The dynamics of a resonance single-mass vibratory machine with a vibration exciter of targeted action that operates on the Sommerfeld effect

This paper reports a study into the dynamics of a vibratory machine composed of a viscoelastically-fixed platform that can move vertically and two identical inertial vibration exciters. The vibration exciters' bodies rotate at the same angular velocities in opposite directions. The bodies host a single load in the form of a ball, roller, or pendulum. The loads' centers of mass can move relative to the bodies in a circle with a center on the axis of rotation. The loads' relative movements are hindered by the forces of viscous resistance. It was established that a vibratory machine theoretically possesses the following: – one to three oscillatory modes of movement under which loads get stuck at almost constant angular velocity and generate total unbalanced mass in the vertical direction only; – a no-oscillation mode under which loads rotate synchronously with the bodies and generate total unbalanced mass in the horizontal direction only. At the same time, only one oscillatory mode is resonant and exists at the above-the-resonance speeds of body rotation, lower than some characteristic speed. At the bodies' rotation speeds: ‒ pre-resonant; there is a globally asymptotically stable (the only existing) mode of load jams; ‒ above-the-resonance, lower than the characteristic velocity; there are locally asymptotically stable regimes ‒ both the resonance mode of movement of a vibratory machine and a no-oscillations mode; ‒ exceeding the characteristic velocity: there is a globally asymptotically stable no-oscillations mode. Computational experiments have confirmed the results of theoretical research. At the same time, it was additionally established that it would suffice, to enter a resonant mode of movement, to slowly accelerate the bodies of vibration exciters to the above-the-resonance speed, less than the characteristic speed. The results reported here could be interesting both for the theory and practice of designing new vibratory machines

the development in the field of sports training was discussed. Developments achieved by sporting events

In the first section, the development in the field of sports training was discussed. Developments achieved by sporting events were the result of their reliance on the application of physical exercises. The importance of the research lies in the use of cardio exercises and applied to the research sample as special exercises to increase the strength of players and increase physical fitness. And the definition of trainers the importance of those exercises. 1- The research objectives are represented in Prepare cardio exercises to develop explosive force and characteristic speed of the muscles of the arms and legs of volleyball players 2-identify the impact of cardio exercises in the development of explosive power and characteristic speed of the muscles of the legs and arms of volleyball players As for the imposition of the research, there was no statistically significant differences between the pre- and post-test of the research sample. The researcher used the experimental method for one group and a sample of (18) players representing the team of education Baghdad / Rusafa first year (2016/2017). Homogeneity (8) players were selected to represent the sample of the study and who applied these exercises as well as the use of tools and devices appropriate for the research procedures and identify tests for explosive strength and distinctive speed of the arms and legs, the researcher conducted the tribal tests on the selected sample was developed Coordination and cardio exercises for 8 weeks with three training modules, and tests were conducted posteriori under the same circumstances in which tribal tests were conducted after the results were processed statistically, the researchers reached the door to the fifth set of conclusions recommendations: -The results of the research showed that physical training using cardio exercises was effective in developing physical abilities under investigation. -Research results showed that physical development using cardio exercises was reflected in performance development. The recommendations -The need for serious attention by trainers using cardio exercises in training to develop physical abilities under consideration by allocating sufficient time during the training unit. - The researcher recommends using these training methods to develop other physical abilities.

Modeling of the Relationship Between Speed Limit and Characteristic Speed of Expressway Traffic Flow

Understanding the relationship between speed limit and characteristic speed of expressway traffic flow is of great significance for formulating a reasonable speed limit scheme and improving highway safety and transportation efficiency. In this study, the speed data of the same traffic flow passing through speed limits of 80, 100, and 120 km/h were continuously collected through a field test. The 85th, 15th, and 50th percentile speeds were considered the characteristic speed parameters of the traffic flow. A regression analysis was performed to establish a relationship between the characteristic speed parameters of the traffic flow and the speed limit. Under a free-flow state, the characteristic speed exhibited a strong linear relationship with the speed limit, where the variation ranges of the 85th and 50th percentile speeds were approximately consistent with that of the speed limit. However, a slight inconsistency was found for the 15th percentile speed, which was approximately half the speed limit increase; under a non-free-flow state, the correlation between the speed limit and the vehicle speed was no longer significant.

Focalization of Heat Waves in an Inhomogeneous System

Curved interfaces between material media with different characteristic speed for heat waves may be the basis for thermal lenses, concentrating the energy carried by parallel thermal rays on a focal point. This may be of practical use for the amplification of thermal signals and for the development of sensitive thermal sensors. When dissipative attenuation effects are taken into account, it turns out that these lenses could be of special interest in miniaturized probes, or in micro/nanosystems, and the optimization of the thermal lens for signal amplification may be calculated.

Planetary Nebulae Embryo after a Common Envelope Event

In the centers of some planetary nebulae are found close binary stars. The formation of those planetary nebulae was likely through a common envelope event, which transformed an initially-wide progenitor binary into the currently observed close binary, while stripping the outer layers away. A common envelope event proceeds through several qualitatively different stages, each of which ejects matter at its own characteristic speed, and with a different degree of symmetry. Here, we present how typical post-common envelope ejecta looks kinematically a few years after the start of a common envelope event. We also show some asymmetric features we have detected in our simulations (jet-like structures, lobes, and hemispheres).

Existence and asymptotic stability of stationary waves for symmetric hyperbolic–parabolic systems in half-line

In this paper, we consider a one-dimensional half-space problem for a system of viscous conservation laws which is deduced to a symmetric hyperbolic–parabolic system under assuming that the system has a strictly convex entropy function. We firstly prove existence of a stationary solution by assuming that a boundary strength is sufficiently small. The existence of the stationary solution is characterized by the number of negative characteristics. In the case where one characteristic speed is zero at spatial asymptotic state [Formula: see text], we assume that the characteristic field corresponding to the characteristic speed 0 is genuinely nonlinear in order to show existence of a degenerate stationary solution with the aid of a center manifold theory. We next prove that the stationary solution is time asymptotically stable under a smallness assumption on an initial perturbation in the Sobolev space. The key to proof is to derive the uniform a priori estimates by using the energy method, where the stability condition of Shizuta–Kawashima type plays an essential role.

On the propagation of non-isothermal gravity currents in an inclined porous layer

We consider the buoyancy-driven flow in an inclined porous layer which results when fluid of different temperature and composition to that in the reservoir is injected from a horizontal line well. The thermal inertia of the porous matrix leads to a transition in the temperature of the injectate as it spreads from the well and heats up to reservoir temperature. Since the buoyancy and viscosity of the injectate change across this thermal transition, the alongslope characteristic speed of the current also changes. Density and viscosity typically decrease with temperature and, so, for injectate that is positively buoyant at reservoir temperature, the changes in density and viscosity with temperature have complementary effects on the characteristic speed. In contrast, for injectate that is negatively buoyant at reservoir temperature, the changes in viscosity and density with temperature have competing influences on the characteristic speed. The change in characteristic speed, combined with the change in buoyancy across the thermal transition, leads to a series of different flow morphologies with the thermally adjusted injectate either running ahead of or lagging behind the original injectate. By approximating the thermal transition as a discrete jump, we derive the leading-order structure of these currents for the different possible cases. We then build on this to develop a more detailed boundary layer description of the thermal transition based on the theory of thin gravity driven flows in porous media. Under certain injection conditions, we show that the thermal transition is gravitationally unstable and that this may lead to mixing across the thermal transition. We consider the implications of the models for several industrial processes including geothermal heat recovery, aquifer thermal storage and carbon dioxide sequestration.