• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.2
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• pp.39-48
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• 2023

Background: The position of pitcher requires a lot of repetitive motion, and because of this, it is known that not only professional baseball players, but also middle and high school players are frequently exposed to injuries in baseball. The purpose of this study is to examine the differences in upper extremity muscle activity during repeated pitching and the activity of each muscle during repeated pitching by analyzing middle and high school pitchers, divided into groups by age. Methods: Twenty participants (10 middle school male students and 10 high school male students) were recruited for this research. The outcome measures included neuromuscular motor control, including the upper trapezius (UT), triceps brachii (TB), deltoid (DT), latissimus dorsi (LD), biceps brachii (BB), pectoralis major(PM), extensor carpi radialis(ER), and flexor carpi radialis (FR). Results: The two-way analysis of varaince (ANOVA) was used to compare the muscle activity variables between the middle school and high school students. The one-way ANOVA was used to compare the muscle activity variables within time differences each groups. Conclusion: Our results provided promising clinical evidence that guide for upper extremity muscles to increase pitching efficiency in middle and high school base ball players.

• Journal of the Korean Solar Energy Society
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• v.37 no.1
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• pp.1-14
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• 2017

A series of coupled time domain simulations considering stochastic waves and wind based on five 1-h time-domain analyses are performed in normal operating conditions. Power performance and tower base Fore-Aft bending moment and pitching motion response of the floating spar-buoy wind turbine with 2 MW direct-drive PMSG have been analyzed by using HAWC2 that account for aero-hydro-servo-elastic time domain simulations. When the floating spar-buoy wind turbine is tilted in the wind direction, maximum of platform pitching motion is close to $4^{\circ}$. Statistical characteristics of tower base Fore-Aft bending moment of floating spar-buoy wind turbine are compared to that of land-based wind turbine. Maximum of tower base Fore-Aft bending moment of floating spar-buoy wind turbine and land-based wind is 94,448 kNm, 40,560 kNm respectively. This results is due to changes in blade pitch angle resulting from relative motion between wave and movement of the floating spar-buoy wind turbine.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.191-196
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• 1998

A two-dimensional airfoil flying over a wavy wall is calculated by solving the unsteady Euler equation. Unsteady Transonic flow over an NACA00012 airfoil in pitching motion has been computed for code validation. Some numerical results for NACA6409 airfoil under different wave number, wave length, fly height are presented. The numerical results show the variation of lift and pitching moment coefficients are increased as wave length decrease.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.3
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• pp.252-261
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• 2016

A spar-type floating substructure that is being widely used for offshore wind power generation is vulnerable to resonance in the heave direction because of its small water plane area. For this reason, the stable dynamic response of this floating structure should be ensured by accurately identifying the resonance characteristics. The purpose of this study is to analyze the characteristics of the combination resonance between the excitation frequency of a regular wave and natural frequencies of the floating substructure. First, the nonlinear equations of motion with two degrees of freedom are derived by assuming that the floating substructure is a rigid body, where the heaving motion and pitching motions are coupled. Moreover, to identify the characteristics of the combination resonance, the nonlinear term in the nonlinear equations is approximated up to the second order using the Taylor series expansion. Furthermore, the validity of the approximate model is confirmed through a comparison with the results of a numerical analysis which is made by applying the commercial software ANSYS AQWA to the full model. The result indicates that the combination resonance occurs at the frequencies of ${\omega}{\pm}{\omega}_5$ and $2{\omega}_{n5}$ between the excitation frequency (${\omega}$) of a regular wave and the natural frequency of the pitching motion (${\omega}_{n5}$) of the floating substructure.

• Journal of Navigation and Port Research
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• v.32 no.1
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• pp.15-22
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• 2008

A ship in a sea cruises with rolling, pitching, heaving etc because of environmental causes such as wind and wave. Those motions make crews or passengers feel inconvenience and they feel acceleration changes. Therefore, if lateral and vertical accelerations can be measured at a specific position in a ship, it can be known how discomfortable crews or passengers are. The motion monitoring system developed in this paper consists of measuring and communicating part including five accelerometers and gyro and a main computer which acquires measuring data and calculates motion indices. MSI(Motion Sickness Incidence) and MII(Motion Induced Interrupt) are calculated in real time using measured acceleration and angular rate. The validity of the developed system was confirmed through the real ship test of Hannara which is the school ship of Korea Maritime University.

• International Journal of Automotive Technology
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• v.7 no.4
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• pp.469-475
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• 2006

In this paper, an optimal suspension system with preview of the road input is synthesized for a half tracked vehicle. The main goal of this research is to improve the ride comfort characteristics of a fast moving tracked vehicle in order to maintain the driver's driving capability. Several different kinds of preview control algorithms are evaluated with active or semi-active suspension systems. The road information estimated from the motion of the 1st road-wheel is adequate to make the best use of the preview control algorithm for tracked vehicles. The ride-comfort characteristics of the tracked vehicle are more dependent on pitching angular acceleration than heaving acceleration. The pitching motion is reduced by the suspension system with hard outer suspensions and soft inner suspensions. Simulation results show that the performance of sky-hook algorithms for ride comfort nearly follow that of full state feedback algorithms.

• Proceedings of KOSOMES biannual meeting
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• 2009.06a
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• pp.85-86
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• 2009

The sloshing phenomenon can be defined as the nonlinear movement of the free-surface of liquids inside tanks. It generates dynamic loads on the tank structure and thus becomes a problem of relative importance in the design of marine structures. The present study describes a experiment of the sloshing of flows with free-surface which contained in a rectangular tank moving in pitching motion.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.61-69
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• 1999

A dynamic stability test was performed to determine dynamic stability derivatives for the pure pitching motion of air-to-ground missile model in the low speed wind tunnel. The free vibration technique was employed to acquire oscillation characteristics of the model for damping coefficients. Damping coefficients are obtained by the method of logarithmic decrement. Results show good damping effects and stability capability at Mach numbers 0.1 and 0.2, with the angle of attack ranging from -15 to +20 degrees.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.842-848
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• 2011

The low-floor tram is a kind of railway vehicles which is operated on the street way track. For reducing the radius of curvature of the track, the tram consists of some carbody modules, and the articulation systems connect and support these carbody modules. The kind of articulation systems would be the hinge type and the pitching type. The hinge type articulation could allow only the yawing motion of the carbody modules, and the pitching type articulation could allow the pitching and yawing motions of the carbody modules simultaneously. With these function of the articulation systems, the tram could be operated on the horizontal and vertical curvature of the track. The number of each type of articulation could be decided with the number of carbody modules, and the manufacturer would decided the position of each type of the articulation in the view of the stability of carbody modules in the operation condition.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.950-955
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• 2003

The fluid propulsion mechanism of two oscillating flat plates is studied numerically using a discrete vortex method. Presently, the flat plates are assumed to be rigid. To analyze the closely coupled aerodynamic interference between the flat plates, a core addition scheme and a vortex core model are combined together. A calculated wake pattern for a flat plate in heaving oscillation motion is compared with the flow visualization. The effect of wake shapes on the aerodynamic characteristics of the flat plate in pitching oscillation is investigated. The velocity profiles behind the flat plates in pitching oscillations are plotted to investigate the possible thrust generation mechanism.