• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(II)
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• pp.1195-1204
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• 2002

The impacts of El Nino Southern Oscillation (ENSO) phenomenon on climate are widespread and extend far beyond the tropical Pacific. The phenomenon can be characterized by Southern Oscillation Index (SOI) which is derived from values of the monthly mean sea level pressure barometric difference between Tahiti and Darwin, Australia. Its best-known extreme is the El Nino event. In this study, general statistical characteristics of SOI and the data from which it is derived (i.e. mean sea level pressure data at Tahiti and Darwin) are presented as guidance when using SOI far other analyses. The characteristics include the availability of the barometric pressure data, statistics of monthly pressure data, correlation of SO intensity, frequency analysis of SOI by magnitude and by month (January-December), duration properties of SOI by run analysis.

• 한국소음진동공학회논문집
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• 제16권6호
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• pp.651-657
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• 2006

Active control method is applied to a flexible beam excited by a shock impulse in order to reduce the residual vibrations after the shock event. It is assumed that the shock input can be measured and is always occurred on the same point of the beam. If the system is well identified and the corresponding inverse system is designed reliably, it has shown that a very simple feed-forward active control method may be applied to suppress the residual vibrations without using error sensors and adaptive algorithm. Both numerical simulations and experimental results show a promising Possibility of applying to a practical problem. Also, the performance of the method is examined by considering various practical aspects : shock duration, shock magnitude, and control point.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.65.4-65
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• 2001

In case of data transmission using the upper 10GHz frequency, rain results in attenuation of radio waves. And the most serious atmospheric effect in a satellite link is the rainfall. The attenuation of rainfall very seriously affects the quality of transmission line. Because the rain increases thermal noise and interference, and decreases the amplitude of the signal. KOWACO manages the VSAT system instead of VHF network for communication of rain and water-level data from 1998. The purpose of this system is to monitor the change of water-level and rain data during a flood duration. VHF system acquires the data by a call per a hour. But the satellite network obtains the data whenever event data occur. Thus the satellite network is more powerful than the VHF system. In study ...

• Smart Structures and Systems
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• 제23권2호
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• pp.173-184
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• 2019

The main objective of this study is to evaluate the true fracture energy and monitor the damage progression in steel fibre reinforced concrete (SFRC) specimens using acoustic emission (AE) features. Four point bending test is carried out using pre-notched plain and fibre reinforced (0.5% and 1% volume fraction) - concrete under monotonic loading. AE sensors are affixed at different locations of the specimens and AE parameters such as rise time, AE energy, hits, counts, amplitude and duration etc. are obtained. Using the captured and processed AE event data, fracture process zone is identified and the true fracture energy is evaluated. The AE data is also employed for tracing the damage progression in plain and fibre reinforced concrete, using both parametric- and signal- based techniques. Hilbert - Huang transform (HHT) is used in signal based processing for evaluating instantaneous frequency of the acoustic events. It is found that the appropriately processed and carefully analyzed acoustic data is capable of providing vital information on progression of damage on different types of concrete.

• 전자통신동향분석
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• 제36권2호
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• pp.93-101
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• 2021

The controversy over Artificial Intelligence (AI) chatbot "Iruda," which suspended its service 20 days after its launch, can be seen as the first case to inform the public of AI ethics issues. Based on this context, this study examines the controversy and social semantic formation of "Iruda" service cases using news topic modeling techniques. 963-news articles were used for the analysis, and the event's duration was analyzed based on major events, such as service start, controversy, and suspension, to understand the progress. From the analyses results, we obtain major keywords and a total of 16 topics (5, 4, 7) from the period. Finally, the implications for the development and utilization of AI services obtained through this controversy were discussed based on the analysis results.

• 대한두개안면성형외과학회지
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• 제23권5호
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• pp.232-236
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• 2022

Post-traumatic enophthalmos and hypoglobus are common sequelae of facial bone fractures, even after reduction surgery. They are associated with functional and esthetic issues, which may lower the quality of life. These deformities frequently present late, and adequate correction is difficult. We report three cases of late inferior orbital rim reconstructions with three-dimensional printed implants to help resolve these problems. The average duration between the traumatic event and surgery was 3 years and 4 months. One patient was treated with a completely absorbable implant and exhibited satisfactory results until the implant started to biodegrade at 1 year and 9 months after surgery. Two patients were treated with a permanent implant and demonstrated satisfactory results. However, longer follow-up periods were needed. There were no complications such as infection, diplopia, or restriction of ocular motion and the patients were satisfied with the esthetic results.

• 대한원격탐사학회지
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• 제38권4호
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• pp.375-386
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• 2022

The city of Khartoum, the capital of Sudan, was heavily damaged by the flood of the Nile in 2020. Classification using satellite images can define the damaged area and help emergency response. As Synthetic Aperture Radar (SAR) uses microwave that can penetrate cloud, it is suitable to use in the flood study. In this study, Random Forest classifier, one of the supervised classification algorithms, was applied to the flood event in Khartoum with various sizes of the training dataset and number of images using Sentinel-1 SAR. To create a training dataset, we used unsupervised classification and visual inspection. Firstly, Random Forest was performed by reducing the size of each class of the training dataset, but no notable difference was found. Next, we performed Random Forest with various number of images. Accuracy became better as the number of images in creased, but converged to a maximum value when the dataset covers the duration from flood to the completion of drainage.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.253-268
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• 2022

Using non-destructive Acoustic Emission (AE) and optical Digital Image Correlation (DIC) methods, the moment-curvature behavior of steel and GFRP bars reinforced concrete beams under flexure was explored in this study. In the tension zone, laboratory studies were carried out on steel-RC and GFRP-RC beams with varying percentages of longitudinal reinforcement ratios of 0.33 %, 0.52%, and 1.11%. The distinct mechanism of cracking initiation and fracture progression of failure in steel-RC and GFRP-RC beams were effectively correlated and picked up using AE waveform characteristics of the number of AE hits and their amplitudes, AE energy as well as average frequency and duration. AE XY event plots and longitudinal strain profiles using DIC gives an online and real-time visual display of progressive AE activity and strains respectively to efficaciously depict the crack evolution and their advancement in steel-RC and GFRP-RC beams. They display a close matching with the micro and macro-cracks visually observed in the actual beams at various stages of loading.

• 한국수자원학회논문집
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• 제49권4호
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• pp.275-282
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• 2016

본 연구에서는 가뭄사상과 확률 가뭄심도를 결정하는 새로운 방법을 제안하였다. 강우자료로부터 가뭄사상을 추출하기 위해 연속이론과 누적 강우부족량을 동시에 고려하였다. 절단수준 이상의 강우사상이 발생할 경우, 그 때까지의 누적 강우부족량을 해갈할 수 있을 만큼의 강우량이 발생하였는가를 확인하여 가뭄사상의 종료여부를 최종 결정하였다. 이와 같이 추출된 가뭄사상의 지속기간과 심도의 상호 의존성 구조를 파악하여 결합분포함수를 추정하기 위해 코플라 함수를 적용하였다. 또한 이변량 코플라 함수의 조건부 함수를 이용하여 가뭄의 특정 지속기간에 대한 가뭄심도의 재현특성을 분석하였으며, 신뢰구간을 추정하여 이변량 빈도해석의 불확실성을 정량화하였다. 서울지점의 1909~2015년 강수자료에 적용한 결과 과거 극한가뭄으로 판단되었던 가뭄사상은 대부분 최소 10년에서 최대 50년 정도의 재현기간을 갖는 반면 2013년 발생하여 현재까지 지속되고 있는 2015년 가뭄은 현저히 높은 재현기간을 가지고 있는 것으로 나타났다. 이러한 연구 결과는 향후 가뭄대책을 마련하는 데 있어 빈도개념을 바탕으로 하는 신뢰성 있는 기준으로 활용할 수 있을 것으로 기대된다.

• 한국안광학회지
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• 제19권4호
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• pp.533-538
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• 2014

목적: 모니터 글자 대비 변화에 따른 눈의 피로도를 측정하여 모니터 글자 대비도와 눈의 피로도의 연관성에 대해 연구하고자 하였다. 방법: 최대교정시력 1.0 이상의 피검자 53명(평균연령 $22.68{\pm}1.85$) 중 읽기속도 검사에 통과한 45명(평균연령 $22.68{\pm}1.85$)을 대상으로 각각 Black(대비 100%), Dark gray(대비 80%), Gray(대비 60%), Light gray(대비 30%) 글자로 이루어진 4가지 시표를 무작위로 읽도록 하였다. 피검자가 시표를 읽는 동안 아이트래커로 피검자의 안구를 추적하여 모니터 글자 대비에 따른 피검자의 눈의 피로도의 변화를 측정하였다. 결과: 피검자들의 평균측정시간은 Black, Dark gray, Gray, Light gray에서 33.635 sec, 32.266 sec, 33.936 sec, 34.848 sec로 측정되었다. 평균안구고정시간은 Black, Dark gray, Gray, Light gray에서 0.224 sec, 0.218 sec, 0.239 sec, 0.243 sec로 측정되었다. 평균동공크기는 Black, Dark gray, Gray, Light gray에서 41.133 mm, 41.160 mm, 40.880 mm, 40.459 mm로 측정되었다. 평균 눈깜박임 빈도수는 Black, Dark gray, Gray, Light gray에서 0.211 blinks/sec, 0.206 blinks/sec, 0.221 blinks/sec, 0.238 blinks/sec로 측정되었다. 결론: 피검자들의 평균측정시간과 평균안구고정시간은 Dark gray가 가장 짧았으며, Light gray에서 가장 길었다. 평균 동공크기는 Dark gray에서 가장 컸으며, Light gray에서 가장 작았다. 평균 눈 깜박임 빈도수는 Dark gray에서 가장 적었으며, Light gray에서 가장 많았다. 모니터 글자 밝기에 따른 눈의 피로도는 Dark gray에서 가장 적었으며 Black, Gray, Light gray 순으로 증가하였다.