DNV GL

About: DNV GL is a company organization based out in Sandvika, Norway. It is known for research contribution in the topics: Corrosion & Finite element method. The organization has 1929 authors who have published 2387 publications receiving 34644 citations.

Uncertainties of Joint Long-Term Probabilistic Modelling of Wind Sea and Swell

Abstract: In several practical applications joint environmental description is required. In the last years increasing attention has been given to importance of inclusion of wind sea and swell components in a joint environmental model. Presence of wind sea and swell will affect design and operability of fixed and floating offshore structures as well as LNG terminals. In the present study joint environmental description has been established for three locations: Southern North Sea, Northwest Shelf of Australia and off coast of Nigeria. Hindcast data have been used in the analysis. Uncertainties related to the proposed fits are discussed focusing particularly at wind sea and swell modelling. Attention is given to location specific features of the wave climate and adopted partitioning procedure for the wave components. Implication of the uncertainties for design of marine structures is shown. An approach for joint environmental description for marine operations is proposed.Copyright © 2010 by ASME

Variation in incubation length and hatching asynchrony in Eastern Kingbirds: Weather eclipses female effects

Abstract: Incubation length and hatching asynchrony are integral elements of the evolved reproductive strategies of birds. We examined intra- and interpopulation variation in both traits for Eastern Kingbird (Tyrannus tyrannus) populations from New York (NY), Kansas (KS), and Oregon (OR) and found that both incubation length and hatching asynchrony were not repeatable among females, after controlling for a repeatable trait, clutch size. Instead, incubation length and clutch size were influenced by ambient temperature and precipitation. Incubation length exhibited the same median (15 days) and range (13–17 days) at all sites. Model selection results indicated that incubation periods for the smallest and largest clutches were longer in NY than KS when rain was frequent throughout incubation, in replacement nests, and likely when ambient temperatures were low during egg-laying. Full hatching usually required 2 days (but up to 3), with synchronous hatching associated with small clutch sizes, short incubation periods, frequent rain during the egg-laying period, and low ambient temperatures during the first half of incubation. Nestling starvation was uncommon (5–9% of nestlings monitored) and not associated with greater hatching asynchrony. These results indicate that while clutch size, a repeatable female trait, contributed to variation in incubation length and hatching asynchrony in Eastern Kingbirds, weather was a greater source of variation, especially for incubation length.LAY SUMMARYThe length of time that eggs remain in a nest exposed to causes of mortality has important influences on the reproductive success of birds.We collected data on incubation length, the length of time elapsed between the hatching of the first and last egg (called hatching asynchrony), and probability of nestling starvation in Eastern Kingbirds breeding at 3 locations (Kansas, New York, and Oregon).Incubation length and hatching asynchrony varied considerably within, but also among sites. Incubation length and hatching asynchrony were both greater in nests with more eggs. However, most other variation was likely due to environmental effects. Cool and wet conditions were associated with long incubation periods while greater hatching asynchrony was found during periods when it was warm and dry.Starvation of nestlings was infrequent, and nests with a greater range of nestling ages (caused by high hatching asynchrony) did not experience greater starvation of young. Nestling starvation was thus not a cost of high-hatching asynchrony.Our research demonstrates that environmental temperature and frequency of precipitation have greater effects on incubation period compared to clutch size.

Assessment of Global Wave Datasets for Long Term Response of Ships

Abstract: Ship structure design process begins with the evaluation of environmental conditions a ship is expected to withstand. This paper deals with wave data, and more specifically with global wave dataset that can be used to evaluate waves encountered by a ship along its lifetime track. Benchmark of existing global hindcast datasets is performed, having in mind its use to assess extreme ship response. The presented comparison is thus not limited to the mean and standard deviation but includes also extreme significant wave height. Wave period that can significantly modify ship behaviour is also investigated. Five different hindcast datasets are selected for the present analysis and compared with buoy and altimeter data. Area of interest is region far from the coast, and more specifically the North-Atlantic, which is currently considered the most severe for sailing ships. In such area, the global wave models are expected to provide decent results (as opposed to near shore area where a local mesh would be required). Two datasets are provided by ECMWF (ERA5 and ERA-Interim) that uses WAM model, two others are from NOaAA/NCEP and Ifremer and use WaveWatchIII, finally WAV-ERYS dataset is provided by the Copernicus program, and uses MFWAM. Some differences are observed in the wave parameters projected by different models, especially on extremes. Reasons for this scatter are briefly discussed, but more emphasis is put on the consequence for ship response. This work has been performed within IACS (International Association of Classification Societies) framework.