전자지방정부 구현을 위한 GIS 활용방안 연구(Strategies for implementing GIS-based local E-government)

노트 : 이 연구보고서의 내용은 국토연구원의 자체 연구물로서 정부의 정책이나 견해와는 상관없습니다

산화물 초박막에서 나타나는 발현 현상의 조절 및 연구

학위논문(박사) -- 서울대학교대학원 : 자연과학대학 물리·천문학부(물리학전공), 2024. 2. Changyoung Kim.본 논문에서는 ABO3 페로브스카이트 구조를 갖는 루테네이트와 이리데이트의 초박막 시스템에서 나타나는 새로운 현상들을 연구한다. 여러 흥미로운 현상이 활발히 보고되고 있는 루테네이트의 경우, 다양한 접근법을 통해 발현 현상을 조절하는 데 중점을 두었다. 한편, 이리데이트에 대한 연구는 전자 구조적 관점에서 초박막에서 나타나는 새로운 현상에 초점을 맞추었다. 이 논문의 결과 섹션의 전반부에서는 SRO 초박막의 수송 현상 조작에 대해 다룬다. SRO의 순회 강자성은 초박막 두께 조건에서 부호가 변하는 변칙 홀 효과 (AHE), 홀 저항의 혹 구조, 부호가 변하는 일반 홀 효과 등 다양한 수송 현상을 유도한다. 본 연구에서는 초박막 SRO 필름의 자기 수송 현상을 이해하기 위해 초박막의 반전 대칭성 깨짐 (ISB) 정도를 조절하여 홀 저항의 AHE와 혹 구조를 제어한다. ISB를 제어하기 위한 방법으로 캡핑층 증착과 전기장 게이팅을 사용했다. 특히 초박막 금속 박막의 게이팅 실험에 효과적인 이온성 액체 게이팅 방법을 사용하여 SRO 박막에 전기장을 인가하였다. 다음으로 SRO 초박막의 또 다른 수송 특성인 일반 홀 효과의 부호 변화를 탐구하였다. 이 효과는 SRO에서 나타나는 2차원 (2D) 반 호브 특이점 (VHS)의 전기적 제어를 통해 연구하였다. 2D VHS는 SRO를 포함한 스트론튬 루테네이트의 전자 구조의 핵심 특성으로, SRO의 순회 강자성 및 Sr2RuO4의 초전도성과 관련하여 발산 상태 밀도 (DOS)로 작용하는 것으로 이해되고 있다. 우리는 수송 측정에서 이온성 액체 게이팅 실험과 함께 알칼리 금속 도징에 의한 표면 전자 도핑으로 초박막 SRO 필름의 2D VHS를 조작하여 ARPES 측정을 수행하였다. 결과 섹션 후반부의 초박막 SIO 필름 연구에서는 주로 전자 구조의 변화와 숨겨진 현상들을 연구하는 데 중점을 두었다. 페로브스카이트 이리데이트는 큰 스핀-궤도 결합 (SOC)으로 인해 페르미 준위 근처에서 단일 Jeff = 1/2 상태의 비교적 복잡하지 않은 전자 구조를 보이기 때문에 초박막 SIO 필름에서 치수 감소가 효과적이다. 본 논문에서는 상자성 준금속 SIO가 두 단위셀 (uc)과 1 uc의 두께 사이에서 금속에서 절연체로 전이되는 것을 ARPES의 직접 전자구조 측정을 통해 보였다. 금속-절연체 전이의 이론적 타당성을 동적 평균장 이론 (DMFT) 계산을 통해 논의하고, 압축 변형에 의해 금속 단층을 얻을 수 있음을 본 논문에서 ARPES 측정을 통해 실험적으로도 증명하였다. 또한, 온도 의존적 실험과 함께 금속 SIO 단층에 대한 정밀한 ARPES 측정은 단층 SIO를 포함한 초박막 SIO 필름이 전자 구조 관점에서 평면 내 반자성 질서를 나타낸다는 것을 보여준다. 단층 SIO 필름에서 관찰된 전자 구조는 DFT+SOC+U 계산을 통해 조사되었으며, 평면 내 반자기 질서가 온도에 따른 ARPES 측정 결과를 가장 잘 설명할 수 있음을 입증했다. 평면 내 반자성 금속 단층 SIO 박막에 대한 이 연구는 스트론튬 이리듐 연구의 오랜 목표인 Jeff = 1/2 초전도 실현에 돌파구를 마련하는 데 도움이 될 수 있다.The field of ultrathin film is an emerging area of oxide materials research. In the works in this thesis, we study emergent phenomena within ultrathin film systems of ruthenate and iridate with ABO3 perovskite structure. For ruthenate, where a number of interesting phenomena have been actively reported, our emphasis is on manipulating emergent phenomena through various approaches. Meanwhile, our investigation of iridates focuses on emergent phenomena in ultrathin films from an electronic structure perspective. The first half of the results section in this thesis is dedicated to manipulating transport phenomena in ultrathin SRO films. The itinerant ferromagnetism of SRO gives rise to a variety of transport phenomena, including the sign-changing anomalous Hall effect (AHE), the presence of a hump structure in Hall resistivity, and the occurrence of a sign-changing ordinary Hall effect under ultrathin thickness conditions. To understand these magnetic transport phenomena observed in ultrathin SRO films, we control the AHE and the hump structure in Hall resistivity by manipulating the degree of inversion symmetry breaking (ISB) in the ultrathin film. Two methods, namely capping layer deposition and electric field gating, are employed to control ISB. Specifically, we apply an electric field to the SRO film using the ionic liquid gating method, known for its effectiveness in gating experiments on ultrathin metallic films. Next, we study another transport property of ultrathin SRO films - the sign-changing ordinary Hall effect. This is investigated through the electric control of the two-dimensional (2D) Van Hove singularity (VHS) in oxide ultrathin films. The 2D VHS stands out as a crucial characteristic of the electronic structure of strontium ruthenate, including SRO. It is recognized as a divergent density of states (DOS) associated with the itinerant ferromagnetism of SRO and the superconductivity of Sr2RuO4. We manipulate the 2D VHS of ultrathin SRO films through surface electron doping via alkali metal dosing in angle-resolved photoemission spectroscopy (ARPES) measurements and conduct ionic liquid gating experiments in transport measurements. In the second half of the results section, we focus on ultrathin SIO films to explore the evolution of the electronic structure and hidden emergent phenomena. Thickness reduction proves to be particularly effective in ultrathin SIO films, as perovskite iridates exhibit a relatively straightforward electronic structure characterized by a single Jeff = 1/2 state near the Fermi level due to substantial spin-orbit coupling (SOC). Through direct electronic structure measurements via angle-resolved photoemission spectroscopy (ARPES), we show that the paramagnetic semi-metal SIO undergoes a metal-insulator transition between a thickness of 2 unit-cells (uc) and 1 uc. The theoretical feasibility of this transition is discussed using dynamical mean field theory (DMFT) calculations, demonstrating that a metallic monolayer can be achieved under compressive strain. This is also experimentally validated through ARPES measurements in this thesis. Furthermore, precise ARPES measurements on metallic SIO monolayer, along with temperature-dependent experiments, reveal that ultrathin SIO films, including monolayer SIO, exhibit in-plane antiferromagnetic order from an electronic structure perspective. The observed electronic structure in the monolayer SIO film is scrutinized using density functional theory (DFT)+SOC+U calcula- tions, demonstrating that in-plane antiferromagnetic ordering best explains the temperature-dependent ARPES measurement results. This investigation of in-plane antiferromagnetic metal monolayer SIO films holds the potential to contribute significantly to realizing Jeff = 1/2 superconductivity, a longstanding goal in strontium iridate research.Preface i Abstract ii List of Figures ix 1 Introduction 1 1.1 Ruddlesden-Popper transition metal oxide 2 1.2 Dimensionality and Ruddlesden-Popper series 5 1.3 Two-dimensional (2D) system and emergent phenomena 9 1.4 2D oxide ultrathin film 13 1.5 Outline of the thesis 15 2 Experimental Methods 17 2.1 Pulsed laser deposition 18 2.2 Transport measurements 20 2.2.1 Electrical transport property 20 2.2.2 Ionic liquid gating 22 2.3 Angle-resolved photoemission spectroscopy measurement 25 3 Manipulation of emergent phenomena in SrRuO3 ultrathin films 29 3.1 Capping and gate control of anomalous Hall effect and hump structure in ultra-thin SrRuO3 films 32 3.1.1 Anomalous Hall effect and hump structure in ultrathin SrRuO3 film 32 3.1.2 Experimental methods and film characterization 34 3.1.3 Modulation of AHE and hump structure by STO capping 38 3.1.4 Controlling AHE and hump structures by ionic liquid gating 43 3.1.5 Conclusion 44 3.2 Electric control of 2D Van Hove singularity in oxide ultra-thin films 45 3.2.1 2D Van Hove singularity and divergent density of states 45 3.2.2 Manipulation of the 2D VHS with potassium (K) deposition 48 3.2.3 2D VHS control with ionic-liquid gating 49 3.2.4 Relation between VHS and Hall coefficient of SRO 56 3.2.5 Conclusion 62 3.2.6 Methods 63 4 Investigation of emergent phenomena in SrIrO3 ultrathin films 65 4.1 Strain tunable electronic ground states in two-dimensional iridate thin films 68 4.1.1 2D oxide film and exotic phenomena 68 4.1.2 ARPES measurements of ultrathin SIO films 70 4.1.3 DMFT calculations of ultarthin SIO films 72 4.1.4 Metallic SIO monolayer by strain control 77 4.1.5 Conclusion 81 4.1.6 Experimental section 82 4.2 Two-dimensional antiferromagnetic fluctuations in a SrIrO3 single layer 85 4.2.1 Magnetic fluctuations and superconductivity in 2D system 85 4.2.2 Thickness dependent band evolution and unique band character in monolayer SIO 87 4.2.3 Temperature-dependent ARPES study of monolayer SIO 92 4.2.4 Band structure evidence for in-plane Antiferromagnetic order in monolayer SIO 93 4.2.5 Conclusion 97 References 99 Publication List 112 Korean abstract 118박

퇴행성 슬관절염에서 윤활막의 perlecan에 관한 면역전자현미경적 연구

학위논문(석사)--서울대학교 대학원 :의학과 해부학전공,2002.Maste

Studies on the immediate change in renal function following unilateral nephrectomy

의학과/박사[한글] [영문] Numerous studies have been done on the morphological and functional change in the remaining kidney after an unilateral nephrectomy. Morphologically, a compensatory tubular proliferation (Roll-assn, 1949; Simpson, 1961) and hypertrophy (Rollason, 1947; Maulard and Cier, 1961) have been demonstrated in the remaining kidney after nephrectomy. There are additional reports showing the following increased renal functions: glomerular filtration rate, renal Plasma flow (Smitk, 1941; Krohn et al., 1956), maximum concentrating and diluting capacity (Bradford, 1938; Ceburn et al., 1955), reabsorption and excretion of sodium (Hayslett,1968), oxygen consumption (Van Slyke, 1934 i Levy, 1935) and the activity of ATPase in the renal tubules (Kat2 and Epstein, 1957). Usually these functional and morphological changes in the remaining kidney had appeared by 2 weeks after an unilateral nephrectomy. Although, in recent years, a considerable number of studies concerning the hemodynamic changes and water electrolyte balance following unilateral nephrectomy have appeared; very little is known about the immediate renal change(s) after an unilateral nephrectomy. This experiment evaluated the early compensatory changes in renal function which were demonstrated immediately after an unilateral nephrectomy. Renal functions studied were GFR, RPF and urinary excretion of Na**+, K**+ etc. In addition, the tubular maximum transport capacity of glucose and PAH, and the changes in oxygen consumption were simultaneously determined. Normal healthy adult dogs of either sexes weighing approximately 10-15 kg were used. The animals were subjected to different experimental conditions before nephrectomy depending upon the nature of the experiment i.e. dehydrated, or ECF was expanded by infusing one of 0.9% NaCl, isotonic mannitol or 2% NaCl solutions. After infusions of appropriate amounts of inulin, PAH, three consecutive control samples of plasma and urine at 10 minutes intervals were obtained before unilateral nephrectomy. Samples of plasma and urine were obtained at 20 minutes intervals for 5hours after nephrectomy. The concentration of inulin, PAH, osmolarity, Na**+, K**+ and urea of the samples were determined. Results are summarized briefly as fellows. 1) When the ECF was expanded by the infusion of mannitol and then the d7g was unilaterally nephrectomized, decreases after nephrectomy in both GFR and RPF were demonstrated. However, in other experimental groups, the renal plasma flow gradually declined to level of 20∼40% of nor-mal while there was no change in the GFR. 2) In the dehydrated state, urinary excretion of sodium was slightly increased in the unilaterally nephrectomized animals as compared to the controls. On the contrary, when isotonic or hypertonic(2%) sodium chloride solution was infused pre·operatively into the animals and then they were unilaterally nephhrectomized, the excretion of sodium was markedly increased. This increase in sodium excretion was observed from 3 hours after the unilateral nephrectomy was performed. 3) An increase in Na**+ excretion after nephreotomy was demonstrated only in the groups whose ECF was expanded by infusions of NaCl solution (0.9? and 27) but was not demonstrated in the groups whose ECP had been expanded by isotonic mannitol. 4) The capacity for glucose reabsorption in the remaining kidney was not altered as compared to that seen in control animals. However, the tubular secretion of PAH was significantly reduced. 5) Essentially oxygen consumption was not changed by the unilateral nephrectomy. On the basis of above findings, it is postulated that a significant increase in sodium excretion after unilateral nephrectomy when the ECF had been expanded by an infusion of sodium chloride was the result of inhibition of sodium reabsorption in the distal nephrons and the proximal tubules. The compensatory mechanisms in the remaining kidney appeared as early as 3 hrs. after unilateral nephrectomy. However, the mechanism for the reduced PAH secretion is unknown and further experiments will be required to find the reason for the decrease.restrictio

(A) Study on the Policy Making Process and Determinants of the Military Reorganization : Focused on the 818 Plan and the Military Reform 2020

학위논문(박사) --서울대학교 대학원 :정치학과, 2009.2.Docto

탈 냉전기 일본의 방위정책에 관한 연구 : 대내외적 환경변수와의 인과관계를 중심으로

학위논문(석사)--서울대학교 대학원 :정치학과,2001.Maste

Modeling and adaptive control for a sequencing batch reactor process

학위논문(박사)--서울대학교 대학원 :토목공학과 도시공학전공,1997.Docto