• 제목/요약/키워드: Energy Sharing

검색결과 267건 처리시간 0.023초

Relay-assisted Multiple Access Channel Protocol for Cooperative Diversity

  • 김동현;김기일;이광복
    • 한국통신학회논문지
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    • 제34권1C호
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    • pp.1-8
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    • 2009
  • Cooperative diversity is a novel technique to improve diversity gains, capacity gains, and energy saving. This technique involves multiple terminals sharing resources in order to build a virtual antenna array in a distributed fashion. In this paper, we propose a multi-user cooperative diversity protocol called Relay-assisted Multiple Access Channel(R-MAC) that allows multiple source terminals to transmit their signals simultaneously and the relay terminal forwards the aggregated signal received from the source terminals to the destination terminal. The proposed protocol converts the distributed antenna channels into an effective MIMO channel by exploiting a relay, increasing both diversity gain and system throughput. We investigate the performance of the proposed protocol in terms of outage probability and diversity-multiplexing tradeoff where we assume block fading channel environment. Our simulation results show that the proposed protocol outperforms direct transmission in the high spectral efficiency regime where the conventional cooperative diversity protocols cannot outperform direct transmission.

The Interference Measurement Analysis between 3.412 GHz Band Broadcasting System and UWB Wireless Communication System

  • Song Hong-Jong;Kim Dong-Ku
    • Journal of electromagnetic engineering and science
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    • 제6권1호
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    • pp.76-81
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    • 2006
  • Ultra wideband(UWB) technologies have been developed to exploit a new spectrum resource in substances and to realize ultra-high-speed communication, high precision geo-location, and other applications. The energy of UWB signal is extremely spread from near DC to a few GHz. This means that the interference between conventional narrowband systems and UWB systems is inevitable. However, the interference effects had not previously been studied from UWB wireless systems to conventional wireless systems sharing the frequency bands such as Broadcasting system. This paper experimentally evaluates the interference from two kinds of UWB sources, namely a orthogonal frequency division Multiplex UWB source and an impulse radio UWB source, to a Broadcasting transmission system. The receive power degradations of broadcasting system are presented. From these experimental results, we show that in all practical cases UWB system can coexist 35 m distance in-band broadcasting network.

STATCON과 송전계통의 동적응동 분석을 위한 EMTP 시뮬레이션 모델 (EMTP SIMULATION MODEL TO ANALYZE DYNAMIC INTERACTION BETWEEN STATCON AND TRANSMISSION SYSTEM)

  • 한병문
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1995년도 하계학술대회 논문집 A
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    • pp.446-448
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    • 1995
  • This paper dscribes a detail simulation model with EMTP (Electro-Magnetic Transients Program) which is very effective to analyze the interaction between the ac transmission line and STATCON (static condenser). The SATCON was represented by two voltage-source converters connected in parallel and sharing an energy storage dc capacitor bank. The voltage source converters was modeled with ideal gate turn-off switches. The power system was represented by a detail generator model and a distributed tramnsmission line model for detail performance analyses. Analysis results show that the conceived simulation model is very effective to analyze the interaction between the ac transmission line and STATCON, and to evaluate the performance of STATCON.

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Zigbee MAC 프로토콜기반 인체 응용을 위한 나노 네트워크의 슈퍼 프레임 설계 (Zigbee MAC Protocol based Super frame Design for In-body Nano-Network Applications)

  • 이경환;김성운
    • 한국멀티미디어학회논문지
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    • 제19권9호
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    • pp.1690-1697
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    • 2016
  • In a beacon-enabled Zigbee network, the slotted CSMA/CA mechanism based on the super frame structure fairly provides communication chance for each node and makes a reasonable usage of the available energy. In the case of wireless nano sensors that are implanted into the target human body area for detecting disease symptoms or virus, such a nano-network requires a similar type of channel sharing and transmission of short length event-driven data. In this paper, for nano-network's in-body applications, we aim to design conceptually a new super frame derived from the existing beacon-enabled Zigbee MAC protocol. And we analyze the efficiency of the proposed super frame in the aspect of practical deployment.

물류환경 변화에 따른 철도물류 관련 국가 계획의 전개과정 (A Study on Development Process of National Plan for Railroad Logistics)

  • 이윤미;유재균;정병현
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2008년도 추계학술대회 논문집
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    • pp.742-749
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    • 2008
  • In 21th century, high oil price and environmental pollution appeared by serious social problem. It brought important change of logistics environment, and environmentally-friendliness and sustainability are emphasized. In spite of that railroad has high energy efficiency and environmental-friendliness to advantage traditionally, there is still transport division rate of railroad in declining tendency as investment policy that is concentrated on road and insufficiency of social realization about environmental problem. The construction of environment-friendly transport system and the reasonable role sharing between modes of transportation are important. Transportation policy of Korea is presented through plans to constructs efficiently and manages national transportation system. In this study, examine development process of national railroad logistics plan with logistics environment change, and proposes the following ways to development of railroad logistics policy.

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전력계통 제어시스템 구조에 따른 사이버 보안대책 수립 (Establishment of Cyber Security Countermeasures amenable to the Structure of Power Monitoring & Control Systems)

  • 우필성;김발호
    • 전기학회논문지
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    • 제67권12호
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    • pp.1577-1586
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    • 2018
  • The emergence of the Smart Grid is an integrated solution for the next generation power system that combines IT technology in the power system to create optimal energy utilization and various services. However, these convergence technologies (power systems and information communications) are not only improving the related technologies but also producing various problems especially exposure to cyber risk. In particular, the intelligent power grid has security vulnerabilities through real-time information sharing among various organically linked systems, and it is more complicated than the cyber risk problem in the existing IT field and is directly connected to national disaster accidents. Therefore, in order to construct and operate a more stable smart grid, this paper analyzes the system of power system control system in Korea, and proposes a cyber security element definition and a countermeasure establishment method of power monitoring & control systems based on security standards of smart grid (No. SPS-SGSF-121-1-1).

A Privacy-preserving Image Retrieval Scheme in Edge Computing Environment

  • Yiran, Zhang;Huizheng, Geng;Yanyan, Xu;Li, Su;Fei, Liu
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제17권2호
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    • pp.450-470
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    • 2023
  • Traditional cloud computing faces some challenges such as huge energy consumption, network delay and single point of failure. Edge computing is a typical distributed processing platform which includes multiple edge servers closer to the users, thus is more robust and can provide real-time computing services. Although outsourcing data to edge servers can bring great convenience, it also brings serious security threats. In order to provide image retrieval while ensuring users' data privacy, a privacy preserving image retrieval scheme in edge environment is proposed. Considering the distributed characteristics of edge computing environment and the requirement for lightweight computing, we present a privacy-preserving image retrieval scheme in edge computing environment, which two or more "honest but curious" servers retrieve the image quickly and accurately without divulging the image content. Compared with other traditional schemes, the scheme consumes less computing resources and has higher computing efficiency, which is more suitable for resource-constrained edge computing environment. Experimental results show the algorithm has high security, retrieval accuracy and efficiency.

청소년의 간식을 통한 첨가당섭취량 및 고당류식품 관련 이벤트 데이 참여행동에 대한 조사 (A Survey on Added Sugar Intakes from Snacks and Participation Behaviors of Special Event Days Sharing Sweet Foods among Adolescents in Korea)

  • 김현주;김선효
    • Journal of Nutrition and Health
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    • 제42권2호
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    • pp.135-145
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    • 2009
  • 본 연구는 간식 중의 첨가당 함량에 관한 자체 DB를 제작해 청소년의 간식을 통한 1일 첨가당섭취량을 파악하고, 고당류식품 섭취와 밀접한 관계가 있는 고당류식품 관련 이벤트 데이에 대한 청소년의 참여행동을 알아보고자 실시되었다. 본 연구에서 설문조사, 식사조사, 간식조사가 실시되었는데, 설문 조사대상자는 전국의 읍 면, 중소도시, 대도시에 소재한 일반계 및 실업계 중 고등학교에 재학 중인 $12{\sim}18$세의 남녀 학생 959명, 식사조사 대상자는 공주시에 소재한 중학교에 재학 중인 남녀 학생 71명, 간식조사 대상자은 공주시와 서울시에 소재한 중 고등학교에 재학 중인 남녀 학생 230명을 대상으로 실시하였으며, 설문조사, 간식조사, 식사조사 간에 대상자는 서로 중복되도록 구성하였다. 본 연구에서 얻어진 결과는 다음과 같다.1) 조사대상자는 평소 간식으로 빵/패스트푸드를 가장 즐겨 먹으며, 그 다음이 과자류, 우유 및 발효유의 순이었다. 중학생은 고등학생에 비해 우유 및 발효유를 선호하며, 고등학생은 중학생보다 빵/패스트푸드를 선호하는 것으로 나타났다 (p < 0.01). 간식 섭취 빈도는 중학생과 고등학생 모두 일주일에 $3{\sim}6$번이 가장 많으며, 그 다음이 하루에 1번인 것으로 나타났다. 중학생은 고등학생보다 간식 섭취 빈도가 낮은 경향이었다 (p < 0.05). 간식 섭취 시간은 중학생은 고등학생보다 점심${\sim}$저녁식사 사이에 섭취하는 경우가 많으며, 고등학생은 중학생보다 오전시간 및 밤 9시${\sim}$잠자기 전에 섭취하는 경우가 많았다 (p < 0.001). 2) 조사대상자의 1일 평균 에너지섭취량 및 대부분의 비타민과 무기질섭취량은 이들의 성별과 연령에 대한 KDRI를 충족시키는 수준이어서 양호하였다. 그러나 엽산과 칼슘의 1일 평균 섭취량은 남중생과 여중생 모두 KDRI의 1/2 수준이어서 불량하였다. 1일 평균 나트륨섭취량은 남중생의 경우 KDRI의 300%, 여중생은 240%으로 과다 섭취하였다. 3) 이벤트 데이가 주는 장점에 대해‘우리들만의 행사를 즐기는 것'이라는 응답이 가장 많고, 그 다음이‘친구와 어울릴 수 있는 것'으로 나타났으며, 이에 관한 응답은 중 고생간에 차이가 있었다 (p < 0.01). 이벤트 데이에 선물을 주는 대상자로‘학교 친구'가 가장 많으며, 그 다음이‘이성 친구',‘부모' 등의 순이었다. 중학생은 고등학생에 비해‘학교 친구'에게 선물을 주는 비율이 높으며, 고등학생은 중학생에 비해‘이성 친구'에게 선물을 주는 비율이 높았다 (p < 0.001). 이벤트 데이를 위해 고당류식품을 구입할 때 식품표시와 식품포장상태를 확인을 하지 않는 비율 (61.6%)이 높으며, 이 점에 관해 중 고생간에 차이가 없었다. 또한 이벤트 데이를 준비하기 위해 조사대상자가 고당류식품을 구입할 때 선택 기준을‘예쁜 모양'에 두는 비율이 높으며, 그 다음이‘맛',‘가격'의 순이었다. 이점에서 중학생은 고등학생에 비해‘가격'을 중시하며, 고등학생은 중학생에 비해‘예쁜 모양'을 중시하였다 (p < 0.01). 4) 이벤트 데이에 주고받는 선물로는 사탕, 초콜렛, 빼빼로, 엿 등이 있으며, 친구 생일 (68.4%)과 빼빼로데이 (61.5%)에 참여한 비율이 높았다. 중학생은 고등학생보다 빼빼로데이, 발렌타인데이, 화이트데이에 더 참여하였으며, 고등학생은 중학생에 비해 수능이나 학교 정기시험과 같은 큰 시험일에 더 참여하였다. 5) 간식 종류별 1일 첨가당 섭취 비율을 보면 중 고생 모두 /과자, 비스킷, 빵류, 케이크/으로 부터 첨가당을 많이 섭취하며, 그 다음이 음료수, /양갱, 쵸코렛, 캔디/에 의한 것으로 나타났다. 간식을 통한 1일 평균 총첨가당섭취량은 중학생 $30.5{\pm}23.5g/d$ ($3.0{\sim}137.9\;g/d$), 고등학생 $31.7{\pm}23.2g/d$ ($1.2g{\sim}126.1g/d$)으로 나타나 두군간에 차이가 없었다. 그리고 간식 종류별 1일 첨가당섭취량은 대부분의 간식에서 중 고생간에 차이가 없으나, 요구르트에 의한 것은 중학생이 고등학생보다 높았다 (p < 0.05). 간식에 의한 1일 첨가당 에너지 비율은 중학생 $0.6{\sim}26.1%$ (평균 $6.3{\pm}4.7%$), 고등학생 $0.3{\sim}23.9%$ (평균 $6.3{\pm}4.4%$)로 나타났다. WHO/FAO에서 정한 1일 첨가당 에너지 비율인 10%를 초과한 대상자는 중학생 17.8%, 고등학생 20.9%로 나타나, 고등학생이 중학생보다 간식을 통한 총첨가당 섭취량이 높은 경향이었다. 이상에서 우리나라 청소년들 사이에 고당류식품을 주고 받는 각종 이벤트 문화가 이미 자리 잡았고 간식으로 맛이 달은 식품이 자주 섭취되고 있을 뿐만 아니라, 식품 구입시 영양소 함량 등의 내용면보다는 모양이나 포장과 같은 외형이 중시되고 있는 경향 등에 의해, 우리나라 청소년들이 당류를 과다 섭취할 수 있는 식생활 환경에 노출되어 있음을 볼 수 있었다. 실제로 본 연구에서 일부 청소년의 경우 간식만으로도 1일 첨가당 에너지 비율이 WHO/FAO의 상한선인 10% 이상을 초과하고 있어 청소년의 고당류섭취 현상을 확인해주었다. 따라서 청소년의 고당류 섭취 문제에 대한 현실적인 인식과 함께 당류 섭취 저감화를 위한 영양정책 수립 및 영양교육 실시 등의 실효성 있는 지원이 시급히 이루어져야 하겠다.

Learning Free Energy Kernel for Image Retrieval

  • Wang, Cungang;Wang, Bin;Zheng, Liping
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제8권8호
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    • pp.2895-2912
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    • 2014
  • Content-based image retrieval has been the most important technique for managing huge amount of images. The fundamental yet highly challenging problem in this field is how to measure the content-level similarity based on the low-level image features. The primary difficulties lie in the great variance within images, e.g. background, illumination, viewpoint and pose. Intuitively, an ideal similarity measure should be able to adapt the data distribution, discover and highlight the content-level information, and be robust to those variances. Motivated by these observations, we in this paper propose a probabilistic similarity learning approach. We first model the distribution of low-level image features and derive the free energy kernel (FEK), i.e., similarity measure, based on the distribution. Then, we propose a learning approach for the derived kernel, under the criterion that the kernel outputs high similarity for those images sharing the same class labels and output low similarity for those without the same label. The advantages of the proposed approach, in comparison with previous approaches, are threefold. (1) With the ability inherited from probabilistic models, the similarity measure can well adapt to data distribution. (2) Benefitting from the content-level hidden variables within the probabilistic models, the similarity measure is able to capture content-level cues. (3) It fully exploits class label in the supervised learning procedure. The proposed approach is extensively evaluated on two well-known databases. It achieves highly competitive performance on most experiments, which validates its advantages.

종속 접속된 산화아연바리스터 기반의 서지방호장치의 협조 (Coordination of Cascaded Metal Oxide Varistor-Based Surge Protective Devices)

  • 김태기;신희경;이복희
    • 조명전기설비학회논문지
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    • 제29권6호
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    • pp.70-77
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    • 2015
  • This paper describes the experimental results obtained from various installation conditions of cascaded metal oxide varistor(MOV)-based SPDs with the objectives to analyze the coordination of the cascaded surge protective devices(SPDs) and to propose the proper selection and installation methods of the cascaded SPDs. The residual voltage, discharge current and energy sharing between the upstream and downstream SPDs in the $10/350{\mu}s$ direct lightning current wave were measured and discussed. The coordination of cascaded MOV-based SPDs is closely related to the varistor voltage and installation methods of SPDs. In cascaded SPDs without dedicated decoupling elements, the natural impedance of leads connecting two SPDs can act as a decoupler for the coordination of MOV-based SPDs. Even if the varistor voltage of the upstream SPD is higher than that of the downstream SPD at long distances between two SPDs, the energy coordination of cascaded SPDs could effectively be fulfilled in the conditions of large surge currents and the optimum voltage protection level can be achieved. Consequently, if the distance between voltage limiting type SPDs is long, the coordination of the cascaded SPDs should be determined by taking into account the decoupling effects due to the intrinsic inductance of leads connecting the upstream and downstream SPDs.