• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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• pp.211-217
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• 2018

The Pohang earthquake with a magnitude of 5.4 occurred on November 15, 2018. The epicenter of this earthquake located in south-east region of the Korean peninsula. Since instrumental recording for earthquake ground motions started in Korea, this earthquake caused the largest economic and life losses among past earthquakes. Korea is located in low-to moderate seismic region, so that strong motion records are very limited. Therefore, ground motions recorded during the Pohang earthquake could have valuable geological and seismological information, which are important inputs for seismic design. In this study, ground motions associated by the 2018 Pohang earthquake are generated using the point source model considering domestic geological parameters (magnitude, hypocentral distance, distance-frequency dependent decay parameter, stress drop) and site amplification calculated from ground motion data at each stations. A contour map for peak ground acceleration is constructed for ground motions generated by the Pohang earthquake using the proposed model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.11 s.254
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• pp.1408-1416
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• 2006

A mathematical knee model was constructed using MADYMO. The purpose of this study is to present a more realistic model of the human knee to reproduce human knee motion. Knee ligaments were modeled as line elements and the surrounding muscles were considered as passive restraint elements. A calf-free-drop test was performed to validate the suggested model. A calf was dropped from the rest at about 65 degree flexed posture in the prone position. The motion data were recorded using four video cameras and then three dimensional data were acquired by Kwon3D motion analysis software. The results showed that general shapes of angular quantities were similar in both the experiment and computer simulation. Functional stability of the anterior cruciate ligament was explicitly revealed through this model.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.29-37
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• 2015

Objective : The purpose of this study was to investigate the biomechanical properties of shock absorption strategy and postural stability during the drop landing for each types. Methods : The motions were captured with Vicon Motion Capture System, with the fourteen infra-red cameras (100Hz) and synchronized with GRF(ground reaction force) data(1000Hz). Ten male soccer players performed a drop landing with single-leg and bi-legs on the 30cm height box. Dependent variables were the CoM trajectory and the Joint Moment. Statistical computations were performed using the paired t-test and ANOVA with Turkey HSD as post-hoc. Results : The dominant leg was confirmed to show a significant difference between the left leg and right leg as the inverted pendulum model during Drop Landing(Phase 1 & Phase 2). One-leg drop landing type had the higher CoM displacement, the peak of joint moment with the shock absorption than Bi-leg landing type. As a lower extremity joint kinetics analysis, the knee joint showed a function of shock absorption in the anterior-posterior, and the hip joint showed a function of the stability and shock absorption in the medial-lateral directions. Conclusion : These findings indicate that the instant equilibrium of posture balance(phase 1) was assessed by the passive phase as Class 1 leverage on the effect of the stability of shock absorption(phase 2) assessed by the active phase on the effect of Class 2 leverage. Application : This study shows that the cause of musculo-skeletal injuries estimated to be focused on the passive phase of landing and this findings could help the prevention of lower damage from loads involving landing related to the game of sports.

• Physical Therapy Korea
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• v.11 no.4
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• pp.1-6
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• 2004

The kinematics involved in different landing strategies may be related to the occurrence of trauma. Several sources suggest that the angle of knee extension on touchdown and impact with the ground determines the magnitude of the impact force and, indirectly, knee loading. This study compared the initial knee angle and maximum knee flexion angle at the instant of impact on drop-landings between healthy men and women. In this study, 60 participants (30 males, 30 females) dropped from a height of 43 cm. A digital camera and video motion analysis software were used to analyze the kinematic data. When landing, there was significant difference between the two groups ($15.67{\pm}6.05^{\circ}$ in male, $24.10{\pm}6.34^{\circ}$ in female) in the mean knee flexion angle. The range of knee flexion on landing ($44.06{\pm}10.97^{\circ}$ in male, $36.96{\pm}9.99^{\circ}$ in female) also differed significantly (p<.05). The greater knee flexion that was observed in the male subjects would be expected to decrease their risk of injury. Women land with smaller range of knee flexion than men and this might increase the likelihood of a knee injury.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.5
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• pp.360-365
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• 2016

The purpose of this study is to suggest a possibility of the Korean medical treatment in patient with peroneal nerve palsy, and to suggest importance of differential diagnosis of foot drop. Peroneal nerve pasly was diagnosed by lumbar spine magnetic resonance imaging(MRI) and electromyogram(EMG). The patient was treated with acupuncture, herbal medicine, bee-venom acupuncture and moxibustion from March 7th to May 2nd. We measured Numerical Rating Scale(NRS), Range of Motion(ROM) of the ankle, and observed the change in body temperature using Digital Infrared Thermal Imaging(DITI). After received Korean medical treatment, the patient showed improvement in all the scales mentioned above. The result showed that Korean medical treatment is effective in peroneal nerve palsy before operation.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2971-2976
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• 2007

The mode change from Taylor cone-jet to dripping in electrospraying has been analytically investigated. The change has been predicted by the dynamic behavior of a liquid drop at the tip of the cone-jet. Conservation laws are applied to determine the upward motion of the drop, and an instability model of electrified jets is used to determine the jet breakup. Finally, for the first time, the analysis enables prediction of the transition in terms of the Weber number and electric Bond number. The predictions are in good agreement with experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.6
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• pp.52-64
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• 1996

This paper presents an active position control of a single-rod cylinder system featuring an electrorheological(ER) fluid-based valve. The ER fluid consisting of silicone oil and chemically treated particles is firstly composed and its Bingham property is tested as a function of imposed electric field. A multi-channel plate type of ER valve is then designed and manufactured on the basis of the field-dependent Bingham model. Performance test of the ER valve is undertaken by evaluating pressure drop with respect to the number of electrode as well as the intensity of the electric field. Subsequently, the ER valve-cylinder system is constructed and its governing equation of motion is derived. A neural control scheme for position control of the cylinder is formulated by incorporating proportional-plus-derivative(PD) controller and implemented. Experimental results of both regulating and tracking control responses are presented in order to demonstrate the efficacy of the proposed ER valve-cylinder control system.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.165-170
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• 2001

This paper presents performance analysis of two-linked robot system using ER (electro rheological) valve actuators. An ER fluid consisting of soluble chemical starches (particles) and silicone oil is made and its field-dependent yield stress is experimentally distilled using electro-viscometer. From this result, the design parameters of ER valve are determined. Based on parameter study, an ER valve system is designed and manufactured. Furthermore, the measured pressure drop is compared with predicted one obtained from the Bingham model. Following the evaluation of field-dependent pressure drop of ER valve, a two-linked robot system with two ER valve actuators is then constructed and its governing equation of motion is derived. From this equation, PID controller is established. Consequently, control performances of the proposed two-linked robot system featuring ER valve are evaluated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.175-178
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• 2007

The mode transition from cone-jet to dripping in colloid thruster operation has been analytically investigated. The transition has been predicted by the dynamic behavior of a liquid drop at the tip of the cone-jet. Conservation laws are applied to determine the upward motion of the drop, and an instability model of electrified jets is used to determine the jet breakup. Finally, for the first time, the analysis enables prediction of the transition in terms of the Weber number and electric Bond number. The predictions are in good agreement with experimental data.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.22-28
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• 2006

The motion and wave drift forces of floating BBDB (backward-bent duct buoy) wave energy absorbers in regular waves are calculated, taking account of the oscillating surface-pressure due to the pressure drop in the air chamber above the oscillating water column, within the scope of the linear wave theory. A series of model tests has been conducted in order to order to verify the motion and time mean wave drift force reponses in regular waves at the ocean engineering basin, MOERI/KORDI. The pneumatic damping through an orifice-type duct for the BBDB wave energy device are deducted from experimental research. Numerical simulation for motion and drift force responses of the BBDB wave energy device, considering pneumatic damping coefficients, has been carried out, and the results are compared with those of model tests.