Determination of Wave Field Properties in the Spatial Domain From Space Borne SAR Images

2003 ◽  
Author(s):  
Jose C. Nieto Borge ◽  
Andreas Niedermeier ◽  
Susanne Lehner ◽  
Wolfgang Rosenthal
Keyword(s):  
Offshore Structures ◽  
Global Scale ◽  
Sar Images ◽  
New Techniques ◽  
Single Wave ◽  
Local Wave ◽  
Wave Heights ◽  
Wave Groupiness ◽  
Local Variability

New techniques have been developed to study single wave events and wave groupiness from space borne SAR images of the sea surface. These techniques are based on the determination of wave groupiness features from the local wave envelope, estimated by using a two dimensional Hilbert transform, and the analysis of the local variability of the wave height within SAR images. This analysis is carried out on a global scale by using 34,310 SAR images, taken by the European satellite ERS-2. The obtained results are used to generate global maps of maximum wave heights, and other parameters of describing wave events, which are able to inform about potentially dangerous situations for navigation and offshore structures.

scholarly journals Estimation of Significant Wave Heights from ASCAT Scatterometer Data via Deep Learning Network

2021 ◽  
Vol 13 (2) ◽  
pp. 195
Author(s):  
He Wang ◽  
Jingsong Yang ◽  
Jianhua Zhu ◽  
Lin Ren ◽  
Yahao Liu ◽  
...  
Keyword(s):  
Deep Learning ◽  
Wave Height ◽  
Significant Wave Height ◽  
Incidence Angle ◽  
Ocean Waves ◽  
Global Scale ◽  
Learning Technology ◽  
Sea State ◽  
Significant Wave ◽  
Wave Heights

Sea state estimation from wide-swath and frequent-revisit scatterometers, which are providing ocean winds in the routine, is an attractive challenge. In this study, state-of-the-art deep learning technology is successfully adopted to develop an algorithm for deriving significant wave height from Advanced Scatterometer (ASCAT) aboard MetOp-A. By collocating three years (2016–2018) of ASCAT measurements and WaveWatch III sea state hindcasts at a global scale, huge amount data points (>8 million) were employed to train the multi-hidden-layer deep learning model, which has been established to map the inputs of thirteen sea state related ASCAT observables into the wave heights. The ASCAT significant wave height estimates were validated against hindcast dataset independent on training, showing good consistency in terms of root mean square error of 0.5 m under moderate sea condition (1.0–5.0 m). Additionally, reasonable agreement is also found between ASCAT derived wave heights and buoy observations from National Data Buoy Center for the proposed algorithm. Results are further discussed with respect to sea state maturity, radar incidence angle along with the limitations of the model. Our work demonstrates the capability of scatterometers for monitoring sea state, thus would advance the use of scatterometers, which were originally designed for winds, in studies of ocean waves.

scholarly journals Comprehensive Wind and Wave Statistics and Extreme Values for Design and Analysis of Marine Structures in the Adriatic Sea

2021 ◽  
Vol 9 (5) ◽  
pp. 522
Author(s):  
Marko Katalinić ◽  
Joško Parunov
Keyword(s):  
Adriatic Sea ◽  
Extreme Values ◽  
Wave Climate ◽  
Offshore Structures ◽  
Model Parameters ◽  
Peak Period ◽  
Significant Wave ◽  
Wave Statistics ◽  
Wave Heights ◽  
Almost All

Wind and waves present the main causes of environmental loading on seagoing ships and offshore structures. Thus, its detailed understanding can improve the design and maintenance of these structures. Wind and wave statistical models are developed based on the WorldWaves database for the Adriatic Sea: for the entire Adriatic Sea as a whole, divided into three regions and for 39 uniformly spaced locations across the offshore Adriatic. Model parameters are fitted and presented for each case, following the conditional modelling approach, i.e., the marginal distribution of significant wave height and conditional distribution of peak period and wind speed. Extreme significant wave heights were evaluated for 20-, 50- and 100-year return periods. The presented data provide a consistent and comprehensive description of metocean (wind and wave) climate in the Adriatic Sea that can serve as input for almost all kind of analyses of ships and offshore structures.

Downtime Analysis Techniques for Complex Offshore and Dredging Operations

2004 ◽  
Author(s):  
Remmelt J. van der Wal ◽  
Gerrit de Boer
Keyword(s):  
Wind Waves ◽  
Weather Forecast ◽  
Offshore Structures ◽  
Operational Mode ◽  
Offshore Structure ◽  
Hydrodynamic Models ◽  
Time Step ◽  
Made In

Offshore operations in open seas may be seriously affected by the weather. This can lead to a downtime during these operations. The question whether an offshore structure or dredger is able to operate in wind, waves and current is defined as “workability”. In recent decades improvements have been made in the hydrodynamic modelling of offshore structures and dredgers. However, the coupling of these hydrodynamic models with methods to analyse the actual workability for a given offshore operation is less developed. The present paper focuses on techniques to determine the workability (or downtime) in an accurate manner. Two different methods of determining the downtime are described in the paper. The first method is widely used in the industry: prediction of downtime on basis of wave scatter diagrams. The second method is less common but results in a much more reliable downtime estimate: determination of the ‘job duration’ on basis of scenario simulations. The analysis using wave scatter diagrams is simple: the downtime is expressed as a percentage of the time (occurrences) that a certain operation can not be carried out. This method can also be used for a combination of operations however using this approach does not take into account critical events. This can lead to a significant underprediction of the downtime. For the determination of the downtime on basis of scenario simulations long term seastate time records are used. By checking for each subsequent time step which operational mode is applicable and if this mode can be carried out the workability is determined. Past events and weather forecast are taken into account. The two different methods are compared and discussed for a simplified offloading operation from a Catenary Anchor Leg Mooring (CALM) buoy. The differences between the methods will be presented and recommendations for further applications are given.

Progressive Collapse Approach Compared to the Traditional Temperature Screening on Structural Assessment of Offshore Structures Against Fire

2016 ◽  
Author(s):  
Paula T. Nascimento ◽  
Marco A. P. Rosas ◽  
Leonardo Brandão ◽  
Fernando Castanheira
Keyword(s):  
Traditional Approach ◽  
Progressive Collapse ◽  
Screening Method ◽  
Substantial Reduction ◽  
Cost Savings ◽  
Offshore Structures ◽  
Significant Cost ◽  
Fire Scenarios

The present study compares the progressive collapse approach with the traditional temperature screening method on determination of PFP requirements at topside offshore structures. The advantage to evaluate the consequences of fire scenarios on the global integrity and stability of topside modules can be revealed by a substantial reduction of the required amount of PFP, and consequently significant cost savings for operators, when compared to the traditional approach. In the case study presented in this paper, there is a reduction of 79% in PFP allocation.

The Progress of Research on Soil Heavy Metals

2012 ◽  
Vol 455-456 ◽  
pp. 1285-1288
Author(s):  
Yin Ye ◽  
Zhen Yang ◽  
Xiao Peng Dang ◽  
Zi Huai Liu
Keyword(s):  
Heavy Metals ◽  
Total Mass ◽  
Research Progress ◽  
New Techniques ◽  
Soil Heavy Metals ◽  
Methods Of Determination ◽  
Morphology Analysis ◽  
Weak Points

Recently, with the developing of new techniques, more new techniques has been used in the area of soil heavy metals monitoring. This paper reviewed the methods utilized in determination of total mass and morphology analysis of soil heavy metals, summarized the current research progress on soil heavy metals and pointed out the weak points of recent works. The article also forecasted the developing tendency of the methods of determination of total mass and morphology analysis of soil heavy metals.

scholarly journals ON THE IMPORTANCE OF CONSIDERING MULTIPLE SEASTATE REALIZATIONS WHEN ESTIMATING DESIGN LOADS IN MULTI-DIRECTIONAL SHALLOW-WATER WAVES

2020 ◽  
pp. 46
Author(s):  
Andrew Cornett ◽  
Scott Baker
Keyword(s):  
Shallow Water ◽  
Water Waves ◽  
Offshore Structures ◽  
Scale Model ◽  
Offshore Structure ◽  
Wave Condition ◽  
Directional Waves ◽  
Wave Heights ◽  
Design Loads ◽  
Peak Pressures

The objectives of this work are to close some of the knowledge gaps facing designers tasked with designing new offshore structures or upgrading older structures located in shallow waters and exposed to energetic multi-directional waves generated by passing hurricanes or cyclones. This will be accomplished by first investigating and characterizing the natural variability of the maximum wave heights and crest elevations found in multiple 2-hour long realizations of several short-crested shallow-water near-breaking seastates. Following this, the variability and repeatability of peak pressures and peak loads exerted on a 1/35 scale model of a gravity-based offshore structure are explored. The analysis focuses on establishing extreme value distributions for each realization, quantifying their variability, and exploring how the variability is diminished when results from multiple seastate realizations and repeated tests are combined. The importance of considering multiple realizations of a design wave condition when estimating peak values for use in design is investigated and highlighted.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/16bCsMd0OMc

scholarly journals THE DYNAMIC RESPONSE OF OFFSHORE STRUCTURES TO TIME-DEPENDENT FORCES

1964 ◽  
Vol 1 (9) ◽  
pp. 29
Author(s):  
William S. Gaither ◽  
David P. Billington
Keyword(s):  
Degrees Of Freedom ◽  
Wind Waves ◽  
Offshore Structures ◽  
Time Dependent ◽  
Wave Forces ◽  
Ocean Bottom ◽  
Single Wave ◽  
Single Degree Of Freedom ◽  
The Many ◽  
Floating Objects

This paper is addressed to the problem of structural behavior in an offshore environment, and the application of a more rigorous analysis for time-dependent forces than is currently used. Design of pile supported structures subjected to wave forces has, in the past, been treated in two parts; (1) a static analysis based on the loading of a single wave, and (2) a dynamic analysis which sought to determine the resonant frequency by assuming that the structure could be approximated as a single-degree-of-freedom system. (Ref. 4 and 6) The behavior of these structures would be better understood if the dynamic nature of the loading and the many degrees of freedom of the system were included. A structure which is built in the open ocean is subjected to periodic forces due to wind, waves, floating objects, and due occasionally to machinery mounted on the structure. To resist motion, the structure relies on the stiffness of the elements from which it is built and the restraints of the ocean bottom into which the supporting legs are driven.

scholarly journals Global accumulation of circRNAs during aging in Caenorhabditis elegans

2017 ◽  
Author(s):  
Mariela Cortés-López ◽  
Matthew Gruner ◽  
Daphne A. Cooper ◽  
Hannah N. Gruner ◽  
Alexandru-Ioan Voda ◽  
...  
Keyword(s):  
Global Scale ◽  
Circular Rnas ◽  
Rna Seq ◽  
Aging Research ◽  
C Elegans ◽  
Fourth Larval Stage ◽  
Functional Consequences ◽  
Exceptional Stability ◽  
Massive Accumulation

SummaryCircular RNAs (CircRNAs) are a newly appreciated class of RNAs that lack free 5´ and 3´ ends, are expressed by the thousands in diverse forms of life, and are mostly of enigmatic function. Ostensibly due to their resistance to exonucleases, circRNAs are known to be exceptionally stable. Here, we examined the global profile of circRNAs in C. elegans during aging by performing ribo-depleted total RNA-seq from the fourth larval stage (L4) through 10-day old adults. Using stringent bioinformatic criteria and experimental validation, we annotated 1,166 circRNAs, including 575 newly discovered circRNAs. These circRNAs were derived from 797 genes with diverse functions, including genes involved in the determination of lifespan. A massive accumulation of circRNAs during aging was uncovered. Many hundreds of circRNAs were significantly increased among the aging time-points and increases of select circRNAs by over 40-fold during aging were quantified by qRT-PCR. The age-accumulation of circRNAs was not accompanied by increased expression of linear RNAs from the same host genes. We attribute the global scale of circRNA age-accumulation to the high composition of postmitotic cells in adult C. elegans, coupled with the high resistance of circRNAs to decay. These findings suggest that the exceptional stability of circRNAs might explain age-accumulation trends observed from neural tissues of other organisms, which also have a high composition of post-mitotic cells. Given the suitability of C. elegans for aging research, it is now poised as an excellent model system to determine if there are functional consequences of circRNA accumulation during aging.

scholarly journals The predictability of the "Voyager" accident

2008 ◽  
Vol 8 (3) ◽  
pp. 533-537 ◽  
Author(s):  
L. Bertotti ◽  
L. Cavaleri
Keyword(s):  
Experimental Data ◽  
Measured Data ◽  
Balearic Islands ◽  
Local Conditions ◽  
Best Estimate ◽  
Non Linear ◽  
Local Wave ◽  
Wave Heights ◽  
Wave Conditions

Abstract. On 14 February 2005 a severe mistral storm caused substantial damage to the passenger cruiser "Voyager" between Balearic Islands and Sardinia. The storm had been well predicted. However, the ship was hit by one or more, apparently unexpected, large waves. Our aim was to understand if this was a freak event or it was within the expectable probability. At this aim we use our best estimate of the local wave conditions, obtained combining modelling and measured data. Starting from these we derive the probability of large waves, considering both linear and non-linear cases. Notwithstanding a correction towards the worse of the, otherwise inconsistent, available reports, on the basis of the data at disposal we conclude that, given the local conditions, the event was within the range of the potentially expectable wave heights. This turns out to be even more the case on the basis of recent results based on theoretical and experimental data.

Statistical Uncertainties in Wave Heights and Combined Loads on Offshore Structures

1991 ◽  
Vol 113 (2) ◽  
pp. 156-161
Author(s):  
S. R. Winterstein ◽  
S. Haver
Keyword(s):  
Environmental Variables ◽  
Probabilistic Models ◽  
Offshore Structures ◽  
Annual Maximum ◽  
Storm Events ◽  
Base Shear ◽  
Combined Loads ◽  
Wave Heights ◽  
Gumbel Model ◽  
Non Gaussian

Probabilistic models of combined environmental variables are shown, and their effect on the probability distribution of annual maximum base shear is estimated. A new “generalized Gumbel” model is introduced for the critical wave height parameter. By preserving higher statistical moments, this model better follows extreme storm events. Uncertainty in this model is included through statistical uncertainty in these moments. Corresponding reliability confidence intervals are also shown as a function of the sample size of hindcast data. Finally, models of the non-Gaussian crest and the drag parameter are found to be of similar importance in predicting the 100-yr base shear.

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