• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.8
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• pp.2666-2687
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• 2022

As a new alternative communication scheme in 5G, unmanned aerial vehicle (UAV) is used as a relay in the remote base station (BS) for assistant communication. In order to ameliorate the quality of the backhaul link, a UAV backhaul transmission scheme based on improved Nash equilibrium (NE) strategy is proposed. First, the capacity of air-to-ground (A2G) channel by the link preprocess is maximized. Then, the maximum utility function of each UAV is used as the basis of obtaining NE point according to the backhaul channel and the backhaul congestion. Finally, the improved NE strategy is applied in multiple iterations until maximum utility functions of all the UAVs are reached, and the UAVs which are rejected by air-to-air (A2A) link during the process would participate in the source recovery process to construct a multi-hop backhaul network. Simulation results show that average effective backhaul rate, minimum effective backhaul rate increases by 10%, 28.5% respectively in ideal A2G channel, and 11.8%, 42.3% respectively in fading channel, comparing to pure NE strategy. And the average number of iterations is decreased by 5%.

• New & Renewable Energy
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• v.19 no.4
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• pp.61-71
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• 2023

The necessity of energy utilization using livestock manure has been proposed with the decrease in domestic agricultural land. Livestock manure solid fuel has been investigated as a promising energy resource owing to its convenient storage and use in agricultural and livestock fields. Additional electricity production is possible through the integration of a biomass combustion boiler with the organic Rankine cycle (ORC). In this study, a mathematical system model of the cattle manure solid fuel boiler integrated with the ORC was developed to analyze the components' performance under variable operating conditions. A sensitivity analysis was conducted to confirm the electrical efficiency of the ORC turbine and the applicability of this system. The minimum required waste heat recovery rate was derived considering the system marginal price and levelized cost of electricity of the ORC. The simulation results showed that, in Korea, more than 77.98% of waste heat recovery and utilization in ORC turbines is required to achieve economic feasibility through ORC application.

• Clean Technology
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• v.24 no.2
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• pp.87-98
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• 2018

Phosphorus (P) is an essential and irreplaceable element for all living organisms, and it is widely used as a fertilizer. Unfortunately, it is estimated that phosphate reservoir is depleted within about 100 years. Sewage sludge ash (SSA) is an alternative resource for P recovery because of its high P content. However, SSA cannot be directly used as a fertilizer due to heavy metals in it and low P bioavailability. Thermochemical treatment with Cl donor is known to reduce heavy metal contents and increase P bioavailability of SSA. Literature review on thermochemical technologies of SSA for the reduction of heavy metals and bioavailability enhancement has been carried out to estimate the status of current P recovery technology and to develop strategic future research plan for P recovery. The review showed that $CaCl_2$ and $MgCl_2$ were the most effective Cl donors and reaction temperature (< $1000^{\circ}C$) was the critical operation condition for the reduction. The removal efficiency depends on the species of heavy metals. Thermochemical technology of SSA for P recovery showed the possibility of commercial application in the near future to overcome the coming crisis of human sustainability by P depletion, but it needs cost effectiveness and more ecofriendly process to reduce energy consumption.

• Journal of Korea Society of Waste Management
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• v.35 no.7
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• pp.606-615
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• 2018

Over the past two decades, the options for solid waste management have been changing from land disposal to recycling, waste-to-energy, and incineration due to growing attention for resource and energy recovery. In addition, the reduction of greenhouse gas (GHG) emission has become an issue of concern in the waste sector because such gases often released into the atmosphere during the waste management processes (e.g., biodegradation in landfills and combustion by incineration) can contribute to climate change. In this study, the emission and reduction rates of GHGs by the municipal solid waste (MSW) management options in D city have been studied for the years 1996-2016. The emissions and reduction rates were calculated according to the Intergovernmental Panel on Climate Change guidelines and the EU Prognos method, respectively. A dramatic decrease in the waste landfilled was observed between 1996 and 2004, after which its amount has been relatively constant. Waste recycling and incineration have been increased over the decades, leading to a peak in the GHG emissions from landfills of approximately $63,323tCO_2\;eq/yr$ in 2005, while the lowest value of $35,962tCO_2\;eq/yr$ was observed in 2016. In 2016, the estimated emission rate of GHGs from incineration was $59,199tCO_2\;eq/yr$. The reduction rate by material recycling was the highest ($-164,487tCO_2\;eq/yr$) in 2016, followed by the rates by heat recovery with incineration ($-59,242tCO_2\;eq/yr$) and landfill gas recovery ($-23,922tCO_2\;eq/yr$). Moreover, the cumulative GHG reduction rate between 1996 and 2016 was $-3.46MtCO_2\;eq$, implying a very positive impact on future $CO_2$ reduction achieved by waste recycling as well as heat recovery of incineration and landfill gas recovery. This study clearly demonstrates that improved MSW management systems are positive for GHGs reduction and energy savings. These results could help the waste management decision-makers supporting the MSW recycling and energy recovery policies as well as the climate change mitigation efforts at local government level.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.243-250
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• 2010

Froth flotation of complex copper ore from Indonesia Jambi mine has been carried out to produce high-grade Cu concentrate. Since the ore contained minor Cu sulfides in addition to major Cu carbonate (malachite), copper concentrate was recovered by two-stage process of flotation, which consisted of copper sulfide flotation using xanthate followed by copper oxide flotation using oleic acid. The copper sulfide concentrate of 57.5% Cu grade with 9.5% recovery was obtained by copper sulfide flotation under conditions of 300 g/t collector (1 : 1 mixture of xanthate series Aero Promoter 211 and Aero Promoter 242) and pH 6.0 pulp. In subsequent copper oxide flotation on sink products, the concentrate of 30.8% Cu grade with 92.1% recovery was obtained under the conditions of oleic acid 300 g/t, AF65 50 g/t, pH 8.0 and 2 times cleaning. The flotation techniques which can achieve a Cu grade of 36.1% and a recovery of 92.1% have been developed from the two-stage process of flotation.

• Resources Recycling
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• v.31 no.2
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• pp.40-48
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• 2022

In this study, the effects of solution components were investigated in the recovery of vanadium as ammonium metavanadate from vanadium-ore-salt roasting-water leaching solution. The vanadium-containing solution is strongly alkaline (pH 13), so the pH must be lowered to 9 or less to increase the ammonium metavanadate precipitation efficiency. However, in the process of adjusting the solution pH using sulfuric acid, aluminum ions are co-precipitated, which must be removed first. In this study, aluminum was precipitated in the form of an aluminum-silicate compound using sodium silicate, and the conditions for minimizing vanadium loss in this process were investigated. After aluminum removal, the silicate was precipitated and removed by adjusting the solution pH to 9 or less using sulfuric acid. In this process, the concentration and addition rate of sulfuric acid have a significant influence on the loss of vanadium, and vanadium loss was minimized as much as possible by slowly adding dilute sulfuric acid. Ammonium metavanadate was precipitated using three equivalents of ammonium chloride at room temperature from the aluminum-free, aqueous solution of vanadium following the pH adjustment process. The recovery yield of vanadium in the form of ammonium metavanadate exceeded 81%. After washing the product, vanadium pentoxide with 98.6% purity was obtained following heat treatment at 550 ℃ for 2 hours.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.2
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• pp.516-525
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• 2015

In this study, Life Cycle Assessment(LCA) was applied to the production processes of waste cooking oil recycling products. Recycling products as defined in the Law of Saving of Resources and Recycling Promotion are biodiesel and soap. Weighting result of biodiesel production process showed that the most significant impact potential was abiotic resource depletion(84.17%) followed by global warming(13.93%). In the case of the soap, the most significant impact potential was also abiotic resource depletion(58.59%) followed by global warming(33.71%). In terms of the whole system of the biodiesel production process, methanol showed the largest environmental impact potential(87.35%). While in the case of the soap, sodium chloride showed the largest environmental impact potential(99.99%). This study suggests that there should be improvement of the methanol recovery system in the biodiesel production process and also appropriate use of the major environmental impact materials in both processes.

• The Journal of Fisheries Business Administration
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• v.51 no.3
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• pp.33-47
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• 2020

This study is aimed to prepare the promotion strategy to spawn snow crab resources and create their habitats using SWOT-AHP analysis. Currently, the creation program of spawning and habitat ground (CPSH) of various fisheries resource is a continuing process, however, none of these CPSH can be labeled as being effective in Korea. In order for CPSH to be effective, it must be planned systematically. Therefore, it is necessary for establishing promotion strategy on the CPSH. SWOT-AHP analysis is used to improve explanation ability of SWOT analysis. In this research, we suggested three strategies and 15 implementation plans of the CPSH using SWOT-AHP analysis. It is expected that the economic feasibility, ecosystem and recovery of fisheries resources will improve significantly. Consequently, to increase the performance of CPSH, it is necessary to focus on the developing an efficient and executive promotion strategy on the CPSH.

• The Journal of Fisheries Business Administration
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• v.42 no.1
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• pp.37-55
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• 2011

This study is to examine the economic effects of seaweed forest creation project in the case of Jeju Woodo Seokwang－ri. Seaweed forest creation project will raise up the quality and quantity of coastal fisheries resource and improve the structure of coastal ecosystem as a project the recovery of coastal fisheries resource against barren ground like whitening event. The economic effect by seaweed forest creation project can be found not only in the income increase of fishermen but also in reduction of carbon dioxide. The results of this study are summarized as follows: First, the income increase effect of fishermen has economic value of 26,945 thousand won under a 30-year cash flow based on a 8.5% discount rate. This suggests that the seaweed forest creation project increases income of fishermen. Second, the reduction effect of carbon dioxide has economic value of 1,083 thousand won per year. This indicates that the seaweed forest creation project reduces carbon dioxide. In conclusion, the results of this study suggest the seaweed forest creation project has economic value in the case of Jeju Woodo Seokwang-ri.

• Environmental and Resource Economics Review
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• v.14 no.2
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• pp.419-445
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• 2005

In 2002, the waste was generated about 277,533tons per day. The treatments of waste were recycling, which had accounted for almost 70%, landfill, which had accounted for 19.8%, and incineration, which had accounted for 6.5%. The energy recovery from incineration has been increased since 1995. The portion of waste in the renewable energy has been increased. Waste incineration heating system generates total 134TOE of $CO_2$ as compared to 6,800TOE of GHG from LNG boiler centralized heating system to bring 98% reduction rate of GHG emissions. We need the integrated model to examine the impacts of waste managements on economy and environments. The Asia-Pacific Integrated Model is introduced as the example of the integrated model.