• 한국제4기학회지
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• 제7권1호
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• pp.69-91
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• 1993

한반도 서해안의 금강하구와 연안 조간대 및 황해 동부 대륙붕에서 채취된 76개의 표층퇴적물 시료에 대하여 Al, Fe, Na, K, Mg, Ca, Ti, Mn 등 9개 주성분원소와 Sr, Ba, V, Cr, Co, Ni, Cu, Zn 등 8개 미량 금속원소, 그리고 유기탄소 함량과 탄산염 함량 등의 화학성분을 분석하여 퇴적물의 지구화학적 특성을 연구하였다. 분석된 원소들의 함량은 K과 Ba을 제외하곤 지각의 평균함량에 비해 전반적으로 낮게 나타났으며, K과 Ca 등을 제외한 대부분 원소의 함량이 퇴적물 입도와 관련성을 보였다. 연구지역 내에서 퇴적물의 화학성분 함량은 퇴적환경 이나 위치에 따라 서로 다른 특성을 나타내었으며, 세립퇴적물의 경우 금강하구의 퇴적물에서 상대적으로 높은 Mn, Co, Ni의 함량이, 그리고 황해중앙이토에서는 높은 Fe, Na, K, Mg, Ca, V의 함량이 특징으로 나타났다. 한편. 원소함량을 Al함량으로 나눈 함량비의 공간적 분포로부터는 황해중앙이토에서 Fe, Mg, V, Ni, Cu, Zn 등이, 그리고 한반도 연안에서는 K, Mn, Ba, Sr 등이 높아지는 경향이 나타났다. 이렇게 분석된 세립퇴적물 지화학 특성의 지역적 차이, Al에 대한 함량비의 분포경향, 지각 평균함량을 기준한 원소의 농축비, 특정 광물분포의 영향, 오염의 가능성 등 제반 사항들을 종합적으로 검토하여 본 연구지역에 유입되는 한반도 기원 세립물질과 중국 기원 세립물질을 구분할 수 있는 지화학적 지표로서 각각 Mn과 Mg-V이 제시되었다.

• 암석학회지
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• 제28권2호
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• pp.129-141
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• 2019

옥천변성대의 북서부에 위치하는 충주 어래산 지역은 주로 신원생대 계명산층과 이를 관입하는 중생대 화성암류로 구성되어 있다. 계명산층의 변성산성암의 방사능 값은 매우 높게 나타나고, 전기 쥬라기 흑운모 화강암은 이 지역에 광범위하게 분포한다. 이 논문에서는 변성산성암을 중심으로 희토류 광물인 갈렴석의 성장과 관련된 미구조 연구를 수행하여 희토류 광화작용의 기원과 발생 시기를 고찰하였다. 변성산성암은 주로 알칼리장석(주로 미사장석), 석영, 철산화광물, 흑운모, 사장석, 각섬석, 갈렴석, 저어콘, 녹렴석, 형석, 인회석, 석류석, (사)유렴석 등으로 구성되어 있다. 갈렴석은 흑운모와의 접촉부에 방사선 손상에 의한 짙은 갈색 광륜을 형성시키기도 하고, 광역엽리를 따라 집합체로 산출되기도 한다. 대부분의 갈렴석(집합체)의 주변부에서는 광역엽리가 형성되기 이전에 이들이 성장하였음을 지시하는 변형그늘이나 광역엽리의 굴곡면은 관찰되지 않는다. 갈렴석 집합체에 포획된 철산화광물의 입자 크기와 방향성은 광역엽리를 따라 산출하는 기질부의 철산화광물과 동일하다. 후기 화성암의 관입에 의한 열수변질작용으로 각섬석의 흑운모화가 인지되고, 이차적으로 성장한 흑운모는 갈렴석, 저어콘, 녹렴석 등과 접촉 공생한다. 이러한 미구조로부터 희토류 광물인 갈렴석(집합체)은 주로 광역엽리가 형성된 이후에 화성암의 관입과 관련된 열수변질작용으로 성장하였으며, 충주 어래산 지역의 희토류 광화작용은 이 지역에 광범위하게 산출되는 전기 쥬라기 흑운모화강암의 관입과 밀접한 관련성이 있는 것으로 고찰된다.

• Journal of Magnetics
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• 제7권3호
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• pp.63-71
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• 2002

Three fabrication techniques for forming thin barrier layer with uniform thickness and large barrier height in magnetic tunnel junction (MTJ) are discussed. First, the effect of immiscible element addition to Cu layer, a high conducting layer generally placed under the MTJ, is investigated in order to reduce the surface roughness of the bottom ferromagnetic layer, on which the barrier is formed. The Ag addition to the Cu layer successfully realizes the smooth surface of the ferromagnetic layer because of the suppression of the grain growth of Cu. Second, a new plasma source, characterized as low electron energy of 1 eV and high density of $10^{12}$ $cm^{-3}$, is introduced to the Al oxidation process in MTJ fabrication in order to reduce damages to the barrier layer by the ion-bombardment. The magnetotransport properties of the MTJs are investigated as a function of the annealing temperature. As a peculiar feature, the monotonous decrease of resistance area product (RA) is observed with increasing the annealing temperature. The decrease of the RA is due to the decrease of the effective barrier width. Third, the influence of the mixed inert gas species for plasma oxidization process of metallic Al layer on the tunnel magnetoresistance (TMR) was investigated. By the use of Kr-O$_2$ plasma for Al oxidation process, a 58.8 % of MR ratio was obtained at room temperature after annealing the junction at $300{^{\circ}C}$, while the achieved TMR ratio of the MTJ fabricated with usual Ar-$0_2$ plasma remained 48.4%. A faster oxidization rate of the Al layer by using Kr-O$_2$ plasma is a possible cause to prevent the over oxidization of Al layer and to realize a large magnetoresistance.

• Corrosion Science and Technology
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• 제15권3호
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• pp.120-124
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• 2016

The effect of alloying element Ca (0, 1, and 2 wt%) on corrosion resistance and bioactivity of the as-received and anodized surface of rolled plate AM60 alloys was investigated. A plasma electrolytic oxidation (PEO) was carried out to form anodic oxide film in $0.5mol\;dm^{-3}\;Na_3PO_4$ solution. The corrosion behavior was studied by polarization measurements while the in vitro bioactivity was tested by soaking the specimens in Simulated Body Fluid (1.5xSBF). Optical micrograph and elemental analysis of the substrate surfaces indicated that the number of intermetallic particles increased with Ca content in the alloys owing to the formation of a new phase $Al_2Ca$. The corrosion resistance of AM60 specimens improved only slightly by alloying with 2 wt% Ca which was attributed to the reticular distribution of $Al_2Ca$ phase existed in the alloy that might became barrier for corrosion propagation across grain boundaries. Corrosion resistance of the three alloys was significantly improved by coating the substrates with anodic oxide film formed by PEO. The film mainly composed of magnesium phosphate with thickness in the range $30-40{\mu}m$. The heat resistant phase of $Al_2Ca$ was believed to retard the plasma discharge during anodization and, hence, decreased the film thickness of Ca-containing alloys. The highest apatite forming ability in 1.5xSBF was observed for AM60-1Ca specimens (both substrate and anodized) that exhibited more degradation than the other two alloys as indicated by surface observation. The increase of surface roughness and the degree of supersaturation of 1.5xSBF due to dissolution of Mg ions from the substrate surface or the release of film compounds from the anodized surface are important factors to enhance deposition of Ca-P compound on the specimen surfaces.

• 복식문화연구
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• 제17권3호
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• pp.499-511
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• 2009

As the demand of the consumer for high-sense clothing, relation with materials is becoming important even in clothing construction. Especially, the cutting angle of materials is becoming an crucial element in the formation of silhouette, and drape of Hem line, of skirts. Accordingly, in this study, Hem line shapes between real clothing and 3D virtual clothing of "i-Designer" were analyzed by manufacturing semi-flare skirts of polyester 100% according to a cutting angle, and the results are as follows. As a result of comparison of silhouette between the real clothing and the virtual clothing, the real and the virtual have a similar feeling regardless of a cutting angle. In case of drape shapes, both the front and the lateral side were represented in almost similar shapes. The back side, however, the real and the virtual showed a great difference in case of grain direction. And in the whole silhouette, the real and the virtual were represented similarly. It could be known that with regard to Hem-line drape shapes between the real clothing and the virtual according to a cutting angle, the real clothing is represented in a location farther from the body than the virtual clothing and, the location or number of node was similarly showed in the real and the virtual.

• Corrosion Science and Technology
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• 제13권5호
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• pp.178-185
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• 2014

Alloy 617 is considered as a candidate Ni-based superalloy for the intermediate heat exchanger (IHX) of a very high-temperature gas reactor (VHTR) because of its good creep strength and corrosion resistance at high temperatures. Helium is used as a coolant in a VHTR owing to its high thermal conductivity, inertness, and low neutron absorption. However, helium inevitably includes impurities that create an imbalance in the surface reactivity at the interface of the coolant and the exposed materials. As the Alloy 617 has been exposed to high temperatures at $950^{\circ}C$ in the impure helium environment of a VHTR, the degradation of material is accelerated and mechanical properties decreased. The high-temperature strength, creep, and corrosion properties of the structural material for an IHX are highly important to maintain the integrity in a harsh environment for a 60 year period. Therefore, an alloy superior to alloy 617 should be developed. In this study, the mechanical and high-temperature corrosion properties for Ni-Cr alloys fabricated in the laboratory were evaluated as a function of the grain boundary strengthening and alloying elements. The ductility increased and decreased by increasing the amount of Mo and Cr, respectively. Surface oxide was detached during the corrosion test, when Al was not added to alloy. However the alloy with Al showed improved oxide adhesive property without significant degradation and mechanical property. Aluminum seems to act as an anti-corrosive role in the Ni-based alloy.

• 한국군사과학기술학회지
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• 제7권4호
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• pp.70-78
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• 2004

A study has been made to investigate the high temperature deformation behavior of Ti-6Al-4V alloyand to predict the final microstructure under given forming conditions. Equiaxed and $Widmanst\ddot{a}tten$ microstructures of Ti-6Al-4V alloys were prepared as initial microstructures. By performing the compression tests at high temperatures$(700\~1100^{\circ}C)$ and at a wide range of strain rates$(10^{-4}\~10^2/s)$, various parameters such as strain rate sensitivity(m) and activation energy(Q) were calculated and used to establish constitutive equations. When the specimens were deformed up to strain 0.6, equiaxed microstructure did not show any significant changes in microstructure, while $Widmanst\ddot{a}tten$ microstructure revealed considerable flow softening, which was attributed to the globularization of a platelet at the temperature range of $800\~970^{\circ}C$ and at the strain rate range of $10^{-4}\~10^{-2}/s$. To predict the final microstructure after forming, finite element analysis was performed considering the microstructural evolution during the deformation. The grain size and the volume fraction of second phase of deformed body were predicted and compared with the experimental results.

• 터널과지하공간
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• 제26권4호
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• pp.316-326
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• 2016

본 연구는 화강암에 존재하는 결 이방성이 간접인장강도에 미치는 영향을 평가하였다. 표준 간접인장시험 및 3개의 서로다른 중공 크기에 대한 중공 간접인장시험을 수행하였다. 2차원 개별요소 수치해석을 통해 간접인장시험에서의 파괴 과정 및 메커니즘을 고찰하였다. 간접인장강도는 화강암의 결에 따라 하드웨이, 그레인, 리프트 면의 순으로 감소하였다. 중공 간접인장강도는 일반 간접인장강도에 비해 2.5~6.4배 정도 크게 나타났으며, 중공 크기가 클수록 크게 나타났다. 중공 시편에 대한 간접인장 파괴 유형은 중공 크기 및 결과 하중방향 각도에 영향을 받는 것으로 나타났다.

• 대한기계학회논문집A
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• 제34권10호
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• pp.1543-1548
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• 2010

분말단조 공정은 정형의 자동차부품을 제작하는데 널리 이용되고 있다. 분말야금이란 금속 원료 분말을 사용하여 원하는 제품의 형태로 성형을 한 다음 적정온도에서 소결하여 필요한 금속 제품을 제조하는 기술을 말한다. 본 연구에서는 자동차 엔진의 경량화를 위한 피스톤 제작에 관한 것이다. 분말단조로 제작 되어진 엔진 피스톤의 특성을 유한요소해석을 통해서 알아보겠다. 유한요소해석은 DEFORM/3D 를 이용해서 성형성을 평가하도록 하겠다. 성형온도, 구배각도, 마찰계수의 변화에 따른 피스톤의 성형성을 알아보겠다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.620-625
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• 2002

Considering the fuel consumption of car, a light structure of aluminum alloys is desired for car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. ill the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6N01 alloy welds. Aluminum alloy plate of 2.0mm in thickness with filler metal bar was welded by twin beam Nd:YAG laser facility (total power:5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 l/min was used. The defocusing distance is kept at 0 mm. At travel speeds of 3 to 9 m/min and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.