• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.195-208
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• 2009

In this paper, we introduce a grid-based key pre-distribution scheme in wireless sensor networks, which aims to improve the connectivity and resiliency while maintaining a reasonable overhead. We consider simplification of the key establishment logic and enhancement of the connectivity via plat polynomial assignment on a three-dimensional grid for node allocation and keying material assignment. We demonstrate that our scheme results in improvements via a detailed discussion on the connectivity, resource usage, security features and resiliency. A comparison with other relevant works from the literature along with a demonstrated implementation on typical sensor nodes shows the feasibility of the introduced scheme and its applicability for large networks.

• 한국정보과학회논문지:소프트웨어및응용
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• 제37권10호
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• pp.751-759
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• 2010

본 논문에서는 초음파 영상에서 끊어진 구조의 연결성을 향상시키는 방법을 제안한다. 본 제안 방법은 대상 픽셀의 밝기값과 주변픽셀의 그라디언트 정보를 사용하여 연결 여부를 결정하게 된다. 끊어진 구조로 판단되어진 픽셀은 그 밝기값을 증가시켜 연관성 있는 구조로 연결시키게 된다. 이후 시각적 자연스러운 표현을 위하여 비등방성 확산 필터링을 적용하여 수행하게 된다. 연산속도의 이득을 위하여 제안하는 연결성 향상 방법의 구조행렬은 그라디언트 정보와 확산 방향을 결정하는 확산 필터의 구조행렬과 통일한 구조행렬을 사용하였다. 실험은 끊어진 구조가 나타나는 실제 초음파 영상에 대해 수행하였으며 제안된 방법에 의해 끊어진 구조가 연결되어 졌음을 확인할 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.5035-5048
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• 2016

Nano scale networks are futuristic networks deemed as enablers for the Internet of Nano Things, Body area nano networks, target tracking, anomaly/ abnormality detection at molecular level and neuronal therapy / drug delivery applications. Molecular communication is considered the most compatible communication technology for nano devices. However, connectivity in such networks is very low due to inter-symbol interference (ISI). Few research papers have addressed the issue of ISI mitigation in molecular communication. However, many of these methods are not adaptive to dynamic environmental conditions. This paper presents an enhancement over original Memory-1 ISI cancellation scheme using maximum likelihood estimation of a channel parameter (λ) to make it adaptable to variable channel conditions. Results of the Monte Carlo simulation show that, the connectivity (P_conn) improves by 28% for given simulation parameters and environmental conditions by using enhanced Memory-1 cancellation method. Moreover, this ISI mitigation method allows reduction in symbol time (Ts) up to 50 seconds i.e. an improvement of 75% is achieved.

• 한국환경복원기술학회지
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• 제17권3호
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• pp.75-86
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• 2014

An urban ecosystem is a complex system that includes social, economic and ecosystems. Therefore, it is important to consider its environmental capacity while developing a city plan. Most of the plans, however, consider only the social aspects, which fragments the green spaces and disturbs the movement of species. Sungnam has approximately 100 parks with unexecuted development plans and with great potential to contribute towards urban ecosystem enhancement. Therefore, this study applied network analysis to prioritize the development of city parks and contribute towards improving the green network, with Parus spp. as the target species. To compensate for the drawbacks of binary and possibility-based network analysis, this study included two indices, namely $BC^{PC}_K$, $BC^{IIC}_K$, $dPCconnector_k$ and $dIICconnector_k$. These indices make it possible to find patches that could play an important role in green network enhancement. The urban park with greater value gets a higher priority to be transformed into a park. Thus, our methodology could prove to be very useful in prioritizing the undeveloped parks, thereby supporting decision-making.

• 한국정보과학회논문지:정보통신
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• 제32권2호
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• pp.215-219
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• 2005

Ad-hoc 네트워크 내의 무선 이동 노드들은 일반적으로 전원 용량이 충분하지 않기 때문에 통신 중의 전원관리가 매우 중요하다. 이러한 전력 소모를 고려한 프로토콜로 MTPR, MBCR, MMBCR, CMMBCR 등이 제안되어 있으나, 전송 중 중간노드가 방전되어 링크가 단절되는 현상은 고려하지 못하고 있다. 따라서 경로의 연속성을 보장하기에는 미흡하다. 본 논문에서는 경로의 연속성을 증대하기 위한 세 가지 방안을 제안한다. 신호 세기가 임계치 이하인 경우 사전에 대체 경로를 설정하여 링크 단절에 대비한다. 전원용량이 임계치 이하로 떨어지는 경우에도 이를 미리 알려 대체 경로를 설정한다. 또한 멀티채널상의 중간 노드는 잔여 용량과 신규 링크 설정 요청에 필요한 전력을 비교하여 선택적으로 허락함으로써 중간 노드의 수명을 연장시키는 방안을 제안한다. 시뮬레이션 결과를 통하여 제안된 방안이 경로 연속성을 강화시키며, 신뢰적인 연결 관리에 의하여 지연 시간을 줄이는 성능 향상을 보였다.

• 한국환경복원기술학회지
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• 제22권5호
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• pp.45-56
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• 2019

Urban green areas are generally composed of relatively small and fragmented patches, but it is a critical factor for the quality of an urban environment. They have positive effects such as increasing green connectivity, reducing runoff, and mitigating urban heat. But, there is a lack of urban greening plans that consider the comprehensive effects of green space in real urban areas. To fill this gap in this literature, this study identifies a planning model that determines the optimal locations for maximizing green areas' multiple effects(e.g., heat mitigation and enhancement of connectivity) by using unused lots. This model also considers minimizing costs using meta-heuristic optimization algorithms. As a results, we finds 50 optimal plans that considers two effects within the limited cost in Nowon-gu. The optimal plans show the trade-off effect between connectivity, heat mitigation and cost. They also show the critical unused land lots for urban greening that are commonly selected in various plans. These optimal plans can effectively inform quantitative effectiveness of green space and their trade-off. We expect that our model will contribute to the improvement of green planning processes in reality.

• 한국환경복원기술학회지
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• 제24권1호
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• pp.15-24
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• 2021

This study was carried out to propose the functional assessment and a wise use strategy on the ecologically valuable 'village wetlands' distributed in living area in Geumsan gun, Chungnam province, Korea. The targets of the functional evaluation were 24 wetlands, selected from 123 village wetlands, where villages and agricultural lands or core ecosystems are located within living area near the wetland and wetlands with historical and cultural significance. The functional evaluation was carried out by RAM (Rapid Assessment Model) and the conservation strategies were suggested. As a result of the functional evaluation, 9 wetlands were rated 'high' (2 'absolute conservation' and 7 'conservation' strategies), 14 wetlands were rated 'medium' ('enhancement' strategies), and one wetland was rated 'low' ('restore or enhancement' strategy). In consideration of the results of the functional evaluation, interviews with village residents, and historic meaning, 6 important village wetlands were selected that require additional management strategies, such as conservation, enhancement, and restoration. 2 wetlands were from "absolute conservation" strategy and 4 wetlands derived from "conservation" and "enhancement" strategy wetlands in consideration of the ecological connectivity of wetlands, the use of surrounding land, and the function as a biological habitat. The wise use and conservation strategy was specifically proposed respectively.

• 한국통신학회논문지
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• 제33권7B호
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• pp.488-501
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• 2008

Convergence of various wireless systems can be cost effectively achieved through enhancement of existing technology. The emergence of Wireless Mesh Network (WMN) entails the interoperability and interconnection of various wireless technologies in one single system. Furthermore, WMN can be implemented with multi-radio and multi-channel enhancement. A multi-radio, multi-channel wireless mesh network could greatly improve certain networking performance metrics. In this research, two approaches namely, clustering and topology control mechanisms are integrated with multi-radio multi-channel wireless mesh network. A Clustering and Topology Control Algorithm (CTCA)is presented that would prolong network lifetime of the client nodes and maintain connectivity of the routers.

• Journal of Communications and Networks
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• 제9권3호
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• pp.282-295
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• 2007

Due to the nature that high datarate leads to shorter transmission range, the performance enhancement by high datarate 802.11 WLANs may be degraded when applying high datarate to an 802.11 based multihop ad hoc network. In this paper, we evaluate, through extensive simulations, the performance of multihop ad hoc networks at multiple transmission datarates, in terms of the number of hops between source and destination, throughput, end-to-end delay and packet loss. The study is conducted based on both stationary chain topology and mesh topologies with or without node mobility. From numerical results on network performance based on chain topology, we conclude that there is almost no benefit by applying the highest datarate when the chain length is 6 hops or more. With node mobility in mesh topology, the benefit of using high datarate diminishes at even shorter number of hops. To explore the main reasons for this behavior, analyses on multihop end-to-end throughput and network k-connectivity have been conducted later in the paper, and correspondingly an auto-rate adaptation algorithm has been proposed.

• 한국초전도ㆍ저온공학회논문지
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• 제8권1호
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• pp.1-4
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• 2006

The $MgB_2$ tapes with several metal powder addition were fabricated by PIT method with or without heat treatment. The $J_c$ value of $5.600A/cm^2$ and $16.000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol % of Cu added $MgB_2$ tape without heat treatment respectively. The $J_c$ value of $8.000A/cm^2$ and $35,000A/cm^2$ at 4.2 K and 5 T were obtained for the $MgB_2$ tape and 10 vol. % of Al added $MgB_2$ tape with heat treatment, respectively. The $J_c-B$ curve shows enhancement in $J_c$ under magnetic field. which suggests enhancement in workability and grain connectivity with several metal powder addition.