최적의 터치 동작 설계를 위한 인간 성능 모형 개발

학위논문 (박사)-- 서울대학교 대학원 공과대학 산업공학과, 2017. 8. 윤명환.Touch interface has evolved into dominant interface system for smartphones over the last 10 years. This evolutionary process has been applicable not only to the smartphone, but also to small hand-held smart devices like portable game consoles and tablet devices. Even further, the most recent Microsoft Windows operating system supports both traditional point and click interface as well as touch interface for broader coverage of OS on digital devices. Identifying factors contributing the human performance on touch interface system has been studied by wide range of researchers globally. Designers and manufacturers of smart devices with touch interface system could benefit from the findings of these studies since they may provide opportunities to design and implement better performing and more usable product with competitive edge over competitors. In this study, we investigated factors affecting human performance on touch interface systems to establish practical design guidelines for designers and manufacturers of smart devices with touch interface system. The first group of factors is demography related variables such as gender, regions and age. The second group of factors is interaction related variables such as number of hands involved in interacting with touch system – one handed versus two handed postures. Finally and most importantly, design-related variables such as sizes, shapes or locations of touch targets are investigated. Our main goal of this study is to identify what are the most affecting factors to human performance of touch interface systems and establish mathematical modeling among them. Developed performance modeling will be leveraged to estimate expected human performance without conducting usability testing on given touch interface system. Once demography, interaction and design related variables are given, we will be able to propose expected performance level by inputting those variables into the established model, thus will contribute to the optimal design practice. Touch gestures considered in this study are tap touch, move touch and flick touch, which are the most widely used touch gestures in designing and implementing touch interface system. We have recruited 259 subjects from 4 major metropolitan areas across 3 different countries – New York, San Francisco, London and Paris and conducted controlled laboratory experiment. In order to assess human performance of each touch gesture, we have defined individual performance measures of each gesture such as task completion time, velocity, throughput introduced by Fitts law (Fitts, 1954), variance/accuracy ratio introduced by Chan & Childress (1990), accuracy or offset tendency from a desired line of target. By investigating these performance measures, we could come up with design guidelines about design specifications such as size and movement direction as well as qualitative insights on how touch gestures are different across all the factors we have gathered from the experimental setup. Design strategies and guidelines as well as human performance modeling will contribute to develop effective and efficient touch interface systems.Introduction 1 1.1Background 1 1.2Research questions 2 1.3Document Outline 3 Literature reviews 5 2.1Potential variables affecting touch interface 5 2.2Gestures used in touch interface design 6 2.3How people hold mobile devices 9 2.4Design for thumbs 13 2.5Touch target size guidelines 14 2.6Estimating touch sizes 17 2.7Human performance models 20 2.8Human performance by gender and age 27 2.9Thumb-based touch interaction 29 2.10Models of human motor control 32 Tap touch experiment 37 3.1Introduction 37 3.2Methods 40 3.2.1 Task design 40 3.2.2 Experimental design 41 3.2.3 Subjects 42 3.2.4 Data analysis method 43 3.3Results 45 3.3.1 Normality check 45 3.3.2 Variables affecting task completion time on tap touch 47 3.3.3 Variables affecting distance to target on tap touch 55 3.3.4 Variables affecting angle from positive x-axis to touch point on tap touch 62 3.3.5 Variables affecting speed accuracy ratio on tap touch 68 3.4Conclusion and discussion 75 3.4.1 Speed accuracy trade off 75 3.4.2 Implications on angle from X axis 78 3.4.3 Leveraging performance prediction models 79 3.4.4 Recommended design strategies 80 3.4.5 Tap target size recommendation 81 Move touch experiment 85 4.1Introduction 85 4.2Methods 88 4.2.1 Task design 88 4.2.2 Experimental design 89 4.2.3 Subjects 90 4.3Data analysis method 91 4.3.1 Data handling 92 4.3.2 Result 92 4.3.3 Normality check 92 4.3.4 Variables affecting task velocity on move touch 94 4.3.5 Variables affecting accuracy of initial touch on move touch 105 4.3.6 Variables affecting accuracy of final release on move touch 113 4.3.7 Variables affecting throughput on move touch 121 4.4Conclusion and discussion 130 4.4.1 Design strategy for one hand versus two hands 130 4.4.2 Design strategy on moving direction 131 4.4.3 Design strategy on object sizes 132 4.4.4 Leveraging performance prediction models 132 Flick touch experiment 135 5.1Introduction 135 5.2Method 137 5.2.1 Task design 137 5.2.2 Experimental design 137 5.3Data analysis method 139 5.3.1 Data handling 140 5.4Results 140 5.4.1 Normality check 140 5.4.2 Variables affecting task completion time on flick touch 142 5.4.3 Variables affecting travel distance on flick touch 148 5.4.4 Variables affecting angle on flick touch 154 5.4.5 Variables affecting offset Y on flick touch 159 5.5Conclusion and discussion 164 5.5.1 Design strategy on demography and interaction related variables for flick movement 165 5.5.2 Design strategy on design-related variables for flick movement 166 5.5.3 Leveraging performance prediction models 167 Conclusion 169 6.1Research goals 169 6.2Summary of findings 170 6.3Performance prediction models 172 6.4Limitations and future studies 172 Bibliography 175 Abstract (in Korean) 186Docto

High-resolution Observation of Nucleation and Growth Behavior of Nanomaterials on Graphene

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 김미영.Studying nucleation and growth has been one of the major goals in materials science. Fundamental understanding of initial growth is essential for fabrication of nanomaterials with desired physical properties. Consequently, atomic level investigation on as-grown nuclei and local atomic arrangements around defects is required. Such high-resolution study along with crystallographic analysis could be performed using transmission electron microscopy (TEM). Here, we report on atomic-resolution observation of initial growth behavior using TEM by growing nanomaterials directly on graphene. Graphene exhibiting excellent electron beam transparency and high mechanical strength is an ideal supporting layer for TEM measurements by minimizing the background signal from the underlying membrane. In addition to merely sustaining nanomaterials as a support, graphene can be further used as a substrate for nanomaterials growth. The crystalline nature of graphene along with its electron beam transparency ultimately enables direct imaging of nanomaterials and allows us to systematically investigate the initial growth mechanisms. Using direct growth and imaging method, we could clearly observe the initial states of Zinc oxide (ZnO) nanomaterials. This enabled the observation of the transition in crystal structure of ZnO nuclei along with their orientational relationship with graphene. Furthermore, formation of various defects during nanomaterial growth could be clearly visualized with atomic-resolution. More generally, we believe that this simple technique may be readily expanded to investigate the growth mechanisms of many other nanomaterials on various two-dimensional layered substrates.Chapter 1 Introduction 1 1.1 Importance of studying the initial growth behavior of nanomaterials 1 1.2 Materials of interest 10 1.2.1 ZnO 10 1.2.2 Graphene 12 Chapter 2 Literature Survey 17 2.1 Direct crystal growth on prefabricated thin membranes for TEM measurements 17 2.2 Graphene as a supporting layer for TEM measurements 23 Chapter 3 Experimental Method 30 3.1 Growth of CVD graphene 30 3.2 Transfer of CVD graphene onto a TEM grid 31 3.3 Growth of ZnO nanomaterials on graphene placed on a TEM grid 35 3.4 Structural characterization of ZnO nanomaterials 35 3.4.1 SEM 35 3.4.2 TEM 36 3.5 First principles calculations 39 Chapter 4 Results and Discussions 40 4.1 Feasibility of the experimental technique for ZnO growth and TEM measurements 40 4.2 Overall growth behavior of ZnO nanomaterials on graphene 43 4.2.1 Nucleation and cluster growth stages 43 4.2.2 Postnucleation stages: coalescence 45 4.2.3 Postnucleation stages: formation of epitaxial relationship 46 4.3 Crystal structure of ZnO in the initial stage of growth 51 4.3.1 Formation of rocksalt ZnO structure 51 4.3.2 Nucleation barrier in heteroepitaxial growth 52 4.4 Disorder in the atomic arrangements around defects 58 4.5 Diverse applicability of the experimental technique for the initial growth study: ZnO nanomaterials on h-BN 63 4.5.1 Hexagonal boron nitride 63 4.5.2 Initial growth behavior of ZnO nanomaterials on h-BN 64 Chapter 5 Conclusions 73 References 74 Abstract 81Maste

개선된 투과전자현미경 분석법을 이용한 이차원 물질 위에서의 화합물 반도체 나노구조물의 결정성장 메커니즘 연구

학위논문 (박사)-- 서울대학교 대학원 공과대학 재료공학부, 2017. 8. 김미영.Atomically thin layered crystals isolated by mechanical exfoliation method have exhibited new physical properties and provided novel applications. Moreover, hybrid structures of these 2-dimensional (2-D) layered materials with semiconductor thin films and nanostructures offer additional functionalities, such as flexibility and transferability, thereby greatly extending the applicability to the electronic and optoelectronic devices. Accordingly, many efforts have focused on the growth of nanomaterials using 2-D materials as substrates. In order to fabricate such nanomaterials with desired shapes and physical properties, the study on the initial growth mechanisms, such as nucleation, nuclei growth, and orientational relationship with substrate, should be accompanied in detail. This work mainly focuses on exploring the growth mechanisms of compound semiconductor nanomaterials on graphene, as a representative material among various 2-D layered materials, using transmission electron microscopy (TEM). In order to avoid unintentional damages arising from conventional TEM sample preparation processes, direct growth and observation method was developed to observe nanomaterials at the early growth stages. In this method, electron-beam transparent graphene was exploited as a supporting layer for TEM measurements as well as a substrate for nanomaterials growth. Compound semiconductor nanomaterials including ZnO, InAs, and GaAs were grown on graphene which had been transferred onto a TEM grid, followed by TEM measurements conducted without TEM sample preparation processes. Reflection high-energy electron diffraction (RHEED) transmission mode was also employed to analyze the structural information of nanostructures in real time during the growth. Contrary to its conventional usage in reflection mode, RHEED was used in transmission mode. This new technique allows us to obtain diffraction patterns containing the structural information of nanomaterials, which is analogous to the principle of electron diffraction in TEM. Using these newly developed methods, the growth mechanisms of compound semiconductor nanomaterials were thoroughly investigated. First, the growth behavior of ZnO nanomaterials was clearly observed with atomic-resolution and high-sensitivity using a graphene template for the direct growth and observation method. This method successfully disclosed the growth behavior of ZnO nanomaterials on graphene, such as nucleation of ZnO cubic phase and formation of ∑7 coincidence site lattice boundary, which are previously unknown. Second, the growth mechanisms of GaAs/single-layer graphene (SLG)/InAs double heterostructures were unraveled with an aid of a further improved direct growth and observation method. This study showed that InAs nanorods grown on SLG can influence on the nucleation and growth behavior of GaAs nanomaterials on the other side of SLG. Lastly, the growth behavior of InAs nanorods were investigated in real time using the RHEED transmission mode. Time-resolved observation using RHEED transmission mode revealed the transition in local growth condition from In-rich to As-rich at the very early stage of InAs nanorods growth and the strain relaxation process of GaAs/InAs coaxial nanorods during the shell layer coating.Table of contents Abstract i Table of contents iv List of Tables vii List of Figures viii CHAPTER 1 1 CHAPTER 2 9 2.1 Theory 10 2.1.1 Crystal growth: nucleation and growth 10 2.1.2 Heteroepitaxy 20 2.1.3. Van der Waals epitaxy 22 2.1.4. III-V nanorod growth mechanism: VLS growth 24 2.1.5. III-V nanorod growth mechanism: VS growth 26 2.2 Transmission electron microscopy 27 2.2.1 High-resolution TEM 27 CHAPTER 3 34 3.1 Fabrication of graphene templates 35 3.1.1 Growth of CVD graphene 35 3.1.2 Fabrication of SiNx membrane TEM grid 36 3.1.3 Graphene transfer 42 3.2 Materials growth 43 3.2.1 ZnO nanomaterials on a graphene template 43 3.2.2 GaAs/SLG/InAs double heterostructures 45 3.2.3 InAs coaxial nanorods on Si(111) and graphene 48 3.3 Materials characterization 50 3.3.1 Scanning electron microscopy 50 3.3.2 Transmission electron microscopy 50 3.3.3 Reflection high-energy electron diffraction 51 CHAPTER 4 53 4.1 Introduction 54 4.2 Direct growth and observation of nanomaterials using a graphene template 56 4.3 Feasibility of the new method for crystal growth and TEM measurements 59 4.4 Growth mechanism of ZnO nanomaterials on graphene 62 4.4.1 Nucleation 62 4.4.2 Grain boundary formation 67 4.5 Summary and outlook 71 CHAPTER 5 73 5.1 Introduction 74 5.2 Direct growth and observation of nanomaterials using a graphene and prefabricated SiNx membrane TEM grid 79 5.2.1 Prefabricated SiNx membrane TEM grid 79 5.2.2 Direct growth and observation of GaAs and InAs nanomaterials 84 5.3 Feasibility of the improved method for crystal growth and TEM measurements 86 5.4 Growth mechanism of GaAs/SLG/InAs double heterostructures 90 5.4.1 Control group: growth behavior of GaAs on SLG 90 5.4.2 Experimental group: growth behavior of GaAs on SLG/InAs 94 5.4.3 General growth mechanism of double heterostructures 103 5.5 Summary and outlook 106 CHAPTER 6 107 6.1 Introduction 108 6.2 RHEED transmission mode 110 6.3 Feasibility of RHEED transmission mode for the real-time structural analysis of nanomaterials 113 6.4 Growth mechanism of InAs nanorods and GaAs(InxGa1-xAs)/InAs coaxial nanorods 121 6.4.1 Initial growth behavior of InAs nanorods 121 6.4.2 Strain relaxation of shell layers during the epitaxial growth 128 6.4.3 InAs nanorods growth on graphene layers 134 6.5 Summary and outlook 136 CHAPTER 7 138 7.1 Summary 138 7.2 Outlook 141 REFERENCES 142 ABSTRACT (IN KOREAN) 150Docto

Galileo's Study on Sunspots and His Argument on the Solar Rotation

학위논문(석사)--서울대학교 대학원 :자연과학대학 협동과정 과학사및과학철학전공,2020. 2. 홍성욱.This paper examines how Galileo Galilei(1564-1642), a mathematician, astronomer, and philosopher from Florence, Italy, proved the rotation of the Sun. In particular, by analyzing his works Letters on the Sunspots and Discourse on Bodies in Water, this paper reveals that Galileo could reach his conclusion by introducing extra elements of the natural philosophy in addition to the elements of the mixed mathematical sciences, unlike previous studies which suggested that Galileo reached his conclusion of solar rotation only with observations of sunspots and mathematical reasoning on the location of sunspots. First of all, against the backdrop of the fluid-heaven view which had emerged as an alternative to the Aristotle-Ptolemy's universe system since the end of the 16th century, Galileo compared the Sun to the Earth and argued that the fluid-like atmosphere including sunspots surrounded the Sun. Furthermore, by applying his material theory which had been established for the purpose of determining the structures and properties of solids and fluids, Galileo reasoned that because there is no "coherence" in the fluid, the regular motion of sunspots inevitably comes from the rotation of the Sun, and because there is "affinity" between the Sun and the atmosphere, the Sun's motion is transmitted to the atmosphere. Out of this reasoning, Galileo drew his conclusion of solar rotation. As such, the primary purpose of this paper is to show that to claim the solar rotation, Galileo introduced elements of the natural philosophy, such as fluid-heaven view, the atmosphere of the Sun, and material theory, in addition to observations of sunspots and mathematical reasoning based on them. Furthermore, beyond showing that previous researchers have not faithfully read Galileo's historical records, this paper aims to point out that the hybrid of natural philosophy and mathematics, an important innovation that Galileo has made, has not been fully appreciated. The fact that previous research suggested that Galileo reached the conclusion of the solar rotation only with observation of sunspots and mathematical reasoning seems to be in line with the fact that among Galileos various works, scholars have emphasized Galileos practice as a mathematician by studying Galileo in relation to the so-called the Scientific Revolution, a period when the importance of the mixed mathematical science was increasing. As this paper shows, however, Galileo was able to draw the conclusion that the Sun rotates by introducing natural philosophical discourse besides observation and mathematical reasoning. This means that in Galileos argument for solar rotation, the strict boundaries that had existed between the two disciplines of the mixed mathematical science and natural philosophy were starting to blur. The conclusion of the solar rotation was the product of a hybrid discipline, in which Galileo crisscrossed between the two disciplines, combining elements of the mixed mathematical sciences such as mathematical reasoning with elements of the natural philosophy such as cosmology and material theory.본 논문은 이탈리아 피렌체 출신의 수학자 및 천문학자이자 철학자였던 갈릴레오 갈릴레이(1564-1642)가 어떻게 태양의 자전을 증명했는지 살펴본다. 특히 그의 저작 『흑점에 관한 편지』와 『물속의 물체에 대한 논설』을 중점적으로 분석함으로써, 갈릴레오가 흑점 관측 자료와 흑점의 위치에 관한 수학적 논증만으로 태양 자전의 결론에 도달했다고 본 기존 연구와는 달리 그가 그러한 수리과학적 요소 이외에도 여러 자연철학적 요소를 도입해서야 태양 자전이라는 결론을 내릴 수 있었음을 밝힌다. 우선 갈릴레오는 16세기 말부터 아리스토텔레스-프톨레마이오스 우주체계의 대안으로 부상했던 유체우주설의 배경 아래, 태양을 지구에 비유하여 유체의 성질을 가진 대기가 흑점을 포함한 채 태양을 둘러싸고 있다고 주장했다. 더 나아가 갈릴레오는 고체와 유체의 구조와 성질 규명을 목적으로 수립한 자신의 물질 이론을 태양 자전 논증에 적용했다. 유체에는 응집성이 없으므로 흑점의 관측상 규칙적인 운동이 태양의 자전으로부터 올 수밖에 없고 태양과 대기 사이에는 친화성이 존재하므로 태양의 운동이 대기로 전달되기 때문에 태양 자전의 결론이 도출된다고 보았던 것이다. 이렇게 갈릴레오가 태양 자전을 주장하기 위하여 흑점의 관측 자료와 이에 기초한 수학적 논증 이외에도 유체우주설, 태양의 대기, 물질론 등의 자연철학적 요소를 도입했다는 사실을 보이는 것이 본 논문의 일차적인 목적이다. 더 나아가 기존 연구자들이 갈릴레오가 남긴 사료를 충실히 독해하지 못했다는 점을 넘어, 갈릴레오가 이룩한 중요한 혁신인 자연철학과 수학의 융합이 충분히 이해되지 못했다는 사실을 지적하는 것이 본 논문의 이차 목적이다. 기존 연구가 관측과 수학 논증만으로 갈릴레오가 태양 자전이라는 결론에 도달했다고 보았다는 점은 그동안 주로 갈릴레오를 수리과학의 중요성이 증진하던 시기인 이른바 과학혁명기와 관련하여 다룸으로써 그의 작업에서 대체로 수학자로서의 실천이 강조되었다는 사실과 궤를 같이한다. 그러나 본 논문이 보여주듯이, 갈릴레오는 관측과 수학 논증 이외에도 여러 자연철학적 담론을 도입해서야 태양이 자전한다는 결론을 도출할 수 있었다. 이는 갈릴레오의 태양 자전 논증 속에서 수리과학과 자연철학이라는 두 분과 사이에 존재했던 엄격한 경계선이 흐려지고 있었음을 의미한다. 태양의 자전이라는 결론은 갈릴레오가 두 분과 사이를 종횡무진 넘나들며 관측 및 수학적 논증이라는 수리과학적 요소와 우주설 및 물질 이론과 같은 자연철학적 요소를 엮어 만들어냈던 혼종적 분과의 산물이었던 것이다.1 서론 1 2 망원경 제작에서 흑점 연구까지: 갈릴레오 흑점 연구의 배경 10 3 흑점의 위치에 관한 수학적 논증 17 4 유체우주설과 지구태양 비유에 기반한 태양 대기 추론 38 5 물질론에 기초한 태양 자전 논증 50 6 결론 67 참고문헌 70Maste

Discharge characteristics and thermal analysis of large capacity thermal battery with pure lithium anodes and heat sources

군사 및 우주용으로 사용되는 열전지(thermal battery)의 대용량화를 위해서는 합금형 음극 소재(예, Li-Si)보다 고에너지 특성과 고 출력 특성을 갖는 순수 리튬 음극 소재에 대한 연구가 반드시 필요하다. 본 논문에서는 고 에너지와 고출력 특성을 갖는 순수 리튬 음극 기반의 열전지 개발 연구를 위하여, 문헌조사, 이론적 해석, 단위전지 조성설계, 단위전지 방전시험, 대용량 열전지 제작, 열설계/열해석, 실제 대용량 전지 시험/비교 순으로 진행하였다. 먼저, 문헌조사와 기술노하우 등을 통해 리튬 음극(LiFe anode) 제작 공정을 확립하였다. 글로브박스 내의 수분, 수소, 질소, 산소 농도가 1 ppm 미만인 조건에서 최적의 '용융 리튬과 철 분말의 교반 조건'을 도출하였다. 교반용기를 350도로 가열하고, 교반기의 회전속도를 150 rpm으로 설정하여 약 15~20 분마다 반복해서 철 분말을 교반용기 내의 용융리튬에 투입하였다. 이렇게 교반된 잉곳을 압연(press), 롤링하여 음극으로 만드는 공정을 확립하였다. 더 나아가 교반의 편리성을 위하여 자동교반장치까지 설계/제작하였다. 위의 공정으로 제작되는 LiFe 음극의 최적 조성 설계를 위해, 순수 리튬 함량(13, 15, 17, 20 wt%)을 조절하여 제작하였다. 전극 누액이 발생하지 않는 지를 확인하기 위한 가압시험(3, 4, 6, 10 kg$_f$/cm$^2$)을 수행하였다. 그 결과, 최적의 LiFe 음극 내 리튬 함량( Li wt %)은 13 wt% 임을 확인하였다. 또한, LiFe 음극의 균일한 제작 및 내부의 Li:Fe간 조성 상태 및 방전 전후의 전극 내부 생성물질 등을 확인하기 위하여 미세구조를 분석하였다. LiFe 단위셀을 제작하여 Li-Si 단위셀과 성능 비교한 결과, LiFe 단위셀은 807.1 Wh/l, Li-Si 단위셀은 522.2 Wh/l의 비에너지 밀도 차이가 발생하였다. 이는 LiFe 단위셀이 Li-Si 단위셀보다 50 % 가량 우수함을 보이는 것이다. 열전지의 열해석 및 최적 방전온도를 확인하기 위하여, 기존의 합금 음극(Li-Si)형 열전지와 순수 리튬 음극(LiFe)형 열전지를 대상으로 성능이 최적으로 발현되는 셀 온도를 단위셀 방전실험을 통하여 확인하였다. 그 결과, Li-Si 열전지 전극의 최적 방전온도는 500도 범위이고, LiFe 열전지 전극의 최적 방전온도는 550도 내외임을 확인하였다. 위의 실험결과를 바탕으로 1 kWh급 대용량 열전지(80셀, 150V)를 대상으로 COMSOL Multiphysics 프로그램을 활용하여 Li-Si 및 LiFe 열전지용 열원의 최적 설계 열량을 도출하였다. 해석결과, 열전지 전극의 최적 방전온도에 맞춰 설계한 최적의 열용량 값은 Li-Si의 경우 100 cal/g이고, LiFe 열전지의 경우 110 cal/g 이다. 위의 COMSOL 프로그램을 통해 얻은 열원의 열량 설계 기준으로 대용량 열전지를 제작하여 정전류(40A) 방전시험을 수행하였다. 그 결과, COMSOL 해석 결과와 방전시험 결과가 일치함을 확인하였다. 또한, 대용량 80셀, 1 kWh급 열전지의 경우 Li-Si 열전지보다 LiFe 열전지의 부피 비에너지 에너지 밀도가 2.34배 증가함을 확인하였다. 본 연구결과는 대용량 고전압 열전지 음극 조성 및 열설계를 위한 연구자료로써 활용 될 수 있을 것이다.한국과학기술원 :기계공학과,학위논문(박사) - 한국과학기술원 : 기계공학과, 2021.2,[xiii, 123 p. :