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Modeling o fRebound Phenomenon between Ball and Racket Rubber with Spinning Effect
Akira Nakashima,Yosuke Kobayashi,YukiOgawa,YoshikazuHayakawa 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
We model the rebound phenomenon between a ping-pong ball and the table/racket rubber. In the model between the ball and racket rubber, it is assumed that the kinetic energy of the contact velocity is stored as the potentialen ergy due to the elasticity of the rubber. This assumption leads to that the impulse in the horizontal direction is propor-tional to the contactve locity. The vertical and horizontal COR in the models of the table and rubber are identified with the measured velocity and spin of the ball by high-speed vision sensors. The models are verified by other experimental data.
Racket Control for Robot Playing Table Tennis Ball
Chunfang Liu,Yoshikazu Hayakawa,Akira Nakashima 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10
This paper proposes a racket control method for returning a table tennis ball to a reference position with a desired translational/ rotational velocity. The method determines the racket’s state, i.e., the racket’s striking posture and translational velocity by using two physical models: racket rebound model and aerodynamics model. The paper makes clear what the racket can control among the reference position, translational and rotational velocities. The algorithm of determining the racket’s state is derived by solving nonlinear equations and solving two points problems of differential equation. Two approximate aerodynamic models are proposed for real-time treatments. Then numerical simulations show effectiveness of the proposed methods.
Neutron Energy Spectra at 180˚ from 140 MeV Proton Incident Reactions
Yosuke Iwamoto,Daiki Satoh,Yoshihiro Nakane,Hiroshi Nakashima,Akira Endo,Yukio Sakamoto 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The neutron energy spectra of carbon, iron, and gold targets with 140 MeV protons at 180˚ were measured at the RCNP cyclotron facility using the time-of-flight technique. The results were compared with results calculated using the evaluated nuclear data file (the LA150 library) and the intranuclear cascade models (JAM and JQMD) implemented in the PHITS code. The results using LA150 and JQMD generally agreed with the experimental data except for the carbon target, but the JAM could not reproduce high-energy neutrons above .
String Cavitation and 3D PIV in Multi-Hole Injector
( Hiroaki Nakano ),( Rubby Prasetya ),( Shinichiro Deguchi ),( Takashi Miwa ),( Akira Sou ),( Keiya Nishida ),( Akira Nakashima ),( Yoshitaka Wada ),( Yoshiharu Ueki ),( Hideaki Yokohata ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
It is essential to control fuel spray characteristics in diesel engines for cleaning up exhaust gases and improving combustion efficiency. Turbulent cavitating flow in fuel injectors plays an important role in fuel spray characteristics. String cavitation may occur in a sac and nozzles of multi-hole fuel injectors, which strongly affects fuel spray characteristics. It should be caused by the vortex flow in the sac. However, the occurrence mechanism of string cavitation has not been clarified yet. The purpose of this study is to clarify the mechanism and condition of string cavitation occurrence by conducting a high-speed visualization experiment in a transparent injector of cavitation and a discharged liquid jet at various needle lifts and flow rates. We also measure the three-dimensional flow field in the sac by 3D PIV. The transparent acrylic multi-hole mini-sac nozzle is designed to visualize cavitation. Sodium iodide aqueous solutions or diesel oil with α-methyl naphthalene is used as a working fluid to avoid the refraction at the surface of the acrylic walls and these liquids. As a result, it is found that at low needle lift string cavitation often occurs which is surrounded by a vortical flow in the sac and increases the discharged hollow-cone liquid jet angle, while at high needle lift thin and short string cavitation may occur, which does not strongly influence discharged liquid jet and spray. The probability of the string cavitation appearance under various conditions as well as the transient motion of string cavitation and liquid jet is also clarified.