• The Journal of Korean Physical Therapy
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• v.17 no.1
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• pp.27-42
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• 2005

This study aims to investigate the effect of Early Weight Bearing and Vibration Exercise and is focusing on the difference between changes if experimental before and after on 30 stroke patients. The obtained results are as follows; First, the chang due to Early Weight Bearing and Vibration in the comparison of experimental duration, Early Weight Bearing and Vibration Exercise showed improvement of Bone Density(P<.05). Second, in the comparison of change according to Early Weight Bearing and Vibration Exercise, Bone Density was significantly changed between two experimental group(P<.05). Third, the chang due to Early Welght Bearing and Vibration Exercise, Bone Density of sound femoral head and affected femoral head was significantly changed(P<.05). Fourth, the chang due to Early Weight Bearing and Vibration Exercise, Bone Density of femoral head was significantly changed between two experimental group(P<.05).

• Journal of KSNVE
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• v.5 no.1
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• pp.117-122
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• 1995

The transfer matrix method is proposed to compensate the attachment effect of a piezo-electric impedance head. To validate the proposed method, an experiment is carried out for axial vibration of a uniform rod for which an analytical solution is known. The impedance head is attached to the test rod by a stud and is connected to the exciter. The frequency response function is mesured by applying random excitation from the electro-magnetic exciter. The frequency response function compensated by the method proposed in this research shows good agreement with the analytical solution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1105-1110
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• 2001

본 논문은 머리진동 측정용 바이트 바의 동적 특성에 관한 연구이다. 머리진동의 관심주파수 영역은 0.5Hz~30Hz 범위의 주파수이며 기구학적 이론들을 이용하여 측정된 선형 가속도로부터 머리의 각각속도를 계산하는 과정을 소계한다. 본 논문에서는 9개의 선형가속도를 이용하여 각각속도를 구하는 방법에 대한 검증뿐 아니라 나아가 센서의 측정점의 Offset 영향을 고려한 이론식을 제시한다.

• The Journal of Korean Physical Therapy
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• v.26 no.3
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• pp.156-162
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• 2014

Purpose: The purpose of this study was to investigate muscle activation related to postural stability depending on different head positions with whole body vibration (WBV) in standing. Methods: Eighteen healthy subjects voluntarily participated in this single-group, repeated-measures study in which the surface electromyography (EMG) data from upper trapezius, rectus abdominis, external oblique abdominis, erector spinae, gluteus maximus, rectus femoris, semitendinosus, medial gastrocnemius were collected over 3 different frequencies (0-10-20Hz) and 4 different head positions (neutral, flexion, extension, chin tuck) for each subject on WBV while standing. Results: The results of this study demonstrated that the EMG activity of all recorded muscles shows significant difference between three different frequencies and four head positions of WBV while standing (p<0.05). In the multiple comparison, significant differences could be observed for most of different frequency conditions except 0-10Hz of RA, 10-20Hz of ST. In contrast, no significant difference showed the comparison of the EMG activity depending on different head positions (p<0.05). Conclusion: These findings suggest that different head positions on WBV do not activate muscles related to postural stability. However, higher frequency on WBV is highly effective to activate whole body muscles included postural muscles regardless of different head positions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.533-538
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• 2002

This research demonstrates the transient response of a head disk assembly subjected to a half-sine shock pulse in the axial direction. In case of disk analysis, the numerical method presented by Barasch and Chen is used. Galerkin method is used with mode shape by numerical method. head-suspension system is modeled by the cantilever in order to get simulation results. Simulation results about total system of HDA are calculated by Runge-Kutta method.

• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.87-97
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• 2000

This study was performed to investigate the effects of repetitive mandibular opening movement and change of head posture on the vibration of temporomandibular(TM) joint. For this study, 23 patients with internal derangement of TM joint were selected. All they had clinically noticeable TM joint sound. Observation of the joint vibration were performed in four head postures, namely, natural head posture (NHP), forward head posture(FHP), upward head posture(UHP), and downward head posture(DHP). For recording of joint sound vibration, Sonopak of Biopak system(Bioresearch Inc., Milwaukee, USA) was used, The author could take results related to integral higher than 300Hz, integral lower than 300Hz, ratio of integral higher than 300Hz to integral lower than 300Hz, total integral which was sum of higher and lower integral, peak amplitude, and peak frequency in each opening movement, which was carried out three times in each head posture. Integral means amount of vibration. The data obtained were analysed by SPSS windows program and the results of this study were as follows : 1. In NHP, total integral in right TM joint was 5O.3Hz in the first opening, 67.9Hz in the second opening, and 74.0Hz in the third opening movement, bur there was no significant increase of total integral with repetitive opening movement. This finding was similar in left TM joint. Integral lower than 300Hz were higher than integral higher than 300Hz in almost every opening movement. 2. There was no significant difference of total integral between right and left side of TM joint, but there was a tendency of higher total integral in right TM joint than that in left TM joint except for results in DHP. 3. Peak amplitude in NHP ranged from 2.0 to 4.7, and peak frequency in NHP were 101.4-170.0Hz. And there was no consistent findings related to increase or decrease of these value according to repetitive opening in each head posture. 4. Change of head posture did not result any difference in integral, peak amplitude, and peak frequency. In conclusion, change of head posture and repetitive mandibular opening movement did not make any significant effect on the vibration of temporo-mandibular joint, especially, on total integral, peak amplitude, and peak frequency.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.122-132
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• 2000

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in 'Free Vibration of Car seat and Mannequin System' nonlinear and linear equations of motions were rederived for forced vibration and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests mannequin's head had a lot of problems and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints linear analyses were performed. New sets of linear spring and damping coefficients and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance indicating that this is a feasible method of modeling seated occupants.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.8
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• pp.841-848
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• 2008

Based on the averaged Korean head shapes that are the results of digital Korean project by KISTI and Catholic university, experimental apparatus of head dummies of Korean male and female are developed in order to measure head-related transfer functions(HRTF) by using a reverse engineering and rapid prototyping techniques. For the Korean dummies, HRTFs are measured using the substitution method ever 12kHz frequency bands. At every azimuth angle $15^{\circ}$ HRTFs are measured for elevation angles $-30^{\circ}$, $0^{\circ}$ and $-30^{\circ}$. The measured HRTFs are compared with those of KEMAR(knowles electronic manikin for acoustic research) dummy head, which shows $3{\sim}5\;dB$ difference over $4{\sim}5\;kHz$ kHz frequency band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.669-673
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• 2008

Based on the averaged Korean head shapes that are the results of digital Korean project by KISTI and Catholic university, experimental apparatus of head dummies of Korean male and female are developed in order to measure head-related transfer functions (HRTF) by using a reverse engineering and rapid prototyping techniques. For the Korean dummies, HRTFs are measured using the substitution method over 12 kHz frequency bands. At every azimuth angle $15^{\circ}$ HRTFs are measured for elevation angles $-30^{\circ}$, $0^{\circ}$, and $30^{\circ}$. The measured HRTFs are compared with those of KEMAR (Knowles Electronic Manikin for Acoustic Research) dummy head, which shows a little different frequency characteristic beyond 2 kHz frequency band.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.141-145
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• 2014

A minimally appropriate time delay of audio data processing is investigated for rendering virtual sound source direction in real-time head-tracking environment under headphone listening. Less than 3.7 degree of angular mismatch should be maintained in order to keep desired sound source directions in virtually fixed while listeners are rotating their head in a horizontal plane. The angular mismatch is proportional to speed of head rotation and data processing delay. For 20 degree/s head rotation, which is a relatively slow head-movement case, less than total of 63ms data processing delay should be considered.