714 research outputs found
Revisiting the martensite/ferrite interface damage initiation mechanism:The key role of substructure boundary sliding
Martensite/ferrite (M/F) interface damage plays a critical role in controlling failure of dual-phase (DP) steels and is commonly understood to originate from the large phase contrast between martensite and ferrite. This however conflicts with a few, recent observations, showing that considerable M/F interface damage initiation is often accompanied by apparent martensite island plasticity and weak M/F strain partitioning. In fact, martensite has a complex hierarchical structure which induces a strongly heterogeneous and orientation-dependent plastic response. Depending on the local stress state, (lath) martensite is presumed to be hard to deform based on common understanding. However, when favourably oriented, substructure boundary sliding can be triggered at a resolved shear stress which is comparable to that of ferrite. Moreover, careful measurements of the M/F interface structure indicate the occurrence of sharp martensite wedges protruding into the ferrite and clear steps in correspondence with lath boundaries, constituting a jagged M/F interfacial morphology that may have a large effect on the M/F interface behaviour. By taking into account the substructure and morphology features, which are usually overlooked in the literature, this contribution re-examines the M/F interface damage initiation mechanism. A systematic study is performed, which accounts for different loading conditions, phase contrasts, residual stresses/strains resulting from the preceding martensitic phase transformation, as well as the possible M/F interfacial morphologies. Crystal plasticity simulations are conducted to include inter-lath retained austenite (RA) films enabling the substructure boundary sliding. The results show that the substructure boundary sliding, which is the most favourable plastic deformation mode of lath martensite, can trigger M/F interface damage and hence control the failure behaviour of DP steels. The present finding may change the way in which M/F interface damage initiation is understood as a critical failure mechanism in DP steels
Verantwoorde en communiceerbare argumenten bij biologische producten: milieueffecten
Het project ‘Verantwoorde en communiceerbare argumenten bij biologische producten’ bestaat uit vijf deelprojecten/aandachtsgebieden: veiligheid, gezondheid en smaak; dierenwelzijn; milieu; biodiversiteit, natuur en landschap; klimaat, broeikasgassen en waterberging. In dit rapport worden de onderdelen milieu, eindige grondstoffen, broeikasgassen en watergebruik behandel
Astro-WISE: Chaining to the Universe
The recent explosion of recorded digital data and its processed derivatives
threatens to overwhelm researchers when analysing their experimental data or
when looking up data items in archives and file systems. While current hardware
developments allow to acquire, process and store 100s of terabytes of data at
the cost of a modern sports car, the software systems to handle these data are
lagging behind. This general problem is recognized and addressed by various
scientific communities, e.g., DATAGRID/EGEE federates compute and storage power
over the high-energy physical community, while the astronomical community is
building an Internet geared Virtual Observatory, connecting archival data.
These large projects either focus on a specific distribution aspect or aim to
connect many sub-communities and have a relatively long trajectory for setting
standards and a common layer. Here, we report "first light" of a very different
solution to the problem initiated by a smaller astronomical IT community. It
provides the abstract "scientific information layer" which integrates
distributed scientific analysis with distributed processing and federated
archiving and publishing. By designing new abstractions and mixing in old ones,
a Science Information System with fully scalable cornerstones has been
achieved, transforming data systems into knowledge systems. This break-through
is facilitated by the full end-to-end linking of all dependent data items,
which allows full backward chaining from the observer/researcher to the
experiment. Key is the notion that information is intrinsic in nature and thus
is the data acquired by a scientific experiment. The new abstraction is that
software systems guide the user to that intrinsic information by forcing full
backward and forward chaining in the data modelling.Comment: To be published in ADASS XVI ASP Conference Series, 2006, R. Shaw, F.
Hill and D. Bell, ed
Deep-water macroalgae from the Canary Islands: new records and biogeographical relationships
Due to the geographical location and paleobiogeography of the Canary Islands, the
seaweed flora contains macroalgae with different distributional patterns. In this contribution, the biogeographical relations of several new records of deep-water macroalgae recently collected around the Canarian archipelago are discussed. These are Bryopsidella neglecta (Berthotd) Rietema,Discosporangium mesarthrocarpum (Meneghini) Hauck, Hincksia onslowensis (Amsler et Kapraun)P.C. Silva, Syringoderma floridana Henry, Peyssonnelia harveyana J. Agardh, Cryptonemia seminervis(C. Agardh) J. Agardh, Botryodadia wynnei Ballantine, Gloiocladia blomquistii (Searles) R. E.Norris, PIahchrysis peltata (W. R. Taylor) P. Huv4 et H. Huv4, Leptofauchea brasiliensis Joly, and Sarcodiotheca divaricata W. R. Taylor. These new records, especially those in the Florideophyceae,support the strong affinity of the Canary Islands seaweed flora with the warm-temperate Mediterranean-Atlantic region. Some species are recorded for the first time from the east coast of the Atlantic Ocean, enhancing the biogeographic relations of the Canarian marine flora with that of the western Atlantic regions
The stellar content, metallicity and ionization structure of HII regions
Observations of infrared fine-structure lines provide direct information on
the metallicity and ionization structure of HII regions and indirectly on the
hardness of the radiation field ionizing these nebulae. We have analyzed a
sample of Galactic and Magellanic Cloud HII regions observed by the Infrared
Space Observatory (ISO) to examine the interplay between stellar content,
metallicity and the ionization structure of HII regions. The observed
[SIV]10.5/[SIII]18.7 mum and [NeIII]15.5/[NeII]12.8 mum line ratios are shown
to be highly correlated over more than two orders of magnitude. We have
compared the observed line ratios to the results of photoionization models
using different stellar energy distributions. The derived characteristics of
the ionizing star depend critically on the adopted stellar model as well as the
(stellar) metallicity. We have compared the stellar effective temperatures
derived from these model studies for a few well-studied HII regions with
published direct spectroscopic determinations of the spectral type of the
ionizing stars. This comparison supports our interpretation that stellar and
nebular metallicity influences the observed infrared ionic line ratios. We can
explain the observed increase in degree of ionization, as traced by the
[SIV]\[SIII] and [NeIII]\[NeII] line ratios, by the hardening of the radiation
field due to the decrease of metallicity. The implications of our results for
the determination of the ages of starbursts in starburst galaxies are assessed.Comment: 9 pages; accepted for publication in A&A; figure 3 modifie
Effects of competition on pattern formation in the rock-paper-scissors game
We investigate the impact of cyclic competition on pattern formation in the
rock-paper-scissors game. By separately considering random and prepared initial
conditions, we observe a critical influence of the competition rate on the
stability of spiral waves and on the emergence of biodiversity. In particular,
while increasing values of promote biodiversity, they may act detrimental
on spatial pattern formation. For random initial conditions, we observe a phase
transition from biodiversity to an absorbing phase, whereby the critical value
of mobility grows linearly with increasing values of on a log-log scale,
but then saturates as becomes large. For prepared initial conditions, we
observe the formation of single-armed spirals, but only for values of that
are below a critical value. Once above, the spirals break up and form
disordered spatial structures, mainly because of the percolation of vacant
sites. Thus, there exists a critical value of the competition rate for
stable single-armed spirals in finite populations. Importantly though,
increases with increasing system size, because noise reinforces the
disintegration of ordered patterns. In addition, we also find that
increases with the mobility. These phenomena are reproduced by a deterministic
model that is based on nonlinear partial differential equations. Our findings
indicate that competition is vital for the sustenance of biodiversity and
emergence of pattern formation in ecosystems governed by cyclical interactions.Comment: 7 two-column pages, 7 figures; accepted for publication in Physical
Review
Global Phylogenomic Assessment of \u3ci\u3eLeptoseris\u3c/i\u3e and \u3ci\u3eAgaricia\u3c/i\u3e Reveals Substantial Undescibed Diversity at Mesophotic Depths
Background: Mesophotic coral communities are increasingly gaining attention for the unique biological diversity they host, exemplified by the numerous mesophotic fish species that continue to be discovered. In contrast, many of the photosynthetic scleractinian corals observed at mesophotic depths are assumed to be depth-generalists, with very few species characterised as mesophotic-specialists. This presumed lack of a specialised community remains largely untested, as phylogenetic studies on corals have rarely included mesophotic samples and have long suffered from resolution issues associated with traditional sequence markers.
Results: Here, we used reduced-representation genome sequencing to conduct a phylogenomic assessment of the two dominant mesophotic genera of plating corals in the Indo-Pacific and Western Atlantic, respectively, Leptoseris and Agaricia. While these genome-wide phylogenies broadly corroborated the morphological taxonomy, they also exposed deep divergences within the two genera and undescribed diversity across the current taxonomic species. Five of the eight focal species consisted of at least two sympatric and genetically distinct lineages, which were consistently detected across different methods.
Conclusions: The repeated observation of genetically divergent lineages associated with mesophotic depths highlights that there may be many more mesophotic-specialist coral species than currently acknowledged and that an urgent assessment of this largely unstudied biological diversity is warranted
Совершенствование механизмов формирования доходов бюджета АРК
Целью нашей работы является исследование механизмов формирования доходов бюджета Автономной Республики Крым и разработка мероприятий по их совершенствованию
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