• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 춘계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• 한국농림기상학회지
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• 제25권3호
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• pp.129-141
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• 2023

작물 모형은 작물의 유전적 특성을 나타내는 품종모수를 요구하며, 품종모수는 작물의 개별 품종별로 추정되어야 한다. 품종모수의 추정에는 고품질의 많은 생육 자료가 요구되지만, 자료의 생산에 상당한 비용이 필요하다. 비교적 낮은 품질의 가용성이 높은 자료를 활용하는 대신, 대량의 랜덤 모수를 생성하고 이를 평가하여 품종모수를 추정할 수 있다. 본 연구에서는 SIMPLE 작물 모델의 불확도를 최소화하기 위해 품종모수 추정 방식을 비교하고, 두 앙상블 방식과 대한 비교를 하였다. 모수 추정을 위한 Metropolis-Hastings (MH) 알고리즘에 대한 목적함수로 로그 가능도(log-likelihood: LL)와 generic composite similarity measure (GCSM)를 사용하였다. 또한 품종모수의 평균값을 사용한 예측(E_pm)과 개별 모수들로부터 얻어진 추정값의 평균값(E_em)의 일치도를 분석하여 앙상블 방식에 따른 불확도 변화를 파악하였다. 국내에서 재배되는 사료용 벼 품종인 조우 벼와 영우 벼를 대상으로 품종모수를 추정하였다. 2013년, 2014년, 2016년에 대한 수원, 전주, 나주, 익산에 위치한 실험포장에서 얻은 수량 관측 자료를 사용하였다. 또한 2016년부터 2018년까지 수원에서 보고된 별도의 수량 관측 자료를 사용하였다. 목적함수에 따라 추정된 품종모수의 분포에 차이가 있었다. LL을 통해 얻은 품종모수는 GCSM으로 얻은 품종모수보다 좁은 범위에 분포하였다. 두 가지 앙상블 접근법은 통계적으로 유의한 차이가 나타나지 않음을 확인하였다. GCSM의 상대적으로 높은 불확도는 수용확률을 조정하여 낮출 수 있다고 사료되고, E_pm의 결과는 기존과 다른 앙상블 방식을 통해 적은 연산을 통해 불확도를 낮출 수 있음을 보인다.

• Reproductive and Developmental Biology
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• 제32권4호
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• pp.255-261
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• 2008

The early diagnosis of bovine pregnancy is an essential component of successful reproductive planning on farms, because lack of bovine pregnancy over the long term results in reproductive failure and low milk yield-the latter of which is a special concern on dairy farms. This study was designed to identify early pregnancy-specific whey proteins in bovine, by comparing milk samples collected from cattle during pregnancy (Days 30 and 50) and from non-pregnant cattle. In this study, differentially expressed proteins in five pregnant and five non-pregnant Holstein dairy cattle were investigated and compared, using proteomics analysis. The first dimension was applied to a pH $3.0{\sim}10.0$ strip, by loading a 2-mg milk protein sample. After the second-dimension separation was performed, the gels were stained with colloidal Coomassie brilliant blue. The stained gels were scanned and the images were analyzed, to detect variations in protein spots between non-pregnant and pregnant cattle milk protein spots, using ImageMaster, this was followed by analysis with MALDI TOF-MS. Analysis of the 2-DE gel image resulted in a total of approximately $500{\sim}600$ protein spots, of which 12 spots were differentially expressed, six spots were up-regulated, and four spots were down-regulated; two spots were identified as pregnancy-specific proteins. These proteins were identified as lactoferrin, NA-DH dehydrogenase subunit 2, albumin, serum albumin precursor and transferrin. Our results via 2-D PAGE analysis revealed composite profiles of several milk proteins related to early bovine pregnancy, implying the possible use of these milk proteins in the early detection of bovine pregnancy.

• 한국산학기술학회논문지
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• 제21권6호
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• pp.592-602
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• 2020

본 연구는 한국인 심혈관질환 발생에 기여하는 위험인자들의 기여도를 평가해보고자 하였다. 연구대상은 2005년~2013년 국민건강영양조사 자료를 이용하였으며 30세~74세 대상자 중 심혈관질환 기왕력이 없고, 6개 위험인자 관련 응답이 모두 존재하는 20,012명을 연구대상으로 하였다. 자료 분석은 SAS 9.3으로 수행하였으며 가중치를 적용한 복합표본설계분석을 수행하였고 기여도는 준부분상관제곱분석(squared semi-partial correlation)을 적용하여 구하였다. 연구결과, 남성은 연령(63.9%), 흡연(17.3%), 수축기 혈압(7.9%), 당뇨병(6.9%), 고혈압 치료약물 복용(3.0%), 체질량지수(0.9%) 순이었으며, 반면 여성은 연령(54.1%), 수축기 혈압(23.5%), 당뇨병(13.6%), 고혈압 치료약물 복용(5.1%), 흡연(3.1%), 체질량지수(0.6%) 순이었다. 심혈관질환 발생 위험인자 중에서 연령이 남녀 모두에게 기여도가 가장 높았다. 연령대별 분석결과는 남성은 흡연(51.8~33.7%)이 전 연령대에서 가장 높은 위험인자였으며, 그 다음으로 30대는 연령(26.6%), 40대 이상은 수축기 혈압(17.3%~21.0%) 이었다. 여성은 수축기 혈압(56.2~40.5%)이 전 연령대에서 가장 높았으며 그 다음으로 30대는 연령(24.0%), 40대 이상은 당뇨병(13.6%~32.6%)이었다. 소득수준별로는 기여도에 큰 차이가 없었다. 본 연구결과 향후 심혈관질환 예방을 위해서는 어떤 위험인자를 중점 관리해야 하는지 확인할 수 있었다. 심혈관질환 발생 예방을 위해서는 위험인자의 기여도가 반영된 심혈관질환 예방·관리 프로그램이 개발되어야 하며, 본 연구결과에서 보여준 결과가 기초자료로 활용되기를 제안한다.

• 유통과학연구
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• 제13권9호
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• pp.37-45
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• 2015

Purpose - This paper's aim is to investigate whether or not gross profitability explains the cross-sectional variation of the stock returns in the Korean stock market. Gross profitability is an alternative profitability measure proposed by Novy-Marx in 2013 to predict cross-sectional variation of stock returns in the US. He shows that the gross profitability adds explanatory power to the Fama-French 3 factor model. Interestingly, gross profitability is negatively correlated with the book-to-market ratio. By confirming the gross profitability premium in the Korean stock market, we may provide some implications regarding the well-known value premium. In addition, our empirical results may provide opportunities for the fund distribution industry to promote brand new styles of funds. Research design, data, and methodology - For our empirical analysis, we collect monthly market prices of all the companies listed on the Korea Composite Stock Price Index (KOSPI) of the Korea Exchanges (KRX). Our sample period covers July1994 to December2014. The data from the company financial statementsare provided by the financial information company WISEfn. First, using Fama-Macbeth cross-sectional regression, we investigate the relation between gross profitability and stock return performance. For robustness in analyzing the performance of the gross profitability strategy, we consider value weighted portfolio returns as well as equally weighted portfolio returns. Next, using Fama-French 3 factor models, we examine whether or not the gross profitability strategy generates excess returns when firmsize and the book-to-market ratio are controlled. Finally, we analyze the effect of firm size and the book-to-market ratio on the gross profitability strategy. Results - First, through the Fama-MacBeth cross-sectional regression, we show that gross profitability has almost the same explanatory power as the book-to-market ratio in explaining the cross-sectional variation of the Korean stock market. Second, we find evidence that gross profitability is a statistically significant variable for explaining cross-sectional stock returns when the size and the value effect are controlled. Third, we show that gross profitability, which is positively correlated with stock returns and firm size, is negatively correlated with the book-to-market ratio. From the perspective of portfolio management, our results imply that since the gross profitability strategy is a distinctive growth strategy, value strategies can be improved by hedging with the gross profitability strategy. Conclusions - Our empirical results confirm the existence of a gross profitability premium in the Korean stock market. From the perspective of the fund distribution industry, the gross profitability portfolio is worthy of attention. Since the value strategy portfolio returns are negatively correlated with the gross profitability strategy portfolio returns, by mixing both portfolios, investors could be better off without additional risk. However, the profitable firms are dissimilar from the value firms (high book-to-market ratio firms); therefore, an alternative factor model including gross profitability may help us understand the economic implications of the well-known anomalies such as value premium, momentum, and low volatility. We reserve these topics for future research.

• 한국재료학회지
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• 제4권1호
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• pp.37-43
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• 1994

Y-BA-Cu-O계 고온초전도체의 미세조직을 가공과 열처리로써 제어하여 조직의 배향화와 치밀화를 기하여 높은 임계전류밀도($J_c$)를 갖는 초전도체의 개발을 목적으로sinter forging법으로 Y-BA-Cu-O/Ag 고온초전도복합체를 제조하였다. sinter forging을 통하여 고온 초전도체의 미세조직의 texture화를 가져왔으며, 이 경우 (123)결정립의 C축 방위가 단일축의 압축방향으로 배향화 되었다. 한편, texture의 orientation facter는 고온일수록, 압력이 클수록 크고, 조직의 배향화도 뚜렷하였으며 그에 따라 $J_c$역시 증가하였다. 이러한 결과로 미루어 결정의 배향도는 $J_c$를 좌우하는 중요한 변수라고 사려되었다. 또한 sinter forging 시킨Y-MA-Cu-O/Ag 복합체의 on set온도는 sinter forging온도에 크게 의존치 않았으나, 고온일수록 off set 온도($T_c\;^{zero}$)가 다소 떨어졌다. 한편, 첨가된 Ag는 주고(123)결정입계에 존재하였으며, 이들이 (123)결정립간의 결합을 촉진시켜 임계전류밀도를 크게 향상시켰으며, Y-BA-Cu-O/Ag 복합체의 $J_c$는 2,000 A/$\textrm{cm}^2$ 이상이었다.

• Restorative Dentistry and Endodontics
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• 제21권1호
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• pp.227-241
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• 1996

The effect of collagen dissolution in acid conditioned dentin was morphologically examined by both scanning and transmission electron microscopy. 18 freshly extracted human molars and dentin bonding systems of All Bond 2, Scotchbond Multipurpose, Superbond D-Liner were used in this study. For SEM preparation, each 3 of ~ exposed dentin surfaces were acid conditioned by using various acids within the above three bonding systems respectively. After acid conditioning of the other 3 exposed dentin surfaces as above, they were treated with 1.7% NaOCl for 2 minutes. The remaining 3 dentin surfaces were acid conditioned and treated with 3.3 % NaOCl for 2 minutes. All of the specimens were then fixed in 4 % glutaraldehyde for 12 h at $4^{\circ}C$ and dehydrated in ethanols grades from 50 % to 100 %, then surface changes of the specimens were observed by using SEM. For TEM preparation, exposed dentin surfaces were acid conditioned with the same acid as SEM specimens and treated with 1.7%, 3.3 % NaOCl respectively, then applied with corresponding bonding agents. After the procedures were finished, composite resin were applied on the dentin surfaces and light cured. Small, rectangular sticks with end dimensions of approximately 1 by 1 mm were sectioned and further sample preparative techniques for transmission electron microscopy were performed in accordance with the procedures used for ultrastructural TEM observations of calcified tissues. The results were as follows : 1. In the 1.7 % NaOCl retreated specimens after acid conditioning, the porous dentin surface of intertubular dentin and wide opening of dentinal tubules were appeared. And there were fine irregularities on the intertubular dentin, indicating a clear difference as compared with the acid conditioned specimens. 2. In the 3.3% NaOCl retreated specimens after acid conditioning, the intertubular dentin was further eroded causing a more porous and wider opening of dentinal tubules. Moreover, sharp irregularities on the intertubular dentin were more evident than those of acid conditioned and 1.7% NaOCl retreated specimens. 3. In all of the acid conditioned specimens, the resin-dentin hybrid layer of approximately 3.5mm thickness was formed and the collapsed collagen layer was observed on the uppermost part of hybrid layer in the specimens applied with All Bond 2. The collgen fibrils of intertubular dentin in specimens applied with Scotchbond Multipurpose were running perpendicular to the interface, and electron dense black layer demarcated from the deep unaltered dentin was more evident in the specimen applied with Superbond D-Liner than any other specimens. 4. In the 1.7 % NaOCl retreated specimens after acid conditioning, the resin-dentin hybrid layer of approximately 2.5-3.0mm thickness was formed and the collapsed collagen layer and longitudinally running collagen fibrils as shown in the acid conditioned specimens were observed in the specimens applied with All Bond 2 and Superbond D-Liner. 5. In all of the 3.3% NaOCl retreated specimens after acid conditioning, the evidence of resin-dentin hybrid layer was not identified ; nevertheless, the longitudinally running collagen fibrils remained slightly in the specimens applied with All Bond 2.

• 대한치과보철학회지
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• 제35권1호
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• pp.221-243
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• 1997

The objective of this study was to characterize the mechanical properties of $Y_{2}O_{3}$-containing glass infiltrated ceramic core material, which was made by pressureless powder packing method. A pure alumina powder with a grain size of about $4{\mu}m$ was packed without pressure is silicon mold to form a bar shaped sample, and applied PVA solution as a binder. Samples were sinterd at $1350^{\circ}C$ for 1 hour. After cooling, $Y_{2}O_{3}$-containing glass($SiO_{2},\;Y_{2}O_{3},\;B_{2}O_{3},\;Al_{2}O_{3}$, ect) was infiltrated to the sinterd samples at $1300^{\circ}C$ for 2 hours and cooled. Six different proportions $Y_{2}O_{3}$ of were used to know the effect of the mismatch of the thermal expansion coefficient between alumina powder and glass. The samples were ground to $3{\times}3{\times}30$ mm size and polished with $1{\mu}m$ diamond paste. Flexural strength, fracture toughness, hardness and other physical properties were obtained, and the fractured surface was examined with SEM and EPMA. Ten samples of each group were tested and compared with In-Ceram(tm) core materials of same size made in dental laboratory. The results were as follows : 1. The flexural strengths of group 1 and 3 were significantly not different with that of In-Ceram, but other experimental groups were lower than In-Ceram. 2. The shrinkage rate of samples was 0.42% after first firing, and 0.45% after glass infiltration. Total shrinkage rate was 0.87%. 3. After first firing, porosity rate of experimental groups was 50%, compared with 22.25% of In-Ceram. After glass infiltration, porosity rate of experimental groups was 2%, and 1% in In-Ceram. 4. There was no statistical difference in hardness between two materials tested, but in fracture toughness, group 2 and 3 were higher than In-Ceram. 5. The thermal expansion coefficients of experimental groups were varied to $4.51-5.35{\times}10^{-6}/^{\circ}C$ according to glass composition, also the flexural strengths of samples were varied. 6. In a view of SEM, many microparticles about $0.5{\mu}m$ diameter and $4{\mu}m$ diameter were observed in In-Ceram. But in experimental group, the size of most particles was about $4{\mu}m$, and a little microparticles was observed. The results obtained in this study showed that the mismatch of the thermal expansion coefficients between alumina powder and infiltrated glass affect the flexural strength of alumin/glass composite. The $Y_{2}O_{3}$-containing glass infiltrated ceramic core made by powder packing method will takes less time and cost with sufficient flexural strength similar to all ceramic crown made with slip casting technique.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.303-311
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• 2018

본 연구의 목적은 '국민건강영양조사 제 5기(2010-2012)' 자료를 이용하여 만 20-29세 연령의 한국인에서의 비타민 D 수준과 비타민 D 결핍관련요인을 알아보고자 하였다. '국민건강영양조사 제 5기(2010년-2012년) 완료자중에서 비타민 D 결측치가 없는 만 20세 이상 만 29세 미만 1,837명을 대상으로 분석하였다. 사용된 데이터는 가중치가 적용된 복합표본분석을 이용하여 카이제곱검정 및 다중로지스틱 회귀분석으로 분석하였다. 20대의 84.2%가 비타민 D 결핍으로 조사되었으며 여성이 88.6%로 남성 79.4%보다 높은 결핍률을 보였다. 다중 로지스틱 회귀분석 결과, 비타민 D 결핍에 대한 위험도가 여성인 경우(OR 1.84; 95% CI 1.31-2.56), 미혼인 경우(OR 2.12; 95% CI 1.41-3.19), 주관적 건강상태가 나쁨인 경우(OR 1.94; 95% CI 1.16-3.25) 그리고 중등도 이상 신체활동을 하지 않는 경우(OR 3.38; 95% CI 1.85-6.16)에 높았다. 불확실한 미래를 위해 다양한 노력과 활동을 하는 20대의 비타민 D 결핍은 개인적으로나 사회적으로 매우 중요한 건강문제로 영향을 주기 때문에 이 시기의 비타민 D 수준에 대한 지속적인 연구가 필요할 것이다. 또한 비타민 D는 햇빛에 노출되는 시간과 신체활동 여부와 밀접한 관련이 있는 것으로 나타나 20대의 야외활동 및 중등도 이상의 신체활동을 할 수 있는 학교 및 직장 내 기반시설을 조성하는 등 국가차원에서의 장기적이고 계획적인 노력이 필요하리라고 생각된다.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.155-163
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• 2018

본 연구의 목적은 '제11차(2015년) 청소년건강행태온라인조사'를 이용하여 흡연을 경험한 청소년의 흡연특성과 흡연유형에 따른 특성을 파악하여 복합흡연에 관련된 요인을 알아보고자 하였다. '제11차(2015년) 청소년건강행태온라인조사'에 응답한 68,043명 중 일반담배 및 전자담배 흡연 경험이 있는 중 고등학생 5,347명을 대상으로 분석하였다. 사용된 데이터는 가중치가 적용된 복합표본분석을 이용하여 빈도분석, 카이제곱 검정, 로지스틱 회귀분석으로 분석하였다. 전체 흡연 청소년의 20%가 복합흡연자였으며 전자담배 이용자 85.6%가 니코틴을 사용하였다. 다중 로지스틱 회귀분석 결과 남학생인 경우(OR 1.63; 95% CI 1.15-2.31), 대도시에 거주하는 경우(OR 1.76; 95% CI 1.32-2.33), 하루에 패스트푸드를 1-2회 먹는 경우(OR 2.48; 95% CI 1.33-4.64), 최초흡연 경험 시기가 고등학교인 경우(OR 0.76; 95% CI 0.58-0.98), 간접흡연 경험이 있는 경우(OR 1.24; 95% CI 1.07-1.44), 음주경험이 있는 경우(OR 2.03; 95% CI 1.65-2.48), 일주일간 용돈수준이 높을수록 복합흡연의 위험이 높았다. 본 연구는 청소년의 전자담배와 복합흡연에 대한 기초자료를 제공하고 금연 프로그램 및 정책 개발에 도움이 되리라 판단된다.