• Environmental Analysis Health and Toxicology
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• v.14 no.4
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• pp.135-144
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• 1999

Environmental toxicities of priority water pollutants were evaluated by two selected bioassays, Lettuce seed germination/elongation test and Microtox acute toxicity test. Toxic chemicals (heavy metals, polycyclic aromatic hydrocarbons, and phenolic compounds) inhibited the germination rate and root elongation of Lettuce seed, as well as the bioluminescence of Microtox bacteria. When test biota were exposed to target chemicals, the sensitivity of Lettuce bioassay was relatively lower than that of Microtox bioassay. However, Lettuce bioassay may be a good candidate for prescreening the environmental toxicities of priority water pollutants, since the testing method with Lettuce seed was relatively easier and more economic than with Microtox bacteria. Toxicity tests were conducted to compare the validity and sensitivity of both bioassays for sediment from a small stream passed through urban area as well as leachate from a municipal solid waste landfill. From experimental results, we found that Lettuce test and Microtox test are compensated each other as a battery of bioassay for evaluating the environmental toxicities of field samples obtained from a small stream contaminated by pollutants.

• Journal of Biomedical Engineering Research
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• v.38 no.5
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• pp.242-247
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• 2017

This study presents a bio-chemical energy harvesting system which can generate electric power from bioorganic substance contained in vermicompost. It produced electricity by inoculating microbial fuel cell(MFC) with earthworm-composted food waste. The generated electricity was converted into usable voltage level for mobile electronics through power conditioning circuits. The implemented prototype showed $200{\mu}W$ of maximum output electric power, which successfully supplied a beacon device which continuously transmitted data to nearby smartphone without a battery. The proposed system can help develop portable or bio-mimetic energy supply for sustainable use with further improvement.

• Journal of the Korea Society of Computer and Information
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• v.21 no.2
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• pp.25-32
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• 2016

In this paper, we design a middleware for context-awareness which provides compound contexts from diverse sensors on a mobile device. Until now, most of context-aware application developers have taken responsibility for context processing from sensing data. Such application-level context processing causes heavily redundant data processing and leads to significant resource waste in energy as well as computing. In the proposed scheme, we define primitive and compound context map which consists of relavant sensors and features. Based on the context definition, each application demands a context of interest to the middleware, and thus similar context-aware applications inherently share context information and procesing within the middleware. We show that the proposed scheme significantly reduces the resource amounts of cpu, memory, and battery, and that the performance gain gets much more when multiple applications which need similar contexts are running.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.3
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• pp.57-70
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• 2011

To address global climate change, various governments are investing in electric vehicle research and, especially in Korea, the application of electric vehicles to public transportation. The lithium batteries used in electric vehicles typically have an expected life cycle of 2-5 years. If electric vehicles become commonly used, they will generate many discarded batteries that could be harmful to the environment. Additionally, lithium batteries are potentially explosive and should be handled appropriately. Thus, reverse logistics issues are involved in handling expired batteries efficiently and safely. Reverse logistics includes the collection, recycling, remanufacturing, and discarding of waste. This study developed a reverse logistics process for electric vehicle batteries after analyzing the as-is process for lead and lithium batteries. It also developed possible disposal regulations for electric vehicle batteries based on current laws regarding conventional batteries.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.197-200
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• 2008

In most sensor networks, nodes can be easily compromised by adversaries due to hostile environments. Adversaries may use compromised nodes to inject false reports into the sensor networks. Such false report attacks will cause false alarms that can waste real-world response effort, and draining the finite amount of energy resource in the battery-powered network. A dynamic enroute scheme proposed by Yu and Guan can detect and drop such false reports during the forwarding phase. In this scheme, choosing a threshold value is very important, as it trades off between security power and energy consumption. In this paper, we propose a threshold determining method which uses the fuzzy rule-based system. The base station periodically determines a threshold value though the fuzzy rule-based system. The number of cluster nodes, the value of the key dissemination limit, and the remaining energy of nodes are used to determine the threshold value.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.144-150
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• 2022

In this paper, we analyze the current research technology trends through the literature reviews of technical outlines of electric vehicles and hydrogen fuel cell vehicles, domestic and overseas policy trends, etc. After analyzing the literature, we found out while the re-use and recycling of waste batteries and the in-wheel motor systems are essential areas for the development of electric vehicles and hydrogen fuel cell vehicles, the related research is not quite sufficient, so the direction for further research is proposed at the conclusion.

• Applied Chemistry
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• v.16 no.1
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• pp.73-76
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• 2012

Due to the developments of communications equipment and electronic devices, lithium ion secondary battery usage is growing. Along with demand increasing, the amount of scrap has been steadily increasing. In this study, method of cobalt recovery using organic eco-friendly is proposed. Sulfuric acid, Malic acid, Citric acid at reflux device had good cobalt leaching efficiency. And Sulfuric acid, Malic acid at the autoclave increased cobalt leaching efficiency.

• Resources Recycling
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• v.31 no.4
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• pp.40-48
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• 2022

In waste lithium iron phosphate (LFP) batteries, the cathode material contains approximately 4% lithium. Recycling the constituent elements of batteries is important for resource circulation and for mitigating the environmental pollution. Li contained in the waste LFP cathode powder was selectively leached using persulfate-based oxidizing agents, such as sodium persulfate, potassium persulfate, and ammonium persulfate. Leaching efficiency and waste LFP powder properties were compared and analyzed. Pulp density was used as a variable during leaching, which was performed for 3 h under each condition. The leaching efficiency was calculated using the inductively coupled plasma (ICP) analysis of the leachate. All types of persulfate-based oxidizing agents used in this study showed a Li leaching efficiency over 92%. In particular, when leaching was performed using (NH₄)₂S₂O₈, the highest Li leaching percentage of 93.3% was observed, under the conditions of 50 g/L pulp density and an oxidizing agent concentration of 1.1 molar ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.3A
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• pp.221-229
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• 2007

In this paper, we propose and analyze the optimized sleep mode for a mobile node (MN) in IEEE 802.16e wireless metropolitan area networks. Because a MN in a sleep mode specified in 802.16e specification should maintain state information with the base station currently attached, it must renew sleep state with a new base station after handover which leads to unnecessary waste of battery power. Noting that the mobility pattern of a MN is independent of call arrival patterns, we propose an optimized sleep mode to eliminate unnecessary standby period of a MN in sleep state after handover. We also propose an analytical model for the proposed scheme in terms of power consumption and the initial call response time. Simulation studies that compare the performance between the sleep mode and the optimized sleep mode show that our scheme marginally increases initial call response delay with the huge reduction in power consumption.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.219-228
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• 2007

End-to-end path setup and maintenance are very important for mobile ad-hoc wireless communications, because of the mobility and the limited battery capacity of the nodes in the networks. the AODV routing protocol is the one of mary proposed protocols. However, there are route failure problem with the Proposed protocols between intermediate nodes due to such mobility and exhausted battery characteristics, and this is because only the shortest hop count is considered for the route setup. If route failure happens. Problem such as the waste of bandwidth and the increment of the energy consumption occur because of the discarding data packets in the intermediate nodes and the path re-setup process required by the source node. In addition, it obviously causes the network lifetime to be shortened. This paper proposes a routing protocol based on the AODV routing protocol that it makes use of the remaining energy, signal strength and SNR of the MAC layer resources to setup a path.