천연가스 공급망 내 초구조 최적화 및 다중모듈방식을 이용한 공정설계 및 운전

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 화학생물공학부, 2019. 2. 이원보.본 논문은 공정시스템 분야의 최신기술 수요에 상응하는 최적 공정설계 및 운전기술 개발을 주목적으로 한다. 최근 셰일가스 등 변화하는 천연가스 자원으로부터 지속적인 부가가치 창출과 플랜트의 내재적 안전성을 제고할 수 있는 설계 및 운전을 도모하였다는 점에서 실제 산업에의 응용가치가 매우 높다. 첫 번째로 천연가스 가솔린회수 및 액화 통합공정에 질소회수공정을 추가하여, 저품질 천연가스로부터 지속적인 액화천연가스 생산이 가능한 공정을 설계하였다. 열교환망 및 분리공정 최적화를 위해 공정요소들의 엑서지를 최소화할 수 있는 초구조를 설계함으로써 기존의 연구가 찾지 못하였던 새로운 최적 구조 및 운전조건을 결정하였다. 나아가 서로 다른 천연가스 조성에 따라 각기 적용이 가능한 대안공정을 추가 설계·최적화함으로써 변화되는 천연가스 자원에 지속적인 가치창출을 위한 해답을 제시하고 있다. 두 번째로 공정의 예비설계단계에서 내재적 안전성의 개념을 도입하여, 경제성과 안전성의 균형을 유지하기 위한 새로운 다목적최적화 알고리즘을 개발하였다. 잠재적 위험도가 높은 천연가스 액화공정을 대상으로 액화사이클에 따른 초구조를 모사하여 두 가지 목적함수의 가중치에 따른 최적해를 결정함으로써 기존 최적화의 한계를 보완하였다. 마지막으로 플랜트 안전운전을 위해 공정이상에서부터 사고의 발생 및 전파과정을 실시간으로 구현할 수 있는 시뮬레이션 모듈을 개발하였다. 동적공정시뮬레이션 및 사고시뮬레이션의 두 가지 독립된 모듈을 객체연결매입 기법을 이용하여 연동함으로써 사고상황에서 운전원의 임의조치가 모듈에 실시간 반영되도록 하였다. 해당 모듈은 임의의 사고상황에서 제어실 및 현장 운전원의 적절한 대응을 효과적으로 유도할 수 있으며 나아가 플랜트 안전시스템설계에 객관화된 지표를 제시할 수 있었다. 본 논문은 위와 같이 실제 산업의 기술적 수요를 충족시키고 이를 발전시킴으로써 공정시스템 학술분야에 기여하였다.Recently in the field of process systems engineering in natural gas processing, various researches trying to make changes in the existing framework of process design and operation have been studied with the emerging need of sustainability and safety in the chemical processes. These two considerations of sustainability and safety either result in a totally new solution for a certain decision making or require far different methods or technologies for it. Especially for a natural gas supply chain broadly from drilling of the gas/oil reservoirs to distributing the product gas to end-users like households or offices, new frameworks of process design and operation critically influence the way of producing desired products and supplying them to the users in the associated industries. Then it determines the structure, operating conditions, and operation procedures of chemical processes which are economically powerful and good in operability. Recently, as the natural gas sources becomes unconventional varying from mid-to-small size reservoirs or shale gases, this change makes the offshore natural gas plants emerge as an alternative and vital site of producing LNG (liquefied natural gas) with strict requirements of safety. It also makes additional processing units like a cryogenic nitrogen recovery be necessary for sustainable production of LNG with leaner feed natural gases. Among various processes in the overall natural gas supply chain, this thesis dealt with largely three parts including gas pre-treatment, liquefaction, and distribution to the end-users, attempting to design new processes or develop new methods of decision making in the context of the new framework considering sustainability and safety in process systems engineering. In this thesis, I will discuss the process synthesis, intensification, and optimization for sequential units, multi-objective optimization for economic feasibility and inherent safety, and multi-modular approach for interactive simulation of dynamic process and 3D-CFD (computational fluid dynamics) accident models. First of all, for designing a sustainable process of producing LNG from feed natural gases with high amounts of nitrogen, two cryogenic nitrogen recovery processes integrated with LNG production and NGL (natural gas liquid) recovery were designed and optimized based on the structural analysis of components separation: one for integrated nitrogen recovery unit and the other for standalone one. The difference of each process is the way the nitrogen is removed from the natural gas. The former recovers nitrogen in the integrated heat and mass transfer structure with natural gas liquefaction while the latter separates the nitrogen recovery unit into an independent structure apart from the liquefaction section. These sophisticated nitrogen recovery solutions follow the recent demand of highly efficient electric motors as alternative compressor drivers which require less or no fuel gas, the major sink of nitrogen in the feed gas. These two processes were compared with each other in terms of specific power (kWH/kg_LNG), which is equivalent to the overall process efficiency, with respect to the nitrogen content in the feed gas from 0mol% to 20mol%. Consequently, as the nitrogen content in the feed gas increases, the specific power of each process also increases while the standalone solution has a priority over the other until around 17mol% of nitrogen and after that point the integrated solution becomes relatively more efficient. It should be noted that all of the optimization results of each configuration were improved with the reduced specific power by up 38.6% compared to those from previous studies which have similar configurations. The way this study aimed could be reasonable guidelines for other chemical process designs as well as nitrogen recovery in natural gas processing. Secondly, for designing a safer process of natural gas processing, two different systematic approaches were newly proposed in this study: one for risk reduction method based on rigorous QRA (quantitative risk assessment) results through process design modification of an existing plant which already finished up to the detailed design stage, and the other for deciding an optimal process design through multi-objective optimization for minimizing both the TAC (total annual cost) and the risk (fatality frequency) at the preliminary design stage. This latter approach could largely lower the cost required for finalizing the design as it doesnt need to follow the general QRA procedure where the recursive loop is recycled until the risk is reduced to an acceptable level. But before this approach starts to be applied, the suitability of its method should be verified as it has to make some assumptions in assessing the safety level of the process with limited information. Also the computation load would be higher as it needs to simultaneously consider the economic feasibility and inherent safety in designing a process. Despite the differences these two approaches have each other, however, they are essentially in the same context in that they share the same purpose of deciding a process design which is safer and/or even cheaper than the existing processes. Consequently, for the former approach of which the target process is the GTU (gas treatment unit) of an existing GOSP (gas oil separation plant) for processing associated natural gas, the modified design with different operation conditions reduced the total risk integrals by 27% at the expense of only the additional $50,000 for capital cost. In addition, sensitivity analysis of total risk with respect to probability of success for safety barriers was carried out in order to show the preferences of process design modification, this study proposed, over the improvement of safety systems. Meanwhile, the latter approach of superstructure formulation and multi-objective optimization for designing an optimal heat transfer structure and operating conditions was applied to the natural gas liquefaction processes, deciding that the SMR (single-stage mixed refrigerant process) structure with the TAC of 626.6MM$/yr and fatality frequency of 1.28E-03/yr has the highest priority over all possible solutions. Finally, with the aim of safely operating a chemical plant, a new operator training module which mainly targets the interactive cooperation of control room operators and field operators was developed through using multi-modular approach with advanced simulations and data processing technologies. This interactive simulation modeling delivers the online simulation results of process operation to the operators and induces them to take proper actions in case of a random accidental situation among pre-identified scenarios in a chemical plant. Developed model integrates the real-time process dynamic simulations with the off-line database of 3D-CFD accident simulation results in a designed interface using OLE (Object Linking and Embedding) technology so that it could convey the online information of the accident to trainees which is not available in existing operator training systems. The model encompasses the whole process of data transfer till the end of the training at which trainees complete an emergency shutdown system in a programmed model. The developed module was applied to a natural gas pressure regulating station where the high pressure gas is depressurized and distributed to the end-users like households or offices. An overall scenario is simulated in the interactive simulation model, which starts from an abnormal increase of the discharge (2nd) pressure of the main valve due to its malfunction, spreads to an accidental gas release through the crack of a pressure recorder, and ends with gas dispersion and explosion. Then the magnitude of the accident outcomes with respect to the lead time of each trainees emergency response is analyzed. Consequently, the module could improve the effectiveness of operator training system through interactively linking the trainee actions with the model interface so that the associated accident situations would vary with respect to each trainees competence facing an accident.Abstract i Table of Contents vii List of Figures x List of Tables xiv CHAPTER 1. Introduction 1 1.1. Research motivation 1 1.2. Research objectives 4 1.3. Outline of the thesis 6 1.4. Associated publications 11 CHAPTER 2. Process Intensification 12 2.1. Introduction 13 2.2. Conceptual Design of the Nitrogen Recovery 17 2.3. Design Improvement and Optimization 26 2.3.1. Integrated Nitrogen Recovery Unit 26 2.3.2. Optimization of the Base Case 32 2.3.3. Design Improvement 40 2.4. Alternative Process Design and Optimization 65 2.4.1. Standalone Nitrogen Recovery Unit 65 2.4.2. Optimization of Standalone Nitrogen Recovery Unit 74 2.4.3. Comparison between End-flash and Stripping Options 78 2.5. Varying Feed Composition and Optimization 95 2.6. Concluding Remarks 105 CHAPTER 3. Safer Process Design 107 3.1. Introduction 109 3.2. Risk Reduction through Process Design Modification 112 3.2.1. Risk Assessment for the Target Process 113 3.2.2. Risk Reduction to ALARP 141 3.3. Multi-objective Optimization Including Inherent Safety 154 3.3.1. New Decision Making Schemes for Inherent Safety 159 3.3.2. Superstructure for Natural Gas Liquefaction Processes 168 3.3.3. Multi-objective Optimization 187 3.3.4. Decision Making for Final Optimal Solution 203 3.3.5. Future Works 208 3.4. Concluding Remarks 210 CHAPTER 4. Safe Operation with Multi-modular Approach 212 4.1. Introduction 213 4.2. Interactive Simulation Modeling 218 4.2.1. Model Structure 218 4.2.2. Dynamic Process and Accident Simulation Engine 221 4.2.3. Real-time 3D-CFD Data Processing Method 225 4.3. Case Study – Pressure Regulating Station 231 4.3.1. Developing a Program Prototype 231 4.3.2. Prototype Test and Training Evaluation 252 4.4. Concluding Remarks 256 CHAPTER 5. Conclusion 257 Nomenclature 261 Reference 263 Abstract in Korean (국문초록) 270Docto

의학 연구에서의 과학적 증거의 활용을 위한 시각적 분석 시스템 디자인

학위논문(박사) -- 서울대학교대학원 : 공과대학 컴퓨터공학부, 2022. 8. 서진욱.Evidence-based medicine, "the conscientious, explicit, and judicious use of current best evidence in healthcare and medical research" [98], is one of the most widely accepted medical paradigms of modern times. Searching, reviewing, and synthesizing reliable and high-quality scientific evidence is the key step for the paradigm. However, despite the widespread use of the EBM paradigm, challenges remain in applying Evidence-based medicine protocols to medical research. One of the barriers to applying the best scientific evidence to medical research is the severe literature and clinical data overload that causes the evidence-based tasks to be tremendous time-consuming tasks that require vast human effort. In this dissertation, we aim to employ visual analytics approaches to address the challenges of searching and reviewing massive scientific evidence in medical research. To overcome the burden and facilitate handling scientific evidence in medical research, we conducted three design studies and implemented novel visual analytics systems for laborious evidence-based tasks. First, we designed PLOEM, a novel visual analytics system to aid evidence synthesis, an essential step in Evidence-Based medicine, and generate an Evidence Map in a standardized method. We conducted a case study with an oncologist with years of evidence-based medicine experience. In the second study, we conducted a preliminary survey with 76 medical doctors to derive the design requirements for a biomedical literature search. Based on the results, We designed EEEVis, an interactive visual analytic system for biomedical literature search tasks. The system enhances the PubMed search result with several bibliographic visualizations and PubTator annotations. We performed a user study to evaluate the designs with 24 medical doctors and presented the design guidelines and challenges for a biomedical literature search system design. The third study presents GeneVis, a visual analytics system to identify and analyze gene expression signatures across major cancer types. A task that cancer researchers utilize to discover biomarkers in precision medicine. We conducted four case studies with domain experts in oncology and genomics. The study results show that the system can facilitate the task and provide new insights from the data. Based on the three studies of this dissertation, we conclude that carefully designed visual analytics approaches can provide an enhanced understanding and support medical researchers for laborious evidence-based tasks in medical research.근거중심의학(Evidence-Based Medicine)이란 "임상 치료 및 의학 연구에서 현재 존재하는 최고의 증거를 양심적이고, 명백하며, 분별 있게 이용하는 방법론"이며 [98], 현대 의학에서 가장 널리 받아들여지는 의학 패러다임이다. 신뢰할 수 있는 고수준의 과학적 근거를 검색, 검토, 합성하는 것이야 말로 근거중심의학의 핵심이다. 하지만, 근거중심의학이 이미 광범위하게 사용되고 있음에도 불구하고, 의학 연구에 근거중심의학의 프로토콜을 실천하는 데에는 여전히 많은 어려움이 따른다. 의료 문헌 정보, 임상 정보 및 유전체학 정보까지 연구자가 검토해야 할 근거의 양은 방대하며 광범위하다. 또한 의학과 기술의 발전으로 인해 점차 더 빠른 속도로 늘어나고 있기에, 이를 모두 엄밀히 검토하기 위해서는 막대한 양의 시간과 인력이 있어야 한다. 본 논문은 시각적 분석 방법론을 접목하여 의학 연구에서 방대한 과학적 증거를 검색하고 검토할 시 발생하는 막대한 인적 자원의 과부하 문제를 완화하고자 한다. 이를 위하여 근거중심의학의 절차 중 특히 인력 소모가 막심한 절차들을 선정하고, 이러한 난관을 극복하고 보다 효율적이고 효과적으로 데이터에서 유의미한 정보를 도출할 수 있게끔 보조하는 세 가지 시각적 분석 시스템들을 구현하였으며, 각각의 시스템에 관한 디자인 연구를 수행하였다. 우선 첫 디자인 연구에서는 근거중심의학 연구에 있어 필수적 단계인 근거 합성 방법론의 하나인 근거 매핑(Evidence Mapping) 과정을 지원하기 위한 시각적 분석 시스템 PLOEM을 설계했다. 그리고 이를 검증하기 위해 다년간의 근거 기반 의료 경험이 있는 종양학자와 함께 사례 연구를 수행했다. 두 번째 디자인 연구에서는 의학 문헌 검색 시스템의 요구사항 분석을 위해 총 76명의 의사를 상대로 설문조사를 진행하였고, 이러한 분석을 바탕으로 대화형 시각적 분석 시스템인 EEEVis를 설계했다. 이 시스템은 여러 종의 서지 정보 시각화 인터페이스와 PubTator의 주석 정보를 활용하여 PubMed 검색 엔진의 검색 결과를 증강하는 시스템이며, 이를 평가하기 위해 총 24명의 의사와 함께 사용자 연구를 수행하였다. 이 연구 결과를 바탕으로 의학 문헌 검색 시스템에 대한 설계 지침과 과제를 제시한다. 마지막으로 세 번째 디자인 연구에서는 임의의 유전자군의 유전자 발현 패턴을 주요 암 유형에 따라 시각화하고 분석할 수 있는 시스템인 GeneVis를 설계하였다. 암 유형에 따른 유전자 발현 패턴의 분석과 비교는 암 연구자들이 정밀 의학에서 생체 지표(Biomarker)를 발견하기 위해 빈번히 수행하는 작업이다. 우리는 종양학 전문가 및 유전체학 전문가 총 4인을 대상으로 사례 연구를 진행하였고, 그 결과 GeneVis가 해당 작업을 더 수월하게 수행하는 것과 기존의 데이터에서 새로운 정보를 도출하는 것에 도움이 되었음을 확인하였다. 위의 세 디자인 연구의 결과를 바탕으로, 본 논문은 사용자 분석과 작업 분석을 동반한 시각적 분석 방법론이 의학 연구의 근거 관련 작업의 어려움을 해소하고, 분석 데이터에 대한 보다 나은 이해를 제공하는 것이 가능하다고 결론 내린다.CHAPTER1 Introduction 1 1.1 Background and Motivation 1 1.2 Dissertation Outline 5 CHAPTER2 Related Work 7 2.1 Evidence Mapping: Graphical Representation for a Scientific Evidence Landscape 7 2.2 Scientific Literature Visualizations and Bibliography Visualizations 9 2.3 Visual Anlytics Systems for Genomics Data sets and Research Tasks 10 CHAPTER3 PLOEM: An Interactive Visualization Tool for Effective Evidence Mapping with Biomedical literature 12 3.1 Introduction 12 3.2 Visual Representations and Interactions of PLOEM 14 3.2.1 Overview of the PICO Criteria 14 3.2.2 Trend Visualization with the Timeline view 17 3.2.3 Representing the PICO Co-occurrence with the Relation view 20 3.2.4 Study detail view 22 3.3 Usage Scenarios: Visualizing Various Study Sizes with PLOEM 23 3.4 Conclusion 24 CHAPTER4 EEEvis: Efficacy improvement in searching MEDLINE database using a novel PubMed visual analytic system 26 4.1 Introduction 26 4.1.1 Motivation 26 4.1.2 Preliminary Survey: A Questionnaire on conventional literature search methods 28 4.1.3 Design Requirements for Biomedical Literature Search Systems 36 4.2 System and Interface Implementation of EEEVis 37 4.2.1 System Overview 37 4.2.2 Bibliography Filters 40 4.2.3 Timeline View 41 4.2.4 Co-authorship Network View 43 4.2.5 Article List and Detail View 44 4.3 User Study 46 4.3.1 Participants 46 4.3.2 Procedures 48 4.3.3 Results and Observations 50 4.4 Discussion 54 4.4.1 Design Implications 56 4.4.2 Limitations and Future Work 57 4.5 Conclusions 59 CHAPTER5 GeneVis: A Visual Analytics Systemfor Gene Signature Analysis in Cancers 68 5.1 Motivation 68 5.2 System and Interface Implementation 69 5.2.1 System Overview 69 5.2.2 Gene Expression Detail View 71 5.2.3 Gene Vector Projection View 72 5.2.4 Gene x Cancer Type Heatmap view 74 5.2.5 User Interaction in Multiple Coordinated Views 76 5.3 Case Studies 76 5.3.1 Participants 76 5.3.2 Task and Procedures 76 5.3.3 Case1: Identifying SimilarGeneSignatures with TGFB1in Hallmark Gene Sets 80 5.3.4 Case2: Identifying Cluster Patterns in the HRD data set 81 5.3.5 Results 82 5.4 Summary 85 CHAPTER6 Conclusion and future work 86 6.1 Conclusion 86 6.2 Future Work 87 Abstract (Korean) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102박

TEM-CL 기술을 통한 사파이어 기판 위 성장한 β-Ga2O3의 구조적, 광학적 성질에 관한 연구

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 재료공학부, 2020. 8. 김영운.본 논문에서는 β-Ga2O3의 구조적, 광학적 성질을 TEM과 TEM-CL 시스템을 통해 분석하였다. 첫 번째 파트에서는 β-Ga2O3를 사파이어 기판 위에 증착시킨 XTEM 샘플을 명시야상 이미지, 암시야상 이미지, 회절 패턴, 고분해능 이미지를 이용하여 분석을 진행하였다. 일반적으로 사파이어 기판 위에 성장한 β-Ga2O3의 정축 방향은 크게 두 가지로 나뉘었고, 그 중 [102] 정축에 해당하는 회절 패턴을 분석하였다. 분석 결과 중 이전까지는 자세히 연구되지 않았던 새로운 회절 spot을 발견하였으며, 이 spot은 JCPDS와 JEMS software를 사용하여 [1-92] 정축의 (512)라는 것임을 확인하였다. 또한 이론적으로도 타당한지에 대하여 직접 원자를 쌓아 올려 사파이어 기판과의 격자 상수, 성장 방향 등에 대한 검토를 마쳤다. 두 번째 파트에서는 β-Ga2O3의 TEM-CL 음극형광 신호 시스템을 이용하여 peak 분석을 진행하였다. 크게 3가지의 peak으로 나뉘는데, 첫 번째는 중심 파장 350nm를 가지는 UV 대역이다. 이 대역은 사파이어 기판 바로 위에 얇은 폭에서 가장 강한 신호를 나타낸다. 이 부분의 신호가 가장 강하게 나타나는 이유에 대해서는 아직 밝히지 못하였고, 추후 연구를 통해 진행할 사항이다. 두 번째 peak의 중심 파장은 373nm를 가지는 UV 대역이다. 이 파장 대에서는 첫 번째 UV 대역의 얇은 폭 위로 columnar하게 성장하는 β-Ga2O3의 구조를 확인할 수 있다. 세 번째 peak의 중심 파장은 424nm로 BL 대역을 가진다. UV에서 보여준 것과 다르게 이 파장 대에서는 사파이어 기판 바로 위부터 columnar하게 성장하는 β-Ga2O3의 구조를 확인할 수 있다. β-Ga2O3에서 중심 파장 350nm를 가지는 단색 파장 이미지에서 보이는 사파이어 기판 바로 위, 얇은 폭의 β-Ga2O3 영역이 다른 영역과 어떠한 차이를 통하여 발광되는지에 대해서는 정확히 밝히게 된다면 β-Ga2O3의 광학적 성질을 이해하는데 크게 기여할 것으로 판단한다.Cathodoluminescence is a phenomenon when light emitted by accelerated electron beams impacting on a material join together and thereby causing photon emission. This light is emitted in a large range, from ultraviolet to infrared, which is a great advantage in that it allows one to directly measure the band gap of the material. Until now, methods for measuring cathodoluminescence with electron microscope include scanning electron microscope (SEM) and transmission electron microscope (TEM). This disadvantage of using the SEM is that it has low resolution and could provide information from the surface of the material. However, if cathodoluminescence is measured using a TEM, higher resolution allows one to make a more accurate peak analysis on the peak and even on the internal structure of the material thank to the basic characteristics of the TEM that transmits the electron beam. Among the methods of measuring cathodoluminescence using TEM, this study implements the method using a TEM holder produced directly in our laboratory. The TEM holder has a dewer that can hold liquid nitrogen, which can drop the temperature of the sample to extremely low temperature. This minimizes the energy caused by the phonon vibrations, thus confirming a more accurate structure within the band gap. In addition, the implemented method also includes using the software QTCL produced in our laboratory. β-Ga2O3 is a substance with various phases such as α-, β-, γ-, δ-, ε- and so on. Among them, β-Ga2O3 has a monoclinic structure and a C2/m spatial family, known to be the most stable. β-Ga2O3 is a material with a wide band gap of 4.6-4.9eV and is widely used in the application of several electronic devices using these properties. In this study, the structural and optical properties are measured using materials in which β-Ga2O3 grown on sapphire substrates and the analysis is concerned. It is crucial to first discuss the study on the structural properties of β-Ga2O3. Since sapphire has a Hexagonal structure, when observing an XTEM sample, sapphire substrates has two main zone-axis directions [2-1-10] and [10-10]. β-Ga2O3 deposition on sapphire substrates also has two directions [102], [010], of which [102] Diffraction Patterns are not reported much. The experiment was conducted on sapphire substrates with 100 nm depth of deposition of β-Ga2O3 and IGZO (Indium-Gallium-Zinc-Oxygen) respectively. An unconfirmed crystal surface was found during the observation on the XTEM specimen, which was analyzed by its Diffraction Patterns, Dark Field, and High Resolution images. The results for the analysis were found to be β-Ga2O3 (512) on the zone-axis [1-92]. The second part is about the study on the optical properties of β-Ga2O3. β-Ga2O3 has three emission areas: UV, Blue and Green, From near-infrared to visible light. UV lights and Blue lights are wavelength regions that also appear in β-Ga2O3 that are undoped. Based on this point, the cathodoluminescence analysis of β-Ga2O3 was conducted with the TEM-CL system. The experiment was conducted with an XTEM specimen in which β-Ga2O3 200nm was deposited on sapphire substrates. The results showed that the light in the UV region was divided into two parts. UV(I) was strongly derived from the area having a thin width just above the sapphire substrates. UV(Ⅱ) and Blue also confirmed that the cause of luminescence of β-Ga2O3 that we have been working on is due to the transfer between the Self-Trapped-Hole (STH) and the Conduction Band transition and the Donor and the Acceptor transition respectively. Future experiments will greatly contribute to the determination of the optical properties of β-Ga2O3 by analyzing the area where UV(I) occurs most and comparing it to the other areas of β-Ga2O3.1. INTRODUCTION 1 1.1 TEM-Cathodolumienscence(CL) 1 1.2 Basic Properties of β-Ga2O3 4 1.3 Experimental Detail 6 2. STRUCTURAL PROPERTIES OF Β-GA2O3 8 2.1 XTEM Image and DP analysis 8 2.2 Analysis of HR Image 10 2.3 PTEM Image and DP analysis 14 2.4 Atomic modeling 15 3. OPTICAL PROPERTIES OF Β-GA2O3 18 3.1 TEM-CL spectrum analysis 18 3.2 Monochromatic Image analysis 22 3.3 Analyze the cause of thin width in UV(Ⅰ) 25 4. CONCLUSION 27 5. REFERENCES 29Maste

베트남 냐짱 지역의 뎅기 역학조사: 뎅기의 임상진단과 실험실진단의 연관성

학위논문 (석사)-- 서울대학교 대학원 : 보건대학원 보건학과, 2018. 2. 조성일.Dengue is a leading cause of morbidity in Vietnam with gradual increase from 32.5 per 100,000 population in 2000 to 120.0 per 100,000 population in 2009. In Vietnam, almost all cases of dengue virus (DENV) infection are diagnosed clinically based on the WHO guideline (2009), but it is commonly under-reported and many cases are misclassified due to its broad spectrum of symptoms shared with other febrile diseases. On behalf of the Dengue Vaccine Initiative (DVI), the International Vaccine Institute (IVI) assessed the strength of association between clinical and laboratory-confirmed diagnoses of dengue infection from a passive hospital-based surveillance study in Nha Trang City, in Khanh Hoa province, Vietnam from July 2014 to December 2015. The study was designed to determine the true burden of dengue, symptomatic infection of all fever cases among children and adults between 1 and 55 years of age in a defined population. Clinical signs and symptoms of 553 dengue patients and 1,152 non-dengue patients (laboratory-confirmed by IgM and IgG capture ELISA or real-time PCR) were analyzed. Leucopenia (OR = 6.03), thrombocytopenia (OR = 1.97), rash (OR = 1.90), headache (OR = 1.75), arthralgia (OR = 1.75), petechiae (OR = 1.71), and nausea/vomiting (OR = 1.42) were highly associated with laboratory-positive dengue cases in the absence of respiratory signs and symptoms such as rhinorrhea (OR = 0.41) and expectoration (OR = 0.39). A comparison between adults and children of laboratory-confirmed dengue cases revealed that the frequency of clinical signs and symptoms was different between two age groups. DENV infected adults were more likely to present flushed face (OR = 2.13), headache (OR = 2.10), rash (OR = 1.96), thrombocytopenia (OR = 1.91), and arthralgia (OR = 1.83) which were not apparent to DENV infected children. Overall sensitivity and specificity of clinical diagnoses were 57.7% and 92.0% with diagnostic accuracy of 80.9%. Once validated, those key clinical features for children and adult patients with dengue infection may improve the future clinical outcomes, especially in the resource-poor dengue endemic countries, as they would allow more closely monitoring of selected patients and it may affect the sensitivity of clinical diagnosis.I. Introduction 9 1. Dengue virus infection and its clinical manifestations 9 2. Global burden of dengue 11 3. Dengue in Vietnam 12 4. Objective of the study 15 II. Methods 16 1. Study area and population 16 2. Study Design 18 3. Sample collection 19 4. Laboratory testing 19 5. Case definitions of clinical diagnosis 20 6. Data management 21 7. Statistical analysis 22 8. Ethics 22 III. Results 24 1. Study enrollment and lab results 24 2. Demographic information of dengue patients 27 3. Medical information of dengue patients 31 4. Dengue serotypes 31 5. Seasonal and regional distribution of dengue cases 32 6. Clinical features of dengue patients 36 7. Comparison of clinical features between adults and children 41 8. Evaluation of clinical diagnostic accuracy 44 IV. Discussion 47 V. Reference 54 VI. 국문초록 61Maste

The Effect of duration of ischemia and body temperature on the expression of BaxBcl-2 in the hippocampus of gerbil in transient global ischemia

학위논문(박사)--서울대학교 대학원 :의학과 신경과학전공,2000.Docto

액체표적 가속기 빔창의 열적,구조적 건전성 평가 및 설계

Thesis (master`s)--서울대학교 대학원 :원자핵공학과,2001.Maste

Gerbil의 일과성 전뇌허혈모델에서 Lamotrigine에 의한 해마의 지연성 신경세포손상 감소효과

학위논문(석사)--서울대학교 대학원 :의학과 신경과학전공,1998.Maste

도덕적 해이 상황에서 기업의 자본증자방법에 관한 연구

학위논문 (석사)-- 서울대학교 대학원 : 경제학부, 2017. 2. 김선구.본 논문은 금융시장에 도덕적 해이가 존재하고 투자비용이 고정되어 있을 때 기업이 보유한 자본량에 따라 채권발행, 은행 대출, 주식 발행과 같은 자본증자방법 가운데 어떤 것을 선택하는지 밝힌다. 본 논문에서는 주식발행을 기업의 자본증자방법으로 고려하지 않았던 기존 모형에 주식발행을 통한 자본증자방식을 추가하여도 균형이 변하지 않음을 보인다. 또한 기존 모형에 투자계획안 선택 변수를 추가할 경우 기업이 주식발행을 포함한 다양한 형태로 외부자본을 차입하는 것을 밝힌다. 본 모형의 결과는 일본 자본시장에 나타난 변화와 대략적으로 일치함을 밝힌다.This paper studies how a firm determines its financial structure by raising funds through equity issues, bond financing, and bank debt under the moral hazard when the investment cost is fixed. It shows that the equilibrium discussed earlier in the literature which did not consider an option of equity issue does not change even if the option is taken into consideration. It also shows that a firm decides to raise funds in different ways including equity issues in case the firm has a project choice. The predictions of the model presented in this paper are broadly consistent with the changes in corporate financing in Japan during the 1980s and 1990s since the liberalization of its financial market.1. 서론 1 2. 기본 모형 3 3. 회사의 자본증자방법 5 3.1 직접금융 5 3.2 간접금융 10 4. 확장 모형 16 5. 맺음말 22 참고문헌 24 Abstract 25Maste

군소의 장기기억 관련 유전자 및 공포기억에서 NMDA 수용체 NR2B의 기능에 대한 연구

Thesis(doctoral)--서울대학교 대학원 :협동과정 유전공학전공,2006.Docto

Effects of substrate termination of SrTiO3 (111) on the growth characteristics of epitaxial BLT thin films

Maste