고속 유동에서 충격파 및 경계층에 의한 공기광학 효과 비교

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 기계항공공학부, 2020. 8. 이복직.An antiballistic missile seeker is essential for a successful interception. However, aero-optical effects due to the flow field around the seeker window degrade the image captured using the seeker, making it difficult to identify the target. Thus, studying aero-optical phenomena and calibrating the images are necessary to improve the performance of seekers. Flight speed of antiballistic missiles are usually supersonic or hypersonic, where shock waves and boundary layers are inevitable and always exist. Therefore it is important to understand the aero-optical effects due to these flow features. In this dissertation, aero-optical phenomena due to the shock wave and boundary layer in supersonic and hypersonic flow are compared using numerical and experimental methods. In addition, a new experimental method based on background-oriented schlieren (BOS) is suggested and well validated using a Shack-Hartmann wavefront sensor in a subsonic heated jet. Because the BOS-based method could simultaneously visualize the flow and acquire optical characteristics, it is expected that flow properties could be more closely related to aero-optical effects. For supersonic flow, the flow field around the compression ramp is studied, and for hypersonic flow, the flow field around the wedge and cone model is investigated. To study the individual contribution of the shock wave and boundary layer to the wavefront distortion, numerical simulation is conducted. Flow is simulated by solving the two-dimensional Reynolds-averaged Navier-Stokes equations, and the ray-tracing method has been adopted to calculate the propagation of the optical wave. The deflection angle of the ray at the center of the laser beam is analyzed to assess the aero-optical effects caused by the shock wave and boundary layer. In the current wavefront measurement configuration, aero-optical effects due to two boundary layers cancel out and only shock wave effect remains. To compare aero-optical effects due to only one boundary layer and the shock wave, numerical simulations are conducted with a slip condition on the one side of the wall. From these numerical simulations, the aero-optical effects due to shock wave and boundary layer are comparable, Therefore the aero-optical effects due to the shock wave and the boundary layer are both important for the flow field around the window of the seekers.탄도탄 요격유도탄이 성공적으로 요격하기 위해서는 탐색기의 성능이 중요하다. 그런데, 비행 중에는 탐색기창 주위에 유동에 의한 공기광학 효과로 인하여 탐색의 광학 센서로 촬영하는 이미지가 왜곡되어 목표를 분간하기 어려워진다. 따라서 탐색기의 성공적인 작동을 위해서는 공기광학 현상을 연구하여 광학센서로 획득한 이미지를 보정하는 과정이 필수적이다. 또한, 일반적으로 탄도탄 요격유도탄이 초음속 또는 극초음속으로 비행하기 때문에 이러한 고속 유동에 의해 발생하는 공기광학 효과를 분석해야 한다. 특히 초음속과 극초음속에서는 충격파 및 경계층이 반드시 발생하고 피할 수 없기 때문에, 충격파 및 경계층에 의한 공기광학 효과는 반드시 연구해야 한다. 본 연구에서는 초음속 및 극초음속 유동에서 충격파 및 경계층이 각각 공기광학 효과에 어떠한 영향을 미치는가를 실험 및 수치해석을 통해 분석한다. 또한, 배경 지형 슐리렌(BOS)을 기반으로 한 새로운 실험 기법을 제안하고, 이 계측 기법을 다른 파면 계측기를 이용하여 검증하고자 한다. 이에 따라 아음속 고온 제트에서 샥-하트만 파면 계측기 결과와 BOS 기반 실험 기반 계측 결과가 대체로 일치하는 것을 검증하였다. BOS 기반 계측 기법은 유동 성질과 광학 특성을 동시에 획득할 수 있기 때문에, 유동과 공기광학 사이의 관계를 면밀히 파악할 수 있을 것으로 예상된다. 초음속 유동에 대해서는 압축 비탈길 주위의 유동에 의한 공기광학 효과를 연구하였으며 극초음속 유동에 대해서는 쐐기와 원뿔형 모델 주위의 유동에 의한 공기광학 효과를 파악하였다. 충격파 및 경계층 각자에 의한 공기광학 효과를 비교하기 위하여 수치해석도 수행하였다. 유동장은 Reynolds-averaged Navier-Stokes 식을 이차원 가정을 하여 수치적으로 해석하였으며 광선 추적 기법을 이용하여 광학파의 거동을 계산하였다. 전산해석 결과는 실험 결과를 이용하여 검증하였다. 레이저 빔의 중심에 위치한 광선을 따라서 굴절각을 추출하여 충격파 및 경계층 각각에 의한 빔의 굴절각을 비교하였다. 현재의 파면 계측 기법에서는 항상 두 개의 경계층을 지나며, 이 두 개의 경계층이 각각 반대 방향의 밀도 변화율을 가지고 있기 때문에 두 경계층에 의한 공기광학 효과가 서로 상쇄되는 현상을 발견하였다. 따라서 현재의 파면 계측 기법과 같이 두 개의 경계층을 지나는 경우에는 경계층의 효과가 미미하게 나타나고, 충격파의 효과가 상대적으로 크게 나타날 수 있다. 그러나 만약 충격파와 경계층이 하나씩만 존재한다면 각각에 의한 공기광학 효과를 무시할 수 없는 수준이기 때문에 둘 다 많은 영향을 미친다.1 Introduction 1 1.1 Background 2 1.2 Introduction to Aero-optics 5 1.3 Previous Studies 10 1.3.1 Aero-optical effects due to the supersonic turbulent boundary layer 11 1.3.2 Aero-optical effects due to shock waves 14 1.3.3 Aero-optical effects due to hypersonic flow 19 1.3.4 Experimental methods for the aero-optics study 23 1.3.5 Numerical methods for the aero-optics study 26 1.4 Objectives 28 2 Experimental Methods 31 2.1 Experimental Facility 32 2.1.1 Heated subsonic jet 32 2.1.2 Supersonic windtunnel 33 2.1.3 Hypersonic shock tunnel 36 2.2 Experimental Configuration and Test Model 41 2.2.1 Heat gun for the subsonic experiment 41 2.2.2 Supersonic flow over a compression ramp 44 2.2.3 Hypersonic flow over a wedge 46 2.2.4 Hypersonic flow over an ogive nose cone 47 2.3 Data Acquisition 50 2.3.1 Flow visualization 50 2.3.2 Wavefront measurement system 54 3 Numerical Methods 59 3.1 Overview of the Numerical Simulation 60 3.2 Numerical Methods to Obtain the Flow Density 61 3.2.1 Density from the BOS technique 62 3.2.2 Flow-simulation method 66 3.3 Optical Calculation 69 4 Aero-optics in Subsonic Heated Flow 79 4.1 Flow Field of the Heated Subsonic Jet 80 4.2 Density Acquisition from Background-oriented Schlieren Images 84 4.3 Quantitative Evaluation of Background-oriented Schlieren for Aero-optics 90 5 Aero-optics in Supersonic Flow 97 5.1 Supersonic Flow Field Over the Compression Ramp 98 5.2 Wavefront Measured with the Shack-Hartmann Wavefront Sensor 101 5.3 Simulation of the Propagation of the Optical Wave 103 5.3.1 Validation of the numerical simulation result 103 5.3.2 Effect of the refraction due to windows 107 5.3.3 Deflection along the ray depending on the line of sight 108 5.3.4 Numerical simulation with slip conditions on the top wall 114 6 Aero-optics in Hypersonic Flow 119 6.1 Flow Conditions for the Hypersonic Experiment 120 6.2 Hypersonic Flow Field Around a Wedge 121 6.3 Wavefront Measurement in the Hypersonic Wedge Flow 124 6.4 Numerical Simulation for Hypersonic Wedge Flow 132 6.4.1 Numerical simulation considering only the flow field 132 6.4.2 Effect of refraction due to windows 133 6.4.3 Deflection depending on the line of sight 137 6.4.4 Numerical simulations with slip conditions on the up-plate 141 6.5 Aero-optical Experiments on the Ogive Nose Cone Model 146 7 Conclusions 149Docto

극초음속 유동 내 충격파에 의한 공기광학 특성

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2015. 2. 정인석.Hypersonic flow field around flight vehicle is complicated and induce various problem. Especially, flight vehicle with optical system experience aero-optical aberration induced by hypersonic flow field. Aero-optics is a field which studies interaction between flow field and electromagnetic wave propagation near flight vehicle. Turbulence, shock wave and boundary layer at near flow field of flight vehicle induce index of refraction variation, distorting electromagnetic wave propagation characteristics. Aero-optical phenomena decrease optical performance and limits accuracy of optical system loaded on flight vehicle. Research have been conducted to find out the relation between flow field characteristics and optical characteristics. Accordingly, various devices have been developed to measure and analyze aero-optical characteristics. Recently, an optical sensor called Shack-Hartmann sensor was developed and performance was compared with other optical sensor. In this thesis, hypersonic flow field is demonstrated through shock tunnel and aero-optics experiment is conducted. Shock tunnel performance is validated by analyzing pressure distribution inside driven tube and measuring test time inside test section. Conical nozzle and contoured nozzle is installed at the shock tunnel to generate Mach 7 flow. Nozzle flow characteristics is studied through stagnation pressure measurement with pitot rake and flow visualization of wedge model with shadowgraph or schlieren technique. Conical nozzle has 63% decrease of stagnation pressure during nozzle flow expansion and exit flow is Mach 6.8. Contoured nozzle has little loss of stagnation pressure and exit flow is Mach 6.9. After shock tunnel performance and nozzle performance is validated, aero-optical characteristics is measured using Shack-Hartmann sensor. Shack-Hartmann sensor performance is studied and validated with experiments on optical table. Wedged window and hot wire is used as a density disturbance. Wedged window tilts the laser to angle which is same as refractive angle calculated through refraction law. Hot wire experiment result reveals increase of optical aberration as power consumption of hot wire increase. Aero-optical characteristics induced by shock wave in hypersonic flow field is studied. Wedge model is installed inside shock tunnel test section and Shack-Hartmann sensor measured phase and intensity, which is converted to point spread function (PSF). From PSF, aero-optical parameter such as bore sight error (BSE), Strehl ratio is calculated. In the results, average BSE and tilt increased as stagnation pressure increased. Average BSE is 80 ~ 160μrad, and Strehl ratio is 0.65 ~ 0.835. Shock wave in hypersonic flow increase BSE, tilt and decrease Strehl ratio.Abstract ⅰ Table of Contents iii List of Tables ⅴ List of Figures ⅵ Nomenclature ⅷ 1. Introduction 1 1.1 Background 1 1.2 Hypersonic flow field around flight vehicle 1 1.3 Aero-optics 2 1.4 Previous study 3 1.5 Research objectives 4 2. Experimental setup 6 2.1 Facility 6 2.1.1 Conical nozzle 8 2.1.2 Contoured nozzle 9 2.2 Model design and installation 10 2.2.1 Laser 12 2.2.2 Optical components 12 2.2.3 Sensor 15 2.2.4 Model 17 2.3 Measurement 19 2.3.1 Aero-optics measurement 19 2.3.2 Hypersonic flow field measurement 22 2.3.3 Measurement trigger system 25 3. Experiments results 28 3.1 Aero-optical characteristics in static flow 28 3.1.1 Experiment using wedged window 28 3.1.2 Experiment using hot wire 30 3.2 Hypersonic flow field characteristics 33 3.2.1 Shock tunnel performance validation 33 3.2.2 Nozzle flow characteristics 35 3.3 Aero-optical characteristics in hypersonic flow field 42 4. Conclusion 47 Bibliography 48Maste

인간 PD-L1 항체와 인터페론 베타 변이체를 통한 면역 사이토카인 개발 연구

학위논문 (석사)-- 서울대학교 대학원 약학대학 약학과, 2017. 8. 신영기.면역 항암요법(Immunotherapy)은 기존 항암요법에 비해 암 환자의 장기 생존율을 크게 증대시켜 준다는 점에서 큰 주목을 받고 있다. 그 중 대표적인 타겟으로 알려진 PD-L1 (Programmed cell death Ligand 1)은 PD-1에 결합하여 암세포의 면역회피를 일으키고 항원제시세포의 조절 T 세포 성숙능력을 증가시키는 등 다각적으로 작용하는 단백질이다. 본 연구에서는 파지 디스플레이 기법을 활용하여 인간 PD-L1에 선택적으로 결합하는 단일 클론 항체 후보물질 두 가지를 선별하였으며, 이것들은 미FDA가 승인한 PD-L1 항체 Atezolizumab보다 더 낮은 농도에서 PD-1/PD-L1 신호를 차단함을 확인하였다. 하지만 PD-L1 항체는 미세종양환경에서의 종양 침윤 림프구 부족으로 인해 많은 환자들에서 효과를 보이지 않는다고 알려져 있다. 이를 해결하기 위하여 종양 침윤 림프구를 증가시킬 것으로 기대되는 인터페론 베타 변이체를 PD-L1 항체에 연결시킨 형태인 면역사이토카인을 구상하였고, 다양한 형태의 면역 사이토카인을 디자인하여 생산 후 각 형태별 특성을 측정하였다. 그 결과, scFv-Fc-인터페론 베타 변이체 형태의 면역사이토카인이 생산성, 생물학적 활성, PD-1/PD-L1 신호 차단 능력 그리고 PD-L1 타겟팅 능력에서 다른 형태의 면역사이토카인보다 우수한 것으로 나타났다. 본 연구는 PD-L1 항체를 선별하고 이를 면역사이토카인으로 활용하기 위한 최적의 형태를 보여주었다.Immunotherapy has received a great deal of attention due to its great enhancement of the long term survival rate of patients compared to conventional anti-cancer therapy. PD-L1(Programmed cell death Ligand 1), a typical target for immunotherapy, is a protein that binds to PD-1 and has various wide-reaching functions, which can cause avoiding immune destruction of cancer cells and increase regulatory T cell maturation by antigen presenting cells. In this study, two antibody candidates selectively bound to human PD-L1 were screened using Phage display technique, which confirmed that these antibodies neutralized PD-1/PD-L1 signal at a lower concentration compared to Atezolizumab, a FDA approved PD-L1 antibody. However, PD-L1 antibodies are known to be ineffective in more than half of the patients due to the lack of TIL(tumor infiltrating lymphocyte cells) in the tumor micro-environment. In order to solve this problem, immunocytokines were designed by linking interferon-β-1b mutein, which is known to increase TIL, to the PD-L1 antibody and various types of immunocytokines were designed. In addition, their properties were measured after production to find the most optimal forms of immunocytokine. From our results, we found that scfv-Fc-interferon-β-1b mutein type of immunocytokine is superior than other forms of immunocytokines in productivity, biological activity, PD-1/PD-L1 signal neutralizing ability, and PD-L1 targeting ability. This study is significant in that it has searched for an effective human PD-L1 antibody and found an optimal form to be utilized as an immunocytokine.INTRODUCTION 1 Materials and Methods 3 Molecular cloning and expression of PD-L1 antigen 3 Cleavage of Fc domain from PD-L1 antigen 3 Phage display 4 Expression of single chain fragment variables 4 ELISA for PD-L1 candidate screening 4 PD-L1 candidates CDR sequencing 5 IGG conversion and expression of PD-L1 antibody candidates 5 Cell culture 6 Flow cytometry 6 PD-1/PD-L1 competitive inhibition ELISA 6 Type 1 IFN responsive Luciferase reporter assay 7 Molecular cloning and expression of various immunocytokines 7 RESULT 8 DISCUSSION 26 REFERENCES 30 국 문 초 록 34Maste

Pamidronate Down-regulates Tumor Necrosis Factor-alpha Induced Matrix Metalloproteinases Expression in Human Intervertebral Disc Cells

BACKGROUND: N-containing bisphosphonates (BPs), such as pamidronate and risedronate, can inhibit osteoclastic function and reduce osteoclast number by inducing apoptotic cell death in osteoclasts. The aim of this study is to demonstrate the effect of pamidronate, second generation nitrogen-containing BPs and to elucidate matrix metallo-proteinases (MMPs) mRNA expression under serum starvation and/or tumor necrosis factor alpha (TNF-α) stimulation on metabolism of intervertebral disc (IVD) cells in vitro. METHODS: Firstly, to test the effect of pamidronate on IVD cells in vitro, various concentrations (10(-12), 10(-10), 10(-8), and 10(-6) M) of pamidronate were administered to IVD cells. Then DNA and proteoglycan synthesis were measured and messenger RNA (mRNA) expressions of type I collagen, type II collagen, and aggrecan were analyzed. Secondly, to elucidate the expression of MMPs mRNA in human IVD cells under the lower serum status, IVD cells were cultivated in full serum or 1% serum. Thirdly, to elucidate the expression of MMPs mRNA in IVD cells under the stimulation of 1% serum and TNF-α (10 ng/mL) In this study, IVD cells were cultivated in three dimensional alginate bead. RESULTS: Under the lower serum culture, IVD cells in alginate beads showed upregulation of MMP 2, 3, 9, 13 mRNA. The cells in lower serum and TNF-α also demonstrated upregulation of MMP-2, 3, 9, and 13 mRNA. The cells with various doses of pamidronate and lower serum and TNF-α were reveled partial down-regulation of MMPs. CONCLUSIONS: Pamidronate, N-containing second generation BPs, was safe in metabolism of IVD in vitro maintaining chondrogenic phenotype and matrix synthesis, and down-regulated TNF-α induced MMPs expression.ope

힘줄 손상 백서 모델에서의 인간 지방유래 중간엽 줄기세포의 치료 기전

학위논문 (박사)-- 서울대학교 대학원 : 의과대학 의학과 재활의학전공, 2016. 2. 정선근.Introduction: Mesenchymal stem cell (MSC) in treating tendon injury is well investigated by experimental animal models and several clinical trials have also reported safety and efficacy of the MSC therapy. However, therapeutic mechanisms of MSC for tendon injury have not fully understood and there is no in vivo study that MSCs can function as differentiated cells after transplantation. We aimed to investigate whether MSCs can differentiate into the tenogenic lineage and secrete their own proteins using a xenogeneic MSC transplantation model. Methods: Bilateral Achilles tendons of 57 SD rats were given full-thickness rectangular injuries at the tendon insertion site to the midsubstance. They were randomly assigned to 3 groups after the modeling: 1) human adipose-derived mesenchymal stem cells (hASC) implantation with fibrin glue (106 cells in 60 μL) (Cell group), 2) fibrin glue injection with cell media by the same volume (Fibrin group), and 3) identical surgical procedure without any treatment (Sham group). After 2 and 4 weeks after modeling, all groups were evaluated by morphological, biomechanical, and histopathological (using modified Bonar score) analyses. Viability of tagged hASC was observed by immunofluorescence staining and protein expressions (collagen type I/III and tenascin-C) were evaluated by immunohistochemistry and Western blot analyses. Results: Rupture rate of Cell group (11.1%) was lower than the rates of Sham (25.0%) and Fibrin (22.2%) groups. Cross sectional areas of tendons in Cell group were decreased (P = 0.008) while those in Sham group were increased (P = 0.005) from 2 to 4 weeks. At 2 weeks, ultimate tensile strength and stiffness of Cell group (49.4 ± 17.4 N and 10.1 ± 3.9 N/mm) were significantly higher than those of Sham group (31.2 ± 7.5 N, P = 0.037 and 4.7 ± 1.4 N/mm, P = 0.010, respectively). Stiffnesses of Cell group at 2 and 4 weeks were also significantly higher than those of Fibrin group (P = 0.037 in both). However, there were no significant differences of total modified Bonar score among three groups at both 2 and 4 weeks. From the immunofluorescent scanning at 1, 2, and 4 weeks after cell implantations, tagged hASCs were all observed. Cell group showed higher optical densities in immunohistochemistry than those of Sham and Fibrin groups in human-specific collagen type I at both 2 and 4 weeks and in human-specific tenascin-C at 2 weeks. Western blot analysis also revealed human-specific collagen type I expression was higher than that of Sham group. Conclusions: Implanted hASCs to rat tendon injury model survived for 4 weeks and secreted human-specific collagen type I and tenascin-C. Human stem cells biomechanically enhanced rat tendon healing superior to sham and active control groups. To the best of the author's knowledge, this is the first in vivo report which proves the cell-originated protein synthesis by the implanted stem cells.Introduction 1 Materials and Methods 3 1. Study design 3 2. Stem cell preparation 3 3. Fluorescent cell labeling and immunofluorescence staining 5 4. Surgical procedure and treatment 6 5. Rupture rate and cross sectional area calculation 9 6. Biomechanical test 9 7. Tissue preparation and histological analysis 12 8. Immunohistochemistry 12 9. Western blot analysis 14 10. Statistical analysis 15 Results 16 1. Rupture rate and cross sectional area of tendon 16 2. Biomechanical test 19 3. Histological analysis (modified Bonar score) 21 4. Immunohistochemistry and immunofluorescent staining 24 5. Western blot analysis 29 Discussion 31 Conclusion 39 References 40 Abstract in Korean 46Docto

Block과 particle 골이식재의 pore density와 interconnectivity의 차이 및 골형성에 미치는 영향

Thesis(masters) --서울대학교 치의학대학원 :치의학과,2010.2.Maste

원격 네비게이션에서의 실재감과 성능에 대한 햅틱 피드백과 시각적 요소들의 효과들

Docto

작업장 누적소음노출과 혈압과의 관련성에 대한 단면 연구

학위논문(석사)--서울대학교 대학원 :의학과 예방의학전공,2000.Maste

L1210세포 포스포리파제 D의 특성 연구

Thesis (master`s)--서울대학교 대학원 :화학과 생화학전공,1997.Maste

재고관리 문제에 대한 분포 강건 최적화

학위논문(박사)--서울대학교 대학원 :공과대학 산업공학과,2020. 2. 문일경.The inventory problem is a classical problem in the operations management society to decide an optimal order policy under demand uncertainty. A decision maker chooses order quantities over the planning horizon to achieve the company's objective with respect to performance measures. Classical inventory management researches assume that complete information about the probability distribution of random demand is known, however, only limited information of the probability distribution is available in practice. To tackle this difficulty, a decision maker considers an ambiguity set which is a set of candidate distributions that may contain the unknown true distribution, and minimizes the worst-case expected cost over the ambiguity set. This approach is called distributionally robust optimization (DRO) and widely applied to many operations management problems. We adopt the distributionally robust approach to inventory problems to handle distributional ambiguity. In this dissertation, we consider three different but closely related problems: newsvendor problem, inventory problem, and empty container repositioning problem. For all three problems, we study decision making under demand uncertainty, but limited information about probability distributions of random demand is given. Hence, we adopt the distributionally robust approach and analyze various aspects of distributionally robust models. First, we study the data-driven distributionally robust newsvendor model with a set of distributions close to the empirical distribution in terms of the Wasserstein distance, and derive the closed-form solution of an optimal order quantity. Second, the inventory problem is considered, which is an extension of the newsvendor problem to the multistage setting. In the multistage setting of distributionally robust inventory problems, the decision maker carefully considers time consistency issue. Time consistency means that the optimal policy derived in the first period maintains its optimality through the planning horizon. We analyze the time consistency issue of the distributionally robust inventory model with a Wasserstein ambiguity set. Third, the empty container repositioning problem with foldable containers is considered, which is a practical application of the inventory problem. We propose a mathematical model of the empty container repositioning problem considering the use of foldable containers under demand uncertainty. To tackle the intractability of the multistage stochastic programming formulation, the linear decision rule formulation is proposed for the tractable and distributionally robust approximation of the multistage stochastic programming formulation. We also conduct computational experiments to validate respective models and findings.재고관리는 운영 관리 분야에서 전통적인 문제로, 수요의 불확실성 하에서 최적의 주문 정책을 결정하는 문제다. 의사결정자는 성과 척도로 표현되는 회사의 목적을 달성하기 위해 계획 기간 동안의 주문량을 선택한다. 전통적인 재고 관리 연구에서는 수요의 확률 분포에 대한 정확한 정보를 알고 있다고 가정하지만, 현실에서는 확률 분포에 대한 제한된 정보만 이용가능하다. 이러한 어려움을 해결하기 위해 의사결정자는 알려지지 않은 수요의 확률 분포를 포함할 수 있는 후보 분포들의 집합인 모호성 집합을 고려하고, 이 집합 위에서 최악의 평균 비용을 최소화한다. 이 접근방법을 분포 강건 최적화라고 하며, 많은 운영 관리 문제에 널리 적용되고 있다. 재고관리 문제의 분포에 대한 정보 부족을 다루기 위해 분포 강건 방법을 활용한다. 본 논문에서는 신문가판원 문제, 재고관리 문제, 공컨테이너 재배치 문제 등 세 가지 서로 밀접하게 관련된 문제를 고려한다. 세 가지 문제 모두 수요의 불확실성 하에서 의사결정을 연구하지만, 수요의 확률 분포에 대한 제한된 정보만 주어진다. 이에 따라 분포 강건 방법을 적용하고 분포 강건 모형들의 다양한 측면을 분석한다. 첫째, 데이터로부터 만들어진 경험적 분포로부터 Wasserstein 거리 기준으로 가까운 확률 분포들을 고려한 데이터 기반의 분포 강건 신문가판원 모형을 연구하고, 최적 주문량의 닫힌 형태의 표현을 도출한다. 둘째, 신문가판원 모형이 다단계 문제로 확장된 재고관리 문제를 고려한다. 분포 강건 재고 문제의 다단계 특성에서 의사결정자가 신중하게 고려해야할 사항은 시간 일관성이다. 시간 일관성은 첫 시점에 도출한 최적 정책이 계획 기간 동안 최적성을 유지해야 한다는 것을 의미한다. Wasserstein 모호성 집합을 고려한 분포 강건 재고 모형의 시간 일관성을 분석하고자 한다. 셋째, 접이식 컨테이너를 고려한 공컨테이너 재배치 문제를 고려하는데, 이는 재고 관리 문제의 현실적인 응용 문제이다. 수요 불확실성 하에서 접이식 컨테이너의 사용을 고려한 공컨테이너 재배치 문제의 수리적 모형을 제안한다. 다단계 추계 계획의 계산 복잡도 문제를 해결하기 위해 선형 결정 규칙에 기반한 수리 모형을 제시하는데, 이는 다단계 추계 계획의 계산가능하며 분포 강건한 근사가 된다. 또한 각각의 모형과 연구 결과를 검증하기 위해 수치 실험을 진행한다.Chapter 1 Introduction 1 1.1 Inventory Problems 1 1.2 Distributionally Robust Optimization 4 1.3 Research Motivations and Contributions 7 1.4 Outline of the Dissertation 10 Chapter 2 Distributionally Robust Newsvendor Model with a Wasser stein Ambiguity Set 11 2.1 Problem Description and Literature Review 11 2.2 Distributionally Robust Optimization with the Wasserstein Distance 16 2.3 Distributionally Robust Newsvendor Model 22 2.3.1 Wasserstein Order p = 1 24 2.3.2 Wasserstein Order p > 1 29 2.4 Risk-averse Newsvendor Model 40 2.4.1 Wasserstein Order p = 1 42 2.4.2 Wasserstein Order p > 1 45 2.5 Computational Experiments 48 2.5.1 Out-of-sample Performance 48 2.5.2 Convergence Property 51 2.5.3 Risk-aversion of the CVaR Solution 55 2.6 Summary 56 Chapter 3 Distributionally Robust Inventory Model with a Wasserstein Ambiguity Set 58 3.1 Problem Description and Literature Review 58 3.2 Distributionally Robust Inventory Model and Time Consistency 63 3.3 Sufficient Condition for Weak Time Consistency 73 3.3.1 Newsvendor Policy 77 3.3.2 Distributionally Robust Newsvendor Model with Unit Purchase Cost 84 3.4 Further Analysis About the Dynamic Programming Formulation 87 3.4.1 Computation of Base-Stock Levels for Dynamic Programming Formulations 87 3.4.2 Non-zero Fixed Order Cost 89 3.4.3 Desirable Properties of Wasserstein DRO 91 3.5 Computational Experiments 93 3.5.1 Monotonicity 93 3.5.2 Conservativeness 96 3.5.3 Out-of-sample Performance Guarantee 99 3.5.4 Convergence Property 101 3.6 Summary 103 Chapter 4 Empty Container Repositioning with Foldable Containers 104 4.1 Problem Description and Literature Review 104 4.2 Multistage Stochastic Programming Formulation 112 4.2.1 Cycle of Container Flows 112 4.2.2 Assumptions and Nomenclature 114 4.2.3 Deterministic Formulation 118 4.2.4 Multistage Stochastic Programming Formulation 121 4.3 Affinely Adjustable Robust Formulation 125 4.3.1 Factor-Based Demand Model 125 4.3.2 Bound on Expectations of Positive Parts 126 4.3.3 Linear Decision Rule Formulation 130 4.3.4 Restricted Linear Decision Rule Formulation 136 4.4 Computational Experiments 141 4.4.1 Experimental Setting 142 4.4.2 Computational Results 146 4.4.3 Simulation Results 152 4.5 Summary 157 Chapter 5 Conclusions 158 5.1 Summary and Contributions 158 5.2 Future Research 160 Bibliography 162 국문초록 177Docto