• Title/Summary/Keyword: Energy Efficiency

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QoE-aware Energy Efficiency Maximization Based Joint User Access Selection and Power Allocation for Heterogeneous Network

  • Ji, Shiyu;Tang, Liangrui;Xu, Chen;Du, Shimo;Zhu, Jiajia;Hu, Hailin
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.10
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    • pp.4680-4697
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    • 2017
  • In future, since the user experience plays a more and more important role in the development of today's communication systems, quality of experience (QoE) becomes a widely used metric, which reflects the subjective experience of end users for wireless service. In addition, the energy efficiency is an increasingly important problem with the explosive growth in the amount of wireless terminals and nodes. Hence, a QoE-aware energy efficiency maximization based joint user access selection and power allocation approach is proposed to solve the problem. We transform the joint allocation process to an optimization of energy efficiency by establishing an energy efficiency model, and then the optimization problem is solved by chaotic clone immune algorithm (CCIA). Numerical simulation results indicate that the proposed algorithm can efficiently and reliably improve the QoE and ensure high energy efficiency of networks.

Energy-Efficient Base Station Sleep Scheduling in Relay-Assisted Cellular Networks

  • Chen, Hongbin;Zhang, Qiong;Zhao, Feng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.3
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    • pp.1074-1086
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    • 2015
  • We Relay-assisted cellular network architecture has been developed to cover cell-edge users and to improve capacity. However, the deployment of relay stations (RSs) in cellular networks may increase the total energy consumption. Though energy efficiency has become a major concern in cellular networks, little work has studied the energy efficiency of relay-assisted cellular networks by sleep scheduling. In this paper, a distributed base stations (BSs) sleep scheduling scheme in relay-assisted cellular networks is proposed. The goal is to maximize the energy efficiency under the spectral efficiency constraint. Firstly, whether the BSs should be sleeping or active is determined by the traffic profile. Then, the transmission powers of the active BSs are optimized within the game-theoretic framework, by using an interior-point method, so as to maximize the energy efficiency. Simulation results demonstrate that the effectiveness of the proposed scheme is superior to that turning on all the BSs without sleep scheduling.

A bond graph approach to energy efficiency analysis of a self-powered wireless pressure sensor

  • Cui, Yong;Gao, Robert X.;Yang, Dengfeng;Kazmer, David O.
    • Smart Structures and Systems
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    • v.3 no.1
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    • pp.1-22
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    • 2007
  • The energy efficiency of a self-powered wireless sensing system for pressure monitoring in injection molding is analyzed using Bond graph models. The sensing system, located within the mold cavity, consists of an energy converter, an energy modulator, and a ultrasonic signal transmitter. Pressure variation in the mold cavity is extracted by the energy converter and transmitted through the mold steel to a signal receiver located outside of the mold, in the form of ultrasound pulse trains. Through Bond graph models, the energy efficiency of the sensing system is characterized as a function of the configuration of a piezoceramic stack within the energy converter, the pulsing cycle of the energy modulator, and the thicknesses of the various layers that make up the ultrasonic signal transmitter. The obtained energy models are subsequently utilized to identify the minimum level of signal intensity required to ensure successful detection of the ultrasound pulse trains by the signal receiver. The Bond graph models established have shown to be useful in optimizing the design of the various constituent components within the sensing system to achieve high energy conversion efficiency under a compact size, which are critical to successful embedment within the mold structure.

Estimating Potential Energy Consumption and Carbon Emission Reduction in South Korea Using Non-radial Data Envelopment Analysis Approach (Non-radial Data Envelopment Analysis를 적용한 지역별 에너지 및 이산화탄소 저감가능성 추정)

  • Kim, Kwang-Uk;Kang, Sang-Mok
    • Environmental and Resource Economics Review
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    • v.25 no.2
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    • pp.299-320
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    • 2016
  • This study estimates an energy efficiency of 16 metropolitans and provinces in Korea, and measures potential energy-saving and carbon emission reduction using a non-radial data envelopment analysis method. Based on energy mix scenarios, this study also evaluates the impact of changes in energy structural adjustment on a regional environmental performance. The empirical results show that, on average, 12.70% of energy consumption and 13.73% of carbon emission can be reduced by improvement in energy efficiency, and low efficiency of oil usage in metropolitan cities is a major source of the inefficiency. Furthermore, it is found that energy mix policy should be considered to achieve an extra energy-saving and carbon reduction.

Impact of energy efficiency improvement on greenhouse gas in off-season tomato farming: Evidence from Punjab, Pakistan

  • Ali, Qamar;Khan, Muhammad T.I.;Khan, Muhammad N.I.
    • Advances in Energy Research
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    • v.5 no.3
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    • pp.207-217
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    • 2017
  • Energy consumption in agriculture is responsible for greenhouse gas emission but it can be reduced after efficient utilization of energy inputs. Therefore, the present study aims for the estimation of energy efficiency and extent of greenhouse gas reduction after benchmarking of inefficient farms in off-season tomato in Punjab province of Pakistan. Primary data were collected from 70 farmers with simple random sampling. By using data envelopment analysis, the average value of technical, pure technical and scale efficiency was 0.80, 0.92 and 0.87, respectively while increasing, constant and decreasing return to scale was observed in 33, 26 and 11 farmers, respectively. Total input energy was reduced by $12,688.91MJ\;ha^{-1}$ (13.89%) if inefficient farms used the energy inputs according to recommendations or benchmarking. A major portion of energy saving comes from fertilizers (68.79%) followed by diesel (15.70%), chemicals (5.91%), machinery (4.37%) and water (4.00%). Total greenhouse gases reduction was $499.17kg\;CO_2\;eq.ha^{-1}$ (14.57%) as a result of improvement in energy efficiency or benchmarking of inefficient farms. Agricultural extension staff should visit the vegetable farms on regular basis and give necessary information about efficient utilization of energy inputs. The government should create awareness about the optimum use of input through seminars and pamphlets.

Enhanced Switching Pattern to Improve Energy Transfer Efficiency of Active Cell Balancing Circuits Using Multi-winding Transformer (다중권선 변압기를 이용한 능동형 셀 밸런싱 회로의 에너지 전달 효율을 높이기 위한 향상된 스위칭 패턴)

  • Lee, Sang-Jung;Kim, Myoungho;Baek, Ju-Won;Jung, Jee-Hoon
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.4
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    • pp.279-285
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    • 2019
  • This study proposes an enhanced switching pattern that can improve energy transfer efficiency in an active cell-balancing circuit using a multiwinding transformer. This balancing circuit performs cell balancing by transferring energy stored in a specific cell with high energy to another cell containing low energy through a multiwinding transformer. The circuit operates in flyback and buck-boost modes in accordance with the energy transfer path. In the conventional flyback mode, the leakage inductance of the transformer and the stray inductance component of winding can transfer energy to an undesired path during the balancing operation. This case results in cell imbalance during the cell-balancing process, which reduces the energy transfer efficiency. An enhanced switching pattern that can effectively perform cell balancing by minimizing the amount of energy transferred to the nontarget cells due to the leakage inductance components in the flyback mode is proposed. Energy transfer efficiency and balancing speed can be significantly improved using the proposed switching pattern compared with that using the conventional switching pattern. The performance improvements are verified by experiments using a 1 W prototype cell-balancing circuit.

Research on a handwritten character recognition algorithm based on an extended nonlinear kernel residual network

  • Rao, Zheheng;Zeng, Chunyan;Wu, Minghu;Wang, Zhifeng;Zhao, Nan;Liu, Min;Wan, Xiangkui
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.1
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    • pp.413-435
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    • 2018
  • Although the accuracy of handwritten character recognition based on deep networks has been shown to be superior to that of the traditional method, the use of an overly deep network significantly increases time consumption during parameter training. For this reason, this paper took the training time and recognition accuracy into consideration and proposed a novel handwritten character recognition algorithm with newly designed network structure, which is based on an extended nonlinear kernel residual network. This network is a non-extremely deep network, and its main design is as follows:(1) Design of an unsupervised apriori algorithm for intra-class clustering, making the subsequent network training more pertinent; (2) presentation of an intermediate convolution model with a pre-processed width level of 2;(3) presentation of a composite residual structure that designs a multi-level quick link; and (4) addition of a Dropout layer after the parameter optimization. The algorithm shows superior results on MNIST and SVHN dataset, which are two character benchmark recognition datasets, and achieves better recognition accuracy and higher recognition efficiency than other deep structures with the same number of layers.

Real Time Monitoring of Energy Efficiency Operation Indicator on Merchant Ships

  • Barro, Ronald Dela Cruz;Kim, Jun-Seong;Lee, Don-Chool
    • Journal of Advanced Marine Engineering and Technology
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    • v.35 no.3
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    • pp.301-308
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    • 2011
  • International Maritime Organization (IMO) proposed the Energy Efficiency Operation Indicator (EEOI) in 2005 and the Energy Efficiency Design Index (EEDI) in 2008 so as to address emission concern and regulation. Likewise, Ship Energy Efficiency Management Plan (SEEMP) and Greenhouse Gas (GHG) monitoring and management are also becoming an issue lately. This paper introduces the energy efficiency design index (operation indicator) monitoring system (EDiMS) software can continuously monitor $CO_2$, $NO_x$, $SO_x$, and PM values emitted from ship. The accurate inventory of ships GHG can be obtained from base of emission result during the engine shop test trial and the actual monitoring of shaft power and ship speed. In addition, the ability to store all exhaust emission and engine operation data can be applied as the useful tool of the inventory work of air pollution and ship energy management plan for the mitigation or reduction of ship emissions.

A Feasibility Study on DC Microgrids Considering Energy Efficiency (에너지 효율분석을 통한 DC 마이크로그리드의 타당성 검토)

  • Yu, Cheol-Hee;Chung, Il-Yop;Hong, Sung-Soo;Chae, Woo-Kyu;Kim, Ju-Yong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.9
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    • pp.1674-1683
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    • 2011
  • More than 80% of electric loads need DC electricity rather than AC at the moment. If DC power could be supplied directly to the terminal loads, power conversion stages including rectifiers, converters, and power adapters can be reduced or simplified. Therefore, DC microgrids may be able to improve energy efficiency of power distribution systems. In addition, DC microgrids can increase the penetration level of renewable energy resources because many renewable energy resources such as solar photovoltaic(PV) generators, fuel cells, and batteries generate electric power in the form of DC power. The integration of the DC generators to AC electric power systems requires the power conversion circuits that may cause additional energy loss. This paper discusses the capability and feasibility of DC microgrids with regard to energy efficiency analysis through detailed dynamic simulation of DC and AC microgrids. The dynamic simulation models of DC and AC microgrids based on the Microgrid Test System in KEPCO Research Institute are described in detail. Through simulation studies on various conditions, this paper compares the energy efficiency and advantages of DC and AC microgrids.

A Genetic-Algorithm-Based Optimized Clustering for Energy-Efficient Routing in MWSN

  • Sara, Getsy S.;Devi, S. Prasanna;Sridharan, D.
    • ETRI Journal
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    • v.34 no.6
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    • pp.922-931
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    • 2012
  • With the increasing demands for mobile wireless sensor networks in recent years, designing an energy-efficient clustering and routing protocol has become very important. This paper provides an analytical model to evaluate the power consumption of a mobile sensor node. Based on this, a clustering algorithm is designed to optimize the energy efficiency during cluster head formation. A genetic algorithm technique is employed to find the near-optimal threshold for residual energy below which a node has to give up its role of being the cluster head. This clustering algorithm along with a hybrid routing concept is applied as the near-optimal energy-efficient routing technique to increase the overall efficiency of the network. Compared to the mobile low energy adaptive clustering hierarchy protocol, the simulation studies reveal that the energy-efficient routing technique produces a longer network lifetime and achieves better energy efficiency.