• 대한의용생체공학회:의공학회지
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• 제36권5호
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• pp.228-234
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• 2015

The balance ability significantly decreased in the elderly because of deterioration of the neural musculature regulatory mechanisms. Several studies have investigated methods of improving balance ability using real-time systems, but it is limited by the expensive test equipment and specialized resources. Recently, Kinect system based on depth data has been applied to address these limitations. Little information about accuracy/inaccuracy of Kinect system is, however, available, particular in motion analysis for evaluation of effectiveness in rehabilitation training. Therefore, the aim of the current study was to evaluate accuracy/inaccuracy of Kinect system in specific rotational movement for balance rehabilitation training. Six healthy male adults with no musculoskeletal disorder were selected to participate in the experiment. Movements of the participants were induced by controlling the base plane of the balance training equipment in directions of AP (anterior-posterior), ML (medial-lateral), right and left diagonal direction. The dynamic motions of the subjects were measured using two Kinect depth sensor systems and a three-dimensional motion capture system with eight infrared cameras for comparative evaluation. The results of the error rate for hip and knee joint alteration of Kinect system comparison with infrared camera based motion capture system occurred smaller values in the ML direction (Hip joint: 10.9~57.3%, Knee joint: 26.0~74.8%). Therefore, the accuracy of Kinect system for measuring balance rehabilitation traning could improve by using adapted algorithm which is based on hip joint movement in medial-lateral direction.

• 한국정보기술학회 영문논문지
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• 제9권2호
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• pp.65-74
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• 2019

In this paper, we describe a new swing analysis system. We design this system to provide various information about golf swings and to help to correct wrong swings. We visualize three-dimensional skeletal information obtained from Kinect through various views. Golfers can see their swing behavior through these views. This system can calculate the similarity between the two trajectories obtained from Kinect to determine the similarity of swing trajectories of different golfers. Input trajectories are resampled to have equal spacing and are performed scaling and translation for accurate trajectory comparison. We have verified the usefulness of the proposed system through various analyzes.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1306-1313
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• 2009

Dynamic and static behaviors of a three-dimensional catenary system for a high-speed railway are analyzed by using the finite element method. Considering tensions in the contact wire and the messenger wire, we drive the equations of motion for the catenary system. These equations are for the longitudinal, transverse, vertical and torsional motions. After establishing the weak form, the weak forms are spatially discretized with newly defined two-node beam elements. With the discretized equations, a finite element computer program is developed for the static and dynamic analyses. The static deflections of the catenary system, which are important for good contact between the pantograph and the contact line, are computed when the gravity is applied. On the other hand, we analyze the natural frequencies and the corresponding natural modes of the catenary system. The dynamic responses of the system are also investigated when applying a load to the contact line. For verification of the developed finite element program, vibrations of the catenary system are measured and they are compared to computed time responses.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1391-1398
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• 2011

본 논문은 장비의 동작분석기법을 이용하여 운전자가 핸들을 돌릴 때 팔의 관절 운동에 대한 생체역학적 해석을 수행하였다. 모형 운전석에서 운전자가 핸들을 돌릴 때 모션 캡쳐(motion capture) 시스템을 이용하여 팔의 3차원 운동궤적을 구하고, 이 결과를 이용하여 팔의 근-골격계 모델에 대한 역기구학 해석과 역동역학 해석을 수행함으로써 팔 관절의 변위와 관절 토크의 크기를 계산하였다. 각 관절의 회전 운동은 동시에 복합적으로 발생하며, 관절 운동의 크기의 관점에서 팔꿈치 관절의 회내-회외, 어깨 관절의 내전-외전, 굴곡-신전, 손목 관절의 굴곡-신전 등이 주요한 운동임을 확인할 수 있었다. 모형 운전석의 운전 자세, 핸들의 각도 및 좌석에 대한 상대적 위치와 관련된 설계변수에 대한 관절운동의 민감도 해석을 통하여 운전 자세와 핸들의 위치가 조향 동작에 미치는 영향을 정량적으로 분석하였다.

• 로봇학회논문지
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• 제5권2호
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• pp.110-119
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• 2010

This paper aims to add the autonomous driving capability to the inverted pendulum system which maintains the inverted pendulum upright stably. For the autonomous driving from the starting position to the goal position, the motion control algorithm is proposed based on the dynamics of the inverted pendulum robot. To derive the dynamic model of the inverted pendulum robot, a three dimensional robot coordinate is defined and the velocity jacobian is newly derived. With the analysis of the wheel rolling motion, the dynamics of inverted pendulum robot are derived and used for the motion control algorithm. To maintain the balance of the inverted pendulum, the autonomous driving strategy is derived step by step considering the acceleration, constant velocity and deceleration states simultaneously. The driving experiments of inverted pendulum robot are performed while maintaining the balance of the inverted pendulum. For reading the positions of the inverted pendulum and wheels, only the encoders are utilized to make the system cheap and reliable. Even though the derived dynamics works for the slanted surface, the experiments are carried out in the standardized flat ground using the inverted pendulum robot in this paper. The experimental data for the wheel rolling and inverted pendulum motions are demonstrated for the straight line motion from a start position to the goal position.

• 재활복지공학회논문지
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• 제7권2호
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• pp.47-54
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• 2013

본 논문은 몸 전체의 움직임을 측정하고 분석할 수 있는 관성센서 기반 모션 캡처링 시스템에 관한 것이다. 본 시스템 구현을 위해 자이로스코프, 가속도계 및 지자계 신호를 이용한 자세 방위 측정장치 모듈을 개발하였으며, 다수의 모듈을 환자의 분절에 부착하고 공간상에서 각 분절의 방위각을 계산하여 3차원 모션캡처를 수행하였다. 또한 재활과 관련된 많은 응용에 있어 중요한 생체역학 측정값인 신체 분절간의 관절각을 추출하는 알고리즘을 제안하였다. 개발한 자세 방위 측정장치 모듈의 성능을 평가하기 위하여 3차원 공간상의 변위 및 방위를 밀리미터 해상도로 제공할 수 있는 Vicon을 참조 측정 시스템으로 이용하였으며, 2.56도의 평균 제곱근 오차를 얻을 수 있었다. 실험 결과 본 연구에서 개발한 시스템은 뇌졸중 후 회복단계 동안 사지 및 보행 동작을 실시간으로 분석, 제공함으로서 재활의 효과, 난이도 조절 및 피드백 요소를 제공할 수 있을 것으로 판단된다.

• 대한물리의학회지
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• 제16권3호
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• pp.21-27
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• 2021

PURPOSE: This study examined the relationship between the severity of a hallux valgus (HV) deformity and the kinetic three-dimensional ground reaction force (GRF) through a motion analysis system with force platforms in individuals with a HV deformity during normal speed walking. METHODS: The participants were 36 adults with a HV deformity. The participants were asked to walk on a 6 m walkway with 40 infrared reflective markers attached to their pelvic and lower extremities. A camera capture system and two force platforms were used to collect kinetic data during gait. A Vicon Nexus and Visual3D motion analysis software were used to calculate the kinetic GRF data. RESULTS: This research showed that the anterior maximal force that occurred in the terminal stance phase during gait had a negative correlation with the HV angle (r = -.762, p < .01). In addition, the HV angle showed a low negative correlation with the second vertical maximal force (r = .346, p < .05) and a moderate positive correlation with the late medial maximal force (r = .641, p < .01). CONCLUSION: A more severe HV deformity results in greater abnormal translation of the plantar pressure and a significantly reduced pressure force under the first metatarsophalangeal joint.

• Structural Engineering and Mechanics
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• 제26권2호
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• pp.111-126
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• 2007

Dynamic responses of the bridge for a straddle-type monorail subjected to the ground motion of high probability to occur are investigated by means of a three-dimensional traffic-induced vibration analysis to clarify the effect of a train's dynamic system on seismic responses of a monorail bridge. A 15DOFs model is assumed for a car in the monorail train. The validity of developed equations of motion for a monorail train-bridge interaction system is verified by comparison with the field-test data. The inertia effect due to a ground motion is combined with the monorail train-bridge interaction system to investigate the seismic response of the monorail bridge under a moving train. An interesting result is that the dynamic system of the train on monorail bridges can act as a damper during earthquakes. The observation of numerical results also points out that the damper effect due to the dynamic system of the monorail train tends to decrease with increasing speed of the train.

• 대한기계학회논문집B
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• 제23권8호
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• pp.945-956
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• 1999

This work reports a set of approximate analytical solutions describing the initial transient process of close-contact melting between a rectangular parallelepiped solid and a flat plate on which either constant temperature or constant heat flux is imposed. Not only relative motion of the solid block tangential to the heating plate, but also the density difference between the solid and liquid phase is incorporated in the model. The thin film approximation reduces the force balance between the solid weight and liquid pressure, and the energy balance at the melting front into a simultaneous ordinary differential equation system. The normalized model equations admit compactly expressed analytical solutions which include the already approved two-dimensional solutions as a subset. In particular, the normalized liquid film thickness is independent of all pertinent parameters, thereby facilitating to define the transition period of close-contact melting. A unique behavior of the solid descending velocity due to the density difference is also resolved by the present solution. A new geometric function which alone represents the three-dimensional effect is introduced, and its properties are clarified. One of the representative results is that heat transfer is at least enhanced at the expense of the increase in friction as the cross-sectional shape deviates from the square under the same contact area.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.721-733
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• 2020

In nuclear engineering, the occurrence of critical heat flux (CHF) is complicated for rod bundle, and it is much more difficult to predict the CHF when it is in natural circulation under motion condition. In this paper, the dryout-type CHF is investigated for the rod bundle in a natural circulation loop under rolling motion condition based on the coupled analysis of subchannel method, a one-dimensional system analysis method and a CHF mechanism model, namely the three-fluid model for annular flow. In order to consider the rolling effect of the natural circulation loop, the subchannel model is connected to the one-dimensional system code at the inlet and outlet of the rod bundle. The subchannel analysis provides the local thermal hydraulic parameters as input for the CHF mechanism model to calculate the occurrence of CHF. The rolling motion is modeled by additional motion forces in the momentum equation. First, the calculation methods of the natural circulation and CHF are validated by a published natural circulation experiment data and a CHF empirical correlation, respectively. Then, the CHF of the rod bundle in a natural circulation loop under both the stationary and rolling motion condition is predicted and analyzed. According to the calculation results, CHF under stationary condition is smaller than that under rolling motion condition. Besides, the CHF decreases with the increase of the rolling period and angular acceleration amplitude within the range of inlet subcooling and mass flux adopted in the current research. This paper can provide useful information for the prediction of CHF in natural circulation under motion condition, which is important for the nuclear reactor design improvement and safety analysis.