The leaking soft stadium

We soften the non zero y-boundary on a Bunimovich like quarter-stadium. The smoothing procedure is performed via an exponent monomial potential, the system becomes partially reflective, preserving the particle’s translation and rotational motion. By increasing the exponent value, the stadium’s boundaries become rigid and the system’s dynamics reaches a chaotic regime. We set a leaking soft stadium family by opening a limited region located at some place of its basis’s boundary, throughout which the particles can leak out. This work is an extension of our recently reported paper on this matter. We chase the particle’s trajectory and focus on the stadium transient behavior by means of the statistical analysis of the survival probability on the marginal orbits that never leave the system, the so called bouncing ball orbits. We compare these family orbits with the billiard’s transient chaos orbits.

Peningkatan kemampuan psikomotorik siswa dalam pembelajaran bola voli passing atas menggunakan teknik bola pantul pada siswa kelas X MAN 1 Kota Semarang

Angga Pratama, "Increasing the Psychomotor abilities of Students in Learning Top Passing Volleyball Using the Bounce Ball Technique in Class X Students of MAN 1 Semarang City". Essay. Department of Physical Education for Health and Recreation, Faculty of Social Sciences and Sport Education, PGRI University Semarang, 2020. Utvi Hinda Zhannisa, S.Pd., M.Ordan Ibnu Fatkhu Royana, S.Pd., M.Pd. Education is a very important field, especially in Indonesia. In the language of the definition of education is the process of changing the attitudes and behaviour of a person or group of people in an effort to mature humans through teaching and training efforts that are in accordance with the educational procedure itself. The purpose of this study was to determine the improvement of students' psychomotor abilities in learning volleyball using the bounce ball technique in class X students in MAN 1 Semarang City. The design used in this study belongs to the type of quantitative research. The use of a quantitative approach with pre-experimental methods. The population in this study were students of class X in MAN 1 Semarang City. The research sample was taken by means of random sampling. This research will involve 106 students of MAN 1 Semarang City. Based on the calculation, the sig value for pretest data obtained the sig value = 0.064> 0.05. For the posttest data, the sig = 0.056> 0.05 was obtained, so it can be concluded that the pretest and posttest data are homogeneous. The increase in the ability to pretest all volley passing is a minimum of 82,675%. for a maximum value of 89.33%. Data analysis and discussion obtained the following conclusions: There are differences in the psychomotor abilities of students in learning volleyball passing over before and after being given training using the bouncing ball technique in class X MAN 1 Semarang City. From these results, it can be concluded that there is an increase in the psychomotor abilities of students in learning volleyball passing overusing the bouncing ball technique in class X MAN 1 Semarang City students. The increase in the percentage of overpassing ability is 22.38%. It is better if the class X student coaches of MAN 1 Semarang City apply exercises using the bouncing ball technique considering that this exercise has been proven effective in improving students' psychomotor skills in learning volleyball passing over.

The bouncing ball and the Grünwald-Letnikov definition of fractional derivative

This paper proposes a conceptual experiment embedding the model of a bouncing ball and the Grünwald-Letnikov (GL) formulation for derivative of fractional order. The impacts of the ball with the surface are modeled by means of a restitution coefficient related to the coefficients of the GL fractional derivative. The results are straightforward to interpret under the light of the classical physics. The mechanical experiment leads to a physical perspective and allows a straightforward visualization. This strategy provides not only a motivational introduction to students of the fractional calculus, but also triggers possible discussion with regard to the use of fractional models in mechanics.

Nonlinear reduced-order model for vertical sloshing by employing neural networks

The aim of this work is to provide a reduced-order model to describe the dissipative behavior of nonlinear vertical sloshing involving Rayleigh–Taylor instability by means of a feed forward neural network. A 1-degree-of-freedom system is taken into account as representative of fluid–structure interaction problem. Sloshing has been replaced by an equivalent mechanical model, namely a boxed-in bouncing ball with parameters suitably tuned with performed experiments. A large data set, consisting of a long simulation of the bouncing ball model with pseudo-periodic motion of the boundary condition spanning different values of oscillation amplitude and frequency, is used to train the neural network. The obtained neural network model has been included in a Simulink® environment for closed-loop fluid–structure interaction simulations showing promising performances for perspective integration in complex structural system.