• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.151-157
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• 2014

Since recently developed Ultra-High-Performance-Concrete (UHPC) provides very high strength, stiffness, and durability, many studies have been made on the application of the UHPC to bridge decks. Due to high strength and stiffness of UHPC bridge deck, the structural contribution of top flange of steel girder composite to UHPC deck would be much lower than that of conventional concrete deck. At this point of view, this study proposes a inverted-T shaped steel girder composite to UHPC deck. This girder requires a new type of shear connector because conventional shear connectors are welded on top flange. This study also proposes three different types of shear connectors, and evaluate their ultimate strength via push-out static test. The first one is a stud shear connector welded directly to the web of the girder in the transverse direction. The second one is a puzzle-strip type shear connector developed by the European Commission, and the last one is the combination of the stud and the puzzle-strip shear connectors. Experimental results showed that the ultimate strength of the transverse stud was 26% larger than that given in the AASHTO LRFD Bridge Design Specifications, but a splitting crack observed in the UHPC deck was so severe that another measure needs to be developed to prevent the splitting crack. The ultimate strength of the puzzle-strip specimen was 40% larger than that evaluated by the equation of European Commission. The specimens combined with stud and puzzle-strip shear connectors provided less strength than arithmetical sum of those. Based on the experimental observations, there appears to be no advantage of combining transverse stud and puzzle-strip shear connectors.

• Journal of the Korean earth science society
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• v.39 no.1
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• pp.53-66
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• 2018

The information of surface reflectance ($R_{sfc}$) is important for the heat balance and the environmental/climate monitoring. The $R_{sfc}$ sensitivity to error-induced variables for the Geostationary Environment Monitoring Spectrometer (GEMS) retrieval from geostationary-orbit satellite observations at 300-500 nm was investigated, utilizing polar-orbit satellite data of the MODerate resolution Imaging Spectroradiometer (MODIS) and Ozone Mapping Instrument (OMI), and the radiative transfer model (RTM) experiment. The variables in this study can be cloud, Rayleigh-scattering, aerosol, ozone and surface type. The cloud detection in high-resolution MODIS pixels ($1km{\times}1km$) was compared with that in GEMS-scale pixels ($8km{\times}7km$). The GEMS detection was consistent (~79%) with the MODIS result. However, the detection probability in partially-cloudy (${\leq}40%$) GEMS pixels decreased due to other effects (i.e., aerosol and surface type). The Rayleigh-scattering effect in RGB images was noticeable over ocean, based on the RTM calculation. The reflectance at top of atmosphere ($R_{toa}$) increased with aerosol amounts in case of $R_{sfc}$<0.2, but decreased in $R_{sfc}{\geq}0.2$. The $R_{sfc}$ errors due to the aerosol increased with wavelength in the UV, but were constant or slightly decreased in the visible. The ozone absorption was most sensitive at 328 nm in the UV region (328-354 nm). The $R_{sfc}$ error was +0.1 because of negative total ozone anomaly (-100 DU) under the condition of $R_{sfc}=0.15$. This study can be useful to estimate $R_{sfc}$ uncertainties in the GEMS retrieval.

• Journal of Periodontal and Implant Science
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• v.23 no.1
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• pp.97-108
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• 1993

One of the important initial events required for periodontal regeneration is the attachment and subsequent spreading of periodontal ligament cells on the root surface. The purposes of this study is to investigate the attachment and spreading pattern of human periodontal ligament cell on the surface of glass slides. After establishment of a cell line of the primary cell culture from the periodontal ligament of 1st premolar teeth which were extracted for the purpose of orthodontic treatment, author dispersed the cells at $5{\times}10^3\;cells/ml$ into the each 35mm culture petri-dish containing 2 glass slides. To observe the morphological changes of the cells which attached to the surfaces of glasses at every designed time schedule, author used the inverted phase contrast microscope and scanning electron microscope. During the whole experiment culture condition was at $37^{\circ}C$, 100% Humidity, 5% $CO_2$ gas incubator. The following results were obtained. Periodontal ligament cells showed spherical outline and started to attach to glass surface by basal sytoplasmic extension after 10min in culture. After 30min in culture, periodontal ligament cells were attached to glass surface by well - developed filopodia which protruded from the lamellipodia. The cell surface is covered with bubble-like structures and occasional microvillus can be seen with diffculty among these structures. After 1.5hr in culture, peridontal ligament cells shhowed radially well-spread cytoplasm and the nucleus was centered on its cytoplasm. Unspread central region of the cell was covered with numerous microvilli. The change of cell attachment and spreading pattern was manifest at 6hr in culture. At this time, periodontal ligament cell showed elongated outline and an oval-shaped nucleus. After 12hr in culture, periodontal ligament cells showed more stretched fibroblast-like appearance with polarity. Two long lamellipodia can be seen around the both terminal ends of cells. After 24hr in culture, periodontal ligament cells showed spindle shapes and an oval-shaped nucleus was slanted toward one side of the cell.

• Journal of the Korean Electrochemical Society
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• v.3 no.1
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• pp.49-56
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• 2000

In the present we.k, temperature dependence of oxygen diffusivity in the polyvinyl chloride (PVC) film $D_f$ formed on gold electrode was investigated using steady-state rotating disk electrode (RDE) technique and modulated electrohydrodynamic (EHD) impedance technique. Both the diffusion rate defined as the ratio of oxygen diffusivity in the PVC film to the film thickness $D_f/\delta_f$ and the time constant $\delta_f^2/D_f$ for oxygen diffusion through the PVC film were obtained from plot of the limiting current versus disk rotation speed and from filing the EHD impedance spectra experimentally measured to those theoretically calculated on the basis of the diffusion equation for mass transport through the non-conductive and porous film, respectively. By combining measured $D_f/\delta_f$ with $\delta_f^2/D_f$, we determined $\delta_f\;and\;D_f$ at room temperature separately. As temperature increased, it appeared that the $D_f$ value measured for the PVC film-covered gold RDE was enhanced more rapidly than that $D_s$ value in the solution measured for the PVC film-free gold RDE. This means that the pores glowing with increasing temperature act as effective diffusion paths within the film. The present in-situ steady-state and modulated EHD measurements prove to be effective for determining $\delta_f\;and\;D_f$, separately and at the same time the porosity of the PVC film at temperatures below glass temperature $T_g$ of the film.

• The korean journal of orthodontics
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• v.30 no.2 s.79
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• pp.197-204
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• 2000

[$K^+$]-selective ion channels were studied in excised inside-out membrane patches from human osteoblast-like cells (G292). Three classes of $K^+$channels were present and could be distinguished on the basis of conductance. Conductances were $270\pm27\;pS,\;113\pm12\;pS,\;48\pm8\;pS$ according to their approximate conductances in symmetrical 140 mM KCl saline at holding potential of -80 mV It was found that the small conductance (48 pS) $K^+$channel activation was dependent on membrane voltage. In current-voltage relationship, small conductance $K^+$channel showed outward rectification, and it was activated by the positive potential inside the membrane. In recordings, single channel currents were activayed by a negative pressure outside the membrane. The membrane pressure increased $P_{open}$ of the $K^+$ channel in a pressure-dependent manner. In the excised-patch clamp recordings, G292 osteoblast-like cells have been shown to contain three types of $K^+$ channels. Only the small conductance (48 pS) $K^+$channel is sensitive to the membrane stretch. These findings suggest that a hyperpolarizing current, mediated in part by this channel, may be associated with early events during the mechanical loading of the osteoblast. In G292 osteoblast-like cells, $K^+$channel is sensitive to membrane tension, and may represent a unique adaptation of the bone cell membrane to mechanical stress.

• Journal of Korean Society of Forest Science
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• v.50 no.1
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• pp.56-71
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• 1980

To study the changes of vegetational composition of each plant successional stage of Pinus densiflora forest caused by pine gall midge damage, Thecodiplosis japonensis, located in Kyonggi-do area, the middle part of Korea, four districts, Anseong, Yongin, Gwangju, and Gapyeong, were selected according to the length of insect damage duration. The forest in the Anseong district was the noninfested one selected as the check. And forests in Yongin, Gwangju, and Gapyeong were the recent]y damaged, severely damaged, and damage prolonged ones in sequence. It was considered that this order could be in concord with the gradual transition of plant successional stage. In view of temperature, precipitation and soil factors, these four districts were sited within the same environment. Four survey plots were selected from each district and the distance between them was 3~4 km. Then again four subplots were set within a plot. Through needle accumulation after insect infestation, light intensity, soil moisture content, and the amount of soil organic matter were increased and these conditions could create a favorable environment enabling the new species invasion and their growth. These were naturally closely related with the increase in quantity of Pinus densiflora defoliation. After considerable time lapse, the quantities of above mentioned factors decreased with the development of the new substitute tree species. It was found that Quercus mongolica was an excellently substitute tree species come first in this studied area. Species diversity increased to a degree at the early stage of the duration of pine gall midge damage and decreased thereafter. As the same manner, similarity index value between plots in the same district decreased to a degree and increased thereafter. This was linked admittedly with the increase and decrease of tree species and evenness. Synthesizing above mentioned results, the process of plant succession studied quantitatively by changes of relative density and relative importance value, it can be concluded that Pinus densiflora forest gives way to Genus Quercus forest in which Genus Lespedeza and Genus Rhododendron species become as subdominance species after removal of the Pinus densiflora trees damaged by pine gall midge.

• Journal of Korean Society of Forest Science
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• v.54 no.1
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• pp.49-59
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• 1981

In order to elucidate the process of plant succession of the Japanese red pine forests caused by pine gall midge, Thecodoplosis japonensis, in the area of Chungbuk and Kyongbuk, 12 study plots, 4 plots from each three districts, were set up. Districts A (Cheongwon)not attacked by this insect, as the check, District B(Gumi) in which the insect outbreak occured 5 years ago, and District C(Yeongdong)in which the insect outbreak occured 10 years ago, were sampled. The surveyed were some environmental factors, the number of woody plants, relative density, relative dominance values, species composition of plots by layer(upper, middle and ground), importance values, species diversity, similarity and dissimilarity index, etc. The results obtained are summarized as follows: The accumulation of litter on the ground was increased with the lengthening the insect damage duration. Through the crown opening and litter accumulation, the light intensity, temperature condition and soil moisture and nutrient content might be altered. According to the changes of species composition were forced. In general, the Genus Quercus, as a compensation species, has sprung up. The relative importance values for Q.aliena, Q.serrata, and Q.variabilis were significantly increased in the insect infested forests. 2. the stand structure and species composition of the insect attacked forest about 5 years later after the outbreak become complex and diverse. However, since this time, the simplicity of these regards become restored up to 10 years after the outbreak. 3. As the synthetic analysis of plant succession process, the relative values calculated from the relative density and the relative dominance values shown the dominant status of Genus Quercus in the heavily damaged forests. In addition, Genus Rhododendron and Genus Lespedeza with higher frequency become the ground vegetation components. They were gradually increased along the time elapsing after the insect out-break. 4. The differences in connection with the soil moisture contents, the organic matter contents which might give some influences to the vegetation change were hardly recognizable statistically among the studied plots by three district groups. We estimated that the annual mean precipitation and the annual mean temperature did not operated any meaningful effects on the vegetation alteration among plots between districts.

• Korean Journal of Environmental Agriculture
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• v.33 no.4
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• pp.327-333
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• 2014

BACKGROUND: Rabbiteye blueberry(Vaccinium ashei) is one of the most widely grown blueberry types in the world, together with Northern and Southern highbush blueberry(Vaccinium corymbosum). Rabbiteye blueberry have higher soil adaptability and fruit productivity but less cold tolerance to low temperature than highbush blueberry. The objective of this study is to investigate freezing tolerance of floral buds and establish a cultivation zone for rabbiteye blueberry cultivars. METHODS AND RESULTS: Bearing branches which have similar thickness and same number of floral buds were collected in the early January at the blueberry germplasm preservation plot located in Namhae Sub-station, National Institute of Horticultural and Herbal Science in Gyeongsangnamdo. Cold response of bearing branches were investigated by electrolyte leakage and freezing tolerance of floral buds were determined by ovary browning ratio of 50%($LT_{50}$). Cultivation zone was established based on mean annual extreme minimum temperature for 30 years, from 1981 to 2010. The electrolyte leakage of bearing branches in rabbiteye blueberry increased as temperature decreased and was lowest in 'Brightwell' but highest in 'Bluegem' when they were kept in $-5^{\circ}C$. Besides, the electrolyte leakage increased in 'Brightblue', 'Brightwell', 'Climax', 'Delite', 'Gardenblue', 'Southland' and 'Woodard' in $-20^{\circ}C$. Freezing tolerance($LT_{50}$) was lowest in 'Bluegem' and 'Homebell'($-13.3^{\circ}C$), and highest in 'Tifblue'($-25^{\circ}C$) among different rabbiteye blueberry cultivars. $LT_{50}$ of 'Southland' was from -15.0 to $-16.7^{\circ}C$, that of 'Delite', 'Brightwell',' Austin' and 'Climax' was $-18.3^{\circ}C$, and that of 'Bluebelle', 'Woodard' and 'Powderblue' was $-20^{\circ}C$. CONCLUSION: This study indicate that The hardiness zones of rabbiteye blueberry were classified into Six cultivation zones and cultivation zones of most cultivars were the south of Jeollanam-do and Gyeongdangnam-do, except for 'Tifblue.'

• Development and Reproduction
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• v.4 no.2
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• pp.153-160
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• 2000

In this study, genetic variation in the 5 strains of 2N-cont, meiotic-G2N, mitotic-G2N and two types of clones with different genetic backgrounds was investigated by developing their tolerance to water temperature and salinity, which is a physiological trait, into a quantitative trait. The temperature was set at 19$^{\circ}C$, 22.5$^{\circ}C$, 25$^{\circ}C$ and 30$^{\circ}C$, each of which was combined with 0$\textperthousand$, 15$\textperthousand$ and 30$\textperthousand$ of salinity respectively, making 12 groups in all. In the mean survival time (MST), samples with 15$\textperthousand$ of salinity showed the longest survival time at all temperatures. The 2N-cont had the longest 126.16 h followed by clone-11 and clone-15 surviving for 113.22 h and 91.05 h respectively. Gynogenetic diploids showed the shortest 87,32 h and 36.56 h. At 22.5 and 25$^{\circ}C$, MST of each strain was significantly short, showing similar results to those of the groups at 19$^{\circ}C$. The 2N-cont had the longest MST while clones had a longer MST than gynogenetic diploids. This could be due to gynogenesis which causes homozygosis among malignant harmful genes, leading to its appearance in populations and resulting in early death in individuals with such genes. On the other hand, MST of clones was longer than that of gynogenetic fish. This could be because the 1st gynogenetic generation, which is a parental population, has already had its malignant genes removed, while the clones of the 2nd gynogenetic generation have had their superior genes fixed as well as their tolerance and survival improved. When temperature was raised to 22.5$^{\circ}C$ and 25$^{\circ}C$, increase in variation was observed in gynogenetic diploids and decrease in clones in 15$\textperthousand$ of salinity. This shows that such a trait is genetic to a certain extent. Consequently, if this character is developed into a quantitative trait and applied to selective breeding, it could be a useful character to secure superior strains and individuals, and also it would be possible to improve populations genetically through selection.

• Korean Journal of Soil Science and Fertilizer
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• v.8 no.3
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• pp.121-133
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• 1975

Soils of the agricultural land derived mostly from volcanic ash in Jeju island may be characterized by relatively high PH, high contents of organic matter and exchangeable bases, and significantly low content of available phosphorus. The PH, organic matter, and available phosphorus of the soils in northern Jeju are 6.1, 12.6%, and 23 ppm, while those of the soils in the southern Jeju are 6.4, 3.7 %, and 76 ppm respectively. Upland soils in Jeju may be classified into 4 groups on the basis of soil fertility: black soil, very dark brown soil, dark brown, and red yellow soil. The organic matter content of black soil, very dark soil and dark brown soil is 15%, 7%, and 3% respectively. The soils of high organic matter content show the high phosphorus absorption coefficient, low content of available phosphorus, and low degree of the base saturation. The soil productivity for barley in the northern Jeju is higher than that in the southern Jeju and the productivity in the western Jeju is higher than that in the eastern part. The productivity for barley is in decreasing order of dark brown soil, very dark brown soil and black soil. Yields of potato and sweet potato in Jeju are higher than in the mainland. Those crops are considered to be tolerant to aluminumtoxicity. The response of sweet potato to nitrogen, phosphorus, and potassium in Jeju soils is lower than that in the mainland, while the response of barley and rape to nitrogen and phosphorus is higher than that in the mainland. The response to fertilizer applied is greater in the northern Jeju than in the southern Jeju. Lime requirement for the Jeju soils calculated on the basis of laboratory tests is so tremendous that single application of lime required might induce adverse effect. Most of the phosphorus applied to the Jeju soils is readily fixed as unavailable form and application of phosphorus in the level of 30 to 40 kg/10a is thought to give little effect.