The paper deals with the modelling of forced vibrations of reactor components excited by pressure pulsations generated by main circulation pumps. For the vibration analysis a new generalised model of the reactor with spatial localization of the nuclear fuel assemblies and protection tubes, continuously mass distribution of beam type components and more accurate model of the linear stepper drives for actuation of control cassettes was applied. Slightly different pump revolutions are sources of the heating which causes an amplification of vibration and possibility of the contact loss in internal linkages of the core barrel. and Obsahuje seznam literatury
The paper deals with the dynamic transmission error (ТЕ) measurements of a simple gear set at gearbox operational conditions that means under load and during rotation.
The analysis method is focused on the processing of impulse signals generated by incremental rotary encoders attached to the gears in mesh. The analysis technique benefits from demodulation of a phase-modulated signal. The theory is illustrated by experiments with a car gearbox and measurement errors are discussed. and Obsahuje seznam literatury
According to the present author´s results a following system of the galactic dynamical constants is proposed: local escape velocity, u = (520+30) km s^-1, local circular velocity, u = (230+30) km s^-1, local angular velocity of rotation, ω = (25+5) km s^-1 kpc^-1, local circular frequency of planar oscillations, κp = (40+10) km s^-1, local circlar frequency of vertical oscillations, κz = (70120) km^-1 kpc^-1. The value of (9+1), kpc is assumed fpar the galactocentric distance of the Sun. The latter three values yield (0.09±0.03) pc^-3 for the local matter density, a value very close to the density obtained by use of statistical methods. On the basis of the proposed value it is concluded that the dark matter should to present in the form of a large, rerefied, massive, spherical corona.
The dynamical evolution of short-period comets, and in particular of those belonging to the so-called Jupiter family, is reviewed. Encounters with Jupiter play a dominant role in determining the
dynamical fate of these objects, although, in some peculiar cases, also interactions with other planets may be important. Frequent although temporary librations around resonances with Jupiter are displayed by more than one third of short-period comets. Integrations of motion of observed comets, over a time span comparable with their lifetime as active objects, are compared with previous numerical investigations, to get insight into the non observed phases of the dynamical evolution of these objects.
The dynamical evolution of star clusters is discussed. We investigate especially the possible disruption of globular clusters by massive black holes, which have been proposed as the major constituents of dark galactic coronae. As an example, we discuss here the globular clusters in the elliptical galaxy M87. The proposed massive black holes could be responsible for the observationally indicated depletion of the globular cluster system in the inner parts of M87 with respect to the stellar light distribution of this galaxy.
The paper deals with derivation of the dynamical model of the turbochargers with rotor supported on the two floating ring bearings. The model respects the bearing forces acting upon the journals and floating bearing rings by means of inner and outer oil-films. The gyroscopic effects, external and internal damping of the flexible rotor shaft and the rigid turbine and compressor wheels are respected. The modal analysis and the Campbell diagram is used in the turbocharger linearized model to find the critical speeds. and Obsahuje seznam literatury
We have studied the role of external current stimuli in a four-dimensional Hodgkin-Huxley-type model of cold receptor in this paper. Firstly, we researched its firing patterns from direct current (DC) and alternating current (AC) stimuli. Under different values of DC stimulus intensity, interspike intervals (ISIs) with period-doubling bifurcation phenomena appeared. Second, research has shown that neurons are extremely sensitive to changes in the frequency and amplitude of the current used to stimulate them. As the stimulus frequency increased, discharge rhythms emerged ranging from burst firing to chaotic firing and spiking firing. Meanwhile, various phase-locking patterns have been studied in this paper, such as p : 1 (p > 1), 1 : q (q > 1), 2 : q (q > 1) and p : q (p; q > 1), etc. Finally, based on the fast-slow dynamics analysis, codimension-two bifurcation analysis of the fast subsystem was performed in the parameter (asr;B)-plane. We mainly investigated cusp bifurcation, fold-Hopf bifurcation, Bogdanov-Takens bifurcation and generalized Hopf bifurcation. These results revealed the effect of external current stimuli on the neuronal discharge rhythm and were instructive for further understanding the dynamical properties and mechanisms of the Huber-Braun model.
Position actuator with small DC motor, torque 1 Nm, range 210 grad, using dynamic superposition of vibrations for decreasing of friction effect and clearances in gear box. and Polohový servomechanismus s malým stejnosměrným motorkem, točivý moment 1 Nm, rozsah 210 grad, využívající dynamické superposice vibrací pro potlačení vlivu tření a vůlí v převodovce.
H. Weyl, jeden z prvních, kdo se zabýval rolí symetrie v kvantové mechanice, podal následující definici symetrie [1]: „Věc je symetrická, pokud se s ní dá něco udělat tak, že i po dokončení toho udělání vypadá stejně jako před tím.“ Tato věta se dá přeložit do poněkud exaktnějšího jazyka pomocí teorie grup - matematické disciplíny, která byla ještě na začátku 20. století považována za nepraktickou, spíše poněkud exotickou doménu ryze teoretického bádání. Především zásluhou fyziků se v následujících desetiletích z teorie grup stal jeden z nejdůležitějších nástrojů k uchopení reality. Fyzikální svět je plný symetrií!, Pavel Cejnar., and Obsahuje seznam literatury