• 대한물리의학회지
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• 제15권3호
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• pp.1-9
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• 2020

PURPOSE: This study examined the effects of muscle fatigue on proprioception in the type of taekwondo training, causing injury to taekwondo athletes. METHODS: The subjects were divided into Taekwondo Kyorugi athletes (n = 14) and Taekwondo Poomsae athletes (n = 14). After inducing muscle fatigue to the subjects, the joint position sense (JPS) and the force reproduction sense (FRS) were measured before and immediately after the induction of muscle fatigue. RESULTS: Studies have shown no significant impact on the JPS and FRS caused by muscle fatigue induced by Poomsae and Kyorugi (p > .05). The JPS, however, showed a significant difference before and after Kyorugi (p < .05). The FRS showed significant differences before and after Poomsae (p < .05). Through this study, the injuries to taekwondo athletes appear to be influenced by the joint position and force reproduction. Moreover, the injury appears to affect the joint position sense in Kyorugi athletes and the force reproduction sense in Poomsae athletes. CONCLUSION: The results will contribute to injury prevention and athlete protection. In addition, the information can be used as basic data for the development of sports injuries prevention and rehabilitation programs for Taekwondo athletes. Research is needed on the customized management of sports methods and self-care to prevent sports damage, considering the athletic characteristics of the taekwondo athletes in the future.

• 한국융합학회논문지
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• 제7권5호
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• pp.51-57
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• 2016

본 연구는 초음파 영상(ultrasound imaging)을 이용하여 네발기기 자세(quadruped position)에서 골반압박벨트(pelvic compression belt)가 뭇갈래근과 척추세움근의 근두께에 융합적으로 미치는 영향을 알아보기 위해 실시되었다. 대상자는 30명의 남자대학생으로 실험에 자발적으로 참여한 자로 선정하였다. 골반압박벨트를 위앞엉덩뼈가시아래(anterior superior iliac spines)에 착용한 상태와 착용하지 않은 상태에서 네발기기 자세를 실시하였고, 초음파영상 진단장치를 이용하여 근 두께를 측정하였다. 자료분석은 반복측정분산분석을 이용하였다. 연구결과, 뭇갈래근의 경우 골반압박벨트를 착용하였을 때가 착용하지 않았을 때보다 근두께가 유의하게 증가하였고(p<.05), 척추세움근의 경우도 골반압박벨트를 착용하였을 때가 착용하지 않았을 때보다 근두께가 유의하게 증가하였다(p<.05). 따라서 본 연구결과를 통해 골반압박벨트의 착용이 요통환자에게 효과적이며, 임상에서 다양한 네발기기 자세운동의 처방과 적용 시에 유용한 자료로 활용하고자 한다.

• 한국음향학회지
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• 제38권6호
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• pp.630-636
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• 2019

수동측거소나는 잠수함 플랫폼의 좌/우현에 각각 3개의 부배열로 구성된 수동소나의 한 종류로서 표적을 탐지하고 방위와 거리를 산출하는 특성을 갖는다. 방위와 거리 산출에는 물리적인 부배열 위치로 인하여 발생되는 시간지연과 삼각측량 기법이 활용된다. 이러한 기법에는 부배열의 정확한 위치정보가 요구되며 부배열의 위치정보가 부정확할 경우 방위와 거리정확도 성능이 저하되는 한계가 있다. 특히 하나의 시간지연을 사용하는 방위보다 두 개의 시간지연 값을 사용하는 거리 정확도 성능에 미치는 영향이 더 크다. 이를 개선하기 위하여 부배열의 위치 오차 추정 및 오차보상에 대한 연구가 필요하다. 본 논문에서는 최적화 탐색 기법인 유전자 알고리즘을 바탕으로 부배열 위치오차를 추정하며, 위치오차로 인한 시간지연 오차 값을 보상하여 거리정확도 성능 개선 방법을 제시하고자 한다. 또한 해상시험 데이터를 이용하여 제시한 알고리즘과 성능을 검증하고자 한다.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1113-1118
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• 2010

차량의 내장부품 설계에 있어 내장 부품의 탑승자 보호를 위한 FMVSS 201 법규에 따른 FMH 충격성능 만족을 위한 충격흡수구조 설계 방법이 필요하다. 충격흡수구조 설계 과정에 있어 FMH 충격 성능은 헤드라이닝의 타격 위치 및 헤드폼의 접근각에 따라 위치별로 각각 다르게 설정되며, FMH 충격 흡수부재는 위치에 따른 차체의 강성 및 상관부품을 고려하여 각 타격 위치에 따른 적절한 충격 흡수 성능을 가져야 하며 차체 강성의 변화를 고려한 효율적인 설계 방법이 필요하다. 본 연구에서는 충격 흡수구조 설계 과정에 있어 초기 설계안에 대한 충격 강도 검토의 시간을 줄이기 위해 전차량 시뮬레이션에서 수행하던 FMH 충격흡수부재 설계를 단위 모델의 압궤 시뮬레이션을 통해 진행함으로써 보다 빠르고 효율적으로 타격 위치별 적합한 충격 흡수구조를 설계하는 방법을 검토하였다.

• 한국운동역학회지
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• 제24권1호
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• pp.43-50
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• 2014

The purpose of this study was to analyze of the GRF (ground reaction force) parameters according to the change of positions and weights of bag during downward stairs between dominant and non-dominant in upper & lower limbs. To perform this study, participants were selected 9 healthy women (age: $21.40{\pm}0.94yrs$, height: $166.50{\pm}2.68cm$, body mass: $57.00{\pm}3.61kg$, BMI: $20.53{\pm}1.03kg/m^2$), divided into 2 carrying bag positions (dominant arm/R, non-dominant arm/L) and walked with 3 type of bag weights (0, 3, 5 kg) respectively. One force-plate was used to collect GRF (AMTI OR6-7) data at a sample rate of 1000 Hz. The variables analyzed were consisted of the medial-lateral GRF (Fx), anterior-posterior GRF (Fy), vertical GRF (Fz), impact loading rate and center of pressure (COPx, COPy, COP area, COPy posterior peak time) during downward stairs. 1) The Fx, Fy, Fz, COPx, and COP area of GRF were not statistically significant between dominant leg and non-dominant leg, but non-dominant leg, that is, showed the higher COPy, and showed higher impact loading rate than that dominant leg during downward stairs. 2) In bag wearing to non-dominant arm, Fx, Fz, COPx, COPy, impact loading rate and COP area showed increase tendency according to increase of bag weights. Also, against bag wearing to dominant arm, non-dominant showed different mechanism according to increase of bag weights. The Ground Reaction Force parameters showed different characteristics according to the positions and weights of bag during downward stairs between dominant and non-dominant arm.

• 대한기계학회논문집A
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• 제40권2호
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• pp.185-198
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• 2016

본 논문에서는 통계적인 기법을 기반으로 유한 요소 모델을 개선하기 위해 수행되는 임팩트 해머 실험에서 발생할 수 있는 오차 요인을 분석하고, 오차를 줄일 수 있는 방안을 제시한다. 먼저, 이론 모델과 실험을 통해, 실험 과정과 측정된 신호를 후처리 하는 과정에서 발생할 수 있는 오차 요인을 파악한다. 실험 오차 요인으로 가진력의 지속 시간과 크기, 시편을 지지대와 연결하는 고무줄의 강성과 위치, 응답 신호를 측정하기 위해 시편에 부착하는 가속도계의 위치와 질량을 고려하고, 이에 따른 고유 모드와 고유 주파수의 변화를 살펴본다. 그리고, 디지털 신호 처리 과정에서는 말뚝 울타리 효과, 누설, 지수창 함수 사용에 의한 오차를 살펴보고, 이런 오차를 줄일 수 있는 방법을 제시한다.

• Journal of Astronomy and Space Sciences
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• 제34권2호
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• pp.127-138
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• 2017

The current study designs the mission orbit of the lunar CubeSat spacecraft to measure the lunar local magnetic anomaly. To perform this mission, the CubeSat will impact the lunar surface over the Reiner Gamma swirl on the Moon. Orbit analyses are conducted comprising ${\Delta}V$ and error propagation analysis for the CubeSat mission orbit. First, three possible orbit scenarios are presented in terms of the CubeSat's impacting trajectories. For each scenario, it is important to achieve mission objectives with a minimum ${\Delta}V$ since the CubeSat is limited in size and cost. Therefore, the ${\Delta}V$ needed for the CubeSat to maneuver from the initial orbit toward the impacting trajectory is analyzed for each orbit scenario. In addition, error propagation analysis is performed for each scenario to evaluate how initial errors, such as position error, velocity error, and maneuver error, that occur when the CubeSat is separated from the lunar orbiter, eventually affect the final impact position. As a result, the current study adopts a CubeSat release from the circular orbit at 100 km altitude and an impact slope of $15^{\circ}$, among the possible impacting scenarios. For this scenario, the required ${\Delta}V$ is calculated as the result of the ${\Delta}V$ analysis. It can be used to practically make an estimate of this specific mission's fuel budget. In addition, the current study suggests error constraints for ${\Delta}V$ for the mission.

• 한국운동역학회지
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• 제13권1호
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• pp.155-171
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• 2003

The purpose of this study was to analyze the kinematic variables of over head kick(OHK) in soccer with three dimensional analysis technique and show the kinematic characteristics of it. The 7 subjects were university football player who have been playing football more than 7 years. The OHK was filmed on 16mm video camera(30frame/sec.) kinematic variables were temporal, postures, and COG(center of gravity). The mean values and the standard deviation for each variables were obtained and used as basic factors for examining characteristics of OHK. The results of this analysis were as follows : Temporal variables : The total time elapsed(TE) of OHK was $0.95{\sim}1.14sec$, the 1st phase was 0.35sec., 2nd phase was 0.46sec., and 3rd phase was 0.22sec.. Posture variables : When subjects performed OHK at the impact event, the ankle and knee angle of kicking foot were more extend than supporting foot. but the hip angle of supporting foot were more extend than kirking foot. Moving distance of the center of mass of the both foot. When subject performed OHK at the impact event, the range of distance on mediolateral direction aspect into right left shoulder line, anteroposterior direction aspect was $20.9{\pm}10.5cm$, vertical direction aspect was $92.3{\pm}19.9cm$. Angular velocity : the faster angular velocity of knee ankle on the kicking foot pew form jump position to landing position, the faster velocity of ball became. C. O. G. variables. When subject performed OHK at the impact event, upper part of the body was getting lower, lower part of the body was getting higher.

• 대한의용생체공학회:의공학회지
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• 제13권4호
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• pp.285-298
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• 1992

An analysis of the dynamics in the closing phase of the occluder of a mechanical monoleaflet heart valve prosthesis is presented. The dynamic analysis of the fluid in the vicinity of the occluder was based on the control vo]use approach. The backflow velocity of the fluid was computed by applying the continuity, Bernoulli's and momentum equations in the unsteady state. By considering the fluid pressure and gravity as external forces acting on the occluder, the moment equilibrium on fine occluder was employed to analyze the motion of the occluder during closing and the force of impact between the occluder and the guiding struts. Occluder comes to rest after several oscillations in about 10-18 msec after the Inltiaton of closing. As the aortic pressure increases, the occludes closes faster and comes to the final resting position earlier and the impact force increases also. But backflow is not af footed by the variation of the aortic pressure. With decreasing time delay of the ventricle pressure, the occluder closes faster and impact force Increases. The computed magnitudes of the occluder tiP velocities as well as the backflow of the fluid during the closing phase using this model were in agreement with previously reported experimental measurements.

• Structural Engineering and Mechanics
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• 제28권5호
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• pp.525-548
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• 2008

This article deals the theory for solving an inverse problem of plate structures using the frequency-domain information instead of classical time-domain delays or free vibration eigenmodes or eigenvalues. A reduced set of output parameters characterizing the defect is used as a regularization technique to drastically overcome noise problems that appear in imaging techniques. A deconvolution scheme from an undamaged specimen overrides uncertainties about the input signal and other coherent noises. This approach provides the advantage that it is not necessary to visually identify the portion of the signal that contains the information about the defect. The theoretical model for Quantitative nondestructive evaluation, the relationship between the real and ideal models, the finite element method (FEM) for the forward problem, and inverse procedure for detecting the defects are developed. The theoretical formulation is experimentally verified using dynamic responses of a steel plate under impact loading at several points. The signal synthesized by FEM, the residual, and its components are analyzed for different choices of time window. The noise effects are taken into account in the inversion strategy by designing a filter for the cost functional to be minimized. The technique is focused toward a exible and rapid inspection of large areas, by recovering the position of the defect by means of a single accelerometer, overriding experimental calibration, and using a reduced number of impact events.