• Journal of the Economic Geographical Society of Korea
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• v.23 no.2
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• pp.147-165
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• 2020

The aim of this study is to find out Korean electronic industries' production network in Hanoi Red River Delta, Vietnam and its change based on customer-following overseas expansion. In-depth interviews with Korean subcontractors were conducted to examine the characteristics of customer-following overseas expansion of Korean subcontractors. Korean subcontracting corporations in electronic industries have expanded into Vietnam as the suppliers to Korean transnational corporations. Since 1990s, Korean corporations have invested into Vietnam but since late 2000s its industrial and geographical concentration has been shifted from textile and clothing industries in Southern Vietnam to electronics in Northern Vietnam. The customer-following overseas expansion of the subcontractors has emerged in three aspects: physical proximity, asymmetrical inter-firm relations and organizational embeddedness. During the process of customer-following overseas expansion, Korean electronic industry production network was transplanted into Vietnam and partially modified. This is because the company's hierarchy and difficulties in changing its trading relationship have affected the process of advancing into overseas markets. Korean transnational corporations seek to establish a stable suppliers through expansion accompanying with its subcontractors, and providing financial and non-financial support to its subcontractors.

• 한국체육학회지인문사회과학편
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• v.57 no.2
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• pp.279-289
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• 2018

The purpose of this study is to investigate features of leisure and recreation scholarship study in The Korean Journal of physical education based on co-authors network and topic modeling through using Word Cloud and LDA Topic Modeling(Latent Dirichlet Allocation). The data collected for this study are 2,697 papers published online from January 2008 to March 2017 on the Korean journal of physical education. Respectively ordered analysis targets are the major author, author of correspondence, co-author 1, co-author 2, co-author n in related document to explore studies' trends using the 369 documents. As a result, the co-author network analysis result found that 451 were linked to the research network, on average researchers had 1.52 relationships and the average distance between researchers was 2.33. The Representative author's concentration of connection was ranked high in the order of the following, Lee. K. M., Hwang. S. H., H., Lee. C. S., and proximity centers were shown in Seo K. B., Han. J. H., Kim. K. J. Finally, parameter-centric features appeared in order of Lee. C. W. and Seo. K. B. was most actively connected between the researchers of the leisure-related academic papers. Future research needs discussions among scholars regarding the trend and direction of future leisure research.

• Journal of the Economic Geographical Society of Korea
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• v.26 no.2
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• pp.123-136
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• 2023

Upon examining land prices in the eastern district of Gyeongseong, it was observed that there were variations in land prices between the northern and southern areas, with the central part being densely populated with modern facilities such as hospitals, schools, and research institutions. As a result, the eastern district of Gyeongseong was further divided into specific sub-areas, namely the northeastern and southeastern, for a more detailed analysis of the land market in each area. In the northeastern area, factors such as distance from the central area and proximity to planned roads were found to have an impact on land prices. On the other hand, in the southeastern area, the distance between the main road, whice were IHyun Road and Jongro, was identified as a significant influencer of land prices. Therefore, the northeastern area exhibited characteristics of a hinterland, influenced by the concentration of major facilities in the central area, while the southeastern area had a strong commercial orientation, largely shaped by the influence of Jongro as a bustling commercial district. This study is significant in that it sheds light on certain aspects of the modern land market by demonstrating that factors such as accessibility to roads and anchor facilities, as well as the segmentation of the land market, were also influential in the land market a century ago.

• Journal of the Korean earth science society
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• v.21 no.3
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• pp.287-301
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• 2000

In order to investigate the factors and processes affecting the vertical distributions of ozone, we analyzed the ozone profile data measured using ozonesonde from 1995 to 1997 at Pohang city, Korea. In the course of our study, we analyzed temporal and spatial distribution characteristics of ozone at four different heights: surface (100m), troposphere (10km), lower stratosphere (20km), and middle stratosphere (30km). Despite its proximity to a local, but major, industrial complex known as Pohang Iron and Steel Co. (POSCO), the concentrations of surface ozone in the study area were comparable to those typically observed from rural and/or unpolluted area. In addition, the findings of relative enhancement of ozone at this height, especially between spring and summer may be accounted for by the prevalence of photochemical reactions during that period of year. The temporal distribution patterns for both 10 and 20km heights were quite compatible despite large differences in their altitudes with such consistency as spring maxima and summer minima. Explanations for these phenomena may be sought by the mixed effects of various processes including: ozone transport across two heights, photochemical reaction, the formation of inversion layer, and so on. However, the temporal distribution pattern for the middle stratosphere (30km) was rather comparable to that of the surface. We also evaluated total ozone concentration of the study area using Brewer spectrophotometer. The total ozone concentration data were compared with those derived by combining the data representing stratospheric layers via Umkehr method. The results of correlation analysis showed that total ozone is negatively correlated with cloud cover but not with such parameter as UV-B. Based on our study, we conclude that areal characteristics of Pohang which represents a typical coastal area may be quite important in explaining the distribution patterns of ozone not only from surface but also from upper atmosphere.

• Korean Journal of Pharmacognosy
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• v.5 no.2
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• pp.111-124
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• 1974

The radioactive compound sodium $acetate-U-C^{14}\;(C^{14}-acetate)$ was administered to two- and four-year-old July and September American ginseng (Araliaceae, Panax quinquefolium L.) plants and cuttings. The $C^{14}-acetate$ uptake was approximately 99%. The autoradiochromatograms suggest that the saponins isolated by preparative thin-layer chromatography contained impurities, especially those isolated from the leaf and stem extracts. The root and fruit methanol extracts yielded relatively pure saponins. The large amounts of panaquilin B and its proximity to panaquilin C on preparative thin-layer plates resulted in some admixing. The average concentration (% plant dry weight) of semi-purified saponins were high in the leaves (13.8%), as compared to fruits (9.8%), stems (7.9%) and roots (6.3%). The average percentage of $C^{14}-acetate$ incorporation into panaquilins was 4.8%. The average percentage of $C^{14}-acetate$ incorporation into panaquilins B and C was higher (1.40% and 1.13%, respectively) than that into panaquilins C, (d), G-1 and G-2 (0.75%, 0.65%, 0.13% and 0.53%, respectively). Panaquilin synthesis may be depending upon the part, collection period and age of the plant. The average percentage of $C^{14}-acetate$ incorporation into panaquilin B is high in roots (0.58%) and stems (0.48%); that into panaquilins C and (d) high in leaves (0.40% and 0.45%, respectively); and that into panaquilin E high in roots and leaves (0.55% and 0.50%, respectively). Panaquilin G-2 was synthesized in all parts of plants. The panaquilins appear to be biosynthesized more actively in July than September (exception-panaquilin G-1). Panaquilins B, C and G-1 may be biosynthesized more actively in four-year-old plants and panaquilins (d) and E more actively in two-year-old plants. The results from expectance with cuttings suggest that the panaquilins are synthesized de novo in the above-ground parts of ginseng plants, and that panaquilin G-1 may be synthesized de novo in the leaf. It is known from the tissue culture studies that panaquilins are produced by leaf, stem and root callus tissues and cailus-root cultures of American and Korean ginseng plants. Panaquilins may actively be synthesized de novo in most any cell or organ of the ginseng plants. It was verified that $C^{14}-acetate$ was incorporated into the panaxadiol portions of the panaquilins of two-year-old plants (sp. act. 0.56 mmcCi/mg) and four-year-old plants $(sp.\;act.\;0.54\;m{\mu}Ci/mg)$.

• Journal of the Korean Chemical Society
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• v.66 no.2
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• pp.78-85
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• 2022

Natural white clay was treated with 6 M of H₂SO₄ and heated at 80℃ for 6 h under mechanical stirring and the resulting acid active clay was used as an adsorbent for the removal of Cs⁺ in water. The physicochemical changes of natural white clay and acid active clay were observed by X-ray Fluorescence Spectrometry (XRF), BET Surface Area Analyser and Energy Dispersive X-line Spectrometer (EDX). While activating natural white clay with acid, the part of Al₂O₃, CaO, MgO, SO₃ and Fe₂O₃ was dissolved firstly from the crystal lattice, which bring about the increase in the specific surface area and the pore volume as well as active sites. The specific surface area and the pore volume of acid active clay were roughly twice as high compared with natural white clay. The adsorption of Cs⁺ on acid active clay was increased rapidly within 1 min and reached equilibrium at 60 min. At 25 mg L^- of Cs⁺ concentration, 96.88% of adsorption capacity was accomplished by acid active clay. The adsorption data of Cs⁺ were fitted to the adsorption isotherm and kinetic models. It was found that Langmuir isotherm was described well to the adsorption behavior of Cs⁺ on acid active clay rather than Freundlich isotherm. For adsorption Cs⁺ on acid active clay, the Langmuir isotherm coefficients, Q, was found to be 10.52 mg g^-1. In acid active clay/water system, the pseudo-second-order kinetic model was more suitable for adsorption of Cs⁺ than the pseudo-first-order kinetic model owing to the higher correlation coefficient R² and the more proximity value of the experimental value q_e,exp and the calculated value q_e,cal. The overall results of study showed that acid active clay could be used as an efficient adsorbent for the removal of Cs⁺ from water.

• Journal of the Korean Chemical Society
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• v.65 no.3
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• pp.197-202
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• 2021

In this study, activated clay treated with H₂SO₄ (20% by weight) and heat at 90 ℃ for 8 h for acid white soil was used as an adsorbent for the removal of PO₄^3--P in water. Prior to the adsorption experiment, the characteristics of activated clay was examined by X-ray Fluorescence Spectrometry (XRF) and BET surface area analyser. The adsorption of PO₄^3--P on activated clay was steeply increased within 0.25 h and reached equilibrium at 4 h. At 5 mg/L of low PO₄^3--P concentration, roughly 98% of adsorption efficiency was accomplished by activated clay. The adsorption data of PO₄^3--P were introduced to the adsorption isotherm and kinetic models. It was seen that both Freundlich and Langmuir isotherms were applied well to describe the adsorption behavior of PO₄^3--P on activated clay. For adsorption PO₄^3--P on activated clay, the Freundlich and Langmuir isotherm coefficients, K_F and Q, were found to be 8.3 and 20.0 mg/g, respectively. The pseudo-second-order kinetics model was more suitable for adsorption of PO₄^3--P in water/activated clay system owing to the higher correlation coefficient R² and the more proximity value of the experimental value q_e,exp and the calculated value q_e,cal than the pseudo-first-order kinetics model. The results of study indicate that activated clay could be used as an efficient adsorbent for the removal of PO₄³-P from water.