scholarly journals Bayesian Statistics of Wide-Band Radar Reflections for Oil Spill Detection on Rough Ocean Surface

2019 ◽  
Vol 7 (1) ◽  
pp. 12 ◽  
Author(s):  
Bilal Hammoud ◽  
Fabien Ndagijimana ◽  
Ghaleb Faour ◽  
Hussam Ayad ◽  
Jalal Jomaah
Keyword(s):  
Bayesian Statistics ◽  
Oil Spills ◽  
Probabilistic Approach ◽  
Single Layer ◽  
Wide Band ◽  
Ocean Surface ◽  
Probability Of Detection ◽  
Dual Frequency ◽  
Multiple Observations ◽  
The Difference

In this paper, we present a probabilistic approach which uses nadir-looking wide-band radar to detect oil spills on rough ocean surface. The proposed approach combines a single-layer scattering model with Bayesian statistics to evaluate the probability of detection of oil slicks, within a plausible range of thicknesses, on seawater. The difference between several derived detection algorithms is defined in terms of the number of frequencies used (within C-to-X-band ranges), as well as of the number of radar observations. Performance analysis of all three types of detectors (single-, dual- and tri-frequency) is done under different surface-roughness scenarios. Results show that the probability of detecting an oil slick with a given thickness is sensitive to the radar frequency. Multi-frequency detectors prove their ability to overcome the performance of the single- and dual-frequency detectors. Higher probability of detection is obtained when using multiple observations. The roughness of the ocean surface leads to a loss in the reflectivity values, and therefore decreases the performance of the detectors. A possible way to make use of the drone systems in the contingency planning is also presented.

scholarly journals A New Mixed Functional-probabilistic Approach for Finite Element Accuracy

2020 ◽  
Vol 20 (4) ◽  
pp. 799-813
Author(s):  
Joël Chaskalovic ◽  
Franck Assous
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Asymptotic Relation ◽  
Probabilistic Approach ◽  
Random Variable ◽  
High Order ◽  
Relative Accuracy ◽  
The Difference ◽  
New Perspective

AbstractThe aim of this paper is to provide a new perspective on finite element accuracy. Starting from a geometrical reading of the Bramble–Hilbert lemma, we recall the two probabilistic laws we got in previous works that estimate the relative accuracy, considered as a random variable, between two finite elements {P_{k}} and {P_{m}} ({k<m}). Then we analyze the asymptotic relation between these two probabilistic laws when the difference {m-k} goes to infinity. New insights which qualify the relative accuracy in the case of high order finite elements are also obtained.

scholarly journals Independently Tunable Multipurpose Absorber with Single Layer of Metal-Graphene Metamaterials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 284
Author(s):  
Chen Han ◽  
Renbin Zhong ◽  
Zekun Liang ◽  
Long Yang ◽  
Zheng Fang ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Fermi Level ◽  
Potential Application ◽  
Single Layer ◽  
Wide Band ◽  
Metamaterial Absorber ◽  
Unit Cell ◽  
Perfect Absorption ◽  
Solar Energy Harvesting ◽  
Band Absorption

This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption values higher than 99%. The mechanism of absorption was analyzed theoretically. The independent tunability of the metamaterial absorber (MA) was realized by varying the Fermi level of graphene under a set of resonators. Furthermore, multi-band and wide-band absorption were observed by the proposed structure upon increasing the number of resonators and resizing them in the unit cell. The obtained results demonstrate the multipurpose performance of this type of absorber and indicate its potential application in diverse applications, such as solar energy harvesting and thermal absorbing.

scholarly journals Near-Storm Environments of Outbreak and Isolated Tornadoes

2018 ◽  
Vol 33 (5) ◽  
pp. 1397-1412 ◽  
Author(s):  
Alexandra K. Anderson-Frey ◽  
Yvette P. Richardson ◽  
Andrew R. Dean ◽  
Richard L. Thompson ◽  
Bryan T. Smith
Keyword(s):  
United States ◽  
Great Plains ◽  
Southeastern United States ◽  
Probability Of Detection ◽  
Geographical Region ◽  
Self Organizing Maps ◽  
Specific Shape ◽  
The Difference ◽  
Tornado Warning ◽  
Tornado Outbreaks

Abstract Between 2003 and 2015, there were 5343 outbreak tornadoes and 9389 isolated tornadoes reported in the continental United States. Here, the near-storm environmental parameter-space distributions of these two categories are compared via kernel density estimation, and the seasonal, diurnal, and geographical features of near-storm environments of these two sets of events are compared via self-organizing maps (SOMs). Outbreak tornadoes in a given geographical region tend to be characterized by greater 0–1-km storm-relative helicity and 0–6-km vector shear magnitude than isolated tornadoes in the same geographical region and also have considerably higher tornado warning-based probability of detection (POD) than isolated tornadoes. A SOM of isolated tornadoes highlights that isolated tornadoes with higher POD also tend to feature higher values of the significant tornado parameter (STP), regardless of the specific shape of the area of STP. For a SOM of outbreak tornadoes, when two outbreak environments with similarly high magnitudes but different patterns of STP are compared, the difference is primarily geographical, with one environment dominated by Great Plains and Midwest outbreaks and another dominated by outbreaks in the southeastern United States. Two specific tornado outbreaks are featured, and the events are placed into their climatological context with more nuance than typical single proximity sounding-based approaches would allow.

The Retrieval of Marine Stratiform Cloud Properties from Multiple Observations in the 3.9-µm Window under Conditions of Varying Solar Illumination

1995 ◽  
Vol 34 (7) ◽  
pp. 1512-1524 ◽  
Author(s):  
Thomas J. Kleespies
Keyword(s):  
Climate Modeling ◽  
Thermal Structure ◽  
Cloud Microphysics ◽  
Time Interval ◽  
Short Time Interval ◽  
Cloud Parameters ◽  
Cloud Properties ◽  
Multiple Observations ◽  
Simplifying Assumptions ◽  
The Difference

Abstract Radiometric observations in the 3.9-µm region have been used by a number of investigators for the determination of cloud parameters or sea surface temperature at night. Only a few attempts have been made to perform quantitative assessments of cloud and surface properties during the daytime because of the inability to distinguish between the thermal and solar components of the satellite-sensed radiances. This paper presents a new method of separating the thermal and solar components of upwelling 3.9-µm radiances. Two collocated satellite observations are made under conditions where the solar illumination angle changes but the thermal structure of the cloud and atmosphere, as well as the cloud microphysics change very little. These conditions can easily be met by observing the same cloud from geosynchoronous orbit over a short time interval during the morning hours. When the radiances are differenced under these constraints, the thermal components cancel, and the difference in the radiances is simply the difference in the solar component. With a few simplifying assumptions, a cloud microphysical property, specifically effective radius, can be inferred. This parameter is of particular importance to both climate modeling and global change studies. The methodology developed in this paper is applied to data from the Visible-Infrared Spin Scan Radiometer Atmospheric Sounder onboard the GOES-7 spacecraft for a period in August 1992.

Shape-driven control of layer height in robotic wire and arc additive manufacturing

2019 ◽  
Vol 25 (10) ◽  
pp. 1637-1646 ◽  
Author(s):  
Bohao Xu ◽  
Xiaodong Tan ◽  
Xizhi Gu ◽  
Donghong Ding ◽  
Yuelin Deng ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Deposition Rate ◽  
Control Method ◽  
Single Layer ◽  
Optimization Method ◽  
Content Type ◽  
Layer Height ◽  
Layer Deposition ◽  
Complex Shapes ◽  
The Difference

Purpose Once an uneven substrate is aligned, traditional control theories and methods can be used on it, so aligning is of great significance for the development of wire and arc additive manufacturing (WAAM). This paper aims to propose a shape-driven control method for aligning a substrate with slopes to expand the application of WAAM. Design/methodology/approach A substrate with slopes must be aligned by depositing weld beads with slopes. First, considering the large height differences of slopes, multi-layer deposition is needed, and the number of layer of weld beads must be ascertained. Second, the change in the deposition rate is controlled as a ramp function to generate weld beads with slopes. Third, the variation of the deposition rate must be fine-tuned to compensate for the deviation between the actual and theoretical layer heights at the deposition of each layer. Finally, the parameters of the ramp functions at the deposition of each layer are determined through an optimization method. Findings First, to model the response function of layer height to deposition rate, the experiments are conducted with the deposition rate jumping from 4 to 8 mm/s and from 8 to 4 mm/s. When the deposition rate jumps from 4 to 8 mm/s and from 8 to 4 mm/s, the difference in the height of each layer decreases as the number of layer increases. Second, the variation of the deposition rate can be fine-tuned based on the deviation between the measured and theoretical layer heights because the variation of the deposition rate is proportional to the layer height when the initial and end deposition rates are near 4 or 8 mm/s, respectively. Third, the experimental results demonstrate that the proposed method is effective for single-layer aligning and aligning a substrate with one or more slopes. Originality/value The proposed method can expand the application of WAAM to an uneven substrate with slopes and lays the foundation for aligning tasks focused on uneven substrates with more complex shapes.

scholarly journals Understanding the Reasons behind the Energy Performance Gap of an Energy-Efficient Building, through a Probabilistic Approach and On-Site Measurements

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6178
Author(s):  
Pierryves Padey ◽  
Kyriaki Goulouti ◽  
Guy Wagner ◽  
Blaise Périsset ◽  
Sébastien Lasvaux
Keyword(s):  
Energy Efficient ◽  
Probabilistic Approach ◽  
Energy Performance ◽  
High Energy ◽  
Performance Gap ◽  
Post Evaluation ◽  
Energy Efficient Buildings ◽  
Ex Post ◽  
The Difference ◽  
Energy Efficient Building

The performance gap, defined as the difference between the measured and the calculated performance of energy-efficient buildings, has long been identified as a major issue in the building domain. The present study aims to better understand the performance gap in high-energy performance buildings in Switzerland, in an ex-post evaluation. For an energy-efficient building, the measured heating demand, collected through a four-year measurement campaign was compared to the calculated one and the results showed that the latter underestimates the real heating demand by a factor of two. As a way to reduce the performance gap, a probabilistic framework was proposed so that the different uncertainties of the model could be considered. By comparing the mean of the probabilistic heating demand to the measured one, it was shown that the performance gap was between 20–30% for the examined period. Through a sensitivity analysis, the active air flow and the shading factor were identified as the most influential parameters on the uncertainty of the heating demand, meaning that their wrong adjustment, in reality, or in the simulations, would increase the performance gap.

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