• 한국주조공학회지
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• 제37권1호
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• pp.21-29
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• 2017

The effects of W content and heat treatment on the microstructure and mechanical properties of Hastelloy C-276 alloy investment castings were discussed. As the W content was increased, dendritic microstructure was refined and network type precipitate formed during solidification was distributed on the dendritic grain boundaries. Cr, Fe and Mn were highly segregated in the Ni-based dendrite matrix, and Mo, W, C and Si were in the precipitates. Due to the heat treatment, fine granular and flake precipitates were newly formed in the matrix, and unresolved network type precipitates remained on the grain boundary. The network type precipitates and the granular and flake precipitates formed by heat treatment were confirmed to be ${\mu}$ phase intermetallic compounds with similar compositions. Due to the increase of the W content and the heat treatment, hardness and tensile strength were significantly increased. However, tensile strength after aging treatment was decreased with the W content. These results can be explained in that brittle fracturing by the unresolved network type precipitates dispersed in the grain boundary was predominant over ductile fracturing by the dimple ruptures originating from the fine granular precipitates in the matrix.

• 한국의학물리학회지:의학물리
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• 제19권4호
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• pp.219-226
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• 2008

이 연구에서는 저자들이 개발한 비정질 셀레늄층과 비정질 실리콘TFT배열을 사용하는 직접방식 디지털 X-선 영상 검출기에 대해 IEC (international electrotechnical commission)와 같은 국제표준으로 권고된 측정방법에 따라 특성을 평가하였다. 영상 성능 묘사에 사용되는 측정은 응답특성(response characteristic), 변조전달함수(MTF, modulation transfer function), 잡음전력스펙트럼(NPS, noise power spectrum), 양자검출효율(DQE, detective quantum efficiency), 양자제한 성능을 포함하고 있다. 영상특성평가 결과, 개발된 검출기의 DQE 값은 최저주파수와 최고주파수에서 각각 40%와 25%이었다. 해외 타사의 제품과 비교해서도 우월한 값을 나타내었다. 또한 MTF는 간접방식 DR, CR과 비교하면 매우 우월한 성능을 보이고 있다. 또한 양자 제한된 특성을 평가한 결과, 0.023 mR 이하에서만 제한된 특성을 보여 일반촬영용도로서 적합성을 확인할 수 있었다.

• 센서학회지
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• 제4권1호
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• pp.3-8
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• 1995

ITO(indium tin oxide)와 PSL(porous silicon layer)을 이용하여 n-ITO/p-PSL 이종접합형 광검출 소자를 실리콘 기판상에 제조하였다. 실리콘 질화막과 Ni-Cr/Au를 이용하여 선택적으로 양극반응을 시켰으며, 각 소자를 메사구조로 정의하여 소자간을 격리하였고 ITO를 이용하여 소자의 열화문제를 억제시켰다. 제조된 소자에 백색광을 $0{\sim}3000Lux$까지 변화시키면서 얻은 I-V 특성으로부터 광전류가 입사된 광량에 선형적으로 비례함을 알았다. 제조된 소자는 약 -40V의 역방향 바이어스까지 안정되게 동작하였으며 암전류 밀도가 약 $40nA/mm^{2}$로 나타났다. Xe램프를 이용하여 $400nm{\sim}1100nm$까지 파장을 변화시키면서 측정한 결과 $600nm{\sim}700nm$사이에서 약 0.6A/W의 광응답을 나타내었다. 또한 제조된 소자는 3주 경과 후에도 거의 특성의 변화가 관찰되지 않았다.

• 한국환경과학회지
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• 제11권7호
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• pp.651-662
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• 2002

Weather elements were observed by the AWS (Automatic Weather System) and dustfall particles were collected by the modified American dust jar (wide inlet bottle type) at 4 sampling sites in Busan area from March. 1999 to February, 2000. Thirteen chemical species (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Si, and Zn) were analyzed by AAS and ICP. The purposes of this study were to estimate qualitatively various bulk deposition flux of dustfall and insoluble components by applying regional and seasonal wind intensity. Frequency of wind speed were found in order of low(1-3m/s), very low(<1m/s), medium(3-8m/s) and high(>8m/s), and annual mean had higher range at low(1-3m/s) for 56.3%. Strong negative linear correlation were observed between dustfall and wind direction (northeastern and eastern), but strong positive linear correlation were observed between dustfall and wind direction (western and northwestern) at industrial, commercial and coastal zone(p<0.05). While a negative correlation were observed between wind speed frequency of very low(<1 m/s) and dustfall, and positive correlation were observed between wind speed frequency of low(1-3m/s) and dustfall in coastal zone(p<0.05). The correlation coefficient was observed 0.556 between wind speed frequency of low(1-3m/s) and Ni by commercial zone(p<0.05). The correlation coeffcient show well-defined insoluble trace metals (Al, Ca, Cr, Cu, Fe, Pb, and Zn) and wind speed frequency of low(1-3m/s) at coastal zone, which was found significant difference(p<0.01).

• 대한금속재료학회지
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• 제48권7호
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• pp.589-597
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• 2010

In the present study, the effect of variation in alloying elements on the carbide formation behavior during casting and homogenization treatment of M2 high speed steels was investigated. M2 high speed steels of various compositions were produced by vacuum induction melting. Contents of C, Cr, W, Mo, and V were varied from the basic composition of 0.8C, 0.3Si, 0.2Mn, 4.0Cr, 6.0W, 5.0Mo, and 2.0V in weight percent. Homogenization treatment at $1150^{\circ}C$ for 1.5 hr followed by furnace cooling was performed on the ingots. Area fraction and chemical compositions of eutectic carbide in as-cast and homogenized ingots were analyzed. Area fraction of eutectic carbide appeared to be higher in the ingots with higher contents of alloying elements the area fraction of eutectic carbide also appeared to be higher on the surface regions than in the center regions of ingots. As a result of the homogenization treatment, $M_2C$ carbide, which was the primary eutectic carbide in the as-cast ingots, decomposed into thermodynamically stable carbides, MC and $M_6C$. The latter carbide was found to be the main one after homogenization. Fine carbides uniformly distributed in the matrix was found to be MC type carbide and coarsened by homogenization.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.647-653
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• 2020

Stainless steel is used commonly in nuclear applications for shielding radiation, so in this study, three different types of new stainless steel samples were designed and developed. New stainless steel compound ratios were determined by using Monte Carlo Simulation program Geant 4 code. In the sample production, iron (Fe), nickel (Ni), chromium (Cr), silicium (Si), sulphur (S), carbon (C), molybdenum (Mo), manganese (Mn), wolfram (W), rhenium (Re), titanium (Ti) and vanadium (V), powder materials were used with powder metallurgy method. Total macroscopic cross sections, mean free path and transmission number were calculated for the fast neutron radiation shielding by using (Geant 4) code. In addition to neutron shielding, the gamma absorption parameters such as mass attenuation coefficients (MACs) and half value layer (HVL) were calculated using Win-XCOM software. Sulfuric acid abrasion and compressive strength tests were carried out and all samples showed good resistance to acid wear and pressure force. The neutron equivalent dose was measured using an average 4.5 MeV energy fast neutron source. Results were compared to 316LN type stainless steel, which commonly used in shielding radiation. New stainless steel samples were found to absorb neutron better than 316LN stainless steel at both low and high temperatures.

• 한국환경과학회지
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• 제10권3호
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• pp.209-216
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• 2001

Dustfall particles were collected by the modified American dust jar (wide inlet bottle type) at 6 sampling sites in Pusan area from March, 1999 to February, 2000. Thirteen chemical species (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Si, and Zn) were analyzed by AAS and ICP. The purposes of this study were to estimate qualitatively various bulk deposition flux of dustfall and insoluble components by applying regional and seasonal distribution. Dustfall amount of regional variations were found in order of coastal zone, industrial zone, commercial zone, agricultural zone and residential zone, and seasonal total dustfall had higher concentrations during spring for 6.741 ton/${km}^2$/season, lower concentrations during summer for 1.989 ton/${km}^2$/season, and annual total concentration was 17.742 ton/${km}^2$/year. The regional distributions of enrichment factor show well-defined anthropogenic metals (Cd, Cu, Pb, and Zn) at industrial and agricultural zone, and contribution rate of soil particles were found in order of summer, fall, winter and spring. Factor loading effects of chemical composition of dustfall were found in order of road traffic emission source and combustion processed source, industrial activity source, soil source and marine source.

• 천문학회보
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• 제36권1호
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• pp.27.1-27.1
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• 2011

We obtained the spectra of 93 Planet host stars and 73 normal field stars in F, G, K type using BOES at BOAO. We measured the equivalent width of Fe and 25 elements lines using the automatic EW measurement program, TAME(Tools for Automatic Measurement of Equivalent-widths) and estimated the elemental abundances by synth and abfind driver of MOOG code. Since the absence of planets in the normal field stars cannot be "completely" proved, this work focused on the chemical abundances and planet properties of planet host stars, which have the massive planets close to the parent star relatively. We carried out an investigation for the difference of abundances between stars with "Hot Jupiter" and normal field stars with no known planets. We examined the chemical composition of 25 elements, such as C, N, O, S, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, and Eu by EW measurements, and the S abundances were estimated using synthetic spectrum. We have found that [Mg/Fe] and [Al/Fe] for planet host stars have lower limit comparing with those of comparison stars, and [Ca/Fe] of host star with Neptunian planets is relatively lower than the other host stars with massive planets. We have performed the Kolmogorov-Smirnov test, and examined the ratio of planet host stars to all stars for each bin of [X/H]. As a result, we noted that the O, Si, and Ca abfor undances are strongly related with the presence of planets.

• 한국지구과학회지
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• 제21권3호
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• pp.323-336
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• 2000

충남지역의 초염기성암체는 주로 활석과 석면광상의 모암을 이루는 사문암체로서 홍성-광천과 온양-유구-청양을 연결하는 선 내부의 선캄브리아기 편마암복합체내에서 북북동 방향에 따라 단속적으로 평행하게 발달하는 10여개조의 렌즈상관입암체들이다. 사문암체의 규모는 폭 수십 cm${\sim}$1km, 연장 수 m${\sim}$5km로서 곳에 따라 그 규모가 다양하다. 이 사문암들은 주로 SiO$_2$(평균 39.99wt.%)와 MgO(평균 38.46wt.%)로 구성되었고, Cr(>1011ppm), Ni(>1660ppm) 및 Co(>80ppm)의 함량이 많다. 이 사문암들은 주로 사문석의 양이 50% 이상인 것이 대부분이며, 부위에 따라 기원암의 잔류광물인 감람석과 휘석, 크롬철석 등이 발견되는 데 사문암체 내에는 부분적으로 이들 잔류광물의 함량이 50% 이상 되는 사문석화감람암과 활석 및 석면광체를 포함한다. 충남지역 사문암의 기원암은 알파인형 초염기성암으로서 약간 결핍된 상부 맨틀(깊이: 30${\sim}$40km)기원의 더나이트 내지 해즈버자이트였으며, 대규모 단층을 따라 상승한 것으로 해석된다. 이들 사문암의 기원암으로부터의 주 사문석화작용은 충남지역에서 일어난 녹색편암상 내지 각섬암상의 광역변성작용시에 일어난 것으로 해석된다.

• 한국지반환경공학회 논문집
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• 제9권5호
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• pp.37-43
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• 2008

무기질계 주입재는 지반개량 재료로서 기존의 물유리계 재료를 사용할 경우 발생하는 용출현상 및 강도저하를 보완한 시멘트계 급결재와 무기질계 초미립자를 주원료로 하는 순수 무기질 재료를 사용한 것으로서, 시공 후 내구성 및 강도가 우수하고 주입재의 용출 현상이 발생하지 않아 환경오염 문제가 거의없는 영구적인 차수 및 보강에 적합한 친환경적인 재료이다. 본 연구는 지반개량 재료로서 급결성 시멘트계 재료와 순수 무기질 주입재를 주원료로 배합된 MIS(Micro Injection-process System)와 기존에 많이 쓰여지고 있는 물유리계 주입재인 SGR의 내구성 및 친환경적특성을 일축압축강도시험, 내화학성시험, 어독성시험, 화학성분 분석 등의 실험으로 비교 분석 하였다. 일축압축 시험결과 재령 28일 강도는 MIS가 SGR재료에 비해 1.7배 크게 발현 되었고, 재령 40일 이후 SGR재료는 강도가 저하하는 반면 MIS는 지속적으로 증가하는 경향을 보였다. 내화학성시험 결과 MIS의 길이변화율이 물유리계주입재에 비해 10배~25배 작게 나타났다. 그리고, 어독성시험 결과 MIS가 물유리계주입재에 비해 친환경적임이 증명되었고, 화학성분 분석 결과 MIS 용출액이 물유리계주입재의 용출액에 비해 $Cr^{6+}$, Pb, Si 성분이 적게 검출됨을 확인할 수 있었다. 따라서, MIS 주입재는 기존의 SGR 주입재에 비해 고강도로 공기단축 및 기초지반의 구조적 안정성이 우수하며 친환경적이라 지하수오염 등의 문제도 적을 것으로 판단된다.