Predicting the long-term distribution of extreme loads from limited duration data - Comparing full integration and approximate methods

2002 ◽  
Author(s):  
L. Fitzwater ◽  
S. Winterstein ◽  
C. Cornell
Keyword(s):  
Approximate Methods ◽  
Duration Data ◽  
Extreme Loads ◽  
Limited Duration

Predicting the Long Term Distribution of Extreme Loads From Limited Duration Data: Comparing Full Integration and Approximate Methods

2002 ◽  
Author(s):  
LeRoy M. Fitzwater ◽  
Steven R. Winterstein ◽  
C. Allin Cornell
Keyword(s):  
Load Distribution ◽  
Robust Methods ◽  
Short Term ◽  
Approximate Methods ◽  
Wind Speeds ◽  
Extreme Loads ◽  
Long Run ◽  
Extreme Load ◽  
Limited Duration

In this paper we present a methodology for proceeding from the short-term observations of extreme loads to the long-run load distribution of these extreme events, for both flap and edge loading in both operating and parked wind turbine conditions. First a general approach utilizing full integration, where numerical routines are used to directly integrate the conditional short-term load distribution over the annual occurrence of wind speeds and turbulence intensities, is presented. Then starting from this general approach, a qualitative analysis is undertaken to explore the extent of the contribution of each of the three variables, in the governing equation, to the variability in the long-term extreme load distribution. From this analysis, lower order models are considered, where instead of using the entire distribution of the variables, a constant fractile of the short-term extreme load distribution, turbulence intensity distribution, or both are used. Finally recommendations are given to guide the analyst to decide when simpler, yet robust, methods which account for sufficient variability in extreme load event may be employed with confidence.

Predicting the Long Term Distribution of Extreme Loads From Limited Duration Data: Comparing Full Integration and Approximate Methods

2002 ◽  
Vol 124 (4) ◽  
pp. 378-386 ◽  
Author(s):  
LeRoy M. Fitzwater ◽  
C. Allin Cornell
Keyword(s):  
Load Distribution ◽  
Robust Methods ◽  
Short Term ◽  
Approximate Methods ◽  
Wind Speeds ◽  
Extreme Loads ◽  
Long Run ◽  
Extreme Load ◽  
Limited Duration

In this paper, we present a methodology for proceeding from the short-term observations of extreme loads to the long-run load distribution of these extreme events, for both flap and edge loading in both operating and parked wind turbine conditions. First, a general approach utilizing full integration, where numerical routines are used to directly integrate the conditional short-term load distribution over the annual occurrence of wind speeds and turbulence intensities, is presented. Then starting from this general approach, a qualitative analysis is undertaken to explore the extent of the contribution of each of the three variables in the governing equation to the variability in the long-term extreme load distribution. From this analysis, lower-order models are considered, where instead of using the entire distribution of the variables, a constant fractile of the short-term extreme load distribution, turbulence intensity distribution, or both are used. Finally recommendations are given to guide the analyst to decide when simpler, yet robust, methods which account for sufficient variability in extreme load events may be employed with confidence.

Diarrheal Episodes and Diarrheal Disease: Acute Disease with Chronic Implications

1984 ◽  
Vol 47 (4) ◽  
pp. 321-327 ◽  
Author(s):  
DOUGLAS L. ARCHER
Keyword(s):  
Defense Mechanisms ◽  
Diarrheal Disease ◽  
Systemic Circulation ◽  
Structure And Function ◽  
Opportunistic Pathogens ◽  
Essential Nutrient ◽  
And Function ◽  
Limited Duration ◽  
Normal Defense

Diarrheal episodes and diarrheal disease are often considered to be acute events of limited duration; a review of current literature indicates that this is not true. Diarrheal episodes caused by many bacteria, viruses, protozoans and other parasites cause alteration of intestinal structure and function. Consequences of such diarrhea-associated gut alterations include loss of normal defense mechanisms against secondary opportunistic pathogens and the ability to exclude macromolecules from systemic circulation. Additionally, loss of endogenous nutrients and malabsorption of essential nutrients result from diarrheal episodes; the consequences of such losses, even of a single essential nutrient, is compromised immune function, which predisposes to further infection. The net result of such events in some persons is long-term debilitating disease(s) such as allergy, autoimmune disorders and neoplasia.

Probabilistic Analysis of LIST Data for the Estimation of Extreme Design Loads for Wind Turbine Components*†

2003 ◽  
Vol 125 (4) ◽  
pp. 531-540 ◽  
Author(s):  
M. D. Pandey ◽  
H. J. Sutherland
Keyword(s):  
Wind Turbine ◽  
Sampling Error ◽  
Test List ◽  
Structural Data ◽  
Value Theory ◽  
Extreme Value ◽  
Sampling Errors ◽  
Extreme Loads ◽  
Design Loads

The robust estimation of wind turbine design loads for service lifetimes of 30 to 50 years that are based on limited field measurements is a challenging problem. Estimating the long-term load distribution involves the integration of conditional distributions of extreme loads over the mean wind speed and turbulence intensity distributions. However, the accuracy of the statistical extrapolation can be sensitive to both model and sampling errors. Using measured inflow and structural data from the Long Term Inflow and Structural Test (LIST) program, this paper presents a comparative assessment of extreme loads using three distributions: namely, the Gumbel, Weibull and Generalized Extreme Value distributions. The paper uses L-moments, in place of traditional product moments, with the purpose of reducing the sampling error. The paper discusses the effects of modeling and sampling errors and highlights the practical limitations of extreme value theory.

Long-Term Extreme Load Prediction of Spar and Semisubmersible Floating Wind Turbines Using the Environmental Contour Method

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
D. Karmakar ◽  
Hasan Bagbanci ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Contour Method ◽  
Return Periods ◽  
Extreme Loads ◽  
Floating Wind Turbine ◽  
Extreme Load ◽  
Design Loads ◽  
Offshore Floating Wind Turbine

The prediction of extreme loads for the offshore floating wind turbine is analyzed based on the inverse reliability technique. The inverse reliability approach is in general used to establish the design levels associated with the specified probability of failure. The present study is performed using the environmental contour (EC) method to estimate the long-term joint probability distribution of extreme loads for different types of offshore floating wind turbines. The analysis is carried out in order to predict the out-of-plane bending moment (OoPBM) loads at the blade root and tower base moment (TBM) loads for a 5 MW offshore floating wind turbine of different floater configuration. The spar-type and semisubmersible type offshore floating wind turbines are considered for the analysis. The FAST code is used to simulate the wind conditions for various return periods and the design loads of various floating wind turbine configurations. The extreme and operation situation of the spar-type and semisubmersible type offshore floating wind turbine are analyzed using one-dimensional (1D) and two-dimensional (2D)-EC methods for different return periods. The study is useful to predict long-term design loads for offshore wind turbines without requiring excessive computational effort.

Long-Term Analysis of Extreme Global Restoring Loads on a FPSO Turret Structure Using a Coupled Model

2018 ◽  
Author(s):  
Isabel Jimenez Puente ◽  
Kjell Larsen
Keyword(s):  
Coupled Model ◽  
Element Model ◽  
Contour Line ◽  
Structural Element ◽  
Mooring Lines ◽  
Probability Of Exceedance ◽  
Extreme Loads ◽  
Annual Probability ◽  
Term Analysis

A turret structure can be a major design driver for FPSO systems. Therefore, careful attention needs to be given to the estimation of extreme loads on this structural element. This paper presents an all seas long-term analysis of the extreme global restoring forces acting on a FPSO turret structure, and a comparison with the results obtained through the contour line approach. The analysis is performed in the time domain using a coupled model, where the floater is modelled in the software SIMO, and the risers and mooring lines are represented by a Finite Element Model in RIFLEX. The characteristic responses of the turret structure with q-annual probability of exceedance are estimated from a full long-term analysis where both the short and long-term variability are considered. These results are compared to those obtained through the long-term estimate from the contour line approach when assuming 90th percentile for the worst sea state with q-annual probability of exceedance. The results from the full long-term analysis will allow us to verify the adequate percentile level to be used with a contour line approach when estimating extreme turret structure loads.

Evaluating the Long-Term Fatigue Response of Mooring Lines Using an Asymptotic Approximation

2012 ◽  
Author(s):  
Ying Min Low ◽  
Sai Hung Cheung
Keyword(s):  
Asymptotic Approximation ◽  
Classical Method ◽  
Joint Probability ◽  
Approximate Solutions ◽  
Mooring Line ◽  
Perturbation Approach ◽  
Mooring Lines ◽  
Approximate Methods ◽  
Direct Numerical Integration

A major challenge in the design of a mooring line or riser is the evaluation of the fatigue damage accumulated over the lifetime of the structure. The long-term environmental condition is usually represented by a scatter diagram, or a joint probability density of the significant waveheight and a characteristic wave period. Since it is computationally impractical to consider a large number of sea states, a common practice is to condense the sea states into a small number of blocks, but this procedure inevitably introduces significant errors owing to the coarse discretization. In view of the need for efficient but accurate approaches, this paper investigates the application of an asymptotic approximation, which is an established technique for estimating probability integrals, but it has so far not been applied to the fatigue design of moorings and risers. In addition, a classical method known as the perturbation approach is examined. The above approximate methods are implemented on an FPSO floating system, and direct numerical integration is carried out to ascertain the accuracy of the approximate solutions.

scholarly journals Pediatric chronic myeloid leukemia is a unique disease that requires a different approach

Blood ◽  
2016 ◽  
Vol 127 (4) ◽  
pp. 392-399 ◽  
Author(s):  
Nobuko Hijiya ◽  
Kirk R. Schultz ◽  
Markus Metzler ◽  
Frederic Millot ◽  
Meinolf Suttorp
Keyword(s):  
Myeloid Leukemia ◽  
Progressive Disease ◽  
Kinase Inhibitor ◽  
Myelogenous Leukemia ◽  
Prognostic Scores ◽  
Active Growth ◽  
Blood And Marrow Transplantation ◽  
Children And Young Adults ◽  
Limited Duration

AbstractChronic myelogenous leukemia (CML) in children is relatively rare. Because of a lack of robust clinical study evidence, management of CML in children is not standardized and often follows guidelines developed for adults. Children and young adults tend to have a more aggressive clinical presentation than older adults, and prognostic scores for adult CML do not apply to children. CML in children has been considered to have the same biology as in adults, but recent data indicate that some genetic differences exist in pediatric and adult CML. Because children with CML may receive tyrosine kinase inhibitor (TKI) therapy for many decades, and are exposed to TKIs during a period of active growth, morbidities in children with CML may be distinct from those in adults and require careful monitoring. Aggressive strategies, such as eradication of CML stem cells with limited duration and intensive regimens of chemotherapy and TKIs, may be more advantageous in children as a way to avoid lifelong exposure to TKIs and their associated adverse effects. Blood and marrow transplantation in pediatric CML is currently indicated only for recurrent progressive disease, and the acute and long-term toxicities of this option should be carefully evaluated against the complications associated with lifelong use of TKIs.

Wave Sector Dependent Contour Lines

2007 ◽  
Author(s):  
Gro Sagli Baarholm ◽  
Sverre Haver ◽  
Carl M. Larsen
Keyword(s):  
Linear Response ◽  
Contour Line ◽  
Exceedance Probability ◽  
Wave Direction ◽  
Short Term ◽  
Sea State ◽  
Extreme Loads ◽  
Contour Lines ◽  
Term Analysis

This paper is concerned with estimating the response value corresponding to given annual exceedance probability. In principle, this requires that a full long term analysis is executed. For a linear response this can easily be done. For a non-linear response quantity however, where time domain simulations are required in order to obtain the short term stochastic structure a full long term analysis will be time consuming. An approximate method to determine the long-term extremes by considering only a few short term sea states is outlined. All sea states corresponding to a certain probability of occurrence and are given by a contour line of Hs, Tp for each wave direction. The advantage of the method is that a proper estimate of the long term extreme can be obtained by considering the most unfavourable sea state along the contour line. This will make possible practical estimation of the extreme loads the structure is exposed to. The purpose of the present paper is to illustrate how to apply directional contour lines in order to obtain a characteristic design value according to requirements regarding the marginal exceedance probability.

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