pinecone/core-2020-05-10-deduplication huggingface dataset:
A Semantic E-Wallet to Reconcile Privacy and Context Awareness

International audienceIncreasingly, application developers are looking for ways to provide users with higher levels of personalization that capture different elements of a user's operating context, such as her location, the task that she is currently engaged in, who her colleagues are, etc. While there are many sources of contextual information, they tend to vary from one user to another and also over time. Different users may rely on different location tracking functionality provided by different cell phone operators; they may use different calendar systems, etc. In this paper, we describe work on a Semantic e-Wallet aimed at supporting automated discovery and access of personal resources, each represented as a Semantic Web Service. A key objective is to provide a Semantic Web environment for open access to a user's contextual resources, thereby reducing the costs associated with the development and maintenance of context-aware applications. A second objective is, through Semantic Web technologies, to empower users to selectively control who has access to their contextual information and under which conditions. This work has been carried out in the context of myCampus, a context-aware environment aimed at enhancing everyday campus life. Empirical results obtained on Carnegie Mellon's campus are encouraging
Active Galactic Nuclei at the Crossroads of Astrophysics

Over the last five decades, AGN studies have produced a number of spectacular examples of synergies and multifaceted approaches in astrophysics. The field of AGN research now spans the entire spectral range and covers more than twelve orders of magnitude in the spatial and temporal domains. The next generation of astrophysical facilities will open up new possibilities for AGN studies, especially in the areas of high-resolution and high-fidelity imaging and spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These studies will address in detail a number of critical issues in AGN research such as processes in the immediate vicinity of supermassive black holes, physical conditions of broad-line and narrow-line regions, formation and evolution of accretion disks and relativistic outflows, and the connection between nuclear activity and galaxy evolution
Towards the Event Horizon - High Resolution VLBI Imaging of Nuclei of Active Galaxies

We report on new developments in VLBI, with emphasis on experiments performed at the highest frequencies possible to date (so called mm-VLBI). We have observed the nucleus of M 87 (Virgo A) with global VLBI at 3 mm. We show a new image of the inner-most jet region with an angular resolution of approx. 300 x 60 micro-arcseconds. In terms of Schwarzschild radii, this leads to an upper limit of the jet base of approx. 100 x 20 Schwarzschild radii. We also report on two VLBI pilot-experiments, which demonstrate the technical feasibility of global VLBI at 150 and 230 GHz (2 mm and 1.3 mm). The experiments lead to upper limits to the size of the unresolved AGN-cores in the 25 - 30 micro-arcsecond range. The participation of new and near-future mm-telescopes (like APEX, CARMA, SMA, LMT, ALMA, etc.) in global mm-VLBI will provide the necessary sensitivity for the imaging of black holes and their immediate environment
Exact solutions of nonlinear partial differential equations by
  singularity analysis

Whether integrable, partially integrable or nonintegrable, nonlinear partial
differential equations (PDEs) can be handled from scratch with essentially the
same toolbox, when one looks for analytic solutions in closed form. The basic
tool is the appropriate use of the singularities of the solutions, and this can
be done without knowing these solutions in advance. Since the elaboration of
the \textit{singular manifold method} by Weiss et al., many improvements have
been made. After some basic recalls, we give an interpretation of the method
allowing us to understand why and how it works. Next, we present the state of
the art of this powerful technique, trying as much as possible to make it a
(computerizable) algorithm. Finally, we apply it to various PDEs in 1+1
dimensions, mostly taken from physics, some of them chaotic: sine-Gordon,
Boussinesq, Sawada-Kotera, Kaup-Kupershmidt, complex Ginzburg-Landau,
Kuramoto-Sivashinsky, etc.Comment: LaTeX, 85 pages, subject index, no figure, to appear in Direct and
  inverse methods in nonlinear evolution equations, ed. A. Greco (Springer,
  Berlin). CIME school, Cetraro, 5--12 September 199
Imperative Object-based Calculi in (Co)Inductive Type Theories

We discuss the formalization of Abadi and Cardelli's imps, a paradigmatic object-based calculus with types and side effects, in Co-Inductive Type Theories, such as the Calculus of (Co)Inductive Constructions (CC(Co)Ind).\ud
\ud
Instead of representing directly the original system "as it is", we reformulate its syntax and semantics bearing in mind the proof-theoretical features provided by the target metalanguage. On one hand, this methodology allows for a smoother implementation and treatment of the calculus in the metalanguage. On the other, it is possible to see the calculus from a new perspective, thus having the occasion to suggest original and cleaner presentations.\ud
\ud
We give hence anew presentation of imps, exploiting natural deduction semantics, (weak) higher-order abstract syntax, and, for a significant fragment of the calculus, coinductive typing systems. This presentation is easier to use and implement than the original one, and the proofs of key metaproperties, e.g. subject reduction, are much simpler.\ud
\ud
Although all proof developments have been carried out in the Coq system, the solutions we have devised in the encoding of and metareasoning on imps can be applied to other imperative calculi and proof environments with similar features
Asymptotic solutions of the nonlinear Boltzmann equation for dissipative
  systems

Analytic solutions $F(v,t)$ of the nonlinear Boltzmann equation in
$d$-dimensions are studied for a new class of dissipative models, called
inelastic repulsive scatterers, interacting through pseudo-power law
repulsions, characterized by a strength parameter $\nu$, and embedding
inelastic hard spheres ($\nu=1$) and inelastic Maxwell models ($\nu=0$). The
systems are either freely cooling without energy input or driven by
thermostats, e.g. white noise, and approach stable nonequilibrium steady
states, or marginally stable homogeneous cooling states, where the data,
$v^d_0(t) F(v,t)$ plotted versus $c=v/v_0(t)$, collapse on a scaling or
similarity solution $f(c)$, where $v_0(t)$ is the r.m.s. velocity. The
dissipative interactions generate overpopulated high energy tails, described
generically by stretched Gaussians, $f(c) \sim \exp[-\beta c^b]$ with $0 < b <
2$, where $b=\nu$ with $\nu>0$ in free cooling, and $b=1+{1/2} \nu$ with $\nu
\geq 0$ when driven by white noise. Power law tails, $f(c) \sim 1/c^{a+d}$, are
only found in marginal cases, where the exponent $a$ is the root of a
transcendental equation. The stability threshold depend on the type of
thermostat, and is for the case of free cooling located at $\nu=0$. Moreover we
analyze an inelastic BGK-type kinetic equation with an energy dependent
collision frequency coupled to a thermostat, that captures all qualitative
properties of the velocity distribution function in Maxwell models, as
predicted by the full nonlinear Boltzmann equation, but fails for harder
interactions with $\nu>0$.Comment: Submitted to: "Granular Gas Dynamics", T. Poeschel, N. Brilliantov
  (eds.), Lecture Notes in Physics, Vol. LNP 624, Springer-Verlag,
  Berlin-Heidelberg-New York, 200
Development of a density inversion in driven granular gases

Granular materials fluidized by a rapidly vibrating bottom plate often
develop a fascinating density inversion: a heavier layer of granulate supported
by a lower-density region. We employ the Navier-Stokes granular hydrodynamics
to follow a density inversion as it develops in time. Assuming a dilute
low-Mach-number flow, we derive a reduced time-dependent model of the late
stage of the dynamics. The model looks especially simple in the Lagrangian
coordinates. The time-dependent solution describes the growth of a density peak
at an intermediate height. A transient temperature minimum is predicted to
develop in the region of the density peak. The temperature minimum disappears
at later times, as the system approaches the steady state. At late times, the
predictions of the low-Mach-number model are in good agreement with a numerical
solution of the full hydrodynamic equations. At an early stage of the dynamics,
pressure oscillations are predicted.Comment: 13 pages, 6 figures. To appear in "Granular Gas Dynamics", ed. by T.
  Poeschel and N. Brilliantov, vol. 624 of "Lecture Notes in Physics", Springe
Vibrated granular media as experimentally realizable Granular Gases

We report numerical simulations of strongly vibrated granular materials
designed to mimic recent experiments performed both in presence [1] or absence
[2] of gravity. We show that a model with impact velocity dependent restitution
coefficient is necessary to bring the simulations into agreement with
experiments. We measure the scaling exponents of the granular temperature,
collision frequency, impulse and pressure with the vibrating piston velocity.
As the system changes from a homogeneous gas state at low density to a
clustered state at high density, these exponents are all found to decrease
continuously with the particle number. In absence of gravity, a loose cluster
appears near the upper wall, opposite the piston, and acts as a buffer for
fastest particles leading to unexpected non-extensive scaling exponents ;
whereas in presence of gravity, the cluster bounces as a single inelastic body.
All these results differ significantly from classical inelastic hard sphere
kinetic theory and previous simulations, both based on a constant restitution
coefficient.Comment: In: T. Poeschel, N.V. Brilliantov (eds.) "Granular Gas Dynamics",
  Lecture Notes in Physics Vol. 624, Springer (Berlin, 2003), p. 131-16
Velocity fluctuations in cooling granular gases

We study the formation and the dynamics of correlations in the velocity field
for 1D and 2D cooling granular gases with the assumption of negligible density
fluctuations (``Homogeneous Velocity-correlated Cooling State'', HVCS). It is
shown that the predictions of mean field models fail when velocity fluctuations
become important. The study of correlations is done by means of molecular
dynamics and introducing an Inelastic Lattice Maxwell Models. This lattice
model is able to reproduce all the properties of the Homogeneous Cooling State
and several features of the HVCS. Moreover it allows very precise measurements
of structure functions and other crucial statistical indicators. The study
suggests that both the 1D and the 2D dynamics of the velocity field are
compatible with a diffusive dynamics at large scale with a more complex
behavior at small scale. In 2D the issue of scale separation, which is of
interest in the context of kinetic theories, is addressed.Comment: 24 pages, 16 figures, conference proceedin
Kinetic Integrals in the Kinetic Theory of dissipative gases

The kinetic theory of gases, including Granular Gases, is based on the
Boltzmann equation. Many properties of the gas, from the characteristics of the
velocity distribution function to the transport coefficients may be expressed
in terms of functions of the collision integral which we call kinetic
integrals. Although the evaluation of these functions is conceptually
straightforward, technically it is frequently rather cumbersome. We report here
a method for the analytical evaluation of kinetic integrals using computer
algebra. We apply this method for the computation of some properties of
Granular Gases, ranging from the moments of the velocity distribution function
to the transport coefficients. For their technical complexity most of these
quantities cannot be computed manually.Comment: 32 page
Kinetics of Fragmenting Freely Evolving Granular Gases

We investigate the effect of fragmentation on the homogeneous free cooling of
inelastic hard spheres, using Boltzmann kinetic theory and Direct Monte Carlo
simulations. We analyze in detail a model where dissipative collisions may
subsequently lead to a break-up of the grains. With a given probability, two
off-springs are then created from one of the two colliding partners, with
conservation of mass, momentum and kinetic energy. We observe a scaling regime
characterized by a single collisional average, that quantifies the deviations
from Gaussian behaviour for the joint size and velocity distribution function.
We also discuss the possibility of a catastrophe whereby the number of
particles diverges in a finite time. This phenomenon appears correlated to a
``shattering'' transition marked by a delta singularity at vanishingly small
grains for the rescaled size distribution.Comment: 22 pages, 8 figure
Linearized Boltzmann Equation and Hydrodynamics for Granular Gases

The linearized Boltzmann equation is considered to describe small spatial
perturbations of the homogeneous cooling state. The corresponding macroscopic
balance equations for the density, temperature, and flow velocity are derived
from it as the basis for a hydrodynamic description. Hydrodynamics is defined
in terms of the spectrum of the generator for the dynamics of the linearized
Boltzmann equation. The hydrodynamic eigenfunctions and eigenvalues are
calculated in the long wavelength limit. The results allow identification of
the hydrodynamic part of the solution to the linearized Boltzmann equation.
This contribution is used to calculate the fluxes in the macroscopic balance
equations, leading to the Navier-Stokes equations and associated transport
coefficients. The results agree with those obtained earlier by the
Chapman-Enskog method. The implications of this analysis for application of
methods of linear response to granular fluids and derivation of Green-Kubo
expressions for transport coefficients are discussed
Combined optimization of feature selection and algorithm parameters in machine learning of language

Comparative machine learning experiments have become an important methodology in empirical approaches to natural language processing (i) to investigate which machine learning algorithms have the 'right bias' to solve specific natural language processing tasks, and (ii) to investigate which sources of information add to accuracy in a learning approach. Using automatic word sense disambiguation as an example task, we show that with the methodology currently used in comparative machine learning experiments, the results may often not be reliable because of the role of and interaction between feature selection and algorithm parameter optimization. We propose genetic algorithms as a practical approach to achieve both higher accuracy within a single approach, and more reliable comparisons
Last interaction based paging in mobile cellular networks

In a mobile network, the paging operation is used to indicate the subscriber's position in order to establish a connection with another user, calling from a fixed or mobile environment. The currently employed scheme, blanket paging, incurs a significant cost in radio bandwidth utilization and is cost-effective only in small networks. In this paper, we introduce a new strategy that combines an optimal partitioning of the location area with a model to predict user movements, based on the additional information of the cell where the last interaction between the network and the terminal took place. We study the performance of the strategy under delay bounds and different mobility and call arrival characteristics. It is found that the new scheme further minimizes signaling costs and enhances previous sequential paging algorithms. © IFIP International Federation for Information Processing 2003
Providing internet access to IPv6 mobile personal area networks through UMTS

This paper describes a mechanism and suggests a protocol enhancement to provide global Internet access to Mobile Personal Area Networks and support mobility under different scenarios. For this purpose the concept of the user's Mobile Station acting as a Mobile Multi-link Subnet Router is introduced, which provides the necessary IPv6 connectivity and mobility service to the nodes connected to the Personal Area Network. The Mobile Station can distinguish between the nodes that need mobility support and the ones that do not in order to provide the appropriate type of IPv6 connectivity service. The main issues discussed are UMTS IPv6 connectivity, routing and mobility for the Mobile Station and the other nodes of the Mobile Personal Area Network. © IFIP International Federation for Information Processing 2003
Distances to Local Group Galaxies

Distances to galaxies in the Local Group are reviewed. In particular, the distance to the Large Magellanic Cloud is found to be $(m-M)_0 = 18.52 \pm 0.10$, corresponding to $50,600 \pm 2,400$ pc. The importance of M31 as an analog of the galaxies observed at greater distances is stressed, while the variety of star formation and chemical enrichment histories displayed by Local Group galaxies allows critical evaluation of the calibrations of the various distance indicators in a variety of environments
Calibration of the Distance Scale from Cepheids

We have used the infrared surface brightness technique to obtain a new absolute calibration of the Cepheid PL relation in optical and near-infrared bands from improved data on Galactic stars. The infrared surface brightness distances to the Galactic variables are consistent with direct interferometric Cepheid distance measurements, and with the PL calibration coming from Hipparcos parallaxes of nearby Cepheids, but are more accurate than these determinations. We find that in all bands, the Galactic Cepheid PL relation appears to be slightly, but significantly steeper than the corresponding relation defined by the LMC Cepheids. Since the slope of our LMC Cepheid sample is clearly better defined than the one of the much smaller Galactic sample, we fit the LMC slopes to our Galactic calibrating Cepheid sample (which introduces only a small uncertainty) to obtain our final, adopted and improved absolute calibrations of the Cepheid PL relations in the VIWJHK bands. Comparing the absolute magnitudes of 10-day period Cepheids in both galaxies which are only slightly affected by the different Galactic and LMC slopes of the PL relation, we derive values for the LMC distance modulus in all these bands which can be made to agree extremely well under reasonable assumptions for both, the reddening law, and the adopted reddenings of the LMC Cepheids. This yields, as our current best estimate from Cepheid variables, a LMC distance modulus of 18.55 +- 0.06
Blue Supergiants as a Tool for Extragalactic Distances - Theoretical Concepts

Because of their enormous intrinsic brightness blue supergiants are ideal stellar objects to be studied spectroscopically as individuals in galaxies far beyond the Local Group. Quantitative spectroscopy by means of efficient multi-object spectrographs attached to 8m-class telescopes and modern NLTE model atmosphere techniques allow us to determine not only intrinsic stellar parameters such as effective temperature, surface gravity, chemical composition and absolute magnitude but also very accurately interstellar reddening and extinction. This is a significant advantage compared to classical distance indicators like Cepheids and RR Lyrae. We describe the spectroscopic diagnostics of blue supergiants and introduce two concepts to determine absolute magnitudes. The first one (Wind Momentum -- Luminosity Relationship) uses the correlation between observed stellar wind momentum and luminosity, whereas the second one (Flux-weighted Gravity -- Luminosity Relationship) relies only on the determination of effective temperature and surface gravity to yield an accurate estimate of absolute magnitude. We discuss the potential of these two methods
Blue Supergiants as a Tool for Extragalactic Distances - Empirical Diagnostics

Blue supergiant stars can be exceptionally bright objects in the optical, making them prime targets for the determination of extragalactic distances. I describe how their photometric and spectroscopic properties can be calibrated to provide a measurement of their luminosity. I first review two well-known techniques, the luminosity of the brightest blue supergiants and, with the aid of recent spectroscopic data, the equivalent width of the Balmer lines. Next I discuss some recent developments concerning the luminosity dependence of the wind momentum and of the flux-weighted gravity, which can provide, if properly calibrated, powerful diagnostics for the determination of the distance to the parent galaxies
Subgraph Induced Connectivity Augmentation

Given a planar graph G=(V,E) and a vertex set Wsubseteq V , the subgraph induced planar connectivity augmentation problem asks for a minimum cardinality set F of additional edges with end vertices in W such that G'=(V,Ecup F) is planar and the subgraph of G' induced by W is connected. The problem arises in automatic graph drawing in the context of c -planarity testing of clustered graphs. We describe a linear time algorithm based on SPQR-trees that tests if a subgraph induced planar connectivity augmentation exists and, if so, constructs an minimum cardinality augmenting edge set
Formal proof of a polychronous protocol for loosely time-triggered architectures

International audienceThe verification of safety-critical systems has become an area of increasing importance in computer science. The notion of reactive system has emerged to concentrate on problems related to the control of interaction and response-time in mission-critical systems. Synchronous languages have proved to be well-adapted to the verification of reactive systems. It is nonetheless commonly argued that real-life systems often do not satisfy the strong hypotheses assumed by the synchronous approach: they are not synchronous. Protocols have however been proposed (e.g. in [1]) to provide an abstract synchronous specification on top of real-time architectures (e.g. loosely time-triggered architectures or LTTA). This abstract model is designed so as to satisfy the synchronous hypotheses and meet the implementation architecture constraints. It makes it possible to design, specify and verify reactive systems in the context of the synchronous approach. In this aim, the present article formalizes the LTTA protocol in the theorem prover Coq and proves its correctness
Musical pattern extraction using genetic algorithms

This paper describes a research work in which we study the possibility of applying genetic algorithms to the extraction of musical patterns in monophonic musical pieces. Each individual in the population represents a possible segmentation of the piece being analysed. The goal is to find a segmentation that allows the identification of the most significant patterns of the piece. In order to calculate an individual’s fitness, all its segments are compared among each other. The bigger the area occupied by similar segments the better the quality of the segmentation