• 한국경영과학회지
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• 제38권4호
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• pp.11-33
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• 2013

We analyzed the structures and properties of the global financial market networks using social network analysis approach. The Minimum Spanning Tree (MST) lengths and networks of the global financial markets based on the correlation coefficients have been analyzed. Firstly, similar to the previous studies on the global stock indices using MST length, the diversification effects in the global multi-asset portfolio can disappear during the crisis as the correlations among the asset class and within the asset class increase due to the system risks. Second, through the network visualization, we found the clustering of the asset class in the global financial markets network, which confirms the possible diversification effect in the global multi-asset portfolio. Meanwhile, we found the changes in the structure of the network during the crisis. For the last one, in terms of the degree centrality, the stock indices were the most influential to other assets in the global financial markets network, while in terms of the betweenness centrality, Gold, Silver and AUD. In the practical perspective, we propose the methods such as MST length and network visualization to monitor the change of the correlation risk for the risk management of the multi-asset portfolio.

• Journal of information and communication convergence engineering
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• 제13권1호
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• pp.7-14
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• 2015

In a multi-hop wireless network, connectivity is determined by the link that is established by the receiving signal strength computed by subtracting the path loss from the transmission power. Two path loss models are commonly used in research, namely two-ray ground and shadow fading, which determine the receiving signal strength and affect the link quality. Link quality is one of the key factors that affect network performance. In general, network performance improves with better link quality in a wireless network. In this study, we measure the network connectivity and performance in a shadow fading path loss model, and our observation shows that both are severely degraded in this path loss model. To improve network performance, we propose power control schemes utilizing link quality to identify the set of nodes required to adjust the transmission power in order to improve the network throughput in both homogeneous and heterogeneous multi-hop wireless networks. Numerical studies to evaluate the proposed schemes are presented and compared.

• Journal of Microbiology and Biotechnology
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• 제32권3호
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• pp.387-395
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• 2022

Deciphering the metabolites of human diseases is an important objective of biomedical research. Here, we aimed to capture the core metabolites of Fanconi anemia (FA) using the bioinformatics method of a multi-omics composite network. Based on the assumption that metabolite levels can directly mirror the physiological state of the human body, we used a multi-omics composite network that integrates six types of interactions in humans (gene-gene, disease phenotype-phenotype, disease-related metabolite-metabolite, gene-phenotype, gene-metabolite, and metabolite-phenotype) to procure the core metabolites of FA. This method is applicable in predicting and prioritizing disease candidate metabolites and is effective in a network without known disease metabolites. In this report, we first singled out the differentially expressed genes upon different groups that were related with FA and then constructed the multi-omics composite network of FA by integrating the aforementioned six networks. Ultimately, we utilized random walk with restart (RWR) to screen the prioritized candidate metabolites of FA, and meanwhile the co-expression gene network of FA was also obtained. As a result, the top 5 metabolites of FA were tenormin (TN), guanosine 5'-triphosphate, guanosine 5'-diphosphate, triphosadenine (DCF) and adenosine 5'-diphosphate, all of which were reported to have a direct or indirect relationship with FA. Furthermore, the top 5 co-expressed genes were CASP3, BCL2, HSPD1, RAF1 and MMP9. By prioritizing the metabolites, the multi-omics composite network may provide us with additional indicators closely linked to FA.

• 한국항행학회논문지
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• 제26권6호
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• pp.412-417
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• 2022

본 논문에서는 MATLAB GUI 기반으로 개발된 다중 위성군 network RTK MAC 보정정보 생성 소프트웨어에 대해서 소개한다. 해당 소프트웨어는 GPS와 GLONASS, Galileo를 포함한 다중 위성군의 보정정보를 생성하는 알고리즘의 유효성을 평가하기 위해 시뮬레이션 데이터 기반 후처리 소프트웨어로 개발되었다. 소프트웨어 구동 결과 다중 위성군의 시스템별 network RTK 보정정보가 MATLAB 파일 형식으로 출력된다. 본 논문에서는 개발된 소프트웨어의 성능을 평가하기 위해 소프트웨어를 통해 생성된 보정정보를 사용자에게 적용한 후 잔여 오차를 분석하였다. 분석 결과 사용자 잔여 오차의 크기가 10 cm 이하를 유지하는 것을 확인함으로써, 유효한 network RTK 보정정보 생성이 가능함을 확인하였다.

• 정보처리학회논문지C
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• 제13C권2호
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• pp.235-240
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• 2006

SCTP(Stream Control Transmission Protocol) 프로토콜의 '멀티홈잉(multi-homing)' 특성을 통해 SCTP 응용은 두 개 이상의 IP 주소를 통해 데이터를 전송할 수 있다. 본 논문에서는 리눅스 기반 테스트베드 환경에서 SCTP 멀티홈잉 특성이 처리율 성능에 미치는 영향을 분석한다. 실험을 위해 MSTNET 에뮬레이터를 활용하여 다양한 패킷손실율, 링크대역폭, 및 전송지연 환경을 구성하여 SCTP 처리율을 비교 분석 하였다. 실험 결과, 패킷 손실이 존재하는 망 환경에서 SCTP 멀티흠잉은 단일홈잉 경우에 비해 높은 성능을 보이며, 이는 SCTP 멀티홈잉에서 대체경로 재전송에 의한 효과로 볼 수 있다. 반면에, 링크대역폭 및 전송지연 요소는 상대적으로 SCTP 처리율 성능에 미치는 효과가 미미하였다.

• Journal of Information Processing Systems
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• 제18권1호
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• pp.159-172
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• 2022

The role of the interconnect network, which connects computing nodes to each other, is important in high-performance computing (HPC) systems. In recent years, the peripheral component interconnect express (PCIe) has become a promising interface as an interconnection network for high-performance and cost-effective HPC systems having the features of non-transparent bridge (NTB) technologies. OpenSHMEM is a programming model for distributed shared memory that supports a partitioned global address space (PGAS). Currently, little work has been done to develop the OpenSHMEM library for PCIe-interconnected HPC systems. This paper introduces a prototype implementation of the OpenSHMEM library through a switchless interconnect network using PCIe NTB to provide a PGAS programming model. In particular, multi-interrupt, multi-thread-based data transfer over the OpenSHMEM shared memory model is applied at the implementation level to reduce the latency and increase the throughput of the switchless ring network system. The implemented OpenSHMEM programming model over the PCIe NTB switchless interconnection network provides a feasible, cost-effective HPC system with a PGAS programming model.

• 한국정보통신학회논문지
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• 제15권7호
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• pp.1465-1470
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• 2011

본 논문에서는 무선 애드혹 네트워크에서 복수개 채널을 이용한 효율적인 매체접속제어 프로토콜로써 DM-MMAC (Doze Mode Multi-Chanel MAC)을 제안한다. 기존의 IEEE 802.11 프로토콜의 경우 물리계층에서 복수개의 가용 채널이 주어지나 MAC 계층에서는 오직 고정된 단일채널을 통한 접속만이 가능하다. 이를 보완하기 위한 프로토콜로써 여러 가지 멀티채널 MAC 프로토콜이 제안되었으나 대부분의 경우 채널수가 적고 호스트의 수가 많아지면 전송 처리율(throughput)이 급격히 저하되는 문제점이 있다. 본 연구에서는 기존 MMAC 프로토콜의 채널 할당 및 채널점유 과정을 단순화하고 호스트 간 충돌가능성을 줄임으로써 절전효과와 함께 전송률 향상을 도모하였다.

• 정보처리학회논문지C
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• 제18C권2호
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• pp.111-118
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• 2011

최근 스마트폰의 인기로 인해 무선 멀티인터페이스를 이용한 네트워킹 서비스에 관심이 증가하고 있다. 이로 인해 무선 멀티인터페이스 지원을 위한 네트워킹 기술 연구가 활발히 진행 중이다. 이와 관련된 연구로써 IETF NetExt WG 에서 Proxy Mobile IPv6 (PMIPv6) 기반 멀티인터페이스 지원 기술에 대한 표준 기술이 논의 중에 있다. 기존 PMIPv6 프로토콜은 멀티 인터페이스 이동 노드가 PMIPv6 도메인에서 접속시 멀티인터페이스를 이용하여 동시 접속 및 인터페이스 사이에서의 핸드오버 지원을 위한 기본 기능을 제공하고 있다. 하지만 기존 프로토콜이 가진 기능은 동시 접속 후 이동 노드가 Inter-Technology Handover을 수행한 후 동시 접속 상황이 불가능하게 되는 문제점을 가지고 있다. 따라서 기존 프로토콜을 통한 플로우 기반의 멀티 호밍 서비스가 제공되지 못한다. 본 논문에서는 멀티인터페이스 이동 노드가 PMIPv6 도메인에 접속하는 시나리오에서 언급한 문제점을 정의하고 이를 해결하기 위한 방안으로 Hybrid Home Network Prefix 할당 방법을 제안한다.

• International Journal of Contents
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• 제5권2호
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• pp.43-52
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• 2009

The article first presents a broad overview of the design and management for survivable network. We review the concept of network survivability, various protection and restoration schemes. Also we introduce design architectures of Quantitative model and a Survivable Ad hoc and Mesh Network Architecture. In the other side of study like these(traditional engineering approach), there is the concept of the survivable network systems based on an immune approach. There is one sample of the dynamic multi-routing algorithms in this paper.

• Journal of Communications and Networks
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• 제18권1호
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• pp.65-74
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• 2016

Ship ad-hoc network (SANET) extends the coverage of the maritime communication among ships with the reduced cost. To fulfill the growing demands of real-time services, the SANET requires an efficient clock time synchronization algorithm which has not been carefully investigated under the ad-hoc maritime environment. This is mainly because the conventional algorithms only suggest to decrease the beacon collision probability that diminishes the clock drift among the units. However, the SANET is a very large-scale network in terms of geographic scope, e.g., with 100 km coverage. The key factor to affect the synchronization performance is the signal propagation delay, which has not being carefully considered in the existing algorithms. Therefore, it requires a robust multi-hop synchronization algorithm to support the communication among hundreds of the ships under the maritime environment. The proposed algorithm has to face and overcome several challenges, i.e., physical clock, e.g., coordinated universal time (UTC)/global positioning system (GPS) unavailable due to the atrocious weather, network link stability, and large propagation delay in the SANET. In this paper, we propose a logical clock synchronization algorithm with multi-hop function for the SANET, namely multi-hop clock synchronization for SANET (MCSS). It works in an ad-hoc manner in case of no UTC/GPS being available, and the multi-hop function makes sure the link stability of the network. For the proposed MCSS, the synchronization time reference nodes (STRNs) are efficiently selected by considering the propagation delay, and the beacon collision can be decreased by the combination of adaptive timing synchronization procedure (ATSP) with the proposed STRN selection procedure. Based on the simulation results, we finalize the multi-hop frame structure of the SANET by considering the clock synchronization, where the physical layer parameters are contrived to meet the requirements of target applications.