새만금 간척지의 염생식물 군락지 조성 요인과 환경적 효과 연구

학위논문 (박사)-- 서울대학교 대학원 : 농생명공학부 응용생명화학 전공, 2013. 2. 김민균.The two objectives of the present dissertation are to clarify development of halophyte communities constructed in Saemangeum reclaimed land and to quantify the environmental effects of halophyte communities. Through halophyte community development using 11,652 kg of eight halophytic species in 2,866 ha of the land from 2006 to 2008, halophytic area confined to autogenous 689 ha in 2005 increased to 4,364 ha by 6.3 times. The number of halophytic species increased from 4 in 2006 to 25 in 2008 and both average and maximum population densities rapidly increased. Besides, the number of plant species increased in 79% of the common quadrats for three years and halophyte community growth classified into five classes (from Class 1 to Class 5 with smaller numbers indicating better growth) was improved as the proportion of quadrats belonging to Class 1 or Class 2 increased from 38% to 86.8%. In salt response and flooding experiments, halophytic species with ever-increasing emergence percentage as soil electrical conductivity (EC) dropped to 0.88 dS m-1 through four-time desaltings were Suaeda asparagoides, Suaeda japonica, Limonium tetragonum, and Atriplex gmelini. S. asparagoides and S. japonica had an advantage for growing in the intermittently-flooded condition. Annual halophytes of S. asparagoides, S. japonica, and S. europaea were categorized into the upper EC group. Halophyte communities always located above high water level during the growing seasons and did not emerge in the seawater-flooded areas. In 2006, magnesium, potassium and sodium as well as soil EC had a significantly negative relationship with halophyte community growth. The negative relationship between plant species and soil EC persisted until 2008. Plant height was found to have a significantly negative relationship (R2=0.95) with soil EC. The electrical conductivity of a saturated soil extract (ECe) according to halophyte community growth from seven ECe maps made by electromagnetic measurement system was 24 to 27(±9) dS m-1 for Class 1, 31 to 36(±8) dS m-1 for Class 2, 33 to 37(±10) dS m-1 for Class 3, and 29 to 33(±13) dS m-1 for Class 4 respectively. Sixty eight % of quadrats in rake-plowing area showed growth better than Class 4, whereas 53% of quadrats in non-plowing area did. In the experiments on wind reduction by halophyte communities, the wind was blocked at a height of 20 cm within a halophyte community beginning to be clearly reduced from the starting point of halophytes and stabilized through halophytes. The maximum wind reduction was 82 to 38% at a height of 20 cm within a halophyte community. Wind velocity was reduced through halophytes largely at heights of below 60 cm, which are lower than halophytes. Wind reduction percentage by a halophyte community was maximally 76% at a height of 20 cm. Total suspended particulate (TSP) decreased by 60.7% passing through a group of transplanted halophytes and the reduction effect continued almost the same to 50 m behind the community. Dust reduction behind halophyte communities amounted to 43.8 ug m-3 for TSP and 14.7 ug m-3 for PM10 (Particlulates <10 μm). TSP collected within halophyte communities averaged 37.0 ug m-3 with differenences among four halophyte communities of S. asparagoides, Phragmites communis, Atriplex subulatus, and S. europaea. Nitrogen (total nitrogen), phosphorus (P2O5), and sodium (Na+) contents absorbed by halophytes in 2005 before halophyte community development were 2.60, 0.14, and 4.98 g m-2 respectively. Nitrogen, phosphorus, and sodium contents in S. asparagoides, S. japonica, and S. europaea were 1.24 to 2.20 g m-2, 0.07 to 0.13 g m-2, and 2.91 to 4.59 g m-2. However, in 2010 after halophyte community development, they were 0.45 g m-2, 0.04 g m-2, and 0.08 g m-2 respectively. On the basis of halophyte community area developed in 2006 (1,236 ha), the amount of total nitrogen (T-N), P2O5 and Na+ absorbed by only a major halophytic species of S. asparagoides amounted up to 439, 78, and 914 ton respectively. In conclusion, it was most critical to select halophytic species with superior qualities against the harsh environment of reclaimed land such as salinity and flooding for halophyte community development. The annual halophytes mainly used in sowing not only held high germination capacity and velocity but also displayed broad salt-adaptability and tolerance to flooding. Sowing in the area at higher elevation than high level of seawater was important for halophyte communities to emerge. EC among soil properties had a significantly negative relationship with halophyte community until 2008. It was found that halophyte communities were capable of collecting significant dust as well as definitely reducing and stabilizing wind velocity. A great deal of nitrogen, phosphorus, and sodium absorbed into halophytic species in the reclaimed land can consequently contribute for lowering the levels of soil nitrogen and phosphorus leading to freshwater lake eutrophication or improving salt-affected soils.CONTENTS ABSTRACT ........................................................................................... i LITERATURE REVIEW .................................................................... 1 1. Halophyte community development ..................................................... 1 2. Factors affecting halophyte communities ............................................. 1 3. Soil EC measurement ............................................................................ 7 4. Analysis of halophyte community distribution ..................................... 8 5. Practical uses of halophytes .................................................................. 9 REFERENCES ................................................................................... 11 Chapter I. Development of Halophyte Communities ABSTRACT ........................................................................................ 24 INTRODUCTION .............................................................................. 26 MATERIALS AND METHODS ....................................................... 29 1. Germination experiment ..................................................................... 29 2. Salt response experiment .................................................................... 29 3. Flooding experiment ........................................................................... 30 4. Halophyte community development ................................................... 30 5. Halophyte community monitoring ...................................................... 46 6. Soil analysis ........................................................................................ 50 RESULTS ............................................................................................ 56 1. Methodology of halophyte community development ......................... 56 2. Change of halophyte communities ...................................................... 62 3. Development of halophyte communities ............................................ 78 DISCUSSION .................................................................................... 133 REFERENCES ................................................................................. 143 Chapter II. Environmental Effects of Halophyte Communities ABSTRACT ...................................................................................... 152 INTRODUCTION ............................................................................ 154 MATERIALS AND METHODS ..................................................... 156 1. Wind reduction experiments ............................................................. 156 2. Dust collection experiments .............................................................. 157 3. Absorbed nutrient analysis ................................................................ 161 RESULTS .......................................................................................... 164 1. Wind reduction .................................................................................. 164 2. Dust collection .................................................................................. 168 3. Nutrient absorption ........................................................................... 174 DISCUSSION .................................................................................... 182 REFERENCES ................................................................................. 187 CONCLUSION ................................................................................. 190 ABSTRACT IN KOREAN .............................................................. 192 ACKNOWLEDGEMENTS ............................................................. 196 APPENDIXES ................................................................................... 197Docto

건설기계 엔진마운트 최적설계에 관한 실용적 연구

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2014. 2. 강연준.엔진마운트 최적설계에 관한 기존의 연구는 마운트 강성을 고정된 값으로 가정하였다. 하지만 마운트 강성은 탑재조건(주파수, 변위, 초기하중)에 따라서 달라지며 외부환경 조건(온도)에 따라서도 다른 값을 가진다. 본 연구에서는 조건에 따라 달라지는 마운트 강성을 평균과 표준편차를 가지는 정규확률분포로 표현하여 최적설계를 수행하였고 이를 신뢰성기반 최적설계 (Reliability Based Design Optimization)라고 한다. 최적설계는 목적함수, 제한조건, 설계변수로 이루어지며 목적함수는 가중치가 부여된 전달력의 합으로 표현되고 제한조건은 주요 가진모드의 주파수비이며 설계변수는 마운트 강성과 마운트 위치이다. 본 연구에서는 5기통 엔진에 대한 신뢰성기반 최적설계를 수행하여 신뢰도에 따른 최적의 설계변수값을 찾아내었다.초 록 …………………………………………………………………………… i 목 차 …………………………………………………………………………… ii LIST OF TABLES ……………………………………………………………… iii LIST OF FIGURES …………………………………………………………… iv 1. 서 론 ………………………………………………………………………… 1 2. 엔진마운트 강성의 특성 ………………………………………………… 2 2.1 운전조건(주파수, 변위, 초기하중) ………………………………… 2 2.2 온도조건 ……………………………………………………………… 4 2.3 기타 고려사항 ………………………………………………………… 5 3. 전달력 및 엔진가진력 해석 …………………………………………… 6 3.1 전달력 해석 ………………………………………………………… 6 3.2 엔진가진력 해석 …………………………………………………… 7 3.3 전달력 시험 ………………………………………………………… 9 4. 최적설계 수행 …………………………………………………………… 11 4.1 신뢰성기반 최적설계(RBDO) …………………………………… 11 4.2 목적함수 ……………………………………………………………… 12 4.3 설계변수 및 제한조건 ……………………………………………… 13 4.4 최적설계 예 ………………………………………………………… 14 5. 결 론 ……………………………………………………………………… 31 참고 문헌 ……………………………………………………………………… 32 ABSTRACT …………………………………………………………………… 34Maste

Optimal Tuning of a Digital PID Controller Based on the PPGA and Model

In this paper, a methodology for estimating the parameters of discrete-time systems and designing a digital PID controller is presented. To deal with optimization problems occurring regarding parameter estimation and controller design, a pseudo parallel genetic algorithm(PPGA) is developed. The PPGA is characterized by several serial GAs, the migration model and the ring topology . The parameters of a discrete-time system are estimated using both the model technique and a PPGA. The digital PID controller is described by the pulse transfer function and its parameters are tuned based on both the model reference technique and another PPGA. A set of experimental works on two processes are carried out to illustrate the performance of the proposed method.제1장 서론 1 제2장 최적화 도구로서의 병렬 유전알고리즘 4 2.1 직렬 유전알고리즘의 구조 4 2.1.1 염색체의 표현 및 집단의 초기화 4 2.1.2 적합도 평가 5 2.1.3 유전 연산자 6 2.1.4 기타 전략 8 2.1.5 정지조건 9 2.2 유전알고리즘의 병렬화 10 2.2.1 이주모델 구조의 병렬화 11 2.2.2 이주방법 11 2.3 PPGA의 구현 13 제3장 이산시간 시스템의 파라미터 추정 16 3.1 제어대상 시스템의 표현 16 3.2 제어대상 시스템의 모델 18 3.3 파라미터의 추정 19 제4장 디지털 PID 제어기의 최적동조 23 4.1 디지털 PID 제어기 23 4.2 PPGA와 기준모델 제어기법을 이용한 최적동조 27 4.2.1 기준모델 27 4.2.2 PPGA를 이용한 PID 제어기의 최적동조 29 제5장 시뮬레이션 및 결과검토 31 5.1 이산시간 모델의 파라미터 추정 31 5.1.1 시스템 I 31 5.1.2 시스템 II 36 5.2 디지털 PID 제어기의 최적동조 40 5.2.1 시스템 I 40 5.2.2 시스템 II 44 제6장 결론 48 참고문헌 4

A Study of the Classification of 4-Year University Students by Job Preference and the Length of Job Searching Period

본 연구는 250명의 4년제 대학생을 대상으로 취업선호도에 따른 잠재집단분석과 각 잠재집단별 취업소요기간 분석 및 영향요인을 검증하였다. 졸업 시점의 취업선호도에 따른 잠재집단분석 결과, 이상추구형, 직업탐색형, 자아실현형, 사무직선호형, 비사무직선호형의 5개 집단이 도출되었다. 각 취업소요기간에 대한 생존분석결과, 잠재집단 별로 상이한 취업소요기간과 미취업률을 보였다. 취업소요기간에는 인적자본 요인의 영어점수와 사회경제적 요인의 어머니 월평균 소득이 유의한 영항을 주는 변수로 나타났다. 토익 점수가 없을 경우에 비해 800점 이상일 경우, 어머니 월평균 소득이 없을 경우에 비해 500만원 미만 1,000만원 미만일 경우 취업소요기간이 단축될 가능성이 높은 것으로 분석되었다. 본 연구가 고용의 질에 대한 불균형을 해소하고, 청년 미취업자들이 자신의 직업가치에 부합하는 다양한 일자리를 탐색할 수 있도록 지원하는 효과적인 방향성이 제시되기를 기대한다.The present study applied Latent Class Analysis and Survival Analysis to classify college students by their job preferences and investigate the length of job searching period. According to the results of identifying latent classes by job preference, five classes were discerned for 250 college students. Each class showed distinctive length of job searching period and the unemployment rate. Also, the results of Survival Analysis showed that English test score (TOEIC) and mother’s average monthly income were significant determinants of length of job searching period. Based on the findings from this study, it is suggested that insightful measures to enhance imbalance of employment quality should be considered

決明(Cassia tora), 쑥(Artemisia asiatica), 木材타르 抽出物에 의한 밭土壤中 尿素分解와 窒酸化作用 抑制效果

Thesis (master`s)--서울대학교 대학원 :농화학과,1997.Maste

사회계층간 자녀의 학업성취도 격차와 양육문화

학위논문(석사) --서울대학교 대학원 :인류학과 인류학전공, 2004.Maste

Why do the children from affluent families show better academic performance?: -The academic performance gap between social classes and parenting practices-

학위논문(박사) --서울대학교 대학원 :사회복지학과,2010.2.Docto

Generalized Ligamentous Laxity Is an Independent Predictor of Poor Outcomes After the Modified Brostr?m Procedure for Chronic Lateral Ankle Instability

BACKGROUND: The modified Brostr?m procedure for chronic lateral ankle instability (CLAI) has presented outstanding clinical results. However, after the procedure, some patients with generalized ligamentous laxity have experienced a recurrence of ankle instability. PURPOSE: To understand the effect of generalized ligamentous laxity on prognosis and risk of recurrence in a cohort of patients with CLAI after the modified Brostr?m procedure. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 199 ankles from 188 patients underwent the modified Brostr?m procedure for CLAI with a mean follow-up of 60.1 months (range, 48-108 months). Generalized ligamentous laxity was assessed in all patients. The Karlsson-Peterson ankle score (Karlsson score), talar tilt angle, and anterior displacement of the talus were used to evaluate clinical and radiological outcomes. Risk factors associated with clinical outcomes were evaluated using bivariate analysis and logistic regression analysis. Survival outcomes were compared using Kaplan-Meier analysis. RESULTS: Generalized ligamentous laxity was evident in 42 cases (21.1%). The average Karlsson score improved from 54.6 ± 7.1 preoperatively to 87.9 ± 7.2 at last follow-up (P 15°), and high preoperative anterior displacement of the talus (>10 mm) were significantly associated with clinical failure. Multivariate logistic regression analysis revealed that generalized ligamentous laxity was the most important independent predictor of clinical failure after the modified Brostr?m procedure. The cumulative success rates for the nonlaxity group were significantly superior to those for the laxity group in Kaplan-Meier curves (P < .001). CONCLUSION: Generalized ligamentous laxity is an independent predictor of poor outcomes and a risk factor of recurrent instability following the modified Brostr?m procedure for CLAI.restrictio