• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.191-192
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• 2018

해안을 따라 인구밀도가 증가하고 임해지역공단 등 산업시설이 밀집하여 처리되지 않은 하 폐수가 증가하고 있다. 특히, 최근엔 필리핀 보라카이와 같이 관광 위락시설에 의한 하수가 대량으로 발생하고 있다. 또한, 세계적으로 거의 모든 국가의 주요 해안도시는 이러한 도시하수를 바다로 방류하고 있다. 현재로선 이러한 하 폐수의 처리는 바다의 자정능력(self-purification capacity) 한계를 고려한 하수의 해양으로의 방류가 최선의 방법으로 판단된다. 현재 국내에서는 지역에 따른 배출허용기준에 따라 하수의 처리수 방류가 규제되고 있지만, 확산영역에 대한 법적 기준치는 제시되지 않고 있으며, 인근에 위치한 권리자들과의 이해관계 해결에만 몰두하고 있는 실정이다. 또한 확산영향예측이 원역 해석모형(Far Field analysis model)에 의해 수행되기 때문에 근역(Near Field)에서의 영향을 간과하고 있다고 판단된다. 따라서 금회 연구에서는 기존 연구결과를 기준하여 특정해역에 대한 원역과 근역 해석에 따른 확산영향 예측을 수행하고 그 결과를 비교하여 앞으로의 해석방법을 제시하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10a
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• pp.205-207
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• 2001

이동 객체는 현실 세계의 차량과 같이 시간에 따라 움직이는 모든 객체를 말한다. 이동체 데이터베이스는 이동 객체가 연속적으로 위치 정보가 변하기 때문에 기존의 데이터베이스 기법과 차이가 있다. 이동 객체의 위치 변경은 빈번한 갱신 연산을 수행해야 하는 문제점이 있고, 이동체의 움직임을 모두 저장할 수 없으므로 이동 객체의 움직임을 이산적 표현 방법을 사용하여 이동 객체의 현재와 미래 위치를 계산해야 한다. 이동 객체의 빈번한 위치 변경은 색인 처리 비용이 증가를 초래한다. 이 논문에서는 빈번한 갱신으로 발생하는 색인의 과부하를 최소화하는 해쉬 기반의 공간 색인 구조를 사용한 이동 객체의 위치 변경 처리 기법을 제안한다. 또한 이동 객체의 이산적 표현을 위한 자료 구조를 제시하며, 이동 객체의 밀집화 문제를 해결하기 위하여 오버플로우 처리 방법을 기존의 해슁 오버플로우 처리 방법을 응용하여 3가지 방법으로 제안한다. 버퍼질의를 이용하여 이동 객체의 영역 질의 방법을 제안한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.66-66
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• 2010

알루미나는 높은 온도에서 열적으로 안정되고 경도가 높으며 내화학, 내마모 특성이 우수하며 또한 강도대비 비중이 낮아 무게를 줄일 수 있다는 장점을 가지고 있다. 이러한 특성으로 인하여 우주항공, 국방, 원자력등 극한의 온도를 견뎌야 하는 고도의 신뢰성이 요구되는 고온구 조물로서 응용이 되고 있다. 특히 알루미나를 휘스커 형태로 만들어 세라믹 복합체에 결합 할 경우 복합체의 기지 내에서 강화재의 역할을 함으로써 취성 파괴를 억제하고 열 전도율 저하등의 이점을 가져올 수 있다. 그리하여 본 연구에서는 알루미나 휘스커를 성장을 위하여 Al-triisoproxide계를 이용하여 화학기상증착법으로 가장 안정된 열적 특성을 가지고 온도의 변화에 따라 상 변화가 일어 나지 않는 알파 알루미나 상을 가지는 알루미나 휘스커를 성장시키기 위한 연구를 하였다. 또한 증착 온도, 압력, 입력기체비등 증착 조건을 변화시켜가면서 알파 알루미나 휘스커의 성장 거동을 살펴 보았다. 증착 조건 변화에 따라 알파 알루미나는 막이 증착되는 부분과 휘스커가 성장되는 부분이 있으며 휘스커의 밀집도와 길이방향, 직경방향 성장등 여러 가지 성장 특성을 달리하였다. 이러한 결과를 바탕으로 증착조건에 따른 알파 알루미나 휘스커 성장영역을 도식화하였다.

• Journal of KIISE:Software and Applications
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• v.26 no.10
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• pp.1193-1203
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• 1999

본 논문에서는 한글과 영문 문서 영상들에 대한 기울어짐 추정(skew estimation) 알고리즘을 제안한다. 제안 방법은 전체 문서 영상에서 텍스트 요소들이 밀집되어 있는 영역을 선별하고, 선별된 영역에 대해 허프 변환을 적용하는 선택적 주의집중(selective attention) 방식을 채택한다. 제안 방법의 기울기 추정 과정은 2단계로 구성되는데, coarse 단계에서는 전체 영상을 몇 개의 영역으로 나누고 동일한 영역에 속하는 데이타들간의 연결 각도를 계산하여 각 영역별 accumulator에 저장한다. accumulator에 저장된 빈도치를 기준으로 $\pm$45$^{\circ}$범위 내에서 최대 $\pm$1$^{\circ}$의 오차를 가진 각 영역별 기울기를 계산한 후, 이들 중 최대 빈도값을 갖는 영역을 선정하고 그 영역의 기울기 각도를 문서 영상의 대략적인 기울기 각도로 결정한다. Refine 단계에서는 coarse 단계에서 선정된 영역에 허프 변환을 적용하여 정확한 기울기를 계산하는데, coarse 단계에서 추정한 기울기의 $\pm$1$^{\circ}$범위 내에서 0.1$^{\circ}$간격으로 측정한다. 이와 같은 선택적 주의집중 방식을 통해 기울기 추정에 소요되는 시간 비용은 최소화하고, 추정의 정확도는 최대화 할 수 있다.제안 방법의 성능 평가를 위한 실험은 다양한 형태의 영문과 한글 문서 영상 2,016개에 적용되었다. 제안 방법의 평균 수행 시간은 Pentium 200MHz PC에서 0.19초이고 평균 오차는 $\pm$0.08$^{\circ}$이다. 또한 기존의 기울기 추정 방법과 제안 방법의 성능을 비교하여 제안 방법의 우수성을 입증하였다.Abstract In this paper we propose a skew estimation algorithm for English and Korean document images. The proposed method adopts a selective attention strategy, in which we choose a region of interest which contains a cluster of text components and then apply a Hough transform to this region. The skew estimation process consists of two steps. In the coarse step, we divide the entire image into several regions, and compute the skew angle of each region by accumulating the slopes of lines connecting any two components in the region. The skew angle is estimated within the range of $\pm$45 degree with a maximum error of $\pm$1 degree. Next we select a region which has the most frequent slope in the accumulators and determine the skew angle of the image roughly as the angle corresponding to the most frequent slope. In the refine step, a Hough transform is applied for the selected region within the range of $\pm$1 degree along the angle computed from the coarse step, with an angular resolution of 0.1 degree. Based on this selective attention strategy, we can minimize the time cost and maximize the accuracy of the skew estimation.We have measured the performance of the proposed method by an experiment with 2,016 images of various English and Korean documents. The average run time is 0.19 second on a Pentium 200MHz PC, and the average error is $\pm$0.08 degree. We also have proven the superiority of our algorithm by comparing the performance with that of other well-known methods in the literature.

• Journal of Korea Multimedia Society
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• v.7 no.4
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• pp.550-558
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• 2004

Previous researches on scalability problem of distributed virtual environment (DVE) have been mainly focused on spatial partitioning of area of interest (AOI). Congestion phenomena by avatar groups in AOI have been neglected relatively However, AOI congestion is highly related to scalability of DVE because it exhausts system resources such as network bandwidth and rendering time, and could be a bar to perform collaboration among participants. In this paper, this will be defined as the problem that must be solved for the realization of the scalable DVE, and a model will be proposed to measure and control congestion situation in AOI. The purposes of the proposed model are to prevent high density of participants in AOI, and to protect stable collaboration in DVE. For evaluation of the performance it is compared with a previous method by defining the resource cost model which is dynamically activated to AOI congestion.

• Journal of IKEEE
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• v.12 no.2
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• pp.110-117
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• 2008

This paper presents a new Insulated Gate Bipolar Transistor(IGBT) based on Non Punch Through(NPT) IGBT structure for power switching device. The proposed structure has adding N+ beside the P-base region of the conventional IGBT structure. The added n+ diffusion of the proposed device ensure device has faster turn-off time and lower forward conduction loss than the conventional IGBT structure. But, added n+ region can reduce th breakdown voltage and latching current density of the proposed device due to its high doping concentration. This problems can be overcome by using diverter on the right side of the device. In the simulation results, turn-off time of the proposed device is 0.3us and the on-state voltage drop is 3V. The results show that the proposed device has superior characteristic than conventional structure.

• Journal of the Korea Society of Computer and Information
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• v.26 no.11
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• pp.149-156
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• 2021

Among various implementation techniques of recommender systems, collaborative filtering selects nearest neighbors with high similarity based on past rating history, recommends products preferred by them, and has been successfully utilized by many commercial sites. Accurate estimation of similarity is an important factor that determines performance of the system. Various similarity measures have been developed, which are mostly based on integrating traditional similarity measures and several indices already developed. This study suggests a similarity measure of a novel approach. It separates the common rating area between two users by the magnitude of ratings, estimates similarity for each subarea, and integrates them with weights. This enables identifying similar subareas and reflecting it onto a final similarity value. Performance evaluation using two open datasets is conducted, resulting in that the proposed outperforms the previous one in terms of prediction accuracy, rank accuracy, and mean average precision especially with the dense dataset. The proposed similarity measure is expected to be utilized in various commercial systems for recommending products more suited to user preference.

• Korean Journal of Plant Resources
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• v.32 no.5
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• pp.519-542
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• 2019

Twenty soybean cultivars developed recently were assessed using 27 insertion and deletion (InDel) markers derived from dense variation blocks (dVBs) of soybean genome. The objective of this study is to identify the distinctness and genetic relationships among a total of 169 soybean accessions including new cultivars. The genetic homology between 149 accessions in the soybean barcode system and 20 new cultivars was 61.3% on average with the range from 25.9% to 96.3%, demonstrating the versatile application of these markers for cultivars identification. The phylogenic analysis revealed four subgroups related to their usage. The 80% of cultivars for vegetable and early maturity and the 65.9% of cultivars for bean sprouts were clustered in subgroup I-2 and II-2, respectively, indicating of the limited gene pools of their crossing parents in breeding. On the other hands, the cultivars for soy sauce and tofu with considerable gene flow by genome reshuffling were distributed evenly to several subgroups, I-1 (44.4%), I-2 (26.4%) and II-2 (23.6%). We believe that the 27 InDel markers specific to dVBs can be used not only for cultivar identification and genetic diversity, but also in breeding purposes such as introduction of genetic resources and selection of breeding lines with target traits.

• Journal of KIISE:Databases
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• v.27 no.1
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• pp.53-63
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• 2000

The mobile computing service market is increasing rapidly due to the development of low-cost wireless network technology and the high-performance mobile computing devices. In recent years, several methods have been proposed to effectively deal with restrictions of the mobile computing environment such as limited bandwidth, frequent disconnection and short-lived batteries. Amongst those methods, much study is being done on the caching method - among the data transmitted from a mobile support station, it selects those that are likely to be accessed in the near future and stores them in the local cache of a mobile host. Existing cache replacement methods have some limitations in efficiency because they do not take into consideration the characteristics of user mobility and spatial attributes of geographical data. In this paper, we show that the value and the semantic of the data, which are stored in the cache of a mobile host, changes according to the movement of the mobile host. We argue it is because data that are geographically near are better suited to provide an answer to a users query in the mobile environment. Also, we define spatial location of geographical data has effect on, using the spatial attributes of data. Finally, we propose two new cache replacement methods that efficiently support user mobility and spatial attributes of data. One is based on the location of data and the other on the meaningful region of data. From the comparative analysis of the previous methods and that they improve the cache hit ratio. Also we show that performance varies according to data density using this, we argue different cache replacement methods are required for regions with varying density of data.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.1033-1041
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• 2014

Rapid urbanization of Korea was an unprecedented example in the world and urban population increased significantly. As a result, unbalanced distribution of population is serious problem in Korea because approximately 50% of the population is concentrated in the capital area that is 10% of nation's territory, thereby occurring various urban problems including UHI. Hence, Sejong Special Autonomous City was inaugurated officially on 2 July 2012 in order to decentralize population of capital area and induce more balanced regional development. The Sejong City has been changed drastically over a period of years as developed practically since the late 2000's and is expected to have new problems of urbanization. The land cover change due to urbanization is the main cause of UHI that urban area is significantly warmer than its surrounding areas and UHI is not only affecting urban climate change but also natural environment. So the purpose of this research is to analyze level of urbanization and UHI effect and to provide the correlation analysis between Land Surface Temperature and spectral indices. To achieve this, satellite imagery from LANDSAT were used. NDVI, NDBI, and UI were calculated using red, near-infrared, mid-infrared ($0.63{\mu}m-1.75{\mu}m$) images and LST was retrieved utilizing thermal infrared ($10.4{\mu}m-12.5{\mu}m$) image. Based on each index and LST, Changes of NDVI, UI and UHI through TVI were analyzed in Sejong City. UHI effect increased around newly constructed multi-functional administrative city, the correlation between LST and NDVI was negative and UI was strong positive.