Oscillation of Thermal Insulation Three-Layer Cylindrical Pipes under Operating Loads

Equipment and pipes are the main components of a nuclear power plant (NPP) that ensure transfer of heat energy into electric one. The pipes with nominal diameter from DN10 to DN1200 are the main types of pipes that also include different fragments such as bends, cones, tees, branches, etc. Common length of all NPP pipes is hundreds of kilometers. All these components can be combined by one common feature: they are shell structures that found wide application in daily activities. The use of such components in the design and manufacture of equipment and pipelines of NPP power units requires appropriate practical and theoretical studies. The use of filler made of light materials allows for a small increase in the weight of the structure to significantly increase its bending stiffness and improve its thermal insulation properties. The oscillations of three-layer cylindrical pipes are considered in this paper. The equations of motion of a three-layer cylindrical shell with lightweight filler reinforced by stiffening ribs with non-stationary loading have been provided through these efforts. The model of Timoshenko’s theory of shells and rods have been used in this study under analysis of components with flexible structures. Numerical results of oscillations of the three-layer elastic structure were obtained using the finite element method. The impact of the physical and mechanical parameters of the shell layers is investigated on its stress strain state under an axisymmetric internal impulse loading.

Fast cyclic stimulus flashing modulates perception of bi-stable figure

Many experiments have demonstrated that the rhythms in the brain influence an initial information processing. We investigated whether the alternation rate of the perception of a Necker cube depended on the degree of synchronization between two streams of spikes, one stemming from an external flashing image and the other from the action of an internal impulse stream. Knowing how a flickering stimulus with a given frequency and duration affects the alternation rate of bi-stable perception we could estimate properties of the internal signal. As the internal spike frequency is difficult to control, we varied the frequency of the flicker stimulus. Our results show that the duration of the dominant stimulus perception depends on the frequency or duration of the flashing stimuli. The values of the stimuli, at which the changes of the duration of the perceived image was maximal, we have called ‘extremal’. While changing the flash duration, the extremal parameters repeated periodically at 4ms intervals. Increasing the duration of the extremal stimuli by less than 4 ms shortens the duration of the dominant stimulus perception. Hence we may conclude that it is not the stimulus duration but the accurate coincidence (timing) of the moments of switching on of external stimuli to match the internal stimuli which explains our experimental results.

Fast cyclic stimulus flashing modulates perception of bi-stable figure

Many experiments have demonstrated that the rhythms in the brain influence an initial information processing. We investigated whether the alternation rate of the perception of a Necker cube depended on the degree of synchronization between two streams of spikes, one stemming from an external flashing image and the other from the action of an internal impulse stream. Knowing how a flickering stimulus with a given frequency and duration affects the alternation rate of bi-stable perception we could estimate properties of the internal signal. As the internal spike frequency is difficult to control, we varied the frequency of the flicker stimulus. Our results show that the duration of the dominant stimulus perception depends on the frequency or duration of the flashing stimuli. The values of the stimuli, at which the changes of the duration of the perceived image was maximal, we have called ‘extremal’. While changing the flash duration, the extremal parameters repeated periodically at 4ms intervals. Increasing the duration of the extremal stimuli by less than 4 ms shortens the duration of the dominant stimulus perception. Hence we may conclude that it is not the stimulus duration but the accurate coincidence (timing) of the moments of switching on of external stimuli to match the internal stimuli which explains our experimental results.

Metal Explosion Chambers and their Application

The paper presents the principles of stress calculations for metal shells sustaining internal impulse loading. The designs of metal explosion chambers (EC) are described; examples of their utilization in scientific research and engineering applications are presented. Aside from conventional methods of the EC use, i.e. explosion welding, explosion hardening, powder compacting, synthesis of new materials, etc., recently the EC has found ever-widening applications in recycling discarded parts containing explosives, such as ammunition. The metal EC provides localization of every explosion damaging effect, improves the safety of works, and enables performing blasting operations both in industrial and laboratory conditions.

MODELING OF EXTERNAL AND INTERNAL IMPULSES IN CASE OF MULTIPLE COLLISIONS

When a robot system collides with environment, not only the contact point but also the joints of the robot system experience impulsive forces or moments. In the real environment, the structure collides with environment at multiple points. However, most previous modeling methods have assumed one point contact to environment. In this work, we propose external and internal impulse models in case of multiple contact. The case of one point contact is compared to the case of multiple points contact through simulation.