• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.567-575
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• 2001

A methodology is developed for designing the minimum-cost water distribution network. The method is based on network simulations and an optimization scheme using genetic algorithms. Being a stochastic optimization scheme, genetic algorithms have advantages over the conventional search algorithms in solving network problems known for their nonlinearities and herculean computational costs. While existing methods focus on the design of either entirely new or parallel augmentation of network systems, the proposed method can be applied to problems having both new branches of tree-type and paralle augmentation in loops. The applicability of the method was shown through a case study for Baekryeon water supply system. The optimized design resulted in the maximum 5.37% savings compared to the conventional design without optimization, while meeting the hydraulic constraints.

• The KIPS Transactions:PartD
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• v.12D no.6 s.102
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• pp.915-920
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• 2005

In this paper we expanded a existing web based B2B system to support users in low speed network. To guarantee shared dat a consistency between clients and a server, we proposed a method of data change detection by using a time stamp tree and the performance analysis of the proposed method was proved by a simulation. Under the worst condition that leaf nodes of a times tamp tree were changed uniform distribution, the simulation result showed that the proposed method was more efficient than a sequential detection until the percentage of changed nodes were below $15\%$. According to our observation, the monthly average of data change was below $7\%$ on a web-based construction MRO B2B system or a company A from April 2004 to August 2004. Therefore the Proposed method improved performance of data change detection in practice. The proposed method also reduced storage consumption in a server because it didn't require a server to store replicated data for every client.

• Journal of KIISE:Information Networking
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• v.36 no.5
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• pp.437-455
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• 2009

In the near future, various multicast based services will be provided over clustered wireless networks. To provide multicast services in secure manner, multicast messages are encrypted by using group key which is shared by group members. Therefore, various group key management schemes have been introduced until now. Among them, tree based approach is one of the most representative paradigms in group key management. Traditional tree based approaches effectively reduce rekeying message transmissions of the key distribution center. However, they do not consider the network bandwidth used for transmitting the rekeying messages. In this paper, we firstly present formulas that describe bandwidth consumption of tree based group key management scheme. Based on our formulations, we propose a bandwidth efficient key tree management scheme for clustered wireless networks where membership changes occur frequently. Simulation results show that our scheme effectively reduces the bandwidth consumption used for rekeying compared to existing key tree schemes.

• The Korean Journal of Quaternary Research
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• v.21 no.1
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• pp.15-26
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• 2007

A wide tree-ring data network from Western Himalayan region as well as from Central and Peninsular India have been established by the Indian Institute of Tropical Meteorology (IITM), Pune, India. This includes several ring width and density chronologies of Himalayan conifers (Pinus, Picea, Cedrus, Abies)covering entire area of Western Himalaya and teak (Tectona grandis L.F.) from central and peninsular India. Many of these chronologies go back to $15^{th}$ century. Tree-ring based reconstructed pre-monsoon (March-April-May) summer climate of Western Himalaya do not show any significant increasing or decreasing trend since past several centuries. High altitude tree-ring chronologies near tree line-glacier boundary are sensitive to the winter temperature. Unprecedented higher growth in recent decades is closely associated with the warming trend over the Himalayan region. Dendroclimatic analysis of teak (Tectona grandis) from Central and Peninsular India show significant relationship with pre-monsoon and monsoon climate. Moisture index over the region indicates strong association with tree-ring variations rather than the direct influence of rainfall. It is evident that, two to three consecutive good monsoon years are capable of maintaining normal or above normal tree growth, even though the following year is low precipitation year.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.4
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• pp.51-69
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• 1997

Recently Lee et al[5] developed an approximation algorithm for the performance evaluation of the open queueing networks with blocking. This algorithm, which solves the exponential queueing networks with general configuration is developed based on the symmetrical decomposition approach and is reported to have many advantages over the previous algorithmsf. In addition to being very accurate, this algorithm is reported to be quite simple, pretty fast and solves very general configurations. In this study, we show that if a network has a tree-like configurations, the algorithm developed by Lee at al, always converges to the unique solution. To prove the theoretical results pertaining to the algorithm, some properties associated with symmetrical decomposition approach are exploited. The results obtained in this study such as the proofs of convergence of the algorithm as well as uniquences of the solution would contribute to the theoretical study for the non-tandem configurating of open queueing network.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2936-2938
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• 2005

The deployment of multicast communication services in the internet is expected to lead a stable packet transfer even in heavy traffic as in network system environment. The core based tree scheme among many multicast protocols is the most popular and suggested recently. However, CBT exhibit two major deficiencies such as traffic concentration or poor core placement problem. so, measuring the bottleneck link bandwidth along a path is important for understanding th performance of multicast. We propose not only a definition of CBT's core link state that Steady-State, Normal-State and Bottleneck State according to the estimation link speed rate, but also the changeover of multicast routing scheme for traffic overload. In addition, we introduce anycast routing tree, a efficient architecture for construst shard multicast trees.

• Environmental Engineering Research
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• v.14 no.2
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• pp.102-110
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• 2009

Application of artificial intelligence (AI) approaches in eco-environmental modeling has gradually increased for the last decade. Comprehensive understanding and evaluation on the applicability of this approach to eco-environmental modeling are needed. In this study, we reviewed the previous studies that used AI-techniques in eco-environmental modeling. Decision Tree (DT) and Artificial Neural Network (ANN) were found to be major AI algorithms preferred by researchers in ecological and environmental modeling areas. When the effect of the size of training data on model prediction accuracy was explored using the data from the previous studies, the prediction accuracy and the size of training data showed nonlinear correlation, which was best-described by hyperbolic saturation function among the tested nonlinear functions including power and logarithmic functions. The hyperbolic saturation equations were proposed to be used as a guideline for optimizing the size of training data set, which is critically important in designing the field experiments required for training AI-based eco-environmental modeling.

• Nuclear Engineering and Technology
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• v.40 no.5
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• pp.375-386
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• 2008

Conventional static reliability analysis methods are inadequate for modeling dynamic interactions between components of a system. Various techniques such as dynamic fault tree, dynamic Bayesian networks, and dynamic reliability block diagrams have been proposed for modeling dynamic systems based on improvement of the conventional modeling methods. In this paper, we review these methods briefly and introduce dynamic nodes to the existing reliability graph with general gates (RGGG) as an intuitive modeling method to model dynamic systems. For a quantitative analysis, we use a discrete-time method to convert an RGGG to an equivalent Bayesian network and develop a software tool for generation of probability tables.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.5
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• pp.241-247
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• 2001

Network reconfiguration in distribution systems is realized by changing the status of sectionalizing switches, and is usually done for loss reduction of load balancing in the system. This paper presents an effective heuristic based switching scheme to solve the distribution feeder loss reduction problem. The proposed algorithm consists of two parts. One is to set up a decision tree to represent the various switching operations available. Another is to apply a proposed technique called cyclic best first search. the proposed algorithm identify the most effective the set of switch status configuration of distribution system for loss reduction. To demonstrate the validity of the proposed algorithm, numerical calculations are carried out the 32, 69 bus system models.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.2 no.1
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• pp.32-41
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• 2021

South Korea presently harbors less than 800 long-tailed gorals (Naemorhedus caudatus), an endangered species. I report for the first time on the taxonomic status and genetic diversity of the Korean species using non-invasive fecal sampling based on mitochondrial cytochrome b gene sequence analyses. To determine the taxonomic status of this species, I reconstructed a consensus neighbor-joining tree and generated a minimum spanning network combining haplotype sequences obtained from feces with a new goral-specific primer set developed using known sequences of the Korean goral and related species (e.g., Russian goral, Chinese goral, Himalayan goral, Japanese serow, etc.). I also examined the genetic diversity of this species. The Korean goral showed only three different haplotypes. The phylogenetic tree and parsimony haplotype network revealed a single cluster of Korean and Russian gorals, separate from related species. Generally, the Korean goral has a relatively low genetic diversity compared with that of other ungulate species (e.g., moose and red deer). I preliminarily showcased the application of non-invasive fecal sampling to the study of genetic characteristics, including the taxonomic status and genetic diversity of gorals, based on mitochondrial DNA. More phylogenetic studies are necessary to ensure the conservation of goral populations throughout South Korea.