2,595 research outputs found
A Data Flow Perspective for Business Process Integration
Business process integration has become prevalent as business is increasingly crossing organizational boundaries. While workflow technology is a standard solution for business process management, it is imperative for workflow management systems to provide effective and efficient support for collaboration. To address the issue of protecting organizationsâ competitive knowledge and private information while also enabling business-to-business (B2B) collaboration, past research has focused on customized public and private process design and structure correctness of the integrated workflow. However, data flow is important for business process integration because data is always sensitive when conducting inter-organizational business and data errors could still happen even given syntactically correct activity dependence. This paper presents a data flow perspective. It gives an approach to define a âpublic data setâ for each involved organization exemplifying the integrated workflow that is needed in order to be free from data anomalies e.g., missing data and redundant data errors
Effect of Al addition on microstructure of AZ91D
Casting is a net shape or near net shape forming process so work-hardening will not be applicable for improving properties of magnesium cast alloys. Grain refinement, solid-solution strengthening, precipitation hardening and specially designed heat treatment are the techniques used to enhance the properties of these alloys. This research focusses on grain refinement of magnesium alloy AZ91D, which is a widely used commercial cast alloy. Recently, Al-B based master alloys have shown potential in grain refining AZ91D. A comparative study of the grain refinement of AZ91D by addition of 0.02wt%B, 0.04wt%B, 0.1wt%B, 0.5wt%B and 1.0wt%B of A1-5B master alloy and equivalent amount of solute element aluminium is described in this paper. Hardness profile of AZ91D alloyed with boron and aluminium is compared
Inside-Out Planet Formation: VI. Oligarchic Coagulation of Planetesimals from a Pebble Ring?
Inside-Out Planet Formation (IOPF) is a theory addressing the origin of
Systems of Tightly-Packed Inner Planets (STIPs) via {\it in situ} formation and
growth of the planets. It predicts that a pebble ring is established at the
pressure maximum associated with the dead zone inner boundary (DZIB) with an
inner disk magnetorotational instability (MRI)-active region. Using direct
-body simulations, we study the collisional evolution of planetesimals
formed from such a pebble ring, in particular examining whether a single
dominant planet emerges. We consider a variety of models, including some in
which the planetesimals are continuing to grow via pebble accretion. We find
that the planetesimal ring undergoes oligarchic evolution, and typically turns
into 2 or 3 surviving oligarchs on nearly coplanar and circular orbits,
independent of the explored initial conditions or form of pebble accretion. The
most massive oligarchs typically consist of about of the total mass,
with the building-up process typically finishing within years.
However, a relatively massive secondary planet always remains with
of the mass of the primary. Such secondary planets have
properties that are inconsistent with the observed properties of the innermost
pairs of planets in STIPs. Thus, for IOPF to be a viable theory for STIP
formation, it needs to be shown how oligarchic growth of a relatively massive
secondary from the initial pebble ring can be avoided. We discuss some
potential additional physical processes that should be included in the modeling
and explored as next steps.Comment: 15 pages, 10 figures, accepted for publication in MNRA
Stability of exomoons around the Kepler transiting circumbinary planets
The Kepler mission has detected a number of transiting circumbinary planets
(CBPs). Although currently not detected, exomoons could be orbiting some of
these CBPs, and they might be suitable for harboring life. A necessary
condition for the existence of such exomoons is their long-term dynamical
stability. Here, we investigate the stability of exomoons around the Kepler
CBPs using numerical -body integrations. We determine regions of stability
and obtain stability maps in the (a_m,i_pm) plane, where a_m is the initial
exolunar semimajor axis with respect to the CBP, and i_pm is the initial
inclination of the orbit of the exomoon around the planet with respect to the
orbit of the planet around the stellar binary. Ignoring any dependence on i_pm,
for most Kepler CBPs the stability regions are well described by the location
of the 1:1 mean motion commensurability of the binary orbit with the orbit of
the moon around the CBP. This is related to a destabilizing effect of the
binary compared to the case if the binary were replaced by a single body, and
which is borne out by corresponding 3-body integrations. For high inclinations,
the evolution is dominated by Lidov-Kozai oscillations, which can bring moons
in dynamically stable orbits to close proximity within the CBP, triggering
strong interactions such as tidal evolution, tidal disruption, or direct
collisions. This suggests that there is a dearth of highly-inclined exomoons
around the Kepler CBPs, whereas coplanar exomoons are dynamically allowed.Comment: Accepted for publication by MNRAS. 12 pages, 7 figure
Linking the formation and fate of exo-Kuiper belts within solar system analogues
Abstract Escalating observations of exo-minor planets and their destroyed remnants both passing through the solar system and within white dwarf planetary systems motivate an understanding of the orbital history and fate of exo-Kuiper belts and planetesimal discs. Here we explore how the structure of a 40 â 1000 au annulus of planetesimals orbiting inside of a solar system analogue that is itself initially embedded within a stellar cluster environment varies as the star evolves through all of its stellar phases. We attempt this computationally challenging link in four parts: (1) by performing stellar cluster simulations lasting 100 Myr, (2) by making assumptions about the subsequent quiescent 11 Gyr main-sequence evolution, (3) by performing simulations throughout the giant branch phases of evolution, and (4) by making assumptions about the beltâs evolution during the white dwarf phase. Throughout these stages, we estimate the planetesimalsâ gravitational responses to analogues of the four solar system giant planets, as well as to collisional grinding, Galactic tides, stellar flybys, and stellar radiation. We find that the imprint of stellar cluster dynamics on the architecture of âł 100 km-sized exo-Kuiper belt planetesimals is retained throughout all phases of stellar evolution unless violent gravitational instabilities are triggered either (1) amongst the giant planets, or (2) due to a close (âȘ103 au) stellar flyby. In the absence of these instabilities, these minor planets simply double their semimajor axis while retaining their primordial post-cluster eccentricity and inclination distributions, with implications for the free-floating planetesimal population and metal-polluted white dwarfs
Galactic Tide and Local Stellar Perturbations on the Oort Cloud: Creation of Interstellar Comets
Comets in the Oort cloud evolve under the influence of internal and external
perturbations, such as giant planets, stellar passages, and the galactic tidal
field. We aim to study the dynamical evolution of the comets in the Oort cloud,
accounting for external perturbations (passing stars and the galactic tide). We
first construct an analytical model of stellar encounters. We find that
individual perturbations do not modify the dynamics of the comets in the cloud
unless very close (< 0.5pc) encounters occur. Using proper motions, parallaxes,
and radial velocities from Gaia DR2, we construct an astrometric catalogue of
14,659 stars that are within 50pc from the Sun. For all these stars we
calculate the time and the closest distance to the Sun. We find that the
cumulative effect of relatively distant ( pc) passing stars can perturb
the comets in the Oort cloud. Finally, we study the dynamical evolution of the
comets in the Oort cloud under the influence of multiple stellar encounters
within 2.5pc from the Sun and the galactic tidal field over Myr. We
considered two models for the Oort cloud, compact (a 0.25 pc) and
extended (a pc). We find that the cumulative effect of stellar
encounters is the major perturber of the Oort cloud for a compact configuration
while for the extended, the galactic tide is the major perturber. In both
cases, the effect of passing stars and the galactic tide raises the semi-major
axis of \% of the comets at the edge of the cloud up to interstellar
regions (pc). This leads to the creation of transitional interstellar
comets, which might become interstellar objects due to external perturbations.
This raises the question about the existence of a cloud of objects in the
interstellar space which might overlap with our Oort cloud if we consider that
other planetary systems face similar processes for the ejection of comets.Comment: 13 pages, 13 figures, accepted for publication in Astronomy &
Astrophysic
Opportunities for lattice QCD in quark and lepton flavor physics
This document is one of a series of whitepapers from the USQCD collaboration.
Here, we discuss opportunities for lattice QCD in quark and lepton flavor
physics. New data generated at Belle II, LHCb, BES III, NA62, KOTO, and
Fermilab E989, combined with precise calculations of the relevant hadronic
physics, may reveal what lies beyond the Standard Model. We outline a path
toward improvements of the precision of existing lattice-QCD calculations and
discuss groundbreaking new methods that allow lattice QCD to access new
observables.Comment: USQCD whitepape
Nanostructure Evolution of Magnetron Sputtered Hydrogenated Silicon Thin Films
Hydrogenated silicon (Si:H) thin films have been prepared by radio frequency (RF) magnetron sputtering. The effect of hydrogen gas concentration during sputtering on the resultant film structural and optical properties has been investigated by real time spectroscopic ellipsometry (RTSE) and grazing incidence x-ray diffraction (GIXRD). The analysis of in-situ RTSE data collected during sputter deposition tracks the evolution of surface roughness and film bulk layer thickness with time. Growth evolution diagrams depicting amorphous, nanocrystalline and mixed-phase regions for low and high deposition rate Si:H are constructed and the effects of process parameter (hydrogen gas concentration, total pressure and RF power) variations on the deposition rate have been qualified. Virtual interface analysis of RTSE data provides nanocrystalline volume fraction depth profiles in the mixed-phase growth regime. GIXRD measurements show the presence of (111) and (220) oriented crystallites. Vibrational mode absorption features from Si-Hn bonding configurations at 590, 640, 2000 and 2090 cm-1 are obtained by ex-situ infrared spectroscopic ellipsometry. Hydrogen incorporation decreases as films transition from amorphous to nanocrystalline phases with increasing hydrogen gas concentration during sputtering. Published by AIP Publishing
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