• Journal of the Korean Society of Radiology
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• v.12 no.3
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• pp.305-312
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• 2018

A dry and wet wipe test for radioisotope leakage checking was conducted by fixing the radioisotope $^{14}C$ to the glass surface and used for observing the transfer factor and surface shape of the test paper through wipe test. The dry wipe test showed that transfer factor in the tissue paper was twice as high as in the paper filter, and the wet wipe test showed that transfer factor in the paper filter paper was three times higher than the tissue paper. Although paper filters are general choice for leakage checking, it has been shown that tissue paper can be an alternative in the dry wipe test.

• Ocean and Polar Research
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• v.39 no.1
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• pp.35-43
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• 2017

Concentrations of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphate (DOP), and colored dissolved organic matter (CDOM) were measured in the coastal sea off inland aqua farms in northeastern Jeju Island in summer 2015. The highest concentrations of DOC, DON, and DOP were revealed in the surface water off Hado-ri where the lowest salinity conditions prevailed (31.6). The concentrations of DOC, DON, and DOP in the surface water were lower in the inner stations (SH1-1, 1-2, and 1-3) near the aqua farms of the Haengwon-ri than in the outer stations. The concentrations of DOC, DON, and DOP negatively correlated with salinity. These results indicate that the contribution of dissolved organic matter (DOM) from the aqua farms seems to be not significant. On the other hand, the higher concentrations of DON and DOP in the inner stations of Hado-ri (HD 1-1) seem to be attributed to excrement of migrating birds. The three components of CDOM (T, M, and C peaks) showed no relationship with salinity, perhaps due to various in situ productions by marine organisms and decomposition by ultraviolet radiation. The observed lower C:M ratio, an indicator of terrestrial source, and the higher biological index (BIX) of CDOM in the station off Hado-ri indicate that DOM is produced mainly by biological activity. Based on the higher humification index (HIX) of CDOM and the higher DOC:DON ratio off Haengwon-ri, refractory DOM in the inland aqua farms is likely transported to the coastal sea.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.3
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• pp.310-320
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• 2008

Concentration of tropospheric ozone ($O_3$) was investigated for the South Korea. And then the critical ozone levels, expressed as AOT40 (Accumulated exposure over a threshold of 40 ppb) to vegetation have been used in this region within the UNECE (United Nations Economic Commission for Europe) Convention on Long-Range Trans-boundary Air Pollution (CLRTAP). Hourly ozone concentration data from 1996 to 2001 at 26 air monitoring stations was used to estimate the exceedance of the critical levels. It was calculated for daylight hours for each station, and mapped using surface interpolation over the South Korea. The critical levels of ozone have shown the highly exceeded value in the Gyeonggi region, southern coastal region and central inland of the South Korea. It was some different from the typical ozone distribution which represented highly in the western inland and coastal regions. The area exceeding the critical level for crops was founded to be more than 40% of the whole South Korean territory. While that for trees was to be about 17% of the South Korea. The critical ozone critical level was based upon data from experiments on specific species, and thus may not be fully representative for all types of vegetation. Nevertheless, the critical level and its exceedance of the ozone concentration would be one of the useful tools for international agreements on abatement strategies to prevent ecosystem damage.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.20-25
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• 2013

The frame elements of modern high speed trains are typically fabricated with extruded aluminum panels. However, the sound transmission loss (STL) of extruded aluminum panels is less satisfactory than flat panels with the same surface density. This study proposes a method for prediction of the sound transmission loss of extruded aluminum panels using finite element analysis. The panel is modeled by finite element analysis, and the STL is calculated using a measure of Sommerfeld radiation at the specimen surface, boundary conditions, and the internal loss factor of the material. In order to verify the validity of the predicted value, intensity transmission loss was measured on the aluminum specimen according to ASTM E2249-02. The proposed method of analysis will be utilized to predict the sound insulation performance of extruded aluminum panels for railway vehicles in the design stage, and to establish measures for their improvement.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.827-834
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• 2020

Damage of tungsten due to helium ions of a PF device was studied. The tungsten was analyzed by SEM and AFM after irradiation. SEM revealed fine bubbles of helium atoms with diameters of a few nanometers, which join and form larger bubbles and blisters on the surface of tungsten. This observation confirmed the results of molecular dynamics simulation. SEM analysis after etching of the irradiated surface indicated cavities with depth range of 35-85 nm. The average fluence of helium ion of the PF device was calculated about 5.2 × 10¹⁵ cm^-2 per shot, using Lee code. Energy spectrum of helium ions was estimated using a Thomson parabola spectrometer as a function of dN/dE ∝ E^-2.8 in the energy range of 10-200 keV. The characteristics of helium ion beam was imported to SRIM code. SRIM revealed that the maximum DPA and maximum helium concentration occur in the depth range of 20-50 nm. SRIM also showed that at depth of 30 nm, all of the tungsten atoms are displaced after 20 shots, while at depth of higher than 85 nm the destruction is insignificant. There is a close match between SRIM results and the measured depths of cavities in SEM images of tungsten after etching.

• KIEAE Journal
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• v.16 no.6
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• pp.159-166
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• 2016

Purpose: The architectural structures in the engineering field include more than one material, and the heat transfer through these multiple materials becomes complicated. More or less, the analytic solutions obtained by the hand calculation can provide the limited information of heat transfer phenomena. However, the engineers have generally been forced to obtain reliable results than those of the hand calculation. The numerical calculation such as a finite volume methods with the unstructured grid system is only the suitable means of the analysis for the complex and arbitrary domains that consists of multiple materials. In this study, a new numerical code is developed to provide temperature distributions in the multiple material domains, and the results of this code are compared with the validation cases in ISO10211. Method: Finite volume methods with an unstructured grid is employed. In terms of numerical methods, the heat transfer conduction coefficient is not defined on the surface of the cell between different material cells. The heat transfer coefficient is properly defined to accurately mimic the heat transfer through the surface. The boundary conditions of heat flux considering radiation or heat convection are also developed. Result: The comparison between numerical results and ISO 10211 cases. We are confirmed that the numerical method provides the proper temperature distributions, and the heat transfer equation and its boundary conditions are developed properly.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.403-412
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• 2006

The effect of a wall temperature on the soot deposition process from a diffusion flame to a solid wall was investigated in a microgravity environment to attain in-situ observations of the process. The fuel for the flames was an ethylene ($C_2H_4$). The surrounding oxygen concentration was 35% with surrounding air temperatures of $T_a=600K$. In the study, three different wall temperatures. $T_w$=300, 600, 800K, were selected as major test conditions. Laser extinction was adopted to determine the soot volume fraction distribution between the flame and burner wall. The experimental results showed that the maximum soot volume fractions at $T_w$=300, 800 K were $8.8{\times}10^{-6},\;9.2{\times}10^{-6}$, respectively. However, amount of soot deposition on wall surface was decreased because of lower temperature gradient near the wall with increasing wall temperature. A numerical simulation was also performed to understand the motion of soot particles in the flame and the characteristics of the soot deposition to the wall. The results from the numerical simulation successfully predicted the differences in the motion of soot particles by different wall temperature near the burner surface and are in good agreement with observed soot behavior that is, the 'soot line', in microgravity.

• Journal of Yeungnam Medical Science
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• v.17 no.2
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• pp.123-128
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• 2000

Purpose: This study was aimed to develop a new vaginal applicator(Shin's Applicator) for 2-channel high-dose rate vaginal brachytherapy to evaluate uniformity of surface dose, and to present 3-dimensional dose distribution of the applicator. Methods: Shin's Applicator was inexpensively constructed using human soft tissue equivalent acrylic bar. We evaluated dose uniformity along the applicator surface using film densitometer and performed vaginal intracavitary brachytherapy after insertion of the applicator using HDR brachytherapy planning software and brachytherapy unit(Ralstron-20B). Results: Shin's Applicator allows improved dose distribution than the existing 1-channel cylinder and achieves diminished urinary bladder and rectal dose by 20%. Conclusions: From the above results, it can be concluded that Shin's Applicator may be an improved form of a vaginal applicator. Furthermore, it can be suggested that this applicator has an advantage, for it prevents vaginal stenosis after radiation therapy and can be used as a disposable vaginal dilator. Further follow up examination with radiological study may be helpful to evaluate the therapeutic efficacy of this applicator.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.27-38
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• 1997

This paper is concerned with the calculation of the wave resistance for SWATH ships based on a low order Rankine source panel method. Two types of free surface boundary conditions, Dawson type (double model approximation) and Kelvin type (free stream approximation) are used. For the free surface boundary calculation, an analytic differentiation is employed instead of implementing a finite difference scheme. Then, the radiation condition is satisfied by, so called, the panel shift method. The numerical results using the above two methods are compared with those using the thin ship/modified slender body approximation and also with the experimental results. The SWATH models considered are a single strut SWATH and a twin strut SWATH together with the variations of two demihull separation distance. In order to prove the validity of the program developed, the numerical calculations for a Wigley mono hull and Wigley twin hulls are compared with the available experimental results.

• 한국해양학회지
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• v.30 no.5
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• pp.512-521
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• 1995

To investigate a short-term (from 2 hours to 24 hours) variability of a mixed layer, oceanographical data (water temperature, salinity, current) and meteorological data (wind, air temperature, solar radiation) were collected at a site in the Korea Strait at the interval of one hour for 48 hours from October 12 to 14, 1993. The average rates of temporal variations of the mixed layer depth (MLD) and temperature of the mixed layer (MLT), which are very weakly correlated with the wind stress and buoyancy flux at the sea surface, are about 5.2 m/hour and 0.2$^{\circ}C$/hour, respectively. The mixed layer is relatively shallow when both MLT and MLS (salinity of the mixed layer) are low, while MLD is relatively deep when they are high. MLT shows a sudden decrease or increase. Analysis of satellite infrared images and XBT data shows that sudden increase of MLT is caused by advection of warm water. These results suggest that the short-term variation of the mixed layer in the Korea Strait in autumn, in which surface current is relatively strong and different water masses exist, is mainly determined by advection rather than air0sea interaction such as wind stress or buoyancy flux.