• 한국해양학회지
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• 제6권2호
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• pp.63-77
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• 1971

An year-long survey of chemical water quality for Lake Eui-am in Kang-won Province, Korea, was conducted from June 1970 to May 1971 to study the water quality and seasonal variations of productivities in relation to selected physical and chemical environmental factors. A monthly series of water samples were taken at the deepest basin of 18m depth of the lake. Water quality parameters determined were water temperature, Secchi disc reading(transparency), pH, O$\_$2/, CO$\_$2/, alkalinity, acidity, Cl, hardness, Ca, Mg, total residue, total ignitious residue, COD, BOD$\_$5/, nutrients, total-Fe, soluble Fe, Mn and Cu. On the whole, the results indicate that the chemical water quality of Lake Eui-am is high, and vary with season. The lake water is characterized that higher levels of dissolved oxygen(8.6 ml/L in mean of whole water) or percent saturation of dissolved oxygen(114%), and of nitrate nitrogen (523 $\mu\textrm{g}$/L). On the other hand, CO$\_$2/(9.6ppm), chlorides(3.5ppm), Ca(7.7ppm) Mg(2.2ppm), hardness(28.5ppm), silica(2.4ppm) and BOD$\_$5/(1.08ppm) are quite low. In terms of nutrient levels, the lake water exhibit slight signs of eutrophication. The high values for nitrate nitrogen, soluble iron and Cu of the lake water suggest that there are some imputs such as domestic and industrial discharges to the lake.

• 대한소아치과학회지
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• 제48권3호
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• pp.344-351
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• 2021

이 연구의 목적은 타이타늄-질소 코팅된 금속관(TiNCs)의 표면 경도와 스테인리스 스틸 금속관(SSCs)의 표면 경도를 비교하고, TiNCs의 부식 저항성 및 물리적 자극에 대한 금색 코팅의 안정성을 평가하는 것이다. 표면 경도 시험을 위해 10개의 TiNCs와 10개의 SSCs를 사용하였다. 각 금속관 종류당 총 30번의 경도를 측정하여 평균값을 구하고 비교하였다. 부식 저항성 시험을 위해 직사각형 형태의 TiNC와 SSC의 원재료(금속관으로 가공되기 전 판상 형태)를 준비하였다. 각 금속관 종류 당 2회의 부식 시험을 시행하였다. 부식 용액에 용출된 금속 이온의 총 양을 유도결합 플라즈마 분광분석기로 측정하였다. 5개의 TiNCs로 반복적으로 가해지는 칫솔력에 대한 색조 안정성 시험을 시행하였다. TiNCs의 평균 경도는 SSCs의 평균 경도보다 유의미하게 높았다. TiNCs와 SSCs의 원재료로부터 용출된 금속 이온의 총 합은 ISO 22674(재료의 무결성에 관한 기준) 기준치를 넘지 않음을 확인했다. TiNCs의 금색 코팅은 반복적인 물리적 자극에 대하여 주어진 시간 동안 안정성을 가졌다.

• 한국식품영양학회지
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• 제10권3호
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• pp.287-294
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• 1997

When bread making, the condition of thawing-fermentation for frozen dough were tested in variable temperature, and measured thawing-fermentation time and volume of frozen dough. L-Ascorbic acid (L-Aa) was added in frozen dough for the comparison test of develop volume in bread staling degree of baking bread were measured additive frozen dough which was stoppages in freezing, staling degrees were tested hardness with Rheometer. The test for comparison of thawing-fermentation time in variable temperature was shown the condition of dough conditioner at 3$0^{\circ}C$ was most effective for bread making, Because That condition was required very short time(74 min) But, in this comparison of volume in final products was shown the products in the condition of thawing-fermentation at 3$0^{\circ}C$ was smaller than the products at 5$^{\circ}C$(418 ml). The baking volume of L-Aa additive frozen dough which has under gone thawing-fermentation at 3$0^{\circ}C$, were shown baking volume of 420 ml in 2 weeks storage terms to 100 mg/kg L-Aa additive dough and shown baking volume of 454 ml in 4 weeks storage terms to dough of 200 mg/kg additive weight. Staling degrees of L-Aa additive frozen bread were measured with Rheometer. The hardness of 100 mg/kg L-Aa additive frozen bread was sown low level hardness in 1~2 weeks freezing term, 150 mg/kg L-Aa additive frozen bread was shown low level hardness in 3 weeks freezing term. In 4 weeks freezing term, 200 mg/kg L-Aa additive frozen bread was shown low level hardness compared with non-additive L-Aa frozen bread. In comparison of frozen bread quality, non-additive L-Aa products was better than additive L-Aa products in equality of baking shape and external apparence. But in total quality in external and internal apparence, additive L-Aa products was better than non-additive L-Aa products.

• The Journal of Advanced Prosthodontics
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• 제16권2호
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• pp.115-125
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• 2024

PURPOSE. The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials. MATERIALS AND METHODS. A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05). RESULTS. The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE₀₀ value were observed in PMMA resin for all materials (P < .05). CONCLUSION. 3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.

• 한국식품과학회지
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• 제54권2호
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• pp.141-146
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• 2022

본 연구는 생리활성물질이 풍부한 아로니아를 활용하여 가공식품 개발에 필요한 기초 연구 데이터를 제공하기 위해 아로니아와 설탕의 배합비율별 프리저브 잼을 제조한 뒤 그 품질 특성과 항산화 활성을 조사하였다. 배합비율에 따라 아로니아의 함량이 낮아질수록 당도는 높아졌으며 수분함량은 낮아지는 경향을 나타내었다. 강도와 최대응력은 아로니아 함량이 줄어들고 설탕의 함량이 증가할수록 높은 값을 나타내었다. 잼의 비율별 항산화 활성은 아로니아 함량 70%에서 DPPH radical 저해율이 가장 높았다. 총 페놀 함량, TEAC, FRAP, ORAC의 값은 모두 아로니아 함량에 따라 비례적으로 증가하는 경향을 나타내었다. 관능평가에서 단맛과 식감이 모두 강하다고 평가된 아로니아 함량 30%에서는 오히려 종합적 선호도에서 가장 낮게 나타났으며 아로니아 함량 40%에서 가장 높은 선호도를 나타내었다. 본 연구에서는 아로니아와 설탕 배합비율에 따른 품질 특성과 항산화 연구를 진행하였으며 국산 아로니아를 활용한 제품의 개발에 기초 자료로서 활용될 것으로 기대된다.

• 한국산학기술학회논문지
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• 제18권10호
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• pp.1-7
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• 2017

본 논문에서는 자동차에서 사용되는 부품 중 Sway bar link에 사용되는 볼 스터드의 고주파 열처리 시 고주파 열처리 코일과의 사이 간극에 따른 고주파 열처리 특성에 관하여 연구하였다. 오늘날 세계 완성차 업체는 소비자의 요구와 각 국가의 환경정책에 따라 연비향상 및 배기가스 감축함과 동시에 고성능의 자동차를 개발하기 위하여 많은 연구를 하고 있다. 그러나 고주파 열처리에 대한 대부분의 연구가 실험적으로 이루어지고 있어 특정 제품에 맞는 열처리 조건을 구하기가 매우 어렵다. 이러한 문제로 인하여 본 연구에서는 고주파 열처리 조건 중 고주파 열처리 코일과 피가열물 사이 간극을 제외한 모든 조건은 동일하게 유지하여 열처리를 하고, 표면경도와 유효경화깊이 및 전경화깊이를 측정하여 최적의 고주파 열처리 코일과 피가열물 사이 간극은 1~2 mm 임을 알아내었다. 또한 고주파 열처리 코일과 피가열물 사이 간극이 3 mm 이상일 때는 유효경화깊이 및 전경화깊이의 기준 값을 만족하지 못하였다.

• 한국식품과학회지
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• 제21권5호
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• pp.613-618
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• 1989

한국산 미곡 통일계 및 일반계 품종들의 미질특성을 구명하기 위하여 1985년에 3개 작물시험장(수원작물시험장, 영남작물시험장 및 호남작물시험장)에서 생산된 통일계 13품종과 일반계 10품종을 재료로 하여 백미의 취반특성 및 밥의 texture 특성을 조사하였다. 취반특성 중 흡수율 및 취반시 사용한 용액 중 용출고형물은 각각 $p<2.172^*$ 및 $p<2.419^*$로 계통간에 유의차를 보였는데 흡수율은 일반계가 통일계보다 높았으며, 용출고형물은 통일계가 일반계보다 높았다. 밥의 texture 특성에서 hardness와 cohesiveness는 $p<4.370^{***}$ 및 $p<2.371^*$로 계통간에 유의성이 인정되었으며, hardness는 일반계가, cohesiveness는 통일계가 높았다. Amylose 함량과 adhesiveness 사이에는 통일계에서 $r=-0.922^{**}$ 일반계에서 $r=-0.915^{**}$으로 역상관을 이루었으며, 단백질 함량과 hardness 사이에는 통일계에서 $r=0.954^{**}$, 일반계에서 $r=0.915^{**}$로 정상관을 이루었다.

• 한국재료학회지
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• 제22권1호
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• pp.16-23
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• 2012

Research into the development of high strength (1 GPa) and superior formability, such as total elongation (10%), and stretch-flangeability (50%) in hot-rolled steel was conducted with a thermomechanically controlled hot-rolling process. To improve the overall mechanical properties simultaneously, low-carbon steel using precipitation hardening of Ti-Nb-V multimicroalloying elements was employed. And, ideal microstructural characteristics for the realization of balanced mechanical properties were determined using SEM, EBSD, and TEM analyses. The developed steel, 0.06C-2.0Mn-0.5Cr-0.2(Ti + Nb + V), consisted of ferrite as the matrix phase and second phase of granular bainite with fine carbides (20-50 nm) in both phases. The significant factor of the microstructural characteristics that affect stretch-flangeability was found to be the microstructural homogeneity. The microstructural homogeneity, manifest in such characteristics as low localization of plastic strain and internally stored energy, was identified by grain average misorientation method, analyzed by electron backscattered diffraction (EBSD) and hardness deviation between the phases. In summar, a hot-rolled steel having a composition 0.06C-2.0Mn-0.5Cr-0.2(Ti + Nb + V) demonstrated a tensile strength of 998 MPa, a total elongation of 19%, and a hole expansion ratio of 65%. The most important factors to satisfy the mechanical property were the presence of fine carbides and the microstructural homogeneity, which provided low hardness deviation between the phases.

• 한국식품영양학회지
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• 제27권4호
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• pp.742-750
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• 2014

This study was done in order to investigate the changes in quality of Cheonggukjang for soybean cultivars during fermentation. Cheonggukjang of 14 cultivars that were inoculated with Bacillus subtilis 15893 was produced, and, then, it was measured for hardness, proximate composition, amino nitrogen, enzyme activity, and total aerobic bacteria counts. In a raw bean, the highest hardness value was 16,975 g from Sunyu. In a steaming bean, Jangwon had the highest hardness value and the lowest aerobic bacteria counts of forty-eight hours fermented Cheonggukjang. Saedanbaek, whose protein contents was highest in raw bean, was also highest in Cheonggukjang. The amino nitrogen content of twenty-four hours fermented Cheonggukjang was highest in Saeol and Sunyu while forty-eight hours fermented Cheonggukjang was highest in Singi, Daol, and Milyang 231. In the protease activity, Saedanbaek had the highest and total aerobic bacteria count that were either increased or held as time went on ; twenty-four hours fermented Cheonggukjang was highest in Milyang 231 and Keunol while forty-eight hours fermented Cheonggukjang was highest in Chunsang.

• 한국세라믹학회지
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• 제50권1호
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• pp.43-49
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• 2013

${\beta}$-SiC was deposited onto a graphite substrate by a LPCVD method and the effect of the crystallographic orientation on mechanical properties of the deposited SiC was investigated. The deposition was performed at $1300^{\circ}C$ in a cylindrical hot-wall LPCVD system by varying the deposition pressure and total flow rate. The texture and crystallographic orientation of the SiC were evaluated by XRD. The deposition rate increased linearly with the gas flow rate from 800 sccm to 1600 sccm. It also increased with the pressure but became saturated above a total pressure of 3.3 kPa. In the range of 3.3 - 10 kPa, the preferred orientation changed from the (220) and (311) planes to the (111) plane. The hardness and elastic modulus showed maximum values when the SiC had the (111) preferred orientation, though it gradually decreased upon a change to the (220) and (311) preferred orientations.