280 research outputs found
A classification of the galaxy groups
A statistical criterion has been proposed to reveal the random and physical clusterings among stars, galaxies and other objects. This criterion has been applied to the galaxy triples of the list by Karachentseva, Karaschentsev and Scherbanovsky, and the double galaxies of the list by Dahari where the primary components are the Seyfert galaxies. The confident physical, probable physical, probable optical and confident optical groups have been identified. The limit difference of radial velocities of components for the confident physical multiple galaxies has also been estimated
Typical motions in multiple systems
In very old times, people counted - one, two, many. The author wants to show that they were right. Consider the motions of isolated bodies: (1) N = 1 - simple motion; (2) N = 2 - Keplerian orbits; and (3) N = 3 - this is the difficult problem. In general, this problem can be studied only by computer simulations. The author studied this problem over many years (see, e.g., Agekian and Anosova, 1967; Anosova, 1986, 1989 a,b). The principal result is that two basic types of dynamics take place in triple systems. The first special type is the stable hierarchical systems with two almost Keplerian orbits. The second general type is the unstable triple systems with complicated motions of the bodies. By random choice of the initial conditions, by the Monte-Carlo method, the stable systems comprised about approx. 10% of the examined cases; the unstable systems comprised the other approx. 90% of cases under consideration. In N greater than 3, the studies of dynamics of such systems by computer simulations show that we have in general also the motions roughly as at the cases 1 - 3 with the relative negative or positive energies of the bodies. In the author's picture, the typical trajectories of the bodies in unstable triple systems of the general type of dynamics are seen. Such systems are disrupted always after close triple approaches of the bodies. These approaches play a role like the gravitational slingshot. Often, the velocities of escapers are very large. On the other hand, the movie also shows the dynamical processes of a formation, dynamical evolution and disruption of the temporary wide binaries in triples and a formation of final hard massive binaries in the final evolution of triples
Ducks on the torus: existence and uniqueness
We show that there exist generic slow-fast systems with only one
(time-scaling) parameter on the two-torus, which have canard cycles for
arbitrary small values of this parameter. This is in drastic contrast with the
planar case, where canards usually occur in two-parametric families. Here we
treat systems with a convex slow curve. In this case there is a set of
parameter values accumulating to zero for which the system has exactly one
attracting and one repelling canard cycle. The basin of the attracting cycle is
almost the whole torus.Comment: To appear in Journal of Dynamical and Control Systems, presumably
Vol. 16 (2010), No. 2; The final publication is available at
www.springerlink.co
Knowledge structures and their representation in the language
The authors define and describe the components which build the structure of the frame "touch
Innovative practices in the system of higher education: impact, dynamics, challenges determining their development and M-plementation
This paper is an attempt to analyze the contemporary phenomena affecting higher education. The main impact and dynamics of the innovative practices in the system of higher education are studied. The authors consider the process of globalization, the changing of supply and demand in higher education, and changes in funding of higher education as factors that have the most significant impact on the functioning of the world market of educational services, and determine the development and implementation of the innovative practices in the higher education system at the present stage of its developmen
Differential Radial Velocities and Stellar Parameters of Nearby Young Stars
Radial velocity searches for substellar mass companions have focused
primarily on stars older than 1 Gyr. Increased levels of stellar activity in
young stars hinders the detection of solar system analogs and therefore there
has been a prejudice against inclusion of young stars in radial velocity
surveys until recently. Adaptive optics surveys of young stars have given us
insight into the multiplicity of young stars but only for massive, distant
companions. Understanding the limit of the radial velocity technique,
restricted to high-mass, close-orbiting planets and brown dwarfs, we began a
survey of young stars of various ages. While the number of stars needed to
carry out full analysis of the problems of planetary and brown dwarf population
and evolution is large, the beginning of such a sample is included here. We
report on 61 young stars ranging in age from beta Pic association (~12 Myr) to
the Ursa Majoris association (~300 Myr). This initial search resulted in no
stars showing evidence for companions greater than ~1-2 M_Jup in short period
orbits at the 3 sigma-level. Additionally, we present derived stellar
parameters, as most have unpublished values. The chemical homogeneity of a
cluster, and presumably of an association, may help to constrain true
membership. As such, we present [Fe/H] abundances for the stars in our sample.Comment: Accepted for publication in the PAS
Dynamics and configurations of galaxy triplets
The purpose is to infer the probable dynamical states of galaxy triplets by the observed data on their configurations. Two methods are proposed for describing the distributions of the triplet configuration parameters characterizing a tendency to alignment and hierarchy: (1) obtaining a representative sample of configurations and determining its statistical parameters (moments and percentages); and (2) dividing the region of possible configurations of triple systems (Agekian and Anosova, 1967) into a set of segments and finding the probabilities for the configurations to find themselves in each of them. Both these methods allow representation of the data by numerical simulations as well as observations. The effect of projection was studied. It rather overestimates the alignment and hierarchy of the triple systems. Among the parameters of interest there are found some parameters that are least sensitive to projection effects. The samples consist of simulated galaxy triplets (with hidden mass) as well as of 46 probably physical triple galaxies (Karachentseva et al., 1979). The observed triples as well as numerical models show a tendency to alignment. The triple galaxies do not show any tendency to hierarchy (formation of the temporary binaries), but this tendency may be present for simulated triplets without significant dark matter. The significant hidden mass (of order ten times the total mass of a triplet) decreases the probability of forming a binary and so weakens the hierarchy. Small galaxy groups consisting of 3 to 7 members are probably the most prevalent types of galaxy aggregate (Gorbatsky, 1987). Galaxy triplets are the simplest groups, but dynamically nontrivial ones
Are Proxima and Alpha Centauri Gravitationally Bound?
Using the most recent kinematic and radial velocity data in the literature,
we calculate the binding energy of Proxima Centauri relative to the center of
mass of the Alpha Centauri system. When we adopt the centroids of the observed
data, we find that the three stars constitute a bound system, albeit with a
semi-major axis that is on order the same size as Alpha Centauri AB's Hill
radius in the galactic potential. We carry out a Monte Carlo simulation under
the assumption that the errors in the observed quantities are uncorrelated. In
this simulation, 44% of the trial systems are bound, and systems on the 1-3
sigma tail of the radial velocity distribution can have Proxima currently
located near the apastron position of its orbit. Our analysis shows that a
further, very significant improvement in the characterization of the system can
be gained by obtaining a more accurate measurement of the radial velocity of
Proxima Centauri.Comment: 10 pages total, 4 pages of text, 1 page of references, 3 figures, and
2 tables This article will be published in The Astronomical Journa
The use of active learning methods for lifelong education
The aim was to study an impact of lifelong learning skills on using active learning methods by
teachers to improve their qualifications and teaching practice and evaluate an active methods
efectiveness for teachers with different duration of pedagogical experience. Methods. The study was
conducted using mixed methods. Questionnaires, pedagogical experiment, methods of mathematical
statistics were used. Results. The duration of pedagogical experience has equally affects the use of
active methods of teaching men and women. Feynman Technique proved to be an effective active
learning method for most teachers, which may be determined by the specifics of teaching and the
peculiarities of this technique. Full Turn and Case Studies were the least effective methods.
Conclusions. Men and women with smaller pedagogical experience are more interested in using
active teaching methods for self-study and using in pedagogical practice. The ability of teachers to
self-study have an influence on using of active teaching methods. Prospects. The results of the study
are effective for improving self-learning skills of teachers and the representative of other professions;
the Programme of studying active learning methods with their simultaneous use is effective for
solving problems of varying complexity and in all spheres of human activity
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