scholarly journals A Method for Estimating Dominant Acoustic Backscatter Mechanism of Water-Seabed Interface via Relative Entropy Estimation

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Bo Zou ◽  
Jingsheng Zhai ◽  
Jian Xu ◽  
Zhaoxing Li ◽  
Sunpei Gao
Keyword(s):  
Relative Entropy ◽  
Acoustic Scattering ◽  
Interface Roughness ◽  
Acoustic Backscatter ◽  
Bayesian Inversion ◽  
Observation Data ◽  
Fluid Approximation ◽  
Identification Scheme ◽  
Sediment Volume ◽  
Posterior Probability Density

It is important to distinguish the dominant mechanism of seabed acoustic scattering for the quantitative inversion of seabed parameters. An identification scheme is proposed based on Bayesian inversion with the relative entropy used to estimate dominant acoustic backscatter mechanism. DiffeRential Evolution Adaptive Metropolis is used to obtain samples from posterior probability density in Bayesian inversion. Three mechanisms for seabed scattering are considered: scattering from a rough water-seabed interface, scattering from volume heterogeneities, and mixed scattering from both interface roughness and volume heterogeneities. Roughness scattering and volume scattering are modelled based on Fluid Theories using Small-Slope Approximation and Small-Perturbation Fluid Approximation, respectively. The identification scheme is applied to three simulated observation data sets. The results indicate that the scheme is promising and appears capable of distinguishing sediment volume from interface roughness scattering and can correctly identify the dominant acoustic backscatter mechanism.

scholarly journals Sea–ice and water dynamics and moonlight impact the acoustic backscatter diurnal signal over the eastern Beaufort Sea continental slope

2020 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Petrusevich ◽  
Gérald Darnis ◽  
Sergei A. Kirillov ◽  
Alexander S. Komarov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Continental Slope ◽  
Light Transmission ◽  
Acoustic Scattering ◽  
Water Layer ◽  
Beaufort Sea ◽  
Water Dynamics ◽  
Acoustic Backscatter ◽  
Intermediate Water ◽  
Upwelling And Downwelling

Abstract. A two-year-long time series of currents and acoustic backscatter from an Acoustic Doppler Current Profiler, moored over the eastern Beaufort Sea continental slope from October 2003 to September 2005, were used to assess dynamics and variability of the sound-scattering layer. It has been shown that acoustic backscatter is dominated by a synchronized diel vertical migration (DVM) of the zooplankton. Our results show that DVM timings (i) were synchronous with sunlight, and (ii) were modified by moonlight and sea-ice, which attenuates light transmission to the water column. Moreover, DVM is modified or completely disrupted during highly energetic current events. Thicker ice observed during winter 2004–2005 lowered the backscatter values, but favored extending DVM toward the midnight sun. In contrast to many previous studies, DVM occurred through the intermediate water layer during the ice-free season of the midnight sun in 2004. In 2005, the midnight sun DVM was likely masked by a high acoustic scattering generated by suspended particles. During full moon at low cloud cover, the nighttime moonlight illuminance led to zooplankton avoidance of the sub-surface layer disrupting DVM. Moreover, DVM was disrupted by upwelling, downwelling and eddy passing. We suggest that these deviations are consistent with DVM adjusting to avoid enhanced water dynamics. For upwelling and downwelling, zooplankton likely respond to the along-slope water dynamics dominated by surface- and depth-intensified flow, respectively. This drives zooplankton to adjust DVM by aggregating in the low or upper intermediate water layer for upwelling and downwelling, respectively. The baroclinic eddy reversed DVM below the eddy core.

A New Adaptive UPF Algorithm through Improved Relative Entropy

2013 ◽  
Vol 658 ◽  
pp. 569-573
Author(s):  
Wen Tao Yu ◽  
Jun Peng ◽  
Xiao Yong Zhang
Keyword(s):  
Particle Filter ◽  
Relative Entropy ◽  
Particle Number ◽  
Time Step ◽  
Unscented Particle Filter ◽  
Posterior Probability Density ◽  
The Difference ◽  
Particle Filter Algorithm ◽  
Non Gaussian ◽  
Number Of Particles

Unscented particle filter (UPF) has high accuracy of state estimation for nonlinear system with non-Gaussian noise. While the computation of traditional unscented particle filter is huge and this depends on the particle number. In this paper we propose a new adaptive unscented particle filter algorithm AUPF through improved relative entropy which can adaptively adjust the particle number during filtering. Firstly the relative entropy is used to measure the distance between the posterior probability density and the importance proposal and the least number of particles for the next time step is decided according to the relative entropy. Then the least number is adjusted to offset the difference between the importance proposal and the true distribution. This algorithm can effectively reduce unnecessary particles meanwhile reduce the computation. The simulation results show the effectiveness of AUPF.

scholarly journals Prediction of Shoreline Change for the Calculation of the Integrated Littoral Sediment Budget

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 232
Author(s):  
Yeon-Joong Kim ◽  
Jong-Sung Yoon
Keyword(s):  
Sediment Transport ◽  
Coastal Erosion ◽  
Evaluation System ◽  
Shoreline Change ◽  
Sediment Budget ◽  
Prediction Performance ◽  
Sediment Supply ◽  
Sediment Runoff ◽  
Observation Data ◽  
Sediment Volume

The severe coastal erosions are being accelerated along the east coast of South Korea owing to the intermittent erosions and depositions caused by the imbalance between the effective sediment volume supplied from coasts and rivers and the sediment transport rate. Consequently, many studies are being conducted to develop coastal-erosion reduction measures. To accurately determine the cause of coastal erosion, the causes of the erosion and deposition should be accurately diagnosed, and a comprehensive evaluation system for the sediment transport mechanism in the watershed and sea while considering regional characteristics is required. In particular, realizing the evaluation of the effective sediment volume that flows from the river to the sea through observations is a highly challenging task, and various research and developments are required to realize it, as it is still in the basic research stage. The purpose of this study was to systematically analyze the comprehensive sediment budget for coastal areas. First, an analytical system was developed. Then, a shoreline model was constructed by considering the size of the mixed particles. The parameters required for developing the model were determined using the observation data to improve the shoreline model. A sediment runoff model was applied to evaluate the effective sediment volume supplied from the river to the sea, and the applicability of this model was evaluated by comparing it with the sediment supply volume according to the soil and water assessment tool model. The representative wave and the input parameters of the model were set using the observation data of several years. It was found that the prediction performance of the shoreline change model improved when the effective sediment volume was considered, and the particles of the sediment on the shore were assumed to comprise multiple sizes. In particular, the prediction performance improved when the balance of the sediment budget was adjusted by applying a groin having a structurally similar performance to take into consideration the geographic features of the Deokbongsan (island) in front of the river mouth bar. The model demonstrated a good performance in reproducing long-term shoreline changes when the characteristics of the sea waves and the effective sediment volume were considered.

scholarly journals Sediment dynamics of mountain streams as a function of variation in sediment deposition

2018 ◽  
Vol 55 (1) ◽  
pp. 23-29
Author(s):  
Ryunosuke Nakanishi ◽  
Yuki Okajima ◽  
Akira Baba ◽  
Yasuhiro Mitani ◽  
Hiro Ikemi
Keyword(s):  
Sediment Transport ◽  
Catchment Area ◽  
Heavy Rain ◽  
Sediment Dynamics ◽  
Sediment Deposition ◽  
Observation Data ◽  
Sediment Discharge ◽  
Regional Geology ◽  
Sediment Volume ◽  
Dam Reservoirs

 In Japan, the management of sediment in dam reservoirs has become challenging owing to heavy rain. Unexpected increase of sediment volume in dam reservoirs can increase flood risk owing to a rise in the level of the riverbed. It is therefore necessary to conduct sediment management to clarify the area of sediment production to control the amount of sediment transported and the timing of its movement. Sediment discharge from tributaries is often calculated based on catchment area and the deposited sediment volume already present in the dam reservoir. However, our preliminary surveys have implied that it is also necessary to consider regional geology in the evaluation of sediment transport. Moreover, variations in sediment deposition should be evaluated for each site where the geology changes. In this study, we observe in detail changes in the riverbed in two tributaries with different regional geologies. Changes in the shape of the riverbed were analyzed from unmanned aerial vehicle observation data, following which the effects of erosion and sedimentation on the riverbed were quantitatively evaluated. Finally, sediment discharge was calculated by a one-dimensional numerical model of sediment transport. These results indicate that the tributary that is mostly composed of mudstone produced considerably more sediment than the tributary composed mainly of sandstone. This suggests that an understanding of regional geology is necessary in the evaluation of sediment dynamics and should be considered in addition to the catchment area.

scholarly journals Accounting for biological and physical sources of acoustic backscatter improves estimates of zooplankton biomass

2008 ◽  
Vol 65 (7) ◽  
pp. 1321-1333 ◽  
Author(s):  
Joseph D. Warren ◽  
Peter H. Wiebe
Keyword(s):  
Water Column ◽  
Gulf Of Maine ◽  
Acoustic Scattering ◽  
Zooplankton Community ◽  
Zooplankton Biomass ◽  
Acoustic Energy ◽  
Acoustic Backscatter ◽  
Data Sets ◽  
Measured Temperature ◽  
Acoustic Frequency

To convert measurements of backscattered acoustic energy to estimates of abundance and taxonomic information about the zooplankton community, all of the scattering processes in the water column need to be identified and their scattering contributions quantified. Zooplankton populations in the eastern edge of Wilkinson Basin in the Gulf of Maine in the Northwest Atlantic were surveyed in October 1997. Net tow samples at different depths, temperature and salinity profiles, and multiple frequency acoustic backscatter measurements from the upper 200 m of the water column were collected. Zooplankton samples were identified, enumerated, and measured. Temperature and salinity profiles were used to estimate the amount of turbulent microstructure in the water column. These data sets were used with theoretical acoustic scattering models to calculate the contributions of both biological and physical scatterers to the overall measured scattering level. The output of these predictions shows that the dominant source of acoustic backscatter varies with depth and acoustic frequency in this region. By quantifying the contributions from multiple scattering sources, acoustic backscatter becomes a better measure of net-collected zooplankton biomass.

scholarly journals Sea-ice and water dynamics and moonlight impact the acoustic backscatter diurnal signal over the eastern Beaufort Sea continental slope

Ocean Science ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1261-1283
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Petrusevich ◽  
Gérald Darnis ◽  
Sergei A. Kirillov ◽  
Alexander S. Komarov ◽  
...  
Keyword(s):  
Sea Ice ◽  
Continental Slope ◽  
Subsurface Layer ◽  
Acoustic Scattering ◽  
Water Layer ◽  
Beaufort Sea ◽  
Water Dynamics ◽  
Acoustic Backscatter ◽  
Intermediate Water ◽  
Upwelling And Downwelling

Abstract. A 2-year-long time series of currents and acoustic backscatter from an acoustic Doppler current profiler, moored over the eastern Beaufort Sea continental slope from October 2003 to September 2005, were used to assess the dynamics and variability of the sound-scattering layer. It has been shown that acoustic backscatter is dominated by a synchronized diel vertical migration (DVM) of zooplankton. Our results show that DVM timings (i) were synchronous with sunlight and (ii) were modified by moonlight and sea ice, which attenuates light transmission to the water column. Moreover, DVM is modified or completely disrupted during highly energetic current events. Thicker ice observed during winter–spring 2005 lowered the backscatter values but favored extending DVM toward the midnight sun. In contrast to many previous studies, DVM occurred through the intermediate water layer during the ice-free season of the midnight sun in 2004. In 2005, the midnight-sun DVM was likely impacted by a high acoustic scattering generated by suspended particles. During full moon at low cloud cover, the nighttime moonlight illuminance led to zooplankton avoidance of the subsurface layer, disrupting DVM. Moreover, DVM was disrupted by upwelling, downwelling, and eddy passing. We suggest that these deviations are consistent with DVM adjusting to avoid enhanced water dynamics. For upwelling and downwelling, zooplankton likely respond to the along-slope water dynamics dominated by surface- and depth-intensified flow, respectively. This drives zooplankton to adjust DVM by aggregating in the low or upper intermediate water layer for upwelling and downwelling, respectively. The baroclinic eddy reversed DVM below the eddy core.

scholarly journals Coastal Polynya Disrupts the Acoustic Backscatter Diurnal Signal Over the Eastern Laptev Sea Shelf

2021 ◽  
Vol 8 ◽  
Author(s):  
Igor A. Dmitrenko ◽  
Vladislav Y. Petrusevich ◽  
Ksenia Kosobokova ◽  
Alexander S. Komarov ◽  
Caroline Bouchard ◽  
...  
Keyword(s):  
Time Series ◽  
Acoustic Scattering ◽  
The Arctic ◽  
Acoustic Backscatter ◽  
Laptev Sea ◽  
Polar Night ◽  
Sea Ice Decline ◽  
Polar Day ◽  
Fast Ice ◽  
Ice Edge

The diel vertical migration (DVM) of zooplankton is one of the largest species migrations to occur globally and is a key driver of regional ecosystems and the marine carbon pump. The dramatic changes in the Arctic environment in recent years, mainly associated with sea-ice decline, may have wide significance for the Arctic shelf ecosystems including DVM. Observations have revealed the occurrence of DVM in ice-covered Arctic waters, however, there have yet to be observations of DVM from the extensive Siberian shelves in the Eurasian Arctic and no analysis of how the sea-ice decline may affect DVM. Here, 2 yearlong time series of acoustic backscatter, collected by moored acoustic Doppler current profilers in the eastern Laptev Sea from August 1998 to August 1999, were used to examine the annual cycle of acoustic scattering, and therefore the annual cycle of DVM in the area. The acoustic time series were used along with atmospheric and oceanic reanalysis and satellite data. Our observations show that DVM did not occur during polar night and polar day, but is active during the spring and fall transition periods when there is a diurnal cycle in light conditions. DVM began beneath the fast ice at the end of polar night and increased in intensity through spring. However, the formation of a large polynya along the landfast ice edge in late March 1999 caused DVM to abruptly cease near the fast ice edge, while DVM persisted through spring to the start of polar day at the onshore mooring. We associate this cessation of synchronized DVM ∼1 month ahead of polar day with a predator-avoidance behavior of zooplankton in response to higher polar cod abundance near the polynya. During polar day, the intensity of acoustic scattering was attributed to the riverine suspended particles. Overall, our results highlight the occurrence of DVM on the Siberian shelves, the cessation of synchronized DVM when a polynya opens up nearby, and the potential impact of significant trends toward a more extensive Laptev Sea polynya as part of changing ice conditions in the Eurasian Arctic and their impact on the Arctic shelf ecology.

TEM study of Cosi2 formation via annealing of Co-Ti bilayers on Si

1995 ◽  
Vol 53 ◽  
pp. 464-465
Author(s):  
N. David Theodore ◽  
Andre Vantomme ◽  
Peter Crazier
Keyword(s):  
Thermal Instability ◽  
Lattice Mismatch ◽  
Field Effect Transistors ◽  
Contact Layer ◽  
Interface Roughness ◽  
Oxide Semiconductor ◽  
Surface Layers ◽  
Silicide Layer ◽  
Small Lattice ◽  
Buried Layers

Contact is typically made to source/drain regions of metal-oxide-semiconductor field-effect transistors (MOSFETs) by use of TiSi2 or CoSi2 layers followed by AI(Cu) metal lines. A silicide layer is used to reduce contact resistance. TiSi2 or CoSi2 are chosen for the contact layer because these silicides have low resistivities (~12-15 μΩ-cm for TiSi2 in the C54 phase, and ~10-15 μΩ-cm for CoSi2). CoSi2 has other desirable properties, such as being thermally stable up to >1000°C for surface layers and >1100°C for buried layers, and having a small lattice mismatch with silicon, -1.2% at room temperature. During CoSi2 growth, Co is the diffusing species. Electrode shorts and voids which can arise if Si is the diffusing species are therefore avoided. However, problems can arise due to silicide-Si interface roughness (leading to nonuniformity in film resistance) and thermal instability of the resistance upon further high temperature annealing. These problems can be avoided if the CoSi2 can be grown epitaxially on silicon.

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