• Journal of the Korean earth science society
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• v.34 no.1
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• pp.51-58
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• 2013

An appropriate determination of time step is one of the important problems in atmospheric modeling. In this study, we investigate the sensitivity of numerical solutions to time step in a nonlinear atmospheric model. For this purpose, a simple nondimensional dynamical model is employed, and numerical experiments are performed with various time steps and nonlinearity factors. Results show that numerical solutions are not sensitive to time step when the nonlinearity factor is not influentially large and truncation error is negligible. On the other hand, when the nonlinearity factor is large (i.e., in a highly nonlinear regime), numerical solutions are found to be sensitive to time step. In this situation, smaller time step increases the intensity of the spatial filter, which makes small-scale phenomena weaken. This conflicts with the fact that smaller time step generally results in more accurate numerical solutions owing to reduced truncation error. This conflict is inevitable because the spatial filter is necessary to stabilize the numerical solutions of the nonlinear model.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.75.2-75.2
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• 2010

We investigate the dependence of occurrence of bar in galaxies on galaxy properties and environment. The environmental conditions considered include the large-scale background density and distance to the nearest neighbor galaxy. We use a volume-limited sample of 33,296 galaxies brighter than $M_r$=-19.5+5logh at $0.02{\leqq}z{\leqq}0.05489$, drawn from the Sloan Digital Sky Survey Data Release 7. We classify the galaxies into early and late types, and identify bars by visual inspection. We find that the fraction of barred galaxies ($f_{bar}$) is 18.2% on average in the case of late-type galaxies, and depends on both u-r color and central velocity dispersion $(\sigma);f_{bar}$ is a monotonically increasing function of u-r color, and has a maximum value at intermediate velocity dispersion (${\sigma}{\simeq}170km\;s^{-1}$). This trend suggests that bars are dominantly hosted by systems having intermediate-mass with no recent interaction or merger history. We also find that $f_{bar}$ does not directly depend on the large-scale background density as its dependence disappears when other physical parameters are fixed. We discover the bar fraction decreases as the separation to the nearest neighbor galaxy becomes smaller than 0.1 times the virial radius of the neighbor regardless of neighbor's morphology. These results imply that it is difficult for bars to be maintained during strong tidal interactions, and that the source for this phenomenon is gravitational and not hydrodynamical.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.9
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• pp.503-513
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• 2002

Since CC-NUMA architecture has to access remote memory, the interconnection network determines the performance of the CC-NUMA system. Bus which has been used as a popular interconnection network has many limits in a large-scale system because of the limited physical scalability and bandwidth. The dual ring interconnection network, composed of high-speed point-to-point links, is made to resolve the defects of the bus for the large-scale system. However, it also has a problem, in that the response latency is rapidly increased when many nodes are attached to the snooping based CC-NUMA system with the dual ring. In this paper, we propose a ring architecture with repeater nodes in order to overcome the problem of the dual ring on a snooping based CC-NUMA system, and design a repeater node adapted to this architecture. We will also analyze the effects of proposed architecture on the system performance and the response latency by using a probability-driven simulator.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1307-1323
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• 2014

With the exhaustion of global IPv4 addresses, IPv6 technologies have attracted increasing attentions, and have been deployed widely. Meanwhile, new applications running over IPv6 networks will change the traditional traffic characteristics obtained from IPv4 networks. Traditional models obtained from IPv4 cannot be used for IPv6 network monitoring directly and there is a need to investigate those changes. In this paper, we explore the flow features of IPv6 traffic and compare its difference with that of IPv4 traffic from flow level. Firstly, we analyze the differences of the general flow statistical characteristics and users' behavior between IPv4 and IPv6 networks. We find that there are more elephant flows in IPv6, which is critical for traffic engineering. Secondly, we find that there exist many one-way flows both in the IPv4 and IPv6 traffic, which are important information sources for abnormal behavior detection. Finally, in light of the challenges of analyzing massive data of large-scale network monitoring, we propose a group flow model which can greatly reduce the number of flows while capturing the primary traffic features, and perform a comparative measurement analysis of group users' behavior dynamic characteristics. We find there are less sharp changes caused by abnormity compared with IPv4, which shows there are less large-scale malicious activities in IPv6 currently. All the evaluation experiments are carried out based on the traffic traces collected from the Northwest Regional Center of CERNET (China Education and Research Network), and the results reveal the detailed flow characteristics of IPv6, which are useful for traffic management and anomaly detection in IPv6.

• Journal of the Korean GEO-environmental Society
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• v.16 no.5
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• pp.43-53
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• 2015

In this study, detection methods of outlier in various monitoring data that fit into big data category were developed and outlier detections were conducted for both artificial data and real field monitoring data. Rule-based methods applied rate of change and probability of error for monitoring data are effective to detect a large-scale short faults and constant faults having no change within a certain period. There are however, problems with misjudgement that consider the normal data with a large scale variation as outlier caused by using independent single dataset. Rule-based methods for noise faults detection have a limit to application of real monitoring data due to the problem with a choice of proper window size of data and finding of threshold for outlier judgment. A correlation analysis among different two datasets were very effective to detect localized outlier and abnormal variation for short and long-term monitoring dataset if reasonable range of training data could be selected.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.6
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• pp.1197-1213
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• 2014

Due to the increase in size of the computer network, the network security systems such as a firewall, IDS, IPS generate much more vast amount of information related to network security. So detecting signs of hidden security threats has become more difficult. Security personnels' 'Network Security Situational Awareness(NSSA)' is effectively determining the security situation of overall computer network on the basis of the relation between the security events that occur in the several views. The process of situational awareness is divided into three stages of the 'identification,' 'understanding' and 'prediction'. And 'identification' and 'understanding' are prerequisites for 'predicting' and the following appropriate responses. But 'identification' and 'understanding' in the vast amount of information became more difficult. In this paper, we propose Honeycomb security situational awareness visualization system that is designed to help NSSA in large-scale networks by using visualization techniques known effective to the 'identification' and 'understanding' stages. And we identified the empirical effects of this system on the basis of the 'VAST Challenge 2012' data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.7
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• pp.1344-1356
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• 2009

The DDS (Data Distribution Service) is a data-centric communication technology that provides an efficient communication service that supports a dynamic plug & play through an automatic setting of participants' location information for each data (Topic) by using DDS discovery technique. This paper proposes the hierarchical-structured DDS discovery technique (SPDP-TBF) suitable for the large-scale distributed systems by comparing and analyzing the existing DDS discovery techniques in terms of performance and problem areas. The proposed SPDP-TBF performs the periodic discovery of the involved participants only by having separate hierarchical managers which take charge of the registration and search (of participants) so that a participant sends its information to the related participants only, and it enhances the effectiveness of the message transfer. Moreover, the proposed SPDP-TBF provides the improved scalability by performing the hierarchical discovery through hierarchical manager nodes so that it can be applied to the large-scale distributed system.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.2
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• pp.105-115
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• 2002

Since NUMA architecture has to access remote memory an interconnection network determines the performance of CC-NUMA system Bus which has been used as a popular interconnection network has many limits to build a large-scale system because of the limited physical scalabilty and bandwidth Dual ring interconnection network composed of high speed point-to-point links is made up for resolving the defects of the bus for large-scale system But it also has a problem that the response latency is rapidly increased when many node are attached to snooping based CC-NUMA system with dual ring In this paper we propose a chordal ring architecture in order to overcome the problem of the dual ring on snooping based CC-NUMA system and design and efficient link controller adopted to this architecture. We also analyze the effects of chordal ring architecture on the system performance and the response latency by using probability driven simulator.

• Animal cells and systems
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• v.5 no.2
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• pp.153-156
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• 2001

A key aspect of genomic research in the “post-genome era”is to associate sequence variations with heritable phenotypes. The most common variations in the human genome are single nucleotide polymorphisms (SNPs) that occur approximately once in every 500 to 1,000 bases. Although analyzing the phenotypic outcome of these SNPs is crucial to facilitate large-scale association studies of genetic diseases, detection of SNPs from an extended number of human DNA samples is often difficult, labor-intensive and time-consuming. Recent development in SNP detection methods using DNA microarrays and mass spectrophotometry has allowed automated high throughput analyses, but such equipments are not accessible to many scientists. In this study, we demonstrate that a simple PCR-based method using primers with a mismatched base at the 3'-end provides a fast and easy tool to identify known SNPs from human genomic DNA in a regular molecular biology laboratory. Results from this PCR amplification of specific alleles (PASA) analysis efficiently and accurately typed the Q576R polymorphism of human IL4 receptor from the genomic DNAs of 29 Koreans, including 9 samples whose genotype could not be discerned by the conventiona1 PCR-SSCP (single strand conformation polymorphism) method. Given the increasing attention to disease-associated polymorphisms in genomic research, this alternative technique will be very useful to identify SNPs in large-scale population studies.

• Journal of the Korean Society of Safety
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• v.38 no.2
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• pp.68-80
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• 2023

Cooperation between government agencies is important for disaster management, and a thorough and objective cause investigation is important to prevent the recurrence of similar disasters. In South Korea, individual laws are scattered by ministries according to the disaster type, and most are operated as non-permanent organizations that are employed when disasters occur. Although expertise is recognized for each disaster type, each government agency's operation method is different, so when a large-scale disaster involving multiple ministries occurs, there is a limit to the coordination of roles and integrated management between government agencies. In particular, whenever a large-scale complex disaster occurs, problems arise regarding the independence, professionalism, and fairness of the cause investigation. Therefore, to supplement this, reviewing the management methods and systems of disaster cause investigations in advanced countries is necessary. Thus, in this study, the organization status, manpower, organizational structure, and cause investigation work system of NTSB of the United States, JTSB of Japan, and SHK of Sweden are identified to improve the disaster cause investigation system in Korea and are compared and analyzed with Korea's GDCIG. Additionally, issues and problems for the advancement of Korea's disaster cause investigation system are considered and improvements are suggested.