Fatigue Damage Assessment Using a Bandwidth Parameter for VIV Applied to the Foinaven Dynamic Umbilical

2005 ◽  
Author(s):  
F. Trarieux ◽  
G. J. Lyons
Keyword(s):  
Fatigue Damage ◽  
Damage Assessment ◽  
Narrow Band ◽  
Broad Band ◽  
Environmental Data ◽  
Counting Approach ◽  
Bandwidth Parameter ◽  
Fatigue Estimation ◽  
Intense Activity ◽  
The Impact

The application of a method for fatigue damage assessment applied to the relative effects of mooring, wave, and Vortex Induced Vibration (VIV) is presented. It is a simpler procedure than rainflow counting and uses a bandwidth parameter with standard deviation applied to modify narrow band fatigue estimation. This bandwidth parameter has been successfully applied by the authors to investigate in detail the curvature (bending stress) response of the Foinaven lazy-wave umbilical for investigations into VIV. This parameter is valuable since as a single value it may be used to track the variation of bandwidth response with time and against other measures such as varying current speed. The method is conveniently based on a peak counting approach. Low values close to zero indicate a narrow band process whereas values near unity indicate a broad-band process. It is a much better measure than kurtosis for determining bandwidth. Curvature and environmental data were gathered by the Foinaven Umbilical Monitoring System installed on the Foinaven Petrojarl IV floating production unit located in the Altantic margin, West of Shetland. The VIV frequency range owing to current excitation considered is that which is considered as being above consequential wave frequencies (0.2 to 2Hz). This paper presents results of fatigue damage assessment for the periods where a strong variation of bandwidth was observed. 64 records (each lasting about 10 minutes) representing a daily acquisition of about 8 hours were processed showing the correlation between the bandwidth of curvature and the amount of fatigue experienced by the umbilical. Strong VIV regimes are often characterized by an intense activity around a particular frequency and the impact of such narrow-band events on the fatigue life of the structure is clearly demonstrated. This paper also presents the relative contributions of mooring, and waves/vessel motions, and VIV to fatigue damage. Although wave excitation remains the main source of fatigue, VIV appears to potentially contribute to a significant part of the overall fatigue damage.

The Effects of Modelling Techniques and Data Uncertainty in Wellhead Fatigue Life Calculation

2012 ◽  
Author(s):  
Dara Williams ◽  
John Greene
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Fatigue Damage ◽  
Environmental Data ◽  
Nonlinear Load ◽  
Soil Response ◽  
Load Response ◽  
Highly Nonlinear ◽  
Non Linear ◽  
The Impact

Offshore oil and gas exploration continues to move into deeper and more harsh environments and consequently the response of drilling riser systems and associated fatigue loading transmitted to the wellhead and conductor system are of key importance in the design of offshore wells. In addition the presence of ageing infrastructure in mature areas combined with requirements for future workover operations requires careful consideration of both past and future fatigue damage accumulation. In order to estimate remaining fatigue life for the wellhead and conductor the accumulation of damage from each stage of a drilling campaign and phase of operation of a well, including workover and completion operations, must be considered. Thus a detailed global finite element analysis of the impact of riser response, under wave and vortex induced vibration (VIV), on the conductor and wellhead structure is of critical importance. Traditional engineering evaluation methods to estimate fatigue of wellhead systems in offshore regions with limited availability of environmental data may result in an over estimation of fatigue damage accumulated in the wellhead. Any assumptions regarding fatigue current profiles can also lead to over-prediction of fatigue damage in the wellhead. This can have implications for the planning of future workover operations and may also lead to unnecessary over-design of the system. A further limitation of traditional wellhead fatigue evaluation criteria lies in the assumptions regarding riser tensioner system load response. These methods do not account for the highly nonlinear load response of the tensioner system and can thus significantly underestimate fatigue damage contribution. This paper presents a more detailed wellhead fatigue analysis methodology to incorporate new analysis techniques, as used for a number of recent applications, to assess with a greater level of refinement the impact of the riser motions on the wellhead fatigue. Specifically this methodology incorporates the generation of a detailed global finite element model of the riser and wellhead system to include detailed non-linear riser tensioner system models, accurate models of the wellhead and conductor, detailed non-linear soil response characteristics and the use of more refined current data as input to VIV calculations. The details of the riser and wellhead system model are presented and the conservatisms associated with traditional modeling methods with regard to VIV and riser tensioner load variations are discussed. A number of case studies are presented to illustrate the effects of various data assumptions and simplifications on estimated wellhead fatigue.

Estimation of Wave Loading Induced Fatigue Accumulation and Extreme Response of a Container Ship in Severe Seas

2010 ◽  
Author(s):  
Wengang Mao ◽  
Zhiyuan Li ◽  
Thomas Galtier ◽  
Jonas W. Ringsberg ◽  
Igor Rychlik
Keyword(s):  
Narrow Band ◽  
Moving Average ◽  
Gaussian Model ◽  
Numerical Code ◽  
Container Ship ◽  
Counting Approach ◽  
Extreme Response ◽  
Fatigue Estimation ◽  
The Time Domain ◽  
Rainflow Counting

The hydrodynamic analysis of a 4400 TEU container ship with constant forward speed is carried out by the nonlinear numerical code WASIM in the time domain under severe sea states. Straightforward fatigue estimation is performed using the rainflow counting approach based on simulated time series of stresses. The narrow-band approximation, which has been validated in previous work with good accuracy by full-scale measurement of a 2800 TEU container ship, is implemented to estimate the fatigue damage based on the same responses. It is concluded that a slight deviation from the Gaussian process does not influence the fatigue estimation by narrow-band approximation. In addition, extreme response is defined by the level up-crossing approach. The Gaussian crossing model using Rice’s formula is employed to predict the extreme response based on the responses from above numerical analysis. It shows that the Gaussian model is not suitable for this prediction. A more complicated level crossing model is proposed which is based on the Laplace Moving Average method. Its accuracy in prediction of extreme responses is analyzed and presented with good agreement by means of numerical simulations.

scholarly journals J-PLUS: Synthetic galaxy catalogues with emission lines for photometric surveys

2019 ◽  
Vol 631 ◽  
pp. A82 ◽  
Author(s):  
David Izquierdo-Villalba ◽  
Raul E. Angulo ◽  
Alvaro Orsi ◽  
Guillaume Hurier ◽  
Gonzalo Vilella-Rojo ◽  
...  
Keyword(s):  
Emission Line ◽  
Narrow Band ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Line Emission ◽  
Spectral Energy ◽  
Filter Method ◽  
Medium Band ◽  
Emission Line Galaxies ◽  
The Impact

We present a synthetic galaxy lightcone specially designed for narrow-band optical photometric surveys. To reduce time-discreteness effects, unlike previous works, we directly include the lightcone construction in the L-Galaxies semi-analytic model applied to the subhalo merger trees of the Millennium simulation. Additionally, we add a model for the nebular emission in star-forming regions, which is crucial for correctly predicting the narrow- and medium-band photometry of galaxies. Specifically, we consider, individually for each galaxy, the contribution of 9 different lines: Lyα (1216 Å), Hβ (4861 Å), Hα (6563 Å), [O II] (3727 Å, 3729 Å), [O III] (4959 Å, 5007 Å), [Ne III] (3870 Å), [O I] (6300 Å), [N II] (6548 Å, 6583 Å), and [S II] (6717 Å, 6731 Å). We validate our lightcone by comparing galaxy number counts, angular clustering, and Hα, Hβ, [O II], and [O III]5007 luminosity functions to a compilation of observations. As an application of our mock lightcones, we generated catalogues tailored for J-PLUS, a large optical galaxy survey featuring five broad-band and seven medium-band filters. We study the ability of the survey to correctly identify, with a simple three-filter method, a population of emission-line galaxies at various redshifts. We show that the 4000 Å break in the spectral energy distribution of galaxies can be misidentified as line emission. However, all significant excess (> 0.4 mag) can be correctly and unambiguously attributed to emission-line galaxies. Our catalogues are publicly released to facilitate their use in interpreting narrow-band surveys and in quantifying the impact of line emission in broad-band photometry.

scholarly journals The Impact of Narrow-band Imaging on the Pre- and Intra- operative Assessments of Neoplastic and Preneoplastic Laryngeal Lesions. A Systematic Review

2020 ◽  
Author(s):  
Carmelo Saraniti ◽  
Enzo Chianetta ◽  
Giuseppe Greco ◽  
Norhafiza Mat Lazim ◽  
Barbara Verro
Keyword(s):  
White Light ◽  
Diagnostic Tool ◽  
Narrow Band ◽  
Narrow Band Imaging ◽  
Resection Margins ◽  
Predictive Values ◽  
White Light Endoscopy ◽  
Laryngeal Lesions ◽  
Sensitivity Specificity ◽  
The Impact

Introduction Narrow-band imaging is an endoscopic diagnostic tool that, focusing on superficial vascular changes, is useful to detect suspicious laryngeal lesions, enabling their complete excision with safe and tailored resection margins. Objectives To analyze the applications and benefits of narrow-band imaging in detecting premalignant and malignant laryngeal lesions through a comparison with white-light endoscopy. Data Synthesis A literature search was performed in the PubMed, Scopus and Web of Science databases using strict keywords. Then, two authors independently analyzed the articles, read the titles and abstracts, and read completely only the relevant studies according to certain eligibility criteria. In total, 14 articles have been included in the present review; the sensitivity, specificity, positive and negative predictive values, and accuracy of pre- and/or intraoperative narrow-band imaging were analyzed. The analysis showed that narrow-band imaging is better than white-light endoscopy in terms of sensitivity, specificity, positive and negative predictive values, and accuracy regarding the ability to identify cancer and/or precancerous laryngeal lesions. Moreover, the intraoperative performance of narrow-band imaging resulted more effective than the in-office performance. Conclusion Narrow-band imaging is an effective diagnostic tool to detect premalignant and malignant laryngeal lesions and to define proper resection margins. Moreover, narrow-band imaging is useful in cases of leukoplakia that may cover a possible malignant lesion and that cannot be easily assessed with white-light endoscopy. Finally, a shared, simple and practical classification of laryngeal lesions, such as that of the European Laryngological Society, is required to identify a shared lesion management strategy. Key Points

scholarly journals Assessing population collapse of Drupella spp. (Mollusca: Gastropoda) 2 years after a coral bleaching event in the Republic of Maldives

Hydrobiologia ◽  
2021 ◽  
Author(s):  
L. Saponari ◽  
I. Dehnert ◽  
P. Galli ◽  
S. Montano
Keyword(s):  
Coral Bleaching ◽  
Prey Availability ◽  
Coral Cover ◽  
Environmental Data ◽  
High Plasticity ◽  
Bleaching Event ◽  
Coral Recovery ◽  
The Republic ◽  
The Impact ◽  
Line Intercept

AbstractCorallivory causes considerable damage to coral reefs and can exacerbate other disturbances. Among coral predators, Drupella spp. are considered as delayer of coral recovery in the Republic of Maldives, although little information is available on their ecology. Thus, we aimed to assess their population structure, feeding behaviour and spatial distribution around 2 years after a coral bleaching event in 2016. Biological and environmental data were collected using belt and line intercept transects in six shallow reefs in Maldives. The snails occurred in aggregations with a maximum of 62 individuals and exhibited a preference for branching corals. Yet, the gastropods showed a high plasticity in adapting feeding preferences to prey availability. Drupella spp. were homogenously distributed in the study area with an average of 9.04 ± 19.72 ind/200 m2. However, their occurrence was significantly different at the reef scale with the highest densities found in locations with higher coral cover. The impact of Drupella spp. appeared to be minimal with the population suffering from the loss of coral cover. We suggest that monitoring programs collect temporal- and spatial-scale data on non-outbreaking populations or non-aggregating populations to understand the dynamics of predation related to the co-occurrence of anthropogenic and natural impacts.

scholarly journals Building Damage Detection Using U-Net with Attention Mechanism from Pre- and Post-Disaster Remote Sensing Datasets

2021 ◽  
Vol 13 (5) ◽  
pp. 905
Author(s):  
Chuyi Wu ◽  
Feng Zhang ◽  
Junshi Xia ◽  
Yichen Xu ◽  
Guoqing Li ◽  
...  
Keyword(s):  
Damage Assessment ◽  
Large Scale ◽  
Binary Classification ◽  
Open Data ◽  
Building Damage ◽  
Attention Mechanism ◽  
Large Scale Dataset ◽  
Data Program ◽  
The Impact ◽  
Post Disaster

The building damage status is vital to plan rescue and reconstruction after a disaster and is also hard to detect and judge its level. Most existing studies focus on binary classification, and the attention of the model is distracted. In this study, we proposed a Siamese neural network that can localize and classify damaged buildings at one time. The main parts of this network are a variety of attention U-Nets using different backbones. The attention mechanism enables the network to pay more attention to the effective features and channels, so as to reduce the impact of useless features. We train them using the xBD dataset, which is a large-scale dataset for the advancement of building damage assessment, and compare their result balanced F (F1) scores. The score demonstrates that the performance of SEresNeXt with an attention mechanism gives the best performance, with the F1 score reaching 0.787. To improve the accuracy, we fused the results and got the best overall F1 score of 0.792. To verify the transferability and robustness of the model, we selected the dataset on the Maxar Open Data Program of two recent disasters to investigate the performance. By visual comparison, the results show that our model is robust and transferable.

scholarly journals The impact of environmental variables on the spread of COVID-19 in the Republic of Korea

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong Kwan Lim ◽  
Oh Joo Kweon ◽  
Hye Ryoun Kim ◽  
Tae-Hyoung Kim ◽  
Mi-Kyung Lee
Keyword(s):  
Environmental Factors ◽  
Virus Disease ◽  
Environmental Parameters ◽  
Environmental Data ◽  
Republic Of Korea ◽  
Metropolitan Region ◽  
Health Concern ◽  
Ozone Level ◽  
The Republic ◽  
The Impact

AbstractCorona virus disease 2019 (COVID-19) has been declared a global pandemic and is a major public health concern worldwide. In this study, we aimed to determine the role of environmental factors, such as climate and air pollutants, in the transmission of COVID-19 in the Republic of Korea. We collected epidemiological and environmental data from two regions of the Republic of Korea, namely Seoul metropolitan region (SMR) and Daegu-Gyeongbuk region (DGR) from February 2020 to July 2020. The data was then analyzed to identify correlations between each environmental factor with confirmed daily COVID-19 cases. Among the various environmental parameters, the duration of sunshine and ozone level were found to positively correlate with COVID-19 cases in both regions. However, the association of temperature variables with COVID-19 transmission revealed contradictory results when comparing the data from SMR and DGR. Moreover, statistical bias may have arisen due to an extensive epidemiological investigation and altered socio-behaviors that occurred in response to a COVID-19 outbreak. Nevertheless, our results suggest that various environmental factors may play a role in COVID-19 transmission.

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