• International journal of advanced smart convergence
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• 제7권4호
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• pp.174-184
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• 2018

The efficiency and safety of social-overhead capital (SOC) public infrastructures have become an eminent social concern. In this regard, a continuous structural health monitoring has been widely implemented to oversee the robustness of such public infrastructures for the safety of the public. This paper deals with the analysis of a distributed mobility management (DMM) support for wireless sensor network (WSN) based information transmission system. The partial DMM support separates the data and control plane infrastructures, wherein, the control plane is managed by a particular mobility management network entity, while the data plane is distributed by the mobility anchors. The system will be able to optimize the information transmission for a wireless structural health monitoring of SOC public infrastructures specifically designed for bridges, and thus, guarantees the safety of public commuters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.443-444
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• 2019

DC마이크로그리드에서, 양방향 컨버터를 통한 계통과 배터리와의 전력교환은 필수적으로 요구 된다. 일반적으로 계통이 연결 되었을 때 배터리를 충전시키고, 계통이 끊어 졌을 때는 배터리를 통해 계통에 전력을 공급하는 양방향 동작을 한다. 이러한 전력방향전환 과도상태를 줄이기 위해 무순단 절체 기능이 필요한데, 전류 제어기를 공유하는 방식의 경우 전압제어기의 포화가 발생하면 양방향 컨버터의 출력응답이 늦어지거나, 출력이 불안정해 진다. 이 문제를 해결하기 위해 양방향 컨버터의 대표적인 포화방지(Anti-windup)기법을 적용하여 성능을 비교하였다. 또한 PSIM 소프트웨어를 통해 DC마이크로그리드 시스템을 구현해 효과를 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권11호
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• pp.4611-4624
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• 2020

Future network scenario will be a heterogeneous wireless network environment composed of multiple networks and multimode terminals (MMT). Seamless switching and optimal connectivity for MMT among different networks and different services become extremely important. Here, a vertical handoff algorithm combined an improved entropy weighting method based on grey relational analysis (GRA) is proposed. In which, the improved entropy weight method is used to obtain the objective weights of the network attributes, and GRA is done to rank the candidate networks in order to choose the best network. Through simulation and comparing the results with other vertical handoff decision algorithms, the number of handoffs and reversal phenomenon are reduced with the proposed algorithm, which shows a better performance.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2021년도 추계학술발표대회
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• pp.128-130
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• 2021

Smart cities collect data from thousands of IoT-based sensor devices for intelligent application-based services. Centralized cloud servers support application tasks with higher computation resources but introduce network latency. Fog layer-based data centers bring data processing at the edge, but fewer available computation resources and poor task allocation strategy prevent real-time data analysis. In this paper, tasks generated from devices are distributed as high resource and low resource intensity tasks. The novelty of this research lies in deploying a virtual node assigned to each cluster of IoT sensor machines serving a joint application. The node allocates tasks based on the task intensity to either cloud-computing or fog computing resources. The proposed Task Allocation Strategy provides seamless allocation of jobs based on process requirements.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2008년도 춘계학술발표대회
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• pp.999-1002
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• 2008

Many schemes to reduce the inter-MAP handoff delay in hierarchical mobile IPv6 have been proposed but the previous schemes waste relatively large network resources to decrease the path rerouting delay. In this paper, we propose the 2-layered MAP concept, where the seamless inter-MAP handoff can be supported regardless of path rerouting time. As a result, the waste of wired resources and the rate of the inter-MAP handoff can be reduced. From the performance analysis and simulation, the inter-MAP handoff rate for non-real-time traffic is only about 1/3 of the conventional result. Such advantageous features of the proposed scheme neither incur any increase of the total handoff rate nor require additional MAPs.

• 경영정보학연구
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• 제13권1호
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• pp.33-59
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• 2011

현재 온라인 사회연결망 서비스는 인맥 관리, 고용관련 분야에서 널리 활용되고 있으나, 오프라인과 온라인의 이음매 없는 연결의 어려움, 비대면 프로파일 정보 교환에 의한 정보의 불완전성과 신뢰성 부족, 중앙집중형 통제에 의한 사용자 자율성의 제약이라는 한계점을 드러내고 있다. 이에 이 논문에서 는 WPAN(Wireless Personal Area Network)을 기반으로 하는 실세계 공간에서 동일한 관심을 가진 사용자들간의 실시간 변대변 사회적 상호작용을 이음매 없이 가능하게 하는 유비쿼터스 사회연결망관리를 정의하고, 이에 기반하여 사회연결망관리 프레임워크를 도출하였다. 유비쿼터스 사회연결망관리의 사례로서 u-구인 구직 서비스 모델을 설계하고 평가하고자 한다. 이를 위해 발생 가능한 시나리오를 제시하고, 서비스 모델 참여자 역할 및 참여자 별 제공 가치와 참여자들의 잠재적 이익을 비즈니스 모델 관점에서 분석한다. 그리고 본 연구에서 제시하고자 하는 모텔의 상대적 우위를 평가하기 위해서, 관련 6개 사례를 비교한다.

• 한국통신학회논문지
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• 제29권8A호
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• pp.909-917
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• 2004

무선 통신망에서 끊임없는 데이터 전달을 제공하는 것은 실시간 멀티미디어 서비스들에 있어서 매우 주요한 기능들 중의 하나이다 본 논문에서는, IP 이동성 지원을 위한 유망한 방법들인 MIP-RO, SIP, MIP-RO/CIP와 SIP/CIP들에 대한 핸드 오프 지연시간을 분석하고 비교한다. 핸드오프 지연시간 분석은 이들 방법들에 대한 핸드오프 처리를 위하여 교환되는 메시지 플로우를 기반으로 하여 만들었다 실험 결과는 SIP/CIP 방법이 다른 방법들에 비하여 핸드오프 지연시간 측면에서 가장 좋은 성능을 보여준다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1234-1239
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• 2003

In the product design process computer-aided engineering and optimization tools are widely utilized in order to reduce the total development time and cost. Since several simulation tools are involved in the process, information losses, omissions, or errors are common and the importance of seamless information exchange among the tools has been increased. In this study ISO STEP standards are adopted to represent the neutral format for CAE/CAO information exchange. The schema of AP209 is used to define the information of finite element analysis and the new schema is proposed to describe the information of structural optimization based on the STEP methodology. The schema is implemented by EXPRESS, information modeling language, and ST-Developer is employed to generate C++ classes and STEP Rose Library by using the schema denoted. To substantiate the proposed approach, the information access interfaces of the finite element modeling software (FEMAP), structural optimization software (GENESIS) and in-house topology optimization program are developed. Examples of the size optimization of a three-bar truss and topology optimization of a MBB beam are shown to validate the information exchange of finite element analysis and structural optimization using STEP standards.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.80-86
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• 2009

Main bearing cap is one of the essential structural elements in internal combustion engine. Main bearing cap guides and holds the crankshaft, withstanding the full combustion and inertia loads of the engine. A seamless design methodology using FEA has been proposed to produce a reliable design of main bearing cap. A Levy's thick cylinder model was applied to calculate the contact pressure between bearing shell and housing bore. A calculated contact pressure at housing bore is within the allowed limit comparing with that from bearing shell model. An adequate FEA model was suggested to obtain reliable solutions for the durability of main bearing cap. 3D global model consists of engine bulkhead, main bearing cap, and bolts. Sub-model consisting of cap and part of bolts is used to get detailed solution of main bearing cap. A very careful contact modeling practice is needed to resolve the convergence problems frequently encountering during combined geometric and material non-linear problems. A proposed methodology has been applied to the main bearing cap model successfully and obtained reliable stress results and fatigue safety factors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권3호
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• pp.266-284
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• 2009

The challenges of rapidly growing numbers of mobile nodes in IPv6-based networks are being faced by mobile computing researchers worldwide. Recently, IETF has standardized Mobile IPv6 and Fast Handover for Mobile IPv6(FMIPv6) for supporting IPv6 mobility. Even though existing literatures have asserted that FMIPv6 generally improves MIPv6 in terms of handover speed, they did not carefully consider the details of the whole handover procedures. Therefore, in conventional protocols, the handover process reveals numerous problems manifested by a time-consuming network layer based movement detection and latency in configuring a new care of address with confirmation. In this article, we study the impact of the address configuration and confirmation procedure on the IP handover latency. To mitigate such effects, we propose a new scheme which can reduce the latency taken by the movement detection, address configuration and confirmation from the whole handover latency. Furthermore, a mathematical analysis is provided to show the benefits of our scheme. In the analysis, various parameters are used to compare our scheme with the current procedures, while our approach is focused on the reduction of handover latency. Finally, we demonstrate total handover scenarios for the proposed techniques and discussed the major factors which contribute to the handover latency.