• Journal of the Society of Cosmetic Scientists of Korea
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• v.31 no.2 s.51
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• pp.141-146
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• 2005

Unstable cosmetic active ingredients could rapidly break down in chemical and photochemical process. Therefore, it has become a very important issue to encapsulate active ingredient for the stabilization. 7-Dehydrocholesterol (7-DHC), a precursor of vitamin $D_3$, has been shown to increase levels of protein and mRNA for heat shock protein in normal human epidermal keratinocytes. However, topical dermal application of 7-DHC is restricted due to its poor solubility and chemical unstability. In this study, 7-DHC was incorporated into nano-emulsion (NE), solid lipid nano-particle (SLN), and chitosan coated solid lipid nano-particle (CASLN), respectively. In order to prepare NE and SLN dispersion, high-pressure homogenization at temperature above the melting point of lipid was used Hydrogenated lecithin and polysorbate 60 were used as stabilizer for NE and SLN. CASLN was prepared by high speed homogenizing after adding chitosan solution to the SLN dispersion and showed positively charged particle properties. Decomposition rate of 7-DHC in NE, SLN and CASLN was studied as a function of time at different temperature. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies were performed to characterize state of lipid modification. It appeared that CASLN is the most effective to stabilize 7-DHC and may be used for a useful topical dermal delivery system.

• KSBB Journal
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• v.21 no.2
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• pp.157-163
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• 2006

A supercritical fluid process, called aerosol solvent extraction system(ASES), is especially suitable to the pharmaceutical, cosmetic and food industries due to its environmentally-friendly, non-toxic and residual solvent-free properties. In particular, the application of the ASES process to the processing of thermo-labile bioactive compounds has received attention of many scientists and engineers because of its low-temperature operating conditions. Unstable substances such as Vitamin-C and Vitamin-A can be effectively protected from degradation during the preparation process, because the ASES process is free from oxygen and moisture. In this study, Vitamin-C was formulated with 2-hydroxypropyl-${\beta}$-cyclodextrin (HP-${\beta$-CD) for enhancement of Vitamin-C stability and bioavailability using the ASES process. To investigate the influence of the preparation process on the stability of Vitamin-C, Vitamin-C/HP-${\beta}$-CD inclusion complexes were prepared using both conventional solvent evaporation method and ASES process, and stored in a 50 mM phosphate buffer solution of pH 7.0 at $25^{\circ}C$ for 24 hours. From the experimental results, the stability of the Vitamin-C/HP-${\beta}$-CD inclusion complex prepared from the ASES process was found to be much higher than that of pure Vitamin-C and the Vitamin-C/HP-${\beta}$-CD inclusion complex prepared by the solvent evaporation method. The stability of Vitamin-C was observed to increase with the decrease of temperature at a constant pressure or with the increase of pressure at a constant temperature.

• Journal of the Korean earth science society
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• v.29 no.7
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• pp.579-585
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• 2008

The time-dependent evolution of disk mass for outburst limit cycle in a black hole microquasar is calculated based on the non-linear hydrodynamic model of thermally unstable accretion disk. The physical parameters such as black hole mass, disk size and mass transfer rate are adopted to reproduce the historical 1975 outburst observed in a prototype black hole X-ray nova A0620-00. The time-dependent effect of irradiation from the central hot region to the disk is considered in two ways: direct irradiation and indirect irradiation reflected from hot accretion flow above the disk. The accretion disk thermal instability model can account for the bolometric luminosity appropriate to typical characteristics of system luminosity observed in X-ray transients during the whole cycle of the outburst evolution. The maximum mass of the accretion disk, ${\sim}4.03{\times}10^{24}g$, is achieved at the ignition of an outburst, and the minimum value, ${\sim}8.54{\times}10^{23}g$, is reached during the cooling decay to quiescence. The disk mass varies ${\sim}5$ times during outburst limit cycle.

• Korean Journal of Construction Engineering and Management
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• v.19 no.3
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• pp.89-96
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• 2018

This study derived big issues in overseas construction through big data analysis. To derive big issues in overseas construction, candidate groups of big issues were identified through big data analysis targeting 53,759 issues including 39,436 issues from major portal sites, 10,387 issues from daily newspapers, and 336 issues in construction magazines from Oct. 1, 2016 to Sep. 30, 2017. The main results are as follows: First, the main issues of overseas construction for the past one year showed that markets were concentrated in Middle East Asia and most of them were low-price order plant projects, which revealed the limitations. Although orders of overseas construction were slightly upward in the first half of 2017 compared to previous year, overseas construction orders are still unstable due to uncertainties in the international affairs and drops in oil prices. Second, the interest topics based on the 8th core keywords of overseas construction among the overseas construction issues for the past one year showed that region (29.9%), corporation environment (22.0%), profitability (17.0%), organizations (15.1%), projects (5.2%), market environment (3.6%), policy and system (3.6%), and education (3.5%) in the order of interest. Third, 10 core issues that have expandability and persistence of discourse were extracted out of 30 issue candidates with regard to eight keywords. Based on the extracted issues, detailed analysis on each of the core issues in overseas construction and correlation analysis between 10 core issues were conducted.

• Journal of Bio-Environment Control
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• v.18 no.1
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• pp.51-59
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• 2009

Bulb onion cultivation area has been restricted in southern part of Korea to avoid blotting and bulb division. The traditional culture method is transplanting bare-rooted plantlet into the field at the end of summer and harvesting at the beginning of next summer. The hot weather and weak plantlets occasionally causes unstable supply of onions in autumn. In order to enlarge cultivation area and to reduce culture period, long nursery system using plug tray and spring transplanting was tried. Forty cultivars collected from Korea and Japan were nursed using 200-plug tray and transplanted to the field in spring. Marketable yield was not related to the seedling size but lodging time. Cultivar of 'Hamasodachi' was lodged early and resulted low marketable yield. Cultivar of 'Cheonjudaego' was not lodged and yielded high but not in accordance with storability. Generally early lodged cultivars showed low storability. In order to avoid rainy harvesting season, cultivars requires excessive long time for lodging is not recommended for spring culture. Using plug nursery and spring transplanting, we successfully produced marketable onions in 3 months. But immediate using of the harvested onion is recommended. The storability of produced onions showed different result among cultivars, storage of spring onion was not recommended.

• Journal of Environmental Science International
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• v.2 no.2
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• pp.153-160
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• 1993

The problem of supply and transport of sediment from a mountainous catchment is very important in explaining dynamic geomorphology and the hydrological cycle. The discharge of suspended sediment is determined by a morphological system. Human interference to environment Is also an important, not negligible factor in sediment production. Moreover, growing concern in recent years for the problems of nonpoint pollution and for the transport of contaminants through terrestrial and aquatic ecosystems has highlighted the role of sediment-associated transport in fluvial systems. This study was conducted in forested and quarried catchments in order to clarify the different discharge process and the mechanism of suspended sediment dynamics for each catchment. As a forested catchment, the Yamaguchi River catchment which drains a $3.12km^2$ area was chosen. On the other hand, the Futagami River basin which is formed by three subbasins (1.07, 1.59 and $1.78km^2$), as a quarried catchment was selected. These catchments are situated to the north and east of Mt. Tsukuba, Ibaraki, Japan. The discharge pattern of suspended sediment from the Futagami River basin is more unstable and irregular than that from forested catchment, the Yamaguchi River catchment. Under the similar rainstorm conditions, suspended sediment concentration from quarried catchment during a rainstorm event increases from 43 to 27,340 mg/l. However, in the case of the forested catchment it changes only from nearly zero to 274 mg/l. Generally, the supply source of suspended sediment is classified into two areas, the in-channel and non-channel source areas. As a result of field measurements, in the case of the forested catchment the in-channel (channel bed, channel bank and channel margin) is the main source area of suspended sediment. On the other hand, remarkable sediment source area on the Quarried catchment is the non-channel that is unvegetated ground.

• Journal of the Korean association of regional geographers
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• v.3 no.1
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• pp.1-12
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• 1997

The climatic characteristics of Korea are analized with the data observed from 1972 to 1995 in 66 stations, using the climatic year method expressed by the $K{\ddot{o}}ppen's$ system of climatic classification. The climate of Korea is composed of the six climatic year types : Cfa, Cwa, Cwb, Dfa, Dwa and Dwb type. The Cwa and Dwa type occupy 95% occurrence frequency. The Cwa climatic year type predominates in the greater part of the Southern Area, the east slopes of the Taebaek Range and Cheju-do, the Dwa type does in Yongso Area and the northeastern part of Kyonggi Province. and the Cfa type does in Ullung-do. Such dominant climatic year regions become the stable climatic regions, while the regions where the various climatic types appear become the unstable climatic regions which are distributed in the northern part of the Southern Area and in the southern part of the Central Area owing to the shifts of the border between C type and D type. The border between C and D type is located in the Central Inland Area in the first half of the 1990's which the Cwa type predominates most. On the other hand the border is located in the middle part of the Southern Area in the first half of the 1980's which the Dwa type prevails most. Therefore the extents of the climatic year regions vary each year. In the interannual change of the main climatic year types, the Cwa type shows the increasing trend, while the Cfa and Dwa type reflets the decreasing tendency. The extending trend of the Cwa climatic year region appears during the period of the first half of the 1970's and the period between the latter half of the 1980's and the first half of the 1990's centering around the Southern Area. The Dwa climatic year region which was predominant in the Central Area in the first half of the 1980's has been reduced up till the recent years.

• Journal of the Korean association of regional geographers
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• v.15 no.1
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• pp.1-15
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• 2009

This study aims to provide preliminary data needed for establishing policies on the environment and disasters of Goryeong county. The main results are as follows. First, the present master plan of the region does not reflect local socio-economic and environmental conditions and the local people's opinion. Second, The air conditions of Gyeongbuk province and Goryeong county are within the permitted limit of air pollution of Korea. Third, the analysis of water pollution index in Nakdong river system shows improvement of water quality in both Andong and Goryeong. Fourth, the conditions of waste collection and disposal are improved in both Gyeongbuk province and Goryeong county. Fifth, in case of environmental pollutant emitting facilities of Gyeongbuk province, the proportion of 1st to 4th grade(relatively much more environmental pollutant emitting quantity than 5th grade) tends to be increasing. Sixth, environmental pollutant emitting facilities of Goryeong county are remarkably increasing in Dasan, Gaegin, Ssangrim, involving industrial complex. Finally, in case of disasters, it is relatively stable in Yecheon, Gumi, Uiseong, Yeongju and Cheongdo, while relatively unstable in Seongju, Gunwi, Yeongcheon, Chilgok, Mungyeong, Bonghwa and Goryeong.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.12 no.2
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• pp.70-80
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• 2000

Princeton Ocean Model (POM) is modified to construct a three-dimensional, semi-implicit hydro¬dynamic model with a wetting-and-drying scheme. The model employs semi-implicit treatment of the barotropic pressure gradient terms and the vertical mixing terms in the momentum equations, and the velocity divergence term in the vertically-integrated continuity equation. Such treatment removes the external mode and thus the mode splitting scheme in POM, allowing the semi-implicit model to use a larger time step. Applied to hypothetical systems, both the semi-implicit model and POM give nearly the same results. The semi-implicit model, however, runs approximately 4.4 times faster than POM showing its improved computational efficiency. Applied to a hypothetical system with intertidal flats, POM employing the mode splitting scheme produces noises at the intertidal flats, that propagate into the main channel resulting in unstable current velocities. Despite its larger time step, the semi-implicit model gives stable current velocities both at the intertidal flats and main channel. The semi-implicit model when applied to Kyeonggi Bay gives a good reproduction of the observed tides and tidal currents throughout the modeling domain, demonstrating its prototype applicability.

• Analytical Science and Technology
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• v.15 no.6
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• pp.502-508
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• 2002

See-through hollow cathode glow discharge cell has been developed for the trace analysis of metal ions. The systems consists of new glow discharge cell improved the cooling system. In the case of previous type of hollow cathode glow discharge cell, it had been utilized for the trace analysis of metal ions but it had a problem that the plasma becomes unstable by air-cooled device. In this study, the modified hollow cathode glow discharge cell has been developed in order to minimize the problem associated with the air-cooled device. thus the stability of the plasma with water-cooling device has been improved and also the higher plasma temperature has been measured. The fundamental characteristics of modified systems have been investigated. And the discharge parameters, such as discharge pressure, material, and diameter of cathode, have been studied to find optimum discharge conditions.