• Journal of the Korean Society for Precision Engineering
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• v.7 no.3
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• pp.75-82
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• 1990

Automatic monitoring of the cutting conditions is one of the most improtant technologies in machining. In this study, the feasibility in applying acoustic emission(AE) signals for the in-process detection of endmill wear and fracture has been investigated by performing experimental test on the NC vertical milling machine with SM45C for specimen. As the results of detecting and analyzing AE signals on various cutting conditions, the followings have confirmed. (1) The RMS value of acoustic emission is related sensitively to the cutting velocity, but is not affected largely by feed rate. (2) The burst type AE signals of high level have been observed when removing chips distorderly and discontinuously. (3) When the RMS value grows up rapidly due to the increase of wear the endmill are generally broken or fractured, but when the endmills fracture at the conditions of smooth chip-flow or built-up-edge(BUE) occurred frequently, the rapid change of the RMS arenot found. And it is expected that this technigue will be quite useful for in-process sensing of tool wear and fracture.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2114-2118
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• 2010

The purpose of this study was to analyze bradykinesia of toe tapping movement in patients with Parkinson's disease (PD) as compared to those of normal subjects. 39 PD patients (age: $65.5{\pm}11.2$ yrs, H&Y stage:$2.3{\pm}0.5$), 14 eldelry subjects with comparable mean age ($65.0{\pm}3.9$ yrs) and 17 healthy young subjects ($24.1{\pm}2.1$ yrs) participated in this study. Angular velocity during repetitive toe tapping movement was measured in both feet using a gyro sensor system. Suggested quantitative measures of bradykinesia were root-mean-squared (RMS) angular velocity, RMS angle, peak power and total power which were derived from the angular velocity signal. ANOVA showed that all measures were significantly different among three groups (p<0.001). Subsequent post-hoc test revealed that all measures in PD patients were significantly smaller than in healthy elderly and healthy young subjects (p<0.02). All measures were significantly correlated with UPDRS scores(r=-0.689~-0.825). These results suggest that the developed system can be used as quantitative measures of the lower limb bradykinesia in PD patients.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1094-1103
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• 2001

According to standard procedures as defined in the users handbook for sea level data processes, I was compared to Topex/Poseidon sea level data from the first 350days of mission and Tide Gauge sea level data from the Amsterdam- Crozet- Kerguelen region in the South Indian Ocean. The comparison improves significantly when many factors for the corrections were removed, then only the aliased oceanic tidal energy is removed by oceanic tide model(11) in this period. Making the corrections and smoothing the sea level data ()ver 60km along-track segments and the Tide Gauge sea level data for the time series results in the digital correlation and RMS difference between the two data of c=-0.12 and rms= 11.4cm, c=0.55 and rms=5.38cm, c=0.83 and rms=2.83cm, and c=0.24 and rms=6.72 for the Amsterdam, Crozet and Kerguelenplateau, and Kerguelen coast, respectively. It was also found that the Kerguelen plateau has a comparisons due to propagating signals(the baroclinic Rossby wave with velocity of -3.9 ~-4.2cm/sec, period of 167days and amplitude of 10cm) that introduce temporal lags(${\gamma}$: 10~30days) between the altimeter and tide gauge time series. The conclusion is that on timescales longer than about 10days the RMS sea level errors are less than or of the order of several centimeters and are mainly due to the effects of currents rather than the effects of stories(water temperature, density) and winds.

• Korean Journal of Applied Biomechanics
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• v.20 no.2
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• pp.191-196
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• 2010

The purpose of this study was to investigate the effect of gait speed and walkway slope on the body acceleration, for the future validation of using an accelerometer in the estimation of energy consumption. Ten young healthy subjects with accelerometers on the upper thigh and ankle walked on a treadmill at 9 conditions(three speeds ${\times}$ three slopes) for 5 minutes. Acceleration signals of four directions, i.e. anterior-posterior(AP), medio-lateral(ML), superior-inferior(SI) and vector sum(VS) directions, of each sensor were measured, and root means squared(RMS) values of them were used as analysis variables. As statistical analysis, repeated measure two-way ANOVA was performed for RMS accelerations at each attachment sites, with slope and velocity as independent factors. At both the upper thigh and ankle, RMS acceleration of all directions were affected by gait velocities(p<.001) showing greater accelerations for higher velocities. Contrary to expectations, no slope effect existed in RMS accelerations at hip. Moreover, RMS acceleraion at ankle decreased with slope in SI and VS directions(p<.01). These results suggests that RMS acceleration cannot reflect the change in physical activity due to the change in walkway slope.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.240-244
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• 2010

The purpose of this study is to compare finger tapping (FT) movement of patients with Parkinson's disease (PD) with normal subjects. A gyrosensor system was used for the measurement of FT movement, because it provides angular velocity free from the gravitational artifact and it can be used during clinical FT test listed in unified PD rating scale (UPDRS). Forty PD patients (age: 65.7 ${\pm}$ 11.1 yrs, H&Y stage:2.3 ${\pm}$ 0.5), 14 age-matched elderly subjects (65${\pm}$3.9 yrs) and 17 healthy young subjects (24${\pm}$2.1yrs) participated in this study. Angular velocity of finger tapping movement was measured in both right and left index finger. As quantitative measures, root-mean-squared (RMS) angular velocity, RMS angle, peak power and total power were used. ANOVA showed that all measures were significantly different among three groups (p<0.001) in all quantitative measures. Post-hoc test revealed that all quantitative measures except peak power in patients with PD were significantly smaller than in both healthy elderly and young subjects (p<0.01). This suggests that the measures developed in this study can distinguish patients with PD from normal subjects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1051-1056
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• 2006

The mean and RMS velocity field of the respiratory gas flow in the human airway was studied experimentally by particle image velocimetry (PIV). Some researchers investigated the airflow for the mouth breathing case both experimentally and numerically. But it is very rare to investigate the airflow of nose breathing in a whole airway due to its geometric complexity. We established the procedure to create a transparent rectangular box containing a model of the human airway for PIV measurement by combination of the RP and the curing of clear silicone. We extend this to make a whole airway including nasal cavities, larynx, trachea, and 2 generations of bronchi. The CBC algorithm with window offset (64 $\times$ 64 to 32 $\times$ 32) is used for vector searching in PIV analysis. The phase averaged mean and RMS velocity distributions in Sagittal and coronal planes are obtained for 7 phases in a respiratory period. Some physiologic conjectures are obtained. The main stream went through the backside of larynx and trachea in inspiration and the frontal side in expiration. There exist vortical motions in inspiration, but no prominent one in expiration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.995-1001
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• 2012

This paper compares the performance of several tracking filters, namely, alpha-beta filter, Kalman filter and TBM tracking filter for ballistic target tracking problem using multi-function radar. Every of three tracking filters suggested was tested on simulator developed in accordance with TBM trajectory and MFR RSP measurement. The result shows the method using TBM tracking filter gives 75.3 % decreased velocity RMS error than alpha-beta filter. After initialization, the RMS error of range and velocity of the proposed filter is also smaller than the Kalman filter. Finally the proposed filter is suitable for high-speed TBM tracking due to the stable angle tracking accuracy.

• Journal of the Korean Society of Safety
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• v.29 no.1
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• pp.15-20
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• 2014

The silicon as the hyper-elastic material was used to design the shock programmer and dynamic characteristic of the shock programmer was studied. The shock programmer was a structure part that was mounted between the impactor and the test bed. The role of the shock programmer was to generate the acceleration time history by the objective of various impact tests. The effective elastic modulus of the silicon was varied under the velocity of the impactor. The effective elastic modulus of the silicon was estimated by the comparison with results between test and simulation.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.4
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• pp.357-366
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• 2020

This paper addressed a relative navigation method for autonomous rendezvous and docking of cube-satellites using single frequency Differential GPS (DGPS) under the intermittent communication between satellites. Since the ionospheric error of GPS measurement is variable depending on the visible satellites, a few meters error of relative navigation is occurred in the Low-Earth Orbit (LEO) environment. Therefore, it is essential to remove the ionospheric error to perform relative navigation. Besides, an intermittent communication period for receiving GPS measurements of the target satellite is limited for getting information every sampling time. To solve this problem, a method combining range domain DGPS and orbit propagation is proposed in this paper. The proposed method improves the performance of DGPS by using Hatch filter and solves an intermittent communication problem by estimating the relative position and velocity using Hill-Clohessy-Wiltshire Equation. Through the simulation, it is verified that the suggested algorithm provides the relative position error within RMS 0.5 m and the relative velocity error within RMS 3 cm/s. Furthermore, it has the advantage that it is suitable for real-time implementation using single-frequency GPS measurements and is computationally efficient.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.281-285
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• 2001

According to standard procedures as defined in the users handbook for sea level data processes, I was compared to Topex/poseidon sea level data from the first 350days of mission and Tide Gauge sea level data from the Amsterdam- Crozet- Kerguelen region in the South Indian Ocean. The comparison improves significantly when many factors for the corrections were removed, then only the aliased oceanic tidal energy is removed by oceanic tide model in this period. Making the corrections and smoothing the sea level data over 60km along-track segments and the Tide Gauge sea level data for the time series results in the digital correlation and RMS difference between the two data of c=-0.12 and rms=11.4cm, c=0.55 and rms=5.38cm, and c=0.83 and rms=2.83cm for the Amsterdam, Crozet and Kerguelen plateau, respectively. It was also found that the Kerguelen plateau has a comparisons due to propagating signals(the baroclinic Rossby wave with velocity of -3.9~-4.2cm/sec, period of 167days and amplitude of 10cm) that introduce temporal lags($\tau$=10~30days) between the altimeter and tide gauge time series. The conclusion is that on timescales longer than about 10days the RMS sea level errors are less than or of the order of several centimeters and are mainly due to the effects of currents rather than the effects of sterics(water temperature, density) and winds.