• Journal of the Korean Society of Physical Medicine
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• v.7 no.1
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• pp.1-9
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• 2012

Purpose : This study aimed to compare the effect of two modes (proprioceptive neuromuscular facilitation combination patterns and ball exercise) of low back stability for chronic low back patients. Methods : The subjects were recruited fourty patients who had low back pain. All subjects were randomly assigned to PNF combination patterns group, ball exercise group. Measurements were performed fourtimes: pre test, 2weeks, 4weeks, and 6weeks. Main outcome measures comprised the visual analogue scale(VAS), balance performance monitor(BPM). Results : The results were as follows. In the comparison of VAS score, sway area, sway path, and sway velocity according treatment period, score was significantly reduced in both PNF combination pattern group and ball exercise group. In the comparison of the both VAS and sway area between groups, there were significant. PNF combination pattern group significantly more decrease than ball exercise group at 6 weeks. However, both sway path and sway max velocity between group, there were not significantly. Conclusion : These results of this study indicated that PNF combination pattern which performed for six weeks had a significant influence than ball exercise group on low back pain.

• Wind and Structures
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• v.20 no.3
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• pp.469-488
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• 2015

A full-scale instrumented low-rise building with gable roof was built at a coastal site with a high incidence of tropical cyclones for monitoring of wind effects on the building during windstorms. This paper presents the field measurements of the wind velocity field around and the wind-induced pressures on the low-rise building during the passage of severe tropical storm Soudelor. Near-ground wind characteristics such as wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and wind velocity spectra were investigated. The wind-induced pressures on the roof of the building were analyzed and discussed. The results revealed that the eave and ridge edges on the roof were subjected to the most severe suction pressures under quartering winds. These suction pressures showed obvious non-Gaussian behavior. The measured results were compared with the provisions of ASCE 7-10 to assess the suitability of the code of practice for the wind-resistant design of low-rise buildings under tropical cyclones. The field study aims to provide useful information that can enhance our understanding of the extreme wind effects on low-rise buildings in an effort to reduce tropical cyclone wind damages to residential buildings.

• Tribology and Lubricants
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• v.10 no.3
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• pp.29-38
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• 1994

The friction and wear of mild steel at dry sliding surfaces under different vacuum conditions have been investigated to understand the wear mechanisms. For the test, a ball-ondisk typed wear-rig has been built and implemented, allowing control of sliding speed, load and vacuum. Results show that, at a high sliding velocity, friction of low carbon steel (SS41) under a high vacuum is much higher than that of ambient condition and wear is much severer. It is due to lack of effective oxidation film formation on which steel surfaces could protect themselves against the severe wear. It has been shown, however, that there is a critical regime with contact conditions (at a low sliding velocity, a low load, and under a medium vacuum) at which effective, protective films of low carbon steel have been built on the surfaces in a friction process with a self-regulating way, resulting in both very low coefficients of friction (about 0.3) and mild wear. In order to investigate the protective films on steel surfaces, the worn surfaces and the wear debris have been experimentally analyzed with SEM, AES/SAM and XRD. A theoretical analysis of frictional heating at sliding surfaces, and an experimental analysis of the influence of oxidation wear under various vacuum conditions are described. The important variables on which self-formations of protective films at dry sliding surfaces depend, and the wear mechanisms are also investigated.

• Clinical and Experimental Reproductive Medicine
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• v.27 no.4
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• pp.393-403
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• 2000

Objective: To investigate the effects of ROS on kinematic parameters in human spermatozoa. To verify the changes in above parameters, human spermatozoa were incubated with xanthine-xanthine oxidase (X-XO), $H_2O_2$, sodium nitroprusside (SNP) or lymphocyte. Otherwise, spemlatozoa were incubated under low $O_2 (5%) condition. Methods: CASA was employed to analyze sperm motion parameters. Results: Under $H_2O_2 treatment, all kinematic parameters of spermatozoa were dramatically increased during 30 min, but gradually decreased thereafter. Under the low concentration of $H_2O_2 (125 ${\mu}M$ and 250 ${\mu}M$), the movement velocity (VAP, VCL, VSL) decreased, but forward movement increased. Under the 1mM $H_2O_2, sperm showed reduced kinematic parameters except during first 30 min of incubation. In the cases of X-XO and SNP treatment, the movement velocity increased but the forward movement reduced. After incubation for 3 hr treatment, the kinematic parameters gradually decreased in high concentration of X-XO. However these parameters maintained or increased in low concentration of X-XO. There was no obvious changes in the above parameters in the high concentration of SNP. In the presence of high concentration of lymphocytes, all parameters decreased. Under the 5% $O_2 condition, the parameters of the movement velocity and movement pattern increased, but forward movement decreased. Taken togethers, it suggested that ROS increased the movement velocity but decreased the forward movement and lateral head replacement. $H_2O_2, X-XO, SNP and lymphocyte treatment significantly increased capacitated spermatozoa within I h of incubation. There was no significant difference in capacitation between low- and high $O_2 group. Conclusion: The early onset of capacitation in the presence of ROS suggest that ROS might be a positive regulator of sperm capacitation and hyperactivation. These results demonstrate that low concentration ROS facilitates the movement velocity but high concentration ROS was inhibitory.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.235-246
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• 2013

P-wave velocity was measured by the low frequency flaw detector in order to analyze the weathered state of a halo stone Buddha, Unju temple, Hwasun, Korea. By the results of laboratory tests on a fresh acidic tuff with the same rock of a halo stone Buddha, average absorption, average P-wave velocity, and average uniaxial compressive strength were 5.38%, 4,008 m/s, and 70.1 MPa, respectively. The results correspond to moderately strong rock. Average P-wave velocity of a halo stone Buddha measured by the low frequency flaw detector was 2,257 m/s in the left zone, 3,437 m/s in the right zone, and 2,802 m/s overall. Weathering index of a halo stone Buddha was 0.45 in the left zone, 0.21 in the right zone, and 0.33 overall. Comparing the results of a halo stone Buddha with them of laboratory tests, weathered state of a halo stone Buddha was analyzed highly weathered state in the left zone and moderately weathered state in the right zone. Furthermore, it suggests that the left zone of a halo stone Buddha was affected weathering more than the right one. Overall a halo stone Buddha corresponds to moderately weathered state of weathering degrees. In conclusion, it is considered that low frequency flaw detector may be applicable as a valuable method on analyzing the P-wave velocity of the stone cultural heritage with an irregular surface.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.315-320
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• 2004

Swing check valves are the most common type of check valve in nuclear power plant and need to be operated property to perform their functions and to keep the valve internals stable. However, for a swing check valve disc to remain stable, the opening characteristics should be identified and the upstream flow velocity should be enough to hold the disc fully open and without motion. Thus it is necessary to develop a model for predicting the flow velocity for a given disc opening. In the present study, the disc positions with mean flow velocity were measured for 3 inch and 6 inch swing check valves. Comparison of the measurements with the existing models showed that the models underestimate the mean flow velocity for a given disc position. Therefore, the existing model for predicting swing check valve disc position was improved with the realistic disc impingement area perpendicular to the flow stream and the experimental data. The result showed that the improved model with the best estimate of kb = 0.04 predicts well the disc openings of 6 inch swing check valve, especially in the low velocity region. For better prediction of the disc opening at high flow velocity, however, it is recommended to develop a kb correlation with the disc angle.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.75.1-75.1
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• 2012

Narrow-Line Seyfert 1 galaxies are arguably the most important AGN subclass in investigating the origin of the black hole mass-galaxy stellar velocity dispersion (MBH-${\sigma}$) relation because of their high accretion rates close to the Eddington limit. Currently, it is still under discussion whether NLS1s are off from the local MBH-${\sigma}$ relation. We select a sample of 325 NLS1 at relatively low redshift (z<0.1) from the SDSS DR7 by constraining FWHM of $H{\beta}$ in the range of 800-2,200 km/s. Among them, we measured stellar velocity dispersion of 40 objects which show strong stellar absorption lines, e.g. Mg b triplet(${\sim}5175{\AA}$), Fe($5270{\AA}$). In contrast, the other 285 objects show too weak stellar absorption lines to measure velocity dispersion. Using the sample of 40 objects with stellar velocity dispersion measurements, we investigate whether NLS1s follow the same MBH-${\sigma}$ relation as normal galaxies and broad line AGNs. We also test the reliability of the width of narrow lines as a surrogate of stellar velocity dispersion by comparing directly measured stellar velocity dispersion with ${\sigma}$ inferred from [O III], [N II], [S II] line widths, respectively. We will discuss the connection between AGN activity in NLS1s and galaxy evolution based on these results.

• Journal of Hydrogen and New Energy
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• v.26 no.6
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• pp.645-651
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• 2015

Numerical study on human thermal comfort in a low floor bus has been conducted. Human thermal comfort in a bus depends mainly on air temperature, air velocity, mean radiant temperature, humidity, and direct solar flux, as well as the level of activity and thermal properties of clothing. The paper presents the velocity and temperature distribution, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices for the driver and passengers.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.170-173
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• 2001

Low-velocity impact on composite sandwich panel has been investigated. For the study, a finite element program is coded using 18-node assumed strain solid element and Newmark-beta method. Contact force is calculated from a proposed modified contact low. The finite element code is verified by solving typical example. The calculated impact behavior agreed well with experimental result.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.404-412
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• 2008

As a suitable volute configuration in the range of low specific speed, circular casing is suggested in this study. The internal flows in a centrifugal pump with the circular and spiral casings are measured by PIV and analyzed by CFD. The results show that the head and efficiency of the pump by a circular casing of very small radius are almost same as those by the spiral casing. Even at the best efficiency point, the internal flow of the pump by circular casing is asymmetric, and vortex and strong secondary flow occurs in the impeller passage. The radial velocity becomes higher remarkably only near the region of the discharge throat. The flow in the impeller outlet is strongly controlled by the circular casing because the velocity distribution almost does not affected by the position of the impeller blades.