549 research outputs found
Query processing of spatial objects: Complexity versus Redundancy
The management of complex spatial objects in applications, such as geography and cartography,
imposes stringent new requirements on spatial database systems, in particular on efficient
query processing. As shown before, the performance of spatial query processing can be improved
by decomposing complex spatial objects into simple components. Up to now, only decomposition
techniques generating a linear number of very simple components, e.g. triangles or trapezoids, have
been considered. In this paper, we will investigate the natural trade-off between the complexity of
the components and the redundancy, i.e. the number of components, with respect to its effect on
efficient query processing. In particular, we present two new decomposition methods generating
a better balance between the complexity and the number of components than previously known
techniques. We compare these new decomposition methods to the traditional undecomposed representation
as well as to the well-known decomposition into convex polygons with respect to their
performance in spatial query processing. This comparison points out that for a wide range of query
selectivity the new decomposition techniques clearly outperform both the undecomposed representation
and the convex decomposition method. More important than the absolute gain in performance
by a factor of up to an order of magnitude is the robust performance of our new decomposition
techniques over the whole range of query selectivity
Formation and thermal stability of ω-Ti(Fe) in α-phase-based Ti(Fe) alloys
In this work, the formation and thermal stability of the ω-Ti(Fe) phase that were produced by the high-pressure torsion (HPT) were studied in two-phase α-Ti + TiFe alloys containing 2 wt.%, 4 wt.% and 10 wt.% iron. The two-phase microstructure was achieved by annealing the alloys at 470 °C for 4000 h and then quenching them in water. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were utilized to characterize the samples. The thermal stability of the ω-Ti(Fe) phase was investigated using differential scanning calorimetry (DSC) and in situ high-temperature XRD. In the HPT process, the high-pressure ω-Ti(Fe) phase mainly formed from α-Ti. It started to decompose by a cascade of exothermic reactions already at temperatures of 130 °C. The decomposition was finished above ~320 °C. Upon further heating, the phase transformation proceeded via the formation of a supersaturated α-Ti(Fe) phase. Finally, the equilibrium phase assemblage was established at high temperatures. The eutectoid temperature and the phase transition temperatures measured in deformed and heat-treated samples are compared for the samples with different iron concentrations and for samples with different phase compositions prior to the HPT process. Thermodynamic calculations were carried out to predict stable and metastable phase assemblages after heat-treatments at low (α-Ti + TiFe) and high temperatures (α-Ti + β-(Ti,Fe), β-(Ti,Fe))
On the Whitham hierarchy: dressing scheme, string equations and additional symmetrie
A new description of the universal Whitham hierarchy in terms of a
factorization problem in the Lie group of canonical transformations is
provided. This scheme allows us to give a natural description of dressing
transformations, string equations and additional symmetries for the Whitham
hierarchy. We show how to dress any given solution and prove that any solution
of the hierarchy may be undressed, and therefore comes from a factorization of
a canonical transformation. A particulary important function, related to the
-function, appears as a potential of the hierarchy. We introduce a class
of string equations which extends and contains previous classes of string
equations considered by Krichever and by Takasaki and Takebe. The scheme is
also applied for an convenient derivation of additional symmetries. Moreover,
new functional symmetries of the Zakharov extension of the Benney gas equations
are given and the action of additional symmetries over the potential in terms
of linear PDEs is characterized
On the Whitham hierarchy: dressing scheme, string equations and additional symmetrie
A new description of the universal Whitham hierarchy in terms of a
factorization problem in the Lie group of canonical transformations is
provided. This scheme allows us to give a natural description of dressing
transformations, string equations and additional symmetries for the Whitham
hierarchy. We show how to dress any given solution and prove that any solution
of the hierarchy may be undressed, and therefore comes from a factorization of
a canonical transformation. A particulary important function, related to the
-function, appears as a potential of the hierarchy. We introduce a class
of string equations which extends and contains previous classes of string
equations considered by Krichever and by Takasaki and Takebe. The scheme is
also applied for an convenient derivation of additional symmetries. Moreover,
new functional symmetries of the Zakharov extension of the Benney gas equations
are given and the action of additional symmetries over the potential in terms
of linear PDEs is characterized
The Real Combination Problem : Panpsychism, Micro-Subjects, and Emergence
Panpsychism harbors an unresolved tension, the seriousness of which has yet to be fully appreciated. I capture this tension as a dilemma, and offer panpsychists advice on how to resolve it. The dilemma, briefly, is as follows. Panpsychists are committed to the perspicuous explanation of macro-mentality in terms of micro-mentality. But panpsychists take the micro-material realm to feature not just mental properties, but also micro-subjects to whom these properties belong. Yet it is impossible to explain the constitution of a macro-subject (like one of us) in terms of the assembly of micro-subjects, for, I show, subjects cannot combine. Therefore the panpsychist explanatory project is derailed by the insistence that the world’s ultimate material constituents (ultimates) are subjects of experience. The panpsychist faces a choice of abandoning her explanatory project, or recanting the claim that the ultimates are subjects. This is the dilemma. I argue that the latter option is to be preferred. This needn’t constitute a wholesale abandonment of panpsychism, however, since panpsychists can maintain that the ultimates possess phenomenal qualities, despite not being subjects of those qualities. This proposal requires us to make sense of phenomenal qualities existing independently of experiencing subjects, a challenge I tackle in the penultimate section. The position eventually reached is a form of neutral monism, so another way to express the overall argument is to say that, keeping true to their philosophical motivations, panpsychists should really be neutral monists.Peer reviewedFinal Accepted Versio
The ArgoNeuT Detector in the NuMI Low-Energy beam line at Fermilab
The ArgoNeuT liquid argon time projection chamber has collected thousands of
neutrino and antineutrino events during an extended run period in the NuMI
beam-line at Fermilab. This paper focuses on the main aspects of the detector
layout and related technical features, including the cryogenic equipment, time
projection chamber, read-out electronics, and off-line data treatment. The
detector commissioning phase, physics run, and first neutrino event displays
are also reported. The characterization of the main working parameters of the
detector during data-taking, the ionization electron drift velocity and
lifetime in liquid argon, as obtained from through-going muon data complete the
present report.Comment: 43 pages, 27 figures, 5 tables - update referenc
Ontology of core data mining entities
In this article, we present OntoDM-core, an ontology of core data mining
entities. OntoDM-core defines themost essential datamining entities in a three-layered
ontological structure comprising of a specification, an implementation and an application
layer. It provides a representational framework for the description of mining
structured data, and in addition provides taxonomies of datasets, data mining tasks,
generalizations, data mining algorithms and constraints, based on the type of data.
OntoDM-core is designed to support a wide range of applications/use cases, such as
semantic annotation of data mining algorithms, datasets and results; annotation of
QSAR studies in the context of drug discovery investigations; and disambiguation of
terms in text mining. The ontology has been thoroughly assessed following the practices
in ontology engineering, is fully interoperable with many domain resources and
is easy to extend
Autobiography as unconventional history: Constructing the author
The experience of historians as autobiographers has led them to reconsider the nature of historical knowledge and the function of the historian as an intermediary between the past and present. In the new theoretical context of the social sciences and historiography, we can take this proposal further and consider autobiography as a valid form of history—or, at least, as ‘unconventional history’, understood as negotiations with history that transcend or subvert traditional chronological monographs, posit the ‘subjective’ as a useful form of knowledge, and engage the constructed nature of the text. Taking this hypothesis as a starting point, this article reads historians' autobiographical texts to explore if we can/should continue to defend the classic distinction between subject and object, historian scientist and historian author. In this article I compare the work of several historian autobiographers that permit us to identify different methodologies in approaching the story of the self that also reflects different theoretical conceptions of history. I argue that historians that may be considered ‘constructionist’, such as Fernand Braudel, Annie Kriegel, George Duby, and Eric Hobsbawm, design their autobiographies in the same way they articulate their historical texts: by foregrounding objectivity and establishing critical distance between the subject—the historian who narrates the story—and the object—one's own life. Unconventional or experimental approaches, such as those espoused by Robert Rosenstone, Dominick LaCapra, or Clifford Geertz, result in more self-conscious autobiographies, which are, paradoxically, often more realistic and more revealing of the epistemological nature of life writing. ----------------- La experiencia de los historiadores como autobiógrafos les ha llevado a reconsiderar la naturaleza del conocimiento histórico y la función del historiador como un intermediario entre el pasado y el presente. En el nuevo contexto teórico de las ciencias sociales y la historiografía podemos tomar esta propuesta más allá y considerar la autobiografía como una forma válida de historia-o, al menos, de historia ‘poco convencional’-, entendida como negociaciones con la historia que trascienden o subvierten las tradicionales monografías cronológicas, plantean lo "subjetivo" como una forma útil de conocimiento y participan de la naturaleza construida del texto. Tomando esta hipótesis como punto de partida, este artículo lee los textos autobiográficos de los historiadores para explorar si se puede / debe seguir defendiendo la clásica distinción entre sujeto y objeto, historiador científico e historiador escritor. En este artículo comparo el trabajo de varios historiadores autobiógrafos que nos permiten identificar las diferentes metodologías para acercarse a la historia del yo y que también reflejan las diferentes concepciones teóricas de la historia. Sostengo que los historiadores que pueden considerarse "constructivistas", como Fernand Braudel, Annie Kriegel, George Duby y Eric Hobsbawm, diseñan sus autobiografías de la misma forma que articulan sus textos históricos: poniendo en primer plano la objetividad y estableciendo una distancia crítica entre el sujeto -el historiador que narra la historia-y el objeto- la vida de cada uno. Enfoques no convencionales o experimentales, como los expuestos por Robert Rosenstone, Dominick LaCapra, o Clifford Geertz, resultan autobiografías más autoconscientes, que son, paradójicamente, a menudo más realistas y más reveladoras de la naturaleza epistemológica de la escritura de la vida
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