• 전자공학회논문지CI
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• 제39권3호
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• pp.1-17
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• 2002

본 논문은 심볼릭 모델 체커 SMV(Symbolic Model Verifier)를 이용하여, 한국전자통신연구원 (Electronics and Communications Research Institute)에서 개발한 캐쉬 일관성 프로토콜인 RACE(Remote Access Cache coherency Enforcement) 프로토콜의 몇 가지 특성(property)들을 검증함으로써, RACE 프로토콜이 중요 요구사항(requirement)들을 만족함을 보인다. 본 검증에서는 RACE 프로토콜의 모델을 SMV 입력 언어로 명세하며, 검증할 특성들을 CTL(Computational Tree Logic)을 이용하여 나타낸다. 본 검증을 통해서 RACE 프로토콜은 4개의 노드로 구성된 시스템에서 비정상적인 state/input 조합이 발생하지 않으며, liveness와 safety를 만족한다는 것을 검증하였다. 또한, 프로토콜 개발자들이 예상하지 못한 명세서 상의 모호성(ambiguity) 및 기아현상(starvation)을 발견하였으며, 본 검증 사례를 통하여 모델 체킹 기법이 하드웨어 프로토콜 검증에 효과적으로 이용될 수 있다는 것을 제안한다. 그리고, 검증시에 구현된 모델을 이용하여 시뮬레이션 및 테스팅에 유용하게 사용될 수 있는 테스트 케이스를 자동적으로 생성할 수 있는 새로운 방법을 제안한다.

• 한국전자파학회논문지
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• 제26권7호
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• pp.627-635
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• 2015

LTE-Advanced(LTE-A), IEEE802.11ac, 그리고 다중송수신 안테나를 사용하는 레이더 시스템에서 사용할 수 있는 이중계층 차분 동이득 코드북 설계 방법을 제안하고, 성능을 분석한다. 코드북의 코드워드 인자로 M진 위상 편이를 사용하여 단말기에서는 저비용의 전력 증폭기를 사용할 수 있도록 하고, 특히 고출력의 송신 전력을 사용하는 레이더 시스템에서 동이득 전송의 기본 요구사항을 만족시킨다. 차분 코드북은 무선 채널의 시간 상관 특성에 의해 선부호화 행렬 내 양자화된 채널 정보도 천천히 변화하도록 코드북을 설계한다. 이는 시간 상관 특성에 따른 채널 공간 내 일부분 만을 양자화하여 피드백하기 때문에 기존과 동일한 크기의 코드북을 구성해도 가상적으로 보다 정확한 채널정보를 양자화할 수 있어 채널 용량이 증가하는 효과를 갖는다. 제안하는 이중계층 코드북은 LTE 코드북 설계 요구조건을 유지하며, 동이득 전송이 필수인 레이더 시스템에 적용될 뿐만 아니라, 기존의 8진 동이득 코드북보다 향상된 성능을 보인다.

• 대한기계학회논문집A
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• 제35권12호
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• pp.1563-1571
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• 2011

본 연구에서는 인간중이의 소리전달특성 계산을 위한 유한요소모델을 개발하였다. 이소골의 형상을 얻기 위하여 한국인 사체에서 추출한 측두골을 마이크로 CT 촬영하여 3 차원 입체모델로 변환하였다. 유한요소모델은 이소골, 고막, 인대와 근육 등을 포함하여 구성하였다. 유한요소모델을 이용하여 고막에서 등골족판까지의 응답함수를 계산한 후 측정값을 갖는 선행연구와 비교하였고 그 결과 10 kHz 주파수 대역까지 소리전달특성을 잘 표현하고 있음을 보였다. 또한 유한요소 모델을 구성하는 주요 물성인자의 변화에 대한 소리전달특성의 변화를 살피고 침등골관절의 강성값이 중이의 소리전달특성에 큰 영향을 미침을 보였다.

• 시스템엔지니어링학술지
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• 제18권1호
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• pp.66-83
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• 2022

Artificial Intelligence (AI) is to assumed to be one of next generation technology which determine technological competitiveness and strategic advantage of a certain country. By using the patent data, this study aims to have a comparative analysis of the technological competitiveness of evolving artificial intelligence at different stages of development among the five largest intellectual property offices in the world (IP5). For the analysis data, all AI technology patent data from 1956 to 2019 were utilized according to the classification system presented in the "WIPO 2019 Technology Trend: Artificial Intelligence" report published by the World Intellectual Property Organization (WIPO) in 2019. The results shows that China has already surpassed the United States in terms of the number of patent applications in the field of artificial intelligence technology. However, in the domains of the United States, Europe, Japan, and Korea, the technology competitiveness of the United States is far ahead of China. Interestingly, the rate of increase of Korea's technology competitiveness is also very fast, and it has been shown that the technology strength is ahead of China in non-Chinese domains. The significance of this study can be found in the fact that the temporal and spatial change process of technological competitiveness of significant countries in the field of artificial intelligence technology artificial intelligence was viewed as a macro-framework using the technology index (TS) the differences were compared.

• 천문학회지
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• 제53권1호
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• pp.1-7
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• 2020

The recent study of Chae et al. (2017) found a one-to-one correspondence between plasma blobs outflowing along a ray formed after a coronal mass ejection (CME) and small X-ray flares. In the present work, we have examined the spatial configuration and the eruption process of the flares that are associated with the blobs by analyzing EUV images and magnetograms taken by the SDO/AIA and HMI. We found that the main flare and the successive small flares took place in a quadrupolar magnetic configuration characterized by predominant magnetic fields of positive polarity, two minor magnetic fragments of negative polarity, and a curved polarity inversion line between them, which suggests that the formation process of the blobs may be similar to that of the parent CME. We also found that the successive flares resulted in a gradual change of the quadrupolar magnetic configuration, and the relevant migration of flaring kernels. The three-dimensional geometry and the property of the current sheet, that is often supposed to be embedded in an observed post-CME ray, seem to keep changing because of mutual feedback between the successive flares and the temporal change of the magnetic field configuration. Our results suggest that the observed post-CME rays may not reflect the characteristics of the current sheet responsible for the impulsive phase of the flare.

• Earthquakes and Structures
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• 제4권5호
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• pp.557-585
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• 2013

The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

• 한국정보과학회논문지:소프트웨어및응용
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• 제26권10호
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• pp.1178-1178
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• 1999

A spatial join has the property that its execution time exponentially increases in proportion to the number of spatial objects. Recently, there have been many attempts for improving the performance of the spatial join by using parallel processing schemes, In the case of executing parallel spatial join using the parallel machine with shared disk architecture, the disk bottleneck of parallel processing of spatial join worsens in comparison with sequential spatial join. This paper presents the algorithms of task creation and assignment to reduce the disk bottleneck caused by accessing the shared disk at the same time, and to minimize message passing between processors, This paper proposes object caching which is a higher level of abstraction than page caching, and uses it to do creation and assignment of tasks according to temporal and spatial localities for minimizing disk access time. The object caching shows the performance improvement of 50%. The task creation and assignment using localities gives the gain of 30% and 20%. Overall performance evaluation of the proposed algorithms shows 7.2 times speed up than those of sequential execution of spatial joins.

• 한국대기환경학회지
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• 제30권2호
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• pp.139-149
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• 2014

A new technique, namely the combination of satellite and trajectory analysis (CSTA), for exploring the spatio-temporal distribution information of volcanic ash plume (VAP) from volcanic eruption. CSTA uses the satellite derived ash property data and a matching forward-trajectories, which can generate airmass history pattern for specific VAP. In detail, VAP properties such as ash mask, aerosol optical thickness at 11 ${\mu}m$ ($AOT_{11}$), ash layer height, and effective radius from the Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite were retrieved, and used to estimate the possibility of the ash forecasting in local atmosphere near volcano. The use of CSTA for Iceland's Eyjafjallaj$\ddot{o}$kull volcano erupted in May 2010 reveals remarkable spatial coherence for some VAP source-transport pattern. The CSTA forecasted points of VAP are consistent with the area of MODIS retrieved VAP. The success rate of the 24 hour VAP forecast result was about 77.8% in this study. Finally, the use of CSTA could provide promising results for VAP monitoring and forecasting by satellite observation data and verification with long term measurement dataset.

• 천문학논총
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• 제30권2호
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• pp.433-437
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• 2015

We show the results of a time series analysis of the long-term light curves of four blazars. 3C 279, 3C 345, 3C 446, and BL Lacertae. We used densely sampled light curves spanning 32 years at three frequency bands (4.8, 8, 14.5 GHz), provided by the University of Michigan Radio Astronomy Observatory monitoring program. The spectral indices of our sources are mostly flat or inverted (-0.5 < ${\alpha}$ < 0), which is consistent with optically thick emission. Strong variability was seen in all light curves on various time scales. From the analyses of time lags between the light curves from different frequency bands and the evolution of the spectral indices with time, we find that we can distinguish high-peaking flares and low-peaking flares according to the Valtaoja et al. classification. The periodograms (temporal power spectra) of the light curves are in good agreement with random-walk power-law noise without any indication of (quasi-)periodic variability. We note that random-walk noise light curves can originate from multiple shocks in jets. The fact that all our sources are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars. We are going to generalize our approach by applying our methodology to a much larger blazar sample in the near future.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.161-162
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• 2011

최근 초경량 비디오 압축 기술로써 분산 비디오 복호화가 많은 주목을 받고 있다. 하지만 분산 비디오 복호화 전체 과정 중 피드백 채널을 이용한 패리티 비트 량 제어 방식이 복호화 시간증가의 원인이 되고 있다. 시간적 공간적 상관성이 높은 영상의 특성은 프레임 별 동일 위치 LDPCA프레임의 패리티 비트 요구량에 동일하게 적용할 수 있다. 본 논문에서는 프레임간 적응적인 연산을 통해 패리티 비트 요구량을 예측하여 복호화 시간을 줄이는 방식을 제안한다. 제안 방식을 사용한 경우 패리티 비트 요구량을 예측을 하지 않을 때보다 평균 80%의 시간을 단축함을 보인다.