697 research outputs found
Million years of Greenland Ice Sheet history recorded in ocean sediments
Geological records from Tertiary and Quaternary terrestrial and oceanic sections have documented the presence of ice caps and sea ice covers both in the Southern and the Northern hemispheres since Eocene times, approximately since 45 Ma. In this paper focussing on Greenland we mainly use the occurrences of coarse ice-rafted debris (IRD) in Quaternary and Tertiary ocean sediment cores to conclude on age and origin of the glaciers/ice sheets, which once produced the icebergs transporting this material into the adjacent ocean. Deep-sea sediment cores with their records of ice-rafting from off NE Greenland, Fram Strait and to the south of Greenland suggest the more or less continuous existence of the Greenland ice sheet since 18 Ma, maybe much longer, and hence far beyond the stratigraphic extent of the Greenland ice cores. The timing of onset of glaciation on Greenland and whether it has been glaciated continuously since, are wide open questions of its long-term history. We also urgently need new scientific drilling programs in the waters around Greenland, in particular in the segment of the Arctic Ocean to the north of Greenland
Materials for Wind Turbine Blades: An Overview
A short overview of composite materials for wind turbine applications is presented here. Requirements toward the wind turbine materials, loads, as well as available materials are reviewed. Apart from the traditional composites for wind turbine blades (glass fibers/epoxy matrix composites), natural composites, hybrid and nanoengineered composites are discussed. Manufacturing technologies for wind turbine composites, as well their testing and modelling approaches are reviewed
A 10-days heatwave around flowering superimposed on climate change conditions significantly affects production of 22 barley accessions
AbstractExtreme climate events as heatwaves, floods and storms cause acute changes in season variability influencing primary production and are very likely to increase in magnitude and/or frequency (IPCC, AR5, WGI)1,2.In the present study 22 primarily Nordic barley accessions were grown in four basic climate treatments of 1) 19/12°C (day/night) and 400ppm carbon dioxide concentration [CO2] mimicking ambient South Scandinavian summer conditions, 2) elevated temperature (+5°C day/night), 3) elevated [CO2] at 700ppm and 4) the combination of elevated temperature and [CO2]. Temperature and [CO2] were at levels representing a worst case scenario (∼RCP8.5, IPCC) at the end of the 21st century. A 10 day- heatwave of 33/22°C (day/night) was superimposed around the time of flowering on the basic climate treatments.The superimposed heatwave decreased overall grain yield in all combinations, however, vast variation in response was identified among accessions. In the two-factor treatment the decrease in grain yield varied from 2-80%. The heatwave caused the strongest overall effect in the treatment of elevated [CO2] decreasing grain yield by 48% and the least effect (35%) was observed under elevated temperature suggesting elevated temperature to have a priming effect. In all heatwave treatments allocation of biomass was changed, increasing aboveground vegetative biomass and decreasing grain yield as previously reported3.The treatment with the combination of elevated temperature, [CO2] and the superimposed heatwave may best represent a future climate scenario since more than one climate factor most likely will change at a time. From the basic ambient treatment to the two- factor treatment including heatwave, grain yield decreased 52%.Our study emphasizes the need for assessing the effects of extreme events under climate change conditions on numerous accessions in order to select appropriate genotypes for breeding future cultivars that can secure the primary production
Forskellige systemers forventede produktionsmæssige, økonomiske og miljømæssige resultater
Selv om der de sidste fire år har været en kraftig stigning i den økologiske svineproduktion i Danmark, udgør den økologiske slagtesvineproduktion mindre end 0,5% af den totale slagtesvineproduktion, og erfaringsgrundlaget for gennemførelsen af den økologiske svineproduktion er derfor spinkelt. I mange tilfælde er svineproduktionen indrettet således, at søerne holdes på friland, mens slagtesvinene året rundt opstaldes i stalde med tilhørende udearealer, og det er for sådanne systemer, at videngrundlaget er bedst
Neural Modeling and Control of Diesel Engine with Pollution Constraints
The paper describes a neural approach for modelling and control of a
turbocharged Diesel engine. A neural model, whose structure is mainly based on
some physical equations describing the engine behaviour, is built for the
rotation speed and the exhaust gas opacity. The model is composed of three
interconnected neural submodels, each of them constituting a nonlinear
multi-input single-output error model. The structural identification and the
parameter estimation from data gathered on a real engine are described. The
neural direct model is then used to determine a neural controller of the
engine, in a specialized training scheme minimising a multivariable criterion.
Simulations show the effect of the pollution constraint weighting on a
trajectory tracking of the engine speed. Neural networks, which are flexible
and parsimonious nonlinear black-box models, with universal approximation
capabilities, can accurately describe or control complex nonlinear systems,
with little a priori theoretical knowledge. The presented work extends optimal
neuro-control to the multivariable case and shows the flexibility of neural
optimisers. Considering the preliminary results, it appears that neural
networks can be used as embedded models for engine control, to satisfy the more
and more restricting pollutant emission legislation. Particularly, they are
able to model nonlinear dynamics and outperform during transients the control
schemes based on static mappings.Comment: 15 page
COVID-19 restrictions and fathers of infants in neonatal care.
This is a letter without an abstract
Ethical aspects of registry-based research in the Nordic countries
National health care registries in the Nordic countries share many attributes, but
different legal and ethical frameworks represent a challenge to promoting effective joint research.
Internationally, there is a lack of knowledge about how ethical matters are considered in Nordic
registry-based research, and a lack of knowledge about how Nordic ethics committees operate and
what is needed to obtain an approval. In this paper, we review ethical aspects of registry-based
research, the legal framework, the role of ethics review boards in the Nordic countries, and the
structure of the ethics application. We discuss the role of informed consent in registry-based
research and how to safeguard the integrity of study participants, including vulnerable subjects
and children. Our review also provides information on the different government agencies that
contribute registry-based data, and a list of the major health registries in Denmark, Finland,
Iceland, Norway, and Sweden. Both ethical values and conditions for registry-based research
are similar in the Nordic countries. While Denmark, Finland, Iceland, Norway, and Sweden have
chosen different legal frameworks, these differences can be resolved through mutual recognition
of ethical applications and by harmonizing the different systems, likely leading to increased
collaboration and enlarged studies
Maximum likelihood, parametric component separation and CMB B-mode detection in suborbital experiments
We investigate the performance of the parametric Maximum Likelihood component
separation method in the context of the CMB B-mode signal detection and its
characterization by small-scale CMB suborbital experiments. We consider
high-resolution (FWHM=8') balloon-borne and ground-based observatories mapping
low dust-contrast sky areas of 400 and 1000 square degrees, in three frequency
channels, 150, 250, 410 GHz, and 90, 150, 220 GHz, with sensitivity of order 1
to 10 micro-K per beam-size pixel. These are chosen to be representative of
some of the proposed, next-generation, bolometric experiments. We study the
residual foreground contributions left in the recovered CMB maps in the pixel
and harmonic domain and discuss their impact on a determination of the
tensor-to-scalar ratio, r. In particular, we find that the residuals derived
from the simulated data of the considered balloon-borne observatories are
sufficiently low not to be relevant for the B-mode science. However, the
ground-based observatories are in need of some external information to permit
satisfactory cleaning. We find that if such information is indeed available in
the latter case, both the ground-based and balloon-borne experiments can detect
the values of r as low as ~0.04 at 95% confidence level. The contribution of
the foreground residuals to these limits is found to be then subdominant and
these are driven by the statistical uncertainty due to CMB, including E-to-B
leakage, and noise. We emphasize that reaching such levels will require a
sufficient control of the level of systematic effects present in the data.Comment: 18 pages, 12 figures, 6 table
- …