4,317 research outputs found
Commitment system theory:The evolving structure of commitments to multiple targets
Employees form commitments to multiple targets and the coordination of those multiple commitments has become a ubiquitous part of the contemporary workplace. However, commitments are still largely studied in isolation or in one-off combinations and current commitment theory does not account for the dynamic interrelationships among multiple commitments. To address this deficiency, we propose commitment system theory (CST). We draw upon general systems theory to depict commitment systems as malleable and interconnected structures. We present the defining elements by which commitment systems can be described and studied, develop theory regarding when commitment systems will diverge or converge over time, and discuss how taking a systems perspective resolves discrepant findings in the literature. Specifically, CST advances the commitment literature by offering an alternative perspective to explain how commitments behave as parts of larger systems. Specifically, CST accounts for (a) why and when commitments have synergistic, neutral, or conflicting inter-relationships and (b) the temporal dynamics of those inter-relationships as commitments develop, change, and dissipate. CST thus offers a new vocabulary and conceptual “toolkit” for understanding the evolving structure of commitments to multiple targets
Infrared and visual lunar occultations measurements of stellar diameters and new binary stars detections at the Calar Alto 1.5m telescope
We present a program of routine lunar occultations, at optical and near-IR
wavelengths, recently started at the 1.5m Spanish telescope at the Calar Alto
Observatory. Both a CCD and an infrared array detector are used. The program is
aimed mainly at the detection and investigation of binary systems, although
results in other areas of stellar research are also anticipated.
Occultations are reported for a total of 40 stars. Among these, SAO 164567,
SAO 78258 and AG+24 788 have been discovered to be binaries, with projected
separations as small as 0.006". Furthermore, binarity is suspected in the case
of SAO 78119 and SAO 79251. Additionally, the angular diameter of the late-type
giant 30 Psc and of the infrared star V349 Gem have been accurately measured,
this latter for the first time.
We finally evaluate the instrumentation performance in terms of limiting
magnitude and angular resolution, and discuss applications to larger
telescopes.Comment: 15 pages, 3 figures, LaTeX, uses aa.cls. Accepted for publication in
A&
Nuclear break-up of 11Be
The break-up of 11Be was studied at 41AMeV using a secondary beam of 11Be
from the GANIL facility on a 48Ti target by measuring correlations between the
10Be core, the emitted neutrons and gamma rays. The nuclear break-up leading to
the emission of a neutron at large angle in the laboratory frame is identified
with the towing mode through its characteristic n-fragment correlation. The
experimental spectra are compared with a model where the time dependent
Schrodinger equation (TDSE) is solved for the neutron initially in the 11 Be. A
good agreement is found between experiment and theory for the shapes of neutron
experimental energies and angular distributions. The spectroscopic factor of
the 2s orbital is tentatively extracted to be 0.46+-0.15. The neutron emission
from the 1p and 1d orbitals is also studied
Electronic state spectroscopy of methyl formate probed by high resolution VUV photoabsorption, He(I) photoelectron spectroscopy and ab initio calculations
The first ab initio calculations of the vertical excitation energies and oscillator strengths are
presented for the neutral electronic transitions of methyl formate, C2H4O2. The highest resolution VUV photoabsorption spectrum of the molecule yet reported is presented over the wavelength
range 115 to 310 nm (10.8 to 4.0 eV) revealing several new spectral features. Valence and Rydberg transitions and their associated vibronic series, observed in the photoabsorption spectrum, have been assigned in accordance with new theoretical results. The calculations have
been carried out to determine the excitation energies of the lowest energy ionic states of methyl formate and are compared with a newly recorded He(I) photoelectron spectrum (10.4 to 17.0 eV). New vibrational structure is observed in the first photoelectron band. The photoabsorption
cross-sections have been used to calculate the photolysis lifetime of methyl formate in the upper
stratosphere (20-50 km)
Test of the Running of in Decays
The decay rate into hadrons of invariant mass smaller than
can be calculated in QCD assuming global
quark--hadron duality. It is shown that this assumption holds for
~GeV. From measurements of the hadronic mass distribution, the
running coupling constant is extracted in the range
0.7~GeV. At , the result is
. The running of is in good
agreement with the QCD prediction.Comment: 9 pages, 3 figures appended; shortened version with new figures, to
appear in Physical Review Letters (April 1996
Gamma-Ray Burst Sequences in Hardness Ratio-Peak Energy Plane
The narrowness of the distribution of the peak energy of
spectrum of gamma-ray bursts (GRBs) and the unification of GRB population are
great puzzles yet to be solved. We investigate the two puzzles based on the
global spectral behaviors of different GRB population in the
plane (HR the spectral hardness ratio) with BATSE and HETE-2 observations. It
is found that long GRBs and XRFs observed by HETE-2 seem to follow the same
sequence in the plane, with the XRFs at the low end of this
sequence. The long and short GRBs observed by BATSE follow significantly
different sequences in the plane, with most of the short GRBs
having a larger hardness ratio than the long GRBs at a given .
These results indicate that the global spectral behaviors of the long GRB
sample and the XRF sample are similar, while that of short GRBs is different.
The short GRBs seem to be a unique subclass of GRBs, and they are not the
higher energy extension of the long GRBs (abridged).Comment: 9 pages, 3 figure
Value Iteration for Long-run Average Reward in Markov Decision Processes
Markov decision processes (MDPs) are standard models for probabilistic
systems with non-deterministic behaviours. Long-run average rewards provide a
mathematically elegant formalism for expressing long term performance. Value
iteration (VI) is one of the simplest and most efficient algorithmic approaches
to MDPs with other properties, such as reachability objectives. Unfortunately,
a naive extension of VI does not work for MDPs with long-run average rewards,
as there is no known stopping criterion. In this work our contributions are
threefold. (1) We refute a conjecture related to stopping criteria for MDPs
with long-run average rewards. (2) We present two practical algorithms for MDPs
with long-run average rewards based on VI. First, we show that a combination of
applying VI locally for each maximal end-component (MEC) and VI for
reachability objectives can provide approximation guarantees. Second, extending
the above approach with a simulation-guided on-demand variant of VI, we present
an anytime algorithm that is able to deal with very large models. (3) Finally,
we present experimental results showing that our methods significantly
outperform the standard approaches on several benchmarks
Chemical enrichment and star formation in the Milky Way disk III. Chemodynamical constraints
In this paper, we investigate some chemokinematical properties of the Milky
Way disk, by using a sample composed by 424 late-type dwarfs. We show that the
velocity dispersion of a stellar group correlates with the age of this group,
according to a law proportional to t^0.26, where t is the age of the stellar
group. The temporal evolution of the vertex deviation is considered in detail.
It is shown that the vertex deviation does not seem to depend strongly on the
age of the stellar group. Previous studies in the literature seem to not have
found it due to the use of statistical ages for stellar groups, rather than
individual ages. The possibility to use the orbital parameters of a star to
derive information about its birthplace is investigated, and we show that the
mean galactocentric radius is likely to be the most reliable stellar birthplace
indicator. However, this information cannot be presently used to derive radial
evolutionary constraints, due to an intrinsic bias present in all samples
constructed from nearby stars. An extensive discussion of the secular and
stochastic heating mechanisms commonly invoked to explain the age-velocity
dispersion relation is presented. We suggest that the age-velocity dispersion
relation could reflect the gradual decrease in the turbulent velocity
dispersion from which disk stars form, a suggestion originally made by Tinsley
and Larson (1978) and supported by several more recent disk evolution
calculations. A test to distinguish between the two types of models using
high-redshift galaxies is proposed.Comment: 20 pages, 10 encapsulated postscript figures, LaTeX, uses Astronomy
and Astrophysics macro aa.cls, graphicx package, to be published in Astronomy
and Astrophysics (2004), Also available at:
http://www.astro.iag.usp.br/~macie
Enhanced error estimator based on a nearly equilibrated moving least squares recovery technique for FEM and XFEM
In this paper a new technique aimed to obtain accurate estimates of the error
in energy norm using a moving least squares (MLS) recovery-based procedure is
presented. We explore the capabilities of a recovery technique based on an
enhanced MLS fitting, which directly provides continuous interpolated fields,
to obtain estimates of the error in energy norm as an alternative to the
superconvergent patch recovery (SPR). Boundary equilibrium is enforced using a
nearest point approach that modifies the MLS functional. Lagrange multipliers
are used to impose a nearly exact satisfaction of the internal equilibrium
equation. The numerical results show the high accuracy of the proposed error
estimator
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