• 한국해양학회지
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• 제6권2호
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• pp.63-77
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• 1971

An year-long survey of chemical water quality for Lake Eui-am in Kang-won Province, Korea, was conducted from June 1970 to May 1971 to study the water quality and seasonal variations of productivities in relation to selected physical and chemical environmental factors. A monthly series of water samples were taken at the deepest basin of 18m depth of the lake. Water quality parameters determined were water temperature, Secchi disc reading(transparency), pH, O$\_$2/, CO$\_$2/, alkalinity, acidity, Cl, hardness, Ca, Mg, total residue, total ignitious residue, COD, BOD$\_$5/, nutrients, total-Fe, soluble Fe, Mn and Cu. On the whole, the results indicate that the chemical water quality of Lake Eui-am is high, and vary with season. The lake water is characterized that higher levels of dissolved oxygen(8.6 ml/L in mean of whole water) or percent saturation of dissolved oxygen(114%), and of nitrate nitrogen (523 $\mu\textrm{g}$/L). On the other hand, CO$\_$2/(9.6ppm), chlorides(3.5ppm), Ca(7.7ppm) Mg(2.2ppm), hardness(28.5ppm), silica(2.4ppm) and BOD$\_$5/(1.08ppm) are quite low. In terms of nutrient levels, the lake water exhibit slight signs of eutrophication. The high values for nitrate nitrogen, soluble iron and Cu of the lake water suggest that there are some imputs such as domestic and industrial discharges to the lake.

• Journal of Plant Biotechnology
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• 제29권2호
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• pp.93-98
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• 2002

바이러스 설사병의 원인인 VP6유전자를 감자에 형질전환 시키기 위하여 CaMV 35S promoter와 kanamycin 항생제 내성을 갖는 식물발현벡터 pMBP-1에 subcloning하고, 이 재조합 벡터를 A. tumefaciens LBA4404에 도입시킨 후, freeze haw방법을 이용하여 감자에 형질전환 시켰다. 공동배양된 감자의 잎절편은 2,4-D가 2.0 mg/L첨가된 배지에서 2일간 배양 후, 0.01 mg/L NAA, 0.1 mg/L GA$_3$, 2.0 mg/L Zeatin, 100.0 mg/L kanamycin, 500.0 mg/L carbenicillin이 첨가된 선발배지에서 재분화시켰다. 이 때 유도된 신초는 100.0 mg/L의 kanamycin이 포함된 배지에 옮겨준 후, 왕성한 생육을 위해 MS 기본배지에서 다시 배양하였다. 기내배양시 외부유전자의 도입에 의한 외형적인 변화는 찾을 수 없었으며, 형질전환체는 NPT primer를 사용한 PCR방법으로 1차선별 하였다. DIG 표지된 probe를 이용하여 total RNA를 분석한 결과 개체별로 발현양의 차이는 있었으나, 95% 이상의 안정성을 보였고, genomic DNA를 추출해 Southern blot hybridization했을 경우 1~3개의 copy수를 보임으로써 형질전환 식물체에 외래유전자인 VP6유전자가 안정적으로 도입되었음이 확인되었다.

• 한국분말재료학회지
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• 제18권2호
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• pp.141-148
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• 2011

Carbon material shows relatively high strength at high temperature in vacuum atmosphere and can be easily removed as CO or $CO_2$ gas in oxidation atmosphere. Using these characteristics, we have investigated the applicability of carbon mold for precision casting of high melting point metal such as nickel. Disc shape carbon mold with cylindrical pores was prepared and Ni-base super alloy (CM247LC) was used as casting material. The effects of electroless Nickel plating on wettability and cast parameters such as temperature and pressure on castability were investigated. Furthermore, the proper condition for removal of carbon mold by evaporation in oxidation atmosphere was also examined. The SEM observation of the interface between carbon mold and casting materials (CM247LC), which was infiltrated at temperature up to $1600^{\circ}C$, revealed that there was no particular product at the interface. Carbon mold was effectively eliminated by exposure in oxygen rich atmosphere at $705^{\circ}C$ for 3 hours and oxidation of casting materials was restrained during raising and lowering the temperature by using inert gas. It means that the carbon can be applicable to precision casting as mold material.

• Tribology and Lubricants
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• 제30권6호
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• pp.330-336
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• 2014

Sintered metallic brake pads and low alloy heat resistance steel disks are applied to mechanical brake systems in high energy moving machines that are associated with recently developed 200km/h trains. This has led to the speed-up of conventional urban rapid transit. In this study, we use a lab-scale dynamometer to investigate the effects of the composition of friction materials on the tribological characteristics of sintered metallic brake pads and low alloy heat resistance steel under dry sliding conditions. We conduct test under a continuous pressure of 5.5 MPa at various speeds. To determine the optimal composition of friction materials for 200 km/h train, we test and the evaluate frictional characteristics such as friction coefficients, friction stability, wear rate, and the temperature of friction material, which depend on the relative composition of the Cu-Sn and Fe components. The results clearly demonstrate that the average friction coefficient is lower for all speed conditions, when a large quantity of iron power is added. The specimen of 25 wt% iron powder that was added decreased the wear of the friction materials and the roughness of the disc surface. However when 35 wt% iron powder was added, the disc roughness and the wear rate of friction materials increased By increasing the amount of iron powder, the surface roughness, and temperature of the friction materials increased, so the average friction coefficients decreased. An oxidation layer of $Fe_2O_3$ was formed on both friction surfaces.

• Tribology and Lubricants
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• 제29권4호
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• pp.242-247
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• 2013

This study aims to establish the fundamental basis for the design of materials used in high-speed trains, by using a lab-scale dynamometer to evaluate the characteristic behavior of metallic sintered friction materials in relation to the shape of graphite. The test results clearly demonstrate that when flake graphite and granular graphite are added equivalently, the average coefficient of friction is much lower, and it is less influenced by speed variation; moreover, friction wear is observed to be insignificantly low. Adding flake graphite increases the coefficient of friction, which leads to higher friction wear. In addition, the roughness of the disc surface was equivalent regardless of the shape of the graphite.

• 한국진공학회지
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• 제4권S2호
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• pp.100-105
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• 1995

Nitrogen implantation process has been applied for improvement of wear resistance of Zircaloy-4 fuel cladding materials. Nitrogen was implanted at 120keV to a total dose range of $1\times 10^{17}$ions/$\textrm{cm}^2$ to $1\times 10^{18}$ions/$\textrm{cm}^2$ at various temperatures between $270^{\circ}C$ and $671^{\circ}C$. The microstructure changes by nitrogen implantation were analyzed by XRD and AES and wear behavior was evaluated by performing ball-on-disc type wear testing at various loads and sliding velocities under unlubricated condition. Nitrogen implantation produced ZrNx nitride above $3\times 10^{17}$ions/$\textrm{cm}^2$ as well as heavy dislocations, which resluted in an increase in microhardness of the implanted surface of up to 1400 $H_k$ from 200 $H_k$ of unimplanted substrate. Hardness was also found to be increased with increasing implantation temperature up to 1760 $H_k$ at $620^{\circ}C$. The wear resistance was greatly improved as total ion dose and implantation temperature increased. The effective enhancement of wear resistance at high dose and temperature is believed to be due to the significant hardening associated with high degree of precipitation of Zr nitrides and generation of prismatic dislocation loops.

• 대한금속재료학회지
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• 제47권10호
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• pp.667-674
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• 2009

High temperature wear of STD 61 tool steels sliding against the Al-9%Si coated steels used for hot press forming has been studied in comparison with that of the tool steels sliding against the uncoated steels. Wear tests have been performed using a pin-on-disc configuration under an applied normal load of 50N for 20 min with heating the coated and uncoated steels up to 800$^{\circ}C$. It was found on the worn surface of the STD 61 tool steels sliding against the Al-9%Si coated steels that the formation of the glazed layers containing Al transferred from the coated tribopair may contribute to a reduction of the coefficient of friction, and detachment in part occur due to delamination wear, resulting in higher specific wear rate. On the other hand the Fe-oxide wear debris entrapped on the softer surface of the uncoated steels can act as a tribosurface, leading to decreased adhesive wear of the STD 61 tool steels, resulting in a lower specific wear rate.

• 한국철도학회논문집
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• 제17권4호
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• pp.223-227
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• 2014

제동 패드는 철도차량의 기초제동요소 중 하나이다. 제동 패드는 제동 캘리퍼로부터 압부력을 전달받아 제동디스크와의 마찰력으로 철도차량에 제동작용을 한다. 따라서 제동 패드는 주어진 고압의 압부력을 견뎌야 하므로 제동 패드의 주요 성능평가항목으로 압축강도를 관리한다. 압축강도를 측정하는 규격은 KRS, KRCS, KRT 등이 있다. 이들 규격은 압축강도를 측정하기 위한 시험편의 크기를 $20mm{\times}10mm{\times}15mm$ (가로${\times}$세로${\times}$높이)로 규정하고 있다. 압축강도에 대한 불확도를 줄이기 위하여 불확도 요인을 분석한 결과, 단면의 치수를 변경함으로써 불확도를 줄일 수 있음을 알았다. 새로운 단면치수에 의한 불확도를 평가하여 불확도 감소에 대한 유효성을 입증하였다.

• 대한치과보철학회지
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• 제38권1호
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• pp.108-115
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• 2000

This study was designed to compare the effect of polishing on surface roughness of composite resin. We used Z100(3M) composite resin and placed the composite resin in the hole (4mm thick and 4mm in diameter) of vinyl plate and polymerized it under manufacturer's instructions. Samples were divided into 5 groups by polishing methods. Group 1 was control: resin was polymerized under glass plate, Group 2: resin was polymerized without any polishing procedure, Group 3: resin was polymerized with a polishing procedure of abrasive disc, Group 4: bonding agent was applyed in thin layer and polymerized on the polished polymerized resin surface. Group 5: resin was polymerized under transparent celluloid strip. The surface roughness of each specimen was measured with Sufacoder SEF-30D (Kosaka lab. Ltd) under 0.08mm cut off, 0.05mm/s stylus speed, ${\times}40$ horizontal magnification, ${\times}5000$ vertical magnification. The results were as follows : 1. Group 1 showed the most smooth surface in this study. 2. Group 3 showed more rough surface than Group 2. Considering the surface roughness, it would be better to make the shape completely before polymerize the resin. To finish and polish after the polymerization of resin makes less smooth surface. 3. When we use the transparent celluloid strip, minimum finishing procedures are recommended. Any polishing procedure could not recover the smooth resin surface of celluloid strip. 4. Application and polymerization of the thin layer of bonding agent on the polished surface showed the minimum surface smoothing effect.

• 한국동물학회지
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• 제17권2호
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• pp.81-92
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• 1974

山林害蟲인 솔나방(Dendrolimus spectabilis Butler)의 變態에 따른 血蛋白質의 變化를 調査하기 위하여 acrylamide gel 電氣永動法을 이용하여 測定한 結果는 다음과 같다. 1. 血蛋白質의 band는 移動度에 따라 22개(1-22)의 종류를 나타냈다. 2. 血蛋白質의 濃度는 band 數, 染色强度, 移動度를 가지고 비교할 때 stage에 따라서 定量的 差異를 나타내며, 幼蟲이 성장함에 따라 增加하였고, 終齡幼蟲에서 가장 높은 濃度를 나타냈다. 3. 血蛋白質의 band는 終齡幼蟲을 지나 幼蟲器官의 解消가 일어나는 용전기에서 減少하고, 成蟲器官의 新生이 시작되는 용후기에서 다시 增加하였다. 4. PAS 반응, toluidine, Sudan black을 이용한 조직화학적 반응결과 終齡幼蟲에서 가장 많은 glycoprotein, mucopolysaccharide, lipoprotein등이 검출되었다. 5. 脂肪體와 腸에 있어서도 血蛋白質의 band 數와 비슷한 特性을 나타내었고 濃度의 變化도 유사하였다.