• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.67.2-67.2
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• 2011

Schwarzschild-Chang 망원경은 두 개의 반사경을 사용한 비축 망원경이다. 이 망원경에 사용된 비축 광학 이론을 이용하면 선형 비점수차를 완전히 제거할 수 있으며 3차 이상의 고차수차들도 동축 광학계와 동일한 정도로 최소화 시킬 수 있다. 이 망원경 디자인을 응용하면 단일 광학계 망원경을 제작할 수 있을뿐만 아니라 2개의 망원경 시스템을 조합할 경우 색수차나 중앙차폐 없이 대형 망원경의 focal reducer 또는 분광기의 내부 광학 장치로도 사용할 수 있다. 본 연구팀은 현재 구경 50 mm, 유효초점거리 100 mm, 시야각 $8{\times}8^{\circ}$ 인 Schwarzschild-Chang 망원경 시험 모델을 완성했다. 본 발표에서는 적외선 관측을 직접 할 수 있는 Schwarzschild-Chang 망원경의 개발 진행과정에 대하여 설명한다.

• Information and Communications Magazine
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• v.32 no.2
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• pp.34-40
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• 2015

본고에서는 실감 영상회의와 몰입형 텔레프레즌스의 수준을 넘어 물리적으로 떨어져 있는 원격 다지점(Multi-point)의 공간을 초실감적으로 가상 연결할 수 있는 스마트월(Smart-Wall) 기술 개념에 대해 살펴본다. 여기서 초실감이란 UHD-4K/8K급 또는3차원 이상의 초실감 영상기술과 사람의 모든 발성대역을 재현할 수 있는 슈퍼와이드밴드 기반 초실감 음성처리 및 동급 수준의 미디어 통신 기술을 적용한 사용자의 서비스 인지품질 수준을 의미한다. 이러한 초실감 수준의 현장감과 몰입감을 멀리 떨어진 1:1 또는 다지점 간 사용자들에게 안정적인 고품질로 제공할 수 있는 스마트월 핵심기술의 확보는 초실감 스마트워크 뿐 아니라 동급의 원격교육, 원격의료 서비스와 제품에 시급히 요구되고 있다. 원격 다지점 공간을 초실감으로 가상연결 하는 스마트월 기술은 사용자가 마치 현장에 있는 것처럼 실감성을 제공할 수 있는 핵심기술로써, 실감 ICT 올림픽에 접목이 되면 현장에 참석한 것 이상의 실감있는 대면 대화, 인터뷰 및 협업작업이 가능한 서비스를 제공할 수 있어 실감 ICT 올림픽에서 가장 인기있는 세계 최초의 기가미디어급 미래서비스가 될 것으로 예상한다.

• Journal of the Korean Data and Information Science Society
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• v.26 no.3
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• pp.639-652
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• 2015

In today's manufacturing environment, the process data can be easily measured and transferred to a computer for analysis in a real-time mode. As a result, it is possible to monitor several correlated quality variables simultaneously. Various multivariate statistical process control (MSPC) procedures have been presented to detect an out-of-control event. Although the classical MSPC procedures give the out-of-control signal, it is difficult to determine which variable has caused the signal. In order to solve this problem, data mining and machine learning techniques can be considered. In this paper, we applied the technique of decision tree learning to the MSPC, and we did simulation for MSPC procedures to monitor the bivariate normal process means. The results of simulation show that the overall performance of the MSPC procedure using decision tree learning technique is similar for several values of correlation coefficient, and the accurate classification rates for out-of-control are different depending on the values of correlation coefficient and the shift magnitude. The introduced procedure has the advantage that it provides the information about assignable causes, which can be required by practitioners.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.5
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• pp.37-44
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• 2011

This paper proposes a confusion-line separating algorithm in a CIE Lab color space using color segmentation for protanopia and deuteranopia. Images are segmented into regions by grouping adjacent pixels with similar color information using the hue components of the images. To this end, the region growing method and the seed points used in this method are the pixels that correspond to peak points in hue histograms that went through a low pass filter. In order to establish a color vision deficiency (CVD) confusion line map, we established 512 virtual boxes in an RGB 3-D space so that boxes existing on the same confusion line can be easily identified. After that, we checked if segmented regions existed on the same confusion line and then performed color adjustment in an CIE Lab color space so that all adjacent regions exist on different confusion lines in order to provide the best color identification effect to people with CVDs.

• Communications of Mathematical Education
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• v.27 no.4
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• pp.487-498
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• 2013

Sang-Seol Lee(1870-1917) wrote a manuscript BaekSeungHoCho(百勝胡艸) in the late 19th century. BaekSeungHoCho was transcribed in classical Chinese from the 1879 Japanese book Physics(物理學) by Teizo Ihimori (1851-1916). Sang-Seol Lee, a famous independence activist, is also called Father of the Modern Mathematics Education of Korea, because of his early contribution to the modern mathematics education in the 19th century. In this paper, we introduce contents of his manuscript BaekSeungHoCho for the first time and discuss the significance of this book. Also, we show his contribution on the introduction to modern physics in the late 19th century Korea.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.281-281
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• 2012

연꽃잎 효과(Lotus effect)라 불리는 자가 세정 효과(self cleaning effect)는 연꽃이 항상 깨끗한 상태를 유지하는 것이 관찰되면서 꾸준히 관심에 대상이 되어 왔었다. 자가 세정 효과는 접촉각 $150^{\circ}$ 이상의 초소수성 표면에서 구현이 가능하며 이런 표면을 일상생활부터 산업분야까지 응용하고자 하는 많은 노력들이 있었다. 물질의 친수성 또는 소수성은 표면의 거칠기(roughness)와 표면에너지(surface energy)의 두 가지 특성에 의해 결정된다. 하지만 낮은 표면에너지 물질을 사용해도 접촉각 $150^{\circ}$ 이상의 초소수성 표면을 얻긴 힘들며, 표면의 거칠기를 증가시켜야 한다. PTFE (polytetrafluoroethylene)는 낮은 표면에너지를 가진 소수성 물질로 bulk일 경우 접촉각이 약 $108^{\circ}$이지만 거친 표면을 가진 박막으로 만들 경우 접촉각이 $150^{\circ}$ 이상의 값을 가지는 초수수성 표면이 가능한 물질이다. 특히, 초소수성 표면 이외에 우수한 내열성 및 내화학성 특성을 가지고 있어 디스플레이 및 태양전지 등의 자가세정(self cleaning) 보호막으로써 응용이 기대되고 있다. 본 연구에서는 HFPO (hexafluoropropylene)를 원료 가스로 이용하여, Si(100)과 유리 기판위에 Cat-CVD (Catalytic Chemical Vapor Deposition)법으로 PTFE 박막을 증착하였다. 텅스텐(W)을 촉매로 사용하였으며, 촉매온도가 $850^{\circ}C$이상인 조건에서 접촉각이 $150^{\circ}$ 이상인 초소수성 PTFE 표면을 쉽게 얻을 수 있었다. 특히 본 연구에서는 제막압력을 300 mTorr에서 700 mTorr까지 변화시켜 가며 유리와 Si 기판위에 증착하였다. Cat-CVD 제막압력을 변화시켜가며 증착된 PTFE 박막의 접촉각을 측정한 결과, 제막압력이 300 mTorr일 때 glass와 Si 기판위에 증착된 PTFE박막 표면에서의 접촉각은 각각 133, $117^{\circ}$였지만, 제막압력이 400 mTorr이상일 땐 $150^{\circ}$ 이상의 높은 접촉각을 갖는 초소수성 표면을 얻을 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.225-231
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• 2011

The satellite clock anomalies, one of the abnormal signal factors of the GPS satellites, can have a significant impact on the GPS measurements. However, it can be difficult to detect the anomalies of the satellites clock before the range of the satellites clock error becomes bigger than the range of the other factors, due to the measurement including error of the orbit, ionosphere delay, troposphere delay, multipath and receiver clock. In order to perform quick and accurate detection by minimization of critical range in anomalies of the satellites clock, this paper suggested a solution to detect precise anomalies of the satellites clock after application of carrier smoothing filter from measurement by dual-frequency and adjustment of errors which can be occurred by other factor and the receiver clock errors. The performance of the proposed method was confirmed by comparing to the satellite clock biases which are provided by IGS.

• Journal of KIISE:Information Networking
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• v.36 no.3
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• pp.173-183
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• 2009

We present a real-time monitoring system for detecting anomalous network events using the entropy. The entropy accounts for the effects of disorder in the system. When an abnormal factor arises to agitate the current system the entropy must show an abrupt change. In this paper we deliberately model the Internet to measure the entropy. Packets flowing between these two networks may incur to sustain the current value. In the proposed system we keep track of the value of entropy in time to pinpoint the sudden changes in the value. The time-series data of entropy are transformed into the two-dimensional domains to help visually inspect the activities on the network. We examine the system using network traffic traces containing notorious worms and DoS attacks on the testbed. Furthermore, we compare our proposed system of time series forecasting method, such as EWMA, holt-winters, and PCA in terms of sensitive. The result suggests that our approach be able to detect anomalies with the fairly high accuracy. Our contributions are two folds: (1) highly sensitive detection of anomalies and (2) visualization of network activities to alert anomalies.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.6
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• pp.283-288
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• 2016

In recent years, there have been many research efforts on Big Data, and many companies developed a variety of relevant products. Accordingly, we are able to store and analyze a large volume of log data, which have been difficult to be handled in the traditional computing environment. To handle a large volume of log data, which rapidly occur in multiple servers, in this paper we design a new data storage architecture to efficiently analyze those big log data through Apache Hive. We then design and implement anomaly detection methods, which identify abnormal status of servers from log data, based on moving average and 3-sigma techniques. We also show effectiveness of the proposed detection methods by demonstrating that our methods identifies anomalies correctly. These results show that our anomaly detection is an excellent approach for properly detecting anomalies from Hadoop log data.

• Journal of the Korea Society of Computer and Information
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• v.27 no.6
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• pp.23-31
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• 2022

Due to the recent outbreak of COVID-19 and an aging population and an increase in single-person households, the amount of time that household members spend doing various activities at home has increased significantly. In this study, we propose an algorithm for detecting anomalies in members of single-person households, including the elderly, based on the results of human movement and fall detection using an image sensor algorithm through home CCTV, an activity sensor algorithm using an acceleration sensor built into a smartphone, and a 2D LiDAR sensor-based LiDAR sensor algorithm. However, each single sensor-based algorithm has a disadvantage in that it is difficult to detect anomalies in a specific situation due to the limitations of the sensor. Accordingly, rather than using only a single sensor-based algorithm, we developed a fusion method that combines each algorithm to detect anomalies in various situations. We evaluated the performance of algorithms through the data collected by each sensor, and show that even in situations where only one algorithm cannot be used to detect accurate anomaly event through certain scenarios we can complement each other to efficiently detect accurate anomaly event.