• Structural Engineering and Mechanics
• /
• v.55 no.4
• /
• pp.743-763
• /
• 2015

This work presents a new nonlocal hyperbolic shear deformation beam theory for the static, buckling and vibration of nanoscale-beams embedded in an elastic medium. The present model is able to capture both the nonlocal parameter and the shear deformation effect without employing shear correction factor. The nonlocal parameter accounts for the small size effects when dealing with nanosize structures such as nanobeams. Based on the nonlocal differential constitutive relations of Eringen, the equations of motion of the nanoscale-beam are obtained using Hamilton's principle. The effect of the surrounding elastic medium on the deflections, critical buckling loads and frequencies of the nanobeam is investigated. Both Winkler-type and Pasternak-type foundation models are used to simulate the interaction of the nanobeam with the surrounding elastic medium. Analytical solutions are presented for a simply supported nanoscale-beam, and the obtained results compare well with those predicted by the other nonlocal theories available in literature.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.6
• /
• pp.581-591
• /
• 2011

This paper describes the air compressibility effect in the CFD simulation of water impact load prediction. In order to consider the air compressibility effect, two sets of governing equations are employed, namely the incompressible Navier-stokes equations and compressible Navier-Stokes equations that describe general compressible gas flow. In order to describe violent motion of free surface, volume-of-fluid method is utilized. The role of air compressibility is presented by the comparative study of water impact load obtained from two different air models, i.e. the compressible and incompressible air. For both cases, water is considered as incompressible media. Compressible air model shows oscillatory behavior of pressure on the solid surface that may attribute to the air-cushion effect. Incompressible air model showed no such oscillatory behavior in the pressure history. This study also showed that the CFD simulation can capture the formation of air pockets enclosed by water and solid surface, which may be the location where the air compressibility effect is dominant.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.10 no.3
• /
• pp.229-236
• /
• 2016

Magnetic sensors and actuators have been widely used in industry and medical fields. Integrated systems based on sensors and actuators are defined as mechatronics that is the general combination of mechanics and electronics. Recently, magnetic wireless sensors and actuators have been developed and used at a systematic level. In particular, their mechanisms depend on magnetic, such as magnetic material and physical phenomena. However, their research boundary has not been clear. Researchers talk of magnetic micro-robots, magnetic actuators and sensors. Therefore, a new and correct definition is required. In this study, we introduce the advanced and extended concept of mechatronics, which is a magneto-mechantronics for biomedical and rehabilitation. Among various applications, we focused on wireless pump and sensing system for blood vessel rehabilitation and local motion capture, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• v.9 no.1
• /
• pp.309-312
• /
• 2005

Virtual reality(VR) is both one of the high-technology and main paradime in leading next genaration of 21th century. It's application spectrum is various and lead to numorous revolotion as well as transition in technical aspect. These change is a good procept of it's value and influence effect in global fields of human life. In this paper, a development method of virtual reality simulation system is presented, which is based in the shape research about VR.

• Journal of Biomedical Engineering Research
• /
• v.32 no.2
• /
• pp.105-108
• /
• 2011

The purpose of the present study was to analyze the lower stiffness over the difference between soft and stiff landings during hopping. Five male subjects performed hopping on two legs at 2.5 Hz. During the experiments, 3D motion capture system was used to obtain the kinematic data and two force plates were synchronized to calculate the kinetic data. We determined lower extremity stiffness of the knee and ankle from kinetic and kinematic data. Leg stiffness was approximately 1.2-times significantly higher in stiff landing than in soft landing_ There was no significant difference in knee joint stiffness between soft and stiff landings. Ankle joint stiffness was approximately 1.34-times significantly higher in stiff landing than in soft landing. These results suggest that humans adjust lower extremity stiffness over the comparison of two different landing methods we evaluated.

• Korean Journal of Applied Biomechanics
• /
• v.17 no.3
• /
• pp.209-215
• /
• 2007

The purpose of this study was to investigate gait factor and muscle activity depending on hiking poles-using. Eight healthy men volunteered for this experiment. Each of them performed down-hill walking with hiking poles-using and without poles at speed of 3.5km/h for 45 minutes on a treadmill. The treadmill was set 25% down-hill inclination. Kinematic data collected in 60Hz were recorded and analyzed by using 2D motion capture system to measure step time and step length so on. And the lower extremity muscle activities were simultaneously recorded in 1500Hz and assessed by using EMG. The statistical analysis was the paired t-test with repeated measures to compare between hiking poles-using and without poles. The level of statistical significance for all tests was .05. The results of this study were following : Step time was showed statistically different according to pole conditions. That is, the case of poles-using was longer than without poles in step time. Also, step length was showed statistically different between two conditions. Step length about trials with poles was longer than trials without poles. In the muscle activity, the case of all muscles was not showed statistical significance about pole conditions. However, in most muscles IEMG, there were some decreasing-trend relatively when hiking polesusing.

• Korean Journal of Applied Biomechanics
• /
• v.23 no.3
• /
• pp.245-252
• /
• 2013

The purpose of this study was to analyze the effect that various loads have on the lower limb biomechanics. The following variables were measured and analyzed; performance time for each phase, lower limb moments and joint angles, and ground reaction forces. The kinematic and kinetic data was recorded by 2 force platforms and a motion capture system while 12 healthy adults in their twenties stepped down three steps under loads of 0%, 10%, 20% BW. Results are as follows. First, the different loading conditions did not seem to significantly affect the performance times and the joint angles. Second, the largest ground reaction forces were observed at the 1 step at the 10% BW condition. Finally, at the 0% BW loading condition the right hip extension moment was the smallest and the left hip flexion moment was the largest. The results show that there are not any significant changes in the biomechanics of the lower limbs under loading conditions up to 20% BW. Further investigations including more loading conditions with more weights and more additional steps analyzed are needed.

• Korean Journal of Applied Biomechanics
• /
• v.23 no.2
• /
• pp.141-148
• /
• 2013

The purpose of this study was to investigate the scapulothoracic joint movement between different weight bearing contributing to effective bench press exercise. Ten male subjects participated in this study. All subjects were tested on the flat bench press machine which modified weight (50% and 70% of 1RM) and subjects were performed two different conditions(none protraction condition and protraction condition). Weight bar height and vertical velocity, EMG activation was measured using 3D motion capture system and wireless EMG analysis system. As the results, none protraction condition showed that it is more concentrate better pectoralis major muscle activation than protraction condition and middle pectoralis major, anterior deltoid and triceps brachii was significant higher integrated EMG in 70% of 1RM condition. In conclusion, limited scapulothoracic joint movement was more effective activated pectoralis major muscle all the weight through, while we could not find that it was not affected integrated EMG on eight muslces related to shoulder complex between scapulothracic joint movement conditions.

• Journal of Korea Society of Industrial Information Systems
• /
• v.25 no.5
• /
• pp.41-48
• /
• 2020

Recently, as the demand for the mobile platform market in the virtual/augmented/mixed reality field is increasing, experiential content that gives users a real-world felt through a virtual environment is drawing attention. In this paper, as a method of tracking a tracker for user location estimation in a virtual space movement platform for motion capture of trainees, we present a method of estimating 3D coordinates of the 3D cross covariance through the coordinates of the markers projected on the image. In addition, the validity of the proposed algorithm is verified through rigid body tracking experiments.

• Proceedings of the KAIS Fall Conference
• /
• 2011.12a
• /
• pp.241-243
• /
• 2011

인체동작 인식에 대한 연구는 재활치료, 운동선수의 동작 교정 및 모니터링, 3차원 애니메이션 제작등 많은 분야에서 필요로 하고 있다. 동작 인식에 대한 일반적인 방법으로는 반사 마커를 부착하여 여러 대의 적외선 카메라로 관절 운동을 관찰하는 방식이였다. 이러한 방식은 여러 개의 마커를 사용자들이 옷을 벗고 몸에 붙이거나 특수 복장을 착용해야 하는 불편함이 있을 뿐만 아니라 초기 위치 보정에도 많은 시간이 소모된다. 이와 같은 문제점을 해결하기 위하여 본 연구에서는 어떠한 특수 장비를 착용하거나 몸에 부착하지 않고 즉각적으로 인체의 움직임을 트래킹 할 수 있는 마커리스 트래킹시스템을 개발하였다. 이 시스템은 사람의 동작 분석을 하는데 있어 빠르게 측정 및 분석이 가능하고 특수 장비를 착용하지 않아도 됨으로 인해 동작에 방해를 받지 않아서 3차원 영상을 즉각적으로 확인할 수 있는 편리성을 갖추고 있다.