• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.257-264
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• 2016

Objective: The purpose of this study was to determine the periodicity of shank-foot segment coupling and free torque before and after fatigue induced by prolonged running. Method: Fifteen young healthy male participants with a rear-foot strike ran on instrumented dual-belt treadmills at 70% of their maximum oxygen uptake for 65 min. Kinematic and ground reaction force data were collected for 20 continuous strides at 5 and 65 min (considered the fatigued condition). The approximate entropy tool was applied to assess the periodicity of the shank internal-external rotation, foot inversion-eversion, shank-foot segment coupling, and free torque for the two running conditions. Results: The periodicity of all studied parameters, except foot inversion-eversion, decreased after 65 min of running (fatigued condition) for 80% of the participants in this study. Furthermore, 60% of the participants showed similarities in the change of periodicity pattern in shank internal-external rotation, coupling, and free torque. Conclusion: The findings indicated that the foot inversion-eversion motion may pose a higher risk of injury than the shank internal-external rotation, coupling, and free torque in the fatigued condition during prolonged running.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1842-1852
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• 2019

The AP1000 reactor coolant pump is a vertical shielded-mixed flow pump, is the most important coolant power supply and energy exchange equipment in nuclear reactor primary circuit system, whose steadystate and transient performance affect the safety of the whole nuclear island. Moreover, safety demonstration of reactor coolant pump is the most important step to judge whether it can be practiced, among which software simulation is the first step of theoretical verification. This paper mainly introduces the fluid-solid coupling simulation method applied to reactor coolant pump, studying the feasibility of simulation results based on workbench fluid-solid coupling technology. The study found that: for the unsteady calculations of the pure liquid media, the average head of the reactor coolant pump with bidirectional fluid-solid coupling decreases to a certain extent. And the coupling result is closer to the real experimental value. The large stress and deformation of rotor under different flow conditions are mainly distributed on impeller and idler, and the stress concentration mainly occurs at the junction of front cover plate and blade outlet. Among the factors that affect the dynamic stress change of rotor, the pressure load takes a dominant position.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3E
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• pp.110-114
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• 2006

In a previous theoretical paper, we have derived a unified formula by considering 2-D coupled mode vibrations. The unified formula for electromechanical coupling coefficient of piezoelectric resonator was verified experimentally. The capacitance change near the resonant frequency was investigated to estimate the effective coupling coefficient of the resonator instead of the conventional method based on I-D model. The susceptance spectra were measured for the seven samples of piezoelectric resonator with different aspect ratio. Excellent agreement between theoretical and experimental results was obtained.

• Journal of Korean Association for Spatial Structures
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• v.17 no.4
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• pp.77-84
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• 2017

As an alternative to coupling beam in shear wall system, application of the damper which can dissipate energy is increasing. In this study, lintel beam type steel damper which is simple to construct and change depending on design load was proposed. Cyclic loading test was conducted to compare reinforced concrete coupling beam and lintel beam type steel damper. The test results showed that lintel beam type steel damper has higher initial stiffness and energy dissipation capacity than reinforced concrete coupling beam.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.101-106
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• 2002

In a bank-to-turn(BTT) missile, if a 2-gimbaled seeker was stabilized using a 2-axis rate gyro mounted along its primary axis, the change of line of sight(LOS) measured by the seeker would be induced by rolling effects due to bank-to-turn(BTT) steering as well as an actual change. It is observed that the body-coupled effects in a homing loop of BTT missile are mainly concerned with the spurious target maneuver and the coupling due to the rate gyro misalignments. In this paper, we formulate a simple linear BTT homing loop model with seeker model including each body-coupling. With the model, we analyze the effects of the couplings on the homing loop stability, and propose a direct linear compensator for the coupling to recover the stability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.1
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• pp.37-45
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• 2023

The purpose of this study is to prevent diagonal tension failure of existing conventional coupling beams, increase the shear strength of conventional coupling beams, and quantitatively evaluate the increase. Steel fibers can improve shear strength and partially change the failure mechanism, but this is the result of research on general RC beams and columns, and research on the shear strength enhancement of conventional coupling beams for steel fiber reinforced concrete is still lacking. Therefore, in order to confirm the increased shear strength caused by steel fiber and the resulting change in failure mechanism, three specimens were fabricated with the steel fiber volume fraction as a variable (0%, 1%, 2%) and repeated loading experiments were performed. As a result, the shear strength of the specimens reinforced with steel fibers (1%, 2%) increased as the shear resistance contribution of concrete increased after the maximum strength was developed compared to the specimens without it (0%).

• International Area Studies Review
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• v.15 no.3
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• pp.393-405
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• 2011

Three different models have been consecutively employed with the U.S. yield curve and the Korean composite stock price index, firstly to see the coupling between the economies of the U.S. and Korea, secondly to find out the time consumed completing the coupling, and lastly to figure out the impact of the recent U.S. financial crisis on this coupling. This study has, first of all, produced an empirical research outcome which proved the existence of coupling between two countries' economies. The direction of this coupling was consistent with the general expectation that when the yield spread between the U.S. 10-year Treasury Note and the U.S. 3-month Treasury Bill increased which often occurred with better prospects of U.S. economy, the asset price of emerging economies including Korea also rose reflecting the accompanying change in investment atmosphere in favor of risk. It has also found out that the degree of the coupling was maximized with a lag of one week. And finally the recent US financial crisis has been revealed to reduce the degree of the coupling by as much as half in a regression model with a dummy variable.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2019.08a
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• pp.184-185
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• 2019

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.211-216
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• 2001

Top synthetic spin valves wi th structure Ta/NiFe/CoFe/Cu/CoFe(Pl)/Ru/CoFe(P2)/FeMn/Ta on Si (100) substrate with SiO$_2$ of 1500 were prepared by dc magnetron sputtering system. We have changed only the thickness of the free layer and the thickness difference (Pl-P2) in the two ferromagnetic layers separated by Ru, and investigated the effect of magnetic film thickness on the GMR properties and the interlayer coupling field in a spin valve with a synthetic antiferromagnet. As thickness difference of pinned layer was decreased from +25 to -25 , MR ratio was decreased gradually. However, there was a dip zone indicating a big change of MR ratio around Pl = P2, which can be due to the large canting of pinned layers. The modified Neel model was suggested for the top synthetic spin valve to explain the interlayer coupling field according to the thickness change of ferromagnetic layers. The interlayer coupling field was decreased due to the magnetostatic coupling (orange peel coupling) as suggested by model. However, the interlayer coupling field was not explained at the dip zone by the modified Neel model. The deviation of modified Neel model at the dip zone could be due to the largely canting of the pinned layers as well, which depends on different thickness in synthetic antiferromagnetic structure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.57-66
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• 2013

This study investigates structural and vibration analyses due to the change of bolt Numbers on models 1 and 2 of flange couplings connected with both sides of axis. As maximum equivalent stresses of models 1 and 2 are 122.05 and 102.3 MPa respectively by the basis of bolt, these stresses are within the allowable stress of this model and the safety of bolt design is verified. As maximum equivalent stresses of models 1 and 2 are 196.2 and 196.4 MPa respectively by the basis of body, these stresses are within the allowable stress of this model and the safety of body design is verified. Through natural frequency analysis, maximum displacements of model 1 and 2 are shown at the frequencies of 6565.1 and 6614.9 Hz respectively. Maximum displacements in cases of models 1 and 2 are shown at harmonic frequencies of 7760 and 7840 Hz at real loading conditions. By putting these study results together, the durability of vibration at model 2 with bolt numbers of 8 becomes better than model 1 with bolt numbers of 6. These study results can be effectively utilized with the design on flange coupling by anticipating and investigating prevention and durability against its damage.