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Yusaku Fujii 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.3
The present status and future prospects of the levitation mass method(LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers. materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing. providing methods for evaluating material viscoelasticity under an oscillating or impact load. evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.
The Levitation Mass Method: A Precision Mass and Force Measurement Technique
Fujii, Yusaku Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.3
The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.
小?優作(Ogura, Yusaku),藤井勝紀(Fujii, Katsunori),김준동(Kim, Jun-Dong) 한국체육과학회 2019 한국체육과학회지 Vol.28 No.2
Exploration of the physical elements of elite athletes in Japan’s top leagues or around the world is a key issue related to the core aspect of discovering sports talent. We applied a radar chart analysis in evaluating the physical balance of elite athletes. First, we sought to build standards for evaluation of physical balance in each sport. Next, we investigated the sex differences in physical elements. We then also sought the meaning of sports gender in discovering sports talent. We found that both male and female athletes are taller than the general population. Sports in which height is a significant advantage are those in which height is prominent and there is much contact play. The ratio of weight to height tends to be large. With regard to the sex differences in physical elements, a physique chart of males and females in each sport showed almost the same forms in all athletes except short-distance track athletes. Therefore, it is thought that a physical balance suited to the sport is necessary regardless of sex. In terms of talent discovery, the first fundamental condition is thought to be to find individuals, both male and female, who are tall.
Parlapalli, Madhusudhana R,Bin, Gu,Dongwei, Shu,Fujii, Yusaku Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.4
The dynamic response of the head arm assembly (HAA) of a hard disk drive to an impact load was obtained from a 3D non-linear finite element model using ANSYS/LS-DYNA and from experiments using a modified levitation mass method (LMM). In the finite element model, the impact load was created by modeling the mass as a rigid body and making it collide with the HAA. The velocity, displacement, acceleration, and inertial force of the mass were then obtained from the time history data of the finite element analysis. In the LMM, a mass that was levitated with an aerostatic linear bearing, and hence encountered negligible friction, was made to collide with the actuator arm, resulting in a dynamic bending test for the arm. During the collision, the Doppler frequency shift of the laser beam reflected from the mass was accurately measured with an optical interferometer. The velocity, displacement, acceleration, and inertial force of the mass were accurately calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental data and FEA results was observed. The FEA was also used to investigate the dynamic response of the HAA to impact by different masses.