• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.343-355
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• 2015

There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M_⊙). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

• The KIPS Transactions:PartA
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• v.14A no.1 s.105
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• pp.1-14
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• 2007

MPICH-G2 is an MPI implementation to solve complex computational problems by utilizing geographically dispersed computing resources in grid environments. However, the computation nodes in MPICH-G2 are exposed to the external network due to the lack of supporting the private IP clusters, which raises the possibility of malicious security attacks. In order to address this problem, we propose MPICH-GP with a new relay scheme combining NAT(Network Address Translation) service and an user-level proxy. The proxy running on the front-end system of private IP clusters forwards the incoming connection requests to the systems inside the clusters. The outgoing connection requests out of the cluster are forwarded through the NAT service on the front-end system. Through the connection path between the pair of processes, the requested MPI jobs can be successfully executed in grid environments with various clusters including private IP clusters. By simulations, we show that the performance of MPICH-GP reaches over 80% of the performance of MPICH-G2, and over 95% in ease of using RANK management method.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.235-242
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• 2015

Social network technology has been increasing interest in the big data service and development. However, the data stored in the distributed server and not on the central server technology is easy enough to find and extract. In this paper, we propose a big data management techniques to minimize the processing time of information you want from the content server and the management server that provides big data services. The proposed method is to link the in-group data, classified data and groups according to the type, feature, characteristic of big data and the attribute information applied to a hash chain. Further, the data generated to extract the stored data in the distributed server to record time for improving the data index information processing speed of the data classification of the multi-attribute information imparted to the data. As experimental result, The average seek time of the data through the number of cluster groups was increased an average of 14.6% and the data processing time through the number of keywords was reduced an average of 13%.

• Journal of the Korean Magnetics Society
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• v.2 no.2
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• pp.91-98
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• 1992

In a $Co_{67}Fe_{4.5}Nb_{2}Si_{10}B_{15}$ amorphous alloy ribbon the effect to two-step annealing on the soft magnetic properties has been studied. By two-step annealing method which the second annealing at low temperature of $310^{\circ}C$ for 2 hours is undertaken after the primary annealing at high temperature above $480^{\circ}C$ for 20 minutes at the vacuum state, the coercive force and the squareness are not changed nearly but the initial permeability at d.c. and the effective permeability at a.c. are remark-ably increased compared with the one-step annealing. The maxima of the initial permeability and the effective permeability at 1 kHz after the two-step annealing are 290,000 and 41,000, respectively, which are 30% higher than those of the one-step annealing. The change of magnetic properties with annealing temperature is discussed in terms of the residual stress, the domain size, the cluster and the crystalline phase.

• Journal of Digital Convergence
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• v.11 no.10
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• pp.387-394
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• 2013

Data mining is the process of discovering hidden, non-trivial patterns in large amounts of data records in order to be used very effectively for analysis and forecasting. Because hundreds of variables give rise to a high level of redundancy and dimensionality with time complexity, they are more likely to have spurious relationships, and even the weakest relationships will be highly significant by any statistical test. Hence cluster analysis is a main task of data mining and is the task of grouping a set of objects in such a way that objects in the same group are more similar to each other than to those in other groups. In this paper system implementation is of great significance, which defines a new definition based on information-theoretic entropy and analyse the analogue behaviors of objects at hand so as to address the measurement of uncertainties in the classification of categorical data. The sources were taken from a survey aimed to identify of job guidance from students in high school pyeongtaek. we show how variable precision information-entropy based rough set can be used to group student in each section. It is proved that the proposed method has the more exact classification than the conventional in attributes more than 10 and that is more effective in job guidance for students.

• Journal of Digital Convergence
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• v.11 no.10
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• pp.419-429
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• 2013

The Wireless sensor network(WSN) consisting of a large number of sensors aims to gather data in a variety of environments. The sensor nodes operate on battery of limited power. so, To extend network life time is major goals of research in the WSN. In this paper, we state the key point of a energy consumption with minimum&load balancing. The proposed protocol guarantee balance of number of cluster member nodes using the node memory threshold and optimization of distribution of cluster head using the optimized clustering method. The results show that the proposed protocol could support the load balancing and high energy efficiency by distributing the clusters with a reasonable number of member nodes. The simulation results show that our schme ensure longer life time in WSN as compare with existing schemes such as LEACH and CBLM.

• Korean Journal of Environment and Ecology
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• v.11 no.4
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• pp.397-406
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• 1998

To investigate the structure and the conservation strategy of natural forest at Taech'ongbong-Hangyeryong Area in Soraksan. 45 plots(20m*20m) set up with random sampling method were surveted. Four groups - Quercus mongolica - Acer pseudosieboldianum community, Avies nephrolepis - Tilia amurensis - Quercus mongolica community, Abies nephrolepis - Taxus cuspidata community, Abies nephrolepis - Qurecusmongolica community - were classified by cluster analysis. High positive correlations were proved between Abies nephrolepis and Betula ermanii; Abies nephrolepis and Pinus pumila; Aies nephrolepis and Rhododendron mucronulatum var. ciliatum; Betula ermanii and Pinus pumila; Betula ermanii and Rhododendron mucronulatum var. ciliatum; Pinus pumila and Rhododendron mucronulatm var. ciliatum; Quercus mongolica and Rhododendron schlippenbachii; Quercus mongolica and Qeigela subsessilis; Euonymus macroptera and Syringa reticulata; Euonymus macroptera and Viburnum wrightii; Acer ukurunduense and Euonymus oxyphyllus, and high nagative correlations were proved between Betula ermanii and Acer pseudosieboldianum; Quercus mongolica and Tripterygium regelii; Rhododendron schlippenbachii and Tripterygium regelii; Carpinus cordata and Acer pseudosieboldianum. Species diversity(H') of investigated area was calculated 2.1352~2.8016.

• Korean Journal of Environment and Ecology
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• v.7 no.2
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• pp.155-163
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• 1994

To investigate the structure and the conservation strategy of natural forest at Paekryunsa-Hyangcho kpong area in Tokyusan, 21 plots (400$m^2$) set up with random sampling method. Four groups were classified by cluster analysis. High positive correlations was proved between Tripterygium regelii and Acer tschonoskii var. rubripes, Viburnum sargentii and Betula ermanii, Corylus heterophylla var. thunbergii and Stephanandra incisa, Betula costata and Cornus controversa, Acer mono and Tilia amurensis, Tilia amurensis and Kalopanax pictum, Lonicera maackii and Viburum sargentii, and Betula ermanii, Acer tschonoskii var. rubripes and Taxus cuspidata, and Viburnum sargentii, and High negative correlations was proved between Acer pseudo-sieboldianum and Viburnum sargentii, Tripterygium regelii and Stephanandra incisa, Acer tschonoskii var. rubripes, and Stephanandra incisa. Species diversity(H') of investigated area was calculated 0.9402~1.2473. Taxus cuspidata, Betula ermanii and Abies koreana at Hyangchokpong area in Tokyusan should be conserved.

• Korean Journal of Environment and Ecology
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• v.10 no.1
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• pp.151-159
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• 1996

To investigate the structure and the conservation strategy of natural forest at Sangwonsa, Pirobong, Horyongbong area in Odaesan, 23 plots(20*20m) were set up with random sampling method. Three groups were classified by cluster analysis; Quercus mongolica-Abies holophylla community, Acer mandshuricum- Abies nephrolepis community, and A. holophylla-Ulmus laciniata community. High positive correlations were proved betwween Tilia amurensis and Acer mono; Sorbus commixta and Euonymus macropterus, Betula ermanii, and Viburnum sargentii; E. macropterus and V. sargentii; B. ermanii and V. sargentii; A. mephrolepis and Syringa velutina var. kamibayashii; S. velutina var. kamibayashii and Salix hulteni; Pinus densiflora and A. holophylla. High negative correlations were proved between Q. mongolica and Juglans mandhuricum; Sasa vorealis and E. macropterus; Acer mono and Philadelphus schenckii; A. holophylla and E. macropterus, B. ermanii, S. velutina var. kamibayashii, and Salix hulteni. Species diversity(H') of investigated area was 1.2973~1.46331.

• Korean Journal of Environment and Ecology
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• v.10 no.1
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• pp.160-168
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• 1996

To investigate the structure and the conservation strategy of natural forest at Turobong-Sangwangbong area in Odaesan, 19 plots(10*10m) were set up with random sampling method. Several characteristics - needle injury, rate of fallen needle, stem injury, shoot and twig, apical dominance, tree form- of Abies nephrolepis and Tavus cuspidata were investigated with checklist. Two groups(Taxus cuspidata community and Quercus mongolica-Betula ermanii community) were classified by cluster analysis. High positive correlations were prover between Taxus cuspidata and Tripterygium regelii, Sorbus commixta; Quercus mongolica and Euonymus sieboldianus. High negative correlations were proved between Taxus cuspidata and Abies nephrolepis, Quercus mongolica and Betula ermanii; Abies nephrolepis and Trioterygum regelii. Species diversity(H') of investigated area was 0.9608-1.24990. Mean score of Abies nephrolepis was calculated at 6.1 point and ratio of dead individuals was 10.9%. Mean score of Taxus cuspidata was calculated at 17.3 point. Injury of Taxus cuspieata was classified three types, such as branch dieback, wound cavity on the stem and crooked stem.