중력에 의한 결잃음: 열린 양자계 관점으로.

학위논문 (석사)-- 서울대학교 대학원 : 자연과학대학 물리·천문학부, 2018. 2. 이상민.This thesis addresses various sources of fluctuation and discusses how quantum states are affected by these fluctuations based on the semi-classical gravity theory, especially in relation to the macroscopic quantum state. First, due to the time dilation effect of gravity, decoherence with respect to the proper time basis can arise. By taking a different approach from that taken in previous work (Zych et al.), we analyze the case of a constant-acceleration field using the concept of Rindler space-time. Furthermore, given that proper acceleration is proportional to the Unruh temperature, we link it to an experimental proposal of decoherence using the fluctuations in the Unruh temperature. Secondly, in a macroscopic system, the self-localization effect toward the position of the center of mass arises due to fluctuations in the interaction potential. This leads to decoherence with regard to the position basis (the Diósi-Penrose Model). Furthermore, when considering gravity as a classical channel with noise, localization can also be explained by a weak measurement of each mass (the Kafri-Taylor-Milburn Model). Finally, we checked the decoherence effect not merely by examining the quantum characteristics, as is usually done, but with classical fluctuation in the metric field stemming from the dynamics of the field source. In fact, due to the dominance of classical fluctuation, we attempt to analyze this from another perspective. Specifically (In particular), the energy scale between the gravitational wave which represents the classical field and graviton which indicates the quantum field is nearly 3 ∗ 10^37. Hence, the leading effect of gravitational decoherence is followed by fluctuation of the gravitational wave. Furthering this analogy, we obtain additional data pertaining to the kernel in terms of Newtonian interaction in the DP model from the fluctuation in the classical field and clarify what this solution indicates.Chapter 1 Introduction 1 Chapter 2 Decoherence Theory 8 2.1 Density matrix formula 9 2.1.1 Properties of the density matrix 9 2.1.2 Parameters of decoherence in the density matrix 10 2.1.3 Wigner function 11 2.2 Kraus operator sum method 12 2.2.1 Definition of Kraus operator sum method 12 2.2.2 POVM measurement 13 2.3 Quantum error process and decoherence channels 14 2.3.1 Quantum errors 14 2.3.2 Depolarizing channel 15 2.3.3 Amplitude damping 16 2.3.4 Phase dephasing 17 2.4 Environment induced einselection 18 Chapter 3 Quantum Master Equation 21 3.1 Interaction picture 22 3.2 Derivation of the quantum master equation 23 3.3 Approximations 25 3.4 Lindblad equation 31 3.5 Example 1. Spontaneous emission 32 3.6 Example 2. Decoherence of Schrodinger cat state 37 Chapter 4 Decoherence due to time dilation 40 4.1 Hamiltonian approach 41 4.2 Gravity effects in quantum phase 43 4.2.1 Mach-Zehnder interferometry and Hong-Ou-Mandel effect 43 4.2.2 Which-way detector and the proper time state 46 4.3 Prepared state in proposal 49 4.4 Master equation approach 52 4.5 How does interference fall in Rindler spacetime 56 Chapter 5 Quantum leaks of spacetime: Decoherence through semi-classical gravity 58 5.1 Newtonian gravity mechanisms on the localization and decoherence 60 5.2 Schrodinger-Newton equation from Semi-classical gravity: Wave function collapse model 62 5.3 Gravity as classical channel 67 5.4 Classical fluctuation and Decoherence 73 Appendix Chapter A Example of POVM measurement 78 Appendix Chapter B Classical fluctuation and decoherence example:Magnetic field fluctuation. 82Maste

Layer-by-Layer 적층법을 이용한 중공형 그래핀 캡슐 형성에 관한 연구

학위논문 (석사)-- 서울대학교 대학원 : 화학생물공학부(에너지환경 화학융합기술전공), 2012. 8. 차국헌.본 연구는 Layer-by-Layer 적층법을 이용하여 중공형 그래핀 캡슐을 형성하고 이를 구성하는 산화 그래핀이 캡슐의 기계적 특성에 미치는 영향에 대한 연구로서, 산화 그래핀의 적층 횟수에 따른 두께, 크기, 그리고 열적 환원에 의한 캡슐의 구조적 변화를 다각적으로 관찰하였다. 중공형 캡슐 구조를 구현하기 위해 표면을 카르복실기로 치환시킨 실리카 구형 입자를 템플레이트로 사용하여 불화수소산(hydrofluoric acid)으로 선택적으로 제거하였으며, 산화 그래핀의 크기를 조절하기 위해 용매의 pH 값과 초음파처리 시간을 변경하여 다양한 크기 (59 ~ 485 nm)의 산화 그래핀 용액을 형성하였다. 이와 같은 방법으로 준비된 캡슐은 적층 횟수가 많거나 산화 그래핀의 크기가 클수록 본래 템플레이트의 구형 구조를 유지하는 경향을 보였으며, 특히 열적 환원을 가할 경우 그 변화가 가장 분명하게 관찰되었다. 이러한 경향은 힘 분광기 (force spectroscopy)를 통한 각 캡슐의 상대적 경도분석에서도 동일하게 확인되었다.Since the first successful isolation of graphene in 2004, the field of graphene research has blossomed over the last several years owing to their superior properties such as high electrical and thermal conductivity, strong mechanical strength, flexibility, and so forth. Among many production methods of graphene, the exfoliation of graphite oxide (i.e. graphene oxide (GO)) enables the layer- by-layer (LbL) deposition, which takes advantages of electrostatic attractions between GO sheets. In the present study, we report graphene hollow capsules, recently reported 3-dimensional graphene structure, made of differently sized GO sheets with aim of accurate control of their mechanical properties. A fabrication of graphene hollow capsule was carried out by electrostatic LbL deposition of oppositely charged GO sheets on silica colloidal templates followed by template removal with hydrofluoric acid treatment. A dispersion of random-sized GO sheets was separated by modulating their dispersion stability and controlling destruction in grain structure. Dispersion stability of GO sheets was controlled by pH value of solution, directly related to the degree of ionization of their functional groups, and centrifugation. Destruction in grains of GO sheet was simply controlled by ultrasonication. Those size-fractionized GO sheets provide controllability of mechanical properties of capsules, which were confirmed by scanning electron microscopy (SEM) and force spectroscopy by scanning probe microscopy (SPM). Furthermore, the effect of reduction was also investigated via thermal reduction in inert atmosphere. The present study offers hollow capsules with narrowly size-distributed GO sheets which allow the clear pathway for overcoming intrinsic problem of GO composite systema heterogeneity in size of GO sheets due to random destruction during exfoliation. This novel graphene hollow capsule system may be appropriate for replacing organic/inorganic capsules widely studied in drug delivery, bio-imaging, and framework for catalysts as graphene provides unique characteristics of biocompatibility, mechanical strength, electrical and thermal conductivity.Chapter 1. Introduction 1 Chapter 2. Experimental Section 3 2.1 Materials and Characterization 3 2.2 Synthesis of Graphene Oxide 4 2.3 Preparation of Graphene Hollow Capsules 5 2.4 Size Fractionation of Graphene Oxide Sheets 6 2.5 Thermal Reduction of Graphene Oxide Hollow Capsules 6 Chapter 3. Results and Discussion 8 3.1 Layer-by-Layer Deposition of Graphene Oxide 8 3.2 Hollow Capsules: Size Fractionized Graphene Oxide Sheets 13 3.3 Hollow Capsules: Thermally Reduction 18 3.4 Force Spectroscopy of Graphene Hollow Capsules 23 Chapter 4. Conclusion 30 References 31 초록 34Maste

Adaptation of evidence based surgical wound care algorithm

학위논문 (석사)-- 서울대학교 대학원 : 간호학과 간호학전공, 2011.2. 최스미.Maste

전기장으로 제어된 액정 주형을 활용한 패턴화된 나노 섬유 제작

학위논문(석사) - 한국과학기술원 : 화학과, 2024.2,[ii, 30 p. :]Liquid crystals (LCs) have been employed to derive tunable physical properties that arise dynamically from their intrinsic properties in response to external stimuli, which can serve as templates for aligning functional guest materials. One of the ways to use liquid crystal templates is to grow oriented polymers by aligning monomers. We fabricate patterned fiber arrays in electrically modulated nematic liquid crystal molds using a chemical vapor deposition polymerization (CVP) method. Under an electric field, the induced fault structure with the number of turns $-1/2$ contains periodic zigzag displacement lines. It is known that liquid crystal defect structures can trap guest materials such as particles and chemicals. However, the resulting fibers grow along the liquid crystal orientation rather than being trapped in defects. To demonstrate the versatility of our platform, nanofibers were fabricated at different scales with patterned electrodes representing the alphabet letters “CVP”. Additionally, semi-fluorinated moieties were added to the fibers to create a hydrophobic surface, and it was confirmed that patterned fiber arrays can improve both the hydrophilic and hydrophobic properties of the surface. The resulting orientation-controlled fibers are used in controllable smart surfaces that can be used in sensors, electronics, photonics, and biomimetic surfaces.한국과학기술원 :화학과