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완전배정방법을 이용한 도시철도 운행비용 모형의 정립과 적용
송선아(Song, Sun-Ah),서선덕 대한교통학회 2004 대한교통학회 학술대회지 Vol.46 No.-
날로 혼잡해져가는 교통체증 및 자동차 사고로 인한 인명․대물피해, 대기오염문제 등의 해결방안 중 하나로 승용차에서 도시철도(명칭은전철, 지하철, 도시철도로 각 기관마다 상이하지만, 본 연구에서는 도시철도로 통일하여 지칭하도록 한다.)로의 수요전환을 들 수 있다. 도시철도는 같은 대중교통 수단인 버스와 비교했을 때 운행의 정시성 및 대량수송 등의 장점을 갖고 있는 반면에 초기투자비용이 다른 교통수단에 비해 크며, 막대한 부채의 상환, 운행비 지출 등으로 인한 적자를 면하지 못 하고 있는 문제점이 있다. 이러한 적자상태인 비용상의 문제를 해결하기 위하여서는 운행비용함수의 작성을 통하여 운행상태를 평가하고, 좀 더 나은 정책적 방향을 제시하는 과정이 필요하다.
송선아(Sun-Ah Song),김백섭(Baek-Sop Kim),송성호(Seong-Ho Song) 한국정보과학회 2003 정보과학회논문지 : 소프트웨어 및 응용 Vol.30 No.9·10
홍채 인식을 위해서는 먼저 홍채 영역을 추출해야 하는데 이를 위해서는 홍채의 안쪽 경계인 동공 경계와 바깥쪽 경계인 홍채 경계를 검출해야 한다. 경계를 검출하는데는 Daugman이 제안한 원형 경계 검출기가 가장 일반적이고 효과적인 방법으로 알려져 있다. 이 방법은 전역적인 탐색에 의존하기 때문에 정확하지만 계산 시간이 많이 걸리는 단점이 있다. 계산 시간을 줄이기 위해 경험적 방법들이 사용되기도 하지만 정확성이 떨어지는 문제점이 있었다. 본 논문에서는 정확성을 떨어뜨리지 않으면서 계산 속도를 줄이는 홍채 영역 추출 알고리즘을 제안한다. 제안된 방법은 동공 경계와 홍채 경계가 가지는 문제에 대한 지식(problem knowledge)을 사용하여 제한조건을 부가하여 탐색한다. 경계 검출을 위한 탐색 영역은 동공을 포함하는 최대 원과 최소 원을 이용하여 제한하여 탐색 시간을 줄인다. 동공 경계의 경우 이진화된 동공 영상에서 최대 원과 최소 원을 구하고, 홍채 경계의 경우 영상의 분산을 이용하여 얻은 경계점으로부터 최대 원과 최소 원을 구한다. 제안된 방법을 Daugman방법, 히스토그램 분석법, 가중치를 이용한 허프변환 방법 등과 실험을 통해 비교하였다. 그 결과 제안된 방법은 Daugman방법과 동일한 정확도를 보이며, Daugman방법이나 가중치를 이용한 허프변환 방법보다 빠르다는것을 알 수 있었다. It is essential to identify both the pupil and iris boundaries for iris recognition. The circular edge detector proposed by Daugman is the most common and powerful method for the iris region extraction. The method is accurate but requires lots of computational time since it is based on the exhaustive search. Some heuristic methods have been proposed to reduce the computational time, but they are not as accurate as that of Daugman. In this paper, we propose a pupil and iris boundary finding algorithm which is faster than and as accurate as that of Daugman. The proposed algorithm searches the boundaries using the Daugman's circular edge detector, but reduces the search region using the problem domain knowledge. In order to find the pupil boundary, the search region is restricted in the maximum and minimum bounding circles in which the pupil resides. The bounding circles are obtained from the binarized pupil image. Two iris boundary points are obtained from the horizontal line passing through the center of the pupil region obtained above. These initial boundary points, together with the pupil point comprise two bounding circles. The iris boundary is searched in this bounding circles. Experiments show that the proposed algorithm is faster than that of Daugman and more accurate than the conventional heuristic methods.
폴리이미드 모재 위에 증착된 구리 박막의 성형성에 대한 연구
송선아(Sun-Ah Song),김재현(Jae-Hyun KIM),한승우(Seung-Woo Han),이상주(Sang-Joo Lee),이학주(Hak-Joo LEE) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Conductive thin films on flexible substrates are extensively utilized in flexible electronic devices such as paper-like displays, electronic textile, sensitive skins, etc. One of the key functions of the flexible devices is mechanical deformability. Namely, the thin films on flexible substrate should be able to conduct electrical current for a wide operation range of mechanical strain. The conductive films, usually metallic films can't sustain a large strain while the flexible substrate can do. In this study, copper thin film is deposited on polyimide substrate by DC magnetron sputter and the mechanical behavior of the copper film is investigated using a tensile test machine. During the tensile test, the electrical resistance is simultaneously measured and is correlated with the mechanical strain. The microstructures of the film before and after tensile test is studied using Scanning Electron Microscope (SEM) and reveal the failure modes of the copper film on polyimide. Based on the experimental results, the deformability of copper film on polyimide is discussed for the application of flexible electronics.
유연 모재 위에 증착된 CNT 전도성 필름 필름의 전기 전기-기계적 특성에 대한 연구
송선아(Sun-Ah Song),김재현(Jae-Hyun Kim),이학주(Hak-Joo Lee),송진원(Jin-Woo Song),장원석(Won-Seok Chang),한창수(Chang-soo Han) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In this study, electromechanical properties of carbon nanotube (CNT) thin film on flexible substrates were measured using a micro-tensile machine with functionality of simultaneous measurements of displacement, load and electrical resistance. The CNT thin film of about 100 ㎚ thick was deposited on flexible substrates, polyethylene terephthalate (PET) using spraying and ink-jetting techniques. To investigate the effect of process condition on the electromechanical properties of CNT thin film, sets of CNT samples were fabricated under various heat treatments and microwave process. The microstructures of the CNT thin film before and after tensile test were investigated using Scanning Electron Microscope (SEM), and the failure modes of the CNT thin films were identified to understand their electromechanical behaviors and interaction with the flexible substrates. Based on the experimental results, the use of CNT thin film as flexible electrodes and strain gages is discussed.
분산조건이 MWCNT 전도성 필름의 기계적-전기적 특성에 미치는 영향
송선아(Sun-Ah Song),황보윤,김덕종(Duck-jong Kim),김재현(Jae-Hyun Kim),이학주(Hak-Joo Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this study, flexible nano composite film of Multi-Walled Carbon Nano Tube (MWCNT) is deposited on plastic substrates using spraying technique. To make a solution for spraying process, MWCNT is dispersed using sodium dodecyl sulate (SDS). The electromechanical property and the extent of dispersion are affected by a weight ratio between SDS and MWCNT. The electromechanical behavior of MWCNT films on flexible substrates is measured using a micro-tensile machine with functionality of simultaneous measurements of displacement, load and electrical resistance. The microstructures of the MWCNT films before and after tensile test are studied using Scanning Electron Microscope (SEM) and their failure modes are discussed with respect to dispersion condition. Based on the experimental results, the relationship between the dispersion condition and the electromechanical properties is summarized in terms of design guidelines.
장원석(Won-Seok Chang),송선아(Sun-Ah Song),김재현(Jae-Hyun Kim),한창수(Chang-Soo Han) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
In this study, the strain sensing characteristics of SWCNTs networks were investigated to develop a film sensor for strain sensing. The SWCNTs film are formed on flexible substrates of poly (ethylene terephthalate) (PET) using spray process. In this manner we could control the transparency and obtain excellent uniformity of the networked SWCNT film. The carbon nanotube film is isotropic due to randomly oriented bundles of SWCNTs. Using experimental results it is shown that there is a nearly linear change in resistance across the film when it is subjected to tensile stress. The results presented in this study indicate the potential of such films for high sensitive transparent strain sensors on macro scale.
장원석(Won-Seok Chang),송선아(Sun-Ah Song),김재현(Jae-Hyun Kim),한창수(Chang-Soo Han) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.10
In this study, the strain sensing characteristics of single-wall carbon nanotubes(SWCNTs) networks were investigated to develop a film sensor for strain sensing. The SWCNTs film are formed on flexible substrates of poly(ethylene terephthalate) (PET) using spray process. In this manner we could control the transparency and obtain excellent uniformity of the networked SWCNT film. The carbon nanotube film is isotropic due to randomly oriented bundles of SWCNTs. Using experimental results it is shown that there is a nearly linear change in resistance across the film when it is subjected to tensile stress. The results presented in this study indicate the potential of such films for high sensitive transparent strain sensors on macro scale.
속도 의존적 점착 특성을 이용한 나노 스케일 구조물의 능동적 전사 제어
장봉균(Bongkyun Jang),김재현(Jae-Hyun Kim),송선아(Sun-Ah Song),이학주(Hak-Joo Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Transferring nano- and micro-scale objects is one of the promising techniques for fabricating the nanoand micro-scale devices. The key element of the transfer is the control of adhesion for picking and placing the objects. In the picking and placing processes, the adhesion should be actively-controlled for successful transfer of the objects. In this study, we develop an apparatus for transferring nano-thick objects from one substrate to the other. By incorporating the optical microscope, multi-axis alignment stage, a vertical stage with high capacity of acceleration and a load-cell, the transferring process of the objects can be activelycontrolled. The adhesion of the objects can be controlled by adjusting the unloading velocity of the vertical stage, and the corresponding adhesion force is measured during the transfer. The mechanism of contact and detach between the mold and the objects are observed in-situ using the optical microscope installed on the transfer apparatus.