1,954 research outputs found
Rapport préliminaire sur le développement de l'intégration économique de l'Europe; Deuxiéme section: Les obstacles et leur élimination. Exercice 1955-1956 deuxieme session extraordinaire = Preliminary report on the development of the economic integration of Europe; Second section: Obstacles and their solution. Common Assembly: second ordinary session, document No 7 1955-1956, March 1956
Fast rotating stars resulting from binary evolution will often appear to be single
Rapidly rotating stars are readily produced in binary systems. An accreting
star in a binary system can be spun up by mass accretion and quickly approach
the break-up limit. Mergers between two stars in a binary are expected to
result in massive, fast rotating stars. These rapid rotators may appear as Be
or Oe stars or at low metallicity they may be progenitors of long gamma-ray
bursts.
Given the high frequency of massive stars in close binaries it seems likely
that a large fraction of rapidly rotating stars result from binary interaction.
It is not straightforward to distinguish a a fast rotator that was born as a
rapidly rotating single star from a fast rotator that resulted from some kind
of binary interaction. Rapidly rotating stars resulting from binary interaction
will often appear to be single because the companion tends to be a low mass,
low luminosity star in a wide orbit. Alternatively, they became single stars
after a merger or disruption of the binary system during the supernova
explosion of the primary.
The absence of evidence for a companion does not guarantee that the system
did not experience binary interaction in the past. If binary interaction is one
of the main causes of high stellar rotation rates, the binary fraction is
expected to be smaller among fast rotators. How this prediction depend on
uncertainties in the physics of the binary interactions requires further
investigation.Comment: 2 pages, 1 figure, to be published in the proceedings of IAU 272
"Active OB stars: structure, evolution, mass loss and critical limit", Paris
19-23 July 201
Lithospheric cooling trends and deviations in oceanic PP‐P and SS‐S differential traveltimes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97534/1/jgrb50092.pd
New simple digital self-calibration technique for pipeline ADCs using the internal thermal noise
IEEE International Symposium on Circuits and Systems, pp. 232 – 235, Seattle, EUAThis paper describes a new digital-domain selfcalibration technique for high-speed pipeline A/D converters using the internal thermal noise as input stimulus. This lowamplitude noise is amplified and recycled by the ADC itself and, due to the successive foldings, it is naturally converted into
uniform noise. This noise is then used to calculate the required calibrating-codes. As an example, the calibration of a 13-bit pipeline ADC shows that the overall linearity can be significantly improved using this technique
FLUID MECHANICS ANALYSIS IN VOLLEYBALL SERVICES
The service is considered the first attack action in volleyball games. Erratic behavior also appears along the trajectory, hindering reception. We suspect that these effects can be related to the ‘drag crisis’ phenomenon described in fluid mechanics. Thus, we decided to quantify the trajectories of four types of services (underhand, floater, floater with jump, overhand with jump). Altogether, twenty-six real trajectories of service balls were recorded and 3D reconstructed with the DVIDEOW system. Polynomials of the 4th degree of time were adjusted to the coordinates of each trajectory, obtaining the speed and acceleration of the balls.
We compared, in the horizontal and vertical planes, the real trajectories with simulated ones in which the ball was submitted to the same initial conditions but without any aerodynamic drag forces. We calculated the Reynolds Number (Re), the drag coefficient (CD) and the drag force (FD), applying the model presented at the XVI ISB Congress (Deprá et al., 1997). We observed that all services are placed in the region of the so-called drag crisis (1.105 < Re < 3.105) and present great variations of drag coefficient (Fig. 1). We also observed that the four types of services analyzed can be ordered in an increasing sequence of Reynolds numbers. The first three types presented a decreasing sequence of median values of CD, accompanying the CD(Re) literature curve (line in Fig. 1). Even so, we observed the growth of the drag force (FD) as a function of Re (Fig. 2). Comparing the magnitude of the two forces that act on the ball, we estimated that in the case of the overhand service with jump the drag force becomes up to 1.4 times larger than the weight force (mg = 2.55 N). All these kind of quantification may also be used to compare characteristics of different players
Determinação de níveis economicos de NPK na cultura da alface em Macapá.
A produção de alface no Amapá e insuficiente para atender a demanda local, aliado a esse fato, o abastecimento através de outros centros produtores e dificultado pela perecibilidade do produto e pelo isolamento geografico do estado. Com essa preocupação, diversos genotipos de alface foram avaliados, ja possuindo-se no momento, resultados para sua recomendação aos agricultores.bitstream/item/74279/1/AP-1998-niveis-economicos-npk.pd
Determinação de adubação N-P-K em tomateiros no Amapá.
Cerca de 95% do tomate comercializado em Macapá e proveniente de importações de outras unidades da federação. Apesar da pesquisa agropecuária dispor de recomendação de genotipos adaptados as condições edafoclimaticas do estado, entraves de ordem tecnologica tem dificultado a expansão da tomaticultura no Amapá.bitstream/item/97860/1/CPAF-AP-1998-Determinacao-adubacao.pd
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