scholarly journals Viscous Drag Reduction and Contour Feather Geometry in Water and Land Birds

2021 ◽  
Author(s):  
Roelof D. Coertze ◽  
Arie M. Rijke
Keyword(s):  
Parametric Analysis ◽  
Open Water ◽  
Water Repellency ◽  
Viscous Drag ◽  
Width Ratio ◽  
Data Set ◽  
Drag Coefficients ◽  
Phylogenetic Relatedness ◽  
Water Birds ◽  
Statistical Approaches

Water birds have contour feathers in contact with water that show in their distal one-third adaptations to water repellency, resistance to water penetration and forceful impact with water. These qualities vary according to their intimacy with open water. In this study, the geometry of this part of the feather was examined to detect additional features that would affect viscous drag in water. The length-to-width ratio was measured and used to calculate the viscous drag coefficients for 48 water birds and, for comparison, 12 land birds. The lowest values for the drag coefficient were observed for birds with foraging niches as diving and swimming, followed by plunging, surface feeding, aerial and ground feeding. Land birds with no open water in their habitat had the highest drag coefficients. Three statistical approaches were used to validate the results. Allowing for the phylogenetic relatedness of the 60 species obscured any significant differences that may exist, but a non-parametric analysis that does not assume the conditions of equal sample size and variance turned out to be the most appropriate method for our data set.

scholarly journals River ice flux and water velocities along a 600 km long reach of Lena River, Siberia, from satellite stereo

2013 ◽  
Vol 10 (7) ◽  
pp. 9967-9997 ◽  
Author(s):  
A. Kääb ◽  
M. Lamare ◽  
M. Abrams
Keyword(s):  
River Flow ◽  
Thermal Emission ◽  
Time Lag ◽  
Open Water ◽  
Image Resolution ◽  
Surface Velocity ◽  
River Ice ◽  
Data Set ◽  
Hazard Management ◽  
Lena River

Abstract. Knowledge of water-surface velocities in rivers is useful for understanding a range of river processes. In cold regions, river-ice break up and the related downstream transport of ice debris is often the most important hydrological event of the year, leading to flood levels that typically exceed those for the open-water period and to strong consequences for river infrastructure and ecology. Accurate and complete surface-velocity fields on rivers have rarely been produced. Here, we track river ice debris over a time period of about one minute, which is the typical time lag between the two or more images that form a stereo data set in spaceborne, along-track optical stereo-mapping. Using a series of 9 stereo scenes from the US/Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the NASA Terra spacecraft with 15 m image resolution, we measure the ice and water velocity field over a 620 km long reach of the lower Lena River, Siberia, just above its entry into the Lena delta. Careful analysis and correction of higher-order image and sensor errors enables an accuracy of ice-debris velocities of up to 0.04 m s−1 from the ASTER data. Maximum ice or water speeds, respectively, reach up to 2.5 m s−1 at the time of data acquisition, 27 May 2011 (03:30 UTC). Speeds show clear along-stream undulations with a wavelength of about 21 km that agree well with variations in channel width and with the location of sand bars along the river reach studied. The methodology and results of this study could be valuable to a number of disciplines requiring detailed information about river flow, such as hydraulics, hydrology, river ecology and natural-hazard management.

scholarly journals Summarising salient information on historical controls: A structured assessment of validity and comparability across studies

2020 ◽  
Vol 17 (6) ◽  
pp. 607-616
Author(s):  
Anthony Hatswell ◽  
Nick Freemantle ◽  
Gianluca Baio ◽  
Emmanuel Lesaffre ◽  
Joost van Rosmalen
Keyword(s):  
Colorectal Cancer ◽  
Historical Data ◽  
Outcome Measurement ◽  
Disease Process ◽  
Patient Characteristics ◽  
Study Patient ◽  
Data Set ◽  
Cancer Data ◽  
Statistical Approaches ◽  
Randomised Controlled

Background While placebo-controlled randomised controlled trials remain the standard way to evaluate drugs for efficacy, historical data are used extensively across the development cycle. This ranges from supplementing contemporary data to increase the power of trials to cross-trial comparisons in estimating comparative efficacy. In many cases, these approaches are performed without in-depth review of the context of data, which may lead to bias and incorrect conclusions. Methods We discuss the original ‘Pocock’ criteria for the use of historical data and how the use of historical data has evolved over time. Based on these factors and personal experience, we created a series of questions that may be asked of historical data, prior to their use. Based on the answers to these questions, various statistical approaches are recommended. The strategy is illustrated with a case study in colorectal cancer. Results A number of areas need to be considered with historical data, which we split into three categories: outcome measurement, study/patient characteristics (including setting and inclusion/exclusion criteria), and disease process/intervention effects. Each of these areas may introduce issues if not appropriately handled, while some may preclude the use of historical data entirely. We present a tool (in the form of a table) for highlighting any such issues. Application of the tool to a colorectal cancer data set demonstrates under what conditions historical data could be used and what the limitations of such an analysis would be. Conclusion Historical data can be a powerful tool to augment or compare with contemporary trial data, though caution is required. We present some of the issues that may be considered when involving historical data and what (if any) statistical approaches may account for differences between studies. We recommend that, where historical data are to be used in analyses, potential differences between studies are addressed explicitly.

Calibration of Hydrodynamic Coefficients for a Semi-Submersible 10 MW Wind Turbine

2018 ◽  
Author(s):  
Marit I. Kvittem ◽  
Petter Andreas Berthelsen ◽  
Lene Eliassen ◽  
Maxime Thys
Keyword(s):  
Numerical Model ◽  
Line Tension ◽  
Offshore Wind ◽  
Scale Model ◽  
Viscous Drag ◽  
Mooring System ◽  
Drag Coefficients ◽  
Damping Coefficients ◽  
Decay Tests ◽  
Drift Forces

Hydrodynamic model tests and numerical simulations may be combined in a complementary manner during the design and qualification of new offshore structures. In the EU H2020 project LIFES50+ (lifes50plus.eu), a model test campaign of floating offshore wind turbines using Real-Time Hybrid Model (ReaTHM) testing techniques was carried out at SINTEF Ocean in fall 2017. The present paper focuses on the process of calibrating a numerical model to the experimental results. The concepts tested in the experimental campaign was a 1:36 scale model of the public version of the 10MW OO-Star Wind Floater semi-submersible offshore wind turbine. A time-domain numerical model was developed based on the as-built scale model. The hull was considered as rigid, while bar elements were used to model the mooring system and tower in a coupled finite element approach. First-order frequency-dependent added mass, potential damping, and excitation forces/moments were evaluated across a range of frequencies using a panel method. Distributed viscous forces on the hull and mooring lines were added to the numerical model according to Morison’s equation. Potential difference-frequency excitation forces were also included by applying Newman’s approximation. The quasi static properties of the mooring system were assessed by comparing the restoring force and maximum line tension with the pull-out test. Drag coefficients for the line segments were estimated by imposing the measured fairlead motion from model tests as forced displacement and comparing the calculated and measured dynamic line tension. The linear and viscous damping coefficients were first estimated based on the decay tests, and the tuned damping coefficients were compared to initial guesses based on the Reynolds and Keulegan-Carpenter number at model scale. The results were then applied in the numerical model, and simulations in extreme irregular waves were compared to the experiments. It was found that second order drift forces proved to be significant, particularly for the severe irregular seastate. These could not be modelled correctly applying the potential drift forces together with quadratic damping matrix tuned to the free decay test. And the model with viscous drag coefficients tuned to decay tests also underestimated the slow drift motions. Thus, new viscous drag coefficients were determined to match the low frequency platform response. To inverstigate the performance of the tuned model, comparisons were made for a moderate seastate and for a simulation with both waves and wind on an operating turbine. In the end, possible further improvements to the modelling were suggested.

Real-Time Hybrid Model Tests of a Braceless Semi-Submersible Wind Turbine: Part III — Calibration of a Numerical Model

2016 ◽  
Author(s):  
Petter Andreas Berthelsen ◽  
Erin E. Bachynski ◽  
Madjid Karimirad ◽  
Maxime Thys
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Simulation Model ◽  
Wind Turbine ◽  
Real Time ◽  
Hybrid Model ◽  
Test Data ◽  
Viscous Drag ◽  
Drag Coefficients ◽  
Aerodynamic Loads

In this paper, a numerical model of a braceless semi-submersible floating wind turbine (FWT) is calibrated against model test data. Experimental data from a 1:30 scaled model tested at MARINTEK’s Ocean Basin in 2015 using real-time hybrid model testing (ReaTHM) is used for the calibration of the time-domain simulation model. In these tests, aerodynamic loads were simulated in real-time and applied to the physical model. The simulation model is based on the as-built model at full scale. The hull and turbine are considered as rigid, while bar elements are used to model the mooring system in a coupled finite element approach. Frequency-dependent added mass, radiation damping, and excitation forces/moments are evaluated using a panel method based on potential theory. Distributed viscous forces on the hull and mooring lines are added to the numerical model applying Morison’s equation. The viscous drag coefficients in Morison’s equation are calibrated against selected test data, including decay tests in calm water and test with irregular waves. Simulations show that the drag coefficients change when waves are present. Aerodynamic loads are included as time varying loads applied directly at the hub based on the actual physical loads from the experiment. This way, uncertainties related to the aerodynamic loads in the calibrations are removed. The calibrated numerical model shows good agreement with experimental data.

scholarly journals River ice flux and water velocities along a 600 km-long reach of Lena River, Siberia, from satellite stereo

2013 ◽  
Vol 17 (11) ◽  
pp. 4671-4683 ◽  
Author(s):  
A. Kääb ◽  
M. Lamare ◽  
M. Abrams
Keyword(s):  
River Flow ◽  
Thermal Emission ◽  
Time Lag ◽  
Open Water ◽  
Image Resolution ◽  
Surface Velocity ◽  
River Ice ◽  
Data Set ◽  
Hazard Management ◽  
Lena River

Abstract. Knowledge of water-surface velocities in rivers is useful for understanding a range of river processes. In cold regions, river-ice break up and the related downstream transport of ice debris is often the most important hydrological event of the year, leading to flood levels that typically exceed those for the open-water period and to strong consequences for river infrastructure and ecology. Accurate and complete surface-velocity fields on rivers have rarely been produced. Here, we track river ice debris over a time period of about one minute, which is the typical time lag between the two or more images that form a stereo data set in spaceborne, along-track optical stereo mapping. Using a series of nine stereo scenes from the US/Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard the NASA Terra spacecraft with 15 m image resolution, we measure the ice and water velocity field over a 620 km-long reach of the lower Lena River, Siberia, just above its entry into the Lena delta. Careful analysis and correction of higher-order image and sensor errors enables an accuracy of ice-debris velocities of up to 0.04 m s−1 from the ASTER data. Maximum ice or water speeds, respectively, reach up to 2.5 m s−1 at the time of data acquisition, 27 May 2011 (03:30 UTC). Speeds show clear along-stream undulations with a wavelength of about 21 km that agree well with variations in channel width and with the location of sand bars along the river reach studied. The methodology and results of this study could be valuable to a number of disciplines requiring detailed information about river flow, such as hydraulics, hydrology, river ecology and natural-hazard management.

scholarly journals BLACK ALDER DOMINATED FOREST VEGETATION IN THE WESTERN PART OF CENTRAL SLOVAKIA – SPECIES COMPOSITION AND ECOLOGY

Hacquetia ◽  
2013 ◽  
Vol 12 (2) ◽  
pp. 23-37
Author(s):  
Richard Hrivnák ◽  
Jaroslav Košťál ◽  
Michal Slezák ◽  
Anna Petrášová ◽  
Melánia Feszterová
Keyword(s):  
Species Composition ◽  
Expert Knowledge ◽  
Light Availability ◽  
Principal Component ◽  
Environmental Parameters ◽  
Soil Surface ◽  
Open Water ◽  
Forest Vegetation ◽  
Data Set ◽  
Black Alder

Abstract In some regions of Slovakia, black alder forest vegetation has not been documented appropriately yet. This paper is the first vegetation study presenting the phytosociological data and measured environmental parameters from the western part of central Slovakia. The data set was classified by using a modified TWINSPAN algorithm, which allowed us to discern floristically and ecologically distinctive plant communities. They correspond to the associations Stellario nemorum-Alnetum glutinosae Lohmeyer 1957 (riparian alder vegetation on mesic to humid sites along small brooks) and Carici acutiformis-Alnetum glutinosae Scamoni 1935 (eutrophic black alder carr forests in the colline zone) with the variants of Ligustrum vulgare and Galium palustre. The community Carici elongatae-Alnetum glutinosae Schwickerath 1933 (mesotrophic to eutrophic alder carr vegetation growing on permanently waterlogged soils), documented only with two phytosociological relevés, was distinguished following expert knowledge. A floristic and ecological pattern of these associations is presented. The major compositional gradients were interpreted based on Ellenberg’s indicator values and the values of environmental variables recorded during the field sampling in the growing season 2011. The principal component analysis revealed the importance of soil moisture, light availability, portion of open water and soil surface for species composition variability at the association level, whereas the variants of Carici acutiformis-Alnetum glutinosae were sorted along the acidity gradient.

scholarly journals Caisson Breakwater for LNG and Bulk Terminals: A Study on Limiting Wave Conditions for Caisson Installation

2020 ◽  
Author(s):  
Yu Lin ◽  
Ghassan El Chahal ◽  
Yanlin Shao
Keyword(s):  
Water Depth ◽  
Oil And Gas ◽  
Numerical Study ◽  
Wave Structure ◽  
Viscous Drag ◽  
Viscous Effects ◽  
Drag Coefficients ◽  
Simplified Approach ◽  
Wave Conditions ◽  
General Guidance

Abstract As the worldwide oil and gas market continues to grow and environmental concerns with respect to in-port offloading of gas have increased, there has been a boom of interest in new liquefied natural gas LNG terminals in the past years. Loading - offloading operations at LNG and bulk terminals are generally protected by a breakwater to ensure high operability. For these terminals, caisson breakwaters are generally a preferred solution in water depth larger than 15 m due to its advantages compared to rubble mound breakwaters. The caisson installation is generally planned to be carried out in the period where sea conditions are relatively calm. However, many of these terminal locations are exposed to swell conditions, making the installation particularly challenging and subject to large downtime. There is no clear guidance on the caisson installation process rather than contractors’ experiences from different projects/sites. Therefore, studies are required in order to provide general guidance on the range of acceptable wave conditions for the installation operations and to have a better understanding of the influence of the caisson geometry. This paper presents a numerical study to determine the limiting wave conditions for caisson installing operations at larger water depth of 30–35 m for a confidential project along the African coast. Three caisson sizes/geometries are considered in order to assess and compare the wave-structure hydrodynamic interaction. The linear frequency-domain hydrodynamic analysis is performed for various seastates to determine the limiting wave conditions. Viscous effects due to flow separation at the sharp edges of the caisson are considered by using a stochastic linearization approach, where empirical drag coefficients are used as inputs. Parametric studies on caisson size and mooring stiffness are also presented, which can be used as a basis for future optimization. The uncertainty in the applied empirical viscous drag coefficients taken from the literature is examined by using a range of different drag coefficients. Further, the use of clearance-independent hydrodynamic coefficients (e.g. added mass and damping) may be questionable when the caisson is very close to the seabed, due to a possible strong interaction between caisson bottom and seabed. This effect is also checked quantitatively by a simplified approach. The findings of the study are presented in the form of curves and generalized to be used by designers and contractors for general guidance in future projects.

scholarly journals Prediction of the depth of local scouring at a bridge pier using a gene expression programming method

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Waqed H. Hassan ◽  
Halah K. Jalal
Keyword(s):  
Gene Expression ◽  
Mean Squared Error ◽  
Human Life ◽  
Gene Expression Programming ◽  
Absolute Error ◽  
Width Ratio ◽  
Statistical Parameters ◽  
Data Set ◽  
Total Data ◽  
Local Depth

AbstractLocal scouring around the piers of a bridge is the one of the major reasons for bridge failure, potentially resulting in heavy losses in terms of both the economy and human life. Prediction of accurate depth of local scouring is a difficult task due to the many factors that contribute to this process, however. The main aim of this study is thus to offer a new formula for the prediction the local depth of scouring around the pier of a bridge using a modern fine computing modelling technique known as gene expression programming (GEP), with data obtained from numerical simulations used to compare GEP performance with that of a standard non-linear regression (NLR) model. The best technique for prediction of the local scouring depth is then determined based on three statistical parameters: the determination coefficient (R2), mean absolute error (MAE), and root mean squared error (RMSE). A total data set of 243 measurements, obtained by numerical simulation in Flow-3D, for intensity of flow, ratio of pier width, ratio of flow depth, pier Froude number, and pier shape factor is divided into training and validation (testing) datasets to achieve this. The results suggest that the formula from the GEP model provides better performance for predicting the local depth of scouring as compared with conventional regression with the NLR model, with R2 = 0.901, MAE = 0.111, and RMSE = 0.142. The sensitivity analysis results further suggest that the ratio of the depth of flow has the greatest impact on the prediction of local scour depth as compared to the other input parameters. The formula obtained from the GEP model gives the best predictor of depth of scouring, and, in addition, GEP offers the special feature of providing both explicit and compressed arithmetical terms to allow calculation of such depth of scouring.

SNP Associations with Event Free Survival in Myeloma from Two Phase III Clinical Trials Using the Bank On A Cure Chip.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 131-131
Author(s):  
Brian G. Van Ness ◽  
John C. Crowley ◽  
Christine Ramos ◽  
Suzanne M. Grindle ◽  
Antje Hoering ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Genetic Variations ◽  
Gene Set Enrichment Analysis ◽  
Phase Iii ◽  
Survival Outcomes ◽  
Cellular Functions ◽  
Two Phase ◽  
Data Set ◽  
Phase Iii Clinical Trials ◽  
Statistical Approaches

Abstract While there are certain common clinical features in myeloma, the disease shows significant heterogeneity with regard to disease progression, and responses to therapy, affecting both survival and toxicities. Heritable variations in a wide variety of genes and pathways affecting cellular functions and drug responses likely impact patient outcomes. In the Bank On A Cure (BOAC) program we have developed a custom chip that assesses 3,404 SNPs representing variations in cellular functions and pathways that may be involved in myeloma progression and response. The chip has gone through rigorous quality controls checks for high call rates, accuracy, and reproducibility that will be presented. Using the BOAC chip, we have conducted studies to look for SNPs that may identify biologic variations that are associated with good or poor response across a variety of treatments. In this study we looked for SNPs that may distinguish short term and long term survivors in two phase III clinical trials: ECOG E9486 and intergroup trial S9321. E9487 patients were treated with VBMCP followed by randomization to no further treatment, IFN-alpha, or cylcophosphamide; and, although there was variation in survival, no significant differences in survival were noted among the 3 arms of the trial. Patients included in this SNP study from S9321 received VAD induction followed by randomization to VBMCP or high dose melphalan + TBI. SNP profiles were obtained for patients with less than 1 year EFS (n=20 in E9487; n=50 in S9321) and patients showing greater than 3 years EFS (n=32 in E9486; n=41 in S9321). Statistical approaches were performed to identify single and groups of SNPs that best discriminated the survival groups. Previous studies have suggested genetic variations in drug metabolism genes, p-glycoprotein transport, and DNA repair genes may influence survival outcomes. Our results show significant survival associations of genetic variations in genes within these functional categories (eg. GST, XRCC, ABCB, and CYP genes). Although genetic variations were found that were uniquely associated with each clinical trial, several of these genetic variations show survival associations that increase in significance when the two trials were examined as a conglomerate data set. Grouping genetic variations through common pathway approaches using gene set enrichment analysis, as well as clustering or partitioning algorithms, further improve the value of the SNPs as potential prognostic markers of survival outcomes. These results and statistical approaches will be presented, and represent steps toward identifying patient variations in biologic mechanisms important in predicting therapeutic outcomes.

Phylogeny and relations among abundance, geographical range and body size of British breeding birds

1995 ◽  
Vol 349 (1330) ◽  
pp. 345-351 ◽  
Keyword(s):  
Body Size ◽  
Negative Correlation ◽  
Breeding Birds ◽  
Geographical Range ◽  
Published Data ◽  
Data Set ◽  
Phylogenetic Relatedness ◽  
Bird Assemblages ◽  
Positive Correlation ◽  
Weak Influence

Links between bird phylogeny and abundance, geographical range and body size relations were examined with use of a newly published data set on the numbers and distribution of British breeding birds. There was a negative correlation between abundance (and geographical range) and body size across species, but no significant correlations within non-passerine and passerine taxa considered separately. Abundance correlated positively with geographical range across species and within non-passerines and passerines. Three measures of phylogenetic relatedness of bird tribes were considered, termed ‘rootedness’, ‘date of origin’ and ‘radiation d ate’. The date at which a tribe originated (measured as rootedness or date of origin) had a consistent but weak influence on the form of the relation between abundance and body size. Phylogeny was not implicated in the relation between geographical range and body size. Phylogenetically isolated tribes were more likely to show a positive correlation between abundance and body size than more recently evolved tribes. Results are discussed in the context of previous studies of both regional and local bird assemblages and the hypotheses suggested to explain associations with phylogeny.

Sign in / Sign up

Export Citation Format

Share Document