• The Science & Technology
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• no.8 s.423
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• pp.18-20
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• 2004

한국항공우주연구원 채연석(54) 원장은 어릴 때부터 로켓 만들기에 푹 빠져 있었다. 고교 시절 자작 소형 로켓이 귓가에서 터지는 바람에 고막을 다치기도 했다. 그 시절은 닐 암스트롱이 달에 인류의 족적을 처음으로 남기고, 미국과 옛 소련의 우주개발 경쟁으로 우주선 발사 장면이 연일 방송과 신문지상을 장식하던 때였다. 그것을 보는 소년 채연석의 꿈은 직접 만든 로켓을 우주로 쏘아 올리는 것이었다. 그로부터 30여 년이 지난 지금 채 원장은 한국의 우주기술 개발의 총 사령탑이 되어 있다. 그 자리에서 그는 우주를 향한 꿈을 바느질의 한땀 한땀처럼 엮어가고 있는 중이다. 한국항공우주연구원 원장실에서 만난 채연석 원장의 표정에서는 우주항공 기술의 기반을 쌓느라 영일없는 나날을 보내는 것을 금방 느낄 수 있었다. 채 원장은 2002년말 우주 개발용 로켓의 주류를 이루고 있는 액체연료를 사용하는 로켓을 개발해 발사에 성공하기도 했다. 그 로켓의 길이는 14m, 지름 1m로 우리 나라 독자 기술로 개발한 것이다. 그는 우리 나라가 독자적으로 인공위성을 만들어, 역시 독자적으로 개발한 로켓으로 발사에 성공하면 월드컵 4강 진출보다 더 국가 이미지가 높아질 것으로 내다봤다. 그만큼 우주기술은 극한 기술과 첨단기술을 골고루 필요로 하기 때문이다.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.363-370
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• 2003

The object of this study is to investigate the effect of compounded welding by using an acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots are displays showing the chronological course of the test. Also, source location gives the X- and Y-coordinates of the AE source.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.287-300
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• 1997

In this study, an effective application method of AE technique for the detection of fatigue crack in multi-girder steel bridges has been proposed. The applicability has been examined through the laboratory works with bridge model. The proposed analytical method which evaluates the remaining fatigue lives of structural members may improve the rational determination of the priority of inspection for structural members assuming to have fatigue cracks. Laboratory tests for the application of AE technique to steel girder bridges show that the frequency bands of traffic noise are in the range between 10 show that the frequency bands of traffic noise are in the range between 100~200 kHz and the AE signal raised from fatigue cracks is concentrated around 400~500 kHz. Therefore. R30 sensor is proved to be the most suitable for the detection of cracks in steel girder bridges. A linear proportionality between the crack propagation and the frequency of AE signals has been obtained. In addition, an economic and effective source location method for steel girder bridges was studied through experiments.

• Journal of Korean Society of Forest Science
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• v.100 no.3
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• pp.392-396
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• 2011

The purpose of this study was to develop the basic wood density (Abbreviated BWD) for Pinus densiflora and to evaluate the applicability of bootstrap simulation method. The data sets were divided into two groups based on eco-types in Korea, one from Gangwon type and the other from Jungbu type. The estimated BWDs derived from bootstrap simulation, which is one of the non-parametric statistics, were 0.418 ($g/cm^3$) in the Pinus densiflora in Gangwon while 0.464 ($g/cm^3$) in the Pinus densiflora in Jungbu. To evaluate the bootstrap simulation, the mean BWD, standard error and 95% confidence interval of probability density were estimated. The number of replication were 100, 500, 1,000, and 5,000 times that showed constant 95% confidence interval, while tended to decrease in terms of standard errors. The results of this study could be very useful to apply basic wood density values to calculate reliable carbon stocks for Pinus densiflora in Korea.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• Spatial Information Research
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• v.18 no.5
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• pp.37-45
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• 2010

AT(Aerial Triangulation) is the essential procedure for creating orthophoto and transforming coordinates on the photographs into the real world coordinates utilizing GCPs (Ground Control Point) which is obtained by field survey and the external orientation factors from GPS/INS as a reference coordinates. In this procedure, all of the GCPs can be collected from field survey using GPS and Total Station, or obtained from digital maps. Collecting GCPs by field survey is accurate than GCPs from digital maps; however, lots of manpower should be put into the collecting procedure, and time and cost as well. On the other hand, in the case of obtaining GCPs from digital maps, it is very difficult to secure the required accuracy because almost things at each stage in the collecting procedure should rely on the subjective judgement of the performer. In this study, the results from three methods have been compared for the accuracy assessment in order to know if the results of each case is within the allowance error: for the perceivable objects such as road boarder, speed bumps, constructions etc., 1) GCPs selection utilizing the unique LiDAR intensity value reflected from such objects, 2) using LiDAR DSM and 3) GCPs from field survey. And also, AT and error analysis have been carried out w ith GCPs obtained by each case.

• Convergence Security Journal
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• v.17 no.3
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• pp.21-29
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• 2017

Accurate encoding of local patterns is a very important factor in texture classification. However, LBP based methods w idely studied have fundamental problems that are vulnerable to noise. Recently, LDP method using edge response and dire ction information was proposed in facial expression recognition. LDP is more robust to noise than LBP and can accommod ate more information in it's pattern code, but it has drawbacks that it is sensitive to rotation transforms that are critical to texture classification. In this paper, we propose a new local pattern coding method called Rotation Invariant Local Direc tional Pattern, which combines rotation-invariant transform to LDP. To prove the texture classification performance of the proposed method in this paper, texture classification was performed on the widely used UIUC and CUReT datasets. As a result, the proposed RILDP method showed better performance than the existing methods.

• 한국HCI학회:학술대회논문집
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• 2007.02b
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• pp.439-444
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• 2007

정서 전달에는 언어적 의사소통뿐만 아니라 비언어적 의사소통이 거론되곤 한다. 하지만 지금까지의 비언어적 의사소통 연구는 대부분 언어의 음향학적 연구나 얼굴표정 연구에 국한되었다. 또한 음악의 정서에 대한 연구는 음악적 구조 혹은 스타일과 여러 성격적 특질 및 행동 간의 관계, 혹은 생리적 효과 등 어떤 음악(what music)이 특정한 효과를 일으키느냐에 중점을 두고 있었다. 따라서 본 연구에서는 Gabrielsson & Juslin(1996)의 연구에 의거, 음악을 통하여 작곡가가 아닌 연주자의 의도된 정서가 청자에게 얼마나 잘 지각될 수 있는지 알아보고자 하였다. 봉 녕구의 가설은 다음과 같다; 첫째, 연주자의 정서적 의도는 음악의 모든 물리적 변인에 영향을 준다; 둘째, 청자는 의도된 정서를 지각하는 데 일반적으로 성공적이다; 셋째, 특정 정서는 다른 정서보다 더 잘 구분된다. 본 연구에 사용된 곡은 학습 효과를 배제하기 위하여 새롭게 전문 작곡가에 의해 작곡되었으며, 전문 연주자는 동일한 곡을 7종류의 정서(행복한, 슬픈, 화난, 두려운, 다정한, 엄숙한, 정서 표현 없음)를 표현하도록 연주하였다. 하나의 완전한 음악을 표현하기 위하여 각 곡은 멜로디(악기구성: 일렉트릭 기타, 베이스, 그랜드 피아노)와 리듬(드럼)을 포함하였다. 실험참가자는 각 곡을 듣고 7개의 정서 종류 각각에 점수를 평정하였다. 그 결과 이전 연구와 마찬가지로 청자는 연주자의 의도된 정서를 일반적으로 지각하는 데 성공하였으며 7개의 정서 중 특징적인 정서("행복한", "슬픈", "화난", "다정한") 는 다른 정서 보다 더 잘 구별되었다. 본 연구에 사용된 "두려운" 정서 곡의 음향분석 결과 소리 강도의 큰 변산이 특징이었다. 이는 이전 연구에서 "두려운" 정서의 특징인 타이밍의 큰 변산과 함께, "두려운" 정서가 '불규칙적이거나 변화가 커서 예측하기 어려운' 속성을 지니고 있음을 시사한다. 또한 "다정한" 정서에 대해서 본 연구에서는 다른 모든 정서와 유의미한 차이를 보인 반면, 이전 연구에서는 "슬픈"과 유의미한 차이가 없었다. 이는 본 연구에 쓰인 "다정한" 정서의 곡은 리듬 패턴을 다른 정서 버전과는 다르게 보사노바 리듬을 사용하였다. 이전 연구와는 다르게 빠른 템포였음에도 불구하고 구별이 잘 된 이유는 이와 같이 장르 특징적인 영향이 컸기 때문이라고 할 수 있다. 이는 연주자나 음악 스타일 자체의 성격이 정서 판단에 있어 큰 영향을 준다는 사실을 시사한다. 종합적으로 음악을 통한 정서 전달에 있어 연주자, 청자, 악기, 음악 스타일의 차이가 영향을 줄 수 있다는 사실을 확인하였으며 이러한 결과는 Scherer & Oshinsky(1977)가 언급하였듯 음악 연주가 다른 비언어적 의사소통 방법과 공유하는 특징이 있음을 시사한다.

• Journal of Korea Multimedia Society
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• v.23 no.12
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• pp.1464-1475
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• 2020

Due to the spread of COVID-19, the online lecture has become more prevalent. However, it was found that a lot of students and professors are experiencing lack of communication. This study is therefore designed to improve interactive communication between professors and students in real-time online lectures. To do so, we explore deep learning approaches for automatic recognition of students' facial expressions and classification of their understanding into 3 classes (Understand / Neutral / Not Understand). We use 'BlazeFace' model for face detection and 'ResNet-GRU' model for facial expression recognition (FER). We name this entire process 'Degree of Understanding (DoU)' algorithm. DoU algorithm can analyze a multitude of students collectively and present the result in visualized statistics. To our knowledge, this study has great significance in that this is the first study offers the statistics of understanding in lectures using FER. As a result, the algorithm achieved rapid speed of 0.098sec/frame with high accuracy of 94.3% in CPU environment, demonstrating the potential to be applied to real-time online lectures. DoU Algorithm can be extended to various fields where facial expressions play important roles in communications such as interactions with hearing impaired people.

• Journal of Korean Society of Forest Science
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• v.102 no.4
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• pp.477-483
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• 2013

The purpose of this study was to calculate uncertainty of emission factor collected data and to evaluate the applicability of Monte Carlo simulation technique. To estimate the distribution of emission factors (Such as Basic wood density, Biomass expansion factor, and Root-to-shoot ratio), four probability density functions (Normal, Lognormal, Gamma, and Weibull) were used. The two sample Kolmogorov-Smirnov test and cumulative density figure were used to compare the optimal probability density function. It was observed that the basic wood density showed the gamma distribution, the biomass expansion factor results the log-normal distribution, and root-shoot ratio showd the normal distribution for Pinus densiflora in the Gangwon region; the basic wood density was the normal distribution, the biomass expansion factor was the gamma distribution, and root-shoot ratio was the gamma distribution for Pinus densiflora in the central region, respectively. The uncertainty assessment of emission factor were upper 62.1%, lower -52.6% for Pinus densiflora in the Gangwon region and upper 43.9%, lower -34.5% for Pinus densiflora in the central region, respectively.