• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
• /
• v.12 no.1
• /
• pp.37-43
• /
• 2006

PURPOSE: Previous studies have documented the lack of ultrasound's non-thermal effects on nerve conduction using frequencies of 1 MHz and 870 kHz. The purpose of this study was to determine the biophysical effects of continuous ultrasound on median local forearm temperature and motor nerve conduction velocities using frequencies of 3.0 MHz. SUBJECTS: Twelve healthy subjects (6 males, 6 females, age $22.30{\pm}2.41$ yrs, weight $61.33{\pm}10.16$ kg, height $167.58{\pm}8.04$ cm) without a history of neurological or musculoskeletal injury to their dominant arm volunteered for this study. METHODS AND MATERIALS: Each subject received a total of five treatments, one each at .0, 0.5, 1.0, 1.5, 2.0 W/$cm^2$ of 3 MHz continuous ultrasound on the anterior surface of the middle area of dominant forearm for 10 minutes. Dependent measures for forearm local temperature and median motor nerve conduction velocity (MNCV) were taken pretreatment and immediately post-treatment. One-way ANOVA were used for each dependent measure. RESULTS: The posttreatment forearm local temperature were differed significantly (p<0.001) between intensities of ultrasound. The posttreatment forearm local temperature of the ultrasound treated with 1.0 w/$cm^2$, 1.5 w/$cm^2$ and 2.0 w/$cm^2$ were significantly higher than 0.5 w/$cm^2$ and 0.0 w/$cm^2$ of ultrasound (p<0.05). The posttreatment median MNCV were differed significantly from the respective pretreatment velocities (p<0.001). The MNCV of the ultrasound treated with 0.0 w/$cm^2$ and 0.5 w/$cm^2$ were significantly (p<0.05) slower than that observed pretreatment, while the three ultrasound intensities produced significantly increased posttreatment MNCV: 1.0 w/$cm^2$ and 1.5 w/$cm^2$ and 2.0 W/$cm^2$. The posttreatment MNCV at 2.0 w/$cm^2$ and 1.5 w/$cm^2$ was significantly faster than that at 0 w/$cm^2$, 0.5 w/$cm^2$ and 1.0 w/$cm^2$ (p<0.05), the MNCV at 1.0 w/$cm^2$ was significantly faster than that associated with 0 w/$cm^2$ and 0.5 w/$cm^2$ of ultrasound (p<0.05). CONCLUSIONS: The decreased median motor forearm local temperature and MNCV of the ultrasound treated with 0.0 w/$cm^2$ and 0.5 w/$cm^2$ were attributed to the cooling effect by ultrasound transmission gel. Local forearm temperature and nerve conduction velocity were directly related to the intensity of ultrasound. Alterations in MNCV from ultrasound on healthy nerves appeared to be related to temperature changes induced by thermal effects of ultrasound.

• Journal of the Korean earth science society
• /
• v.44 no.6
• /
• pp.594-610
• /
• 2023

The horizontal-to-vertical spectral ratio (HVSR) has been widely applied to evaluate ground characteristics such as site response and thickness of the soft sedimentary layer on top of the bedrock via dominant frequencies and amplification factors of microtremors. Eight seismic stations were selected to investigate the HVSR results at the surface and at varying depths, and their variations due to wind speeds. These stations are equipped with seismic sensors on the surface and downhole(s) at depths. The borehole data analysis reveals that the geological condition at burial depth influences the HVSR results. Their dominant frequencies indicate the entire thickness of the soft layer, not the thickness to the bottom or top of the soft sedimentary layer from the seismometer burial depth. Analysis of the background noise observed at the surface showed that the resonance frequency estimation varied with wind speed changes. In the studied cases, the background noise observed in the sedimentary layer at depths of 20 to 66 meters yielded stable and consistent resonance frequency estimation regardless of wind speed fluctuations. The results of the seismic sensors buried deeper than 100 meters are unstable. The result indicates that the background noise from the buried seismometer at shallow depths (~0.3 m) under light wind conditions (wind speeds less than 3 m/s) is sufficient to achieve the purpose of the HVSR analysis.

• Journal of Environmental Science International
• /
• v.10 no.3
• /
• pp.201-208
• /
• 2001

To investigate the physio-chemical components and properties of aerosol particles in urban area sampling of aerosol particles was carried out in the campus of Hokkaido University, Sapporo, Japan, during snowfall. Aerosol particles were collected on millipore filter papers using a low volume air sampler. Their shapes, sizes and chemical components were analyzed by a SEM(Scanning Electron Microscope) and an EDX(Energy Dispersive X-ray). As a results, ice crystals of dendrite and column types were predominantly shown at mature and developing stage of snowfall intensity. The denerite and sector plate types of ice crystals were mainly originated from the sea but column types were come from soil. Scavenging effect by snowfall was greatly also shown at dendrite type ice crystals that embryo was fully developd. Al, Si elements were shown at high frequencies as compared with others. Na, Cl components were especially shown at high frequencies under the sea-breeze wind during snowfall. Anthropogenic aerosol particles had shown with irregular shapes and sizes, relatively. Mainly 3-7$\mu$m aerosol particles were abundant and coarse particles also could be seen during snowfall. Ca, Zn, Fe components mainly caused by spike tires from vehicles in winter season were dominant before snowfall, however the element S mainly caused by human activity was rich after snowfall. The pH values of snow in Sapporo city were higher than those at coastal area. The concentration of chemical components in aerosol particles was also affected by surface winds. Aerosol particles in urban area, Sapporo were mainly affected by human activities like vehicles and combustion with wind system. And their types were related with snowfall intensity.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2002.09a
• /
• pp.404-406
• /
• 2002

We have investigated the contribution of the scattered x rays to the signal imaging in the radiographs acquired with anti-scatter grids of several grid ratios by separating the line spread functions (LSFs) derived from the signal edge image into the primary and the scatter components. By using a 1.0-mm lead plate in the scattering material, the blurred signal edge images were acquired by use of an imaging plate at a tube voltage of 80 kV with the anti-scatter grids of grid ratios for 5:1, 6:1, 8:1, 10:1 and 12:1. The edge profiles of the signal images were scanned and those in relative exposure were differentiated to obtain the LSFs. To investigate the contribution of the scattered x rays to the signal imaging, we proposed a method for separating the LSFs derived from the signal images into the primary and the scatter components, where the scatter component was approximated with exponential function. Our basic approach is to separate the area of the LSFs by ratios of the scattered x-ray exposure to the primary x-ray exposure, which were obtained for the grid ratios by use of a lead disk method. The LSFs and the two components were Fourier transformed to obtain the modulation transfer functions (MTFs) and their two components. As the result, we found that, by using the anti-scatter grids, the scattered x rays were reduced, but the shape of the LSFs of the scatter component hardly changed. The contributions of the scatter component to the MTFs were not negligible (more than 10 %) for spatial frequencies lower than about 1.0 mm$\^$-l/ and that was greater as the grid ratio decreasing. On the other hand, for higher frequencies, the primary component was dominant compared with the scatter component.

• Journal of The Korean Astronomical Society
• /
• v.48 no.5
• /
• pp.257-265
• /
• 2015

We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its γ-ray flare on 2013 December 20. We followed up this flare with single-dish polarization observations using two 21-m telescopes of the Korean VLBI Network. Observations carried out weekly from 2013 December 25 to 2015 January 11, at 22 GHz, 43 GHz, 86 GHz simultaneously, as part of the Monitoring Of GAmma-ray Bright AGN (MOGABA) program. We measured 3C 279 total flux densities of 22–34 Jy at 22 GHz, 15–28 Jy (43 GHz), and 10–21 Jy (86 GHz), showing mild variability of ≤ 50 % over the period of our observations. The spectral index between 22 GHz and 86 GHz ranged from −0.13 to −0.36. Linear polarization angles were 27°–38°, 30°–42°, and 33°–50° at 22 GHz, 43 GHz, and 86 GHz, respectively. The degree of linear polarization was in the range of 6–12 %, and slightly decreased with time at all frequencies. We investigated Faraday rotation and depolarization of the polarized emission at 22–86 GHz, and found Faraday rotation measures (RM) of −300 to −1200 rad m⁻² between 22 GHz and 43 GHz, and −800 to −5100 rad m⁻² between 43 GHz and 86 GHz. The RM values follow a power law with a mean power law index a of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December γ-ray flare and are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.12
• /
• pp.1351-1358
• /
• 2014

This study numerically simulates brake squeal and validates it experimentally by using a lab-scaled brake dynamometer. The system frequencies of the disc brake are traced with respect to the brake pressure by using a modal test and FEM. Then, the squeal frequencies measured from the brake dynamometer are found to correspond to the brake system mode with the dominant displacement of the caliper and pad. Furthermore, a complex eigenvalue analysis conducted using the finite element model confirms that the caliper mode generating the rotational displacement of the pad becomes unstable owing to the negative friction-velocity slope.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.105-113
• /
• 2003

Because structural systems are becoming lighter and more flexible and have lower natural frequencies and dampings than before, coordinated rhythmic activities such as dancing, audience participation in arenas or concert halls, and aerobics result in undesirable levels of vibration. For rhythmic activities, it is resonant or near resonant behavior that result in significant dynamic amplification and hence human discomfort. The most rational design strategy is to provide enough of a gap between the natural frequency of a floor system and the dominant frequencies excited by planned human activities to assure reasonably that resonance will not occur. For the case study the vibration measurements were performed at the floor of a long-span multi-purpose hall during the rock concert of popular singer.

• The Bulletin of The Korean Astronomical Society
• /
• v.41 no.1
• /
• pp.65.1-65.1
• /
• 2016

We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its ${\gamma}$-ray flare on 2013 December 20. We followed up this flare by means of single-dish polarization observations with two 21-m telescopes of the Korean VLBI Network, carried out weekly from 2013 December 25 to January 11, and at 22, 43, and 86 GHz, simultaneously. These observations were part of the Monitoring Of GAmma-ray Bright AGNs (MOGABA) program. We Measured 3C 279 total flux densities at 22, 43, and 86 GHz, showing a mild variability of a factor of ${\leq}50%$ over the period of our observations. The spectral index ranged from -0.13 to -0.36 at between 22 and 86 GHz. The degree of linear polarization was in the range of 6 ~ 12 %, and slightly decreased with time at all frequencies. We found Faraday rotation measures (RM) of -300 to $-1200rad\;m^{-2}$ between 22 and 43 GHz, and -800 to $-5100rad\;m^{-2}$ between 43 and 86 GHz. The RM values follow a power law ${\mid}RM{\mid}{\propto}{\nu}^{\alpha}$, with a mean ${\alpha}$ of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December ${\gamma}$-ray flare, and that these regions are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.4
• /
• pp.455-467
• /
• 2008

The dynamic vehicle running tests were performed to analyze dynamic behavioral characteristics such as displacement, strain history loop and vibration acceleration in arch bridges. Also, the validity of the modeling was verified by comparing the results of the tests and those of the structural analysis modeling. With the resonance revision of verified modeling, when the ratio of excited frequencies to natural frequencies exceeds ${1{\pm}0.04}$, the stability of the bridge is obtained. Also, in the event of resonance by speed parameter, the second mode shape is dominant to the dynamic behaviors of arch bridges. It is found that manipulating the parameters involving arch ribs can increase the second mode natural frequency. It makes critical velocity greater than operational velocities to guarantee the stability of arch bridges.

• BMB Reports
• /
• v.42 no.12
• /
• pp.834-839
• /
• 2009

DNA methyltransferase (DNMT) 1 is the key enzyme responsible for DNA methylation, which often occurs in CpG islands located near the regulatory regions of genes and affects transcription of specific genes. In this study, we examined the possible association of DNMT1 polymorphisms with HBV clearance and the risk of hepatocellular carcinoma (HCC). Seven common polymorphic sites were selected by considering their allele frequencies, haplotype-tagging status and LDs for genotyping in larger-scale subjects (n = 1,100). Statistical analysis demonstrated that two intron polymorphisms of DNMT1, +34542G > C and +38565G > T, showed significant association with HBV clearance in a co-dominant model (OR = 1.30, $P^{corr}$ = 0.03) and co- dominant/recessive model (OR = 1.34-1.74, $P^{corr}$ = 0.01-0.03), respectively. These results suggest that two intron polymorphisms of DNMT1, +34542G > C and +38565G > T, might affect HBV clearance.