103 research outputs found
Novel symmetries in N = 2 supersymmetric quantum mechanical models
We demonstrate the existence of a novel set of discrete symmetries in the
context of N = 2 supersymmetric (SUSY) quantum mechanical model with a
potential function f(x) that is a generalization of the potential of the 1D
SUSY harmonic oscillator. We perform the same exercise for the motion of a
charged particle in the X-Y plane under the influence of a magnetic field in
the Z-direction. We derive the underlying algebra of the existing continuous
symmetry transformations (and corresponding conserved charges) and establish
its relevance to the algebraic structures of the de Rham cohomological
operators of differential geometry. We show that the discrete symmetry
transformations of our present general theories correspond to the Hodge duality
operation. Ultimately, we conjecture that any arbitrary N = 2 SUSY quantum
mechanical system can be shown to be a tractable model for the Hodge theory.Comment: LaTeX file, 23 pages, Title and Abstract changed, Text modified,
version to appear in Annals of Physic
Scalable RDF Data Compression using X10
The Semantic Web comprises enormous volumes of semi-structured data elements.
For interoperability, these elements are represented by long strings. Such
representations are not efficient for the purposes of Semantic Web applications
that perform computations over large volumes of information. A typical method
for alleviating the impact of this problem is through the use of compression
methods that produce more compact representations of the data. The use of
dictionary encoding for this purpose is particularly prevalent in Semantic Web
database systems. However, centralized implementations present performance
bottlenecks, giving rise to the need for scalable, efficient distributed
encoding schemes. In this paper, we describe an encoding implementation based
on the asynchronous partitioned global address space (APGAS) parallel
programming model. We evaluate performance on a cluster of up to 384 cores and
datasets of up to 11 billion triples (1.9 TB). Compared to the state-of-art
MapReduce algorithm, we demonstrate a speedup of 2.6-7.4x and excellent
scalability. These results illustrate the strong potential of the APGAS model
for efficient implementation of dictionary encoding and contributes to the
engineering of larger scale Semantic Web applications
An intracardiac electrogram model to bridge virtual hearts and implantable cardiac devices
Virtual heart models have been proposed to enhance the safety of implantable
cardiac devices through closed loop validation. To communicate with a virtual
heart, devices have been driven by cardiac signals at specific sites. As a
result, only the action potentials of these sites are sensed. However, the real
device implanted in the heart will sense a complex combination of near and
far-field extracellular potential signals. Therefore many device functions,
such as blanking periods and refractory periods, are designed to handle these
unexpected signals. To represent these signals, we develop an intracardiac
electrogram (IEGM) model as an interface between the virtual heart and the
device. The model can capture not only the local excitation but also far-field
signals and pacing afterpotentials. Moreover, the sensing controller can
specify unipolar or bipolar electrogram (EGM) sensing configurations and
introduce various oversensing and undersensing modes. The simulation results
show that the model is able to reproduce clinically observed sensing problems,
which significantly extends the capabilities of the virtual heart model in the
context of device validation
Efficient Parallel Dictionary Encoding for RDF Data.
The SemanticWeb comprises enormous volumes of semi-structured data elements. For interoperability, these elements are represented by long strings. Such representations are not efficient for the purposes
of SemanticWeb applications that perform computations over
large volumes of information. A typical method for alleviating the impact of this problem is through the use of compression methods that produce more compact representations of the data. The use of dictionary encoding for this purpose is particularly prevalent in Semantic Web database systems. However, centralized implementations
present performance bottlenecks, giving rise to the
need for scalable, efficient distributed encoding schemes. In this paper, we describe a straightforward but very efficient encoding algorithm and evaluate its performance on a cluster of up to 384 cores and datasets of up to 11 billion triples (1.9 TB). Compared to the state-of-art MapReduce algorithm, we demonstrate a speedup of
2:6 - 7:4x and excellent scalability
Efficient Parallel Dictionary Encoding for RDF Data.
The SemanticWeb comprises enormous volumes of semi-structured data elements. For interoperability, these elements are represented by long strings. Such representations are not efficient for the purposes
of SemanticWeb applications that perform computations over
large volumes of information. A typical method for alleviating the impact of this problem is through the use of compression methods that produce more compact representations of the data. The use of dictionary encoding for this purpose is particularly prevalent in Semantic Web database systems. However, centralized implementations
present performance bottlenecks, giving rise to the
need for scalable, efficient distributed encoding schemes. In this paper, we describe a straightforward but very efficient encoding algorithm and evaluate its performance on a cluster of up to 384 cores and datasets of up to 11 billion triples (1.9 TB). Compared to the state-of-art MapReduce algorithm, we demonstrate a speedup of
2:6 - 7:4x and excellent scalability
The DSystemJ programming language for dynamic GALS systems: it's semantics, compilation, implementation, and run-time system
The paper presents a programming language called DSystemJ, for dynamic distributed Globally Asynchronous Locally Synchronous systems (GALS), its formal model, formal syntax and semantics, its compilation and implementation. The language is aimed at dynamic distributed systems, which use socket based communication protocols for communicating between components. DSystemJ allows the creation and control at runtime of asynchronous processes called clock-domains, their mobility on a distributed execution platform, as well as the runtime reconfiguration of the system's functionality and topology. As DSystemJ is based on a GALS model of computation and has formal semantics, it offers very safe mechanisms for implementation of dynamic distributed systems and potential for their formal verification. The principles and details of DSystemJ's compilation, as well as its required runtime support are described. The runtime support is itself implemented in the SystemJ GALS language, which can be considered as a static subset of DSystemJ.Cet article pr´esente un nouveau langage de programmation appel´e DSystemJ, destin´e aux syst`emes r´epartis dynamiques Globalement Asynchrones Localement Synchrones (GALS), ainsi que son mod`ele formel de calcul, sa syntaxe et sa s´emantique formelle, sa compilation et sa mise en oeuvre. Le langage est destin´e `a la conception des syst`emes r´epartis dynamiques, qui utilisent des protocoles de communication bas´es sur les sockets. DSystemJ permet la cr´eation et le contrˆole durant l'ex´ecution de processus asynchrones appel´es clockdomains, leur mobilit´e sur des plateformes d'ex´ecution r´epartie, ainsi que la reconfiguration `a l'ex´ecution des fonctionnalit´es du syst`eme et de sa topologie. Puisque le mod`ele formel de calcul de DSystemJ est bas´e sur le mod`ele GALS et poss`ede une s´emantique formelle, il offre des m´ecanismes tr`es sˆurs pour la mise en oeuvre de syst`emes dynamiques r´epartis et le potentiel pour leur v´erification formelle. Nous donnons les principes et les d´etails de la compilation de DSystemJ ainsi que son environnement de support `a l'ex´ecution. Cet environnement de support est lui-mˆeme mis en oeuvre dans le langage GALS SystemJ, qui peut ˆetre consid´er´e comme un sous-ensemble statique de DSystemJ
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