선박사고에 영향을 주는 자연적 요인에 관한 통계 분석

The ship accidents were caused by various factors. Various factors consist of human factors and natural factors. In this paper, we focus on natural factors. The purpose of this paper is to analyze ship accidents in Busan and Incheon and analyze the effects of natural factors on ship accidents using logistic regression analysis and decision trees. The Korean Peninsula is surrounded by three different seas, and each sea has different natural factors. The data of natural factors were obtained from the Korean Maritime Safety Tribunal and the Korea Meteorological Administration. Each data of tow factors was combined. Ship accident data, general weather data, and marine weather data were refined by propensity score matching(PSM) method. We observed that significant digging, wind speed, daily precipitation, and barometric pressure affected ship accidents in Busan. Also we found that wind speed, daily precipitation, and temperature affected ship accidents in Incheon. In future studies, the factors of ship accidents should be modeled by considering the regional difference.1. 서론 1 2. 이론적 배경 2.1 선박사고의 개념 5 2.2 선박사고의 종류 6 2.3 상향점수 매칭 8 2.4 로지스틱 회귀분석 10 2.5 의사결정 나무 12 3. 연구 방법 3.1 자료수집 절차 16 3.2 자료 소개 19 4. 통계분석 결과 4.1 로지스틱 회귀분석 결과 21 4.2 의사결정 나무분석 결과 25 5. 고찰 및 결론 27 참고 문헌 29 부록 31Maste

크립톤 클로라인 엑실램프를 이용한 식품관련 표면 살균

학위논문 (석사)-- 서울대학교 대학원 농업생명과학대학 농생명공학부, 2017. 8. 강동현.This study was conducted to investigate the basic spectral properties of 222-nm krypton-chlorine (KrCl) excilamp and its inactivation efficacy against major foodborne pathogens on solid media, as well as on sliced cheese compared to conventional 254-nm low-pressure Hg (LP Hg) lamp. The KrCl excilamp showed full radiant intensity from the outset at a wide range of working temperatures, especially at low temperature around 0 to 10 °C. Selective media and sliced cheese inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated with a KrCl excilamp and a LP Hg lamp at the same dose. Irradiation with 222-nm UV-C showed significantly (P < 0.05) higher inactivation capacity against all three pathogens than 254-nm radiation on both of media and sliced cheese surfaces without generating many sublethally injured cells which potentially could recover. The underlying inactivation mechanisms of the 222-nm KrCl excilamp treatment were evaluated by fluorescent staining methods and damage to cellular membranes and intracellular enzyme inactivation were the primary factors contributing to the enhanced bactericidal effect. And this study was also conducted investigate the resistance of Escherichia coli O157:H7 to 222-nm KrCl excilamp and 254-nm LP Hg lamp treatment according to growth temperature. As growth temperature decreased, lag time of E. coli O157:H7 IV significantly increased while the growth rate significantly decreased. Regardless of growth temperature the KrCl excilamp showed higher disinfection capacity compared to the LP Hg lamp at stationary growth phase. KrCl excilamp treatment showed significantly higher reduction as growth temperature decreased. Conversely, reduction levels according to growth temperature were not significantly different when the pathogen was subjected to LP Hg lamp treatment. Inactivation mechanisms were evaluated by the thiobarbituric acid reactive substances (TBARS) assay and SYBR green assay, and confirmed that lipid oxidation capacity following KrCl excilamp treatment increased as growth temperature decreased, which was significantly higher than that of LP Hg lamp treated samples regardless of growth temperature. DNA damage level was significantly higher for LP Hg lamp treated samples compared to those subjected to the KrCl excilamp, but no significant difference pursuant to growth temperature was observed. Consequently, resistance of E. coli O157:H7 to the KrCl excilamp decreased as growth temperature decreased because the ratio of unsaturated fatty acid composition increased at low growth temperature resulting in higher lipid oxidation levels. The results of this study suggest that a 222-nm UV-C surface disinfecting system can be applied as an alternative to conventional LP Hg lamp in the surface disinfectionI. INTRODUCTION 1 II. MATERIALS AND METHODS 6 2.1. KrCl excilamp system. 6 2.2. Irradiance measurement. 9 2.3. Application of 222-nm krypton-chlorine excilamp to control foodborne pathogens on sliced cheese surfaces and mechanism of the bactericidal action. 9 2.3.1. Bacterial cultures and cell suspension 9 2.3.2. Sample preparation and inoculation 10 2.3.3. KrCl excilamp and LP Hg lamp treatment 11 2.3.4. Bactericidal mechanism 12 2.4. Susceptibility of Escherichia coli O157:H7 grown at low temperatures to the krypton-chlorine excilamp. 13 2.4.1. Growth condition and Growth curves. 13 2.4.2. Cell suspension and Inoculation. 14 2.4.3. KrCl excilamp and LP Hg lamp treatment 15 2.4.4. Bactericidal mechanism 15 2.4.5. Membrane composition. 17 2.5. Microbial enumeration 18 2.6. Statistical analysis. 20 III. RESULTS 21 3.1. Application of 222-nm krypton-chlorine excilamp to control foodborne pathogens on sliced cheese surfaces and mechanism of the bactericidal action. 21 3.1.1. Comparison of properties between 222-nm KrCl excilamp and 254-nm LP Hg lamp. 21 3.1.2. Bactericidal effect of UV irradiation on media and sliced cheese surfaces 25 3.1.3. Resuscitation of UV-injured cells 26 3.1.4. Determination of injury sites in 222-nm excilamp treated cells 30 3.2. Susceptibility of Escherichia coli O157:H7 grown at low temperatures to the krypton-chlorine excilamp. 32 3.2.1. Growth curves of E. coli O157:H7 after growing at different temperatures 32 3.2.2. Reduction of E. coli O157:H7. 36 3.2.3. Lipid oxidation and DNA damage 38 3.2.4. Membrane fatty acid composition. 41 IV. DISCUSSIONS. 43 4.1. Application of 222-nm krypton-chlorine excilamp to control foodborne pathogens on sliced cheese surfaces and mechanism of the bactericidal action. 43 4.2. Susceptibility of Escherichia coli O157:H7 grown at low temperatures to the krypton-chlorine excilamp 48 V. Conclusion 51 VI. REFERENCES 53 VII. 국문초록 64Maste

조직 공학을 이용한 장-연골 복합 이식판 개발 기초연구

학위논문(석사)--서울대학교 대학원 :의학과 흉부외과학전공,2004.Maste

Shear bond strength of resin inlay to dentin according to dentin bonding agent application methods : 전단접착강도 시험을 통한 평가

치의학과/석사[한글]간접법을 이용한 복합레진의 성공을 위해서는 레진 시멘트를 이용한 적절한 접착이 필수적이며, 레진 시멘트는 상아질과의 높은 접착강도와 그 자체의 우수한 물리적 성질이 요구된다.이 실험의 목적은 레진 인레이에서 인상 채득 전 상아질 접착제의 도포 여부와 접착시에 상아질 접착제의 두께를 줄여주기 위한 사용방법의 차이가 전단접착 강도에 미치는 영향을 알아보는 것이다.이번 실험에 상아질 접착제는 AdheSE(Ivoclar Vivadent, Schaan, Liechtenstein)가 사용되었고 레진 시멘트는 Z-250((3M ESPE, St. Paul, Minnesota)과 Duo-Link(Bisco, Schaumburg, Illinois)를 사용하였으며 사람의 치아를 교합면에 평행하게 절단한 후 전단 접착강도 시험을 시행하였다. 90개의 치아에 각각 2개씩의 레진 인레이를 접착하여 총 180개의 시편을 얻었고, 인상채득 전 상아질 접착제를 사용하는 I군과 그렇지 않은 II군으로 나누고, 각군을 다시 다음과 같은 소군으로 분류하였다. 접착제를 치아 시편에 도포한 후 낮은 공기압을 접착제에 가하고 광중합 시킨 후 레진 인레이를 레진 시멘트로 접착시키고 광중합한 A군, 높은 공기압을 접착제에 가하고 광중합 시킨 후 레진 인레이를 레진 시멘트로 접착시키고 광중합한 B군, 상아질 접착제를 광중합 시키지 않고 레진 인레이를 레진 시멘트로 접착시키고 광종합한 C군의 소군으로 분류하였다. 각 군내에서 소군의 전단 접착강도를 시험한 결과는 2-way ANOVA와 Duncan’s multiple range test, 그리고 1-way ANOVA와 Duncan’s multiple range test를 통해 비교하였고, 재료별로 각각의 군을 t-test로 신뢰구간 95%에서 분석하였다.실험 결과 I군이 II군보다 높은 전단 접착강도를 보였으며, C군보다는 B군이, B군 보다는 A군이 높은 전단 접착강도를 나타냈다(p<0.05). Z250과 Duo-Link간에는 II-B군을 제외하고는 유의차 없는 결과를 얻었다.위의 결과로 볼 때 상아질 접착제를 와동 형성 직후 사용하여 상아질을 보호하고, 레진 시멘트 사용전에 상아질 접착제를 치아 시편에 도포한 후 낮은 공기압을 접착제에 가하고 광중합 시키는 것이 높은 전단 접착강도를 얻는 방법임을 알 수 있다. [영문]The clinical success and longevity of the bonded esthetic restoration depends on both the adhesive and the resin luting cement forming and optimal attachment to tooth structure.The purpose of this study was to determine whether there were differences in shear bond strength to human dentin using various dentin adhesive methods.90 freshly extracted human premolars were obtained and divided 6 groups. A self etching primer dentin bonding agent (DBA) (AdheSE) was used for all groups. As resin cements, Z-250 and Duo-Link was used. In group I, dentin was sealed by immediately before provisional phase. In group II, DBA was not used before provisional phase. Every group was sub-divided into 3 sub-groups. In group A, before the cementation, DBA was gently dried and light cured as manufacturer’s recommendation. In group B, DBA was over-dried in order to minimize the thickness of DBA. In group C, DBA was used without light curing. After 24-hours storage, the bonded inlays were subjected to shear bond test.When 2-way ANOVA and Duncan’s Multiple Range Test was performed, there was interaction between 2 variables. Within the sub-groups, 1-way ANOVA and Duncan’s Multiple Range Test was used to test the effect of applicant of DBA before impression taking and DBA application methods to shear bond strength. T-tests were also performed to test the effect of resin cements and applicant of DBA before impression taking. All statistical tests were carried out at the 95% level of confidence.The mean shear bond strength of Z-250 was in order of I-A(14.90MPa) > I-B(12.22MPa), II-A(12.16MPa) > II-B(9.61MPa), I-C(9.60MPa) > II-C(3.54MPa)(p I-B(13.04MPa), II-A(12.66MPa) > II-B(10.10MPa) > I-C(8.40MPa) > II-C(2.88MPa)(p0.05) from one another except II-B group.It was concluded that DBA before impression taking as well as gently air blowing and light curing the DBA before resin cementation may improved shear bond strength of resin inlay to dentin.ope

In vivo analysis of the effects nitric oxide and sphingosine 1-phosophate on the pulmonary microstructure : an investigation in a rat model of acute lung injury using an intravital microscopic approach

학위논문(박사)--서울대학교 대학원 :의학과 흉부외과학 전공,2006.Docto

Effects of the electric bias on the deposition of films by hot-wire chemical vapor deposition

Thesis(doctors) --서울대학교 대학원 :재료공학부,2008.8.Docto