical study of rough interface reverberation suppression, clutter elimination and target resonance excitation in heterogeneous media with single channel iterative time reversal.

2009 ◽  
Vol 126 (4) ◽  
pp. 2225
Author(s):  
Yingzi Ying ◽  
Li Ma ◽  
Bingwen Sun
Keyword(s):  
Time Reversal ◽  
Heterogeneous Media ◽  
Single Channel ◽  
Numerical Study ◽  
Resonance Excitation ◽  
Rough Interface

VOLUME CLUTTER ELIMINATION, ROUGH INTERFACE REVERBERATION SUPPRESSION, AND TARGET RESONANCE CONVERGENCE IN HETEROGENEOUS MEDIA USING AN ITERATIVE TIME REVERSAL MIRROR

2010 ◽  
Vol 18 (03) ◽  
pp. 227-243 ◽  
Author(s):  
YINGZI YING ◽  
LI MA
Keyword(s):  
Time Reversal ◽  
Finite Difference Time Domain ◽  
Small Volume ◽  
Heterogeneous Media ◽  
Resonance Mode ◽  
Rough Interface ◽  
Acoustic Signature ◽  
Time Harmonic ◽  
Time Reversal Mirror ◽  
Difference Time

The presence of the clutter of volume scattering and the echo return from rough interface hinders the detection of target in heterogeneous media. This work investigates the application of an iterative time reversal mirror to mitigate the difficulties. Numerical simulations based on pseudospectral finite-difference time-domain method are performed in one and two layered media. A wideband probe pulse is launched to initiate the process, and the time-reversed echo received at the same position is retransmitted as the renewed input signal for next iteration, and repeat the procedures iteratively. The results illustrate as the number of iteration increases, small volume clutter is eliminated, interface reverberation is suppressed relatively, and the echoes will converge to a time-harmonic waveform that corresponds to an object's dominant resonance mode. The detection of target is achieved by extracting this important acoustic signature.

Photoacoustic tomography of heterogeneous media using a model-based time reversal method

2008 ◽  
Author(s):  
Hubert Grün ◽  
Robert Nuster ◽  
Günther Paltauf ◽  
Markus Haltmeier ◽  
Peter Burgholzer
Keyword(s):  
Time Reversal ◽  
Heterogeneous Media ◽  
Photoacoustic Tomography ◽  
Model Based

Influence of Detailing on Aerodynamic Forcing of a Transonic Axial Turbine Stage and Forced-Response Prediction for Low-Engine-Order (LEO) Excitation

2017 ◽  
Author(s):  
Tobias R. Müller ◽  
Damian M. Vogt ◽  
Klemens Vogel ◽  
Bent A. Phillipsen ◽  
Peter Hönisch
Keyword(s):  
Numerical Study ◽  
Response Prediction ◽  
Forced Response ◽  
Resonance Excitation ◽  
Response Analysis ◽  
Turbine Stage ◽  
Flow Induced Vibration ◽  
Axial Turbine ◽  
Timing Data ◽  
Generalized Force

The effects of detailing on the prediction of forced-response in a transonic axial turbine stage, featuring a parted stator design, asymmetric inlet and outlet casings as well as rotor cavities, is investigated. Ensuring the mechanical integrity of components is of paramount importance for the safe and reliable operation of turbomachines. Among others, flow induced resonance excitation can lead to high-cycle fatigue (HCF) and potentially to damage of components unless properly damped. This numerical study is assessing the necessary degree of detailing in terms of spatial and temporal discretization, boundary conditions of the pre-stressed rotor geometry as well as geometrical detailing for the reliable prediction of the aerodynamic excitation of the structure. In this context, the sensitivity of the aerodynamic forcing is analyzed by means of the generalized force criterion, showing a significant influence for some of the investigated variations of the numerical model. Moreover, the origin and further progression of several low-engine-orders (LEO) within the flow field, as well as their interaction with different geometric details has been analyzed based on the numerical results obtained from a full 360° CFD-calculation of the investigated turbine stage. The predicted flow induced vibration of the structure has been validated by means of a full forced-response analysis, where a good agreement with tip-timing data has been found.

scholarly journals Numerical Investigation of a two-inlet PVT air collector

2019 ◽  
Vol 136 ◽  
pp. 05014
Author(s):  
Zhangyang Kang ◽  
Zhaoyang Lu ◽  
Xin Deng ◽  
Qiongqiong Yao
Keyword(s):  
Heat Transfer ◽  
Single Channel ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Thermal Characteristics ◽  
Area Ratio ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Maximum Heat

A numerical study of heat and mass transfer characteristics of a two-inlet PV/T air collector is performed. The influence of thermal characteristics and efficiency is investigated as the area ratios of inlet and outlet of the single channel with two inlets are changed. The design of the two-inlet PV/T air collector can avoid the poor heat transfer conditions of the single inlet PV/T air collector and improve the total photo-thermal efficiency. When the inlet/outlet cross-sectional area ratio is reduced, the inlet air from the second inlet enhances the convection heat transfer in the second duct and the temperature distribution is more uniform. As the cross-sectional area of the second inlet increase, the maximum heat exchange amount of the two-inlet PV/T air collector occurs between the inlet and outlet cross-sectional area ratio L=0.645 and L=0.562.

Identification of a resonant target buried in sediment using iterative, single channel, time reversal

2007 ◽  
Vol 122 (5) ◽  
pp. 3023
Author(s):  
Zachary J. Waters ◽  
R. Glynn Holt ◽  
Ronald A. Roy ◽  
Benjamin R. Dzikowicz
Keyword(s):  
Time Reversal ◽  
Single Channel

Acoustic communications in an enclosure using single-channel time-reversal acoustics

2002 ◽  
Vol 80 (4) ◽  
pp. 694-696 ◽  
Author(s):  
M. G. Heinemann ◽  
A. Larraza ◽  
K. B. Smith
Keyword(s):  
Time Reversal ◽  
Single Channel ◽  
Acoustic Communications ◽  
Time Reversal Acoustics

scholarly journals Impact of multiple channels on the Characteristics of Rectangular GAA MOSFET

2017 ◽  
Vol 7 (4) ◽  
pp. 1899
Author(s):  
Mohammed Khaouani ◽  
Ahlam Guen-Bouazza
Keyword(s):  
Single Channel ◽  
Numerical Study ◽  
Drain Current ◽  
Short Channel Effects ◽  
Short Channel ◽  
Channel One ◽  
A Value ◽  
Device Structures ◽  
Channel Effects ◽  
The Impact

<p>Square gate all around MOSFETs are a very promising device structures allowing to continue scaling due to their superior control over the short channel effects. In this work a numerical study of a square structure with single channel is compared to a structure with 4 channels in order to highlight the impact of channels number<em> </em>on the device’s DC parameters (drain current and threshold voltage). Our single channel rectangular GAA MOSFET showed reasonable ratio Ion/Ioff of 10<sup>4</sup>, while our four channels GAA MOSFET showed a value of 10<sup>3</sup>. In addition, a low value of drain induced barrier lowering<em> (DIBL) of </em>60mV/V was obtained for our single channel GAA and a lower value of with 40mv/v has been obtained for our four channel one. Also, an extrinsic transconductance of 88ms/µm have been obtained for our four channels GAA compared to the single channel that is equal to 7ms/µm.</p>

Sign in / Sign up

Export Citation Format

Share Document