Three-body treatment of the penetration through the Coulomb field of a two-fragment nucleus

On the basis of the Faddeev integral equations method and the Watson- Feshbach concept of the effective (optical) interaction potential, the first fully consistent three-body approach to the description of the penetration of a charged particle through the Coulomb field of a two-particle bound complex (composed of one charged and one neutral particles) has been developed. A general formalism has been elaborated and on its basis, to a first approximation in the Sommerfeld parameter, the influence of the nuclear structure on the probability of the penetration of a charged particle (the muon, the pion, the kaon and the proton) through the Gamow barrier of a two-fragment nucleus (the deuteron and the two lightest lambda hypernuclei, lambda hypertriton and lambda hyperhelium-5, has been calculated and studied.Comment: LaTeX, 30 pages, 4 eps figure

Empirical evaluation of accuracy of mathematical software used for availability assessment of fault-tolerant computer systems

Dependability assessment is typically based on complex probabilistic models. Markov and semi-Markov models are widely used to model dependability of complex hardware/software architectures. Solving such models, especially when they are stiff, is not trivial and is usually done using sophisticated mathematical software packages. We report a practical experience of comparing the accuracy of solutions stiff Markov models obtained using well known commercial and research software packages. The study is conducted on a contrived but realistic cases study of computer system with hardware redundancy and diverse software under the assumptions that the rate of failure of software may vary over time, a realistic assumption. We observe that the disagreement between the solutions obtained with the different packages may be very significant. We discuss these findings and directions for future research

Підвищення якості контуру «літак–система автоматичного керування»

This article deals with model based approach to mathematical modeling process of an aircraftflight control system. Analysis of emergency situations depend on phases of flight is done. Application ofmodern model based technologies for automatic flight control systems development is considered. Theprogram for aircraft-automatic flight control system control loop simulation and visualization is developed.Improvement of the automatic flight control system characteristics is showed. Availability of practicalapplication of developed program in aerospace scope is considered. Use of the mentioned approachallows to facilitate automatic flight control system development, analyze and certification processПредставлен модельно-ориентированный подход к процессу математического моделирования законов системы автоматического управления. Выполнен анализ аварийных ситуаций в зависимости от этапа полета. Рассмотрено применение современной модельно ориентированной технологии разработки законов системы автоматического управления. Разработана программа моделирования и визуализации контура самолет-система автоматического управления. Показано улучшение точности выдерживания параметров системы автоматическогоуправления. Рассмотрена возможность практического применения разработанной программы в авиационнойотрасли. Использование указанного подхода позволит сократить время на разработку, анализ и сертификациюсистемы автоматического управленияПредставлено модельно-орієнтований підхід до процесу математичного моделювання законів системи автоматичного керування. Виконано аналіз аварійних ситуацій в залежності від етапу польоту. Розглянуто використання сучасної модельно-орієнтованої технології розробки законів системи автоматичного керування. Розроблено програму моделювання і візуалізації контуру літак-система автоматичного управління. Показано поліпшення точності витримування параметрів системи автоматичного керування. Розглянуто можливість практичного застосування розробленої програми в авіаційній галузі. Використання вказаного підходу дозволить скоротити час на розробку, аналіз і сертифікацію системи автоматичного керуванн

Selecting Mathematical Software for Dependability Assessment of Computer Systems Described by Stiff Markov Chains

Markov and semi-Markov models are widely used in dependability assessment of complex computer-based systems. Model stiffness poses a serious problem both in terms of computational difficulties and in terms of accuracy of the assessment. Selecting an appropriate method and software package for solving stiff Markov models proved to be a non-trivial task. In this paper we provide an empirical comparison of two approaches to dealing with stiffness – stiffness avoidance and stiffness-tolerance. The study includes several well known techniques and software tools used for solving Kolmogorov’s differential equations derived from complex stiff Markov models. In the comparison we used realistic cases studies developed by others in the past: i) a computer system with hardware redundancy and diverse software, and ii) a queuing system with a server break-down and repair. The results indicate that the accuracy of the known methods is significantly affected by the stiffness of the Markov models, which led us to developing a procedure (an algorithm) for selecting the optimal method and tool for solving a given stiff Markov model. The algorithm is, also included in the paper

Моделювання зіткнення літаків з використанням методики істотних вибірок

We introduce the model of movement of two conflicting aircrafts and state the problem, we apply the importance sampling technique and elaborate an algorithm of collision modeling based on normal distributions, a small simulation studyРассмотрена модель движения двух конфликтующих самолетов. Предложены методика важных выборок и алгоритм моделирования столкновения самолетов, основанный на нормальном распределенииРозглянуто модель руху двох конфліктуючих літаків. Запропоновано методику істотних вибірок і алгоритм моделювання зіткнення літаків, заснований на нормальному розподіл

Shape parameters of Galactic open clusters

(abridged) In this paper we derive observed and modelled shape parameters (apparent ellipticity and orientation of the ellipse) of 650 Galactic open clusters identified in the ASCC-2.5 catalogue. We provide the observed shape parameters of Galactic open clusters, computed with the help of a multi-component analysis. For the vast majority of clusters these parameters are determined for the first time. High resolution ("star by star") N-body simulations are carried out with the specially developed $\phi$GRAPE code providing models of clusters of different initial masses, Galactocentric distances and rotation velocities. The comparison of models and observations of about 150 clusters reveals ellipticities of observed clusters which are too low (0.2 vs. 0.3), and offers the basis to find the main reason for this discrepancy. The models predict that after $\approx 50$ Myr clusters reach an oblate shape with an axes ratio of $1.65:1.35:1$, and with the major axis tilted by an angle of $q_{XY} \approx 30^\circ$ with respect to the Galactocentric radius due to differential rotation of the Galaxy. Unbiased estimates of cluster shape parameters require reliable membership determination in large cluster areas up to 2-3 tidal radii where the density of cluster stars is considerably lower than the background. Although dynamically bound stars outside the tidal radius contribute insignificantly to the cluster mass, their distribution is essential for a correct determination of cluster shape parameters. In contrast, a restricted mass range of cluster stars does not play such a dramatic role, though deep surveys allow to identify more cluster members and, therefore, to increase the accuracy of the observed shape parameters.Comment: 13 pages, 12 figures, accepted for publication in Astronomy and Astrophysic

A Search for EUV Emission from Comets with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS)

We have obtained EUV spectra between 90 and 255 \AA of the cometsC/2002 T7 (LINEAR), C/2001 Q4 (NEAT), and C/2004 Q2 (Machholz) near their perihelion passages in 2004 with the Cosmic Hot Interstellar Plasma Spectrometer (CHIPS). We obtained contemporaneous data on Comet NEAT Q4 with the $Chandra$ X-ray Observatory ACIS instrument, marking the first simultaneous EUV and X-ray spectral observations of a comet. The total CHIPS/EUV observing times were 337 ks for Q4, 234 ks for T7, and 483 ks for Machholz and for both CHIPS and $Chandra$ we calculate we have captured all the comet flux in the instrument field of view. We set upper limits on solar wind charge exchange emission lines of O, C, N, Ne and Fe occurring in the spectral bandpass of CHIPS. The spectrum of Q4 obtained with $Chandra$ can be reproduced by modeling emission lines of C, N O, Mg, Fe, Si, S, and Ne solar wind ions. The measured X-ray emission line intensities are consistent with our predictions from a solar wind charge exchange model. The model predictions for the EUV emission line intensities are determined from the intensity ratios of the cascading X-ray and EUV photons arising in the charge exchange processes. They are compatible with the measured limits on the intensities of the EUV lines. For comet Q4, we measured a total X-ray flux of 3.7$\times 10^{-12}$ ergs cm$^{-2}$ s$^{-1}$, and derive from model predictions a total EUV flux of 1.5$\times 10^{-12}$ erg cm$^{-2}$ s$^{-1}$. The CHIPS observations occurred predominantly while the satellite was on the dayside of Earth. For much of the observing time, CHIPS performed observations at smaller solar angles than it was designed for and EUV emission from the Sun scattered into the instrument limited the sensitivity of the EUV measurements.Comment: 28 pages total, 4 tables, 7 figures. Accepted by The Astrophysical Journa

Long-range behavior of the optical potential for the elastic scattering of charged composite particles

The asymptotic behavior of the optical potential, describing elastic scattering of a charged particle $\alpha$ off a bound state of two charged, or one charged and one neutral, particles at small momentum transfer $\Delta_{\alpha}$ or equivalently at large intercluster distance $\rho_{\alpha}$, is investigated within the framework of the exact three-body theory. For the three-charged-particle Green function that occurs in the exact expression for the optical potential, a recently derived expression, which is appropriate for the asymptotic region under consideration, is used. We find that for arbitrary values of the energy parameter the non-static part of the optical potential behaves for $\Delta_{\alpha} \rightarrow 0$ as $C_{1}\Delta_{\alpha} + o\,(\Delta_{\alpha})$. From this we derive for the Fourier transform of its on-shell restriction for $\rho_{\alpha} \rightarrow \infty$ the behavior $-a/2\rho_{\alpha}^4 + o\,(1/\rho_{\alpha}^4)$, i.e., dipole or quadrupole terms do not occur in the coordinate-space asymptotics. This result corroborates the standard one, which is obtained by perturbative methods. The general, energy-dependent expression for the dynamic polarisability $C_{1}$ is derived; on the energy shell it reduces to the conventional polarisability $a$ which is independent of the energy. We emphasize that the present derivation is {\em non-perturbative}, i.e., it does not make use of adiabatic or similar approximations, and is valid for energies {\em below as well as above the three-body dissociation threshold}.Comment: 35 pages, no figures, revte

Spyware detection technique based on reinforcement learning

Analysis of the antivirus technologies, showed that they are not able to detect new spyware with high efficiency, which significantly reduces the reliability and efficiency of its identification. Techniques based on heuristic analysis have a high rate of false positives. The paper presents a new technique for the spyware detection method in computer systems that provides a principle of proactivity and is based on mechanisms machine learning with the reinforce-mentlearning. The suggested method of spyware detection is based on software behavior analysis in computer systems. The suggested method involves the computer systems monitoring concerning the software, operates with the behavior

Galactic Rotation Parameters from Data on Open Star Clusters

Currently available data on the field of velocities Vr, Vl, Vb for open star clusters are used to perform a kinematic analysis of various samples that differ by heliocentric distance, age, and membership in individual structures (the Orion, Carina--Sagittarius, and Perseus arms). Based on 375 clusters located within 5 kpc of the Sun with ages up to 1 Gyr, we have determined the Galactic rotation parameters Wo =-26.0+-0.3 km/s/kpc, W'o = 4.18+-0.17 km/s/kpc^2, W''o=-0.45+-0.06 km/s/kpc^3, the system contraction parameter K = -2.4+-0.1 km/s/kpc, and the parameters of the kinematic center Ro =7.4+-0.3 kpc and lo = 0+-1 degrees. The Galactocentric distance Ro in the model used has been found to depend significantly on the sample age. Thus, for example, it is 9.5+-0.7 kpc and 5.6+-0.3 kpc for the samples of young (50 Myr) clusters, respectively. Our study of the kinematics of young open star clusters in various spiral arms has shown that the kinematic parameters are similar to the parameters obtained from the entire sample for the Carina-Sagittarius and Perseus arms and differ significantly from them for the Orion arm. The contraction effect is shown to be typical of star clusters with various ages. It is most pronounced for clusters with a mean age of 100 Myr, with the contraction velocity being Kr = -4.3+-1.0 km/s.Comment: 14 pages, 4 figures, 2 table