• Journal of the Korean Data and Information Science Society
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• v.20 no.1
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• pp.11-24
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• 2009

The process controller in the adjustment procedure is often used effectively to control the process level close to target when noise is present and unremovable. Examples of the robust controller are single EWMA controller and double EWMA controller. Double EWMA controller is designed to reduce the offset of the process deviation, which single EWMA can not eliminate. In this paper, the two controllers are modified by taking EWMA of the original controller to reduce the adjustment variance, which may become excessively large when the two given controllers are implemented. It is shown that the EWMA modification of the given controllers is successful in reducing the adjustment variance, while the mean squared deviation increases slightly.

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.824-832
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• 2008

micellar solution which is comprised of surfactant monomers, monodisperse micelles, and solvent(water) is studied from a statistical-mechanical point of view. The model examined in this article is for the ideal mixture of monomers, micelles, and solvent with the dielectric constant identical to that of solvent, which is an assumption common to continuum models. The model also reflects interactions between monomer and solvent molecule, and also between micelle and solvent molecule. The statistical-mechanical model under consideration yields ln $X_{CMC}=A+BT+C/T+D{\ln}T$ with $X_{CMC}$ being critical mcielle concentration (in mole fraction), being temperature, and A, B, C, D being constants which depend on the properties of the surfactant molecules. The statistical-mechanical model discussed in this article provides a theoretical basis on the thermal dependence of critical micelle concentration

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.124-124
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• 2006

• Ceramist
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• v.12 no.3
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• pp.30-34
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• 2009

• The KIPS Transactions:PartC
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• v.13C no.4 s.107
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• pp.405-414
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• 2006

We present a symptom based taxonomy for network security. This taxonomy classifies attacks in the network using early symptoms of the attacks. Since we use the symptom it is relatively easy to access the information to classify the attack. Furthermore we are able to classify the unknown attack because the symptoms of unknown attacks are correlated with the one of known attacks. The taxonomy classifies the attack in two stages. In the first stage, the taxonomy identifies the attack in a single connection and then, combines the single connections into the aggregated connections to check if the attacks among single connections may create the distribute attack over the aggregated connections. Hence, it is possible to attain the high accuracy in identifying such complex attacks as DDoS, Worm and Bot We demonstrate the classification of the three major attacks in Internet using the proposed taxonomy.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.391-393
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• 2004

자바는 쓰레드 상호간의 동기를 프로그래밍 언어 자체의 기능으로 제공하고 있으므로 자바가 제공하는 동기화 메커니즘과 쓰레드는 병행처리를 수행하는 응용프로그램을 작성하는데 상당한 역할을 담당할 수 있다. 이에 따라, 병행처리와 관련된 자바의 기능을 분산된 컴퓨팅 환경에 적용하기 위한 많은 연구결과가 있다. 본 연구팀 에서는 자바 프로그램의 객체변환을 통하여 분산된 컴퓨팅 환경에서 동작하도록 지원하는 시스템을 발표한 바 있으나 분산처리와 관련된 기능을 지원하는 것으로 제한되었다. 병행처리를 수행하는 레거시 자바 프로그램을 분산된 컴퓨팅 환경에서 동작시키기 위하여 TORB(Transparent Object Request Broker)라고 명명된 이 시스템의 기능 확장을 시도하고 있으며 관련된 많은 문제들을 해결하였다. 본 논문에서는 서로 다른 컴퓨터에서 동시에 동작하는 자바 쓰레드간의 동기문제를 해결하기 위한 방안을 제시한다. 이는 단일 컴퓨팅 환경에서의 자바 동기화 메커니즘과 동일한 효과를 분산된 컴퓨팅 환경에서 얻을 수 있도록 지원하는 방안이며 TORB를 위하여 고안된 것이다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.427-429
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• 2001

인터넷을 기반으로 시스템의 규모가 점차 커짐에 따라 연합된 시스템으로 변화되고 있으며, 더 나아가서는 이러한 분산 시스템들이 모여 보다 광범위한 광역 분산처리 환경을 조성하고 있다. 이러한 환경을 이루어 수많은 객체들은 이름이나 속성에 의해 다양한 중복된 성질을 갖는다. 일반적인 객체들을 찾는 방법으로 객체의 이름에 따른 서비스가 대부분이다. 그러나 점차 객체가 갖는 서비스 내용(속성)을 이용하여 객체를 검색하는 메커니즘의 필요성이 높아지고 있다. 광역 분산처리 환경에서는 객체가 갖는 이름과 속성에 따라 네이밍과 트레이딩 기능을 모두 사용하여 사용자에게 투명한 서비스를 제공해야 한다. 따라서 본 논문에서는 광역 분산 환경에서 네이밍과 트레이딩 서비스의 기능을 혼합한 바인딩 서비스 모델을 제시한다. 이는 이름과 속성기반의 단일 객체뿐만 아니라 중복객체의 효과적인 탐색과 바인딩시 부하분배를 꾀하여 네트워크 상의 부하 균형화를 유지하도록 한다. 이를 위해, 먼저 분산 객체에 대한 모델을 제시하고, 이들을 바인eld 처리 방안 그리고 연합을 위한 모델을 보인다.

• Journal of Advanced Navigation Technology
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• v.17 no.1
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• pp.16-23
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• 2013

The effects of dispersion coefficient of dispersion compensating fiber (DCF) and residual dispersion per span (RDPS) on in the dispersion managed optical links for compensating the distorted 960 Gbps wavelength division multiplexd (WDM) signals due to group velocity dispersion (GVD) and optical nonlinear effects of single mode fiber (SMF) are investigated. It is confirmed that optimal net residual dispersion (NRD), which greatly affects compensating for optical signals, should be induced under the large launch power condition, irrelevant on the considered dispersion coefficient of DCF and RDPS. It is also confirmed that system performances are greatly improved by selecting the very small RDPS and very large dispersion coefficient of DCF.

• Journal of KIISE
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• v.43 no.10
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• pp.1131-1143
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• 2016

How can we effectively compress big graphs composed of billions of edges? By concentrating non-zeros in the adjacency matrix through vertex rearrangement, we can compress big graphs more efficiently. Also, we can boost the performance of several graph mining algorithms such as PageRank. SlashBurn is a state-of-the-art vertex rearrangement method. It processes real-world graphs effectively by utilizing the power-law characteristic of the real-world networks. However, the original SlashBurn algorithm displays a noticeable slowdown for large-scale graphs, and cannot be used at all when graphs are too large to fit in a single machine since it is designed to run on a single machine. In this paper, we propose a distributed SlashBurn algorithm to overcome these limitations. Distributed SlashBurn processes big graphs much faster than the original SlashBurn algorithm does. In addition, it scales up well by performing the large-scale vertex rearrangement process in a distributed fashion. In our experiments using real-world big graphs, the proposed distributed SlashBurn algorithm was found to run more than 45 times faster than the single machine counterpart, and process graphs that are 16 times bigger compared to the original method.

• The KIPS Transactions:PartA
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• v.13A no.7 s.104
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• pp.607-614
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• 2006

The checkpointing schemes should reduce the process delay through managing the checkpoints of each node to fit the network load to enhance the performance of the process running on the cluster system that write the checkpoints into its global stable storage. For this reason, a cluster system with single IO space on a distributed RAID chooses a suitable checkpointng scheme to get the maximum IO performance and the best rollback recovery efficiency. In this paper, we improved the striped checkpointing scheme with dynamic stripe group size by adapting to the network bandwidth variation at the point of checkpointing. To analyze the performance of the multi striped checkpointing scheme, we applied Linpack HPC benchmark with MPI on our own cluster system with maximum 512 virtual nodes. The benchmark results showed that the multistriped checkpointing scheme has better performance than the striped checkpointing scheme on the checkpoint writing efficiency and rollback recovery at heavy system load.