Statistics of acoustic normal mode energy for low frequency long range propagation in the ocean: Comparisons between observations and theory.

2010 ◽  
Vol 128 (4) ◽  
pp. 2395-2395
Author(s):  
Tarun K. Chandrayadula ◽  
John A. Colosi ◽  
Peter F. Worcester ◽  
Matthew A. Dzieciuch ◽  
James A. Mercer ◽  
...  
Keyword(s):  
Long Range ◽  
Normal Mode ◽  
Low Frequency ◽  
Mode Energy

Quantifying the Predictive Skill in Long-Range Forecasting. Part II: Model Error in Coarse-Grained Markov Models with Application to Ocean-Circulation Regimes

2012 ◽  
Vol 25 (6) ◽  
pp. 1814-1826 ◽  
Author(s):  
Dimitrios Giannakis ◽  
Andrew J. Majda
Keyword(s):  
Long Range ◽  
Ocean Circulation ◽  
Climate Models ◽  
Markov Models ◽  
Low Frequency ◽  
Model Error ◽  
Ocean Model ◽  
Coarse Grained ◽  
Predictive Skill ◽  
Relaxation To Equilibrium

Abstract An information-theoretic framework is developed to assess the predictive skill and model error in imperfect climate models for long-range forecasting. Here, of key importance is a climate equilibrium consistency test for detecting false predictive skill, as well as an analogous criterion describing model error during relaxation to equilibrium. Climate equilibrium consistency enforces the requirement that long-range forecasting models should reproduce the climatology of prediction observables with high fidelity. If a model meets both climate consistency and the analogous criterion describing model error during relaxation to equilibrium, then relative entropy can be used as an unbiased superensemble measure of the model’s skill in long-range coarse-grained forecasts. As an application, the authors investigate the error in modeling regime transitions in a 1.5-layer ocean model as a Markov process and identify models that are strongly persistent but their predictive skill is false. The general techniques developed here are also useful for estimating predictive skill with model error for Markov models of low-frequency atmospheric regimes.

A Novel Broadband Vibration Energy Harvester

2014 ◽  
Vol 644-650 ◽  
pp. 3560-3563
Author(s):  
Yu Liu ◽  
Xiao Yan He ◽  
Shen Liu ◽  
Ying Wu ◽  
Yi Ou
Keyword(s):  
Resonance Frequency ◽  
Energy Harvester ◽  
Engineering Application ◽  
Low Frequency ◽  
Structure Design ◽  
Vibration Energy ◽  
Vibration Energy Harvester ◽  
Collector Efficiency ◽  
Energy Acquisition ◽  
Mode Energy

A single resonance frequency is the main factor of limiting vibration energy collector efficiency. In this paper, the multi degree of freedom oscillation adjusting bandwidth scheme is reported, designing a kind of new broadband vibration energy harvester, which has multi-mode energy acquisition, multi freedom vibration and broadband characteristics. Firstly, Broadband energy collector structure design. Secondly, Combining with the main vibration form, using the ANSYS carried out a detailed analysis of its working model. Finally, designing the prototype and doing some experimental verification, the results show that the designed energy collector with low frequency and wideband energy acquisition performance, the frequency domain of energy collection is 57.6 to 69.45HZ ,which break through the bottleneck of traditional single resonance frequency of energy acquisition, has a high value of theory and engineering application.

Low-frequency vibrational spectroscopy: a new tool for revealing crystalline magnetic structures in iron phosphate crystals

2021 ◽  
Vol 23 (39) ◽  
pp. 22241-22245
Author(s):  
Zihui Song ◽  
Xudong Liu ◽  
Anish Ochani ◽  
Suling Shen ◽  
Qiqi Li ◽  
...  
Keyword(s):  
Lithium Ion Batteries ◽  
Long Range ◽  
Vibrational Spectroscopy ◽  
Strong Dependence ◽  
Low Frequency ◽  
Lithium Ion ◽  
Iron Phosphate ◽  
Promising Material ◽  
Vibrational Dynamics ◽  
Magnetic Structures

In this report, the strong-dependence of low-frequency (terahertz) vibrational dynamics on weak and long-range forces in crystals is leveraged to determine the bulk magnetic configuration of iron phosphate – a promising material for cathodes in lithium ion batteries.

Spatial structure of long‐range, low‐frequency seafloor reverberation in the Canary Basin

1990 ◽  
Vol 88 (S1) ◽  
pp. S106-S106
Author(s):  
Jonathan M. Berkson ◽  
Fredrick R. Facemire ◽  
Jay A. Wallmark
Keyword(s):  
Spatial Structure ◽  
Long Range ◽  
Low Frequency

Long‐range measurements of the strength and spectral character of low‐frequency surface reverberation

1993 ◽  
Vol 94 (3) ◽  
pp. 1765-1765
Author(s):  
Roger C. Gauss ◽  
Raymond J. Soukup ◽  
David M. Fromm ◽  
Joseph M. Fialkowski
Keyword(s):  
Long Range ◽  
Low Frequency ◽  
Spectral Character ◽  
Range Measurements

scholarly journals The Effect of Attenuation from Fish Shoals on Long-Range, Wide-Area Acoustic Sensing in the Ocean

2019 ◽  
Vol 11 (21) ◽  
pp. 2464 ◽  
Author(s):  
Daniel Duane ◽  
Byunggu Cho ◽  
Ankita D. Jain ◽  
Olav Rune Godø ◽  
Nicholas C. Makris
Keyword(s):  
Remote Sensing ◽  
Long Range ◽  
Cross Sections ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Wide Area ◽  
Line Transect ◽  
Acoustic Sensing ◽  
Underwater Acoustic ◽  
Primary Means

Acoustics is the primary means of long-range and wide-area sensing in the ocean due to the severe attenuation of electromagnetic waves in seawater. While it is known that densely packed fish groups can attenuate acoustic signals during long-range propagation in an ocean waveguide, previous experimental demonstrations have been restricted to single line transect measurements of either transmission or backscatter and have not directly investigated wide-area sensing and communication issues. Here we experimentally show with wide-area sensing over 360° in the horizontal and ranges spanning many tens of kilometers that a single large fish shoal can significantly occlude acoustic sensing over entire sectors spanning more than 30° with corresponding decreases in detection ranges by roughly an order of magnitude. Such blockages can comprise significant impediments to underwater acoustic remote sensing and surveillance of underwater vehicles, marine life and geophysical phenomena as well as underwater communication. This makes it important to understand the relevant mechanisms and accurately predict attenuation from fish in long-range underwater acoustic sensing and communication. To do so, we apply an analytical theory derived from first principles for acoustic propagation and scattering through inhomogeneities in an ocean waveguide to model propagation through fish shoals. In previous experiments, either the attenuation from fish in the shoal or the scattering cross sections of fish in the shoal were measured but not both, making it impossible to directly confirm a theoretical prediction on attenuation through the shoal. Here, both measurements have been made and they experimentally confirm the waveguide theory presented. We find experimentally and theoretically that attenuation can be significant when the sensing frequency is near the resonance frequency of the shoaling fish. Negligible attenuation was observed in previous low-frequency ocean acoustic waveguide remote sensing (OAWRS) experiments because the sensing frequency was sufficiently far from the swimbladder resonance peak of the shoaling fish or the packing densities of the fish shoals were not sufficiently high. We show that common heuristic approaches that employ free space scattering assumptions for attenuation from fish groups can lead to significant errors for applications involving long-range waveguide propagation and scattering.

scholarly journals Observations of low-frequency, long-range acoustic propagation in the Philippine Sea and comparisons with mode transport theory

2020 ◽  
Vol 147 (2) ◽  
pp. 877-897
Author(s):  
Tarun K. Chandrayadula ◽  
Sivaselvi Periyasamy ◽  
John A. Colosi ◽  
Peter F. Worcester ◽  
Matthew A. Dzieciuch ◽  
...  
Keyword(s):  
Long Range ◽  
Transport Theory ◽  
Low Frequency ◽  
Acoustic Propagation ◽  
Philippine Sea
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