15,476,995 research outputs found
ON THE BELETSKY EQUATION
No full textThis paper was presented at the Beletsky Session of the 4th IAA Conference on University Satellite Missions and CubeSat Workshop held in Rome and dedicated to the memory of the great Russian mathematician and pioneer scientist of Astrodynamics. The paper is concentrated to the so called Beletsky equation, concerning the attitude motion of a satellite under gravity gradient torque. In fact Professor Beletsky dealt with many aspects of astrodynamics giving deep and useful contributions and establishing some theoretical basis for the development of the space activity in USSR, then it looks like disappointing that his name is so strictly linked to a simple equation such as(1 + e cos theta)theta '' - 2e sin theta ' + alpha sin theta = 4e sin thetadescribing the planar attitude motion of a satellite in elliptic orbit: The reason of the enormous success of the Beletsky equation is just in its simplicity and in the interesting characteristics of its phase space, where regular and periodic solutions are merged together with unstable and chaotic solutions. This is not unusual for a non linear differential equation, but in the Beletsky equation these characteristics can be understood in deep and the transition to chaos can be checked by various indices, so many researchers were attracted by the results that can be achieved from the abstract point of view of dynamical system theory while obtaining output of concrete interest in space applications. Most of the content presented in this paper is derived from my PhD thesis "Chaos in Astrodymanics" presented at the School of Aerospace Engineering of Rome in 1991 and developed under the supervision of Professor Filippo Graziani
On the pages of «Narbutiana» P. Beletsky
No full textУ статті аналізуються дослідження мистецтвознавця Платона Білецького про життя і творчість Г. Нарбута. Графічний доробок митця у працях П. Білецького. Монографія про життя і творчість художника.The article analyzes the study of an art critic Platon Beletsky about the life and work of G. Narbut. Graphic artist's legacy in the works of P. Beletsky. Monograph on the life and work of the artist
Report on the ESO Workshop ''Spiral Structure in the Milky Way: Confronting Observations and Theory''
No full textThe main objectives of the workshop were to review current observational evidence for spiral arms in our Galaxy and confront them with models of spiral structure in order to arrive at a consistent picture. Of primary importance was to understand just what additional information is required to resolve outstanding issues related to the spiral structure in the Milky Way, especially as new survey instruments (e.g., ALMA, VISTA and VST) are coming online and major space missions like GAIA will be launched in the near future
Model-independent diagnostics of highly reddened Milky Way star clusters: age calibration
No full textContext: The next generation near- and mid-infrared Galactic surveys will yield a large number of new highly obscured star clusters. Detailed characterization of these new objects with spectroscopy is time-consuming.
Aims: Diagnostic tools that will be able to characterize clusters based only on the available photometry will be needed to study large samples of the newly found objects.
Methods: The brightness difference between the red clump and the main-sequence turn-off point have been used as a model-independent age calibrator for clusters with ages from a few 108 to 1010 yr in the optical. Here we apply for the first time the method in the near-infrared.
Results: We calibrated this difference in K-band, which is likely to be available for obscured clusters, and we apply it to a number of test clusters with photometry comparable to the one that will be yielded by the current or near-future surveys.
Conclusions: The new calibration yields reliable ages over the range of ages for which the red clump is present in clusters. The slope of the relation is smoother than that of the corresponding V-band relation, reducing the uncertainty in the age determinations with respect to the optical ones
The Isolated Generating Periodic Solutions to the Beletsky Equation.
No full textAbstract:
We study degeneracies in families of periodic solutions to the Beletsky equation which correspond to intersections of three manifolds of these solutions: the symmetric, the asymmetric ones, and the manifold belonging to one of the integrable cases, i.e. e=0 or μ=0. We obtained equations for these isolated solutions, which allow to compute them with an arbitrary precision. It is shown that additional degeneracies take place in some of these solutions. The method we use is applicable to the wide class of nonlinear ODEs depending on parameters.Note:
Research direction:Mathematical problems and theory of numerical method
Five old open clusters more in the outer Galactic disc
No full textNew photometric material is presented for six outer disc supposedly old, Galactic star clusters: Berkeley 76, Haffner 4, Ruprecht 10, Haffner 7, Haffner 11 and Haffner 15, which are projected against the rich and complex Canis Major overdensity at 225° ≤ l ≤ 248°, -7° ≤ b ≤ -2°. This CCD data set, in the UBVI passbands, is used to derive their fundamental parameters, in particular age and distance. Four of the program clusters turn out to be older than 1 Gyr. This fact makes them ideal targets for future spectroscopic campaigns aiming at deriving their metal abundances. This, in turn, contributes to increase the number of well-studied outer disc old open clusters. Only Haffner 15, previously considered an old cluster, is found to be a young, significantly reddened cluster, member of the Perseus arm in the third Galactic quadrant. As for Haffner 4, we suggest an age of about half a Gyr. The most interesting result we found is that Berkeley 76 is probably located at more than 17 kpc from the Galactic centre, and therefore is among the most peripherical old open clusters so far detected. Besides, for Ruprecht 10 and Haffner 7, which were never studied before, we propose ages larger than 1 Gyr
Art Critic, Artist and Teacher Platon Beletsky (the 80th anniversary of his birth)
No full textЙдеться про історика мистецтва, художника і педагога Платона Білецького (1922-1998). Характерною особливістю є розробка ним декількох тем: творчість Г. Нарбута і Т. Шевченка, український портрет ХVІІ- ХVІІІ ст. Відмічається послідовний історизм мислення вченого.The article is about the art historian, artist and teacher Platon Beletsky (1922-1998). A characteristic feature of the article is the development of its several themes: G. Narbut’s and Shevchenko’s creativity, Ukrainian portrait of the seventeenth and eighteenth centuries. The consistent historicism of scientist’s thinking is noted
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Men Rodríguez de Sanabria : (memorias del tiempo del rey don Pedro el Cruel) : novela histórica
No full textCopia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 201
- …
