scholarly journals DISTRIBUTION OF INDIVIDUAL WAVE OVERTOPPING VOLUMES ON A SLOPING STRUCTURE WITH A PERMEABLE FORESHORE

2020 ◽  
pp. 54
Author(s):  
Md Salauddin ◽  
John O'Sullivan ◽  
Soroush Abolfathi ◽  
Shudhi Dong ◽  
Jonathan Pearson
Keyword(s):  
Weibull Distribution ◽  
Shape Factor ◽  
Shape Parameter ◽  
Accurate Estimation ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Scale Parameters ◽  
Distribution Shape ◽  
Individual Wave ◽  
Set Up

Maximum wave overtopping volumes on sea defences are an indicator for identifying risks to people and properties from wave hazards. The probability distribution of individual overtopping volumes can generally be described by a two-parameter Weibull distribution function (shape and scale parameters). Therefore, the reliable prediction of maximum individual wave overtopping volumes at coastal structures relies on an accurate estimation of the shape factor in the Weibull distribution. This study contributes to an improved understanding of the distribution of individual wave overtopping volumes at sloping structures by analysing the wave-by-wave overtopping volumes obtained from physical model experiments on a 1V:2H sloped impermeable structure with a permeable shingle foreshore of slope 1V:20H. Measurements of the permeable shingle foreshore were benchmarked against those from an identical experimental set-up with a smooth impermeable foreshore (1V:20H) of the same geometry. Results from both experimental set-ups were compared to commonly used empirical formulations, underpinned by the assumption that an impermeable foreshore exists in front of the sea structure. The effect on the shape factor in the Weibull distribution of incident wave steepness, relative crest freeboard, probability of overtopping waves and discharge are examined to determine the variation of individual overtopping volumes with respect to these key parameters. A key finding from the study is that no major differences in Weibull distribution shape parameter were observed for the tested impermeable and permeable sloped foreshores. Existing empirical formulae were also shown to predict reasonably well the Weibull distribution shape parameter, b, at sloping structures with both impermeable and permeable slopes.

scholarly journals VERTICAL SEA WALL CREST MODIFICATIONS FOR OVERTOPPING

2018 ◽  
pp. 71
Author(s):  
Dogan Kisacik ◽  
Gulizar Ozyurt Tarakcioglu ◽  
Cuneyt Baykal ◽  
Gokhan Kaboglu
Keyword(s):  
Urban Areas ◽  
Vertical Wall ◽  
Breaking Wave ◽  
Limited Information ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Wave Basin ◽  
First Results ◽  
Set Up ◽  
Sea Wall

Crest modifications such as a storm wall, parapet or a bullnose are widely used to reduce the wave overtopping over coastal structures where spatial and visual demands restrict the crest heights, especially in urban areas. Although reduction factors of these modifications have been studied for sloped structures in EurOtop Manual (2016), there is limited information regarding the vertical structures. This paper presents the experimental set-up and first results of wave overtopping tests for a vertical wall with several different super structure types: a) seaward storm wall, b) sloping promenade, c) landward storm wall, d) stilling wave basin (SWB), e) seaward storm wall with parapet, f) landward storm wall on the horizontal promenade with parapet, g) landward storm wall with parapet, h) stilling wave basin (SWB) with parapet, under breaking wave conditions. The SWB is made up of a seaward storm wall (may be a double shifted rows) , a sloping promenade (basin) and a landward storm wall. The seaward storm wall is partially permeable to allow the evacuation of the water in the basin.

Study of Sequential Sampling Method for Weibull Distribution

2011 ◽  
Vol 291-294 ◽  
pp. 2195-2198 ◽  
Author(s):  
Xian Zhao Xu ◽  
Hong Liang Lou ◽  
Xing Lin Li
Keyword(s):  
Weibull Distribution ◽  
Sampling Method ◽  
Shape Parameter ◽  
Sequential Sampling ◽  
Acceptance Probability ◽  
Distribution Shape ◽  
Rejection Probability

When sequential sampling method based on MTTF is applied to weibull distribution, shape parameter is considered to be fixed. But, shape parameter in criterions or references is different from that in practice. According to sequential sampling method, with the shape parameter changing, changes of acceptance probability and rejection probability are studied. Finally, the result of simulation evaluating shows that the method of sequential sampling method is feasible and reasonable.

scholarly journals AVERAGE AND WAVE-BY-WAVE OVERTOPPING PERFORMANCE OF STEEP LOW-CRESTED STRUCTURES

2018 ◽  
pp. 77 ◽  
Author(s):  
David Gallach-Sánchez ◽  
Peter Troch ◽  
Andreas Kortenhaus
Keyword(s):  
Change Process ◽  
Coastal Protection ◽  
Knowledge Gap ◽  
Coastal Structures ◽  
Wave Overtopping ◽  
Wave Flume ◽  
Wave Energy Converters ◽  
Individual Wave ◽  
The Individual ◽  
Steep Slopes

Wave overtopping is a key process in coastal protection. The assessment of the wave overtopping rates is an important aspect in the design of coastal structures. In this paper, the focus is on steep low-crested structures, which include structures with steep slopes up to the limit case with vertical structures, with small relative freeboards up to the case with zero freeboards. This type of structures is of use for coastal protection in the case of sea level rise within climate change process and for overtopping wave energy converters. A literature review of the overtopping knowledge available for steep low-crested structures is carried out, identifying a knowledge gap. To fill this knowledge gap, 2D hydraulic model tests were performed at the wave flume of the Department of Civil Engineering at Ghent University, measuring wave conditions and the overtopping performance. Average and individual wave overtopping were analysed and compared to existing prediction formulae. Inaccuracies in the existing prediction formulae are detected and studied, and enhanced prediction formulae are presented for the average overtopping and the probability distribution of the individual overtopping volumes. The new prediction formulae improve the accuracy of wave overtopping volumes for steep low-crested structures range while maintaining the accuracy for other types of structures. The improved understanding of the overtopping behaviour allows a safer design of coastal structures.

scholarly journals Quality Assessment and Identification of Fingerprints by Analysis of the Image’s Structural Properties

2020 ◽  
Vol 15 (4) ◽  
pp. 90-97
Author(s):  
D. G. Asatryan
Keyword(s):  
Weibull Distribution ◽  
Shape Parameter ◽  
Reference Method ◽  
Quality Characteristic ◽  
Image Point ◽  
Mapping Technique ◽  
Image Gradient ◽  
Statistical Estimates ◽  
Distribution Shape

The paper addresses the problem of assessing the quality of fingerprint images using spatial analysis methods. The author proposes using the previously developed mathematical model to describe the set of magnitudes of the image gradient. The model is based on the two-parameter Weibull distribution. The author proposes two approaches to assess the quality of fingerprints. The first approach is implemented by the so-called “Full reference method”, which compares the Weibull distribution parameters’ values of statistical estimates. The results of identifying sweat pores using this method are presented. The second approach is called the “No-Reference method” and is used to assess fingerprints’ quality when analyzing and identifying the information content of their individual sections. It is proposed to use an image blur map as a quality characteristic and a statistical estimate of the Weibull distribution shape parameter as a measure of the blur. The shape parameter is estimated at each image point by the combination of magnitudes of the image gradient in the vicinity of the point; in this, the previously developed blur mapping technique is applied. The specific examples illustrate effectiveness of the proposed approaches.

scholarly journals Estimation of the Shape Parameter of a Wear-Out Failure Period for a Three-Parameter Weibull Distribution in a Small Sample

2020 ◽  
Vol 9 (6) ◽  
pp. 39
Author(s):  
Toru Ogura ◽  
Takatoshi Sugiyama ◽  
Nariaki Sugiura
Keyword(s):  
Monte Carlo ◽  
Weibull Distribution ◽  
Sample Size ◽  
Unbiased Estimator ◽  
Shape Parameter ◽  
Mean Squared Error ◽  
Minimum Variance ◽  
Small Sample ◽  
Scale Parameters ◽  
Squared Error

We propose a method to estimate a shape parameter for a three-parameter Weibull distribution. The proposed method first derives an unbiased estimator for the shape parameter independent of the location and scale parameters and then estimates the shape parameter using a minimum-variance linear unbiased estimator. Since the proposed method is expressed using a hyperparameter, its optimal hyperparameter is searched using Monte Carlo simulations. The recommended hyperparameter used for estimating the shape parameter depends on the sample size, and this causes no problems since the sample size is known when data is obtained. The proposed method is evaluated using a bias and a root mean squared error, and the results are very promising when the population shape parameter is 2 or more in the Weibull distribution representing the wear-out failure period. A numerical dataset is analyzed to demonstrate the practical use of the proposed method.

A Minimax Procedure for Selecting the Population with the Largest (Smallest) Scale Parameter

1972 ◽  
Vol 21 (3-4) ◽  
pp. 143-154 ◽  
Author(s):  
J. B. Ofosu
Keyword(s):  
Weibull Distribution ◽  
Normal Distribution ◽  
Shape Parameter ◽  
Scale Parameter ◽  
Scale Parameters ◽  
Parameter Problem

Summary A MINIMAX procedure is given for selecting the population with the largest scale parameter from k gamma populations with unknown scale parameters and a common known shape parameter. The main results are applied to the scale parameter problem for the Weibull distribution as well as the normal distribution with known and unknown mean.

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