다양한 이온선택성 투과막에서의 나노전기수력학적 현상에 대한 실험적 검증

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2020. 8. 김성재.Perm-selective media has been widely used in various applications such as desalination, electro dialysis and battery, etc. In addition, micro-/nano-electrokinetic phenomena near the permselective media have been intensively studied. In many studies, material or geometry of the perm-selective media were adjusted for the easy fabrication or the new physics. In this thesis, material of the permselective media was adjusted by using ionic hydrogel and bio-based material, and also geometry of Nafion membrane was adjusted to have an undulation shaped surface. So the thesis was divided into two parts, one is the adjusting material, and the other is the adjusting geometry. In Chapter 2, ionic hydrogel was introduced for capillarity ion concentration polarization (CICP). To overcome a world-wide water shortage problem, numerous desalination methods were developed with state-of-the-art power efficiency. However, a natural plant, mangrove can survive in salty environment with optimal power sources. As motivated by the desalting function of mangrove, here we proposed a spontaneous desalting mechanism, CICP. An ion depletion zone was spontaneously formed near a nanoporous material by the perm-selective ion transportation driven by the capillarity of the material, in contrast to an electrokinetic ion concentration polarization which achieves the same ion depletion zone by an external dc bias. This CICP device was shown to be capable of reduced an ambient flourecent signal more than 90% without any external electrical power sources. These results indicated that the CICP system can offer unique and economical approaches for a power-free water purification system. In Chapter 3, biodegradable materials originated from well-known organisms such as human nail plate were rigorously investigated as a role of permselective nanoporous membrane. Most of nanofabrication methods are sophisticated and expensive due to the requirement of high class cleanroom facilities, while low-cost and biocompatible materials have been already introduced in the microfluidic platforms. Thus, an off-the-shelf and biodegradable material for those nanostructures can complete the concept of an eco-friendly micro/nanofluidic platform. A simple micro/nanofluidic device integrated with such materials was fabricated. Distinctive evidences (visualization of ion concentration polarization phenomenon, ohmic/limiting/overlimiting current behavior and surface charge-governed conductance) would fulfill the requirements of functional nanostructures for the nanofluidic applications. Therefore, this bio-based material, nail plate, would be utilized as a one of key elements of the biodegradable and eco-friendly micro/nanofluidic applications. In chapter 4, micro/nano fluidic platform involving undulated surfaced Nafion membrane was investigated for the study of electrokinetic effect depending on the characteristic length scale of the system. Although the several studies have shown that overlimiting current was enhanced due to undulation surface at the long characteristic length (~O(100) mm), there are few studies that have shown undulation effect at the short characteristic length (~O(10) mm). In this chapter, we compared the undulation effect at two characteristic length of 15 mm and 150 mm. I-V characteristics were obtained at both 15mm and 150 mm and investigated the possibility of suppressing the undulation effect according to the depth of the device. In this thesis, experimental investigation of the nanoelectrokinetic phenomena through novel perm-selective media was introduced. In chapter 2, 3, material of perm-selective media was adjusted by ionic hydrogel or bio-based materials and in chapter 4, geometry of the conventional perm-selective media, nafion, was modified to reveal the new physics.이온선택성막은 해수담수화나 전기투석, 배터리등의 어플리케이션에 아주 광범위하게 활용되고 있다. 또한 이론적으로는 이온선택성 막 주변에서 일어나는 마이크로/나노 전기수력학적인 현상들에 대한 많은 보고가 있었다. 특히 이온선택성 막의 특성을 변경하는 것은 새로운 물리적 현상을 보여주거나 쉬운 공정법을 제시한다는 점에 있어서 많은 연구가 이루어 지고 있는데, 크게 이온선택성 막의 내부 구조를 바꾸거나 외부 모양을 바꾸는 두가지로 나누어 볼 수 있다. 본 연구에서는 이온수화젤이나 생체유래물질을 이용하여 내부 구조를 바꾸었을 때 와 나피온막의 표면을 파상형으로 제작하여 외부 구조를 바꾸었을 때 발생하는 현상에 대해 나타내었다. 따라서 본 연구는 두 파트로 나뉘는데 하나는 내부 구조를 바꾼 것이고 하나는 외부 모양을 바꾼 것이다. 두번째 장에서는 이온수화젤이 모세관이온농도분극현상을 발생시키는 이온선택성 막으로써 제시되었다. 전세계적인 물부족 현상을 해결하기 위해 다양한 해수담수화 방법과 효율증대를 위한 연구들이 진행되어 왔다. 하지만 맹그로브와 같은 식물은 극대화된 효율을 활용하여 염수환경에서 살아남는다. 이러한 맹그로브의 담수화 기능에 영감을 받아 모세관 이온농도 분극현상이 자발적인 담수화 메커니즘으로써 제시 되었다. 일반적인 전기동역학적인 이온농도 분극현상이 외부 전기장에 의해 구동되는 것과 달리, 수화젤 본연의 모세관 힘에의해 선택적 이온 수송을 만들어내면서 수화젤 주변에서 자발적으로 이온 농도 분극 현상이 발생한다. 이 모세관 이온농도분극현상은 이온의 표지로써 넣어준 형광물질을 외부 전기장없이 90%이상 줄어들게 하였다. 이러한 결과들은 모세관 이온농도분극현상이 외부 전원 없는 정수 시스템 시장에 도움이 될 것으로 기대된다. 세번째 장에서는 손톱과 같은 잘 알려진 생체 물질을 이용한 생분해성의 물질이 이온선택성 투과막으로써 제시되었다. 이온선택성 투과막을 만들기위한 대부분의 나노 공정은 복잡하거나 높은 수준의 청정단계를 필요로 하는 비싼 공정이다. 반면에 마이크로 유체 플랫폼에서는 이미 싸고 생체적합한 다양한 물질들이 이미 다양하게 연구되어 오고 있다. 따라서 생분해성의 이온선택성 투과막을 활용하면 친환경적인 마이크로/나노 유체 플랫폼의 개념을 완성시킬 수 있다. 간단한 마이크로/나노 장치가 제작되었고, 이온농도분극현상의 시각화, 옴영역, 한계영역, 과한계영역으로 대표되는 전류전압특성 그리고 포면전하 기반의 전도도등을 간단한 실험을 통해 밝혀냈다. 따라서 손톱과 같은 생체유래물질을 사용하면 환경친화적이면서도 생분해성인 마이크로 나노 장치에 적용할 수 있을거라 기대할 수 있다. 네번째 장에서는 파상형구조의 표면을 갖는 나피온 막이 포함된 마이크로/나노 유체 플랫폼이 제작되고 연구되었다. 특히 특성길이에 따른 전기동역학적인 효과들에 대해서 알아보았는데, 일반적인 파상형 구조의 표면을 갖는 연구들은 대부분 긴 특성길이 (~O(100) m)에서 실험되고 해석 되어 온 반면, 본 연구에서는 짧은 특성길이 (~O(10) m)에서의 효과 역시 실험하고 비교되었다. 특히 전류 전압 특성을 통해 파상형 구조의 효과가 짧은 특성길이에서 억제되는지를 살펴보았다. 본 연구에서는 이온선택성 투과막의 외부 모양이나 내부 구조를 변형하여 발생하는 새로운 현상이나 새로운 특징들에 대해 실험하고 보고 하였다. 두번째와 세번째 장에서는 새로운 내부구조를 활용한 이온선택성 투과막에 대해 연구하였고, 네번째 장에서는 외부 모양을 바꾸었을 때 일어나는 새로운 물리적 특징들에 대해 연구하였다. 본 논문을 통해 다양한 이온선택성 투과막에 대한 이해가 높아지고 더 다양한 연구들이 화발히 진행되기를 바란다.Abstract i Contents iii List of Figures vi List of Tables ix Chapter 1. Introduction 1 1.1. Permselectivity of the nanoporus membrane 1 1.2. Examples of permselective structures 7 1.2.1. Ion exchange membrane 7 1.2.2. Nafion 8 1.2.3. Synthetic hydrogel 9 1.2.4. Lithographically defined nanochannels 10 1.2.5. Others 11 1.3. Ion concentration polarization 12 Chapter 2. Ionic Hydrogel Membrane for Capillarity based Ion Concentration Polarization 14 2.1. Introduction 14 2.2. Materials and methods 17 2.2.1. Synthetic hydrogel as a perm selective membrane 17 2.2.2. CICP device fabrication 18 2.2.3. Experimental setup 21 2.2.4. Concentration measurement from reference fluorescent signal 22 2.3. Results and discussion 24 2.3.1. Imbibition rate through the ionic hydrogel 24 2.3.2. The measurement of hydrogel swelling 28 2.3.3. The formation of an ion depletion zone by CICP phenomenon 30 2.3.4. The restoration phase by a diminished imbibition 34 2.3.5. Experimental analysis for the behavior of fluorescent dye 36 2.3.6. Asymmetric formation of the ion depletio zone in the cente-connection device 41 2.4. Conclusions 43 Chapter 3. Bio-based Membranes for Nanofluidic Applications 44 3.1. Introduction 44 3.2. Nail plate as a perm-selective membrane 46 3.3. Materials and methods 48 3.3.1. Nail device fabrication 48 3.3.2. Experimental setup 52 3.4. Results and discussion 53 3.4.1. The formation of ion depletion zone upon nail device 53 3.4.2. The I-V characteristics of the nail device 55 3.4.3. The conductance profile of the nail plate 56 3.5. Conclusions 59 Chapter 4. Undulated Nafion Membrane for Investigation of Electroconvective Instability 60 4.1. Introduction 60 4.2. Materials and methods 64 4.2.1. Undulation device fabrication 64 4.2.2. Experimental setup 67 4.3. Results and discussions 69 4.3.1. Visualization of vortices of Duckhins mode 69 4.3.2. I-V characteristics of the undulation device 71 4.4. Conclusions 72 Appendix 73 A. Analytical and numerical solution of the CICP 73 B. Hen egg yolk and albumen as a bio-based perm-selective membrane 88 Bibliography 99 Abstract in Korean 104Docto

The effects of creep phenomenon in the mooring system with synthetic fiber rope

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called ‘the creep phenomenon’. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.1. 서 론 1.1 연구배경 1 1.2 연구동향 2 1.3 연구내용 3 2. 섬유로프의 특징 2.1 The creep phenomenon 4 2.2 Static-dynamic stiffness model 8 2.3 Upper-lower stiffness model 9 2.4 Quasi-static stiffness 11 2.5 Analysis procedure 12 3. Environments condition 3.1 Environments load 15 3.2 Design condition 18 4. Mooring analysis 4.1 Mooring layout 19 4.2 Mooring stiffness 22 4.3 Simulation case 24 5. Analysis results 5.1 Case 1 and Case 2 26 5.2 Case 3 30 5.3 Case 4 33 5.4 Case 5 36 5.5 Case 6 39 5.6 Case 7 42 6. 결론 47 Reference 49Maste

Prediction of Daytime Hypoglycemic Events Using Continuous Glucose Monitoring Data and Classification Technique

Daytime hypoglycemia should be accurately predicted to achieve normoglycemia and to avoid disastrous situations. Hypoglycemia, an abnormally low blood glucose level, is divided into daytime hypoglycemia and nocturnal hypoglycemia. Many studies of hypoglycemia prevention deal with nocturnal hypoglycemia. In this paper, we propose new predictor variables to predict daytime hypoglycemia using continuous glucose monitoring (CGM) data. We apply classification and regression tree (CART) as a prediction method. The independent variables of our prediction model are the rate of decrease from a peak and absolute level of the BG at the decision point. The evaluation results showed that our model was able to detect almost 80% of hypoglycemic events 15 min in advance, which was higher than the existing methods with similar conditions. The proposed method might achieve a real-time prediction as well as can be embedded into BG monitoring device.1

Manipulation of physical properties in oxide thin films by a local inversion symmetry breaking induced by flexoelectricity

학위논문(박사)--서울대학교 대학원 :자연과학대학 물리학과,2019. 8. 노태원.대칭의 개념은 물리학에서 놀라운 역할을 가지고 있다. 물질이 가지고 있는 대칭의 종류에 따라서 물질이 가질 수 있는 물리적 질서나 특성이 결정된다. 결정 대칭성에 따라서 고체는 잘 알려진 결정질 점군으로 분류될 수 있는데, 1830년에 32가지 유형의 형태학적 결정군으로 분류될 수 있다는 것이 증명되었다. 어떤 결정군에 속해있는지를 통해 복굴절과 같은 광학성 특성이나 압전성과 같은 전기기계적 결합이 나타날 수 있는지 여부를 알 수 있다. 전기적 특성과 기계적 특성 사이의 상관성은 매우 흥미로운 물리적 현상이며, 미시적인 크기의 전자기계부터 압전 엑츄에이터, 모터, 센서, 에너지 발전기, 전동기 단백질 및 세포막과 같은 생물 시스템에 이르기까지 다양한 분야에서 사용되고 있다. 전기 기계적 상관성의 가장 보편적인 예는 균일한 변형이 가해질 때 전기장이 물질 내부에 생성되는 압전성이다. 반면에, 불균일한 변형이 물질에 가해지는 경우에도 물질 내부에 전기장이 형성되게 되는데 이를 변전효과라고 한다. 변전효과는 전기적 분극과 불균일한 변형 사이의 상관관계로 정의될 수 있다. 이 현상의 중요성으로서 변전효과가 압전효과보다 더 보편적으로 나타난다. 즉, 더 많은 결정에서 나타날 수 있는 효과이다. 압전성은 32개중에 20개의 결정군에서 나타날 수 있는 반면, 변전성은 32개 모두의 결정군에서 나타날 수 있는 현상이다. 또한 변전효과는 물질의 크기가 작아지면 작아질수록 효과의 크기가 커진다는 재미있는 특성을 가지고 있다. 이러한 특성 때문에 압전효과가 사용되는 장치를 대체할 수 있는 효과로서 매우 큰 물리적 산업적 중요성을 가지고 있다. 본 박사논문에서는 변전효과에 의해 유도되는 반전 대칭 깨트림을 이용하여 산화물 박막의 물리적 특성을 제어하는 것이 가능하다는 것을 보여줄 것이다. 특히, 국소적인 영역에 날카로운 원자힘 현미경의 탐침을 이용하여 압력을 가하는 기술을 사용함으로써 원하는 영역에만 국소적으로 물리적 특성의 변화를 야기해낸 일들을 소개할 것이다. 나의 연구들은 산화물 박막에서 순수한 힘만을 가지고 흥미로운 물리적 현상 또는 특성을 제어하고 관찰하는 것이 가능하다는 것을 시사한다.Over the last decade, flexoelectric effect at the nanoscale in solid has shown their wide potential both scientifically and technologically. There are already some patents for commercial electronic devices to replace piezoelectric devices such as sensor, and actuator. Also, they have shown rich and intriguing physical phenomena, including the recent hot topic of domain wall and photovoltaic. Despite these extensive studies on flexoelectric effect, I believe that many interesting issues still remain untouched. In this thesis, two novel findings has been addressed: trailing flexoelectric field for manipulation of multiaxial ferroelectric, control of the electrical state in a dielectric with flexoelectric origin. Firstly, I have demonstrated that in multiaxial ferroelectric epitaxial films, the trailing flexoelectric field generated by mobile AFM tip pressing can be used as an effective tool for engineering domain structures. We have suggested several advantageous features over the electrical way. Also, we have overcome the serious drawback of mechanical switching of ferroelectric polarization with AFM tip that is switching is unidirectional, i.e. only switching of polarization up to down is possible. I believe that the finding of this mechanism of trailing flexoelectric will open a great possibility to study exotic ferroelectric domain by creating it without applying electrical bias. Also, we demonstrated flexoelectric control of the electrical state in ultrathin dielectric films. We explained this huge resistivity change in terms of tunable depolarizaton field by controlling the amount of flexoelectric polarization generated inside of the ultrathin dielectric films. Achieving breakdown using very small electric bias, we could prevent extrinsic effect such as Joule heating and permanent damage on the sample even though we applied a huge electrostatic field by means of flexoelectricity. This work overcomes a long-standing dilemma: the electrical-state switching in dielectrics requires strong fields, but when applied by strong static fields, dielectrics inevitably suffer from irreversible damage. Utilizing universal flexoelectricity, we could develop a general approach to apply non-destructive, strong electrostatic fields in various insulating systems, such as the Mott insulator. Also, our results can be extended to realize future novel devices such as flexoelectric switch and transistor. Lastly, there can be many interesting topics we can further study with this AFM tip pressing technique. Since force applied by AFM tip will generate local strain gradients, thus breaking of local inversion symmetry, any change of physical properties or intriguing phenomena induced by the inversion symmetry breaking such as band gap opening in graphene or photovoltaic in centrosymmetric materials can be studied. As those studies would be original in the aspect that mechanism is novel flexoelectricity, it would provide good chances for high-impact publications.The concept of symmetry plays an incredible role in physics. What kinds of symmetries the material possess determine the physical orders or properties the material can have. Depending on crystal symmetries, solid can be classified into well-known crystallopic point group. In solids, there exist 32 types of morphological crystalline symmetries derived in 1830 from a consideration of observed crystal forms. The point group of a crystal determines the directional variation of physical properties that arise from its structure, including optical properties such as birefringency, or electromechanical coupling such as piezoelectricity. Couplings between electrical and mechanical properties are quite intriguing physical phenomena and have been used in many applications ranging from microelectromechanical systems to biological systems such as a piezoelectric actuator, motor, sensor, energy generator, electromotor proteins, and cellular membranes. The most popular example of electromechanical couplings is piezoelectricity in polar systems (where the space inversion symmetry is broken), in which the homogeneous strain can induce electric fields and vice versa. On the other hand, there can occur a novel electromechanical coupling known as flexoelectricity in the presence of a strain gradient (i.e., inhomogeneous strain). The flexoelectricity can be defined as a coupling between polarization and strain gradient. One important aspect of this phenomena is that the flexoelectricity is more universal phenomena than the piezoelectricity. While piezoelectricity can arise in 20 point groups, flexoelectricity can arise in all 32 point groups as the strain gradients itself spontaneously break the inversion symmetry. Other than that, flexoelectricity has another important aspect. Flexoelectricity becomes larger and larger as the scale being reduced since the strain gradient is inversely proportional to the size of the sample given that the applied strain is fixed. Because of those two advantages mentioned above, flexoelectricity can play an important role in both nanoscale physics and application as it might be possible to replace the devices in which the piezoelectricity is in use. In this thesis, I will show that it is possible to tune the physical properties of oxide thin films by breaking the space inversion symmetry induced by flexoelectricity. Specifically, I exploited the technique so-called atomic force microscope (AFM) tip pressing that is applying pressure using a sharp AFM tip to induce local strain gradients, thus, break the local inversion symmetry. With this technique, local control of physical properties of oxide thin films was possible and three works related to AFM tip pressing will be addressed. Our studies on oxide thin films suggest that many interesting control of local physical properties can be possible by means of pure mechanical force.Contents Abstract (English) 1 List of Figures 3 1. Introduction 9 1.1 Flexoelectricity 9 1.2 Types of strain gradients 10 1.3 Ways to generate strain gradients 12 2. Experimental detail 15 2.1 Pulsed-laser deposition 15 2.2 Piezoelectric force mecroscopy 17 2.3 Atomic force microscopy tip pressing for mechanical writing or gating of polarization 21 3. Trailing flexoelectric field and selective control of ferroelectric polarizationin BiFeO3 thin film 24 3.1 Mechanical switching of ferroelectric polarization 24 3.2 Trailing electric field due to the motion of the AFM tip 27 3.3 Mono-domain BFO thin film 28 3.4Selective control of multiple ferroelectric pathways using a mechanical forceinduced by AFM tip pressing 31 3.5Mechanism for selective control of multiple ferroelectric switching pathways:trailing flexoelectric field 35 3.6 Role of piezoelectricity and flexoelectricity in mobile AFM tip pressing studied by phase-field simulations 41 3.7 Comparison between trailing electric field and trailing flexoelectric field 45 3.8 Conclusion 49 4. Controlling electrical state in dielectrics with mechanical force: colossalflexoresistance 53 4.1 Introduction 53 4.2 Estimation of threshold polarization anove which both the conduction band minimum and valance band maximum cross the Fermi level 59 4.3 Experimental results and discussion 62 4.4 Conclusion 78 5. Conclusions 82 Appendix A: Estimation of conversion factor between electric bias and mechanical force 84 Appendix B: Phase field simulation 87 Appendix C: First-principle caculations 94 Appendix D: Detailed sample characterization 99 Appendix E: Measuring nanoscale flexoelectric coefficients by mechanically tunable quantum tunneling Detailed sample characterization 102 Publication List 104 국문 초록 (Abstract in Korean) 105 감사의 글 (Acknowledgements) 107Docto

개에서 광범위한 추궁절제술의 임상적 평가

학위논문(석사)--서울대학교 대학원 :수의학과 수의외과학전공,2000.Maste

Definite article use by Korean EFL college learners

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

D-최적실험설계 계산을 위한 알고리즘

학위논문(석사)--서울대학교 대학원 :자연과학대학 통계학과,2020. 2. 원중호.Finding analytical solution for a locally D-optimal design of non-linear models is a difficult problem even for a relatively simple model. A number of numerical methods for computing D-optimal designs have been proposed but few exhibited satisfying speed with theoretical convergence at the same time. In this thesis, we compare two algorithms, particle swarm optimization (PSO) and second-order cone programming (SOCP) for computing locally D-optimal design. PSO is a heuristic algorithm capable of finding optimal design points and weights simultaneously, but lacks the theoretical guarantee of convergence toward an optimal design. SOCP is a convex optimization method that is guaranteed to find the optimal design weights for discretized design points. We demonstrate that PSO often fails to reproduce known D-optimal designs for non-linear models consistently, and propose an SOCP-based algorithm for k-point design in which at most k design points are selected among a large number of candidate points. We show that this SOCP-based method is competent in computing D-optimal designs compared to PSO, in terms of both speed and accuracy.비선형 모형에 대한 국소 D-최적실험설계를 해석적으로 구하는 것은 비교적 간단한 모형에 대해서도 쉽지 않다고 알려져 있다. D-최적실험설계를 구하기 위한 여러 수치적 방법들이 제안되어 왔지만, 그 중 이론적인 수렴 성질과 준수한 연산 속도를 동시에 지니는 방법은 많지 않았다. 이 논문에서는 국소 D-최적실험설계를 찾는 두 개의 알고리즘, 입자 군집 최적화와 이차원추계획법을 비교한다. 입자 군집 최적화는 직관적인 아이디어에 기반을 둔 알고리즘으로 최적 설계 지점과 가중치를 동시에 구할 수 있지만, 최적 설계로 수렴하는 것이 이론적으로 보장되지 않는다. 반면, 이차원추계획법은 이산형 설계 공간에 대해 최적 가중치를 찾을 수 있는 볼록 최적화 방법이다. 이 논문에서는 D-최적실험설계가 알려져 있는 비선형 모형들에 대해 입자 군집 최적화가 최적 설계를 찾지 못하는 경우가 종종 있음을 보이고, 설계 후보 지점 중 최대 k 개 지점에 대해서만 양의 가중치를 갖도록 하는 이차원추계획법 기반 k-점 설계 알고리즘을 제안하였다. 나아가, 이차원추계획법에 기반을 둔 방법들이 입자 군집 최적화와 비교해 속도와 정확도 모두에서 경쟁력을 지니고 있음을 검증하였다.Chapter 1 Introduction 1 1.1 Exact/Approximate Designs 4 1.2 Equivalence Theorem 5 1.3 Number of Support Points 5 1.4 Extension to Non-linear Models 6 1.4.1 Global Optimality Criterion 7 1.5 Relative Efficiency 8 1.6 Numerical Algorithms 8 Chapter 2 Particle Swarm Optimization 10 2.1 Locally D-optimal Approximate Designs 12 2.1.1 Compartment Model 14 2.1.2 Quadratic Logistic Model 16 2.1.3 Double Exponential Model 20 2.2 Minimax D-optimal design 23 2.2.1 Two Parameter Logistic Model 24 Chapter 3 Second-order Cone Programming 33 3.1 Second-order cone programming 34 3.2 SOCP for D-optimal Design 36 3.2.1 k-point Approximate Design Constraint 38 3.3 Locally D-optimal Approximate Designs 39 3.4 Locally D-optimal Exact Designs 41 3.4.1 Second-order Polynomial Regression 43 3.4.2 Locally D-optimal Exact Designs 47 3.5 Further Applications 48 3.5.1 Sequential Design 48 3.5.2 Laplacian Regularized Active Learning 52 Chapter 4 Discussion 57 국문초록 62Maste

(A)Study on the process of introducing class action : the approach of Institutionalism

학위논문(박사)--서울대학교 행정대학원 :행정학과 정책학전공,2006.Docto

Evaluating the quality of baseball pitch using PITCHf/x

미국 메이저리그 야구 경기는 야구공을 추적하는 3대의 고속 카메라를 통해 모든 투구에 대한 궤적 데이터 PITCHf/x를 수집하고 공개한다. 선행 연구에서는 PITCHf/x 데이터를 통해 각 투구의 기대 피루타수를 계산하고 이를 토대로 투구의 질을 평가했다. 다만 기대 피루타수는 경기 득점으로 매번 이어지지 않기 때문에 각 투구가 승리에 기여하는 영향을 직접적으로 평가하지 못한다. 이 논문에서는 득점 기댓값과 득점 가치의 개념을 조합해 투구에 대한 기대 득점 가치를 계산하고 이를 통해 투구의 질을 랜덤 포레스트 모형으로 평가한 뒤, 기대 피루타수를 이용한 투구의 질 평가와 비교 분석한다. Major League Baseball (MLB) records and releases the trajectory data for every baseball pitch, called the PITCHf/x, using three high-speed cameras installed in every stadium. In a previous study, the quality of the pitch was assessed as the expected number of bases yielded using PITCHf/x data. However, the number of bases yielded does not always lead to baseball scores, or runs. In this paper, we assess the quality of a pitch by combining baseball analytics metric Run Expectancy and Run Value using a Random Forests model. We compare the quality of pitches evaluated with Run Value to the quality of pitches evaluated with the expected number of bases yielded.N

Electromagnetic Modeling of RF Induced Lead Heating-Ensuring MRI for Patients with Active Implanted Medical Devices

1