• 한국진공학회:학술대회논문집
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.120-120
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• 1998

Boron nitride (BN) films have attracted a growing interest for a variety of t technological applications due to their excellent characteristics, namely hardness, c chemical inertness, and dielectrical behavior, etc. There are two crystalline phases 1551; of BN that are analogous to phases of carbon. Hexagonal boron nitride (h-BN) has a a layered s$\sigma$ucture which is spz-bonded structure similar to that of graphite, and is t the stable ordered phase at ambient conditions. Cubic boron nitride (c-BN) has a z zinc blende structure with sp3-bonding like as diamond, 따ld is the metastable phase a at ambient conditions. Among of their prototypes, especially 삼Ie c-BN is an i interesting material because it has almost the same hardness and thermal c conductivity as di없nond. C Conventionally, significant progress has been made in the experimental t techniques for synthesizing BN films using various of the physical vapor deposition 밍ld chemical vapor deposition. But, the major disadvantage of c-BN films is that t they are much more difficult to synthesize than h-BN films due to its narrow s stability phase region, high compression stress, and problem of nitrogen source c control. Recent studies of the metalorganic chemical vapor deposition (MOCVD) of I III - V compound have established that a molecular level understanding of the d deposition process is mandatory in controlling the selectivity parameters. This led t to the concept of using a single source organometallic precursor, having the c constituent elements in stoichiometric ratio, for MOCVD growth of 삼Ie required b binary compound. I In this study, therefore, we have been carried out the growth of h-BN thin f films on silicon substrates using a single source precursors. Polycrystalline h-BN t thin films were deposited on silicon in the temperature range of $\alpha$)() - 900 $^{\circ}$C from t the organometallic precursors of Boron-Triethylamine complex, (CZHs)3N:BRJ, and T Tris(dimethylamino)Borane, [CH3}zNhB, by supersonic molecular jet and remote p plasma assisted MOCVD. Hydrogen was used as carrier gas, and additional nitrogen w was supplied by either aDlIDonia through a nozzle, or nitrogen via a remote plasma. T The as-grown films were characterized by Fourier transform infrared spectroscopy, x x-ray pthotoelectron spectroscopy, Auger electron spectroscopy, x-ray diffraction, t transmission electron diffraction, optical transmission, and atomic force microscopy.roscopy.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.605-612
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• 2013

Removal of decay heat from an operating reactor during a prolonged station blackout condition is a big concern for reactor designers, especially after the recent Fukushima accident. In the case of a prolonged station blackout condition, heat removal is possible only by passive means since no pumps or active systems are available. Keeping this in mind, the AHWR has been designed with many passive safety features. One of them is a passive means of removing decay heat with the help of Isolation Condensers (ICs) which are submerged in a big water pool called the Gravity Driven Water Pool (GDWP). The ICs have many tubes in which the steam, generated by the reactor core due to the decay heat, flows and condenses by rejecting the heat into the water pool. After condensation, the condensate falls back into the steam drum of the reactor. The GDWP tank holds a large amount of water, about 8000 $m^3$, which is located at a higher elevation than the steam drum of the reactor in order to promote natural circulation. Due to the recent Fukushima type accidents, it has been a concern to understand and evaluate the capability of the ICs to remove decay heat for a prolonged period without escalating fuel sheath temperature. In view of this, an analysis has been performed for decay heat removal characteristics over several days of an AHWR by ICs. The computer code RELAP5/MOD3.2 was used for this purpose. Results indicate that the ICs can remove the decay heat for more than 10 days without causing any bulk boiling in the GDWP. After that, decay heat can be removed for more than 40 days by boiling off the pool inventory. The pressure inside the containment does not exceed the design pressure even after 10 days by condensation of steam generated from the GDWP on the walls of containment and on the Passive Containment Cooling System (PCCS) tubes. If venting is carried out after this period, the decay heat can be removed for more than 50 days without exceeding the design limits.

• 대한치과보철학회지
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• 제41권3호
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• pp.319-324
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• 2003

Statement of problem. Adhesives in dentistry playa major role in the success of restorative treatments. In the treatment of all ceramic restoration it is needed to find the adequate bond strength between enamel and dentin. Purpose. The purpose of this study was to evaluate shear bond strength of resin cement bonded to extracted human uncut enamel, cut enamel, and dentin in vitro. Material and methods. Ten freshly extracted anterior teeth without any previous restorative treatments were chosen. The extracted teeth were embedded in PMMA cold acrylic in the shape of a cylinder, 25 mm in diameter by 25 mm in height. The bonding system used was as follow: Uni-Etch (32% phosphoric acid), One-Step adhesive, Duolink resin cement. The specimens were acid etched and rinsed with water. Two layers of One-Step adhesive were coated with a disposable brush on the uncut enamel. VIP curing light at $500mV/cm^2$ was used to cure the adhesive. For cut enamel shear bond test, the specimen used for uncut enamel was further reduced approximately $0.3{\sim}0.5mm$ using a laminate preparation diamond bur (0.3 mm in depth). The specimens were subsequently treated with 320-grit SiC paper followed by 600-grit SiC paper and cleaned with distilled water. The bonding procedure on the cut enamel was same as uncut enamel bonding procedure. For dentin bonding test, the specimen used for cut enamel was further reduced approximately $0.5mm{\sim}1.0mm$ using a laminate preparation diamond bur (0.5 mm in depth of diamond cutting). The amount of reduction was evaluated with the silicone mold. The specimens were subsequently treated with 320-grit SiC paper followed by 600-grit silicon carbon paper and cleaned in distilled water. The bonding procedure on the dentin was same as uncut enamel bonding procedure. All samples were mounted and secured on the Ultradent shear bond test sample holder, and Ultradent restricted shear bond testing device was used with Universal Instron machine until fracture. Analysis of variance (ANOVA) test was performed comparing the result at P<0.05. Multiple comparison (Tukey) was used to compare each groups. Result. The result showed that the mean value in shear bond strength of resin cement bonded to uncut enamel, cut enamel and dentin were 27.04 Mpa, 30.25 Mpa and 26.39 Mpa with respect. Conclusion. Within the limitation of this study, the mean value of the shear bond strength of cut enamel was higher than those of uncut enamel or dentin. However there existed no statistical differences between three different human dentition substrates due to increased adhesive characteristics.

• 자원환경지질
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• 제31권3호
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• pp.249-264
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• 1998

The Creataceous volcanic rocks distributed in the southeastern part (Kyeongsang basin) of Korea peninsula are composed of basalt, basaltic andesite, andesite, dacite and rhyolite. The variation of major elements show that contents of MgO, CaO, $FeO^T$, $Al_2O_3$, $TiO_2$ and $P_2O_5$ decrease with increasing of $SiO_2$, but $K_2O$ contents are increased slightly, $Na_2O$ widely dispersed. We can show slightly inflection point and low frequency of dacites in range between 63-65 wt.% $SiO_2$, while continuous trend exit in variation diagram. Variation trends in Harker diagrams for the major, minor, trace and REEs suggest that the BAV (basaltic to andesitic volcanics) and DRV (dacitic to rhyolitic volcanics) are not related to a simple crystal fractionation process. In the regime of under 65 wt. % in silica content, fractionation of olivine and clinopyroxene is predominant, while that of plagioclase happens strongly higher than 65 wt.% (e.g., $SiO_2$, vs. Eu and Sr, MgO vs. $Al_2O_3$ and CaO). The latter means low-pressure fractional crystallization for DRV. On the discriminant diagram, DRV are located in more mature environment than BAV. The $(Ce/Sm)_N$ vs. CeN digram shows that these two classes cannot be related to crystal fractionation. If they had been produced by fractionation, although they plotted in a slightly elongate cluster along the same horizontal trend, DRV should lie to the right of these primitive compositions. These diagrams clearly rule out a simple fractionation throughout from BAV to DRV. BAV had been influenced greatly subductiong slab as shown by K/Yb vs. Ta/Yb. We suggest that BAV primitive magma generated higher degree of partial melting than DRV primitive magma. LILE (K, Ba, $Rb{\pm}Th$) enriched characteristics as shown in BAV are inherited from subducting slab fluids and/or higher degree of partial melting of mantle material. However, lower degree of partial melting of mantle relative to BA V and contamination at high-level magma reservoir caused LILE enrichment to DRV.

• 한국안전학회지
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• 제26권4호
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• pp.47-58
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• 2011

Halogen free intumescent flame retardants(IFRS), such as the mixture of melamine phosphate(MP) and char forming agents(pentaerythritol(PER), di-pentaerythritol(DiPER), tris(2-hydroxyethyl) isocyanurate(THEIC)), were prepared and characterized. Polypropylene(PP)/$IFR_S$ composites were also prepared in the presence of ethylene diamine phosphate(EDAP) as a synergist and used into flame retardant PP powder coatings. Thermoplastic PP powder coatings at 20 wt% flame retardant loading were manufactured by extruded and then mechanical cryogenic crushed to bring them in fine powder form. These intumescent flame retardant powder coatings($IFRPC_S$) were applied on mild steel surface for the purpose of protection and decorative. It is a process in which a $IFRPC_S$ particles coming in contact with the preheated mild steel surface melt and form a thin coating layer. The obtained MP flame retardant was analyzed by utilizing FTIR, solid-state $^{31}P$ NMR, ICP, EA and PSA. The mechanical properties as tensile strength, melt flow index(MFI) and the thermal property as TGA/DTA and the fire safety characteristics as limiting oxygen index(LOI), UL94 test, SEM were used to investigate the effect of $IFRPC_S$. The experimental results show that the presence of $IFR_S$ considerably enhanced the fire retardant performances as evidenced by the increase of LOI values 17.3 vol% and 32.6 vol% for original PP and $IFRPC_S$-3(PP/MP-DiPER/EDAP), respectively, and a reduction in total flaming combustion time(under 15 sec) in UL94 test of $IFRPC_S$. The prepared $IFRPC_S$-3 have good comprehensive properties with fire retardancy 3.2 mm UL94 V-0 level, LOI value 32.6%, tensile strength $247.3kg/cm^2$, surface roughness Ra $0.78{\mu}m$, showing a better application prospect. Through $IFRPC_S$-2(PP/MP-PER/EDAP) and $IFRPC_S$-3 a better flame retardancy than that of the $IFRPC_S$-1(PP/MP/EDAP) was investigated which was responsible for the formed more dense and compact char layer, improved synergy effect of MP and PER/DiPER.

• 한국산림과학회지
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• 제108권3호
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• pp.311-321
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• 2019

이 연구는 땅밀림위험등급을 구축하기 위하여 수행되었다. 땅밀림지의 평균산지경사는 $23.8^{\circ}$($11.8^{\circ}{\sim}37.0^{\circ}$), 땅밀림지 내에서 미세지형지의 평균사면경사는 $23.5^{\circ}$ ($10.7^{\circ}{\sim}41.5^{\circ}$)로 미소한 차이가 있는 것으로 분석되었다. 땅밀림지 및 땅밀림 재발생지에서 땅밀림지 내 등고선 간격과 땅밀림지 내 미세지형지의 등고선 간격은 5% 수준에서 유의한 결과를 나타내었다. 산사태위험등급에 포함되지 않는 땅밀림지는 전체 땅밀림지 중 1등급이 14개소(약 38.0%), 2등급이 6개소(약 16.0%), 3등급과 4등급이 각각 5개소(약 14.0%), 5등급이 16개소(약 43.0%), 산사태위험지등급 외 지역이 9개소(약 24.0%)이었다. 땅밀림지 중 산사태위험 1~5등급으로 지정되지 않은 면적 비율이 50.0% 이상인 지역은 8개소(약 22.0%), 20.0%~50.0% 이상인 지역은 18개소(약 49.0%), 20.0% 이상인 지역은 26개소(약 70.0%)이었다.

• Nutrition Research and Practice
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• 제15권sup1호
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• pp.32-40
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• 2021

BACKGROUND/OBJECTIVES: Considering the high number of deaths from coronavirus disease 2019 (COVID-19) in Latin American countries, together with multiple factors that increase the prevalence of vitamin D deficiency, we aimed to determine 25-hydroxyvitamin D (25[OH]D) levels and its association with mortality in patients with critical COVID-19. SUBJECTS/METHODS: This was a prospective observational study including adult patients with critical COVID-19. Data, including clinical characteristics and 25(OH)D levels measured at the time of intensive care unit admission, were collected. All patients were followed until hospital discharge or in-hospital death. The patients were divided into those surviving and deceased patient groups, and univariate and multivariate logistic regression analyses were performed to determine independent predictors of in hospital mortality. RESULTS: The entire cohort comprised 94 patients with critical COVID-19 (males, 59.6%; median age, 61.5 years). The median 25(OH)D level was 12.7 ng/mL, and 15 (16%) and 79 (84%) patients had vitamin D insufficiency and vitamin D deficiency, respectively. The median serum 25(OH)D level was significantly lower in deceased patients compared with surviving (12.1 vs. 18.7 ng/mL, P < 0.001). Vitamin D deficiency was present in 100% of the deceased patients. Multivariate logistic regression analysis revealed that age, body mass index, other risk factors, and 25(OH)D level were independent predictors of mortality. CONCLUSIONS: Vitamin D deficiency was present in 84% of critical COVID-19 patients. Serum 25(OH)D was independently associated with mortality in critical patients with COVID-19.

• 생명과학회지
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• 제19권2호
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• pp.277-283
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• 2009

Biogenic amines은 발효제품과 같이 어류 속의 미생물에서 분비된 decarboxylase의 free amino acid의 decarboxylation에 의해 형성된다. 본 연구는 국내 어분 제조원료로 이용되고 있는 참치 부산물의 항영양인자로 작용하는 biogenic amines (histamine, tyramine, tryptamine, putrescine, cadaverine)의 분해조절을 위해 참치 부산물의 특성 구명을 위한 연구로 실시하였다. 참치 부산물의 pH 및 염도 농도는 6.51과 3.35%이었으며, 참치 어분의 pH 및 염도 농도는 5.58과 5.83% 이었다. 참치 부산물 내 존재하고 있는 균주 및 주요 미생물을 확인한 결과 Total bacteria, aerobic plate count (APC), Total coliform (TC), Lactobacillus spp. 및 Bacillus spp.는 각각 9.20, 9.29, 5.67, 7.82 및 7.58(Log CFU/g)이었다. 참치 부산물 내 히스타민 주요 생성균을 확인하기 위해 TLC 방법을 이용하였으며 히스타민 선택배지에서 추출한 미생물 중 총 7종의 히스타민 생성 균주를 선발하였다. 선발된 균주는 HPLC 분석을 통하여 히스타민 농도를 측정하여 아민 생성 미생물을 재확인하였다. Trypicase soy broth에 1% L-histidine (TSBH)을 첨가한 배지에서 분리한 7종의 히스타민 생성 균주를 16SrRNA 염기서열 분석 방법을 통해 분석한 결과, 참치 부산물내 주요 우점 아민 생성 미생물은 L. lactis subsp. lactis, K.pneummonlae, L. garvieae, V. olivaceus, H. alvei, L. garvieae 및 Morganella morganii가 주요 균주로 분석되었다. 16S rRNA 분석결과로 만들어진 phylogenetic tree는 다른 계통임을 보여주며 이는 biogenic amine을 생성하는 그람 양성 및 음성균으로 분류될 수 있다.

• Childhood Kidney Diseases
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• 제14권2호
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• pp.203-209
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• 2010

목 적 : 소아에서 여러 가지 원인으로 반복적 요로감염의 위험성을 줄이기 위한 예방적 항생제 투여시, 새로운 내성균의 출현으로 요로 감염이 재발하게 되는 소위 돌파 감염(breakthrough infection)이 있게 되면 그에 의한 새로운 신 반흔 형성이 문제가 된다. 하지만 지금까지 국내에서 돌파 감염의 임상양상에 대한 보고는 드물었으므로 저자는 본 병원에서 실제 예방적으로 사용하고 있는 항생제의 실태와 그에 따른 돌파 감염의 임상 양상을 알아보고자 본 연구를 시행하였다. 방 법 : 약 5년 6개월간 부산대학교병원 소아과에서 요로감염의 재발을 방지하기 위하여 예방적 항생제를 사용한 150명의 환자를 대상으로 돌파감염의 양상에 대하여 차트와 검사결과를 후향적으로 조사하였다. 결 과 : 예방적 항생제 투여를 시작한 연령 범위는 1-76개월, 중간 연령은 5개월이었으며, 돌파감염은 총 43례(28.7%)에서 61회 발생하였고 발생빈도는 환자 100 patient-months당 1.5회였다. 방광 요관 역류로 예방적 항생제를 사용한 경우, 역류의 정도에 따른 돌파감염의 발생빈도는 grade I-II에서 18.5%, grade III에서 21.1%, grade IV-V에서 41.7%로써 grade가 높을수록 높았으나 통계적 유의성은 없었다(P=0.06). 또한 항생제 사용 전실시한 DMSA 스캔에서 이상이 있었던 경우가 이상이 없었던 경우보다 쉽게(47.3% vs 14.7%) 요로감염이 발생하였다. 돌파 감염의 원인균은 대장균에 의한 경우가 가장 많았지만(29.5%), 일반적인 요로 감염에서 보다 다양한 균주에 의해 고른 분포로 요로 감염이 발생하였다. 사용한 예방적 항생제 중 co-trimoxazole을 사용한 경우가 2세대, 3세대 세파로스포린을 사용한 경우보다 요로감염의 예방에 효과적이었으며(P=0.0386, P=0.0128), 항생제 감수성 검사 결과 27.3%는 사용 중인 예방적 항생제에 감수성이 있었고 59.1%는 저항성을 보였다. 돌파 감염이 발생한 환아 중 39.5%에서 수술적 치료로 바꾸었으며 34.9%에서 항생제를 변경하였고 25.6%에서는 종래의 항생제를 계속 사용하였다. 결 론 : 신 반흔이 있는 경우는 돌파 감염이 쉽게 일어나므로 내시경적인 방법 등을 포함한 수술적 치료의 선택에 고려되어져야하며, 돌파 감염을 방지하기 위해 환자의 항생제 투여의 순응도를 고려해야 하며 세파로스포린 같은 항생제 사용은 자제해야 할 것으로 사료된다.

• 천문학논총
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• 제36권3호
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• pp.47-63
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• 2021

와이즈/네오와이즈 자료를 사용하여 1형 활동은하핵의 근적외선 장기 변광 특성을 살펴보았다. 활동은하핵은 밀리퀘이사 목록을 사용해 가시광에서의 등급 제한을 두어 선정하였고, 여러 번의 다중시점 측광 자료를 확보하기 위해 황도북극과 황도남극에 가까운 대상으로 한정하였다. 이후 와이즈와 네오와이즈 데이터베이스에서 해당 대상들의 측광 자료를 추출하였다. 일부 근적외선에서 검출되지 않은 경우와 관측 횟수가 지나치게 적은 경우를 제외하고 총 73개의 1형 퀘이사 및 활동은 하핵, 140개의 측광학적으로 선택된 활동은하핵 후보에 대해 W1 (3.4 ㎛), W2 (4.6 ㎛) 밴드 광도곡선을 구성하고 이를 이용해 변광 분석을 수행하였다. 변광 여부를 판단하기 위해 초과 분산 값과 변광의 유의확률 P_var를 계산하였다. 초과 분산이 포아송 오차에 의해 추정되는 오차값보다 큰 경우, 그리고 P_var이 0.95보다 크거나 같은 경우를 변광으로 판단했는데, 활동은하핵 73개 중 19개, 활동은하핵 후보 140개 중 12개가 W1, W2 밴드 모두에서 변광 대상으로 판단되었다. W1 밴드보다 W2 밴드에서 변광 대상으로 판단되는 숫자가 작게 나타났는데, 이는 긴 파장으로 갈수록 변광의 정도가 작아짐을 시사하는 것으로 보인다. 약 9 ~ 26%의 대상들이 근적외선 변광을 보였다. 감쇠 랜덤워크 모형을 사용하여 변광 폭(σ)과 완화 시간(τ), W1과 W2 밴드 사이의 시간 지연 등을 추정하였다. 변광 폭 및 완화시간은 W1 등급과 큰 상관관계를 보이지 않았으며, 두 변수 사이에도 특별히 두드러지는 상관관계가 나타나지 않았다. 단, 감쇠 랜덤워크 모형을 사용해서 시간 규모를 추정할 때 광도곡선의 분량이 충분한지를 감안하면, 완화시간이 짧은 대상들에 대해서는 변광 폭과 완화시간이 음의 상관관계를 보인다고도 볼 수 있다. 대상의 개수가 통계적으로 유의미한 결과를 제시하기에는 부족하다. X선 광도와 변광 특성을 비교했을 때에는 상관관계를 찾아보기 어려웠으나, 앞으로 얻어질 X선 탐사자료와 전천 스펙트럼 탐사자료와 결합한 추가 연구가 기대된다. 전체 대상 중에서는 시간에 따라 (W1-W2) 색이 변하는 것으로 판단되는 흥미로운 대상이 4개가 존재했는데, 이들의 특성에 대해서는 추후 연구가 더 필요할 것으로 전망한다.