• 대한기계학회논문집A
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• 제35권12호
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• pp.1599-1606
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• 2011

축소화된 사각형 및 패들형 블레이드, 금속재 및 복합재 허브와 같은 물리적인 축소형 형상의 변화에 따른 실물크기 무힌지 로터의 하중특성에 대하여 연구하였다. 이를 위하여 축소형 로터 모델을 활용한 정적시험, 지상 및 풍동시험을 수행하였다. 정적시험은 구조강성 및 관성특성, 고유진동수 및 감쇄율을 확인하기 위해 수행하였으며, 지상 및 풍동시험은 정지 및 전진 비행조건에서 안정성 및 공력특성을 확인하기 위해 수행하였다. 시험결과에 따르면, 동일한 조건에서 축소형 복합재 허브와 패들형 블레이드를 결합한 경우가 수직하중이 더 높았다. 축소형 복합재 허브와 패들형 블레이드가 결합된 형태가 금속재 허브의 결합된 형태보다 패들형 블레이드의 운동을 더 유연하게 구속하고 있음을 확인할 수 있었다.

• 디지털융복합연구
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• 제12권11호
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• pp.451-459
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• 2014

본 연구는 정상 성인의 팔 흔들기 종류에 따른 보행 시 운동역학적인 변화를 알아보기 위해서 실시하였다. 정상 성인 대학생 45명을 대상으로 정상 팔 흔들기, 한 팔 흔들기, 두 팔 움직임 없음 보행, 인위적인 팔 흔들기의 4가지 팔 흔들기 종류에 따라 실험을 진행하였다. 이들의 운동역학적인 변화를 알아보기 위해 3차원적 관절 운동역학적 변화 검사인 6-camera Vicon MX motion analysis system을 통해 보행 변수를 측정하였다. 팔 흔들기에 따른 운동역학적인 매개 변수들인 각 관절에서 보행속도, 엉덩관절 일률, 말기 디딤기의 수직 지면반발력에서 유의한 차이를 보였다(p<.05). 이러한 연구결과는 팔 흔들기 종류에 따라서 정상인과 환자들의 치료와 평가를 위한 지침으로서 임상에서 사용할 수 있을 것으로 생각된다.

• 한국운동역학회지
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• 제17권1호
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• pp.1-8
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• 2007

Ground reaction force (GRF) measures are one of the most commonly used in biomechanical study. GRF system is very useful educational tool to explain and demonstrate the Newton's law of universal gravitation and laws of motion as well. However, accuracy, intra- and inter- force platform measures' consistency, reliability, noise, and the effect of platform mounting to GRF measures were not clearly viewed. The aim of this study was to examine the above. GRFs of a plastic dummy and two subjects' quiet upright standing were collected at four university laboratories eight force platforms. The types of platforms, analysis programs, and platform set-up were various. Three 100s-trials were conducted with sampling frequency of 100 Hz. First two trials' vertical component of GRFs, Fz, and CoP sway ranges of mid-60s-portion of 100s trials were analyzed by the paired t-tests and one-way ANOVA. Six of eight platforms' 1st and 2nd trial dummy Fz were statistically different (p<.05) and all platforms ICC were poor (<.28). Fz of the two platforms in every four laboratories were statistically different (p<.05). There were white noises and/or very distinctive noises at specific frequency ranges in all Fz measures. 5 Hz low-pass filtering made clear the Fz differences. CoP ranges of dummy were less than 0.5 cm and the best was 0.02 cm. This CoP range finding agrees with previous results suggests the importance of force platform mounting and A/D card resolution.

• 한국운동역학회지
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• 제29권4호
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• pp.255-261
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• 2019

Objective: The purpose of this study was to investigate differences of shock attenuation strategies between double-leg and single-leg landing on sagittal plane using statistical parametric mapping. Method: Nine healthy female professional soccer players (age: 24.0±2.5 yrs, height: 164.9±3.3 cm, weight: 55.7±6.6 kg, career: 11.2±1.4 yrs) were participated in this study. The subjects performed 10 times of double-leg and single-leg landing from the box of 30 cm height onto force plates respectively. The ground reaction force, angle, moment, angular velocity, and power of the ankle, knee, and hip joint on sagittal plane was calculated from initial contact to maximum knee flexion during landing phase. Statistical parametric mapping was used to compare the biomechanical variables of double-leg and single-leg landing of the dominant leg throughout the landing phase. Each mean difference of variables was analyzed using a paired t-test and alpha level was set to 0.05. Results: For the biomechanical variables, significantly increased vertical ground reaction force, plantarflexion moment of the ankle joint, negative ankle joint power and extension moment of the hip joint were found in single-leg landing compared to double-leg landing (p<.05). In addition, the flexion angle and angular velocity of the knee and hip joint in double-leg landing were observed significantly greater than single-leg landing, respectively (p<.05). Conclusion: These findings suggested that negative joint power and plantarflexion moment of the ankle joint can contribute to shock absorption during single-leg landing and may be the factors for preventing the musculoskeletal injuries of the lower extremity by an external force.

• Geomechanics and Engineering
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• 제36권2호
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• pp.167-181
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• 2024

The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

• 한국운동역학회지
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• 제12권2호
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• pp.279-293
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• 2002

본 연구의 목적은 남자 대학 골프선수들을 대상으로 지면반력의 성분들이 골프 퍼팅의 정확성에 어떤 영향을 미치는지 알아보고 바른 기술을 습득할 수 있돌고 기초자료를 제시하며, 일선지도자나 코치들에게는 합리적이고 과학적인 훈련으로 지도할 수 있도록 하고, 특히 골프라는 운동에 있어 퍼팅의 중요도를 인식시키는 데 그 목적이 있으며, 대학 골프 선수 10명에게 골프 퍼팅 스윙을 수행하게 하여 지면반력 시스템을 통해 각 운동역학적 변인들을 분석한 결과 다음과 같은 결론을 얻었다. 국면별 전후방향의 지면반력 성분은 성공시 왼발이 실패시 왼발보다 전 국면에서 높게 나타났고, 오른발은 AD, BS, FS에서 실패시 오른발이 높게 나타났으며, IP시 성공시 오른발이 높게 나타났다. 국면별 좌우방향의 지면반력 성분은 성공시 왼발이 IP, FS에서 높게 나타났으며, AD, BS에서 실패시 왼발이 높게 나타났고, 오른발은 IP에서 실패시 오른발이 높게 나타났으며, AD, BS, FS시 성공시 오른발이 높게 나타났다. 국면별 수직방향의 지면반력 성분은 성공시 왼발이 AD, BS, FS에서 높게 나타났으며, IP시 실패시 왼발이 높게 나타났고, 오른발은 IP에서 실패시 오른발이 높게 나타났으며, AD, BS, FS에서 높게 나타났으며, IP시 실패시 왼발이 높게 나타났고, 오른발은 IP에서 실패시 오른발이 높게 나타났으며, AD, BS, FS시 성공시 오른발이 높게 나타났다. 국면별 회전력의 지면반력 성분은 성공시 왼발과 오른발의 전 국면에서 높게 나타났다. 위의 결과에 대한 결론을 요약해 볼 때 첫째, 전후방향의 힘은 무분별한 힘의 변화보다는 안정된 자세에서 리드미컬한 힘의 변화가 나타나는 동작이 필요하고, 둘째 안정된 자세에서 힘의 좌우 이동 폭이 큰 동작보다는 작은 동작이 퍼팅을 잘 할 수 있는 것으로 생각되었으며, 셋째 공의 진행 방향 즉 클럽의 진행 방향으로 체중이 이동하는 것이 바람직한 동작이며, 넷째, 완벽한 진자운동에 가까운 퍼팅이 바람직한 동작이라 생각되었다.

• 대한의용생체공학회:의공학회지
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• 제32권2호
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• pp.165-176
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• 2011

The femoral nerve innervates the quadriceps muscles and its dermatome supplies anteromedial thigh and medial foot. Paralysis of the quadriceps muscles due to the injury of the femoral nerve results in disability of the knee joint extension and loss of sensory of the thigh. A child could walk independently even though he had injured his femoral nerve severely due to the penetrating wound in the medial thigh. We measured and analyzed his gait performance in order to find the mechanisms that enabled him to walk independently. The child was eleven-year-old boy and he could not extend his knee voluntarily at all during a month after the injury. His gait analysis was performed five times (GA1~GA5) for sixteen months. His temporal-spatial parameters were not significantly different after the GA2 or GA3 test, and significant asymmetry was not observed except the single support time in GA1 results. The Lower limb joint angles in affected side had large differences in GA1 compared with the normal normative patterns. There were little knee joint flexion and extension motion during the stance phase in GA1 The maximum ankle plantar/dorsi flexion angles and the maximum knee extension angles were different from the normal values in the sound side. Asymmetries of the joint angles were analyzed by using the peak values. Significant asymmetries were found in GA1with seven parameters (ankle: peak planter flexion angle in stance phase, range of motion; ROM, knee: peak flexion angles during both stance and swing phase, ROM, hip: peak extension angle, ROM) while only two parameters (maximum hip extension angle and ROM of hip joint) had significant differences in GA5. The mid-stance valleys were not observed in both right and left sides of vertical ground reaction force (GRF) in the GA1, GA2. The loading response peak was far larger than the terminal stance peak of vertical ground reaction curve in the affected side of the GA3, GA4, GA5. The measured joint moment curves of the GA1, GA2, GA3 had large deviations and all of kinetic results had differences with the normal patterns. EMG signals described an absence of the rectus femoris muscle activity in the GA1 and GA2 (affected side). The EMG signals were detected in the GA3 and GA4 but their patterns were not normal yet, then their normal patterns were detected in the GA5. Through these following gait analysis of a child who had selective injuries on the knee extensor muscles, we could verify the actual functions of the knee extensor muscles during gait, and we also could observe his recovery and asymmetry with quantitative data during his rehabilitation.

• 한국운동역학회지
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• 제17권1호
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• pp.165-174
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• 2007

The subject of this study was male apparatus gymnastics athlete who had scored high points doing basket with 1/2 turn on parallel bars. Then 3D motion analysis were used to calculate & analyse kinematic variables of Basket with 1/2 turn to Handstand. 1. The total average time spent for Basket with 1/2 turn took $2.16{\pm}.08sec$, at the downward upward phase took $.58{\pm}0.00sec$, $.23{\pm}.00sec$, at flight phase took $.28{\pm}.01sec$, at connected area phase took $.72{\pm}0.21sec$, at rotation area phase took $.35{\pm}.14sec$. To have a successful performance, there should be faster speed and velocity to rotate at the downward upward phase, then the upward velocity and height must be used adequately. Moreover, the speed must be faster at the flight connect phase to stabilize Center of Mass(CM) for the body, and must secure more time at the rotation area to have more stable performance. 2. After handstand on parallel bars while moving CM to right hand side, and It must be performed with big and magnificent performance with putting both hand's center to far away from the parallel bars. 3. Furthermore, CM must be moved fast from downwards to right hand side, and CM must be moved fast in vertical movement at upward and flight phase to avoid CM from moving back and forth, and left and right. 4. At downwards, the subject must rotate as bis as possible using hip-joint as wide as possible and at upwards, must put his body to vertical to have stable performance. While rotating or turning, it is better to do with bigger shoulder angle and have to make sure that trunk angle must be not scattered. To perform better and more positive in basket with 1/2 turn on parallel bars, the centrifugal force must be used big and fast at downward, and at upward and flight phase, downward movement must change to vertical movement as soon as possible while turning movement must happen at handstand position. Time spent must be shorten at connected area to stabilize CM and turning must be natural as possible while securing the necessary time of movement to well-balanced. Also, the body must be vertically closed from the ground.

• 한국운동역학회지
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• 제19권2호
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• pp.359-367
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• 2009

본 연구의 목적은 배구경기의 스파이크 동작에서 시간, 거리, 속도, 각도요인 등 제반 운동학적 변인들을 분석하여 스파이크의 과학적 훈련이나 지도에 유용한 정보를 제공하는데 있다. 대상자는 2008-2009 V-리그에 출전한 남자 용병선수 4명이다. 두 대의 고속비디오카메라를 사용했으며 3차원 동작분석 법으로 분석한 결과를 토대로 한 결론은 다음과 같다. 도약스텝의 소요시간은 .33초였으며, 안젤코 선수는 다른 선수들보다 발구름 시간을 조금 더 길게했다. 현재 공격력에서 더 상위에 있는 안젤코와 앤더슨은 전체 스파이크 동작구간의 거리를 4m 이내로 비교적 짧게 했다. 신체중심이 최저에 이른 순간은 도약스텝에서 지지하고 있는 오른발을 왼발이 통과하는 시점이었으며, 신체중심의 최대 높이는 2.30m로 임팩트 직전에 나타났다. 신체중심의 수평속도는 도약스텝의 초반부에 4.19m/s로 가장 높았으며, 도약 직전 앞발의 지지기에 최저치에 도달하는 것으로 나타났다. 신체중심의 수직속도는 도약구간에 오른발의 접지 후 최저치에 이르렀으며, 앞발의 이지 후 최대 속도에 이르는 것으로 나타났다. 타점은 3.22m, 볼속도는 최대 28.18m/s로 나타났다.

• 한국지진공학회논문집
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• 제22권3호
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• pp.175-184
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• 2018

In this paper, comparative analysis of the 9.12 Gyeongju and 11.15 Pohang earthquakes was conducted in order to provide probable explanations and reasons for the damage observed in the 11.15 Pohang earthquake from both earthquake and structural engineering perspectives. The damage potentials like Arias intensity, effective peak ground acceleration, etc observed in the 11.15 Pohang earthquake were generally weaker than those of the 9.12 Gyeongju earthquake. However, in contrast to the high-frequency dominant nature of the 9.12 Gyeongju earthquake records, the spectral power of PHA2 record observed in the soft soil site was highly concentrated around 2Hz. The base shear around 2 Hz frequency was as high as 40% building weight. This frequency band is very close to the fundamental frequency of the piloti-type buildings severely damaged in the northern part of Pohang. Unfortunately, in addition to inherent vertical irregularity, most of the damaged piloti-type buildings had plan irregularity as well and were non-seismic. All these contributed to the fatal damage. Inelastic dynamic analysis indicated that PHA2 record demands system ductility capacity of 3.5 for a structure with a fundamental period of 0.5 sec and yield base shear strength of 10% building weight. The system ductility level of 3.5 seems very difficult to be achievable in non-seismic brittle piloti-type buildings. The soil profile of the PHA2 site was inversely estimated based on deconvolution technique and trial-error procedure with utilizing available records measured at several rock sites during the 11.15 Pohang earthquake. The soil profile estimated was very typical of soil class D, implying significant soil amplification in the 11.15 Pohang earthquake. The 11.15 Pohang earthquake gave us the expensive lesson that near-collapse damage to irregular and brittle buildings is highly possible when soil is soft and epicenter is close, although the earthquake magnitude is just minor to moderate (M 5+).