• 폴리머
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• 제30권3호
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• pp.271-278
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• 2006

어랙틱 폴리(비닐 알코올)(PVA) 수용액 시스템의 준희박농도에서의 고분자 사슬의 구조 및 거동을 살펴보기 위하여, 온도 $25^{\circ}C$에서 광산란 실험을 실시하였다. 산란 벡터 q에서 얻은 산란광의 세기 I(q)는 Onstein-Zernike 식으로 해석이 불가능하여 단순히 $I(q){\sim}q^{-m}$을 이용하여 fractal 차원 m을 얻었다. 그 결과 농도 3 wt% 이상에서는 $m=2.6{\pm}0.3$으로 일정하게 유지되었다. 동적 광산란으로 얻은 시간상관함수에는 항상 빠른 거동과 느린 거동의 두 종류가 공존하였으며, 빠른 거동의 협동확산계수는 reptation 이론의 농도의존지수 값(=3/4)과 달리 농도 의존성이 거의 나타나지 않았다. 또한 느린 거동은 거대한 크기의 불균일 영역대의 운동으로 해석되며, 이 거동의 농도지수는 -3.0으로써 매우 강한 농도 의존성을 보여 주었다. 이 불균일 영역대의 형성에는 어택틱 PVA의 -OH기 4개의 메소(meso)가 입체 규칙적으로 배향한 부분이 매우 중요한 역할을 하는 것으로 생각되어진다.

• 한국물환경학회지
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• 제32권3호
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• pp.271-280
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• 2016

The aim of this study was to analyze spatial and temporal patterns of bacterial pollution levels and the relationship between bacterial pollutants and environmental parameters at the main stream and tributaries of Nakdong River. Water quality data including total coliform and fecal coliform were compiled from a total of 50 monitoring sites (30 at the main stream and 20 at the tributaries) along with rainfall and discharge data for three consecutive years from 2012 to 2014. During the study periods, the geometric mean values of total coliforms and fecal coliforms in the main stream were 74 (22~465) CFU/100 mL and 8 (3~42) CFU/100 mL, respectively. The geometric mean values of total coliforms and fecal coliforms in the tributaries were 275 (36~5,145) CFU/100 mL and 6 (1~1,352) CFU/100 mL, respectively. High concentrations of fecal coliforms were observed at Gumi (M 10), Hyeonpung (M 19), Hapcheon (M 23), and Namji (M 25) in the main stream, whereas Gamcheon (T 6), Bakcheon (T 7), Geumho-gang (T 8), and Gyeseongcheon (T 16) were identified as pollution hot spots in the tributaries. Although bacterial pollution levels showed complex behavior across monitoring sites and time, the highest coliform concentrations were routinely observed in the monsoon season between July and September of each year, indicating that the pollution levels were strongly dependent on precipitation in addition to other physiochemical parameters. Statistically significant correlations were found between fecal coliform concentrations and precipitation (r=0.403, p<0.01), followed by SS (r=0.425, p<0.01), nutrient TP (r=0.388, p<0.01), organic matter COD (r=0.322, p<0.01), and PO₄-P (r=0.317, p<0.01) in the main stream in the order of correlation coefficient from high to low.

• 한국지반공학회논문집
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• 제19권6호
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• pp.261-271
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• 2003

본 연구에서는 다단계 하중 Falling Weight Deflectometer를 사용하여 도로기초의 상태를 평가하는 방법을 제시하였다. 응력의존 재료모델을 포함한 동적 유한요소법을 활용하여 가상의 처짐과 응력/변형률 데이터베이스를 구축하였다. 이러한 가상의 데이터베이스를 바탕으로 표면처짐 및 보조기층 또는 노상의 중요한 위치에서 발생하는 응력/변형률과의 관계를 제시하였다. 미국의 LTPP와 노스캐롤라이나 주도로국에서 실시한 FWD 처짐값, 동적관입시험 결과, 그리고 반복하중 탄성계수시험을 활용하여 평가방법을 개발하였다. 특히 본 연구는 FWD 하중크기가 상태평가 방법에 미치는 영향에 대하여 연구의 초점을 맞추었다. 연구결과, 구조적으로 수정된 보조기층 손상지수와 보조기층 곡률지수가 각각 보조기층과 노상토의 강성도 특성을 예측할 수 있는 좋은 인자들로 판단되었다. 66.7kN 또는 그 보다 작은 하중은 예측의 정밀도를 높이는데 부족하였다. 도로기초의 비선형 거동에 대한 연구결과, 다단계 하중으로부터 발생하는 처짐비는 도로기초 재료의 종류와 상태를 판단할 수 있었다.

• Asian Pacific Journal of Cancer Prevention
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• 제15권4호
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• pp.1711-1714
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• 2014

Objective: To explore the effect of Withaferin A on A549 cellular proliferation and apoptosis in non-small cell lung cancer (NSCLC). Materials and Methods: NSCLC cell line A549 was selected to explore the effect of Withaferin A on A549 cellular proliferation, apoptosis and the PI3K/Akt signal pathway capable of regulating tumor biological behavior by assessment of cellular proliferation, cellular apoptotic rates and cellular cycling as well as by immuno-blotting. Results: Withaferin A could inhibit A549 cellular proliferation and the control rate was dosage-dependent (P<0.05), which also increased time-dependently with the same dosage of Withaferin A (P<0.05). The apoptotic indexes in A549 cells treated with 0, 2.5, 5.0, 10.0 and 20.0 ${\mu}mol{\cdot}L^{-1}$ Withaferin A for 48 h were significantly different (P<0.05). In addition, the apoptotic rates of each group in both early and advanced stages were higher than those in 0 ${\mu}mol{\cdot}L^{-1}$ (P<0.05), which were evidently higher after 48 h than those after 24 h (P<0.05). A549 cells treated by Withaferin A for 48 h were markedly lower in Bcl-2 level and obviously higher in Bax and cleaved caspase-3 levels than those treated by 0 ${\mu}mol{\cdot}L^{-1}$ Withaferin A (P<0.05), and there were significant differences among 5, 10 and 20 ${\mu}mol{\cdot}L^{-1}$ Withaferin A (P<0.05). The ratios of A549 cells treated by Withaferin A for 48 h in G0/G1 stage were higher than those in 0 ${\mu}mol{\cdot}L^{-1}$, while those in S and G2/M stages were obviously lower than those in G2/M stage, and there were significant differences in 5.0, 10.0 and 20.0 ${\mu}mol{\cdot}L^{-1}$ Withaferin A (P<0.05). Additionally, p-Akt/Akt values were in reverse association with dosage, and the differences were significant (P<0.05). Conclusion: Withaferin A can inhibit the proliferation and apoptosis of A549 cells by suppressing activation of the PI3K/Akt pathways.

• 대한두경부종양학회지
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• 제14권1호
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• pp.40-45
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• 1998

Backgroud and Objectives: Major salivary gland tumor is a rare disease with a largely unknown origin. And also corresponding to the diversity of histopathologic characteristics is an equally wide distribution of clinical behavior that makes treatment decisions difficult. The aim of this study is to analysis the clinical experience of our major salivary gland tumor and to suggest a guidline of management. Materials and Methods : We studied clinical manifestations and treatment results of 104 patients who were diagnosed as major salivary gland tumors. Tumor site, patient age and sex of the patients were analysed. Histopathologic diagnosis, treatment modality, lymph nodes metastasis, recurrence rate and 5-year survival rate were studied on malignant tumors. Results: 1) 48 patients were male and 56 patients were female. 2) Benign tumors were 79 cases. They consisted of 57 cases(72%) of parotid tumor, 22 cases(27%) of submandibular tumor. And pleomorphic adenoma was the most common benign tumor. 3) Malignant tumors were 25 cases and were consisted of 19 cases(76%) of parotid tumor, 4 cases(l6%) of submandibular tumor and 2 cases(8%) of sublingual gland tumor with high-grade mucoepidermoid carcinoma as the most common cause. 4) In the malignant tumors, the number of stage I, II tumors was 14 and that of stage III, IV tumors was 11. Neck node metastasis was noted in 8 cases. 5) 8 cases of malignant tumor were died and all of them had high-grade malignancy. And they were dead before 17 months from the time of diagnosis. 6) Mean survival duration in the malignant salivary gland tumor was 56 months. 7) High-grade malignancy had a 5-year survival rate of 57.9%. A 5-year survival rate of TI, T2 patients was 92.9% and that of T3, T4 patients was 36.4%. That of patients who had neck node metastasis was 37.5% and that of those who had tree neck was 82.4%. Conclusion: The results of this study suggest that the survival rate is dependent on the tumor size, lymph node matastasis and histologic grade. And also the early diagnosis and radical surgery result in the increased survival rate and are effective for prevention of the tumor recurrance.

• 한국강구조학회 논문집
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• 제9권3호통권32호
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• pp.421-430
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• 1997

본 연구에서는 숏브라스트한 후 무기징크 페인트로 도장한 무기징크면, 연마면, 흑피면에 대하여 정적 및 피로시험을 수행하여 기존의 연구결과와 비교평가함으로써 마찰면의 표면상태에 따른 고장력볼트 마찰이음부의 정적 및 피로거동을 규명하고자 하였다. 본 연구의 목적을 달성하기 위하여 일련의 정적 및 피로시험을 실시하고 토크관리법의 타당성 평가, 미끄러짐계수의 도출, 도입축력의 감소률 규명, 피로강도의 평가, 마찰면의 압축력 분포 조사 등을 수행하였다. 본 실험결과와 기존 연구자들의 연구결과를 종합적으로 검토한 결과 볼트의 설계축력 도입을 위한 토크관리법은 타당하며, 시간경과 및 반복하중의 작용에 따른 축력감소율을 고려할 때 설계축력의 110%로 초기축력을 도입하도록 규정한 시방서 기준은 적합한 것으로 평가되었다. 시간경과에 따른 도입축력의 초기감소율은 경과시간의 상용로그에 비례하는 것으로 나타났으며, 도입직후 약 20시간이 경과하면 일정한 값으로 수렴되고 있음을 알 수 있었고 이들은 마찰면의 표면조도와는 상관관계가 없는 것으로 평가되었다. 미끄러짐계수는 연마면, 무기징크프라이머 도포면, 흑피면 순으로 크게 나타났으며 미끄러짐하중은 도입축력에 크게 좌우되나 도입축력이 크면 마찰면의 표면조도의 손상으로 인하여 미끄러짐계수가 작아져 도입축력과 미끄러짐하중 사이에는 선형적 비례관계가 성립되지 않음을 알 수 있었다. 마찰면의 압축력 분포를 조사한 결과 내측볼트 주변의 마찰면적이 외측볼트 주변보다 응력방향에 있어서 더 넓게 분포하고 있는 것을 알 수 있었으며, 이는 외측볼트로부터 마찰접합에서 지압접합으로 천이되고 있는 것으로 판단된다.

• 한국지반공학회논문집
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• 제20권7호
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• pp.57-68
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• 2004

연약점토지반에 성토 등의 상재하중을 재하하게 되면 측방유동이라고 하는 측방변위가 발생하게 된다. 이 측방유동은 파일기초의 변형, 교대의 이동, 지중매설관의 파괴 등 성토에 인접한 지중구조물에 피해를 가하게 된다. 그렇지만, 측방유동은 체적변형과 전단변형도 동시에 발생할 뿐만 아니라 이 측방유동에 영향을 미치는 인자가 많기 때문에 측방유동에 의해서 발생하는 측방토압의 발생 메커니즘이 아직 명확히 밝혀지지 않았다. 그리고 최근 근접시공 등 기존구조물에 근접해서 공사가 진행되는 경우가 많아 이러한 근접구조물에 어떠한 피해를 가할 것인가 또는 대책공법을 설계하기 위한 설계하중으로서 측방토압을 구해야 하는 필요성이 커지고 있는 것 또한 현실이다. 그러므로 본 연구에서는 성토에 의해서 연약지반에 발생하는 측방토압에 미치는 재하속도의 영향을 조사하기 위해서 실내모형실험을 실시하였다. 그 결과, 측방토압이 삼각형 분포를 이룬다는 것과 재하속도가 빠를수록 측방토압의 최대치가 커지고 부등침하가 커진다는 것을 알 수 있었다. 그리고 이러한 재하속도의 영향은 부의 dilatancy에 의한 과잉간극수압의 발생에 기인한다는 것을 알았다.

• 대한치과보철학회지
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• 제28권1호
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• pp.165-191
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• 1990

Although a number of studies have been performed to assure that residual stress caused by a mismatch of alloy porcelain thermal expansion can contribute to clinical failure of a ceramometal restoration, the interactive influence of cooling rate on the magnitude of thermal expansion difference and on bond strength between them have not been extensively analyzed. The objective of this study was to determine the influence of cooling rate and the number of firing cycles on the expansion mismatch and the flexural failure resistance of metal porcelain strip. Tested alloys included one Pd-Ag alloy, one Ni-Cr-Be alloy with two kinds of porcelain, Vita and Ceramco. Metal specimens were cast into rods with a height of 13mm and a diameter of 5mm. Subsequently, the castings were subjected to scheduled firing cycles without porcelain. And the porcelain specimens after being fired were trimmed into a bar with a final dimension of $5{\times}5{\times}25mm$. Thermal expansions of the alloys and porcelains were measured by using a push rod or a differential dialometer respecitvely. Porcelain glass transition temperatures and expansion values were derived alloy-porcelain pairs were assessed by comparing expansion values of the components at a porcelain glass transition temperature. Calculations were made using combinations of a Ni-Cr alloy or Pd-Ag alloy with each of two porcelain products. Metal-porcelain strip specimens were subjected to four point loading in an Instron testing machine until crack occured at the metal-cramic interface at the time of sharp decrease of load on recorder. On the basis of this study, the following conclusions may be stated: 1. Regardless of the kinds of ceramometal combinations, both of calculated and experimental data revealed that the double fired specimens exhibited a significantly lower flexural strength. 2. By the rise of the amount of mismatch, bond strength were decreased. 3. Thermal expansion value of Pd-Ag alloys were higher than that of Ni-Cr alloys. 4. Expansion curves of metal were proportional to the increase of temperature and were not affected by the experimental conditions, however porcelains did not show the same magnitude of metal, and a shift of the glass transition temperature to higher temperatures was observed when cooled rapidly 5. Alloy-porcelain thermal compatibility appeared more dependent on the porcelain than the alloy.

• 한국치위생학회지
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• 제17권2호
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• pp.181-191
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• 2017

Objectives: The objective of the study was to investigate the use of dental hygiene devices in Korean adolescents. Methods: The study subjects were 70,362 adolescents in 800 schools who completed the 2015 Korean Youth Risk Behavior Web-based survey. Dependent variables included usage of dental floss, interdental brushes and mouthwash solutions. Independent variables included demographic characteristics of the subjects, health state and behaviors, and oral health behaviors and experience of oral diseases. Results: The related factors of usage of dental hygiene devices included gender, where females showed higher usage (OR=1.10) compared to males, father and mother's level of education where usage was higher in above university graduates (OR=1.20, OR=1.14) compared to less than high school graduation, economic status where usage was higherin high and middle (OR=1.93, OR=1.26) compared to low, vigorous physical activity where usage was higher in those who responded yes (OR=1.35) compared to no, subjective weight recognition where usage was higher in normal (OR=1.07) compared to under weight, sleep time where usage was higher in enough (OR=1.12) compared to not enough, number of toothbrushing (day) where usage was higher in 2 times or over 3 times (OR=1.35, OR=1.75) compared to below 1, oral health education experience (OR=1.10), sealant experience (OR=1.17) and scaling experience (OR=1.45) where usage was higher in those who responded yes compared to no, school where usage was lower in high school (OR=0.64) compared to middle school, residential type where usage was lower in rural area (OR=0.74) compared to metropolitan area, living form where usage was lower in other (OR=0.77), compared to with family, smoking (OR=0.93), and alcohol drinking (OR=0.90) where usage was lower in those who engage in the activities compared to those who didn't, BMI where usage was lower in normal (OR=0.87) and over weight (OR=0.98) compared to under weight. Conclusions: To expand the use of dental hygiene devices in the adolescents, it is necessary to improve the continuing education program for need and motivation of dental hygiene device usage.

• 터널과지하공간
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• 제25권6호
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• pp.568-576
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• 2015

본 연구에서는 압축공기에너지저장 설비를 운영함에 있어 위험성이 크다고 분석된 '내조시스템 파손에 따른 압축공기 유출'과 '접근갱도 내 화재 발생' 리스크를 대상으로 시나리오를 작성하여 분석을 실시하였다. Bernoulli 방정식과 운동량 방정식을 결합하여 압축공기 분출에 따른 충격력을 계산하기 위한 식을 유도하였다. 이 식을 바탕으로 시나리오를 작성하여 충격력을 계산한 결과 충격력은 균열 직경의 제곱 및 압축공기의 압력에 비례하는 것으로 나타났다. 계절의 변화 및 화원의 위치에 따른 연기 확산 거동을 분석하기 위하여 4가지의 화재 시나리오를 작성하였다. 저장 공동 벽면 근처에서 화재가 발생한 경우는 10 m 떨어진 지점에서 화재가 발생한 경우보다 연기가 호흡한계선까지 하강하는 데 소요되는 시간이 더 짧은 것으로 나타났는데 이는 연기 파선단 전파로 인해 발생한 것으로 예측된다. 갱내로의 공기 유동 방향에 따라 연기의 확산 거동이 달라지기 때문에 겨울에 화재가 발생한 경우는 여름에 발생한 경우보다 연기의 확산속도가 빠르고 더 멀리까지 연기가 퍼지는 것으로 나타났다. 피난 시뮬레이션 해석 결과 여름과 겨울 화재에서의 피난요구시간(RSET)은 각기 262, 670 s로 분석되었다.