• 대한원격탐사학회지
• /
• 제25권6호
• /
• pp.517-529
• /
• 2009

Many satellite image fusion techniques have been developed in order to produce a high resolution multispectral (MS) image by combining a high resolution panchromatic (PAN) image and a low resolution MS image. Heretofore, most high resolution image fusion techniques have used IKONOS and QuickBird images. Recently, GeoEye-1, offering the highest resolution of any commercial imaging system, was launched. In this study, we have experimented with GeoEye-1 images in order to evaluate which fusion algorithms are suitable for these images. This paper presents compares and evaluates the efficiency of five image fusion techniques, the $\grave{a}$ trous algorithm based additive wavelet transformation (AWT) fusion techniques, the Principal Component analysis (PCA) fusion technique, Gram-Schmidt (GS) spectral sharpening, Pansharp, and the Smoothing Filter based Intensity Modulation (SFIM) fusion technique, for the fusion of a GeoEye-1 image. The results of the experiment show that the AWT fusion techniques maintain more spatial detail of the PAN image and spectral information of the MS image than other image fusion techniques. Also, the Pansharp technique maintains information of the original PAN and MS images as well as the AWT fusion technique.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.158-167
• /
• 2019

This research comparatively studies three kinds of flux regulation methods, namely, stored capacitor discharge pulse (SCDP), constant current source pulse (CCSP), and quantitative flux regulation pulse (QFRP), which are used for hybrid permanent magnet (PM) axial field flux-switching memory machines (HPM-AFFSMMs). Through an analysis of the operation principle and the series hybrid PM flux regulation mechanism of the objective machine, the circuit topologies and flux regulation process of these flux regulation methods are addressed in detail. On the basis of a simulation, the flux regulation characteristics of the researched machine during the magnetization and demagnetization processes are comparatively evaluated. Then, machine performance, including back EMF, direct and quadrature axis inductances, and magnetization and demagnetization characteristics, is quantitatively investigated. Results show that the QFRP enables the HPM-AFFSMM to achieve a less harmonic component of back EMF by approximately 7.28% and 7.97% at the magnetization and demagnetization states, respectively, and a more complete magnetization process than the SCDP and CCSP.

• 대한금속재료학회지
• /
• 제48권3호
• /
• pp.235-240
• /
• 2010

The interfacial adhesion properties of enamel-coated, alloyed steels were in detail characterized by spectroscopic techniques. The surfaces of alloyed steels existed as oxidized states of $Fe_3O_4$. Therefore, the oxidized surfaces of the steels significantly interacted with the coated enamels for the adhesion. Ti-alloyed steel showed many micro-boundaries during thermal treatment and these micro-boundaries might cause the decline of the interfacial adhesion between enamel and steel. The depth profiles of enamel-coated, alloyed steels were investigated by GDS (glow discharge spectroscopy) and Ti component was found to be related to the interfacial adhesion between enamel and steel.

• 한국IT서비스학회지
• /
• 제21권1호
• /
• pp.61-79
• /
• 2022

In the rapidly changing era of knowledge revolution, user-centered IT services are emerging as a very important component of modern business. However, in order to lead IT services into success, traditional capabilities and competences are not good enough. Development of IT services involve service planners and designers as well as traditional systems developers. This detailed segmentation of job and corresponding competences among involved in IT service development brings in new type of conflicts and contradictions that may require special attention for IT services to be properly development and implemented. This study aims to explore and define competences and roles of newly emerging job groups in IT services: planners, designers, and developers. In order to identify underlying competences of these emergeing groups, two stage interviews were conducted. At the first stage, general competence framework is developed across these groups with different skills for similar competence catogories. Using the categories developed at the first stage, members of each groups were asked to rate and assess the competences of other groups. Comparisons of these reciprocal assessment revealed the conceptual differences and biases across these groups. Detail differences are discussed and implications are discussed.

• Wind and Structures
• /
• 제34권1호
• /
• pp.91-100
• /
• 2022

Numerical simulations are conducted to investigate the uniform flow (UF) and sinusoidal streamwise flow (SSF) over an oscillating 5:1 rectangular cylinder with harmonic heaving motion at initial angles of attack of α = 0° and 3° using two-dimensional, unsteady Reynolds-averaged Navier-Stokes (URANS) equations. First, the aerodynamic parameters of a stationary 5:1 rectangular cylinder in UF are compared with the previous experimental and numerical data to validate the capability of the computationally efficient two-dimensional URANS simulations. Then, the unsteady flow field and aerodynamic forces of the oscillating 5:1 rectangular cylinder in SSF are analysed and compared with those in UF to explore the effect of SSF on the rectangular cylinder. Results show that the alternative vortex shedding is disturbed by SSF both at α = 0° and 3°, resulting in a considerable decrease in the vortex-induced force, whereas the unsteady lift component induced by cylinder motion remains almost unchanged in the SSF comparing with that in UF. Notably, the strong buffeting forces are observed at α = 3° and the energy associated with unsteady lift is primarily because of the oscillations of SSF. In addition, the components of unsteady lift induced by the coupling effects of SSF and cylinder motion are discussed in detail.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2022년도 학술발표회
• /
• pp.475-475
• /
• 2022

The aim of this study is to identify the significant pollutant sources from the tributaries that are affecting the water quality of the study site, the Geum River and provide a solution to enhance the water quality. Multivariate statistical analysis modles such as cluster analysis, Principal component analysis (PCA) and positive matrix factorization (PMF) were applied to identify and prioritize the major pollutant sources of the two major tributaries, Gab-cheon and Miho-cheon, of the Geum River. PCA identifies three major pollutant sources for Gab-cheon and Miho-cheon, respectively. For Gab-cheon, wastewater treatment plant (WWTP), urban, and agricultural pollutions are identified as major pollutant sources. For Miho-cheon, agricultural, urban, and forest land are identified as major pollutant sources. On the contrary, PMF identifies three pollutant sources in Gab-cheon, same as PCA result and two pollutant sources in Miho-cheon. Water quality control scenarios are formulated and improvement of water quality in the river locations are simulated and analyzed with the Environmental Fluid Dynamic Code (EFDC) model. Scenario results were evaluated using a water quality index developed by Canadian Council of Ministers of the Environment. PCA and PMF appears to be effective to identify water pollution sources for the Geum river and also its tributaries in detail and thus can be used for the development of water quality improvement alternative of the above water bodies.

• Journal of Information Technology Applications and Management
• /
• 제30권6호
• /
• pp.17-29
• /
• 2023

In this paper, we aim to propose cyber security considerations and countermeasures for infrastructure and services in the UAM(Urban Air Mobility) Air Traffic Management field, which is one of the key elements of the UAM market that has not yet bloomed. Air traffic management is an important factor for safe navigation and social acceptance of UAM. In order to realize air traffic management, infrastructure and services based on solid network connectivity must be established. And for industries where connectivity is the core component, it can become an infiltration route for cyber threats. Therefore, cyber security is essential for the infrastructure and services. In detail, we will look into the definition of the existing air traffic management field and the cyber threats. In addition, we intend to identify cyber security threat scenarios that may occur in the newly designed UAM air traffic management infrastructure. Moreover, in order to study the cyber security countermeasures of the UAM air traffic management infrastructure, there will be analysis of the UAM operation concept. As a result, countermeasures applicable to the infrastructure and service fields will be suggested by referring to the cyber security frameworks.

• 한국수자원학회논문집
• /
• 제55권8호
• /
• pp.577-588
• /
• 2022

본 연구는 금강의 조류 성장에 대한 제한영양소와 수질에 영향을 미치는 주요 지류를 파악하고 수질개선을 위한 관리대안을 제시하는 것을 목적으로 수행되었다. 금강 대청댐 하류에 위치한 5개 수질측정소에서 약 8년간(2013~202) 환경부의 물환경정보시스템(water.nier.go.kr)과 수자원관리정보시스템(wamis.go.kr)에서 14개의 수질항목의 자료를 분석하였다. 금강의 4대강 수중보 수문 개방 시 TP(총인)와 수온은 하천 하류의 조류 성장에 큰 영향을 미친다. 본 연구에는 수질변수간의 상관관계를 규명하고 금강의 조류 성장에 영향을 미치는 중요인자를 파악하고자 하였다. 최하류에 위치한 백제보수질측정소(WQ5)에서 TP와 수온은 Chl-a와 특별히 높은 상관관계를 보여 조류 번식에 상당한 영향을 미친다는 것을 나타냈다. 또한 본 연구에서는 금강의 양대 지류인 갑천과 미호천의 주요 오염원을 식별하고 우선순위를 지정하기 위해 주성분분석(Principal Component Analysis, PCA) 방법을 이 적용하였다. PCA방법을 이용하여 갑천과 미호천의 수질에 영얗ㅇ을 미치는 3대 오염원을 각각 파악하였다. 갑천의 경우 폐수처리장과 도시·농업 오염이 주요 오염원으로, 미호천의 경우 농지, 도시, 산림이 주요 오염원으로 각각 확인되었다. PCA는 금강 및 그 지류의 수질오염원을 구체적으로 파악하는 데 효과적인 것으로 판단되어 수질관리 전략의 효율을 제고하는 데에, 활용될 수 있을 것으로 보인다.

• 전자공학회논문지
• /
• 제51권1호
• /
• pp.152-157
• /
• 2014

디지털 카메라에서는 일반적으로 높은 공간주파수에 의해 발생하는 주파수 간섭을 제거하기 위해 광저대역 투과 필터(optical lowpass filter)를 사용한다. 그러나 영상을 획득할 때 광저대역 투과 필터의 사용으로 고주파 성분이 제거되어 상세 성분의 손실을 가져오게 된다. 이와 반대로, 광저대역 투과 필터를 제거한 후에 영상을 획득할 경우, 높은 공간주파수를 가지는 영역에서 moir$\acute{e}$가 발생하게 된다. 따라서, 본 논문에서는 카메라의 광저대역 투과 필터를 제거 후 영상의 상세 성분을 보존하고 moire를 제거하는 방법을 제안한다. 먼저 ISO12233 해상도 차트를 사용하여 카메라의 공간해상도(spatial frequency response)를 분석하고, 카메라의 최대 분해능에 해당하는 해상도 차트의 패턴을 모델링하여 moir$\acute{e}$가 발생하는 영역을 검출한다. 검출된 moir$\acute{e}$ 영역을 주파수 도메인에서 분석하고 DC 성분과 최대 주파수 사이의 각 주파수별 최대 값에서 발생하는 변곡점을 검출하고 변곡점에 해당하는 값을 제거하여 moir$\acute{e}$ 성분을 제거한다. 실험 결과 제안한 방법은 상세 성분의 손실을 줄이고 moir$\acute{e}$ 제거에서 우수한 성능을 보였다.

• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
• /
• 제14권6호
• /
• pp.567-581
• /
• 2008

웹의 크기가 폭발적으로 증가함에 따라 인터넷에서 정보를 얻는 수단으로서 검색 엔진의 중요성이 부각되고 있다. 검색 엔진은 사용자에게 최신의 정보를 검색 결과로서 제공하기 위해 웹 페이지를 주기적으로 수집하고 이를 데이타베이스에 저장한다. 웹 크롤러는 이러한 목적으로 웹 페이지를 수집하는 프로그램이다. 대부분의 검색 엔진은 제한된 시간 내에 많은 수의 웹 페이지를 수집하기 위해 다수의 머신을 사용하는 병렬 웹 크롤러를 이용한다. 그러나, 병렬 웹 크롤러의 아키텍처와 세부 구현 방법이 잘 알려져 있지 않기 때문에 실제로 병렬 웹 크롤러를 구현하는 데에 어려움이 많다. 본 논문에서는 병렬 웹 크롤러(parallel web crawler)의 아키텍처와 세부 구현 방법을 제시한다. 병렬 웹 크롤러는 다수의 머신에서 웹 페이지를 병렬적으로 수집하기 위해 조정자(coordinator) 대리자(agent) 구조의 2-티어(tier) 모델을 사용한다. 조정자/대리자 모델은 각 머신에서 웹 페이지를 수집하기 위한 다수의 대리자들과 이 대리자들을 관리하기 위한 하나의 조정자로 구성된다. 병렬 웹 크롤러는 웹 페이지를 수집하기 위한 크롤링(crawling) 모듈, 수집한 웹 페이지를 데이타베이스 로딩 포맷으로 변환하기 위한 컨버팅(converting) 모듈, 수집된 웹 페이지의 중요도를 계산하기 위한 랭킹(ranking) 모듈로 구성된다. 본 논문에서는 병렬 웹 크롤러의 각 모듈들을 설명하고, 세부 구현 방법을 설명한다. 마지막으로, 실험을 통해 병렬 웹 크롤러의 성능을 평가하였다. 실험 결과, 제안된 병렬, 웹 크롤러가 수집해야할 웹 페이지 개수와 머신 개수에 따라 확장 가능함을 보였다.