• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.626-648
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• 2011

Energy consumption of wireless access networks is in permanent increase, which necessitates development of more energy-efficient network management approaches. Such management schemes must result with adaptation of network energy consumption in accordance with daily variations in user activity. In this paper, we consider possible energy savings of wireless local area networks (WLANs) through development of a few integer linear programming (ILP) models. Effectiveness of ILP models providing energy-efficient management of network resources have been tested on several WLAN instances of different sizes. To cope with the problem of high computational time characteristic for some ILP models, we further develop several heuristic algorithms that are based on greedy methods and local search. Although heuristics obtains somewhat higher results of energy consumption in comparison with the ones of corresponding ILP models, heuristic algorithms ensures minimization of network energy consumption in an amount of time that is acceptable for practical implementations. This confirms that network management algorithms will play a significant role in practical realization of future energy-efficient network management systems.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.103-113
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• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.459-469
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• 2016

Gas hydrate desalination process is based on a liquid to solid (Gas Hydrate, GH) phase change followed by a physical process to separate the GH from the remaining salty water. The GH based desalination process show 60.5-90% of salt rejection, post treatment like reverse osmosis (RO) process is needed to finally meet the product water quality. In this study, the energy consumption of the GH and RO hybrid system was investigated. The energy consumption of the GH process is based on the cooling and heating of seawater and the heat of GH formation reaction while RO energy consumption is calculated using the product of pressure and flow rate of high pressure pumps used in the process. The relation between minimum energy consumption of RO process and RO recovery depending on GH salt rejection, and (2) energy consumption of electric based GH process can be calculated from the simulation. As a result, energy consumption of GH-RO hybrid system and conventional seawater RO process (with/without enregy recovery device) is compared. Since the energy consumption of GH process is too high, other solution used seawater heat and heat exchanger instead of electric energy is suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6B
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• pp.316-324
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• 2007

In this paper we proposed an energy consumption model for IR-UWB wireless sensor networks. The model takes the advantages of PHY-MAC cross layer design, and we used slotted and un-slotted sleeping protocols to compare the energy consumption. We addressed different system design issues that are responsible to energy consumption and proposed an optimum model for the system design. We expect the slotted sleeping will consume less energy for bursty load than that of the un-slotted one. But if we consider latency, the un-slotted sleeping model performs better than the slotted sleeping case.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.2
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• pp.514-537
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• 2020

Wireless sensor network (WSN) is a distributed network composed of many sensory nodes. It is precisely due to the clustering unevenness and cluster head election randomness that the energy consumption of WSN is excessive. Therefore, a many-objective optimization WSN energy balance model is proposed for the first time in the clustering stage of LEACH protocol. The four objective is considered that the cluster distance, the sink node distance, the overall energy consumption of the network and the network energy consumption balance to select the cluster head, which to better balance the energy consumption of the WSN network and extend the network lifetime. A many-objective optimization algorithm to optimize the model (LEACH-ABF) is designed, which combines adaptive balanced function strategy with penalty-based boundary selection intersection strategy to optimize the clustering method of LEACH. The experimental results show that LEACH-ABF can balance network energy consumption effectively and extend the network lifetime when compared with other algorithms.

• YAKHAK HOEJI
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• v.57 no.2
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• pp.110-118
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• 2013

High-caffeine energy drink consumption has been increasing in young adults, frequently causing the most common symptoms such as tremor, insomnia, anxiety, and nervousness and rarely leading to serious adverse effects like seizure, acute mania, and stroke due to caffeine overdose. There have been little current studies regarding analysis of high-caffeine energy drink consumption and its adverse effects in Korea. This study was to examine high-caffeine consumption patterns, associated factors, and adverse effects based on responses from 231 college students in a University through survey. About 88.3% (n=204) of total respondents reported that they had energy drinks. College students mostly consumed energy drinks to keep awake (46%) when studying and to recover fatigue (27%). Approximately 44% respondents mainly reported palpitation (73.9%) and insomnia (72.8%) regarding adverse effect questionnaire. Current reports on the risk of recreational use, co-ingestion of alcohol and energy drink as well as energy drink consumption among children and adolescents are increasing, requiring further long-term research and awareness of these issues.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.7 no.1
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• pp.65-71
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• 2011

Recently, central and local governments of Korea have established and implemented various energy policies such as making energy map of city level and establishment of environment friendly city plan to materialize low carbon green city. To implement effectively these policies, however, conditions of energy consumption by each administrative district and each usage have to be verified exactly. This study is aimed to suggest a basic data for planing energy policy and energy demand prediction of city level by analyzing energy consumption unit and conditions of city gas by borough and usage in Busan.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.96-103
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• 2012

Annual energy consumption in detached houses are affected mainly by thermal performance of envelope. In particular the performance of glasses are critical due to global wanning and climatic change. Therefore, this research analyzes annual consumption of cooling and heating energy with various combination of U-value, shading coefficient and building orientation. The simulation results shows that shading coefficient of glazing contributes to the changes of proportion of heating and cooling energy demand and the optimized shading coefficient for minimizing energy consumption varies with buildings orientation.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.1
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• pp.1-6
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• 2012

This study aims to analysis domestic energy consumption in Korea and reduction greenhouse gas by building mechanical system. At this point be tormented the energy depletion and climate change of earth are big problems on the eatrh. In this paper we will find out best methods to reduction greenhouse gas and energy consumption by practical building mechanical system. Enlargement of greenhome and building adopt, greenhouse gas exhaust reduction in building, publication of energy consumption rate, publish building energy management manual, etc.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.8
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• pp.388-393
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• 2014

Energy consumption unit in a building is classified according to uses of electricity, gas, and oil, and it has been studied steadily as a material for establishing policy standards for energy saving in buildings. Meanwhile, consumption unit in apartment house can be calculated differently according to its survey method and area standard. Therefore, with the necessity of reestablishing energy consumption unit, this study has researched thermal energy consumption, Supply dwelling area Exclusive dwelling area, completion year and housing type of 23,791 households of 31 complex in Daejeon. As a result, (1) there was about 20% difference between supply and exclusive dwelling areas. (2) On the basis of exclusive dwelling area, thermal energy consumption unit was calculated as $104.9kWh/m^2{\cdot}a$ in 2010, $104.6kWh/m^2{\cdot}a$ in 2011, and $107.7kWh/m^2{\cdot}a$ in 2012.