• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2010년도 춘계학술발표논문집 2부
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• pp.961-964
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• 2010

A semi-empirical fluctuation term is presented to improve a classical equation of state (EOS) for volumetric properties in the critical region. The term is based on the two assumptions: (1) The Helmholtz energy is individually divided into classical and long-range density fluctuation contribution (2) All molecules form cluster near the critical region due to long-range density fluctuation. To formulate such molecular cluster, we extended the Veytsman statistics originally developed for the cluster due to hydrogen bonding. The probability function in the statistics is modified to represent the characteristics of long-range density fluctuation vanishing far from critical region. The proposed fluctuation contribution was incorporated into the Sanchez-Lacombe EOS and the combined model with 6 adjustable parameters has been tested against experimental VLE data. The combined model is found to well represent flatten critical isotherm for methane and top of the coexistence curve for the tested components. The prediction results for caloric data are in good agreement with the experimental data.

• Bulletin of the Korean Chemical Society
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• 제14권1호
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• pp.63-71
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• 1993

By use of cluster orbitals, analytic solutions of finite face-centered cubic clusters are obtained. Taking interactions between up to the second nearest neighbors into account, the forms of all the elements of the Hamiltonian matrix are found explicitly within Huckel approximation. By adopting $D_{2k}$ point group to the cluster, the matrix is simplified. We assume that the cluster orbitals can mix together only when their state indices are indentical. It is then possible to calculate various physical properties of face-centered cubic metal clusters and example are shown for palladium clusters. The results show that density of states and projected density of states are similar, qualitatively, with those obtained by extended Huckel calculation.

• 정보처리학회논문지C
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• 제13C권6호
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• pp.741-748
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• 2006

센서 기술의 발전으로 무선 센서 네트워크는 빠르게 발전하고 있으며, 다양한 분야의 적용이 예상되고 있다. 무선 센서 네트워크에서 가장 중요한 요소 중의 하나는 네트워크를 에너지 효율적으로 운용하는 것이다. 이러한 목적을 위해 에너지 효율적인 라우팅 프로토콜에 대한 많은 연구가 진행되고 있다. 본 논문에서는 LEACH-C에서 제안한 클러스터 헤드 선정 알고리즘에 노드들의 밀도를 같이 고려한 향상된 클러스터 헤드 선정 알고리즘을 제안하고 시뮬레이션 하였다. 제안된 알고리즘은 LEACH-C와 실행 속도는 거의 유사하면서 11% 이상의 성능 향상 결과를 제공하였다. 본 논문의 시뮬레이션 결과는 클러스터 헤드 선정 시에 헤드와 다른 노드들 간의 거리 뿐 아니라 밀도를 고려하는 것이 센서네트워크의 에너지 이용에 보다 효율적임을 보여주었다.

• 정보처리학회논문지C
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• 제14C권7호
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• pp.589-596
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• 2007

플러딩 방식은 중복 패킷 전송 과 패킷 충돌 같은 근본적인 문제점을 가지고 있으면서도 무선 애드 혹 네트워크에서 임의의 싱크 노드에 대한 경로를 찾기 위해 자주 사용된다. 플러딩 방식이 가지고 있는 이러한 문제점을 개선하기 위한 방법들 중의 하나로 클러스터 플러딩 기법이 제안되어 사용되고 있다. 본 논문에서는 임의의 노드로부터 통신범위 안에 있는 노드들의 수인 노드들의 밀집도 이용하여 헤더를 선출하는 밀도기반 클러스터 플러딩 기법을 제안한다. 네트워크에서 발생하는 중복 패킷전송 및 패킷충돌과 같은 추가비용을 감소하는 방법은 플러딩을 하지 않는 비 플러딩(non-flooding) 노드를 가능한 한 많이 만드는 것이고, 이를 위해서는 가능한 많은 노드들을 멤버로 가지고 있는 클러스터 헤더를 선출하는 것이다. 제안한 방식은 신뢰할 수 있는 네트워크를 유지하고, 네트워크 트래픽의 효율성을 증가시킬 것이다. 본 논문에서는 NS2를 이용한 시뮬레이션을 통하여 기존의 클러스터 방식에 비해 밀도 기반 클러스터가 비 플러딩 노드의 수를 증가시켜 네트워크의 성능저하 없이 네트워크 트래픽의 효율성이 향상되는 것을 확인한다.

• Fisheries and Aquatic Sciences
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• 제13권2호
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• pp.157-166
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• 2010

We investigated the benthic polychaete assemblage in Gwangyang Bay and Yeosu Sound in February 1997. The sediment was an almost entirely muddy facies. The benthic macrofauna comprised 295 species occurring at a mean density of 875 $indiv./m^2$. Polychaetes were the major faunal component; there were 94 species at mean density 765 $indiv./m^2$. The highest abundance and species richness occurred in the Myodo south and north channels, in the mouth of Gwangyang Bay, and in the Noryang channel mouth. The most abundant polychaete was Tharyx sp. (47.9%), followed in rank order by Heteromastus filiformis (9.6%), Melinna cristata (9.3%), and Lumbrineris longifolia (7.3%). Cluster analysis divided the study area into four station groups based on station similarities in benthic polychaete assemblages: the Glycinde-Prionospio cluster in the western inner bay, the H. filiformis cluster in the middle inner bay, the Melinna-Lumbrineris cluster in the Myodo south-north channel, and the Tharyx cluster in the eastern main channel region. The sediment type of Gwangyang Bay has changed gradually from sandy to muddy. Dominant species have also changed from Chone teres and Lagis bocki to Tharyx sp., which is a potential organic pollution indicator.

• 한국정보통신학회논문지
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• 제17권4호
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• pp.996-1004
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• 2013

본 논문에서는 무선 센서 네트워크에서 센서 노드들 간의 에너지 소비 불균형을 개선하여 무선 센서 네트워크의 전체적인 수명을 연장할 수 있는 클러스터링 기법들을 제안한다. 무선 센서 네트워크의 생성 단계에서 무선 센서 네트워크의 에너지 소모를 줄이기 위해서 센서 노드들의 밀도에 따라 클러스터 헤더를 선출하여 클러스터를 형성한다. 그 이후 센서 네트워크가 활성화되는 동안 센서 노드들 간의 에너지 불균형을 개선하기 위하여 에너지 소모량을 추정한 후 릴레이 기반으로 다음 라운드의 클러스터 헤더를 선출한다.

• 천문학회보
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• 제38권1호
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• pp.37.2-37.2
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• 2013

We present the galaxy luminosity function (LF) of the Abell 119 cluster. Deep images in u, g, r bands were taken using MOSAIC 2 CCD on a Blanco 4-m telescope at CTIO. Based on scaling relations at faint magnitudes and spectroscopy at bright magnitudes, accurate membership of galaxies is determined. The LF is fitted by a single Schechter function and a two components (Gauss + Schechter) function. Blue galaxies are well fitted by a single Schechter function with steep slope ${\alpha}$ ~ -1.55). Red galaxies in the inner, high density region are fitted by single Schechter function with shallow slope (${\alpha}$ ~ -1.30), while red galaxies in the outer, low density region are well fitted by a two components function. The different slope of LFs between the inner and outer seems to stem from the luminosity segregation of A119 indicating larger number ratio of luminous to faint ratio towards the cluster center. The different shape of LFs seems to be resulted from the different composition of luminous and faint galaxies among main-cluster, sub-cluster, and infall region.

• 대한화학회지
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• 제61권6호
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• pp.311-319
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• 2017

By using Density Functional Theory (DFT), we have performed alkali metal and alkaline earth metal inside fullerene-like BeO cluster (FLBeOC) in terms of energetic, geometric, charge transfer, work function and electronic properties. It has been found that encapsulated processes of the alkali metal are exothermic and thermodynamically more favorable than alkaline earth metal encapsulation, so that interaction energy ($E_{int}$) of the alkali metal encapsulation FLBeOC is in the range of -0.02 to -1.15 eV at level of theory. It is found that, the electronic properties of the pristine fullerene-like BeO cluster are much more sensitive to the alkali metal encapsulation in comparison to alkaline earth metal encapsulation. The alkali and alkaline earth metal encapsulated fullerene-like BeO cluster systems exhibit good sensitivity, promising electronic properties which may be useful for a wide variety of next-generation nano-sensor device components. The encapsulation of alkali and alkali earth metal may increase the electron emission current from the FLBeOC surface by reducing of the work function.

• 한국재료학회지
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• 제12권1호
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• pp.44-47
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• 2002

DV(Discrete Variation)-X${\alpha}$ cluster calculation was employed to calculate the electronic states of ${\gamma}'- Fe_4N$ which was one of iron nitride phases synthesized from plasma ion nitriding to improve surface hardness and wear resistance. The result of calculated electron density of states for Fe was similar to the result of band calculation. The cluster used for calculation of electronic states of ${\gamma}'-Fe_4N$ was based on $Fe_{14}N$ cluster which comprises 15 atoms. Finally the electronic states of ${\gamma}'- Fe_4N$ such as net-charge, band order, energy level, electron wave-function, and contour map for electron density were derived by the calculation.

• 천문학회지
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• 제2권1호
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• pp.1-9
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• 1969

On the instantaneous tidal relaxation approximation, formulae are derived for the ellipticities and virial theorem of a slightly flattened homogeneous rotating cluster (the largest axis of the cluster is directed towards the Galactic center), in terms of the Galactic tidal force and the characteristic intrinsic plus orbital angular velocity. The expression for a purely tidally-determined ellipticity is identical to that for an incompressible fluid body of uniform density. Orbital motion generally contributes significantly to the shape of the cluster. The virial theorem is identical to that for an isolated cluster except that the gravitational potential energy is multiplied by (1-${\chi}$), where ${\chi}$ is a positive tidal correction term. To obtain the actual mass of a cluster, the virial theorem mass based on an isolated cluster should be multiplied by the factor 1/(1-${\chi}$). The formulae are applied to open star clusters, the globular cluster ${\omega}$ Centauri, and dwarf elliptical galaxies in the Local Group.