• 한국해양공학회지
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• 제29권1호
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• pp.1-8
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• 2015

An analytical model of liquid sloshing is developed to consider the energy-loss effect through a partially submerged porous baffle in a horizontally oscillating rectangular tank. The nonlinear boundary condition at the porous baffle is derived to accurately capture both the added inertia effects and the energy-loss effects from an equivalent non-linear drag law. Using the eigenfunction expansion method, the horizontal hydrodynamic force (added mass, damping coefficient) on both the wall and baffle induced by the fluid motion is assessed for various combinations of porosity, submergence depth, and the tank's motion amplitude. It is found that a negative value for the added mass and a sharp peak in the damping curve occur near the resonant frequencies. In particular, the hydrodynamic force and free surface amplitude can be largely reduced by installing the proper porous baffle in a tank. The optimal porosity of a porous baffle is near P=0.1.

• Ocean Systems Engineering
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• 제2권4호
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• pp.239-255
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• 2012

Analysis of ship parametric roll has generally been restricted to simple analytical models and sophisticated time domain simulations. Simple analytical models do not capture all the critical dynamics while time-domain simulations are often time consuming to implement. The model presented in this paper captures the essential dynamics of the system without over simplification. This work incorporates various important aspects of the system and assesses the significance of including or ignoring these aspects. Special consideration is given to the fact that a hull form asymmetric about the design waterline would not lead to a perfectly harmonic variation in metacentric height. Many of the previous works on parametric roll make the assumption of linearized and harmonic behaviour of the time-varying restoring arm or metacentric height. This assumption enables modelling the roll motion as a Mathieu equation. This paper provides a critical assessment of this assumption and suggests modelling the roll motion as a Hills equation. Also the effects of non-linear damping are included to evaluate its effect on the bounded parametric roll amplitude in a simplified manner.

• 한국콘텐츠학회논문지
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• 제22권3호
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• pp.593-605
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• 2022

본 연구는 Kinect Sensor 기반의 개인 맞춤형 운동 처방 시스템을 개발하고, 개발 시스템의 사용성을 평가하는 것이다. 개발 시스템을 개인 맞춤형 운동 처방 시스템을 모션캡쳐 도구로서 이용할 수 있을지에 대한 가능성 검증을 위해서 스마트 거울 시스템에 부착된 키넥트 센서(Kinect sensor)에서 측정된 인체 움직임 데이터와 적외선 모션캡쳐 장비에서 측정된 인체 움직임 데이터를 비교하여 타당성과 신뢰성을 분석하였다. 타당성 검증 결과 상관계수 r=0.871~0.919로 높은 양의 상관성을 보였고, 예측가능정도가 88%로 높게 나타났다. 신뢰성 검증 결과 r=0.743~0.916 높은 양의 상관성을 보였고, 반복 측정에 대한 일관성도 ICC=0.937로 매우 높게 나타났다. 결론적으로 본 연구에서 개발한 키넥트 센서기반의 운동 처방 시스템에서 인간 골격에 대한 특징 벡터를 통한 관절의 가동범위 평가 및 자세측정평가가 운동 처방을 제공하는데 있어서 하나의 기준이 될 수 있다는 가능성을 보여주었다. 향후 병원, 임상시험센터, 스포츠센터 등의 운동처방사 혹은 물리치료사, 퍼스널 트레이너들에게 전문성 제고에 도움을 줄 수 있을 것으로 사료된다.

• 대한기계학회논문집 C: 기술과 교육
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• 제1권2호
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• pp.205-210
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• 2013

본 연구에서는 스키 시뮬레이터의 사용자 감응형 제어를 위한 물리모델과 동작인식 시스템의 개발되었으며, 스키 선수의 자세 변화에 따른 스키 슬로프 상에서의 거동과의 부합성 확보를 위하여 실제 현장 실험데이터의 회귀분석을 통해 동작인식 시스템에 사용될 파라미터 및 관계식을 도출하였다. 개발된 물리모델 기반 스키 동작 인식 시뮬레이터는 실시간으로 Kinect 장치를 사용하여 사용자의 관절별 질량을 분석하여, 정확한 체중심을 추정하고, 시뮬레이터 하드웨어에서 적용할 수 있도록 힘, 속도, 가속도에 대한 피드백을 전달하도록 구성되었다. 본 연구결과는 스키시뮬레이터의 인식모듈로 사용되었으며, 물리모델 기반 가상 스포츠 시뮬레이터 제작에 응용 할 수 있는 자료로 활용될 것이다.

• 한국항해항만학회지
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• 제32권9호
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• pp.705-709
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• 2008

In the sea various methods have been conducted to capture wave energy which include the use of pendulums, pneumatic devices, etc. Floating devices, such as a cavity resonance device take advantages of both the water motion and the wave induced motions of the floating body itself. The wave energy converter is known commercially as the WAGB(Wave Activated Generator Buoy) and is used in some commercially available buoys to power navigation aids such as lights and horns. This wave energy converter consists of a circular flotation body which contains a vertical water column that has free communication with the sea. A theoretical analysis of this power generated by a pneumatic type wave energy converter is performed and the results obtained from the analysis are used for a real wave energy converter buoy. This paper is shown to have an optimum value for which maximum power is obtained at a given resonant wave period Also, the length of the internal water column corresponds to that of the water mass in the water column. If designed properly, wave energy converter can take advantage not only of the cavity resonance, but also qf the heaving motion of the buoy. Finally, simulation is performed with a LabVIEW program and the simulation results are applied to a wave energy simulator for modifying design data for a wave energy converter.

• 한국운동역학회지
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• 제30권2호
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• pp.165-172
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• 2020

Objective: The purpose of this study was to provide quantitative and objective data of throwing movement in baseball catcher through biomechanical analysis. Method: Eight high school baseball catchers (age: 17.3±0.7 yrs, height: 175.3±4.5 cm, weight: 82.5±9.0 kg, Career: 7.4±2.1 yrs) participated and 3-dimentional motion capture system and electromyography (EMG) were used in this study. Results: The maximum center of mass position displacement was observed in forward direction. The linear velocity magnitude of the upper extremity segments were showed as "wrist>elbow>shoulder" which is indicative of kinematic chain. For kinetic EMG data, we also observed the greater muscle activation in the left brachioradial and erector spine muscles muscle that during throwing movement. Conclusion: We expect that biomechanical data from this study will provide important training implications to baseball coaches and trainers in order to effectively train their baseball catchers.

• 한국정밀공학회지
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• 제20권8호
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• pp.166-174
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• 2003

Hydrostatic bearings are widely used in precision machines due to their high motion guide accuracy, low friction and high load carrying capacity. It is very useful to estimate the moving characteristics of hydrostatic bearings in the design stage. A new method is suggested for the analysis of fluid film in hydrostatic bearings. A combined mesh of 8 node solid elements with negligible deformation resistance and spring-dashpot elements is used in conjunction with the user subroutine of ABAQUS to represent the fluid film. The mesh can be used to capture the deformation of the bearing structure as well as the varying properties of fluid film. Analysis results from the finite element model are compared with theoretical solutions, results from FLUENT analysis and some previous works. With this method, static and dynamic analyses of the system containing the bearings can be performed efficiently.

• 자동차안전학회지
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• 제4권2호
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• pp.37-43
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• 2012

The purpose of this research is to obtain and analyze dynamic responses from human volunteers for the development of the human-like mechanical or mathematical model for Korean males in automotive rear collisions. This paper focused on the introduction to a low-speed rear impact sled test involving Korean male subjects, and the accumulation of the motion of head and neck. A total of 50 dynamic rear impact sled tests were performed with 50 human volunteers, who are 30-50 year-old males. Each subject can be involved in only one case to prevent any injury in which he was exposed to the impulse that was equivalent to a low-speed rear-end collision of cars at 5-8 km/h for change of velocity, so called, ${\Delta}V$. All subjects were examined by an orthopedist to qualify for the test through the medical check-up of their necks and low backs prior to the test. The impact device is the pendulum type, tuned to simulate the crash pulse of a real vehicle. All motions and impulses were captured and measured by motion capture systems and pressure sensors on the seat. Dynamic responses of head and T1 were analyzed in two cases(5 km/h, 8 km/h) to compare with the results in the previous studies. After the experiments, human subjects were examined to check up any change in the post medical analysis. As a result, there was no change in MRI and no injury reported. Six subjects experienced a minor stiffness on their back for no more than 2 days and got back to normal without any medical treatment.

• 대한산업공학회지
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• 제38권2호
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• pp.133-143
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• 2012

The study on social robots has been actively conducted in the robot research community. In the area of robot design, however, there are few studies regarding robot motions that are one of the methods for interaction between humans and robots. This is a preliminary study to find preferred human motions that can be applied to social robots. We conducted a two-phased empirical study about preferred human motions. In the first phase, four representative human motions, such as 'greeting', 'I don't know', 'positive answer', and 'giving', were captured through 28 body makers and video recording. 10 young and 6 elderly Singaporeans participated in the motion capture process. In the second phase, the communication efficiency, emotion, and satisfaction of the human motions recorded in the first phase were measured by a questionnaire and 31 young Koreans, 35 young Singaporeans participated to investigate cultural differences. We drew the conclusion that motions used in the same culture are efficient in communication and also give friendliness and satisfaction. In addition, regardless of user's culture, young people's motions and female motions were preferred in terms of communication efficiency, emotional aspect, satisfaction.

• 한국운동역학회지
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• 제26권2호
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• pp.205-211
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• 2016

Purpose: The aim of this study was to analyze biomechanical factors and PMT (premotor time) of body muscles between elite college and amateur baseball players during the baseball batting motion. Method: Kinematic and electromyographic data were obtained for 10 elite college baseball players and 10 amateur baseball players who participated in this study. All motion capture data were collected at 200 Hz using 8 VICON cameras and the PMT of muscles was recorded using a Delsys Trigno wireless system. The peak mean bat speed and the peak mean angular velocities of trunk, pelvis, and bat with PMT of 16 body muscles were computed. These kinematic and PMT data of both groups were compared by independent t-tests (p < .05). Results: The pelvis, trunk, and bat showed a sequence of angular velocity value during baseball batting. The PMTs of right tibialis anterior, left gastrocnemius, external oblique, and erector spinae were significantly different between the two groups. Conclusion: The PMT of body muscles was related to the shifting of body and rotation of the pelvis and the trunk segment, and this action can be considered the coordinated muscle activity of the lower and upper body.