327,847 research outputs found
Influence diagram modeling of nuclear spare parts process
Spare parts inventory levels at nuclear generation plants have neared all-time highs at some facilities. As part of an ongoing research project, the authors are developing a decision making framework for nuclear spare parts management. This paper describes the use of an influence diagram model to represent the existing spare parts process at a United States nuclear facility. We then discuss how this model can be extended to develop an interview protocol for subsequent data collection using the Analytic Hierarchy Process. The influence diagram drives the overall analysis of determining best practices for the spare parts process for continuous improvement
Practical Application Of Uml Activity Diagrams For The Generation Of Test Cases
Software testing and debugging represents around one third of total effort in development projects. Different factors which have influence on poor practices of testing have been identified through specific surveys. Amongst several, one of the most important is the lack of efficient methods to
exploit development models for generating test cases. This paper presents a new method for automatically generating a complete set of functional test cases from UML activity diagrams complementing specification of use cases. Test cases are prioritized according to software risk
information. Results from experiences with more than 70 software professionals/experts validate benefits of the method. Participants also confirm its interest and effectiveness for testing needs of industry
Derivation of diagnostic models based on formalized process knowledge
© IFAC.Industrial systems are vulnerable to faults. Early and accurate detection and diagnosis in production systems can minimize down-time, increase the safety of the plant operation, and reduce manufacturing costs. Knowledge- and model-based approaches to automated fault detection and diagnosis have been demonstrated to be suitable for fault cause analysis within a broad range of industrial processes and research case studies. However, the implementation of these methods demands a complex and error-prone development phase, especially due to the extensive efforts required during the derivation of models and their respective validation. In an effort to reduce such modeling complexity, this paper presents a structured causal modeling approach to supporting the derivation of diagnostic models based on formalized process knowledge. The method described herein exploits the Formalized Process Description Guideline VDI/VDE 3682 to establish causal relations among key-process variables, develops an extension of the Signed Digraph model combined with the use of fuzzy set theory to allow more accurate causality descriptions, and proposes a representation of the resulting diagnostic model in CAEX/AutomationML targeting dynamic data access, portability, and seamless information exchange
Consequences Of Fully Dressing Quark-Gluon Vertex Function With Two-Point Gluon Lines
We extend recent studies of the effects of quark-gluon vertex dressing upon
the solutions of the Dyson-Schwinger equation for the quark propagator. A
momentum delta function is used to represent the dominant infrared strength of
the effective gluon propagator so that the resulting integral equations become
algebraic. The quark-gluon vertex is constructed from the complete set of
diagrams involving only 2-point gluon lines. The additional diagrams, including
those with crossed gluon lines, are shown to make an important contribution to
the DSE solutions for the quark propagator, because of their large color
factors and the rapid growth in their number
Multi-method-modeling of interacting galaxies. I. A unique scenario for NGC 4449?
(abridged) We combined several N-body methods in order to investigate the
interaction scenario between NGC 4449 and DDO 125, a close companion in
projected space. In a first step fast restricted N-body models are used to
confine a region in parameter space reproducing the main observational
features. In a second step a genetic algorithm is applied for a uniqueness test
of our preferred parameter set. We show that our genetic algorithm reliably
recovers orbital parameters, provided that the data are sufficiently accurate,
i.e. all the key features are included.
In the third step the results of the restricted N-body models are compared
with self-consistent N-body simulations. In the case of NGC 4449, the
applicability of the simple restricted N-body calculations is demonstrated.
Additionally, it is shown that the HI gas can be modeled here by a purely
stellar dynamical approach.
In a series of simulations, we demonstrate that the observed features of the
extended HI disc can be explained by a gravitational interaction between NGC
4449 and DDO 125. According to these calculations the closest approach between
both galaxies happened yr ago at a minimum distance of
kpc on a parabolic or slightly elliptic orbit. In the case of an
encounter scenario, the dynamical mass of DDO 125 should not be smaller than
10% of NGC 4449's mass. Before the encounter, the observed HI gas was arranged
in a disc with a radius of 35-40 kpc around the center of NGC 4449. It had the
same orientation as the central ellipsoidal HI structure. The origin of this
disc is still unclear, but it might have been caused by a previous interaction.Comment: 19 pages with 19 figures, accepted for publication in Astron. &
Astrophys., a full PostScript version is available at
http://www.astrophysik.uni-kiel.de/pershome/theis/pub.htm
Comments on Extended t-J Models, Nodal Liquids and Supersymmetry
In the context of extended t-J models, with intersite Coulomb interactions,
nodal liquids are discussed. We use the spin-charge separation ansatz as
applied to the nodes of a d-wave superconducting gap. Such a situation may be
of relevance to the physics of high-temperature superconductivity. We point out
the possibility that at certain points of the parameter space supersymmetric
points may occur, characterized by dynamical supersymmetries between the spinon
and holon degrees of freedom, which are quite different from the symmetries in
conventional supersymmetric t-J models. Such symmetries pertain to the
continuum effective field theory of the nodal liquid, and one's hope is that
the ancestor lattice model may differ from the continuum theory only by
renormalization-group irrelevant operators in the infrared. We give plausible
arguments that nodal liquids at such supersymmetric points are characterized by
superconductivity of Kosterlitz-Thouless type.Comment: 18 pages latex, one eps figure incorporated (minor typos corrected).
Presented by N.E.M. at the Workshop ``Common Trends in Particle and Condensed
Matter Physics'', September 24-28 1999, Corfu (Greece
The Kinetic Basis of Morphogenesis
It has been shown recently (Shalygo, 2014) that stationary and dynamic
patterns can arise in the proposed one-component model of the analog
(continuous state) kinetic automaton, or kinon for short, defined as a
reflexive dynamical system with active transport. This paper presents
extensions of the model, which increase further its complexity and tunability,
and shows that the extended kinon model can produce spatio-temporal patterns
pertaining not only to pattern formation but also to morphogenesis in real
physical and biological systems. The possible applicability of the model to
morphogenetic engineering and swarm robotics is also discussed.Comment: 8 pages. Submitted to the 13th European Conference on Artificial Life
(ECAL-2015) on March 10, 2015. Accepted on April 28, 201
The Faint Cepheids of the Small Magellanic Cloud: an evolutionary selection effect?
Two problems about the faintest Small Magellanic Cloud (SMC) Cepheids are
addressed. On one hand evolutionary tracks fail to cross the Cepheid
Instability Strip for the highest magnitudes (i.e. I-mag~17) where Cepheids are
observed; Mass-Luminosity relations (ML) obtained from evolutionary tracks
disagree with Mass-Luminosity relations derived from observations. We find that
the above failures concern models built with standard input physics as well as
with non-standard ones. The present work suggests that towards highest
magnitudes, Cepheids stars undergo a selection effect caused by evolution: only
the most metal poor stars cross the Instability Strip during the ``blue loop''
phase and are therefore the only ones which can be observed at low luminosity.
This solution enables us to reproduce the shape of the lower part of the
Instability Strip and improves the agreement between observed and theoretical
ML-relations. Some issues are discussed, among them Beat Cepheids results argue
strongly in favor of our hypothesis.Comment: 13 pages, 8 figure
The influence of the cylindrical shape of the nucleosomes and H1 defects on properties of chromatin
We present a model improving the two-angle model for interphase chromatin
(E2A model). This model takes into account the cylindrical shape of the histone
octamers, the H1 histones in front of the nucleosomes and the vertical distance
between the in and outgoing DNA strands. Factoring these chromatin features
in, one gets essential changes in the chromatin phase diagram: Not only the
shape of the excluded-volume borderline changes but also the vertical distance
has a dramatic influence on the forbidden area. Furthermore, we examined
the influence of H1 defects on the properties of the chromatin fiber. Thus we
present two possible strategies for chromatin compaction: The use of very dense
states in the phase diagram in the gaps in the excluded volume borderline or
missing H1 histones which can lead to very compact fibers. The chromatin fiber
might use both of these mechanisms to compact itself at least locally. Line
densities computed within the model coincident with the experimental values
- …