• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.154-159
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• 1998

In order to assess the susceptibility of the environmentally assisted cracking(EAC) on SA508 Cl.3 steel in primary water condition, potential step test and slow strain rate test(SSRT) were conducted in a simulated crack tip condition. In this test, anodic dissolution was dominant in the crack tip environments. Proposed simple dissolution model is a modification of Hishida's anodic dissolution model at the plastic zone. One can predict actual crack growth rate with the smooth specimen through this model.

• 한국의류학회지
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• 제23권6호
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• pp.800-808
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• 1999

The demand for PU coated synthetic leather is increasing as a high fashion material. But it has some faults of water vapor permeability surface tacky property and static electricity. Therefore the purpose of this study was the produce of PU coated fabric added collagen with hydrophilic property and soft touch. In the PU coated fabric water vapor permeability water vaper absorption and frictional electronic voltage were investigated surface bending and compression properties were also examined by the use of KES-FB System. The followings were the results of this study. 1. There was no Cr in the collagen so that Cr was not treated in the collagen. 2. The surface and cross sectional layer of PU coated fabric with collagen were highly developed by micro porous structure. 3. The water vapor permeability of PU coated fabric was increased as collagen concentration increased. 4. The water vapor absorption of PU coated fabric was increased as collagen concentration increased. 5. The frictional electronic voltage of PU coated fabric was decreased in accordance with the increase of collagen concentration. Especially it effectively decreased by the use of only 5% collagen concentration. 6,. The bending and compression properties of PU coated fabric were increased in accordance with the increase of collagen concentration so that it became stiff. 7. The Value of MIU, SMD was decreased in accordance with the increase of collagen concentration so that the PU coated fabric became smooth.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.92.2-93
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• 2003

Severe soybean-sprout rot was found at the mass productive factory in 2000 and 2001 and it caused 10-20％ loss of the production. Pythium sp. was isolated almost 90％ by potato dextrose agar from rotted root and hypocotylsof the sprouts. And the pathogencity tests using test tubes with 2％ water agar and small containers (30 ${\times}$ 30 ${\times}$ 50 cm, WxLxH) cultivation were shown a similar rot on roots and hypocotyls. The fungal mycelium grew rapidly on the water agar and it prevented the seed germination. Density of the Pythium sp. in the recycled water system at the factory was periodically measured using a selective medium, corn meal agar with Pimaricin 10 mg, Rifampicin 10 mg, Ampicillin 100 mg per 1 liter in order to check the contamination of recycled water. After fitering step using 5 and 1 ml in the recycled system was applied and it was effectively controlled Pythium rot. The daily yield of sprout was stable and the occurrenceof Pythium in the recycled water was much less after filtering. The fungal isolates were identified as Pythium deliense Meurs based on various mycological characteristics on corn meal agar and sucrose-asparagine bentgrass leaf culture medium. P. deliens oogonia were spherical, smooth, 19-23 urn in diameter, and their stalk bending toward antheridia. Antheridia were straw hat-shaped, curred club-shaped, therminal or intercalary, monoclinous, occasionally diclinous, 12∼15 ${\times}$ 8∼11 um, 1(∼2) per oogonium.

• 설비공학논문집
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• 제27권5호
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• pp.233-240
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• 2015

This paper discusses compressors operating number control strategy using cooperative logic to cope with variable partial load for high efficiency of a centrifugal water chiller. The cooperative logic is composed of a speed-up and speed-down controller, enabling smooth operation of compressors and equivalent distribution of thermal load in each compressor. This centrifugal water chiller design can be operated with high efficiency without incurring excessive energy waste and large transient phenomena at partial load states. Simulations in MATLAB and experiments in a real chiller system were conducted and verified the high efficiency control of a centrifugal water chiller achieved by the suggested strategy.

• 한국식품위생안전성학회지
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• 제14권3호
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• pp.227-232
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• 1999

세균오염지표인 대장균군의 균종별 분포를 조사함으로써 세균학적 의미를 조사하고자 본 실험을 실시하였다. 1997년 6-7월에 서울시 보건환경 연구원에 의뢰된 옹달샘 시료와 지하수 시료를 실험에 사용하였고, 옹달샘 유래 대장균군 112주와 지하수 유래 대장균군 24주를 IMViC test와 API 20E kit(BioMeriux)를 사용하여 균 분리 동정한 후 합계 136균주를 대상으로 실험하였다. 대장균군을 분리 동정한 결과 23균종이 분리되었으며, 균종별로는 Esherichia 속균 39주(28.6%), Klebsiella 속균 32주(23.5%), Enterobacter 속균 30주(22.1%), Serratia 속균 19주(14.0%), Citrobacter 속균 6주(4.4%), Kluyvera 속균 4주*3.0%) 그리고 기타 6주 (4.4%)로 나타났다. 분리 균주들의 EMB agar상의 집락 색상은 녹색 금속 광택 50.7%, 분홍색 44.2%, 자주색 5.1%로 나타났고, 형태는 smooth colony 64.7%, mucoid colony 34.6%, rough colony 0.7%로 각각 나타났다. 생화학적 시험결과 lactose broth 에서는 가스를 생성하였으나 KIA에서는 gas를 생성치 않은 균종이 Ent. intermedium, Ser. liquefaciencs, Ser. marcescenes 그리고 Sal. arizoae이었고, H2S를 생성한 대장균군으로는 Kleb. pneumoniae, Kleb. oxytoca, Kleb. ornithinolytica, Ent. sakasakii, Ent. cloacae, Ser. Liquefaciens, Ser. ficaria, Cit. freundii 그리고 Sal. arizoae이었다. 이상의 결과 대장균군 정성시험 양성을 나타내는 대장균군은 대부분이 E. coli, Klebsilla 속균 그리고 Enterobacter 속균이었다. 또한 향후 대장균군 정성시험 시 EMB agar 상에서 녹색 금석성 광택 집락 외에도 분홍색 집락이 주의시되어지며, rough colony는 대장균군 분리에서 제외되는 것이 좋을 것으로 사료된다. 한편, 생화학적 성상 검토 결과 새로운 형태의 대장균군 출현 가능성이 있을 것으로 전망된다.

• 대한기계학회논문집B
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• 제40권5호
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• pp.275-281
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• 2016

본 연구에서는 비등표면 위에 다공판을 설치하여 풀비등을 촉진시키는 방안에 대하여 검토하였다. 실험은 대기압에서 R-123을 사용하여 수행되었다. 다공판은 풀비등을 현저히 촉진시켰다. 이는 다공판이 기포를 비등표면 위에 넓게 퍼뜨려 기포와 비등표면 사이 액막의 면적을 증가시키기 때문이다. 또한 높은 열유속에서는 다공도가 클수록, 낮은 열유속에서는 다공도가 작을수록 비등이 촉진되었다. 본 연구에서는 구멍 직경 2.0 mm, 구멍 간격 $2.5mm{\times}5.0mm$ 또는 $5.0mm{\times}5.0mm$, 비등 표면과의 간격 0.5 mm에서 최적 형상이 얻어졌고 이 형상들의 열전달계수는 상용 GEWA-T의 값에 근접하였다. R-123에서의 최적 다공도는 물이나 에탄올에서 보다 현저히 큰데 이는 R-123의 밀도비가 크고 증발잠열은 작기 때문이다. 한편 다공판의 비등이력은 평판보다 작았다.

• 한국콘텐츠학회논문지
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• 제16권4호
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• pp.614-623
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• 2016

스마트워터그리드의 중요한 요소기술로써 그리드(관망)의 설계는 압력, 마찰계수, 마찰속도, 수두손실, 그리고 에너지 경사와 같은 수리학적 매개변수를 추정하는 것이 필수적이다. 특히, 그리드의 마찰속도는 에너지 경사, 마찰계수, 압력, 수두손실 등의 결합에 있어 매우 중요한 인자이다. 그러나 마찰 수두손실, 마찰속도 등 마찰인자를 정확히 산정하는 것은 매우 어려우며, 경험적 마찰 인자는 여전히 약 100년 전에 개발된 공식과 이론을 사용함으로써 산정된다. 따라서, 본 논문에서는 최대유속과 마찰속도 사이의 새로운 공식을 Darcy-Weisbach의 마찰수두 손실공식과 Schlichting 공식 사이의 적분관계 및 회귀분석을 통하여 개발하였다. 개발된 공식을 증명하기 위하여 매끄러운 관 자료가 사용되었으며 제안한 공식은 관측 자료와 비교하여 높은 정확성을 보여준다. 이 연구의 결과는 안정성 향상과 그리드 설계에 사용이 가능할 것으로 판단된다.

• 대한의용생체공학회:의공학회지
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• 제29권1호
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• pp.52-58
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• 2008

The object of this study is to investigate the effects of intermittent cyclic stretching on the smooth muscle cells (SMCs) seeded onto aligned multi-layered fibrous scaffold. To make multi-layered fibrous scaffold, polyurethane (PU) and poly(ethylene oxide) (PEO) were electrospun alternatively, then were immersed into distilled water to extract PEO. Various types of scaffolds were fabricated depending on fiber directions, i.e., aligned or randomly oriented. The direction of stretching was either parallel or vertical to the fiber direction for the aligned scaffolds. The stretching was also applied to the randomly aligned scaffolds. The duration of stretching was 2 min with 15 min resting period. During the stretching, the maximum and minimum strain was adjusted to be 10 and 7%, respectively with the frequency of 1 Hz. The bioactivities of cells on the scaffolds were assessed by quantifying DNA, collagen, and glycosaminoglycan (GAG) levels. And the cell morphology was observed by staining F-actin. SMCs under parallel stretching to the fiber direction responded more positively than those in other conditions. From the results, we could explain the morphological effect of a substrate on cellular activities. In addition the synergistic effects of substrate and mechanical stimuli effects were confirmed.

• 대한약침학회지
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• 제25권3호
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• pp.209-215
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• 2022

Objectives: Aqueous leaf extract of Tridax procumbens (ALETP) has potent relaxant activity. However, this relaxant activity in respiratory smooth muscle remains uninvestigated. This study investigates the effect of ALETP on the contractile activity of tracheal smooth muscle (TSM) in adult male Wistar rats. Methods: Twelve male Wistar rats divided into 2 groups and were treated with either 100 mg/kg of ALETP (ALETP treatment group) or vehicle (distilled water; control group) through oral gavage for 4 weeks. Dose responses of TSM from the 2 groups to acetylcholine (10^-9 to 10^-5 M), phenylephrine (10^-9 to 10^-5 M), and potassium chloride (KCl; 10^-9 to 10^-4 M) were determined cumulatively. Furthermore, cumulative dose responses to acetylcholine (10^-9 to 10^-5 M) after pre-incubation of TSM with atropine (10^-5 M), L-NAME (10^-4 M), indomethacin (10^-4 M), and nifedipine (10^-4 M), were determined. Results: Treatment with ALETP substantially inhibited TSM contraction stimulated by cumulative doses of acetylcholine, phenylephrine, and KCl. Furthermore, preincubation of TSM from the 2 groups in atropine significantly inhibited contractility in TSM. Incubation in L-NAME and indomethacin also significantly inhibited contractility in TSM of ALETP-treated rats compared to that of controls. Contractile activity of the TSM was also inhibited significantly with incubation in nifedipine in ALETP-treated rats. Conclusion: ALETP enhanced relaxant activity in rat TSM primarily by blocking the L-type calcium channel and promoting endothelial nitric oxide release. ALETP contains agents that may be useful in disorders of the respiratory tract.

• Spatial Information Research
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• 제10권3호
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• pp.439-453
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• 2002

수자원분야에서 DEM을 활용한 연구들이 활발히 진행되고 있으며, 특히 지형 및 수문분석의 기초가 되는 유역과 하천 추출은 GIS 분석에서 일반화되어 있다. 그러나 경사가 완만한 지형에서는 가늘고 긴 슬리버 폴리곤 형태의 유역이나 직선형태의 하천이 추출되므로, 활용측면에서 비 효율적이다 본 연구에서는 완경사지역에서 발생하는 비정상적인 유역과 하천을 효과적으로 추출하기 위해, 하천을 중심으로 완충구간을 설정한 후 점진적인 표고변화를 적용하였다. 특히 점진적인 표고변화를 부여하기 위해 보로노이 다이어그램(Voronoi Diagram)을 활용한 등거리 할당모형을 적용하였다. 또한 추출한 하천인식 DEM과 원시 DEM을 이용하여 유역 및 하천을 추출한 후, 완경사 지역에서의 유역 및 하천의 형태를 상호 비교함으로서 본 연구의 효용성을 평가하였다.