• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3377-3395
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• 2015

Recently, several approaches to share road conditions and/or digital contents through VANETs have been proposed, and such approaches have generally considered the radial distance from the information source as well as the TTL to provision an ephemeral, geographically-limited information sharing service. However, they implement general MANETs and have not been tailored to the constrained movement of vehicles on roads that are mostly linear. In this paper, we propose a novel application-level mechanism that can be used to share road conditions, including accidents, detours and congestion, through a VANET. We assign probabilities to roads around each of the intersections in the neighborhood road network. We then use the graph representation of the road network to build a spanning tree of roads with the information source as the root node. Nodes below the root represent junctions, and the edges represent inter-connecting road segments. Messages propagate along the branches of the tree, and as the information propagates down the branches, the probability of replication decreases. The information is replicated until a threshold probability has been reached, and our method also ensures that messages are not delivered to irrelevant vehicles, independently of their proximity to the source. We evaluated the success rate and performance of this approach using NS-3 simulations, and we used IDM car following and MOBIL lane change models to provide realistic modeling of the vehicle mobility.

• Journal of information and communication convergence engineering
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• v.17 no.4
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• pp.246-254
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• 2019

This paper proposes a solution to the problem of finding a subgraph for a given instance of many terminals on a Euclidean plane. The subgraph is a tree, whose nodes represent the chosen terminals from the problem instance, and whose edges are line segments that connect two corresponding terminals. The tree is required to have the maximum number of nodes while the length is limited and is not sufficient to interconnect all the given terminals. The problem is shown to be NP-hard, and therefore a genetic algorithm is designed as an efficient practical approach. The method is suitable to various probable applications in layout optimization in areas such as communication network construction, industrial construction, and a variety of machine and electronics design problems. The proposed heuristic can be used as a general-purpose practical solver to reduce industrial costs by determining feasible interconnections among many types of components over different types of physical planes.

• The Korean Journal of Quaternary Research
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• v.17 no.2
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• pp.55-61
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• 2003

In the year 2000 we culminated a successful five year investigation of climate change by completing a preliminary east-west transect across Mongolia. An earlier tree-ring study at Tarvagatay Pass, Mongolia indicated unusual warming during the 20th century similar to other paleo-investigations of the northern hemisphere. This record had represented one of the few tree-ring records for central Asia. New data from several sites in western Mongolia confirmed the preliminary temperature. The highest twenty-year growth period for the composite record is from 1973-1994. The western Mongolian record was significantly correlated with the Taimyr Peninsula and two northern hemisphere temperature reconstructions reflecting large-scale temperature patterns while showing some important regional differences. These differences should prove useful for climate models. We have also developed a millennial length temperature-sensitive record at the Solongotyin Davaa site (formerly Tarvagatay Pass) using relict wood and living trees. Conspicuous features over the last 1000 years are a century scale temperature decline punctuated by the end of the Little Ice Age in the late-1800s and 20th century warming. The record also shows a cold period early in the 12th century and warm intervals late in the 10th, early in the 15th and at end of the 18th centuries. Despite a limited sample size before 900 AD, the long Solongotyin Davaa record is useful in indicating severe cold events and suggests some cold intervals nearly as severe. These tree ring series, spanning much of the circumpolar northern treeline, have been compiled to create a long-term reconstruction of the Earth's temperature over centuries. The new chronology, in addition to its value as a detailed record of Mongolian climate, provides independent corroboration for such hemispheric and global reconstructions and their indications of unusual warming during the 20th century.

• The KIPS Transactions:PartA
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• v.14A no.5
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• pp.317-326
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• 2007

We propose more enhanced heuristic for the GOSST(Grade of Services Steiner Minimum Tree) problem in this paper. GOSST problem is a variation of Steiner Tree problem and to find a network topology satisfying the G-Condition with minimum network construction cost. GOSST problem is known as one of NP-Hard or NP-Complete problems. In previous our research, we proposed a heuristic employing Direct Steiner Point Locating strategy with Distance Preferring MST building strategy. In this paper, we propose new Steiner point locating strategy, Zigzag Steiner point Locating strategy. Through the results of out experiments, we can assert this strategy is better than our previous works. The Distance Zigzag GOSST method which hires the Distance Preferring MST building strategy and Zigzag Steiner point Locating strategy defrays the least network construction cost and brings 31.5% cost saving by comparison to G-MST, the experimental control and 2.2% enhancement by comparison to the Distance Direct GOSST method, the best GOSST method in our previous research.

• The KIPS Transactions:PartC
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• v.12C no.1 s.97
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• pp.105-110
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• 2005

With the proliferation of multimedia group applications, the construction of multicast trees satisfying QoS requirements is becoming a problem of prime importance. In this paper, we study the delay- and delay variation-bounded multicast tree (DVBMT) problem which is NP-complete. The problem is to construct a spanning tree for destination node, which has the minimized multicast delay variation, and the delay on the path from the source to each destination is bounded. A solution to this problem is required to provide decent real-time communication services such as on-line games, shopping, and teleconferencing. Performance comparison shows that the proposed scheme outperforms DDVCA which is known to be effective so far in any network topology. The enhancement is up to about $3.6{\%}{\~}11.1{\%}$ in terms of normalized surcharge for DUVCA. The time complexity of our algorithm is $O(mn^2)$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.346-353
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• 2011

Routing schemes that service applications with various delay times, maintaining the long network life time are required in wireless sensor & actor networks. However, it is known that network lifetime and hop count of trees used in routing methods have the tradeoff between them. In this paper, we propose a Pareto Ant Colony Optimization algorithm to find the Pareto tree set such that it optimizes these both tradeoff objectives. As it enables applications which have different delay times to select appropriate routing trees, not only satisfies the requirements of various multiple applications but also guarantees long network lifetime. We show that the Pareto tree set found by proposed algorithm consists of trees that are closer to the Pareto optimal points in terms of hop count and network lifetime than minimum spanning tree which is a representative routing tree.

• The KIPS Transactions:PartC
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• v.15C no.4
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• pp.273-280
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• 2008

In WSN(Wireless Sensor Network) many routing algorithms such as LEACH, PEGASIS and PEDEP consisting of sensor nodes with limited energy have been proposed to extend WSN lifetime. Under the assumption of perfect fusion, these algorithms used convergecast that periodically collects sensed data from all sensor nodes to a base station. But because these schemes studied less energy consumption for a convergecast as well as fairly energy consumption altogether, the minimum energy consumption for a convergecast was not focused enough nor how topology influences to energy consumption. This paper deals with routing topology and energy consumption for a single convergecast in the following ways. We chose major WSN topology as MSC(Minimum Spanning Chain)s, MSTs, PEGASIS chains and proposed LECSEN chains. We solved the MSC length by Linear Programming(LP) and propose the LECSEN chain to compete with MST and MSC. As a result of simulation by Monte Carlo method for calculation of the topology length and standard deviation of link length, we learned that LECSEN is competitive with MST in terms of total energy consumption and shows the best with the view of even energy consumption at the sensor nodes. Thus, we concluded LECSEN is a very useful routing topology in WSN.

• 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.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1144-1147
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• 2009

멀티미디어의 방송 서비스 제공하기 위해서 IP 멀티캐스트의 대안으로써 현재의 인터넷 환경에서도 동시 접속자 수의 제한과 자원 낭비 문제를 효과적으로 해결할 수 있는 다양한 오버레이 멀티캐스트 기법이 제시되고 있다. 본 논문에서는 멀티미디어의 방송 서비스 제공을 위한 병렬 미디어 스트리밍 서버(PMSS : Parallel Media Streaming Server)시스템에 대해 알아보고 오버레이 멀티캐스트 트리 구성 방안으로 분산형 Tree-First 기반의 Spanning tree 구조의 하나인 TBCP기법에 대해 설명하고, TBCP기법의 한계점을 극복하기 위한 오버레이 멀티캐스트 기반의 알고리즘 적용한 효율적이고 향상된 성능을 제공하는 miniOverlay Broadcasting Control Protocol (mOBCP)에 대해 알아본다. 또 제안한 mOBCP 멀티캐스트 기법을 기반으로 PMSS를 이용하여 오버레이 방송 서비스를 제공하는 방안에 제시한다. 성능 비교는 Single 서버와 PMSS로 멀티미디어 방송 서비스를 제공했을 때의 지연시간(Latency)를 비교해 보고 mOBCP기법과 TBCP기법을 PMSS 시스템에서 적용하여 사용자 요구량에 따른 서비스 받는대 걸리는 지연시간을 비교함으로써 제안된 기법의 효율성을 보여주고 있다.

• Journal of KIISE:Information Networking
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• v.27 no.4
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• pp.531-543
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• 2000

본 논문에서는 ATM PNN망에서 경로 배정을 위해 필요로하는 링크상태 정보를 효율적으로 집단화하는 방법을 제시한다. 이 방법은 집단화할 동료 그룹을 효율적으로 집단화하는 방법을 제시한다. 이방법은 집단화할 동료그룹의 경계노드들을 셔플넷의 노드들로 사상시킴으로써 표현해야 할 링크의 수를 완전 그물망 방법의 $N_2$에서 pN(p는 정수 N는 경계노드수)으로 줄인다 이는 공간 복잡도가 O(N)인 신장트리(spanning tree)방법에서 필요로 하는 링크의 수와 비슷하지만 신장 트리방법과는 달리 비대칭망(asymmetric network)에서 사용할 수 있다는 것이 큰 장접이다. 모의 실험결과 셔플넷 방법은 pNro의 링크만을 표현하면서도 상태 정보의 정확성은 완전 그물망 방법에 근접함을 알 수 있었다.