• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.610.2-610.2
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• 2006

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3439-3457
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• 2014

Clustering is an effective method for improving the performance of large scale mobile ad hoc networks. However, when the moving speed is very fast, the topology changes quickly, which leads to frequent cluster topology updates. The drastically increasing control overheads severely threaten the throughput of the network. SCBCS (Signal Characteristic Based Cluster Scheme) is proposed as a method to potentially reduce the control overheads caused by cluster formation and maintenance in aeronautical ad hoc networks. Each node periodically broadcasts Hello packets. The Hello packets can be replaced by data packets, which preserve bandwidth. The characteristics of the received packets, such as the Doppler shift and the power of two successive Hello packets, help to calculate the relative speed and direction of motion. Then, the link connection lifetime is estimated by the relative speed and direction of motion. In the clustering formation procedure, the node with the longest estimated link connection time to its one-hop neighbors is chosen as the cluster head. In the cluster maintenance procedure, re-affiliation and re-clustering schemes are designed to keep the clusters more stable. The re-clustering phenomenon is reduced by limiting the ripple effect. Simulations have shown that SCBCS prolongs the link connection lifetime and the cluster lifetime, which can reduce the topology update overheads in highly dynamic aeronautical ad hoc networks.

• 한국정보통신학회논문지
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• 제19권3호
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• pp.715-723
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• 2015

본 논문에서는 이동 에드혹 네트워크(Mobile Ad hoc Network: MANET)에서의 상황인식 기반의 스케쥴링 기법인 DDV(Dynamic Direction Vector)-hop알고리즘을 제안한다. 기존 MANET에서는 노드의 이동성으로 인한 동적 네트워크 토폴리지, 네트워크 확장성 결여의 대한 취약성을 지니고 있다. 본 논문에서는 계층적 클러스터 단위의 동적인 토폴로지에서 노드가 이동하는 방향성 및 속도에 대한 노드의 이동 속성 정보를 고려하여 클러스터를 생성 및 유지하는 DDV-hop 알고리즘을 제안한다. 제안된 알고리즘은 클러스터 헤드노드를 기준으로 클러스터 멤버노드의 방향성 및 속도의 속성 정보를 비교하여 유사한 노드간 클러스터링을 구성하고, 이로부터 헤드노드를 선택하는 방법이다. 실험결과, 제안하는 알고리즘이 네트워크의 부하를 감소시키고 네트워크 토폴로지를 안정적으로 유지할 수 있음을 확인하였다.

• 식물조직배양학회지
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• 제28권4호
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• pp.209-213
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• 2001

Spathiphyllum floribundum cv. Cupid를 기내에서 대량번식시키기 위하여 일련의 실험을 실시하였다. 신초경정을 LS배지에 TDZ (thidiazuron)와 BA (banzyladenine)가 첨가된 배지에서 배양한 결과, 신초의 증식 및 신초 cluster의 형성은 BA 2.0 mg/L 첨가배지에서 가장 양호하였다. 배지 내 BA와 PBZ (paclobutrazol)의 혼용첨가는 BA 단용첨가보다 신초증식 및 신초 cluster 형성을 촉진하였다. 형성된 신초 cluster를 5∼7 mm로 절단하여 BA또는 TDZ이 첨가된 배지에 배양하였다. BA 2.0∼3.0 mg/L가 첨가된 배지에서 신초수가 가장 많았으며 신초의 증식도 양호하였다. 형성된 신초 cluster 절편체 (5∼7mm)에서 신초의 신장 및 발근은 IBA 2.0∼3.0 mg/L 첨가배지에서 매우 양호하였다. 발근된 식물체는 vermiculite와 pelrlite가 1 : 1로 혼합된 용토에서 95% 이상 순화되었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3494-3510
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• 2019

Wireless sensor networks encounter energy saving as a major issue as the sensor nodes having no rechargeable batteries and also the resources are limited. Clustering of sensors play a pivotal role in energy saving of the deployed sensor nodes. However, in the cluster based wireless sensor network, the cluster heads tend to consume more energy for additional functions such as reception of data, aggregation and transmission of the received data to the base station. So, careful selection of cluster head and formation of cluster plays vital role in energy conservation and enhancement of lifetime of the wireless sensor networks. This study proposes a new mutation chemical reaction optimization (MCRO) which is an algorithm based energy efficient clustering protocol termed as MCRO-ECP, for wireless sensor networks. The proposed protocol is extensively developed with effective methods such as potential energy function and molecular structure encoding for cluster head selection and cluster formation. While developing potential functions for energy conservation, the following parameters are taken into account: neighbor node distance, base station distance, ratio of energy, intra-cluster distance, and CH node degree to make the MCRO-ECP protocol to be potential energy conserver. The proposed protocol is studied extensively and tested elaborately on NS2.35 Simulator under various senarios like varying the number of sensor nodes and CHs. A comparative study between the simulation results derived from the proposed MCRO-ECP protocol and the results of the already existing protocol, shows that MCRO-ECP protocol produces significantly better results in energy conservation, increase network life time, packets received by the BS and the convergence rate.

• 한국시스템다이내믹스연구
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• 제7권2호
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• pp.133-148
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• 2006

This study suggests a Causal Loop Diagram(CLD) of causality mechanism which are integrating matters of localization, networking, embeddedness & institutional thickness and collective learning. These five factors(localization, networking, embeddedness & institutional thickness, collective learning, innovative synergy) have been studied and proofed Also this study suggest a model of industry cluster based on holistic and global system thinking rather than local and linear thinking.

• 천문학회보
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• 제36권1호
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• pp.62.2-62.2
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• 2011

It is well known that the cluster environment can change the atomic gas properties of galaxies through tidal interactions and/or by the hot cluster medium. Meanwhile, the molecular gas is expected to be less vulnerable to its surroundings due to its higher density, and no obvious influence of the environment on the molecular gas properties had been found among cluster spirals until recently. However, in a recent study by Fumagalli et al. (2009) of a sub-sample of Virgo spirals, it has been suggested that HI deficient galaxies can be also CO deficient. In order to further investigate if the HI deficiency indeed can result in the deficiency in molecular gas content, we compare the global CO and HI gas properties of Virgo spirals with those of galaxies in the Ursa Major cluster and the Pisces cluster, much lower density environments than Virgo. We discuss possible consequences of molecular gas deficiency in star formation activity of spiral galaxies in high density environment.

• 천문학회지
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• 제38권2호
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• pp.173-174
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• 2005

On behalf of the IRSF/SIRIUS group, I introduce some recent results from our deep near-infrared surveys (J, Hand Ks bands, limiting magnitude of Ks=17) toward star forming regions in the Milky Way Galaxy (MWG) and Large Magellanic Cloud (LMC) with the near-infrared camera SIRIUS. We discovered a rich population of low-mass young stellar objects associated with the W3 and NGC 7538 regions in the MWG based on the near-infrared colors arid magnitudes. The high sensitivity of our survey enables us to detect intermediate-mass pre-main sequence stars, i.e. HAEBE stars, even in the LMC. We detected many HAEBE candidate stars in the N159/N160 complex star forming region in the LMC with the IRSF 1.4-m telescope. Spatial distributions of the young stellar objects indicate the sequential cluster formation in each star forming region in the complex and large scale (a few ${\times}$ 100 pc) sequential cluster formation over the entire complex.

• Bulletin of the Korean Chemical Society
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• 제22권8호
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• pp.897-902
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• 2001

The protein back-extraction processes were discussed from the viewpoint of the micelle-micelle interaction. Bovine serum albumin (BSA) suppressing the cluster formation of reverse micelle (positive value of ${\beta}pr)$ has the high back-extra cted fraction (Eb), but cytochrome c enhancing the formation of reverse micelle (negative value of ${\beta}pr)$ has the low back-extracted fraction, relatively. We have also examined quantitatively the effects of alcohol addition and protein solubilization on the percolation process of reverse micelle. The alcohols suppressing the formation of micellar cluster (high values of ${\beta}t)$, remarkably improved the back-extraction rates of BSA and cytochrome c. The values of ${\beta}t$, defined by the variation of percolation process, and the back-extraction behavior of proteins have a good linear correlation. These results indicate that the micelle-micelle interaction or micellar clustering plays an important role in the back-extraction process of proteins.

• 천문학회보
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• 제40권1호
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• pp.76.2-76.2
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• 2015

We present the results of the Westerbork Synthesis Radio Telescope (WSRT) HI imaging study of seven late-type galaxies. They are located in the outskirts of the Virgo cluster, possibly along a filament connected to Virgo from the north-west. Most galaxies in this region are found to be HI-rich, containing more HI gas compared to field galaxies with similar size and optical luminosity. The positions of the sample with respect to the cluster and their high HI mass-to-light ratios suggest that the selected galaxies might be accreting more gas from their surroundings while falling into the cluster. By high-resolution HI imaging, we aim to find evidence that galaxies are pre-processed by gas accretion from the intergalactic medium and/or gas-rich neighbors. We probe the detailed HI morphology/kinematics and the star formation properties of the sample. All of these galaxies are found with a large HI disk which is quite extended compared to their stellar disk. Together with kinematical peculiarities, this strongly suggests that cold gas accretion is responsible for active star formation in these galaxies.