3,031 research outputs found
The NBS: Processing/Microstructure/Property Relationships in 2024 Aluminum Alloy Plates
As received plates of 2024 aluminum alloy were examined. Topics covered include: solidification segregation studies; microsegregation and macrosegregation in laboratory and commercially cast ingots; C-curves and nondestructive evaluation; time-temperature precipitation diagrams and the relationships between mechanical properties and NDE measurements; transmission electron microscopy studies; the relationship between microstructure and properties; ultrasonic characterization; eddy-current conductivity characterization; the study of aging process by means of dynamic eddy current measurements; and Heat flow-property predictions, property degradations due to improve quench from the solution heat treatment temperature
Solar-like oscillations in red giants observed with Kepler: comparison of global oscillation parameters from different methods
The large number of stars for which uninterrupted high-precision photometric
timeseries data are being collected with \textit{Kepler} and CoRoT initiated
the development of automated methods to analyse the stochastically excited
oscillations in main-sequence, subgiant and red-giant stars. Aims: We
investigate the differences in results for global oscillation parameters of G
and K red-giant stars due to different methods and definitions. We also
investigate uncertainties originating from the stochastic nature of the
oscillations. Methods: For this investigation we use Kepler data obtained
during the first four months of operation. These data have been analysed by
different groups using already published methods and the results are compared.
We also performed simulations to investigate the uncertainty on the resulting
parameters due to different realizations of the stochastic signal. Results: We
obtain results for the frequency of maximum oscillation power (nu_max) and the
mean large separation () from different methods for over one thousand
red-giant stars. The results for these parameters agree within a few percent
and seem therefore robust to the different analysis methods and definitions
used here. The uncertainties for nu_max and due to differences in
realization noise are not negligible and should be taken into account when
using these results for stellar modelling.Comment: 11 pages, 9 Figures and 7 tables, accepted for publication in
Astronomy and Astrophysic
The most storage economical Runge-Kutta methods for the solution of large systems of coupled first-order differential equations
AbstractIt is shown how the attainable minimum for the memory requirements of Runge-Kutta methods can be realised for methods of the third order. These economisable third order methods belong to a one parameter sub-family from which two particular members with low error bound are selected
Mandate-driven networking eco-system : a paradigm shift in end-to-end communications
The wireless industry is driven by key stakeholders that follow a holistic approach of "one-system-fits-all" that leads to moving network functionality of meeting stringent End-to-End (E2E) communication requirements towards the core and cloud infrastructures. This trend is limiting smaller and new players for bringing in new and novel solutions. For meeting these E2E requirements, tenants and end-users need to be active players for bringing their needs and innovations. Driving E2E communication not only in terms of quality of service (QoS) but also overall carbon footprint and spectrum efficiency from one specific community may lead to undesirable simplifications and a higher level of abstraction of other network segments may lead to sub-optimal operations. Based on this, the paper presents a paradigm shift that will enlarge the role of wireless innovation at academia, Small and Medium-sized Enterprises (SME)'s, industries and start-ups while taking into account decentralized mandate-driven intelligence in E2E communications
Characterisation of red-giant stars in the public Kepler data
The first public release of long-cadence stellar photometric data collected
by the NASA Kepler mission has now been made available. In this paper we
characterise the red-giant (G-K) stars in this large sample in terms of their
solar-like oscillations. We use published methods and well-known scaling
relations in the analysis. Just over 70% of the red giants in the sample show
detectable solar-like oscillations, and from these oscillations we are able to
estimate the fundamental properties of the stars. This asteroseismic analysis
reveals different populations: low-luminosity H-shell burning red-giant branch
stars, cool high-luminosity red giants on the red-giant branch and He-core
burning clump and secondary-clump giants.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society Main Journa
Old puzzle, new insights: a lithium rich giant quietly burning helium in its core
About 1% of giant stars have been shown to have large surface Li abundances,
which is unexpected according to standard stellar evolution models. Several
scenarios for lithium production have been proposed, but it is still unclear
why these Li-rich giants exist. A missing piece in this puzzle is the knowledge
of the exact stage of evolution of these stars. Using low-and-high-resolution
spectroscopic observations, we have undertaken a survey of lithium-rich giants
in the Kepler field. In this letter, we report the finding of the first
confirmed Li-rich core-helium-burning giant, as revealed by asteroseismic
analysis. The evolutionary timescales constrained by its mass suggest that
Li-production most likely took place through non-canonical mixing at the
RGB-tip, possibly during the helium flash.Comment: 16 pages, 4 figures, 1 table, accepted in ApJ Letter
On-chip integrated amplifiers and lasers utilizing rare-earth-ion activation
This contribution reviews our recent results on rare-earth-ion-doped integrated amplifiers and lasers. We have concentrated our efforts on complex-doped polymers, amorphous Al2O3, and crystalline potassium double tungstates
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