• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.4 no.2
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• pp.39-45
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• 2009

Objectives : The aim of this study is to compare the improvement of Low back pain (LBP) depending on male Inpatient's Brachlalankle Pulse Wave Velocity (baPWV), Method : We evaluated 35 LBP inpatients who took pulse wave velocity test during admission at Jaseng hospital from November 2008 to september 2009. We used applanation tonometry method to measure pulse wave velocity and numerical rating scale to measure patient's improvement. Result : At admission, standard deviation of normal group's NRS was $7.44{\pm}1.67$ and high risk group's was $7.57{\pm}2.09$(P=0.678). After 5 days of admission, standard deviation of normal group's NRS was $5.67{\pm}1.94$ and high risk group's was $6.00{\pm}2.17$(P=0.680). After 10 days of admission, standard deviation of normal group's NRS was $4.00{\pm}1.80$ and high risk group's was $4.95{\pm}1.96$(P=0.281). After 15 days of admission, standard deviation of normal group's NRS was $2.89{\pm}1.62$ and high risk group's was $4.10{\pm}1.92$(P=0.124). At discharge, standard deviation of normal group's NRS was $5.11{\pm}1.69$ and high risk group's was $4.86{\pm}2.08$(P=0.504). Comparison between admission and discharge, standard deviation of normal group's NRS was $5.11{\pm}1.69$ and high risk group's was $4.86{\pm}2.08$(P=0.504) Conclusion : Low back patients with high Brachialankle Pulse Wave Velocity, showed slower improvement rate compare to patients within normal rate. But statically, had no significance.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.588-591
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• 2009

We had experimental studies of microwave output generator. We experimented with a corrugate-shped K-band slow wave guide in the backward wave oscillator. It generated output 표 interaction between electron beam's generation and magnetic field. We estimated oscillation frequency at 24GHz by changing propagation velocity and group velocity. We identified movement by second harmonic of Cherencov interaction and slow cyclotron mode. In our study we achieved oscillation stabilization, generation of long pulse, improvement of oscillation efficiency and output.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.673-680
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• 2019

This study was conducted to investigate the effects of plasma homocysteine concentration on the brachial-ankle pulse wave velocity between the normal homocysteine group and the asymptomatic high homocysteine group. 435 subjects who visited the general health examination center from April 1 to October 31, 2016, as well as to compare the direct correlation of the brachial-ankle pulse wave velocity, which indirectly reflects the homocysteine test and arterial stiffness, as a predictor of future cardiovascular outcome. As a result of the study, age, waist circumference, BUN, and plasma creatinine were significantly higher, and HDL was significantly lower in the high homocysteine group (> $15{\mu}mol/L$) than in the normal homocysteine group (< $15{\mu}mol/L$) (p=0.05). In addition, homocysteinemia was associated with smoking and drinking (p<0.001) and was significantly higher in males (p<0.001). The right and left brachial-to-ankle pulse wave velocities were significantly higher in the high homocysteine group (right p<0.001, left p=0.003) before calibrating the relevant variables. There was no significant difference between right and left brachial-to-ankle pulse wave velocities after calibrating the relevant variables. Therefore, further studies on the independent association of lowering homocysteine concentration and prevention of cardiovascular disease and the relationship between homocysteine and renal function are needed.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.435-444
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• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.12-17
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• 2017

We construct 3D SV-wave velocity structure of the crust and the upper mantle beneath East Asia from Rayleighwave group-velocity measurements. For the construction of the SV-wave velocity model at 10 ~ 100 km depth, we used seismic data recorded at 321 broadband stations in Korea, Japan, and China. Rayleigh-wave group-velocity dispersion curves were obtained by using the multiple filtering technique in the period range from 3 to 150 s. High SV-velocity anomalies are imaged beneath the East Sea from 10 km depth to deeper depth, implying that the Moho beneath the East Sea is between at 10 ~ 20 km depth. We estimated the Moho beneath the Korean peninsula to be around 35 km based on the depth where a high-velocity anomaly is observed. The SV-wave velocity model shows prominent fast S-velocity anomalies near northeastern Japan, associated with the subducting Pacific plate. Low-velocity anomalies are found beneath the east coast of the Korean peninsula at 100 km depth, which may play a role in the formation of the Ulleungdo and the Ulleung basin. We observed low-velocity anomalies beneath the Yamato basin at 100 km depth as well, which may indicate the upwelling of fluid from the Pacific plate via dehydration at deeper depth.

• Structural Engineering and Mechanics
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• v.48 no.4
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• pp.501-518
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• 2013

Apart from thinning of cortical layers, the local bone curvature, varying along bone periphery, modulates ultrasound waves as well, which is however often underestimated or overlooked in clinical quantitative ultrasound (QUS). A dedicated three-dimensional finite element modelling technique for cortical bones was established, for quantitatively exploring and calibrating the effect of local curvature of cortical bone on ultrasound. Using a correlation-based mode extraction technique, high-velocity group (HVG) and low-velocity group (LVG) wave modes in a human radius were examined. Experimental verification using acrylic cylinders and in vitro testing using a porcine femur were accomplished. Results coherently unravelled the cortical curvature exerts evident influence on bone-guided ultrasound when RoC/${\lambda}$ <1 for HVG mode and RoC/${\lambda}$ <2 for LVG mode (RoC/${\lambda}$: the ratio of local bone curvature radius to wavelength); the sensitivity of LVG mode to bone curvature is higher than HVG mode. It has also been demonstrated the local group velocity of an HVG or LVG mode at a particular skeletal site is equivalent to the velocity when propagating in a uniform cylinder having an outer radius identical to the radius of curvature at that site. This study provides a rule of thumb to compensate for the effect of bone curvature in QUS.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.818-823
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• 2005

Creep damage is one of the mosl important characteristics for the stability of high temperature structures such as huge energy converting facilities. Creep failure of Type 316LN stainless steel is highly correlated to generation and growth of the voids. In this paper, in order to investigate the correlation of creep rupture time and ultrasonic parameters (group velocity, angular velocity), creep-damaged Type 316LN specimens and measurements for the ultrasonic parameters were made. However, bi-directional measurements were applied along the load direction and the perpendicular direction to the load line by means of the contact type probe of which the central frequencies are 10MHz, 15MHz and 20MHz. Analyzing the angular velocities of the ultrasonic signals obtained from the load direction, it was confirmed that the angular velocities were declined as the creep time passed when 15MHz and 20MHz probes were used. Also, the group velocities were declined for all three frequencies as the creep time increased. Thus, positive feasibility for the creep damage evaluation by means of the angular and group velocities was confirmed. Moreover, result of analysis for the ultrasonic signal which was obtained from the perpendicular direction upon the angular and group velocities indicated little variation for both of the angular and group velocities. Therefore, the creep damage is likely to represent anisotropic itself.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1237-1240
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• 2007

Tire noise is a major noise source at high speeds. One of the noise source is controlled by pattern and structure. Pattern noise is effected by the shape of tread. And the bending stiffness of tire is influenced to the resonance of tire‘s belt. But in high frequency region, FEA is not appropriated with application. So this paper discusses about wave propagation of tire. There has been much effort to verify the flexural wave velocity with structure design specification.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.25-32
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• 2017

We present a 3D SH-wave velocity model of the crust and uppermost mantle and seismic radial anisotropy beneath East Asia. The SH-wave velocity structure model was built using Love-wave group-velocity dispersion data from earthquake data recorded at broadband seismic networks of Korea, Japan, and China. Love-wave group-velocity dispersion curves were obtained by using the multiple filtering technique in the period range of 3 to 150 s for 3,369 event-station pairs. The inverted model using these data sets provides a crust and upper mantle SH-wave velocity structure down to 100 km depth. At 10 ~ 40 km depths SH-wave velocity beneath the East Sea is higher than beneath the Japanese island region. We estimated the Moho beneath the East Sea to be between 10 ~ 20 km depth, while Moho beneath the Korean Peninsula at around 35 km based on the depth where high-velocity anomalies are detected. We estimated the lithosphere-asthenosphere boundary beneath the East Sea to be at around 50 km based on the depth where strong low-velocity anomalies are observed. Widespread low-velocity anomalies are found between 50 ~ 100 km depth in the study region. Positive radial anisotropy ($V_{SV}$ > $V _{SH}$) is observed down to 35 km depth, while negative radial anisotropy ($V_{SV}$ > $V _{SH}$) is observed for deeper depth.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.5-12
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• 2013

The critical velocity effect on railway trackbed means the amplification of vibration energy when the train running-speed and group velocity of ground surface wave are superimposed. It is called a pseudo-resonance phenomenon of time domain. In the past, it was not issued because the train speed was low and the ground group velocity was higher. But since the high-speed train is introduced, critical velocity reported causing a track irregularity. So far, theoretical analysis has been performed because of the complexity of formation process. However it requires reasonable consideration which is similar to actual track and trackbed conditions. In the present paper, finite element analysis to verify the critical velocity effect is performed considering each track structure and trackbed supporting stiffness. As a result, the deformation amplification caused by the critical velocity effect is verified to analyze each supporting stiffness and track system.