• 한국환경복원기술학회지
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• 제25권1호
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• pp.25-38
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• 2022

Urban problems are constantly occurring around the world due to rapid industrialization and population decline. In particular, as the number of vacant houses is gradually increasing as the population decreases, it is necessary to prepare countermeasures. A plan to utilize vacant houses has emerged to restore the natural environment of the urban ecosystem where forest destruction, damage to habitats of wild animals and plants, and disconnection have occurred due to large-scale development. Through connectivity analysis, it is possible to understand the overall ecosystem flow based on the movement of species and predict the effect when vacant houses are converted into green spaces. Therefore, this study analyzed the green area network to confirm the possibility of greening of vacant houses neglected in Jeonju based on circuit theory. Using Circuitscape and Least-cost path, we tried to identify the connectivity of green areas and propose an ecological axis based on the analysis. In order to apply the resistance values required for analysis based on previous studies, the 2020 subdivision land cover data were integrated into the major classification evaluation items. When the eight forests in the target site were analyzed as the standard, the overall connectivity and connectivity between forests in the area were high, so it is judged that the existing green areas can perform various functions, such as species movement and provision of habitats. Based on the results of the connectivity analysis, the importance of vacant houses was calculated and the top 20 vacant houses were identified, and it was confirmed that the higher the ranking, the more positive the degree of landscape connectivity was when converted to green areas. In addition, it was confirmed that the results of analyzing the least-cost path based on the resistance values such as connectivity analysis and the existing conceptual map showed some differences when comparing the ecological axes in the form. As a result of checking the vacant houses corresponding to the relevant axis based on the width standards of the main and sub-green areas, a total of 30 vacant houses were included in the 200m width and 6 vacant houses in the 80m width. It is judged that the conversion of vacant houses to green space can contribute to biodiversity conservation as well as connectivity between habitats of species as it is coupled with improved green space connectivity. In addition, it is expected to help solve the problem of vacant houses in the future by showing the possibility of using vacant houses.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권5호
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• pp.1354-1372
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• 2012

Route establishment in Mobile Ad Hoc Network (MANET) is the key mechanism to a successful connection between a pair of source and destination nodes. An efficient routing protocol constructs routing path with minimal time, less routing overhead and capable of utilizing all possible link connectivity. In general, most on-demand MANET routing protocols operates over symmetrical and bidirectional routing path, which is infeasible due to the inherent heterogeneous properties of wireless devices. Simulation results show that the presence of unidirectional links on a network severely affect the performance of a routing protocol. In this paper, a robust protocol independent scheme is proposed, which enable immediate rediscovery of alternative route for a path blocked by a unidirectional link. The proposed scheme is efficient; route rediscovery is locally computed, which results in significant minimization of multiple route packets flooding. Nodes may exploit route information of immediate neighbors using the local reply broadcast technique, which then redirect the control packets around the unidirectional links, therefore maintaining the end-to-end bidirectional connection. The proposed scheme along with Ad Hoc On-demand Distance Vector (AODV) and AODV-Blacklist routing protocol is investigated over three types of mobility models. Simulation results show that the proposed scheme is extremely reliable under poor network conditions and the route connectivity can be improved by as much as 75%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권7호
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• pp.3393-3412
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• 2017

As a main challenge in network virtualization, virtual network embedding problem is increasingly important and heuristic algorithms are of great interest. Aiming at the problems of poor correlation in node embedding and link embedding, long distance between adjacent virtual nodes and imbalance resource consumption of network components during embedding, we herein propose a two-stage virtual network embedding algorithm NA-PVNM. In node embedding stage, resource requirement and breadth first search algorithm are introduced to sort virtual nodes, and a node fitness function is developed to find the best substrate node. In link embedding stage, a path fitness function is developed to find the best path in which available bandwidth, CPU and path length are considered. Simulation results showed that the proposed algorithm could shorten link embedding distance, increase the acceptance ratio and revenue to cost ratio compared to previously reported algorithms. We also analyzed the impact of position constraint and substrate network attribute on algorithm performance, as well as the utilization of the substrate network resources during embedding via simulation. The results showed that, under the constraint of substrate resource distribution and virtual network requests, the critical factor of improving success ratio is to reduce resource consumption during embedding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.341-360
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• 2012

The network topology for a wide area sensor network has to support connectivity and a prolonged lifetime for the many applications used within it. The concepts of structure and group in sociology are similar to the concept of cluster in wireless sensor networks. The clustering method is one of the preferred ways to produce a topology for reduced electrical energy consumption. We herein propose a cluster topology method based on sociological structures and concepts. The proposed sociological clustering topology (SOCT) is a method that forms a network in two phases. The first phase, which from a sociological perspective is similar to forming a state within a nation, involves using nodes with large transmission capacity to set up the global area for the cluster. The second phase, which is similar to forming a city inside the state, involves using nodes with small transmission capacity to create regional clusters inside the global cluster to provide connectivity within the network. The experimental results show that the proposed method outperforms other methods in terms of energy efficiency and network lifetime.

• 대한인간공학회지
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• 제33권5호
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• pp.377-386
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• 2014

Objective: In this study, we used resting-state fMRI data to map differences in functional connectivity between a comprehensive set of 8 distinct cortical and subcortical brain regions in healthy controls and Internet addicts. We also investigated the relationship between resting state connectivity strength and the level of psychopathology (ex. score of internet addiction scale and score of Barratt impulsiveness scale). Background: There is a lot of evidence of relationship between Internet addiction and impaired inhibitory control. Clinical evidence suggests that Internet addicts have a high level of impulsivity as measured by behavioral task of response inhibition and a self report questionnaire. Method: 15 Internet addicts and 15 demographically similar non-addicts participated in the current resting-state fMRI experiment. For the connectivity analysis, regions of interests (ROIs) were defined based on the previous studies of addictions. Functional connectivity assessment for each subject was obtained by correlating time-series across the ROIs, resulting in $8{\times}8$ matrixs for each subject. Within-group, functional connectivity patterns were observed by entering the z maps of the ROIs of each subject into second-level one sample t test. Two sample t test was also performed to examine between group differences. Results: Between group, the analysis revealed that the connectivity in between the orbito frontal cortex and inferior parietal cortex, between orbito frontal cortex and putamen, between the orbito frontal cortex and anterior cingulate cortex, between the insula and anterior cingulate cortex, and between amydgala and insula was significantly stronger in control group than in the Internet addicts, while the connectivity in between the orbito frontal cortex and insula showed stronger negative correlation in the Internet addicts relative to control group (p < 0.001, uncorrected). No significant relationship between functional connectivity strength and current degree of Internet addiction and degree of impulsitivy was seen. Conclusion: This study found that Internet addicts had declined connectivity strength in the orbitofrontal cortex (OFC) and other regions (e.g., ACC, IPC, and insula) during resting-state. It may reflect deficits in the OFC function to process information from different area in the corticostriatal reward network. Application: The results might help to develop theoretical modeling of Internet addiction for Internet addiction discrimination.

• 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.

• 사회경제평론
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• 제31권3호
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• pp.271-305
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• 2018

오늘날 우리는 초연결사회에 살고 있다. 초연결사회란 초연결성(hyper-connectivity)으로 연결된 네트워크 사회(network society)를 말한다. 이러한 초연결성의 기술적 토대가 오늘날의 제4차 산업혁명임을 잘 알고 있다. 이 글에서는 산업혁명의 단계적 발전의 패턴을 밝힘으로써 초연결사회의 기원을발견하고자 한다. 산업혁명을 포함한 기술혁명의 변화의 패턴은 다음과 같이 지극히 단순하게 요약할 수 있다. (1) 기술혁명${\rightarrow}$네트워크혁명. (2) 네트워크혁명${\rightarrow}$사회적 네트워크의 변화 (3) 물질의 혁명${\rightarrow}$정신의 혁명. 산업혁명의 단계적 발전의패턴은 다음과 같다. 따라서 네트워크 혁명의 차원에서 본다면 초연결사회의 기원은 1840년 이후 미국에서 일어난 철도혁명(2차 산업혁명)에서 찾아볼 수 있다.

• 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.

• ETRI Journal
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• 제35권1호
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• pp.142-145
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• 2013

Network virtualization opens the door to novel infrastructure services offering connectivity and node manageability. In this letter, we focus on the cost-efficient embedding of on-demand virtual optical network requests for interconnecting geographically distributed data centers. We present a mixed integer linear programming formulation that introduces flexibility in the virtual-physical node mapping to optimize the usage of the underlying physical resources. Illustrative results show that flexibility in the node mapping can reduce the number of add-drop ports required to serve the offered demands by 40%.

• 한국컴퓨터정보학회논문지
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• 제7권3호
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• pp.99-108
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• 2002

무선 이동 망에서는 멀티미디어 서비스의 QoS를 만족시키기 위해서는 사용자 위치관리와 핸드오프관리가 보다 효율적으로 이루어져야 한다. 이를 위해서는 IMT-2000 HLR과 PCS HLR의 차별성 및 지능 망 연계와 패킷 데이터 서비스 제공이 HLR에 미치는 영향을 분석하고 IMT-2000에서 서비스 제공에 대한 전반적인 개념인 VHE와 인터넷 접속을 위한 패킷 데이터서비스와 2세대 이동 망 기술을 기반으로 QoS의 만족을 위한 효율성에 관해서 연구하였다.