Statistics of Wave Crests From Models vs. Measurements

2002 ◽  
Author(s):  
Marc Prevosto ◽  
Geoerge Z. Forristall
Keyword(s):  
Parametric Models ◽  
Wave Crest ◽  
Wave Statistics ◽  
Irregular Wave ◽  
Analysis Phase ◽  
Main Emphasis ◽  
Wave Models ◽  
Intercomparison Study ◽  
Crest Height

The analysis phase of the Wave Crest Sensor Intercomparison Study (WACSIS) focussed on the interpretation of the wave data collected by the project during the winter of 1997–98. Many aspects of wave statistics have been studied, but the main emphasis has been on crest height distributions, and recommendations for crest heights to be used in air gap calculations. In this paper we first describe comparisons of the crest height distributions derived from the sensors (radars, wave staffs, laser) and from simulations based on 3D second order irregular wave models. These comparisons permit us to make conclusions on the quality of these models and to qualify the ability of some sensors to measure the crest heights accurately. In the second part two new parametric models of the crest height distributions are discussed and their superiority to standard parametric models is demonstrated.

Statistics of Wave Crests From Models vs. Measurements

2004 ◽  
Vol 126 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Marc Prevosto ◽  
George Z. Forristall
Keyword(s):  
Parametric Models ◽  
Wave Crest ◽  
Wave Statistics ◽  
Irregular Wave ◽  
Analysis Phase ◽  
Main Emphasis ◽  
Wave Models ◽  
Intercomparison Study ◽  
Crest Height

The analysis phase of the Wave Crest Sensor Intercomparison Study (WACSIS) focussed on the interpretation of the wave data collected by the project during the winter of 1997–98. Many aspects of wave statistics have been studied, but the main emphasis has been on crest height distributions, and recommendations for crest heights to be used in air gap calculations. In this paper, we first describe comparisons of the crest height distributions derived from the sensors (radars, wave staffs, laser) and from simulations based on 3-D second-order irregular wave models. These comparisons permit us to make conclusions on the quality of these models and to qualify the ability of some sensors to measure the crest heights accurately. In the second part, two new parametric models of the crest height distributions are discussed and their superiority to standard parametric models is demonstrated.

scholarly journals Experimental Study of the Statistical Properties of Directionally Spread Ocean Waves Measured by Buoys

2020 ◽  
Vol 50 (2) ◽  
pp. 399-414 ◽  
Author(s):  
M. L. McAllister ◽  
T. S. van den Bremer
Keyword(s):  
Ocean Waves ◽  
Irregular Waves ◽  
Wave Crest ◽  
Free Surface Elevation ◽  
Spectral Parameters ◽  
Peak Period ◽  
Wave Statistics ◽  
Buoy Data ◽  
Crest Height

AbstractWave-following buoys are used to provide measurements of free surface elevation across the oceans. The measurements they produce are widely used to derive wave-averaged parameters such as significant wave height and peak period, alongside wave-by-wave statistics such as crest height distributions. Particularly concerning the measurement of extreme wave crests, these measurements are often perceived to be less accurate. We directly assess this through a side-by-side laboratory comparison of measurements made using Eulerian wave gauges and model wave-following buoys for randomly generated directionally spread irregular waves representative of extreme conditions on deep water. This study builds on the recent work of McAllister and van den Bremer (2019, https://doi.org/10.1175/JPO-D-19-0170.1), in which buoy measurements of steep directionally spread focused waves groups were considered. Our experiments confirm that the motion of a wave-following buoy should not significantly affect the measured wave crest statistics or spectral parameters and that the discrepancies observed for in situ buoy data are most likely a result of filtering. This filtering occurs when accelerations that are measured by the sensors within a buoy are converted to displacements. We present an approximate means of correcting the resulting measured crest height distributions, which is shown to be effective using our experimental data.

Wave Crest Sensor Intercomparison Study: An Overview of WACSIS

2002 ◽  
Author(s):  
George Z. Forristall ◽  
Stephen F. Barstow ◽  
Harald E. Krogstad ◽  
Marc Prevosto ◽  
Paul H. Taylor ◽  
...  
Keyword(s):  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
High Frequencies ◽  
Video Cameras ◽  
Period Distribution ◽  
Wave Sensors ◽  
Intercomparison Study ◽  
Crest Height ◽  
Made In

The Wave Crest Sensor Intercomparison Study (WACSIS) was designed as a thorough investigation of the statistical distribution of crest heights. Measurements were made in the southern North Sea during the winter of 1997–1998 from the Meetpost Noordwijk in 18 m water depth. The platform was outfitted with several popular wave sensors, including Saab and Marex radars, an EMI laser, a Baylor wave staff and a Vlissingen step gauge. Buoys were moored nearby to obtain directional spectra. Two video cameras viewed the ocean under the wave sensors and their signals were recorded digitally. The data analysis focused on comparisons of the crest height measurements from the various sensors and comparisons of the crest height distributions derived from the sensors and from theories. Some of the sensors had greater than expected energy at high frequencies. Once the measurements were filtered at 0.64 Hz, the Baylor, EMI and Vlissingen crest height distributions matched quite closely, while those from the other sensors were a few percent higher. The Baylor and EMI crest distributions agreed very well with the statistics from second order simulations, while previous parameterizations of the crest height distribution were generally too high. We conclude that crest height distributions derived from second order simulations can be used with confidence in engineering calculations. The data were also used in investigations of crest and trough shapes and the joint height/period distribution.

Wave Crest Sensor Intercomparison Study: An Overview of WACSIS

2004 ◽  
Vol 126 (1) ◽  
pp. 26-34 ◽  
Author(s):  
George Z. Forristall ◽  
Stephen F. Barstow ◽  
Harald E. Krogstad ◽  
Marc Prevosto ◽  
Paul H. Taylor ◽  
...  
Keyword(s):  
Second Order ◽  
Wave Crest ◽  
Height Distribution ◽  
High Frequencies ◽  
Video Cameras ◽  
Period Distribution ◽  
Wave Sensors ◽  
Intercomparison Study ◽  
Crest Height ◽  
Made In

The Wave Crest Sensor Intercomparison Study (WACSIS) was designed as a thorough investigation of the statistical distribution of crest heights. Measurements were made in the southern North Sea during the winter of 1997–1998 from the Meetpost Noordwijk in 18 m water depth. The platform was outfitted with several popular wave sensors, including Saab and Marex radars, an EMI laser, a Baylor wave staff and a Vlissingen step gauge. Buoys were moored nearby to obtain directional spectra. Two video cameras viewed the ocean under the wave sensors and their signals were recorded digitally. The data analysis focused on comparisons of the crest height measurements from the various sensors and comparisons of the crest height distributions derived from the sensors and from theories. Some of the sensors had greater than expected energy at high frequencies. Once the measurements were filtered at 0.64 Hz, the Baylor, EMI and Vlissingen crest height distributions matched quite closely, while those from the other sensors were a few percent higher. The Baylor and EMI crest distributions agreed very well with the statistics from second order simulations, while previous parameterizations of the crest height distribution were generally too high. We conclude that crest height distributions derived from second order simulations can be used with confidence in engineering calculations. The data were also used in investigations of crest and trough shapes and the joint height/period distribution.

To Check the Knowledge of Hypertension amongst Undergraduate Physiotherapy Students

2021 ◽  
Vol 6 (2) ◽  
pp. 299-301
Author(s):  
Radha Parekh ◽  
Hardini Prajapati
Keyword(s):  
Salt Intake ◽  
Sedentary Lifestyle ◽  
Medical Condition ◽  
Knowledge Assessment ◽  
Main Emphasis ◽  
The Mean ◽  
Hypertension Knowledge ◽  
Physiotherapy Students ◽  
Assessment Questionnaire

Aim: To check the knowledge of hypertension amongst undergraduate physiotherapy students. Background: Hypertension is considered to be a serious medical condition that significantly increases the risk of heart, brain, kidney and other diseases. It is also called the “silent killer”. Sedentary lifestyle, obesity, excessive salt intake, consumption of tobacco are risk factors of hypertension. Hypertension is present in the curriculum of the 4 year long bachelor of physiotherapy course where main emphasis on this topic is usually in the last year of the course. Methodology: 125 students filled a hypertension knowledge assessment questionnaire. The mean result obtained was 12.8 from an 18 point questionnaire. Conclusion: The study concludes that there is moderate knowledge of hypertension amongst undergraduate physiotherapy students. Clinical Significance: Knowledge of hypertension is needed in physiotherapy students to help prescribe a proper exercise regime for patients suffering from hypertension and also help them improve their quality of life. Physiotherapist can also play a major role in preventing hypertension. Keywords: Hypertension, knowledge, undergraduate physiotherapy students.

Brazil and Russia: Different Trajectories of Development?

2012 ◽  
pp. 92-104
Author(s):  
G. Irishin
Keyword(s):  
Economic Growth ◽  
Human Capital ◽  
Social Development ◽  
Brics Countries ◽  
Long Run ◽  
Main Emphasis ◽  
The World

This publication represents the materials of the regular academic seminar “The current problems of development” conducted by the Center of the problems of development and modernization within IMEMO. The attention of the key speakers and other seminar participants is focused on the comparison of the two BRICS countries – Brazil and Russia. The main emphasis is made on the analysis of the trends of social development. The point is that the quality of human capital determines the quality of economic growth, as well as the country's place in the world in the long run.

Non-Gaussian Extreme Waves in the Central North Sea

1997 ◽  
Vol 119 (3) ◽  
pp. 146-150 ◽  
Author(s):  
J. Skourup ◽  
N.-E. O. Hansen ◽  
K. K. Andreasen
Keyword(s):  
Wave Height ◽  
North Sea ◽  
Upper Bound ◽  
Wave Crest ◽  
Extreme Waves ◽  
Freak Waves ◽  
Freak Wave ◽  
Wave Trains ◽  
Central North Sea ◽  
Crest Height

The area of the Central North Sea is notorious for the occurrence of very high waves in certain wave trains. The short-term distribution of these wave trains includes waves which are far steeper than predicted by the Rayleigh distribution. Such waves are often termed “extreme waves” or “freak waves.” An analysis of the extreme statistical properties of these waves has been made. The analysis is based on more than 12 yr of wave records from the Mærsk Olie og Gas AS operated Gorm Field which is located in the Danish sector of the Central North Sea. From the wave recordings more than 400 freak wave candidates were found. The ratio between the extreme crest height and the significant wave height (20-min value) has been found to be about 1.8, and the ratio between extreme crest height and extreme wave height has been found to be 0.69. The latter ratio is clearly outside the range of Gaussian waves, and it is higher than the maximum value for steep nonlinear long-crested waves, thus indicating that freak waves are not of a permanent form, and probably of short-crested nature. The extreme statistical distribution is represented by a Weibull distribution with an upper bound, where the upper bound is the value for a depth-limited breaking wave. Based on the measured data, a procedure for determining the freak wave crest height with a given return period is proposed. A sensitivity analysis of the extreme value of the crest height is also made.

Alternative Methodologies for Subsea Flexible Strength Analysis

2018 ◽  
Author(s):  
Anskey A. Miranda ◽  
Fred P. Turner ◽  
Nigel Barltrop
Keyword(s):  
Real World ◽  
Wave Train ◽  
Irregular Waves ◽  
Wave Crest ◽  
Strength Analysis ◽  
New Wave ◽  
Regular Wave ◽  
Wave Analysis ◽  
Sea State ◽  
Irregular Wave

This paper presents a study of the analysis methodologies used to predict the most likely response of flexibles in a subsea environment, with the aim of determining an efficient and reliable prediction methodology. The most accurate method involves simulating multiple wave realisations of a real world sea state, i.e. irregular waves, and post-processing the results to determine the most probable maximum (MPM). Due to the computationally intensive nature of this approach, however, regular wave analysis is typically used to determine flexible response. This approach considers the maximum wave within a design storm at a desired period; the choice of periods may leave room for uncertainty in the conservatism of the approach. With proper screening, regular wave analysis can be a valid yet overly conservative approach resulting in over design and additional cost. However, if screened incorrectly, there is a possibility that the choice of periods could give results that are under conservative. In addition to regular wave analysis, the paper presents two alternative methodologies to determine the most likely response, with the focus on reducing the computational resources required. The first alternative is an ‘Irregular Wave Screen’ approach in which the wave train is screened at areas of interest for waves within a user defined threshold of the maximum wave height, in addition to other user defined parameters. Only waves within these parameters are simulated to determine responses. The second alternative is the ‘New Wave’ approach, which models the most probable wave elevation around the maximum wave crest. The calculated new wave is then placed at the desired location to determine responses. The responses of the Regular, Irregular Wave Screen and New Wave methodologies are compared with the Irregular MPM approach to determine their feasibility to predict the response of flexibles in a real world irregular sea state with lower computational requirements.

scholarly journals RESEARCH METHODOLOGY IN ENTERPRISES, AUDIT AND INNOVATIONS TO IMPROVE ENTERPRISE MANAGEMENT

2021 ◽  
Author(s):  
Valerii Nemchenko ◽  
Yurii Melnyk ◽  
Hanna Nemchenko
Keyword(s):  
Life Expectancy ◽  
Raw Materials ◽  
Scientific Research ◽  
Enterprise Management ◽  
Environmental Friendliness ◽  
Medical Standards ◽  
Main Emphasis ◽  
The World ◽  
Financial Research

The article considers the methodology of scientific research at enterprises, the main emphasis is placed on the issue of audit and innovation in improving enterprise management. Yes, today the world is in crisis in the economy due to the COVID-19 virus. However, appropriate measures are needed to get out of this situation as soon as possible. Universities pay special attention to research that provides new knowledge, helps in solving problems, decision-making, discovery, invention, conflict resolution. Without "theory", appropriate research, practice is impossible, as the article proves. Yes, an important factor that determines the success of the audit is the audit. Its absence causes a crisis in the company, which can lead to bankruptcy. Therefore, sufficient attention should be paid to the issue of audit in scientific research. Moreover, innovations contribute to the development of enterprises. However, it does not make sense to implement them without appropriate scientific and financial research - innovations must be relevant to the company, make a profit after their implementation, as well as stimulated by the state. However, it is equally important to take into account innovation, environmental friendliness and profitability. Food quality management depends not only on the company that produces them, processing technology, suppliers of raw materials (agriculture), but also on medical standards, recommendations, marketing, consumer market research, their features. Production in the world is becoming human-oriented, so it changes the guidelines, management not only in the enterprise but also in the regions and society. It is no coincidence that in international practice more and more often to determine the quality of life in the country instead of GDP use the happiness index, which includes along with the level of income and life expectancy. There is a need to "supplement" medical expertise with economic and environmental ones. We are talking about the "birth" of a new medical, economic and environmental examination of food products (MEEEFP). The higher the quality of food, the higher its competitiveness, better management in a saturated market, the quality of the environment and the quality of labor reproduction, increase life expectancy, GDP of the region and the country. This quality can be achieved only with the help of innovative technologies.

scholarly journals 2D Image-To-3D Model: Knowledge-Based 3D Building Reconstruction (3DBR) Using Single Aerial Images and Convolutional Neural Networks (CNNs)

2019 ◽  
Vol 11 (19) ◽  
pp. 2219 ◽  
Author(s):  
Fatemeh Alidoost ◽  
Hossein Arefi ◽  
Federico Tombari
Keyword(s):  
Test Data ◽  
3D Models ◽  
Parametric Models ◽  
Aerial Images ◽  
Aerial Image ◽  
Absolute Deviation ◽  
Multi Scale ◽  
Knowledge Based ◽  
Linear Elements

In this study, a deep learning (DL)-based approach is proposed for the detection and reconstruction of buildings from a single aerial image. The pre-required knowledge to reconstruct the 3D shapes of buildings, including the height data as well as the linear elements of individual roofs, is derived from the RGB image using an optimized multi-scale convolutional–deconvolutional network (MSCDN). The proposed network is composed of two feature extraction levels to first predict the coarse features, and then automatically refine them. The predicted features include the normalized digital surface models (nDSMs) and linear elements of roofs in three classes of eave, ridge, and hip lines. Then, the prismatic models of buildings are generated by analyzing the eave lines. The parametric models of individual roofs are also reconstructed using the predicted ridge and hip lines. The experiments show that, even in the presence of noises in height values, the proposed method performs well on 3D reconstruction of buildings with different shapes and complexities. The average root mean square error (RMSE) and normalized median absolute deviation (NMAD) metrics are about 3.43 m and 1.13 m, respectively for the predicted nDSM. Moreover, the quality of the extracted linear elements is about 91.31% and 83.69% for the Potsdam and Zeebrugge test data, respectively. Unlike the state-of-the-art methods, the proposed approach does not need any additional or auxiliary data and employs a single image to reconstruct the 3D models of buildings with the competitive precision of about 1.2 m and 0.8 m for the horizontal and vertical RMSEs over the Potsdam data and about 3.9 m and 2.4 m over the Zeebrugge test data.

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