• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.3
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• pp.50-57
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• 2002

The restoration techniques of large disturbed land containing native forest resources and soil animals were investigated on the new campus area of Kyushu University in Japan. Important techniques to restore native forest and biodiversity in that area are transplantation of existing large trees, transplantation of the forest soil, transplantation of native tree stools, and the reuse of wood and bamboo chips. The benefits can be obtained by using these methods. Firstly, the native genetic resources that would be discarded as part of the land development can be reused. Secondary, the time taken to become a high growth forest as opposed to the practice of planting saplings or grass seeds can be reduced. At last, the native forest ecosystem containing various under-story vegetations and soil animals can be conserved and regenerated. In addition, big and small ponds were constructed in the biodiversity preservation zone to preserve rare plants, rare animals, and native aquatic animals. And these plants and animals were transplanted and moved to ponds.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.3
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• pp.73-86
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• 2018

An analysis of Airbnb and Kozaza will show how valuable and rare resource can have an impact on company performances. Airbnb applied the sharing economy platform, and this business model had disrupted the hospitality industry. Thus, this paper will investigate a Korean company called Kozaza which had benchmarked Airbnb. Furthermore, it will apply the theory of VRIO framework, which consists of how valuable, rare, costly to imitate (imitability), and organization (exploited by the organization) to find competitiveness of Kozaza in the hospitality industry. Thus, it will attempt to show that Kozaza's business model of utilizing the unused resource of Hanok (traditional Korean house) and partnerships with Hanokstay, Seoul Metropolitan Government and Soul Tourism Organization and others have enhanced their resource and capability to strengthen their business model. Furthermore, this research will explore how Kozaza can competitively be successful in the future.

• Korean Journal of Plant Taxonomy
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• v.50 no.1
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• pp.1-7
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• 2020

Cynanchum L. in the subfamily Asclepiadoideae (Apocynaceae) includes four recognized species on the Korean peninsula, two of which are native to South Korea. However, the species ranges in South Korea are poorly defined. During a field survey, we discovered C. thesioides, previously unrecorded in South Korea, in Gimpo-si, Gyeonggi-do, and found an additional population of C. chinense, for which only one population has been reported in South Korea. The two taxa are considered rare species with extremely restricted distributions in South Korea, especially C. thesioides. We provide fundamental information, including descriptions, images of the habitats and morphological characters, and a taxonomic key for identification and assessments of the conservation status of Cynanchum species in Korea.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1165-1173
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• 2018

Recently, owing to environmental problems and instability of rare earth resources market, non-rare earth electric motors are attracting attention. As a non-rare earth motor type, a wound rotor synchronous motor(WRSM) has high power density and wide driving range further it can reduce loss by field current control during field weakening control at high speed. However, since the d-axis flux of the WRSM is coupled with the rotor circuit, the fluctuation in the d-axis flux linkage affects the rotor circuit, which causes ripple of the field current and torque. In this paper, we propose the field current ripple compensation method by injecting the feedforward voltage. the proposed compensating method was demonstrated by simulation and experiments.

• Korean Journal of Plant Resources
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• v.12 no.3
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• pp.221-233
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• 1999

The vegetation and plant resources of Paeaknokdam, the crater of Mt. Halla, was investigated from 1996 to 1998. The vegetation was classified into Diapensia lapponica var. obovata-Tofieldia fauriel association and Festuca ovina-Carex erythrobasis association. The latter was divided into Rhododendron mucronulatum var. ciliatum-Empetrum nigrum var. japonicum subassociation, which was composed partly of Abies koreana-Betula ermani var. saitoana variant. The plant resources of 162 taxa were composed of 49 families, 122 genera, 127 species, 2 subspecies, 30 varieties and 3 formae, of which 63 taxa were newly found in this area. Among the investigated plants, 27 taxa were endemic to Korea or Cheju islands, 39 taxa were rare or endangered, and 65 taxa were identified as alpine plants. One hundred and twenty-one taxa(75.6%) were identified to be useful: 82 for ornament, 75 for medice, 66 for food, 17 for nectar-producing, 15 for pasture, and 10 for industry.

• Resources Recycling
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• v.26 no.4
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• pp.79-87
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• 2017

Extraction and separation behaviors of La, Ce, Pr, Nd and Sm from light rare earth multi - component mixed solutions by Cyanex 572 were studied. As extractant concentration increased, the $pH_{50}$ values of all the five components decreased. When extractant concentration was larger than 0.6 M, the separation factor of La and Ce, Nd and Sm was higher than 10, while the separation factor between Ce and Pr, Pr and Nd was as low as 0.5~2.2. Addition of TBP to the 0.6 M Cyanex 572 had little synergistic effect on the phase separation rate and separation factor. From the analysis of experiment results, group separation of [La]/[Pr, Nd, Sm] and [Pr, Nd]/[Sm] could be possible, but in case of the group separation between [La, Ce] and [Pr, Nd] was not available because of the low separation factor between Ce and Pr.

• Resources Recycling
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• v.27 no.4
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• pp.50-56
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• 2018

For the purpose of optimizing the counter current extraction process for separation of [Pr, Nd, Sm] group and [La] in mixed solution using Cyanex 572 as an extractant, the theory of Xu Guangxian was derived for calculating the optimized extraction factors. From the basic batch test result, the separation factor was 16.80 at extraction process and 21.48 at scrubbing process, and the loading capacity of 1.0 M Cyanex 572 was 0.12 M of rare earth element. The process parameters such as the stage number at extraction and scrubbing process, the flow rate ratio of feed and solvent solution can be calculated using an equation of optimum extraction ratio proposed by Xu Guangxian. From the result of calculation, 7 extraction stages and 4 scrubbing stages were required for rare earth separation, and the flow rate ratio of feed solution, solvent solution, scrubbing solution was 25 : 5.67 : 12.27.

• Resources Recycling
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• v.29 no.1
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• pp.17-24
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• 2020

In this study, rare earth elements (REE) leaching from a refractory REE ore containing goethite as a major gangue mineral was conducted, introducing a two-stage method of chemical decomposition-acid leaching. At the chemical decomposition step, using one of alkaline agent, NaOH, the ore was decomposed, changing NaOH concentration from 20 to 50 wt% at 10% (w/w) of pulp density and the maximum temperature achieved without boiling at each NaOH concentration. With increasing NaOH concentration, light REE (Ce, La and Nd) and iron were concentrated in the solid phase which is the decomposed product, while aluminum (Al) and phosphorus (P) were removed to the liquid phase, and their concentrations in the solid phase were down to 0.96 and 0.17%, respectively. In addition, through XRD analysis, it was found that the crystallinity of goethite was considerably decreased. At the acid leaching step, the product decomposed by 50 wt% NaOH was leached at 3.0 M HCl and 80 ℃ for 3 hr, then the REE leaching efficiency was above 94% (Ce 80%), and the leaching efficiencies of Al and P were decreased to 12 and 0%, respectively. Therefore, in terms of both REE leaching efficiency and impurity removal, those decomposition and leaching conditions were chosen as optimum processing methods of the investigated material. In terms of REE leaching mechanism, because REE and iron leaching efficiencies showed the positive correlation each other, so it can be concluded that decreasing crystallinity of goethite affect the improvement of REE leaching.

• Journal of Energy Engineering
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• v.27 no.2
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• pp.61-69
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• 2018

Rare earth elements together with Y and Sc (REEs) are essential in the development of technology for clean and efficient use of energy. In recent years coal deposits have much attention and attracted as a promising alternative raw sources for rare earth elements, not only because the REEs concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of REEs ores but also because of the world wide demand for REEs in recent years has been greater than supply. In the coal ashes, REEs are mainly associated with carbonates, silicates and aluminosilicates in ashes at 800 and $1100^{\circ}C$. These elements are known to be powerful environmental tracers in natural biogeochemical compartments. In this study, to reviewed the REEs originating and distribution patterns in coal ash samples from the bedrock and/or soil weathering that were entrapped by lichens and mosses was investigated. The REEs patterns of different organisms species allowed minor influence of the species to be highlighted compared to the regional lithology.

• Journal of Powder Materials
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• v.28 no.2
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• pp.91-96
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• 2021

Rare earth magnets with excellent magnetic properties are indispensable in the electric device, wind turbine, and e-mobility industries. The demand for the development of eco-friendly recycling techniques has increased to realize sustainable green technology, and the supply of rare earth resources, which are critical for the production of permanent magnets, are limited. Liquid metal extraction (LME), which is a type of pyrometallurgical recycling, is known to selectively extract the metal forms of rare earth elements. Although several studies have been carried out on the formation of intermetallic compounds and oxides, the effect of oxide formation on the extraction efficiency in the LME process remains unknown. In this study, microstructural and phase analyses are conducted to confirm the oxidation behavior of magnets pulverized by a jaw crusher. The LME process is performed with pulverized scrap, and extraction percentages are calculated to confirm the effect of the oxide phases on the extraction of Dy during the reaction. During the L ME process, Nd is completely extracted after 6 h, while Dy remains as Dy₂Fe₁₇ and Dy-oxide. Because the decomposition rate of Dy₂Fe₁₇ is faster than the reduction rate of Dy-oxide, the importance of controlling Dy-oxide on Dy extraction is confirmed.