1,792 research outputs found
Metamodel-based model conformance and multiview consistency checking
Model-driven development, using languages such as UML and BON, often makes use of multiple diagrams (e.g., class and sequence diagrams) when modeling systems. These diagrams, presenting different views of a system of interest, may be inconsistent. A metamodel provides a unifying framework in which to ensure and check consistency, while at the same time providing the means to distinguish between valid and invalid models, that is, conformance. Two formal specifications of the metamodel for an object-oriented modeling language are presented, and it is shown how to use these specifications for model conformance and multiview consistency checking. Comparisons are made in terms of completeness and the level of automation each provide for checking multiview consistency and model conformance. The lessons learned from applying formal techniques to the problems of metamodeling, model conformance, and multiview consistency checking are summarized
Pilot and Controller Workload and Situation Awareness with Three Traffic Management Concept
This paper reports on workload and situation awareness of pilots and controllers participating in a human-in-the-loop simulation using three different distributed air-ground traffic management concepts. Eight experimental pilots started the scenario in an en-route phase of flight and were asked to avoid convective weather while performing spacing and merging tasks along with a continuous descent approach (CDA) into Louisville Standiford Airport (SDF). Two controllers managed the sectors through which the pilots flew, with one managing a sector that included the Top of Descent, and the other managing a sector that included the merge point for arrival into SDF. At 3-minute intervals in the scenario, pilots and controllers were probed on their workload or situation awareness. We employed one of three concepts of operation that distributed separation responsibility across human controllers, pilots, and automation to measure changes in operator situation awareness and workload. We found that when pilots were responsible for separation, they had higher levels of awareness, but not necessarily higher levels of workload. When controllers are responsible and actively engaged, they showed higher workload levels compared to pilots and changes in awareness that were dependent on sector characteristics
Derivation of FEO Abundances in Lunar Pyroclastic Deposits Using Diviner
Telescopic observations and orbital images of the Moon reveal at least 75 lunar pyroclastic deposits (LPDs), interpreted as the products of explosive volcanic eruptions [1]. The deposits are understood to be composed primarily of sub-millimeter beads of basaltic composition, ranging from glassy to partially-crystallized [2]. Delano [3] documented 25 distinct pyroclastic bead compositions in lunar soil samples, with a range of FeO abundances from 16.5 - 24.7 wt%. Green glasses generally have lower FeO abundances and red, yellow, and orange glasses generally have higher FeO abundances. The current study employs data from the Diviner Lunar Radiometer Experiment onboard the Lunar Reconnaissance Orbiter (LRO) to derive the FeO compositions of glasses from unsampled lunar pyroclastic deposits. The pyroclastic glasses are the deepest-sourced and most primitive basalts on the Moon [4]. Recent analyses have documented the presence of water in these glasses, demonstrating that the lunar interior is considerably more volatile-rich than previously understood [5]. Experiments have shown that the iron-rich pyroclastic glasses release the highest percentage of oxygen of any Apollo soils, making these deposits promising lunar resources [6]
Situation Awareness, Workload, and Performance in Midterm Nextgen: Effect of Dynamic Variations in Aircraft Equipage Levels
NextGen changes in air traffic management promise to bring many benefits to the current airspace system, but these changes must be evaluated for their impact on mid-term air traffic management in which mixed-equipage is certain. We examined mixed equipage environments in which the equipage levels changed over the course of the scenario to reflect changes in sector characteristic over the course of a day or controller’s work shift. Six retired ATCs managed mixed-equipage traffic that either began with low levels of NextGen equipped aircraft and increased midway through the scenario or vice-versa. These were compared to a scenario in which the equipage mix was held constant. ATC performance, workload and situation awareness were affected differently by these scenarios
Linking Dynamical and Thermal Models of Ultrarelativistic Nuclear Scattering
To analyse ultrarelativistic nuclear interactions, usually either dynamical
models like the string model are employed, or a thermal treatment based on
hadrons or quarks is applied. String models encounter problems due to high
string densities, thermal approaches are too simplistic considering only
average distributions, ignoring fluctuations. We propose a completely new
approach, providing a link between the two treatments, and avoiding their main
shortcomings: based on the string model, connected regions of high energy
density are identified for single events, such regions referred to as quark
matter droplets. Each individual droplet hadronizes instantaneously according
to the available n-body phase space. Due to the huge number of possible hadron
configurations, special Monte Carlo techniques have been developed to calculate
this disintegration.Comment: Complete paper enclosed as postscript file (uuencoded
Syntactic Markovian Bisimulation for Chemical Reaction Networks
In chemical reaction networks (CRNs) with stochastic semantics based on
continuous-time Markov chains (CTMCs), the typically large populations of
species cause combinatorially large state spaces. This makes the analysis very
difficult in practice and represents the major bottleneck for the applicability
of minimization techniques based, for instance, on lumpability. In this paper
we present syntactic Markovian bisimulation (SMB), a notion of bisimulation
developed in the Larsen-Skou style of probabilistic bisimulation, defined over
the structure of a CRN rather than over its underlying CTMC. SMB identifies a
lumpable partition of the CTMC state space a priori, in the sense that it is an
equivalence relation over species implying that two CTMC states are lumpable
when they are invariant with respect to the total population of species within
the same equivalence class. We develop an efficient partition-refinement
algorithm which computes the largest SMB of a CRN in polynomial time in the
number of species and reactions. We also provide an algorithm for obtaining a
quotient network from an SMB that induces the lumped CTMC directly, thus
avoiding the generation of the state space of the original CRN altogether. In
practice, we show that SMB allows significant reductions in a number of models
from the literature. Finally, we study SMB with respect to the deterministic
semantics of CRNs based on ordinary differential equations (ODEs), where each
equation gives the time-course evolution of the concentration of a species. SMB
implies forward CRN bisimulation, a recently developed behavioral notion of
equivalence for the ODE semantics, in an analogous sense: it yields a smaller
ODE system that keeps track of the sums of the solutions for equivalent
species.Comment: Extended version (with proofs), of the corresponding paper published
at KimFest 2017 (http://kimfest.cs.aau.dk/
Neutralino, axion and axino cold dark matter in minimal, hypercharged and gaugino AMSB
Supersymmetric models based on anomaly-mediated SUSY breaking (AMSB)
generally give rise to a neutral wino as a WIMP cold dark matter (CDM)
candidate, whose thermal abundance is well below measured values. Here, we
investigate four scenarios to reconcile AMSB dark matter with the measured
abundance: 1. non-thermal wino production due to decays of scalar fields ({\it
e.g} moduli), 2. non-thermal wino production due to decays of gravitinos, 3.
non-thermal wino production due to heavy axino decays, and 4. the case of an
axino LSP, where the bulk of CDM is made up of axions and thermally produced
axinos. In cases 1 and 2, we expect wino CDM to constitute the entire measured
DM abundance, and we investigate wino-like WIMP direct and indirect detection
rates. Wino direct detection rates can be large, and more importantly, are
bounded from below, so that ton-scale noble liquid detectors should access all
of parameter space for m_{\tz_1}\alt 500 GeV. Indirect wino detection rates via
neutrino telescopes and space-based cosmic ray detectors can also be large. In
case 3, the DM would consist of an axion plus wino admixture, whose exact
proportions are very model dependent. In this case, it is possible that both an
axion and a wino-like WIMP could be detected experimentally. In case 4., we
calculate the re-heat temperature of the universe after inflation. In this
case, no direct or indirect WIMP signals should be seen, although direct
detection of relic axions may be possible. For each DM scenario, we show
results for the minimal AMSB model, as well as for the hypercharged and gaugino
AMSB models.Comment: 29 pages including 13 figure
Spectral Statistics in Chiral-Orthogonal Disordered Systems
We describe the singularities in the averaged density of states and the
corresponding statistics of the energy levels in two- (2D) and
three-dimensional (3D) chiral symmetric and time-reversal invariant disordered
systems, realized in bipartite lattices with real off-diagonal disorder. For
off-diagonal disorder of zero mean we obtain a singular density of states in 2D
which becomes much less pronounced in 3D, while the level-statistics can be
described by semi-Poisson distribution with mostly critical fractal states in
2D and Wigner surmise with mostly delocalized states in 3D. For logarithmic
off-diagonal disorder of large strength we find indistinguishable behavior from
ordinary disorder with strong localization in any dimension but in addition
one-dimensional Dyson-like asymptotic spectral singularities. The
off-diagonal disorder is also shown to enhance the propagation of two
interacting particles similarly to systems with diagonal disorder. Although
disordered models with chiral symmetry differ from non-chiral ones due to the
presence of spectral singularities, both share the same qualitative
localization properties except at the chiral symmetry point E=0 which is
critical.Comment: 13 pages, Revtex file, 8 postscript files. It will appear in the
special edition of J. Phys. A for Random Matrix Theor
Signal and Backgrounds for the Single Production of Scalar and Vector Leptoquarks at the LHC
We perform a detailed analysis of the potentiality of the CERN Large Hadron
Collider to study the single production of leptoquarks via
leptoquark , with generated by the splitting of photons
radiated by the protons. Working with the most general
invariant effective lagrangian for scalar and vector leptoquarks, we analyze in
detail the leptoquark signals and backgrounds that lead to a final state
containing an and a hard jet with approximately balanced transverse
momenta. Our results indicate that the LHC will be able to discover leptoquarks
with masses up to 2--3 TeV, depending on their type, for Yukawa couplings of
the order of the electromagnetic one.Comment: Revtex, 23 pages, 11 postscript files. Uses axodraw.sty (included)
and epsfig.sty. Typos corrected. To be published in Phys. Rev.
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