scholarly journals Detection of Multi-pixel Low Contrast Object on a Real Sea Surface

2021 ◽  
Author(s):  
Victor Golikov ◽  
Oleg Samovarov ◽  
Daria Chernomorets ◽  
Marco Rodriguez-Blanco
Keyword(s):  
Spectral Characteristics ◽  
False Alarm Probability ◽  
Sea Surface ◽  
Statistical Characteristics ◽  
Statistical Parameters ◽  
Low Contrast ◽  
Video Images ◽  
Floating Object ◽  
The Difference ◽  
Floating Objects

The video images captured at long range usually have low contrast floating objects of interest on a sea surface. A comparative experimental study of the statistical characteristics of reflections from floating objects and from the agitated sea surface showed the difference in the correlation and spectral characteristics of these reflections. The functioning of the recently proposed modified matched subspace detector (MMSD) is based on the separation of the observed data spectrum on two subspaces: relatively low and relatively high frequencies. In the literature the MMSD performance has been evaluated in generally and moreover using only a sea model (additive Gaussian background clutter). This paper extends the performance evaluating methodology for low contrast object detection and moreover using only the real sea dataset. This methodology assumes an object of low contrast if the mean and variance of the object and the surrounding background are the same. The paper assumes that the energy spectrum of the object and the sea are different. The paper investigates a scenario in which an artificially created model of a floating object with specified statistical parameters is placed on the surface of a real sea image. The paper compares the efficiency of the classical Matched Subspace Detector (MSD) and MMSD for detecting low-contrast objects on the sea surface. The article analyzes the dependence of the detection probability at a fixed false alarm probability on the difference between the statistical means and variances of a floating object and the surrounding sea.

scholarly journals Detección óptica en 3D de un objeto flotante en una superficie marina agitada

2020 ◽  
pp. 7-16
Author(s):  
Ana Karen Paredes-Perez ◽  
Victor Golikov ◽  
Hussain Alazki
Keyword(s):  
A Priori ◽  
Computer Software ◽  
Probability Of Detection ◽  
Sea Surface ◽  
Ratio Test ◽  
Gaussian Random Process ◽  
Probability Of False Alarm ◽  
Floating Object ◽  
The Difference ◽  
Object Parameters

In this paper we realize a comparison between two detectors: Matched Subspace Detector (MSD) and Modify Matched Subspace Detector (MMSD) when there is a images secuence (3D detection), where the parameters of sea surface and the parameters of floating object are priori unknown in computer simulation, with help of computer software MATLAB. Both detectors (MSD and MMSD) are based in the General Likelihood Ratio Test (GLRT); this method helps solve detection problems when the sea surface and floating object parameters are unknown. The sea surface is simulated as a Gaussian random process, and the floating object is simulated as a priori unknown deterministic process. The paper considers the dependence of the probability of detection with a fixed probability of false alarm on the difference between the average values of reflections from the sea surface and from a floating object with different ratios of the power of fluctuations of reflections from the object and from the sea Surface.

Removal of inelastically scattered electrons substantially increases phase contrast on frozen-hydrated molecules

1987 ◽  
Vol 45 ◽  
pp. 652-653
Author(s):  
John P. Langmore ◽  
Brian D. Athey
Keyword(s):  
Electron Diffraction ◽  
Phase Contrast ◽  
Low Dose ◽  
Dark Field ◽  
Biological Structure ◽  
Bright Field ◽  
Low Contrast ◽  
Negative Stain ◽  
The Difference ◽  
Better Than

Although electron diffraction indicates better than 0.3nm preservation of biological structure in vitreous ice, the imaging of molecules in ice is limited by low contrast. Thus, low-dose images of frozen-hydrated molecules have significantly more noise than images of air-dried or negatively-stained molecules. We have addressed the question of the origins of this loss of contrast. One unavoidable effect is the reduction in scattering contrast between a molecule and the background. In effect, the difference in scattering power between a molecule and its background is 2-5 times less in a layer of ice than in vacuum or negative stain. A second, previously unrecognized, effect is the large, incoherent background of inelastic scattering from the ice. This background reduces both scattering and phase contrast by an additional factor of about 3, as shown in this paper. We have used energy filtration on the Zeiss EM902 in order to eliminate this second effect, and also increase scattering contrast in bright-field and dark-field.

Double Beam Spectrophotometer for Simultaneous Measurements of the Upwelling Sea Radiance and the Incident See Irradiance

2019 ◽  
pp. 105-110
Author(s):  
Mikhail Yongon Lee ◽  
Sergei V. Fedorov
Keyword(s):  
Spectral Characteristics ◽  
Sea Surface ◽  
Input Port ◽  
Silicon Photodiode ◽  
New Approach ◽  
Surface Irradiance ◽  
Simultaneous Measurements ◽  
Double Beam

The article describes the structure and the operation principle of the spectrophotometer developed on the basis of a compact rapid monochromator with one input port and two output ports and a radiometric unit where upwelling radiation radiance and sea surface irradiance channels are located. A new approach to measurements of spectral characteristics of upwelling radiation of sea based on combination of advantages of a double beam photometer with a photomultiplier and a directreading photometer with a highstability silicon photodiode for its absolute adjustment in energy units is implemented.

Free-Surface Flow Simulations With Interactively Moving Bodies

2017 ◽  
Author(s):  
Arthur E. P. Veldman ◽  
Henk Seubers ◽  
Peter van der Plas ◽  
Joop Helder
Keyword(s):  
Free Surface ◽  
Free Fall ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Numerical Solution Method ◽  
Flow Simulations ◽  
Floating Object ◽  
Offshore Industry ◽  
Floating Objects ◽  
Moving Bodies

The simulation of free-surface flow around moored or floating objects faces a series of challenges, concerning the flow modelling and the numerical solution method. One of the challenges is the simulation of objects whose dynamics is determined by a two-way interaction with the incoming waves. The ‘traditional’ way of numerically coupling the flow dynamics with the dynamics of a floating object becomes unstable (or requires severe underrelaxation) when the added mass is larger than the mass of the object. To deal with this two-way interaction, a more simultaneous type of numerical coupling is being developed. The paper will focus on this issue. To demonstrate the quasi-simultaneous method, a number of simulation results for engineering applications from the offshore industry will be presented, such as the motion of a moored TLP platform in extreme waves, and a free-fall life boat dropping into wavy water.

scholarly journals Effect Study of Aperture Distribution on the Capillary Pressure-Saturation Relation for the Single Fracture

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-13
Author(s):  
Yuan Wang ◽  
Chenglong Wu ◽  
Yuntian Zhou
Keyword(s):  
Capillary Pressure ◽  
Effect Study ◽  
Single Fracture ◽  
Saturation Curve ◽  
Static Displacement ◽  
Statistical Parameters ◽  
Dual Connectivity ◽  
Fluid Saturation ◽  
The Difference ◽  
Aperture Distribution

A systematic numerical method was presented to investigate the effect of aperture distribution on the relation of capillary pressure versus fluid saturation (P-S relation) for a single fracture. The fracture was conceptualized as a two-dimensional lattice-grid model and its aperture field was described by a probability distribution. Based on the invasion percolation theory, a program was developed to simulate the quasi-static displacement. The simulation was verified validly by comparisons of the experimental results. The effects of the statistical parameters were further quantified. The results show that the largest local aperture on the fracture boundary determines the AEV. The larger mean decreases the variation coefficient, which causes the more uniform aperture field, smoother air invasion front, and steeper capillary pressure-saturation curve (CPSC). The larger standard deviation increases not only the range but also the contrast degree of the apertures, thus providing a nondeterministic rule in the P-S relation. The larger correlation length causes a more homogeneous aperture field and a dual connectivity of the fracture. The increase of the difference and contrast degree between the small and large apertures results in dual-aperture fields. The dual-aperture field and dual connectivity of the fracture both contribute to the bimodal characteristic of the CPSC.

scholarly journals Can an Earth System Model simulate better climate change at mid-Holocene than an AOGCM? A comparison study of MIROC-ESM and MIROC3

2013 ◽  
Vol 9 (4) ◽  
pp. 1519-1542 ◽  
Author(s):  
R. Ohgaito ◽  
T. Sueyoshi ◽  
A. Abe-Ouchi ◽  
T. Hajima ◽  
S. Watanabe ◽  
...  
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Earth System Model ◽  
Sea Surface ◽  
System Model ◽  
Earth System ◽  
Intercomparison Project ◽  
The Difference ◽  
Precipitation Enhancement

Abstract. The importance of evaluating models through paleoclimate simulations is becoming more recognized in efforts to improve climate projection. To evaluate an integrated Earth System Model, MIROC-ESM, we performed simulations in time-slice experiments for the mid-Holocene (6000 yr before present, 6 ka) and preindustrial (1850 AD, 0 ka) periods under the protocol of the Coupled Model Intercomparison Project 5/Paleoclimate Modelling Intercomparison Project 3. We first give an overview of the simulated global climates by comparing with simulations using a previous version of the MIROC model (MIROC3), which is an atmosphere–ocean coupled general circulation model. We then comprehensively discuss various aspects of climate change with 6 ka forcing and how the differences in the models can affect the results. We also discuss the representation of the precipitation enhancement at 6 ka over northern Africa. The precipitation enhancement at 6 ka over northern Africa according to MIROC-ESM does not differ greatly from that obtained with MIROC3, which means that newly developed components such as dynamic vegetation and improvements in the atmospheric processes do not have significant impacts on the representation of the 6 ka monsoon change suggested by proxy records. Although there is no drastic difference between the African monsoon representations of the two models, there are small but significant differences in the precipitation enhancement over the Sahara in early summer, which can be related to the representation of the sea surface temperature rather than the vegetation coupling in MIROC-ESM. Because the oceanic parts of the two models are identical, the difference in the sea surface temperature change is ultimately attributed to the difference in the atmospheric and/or land modules, and possibly the difference in the representation of low-level clouds.

scholarly journals Result of modeling temperature anomalies on the water surface of the research basin of the institute of hydromechanics NAS of Ukraine

2018 ◽  
pp. 40-45
Author(s):  
Oleksandr Fedorovsky ◽  
Vitalii Filimonov ◽  
Iryna Piestova ◽  
Stanislav Dugin ◽  
Vladyslav Yakymchuk ◽  
...  
Keyword(s):  
Water Surface ◽  
Water Layer ◽  
Sea Surface ◽  
National Academy Of Sciences ◽  
Near Surface ◽  
Aerial Photos ◽  
Temperature Anomalies ◽  
Structural And Textural Parameters ◽  
The Difference ◽  
Hydrocarbon Deposits

The results of the research and physical modeling of temperature anomalies of natural or man-made origin on the water surface are presented.  The information for the research was obtained from the experimental basin of the Institute of Hydromechanics of the National Academy of Sciences of Ukraine from the self-propelled model as the generator of hydrodynamic processes. The information obtained after image processing allowed to significantly expand the existing ideas about the mechanism of formation of anomalies on the open surface with the hydrodynamic disturbances from hydrocarbon deposits and moving submerged object. The interaction of the emerging hydrodynamic disturbances with the near-surface water layer and the occurrence of unmasking temperature anomalies on the open sea surface have a lot in common between the hydrocarbon deposits and the moving submerged object. The application of the difference of the above structural and textural parameters by calculating the value of "entropy" has been proposed as the informative feature for decoding the images of the water surface with the presence of hydrocarbon deposits or moving immersed objects. The decoding of temperature anomalies consists of two stages: learning and proper decoding. The first stage is the supervised learning, during which the system is being researched using the existing set of images, in which only the background and no hydrocarbon deposits or moving submerged object. Training is carried out in order to determine the signs of belonging to the background or hydrocarbon deposits, moving submerged object. It was determined that the background has minimal entropy values, and with the appearance of an anomaly, the entropy grows to the maximum value, after which, as the temperature trace dissipates, it begins to fall to background values. This confirms the informativity of the entropy feature for decoding the optical anomalies of man-made and natural origin on the sea surface from aerial photos.

scholarly journals Quasi-biennial and quasi-triennial oscillations in the growth rates of atmospheric chlorofluorocarbons 11 and 12

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 349-358
Author(s):  
R. P. KANE
Keyword(s):  
Southern Hemisphere ◽  
Growth Rates ◽  
Southern Oscillation ◽  
Spectral Characteristics ◽  
Linear Increase ◽  
Transport Processes ◽  
Emission Rates ◽  
Low Latitude ◽  
The Difference ◽  
Prominent Peak

The 12-monthly running means of CFC-11 and CFC-12 were examined for 1977-1992. As observed by earlier workers, during 1977-1988, there was a rapid, almost linear increase of these compounds, ~70% in the northern and ~77% in the southern hemisphere. From 1988 up to 1992, growth rates were slower, more so for CFC-11 in the northern hemisphere. Superposed on this pattern were QBO, QTO (Quasi-Biennial and Quasi-Triennial Oscillations). A spectral analysis of the various series indicated the following. The 50 hPa low latitude zonal wind had one prominent QBO peak at 2.58 years and much smaller peaks at 2.00 (QBO) and 5.1 years. The Southern oscillation index represented by (T-D), Tahiti minus Darwin atmospheric pressure, had a prominent peak at 4.1 years and a smaller peak at 2.31 years. CFC-11 had only one significant peak at 3.7 years in the southern hemisphere, roughly similar to the 4.1 year (T-D) peak. CFC-12 had prominent QBO (2.16-2.33 years) in both the hemispheres and a QTO (3.6 years) in the southern hemisphere. For individual locations, CFC-11 showed barely significant QBO in the range (1.95-3.07 years), while CFC 12 showed strong QBO in the range (1.86-2.38 years). The difference in the spectral characteristics of CFC-11 and CFC 12 time series is attributed to differences in their lifetimes (44 and 180 years), source emission rates and transport processes.

scholarly journals Sea-surface salinity variations in the Northern Caribbean Sea across the mid-Pleistocene transition

2010 ◽  
Vol 6 (3) ◽  
pp. 1229-1265
Author(s):  
S. Sepulcre ◽  
L. Vidal ◽  
K. Tachikawa ◽  
F. Rostek ◽  
E. Bard
Keyword(s):  
Temperature Gradient ◽  
Planktonic Foraminifera ◽  
Caribbean Sea ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Sea Surface Salinity ◽  
Surface Salinity ◽  
Inter Tropical Convergence Zone ◽  
The North ◽  
The Difference

Abstract. This study aimed at documenting climate changes in tropical area in response to the Mid-Pleistocene Transition (MPT) by reconstructing past hydrologic variations in the Northern Caribbean Sea and its influence on the stability of the Atlantic Meridional Overturning Circulation (AMOC) during the last 940 kyr. Using core MD03-2628, we estimated past changes in sea surface salinity (SSS) using Δδ18O, the difference between the modern and the past δ18O of seawater (obtained by combining alkenone thermometer data with the δ18O of the planktonic foraminifera Globigerinoides ruber (white) and corrected for ice-sheet volume effects). Today, the lowest SSS values in the studied area are associated with the northernmost location of the Inter-Tropical Convergence Zone (ITCZ). The Δδ18O record exhibits glacial/interglacial cyclicity with higher values during all glacial periods spanning the last 940 kyr, indicating increased SSS. At a longer timescale, the Δδ18O exhibits a shift toward lower values for interglacial periods during the last 450 kyr, when compared to interglacial stages older than 650 kyr. A rise in SSS during glacial stages may be related to the southernmost location of the ITCZ, which is induced by a steeper interhemispheric temperature gradient and associated with reduced northward cross equatorial oceanic transport. Therefore, the results suggest a permanent link between the tropical salinity budget and the AMOC during the last 940 kyr. Following the MPT, lower salinities during the last five interglacial stages indicate a northernmost ITCZ location, forced by changes in the interhemispheric temperature gradient that is associated with the poleward position of Southern Oceanic Fronts that amplified the transport of heat and moisture to the North Atlantic. These processes may have contributed to amplification of the climate cycles that followed the MPT.

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