고성능 나노탄소 전계 방출 소자

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 김용협.By taking advantage of the superior material properties and high aspect ratio geometry of nanocarbon materials, many researchers have been able to devote their efforts toward the development of nanocarbon emitters, which are capable of providing low turn-on voltage, high emission current density and long-term emission stability. Electron beams of field emitter are widely employed in various applications, including X-ray photography and computed tomography (CT) scans in hospitals, fault detection of semiconductor devices, airport security, and terahertz generation. Moreover, electron beam generators are progressively becoming more miniaturized, light-weighted, and low-powered so that they can be applied to diverse areas. For a high performance field emitter, new concept of field emitter is needed to overcome the previous research. In this thesis, four novel approaches are developed in terms of fabricating the multidimensional field emitters. 1) CNT point emitter with graphene interfacial layer: we report graphene as an interfacial layer between the metal and CNTs to improve the interfacial contact. The interfacial graphene layer results in a dramatic decrease of the electrical contact resistance by an order of 2 and an increase of the interfacial thermal conductivity by 16%. Such a high improvement in the electrical and thermal interface leads to superior field emission performance with a very low turn-on field of 1.49 V μm−1 at 10 μA cm−2 and a threshold field of 2.00 V μm−1 at 10 mA cm−2, as well as the maximum current of 16 mA (current density of 2300 A cm−2). 2) CNT line emitter using clamping process: we report a robust and scalable method to fabricate high-performance carbon nanotube (CNT) line emitters by using a macroscopic mechanical clamping process. The process utilizes a handheld, metallic tongs (which also serves as an electrode for field emission) to pick up vertically aligned, super-grown CNTs from a substrate. By applying mechanical compression to a CNT forest in the uniaxial direction, the hemicylindrical shape of CNT structure strongly held with the tongs electrode is fabricated. With robust mechanical, thermal, and electrical contact characteristics created by mechanical clamping of CNTs, the CNT line emitter shows superior field emission performance with an emission current of 43 mA, a current density of 2700 mAcm-2, and stable operation over 10 hours. Furthermore, an extremely high emission current of 103 mA is achieved by clamping multiple CNT forests in a single tongs, showing prompt applicability of the present emitter for high-power electron beam sources. 3) Holey graphene film as a planar field emitter: we introduce an emitter in the shape of a hole, or hole emitter. An array of holes in graphene film can serve as a planar emitter, in which each circular hole is an emitter. Because of the nature of the sidewall emission through the edge of graphene film, the present planar emitter does not need any cumbersome process of leveling off emitter height and contriving to obtain the desirable inter-distance between emitters. Therefore, the screening effect and the field emission uniformity considered as obstacles in developing high efficiency planar emitters are easily resolved by an optimal design of the circular hole array. Moreover, the graphene film emitter is so flexible that it can be wrapped around a cylindrically shaped anode. This flexibility allows the present emitter to be used as a high power electron beam source because of the focusing of the emitted electron beams rendered by the concavely curved surface. 4) Carbonized cork emitter for multi-dimensional field emission: to broaden the range of application of electron beams, low power field emitters are needed that are miniature and light. We introduce here carbonized cork as a material for field emitters. The light natural cork becomes graphitic honeycomb upon carbonization, with the honeycomb cell walls 100-200 nm thick and the aspect ratio larger than 100, providing an ideal structure for the field electron emission. Compared to nanocarbon field emitters, the cork emitter produces a high current density and long-term stability with a low turn-on field. The nature of cork material makes it quite simple to fabricate the emitter. Furthermore, any desired shape of emitter tailored for the final application can easily be prepared for point, line, or planar emission.Chapter 1 Introduction 1 Chapter 2 CNT point emitter with graphene interfacial layer 5 2.1 Background of CNT point emitter 6 2.2 Experimental section 8 2.3 Result and discussion 10 2.4 Conclusion 27 Chapter 3 CNT line emitter using clamping process 28 3.1 Background of CNT line emitter 29 3.2 Experimental section 31 3.3 Result and discussion 32 3.4 Conclusion 46 Chapter 4 Holey graphene film as a planar field emitter 47 4.1 Background of planar emitter 48 4.2 Result and discussion 50 4.3 Conclusion 64 Chapter 5 Carbonized cork emitter for multidimensional field emission 65 5.1 Background of low turn-on field emitter 66 5.2 Experimental section 68 5.3 Result and discussion 72 5.4 Conclusion 93 Chapter 6 Conclusions 94 Bibliography 97 Abstract 122Docto

A Study on Navigable Spatial Planning using Big Data on Maritime Traffic in Geographic Information System Environment

최근 해양공간은 사용하는 주체들에 의해 구체적 관리체계 없이 선점식으로 이용되고 있다. 해양공간을 이용하는 주체들 간의 갈등이 심화되면서 해양 난개발이 발생하며 사회적인 문제가 되고 있다. 이러한 문제를 해결하기 위해 영국, 벨기에, 미국, 네덜란드 등은 해양공간의 용도를 체계적, 정량적으로 분리하여 이용 주체들에게 제공하고 있다. 특히, 해양공간 이용 주체 중 항행구역은 다른 목적의 해양 용도보다 최우선시 되고, 항행을 확보할 수 있게 한다. 우리나라는 부산 인근 해역에 해양공간관리계획을 수립 및 발표하였다. 해양용도구역으로 어업활동보호구역, 골재·광물자원개발구역, 해양관광구역, 환경·생태계관리구역, 연구·교육보전구역, 항만·항행구역, 군사활동구역, 안전관리구역으로 분리하였다. 여기서 항만·항행구역이 포함하는 영역은 영해의 경우 17.36%이며, 배타적 경제수역에서는 1.07%로 나타난다. 영해 영역은 항계 내부, 교통안전특정해역으로만 선정되어 있으며, 선박이 항행하기 위한 이외의 해역에서는 항행구역으로 선정되어 있지 않다. 본 연구는 해양공간계획(Marine Spatial Planning, MSP)에서 정량적인 방법으로 항행공간계획의 수립 방법을 제시하고자 한다. 실측 해상교통 데이터 기반으로 선박의 항행 밀집도를 산출한 후, 새로운 방법의 항로 생성 알고리즘을 적용하여 항로의 안전성을 검증한다. 생성된 항로의 안전성 검증 이후, 항행구역에 적용이 가능한지 파악하고 항로를 신설할 해역 또는 항로의 수정이 요구되는 해역에 적용하고자 한다. 항로 생성 알고리즘을 적용하기 위해 1년간의 선박자동식별시스템(Automatic Identification System, AIS) 해상교통 빅데이터 기반으로 KDE(Kernel Density Estimation)분석을 수행하였다. 사용된 Kernel 함수는 Quartic을 사용하였고, 전체 해상 교통량에서 90%를 항행구역으로 선정한 해외 사례를 적용하여 분석하였다. 90%의 KDE 분석 결과를 기반으로 이미지 처리 알고리즘을 수행하여 항로 부분과 그렇지 않은 부분으로 나누기 위해 Otsu 이진화 알고리즘을 수행하였다. 이진화 과정 수행 후, 항로의 가장자리를 추출하기 위해 Sobel, Laplacian, Canny의 알고리즘을 적용하였으며, 이 중 가장 정확하게 추출되는 Canny 알고리즘을 분석에 사용하였다. 항로의 가장자리는 선으로 이루어져 있으며 선과 선이 만나는 지점인 코너를 추출하기 위해 Harris 탐지 알고리즘을 사용하였다. 이와 같이 이미지 처리 알고리즘을 수행한다면 생성된 항로의 초기 모습을 나타낼 수 있다. 하지만, 생성된 항로의 초기모습은 일부 구간이 울퉁불퉁하며 끊어져 있는 부분이 존재한다. 이를 라인 스무싱 작업을 통해 항로를 부드럽게 만들어주고 끊어져 있는 부분을 연결한다. 부드럽게 생성된 항로 구역을 들로네 삼각분할을 적용하여 삼각형으로 분할한다. 생성된 삼각형에 이웃한 삼각형의 개수에 따라 속성값을 1 ~ 3까지 입력 하고, 개별 속성값은 노드, 커브, 세그먼트를 구성할 수 있다. 세그먼트를 모두 연결하면 최종적으로 항로의 센터라인을 생성할 수 있다. 생성된 센터라인은 항로 안전성 측면에서 비교하기 위해 기존 항로의 센터라인과 굴곡도 검증, 교각 검증, RCE(Route Change Envelope) 검증을 수행한다. 일부 구간을 제외하고, 생성된 센터라인은 안전성 측면에서 우수한 결과를 가져왔으며, 이를 해양공간계획의 항행구역으로 선정한다.So far, various user using marine space around the world have been using it preemptively without a comprehensive management. Such practice has caused such social problems as increased conflicts between marine users and has led to excessive development of marine space. In an effort to resolve such issues, European countries, China, Japan, and the United States categorized marine space systematically and quantitatively prior to providing the area to the users. Especially, the navigation areas among the user using marine space are given priority over other purposes of marine use, and enables navigation routes to be secured. In the Republic of Korea, the Ministry of Oceans and Fisheries and Busan Metropolitan City established and announced the Marine Spatial Management Planning for exclusive economic zones and territorial sea for the first time since the implementation of the Marine Spatial Planning Act. The planning divided marine-use areas into the following zones: fishery activity protection zone; aggregate, mineral resource development zone; marine tourism zone; environment, ecosystem management zone; research and education conservation zone; port, shipping zone; military activity zone; and safety management zone. Here, the area covered by the port, shipping zone represents 17.36% of the territorial sea, and the figure stands at 1.07% in the exclusive economic zone. The designated territorial sea refers to the selected areas only inside the busan harbour limit and the traffic safety designated areas. The sea is not designated as a navigable area if it does not serve the purpose of the space required for sailing. With the aid of a quantitative method, this study attempts to create novel maritime routes – while employing the big data of the maritime traffic to establish navigable areas - in the Marine Spatial Planning (MSP). To perform such task, the traffic density would be calculated based on the actual traffic data, while the safety of the novel maritime route would be verified by applying the new method of the route generating algorithms. Following the verification of the safety of the novel maritime route, this research will subsequently determine whether it can be applied to the navigable areas of the marine spatial planning, and then use it to the areas where the route is to be established or the areas requiring modification of the routes. To apply the route generating algorithms, a one-year KDE (Kernel Density Estimation) analysis, based on the AIS (Automatic Identification System) marine traffic big data, was performed. The Quartic was used for Kernel function, and it was analyzed by applying overseas cases, in which 90% of the total sea traffic was selected as a navigation zone. The image processing algorithm based on the result of 90% KDE analysis was conducted. Also, in order to separate the areas into the route part and the non-route part, the Otus binarization algorithm was used. After performing the image binarization process, Sobel, Laplacian, and Canny's algorithms were applied to extract the boundary of the routes. As a result, Canny algorithm - the most accurate on obtaining boundaries - was used for the analysis. The boundary of the route consists of lines, and the Harris detection algorithm was used to extract the corners where the lines meet one another. When the image processing algorithms are executed as above, it is possible to present the initial appearance of the generated route. However, the routes created by applying the image processing algorithms display some sections as uneven or cut off. The line smoothing operation could smoothen out the lines and combine cut-off parts. Then, the smoothened out route areas could be divided into triangles by applying the Delaunay triangulation. Depending on the number of triangles adjacent to the generated triangles, we can enter the attribute values from 1 to 3, and the individual attribute value can be composed of nodes, curves, and segments. When all segments are connected, it becomes finally possible to create the centerline of the route. The generated centerline is compared with the centerline of the original route in terms of stability. To carry out the comparisons, the sinuosity verification, the intersection angle verification, and the route change envelope(RCE) are performed. In the end, the centerline of the newly generated route, with few exceptions, achieved excellent results in terms of stability, and we intend to select it as a navigable area of the Marine Spatial Planning.목 차 Abstract vii 국문초록 x 제 1 장 서 론 1 1.1 연구 배경 및 목적 1 1.2 연구 방법 4 제 2 장 국내외 항행공간계획 동향 6 2.1 해양공간계획(Marine Spatial Planning, MSP) 정의 6 2.2 항행공간계획 해외동향 7 2.2.1 영국 8 2.2.2 벨기에 12 2.2.3 미국 15 2.2.4 네덜란드 20 2.3 항행공간계획 국내동향 21 2.3.1 해양공간계획 수립 현황 21 2.3.2 항만 및 항행구역 한계점 23 제 3 장 수집 데이터 전처리 및 분석 프로그램 27 3.1 선박자동식별시스템 개요 27 3.2 AIS 데이터 특징 및 전처리 과정 30 3.3 분석 프로그램 35 3.3.1 지리공간정보시스템 35 3.3.2 공간정보 분류 35 제 4 장 항로 생성 알고리즘 적용 43 4.1 항로 생성 알고리즘 43 4.1.1 항로 생성 해역 모델링 43 4.1.2 항로 생성 알고리즘 개요 44 4.2 KDE(Kernel Density Estimation) 분석 46 4.2.1 KDE 개요 46 4.2.2 GIS 기반 KDE 분석 47 4.2.3 KDE 분석 결과 49 4.3 항로 생성 이미지 처리 기법 53 4.3.1 이미지 이진화 알고리즘 53 4.3.2 가장자리 추출 알고리즘 58 4.3.3 코너 탐지 알고리즘 64 4.4 항로 센터라인 추출 모델링 69 4.4.1 라인 스무싱 알고리즘 69 4.4.2 들로네 삼각분할 알고리즘 74 제 5 장 생성 항로의 비교 및 검증 80 5.1 항로 안전성 검증 80 5.1.1 굴곡도 검증 80 5.1.2 교각 검증 84 5.1.3 RCE 검증 87 5.2 생성 항로 항행공간계획 적용 92 제 6 장 결 론 94 6.1 연구의 결론 94 6.2 향후 연구 과제 96 참고문헌 98Maste

Relationship between abstract thinking and eye gaze pattern in patients with schizophrenia

BACKGROUND: Effective integration of visual information is necessary to utilize abstract thinking, but patients with schizophrenia have slow eye movement and usually explore limited visual information. This study examines the relationship between abstract thinking ability and the pattern of eye gaze in patients with schizophrenia using a novel theme identification task. METHODS: Twenty patients with schizophrenia and 22 healthy controls completed the theme identification task, in which subjects selected which word, out of a set of provided words, best described the theme of a picture. Eye gaze while performing the task was recorded by the eye tracker. RESULTS: Patients exhibited a significantly lower correct rate for theme identification and lesser fixation and saccade counts than controls. The correct rate was significantly correlated with the fixation count in patients, but not in controls. CONCLUSIONS: Patients with schizophrenia showed impaired abstract thinking and decreased quality of gaze, which were positively associated with each other. Theme identification and eye gaze appear to be useful as tools for the objective measurement of abstract thinking in patients with schizophrenia.ope

A hybrid technique for sinus floor elevation in the severely resorbed posterior maxilla

PURPOSE: This study aimed to evaluate the effectiveness of the modified sinus floor elevation technique described hereafter as a "hybrid technique," in 11 patients with severely resorbed posterior maxillae. METHODS: Eleven patients who received 22 implants in the maxillary premolar and molar areas by the hybrid technique were enrolled in this study. A slot-shaped osteotomy for access was prepared on the lateral wall along the lower border of the sinus floor. The Schneiderian membrane was fully reflected through the lateral slot. Following drilling with the membrane protected by a periosteal elevator, the bone was grafted. All implants were placed simultaneously with sinus augmentation. The cumulative success rate was calculated and clinical parameters were recorded. Radiographic measurements were performed. RESULTS: All implants were well maintained at last follow up (cumulative success rate=100%). The mean residual bone height, augmented bone height, crown-to-implant ratio, and marginal bone loss were 4.1+/-1.64 mm, 8.76+/-1.77 mm, 1.21+/-0.33 mm, and 0.34+/-0.72 mm, respectively. CONCLUSIONS: Simultaneous implant placement with sinus augmentation by hybrid technique showed successful clinical results over a 2-year observation period and may be a reliable modality for reconstruction of a severely resorbed posterior maxillaope

암반에 근입된 군말뚝의 거동에 대한 실험적 연구

학위논문(석사)--서울대학교 대학원 :토목공학과,1998.Maste

(A) study of oral flora and inorganic constituents of dental plaque of Korean women

의학과/박사[한글] [영문] Dental plaque is generally considered to be of paramount significance in the etiology of dental caries and periodontal disease. Its microbial content, biochemical composition and its mode of formation may be great important to control of dental disease. Since Miller(1890) had proposed that bacteria which producing sufficient acid to decalcify the tooth were etiologic agents of dental caries, almost all investigators aimed at the control of caries was directed towards increasing the resistance of the tooth to acid dissolution. Stephan(1953) has reviewed the historical development of the plaque concept. In the intervening years, a number of investigators attempted to equate the specific microorganisms with plaque formation and dental caries because of their ability to produce mucinous polysaccharides from sucrose. A nummerous researchers have been participated to seek for the nature and role of dental plaques by bacteriological, biochemical and pathological methods or electron microscopic examination and fluorescent antibody techniques. Its microbial content, mode of formation and relationship to dental caries and periodontal disease, have been discussed in several recent reviews(Mandel, 1966; Leach, 1970; Dawes, 1968; Jenkins 1968, 1972; Keyes, 1968; Meckel, 1968; Schroeder, 1969, Egelberg, 1970; Kleinberg, 1970; Socransky, 1970; Gibbons and van Houte, 1973). And, there are two intraoral processes, those are, microbial colonization and mineralization processes. It iss ure that plaque are concerned in periodontal inflammation by endotoxins, enzymes, and antigens; in caries by acid production: and in calculus formation with mineralization. This study was dealt with oral flora and inorganic constituents of dental plaque of 279 Korean women: 1) Oral examination by the recommanded criteria of W.H.O. 2) Dental plaqnes of low right canine and first molor of each subject were collected and were cultured on the plate, of blood agar, nutrien agar, eosin methylene blue(E.M.B.) agar, sabouraud's media and bromcresol purple(B.C.P.) media in an aerobic condition. The specimen was also cultured anaerobically in thioglycollate broth medium and on blood agar plate in Torbal jar. On the other hand, direct smear were obtained and stained by gram and acid-fast staining. 3) On blood agar those were cultured anaerobically and aerobically, colony countings were done for the total viable count. 4) Attaching the alminium foils on the lingual surfaces of ower central incisors for 1, 2, 3, 5, 10 and 15-days, measured their weight. Then, dried for three hours in 110℃. for the measurement of Ca, Mg, K, and Zn, the quantity was analysed by the atomic absoption spectrometry, Model 303 of Perkin-elmer Co.. And the measurement of phosphorus was done by Fiske-Subba-row method. 5) For the electron microscopic study, the following processes had done: fixation of plaque at 4℃ with 3% glutaraldehyde and osmium tetroxide solution; dehydration with alcohol and propylene oxide; embedding(Epon 812); ultrathin section of 500∼600A; staining of uranyl acetate and lead citrate; and observation with electron microscope(Hitachi, HU-11, E-1 type). The results obtained in this study were as follows: 1.l Prevalence of dental caries of the subject was 91.9%, while the control group reveals 83.3%. 2. In identification of microflora isolated from dental plaque(N=279), 127 cases(45.1%) were identified. Bacterioides sp.(9.8%), Straphylococcus(9.1%), Streptococcus(7.1%) are found as predominant species; and the unidentified 170 cases could be classify into species only morphologically. Among them the gram negative bacillus, long and thin from were in 52 cases(17.5%), short and coccoid from in 47 cases(15.8%); and unidentified of gram positive bacilli in 25 cases(8.4%). 3. The total viable count of the anaerobic and aerobic culture reveals increasing with the age of deposit day by the eleventh day except the fifty day. The count of the eleventh day was 27.0×10**7 cell/ml and 12.5×10**7 cell/ml of aerobic cultivation. After the fifteenth day it decreased to 1.4×10**7 cell/ml and 1.5×10**7 cell/ml respectively. 4. The analysis of inorganic constituents of dental plaque which were obtained from alminium foils showed increasing tendency with the age of deposit day, especially by fifth day. Calcium, magnessium, potasium, zinc, and phosphorus are increased. Ca/P ratios of 1, 2, 3, 5, 10, and 15 day were 1.00, 1.11, 1.80, 1.80, 1.70, and 1.67. 5. Of electron microscopic finding, nummerous microorganisms were found in early stage. However, after two weeks, especially after five weeks, crystal-like substance, those are, needle-shaped crystal and platelet-sharped crystal revealed obviously as other investigators reported.restrictio

How strategic rivalries impede the emergence of balance of power : the case of Eastern Europe between the World Wars, 1919-1939

학위논문(석사) --서울대학교 대학원 :외교학과,2009.8.Maste

지방자치시대 환경행정기능의 적정배분 방안에 관한 연구 : 지방환경관리청과 지방자치단체간의 관계를 중심으로

학위논문(석사)--서울대학교 환경대학원 :환경계획학과,1997.Maste

퇴적물 내 황화물, 중금속 농도가 이매패류와 다모류의 체내 중금속 축적(Cd, Ni,Zn)에 미치는 영향

Thesis (master`s)--서울대학교 대학원 :해양학과,1998.Maste

손상평가도를 이용한 용접 구조물의 균열형 결함에 대한 건전성 평가

학위논문(석사)--서울대학교 대학원 :재료공학부,2002.Maste