80 research outputs found
Use of satellite erythemal UV products in analysing the global UV changes
Long term changes in solar UV radiation affect global bio-geochemistry and climate. The satellite-based dataset of TOMS (Total Ozone Monitoring System) and OMI (Ozone Monitoring Instrument) of erythemal UV product was applied for the first time to estimate the long-term ultraviolet (UV) changes at the global scale. The analysis of the uncertainty related to the different input information is presented. OMI and GOME-2 (Global Ozone Monitoring Experiment-2) products were compared in order to analyse the differences in the global UV distribution and their effect on the linear trend estimation. <br></br> The results showed that the differences in the inputs (mainly surface albedo and aerosol information) used in the retrieval, affect significantly the UV change calculation, pointing out the importance of using a consistent dataset when calculating long term UV changes. The areas where these differences played a major role were identified using global maps of monthly UV changes. Despite the uncertainties, significant positive UV changes (ranging from 0 to about 5 %/decade) were observed, with higher values in the Southern Hemisphere at mid-latitudes during spring-summer, where the largest ozone decrease was observed
Stainless steel weld metal designed to mitigate residual stresses
There have been considerable efforts to create welding consumables which on solid state phase transformation partly compensate for the stresses which develop when a constrained weld cools to ambient temperatures. All of these efforts have focused on structural steels which are ferritic. In the present work, alloy design methods have been used to create a stainless steel welding consumable which solidifies as δ ferrite, transforms almost entirely into austenite which then undergoes martensitic transformation at a low temperature of about 220◦C. At the same time, the carbon concentration has been kept to a minimum to avoid phenomena such as sensitisation. The measured mechanical properties, especially toughness, seem to be significantly better than commercially available martensitic stainless steel welding consumables, and it has been demonstrated that the use of the new alloy reduces distortion in the final joint
Binding energies of ground and isomeric states in neutron-rich ruthenium isotopes: measurements at JYFLTRAP and comparison to theory
We report on precision mass measurements of Ru performed with
the JYFLTRAP double Penning trap mass spectrometer at the Accelerator
Laboratory of University of Jyv\"askyl\"a. The phase-imaging
ion-cyclotron-resonance technique was used to resolve the ground and isomeric
states in Ru and enabled for the first time a measurement of the
isomer excitation energies, Ru keV and
Ru keV. The ground state of Ru was measured
using the time-of-flight ion-cyclotron-resonance technique. The new mass-excess
value for Ru is around 36 keV lower and 7 times more precise than the
previous literature value. With the more precise ground-state mass values, the
evolution of the two-neutron separation energies is further constrained and a
similar trend as predicted by the BSkG1 model is obtained up to the neutron
number .Comment: 12 pages, 9 figures, submitted to Physical Review
Validation of satellite-based noontime UVI with NDACC ground-based instruments: influence of topography, environment and satellite overpass time
Spectral solar UV radiation measurements are performed in France using three
spectroradiometers located at very different sites. One is installed in
Villeneuve d'Ascq, in the north of France (VDA). It is an urban site in a
topographically flat region. Another instrument is installed in Observatoire
de Haute-Provence, located in the southern French Alps (OHP). It is a rural
mountainous site. The third instrument is installed in Saint-Denis,
Réunion Island (SDR). It is a coastal urban site on a small mountainous
island in the southern tropics. The three instruments are affiliated with the
Network for the Detection of Atmospheric Composition Change (NDACC) and carry
out routine measurements to monitor the spectral solar UV radiation and
enable derivation of UV index (UVI). The ground-based UVI values observed at
solar noon are compared to similar quantities derived from the Ozone
Monitoring Instrument (OMI, onboard the Aura satellite) and the second Global
Ozone Monitoring Experiment (GOME-2, onboard the Metop-A satellite)
measurements for validation of these satellite-based products. The present
study concerns the period 2009–September 2012, date of the implementation of
a new OMI processing tool. The new version (v1.3) introduces a correction for
absorbing aerosols that were not considered in the old version (v1.2). Both
versions of the OMI UVI products were available before September 2012 and are
used to assess the improvement of the new processing tool. On average,
estimates from satellite instruments always overestimate surface UVI at solar
noon. Under cloudless conditions, the satellite-derived estimates of UVI
compare satisfactorily with ground-based data: the median relative bias is
less than 8 % at VDA and 4 % at SDR for both OMI v1.3 and GOME-2, and
about 6 % for OMI v1.3 and 2 % for GOME-2 at OHP. The correlation
between satellite-based and ground-based data is better at VDA and OHP (about
0.99) than at SDR (0.96) for both space-borne instruments. For all sky
conditions, the median relative biases are much larger, with large dispersion
for both instruments at all sites (VDA: about 12 %; OHP: 9 %; SDR:
11 %). Correlation between satellite-based and ground-based data is still
better at VDA and OHP (about 0.95) than at SDR (about 0.73) for both
satellite instruments. These results are explained considering the time of
overpass of the two satellites, which is far from solar noon, preventing a
good estimation of the cloud cover necessary for a good modelling of the UVI.
Site topography and environment are shown to have a non-significant
influence. At VDA and OHP, OMI v1.3 shows a significant improvement with
respect to v1.2, which did not account for absorbing aerosols
Nuclear charge radius of Al and its implication for V in the quark-mixing matrix
Collinear laser spectroscopy was performed on the isomer of the aluminium
isotope Al. The measured isotope shift to Al in the
3s^{2}3p\;^{2}\!P^\circ_{3/2} \rightarrow 3s^{2}4s\;^{2}\!S_{1/2} atomic
transition enabled the first experimental determination of the nuclear charge
radius of Al, resulting in =\qty{3.130\pm.015}{\femto\meter}. This
differs by 4.5 standard deviations from the extrapolated value used to
calculate the isospin-symmetry breaking corrections in the superallowed
decay of Al. Its corrected value, important for the
estimation of in the CKM matrix, is thus shifted by one standard
deviation to \qty{3071.4\pm1.0}{\second}.Comment: 5 pages, 2 figures, submitted to Phys. Rev. Let
Comparison of GOME-2/Metop total column water vapour with ground-based and in situ measurements
Total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde and Global Positioning System (GPS) observations. The comparisons are performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7.
The comparisons are performed for the period of January 2007–July 2013 (GOME-2A) and from December 2012 to July 2013 (GOME-2B). Radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by National Climatic Data Center (NCDC) and screened for soundings with incomplete tropospheric column. Ground-based GPS observations from COSMIC/SuomiNet network are used as the second independent data source.
Good general agreement between GOME-2 and the ground-based observations is found. The median relative difference of GOME-2 to radiosonde observations is −2.7% for GOME-2A and −0.3% for GOME-2B. Against GPS observations, the median relative differences are 4.9 and 3.2% for GOME-2A and B, respectively. For water vapour total columns below 10 kg m−2, large wet biases are observed, especially against GPS observations. Conversely, at values above 50 kg m−2, GOME-2 generally underestimates both ground-based observations
The effects of laser welding parameters on the microstructure of ferritic and duplex stainless steels welds
AbstractThis study is focused to determine empirically, which microstructural changes occur in ferritic and duplex stainless steels when heat input is controlled by welding parameters. Test welds were done autogenously bead-on-plate without shielding gas using 5 kW fiber laser. For comparison, some gas tungsten arc welds were made. Used test material were 1.4016 (AISI 430) and 1.4003 (low-carbon ferritic) type steels in ferritic steels group and 1.4162 (low-alloyed duplex, LDX2101) and 1.4462 (AISI 2205) type steels in duplex steels group. Microstructural changes in welds were identified and examined using optical metallographic methods
Operational surface UV radiation product from GOME-2 and AVHRR/3 data
The surface ultraviolet (UV) radiation product, version 1.20,
generated operationally in the framework of the Satellite
Application Facility on Ozone and Atmospheric Chemistry Monitoring
(O3M SAF) of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is described. The product is
based on the total ozone column derived from the measurements of the
second Global Ozone Monitoring Experiment (GOME-2) instrument aboard
EUMETSAT's polar orbiting meteorological operational (Metop)
satellites. Cloud cover is taken into account by retrieving
cloud optical depth from the channel 1 reflectance of the third
Advanced Very High-Resolution Radiometer (AVHRR/3) instrument aboard
both Metop in the morning orbit and Polar Orbiting Environmental Satellites (POES) of the National Oceanic and Atmospheric
Administration (NOAA) in the afternoon orbit. In addition,
more overpasses are used at high latitudes where the
swaths of consecutive orbits overlap. The input satellite data are
received from EUMETSAT's Multicast Distribution System (EUMETCast).
The surface UV product includes daily
maximum dose rates and integrated daily doses with different
biological weighting functions, integrated ultraviolet B (UVB) and ultraviolet A (UVA) radiation,
solar noon UV index and daily maximum photolysis frequencies of
ozone and nitrogen dioxide at the surface level. The quantities are
computed in a 0.5°×0.5° regular
latitude–longitude grid and stored as daily files in the
hierarchical data format (HDF5) within 2 weeks from sensing. The
product files are archived in the O3M SAF distributed archive and
can be ordered via the EUMETSAT Data Centre
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