• Resources Recycling
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• v.25 no.1
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• pp.24-30
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• 2016

The study to obtain tantalum concentration from electronic components (ECs) on Printed circuit board assembly (PCBA) of laptop was conducted. Electronic components on laptop PCBA were detached from boards by using self-developed experimental apparatus. The detached electronic components were sieved and 93.2 wt.% of tantalum capacitors were concentrated from the size interval from 2.80 mm to 6.35 mm. The tantalum capacitors were pulverized by hammer mill and electrodes (anode and cathode) were removed from the grinding products by using magnetic separators under the magnetic force of 300 Gauss. Finally, tantalum concentrate was concentrated from the magnetic separator products by using Knelson concentrator, and the maximum efficiency of 76.9% was achieved under the operating condition of bowl rotating speed of 200 rpm, and fluidizing water flowrate of 7 L/min. The grade and recovery of Ta concentrate under the condition were 81.1% and 78.8%, respectively.

• Resources Recycling
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• v.8 no.3
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• pp.37-42
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• 1999

Ths sludy was canied out to recover gold and sllics from abandoned gold mine talings with about 4.5 ghonAu and 84.88 wt% SOz. Tl~bee nef~cialiop~ro~c esses including crushing, screening, magnelic and gravity (humprey sp~rals,h aking table) separation \ulcornervex employed. Results were Feasible to rccovn h e gold concentrates (307.1 gltoilon .4u . 0.60 wr%, 97.7 giton Au : 0.27 wl%, 15.3 &/ton Au . 5.23 wt%, 21.2 g/ton Au : 2.42 wl%) and silica (96.40 wi% SiO\ulcorner yield 60 65 ~ 1 % )

• Resources Recycling
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• v.22 no.5
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• pp.20-28
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• 2013

This study was carried out to evaluate the possibility of resource recovery for municipal solid waste(MSW) that sorted by a MBT system. First, physical property of MSW was similar to wastes carried into Sudokown landfill site. However, moisture of MSW was little higher than that. As a result of BMP test using organic fraction of MSW(OFMSWs), approximately 60 ~ 80 mL $CH_4/g$-VS of methane was occurred. Compared to the other studies, the value of methane is lower. It seems to be caused that high ratio of vinyl/plastic in OFMSWs. The other BMP test using sample of MBT system located in Sudokwon landfill was conducted each physical properties. According to the result of experiment, food waste makes 193 mL $CH_4/g$-VS, and paper is 102 mL $CH_4/g$-VS. However, there was not methane production in vinyl and rubber. Additionally, others that can't sort no more show 30 m $CH_4L/g$-VS of methane production. From the result of experimental data OFMSWs has high fraction of vinyl, rubber and other substance that difficult for biodegradation. Therefore it is need to sort of them.

• Resources Recycling
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• v.29 no.6
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• pp.3-14
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• 2020

This study aims to introduce and review on the recovery technologies of rare earth elements(REEs) from coal ash. Many researchers have been carried out by various beneficiation processes, such as particle size separation, magnetic separation, specific gravity, and flotation to recover rare earth elements from coal ash generated from Pulverized Coal(PC) boiler. Through the beneficiation process, it was confirmed that concentration of rare earth elements was much lower than the 4,700 ppm, and that additional enrichment treatment through wet process was needed for the products recovered after the beneficiation process. It was confirmed that the rare earth elements contained in coal ash were applied to the leaching process after pretreatment such as alkali-fusion to improve leaching efficiency. Although beneficiation and leaching methods have been studied, its optimum recovery technologies for rare earth elements not been confirmed up to now, research on the recovery of rare earth contained in coal ash is reported to continue. In case of Korea, the technology for the recovery of rare earth elements from coal ash and coal by-product could not been confirmed up to present. In these reasons, it is urgent to develop technologies such as beneficiation and leaching process continuously.

• 한국벤처창업학회:학술대회논문집
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• 2024.04a
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• pp.17-20
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• 2024

우리는 대표적인 디지털 플랫폼인 온라인 음식 주문 배달 산업을 대상으로 디지털 경제의 긴꼬리 효과를 계량화한다. 특히, 코로나19 시기를 거치면서 음식배달플랫폼 입점으로 인한 긴꼬리 효과의 변화 양상을 고찰한다. 배달의민족에 입점한 음식점 15,000곳을 무작위로 선별하고 이들 매장의 2019년부터 2021년까지 전체 주문 정보를 취합(aggregation)하여 선형로그변환 후 기울기를 추정하여 디지털 경제의 긴꼬리 효과를 실증 분석하였다. 2019년부터 2021년까지 관찰기간 동안 음식 배달 플랫폼 활용 음식점 주비모수 분포의 긴꼬리 효과는 강건하게 관찰되었다. 이는 코로나19 이후 음식배달 플랫폼을 통한 음식점의 디지털 전환이 틈새시장 확장에 일정 부분 기여하였음을 의미한다. 또한, 긴꼬리 효과는 객단가가 높을수록 매출액 상위 집단일수록 더 커지는 반면, 비황금 시간대 매출비중이 높은 경우 긴꼬리 효과가 통계적으로 유의하게 증가하지 않았다. 이 결과는 피자, 족발 등 단가가 높고 비교적 배달서비스가 활발한 카테고리에서 음식 주문 및 배달 산업의 디지털 전환 효과가 증가한다는 업계 실무자들의 관찰과 부합한다. 타 업종에서도 상대적으로 경쟁이 치열한 시장 구분에서 디지털 경제의 긴꼬리 효과가 보다 강건하게 관찰될 것이라고 여겨진다. 음식점 간 경쟁강도가 상대적으로 약한 비황금시간대 매출비중이 긴꼬리 효과에 통계학적으로 유의한 영향을 주지 않는다는 실증결과 또한 동일한 함의가 있다.

• The Journal of the Korea Contents Association
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• v.21 no.9
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• pp.806-816
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• 2021

This study aims to describe the reporting patterns of articles on the Emergency Grant for all citizens(EGAC) and compare the reporting attitudes by newspaper companies. The main results are as follows: First, conservative newspapers reported more than four times as much coverage of EGAC as liberal newspapers. Newspaper articles reported during the week of the National Assembly Election Day accounted for about a quarter of the total, and 79.1% of the articles were reported in the political realm of newspapers, and only 2.8% in the social realm. Second, a conservative newspaper reported a critical attitude toward EGAC at 52.6% and favorable articles at 5.3%. On the other hand, in a liberal newspaper, critical articles were 17.1% and favorable articles were 37.1%. The inefficiency of selectivism was reported as the basis for the argument in favor, and concerns about the burden of deterioration in the financial soundness of the opponents were reported the most. Politicians are the most cited sources of information in articles. Finally, in prior to policymaking, the proportion of the media in favor of and against the news was similar, and the proportion of articles with a neutral attitude accounted for more than half. And in the specific method discussion stage, the articles in favor of the article exceeded the proportion of articles on the opposite side.

• Childhood Kidney Diseases
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• v.4 no.1
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• pp.1-5
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• 2000

Purpose: The plcr of spot urine has been uised to predict the timed urine protein excretion. Although this method reduces errors caused by variations in urine volume, it is relatively thconvenient and expensive. Recently, a more rapid and less expensive screening method with specific gravity(SG) has been reported, and we have examined whether estimated-creatinine(Cr-est) with urine 5G could be used in place of urine creatinine to predict 24-hour collected urine protein excretion in children. Methods: We had retrospectively analyzed protein, creatinine and urine SG in randomized spot urine samples of 147 patients from March 1998 till June 1998 in Korea university Guro hospital and compared the urinary protein creatinine ratio(P/Cr) with the protein estimated-creatinine ratio(P/Cr-est). We compared the correlation of urinary creatinine vs-urine 5G with the timed urine pretein excretion. Results: 1) urine SG accurately estimated urine creatinine concentration (r=0.407, P<0.001, Cr=SG x 4485.82-4482.87). 2) P/Cr correlated with urine protein excretion measured in a 24-hour urine collection (r=0.771, P<0.001, 24-hour collected urine protein : 0.338 x (P/Cr) 4+667.885). 3) P/Cr-est correlated with a 24-hour collected urine protein (r=0.723, P<0.001, 24-hour collected urine protein =0.354 x (P/Cr-est)+726.044), Conclusions: These results suggest that P/Cr-est with urine SG could be useful method for screening proteinuria in children.

• Resources Recycling
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• v.11 no.4
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• pp.11-16
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• 2002

Analysis and separation of constituent materials of old car have been performed by using the industrial shredding line. For this aim, three old cars made by domestic automobile manufacturers, Sonata II, Sephia and Prince were chosen and delivered in pressed form without engine, tires and doors, etc. Shredding line was substantially composed of pre- and main-shredder. cyclone, magnetic separation, eddy current separation and man-power separation. From the separation of shredder products, iron scrap was observed to be the major material of old car accounting for 60.1 ％ of total weight and non-ferrous metals involving Al, Cu and Zn, etc. were about 2％. Light fluff, about 90％ of total fluff product, was comprised with plastic, fiber and sponge, etc. and the fraction of 5 cm undersize in light fluff was 70.5%. In case of heavy fluff, however. rubber and plastic were found to be the major constituent materials of it. Among the constituent materials of fluff, plastic showed the highest calorific value, more than 10,000 cal/gr and leather and rubber showed relatively high chlorine content, 10.3 and 2.55 wt%, respectively.

• Resources Recycling
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• v.12 no.3
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• pp.25-30
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• 2003

The synthesis of SiC used for the parts of the gas turbine and the heat exchanger, was carried out. In this study, wire cutting slurry of silicon wafer and the graphite rod of spent zinc-carbon battery were applied to the starting materials for the synthesis. The powders of Si or Si+SiC were obtained from the waste material by filtration, gravity separation and magnetic separation. Graphite powder was produced by dismantling, grinding and gravity separation from spent zinc-carbon battery. The synthesis of SiC could be completed from the mixture powders of Si and C or Si+SiC and C at the condition of equivalent ratio of Si and C, atmosphere of Ar or vacuum, temperature of above 1$600^{\circ}C$ and 2 hours reactions. The purity of synthesized Si-C was above 99%.

• Journal of Family Resource Management and Policy Review
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• v.26 no.3
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• pp.19-34
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• 2022

There are growing concerns about debt insolvency among youth and low-income households. The deterioration in household debt quality among young people is due to a combination of sluggish employment, an increase in student loan burden and an increase in high-interest loans from the secondary financial sector. The purpose of this study was to explore the possibility of household debt default among young borrowers in Korea and to predict the factors affecting this possibility. This study utilized the 2021 Household Finance and Welfare Survey and used random forest algorithm to comprehensively analyze factors related to the possibility of default risk among young adults. This study presented the importance index and partial dependence charts of major determinants. This study found that the ratio of debt to assets(DTA), medical costs, household default risk index (HDRI), communication costs, and housing costs the focal independent variables.