• Progress in Superconductivity
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• 제10권1호
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• pp.60-67
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• 2008

We present domestic efforts for superconducting fault current limiter (SFCL) application in the Korea Electric Power Corporation (KEPCO) grid and pending points at issue. KEPCO's decision to upgrade the 154 kV/22.9 kV main transformer from 60 MVA to 100 MVA cast a problem of high fault current in the 22.9 kV distribution lines. The grid planners supported adopting an SFCL to control the fault current. This environment friendly to SFCL application must be highly dependent upon the successful development of SFCL having specifications that domestic utility required. The required conditions are (1) small size of not greater than twice of 22.9 kV gas insulated switch-gear (GIS), (2) sustainability of current limitation without the line breaking by circuit breakers (CB) for maximum 1.5 seconds. Also, optionally, recommended is (3) the reclosing capability. Conventional resistive SFCLs do not meet (1) $\sim$ (3) all together. A hybrid SFCL is an excellent solution to meet the conditions. The hybrid SFCL consists of HTS SFCL components for fault detection and line commutation, a fast switch (FS) to break the primary path, and a limiter. This characteristic structure not only enables excellent current limiting performances and the reclosing capability, but also allows drastic reduction of HTS volume and small size of the cryostat, resulting in economic feasibility and compactness of the equipment. External current limiter also enables long term limitation since it is far less sensitive to heat generation than HTS. Semi-active operation is another advantage of the hybrid structure. We will discuss more pending points at issues such as maintenance-free long term operation, small size to accommodate the in-house substation, passive and active control, back-up plans, diagnosis, and so on.

• 한국물환경학회지
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• 제28권6호
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• pp.843-850
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• 2012

Due to the fast response to algae bloom issue in drinking water treatment plant, very fast determination methodology for algal toxin is required. In this study, column switching technique based online preconcentration method was combined with high resolution full scan mass spectrometer to save sample preparation time and to obtain fast and accurate result. After parameter optimization of online preconcentration, 1mL filtered sample was directly injected to trap column with switching valve system. Next, target toxins are eluted by 98% acetonitrile and analysed with 150 - 1,100 amu scan range at 50,000 resolving power. Method detection limit (MDL) for microcystin-LR, the most toxic isomer, was 0.1 ng/mL and others such as microcystin-YR, microcystin-RR and nodularin were 0.08, 0.03 and 0.04 ng/mL, respectively. This is the best improved sensitivities with 1mL volume in the literature. Furthermore, due to the use of ultra pressure HPLC (UPLC), the whole method run was completed in 4 min. Real sample applications for 173 sample including 55 surface water and 118 treatment plant samples for raw and treated water could be done within 16 hours. In our calculation, this methodology is roughly 80% faster than the previous manual solid-phase extraction with LC-MS/MS method.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.183-183
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• 2012

In the era of 45 nm or beyond technology, conventional etch mask using photoresist showed its limitation of etch mask pattern collapse as well as pattern erosion, thus hard mask in etching became necessary for precise control of etch pattern geometry. Currently available hard mask materials are amorphous carbon and polymetric materials spin-on containing carbon or silicon. Amorphous carbon layer (ACL) deposited by PECVD for etch hard mask has appeared in manufacturing, but spin-on carbon (SOC) was also suggested to alleviate concerns of particle, throughput, and cost of ownership (COO) [1]. SOC provides some benefits of reduced process steps, but it also faced with wiggling on a sidewall profile. Diamond like carbon (DLC) was also evaluated for substituting ACL, but etching selectivity of ACL was better than DLC although DLC has superior optical property [2]. Developing a novel material for pattern hard mask is very important in material research, but it is also worthwhile eliminating a potential issue to continuously develop currently existing technology. In this paper, we investigated in-situ dry-cleaning (ISD) monitoring of ACL coated process chamber. End time detection of chamber cleaning not only provides a confidence that the process chamber is being cleaned, but also contributes to minimize wait time waste (WOW). Employing Challenger 300ST, a 300mm ACL PECVD manufactured by TES, a series of experimental chamber cleaning runs was performed after several deposition processes in the deposited film thickness of $2000{\AA}$ and $5000{\AA}$. Ar Actinometry and principle component analysis (PCA) were applied to derive integrated and intuitive trace signal, and the result showed that previously operated cleaning run time can be reduced by more than 20% by employing real-time monitoring in ISD process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권12호
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• pp.6214-6242
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• 2019

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme.

• Korean Journal of Geomatics
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• 제2권2호
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• pp.123-130
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• 2002

LiDAR (Light Detection And Ranging) system has a profound impact on geoinformatics. The laser mapping system is now recognized as being a viable system to produce the digital surface model rapidly and efficiently. Indeed the number of its applications and users has grown at a surprising rate in recent years. Interest is now focused on the reconstruction of buildings in urban areas from LiDAR data. Although with present technology objects can be extracted and reconstructed automatically using LiDAR data, the quality issue of the results is still major concern in terms of geometric accuracy. It would be enormously beneficial to the geoinformatics industry if geometrically accurate modeling of topographic surface including man-made objects could be produced automatically. The objectives of this study are to reconstruct buildings using airborne LiDAR data and to evaluate accuracy of the result. In these regards, firstly systematic errors involved with ALS (Airborne Laser Scanning) system are introduced. Secondly, the overall LiDAR data quality was estimated based on the ground check points, then classifying the laser points was performed. In this study, buildings were reconstructed from the classified as building laser point clouds. The most likely planar surfaces were estimated by the least-square method using the laser points classified as being planes. Intersecting lines of the planes were then computed and these were defined as the building boundaries. Finally, quality of the reconstructed building was evaluated.

• 천문학회보
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• 제36권2호
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• pp.61.2-61.2
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• 2011

Low-ionization nuclear emission-line regions (LINERs) have been generally regarded to be powered by active galactic nuclei (AGNs), yet still a number of alternative explanations on the origin of LINER emission are suggested; for example, planetary nebulae nuclei of massive stars, supernovae shocks from death of massive stars, and old stellar populations. Interestingly, a majority of recent star formation early-type galaxies (ETGs) in local universe presents such LINER emission lines. Given that situation, revealing the true nature of LINERs is a crucial step to constrain the evolution path to quiescent ETGs. To resolve the issue, we use Keck/LRIS to obtain spatially resolved spectra on a carefully selected ETG. The ETG SDSS J091628.05+420818.7 at redshift z ~ 0.024 shows modest LINER emission line features without any detection of 21 cm radio continuum nor X-ray emission. We perform a stellar continuum subtraction and measure emission line strengths and their uncertainties for each spectrum from five apertures along the slit with size of 1 arcsecond (~0.5 kpc). We find that extended spatial distributions of four emission lines $H{\alpha}$, $H{\beta}$, [OIII]${\lambda}5007$, and [NII]${\lambda}6583$, and they can be explained by central emission blurring effect. We conclude that the emissions seem to be centrally concentrated, indicating the AGN-nature of LINERs.

• 한국전기전자재료학회논문지
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• 제24권2호
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• pp.166-171
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• 2011

We use the electrical energy and it is essential energy in modern life, but we lay cable underground due to the issue for environment and safety. Safety for worker is still insufficient for the development of safety equipment and related research has been focused on the cable lifetime diagnosis at underground cable work. I have to develop live line detector around the magnetic field were investigated at underground cable. In this paper, we were investigated by variation of coil turns and load due to detection of magnetic field at lines around. And detected value of developing products compared with measured value of milli-gauss meter. As a result, the value of the number of coil turns was found to be proportional to the measured value. But turn-numbers increase showed that the weak noise. I could be confirmed that sensor showed the optimum value from 4,000 to 5,0000.

• 디지털콘텐츠학회 논문지
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• 제11권1호
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• pp.79-89
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• 2010

날로 지능화되고 고도화되어가는 DDoS 공격과 같이 증가하는 사이버 위협으로부터 자산을 보호하기 위해서 정부와 기업들은 서둘러 DDoS 대응 시스템을 구축하고 있다. 그러나 아직까지도 정보보호시스템은 지난 2009년 7월7일에 발생한 7.7 DDoS 공격과 같은 사회적 사건의 발생이나, 직접적인 피해의 사례가 발생하였을 때에만 단기적으로 이슈가 될 뿐, 이를 위한 지속적인 투자에는 여전히 소극적이라는 것이 일반적인 인식이다. 이는 정보보호 시스템의 특성상 사건이 발생하기 전에는 그 효과를 인식하기 어렵고, 사건이 발생한 경우에는 침해 또는 방어라는 결과에 대한 이분법적인 방식의 성패 판단만 있을 뿐, 이것의 효과와 효율에 대한 상세하고 객관적인 측정의 기준이 없기 때문이다. 비록 최근에는 정보보호관리체계에 대한 평가나 인증 작업이 진행 중이나, 이는 정보보호관리시스템에 대한 일반적인 지침이나 기준만을 제시하고 있어, 그 결과로는 조직의 정보보호관리체계 개선이나 향상이 쉽지 않다는 문제가 있다. 따라서 본 논문에서는 DDoS 대응 체계에 대한 상세하고 객관적인 측정이 가능하도록, 대응 전략 및 프로세스별로 주요 지표들을 개발하기 위한 프레임워크를 제시한다.

• 전자공학회논문지
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• 제50권5호
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• pp.144-149
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• 2013

로봇 기술의 빠른 발전과 더불어 다양한 서비스를 탑재한 로봇 제품의 출시로 시장이 활성화되고 있다. 서비스 로봇은 사람과 로봇간 상호작용에 의한 서비스 제공이 주목적으로 이를 위해 HRI 대표 기술인 얼굴 인식 기술을 많이 활용하고 있다. 하지만 얼굴 인식 엔진이 탑재된 로봇의 성능이 소비자가 만족할만한 수준에 미치지 못하여 로봇 제품에 대한 신뢰도마저 저하되고 있다. 대부분 로봇의 얼굴 인식 성능시험은 제품 관점에서 평가가 아닌 인식 엔진 관점에서 평가로 로봇의 직접적인 성능을 반영하지 못한다. 이에 본 논문에서는 로봇 제품 관점에서 얼굴 인식 성능평가를 위해 실물 영상을 대신하여 LED 모니터의 이용 가능성을 검증하고자 한다. 이를 위해 실물 영상과 LED 모니터 영상의 인식룰 편차를 비교하고 타당성을 제시한다.

• Journal of electromagnetic engineering and science
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• 제11권1호
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• pp.42-50
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• 2011

One of the important applications of THz time-domain spectroscopy (TDS) is the detection of explosive materials through identification of vibrational fingerprint spectra. Most recent THz spectroscopic measurements have been made using pellet samples, where disorder effects contribute to line broadening, which results in the merging of individual resonances into relatively broad absorption features. To address this issue, we used the technique of parallel plate waveguide (PPWG) THz-TDS to achieve sensitive characterization of three explosive materials: TNT, RDX, and HMX. The measurement method for PPWG THz-TDS used well-established ultrafast optoelectronic techniques to generate and detect sub-picosecond THz pulses. All materials were characterized as powder layers in 112 ${\mu}m$ gaps in metal PPWG. To illustrate the PPWG THz-TDS method, we described our measurement by comparing the vibrational spectra of the materials, TNT, RDX, and HMX, applied as thin powder layers to a PPWG, or in conventional sample cell form, where all materials were placed in Teflon sample cells. The thin layer mass was estimated to be about 700 ${\mu}g$, whereas the mass in the sample cell was ~100 mg. In a laboratory environment, the absorption coefficient of an explosive material is essentially based on the mass of the material, which is given as: ${\alpha}({\omega})=[ln(I_R({\omega})/I_S({\omega}))]m$. In this paper, we show spectra of 3 different explosives from 0.2 to 2.4 THz measured using the PPWG THz-TDS.