박막 아이언 셀레나이드 초전도체 : 주사형 탐침 현미경 연구

학위논문 (박사)-- 서울대학교 대학원 자연과학대학 물리·천문학부, 2017. 8. 국양.Since the discovery of superconducting phenomena by H. K. Onnes in 1911[1], superconductors have become a major research field in the solid states physics. Numerous physicists have discovered new superconductors and are working to physically explain superconductivity phenomena. In surface science, superconductors are also an interesting research topic. It mainly studies how low-dimensional physical phenomena appear in superconductors and how superconductivity itself changes at low dimension. I have studied superconductivity phenomenon in low dimension, especially two dimension, using scanning tunneling microscope (STM). The superconducting samples used in the study are tetragonal FeSe on SrTiO3(100) and hexagonal FeSe on SrTiO3(100). Tetragonal FeSe has the simplest structure among the iron chalcogenide superconductor. In 2012, the Xues group in China found that when 1 ML FeSe was grown on SrTiO3(100), the critical temperature rose to over 60 K [2], many physicists have gone into this study and tried to figure out why the critical temperature has improved . This study was initiated to clarify the pairing mechanism of tetragonal FeSe on SrTiO3(100). I analyzed the spectroscopy of STM and found the frequency of the bosonic mode that is involved in the Cooper pairing using the Eliashberg model. And I tried to find out what the expected bosonic mode is. Next, hexagonal FeSe, which is a new phase of FeSe, was grown on SrTiO3(100) and its physical properties were measured using STM. The newly discovered hexagonal phase FeSe shows many experimental results consistent with the superconducting phenomenon, but further studies are needed to confirm it as a new superconductor.Chapter 1. Introduction to Superconductivity 1 1.1 Conventional Superconductor 4 1.1.1 Basic Introduction 5 1.1.2 BCS Theory 7 1.1.3 Eliashberg Theory 11 1.2 Unconventional Superconductivity 19 1.3 Thin-film Superconductivity 22 Chapter 2. Scanning Tunneling Microscopy and Spectroscopy 24 2.1 Principle of STM 24 2.1.1 Tunneling 25 2.1.2 Topography 29 2.1.3 Tunneling Spectroscopy 30 2.1.4 Inelastic Electron Tunneling Spectroscopy 31 2.2 Instrumentation 32 2.2.1 STM Scanner 32 2.2.2 Ultrahigh Vacuum Chamber 34 2.2.3 He3 Sorption Pumping System 36 Chapter 3. STM Study of Surface Phonon on Cu2O 38 3.1 Surface Phonon 38 3.1.1 Basic for Surface Phonon 38 3.1.2 Previous Measurement of STM-IETS 40 3.2 Surface Phonon Measured by STM-IETS 40 3.2.1 Surface Structure of Copper Oxide 41 3.2.2 STM-IETS on Copper Oxide 47 Chapter 4. STM Study of tetragonal FeSe on SrTiO3(100) 56 4.1 Introduction 56 4.1.1 Superconductivity on FeSe : From 3D to 2D 58 4.1.2 Monolayer FeSe on SrTiO3(100) 58 4.2 Experimental Results 60 4.2.1 Superconductivity and Growth Condition 60 4.2.2 Electronic Structure and Symmetry 63 4.2.3 Phase Diagram 66 4.2.4 Bosonic Modes 68 Chapter 5. STM Study of hexagonal FeSe on SrTiO3(100) 71 5.1 Introduction 71 5.1.1 Various Phase of FeSe 71 5.1.2 Hexagonal Phase of FeSe 73 5.2 Experimental Results 74 5.2.1 Structure and Spectroscopy of hexagonal FeSe 74 5.2.2 Possibility as a New Superconductor 76 Chapter 6. Conclusion 79 Appedix. A. Study of (√3×√3)R30°-Se/Au(111) 80 Appedix. B. Various Phase of CuSe on Cu(111) 83 Appedix. C. Magnetic Domain on Co/Pt(111) 84 Bibliography 86Docto

A Study on the Dynamic Analysis of Mooring System During Hook-up Installation

This paper has conducted research on Hook-up installation of offshore site installation process. Hook-up installation is the final step in offshore site installation process, and conducted with AHTS(Anchor Handling Tug Supply vessel) which retrieve the bottom line and tug boat for station keeping. During Hook-up installation, the offshore structure can have a detrimental effect on work stability due to low frequency motion and economic costs can be occurred by increasement of available days of tug boat. This study developed a numerical analysis program for the dynamic behavior of mooring systems during hook-up installation to review the generally performed installation process and determine when the tug boat should be released. In this program, the behavior of offshore structure is calculated by Cummin’s time domain motion equation and the mooring systems are calculated by Lumped Mass Method(LMM). In addition, the program is calculated by tug boat algorithm for hook-up installation. The model used in the calculations is barge type assuming FPSO and has a taut mooring system with 16 moorings connected. The hook-up simulation calculates offset of the structure according to the number of tug boats, and the calculation result is shown using significant value. The hook-up installation procedure was constructed so that the offset of the structure does not exceed 6 m, and the released timing of tug boats was decided considering the stability and economic aspects of the structure.목 차 List of Tables ⅲ List of Figures ⅳ Abstract ⅵ 1. 서론 1.1 연구배경 및 목적 1 1.2 연구동향 2 1.3 연구내용 3 2. 프로그램 개발 2.1 운동방정식 4 2.2 파랑 강제력 5 2.3 계류 해석 5 2.3.1 집중질량법 (Lumped Mass Method, LMM) 6 2.3.2 복원계수행렬 산정법 6 2.4 풍력 및 조류력 7 2.5 예인선 알고리즘 8 2.6 해석 절차 10 3. 프로그램 검증 3.1 모델 정의 11 3.2 계류시스템 정의 12 3.3 운동응답에 대한 검증 13 3.4 예인선 알고리즘에 대한 검증 15 4. Hook-up 시뮬레이션 4.1 Hook-up 설치 개요 16 4.1.1 해양설치작업선(AHTS) 16 4.1.2 일반적인 Hook-up 절차 17 4.2 외력 환경 조건 18 4.3 Hook-up 시뮬레이션 without Tug boats 19 4.3.1 Case 1 ) Exciting force : Wave 19 4.3.2 Case 2 ) Exciting force : Current 22 4.3.3 Case 3 ) Exciting force : Wind 23 4.4 Hook-up 시뮬레이션 with Tug boats 24 4.5 해석 결과 37 5. 결론 참고문헌Maste

Substitution effect of fish meal with meat meal in diet on growth performance, feed consumption, feed utilization, chemical composition, hematology, and innate immune responses of rockfish (Sebastes schleheli)

Fish meal (FM) is widely used as a main protein source in formulated feed for marine fish culture. However, the production of FM has shrunk or plateaued due to the overfishing and climate change in the wild. Meat meal (MM) is known as a good replacer for FM in fish feeds. Dietary replacement effect of MM for FM on the growth, feed consumption, feed utilization, body composition, hematology, and innate immune responses of rockfish was determined. A total of 630 fish (initial weight of 2.3 g) was randomly distributed into 21, 50 L flow-through tanks (30 fish/tank). Seven experimental diets were formulated. The control (MM0) diet contained 55% FM. Then, 10, 20, 40, 60, 80, and 100% FM in the MM0 diet were replaced with MM, referred to as the MM10, MM20, MM40, MM60, MM80, and MM100 diets, respectively. All experimental diets were allocated to triplicate groups of fish. Fish were hand-fed to visual satiation twice a day for 8 weeks. Increased substitution of FM with MM in diets resulted in decreased essential amino acids (EAA), such as lysine and threonine and the sum n–3 highly unsaturated fatty acids, but increased EAA, such as arginine and methionine, and the sums of saturated and monoene FA. Weight gain (9.8 g/fish) of fish fed the MM10 diet was significantly (P < 0.003) greater than that (8.8, 8.9, 8.2, and 7.9 g/fish, respectively) of fish fed the MM0, MM60, MM80, and MM100 diets. Specific growth rate (SGR) (2.93%/day) of fish fed the MM10 diet was significantly (P < 0.004) higher than that (2.79, 2.69, and 2.64%/day, respectively) of fish fed the MM0, MM80, and MM100 diets. Weight gain and SGR of fish fed the MM100 diet were (P < 0.05) significantly lower than those of fish fed the MM0 diet. Feed consumption (9.34 g/fish) of fish fed the MM10 diet was significantly (P 0.05) different among the experimental diets. The chemical composition, and AA and FA profiles of the whole-body fish were not influenced by the experimental diets. In conclusion, dietary substitution FM up to 80% with MM can be made without deteriorating growth performance of rockfish. However, the optimum substitution level of FM with MM in diets were estimated to be 18.5 and 18.2% based on regression analysis of weight gain and SGR of rockfish, respectively.1. Introduction 1 2. Materials and Methods 4 2.1. Preparation of the experimental fish and conditions 4 2.2. Preparation of MM and experimental diets 4 2.3. Measurement of the growth of rockfish 7 2.4. Analysis of the chemical composition of the experimental diets and whole body of fish 8 2.5. Analysis of AA and FA profiles of the experimental diets and fish 8 2.6. Hematological parameters of fish 9 2.7. Analysis of innate immune responses of fish 10 2.8. Statistical analysis 10 3. Results 12 3.1. AA and FA profiles of experimental diets 12 3.2. Performance of rockfish at the end of the 8-week feeding trial 16 3.3. Biological indices of rockfish in the 8-week feeding trial 23 3.4. Chemical composition of the whole-body rockfish at the end of the 8-week feeding trial 25 3.5. Plasma parameters of rockfish in the 8-week feeding trial 27 3.6. Innate immune responses of rockfish in the 8-week feeding trial 29 3.7. AA and FA profiles of the whole body of rockfish in the 8-week feeding trial 31 4. Discussion 35 5. Conclusion 43 References 44Maste

상전이 촉매 알킬화 반응을 통한 -acetylthio--alkylmalonate의 입체선택적 합성

학위논문 (석사)-- 서울대학교 대학원 : 약학과, 2015. 2. 박형근.비대칭적인 -thio malonate는 유기합성에서 높은 합성적 가치를 지니는 출발 물질이며，양쪽의 ester group을 변환시킴에 따라 생물학적 활성이 있는 천연물이나 의약품을 합성 하는데 이용될 수 있다. 황 원소를 포함하는 비대칭적인 4차 탄소 골격을 만들기 위한 많은 시도가 있었으나, 기질의 준비와 작용기의 변형이 어려운 단점이 있었다. 이에 앞서 본 연구실에서는 최초로 상 전이 촉매 반응을 통한 malonate 의 입체 선택적인 α-alkylation을 성공적으로 수행한 바 있다. 앞서 수행한 α-acetoxymalonate와 α-benzoxymalonate를 이용한 1,3-dicarbonyl 화합물의 입체 선택적인 α-hydroxylation 연구를 확장하기 위하여, 본 연구자는 황 원소를 포함하는 비대칭적 4차 탄소 골격을 만들기 위해 촉매로 (S,S)-3,4,5-trifluorophenyl-NAS bromide를 사용하고 tert-butyl diphenylmethyl α-acetylthiomalonate를 기질로 하여 입체선택적인 alkylation을 수행하였고, 상 전이 촉매 반응 (Phase-Transfer Catalysis)을 통해 높은 화학 수율 (99%)과 광학 수율(95% ee)을 보이며 다양한 chiral 중간체로 변환될 수 있는 α-acetylthio-α-alkylmalonate를 성공적으로 합성하였다.INTRODUCTION 1. General characteristics of malonate compounds 2. Phase-transfer catalysis 2-1. Phase-transfer catalysis 2-2. Mechanism of chiral phase-transfer catalysis 2-3. Phase-transfer catalyst 3. Asymmetric alkylation via phase-transfer catalysis 3-1. The first efficient chiral phase-transfer catalysis 3-2. The first chiral phase-transfer catalysis of malonate 3-3. Previous approaches to construct S-bearing chiral carbon center RESULTS AND DISCUSSION 1. Substrate design and preparation for PTC alkylation 2. Enantioselective phase-transfer catalyst reaction of α-acetylthiomalonate 2-1. Optimization of PTC reaction of α-acetylthiomalonate 2-2. Optimization of PTC reaction of α-acetylthiomalonate 3. Application of α-acetylthio-α-alkylmalonates CONCLUSION EXPERIMENTAL SECTIONMaste

아밀로이드 응집체의 구조적 성질과 응집 과정에 대한 계산 연구

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 화학부, 2023. 8. 신석민.Diseases arise from the disruption of precisely regulated networks of interactions among biomolecules in biological systems. Understanding disease origins involves deciphering disease-related regulatory networks, identifying malfunction causes, and restoring normal states. Recently, there has been a growing focus on targeting diseases at the protein level with a specific and systematic approach. The growing focus on age-related diseases, especially neurodegenerative diseases, is motivated by the extended human lifespan. Neurodegenerative diseases encompass various neurological disorders associated with age-related brain dysfunction and neuronal loss. These diseases are characterized by amyloid aggregation, a consequence of protein misfolding, which is an emerging and intriguing field of study. The complexity of amyloid aggregation, with its diverse forms and intermediates, arises due to the characteristics of Intrinsically Disordered Proteins that possess energy landscapes with multiple local minima. In this thesis, three computational discussions for the elucidation of neurodegenerative diseases are introduced: (1) a novel enhanced sampling method which can be used for systems where metastable states play important roles, (2) the structure and aggregation pathway of Aβ42 protofibril which is associated with Alzheimers disease, and (3) the structural stability as the origin of the pathogenicity of α-synuclein protofibrils which is related to Parkinsons disease. These findings provide insights and information that can aid in understanding the structural and dynamical characteristics of the systems associated with neurodegenerative diseases.질병은 생물학적 시스템 내에서 생체 분자 간에 정확하게 규제되고 있던 상호작용 네트워크에 교란이 일어나서 발생한다. 질병의 기원에 대한 연구한다는 것은 관련된 네트워크에 대한 이해, 그 네트워크에 발생한 장애의 원인 식별, 그리고 그것의 정상 상태 회복을 뜻한다. 최근 과학 및 기술의 발달에 따라 단백질 수준에서 질병에 대해 연구하기 시작했다. 특히, 인간의 수명이 늘어나면서 발생하고 있는 연령 관련 질병에 대한 관심이 증가하고 있다. 신경퇴행성 질환은 연령 관련 뇌 기능 장애와 신경세포의 손실과 관련된 다양한 신경학적 장애를 포괄한다. 이러한 질병은 단백질 변형의 결과인 아밀로이드 응집체로 특징 지어지며, 이는 흥미로운 연구 분야인 단백질 변형의 결과로 이해되고 있다. 다양한 형태와 중간체를 가지는 아밀로이드 응집체의 복잡성은 에너지 랜드스케이프에 다중 지역 최소값을 가지는 본질적으로 무질서한 단백질의 특성에 기인한다. 이 학위 논문은 신경퇴행성 질환의 규명을 위해 수행된 세 가지의 계산 연구 결과를 담고 있다. 첫번째는 새로 개발한 강화 샘플링 방법으로 준안정상태들이 중요한 시스템의 샘플링에 사용할 수 있다. 두번째, 알츠하이머병과 관련된 아밀로이드 베타 프로토 파이브릴의 구조적 안정성을 밝혔고 또한 응집 과정을 유추할 수 있는 실마리에 대해 논하였다. 마지막으로 파킨슨병과 관련된 알파 시뉴클린 프로토 파이브릴 구조들의 구조적 안정성을 비교하여 어떤 구조가 병원성 원인으로서 작용할 것인지를 알아보았다. 이 결과들 및 여기에서 사용한 방법론들이 신경퇴행성 질환과 관련된 시스템의 구조적 및 동적 특성을 이해하는 것에 대한 정보와 통찰을 제공할 것으로 기대된다.Abstract i Table of Contents iii List of Figures and Tables v Chapter 1. Introduction 1 Chapter 2. Conformational Sampling of Metastable States: Tq-REM as a Novel Replica Exchange Method 6 2.1. Introduction 6 2.2. Methods 8 2.3. Simulation Protocols 11 2.4. Results 14 2.5. Discussion and Conclusions 26 2.6. Figures 30 Chapter 3. Structure and Aggregation Pathway of Aβ42 Amyloid Protofibril 50 3.1. Introduction 50 3.2. Methods 52 3.3. Results and Discussion 55 3.4. Conclusions 67 3.5. Figures and Tables 70 Chapter 4. In Silico Investigation of the Structural Stability as the Origin of the Pathogenicity of α-Synuclein Protofibrils 91 4.1. Introduction 91 4.2. System Preparation 94 4.3. Simulation Protocols 95 4.4. Results and Discussion 97 4.5. Conclusions 110 4.6. Figures 114 Chapter 5. Conclusion 129 Bibliography 133 국문초록 160박

위상배열 레이다 시스템의 최적 기움각과 빔조사 특성

학위논문(박사) - 한국과학기술원 : 전기및전자공학과, 1999.2, [ viii, 86 p. ]For radar systems, phased array antenna involves many design options. Often, the most important parameters in optimizing the design are cost and weight. In phased array antennas, the number of radiator rows is one of the important factors to minimizing both cost and weight. This is so because cost and weight are directly proportional to the number of radiator rows. Therefore, the choice of antenna tilt angles having relation with element spacing are important design parameters in the radar system design. The optimum tilt angles for several types of uniformly and nonuniformly excited linear arrays are investigated theoretically. Four types of uniform and nonuniform linear arrays are considered, namely, arrays of isotropic elements, of collinear short dipoles, and of parallel short dipoles, and broadside array of dipole crosses. As a nonuniformly excited array case, directivities of Chebyshev array factors are computed to obtain the optimum tilt angle. Next, the exact directivity including phase shift factors for several types of uniformly excited planar arrays is obtained. The approximate directivity calculations are compared with the exact results. Curves of directivity versus interelement spacing and scan angle for planar arrays with these element power patterns are also presented. The optimum tilt angles for several types of dipole planar arrays are obtained. We propose two critera to determine the optimum tilt angles for planar antenna arrays. One is maximizing the directivity in the azimuth direction at the horizon and the other is maximizing the lowest directivity in the azimuth direction. Lastly, the beam steering commands (such as the phase and frequency commands) for a desired beam position in the rotating phase and frequency scan radar (RPFSR) system are derived in terms of the ground based coordinate system. In general, the antenna coordinate system does not coincide with a ground based (or earth fixed) coordinate system. Because the normal of the...한국과학기술원 : 전기및전자공학과