• Title/Summary/Keyword: Cluster density

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A Lattice Model Based on Molecular Clusters for Supercritical Fluids (초임계 유체를 위한 분자 클러스터 기반의 격자모델)

  • Shin, Moon-Sam
    • Proceedings of the KAIS Fall Conference
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    • 2010.05b
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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.

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Analytic Solutions of Finite F.C.C. Metal Clusters with Cluster Orbitals

  • Juhyeok Lee;Geun Ha Ryu;Hojing Kim
    • Bulletin of the Korean Chemical Society
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    • v.14 no.1
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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.

A Cluster Head Selection Algorithm Adopting Sensor Density on Wireless Sensor Networks (무선 센서 네트워크상에서 센서간의 밀도를 고려한 클러스터 헤드 선정 알고리즘)

  • Jung, Eui-Hyun;Lee, Sung-Ho;Park, Yong-Jin;Hwang, Ho-Young;Hur, Moon-Haeng
    • The KIPS Transactions:PartC
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    • v.13C no.6 s.109
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    • pp.741-748
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    • 2006
  • Due to the continuous development of sensor technology, Wireless Sensor Networks are rapidly growing and are expected to be applied to various applications. One of the most important factors in Wireless Sensor Networks is energy-efficient management of network resources. For this purpose, a lot of researches have been ongoing in the development of energy-efficient routing protocol. In this paper, a cluster head selection algorithm considering node density in addition to the cluster head selection algorithm of LEACH-C is proposed and simulated. This algorithm gives nearly the same computational speed compared to that of LEACH-C and shows improvement of network lifetime about 11% better than LEACH-C. The simulation result shows that consideration of density as well as distance between nodes in cluster head selection can be more energy-efficient than considering only the distance between nodes as LEACH-C in energy usage of Wireless Sensor Networks.

Efficient Flooding in Ad hoc Networks using Cluster Formation based on Link Density (애드 혹 네트워크에서 링크밀도기반 클러스터 구축을 이용한 효율적인 플러딩)

  • Lee, Jae-Hyun;Kwon, Kyung-Hee
    • The KIPS Transactions:PartC
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    • v.14C no.7
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    • pp.589-596
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    • 2007
  • Although flooding has the disadvantages like a transmission of duplicated packets and a packet collision, it has been used frequently to find a path between a source and a sink node in a wireless ad hoc network. Clustering is one of the techniques that have been proposed to overcome those disadvantages. In this paper, we propose a new flooding mechanism in ad hoc networks using cluster formation based on the link density which means the number of neighbors within a node's radio reach. To reduce traffic overhead in the cluster is to make the number of non-flooding nodes as large as possible. Therefore, a node with the most links in a cluster will be elected as cluster header. This method will reduce the network traffic overhead with a reliable network performance. Simulation results using NS2 show that cluster formation based on the link density can reduce redundant flooding without loss of network performance.

A Benthic Polychaete Assemblage off the Korean South Coast(Gwangyang Bay and Yeosu Sound)

  • Kim, Yong-Hyun;Shin, Hyun-Chool
    • Fisheries and Aquatic Sciences
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    • v.13 no.2
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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.

A Clustering Scheme to Prolong Lifetime of Wireless Sensor Networks (무선 센서 네트워크의 수명연장을 위한 클러스터링 기법)

  • Park, Si-Yong;Cho, Hyun-Sug
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.17 no.4
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    • pp.996-1004
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    • 2013
  • In this paper, we propose two clustering schemes to prolong lifetime by improving unbalance of energy consumption among sensor nodes in wireless sensor networks. The first proposed scheme make up clusters according to density of sensor nodes in initial stage of wireless sensor networks for reducing energy consumption of wireless sensor networks. After the initial stage, a cluster header is selected by a relay scheme that determines a cluster header of next round among cluster members. by estimating of energy consumption of cluster members for improving unbalance of energy consumption among cluster members.

GALAXY LUMINOSITY FUNCTION OF THE ABELL 119 CLUSTER

  • Lee, Youngdae;Hilker, Michael;Rey, Soo-Chang
    • The Bulletin of The Korean Astronomical Society
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    • v.38 no.1
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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.

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A DFT Study on Alkali and Alkaline Earth Metal Encapsulated Fullerene-Like BeO Cluster

  • Ravaei, Isa;Beheshtian, Javad
    • Journal of the Korean Chemical Society
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    • v.61 no.6
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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.

Electronic States Calculation of Fe4N by DV-Xα cluster calculation (DV-Xα 클러스터 계산법에 의한 Fe4N의 전자상태계산)

  • Song, Dong-Won;Lee, In-Seop;Bae, Dong-Su
    • Korean Journal of Materials Research
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    • v.12 no.1
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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.

The Shape and Virial Theorem of a Star Cluster in the Galactic Tidal Force Field

  • Lee, See-Woo;Rood, Herbert J.
    • Journal of The Korean Astronomical Society
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    • v.2 no.1
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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.

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