• The Korean Journal of Ceramics
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• 제6권4호
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• pp.401-404
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• 2000

Mimicking the bacterial synthesis of magnetosomes, in which the functionalized surface of a cytoplasmic (lipid) membrane is considered to be stimulating the crystal growth of magnetite, we have successfully grown magnetite films at $30^{\circ}C$ using an arachic acid monomolecular layer as a functionalized surface. The lipid monomolecular layer was spread on an aqueous solution of FeCl$_2$ which was oxidized by flowing a mixed gas, with ratio $O_2$/$N_2$=1/2000, on the surface of the lipid layer. Mossbauer and X-ray diffraction analyses revealed that the Fe$_3$O$_4$ films contain small amounts of ferric hydroxyl impurity phases of ${\alpha}$-FeOOH and ${\tau}$-FeOOH. This is because the oxygen partial pressure at the ferrite/aqueous interface changed as the film (through which the gas penetrated) increased in thickness. Methods to obtain single phase magnetite films are proposed.

• 대한금속재료학회지
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• 제47권2호
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• pp.99-106
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• 2009

The high temperature corrosion properties of heat resistant steels were investigated in oxidation atmosphere including sulfur dioxide. The heat resistant steels of T22, T92, T122, T347HFG and T304H were evaluated at 620, $670^{\circ}C$ for 400 hours. The corrosion rates showed a decreasing tendency while chrome contents of those steels increased from 2 mass.% to 19 mass.%. The in crease in temperature increasement has an more effect on the corrosion rates of low chrome steels than high chrome steels. The weight gains of T22, T92, T304H at $670^{\circ}C$ were 3.7, 1.65, 1.23 times compared with those at $620^{\circ}C$. The external scale formed on T22 was composed of hematite, magnetite and Fe-Cr spinel and internal layer including iron oxide mixed with sulfide. The scales formed on T92, T122, T304H consisted of an outer layer of hematite and inner layer of chrome oxide and hematite. The proportion of chrome oxide at inner layer was increased when the chrome contents in heat resistant steels were increased.

• 한국결정성장학회지
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• 제17권1호
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• pp.6-10
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• 2007

R-plane 사파이어 위에 a-plane GaN층이 성장된 기판에 혼합소스 HVPE(mixed-source hydride vapor phase epitaxy) 방법으로 GaN/InGaN의 이종접합구조(heterostructure)를 구현하였다. GaN/InGaN 이종접합구조는 GaN, InGaN, Mg-doped GaN 층으로 구성되어 있다. 각 층의 성장온도는 GaN층은 $820^{\circ}C$, InGaN 층은 $850^{\circ}C$, Mg-doped GaN 층은 $1050^{\circ}C$에서 성장하였다. 이때의 $NH_3$와 HCl 가스의 유량은 각각 500 sccm, 10 sccm 이었다. SAG-GaN/InGaN 이종접합구조의 상온 EL (electroluminescence) 특성은 중심파장은 462 nm, 반치폭(FWHM : full width at half maximum) 은 0.67eV 이었다. 이 결과로부터 r-plane 사파이어 기판위에 multi-sliding boat system의 혼합소스 HVPE 방법으로 이종접합구조의 성장이 가능함을 확인하였다.

• KEPCO Journal on Electric Power and Energy
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• 제5권4호
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• pp.287-293
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• 2019

국내 화력발전소의 석탄회 발생량은 매년 증가하고 있는 상황이다. 특히 Fly Ash보다 상대적으로 생산량이 15 % 정도로 적은 저회의 경우 적은 생산량에도 불구하고 재활용률이 낮아 발전소에 단순 매립되어 있는 실정이다. 하지만, 발전소 마다 매립장이 포화상태에 있고, 새로운 매립장 건설이 어려운 상황이다. 이와 같은 문제를 해결하기 위해서는 매립석탄회를 토목 공사에의 대규모 적용을 촉진하는 방안이 가장 합리적인 방안이라고 할 수 있다. 따라서 본 연구에서는 산업폐기물인 석탄재와 항만 준설을 하면서 대량으로 매립되고 있는 준설토를 혼합한 혼합토의 표층고화처리공법에 대한 적용성을 검토하기 위해서 유동성 및 일축압축시험을 통한 역학적 거동 특성을 연구하였다. 시험결과, 유동성은 준설토와 석탄회 혼합토의 경우 함수비 91-92%에서 유동성 200 mm를 확보하여 우수했고, 준설토 100 %와 모래와 석탄회의 혼합토는 상대적으로 낮은 유동성을 나타냈다. 일축압축강도 역시 준설토와 석탄회의 혼합토는 28일 강도에서 요구 강도 159 kN/㎡을 만족하면서 우수한 결과를 나타냈으나, 그 외 시료들은 요구 강도를 만족하지 못하는 결과를 나타냈다. 본 연구에서는 시멘트와 양생 기간에 따른 압축강도 거동 예측식을 제시하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.545-552
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• 2005

For the purpose of studying on the seepage characteristics of embedded gravel layer in embankment, laboratory model tests were carried out. The embedded layer under embankment was $19{\sim}26mm$ diameter of gravel and those embankment materials were Saemangum dredged sand, river sand and mixed(1:1) sand with dredged and river one. Those permeability coefficients of three different sands are $5.00{\times}10^{-5}$, $3.00{\times}10^{-4}$, $7.50{\times}10^{-5}m/s$, respectively. Seepage characteristics of these results are as follows; 1) The Reynolds number of water flow through embedded gravel layer in three different permeable soils is less then 10, it is laminar flow. 2) These flow velocities through embedded gravel layer in soils are in proportion to these hydraulic gradients, it is Darcy flow. 3) These Darcian permeability coefficients of water flow through embedded gravel layer in soils show as $2.95{\times}10^{-3}$, $1.38{\times}10^{-2}$, $3.33{\times}10^{-3}$m/s, respectively, by varying permeability of embankment soils and embankment lengths. It is approximately 100 times of those permeability coefficients of embankment materials.

• 열처리공학회지
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• 제13권4호
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• pp.224-230
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• 2000

Garbon steel(SM35C) was gas nitrocarburized at $580^{\circ}C$ in $55%N_2-40%NH_3-5%CO_2$ mixed gas atmosphere, and then the steel was induction hardened at $850^{\circ}C$. The microstructure of gas nitrocarburized surface layer was observed by optical microscope and SEM. The phase analysis was carried out by X-ray diffraction method. The mechanical properties of gas nitrocarburized SM35C steel was evaluated by hardness, wear and fatigue test. The thickness of compound and diffusion layer were increased with increasing the gas nitrocarburizing time and the densest compound layer was obtained at 3 hours gas nitrocarburizing time. In case of 15sec induction hardening after gas nitrocarburizing, the surface hardness was decreased from 800Hv to 630Hv owing to the decomposition of compound layer, but wear resistance was increased because of increased hardness of diffusion layer. The fatigue strength of induction hardened steel after gas nitrocarburizing, $58kgf/mm^2$, was higher than $41.5kg/mm^2$ of gas nitrocarburized steel and $45kg/mm^2$ of induction hardened steel, respectively.

• Journal of the Korean Wood Science and Technology
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• 제27권3호
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• pp.82-90
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• 1999

송광사 삼세불화는 조성년도가 확실하지 않지만 남아있는 서기(書記)와 재질 분석을 통해 19세기초에 제작된 것으로 추정 할 수 있었다. 그리고 공시불화의 보존처리를 위해 안료층과 바탕층, 지지층을 구성하고 있는 재질을 분석하고 이에 적합한 지지층인 배첩지를 초지하여 그 적합성을 시험한 바 다음과 같은 결론을 얻었다. 1. 삼세불화의 단면구조는 안료층과 명주로 된 바탕층 그리고 한지(韓紙)로 이루어진 지지층으로 구성되어 있어 19세기 당시의 불화는 기본적으로 안료층, 바탕층, 지지층으로 구성되어 있음을 알 수 있었다. 또한 안료층과 바탕층의 접착은 아교를 사용하였고 지지층의 sheet 배첩은 호료(糊料)를 사용했음을 알 수 있었다. 2. 삼세불화의 지지층은 5겹으로 구성되어 있고 두 종류의 종이가 사용되었는데 바탕층과 접해 있는 1~2층은 순수한 닥섬유로 제조한 한지(韓紙)를 사용하였고 나머지 3개 층은 폐마섬유(廢麻纖維)에 닥섬유가 혼합된 종이를 사용하였다. 더 많은 자료가 확보되어야만 단언할 수 있지만 재질을 통해 당시의 상황을 파악해 보면 19세기 당시의 사회는 경제적으로 어려움을 겪고 있었고 더욱이 사찰 제지업은 피폐해져 운영이 어려워 후면에 사용한 배첩지는 질이 떨어지는 폐마를 이용 했을 것으로 추측되었다. 3. 본 재료의 바탕층과 지지층간의 인장력을 고려하여 새롭게 제조해 보수용으로 사용한 바 본 공시재료의 보수용 배첩지로서 적합했음을 알 수 있었다.

• 설비공학논문집
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• 제7권2호
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• pp.184-195
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• 1995

A theoretical one-dimensional model for the charging process in stratified thermal storage tanks is established presuming that the fluid ensuing from the tank inlet creates a perfectly mixed, layer above the thermocline. Both the generic and asymptotic closed-form solutions are obtained via the Laplace transformation. The asymptotic solution describes the nature of the charging pertaining to the case of no thermal diffusion, whereas the generic solution is of practical importance to understand the role of operating parameters on the stratification. The present model is validated through comparison with available experimental data, where they agree well with each other within a reasonable limit. An interpretation of the exact solution entails two important features associated with the charging process. The first is that an in-crease in the mixing depth $h_m$ causes a relatively slow temperature rise in the perfectly mixed region, but on the other hand it results in a faster decay of the overall temperature gradient across the thermocline. Next is the predominance of the mixing depth in the presence of the prefectly mixed region. In such a case the effect of the Peclet number is marginal and there-fore the thermal characteristics are solely dependent on the mixing depth paticularly for large $h_m$. The Peclet number affects significantly only for the case without mixing. Variation of the storage efficiency in response to the change in the mass flow rate agrees favorably with the published experimental results, which confirms the utility of the present study.

• 한국미생물·생명공학회지
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• 제6권2호
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• pp.51-57
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• 1978

섬유소 자화세균의 분리 및 이용과정에서 혼합배양하므로써 균체증식이 향상 되었는데, 이러한 혼합배양에 따른 여러 가지 영향과 보조균을 동정한 결과를 요약하면 다음과 같다. 1) Cellulomona flavigena의 단독배양에서는 O.D.가 0.26이였으나, 보조균과 혼합배양하므로써 O.D.가 0.37로 증가하였다. 2) 보조균은 gliding motility가 있었으며, microcyst가 확인되었는데 이것은 Sporocytophga 속과 일치하였다. 3) 혼합배양에서 생육최적 pH는 7.2 부근이 좋았으며, 최적온도는 3$0^{\circ}C$ 부근이었다. 4) 혼합배양에 있어서 두 균의 분포도는 10 : 1 정도로 Cellulomonas flavigena가 주로 분포되어 있었다. 5) Cellulomonas flavigena의 growth factor로서 thiamine과 biotin을 요구하였으며, Sporocytophaga sp.는 vitamin 요구성이 없었다. 6) Cellulomonas flavigena의 단독배양액에서는 추적할 만한 glucose 량이 없었으나, 혼합배양에서는 glucose가 확인되었다. 7) Cellulomonas flavigena의 균체중 필수아미노산으로 valine, leucine, arginime이 비교적 많은 편이였다

• 한국안전학회지
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• 제28권4호
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• pp.14-18
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• 2013

Blades of horizontal axis are nowadays made of composite materials. Generally, composite materials satisfy design provides lower weight and good stiffness, while laminate composites have often damages as like the delamination and cracks at the interface of laminates. The box spar and tail parts of a blade are composed of the CFRP/GFRP hybrid laminate composites. However, delamination and the interfacial crack often occur in the interface of CFRP/GFRP hybrid laminate composites under the mixed mode fracture condition, especially mode I and mode II. Therefore, there is a need for the evaluation of the mixed mode fracture behavior during the delamination of CFRP/GFRP hybrid laminates. This study shows the experimental results for the delamination fracture toughness in CFRP/GFRP hybrid laminate composites. Fracture toughness experiments and estimation are performed by using DMMB(Dissimilar mixed mode bending) specimen. The materials used in the test are a commercial woven type CFRP(Carbon fiber reinforced plastic) prepreg(CF3327) and UD type GFRP(Glass fiber reinforced plastic) prepreg(HD224A). A CFRP/GFRP hybrid laminate composite is composed by the 10 plies CFRP and GFRP prepreg for DMMB. A thickness of CFRP and GFRP layer is 2.5mm and 3.0mm, respectively. Also the fulcrum location which is a loading parameter is changed from 80 to 100mm on the specimen of length 120mm because it defines the ratio of mode I to mode II. In this study, the effects of the fulcrum location are evaluated in the viewpoint of energy release rate in mode I and mode II contribution. The results show that the delamination crack initiates at higher displacement and lower load according to the increase of the fulcrum location ratio. And the variation of the energy release rate for mode I and II contributions for the mode mixity are shown.