• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1073-1079
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• 2009

The proper orthogonal decomposition (POD) method can identify principal modes that optimally capture the energy content from large multi-dimensional data set. In this study unsteady pressure fields on the rotor blade surface of a helicopter in forward flight are expressed by a reduced order model based on the POD method. Special modes containing high energy are analyzed to investigate the aerodynamic characteristics in more efficient way. The CFD simulation of flowfields around helicopter rotor blade in hovering motion is also conducted to validate its prediction with experimental result. In the process 7 modes containing energy ratio 99% from 240 snapshots information are identified and utilized to construct a reduced order model.

• The Journal of the Korea Contents Association
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• v.8 no.2
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• pp.18-26
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• 2008

This paper presents a phased visualization method of facial expression space that enables the user to control facial expression of 3D avatars by select a sequence of facial frames from the facial expression space. Our system based on this method creates the 2D facial expression space from approximately 2400 facial expression frames, which is the set of neutral expression and 11 motions. The facial expression control of 3D avatars is carried out in realtime when users navigate through facial expression space. But because facial expression space can phased expression control from radical expressions to detail expressions. So this system need phased visualization method. To phased visualization the facial expression space, this paper use fuzzy clustering. In the beginning, the system creates 11 clusters from the space of 2400 facial expressions. Every time the level of phase increases, the system doubles the number of clusters. At this time, the positions of cluster center and expression of the expression space were not equal. So, we fix the shortest expression from cluster center for cluster center. We let users use the system to control phased facial expression of 3D avatar, and evaluate the system based on the results.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.3
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• pp.53-60
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• 2009

The vision-based driver fatigue detection is one of the most prospective commercial applications of facial expression recognition technology. The facial feature tracking is the primary technique issue in it. Current facial tracking technology faces three challenges: (1) detection failure of some or all of features due to a variety of lighting conditions and head motions; (2) multiple and non-rigid object tracking; and (3) features occlusion when the head is in oblique angles. In this paper, we propose a new active approach. First, the active IR sensor is used to robustly detect pupils under variable lighting conditions. The detected pupils are then used to predict the head motion. Furthermore, face movement is assumed to be locally smooth so that a facial feature can be tracked with a Kalman filter. The simultaneous use of the pupil constraint and the Kalman filtering greatly increases the prediction accuracy for each feature position. Feature detection is accomplished in the Gabor space with respect to the vicinity of predicted location. Local graphs consisting of identified features are extracted and used to capture the spatial relationship among detected features. Finally, a graph-based reliability propagation is proposed to tackle the occlusion problem and verify the tracking results. The experimental results show validity of our active approach to real-life facial tracking under variable lighting conditions, head orientations, and facial expressions.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.603-607
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• 2004

The vision-based driver fatigue detection is one of the most prospective commercial applications of facial expression recognition technology. The facial feature tracking is the primary technique issue in it. Current facial tracking technology faces three challenges: (1) detection failure of some or all of features due to a variety of lighting conditions and head motions; (2) multiple and non-rigid object tracking and (3) features occlusion when the head is in oblique angles. In this paper, we propose a new active approach. First, the active IR sensor is used to robustly detect pupils under variable lighting conditions. The detected pupils are then used to predict the head motion. Furthermore, face movement is assumed to be locally smooth so that a facial feature can be tracked with a Kalman filter. The simultaneous use of the pupil constraint and the Kalman filtering greatly increases the prediction accuracy for each feature position. Feature detection is accomplished in the Gabor space with respect to the vicinity of predicted location. Local graphs consisting of identified features are extracted and used to capture the spatial relationship among detected features. Finally, a graph-based reliability propagation is proposed to tackle the occlusion problem and verify the tracking results. The experimental results show validity of our active approach to real-life facial tracking under variable lighting conditions, head orientations, and facial expressions.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.31-49
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• 2005

The purpose of this study was to analyze the weight transfer patterns under the different golf swing types which are full swing control swing and putting stroke. Two women golfers participated in this study, one(165cm, 94.3kg)being classified as a low-handicap(LH)player, the other(165cm, 54.5kg) being classified as a high-handicap(HH) player. Both players are right-handed. Two force plates(Kistler, 9286AA) were synchronized with a motion capture system(Qualisys ProReflex MCU240). Anteriorposterior, mediolateral, and vertical forces were used as an indicator of the pattern of swing. Four discrete positions which are address, top of backswing impact, and finish were identified as an event and three phases which are backswing downswing, and follow-through between he events were also identified. The results showed that, at impact, the total force was 1.24BW ring the full swing 1.17BW during the control stroke, 1.00BW during the putting stroke. Depending on the golf swing types, the differences are existed. At impact, the distribution of forces is different with a low-handicap(LH) player and a high-handicap(HH) player. A LH player has 26% in right foot and 74% in left foot during the full swing 49% in right foot and 51% in left foot during the control swing 49% in right foot and 51% in left foot during the putting stroke. A HH, on the other hand, has 74% in right foot and 26% in left foot during the full swing 62% in right foot and 38% in left foot during the control swing 54% in right foot and 46% in left foot during the putting stroke. From address to top of backswing the amount of vertical forces are changed 43:57(right foot: left foot) to 76:24 during the full swing 47:53(right foot: left foot) to 75:25 during the control swing 50:50(right foot: left foot) to 54:46 during the putting stroke. The biggest weight transfer pattern took place in full swing and the control swing is next, and the putting stroke is the final.

• Korean Journal of Applied Biomechanics
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• v.13 no.2
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• pp.13-28
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• 2003

The purpose of this study was to analyze the kinematic characteristics of Ice hockey slap shot. The subjects of this study were four professional ice hockey players. The reflective markers were attached on the anatomical boundary line of body and the subjects were asked to perform the shot. Ariel Performance Analysis System was used to capture and digitize the shooting image, the data were analyzed by LabView 6i. The results were as fellows. 1. The period of the back swing phase was $0.542{\pm}0.062sec$, the down swing phase was $0.28{\pm}0.056sec$ and the total swing time was $0.825{\pm}0.017sec$ 2. The maximum linear velocity of the stick blade for x direction was shown after 7% of impact, for y, z direction were shown before 2%, 8% of Impact. 3. The maximum velocity of each segment for the left arm was $2.35{\pm}0.05m/s$ in the upper arm, $3.56{\pm}0.34m/s$ in the forearm, $4.75{\pm}0.67m/s$ in the hand. 4. The maximum velocity of each segment for the right arm was $4.67{\pm}0.43m/s$ in the upper arm, $7.22{\pm}0.69m/s$ in the forearm, $9.42{\pm}0.89m/s$ in the hand. 5. The angle of left elbow was generally flexed from the ready stance to the impact and was $82.26{\pm}3.45^{\circ}$ the moment of Impact. 6. The angle of the left shoulder was increased ut the down swing phase and was $78.74{\pm}4.78^{\circ}$ on the moment of impact. 7. The angle of the right shoulder was decreased in the down swing phase and increased before the impact. and the angle was $51.28{\pm}3.54^{\circ}$ on the moment of impact.

• Korean Journal of Applied Biomechanics
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• v.22 no.4
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• pp.379-386
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• 2012

The aim of this study was to investigate and identify the differences in lower extremity energy dissipation strategies between drop-landing and countermovement-jump maneuvers. Fourteen recreational athletes(Age : $23.3{\pm}2.1years$, Height : $172.3{\pm}4.0cm$, Weight : $69.2{\pm}4.7kg$) were recruited and instructed to perform drop-landing from 45 cm height and countermovement-jump from 45 cm to 20 cm height. The landing phase was taken as the time between initial contact and peak knee flexion. A motion-capture system consisting of eight infra-red cameras was employed to collect kinematics data at a sampling rate of 200 Hz and a force-plate was used to collect GRF data at a sampling rate of 2000 Hz. Paired t-test was performed to determine the difference in kinematics and kinetics variables between each task. During the countermovement-jump task, all of lower extremity joint ROM and the hip joint eccentric moment were decreased and the ankle joint plantarflexion moment was increased than drop-landing task. In the eccentric work during countermovement-jump task, the ankle joint displayed greater while knee and hip joint showed lesser than drop-landing. Therefore, the knee joint acted as the key energy dissipater during drop-landing while the ankle joint contributed the most energy dissipation during countermovement-jump. Our findings collectively indicated that different energy dissipation strategies were adopted for drop-landing and countermovement-jump.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.425-433
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• 2014

The purpose of the study was to investigate the effect of CAD (Computer Aided Design) based alpine mono-ski bucket design on disabled ski athletes' kinematic characteristics. Two national team ski athletes with LW11 disabilities (Locomotion Winter Classification) category for sit ski participated in both pre and post experiment. Both of the subjects performed 3 trials of carved turn on a ski slope under two conditions. Where, subject "A" performed pre experiment with personal bucket and post experiment with the newly developed CAD based bucket whereas, Subject "B" as control subject performed both pre and post experiment with his personal bucket. For the experiment, 24 Infrared cameras were positioned on the ski slope which covered the path of the ski turn. Also, motion capture suit with reflective markers were worn by both subjects. In the result, decrement in medial/lateral displacement of COM, anterior/posterior displacement of COM, flexion/extension angle of trunk as well as velocity losing rate of COM was observed in subject "A" when using the newly developed CAD based bucket. In contrast, no larger effect on performance was observed when using personal buckets. In conclusion, the findings obtained from the study indicated effectiveness of newly developed CAD based bucket by reducing excessive movement of hip and trunk which is an important factor to perform an effective turn.

• Journal of Korean Philosophical Society
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• v.144
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• pp.235-256
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• 2017

This essay considers Leibniz-Clark correspondence on the nature of space and hole argument. The ontology of space had been debated under the name of substantivalism-relationism controversy. The debates between the two parties are concerned with the nature of existence of parts of space-time. Substantivalism claims that the point of space-time has existence analogous to that of material substance. Relationism argues that space-time should be understood as the framework of possible spatio-temporal relations between bodies. Although these two approaches attempt to respect theoretical context, it seems that the problems of these two interpretive schemes stems from the lack of understanding of the structure of space-time theories, especially how space-time is connected with the laws of motion. In order to appreciate the substance-relation controversy without deviating from the context of space-time theories, it is necessary then to capture how space-time theories are constituted. This essay offers the clear connection of ontology of space-time with present practices of theoretical physicists.

• Smart Structures and Systems
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• v.13 no.2
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• pp.177-201
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• 2014

With the increased size and flexibility of the tower and blades, structural vibrations are becoming a limiting factor towards the design of even larger and more powerful wind turbines. Research into the use of vibration mitigation devices in the turbine tower has been carried out but the use of dampers in the blades has yet to be investigated in detail. Mitigating vibrations will increase the design life and hence economic viability of the turbine blades and allow for continual operation with decreased downtime. The aim of this paper is to investigate the effectiveness of Semi-Active Tuned Mass Dampers (STMDs) in reducing the edgewise vibrations in the turbine blades. A frequency tracking algorithm based on the Short Time Fourier Transform (STFT) technique is used to tune the damper. A theoretical model has been developed to capture the dynamic behaviour of the blades including the coupling with the tower to accurately model the dynamics of the entire turbine structure. The resulting model consists of time dependent equations of motion and negative damping terms due to the coupling present in the system. The performances of the STMDs based vibration controller have been tested under different loading and operating conditions. Numerical analysis has shown that variation in certain parameters of the system, along with the time varying nature of the system matrices has led to the need for STMDs to allow for real-time tuning to the resonant frequencies of the system.