1,574 research outputs found
Properties of Mg-doped Nd-Ba-Cu-O generic seed crystals for the top seeded melt growth of (RE)-Ba-Cu-O bulk superconductors
We have recently developed a new generic seed crystal that has been used successfully to fabricate any oriented, single grain (RE)-Ba-Cu-O bulk superconductor by a cold seeding technique. In this paper we report the chemical, structural and microstructural properties of these seed crystals, including the variation of melting point, crystallographic parameters and volume fraction of Mg-rich inclusions in the Nd1 + xBa 2-x(Cu1-yMgy)3Oz matrix as a function of externally added MgO content. The influence of Mg-doping on the superconducting transition temperatures of YBCO grains fabricated using these seeds is investigated. Finally, an optimum MgO content of the generic seed that effectively controls the orientation of the seeded grain without compromising its superconducting properties is suggested from the many seed crystals fabricated with a wide range of Mg-rich addition
Toric Kahler metrics and AdS_5 in ring-like co-ordinates
Stationary, supersymmetric supergravity solutions in five dimensions have
Kahler metrics on the four-manifold orthogonal to the orbits of a time-like
Killing vector. We show that an explicit class of toric Kahler metrics provide
a unified framework in which to describe both the asymptotically flat and
asymptotically AdS solutions. The Darboux co-ordinates used for the local
description turn out to be ''ring-like.'' We conclude with an Ansatz for
studying the existence of supersymmetric black rings in AdS.Comment: A new appendix derives the explicit co-ordinate transformation
between the ``ring-like'' co-ordinates and the polar co-ordinates of global
AdS. Also, references adde
Test engineering education in Europe: the EuNICE-Test project
The paper deals with a European experience of education in industrial test of ICs and SoCs using remote testing facilities. The project addresses the problem of the shortage in microelectronics engineers aware with the new challenge of testing mixed-signal SoCs far multimedia/telecom market. It aims at providing test training facilities at a European scale in both initial and continuing education contexts. This is done by allowing the academic and industrial partners of the consortium to train engineers using the common test resources center (CRTC) hosted by LIRMM (Laboratoire d'Informatique, de Robotique et de Microelectronique de Montpellier, France). CRTC test tools include up-to-date/high-tech testers that are fully representative of real industrial testers as used on production testfloors. At the end of the project, it is aimed at reaching a cruising speed of about 16 trainees per year per center. Each trainee will have attend at least one one-week training using the remote test facilities of CRTC
The Black Di-Ring: An Inverse Scattering Construction
We use the inverse scattering method (ISM) to derive concentric
non-supersymmetric black rings. The approach used here is fully
five-dimensional, and has the modest advantage that it generalizes readily to
the construction of more general axi-symmetric solutions.Comment: v3: 2 subsections added, typos fixed, more refs, journal version. v4:
a transcription error in the ADM mass fixe
Ultraspinning instability of rotating black holes
Rapidly rotating Myers-Perry black holes in d>5 dimensions were conjectured
to be unstable by Emparan and Myers. In a previous publication, we found
numerically the onset of the axisymmetric ultraspinning instability in the
singly-spinning Myers-Perry black hole in d=7,8,9. This threshold signals also
a bifurcation to new branches of axisymmetric solutions with pinched horizons
that are conjectured to connect to the black ring, black Saturn and other
families in the phase diagram of stationary solutions. We firmly establish that
this instability is also present in d=6 and in d=10,11. The boundary conditions
of the perturbations are discussed in detail for the first time and we prove
that they preserve the angular velocity and temperature of the original
Myers-Perry black hole. This property is fundamental to establish a
thermodynamic necessary condition for the existence of this instability in
general rotating backgrounds. We also prove a previous claim that the
ultraspinning modes cannot be pure gauge modes. Finally we find new
ultraspinning Gregory-Laflamme instabilities of rotating black strings and
branes that appear exactly at the critical rotation predicted by the
aforementioned thermodynamic criterium. The latter is a refinement of the
Gubser-Mitra conjecture.Comment: 38 pages, 6 figures, 1 tabl
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A self-consistent dynamical model of the Milky Way disc adjusted to Gaia data
Context. Accurate astrometry achieved by Gaia for many stars in the Milky Way provides an opportunity to reanalyse the Galactic stellar populations from a large and homogeneous sample and to revisit the Galaxy gravitational potential. Aims. This paper shows how a self-consistent dynamical model can be obtained by fitting the gravitational potential of the Milky Way to the stellar kinematics and densities from Gaia data. Methods. We derived a gravitational potential using the Besancon Galaxy Model, and computed the disc stellar distribution functions based on three integrals of motion (E, Lz, I3) to model stationary stellar discs. The gravitational potential and the stellar distribution functions are built self-consistently, and are then adjusted to be in agreement with the kinematics and the density distributions obtained from Gaia observations. A Markov chain Monte Carlo (MCMC) is used to fit the free parameters of the dynamical model to Gaia parallax and proper motion distributions. The fit is done on several sets of Gaia data, mainly a subsample of the GCNS (Gaia catalogue of nearby stars to 100 pc) with G< 17, together with 26 deep fields selected from eDR3, widely spread in longitudes and latitudes. Results. We are able to determine the velocity dispersion ellipsoid and its tilt for subcomponents of different ages, both varying with R and z. The density laws and their radial scale lengths for the thin and thick disc populations are also obtained self-consistently. This new model has some interesting characteristics that come naturally from the process, such as a flaring thin disc. The thick disc is found to present very distinctive characteristics from the old thin disc, both in density and kinematics. This lends significant support to the idea that thin and thick discs were formed in distinct scenarios, as the density and kinematics transition between them is found to be abrupt. The dark matter halo is shown to be nearly spherical. We also derive the solar motion with regards to the Local Standard of Rest (LSR), finding U· = 10.79 ± 0.56 km s-1, V· = 11.06 ± 0.94 km s-1, and W· = 7.66 ± 0.43 km s-1, in close agreement with recent studies. Conclusions. The resulting fully self-consistent gravitational potential, still axisymmetric, is a good approximation of a smooth mass distribution in the Milky Way and can be used for further studies, including finding streams, substructures, and to compute orbits for real stars in our Galaxy
Relativistic Viscous Fluid Dynamics and Non-Equilibrium Entropy
Fluid dynamics corresponds to the dynamics of a substance in the long
wavelength limit. Writing down all terms in a gradient (long wavelength)
expansion up to second order for a relativistic system at vanishing charge
density, one obtains the most general (causal) equations of motion for a fluid
in the presence of shear and bulk viscosity, as well as the structure of the
non-equilibrium entropy current. Requiring positivity of the divergence of the
non-equilibrium entropy current relates some of its coefficients to those
entering the equations of motion. I comment on possible applications of these
results for conformal and non-conformal fluids.Comment: 25 pages, no figures; v2: matches published versio
Charged Rotating Kaluza-Klein Black Holes Generated by G2(2) Transformation
Applying the G_{2(2)} generating technique for minimal D=5 supergravity to
the Rasheed black hole solution, we present a new rotating charged Kaluza-Klein
black hole solution to the five-dimensional Einstein-Maxwell-Chern-Simons
equations. At infinity, our solution behaves as a four-dimensional flat
spacetime with a compact extra dimension and hence describes a Kaluza-Klein
black hole. In particlar, the extreme solution is non-supersymmetric, which is
contrast to a static case. Our solution has the limits to the asymptotically
flat charged rotating black hole solution and a new charged rotating black
string solution.Comment: 24 page
Bonamia status and its effects in cultured flat oysters in the
Hatchery-reared spat obtained from native oyster stocks was cultured. The spat was placed in baskets on rafts at 12 months of age. Bimonthly samples were taken and the presence of Bonamia, other pathological conditions and mortality were estimated
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