• 대한기계학회논문집A
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• 제28권2호
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• pp.143-148
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• 2004

This paper discussed on the stability of elastic material subjected to dry friction force for low boundary conditions: clamped free, clamped-simply supported, simply supported-simply supported, clamped-clamped. It is assumed in this paper that the dry frictional force between a tool stand and an elastic material can be modeled as a distributed follower force. The friction material is modeled for simplicity into a Winkler-type elastic foundation. The stability of beams on the elastic foundation subjected to distribute follower force is formulated by using finite element method to have a standard eigenvalue problem. It is found that the clamped-free beam loses its stability in the flutter type instability, the simply supported-simply supported beam loses its stability in the divergence type instability and the other two boundary conditions the beams lose their stability in the divergence-flutter type instability.

• 정보처리학회논문지A
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• 제11A권2호
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• pp.203-206
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• 2004

저자는 등각사상을 구하기 위한 기존의 여러 Theodorsen 방정식의 해법 중 가장 유효한 해법으로 알려져 있는 Wegmann의 방법을 다룬바 있다. Wegmann의 방법으로 수치실험을 한 결과 난이도가 높다고 예상되는 문제에 있어 수렴했다가 발산을 하는 불안정현상이 나타났으며 수렵하지 않는 불안정현상의 원인을 분석하여 저주파필터를 적용한 새로운 반복법을 제안하였다. 원래의 Wegmann 반복법으로는 발산하는 모튼 문제에 있어서 새로 제안한 방법에 의해서 수렴하는 수치실험 결과를 얻었는데 본 논문에서는 저주파필터를 적용한 Wegmann해법에 의해 실험적으로 수렴한 결과를 Fourier 분석기법에 의해 이론적으로 증명한다.

• International Journal of Industrial Entomology and Biomaterials
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• 제6권1호
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• pp.63-68
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• 2003

We investigated the sequence divergence of the geographic samples of the queen bumble bee (Bombus ardens) in Korea. A portion of mitochondrial COI gene sequences (423 bp) was analyzed for 44 individuals collected from seven localities. Sequence analysis resulted in four COI haplotypes with the maximum nucleotide divergence of only 0.5% (two bp). One haplotype (BA1) was dominant in all localities surveyed (86.4%). The finding of low sequence divergence and dominance of one haplotype appear to reflect, although limited, the life history of the B. ardens queens subjected to active dispersal and seasonal fluctuation in queen number.

• ETRI Journal
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• 제45권2호
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• pp.267-276
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• 2023

R&D strategies of companies with low and high technological levels are discussed based on the concept of technology convergence and divergence. However, empirically detecting enterprise technology convergence in the distribution of enterprise technology (total productivity increase) over time and identifying key change factors are challenging. This study used a novel statistical indicator that captures the internal technology distribution change with a single number to clearly measure the technology distribution peak as a change in critical bandwidth for enterprise technology convergence and presented it as evidence of each technology convergence or divergence. Furthermore, this study applied the quantitative technology convergence identification method. Technology convergence appeared from the separation of total corporate productivity distribution of 69 IT companies in Korea in 2019-2020 rather than in 2015-2016. Results indicated that when the total technological level was separated from the technology leading and technology catch-up, IT companies were found to be pursuing R&D strategies for technology catch-up.

• Ocean and Polar Research
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• 제26권2호
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• pp.351-360
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• 2004

To investigate latitudinal variations in the zooplankton community along the meridian line ($5^{\circ}N-12^{\circ}N$, $131.5^{\circ}W$), we measured temperature, salinity, nitrate, chlorophyll-a and zooplankton at depths above 200 m from July $10^{th}$ to $25^{th}$, 2003. For comparative analysis, data of the physico-chemical properties and chl-a were matched to the two sampling depths (surface mixed layer and thermocline depth-200 m) of zooplankton. Latitudinal differences in the mesozooplankton distribution were mainly influenced by divergence formed at a boundary line formed by currents of opposing directions, consisting of North Equatorial Current (NEC) and North Equatorial Counter Current (NECC). High concentrations of chl-a south of $9^{\circ}N$, caused by equatorial upwelling related nutrients, is thought to be affected by the role of this divergence barrier, supported by relatively low concentrations in waters north of $9^{\circ}N$. The latitudinal differences of the chl-a were significantly associated with the major groups of zooplankton, namely calanoid and cyclopoid copepods, appendicularians, ostracods, chaetognaths, invertebrate larvae, and others. And temperature significantly affected the latitudinal variation of radiolarians, siphonophores, salps and immature copepods. The latitudinal differences in the two factors, temperature and chl-a, which explained 71.0% of the total zooplankton variation, were characterized by the equatorial upwelling as well as the divergence at $9^{\circ}N$. The physical characteristics also affected the community structure and abundance of zooplankton as well as average ratios of cyclopoid versus calanoid copepods. The abundance of dominant copepods, which were consistent with chl-a, were often associated with the carnivorous zooplankton chaetognaths, implying the relative importance of bottom-up regulation from physical properties to predatory zooplankton during the study period. These results suggested that latitudinal distribution of zooplankton is primarily controlled by current-related divergences, while biological processes are of secondary importance in the northeastern Equatorial Pacific during the study period in question.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1350-1364
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• 2023

2D/1D coupling method is an important neutron transport calculation method due to its high accuracy and relatively low computation cost. However, 2D/1D coupling method may diverge especially in small axial mesh size. To analyze the convergence behavior of 2D/1D coupling method, a Fourier analysis for k-eigenvalue neutron transport problems is implemented. The analysis results present the divergence problem of 2D/1D coupling method in small axial mesh size. Several common attempts are made to solve the divergence problem, which are to increase the number of inner iterations of the 2D or 1D calculation, and two times 1D calculations per outer iteration. However, these attempts only could improve the convergence rate but cannot deal with the divergence problem of 2D/1D coupling method thoroughly. Moreover, the choice of axial solvers, such as DGFEM SN and traditional SN, and its effect on the convergence behavior are also discussed. The results show that the choice of axial solver is a key point for the convergence of 2D/1D method. The DGFEM SN based 2D/1D method could converge within a wide range of optical thickness region, which is superior to that of traditional SN method.

• 생명과학회지
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• 제14권4호
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• pp.593-607
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• 2004

유해성 적조생물 Cochlodinium polykrikoides/Gyrodinium aurelum을 포함한 43 종류의 와편조류를 대상으로 SSU 부위 유전자를 분석했다. 유전자 염기서열에 의거한 상호 계통수는 parisomny, distance, maxium 방법으로 실행했다. Noctilura scintillans, Gonyaulax spinifera와 Crythecodinium cohnii 종들은 와편모조류 중 가장 유전적으로 먼 것으로 보였다. Alexandrium과 Symbiodinium 종간의 bootstrap는 70% 이상의 상호 단일 계통도를 보인 반면에, Gymnodinium과 Gyrodinium은 근립절약계수와 최대 유사도 방법에서 다형 계통도를 나타내었다. Gyroddinium aurelum과 G. dorsum/G. galathenum의 유전적 분화율은 7.4% (45 bp) 였고, G. aurelum과 G. mikimotoi 상호간에는 0.9% (5bp) 밖에 나타나지 않았다. 또한 C. polykrikoides와 G. aurelum도 5.2% (31bp)로 낮은 유전적 분화율을 보였다. 계통도를 분석한 결과 G. aureolum과 C. polykrikoides는 Gyrodinium 보다 Gymnodinim 속에 훨씬 더 근접하게 나타났다.

• 한국안광학회지
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• 제10권3호
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• pp.205-213
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• 2005

교정시력이 1.0 이상인 21세에서 30세 사이인 대학생 90명(남25명, 여65명)을 대상으로 포롭터를 이용하여 양안시 검사를 하였다. 원거리에서 허성상대 폭주력(외전)의 기대치(흐린점/분리점/회복점)내에 포함되는 대상의 비율은 78%/61%/67%로 나타났고, 개산과다는 9%/31%/23%, 개산부족은 13%/8%/9%이었다. 원거리에서 실성상대폭주력(내전)은 20%/46%/39%, 폭주과다는 22%/14%/16%, 폭주부족은 35%/40%/45%를 각각 보였다. AC/A비 측정에서 42명이 정상이었고 38명은 낮음, 나머지는 높음을 보였으며 낮은 AC/A비는 조절관계에서 낮은 이향운동의 결과로 볼 수 있다. 근거리에서 허성상대 폭주력 기대치는 26%/29%/44%로 나타났고, 개산과다는 61%/33%/24%, 개산부족은 3%138%/32%이었으며 실성상대 폭주력의 기대치내에 포함되는 대상의 비율은 33%/40%/31%, 폭주과다는 61%/23%/42%, 폭주부족은 6%/37%/27%로 각각 나타났다. 폭주근점 검사에서 58%는 8cm 이내로 기대치에 포함되었다. 허성상대조절력(NRA)과 실성상대조절력(PRA) 검사 결과 기대지내에 포함되는 대상의 비율은 각각 41%와 33%였다. 그리고 조절부족은 33%와 43% 및 조절과다는 26%와 24%를 각각 나타냈다. 조절과다는 NRA의 낮은값과 관련되었고 초절부족과 폭주과다는 NRA의 높은 값과 관련 있고, 조절과다이면서 폭주과다인 기능 이상은 NRA의 높은 값과 관련 있는 것으로 나타났다.

• 지적과 국토정보
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• 제47권2호
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• pp.79-90
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• 2017

도시지역은 지구상에서 가장 변화가 활발히 일어나는 지역 중의 하나로써, 우리나라에서도 산림지나 녹지, 농경지가 주거지역, 공업지역 등의 주거지역으로 빠르게 변화하고 있다. 이러한 빠른 토지이용의 변화를 모니터링하기 위해서는 신속한 데이터의 취득을 필요로 하게 되고, 위성영상은 이러한 요구의 대안이 될 수 있다. 일반적으로 SAR 위성은 능동적 탐측체계로 영상을 취득하기 때문에 지표면의 거칠기에 따라 영상의 밝기값이 결정되며, 대표적으로 수계영역은 반사강도가 낮아 어둡게 나타나고, 인공구조물이 분포하고 있는 주거지역의 경우 반사강도가 높아 타 지역에 비해 밝기값이 높게 나타난다. 이러한 SAR 영상의 특성을 이용하면 주거지역을 효과적으로 추출할 수 있다. 본 연구에서는 고해상도 X-band SAR 위성인 독일의 TerraSAR-X, 우리나라의 KOMPSAT-5를 이용하여 주거지역의 추출을 수행하였으며, 추출을 위해서 영상분할기법을 통한 객체기반 영상분류를 적용하였다. 영상분할의 정확도를 향상시키기 위해서 스페클 divergence를 먼저 계산하여 주거지역의 반사강도를 조정하였다. 두 위성영상의 정확도 평가를 위해서 추가로 픽셀기반의 K-means 영상분류법을 적용하여 주거지역을 분류하였다. 연구의 결과로써 TerraSAR-X의 객체기반 영상분류법은 약 88.5%, 픽셀기반영상분류법은 75.9%, KOMPSAT-5는 약 87.3%와 74.4%의 overall accuracy를 보였다.

• 소음진동
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• 제7권4호
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• pp.621-629
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• 1997

For computer aided design and costruction of low noisy power plants, indoor and outdoor noise prediction program has been developed. The program utilizes the predefined data of noise sources and building materials and has the faculty to estimate the source level using the empirical formula in case of the measured data not being available. In the noise prediction, the mutual noise propagation between indoor and outdoor sites are considered. The outdoor noise source in the calculation of geometric divergence effects is modelled as the omni-directional finite line or planar source according to the source geometry and the receiving points. Outdoor noise prediction is carried out to consider the diffraction effect due to plant structures as well as the attenuation effect due to atmospheric absorption and soft ground. The results of indoor and outdoor noise prediction for a recently constructed diesel engine power plant show good agreement with the measured.