• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4106-4113
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• 2021

Rare earth doped barium tellurite glasses were synthesised and explored for their radiation shielding applications. All the samples showed good thermal stability with values varying between 101 ℃ and 135 ℃ based on dopants. Structural properties showed the dominance of matrix elements compared to rare earth dopants in forming the bridging and non-bridging atoms in the network. Bandgap values varied between 3.30 and 4.05 eV which was found to be monotonic with respective rare earth dopants indicating their modification effect in the network. Various radiation shielding parameters like linear attenuation coefficient, mean free path and half value layer were calculated and each showed the effect of doping. For all samples, LAC values decreased with increase in energy and is attributed to photoelectric mechanism. Thulium doped glasses showed the highest value of 1.18 cm^-1 at 0.245 MeV for 2 mol.% doping, which decreased in the order of erbium, holmium and the base barium tellurite glass, while half value layer and mean free paths showed an opposite trend with least value for 2 mol.% thulium indicating that thulium doped samples are better attenuators compared to undoped and other rare earth doped samples. Studies indicate an increased level of thulium doping in barium tellurite glasses can lead to efficient shielding materials for high energy radiation.

• 한국콘텐츠학회논문지
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• 제19권4호
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• pp.413-422
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• 2019

본 연구는 40대 - 50대 소비자들을 대상으로 아웃도어 제품에 대한 구매의도를 분석하였다. 구매의도에 미치는 영향요인은 다양한 요인이 있을 수 있으나 탐색적인 관점에서 서비스 품질과 소비가치로 설정하여 분석을 하였다. 서비스 품질은 세부 변수를 유형성, 대응성, 신뢰성으로 설정하였고, 소비가치는 기능적 소비가치, 진귀적 소비가치, 상황적 소비가치로 설정하였다. 분석결과, 서비스 품질의 유형성, 대응성, 신뢰성과 소비가치의 기능적 소비가치는 구매의도에 긍정적인 영향을 미치는 것으로 나타났으나 소비가치의 진귀적 소비가치, 상황적 소비가치는 구매의도에 긍정적인 영향을 미치지 않는 것으로 분석되었다. 이러한 분석결과는 40대 - 50대 소비자들 한테는 서비스 품질이 소비자의 구매의도에 매우 중요한 요인임을 알 수 있었으나 소비가치는 구매의도에 그다지 중요한 요인이 아니라는 점을 알 수 있었다.

• 한국의류학회지
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• 제37권4호
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• pp.618-630
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• 2013

This study investigates the influence of consumption value on attitude and the repurchase intention of secondhand fashion goods. In addition, this study examines the effect of consumption value on attitudes according to self-confidence in fashion coordination. Questionnaire data from 220 university students who made purchases of secondhand fashion goods were analyzed. The results were as follows. First, there were 5 factor solutions for the consumption value of secondhand fashion goods: rare value, emotional value, functional value, social contribution value, and economic value. Second, rare value, social contribution value and economic value had a positive impact on the attitude toward secondhand fashion goods. Third, attitude had positive impact on the repurchase intention of secondhand fashion goods. Fourth, there was a significant difference in the magnitude of the effect of consumption value on attitude according to self-confidence in fashion coordination. The results of this study provide various guidelines for marketers or retailers who are interested in secondhand fashion goods.

• Bulletin of the Korean Chemical Society
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• 제32권8호
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• pp.2732-2736
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• 2011

In pH 4.2 HAc-NaAc buffer solution, horseradish peroxidase (HRP) catalyzed $H_2O_2$ oxidation of nanosilver to form $Ag^+$. After centrifugation, $Ag^+$ in the supernatant can be measured by graphite furnace atomic absorption spectrophotometry (GFAAS) at the silver absorption wavelength of 328.1 nm. When HRP concentration increased, the $Ag^+$ concentration in the supernatant increased, and the absorption value enhanced. The HRP concentration in the range of 0.84-50 $ng{\cdot}mL^{-1}$ was linear to the enhanced absorption value (${\Delta}A$), with a regression equation of ${\Delta}A$=0.012C+0.11, correlation coefficient of 0.9988, and detection limit of 0.41 $ng{\cdot}mL^{-1}$ HRP. The proposed GFAAS method was used to detect HRP in waste water samples, with satisfactory results.

• Journal of Korea Trade
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• 제27권2호
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• pp.96-114
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• 2023

Purpose - This paper elucidates a nexus between the occurrence of rare disaster events and the volatility of economic growth by distinguishing the likelihood of rare events from stochastic volatility. We provide new empirical facts based on a quarterly time series. In particular, we focus on the role of financial liberalization in spreading the economic crisis in developing countries. Design/methodology - We use quarterly data on consumption expenditure (real per capita consumption) from 44 countries, including advanced and developing countries, ending in the fourth quarter of 2020. We estimate the likelihood of rare event occurrences and stochastic volatility for countries using the Bayesian Markov chain Monte Carlo (MCMC) method developed by Barro and Jin (2021). We present our estimation results for the relationship between rare disaster events, stochastic volatility, and growth volatility. Findings - We find the global common disaster event, the COVID-19 pandemic, and thirteen country-specific disaster events. Consumption falls by about 7% on average in the first quarter of a disaster and by 4% in the long run. The occurrence of rare disaster events and the volatility of gross domestic product (GDP) growth are positively correlated (4.8%), whereas the rare events and GDP growth rate are negatively correlated (-12.1%). In particular, financial liberalization has played an important role in exacerbating the adverse impact of both rare disasters and financial market instability on growth volatility. Several case studies, including the case of South Korea, provide insights into the cause of major financial crises in small open developing countries, including the Asian currency crisis of 1998. Originality/value - This paper presents new empirical facts on the relationship between the occurrence of rare disaster events (or stochastic volatility) and growth volatility. Increasing data frequency allows for greater accuracy in assessing a country's specific risk. Our findings suggest that financial market and institutional stability can be vital for buffering against rare disaster shocks. It is necessary to preemptively strengthen the foundation for financial stability in developing countries and increase the quality of the information provided to markets.

• 자원리싸이클링
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• 제28권6호
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• pp.26-35
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• 2019

석탄재로부터 희토류 회수 가능성을 확인하기 위해 경제성 평가 요소를 분석하여 국내 희토류 확보를 위한 검토 자료로 활용하고자 하였다. 석탄재로부터 희토류 회수를 위한 가행 최저품위는 TR EO기준 1,000 ppm으로 확인되었으며, 각 희토류 성분의 함량에 따라 경제적 가치가 변화되는 특성을 보였다. 이는 현재 산업에서 요구하는 희토류 원소별 가격차이 발생에 따른 결과이며, 미래 산업에서 요구되는 희토류 성분에 따라 변동은 가능하다. 석탄재함유 희토류성분에 대해 상용화 회수공정 개발을 목적으로, 희토류 함량 및 석탄재 발생량을 이용한 평가, 산업 수요 특성을 고려한 평가, 실제 산업에서 투자비용과 수익비용의 비교평가 등 다양한 경제성 평가 방법에 대해 연구가 진행되었다. 이러한 연구로부터 확인된 석탄재에 포함된 희토류 회수 관련 기술 수준은 높지 않았으며, 이로 인해 경제성이 확보된 희토류 회수 시스템의 개발이 아직은 미흡한 것으로 확인되었다. 세계 희토류 시장의 문제점 극복을 위한 대책으로 석탄재에 포함된 희토류 회수 연구는 계속 진행될 것으로 보고되었으며, 국내에서도 자원 및 회수기술 확보를 목적으로 이와 관련된 연구가 절실히 요구된다.

• 암석학회지
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• 제14권4호
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• pp.237-250
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• 2005

ICP-MS로 화강암질 암석내 희토류원소의 함량 분석시 표준시료의 선택이 어느 정도 영향을 주는 지를 밝혀내기 위해, 상업용 표준시료(ACCU-standard, No. Cal-1), 화강암의 한국산 표준시료(KG-1), 미국산 표준시료(G-2), 일본산 표준시료(JC-1a, JC-2)를 각각 기준시료로 하여 각각의 희토류원소 함량을 측정하였다. 실험결과에 의하면, 경희토류(La-Gd) 분포도는 표준시료의 변화에 관계없이 대체적으로 추천값과 측정값 모두 일치하였다. 그러나 G-2 혹은 JG-2를 기준으로 측정했을 시, 다른 표준시료의 추천값과 측정값에 의한 중희토류(Gd-Lu)의 분포도는 많은 차이가 발생되었다. 이는 표준시료의 추천값의 오류 혹은 표준시료 암석의 지구화학적 특성에 기인된다. KG-1 혹은 JG-1a를 기준시료로 하여 희토류원소 함량을 측정했을 경우에는 G-2나 JG-2를 기준시료로 했을 때보다 추천값과 측정값에 의한 희토류원소의 분포도의 어긋남이 비교적 약한 편이다. 이는 국내 화강암류의 희토류원소 함량분석에 있어서의 표준시료로서 KG-1 혹은 JG-1a가 보다 더 유용함을 지시해준다.

• 환경영향평가
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• 제6권2호
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• pp.153-164
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• 1997

This study was conducted to develop the new Environmental Impact Assessment techniques for the grading of rareness in plant. 17 EISs which were submitted in 1996 were analyzed to know the problems in existent EIA techniques for the conservation of rare plants. Category of rare plant was reevaluated and evaluation technique for the grading of rareness in plant was developed. The results obtained from this study were as follows: 1. The evaluation technique of rareness in plant was not reflected in the current preparation provision for EIS. And t his fact also appeared in most of the EIS which were reexamined in this study. 2. The category of rare species which have been considered as the subject of protection in EIA have to be enlarged to more than legally protected species designated by MOE. 3. The taxonomic characteristics and status of species, characteristics of population, geographical characters, extent of threat and its possibility by man resulted from the habitat loss were investigated. Each item was endowed scores from 1 to 5 and all the scores were summed, and then this value was used to evaluate the order of conservation. 4. Conservation measures for the rare plants have to be applied according to the levels of rareness grade, and they are absolute conservation, in situ conservation, transplanting and ex situ conservation, post observation and none by the levels from A to E. 5. Considering the phenology of rare plants, investigation for the rare plants have to be made a1 least three times. 6. Size of the MVP(Minimum Viable Population), pollination ecology also have to be considered for the conservation of rare plants. And in the case of adopting ex situ conservation measure, the site and methods for the conservation of rare plants have to be proposed in detail.

• 한국전기전자재료학회논문지
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• 제16권6호
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• pp.538-548
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• 2003

We studied effects by Re$_2$O$_3$(R=Dy, Gd, Ho) addition on the properties of Mn-Zn ferrite. The doping concentration range from 0.05 wt% to 0.25 wt%. All samples were prepared by standard fabrication of ceramics. With increasing the rare earth oxides, specific density and initial permeability increased on the whole. But, the tendencies such as upper result had the measured value on limitation and characteristics saturated or decreased properties after that. In case of excessive addition of additive beyond some level, initial permeability properties of ferrite have gone down in spite of anomalous grain. With increasing the content of additive, both the real and imaginary component of complex permeability and the magnetic loss (tan$\delta$) increased. Because the increased rate of real component had higher than imaginary component, magnetic loss increased none the less for increasing the real component related with magnetic permeability. But, the magnetic loss of ferrite doped with the rare earth oxides was lower than that of Mn-Zn ferrite at any rate. The small amount of present rare earth oxides in Mn-Zn ferrite composition led to enhancement of resistivity in bulk, and more so in the grain boundary. It was seem to be due to the formation of mutual reaction such as between iron ions and rare earth element ions.

• 한국전기전자재료학회논문지
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• 제13권10호
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• pp.887-894
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• 2000

In this paper, we have studied the effect of earth (Gd, Er) on the various properties (microstructure, shrinkage, initial permeability, permeability as a function of frequency, etc) of Ba-ferrite. The permeabilities were analyzed by Impedance Analyzer(100KHz~40MHz) and Network Analyzer(30KHz~3㎓). As the result of XRD, all of the Ba-ferrite doped with rat earth was found to be Y-hexagonal phase. The resonance frequencies at the maximum imaginary value of complex permeability were observed near 2㎓. The complex permeabilities of the Ba-ferrite doped with Gd$_2$O$_3$at 3wt% and doped with Er$_2$O$_3$at 3wt% and 5wt% as a function of frequency showed the highest value at sintered temperature at 95$0^{\circ}C$/3h.