scholarly journals Performance analysis of matched field processing localization with various line array configurations based on normal mode decomposition

2018 ◽  
Vol 67 (17) ◽  
pp. 174302
Author(s):  
Jia Yu-Qing ◽  
Su Lin ◽  
Guo Sheng-Ming ◽  
Ma Li
Keyword(s):  
Performance Analysis ◽  
Normal Mode ◽  
Matched Field Processing ◽  
Mode Decomposition ◽  
Line Array

Performance Analysis of Normal Mode Helical Antenna in Seawater

2020 ◽  
Author(s):  
Siti Harliza Mohd Razali ◽  
Razali Ngah ◽  
Kamalia Kamardin ◽  
Yoshihide Yamada
Keyword(s):  
Performance Analysis ◽  
Normal Mode ◽  
Helical Antenna

Inversion of Pressure Data on a Vertical Array for Sea Floor Geoacoustic Properties

1998 ◽  
Vol 06 (01n02) ◽  
pp. 269-289 ◽  
Author(s):  
Purnima Ratilal ◽  
Peter Gerstoft ◽  
Joo Thiam Goh ◽  
Keng Pong Yeo
Keyword(s):  
Ambient Noise ◽  
Historical Data ◽  
Low Frequency ◽  
Real Data ◽  
Vertical Array ◽  
Trial Site ◽  
Matched Field Processing ◽  
High Frequencies ◽  
Sea Floor ◽  
Line Array

Estimation of the integral geoacoustic properties of the sea floor based on real data drawn from a shallow water site is presented. Two independent inversion schemes are used to deduce these properties. The first is matched-field processing of the pressure field on a vertical line array due to a projected source. The second approach is the inversion of ambient noise on a vertical array. Matched-field processing has shown to be successful in the inversion of high quality field data. Here, we show that it is also feasible with a more practical and less expensive data collection scheme. It will also be shown that low frequency inversion is more robust to variation and fluctuation in the propagating medium, whereas high frequencies are more sensitive to mismatches in a varying medium. A comparison is made of the estimates obtained from the two techniques and also with available historical data of the trial site.

Thermal Properties for Bulk Silicon Based on the Determination of Relaxation Times Using Molecular Dynamics

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Javier V. Goicochea ◽  
Marcela Madrid ◽  
Cristina Amon
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Thermal Properties ◽  
Total Energy ◽  
Normal Mode ◽  
Relaxation Times ◽  
Dispersion Relations ◽  
Boltzmann Transport ◽  
Mode Decomposition ◽  
The Impact

Molecular dynamics simulations are performed to estimate acoustical and optical phonon relaxation times, dispersion relations, group velocities, and specific heat of silicon needed to solve the Boltzmann transport equation (BTE) at 300 K and 1000 K. The relaxation times are calculated from the temporal decay of the autocorrelation function of the fluctuation of total energy of each normal mode in the ⟨100⟩ family of directions, where the total energy of each mode is obtained from the normal mode decomposition of the motion of the silicon atoms over a period of time. Additionally, silicon dispersion relations are directly determined from the equipartition theorem obtained from the normal mode decomposition. The impact of the anharmonic nature of the potential energy function on the thermal expansion of the crystal is determined by computing the lattice parameter at the cited temperatures using a NPT (i.e., constant number of atoms, pressure, and temperature) ensemble, and are compared with experimental values reported in the literature and with those computed analytically using the quasiharmonic approximation. The dependence of the relaxation times with respect to the frequency is identified with two functions that follow the functional form of the relaxation time expressions reported in the literature. From these functions a simplified version of relaxation times for each normal mode is extracted. Properties, such as group and phase velocities, thermal conductivity, and mean free path, needed to further develop a methodology for the thermal analysis of electronic devices (i.e., from nano- to macroscales) are determined once the relaxation times and dispersion relations are obtained. The thermal properties are validated by comparing the BTE-based thermal conductivity against the predictions obtained from the Green–Kubo method. It is found that the relaxation times closely resemble the ones obtained from perturbation theory at high temperatures; the contribution to the thermal conductivity of the transverse acoustic, longitudinal acoustic, and longitudinal optical modes being approximately 30%, 60%, and 10%, respectively, and the contribution of the transverse optical mode negligible.

Normal-mode decomposition for the optical response of cylinder clusters

1998 ◽  
Vol 58 (1) ◽  
pp. 1101-1111 ◽  
Author(s):  
A. J. Reuben ◽  
G. B. Smith
Keyword(s):  
Normal Mode ◽  
Optical Response ◽  
Mode Decomposition

A PE-BASED APPROACH TO MODAL DECOMPOSITION AND SOURCE LOCALIZATION

1994 ◽  
Vol 02 (03) ◽  
pp. 231-250 ◽  
Author(s):  
DAVID J. THOMSON ◽  
GORDON R. EBBESON
Keyword(s):  
Water Environment ◽  
Propagation Model ◽  
Mode Shapes ◽  
Benchmark Problems ◽  
Modal Decomposition ◽  
Matched Field Processing ◽  
Localization Scheme ◽  
Line Array ◽  
Efficient Alternative ◽  
Array Aperture

Matched mode processing is an efficient alternative to matched field processing for locating a source in an acoustic waveguide. The successful application of this method relies on the accurate modal decomposition of the pressure data received on a vertical line array. From the modes that can be resolved by a given array aperture, the source range is determined from modal phases, whereas the source depth is determined from the mode shapes. In this paper, we describe a decomposition method based on the parabolic equation (PE) propagation model for recovering this modal information from vertical array data and which can be used to localize an underwater source by the matched mode processing method. We apply our PE-based decomposition/localization scheme to several benchmark problems involving a narrowband acoustic source operating in a shallow water environment.

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