Perkův dalekohled je největší český přístroj používaný k astronomickému výzkumu od hvězdné fyziky po exoplanety. Během minulého roku proběhla díky dotaci na přístrojové vybavení od Kanceláře Akademie věd ČR jeho významná modernizace, během níž byla vyjmuta zrcadla z optické cesty ke spektrografům a nahrazena nejmodernější oktogonální vláknovou optikou. Tato změna má za následek, že počet fotonů dopadajících do spektrografů a na CCD kamery je několikanásobně větší než v původní konfiguraci. Nyní je možné pozorování i málo jasných objektů. Navíc byla přidána zobrazovací kamera, díky níž lze pořizovat přímé snímky vesmírných objektů. Tato modernizace otevírá nové obzory a nabízí českým astronomům přístroj, který obstojí v mezinárodním měřítku. and Jana Žďárská.
The triggering of the outbursts of dwarf novae isbelieved to be an instability in the accretion disk surrounding the white dwarf. It has become clear that at least some outbursts are preceded by small changes in the emission lines or in the continuum level. This paper reviews what is known about these changes and discusses their potential importance.
Mid-infrared region (2-8) μm is currently in the focus of laser physics, which is trying to develop new materials capable of generating coherent laser radiation in this region. This point of interest is connected to the so called infrared atmospheric window which offers new possibilities for solid-state lasers to be used as radars, LIDARs, tools for atmosphere diagnostics, etc. One of these new materials is the dysprosium doped lead-thiogallate (Dy:PbGa2 S4 ). In this article, we present brief characteristics of this laser active medium from the point of view of laser physics and we demonstrate the output radiation characteristics of three laser systems with dysprosium doped lead-thiogallate as their active media generating radiation at 2400 nm, 4300 nm a 5400 nm. The spatial structure, energy, impulse length and emission spectra of the output radiation were determined. and Stredná infračervená oblasť (2-8) μm je v súčasnosti terčom záujmu laserovej fyziky, ktorá sa snaží vyvinúť nové materiály, ktoré by mohli poskytovať koherentné laserové žiarenie v tejto oblasti. Tento záujem sa spája s existenciou tzv. infračerveného atmosférického okna, ktoré otvára nové možnosti aplikácií laserov generujúcich žiarenie v tejto oblasti ako sú radary, LIDARy, prostriedky pre diagnostiku atmosféry a podobne. Jedným z týchto nových materiálov majúcich takéto vlastnosti je dyspróziom dopovaný olovo-thiogalát (Dy:PbGa2 S4 ). V tomto článku prezentujeme stručnú charakteristiku tohto laserového aktívneho prostredia z pohľadu laserovej fyziky a demonštrujeme vlastnosti troch laserových systémov, obsahujúcich Dy:PbGa2 S4 ako aktívne médium, generujúcich žiarenie na vlnových dĺžkach 2400 nm, 4300 nm a 5400 nm. Výstupné žiarenie charakterizujeme z hľadiska priestorovej štruktúry, energie, dĺžky impulzu a emisného spektra.
The paper presents results of investigations on modeling and optimizing dynamic features of drive systems in order to minimize amplitudes of forces occurring in kinematic pairs of an electromechanical system with an ansynchronous motor and a vector control unit. The genetic algorithm was applied for optimization of design features of the system. The obtained results of numerical calculations confirmed the accuracy of the applied models and research methods for estimation of dynamic feature of drive systems. The set of design variables selected in the optimization process contained parameters describing design features of gear shafts and settings of control units. and Obsahuje seznam literatury
In this paper, the theory of the ballooning yarn has been adapted to the ring spinning process. The effect of the balloon control ring was incorporated into the mathematical model. The control ring is modeled as a frictionless circle constraint on the yarn path in the balloon.The balloon shape os determined by taking into account all the significant phenomena. The method of solution is applicable to more than one control ring in the threadline. The results from dynamic analysis are presented and show a marked effect of balloon control ring in reduce the yarn tension. The developed numerical solution procedures can be used to explore the regions of instability of the balloon. and Obsahuje seznam literatury
This paper presents a dynamic approach to the synthesis of a crank-rocker four-bar mechanism, that is obtained by an optimization problem and its solution using the swarm intelligence algorithm called Modified-Artificial Bee Colony (M-ABC). The proposed dynamic approach states a mono-objective dynamic optimization problem (MODOP), in order to obtain a set of optimal parameters of the system. In this MODOP, the kinematic and dynamic models of the whole system are consider as well as a set of constraints including a dynamic constraint. The M-ABC algorithm is adapted to solve the optimization problem by adding a suitable constraint-handling mechanism that is able to incorporate the kinematic and dynamic constraints of the system. A set of independent computational runs were carried out in order to validate the dynamic approach. An analysis from the mechanical and computational point of view is presented, based on the obtained results. From the analysis of the simulation and its results, it is shown that the solutions for the proposed algorithm lead to a more suitable design based on the dynamic approach.