• Geophysics and Geophysical Exploration
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• v.16 no.4
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• pp.250-256
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• 2013

Using shear wave velocity is more reasonable to estimate strength and integrity of rock compared with using compressional wave. It is often ambiguous to pick the dominant frequency caused by torsional wave when evaluating $V_S$ of rock specimen from FFRC method. It is also sometimes ambiguous to pick the first arrival point of S wave compared with P wave in the signals acquired from ultrasonic velocity method. Otherwise, the procedure of evaluating $V_P$ using ultrasonic velocity method and $V_L$ using FFRC method is relatively stable. Through the relationship between elastic modulus, poisson's ratio and $V_S$ can be obtained from $V_P$, $V_L$. Applicability was checked using model specimens having different material property and length and rock specimens sampled in mine area, and usefulness of proposed procedure was verified.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.357-364
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• 1999

In recently site investigations, the need for the determination of dynamic soil properties such as dynamic modules of rigidity, elasticity, dynamic poison's ratio and damping ratio etc. is increasing for the astigmatic designs of the civil structures. To obtain some of the dynamic properties, measurement of elastic waves velocity, both P and S wave, is required. Among various methods to measure elastic wave velocity such and Down Hole, Cross Hole and Refraction etc., Suspension P.S. Logging has an advantage to use for the off-shore investigation where generation of the shock wave and traveling of the wave is difficult. In suspension P.S. logging, specially designed prove equipped with source of shock wave, two 3-channel receivers, departing 1m distance, and other auxiliary facilities is inserted down in a bore hole bottom and raised in predetermined interval, usually 1m or 2m, and measurement is conducted. P.S. logging have been conducted in a off-shore construction project near InChon in the west coast for the first in the country, and form the result, potential of the liquefaction of the subsoil was evaluated and compared with the conventional method.

• Geophysics and Geophysical Exploration
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• v.14 no.4
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• pp.324-334
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• 2011

Seismic wave velocity change has been monitored due to the accumulation of micro-cracks by uniaxial loads on the rock samples from Seokmo Island with stepwise increase in 5 stages. After the load was applied up to 95% of UCS, P- and S-wave velocities varied in ranges of 0.9 ~ 18.3% and 2.8 ~ 14.8% of fresh rock sample velocities, respectively. Unlike seismic velocity of the dry rock samples that showed overall decreases after the loading, velocity changes of saturated rock samples were much more complicated. These seemed to be due to the mixture of two contradictory mechanisms; i.e. accumulation of micro-crack causes an increase in porosity and a decrease in wave velocity, while saturation causes an increase in wave velocity. Most of tested rocks showed a trend of velocity increase with low axial load and then velocity decrease at later stages. Starting stage of velocity decrease differs from samples to samples. After the failure of rock occurred, noticeable increases of porosity and decreases of wave velocity have been observed. It showed overall trend that the more the quartz contents and the lower the silicate, the higher the Young's modulus.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.25-32
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• 2004

We have carried out laboratory measurements of P-wave velocity and deformation strain during $CO_2$ injection into a porous sandstone sample, in dry and water-saturated conditions. The rock sample was cylindrical, with the axis normal to the bedding plane, and fluid injection was performed from one end. Using a piezoelectric transducer array system, we mapped fluid movement during injection of distilled water into dry sandstone, and of gaseous, liquid, and supercritical $CO_2$ into a water-saturated sample. The velocity changes caused by water injection ranged from $5.61\;to\;7.52\%$. The velocity changes caused by $CO_2$ injection are typically about $-6\%$, and about $-10\%$ for injection of supercritical $CO_2$, Such changes in velocity show that the seismic method may be useful in mapping $CO_2$ movement in the subsurface. Strain normal to the bedding plane was greater than strain parallel to the bedding plane during $CO_2$ injection; injection of supercritical $CO_2$ showed a particularly strong effect. Strain changes suggest the possibility of monitoring rock mass deformation by using borehole tiltmeters at geological sequestration sites. We also found differences associated with $CO_2$ phases in velocity and strain changes during injection.

• 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.

• Geophysics and Geophysical Exploration
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• v.14 no.1
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• pp.58-68
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• 2011

As part of basic studies of monitoring carbon dioxide ($CO_2$) storage using electrical and seismic surveys, laboratory experiments have been conducted to measure resistivity and P-wave velocity changes due to the injection of $CO_2$ into water-saturated sandstone. The rock sample used is a cylinder of Berea sandstone. $CO_2$ was injected under supercritical conditions (10 MPa, $40^{\circ}C$). The experimental results show that resistivity increases monotonously throughout the injection period, while P-wave velocity and amplitude decrease drastically due to the supercritical $CO_2$ injection. A reconstructed P-wave velocity tomogram clearly images $CO_2$ migration in the sandstone sample. Both resistivity and seismic velocity are useful for monitoring $CO_2$ behaviour. P-wave velocity, however, is less sensitive than resistivity when the $CO_2$ saturation is greater than ~20%. The result indicates that the saturation estimation from resistivity can effectively complement the difficulty of $CO_2$ saturation estimations from seismic velocity variations. By combining resistivity and seismic velocity we were able to estimate $CO_2$ saturation distribution and the injected $CO_2$ behaviour in our sample.

• The Journal of Engineering Geology
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• v.13 no.3
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• pp.293-308
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• 2003

New results about the crustal structure down to a depth of 60 km beneath North Korea were obtained using the seismic tomography method. About 1013 P- and S-wave travel times from local earthquakes recorded by the Korean stations and the vicinity were used in the research. All earthquakes were relocated on the basis of an algorithm proposed in this study. Parameterization of the velocity structure is realized with a set of nodes distributed in the study volume according to the ray density. 120 nodes located at four depth levels were used to obtain the resulting P- and S-wave velocity structures. As a result, it is found that P- and S-wave velocity anomalies of the Rangnim Massif at depth of 8 km are high and low, respectively, whereas those of the Pyongnam Basin are low up to 24 km. It indicates that the Rangnim Massif contains Archean-early Lower Proterozoic Massif foldings with many faults and fractures which may be saturated with underground water and/or hot springs. On the other hand, the Pyongyang-Sariwon in the Pyongnam Basin is an intraplatform depression which was filled with sediments for the motion of the Upper Proterozoic, Silurian and Upper Paleozoic, and Lower Mesozoic origin. In particular, the high P- and S-wave velocity anomalies are observed at depth of 8, 16, and 24 km beneath Mt. Backdu, indicating that they may be the shallow conduits of the solidified magma bodies, while the low P-and S-wave velocity anomalies at depth of 38 km must be related with the magma chamber of low velocity bodies with partial melting. We also found the Moho discontinuities beneath the Origin Basin including Sari won to be about 55 km deep, whereas those of Mt. Backdu is found to be about 38 km. The high ratio of P-wave velocity/S-wave velocity at Moho suggests that there must be a partial melting body near the boundary of the crust and mantle. Consequently we may well consider Mt. Backdu as a dormant volcano which is holding the intermediate magma chamber near the Moho discontinuity. This study also brought interesting and important findings that there exist some materials with very high P- and S-wave velocity annomoalies at depth of about 40 km near Mt. Myohyang area at the edge of the Rangnim Massif shield.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.561-571
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• 1997

In this paper, the fundamental equations are developed for the pulsatile laminar flow generated by changing the oscillatory flow with $0{\leq}f{\leq}48Hz$ into a steady one with $0{\leq}Re{\leq}2500$ in a rigid circular pipe. Analytical solutions for the wave propagation factor k, the axial distributions of cross-sectional mean velocity $u_m$ and pressure p are schematically derived and confirmed experimentally. The axial distributions of centerline velocity and pressure were measured by using Pitot-static tubes and strain gauge type pressure transducers, respectively. The cross-sectional mean velocity was calculated from the centerline velocity by applying the parabolic distribution of the laminar flow and it was confirmed by using the ultrasonic flowmeter. It was found that the axial distributions of cross-sectional mean velocity and pressure agree well with theoretical ones and depend only on the Reynolds number Re and angular velocity $\omega$.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.43-54
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• 2005

Care should be taken when performing the P and S wave velocity loggings. Some of them are the effect of casing that is installed to prevent the borehole collapsing when the drilling is done on the loose ground such as soil and/or soft rock, and the discrepancy of the velocities of the same media according to the difference of the source wave frequency spectrum. To overcome these difficulties, the following suggestions are recommended; (1) try a careful drilling technique that can eliminate the necessity of the casing, and (2) apply the logging methods with the proper frequency spectrum that is appropriate to the object of the velocity logging.