• Journal of Environmental Science International
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• v.6 no.5
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• pp.451-459
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• 1997

This paper alms to describe the indoor-outdoor air quality in school environment through the analyses of heavy metal concentration by inductively Coupled Plasma(ICPI, which were observed at some school environment, such as traffic area, industrial area seme-industrial area, and residence area. The results are as follows : (1) Regardless Indoor and outdoor, the area with the highest concentration of heavy metal is industrial area followed by traffic area, residence area and semi-industrial area in descending order of magnitude. And the heavy metal concentration of indoor is higher than that of outdoor. (2) The main heavy metal components with more high level concentration of Indoor than those of outdoor are Zn, Al, Ca and these heavy metal concentrations are higher in class than In corridor and outdoor.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.62-67
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• 2000

Metallurgical characteristics of bonded region and high temperature mechanical properties of heat resistant alloy, Fe-35Ni-26Cr during liquid phase diffusion bonding were investigated employing AM17 insert metal. The insert metal for bonding, AM17 was newly developed Ni-base metal using interpolation method. Bonding of specimens were carried out at 1,403~1,463K for 600s in vacuum. The microconstituents in the bonded interlayer disappeared in the bonding temperature over 1,423K. The microstructures, alloying elements and hardness distribution in the base metal. The tensile strength and elongation of the joints at elevated temperatures were the same level as one of the base metal in the bonding temperature over 1,423K. The creep rupture strength and rupture lives of joints were almost identical to those of base metal.

• Journal of the Korean Home Economics Association
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• v.29 no.2
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• pp.87-120
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• 1991

The purpose of this study was to identify the design characteristics of the multi-leveled chest(jang) which was the main furniture of the master bedrom(anbang) in the Chosun Dynasty. The major findings and conclusions were: 1. The front view of the multi-leveled chest were composed of a protruded top panel(kaepan), drawers, folded doors, sectional panels(chwibyok kan and morum kan) and base stand(madae) in general. Variety in the front view found more frequently in single level chests than bi- or tir-level chests. 2. The overall dimensions of each type of chest increased with increase in number of levels, but the height of the sectional parts decreased. That is, the overall proportion of the single level chests were 10 : 9, bi-level chests were 5 : 6, and tri-level chests were 2 : 3. The proportion of 1 : 1, 4 : 5, 1 : 3, 1 : 4, 1 : 5 were found often in the sectional parts such as drawers, doors, chwibyok kans and morum kans. 3. In general, the surface treatments were subtle. Carved or inlayed ornamentation were seldom seen, and most chess were finished with clear lacquer to show the natural wood grain. There were no distinctive characteristics of surface ornamentation characteristic of any one type of chest. 4. The general patterns of the metal ornaments were spade(yowidu), round, bow, rectangular(yakgua), bat and flower shapes. The multi-level chests were decorated with more metal ornament types compared with the single-level chests. 5. In conclusion, there was more variety in all the design elements in the single level chests compared with the other types of chests. The bi-and tri-level chests were quite stylized in composition, size, proportion, surface treatment, and metal ornamentation.

• The Korean Journal of Ecology
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• v.22 no.2
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• pp.95-100
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• 1999

The heavy metal concentrations in seawater and winkles (Littorina brevicula) collected from the Onsan bay area in southeast of Korea were analyzed. The heavy metal concentrations in the seawater obtained from the most polluted site showed approximately 189. 205. and 110 fold higher cadmium, copper. and zinc concentrations, respectively. than the uncontaminated control site. The contamination levels of these metals in winkles were 11.08 - 2.35, 334.5 - 212.5, and 426.0 - 499.2$\mu\textrm{g}$ per gram dry body weight. respectively. The concentrations of all three metals in both the seawater and winkles decreased gradually with increasing distance from Daejeong stream, suggesting the stream being the major source of heavy metal input into the bay. Among the four body parts of digestive gland and gonad. gill. kidney, and remaining tissue in contaminated winkles, kidney showed the highest accumulation level of cadmium: copper and zinc, however. were more or less distributed among the four body parts. Upon gel filtration chromatography of the cytosol from the kidney of cadmium induced winkles, one cadmium peak corresponded to the elution peak of horse kidney metallothionein.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.612-615
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• 1996

In the continuous casting process, molten metal contacts the mold wall and the molten metal surface is subject to the mold oscillation. The mold oscillation results in the oscillation marks on the surface of solidified steel, which has undesirable effects on the quality of slabs. In order to reduce the oscillation marks by achieving soft contact of molten metal with the mold surface, alternating magnetic field is applied to the surface of molten metal. However, if the magnetic field strength becomes too strong, the melt flow induced by the magnetic field. causes the instability of the molten metal surface, which has also the bad influence on the slab quality. Therefore, it is very important to choose the optimal position of the inductor coil and the optimal level of electric power to minimize the surface defects. In the present work, as a first step toward the optimization problem of the process, numerical studies are performed to investigate the effects of coil position and the electric power level on the meniscus shape and the flow field. As numerical tools, the boundary integral equation method(BIEM) is used for the magnetic field analysis and the finite difference method (FDM) with orthogonal grid generation is used for the flow analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.90-94
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• 2022

Metal 3D-printing technology enables the manufacture of complex features or internal structures, which is not possible in fabrication by conventional cutting methods. The most successful types of metal 3D printing have been powder bed diffusion and directed energy deposition, which use laser heads exploiting high-power laser sintering metal powder. In this study, a cost-effective optical design was proposed for a 2-kW-level fiber laser head. Only two commercial lenses, a beamsplitter and a window, are used in the laser head, satisfying the technological requirements. According to the optical design, the spot size was 2.54 mm, and the stand-off distance from the laser head was 295 mm. The intensity distribution was Gaussian. Thus, smooth power sintering was possible without any laser spot marks. Monte Carlo analysis was employed to verify the consistency of the optical performance under conventional assembly tolerance.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.564-567
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• 2004

FAs and BAs indicated different chemical compositions and physical properties. Leaching of Pb in FAl and Cu in FA2 were 33.2mg/L and 5.92mg/L, these were high concentration above 30 and 2 times respectively in compared to permit level. Leaching of Hg and Cr were about 1/2 of permit level. When diatom was complexly mixed with portland cement, the 28 days compressive strength of mortar with FA2 was similar with that of control mortar. Furtherfore, leaching of heavy metal ions like as Pb, Cu, Hg, Cr was highly reduced.

• Korean journal of food and cookery science
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• v.14 no.1
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• pp.25-32
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• 1998

To measure the contents of several heavy metal elements (Cr, Mn, Ni, Cu, Zn, Cd, Hg, Pb) in Korean seaweeds which are closely related to food resources, various seaweed samples were collected from thirteen to seventeen seaweed-producing districts. The results obtained from the experiment are summarized as follows: 1. The content of heavy metal elements in seaweeds of individual sample ranged from 0.0005 to 25.0373 ppm. Their mean levels were as follows: laver, 0.0024∼3.9297 ppm; sea lettuce, 0.0011∼25.0373 ppm; sea mustard, 0.0005∼23.5071 ppm; sea tangle, 0.0006∼4.8550 ppm. The mean levels of Cd and Pb were specially low in the samples collected from the area II in Kangwon and area Ⅸ in Kyungbook. 2. The mean levels of heavy metal elements of collected samples ranged from 0.0117 to 4.4944 ppm. Laver showed the lowest level of Hg and sea lettuce showed the highest level of Mn. Their mean levels of elements were as follows: laver, 0.0117∼2.3339 ppm; sea lettuce,0.0232∼4.4944 ppm; sea mustard, 0.0129∼1.5139 ppm and sea tangle, 0.0182∼1.7410 ppm. 3. The mean levels of heavy metal elements from several locations ranged from 0.0085 ppm to 8.4148 ppm. The mean levels of heavy metal elements in sea mustard from area V of Kyungbook were the lowest, but the mean levels of heavy metal elements in sea lettuce from area Ⅷ of Kyungnam were the highest. The mean level of heavy metal elements were as follows: laver, 0.3613∼1.1124 ppm; sea lettuce, 0.1415∼8.4148 ppm; sea mustard, 0.0729-3.1182 ppm; sea tangle, 0.0085∼0.7587 ppm. 4. Generally the heavy metal elements were detected in the seaweed samples from all locations. The mean levels of heavy metal elements varied with locations and kinds of samples. The levels of heavy metals of the samples taken from all locations from the East Sea, the South Sea, and the West Sea areas showed 99% safety range.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.87-92
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• 2003

JLF-1 steel (Fe-9Cr-2W-V-Ta), reduced activation ferritic steel, is one of the promising candidate materials for fusion reactor applications. Tensile properties of JLF-1 base metal and its TIG weldments has been investigated at the room temperature, $400^{\circ}C$ and $600^{\circ}C$. The tensile strength of base metal (JLF-1) showed the level between those of weld metal and the Heat Affected Zone (HAZ). When the test temperature was increased from room temperature to high temperature ($400^{\circ}C$ and $600^{\circ}C$), both strength and ductility decreased or base metal, weld metal and the HAZ. The longitudinal specimens of base metal represented similar strength and ductility at room temperature and high temperature, compared to those of transverse specimens. Little anisotropy for the rolling direction was observed in the base metal of JLF-1 steel.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.7
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• pp.533-538
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• 2001

The barrier height is found to increase from 0.25 to 0.690 eV for Schottky contacts on n-InGaAs using deposition of Ag on a substrate cooled to 77K(LT). Surface analysis leads to an interface model for the LT diode in which there are oxide compounds of In:O and As:O between the metal and semiconductor, leading to behavior as a metal-insulator-semiconductor diode. The metal film deposited t LT has a finer and more uniform structure, as revealed by scanning electron microscopy and in situ metal layer resistance measurement. This increased uniformity is an additional reason for the barrier height improvement. In contrast, the diodes formed at room temperature exhibit poorer performance due to an unpassivated surface and non-uniform metal coverage on a microscopic level.