• 제목/요약/키워드: Energy and information transfer

검색결과 407건 처리시간 0.029초

수평관내 R-113 냉매의 비등열전달에 관한 연구 (A study on the boiling heat transfer of R-113 in a horizontal tube)

  • 최병철;김원녕;김경근
    • Journal of Advanced Marine Engineering and Technology
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    • 제10권4호
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    • pp.67-77
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    • 1986
  • The information on the heat transfer characteristics, flow pattern and pressure drop, are very important for the desing of general heat exchanger, refrigerating system, air conditioning system and energy recovery system. In these systems, water or lubricating oil contained in working fluid affects greatly the flow and heat transfer condition and this phenomena must be considered in the practical design. An experiment has been performed for studying the flow and heat transfer characteristics of the forced convective horizontal flow of R-113 under the range of the liquid single phase state to the boiling flow state. Basic experimental results are obtained in the case that water or lubricating oil does not contaminate in the test fluid. Experimental results are as follows; (1) The local heat transfer coefficients in the nucleate boiling region and transition boiling region are almostly ten times as large as that of liquid single phase flow. (2) The measured heat transfer coefficient in the present experimental range is relatively agreed well with the predicted value from the various experimental results for the boiling flow.

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무선 멀티 홉 통신에서 협력적인 무선 에너지 공유를 통한 생존시간 최대화 (Lifetime Maximization with Cooperative Wireless Energy Sharing in Wireless Multi-Hop Communications)

  • Choi, Hyun-Ho
    • 한국정보통신학회논문지
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    • 제24권11호
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    • pp.1550-1553
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    • 2020
  • In this paper, we maximize the lifetime of a multi-hop path through a cooperative wireless energy sharing scheme between constituent nodes in a wireless multi-hop communication. Considering a bidirectional multi-hop communication environment, we present an optimization problem to maximize path lifetime by adjusting the amount of energy each node needs to share with its neighboring nodes. On the basis of solidarity property, i.e., the lifetime of the multi-hop path is maximized when the lifetimes of all nodes are the same, we convert the considered optimization problem into a linear programming problem and solve it easily. Simulation result shows that the proposed two-way wireless energy sharing method maximizes the path lifetime of multi-hop communications and approximately doubles the path lifetime compared with the one-way energy sharing method.

Energy Efficient Wireless Data Transmission for Personal Health Devices

  • Kim, Sang-Kon;Kim, Tae-Kon;Koh, Jin-Hwan
    • Journal of Electrical Engineering and Technology
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    • 제8권6호
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    • pp.1559-1570
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    • 2013
  • The family of ISO/IEEE11073 standards is the basis of the e-health system and provides interoperability for personal health devices. In the early stage of e-health business, it was expected that people would use a health device individually. In this case, a measurement datum was episodically acquired and generally transmitted for one person at a time. Recently, a health device is expected to be used by multiple people, and large amounts of measurement data are gathered in a short time interval. In addition, mobile health devices have become more popular, so that energy efficient measurement data transmission is required, to prolong the use of a device. In IEEE11073 PHD standards, data transmission is classified into three different types: immediate individual transfer, small block transfer, and large block transfer. The large block transfer using PM-store concept provides efficient transmission. However, an existing PM-store has problem when a device is used by multiple people. To address the defined problem, a modified PM-segment that is in compliance with 11073 standards is proposed in this paper. In particular, the proposed PM-segment is designed to minimize the additional complexity of an agent instead of a manager and it is interoperable with the existing manager. The proposed PM-segment shows better performance than the existing PM-segment, in terms of memory requirements and expected queue time. Also, performance comparison among the three transfers is performed in regard to the delay time and communication power consumption points of view.

Physical Layer Secrecy Performance of RF-EH Networks with Multiple Eavesdroppers

  • Truong, Tien-Vu;Vo, Nhan-Van;Ha, Dac-Binh;Tran, Duc-Dung
    • Journal of information and communication convergence engineering
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    • 제14권3호
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    • pp.171-176
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    • 2016
  • In this study, we investigate the physical layer secrecy performance of RF energy harvesting (EH) networks over Rayleigh fading channels. The RF-EH system considered here consists of one power transfer station, one source, one destination, and multiple passive eavesdroppers. The source harvests energy from the power transfer station and transmits the information to the destination by using a time switching-based relaying protocol. The eavesdroppers try to extract the transmitted information without an active attack. By using the statistical characteristics of the signal-to-noise ratio (SNR), the exact closed-form expressions of the existence probability of the secrecy capacity and the secrecy outage probability are derived. Further, we analyze the secrecy performance of the system with respect to various system parameters, such as the location of the system elements and the number of eavesdroppers. Finally, the equivalent Monte Carlo simulation results are provided to confirm the correctness of our calculations.

A Data Transmission Mode Change Method for Improving Energy Efficiency in IoT Environments

  • Lee, Sukhoon;Kim, Kwangsu;Jeong, Dongwon
    • 한국정보기술학회 영문논문지
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    • 제10권1호
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    • pp.57-69
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    • 2020
  • In general, many IoT devices, including smart phones, use LTE, Wi-Fi, and Bluetooth, and these communication modules generate a lot of energy consumption during periodic data transmission. This paper proposes a method of the data transmission mode change for improving energy efficiency in various communication environments that mobile devices may encounter. We propose an algorithm for setting the mode considering energy efficiency, data transmission performance and cost when the mobile device transmits data, and transmitting the data in an optimized manner according to the state of the mobile device. The proposed algorithm is implemented through experiments on energy efficiency for each communication module, and the scenario is used to verify how efficiently the proposed algorithm uses energy.

무선전력전송시스템 제어 기술 비교 연구 (A Study on Comparison of Control Methods in Wireless Power Transfer Systems)

  • 장동원;조인귀
    • 한국정보통신학회:학술대회논문집
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    • 한국정보통신학회 2015년도 추계학술대회
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    • pp.113-116
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    • 2015
  • 본고에서는 블루투스 프로토콜을 이용해서 무선전력전송을 제어하는 시스템에 대해서 기술하였다. 블루투스는 근거리에서 데이터, 음성 신호 등 송수신하기 위해 많은 분야에서 다양하게 응용되어 왔다. 그러나 최근에는 전송 데이터량이 적은 센서 제어 신호를 저전력으로 처리할 수 있는 기존 블루투스 프로토콜보다 단순한 구조의 블루투스 저에너지 프로토콜이 표준화되어 의료, 가전 등 생활과 밀착된 응용에 많이 사용되고 있다. 또한 무선전력 전송시스템에서도 제어를 위해 표준으로 채택되었다. 본고에서는 특히 블루투스 저에너지 프로토콜을 이용해서 무선전력전송시스템을 제어하는 기술에 대해서 분석하고 기술하였다.

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무선 에너지 전송 센서망에서의 공평성을 고려한 라우팅, 스케줄링, 전력 제어 (Joint Routing, Scheduling, and Power Control for Wireless Sensor Networks with RF Energy Transfer Considering Fairness)

  • 문석재;노희태;이장원
    • 한국통신학회논문지
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    • 제41권2호
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    • pp.206-214
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    • 2016
  • 최근들어 무선 센서망에서 센서 노드에 대한 전력 공급을 위한 무선 에너지 전송(radio frequency energy transfer: RFET)에 대한 관심이 높아지고 있다. 기존의 센서망에서는 센서 노드들의 에너지 소비를 줄이는 것이 중요한 연구주제 중의 하나였지만 무선 에너지 전송 센서망에서는 센서 노드들이 계속해서 에너지를 공급받을 수 있기 때문에 에너지 소모를 줄이는 것이 상대적으로 그리 중요한 이슈는 아니다. 하지만 센서 노드들 사이에 가용 에너지양의 차가 발생하게 되기 때문에 무선 에너지 전송 센서망의 성능 향상을 위해서는 이와 같은 성질을 고려하여 프로토콜을 설계하는 것이 중요하게 된다. 이에 본 논문에서는 이를 고려하여 무선 에너지 전송 무선 센서망에서 라우팅, 스케줄링, 전력제어 기법을 'Max-min'과 'Max-min fairness' 두가지의 관점에서 제안을 한다. 또한 본 논문에서 제안한 기법들이 무선 에너지 전송 센서망의 성능을 크게 향상시킴을 보이며 이와 더불어 'Max-min'과 'Max-min fairness' 사이의 차이에 대해서도 논의를 한다.

설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제26권12호
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.

Photoluminescence properties and energy transfer of $Dy^{3+}$ and $Tm^{3+}$ co-activated $CaZrO_3$ phosphor for white LEDs

  • Li, Yezhou;Wang, Yuhua
    • Journal of Information Display
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    • 제12권2호
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    • pp.93-96
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    • 2011
  • Single-phased $CaZrO_3:Dy^{3+}$, $Tm^{3+}$ series have been successfully synthesized by solid-state reaction, and their luminescence properties were investigated. Under 355 nm excitation, $CaZrO_3:Dy^{3+}$ series showed characteristic emission of $Dy^{3+}$, which exhibited yellowish white color. By introducing $Tm^{3+}$ into the matrix, the emitted hue of the $Dy^{3+}$-doped sample could be easily tailored to white, and simultaneously, energy transfer from $Tm^{3+}$ to $Dy^{3+}$ was observed. The color coordinates of the optimum white-emitting sample were (0.321, 0.323), which were very close to the data of the National Television Standard Committee (0.33, 0.33). The co-activated phosphors presented good match to ultraviolet light-emitting diodes (LEDs), which revealed that they could be novel promising phosphors utilized in white LED application.

Interference Management Algorithm Based on Coalitional Game for Energy-Harvesting Small Cells

  • Chen, Jiamin;Zhu, Qi;Zhao, Su
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • 제11권9호
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    • pp.4220-4241
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    • 2017
  • For the downlink energy-harvesting small cell network, this paper proposes an interference management algorithm based on distributed coalitional game. The cooperative interference management problem of the energy-harvesting small cells is modeled as a coalitional game with transfer utility. Based on the energy harvesting strategy of the small cells, the time sharing mode of the small cells in the same coalition is determined, and an optimization model is constructed to maximize the total system rate of the energy-harvesting small cells. Using the distributed algorithm for coalition formation proposed in this paper, the stable coalition structure, optimal time sharing strategy and optimal power distribution are found to maximize the total utility of the small cell system. The performance of the proposed algorithm is discussed and analyzed finally, and it is proved that this algorithm can converge to a stable coalition structure with reasonable complexity. The simulations show that the total system rate of the proposed algorithm is superior to that of the non-cooperative algorithm in the case of dense deployment of small cells, and the proposed algorithm can converge quickly.