Search results for "Spherical geometry"
showing 7 items of 7 documents
Spherical microparticles production by supercritical antisolvent precipitation: Interpretation of results
2008
Abstract Supercritical antisolvent micronization has been the subject of many works aimed at the production of precipitates with controlled particle size and morphology. Several morphologies have been observed; but, the production of spherical micrometric particles has been the major objective of most of the studies performed. Therefore, in this work, literature data analysis on spherical and related morphologies has been performed. The ranges of process conditions at which spherical microparticles have been obtained have been listed and discussed. A possible formation mechanism is proposed that is based on the competition between jet break-up and liquid surface tension vanishing characteri…
INTEGRALobservations of the Be/X-ray binary EXO 2030+375 during outburst
2005
We present a type-I outburst of the high-mass X-ray binary EXO 2030+375, detected during INTEGRAL's Performance and Verification Phase in December 2002 (on-source time about 10e+06 seconds). In addition, six more outbursts have been observed during INTEGRAL's Galactic Plane Scans. X-ray pulsations have been detected with a pulse period of 41.691798+-0.000016 s. The X-ray luminosity in the 5-300 keV energy range was 9.7*10e+36 erg/s, for a distance of 7.1 kpc. Two unusual features were found in the light curve, with an initial peak before the main outburst and another possible spike after the maximum. RXTE observations confirm only the existence of the initial spike. Although the initial pea…
The broad-band spectrum of Cyg X-2 with INTEGRAL
2005
We study the broad band (3-100 keV) spectrum of Cygnus X-2 with INTEGRAL. We find that the spectrum is well fitted by a Comptonized component with a seed-photons temperature of ~1 keV, an electron temperature of ~3 keV and an optical depth tau ~ 8. Assuming spherical geometry, the radius of the seed-photons emitting region is ~17 km. The source shows no hard X-ray emission; it was detected only at a 3 sigma level above 40 keV. We also analyzed public ISGRI data of Cyg X--2 to investigate the presence of a hard X-ray component. We report the possible presence of hard X-ray emission in one data set.
The horospherical Gauss-Bonnet type theorem in hyperbolic space
2006
We introduce the notion horospherical curvatures of hypersurfaces in hyperbolic space and show that totally umbilic hypersurfaces with vanishing cur- vatures are only horospheres. We also show that the Gauss-Bonnet type theorem holds for the horospherical Gauss-Kronecker curvature of a closed orientable even dimensional hypersurface in hyperbolic space. + (i1) by using the model in Minkowski space. We introduced the notion of hyperbolic Gauss indicatrices slightly modified the definition of hyperbolic Gauss maps. The notion of hyperbolic indicatrices is independent of the choice of the model of hyperbolic space. Using the hyperbolic Gauss indicatrix, we defined the principal hyperbolic curv…
A mathematical model of mass transfer in spherical geometry: plum (Prunus domestica) drying
2003
In this paper the analytical solution of a mathematical model of mass transfer in spherical geometry is presented for boundary conditions useful for simulating drying processes of fruit with near spherical stones. This model is applied to analyse the efficiency of a new pre-treatment for a prune drying processes. The new proposed physical abrasion pre-treatment increases the plum drying rate at 60 degreesC. The mathematical model here presented allows a complete comparison of the experimental results obtained with this pre-treatment and with traditional ones. In particular the greater efficiency of the new physical pre-treatment appears to be due to the enhancement of the water diffusivity …
Shell structure and level spacing distribution in metallic clusters
1993
The lattice gas Monte Carlo and tight binding method is used to study the electronic shell structure in large metallic clusters. The average density of states of a large ensemble of deformed clusters shows the same shell structure as the most spherical geometry. The level spacing distribution at the Fermi level is a Wigner distribution.
La théorie des lignes parallèles de Johann Heinrich Lambert
2014
International audience; The memoir "Theory of parallel lines" (1766) by Johannes Heinrich Lambert is one of the founding texts of hyperbolic geometry, even though his author conceived it as an attempt to show that this geometry does not exist. In fact, Lambert developed that theory with the hope of finding a contradiction. In doing so, he obtained several fundamental results of hyperbolic geometry. This was sixty years before the first writings of Lobachevsky and Bolyai appeared in print. This book contains the first complete translation of Lambert's memoir as well as mathematical and historical commentaries.