Development of Simulation-Optimization Models for Agricultural Contaminant Loading Management Considering Effects of Groundwater Pumping

학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2014. 8. 이강근.In agricultural regions, a significant amount of groundwater has been used but agricultural activities, such as greenhouse farming, have often threatened its quality. Therefore, it is necessary to suitably manage the agricultural contaminant loading for sustainable groundwater use in those regions. However, pumping condition should also be considered in the management because groundwater pumping can change the fate of contaminant in the subsurface such as its leaching to the water table and migration in the aquifer. In this study, based on the field investigation and monitoring, an agricultural contaminant loading management model was developed in order to determine the optimal permissible contaminant loading mass for a given pumping condition, using simulation-optimization method. Periodical on-ground contaminant loading on non-point sources such as fertilizer application in greenhouse was simulated by integrating the 1-D analytical solution for solute transport in the unsaturated zone and the 3-D numerical model for groundwater flow and solute transport in the saturated zone. Backward transport simulation was applied to the model in order to evaluate the relative importance of contaminant sources quantitatively. Genetic algorithm was linked to this integrated simulation model as optimization technique. This model could be useful in the agricultural contaminant loading management in the agricultural regions where many potential non-point sources were located at. Using this model, the optimal contaminant loading designs obtained under various pumping conditions were compared in order to examine the effects of pumping conditions in determining the optimal contaminant loading. The results demonstrated that the optimal contaminant loading designs were determined differently according to the given pumping conditions. Another management model was developed to manage permissible on-ground contaminant loading mass and pumping rates simultaneously. This model cannot consider only dynamics between fate of contaminant and pumping but also various conditions such as different usage of, or demand on, each pumping well and contaminant source in a single of optimization process. The optimal design determined from this model allowed more amounts of both of contaminant loading and groundwater pumping than any other optimal design suggested previously. In addition, in the agricultural regions where groundwater has been used intensively in a specific period of time, such as rice-growing season, it must be particularly important to consider such pumping condition in the agricultural contaminant management. Therefore, the model to simultaneously manage agricultural contaminant loading and groundwater use under time-variant pumping condition was also developed. For this, the method to approximate the contaminant leaching to the fluctuating water table caused by a regular schedule of groundwater pumping was suggested and transient groundwater flow simulation was applied. In the optimal design obtained under the time-variant pumping condition, the contaminant loading was restricted considerably because a relatively large amount of contaminant leaching to the shallow depth of water table during the period without groundwater pumping, a strong inflow of contaminant to the wells driven by the large amount of pumping during the period with groundwater pumping, and a sudden increase of contaminant leaching immediately after stopping the operation of pumping. Particularly, the optimal design obtained under the no-pumping condition in this study was to imitate some previous studies about agricultural contaminant management which had not considered any pumping condition, in order to demonstrate the importance of considering pumping condition in the agricultural contaminant loading. The result showed that the agricultural contaminant loading management without considering pumping condition could fail in the regions where groundwater use has been common.ABSTRACT I CONTENTS V LIST OF FIGURES X LIST OF TABLES XV CHAPTER I. INTRODUCTION 1 1. Backgrounds of this study 1 2. Objectives of this study 4 CHAPTER II. SITE DESCRIPTION AND FIELD INVESTIGATION 6 1. Site description 6 2. Field investigation and monitoring in the study area 11 CHAPTER III. MODEL DEVELOPMENT FOR AGRICULTURAL CONTAMINANT LOADING MANAGEMENT 19 1. Introduction 19 2. Methodology 22 2.1. Simulation-optimization model 22 2.1.1. Integrated simulation model 25 2.1.1.1. Analytical solution for approximation of contaminant leaching mass 25 2.1.1.2. Groundwater flow and solute transport in the saturated zone 29 2.1.2. Optimization model 30 2.1.3. Backward transport simulation for relative importance of contaminant sources 34 2.1.3.1. Application of backward transport simulation to the management model 39 3. Results and discussion 45 3.1. Case study for application of backward transport simulation 45 3.1.1 Model domain and settings 45 3.1.2 Effects of the relative importance of source on the optimal contaminant loading design 49 3.2. Optimal design result for agricultural contaminant loading 52 3.2.1. Model domain and settings 52 3.2.2. Prediction under the condition of no-regulations 57 3.2.3. Optimal contaminant loading design under the no-pumping condition 59 3.2.4. Optimal contaminant loading design under the condition of pumping rates on the RWs = 100 m3/day 62 4. Summary and conclusions 65 CHAPTER IV. MODEL DEVELOPMENT FOR AGRICULTURAL CONTAMINANT LOADING MANAGEMENT WITH CONSIDERING PUMPING CONDITION 67 1. Introduction 67 2. Methodology 69 2.1. Comparison of optimal contaminant loading designs obtained under various pumping conditions 69 2.2. Model development for simultaneous optimization of on-ground contaminant loading and pumping rates 70 3. Results and discussion 75 3.1. Optimal contaminant loading designs obtained under various pumping condition 75 3.2 Simultaneous optimization of on-ground contaminant loading and pumping rates 86 4. Summary and conclusions 90 CHAPTER V. MODEL DEVELOPMENT FOR AGRICULTURAL CONTAMINANT LOADING MANAGEMENT UNDER THE TIME-VARIANT PUMPING CONDITION 92 1. Introduction 92 2. Methodology 94 2.1. Approximation of the leaching to fluctuating water table under time-variant pumping condition 94 2.2. Simulation-optimization model for the agricultural contaminant loading management under time-variant pumping condition 101 3. Results and discussion 103 3.1. Estimation results of the leaching mass to fluctuating water table 103 3.2. Simulation and optimization results obtained under time-variant pumping condition 108 3.3. Contaminant loading management without considering pumping conditions 116 4. Summary and conclusions 121 DISCUSSION 123 CONCLUDING REMARKS 129 REFERENCES 134 ABSTRACT (IN KOREA) 146Docto

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Optimum design of buffer structure system under multi-impact conditions using the dynamically equivalent beam approach

학위논문 (박사)-- 서울대학교 대학원 : 산업·조선공학부, 2011.8. 조선호.Docto

A Study on Time and Space in the Backround of Fiction

This paper is aimed to clarify what the typical frame is in Korean fiction by analyzing the background of the structure of fiction. The past studies on Korean fiction have analyzed it by the external literary factels rather than at the standpoint of the literary principles such as ~deological, historical and social background. Therefore these methods depend only on the synchronical background and the way how novelists own fundermental elements vary has been Ignored. Moreover, since historical method emphasize too much the relation ship between the society and the novel orzthe period and the novel, the aesthetic system of fiction tend to be Ignored. In order to make up for this defect the principle of the background should be applied. And the typical frame of Korean fiction is to be clarified in this essay. As a result the followings are produced. The classification of the background IS not subsidiary means helping to make certain the character and the behavior. While the background appeared in the novels of 19th century played a subsidiary role, in modern fiction the background constructs the metaphorical world as spiritual setting and moreover has its own meaning. Time appeared In the fackground can be perceived as the artificial world of consciousness, that is, artificial time. The past novels emphasized the ordering of natural time, but the modern novels Include phylosophical meaning of time more strongly by implying the world of consciousness. Space appeared in the background, which was subsidiary means, has the side corresponding with the symbolism of the character and the events as a stage meaningful in itself. As a example the symbol~sm of the cities in ruins shown in the post-war novels can be taken. In conclusion the typical frame in Korean fiction, which is explained through the conception of "time and space" becomes significant in post Korean-war fiction as a gradual development of artificial time and symbolic space

Inhibitory mechanisms of biofilm growth on membrane surfaces by plant derived quorum sensing inhibitors(QSIs)

학위논문(석사) - 한국과학기술원 : 건설및환경공학과, 2017.8,[iv, 40 p. :]전 세계적으로 물부족 문제가 심화됨에 따라 부족한 수자원의 확보를 위해 해수담수화와 물의 재이용이 주목받고 있다. 해수담수화와 물의 재이용을 가능하게 하는 여러 기술 중 막기반 수처리공정은 높은 처리효율을 장점으로 하여 그 가치를 인정받고 있다. 하지만 막기반의 공정은 파울링의 문제점을 갖고 있다. 이 파울링 중 가장 문제가 되는 것이 미생물에 의해 형성되는 바이오 파울링인데, 이 바이오 파울링은 쿼럼센싱이라 불리는 미생물들의 신호전달과정에 의해 촉진된다. 따라서 이를 저해할 수 있는 쿼럼센싱교란물질(QSIs)을 이용하여 막의 바이오필름을 저감하고자 하는 시도들이 많이 이루어 지고 있다. 이미 많은 연구에서 분리막생물반응조와 역삼투공정에서 QSIs를 적용하여 바이오필름 저감효과가 나타남을 밝힌바 있다. 하지만 아직까지 정삼투공정에서 이를 적용해 보고자 하는 연구 및 QSIs의 작용 메커니즘과 관련된 연구는 이루어 지지 않고 있다. 따라서 본 연구에서는 QSIs가 정삼투 공정의 바이오필름 형성과정에서의 영향과 그때의 저해 기작을 밝히고자 하였다. 1장에서는 몇가지 선정된 QSIs를 정삼투공정에 적용하여 바이오필름 저감효과가 있다는 것을 유량, 바이오매스 정량 등을 통해 확인하고자 하였다. 그 결과 많은 부분에서 QSIs가 정삼투 공정에서도 바이오필름 저감 효과가 있음이 확인되었다. 2장에서는 바이오필름 저감 효과가 QSIs의 어떤 기작에 의한것인지를 총 네 개의 작용 메커니즘으로 구분하여 밝히고자 하였다. 먼저 실험에 사용된 동일 농도의 QSIs가 미생물의 사멸을 유발하는지 여부와 성장 억제효과를 각각 살펴보았다. 분석 결과 실험에 사용한 QSIs의 농도에서는 세포의 사멸이나 성장억제효과가 유발되지 않았다. 그리고 QSIs에 의해 쿼럼센싱 과정이 어떻게 영향을 받는지 두가지 방법으로 나누어 이를 알아보았다. 먼저 QSIs가 신호전달물질을 분해하거나 비활성화 하는 기능이 있는지 CV026미생물을 이용하여 확인한 결과, 일부 QSIs는 신호 물질의 비활성화에 관여하는 것으로 나타났다. RNA분석을 통한 유전자 발현 평가 결과에서는 QSIs물질이 AHL기반의 쿼럼센싱 관련 유전자의 발현을 억제한다는 것이 확인되었고 위와 같은 결과로 인해 바이오필름 형성이 저감 되었음을 확인할 수 있었다. 본 연구를 통해 지금까지 밝혀진 QSIs물질이 정삼투 공정에서도 바이오필름 저감효과가 있음을 확인할 수 있었고, 이때의 기작은 신호물질 비활성화와 QS관련 유전자의 발현 억제로 인한 것이었음이 확인되었다.한국과학기술원 :건설및환경공학과