626 research outputs found
International Global H-Mode Confinement Database
No full textThis is the International Global H-Mode Confinement Database for tokamaks, version 5.2.3. A description of each variable, including selection variables, is available in the file DB5.2.3_variables.pdf.
A more detailed description of the database, as well as its analysis, is provided in the paper referenced below, and sources referenced therein.
Verdoolaege G, Kaye SM, Angioni C, Kardaun OJWF, Maslov M, Romanelli M, et al. "The updated ITPA global H-mode confinement database : description and analysis," Nuclear Fusion vol. 61, no. 7, art. no. 076006 (29pp), 2021, doi:10.1088/1741-4326/abdb91
Classification of ELM types in joint European Torus based on global plasma parameters using discriminant analysis
No full textIn this work, discriminant analysis is used as the main approach for building a physics based automated classifier for the discrimination of the edge-localized mode (ELM) plasma instability. The classifier is then applied for distinguishing type I and type III ELMs from a set of carbon-wall plasmas at JET. This provides a fast, standardized classification of ELM types which is expected to significantly reduce the effort of ELM experts in identifying ELM types. Further, the classifier yields a separation hyperplane in terms of global plasma parameters, which provides an insight into the range of conditions under which specific ELM behaviors occur. (C) 2017 Elsevier B.V. All rights reserved
Clustering based on the geodesic distance on Gaussian manifolds for the automatic classication of disruptions
No full textOver the last few years progress has been made on the front of disruption prediction in tokamaks. The less forgiving character of the new metallic walls at JET emphasized the importance of disruption prediction and mitigation. Being able not only to predict but also classify the type of disruption will enable one to better choose the appropriate mitigation strategy. From this perspective, a new clustering method, based on the geodesic distance on a probabilistic manifold, has been applied to the JET disruption database. This approach allows the error bars of the measurements to be taken into account and has proved to clearly outperform the more traditional classification methods based on the Euclidean distance. The developed technique with the highest success rate manages to identify the type of disruption with 85% confidence, several hundreds of ms before the thermal quench. Therefore, the combined use of this method and the more traditional disruption predictors would significantly improve the mitigation strategy on JET and could contribute to the definition of an optimized approach for ITER
Polyhedral process networks
No full textReference implementations of signal processing applications
are often written in a sequential language that does
not reveal the available parallelism in the application.
However, if an application satisfies some constraints then
a parallel specification can be derived automatically.
In particular, if the application can be represented in
the polyhedral model, then a polyhedral process network
can be constructed from the application.
After introducing the required polyhedral tools,
this chapter details the construction of
the processes and the communication channels
in such a network.
Special attention is given to various properties of
the communication channels including their buffer sizes.edition: 2ndsponsorship: FWO-Vlaanderen, project G.0232.06N.status: Publishe
Bayesiaanse geïntegreerde bepaling van de effectieve ionaire lading via remstralings- en ladingsuitwisselingsspectroscopie in tokamakplasma's
No full textDit doctoraatswerk is gekaderd in de ontwikkeling van gecontroleerde thermonucleaire fusie als een schone, veilige en nagenoeg onuitputtelijke energiebron. Het is geconcentreerd op magnetische opsluiting in de tokamakconfiguratie. In een eerste, experimenteel gedeelte werd een nieuwe diagnostiek ontwikkeld voor remstralingsspectroscopie in het zichtbare aan de TEXTOR-tokamak (Institut fuer Plasmaphysik, Forschungszentrum Juelich, Duitsland). De diagnostiek voorziet 24 zichtlijnen gekoppeld aan een gekoelde CCD-camera, waardoor de voordelen van zowel een relatief hoge tijdsresolutie als ruimtelijke resolutie worden gecombineerd. Emissiviteitsprofielen van remstraling kunnen gereconstrueerd worden door een Abel-inversie. De betrouwbaarheid van de gereconstrueerde profielen werd vergroot door Tikhonov- en Maximum Entropie-regularisatie. Op die manier kunnen samen met profielen van de elektrondichtheid en de elektrontemperatuur, profielen voor de effectieve ionaire lading Zeff afgeleid worden. Een nieuwe methode voor de relatieve calibratie van het systeem werd bedacht en getest, gebaseerd op de consistentievereiste van profielen onder een verandering van zichtgeometrie. In een tweede deel van het doctoraatswerk werd Bayesiaanse waarschijnlijkheidsrekening gebruikt met het oog op de oplossing van het aloude probleem van de incompatibiliteit van Zeff-schattingen afgeleid uit remstralingsspectroscopie enerzijds en uit de gewogen sommatie van individuele onzuiverheidsconcentraties verkregen door ladingsuitwisselingsspectroscopie (CXS) anderzijds. Een probabilistisch model werd opgezet dat metingen van zowel remstralingsspectroscopie als CXS integreert. Inherente statistische en systematische onzekerheden in de metingen werden op een behoorlijke manier in rekening gebracht. Hierdoor werd het mogelijk een meest waarschijnlijke waarde voor Zeff op de magnetische as af te leiden, die consistent is met beide sets metingen en met kleinere foutenmarges dan voordien. Het uiteindelijke doel is de betrouwbaarheid en robuustheid van Zeff-profielen te verbeteren over de volledige plasmadoorsnede, terwijl consistentheid met alle beschikbare ruwe metingen behouden blijft. Een gelijkaardige Bayesiaanse analyse kan toegepast worden op vele (sets van) fusiediagnostieken en dit heeft een aanzienlijk potentieel om in het fusieonderzoek de algemene consistentie en nauwkeurigheid van data te verbeteren
On Ehrhart Polynomials and Probability Calculations in Voting Theory
No full textIn voting theory, analyzing how frequent is an event (e.g. a voting paradox) is, under some specific but widely used assumptions, equivalent to computing the exact number of integer solutions in a system of linear constraints. Recently, some algorithms for computing this number have been proposed in social choice literature by Huang and Chua [17] and by Gehrlein ([12, 14]). The purpose of this paper is threefold. Firstly, we want to do justice to Eug`ene Ehrhart, who, more than forty years ago, discovered the theoretical foundations of the above mentioned algorithms. Secondly, we present some efficient algorithms that have been recently developed by computer scientists, independently from voting theorists. Thirdly, we illustrate the use of these algorithms by providing some original results in voting theory.voting rules, manipulability, polytopes, lattice points, algorithms.
Robust estimation of Tokamak energy confinement scaling through geodesic least squares regression
No full textInteger set coalescing
No full textIn polyhedral compilation, various core concepts such as the set
of statement instances, the access relations, the dependences and
the schedule are represented or approximated using sets and binary
relations of sequences of integers bounded by (quasi-)affine constraints.
When these sets and relations are represented in disjunctive normal form,
it is important to keep the number of disjuncts small, both for efficiency
and to improve the computation of transitive closure overapproximations
and AST generation. This paper describes the set coalescing operation
of isl that looks for opportunities to combine several disjuncts into
a single disjunct without affecting the elements in the set. The main
purpose of the paper is to explain the various heuristics and to prove
their correctness.sponsorship: FWO-Vlaanderen, project G.0232.06Nstatus: Publishe
An integer set library for program analysis
No full textMany program analysis techniques are based on manipulations
of sets of integers bounded by linear constraints. These
integers typically represent iterations of a loop nest or
elements of an array. Double description based libraries
are sometimes used for representing such sets, but these libraries
usually have little or no explicit support for parameters and
existentially quantified variables, which are essential for
some program analysis tasks, and focus on rationals instead
of integers. Furthermore, in our applications, the number
of constraints describing a set is usually fairly small,
while a vertex based description could be very large.
We present a new library exclusively based on constraints
and geared towards the manipulation of integer sets. The
library supports some operations not typically available
in other libraries, such as parametric integer linear
programming and the computation of
the integer affine hull, and produces significantly
improved results in some applications.sponsorship: FWO-Vlaanderen, project G.0232.06Nstatus: Publishe
Detection of resting-state brain activity in magnetic resonance images through wavelet feature cluster analysis
No full textMagnetic resonance imaging studies of the resting brain have recently revealed the existence of low-frequency fluctuations of the cerebral hemodynamics. It has been suggested that these fluctuations are linked to baseline neural activity, organized in functional networks. This paper presents a novel method for the detection of these resting-state networks from blood-oxygen level dependent signals, through their wavelet representation in the appropriate frequency range. A valley-seeking clustering principle is employed, requiring no a priori knowledge of the number of functional networks. The technique is applied to a data set acquired at rest and is shown to retrieve a number of identifiable functional networks. The method is proposed as an alternative to e. g. independent component analysis and exhibits an enhanced network separation capability and stability against noise
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