scholarly journals Geometrical characteristics of Gaussian sea waves

2005 ◽  
Vol 42 (02) ◽  
pp. 407-425 ◽  
Author(s):  
Jean-Marc Azaïs ◽  
José R. León ◽  
Joaquín Ortega
Keyword(s):  
Energy Spectrum ◽  
Level Sets ◽  
Limit Theorems ◽  
Sea Surface ◽  
Gaussian Field ◽  
Sea Waves ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Field Modeling ◽  
The Mean

In this work, we study some geometrical properties of a stationary Gaussian field modeling the sea surface, using the energy spectrum. We consider the length of a crest and the mean speed of contours, which can be expressed as integrals over level sets. We also give central limit theorems for some of these quantities, using chaos expansions.

scholarly journals Geometrical characteristics of Gaussian sea waves

2005 ◽  
Vol 42 (2) ◽  
pp. 407-425 ◽  
Author(s):  
Jean-Marc Azaïs ◽  
José R. León ◽  
Joaquín Ortega
Keyword(s):  
Energy Spectrum ◽  
Level Sets ◽  
Limit Theorems ◽  
Sea Surface ◽  
Gaussian Field ◽  
Sea Waves ◽  
Geometrical Properties ◽  
Geometrical Characteristics ◽  
Field Modeling ◽  
The Mean

In this work, we study some geometrical properties of a stationary Gaussian field modeling the sea surface, using the energy spectrum. We consider the length of a crest and the mean speed of contours, which can be expressed as integrals over level sets. We also give central limit theorems for some of these quantities, using chaos expansions.

scholarly journals Characteristics of maximal energy component of waves in Terpeniya Bay (Sakhalin Island)

2021 ◽  
Vol 946 (1) ◽  
pp. 012020
Author(s):  
A S Borisov ◽  
K V Kirillov
Keyword(s):  
Energy Spectrum ◽  
Water Area ◽  
Sea Surface ◽  
Spectral Energy ◽  
Sea Waves ◽  
Edge Waves ◽  
Energy Component ◽  
Calm Weather ◽  
Terpeniya Bay ◽  
Energy Components

Abstract Analysis of natural sea surface oscillations was performed in order to determine maximal spectral energy components in sea waves in the area of Terpeniya Bay. It has been found out that maximal components appear at periods of 5 and 8 seconds and reach energy of 3 · 106 cm2·s during storms. During calm weather maximums can be observed in the range of swell waves, herewith maximums exist at periods of 12 and 15 seconds. Energy of these maximums doesn’t go upper then 8 · 105 cm2·s and 3 · 105 cm2·s accordingly. Maximum components in the infragravity band of energy spectrum were estimated as well. Two steady energy peaks were determined at periods of 75 and 135 seconds, which are most probably relate to edge waves in considered water area.

scholarly journals Rapid coral mortality following unusually calm and hot conditions on Iriomote, Japan

F1000Research ◽  
2018 ◽  
Vol 6 ◽  
pp. 1728 ◽  
Author(s):  
Andrew H Baird ◽  
Sally A. Keith ◽  
Erika Woolsey ◽  
Ryuta Yoshida ◽  
Tohru Naruse
Keyword(s):  
Water Movement ◽  
Sea Surface ◽  
Bleaching Event ◽  
Coral Mortality ◽  
Average Wind Speed ◽  
Common Cause ◽  
Wind Speeds ◽  
Average Wind ◽  
The Mean ◽  
Low Wind Speeds

Coral bleaching can be induced by many different stressors, however, the most common cause of mass bleaching in the field is higher than average sea surface temperatures (SST). Here, we describe an unusual bleaching event that followed very calm sea conditions combined with higher than average SST. Patterns of mortality differed from typical bleaching in four ways: 1) mortality was very rapid; 2) a different suite of species were most affected; 3) tissue mortality in Acropora spp. was often restricted to the center of the colony; 4) the event occurred early in summer. The two weeks prior to the event included 8 days where the average wind speed was less than 3 ms-1. In addition, SSTs in the weeks preceding and during the event were 1.0-1.5°C higher than the mean for the last 30 years. We hypothesize that this unusual bleaching event was caused by anoxia resulting from a lack of water movement induced by low wind speeds combined with high SST.

Scanning laser wave recorder with registration of “instantaneous” sea surface profiles

2021 ◽  
Author(s):  
V.V. Sterlyadkin ◽  
K.V. Kulikovsky ◽  
A.V. Kuzmin ◽  
E.A. Sharkov ◽  
M.V. Likhacheva
Keyword(s):  
Spatial Scales ◽  
Wind Waves ◽  
Single Point ◽  
Video Recording ◽  
Surface Profile ◽  
Weather Conditions ◽  
Sea Surface ◽  
Sea Waves ◽  
Wide Range ◽  
Wave Recorder

AbstractA direct optical method for measuring the “instantaneous” profile of the sea surface with an accuracy of 1 mm and a spatial resolution of 3 mm is described. Surface profile measurements can be carried out on spatial scales from units of millimeters to units of meters with an averaging time of 10−4 s. The method is based on the synchronization of the beginning of scanning a laser beam over the sea surface and the beginning of recording the radiation scattered on the surface onto the video camera matrix. The heights of all points of the profile are brought to a single point in time, which makes it possible to obtain “instantaneous” profiles of the sea surface with the frequency of video recording. The measurement technique and data processing algorithm are described. The errors of the method are substantiated. The results of field measurements of the parameters of sea waves are presented: amplitude spectra, distribution of slopes at various spatial averaging scales. The applied version of the wave recorder did not allow recording capillary oscillations, but with some modernization it will be possible. The method is completely remote, does not distort the properties of the surface, is not affected by wind, waves and sea currents, it allows you to measure the proportion of foam on the surface. The possibility of applying the proposed method at any time of the day and in a wide range of weather conditions has been experimentally proved.

scholarly journals Geometrical optimization for a photovoltaic installation equipped with flat reflectors based on plane of array estimations

2020 ◽  
Vol 11 ◽  
pp. 1 ◽  
Author(s):  
Christine Abdel Nour ◽  
Anne Migan-Dubois ◽  
Jordi Badosa ◽  
Vincent Bourdin ◽  
Claude Marchand ◽  
...  
Keyword(s):  
Power Production ◽  
Geometrical Parameters ◽  
Estimation Model ◽  
Geometrical Characteristics ◽  
Pv Module ◽  
Geometrical Optimization ◽  
Reflector System ◽  
The Mean ◽  
Experimental Validations ◽  
Geographical Characteristics

In order to design, manage and optimize the performance of a photovoltaic (PV) installation and establish a precise power production estimation, irradiance on the plane of array (POA) in relation with the geometrical characteristics of the PV modules installation occupies a high importance. This study focuses on the development of an estimation model of the POA irradiance for a photovoltaic installation equipped with flat reflectors. The model includes solar irradiance components (global, direct and diffuse), geometrical parameters and geographical characteristics of the PV installation. Experimental validations have been performed with measurements taken at the SIRTA Observatory (48.7°N, 2.2°E) in Palaiseau, France, for the period starting from June 2017 to June 2018. Results show mean absolute errors (relative to the mean) of 6% and 7% for an installation without and with planar reflector. Finally, we present several geometrical optimization strategies of the PV-reflector installation relying on two major variables: the reflector's length (LR) compared to the length of the PV module (LPV) and the tilt angle adjustment frequency (monthly, seasonally, fixed) of the system (for both PV and the reflectors). The objective of such optimization is to discuss about a reasonable configuration to achieve a maximum POA irradiance. Results show that the length of the mirrors highly affects the efficiency and performances of the PV-Reflector system and the annual gain increased from 8.5% to 28.7% when going from LR = LPV/2 to LR = 2 × LPV compared to a monthly-optimized installation without mirrors. As for the adjustment frequency, we show that a monthly-varied architecture is the most advantageous option with a 28.2 and 31.6% increasing in annual gain compared to a seasonal varied or fixed ones, respectively.

Uniqueness and Symmetry for the Mean Field Equation on Arbitrary Flat Tori

2020 ◽  
Author(s):  
Guangze Gu ◽  
Changfeng Gui ◽  
Yeyao Hu ◽  
Qinfeng Li
Keyword(s):  
Field Equation ◽  
Level Sets ◽  
Mean Field ◽  
Flat Torus ◽  
One Dimensional ◽  
Uniqueness Of The Solution ◽  
Flat Tori ◽  
The Mean ◽  
Symmetry Result ◽  
Mean Field Equation

Abstract We study the following mean field equation on a flat torus $T:=\mathbb{C}/(\mathbb{Z}+\mathbb{Z}\tau )$: $$\begin{equation*} \varDelta u + \rho \left(\frac{e^{u}}{\int_{T}e^u}-\frac{1}{|T|}\right)=0, \end{equation*}$$where $ \tau \in \mathbb{C}, \mbox{Im}\ \tau>0$, and $|T|$ denotes the total area of the torus. We first prove that the solutions are evenly symmetric about any critical point of $u$ provided that $\rho \leq 8\pi $. Based on this crucial symmetry result, we are able to establish further the uniqueness of the solution if $\rho \leq \min{\{8\pi ,\lambda _1(T)|T|\}}$. Furthermore, we also classify all one-dimensional solutions by showing that the level sets must be closed geodesics.

scholarly journals A multi-class extension of the mean field Bolker–Pacala population model

2018 ◽  
Vol 26 (3) ◽  
pp. 163-174 ◽  
Author(s):  
Mariya Bessonov ◽  
Stanislav Molchanov ◽  
Joseph Whitmeyer
Keyword(s):  
Population Model ◽  
Limit Theorems ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Geometric Ergodicity ◽  
Equilibrium Solutions ◽  
The Mean ◽  
Number Of Classes ◽  
Population Suppression

Abstract We extend our earlier mean field approximation of the Bolker–Pacala model of population dynamics by dividing the population into N classes, using a mean field approximation for each class but also allowing migration between classes as well as possibly suppressive influence of the population of one class over another class. For {N\geq 2} , we obtain one symmetric nontrivial equilibrium for the system and give global limit theorems. For {N=2} , we calculate all equilibrium solutions, which, under additional conditions, include multiple nontrivial equilibria. Lastly, we prove geometric ergodicity regardless of the number of classes when there is no population suppression across the classes.

scholarly journals Impact of Multiple Altimeter Data and Mean Dynamic Topography in a Global Analysis and Forecasting System

2019 ◽  
Vol 36 (7) ◽  
pp. 1255-1266 ◽  
Author(s):  
Mathieu Hamon ◽  
Eric Greiner ◽  
Pierre-Yves Le Traon ◽  
Elisabeth Remy
Keyword(s):  
Data Assimilation ◽  
Sea Surface ◽  
Global Ocean ◽  
Altimeter Data ◽  
Dynamic Topography ◽  
Mean Dynamic Topography ◽  
Ocean Data Assimilation ◽  
The Mean ◽  
Data Assimilation System ◽  
Assimilation System

AbstractSatellite altimetry is one of the main sources of information used to constrain global ocean analysis and forecasting systems. In addition to in situ vertical temperature and salinity profiles and sea surface temperature (SST) data, sea level anomalies (SLA) from multiple altimeters are assimilated through the knowledge of a surface reference, the mean dynamic topography (MDT). The quality of analyses and forecasts mainly depends on the availability of SLA observations and on the accuracy of the MDT. A series of observing system evaluations (OSEs) were conducted to assess the relative importance of the number of assimilated altimeters and the accuracy of the MDT in a Mercator Ocean global 1/4° ocean data assimilation system. Dedicated tools were used to quantify impacts on analyzed and forecast sea surface height and temperature/salinity in deeper layers. The study shows that a constellation of four altimeters associated with a precise MDT is required to adequately describe and predict upper-ocean circulation in a global 1/4° ocean data assimilation system. Compared to a one-altimeter configuration, a four-altimeter configuration reduces the mean forecast error by about 30%, but the reduction can reach more than 80% in western boundary current (WBC) regions. The use of the most recent MDT updates improves the accuracy of analyses and forecasts to the same extent as assimilating a fourth altimeter.

scholarly journals The highest-energy cosmic-rays – the past, the present and the future

2019 ◽  
Vol 210 ◽  
pp. 00001
Author(s):  
Alan Watson
Keyword(s):  
Energy Spectrum ◽  
Cosmic Rays ◽  
Mass Distribution ◽  
Mass Composition ◽  
Future Prospects ◽  
Telescope Array ◽  
Hadronic Interactions ◽  
The Past ◽  
Shower Maximum ◽  
The Mean

The greater part of this paper is concerned with a historical discussion of the development of the search for the origins of the highest-energy cosmic-rays together with a few remarks about future prospects.Additionally, in section 6, the situation with regard to the mass composition and energy spectrum at the highest energies is discussed. It is shown that the change of the depth of shower maximum with energy above 1 EeV, measured using the Telescope Array, is in striking agreement with similar results from the Auger Observatory. This implies that either the mean mass of cosmic rays is becoming heavier above ~4 EeV or that there is a change in details of the hadronic interactions in a manner such that protons masquerade as heavier nuclei. A long-standing controversy is thus resolved: the belief that pure protons dominate the mass distribution at the highest energies is no longer tenable.

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