• Journal of the Korean Geosynthetics Society
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• v.23 no.1
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• pp.49-60
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• 2024

Recently, the frequency and intensity of typhoon-induced wave loading are increasing due to changed marine environments such as climate change. In addition, frequent earthquakes are causing a lot of damage around the world, including in Japan, Chile, Haiti, China, and Indonesia. In Korea, damage from typhoons has also been increasing since the 2000s, and the frequency and intensity of earthquakes are also increasing. Korea is surrounded by sea on three sides, so typhoons can cause a lot of damage to coastal structures, and earthquakes also cause a lot of damage to coastal structures. As such, the frequency and intensity of typhoon-induced wave loading and earthquakes are increasing both domestically and internationally, but there is no research linking typhoons and earthquakes. Therefore, in this study, numerical analysis was performed for a total of four cases by linking typhoon waves and earthquakes to the caisson breakwater. Numerical analysis was performed by applying wave loads in Case 1 and seismic wave in Case 2, seismic wave after wave loads in Case 3, and wave loads after seismic wave in Case 4. As a result of the numerical analysis, it was confirmed that in Case 3 and Case 4, which linked a typhoon and earthquakes, the damage caused by each load increased compared to Case 1 and Case 2 because the load was applied while the existing ground strength was reduced. In addition, it was confirmed that the greatest damage occurred in Case 3, in which seismic wave were applied after the wave loads.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.27-34
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• 2024

This study was conducted to examine the feasibility of using Fe-activated wood-derived biochar as a conductive filler for manufacturing cement-based strain sensor. To evaluate the compressive and electrical properties of cement composite with 3% Fe-activated biochar, three cubic specimens of size 50 x 50 x 50mm³ and three prismatic cement-based sensors of size 40 x 40 x 80mm³ were prepared respectively. The four-probe method of electrical resistance measurement was used for cement-based sensors. For cement-based sensors with FE-activated biochar, the conductive performance such as electrical resistance and impedance under different water content and repeated compression was investigated. Results showed that the fractional changes in the DC electrical resistivity of cement-based sensors increase with increasing time and the maximum fractional changes in the resistivity decrease with increasing the moisture contents during 900s. At moisture content of 7.5% range, the conductive performance of cement composite including 3% Fe-activated biochar as a conductive filler showed the most stable, while the strain detection ability tended to decrease somewhat as the repeated compressive stress increased between repeated compressive strain and fractional change in resistivity (FCR).

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.3
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• pp.201-207
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• 2007

To reduce both the floatation of the seedling of rice and the failure in standing in the paddy field when the barley straw was applied to paddy field before planting the rice, we tested the effect of rice rooting with plowing methods and irrigation rates for 2 years from 2003 to 2004. This study was carried out in paddy field with Fluvio-Marine deposit in Jeonbug series and the operating accuracy and the change of soil physico-chemical properties depending on plowing methods and irrigation rates following the barley straw applying were examined. There was a less floatation of barley straw in the dry-rotaryI+water-rotaryI(DRI+WRI) plot than in the plowing+water-rotary(PL+WRI) plot. The ratio of miss-planted and floating seedling also decreased by 1.7%, 2.6% in the DRI+WRIplot compared with PL+WRI plot. The soil physical property was improved with the decreasing soil hardness, bulk density and increasing soil porosity after the application of barley straw, especially enhanced greatly in the increase of porosity, gaseous phase and with the decrease of soil hardness, bulk density of subsurface soil in DRI+WRI plot. And the change of soil chemical property were increased the content of total carbon$^{\circ}{\S}$nitrogen$^{\circ}{\S}$organic matter and available phosphate while decreased the content of exchangeable cations and available silicate after the application of barley straw. Also the content of organic matter, available phosphate and cation exchangeable capacity were increased, whereas caron/nitrogen ratio was decreased in DRI+WRI plot compared with PL+WRI plot. The number of panicles, spikelets per square meter were increased and 1,000 grains weight of hulled rice was gained more in DRI+WRI plot at irrigation rate of $500ton\;ha^{-1}$, in DRI+WRII plot at irrigation rate of $700ton\;ha^{-1}$. So the rice yields were increased by 7%, in DRI+WRI and 5% in DRI+WRII plot, respectively compared with PL+WRI plot. The result of this study indicated that the most appropriate plowing method with barley straw application on rice cultivation at double cropping in normal paddy field plain land was DRI+WRI.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.63-75
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• 2013

The Inner Port Phase 2 area of the Pyeongtaek-Dangjin Port is enclosed by a total of three permeable sea-walls, and the disposal site to the east of the Inner Port Phase 2 is also enclosed by two permeable sea-walls. The maximum tidal range measured in the Inner Port Phase 2 and in the disposal site in May 2010 is 4.70 and 2.32 m, respectively. It reaches up to 54 and 27%, respectively of 8.74 m measured simultaneously in the exterior. Regression formulas between the difference of hydraulic head and the rate of interior water volume change, are induced. A three-dimensional numerical hydrodynamic model for the Asan Bay is constructed incorporating a module to compute water discharge through the permeable sea-walls at each computation time step by employing the formulas. Hydrodynamics for the period from 13th to 27th May, 2010 is simulated by driving forces of real-time reconstructed tide with major five constituents($M_2$, $S_2$, $K_1$, $O_1$ and $N_2$) and freshwater discharges from Asan, Sapkyo, Namyang and Seokmoon Sea dikes. The skill scores of modeled mean high waters, mean sea levels and mean low waters are excellent to be 96 to 100% in the interior of permeable sea-walls. Compared with the results of simulation to obstruct the flow through the permeable sea-walls, the maximum current speed increases by 0.05 to 0.10 m/s along the main channel and by 0.1 to 0.2 m/s locally in the exterior of the Outer Sea-wall of Inner Port. The maximum bottom shear stress is also intensified by 0.1 to 0.4 $N/m^2$ in the main channel and by more than 0.4 $N/m^2$ locally around the arched Outer Sea-wall. The module developed to compute the flow through impermeable seawalls can be practically applied to simulate and predict the advection and dispersion of materials, the erosion or deposion of sediments, and the local scouring around coastal structures where large-scale permeable sea-walls are maintained.

• Horticultural Science & Technology
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• v.28 no.4
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• pp.529-534
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• 2010

Occurrence of wilted symptom in watermelon plant ($Citrullus$ $lanatus$ L.) is known to be caused by physiological disorder. The symptom results in the loss of fruit production and thus the economical loss of watermelon growers. The incidence of symptom is often found from the middle of March to the end of May in the major watermelon crop production areas of Korea (i.e. Uiryeong, Gyeongnam (lat $37^{\circ}$56'64"N, long $126^{\circ}$99'97"E)). Despite of extensive information about the physiological disorder, little study has been conducted to understand a relationship between the wilted symptom and accompanying environment factors (e.g. temperature). This study aimed to investigate effects of environmental conditions amended by a forced-ventilation system on physiological characteristics of watermelon and incidence of the wilted symptom. Watermelon plants were grown from January to May, 2009 with either the forced-or natural-ventilation treatment in a greenhouse located in the Uiryeong. In the result, the forced-ventilation treatment decreased the air, leaf and root-zone temperature approximately $4.5^{\circ}C$, $5^{\circ}C$ and $3^{\circ}C$, respectively, compared to the natural-ventilation. The fruit growth rate was maximized twice during the entire growing period. The higher rate of fruit growth was observed under the natural-ventilation than the forced one. Maximization of the fruit growth rate (approximately 430 g per day) was first observed by 12 days after fruiting under the natural-ventilation treatment, while the second one (approximately 350 g per day) was observed by 24 days after fruiting. The wilted symptom started occurring by 22 days after fruiting under the natural-ventilation, whereas no incidence of the symptom was found under the forced-ventilation treatment. Interestingly, the forced-ventilation lowered the fruit growth rate (approximately 320 g per day) compared to the natural one. Maximization of the fruit growth rate under the forced-ventilation was found at 4 days later than that under the natural one. This result coincided with a slower plant growth under the forced-ventilation treatment. These results suggest that the forced-ventilation slows down extension growth of fruit and plant, which may be associated with lowering leaf temperature and saturation deficit. We suggest the hypothesis that the forced-ventilation may alleviate stress of the wilted symptom by avoiding extreme water evaporation from leaves due to high temperature and thus by reducing competition between leaves and fruits for water. More direct and detailed investigations are needed to confirm the effect of the forced ventilation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.33 no.1
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• pp.31-37
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• 1988

Germination and seedling elongation of soybeans [Glycine max. (L.) Merr., cults. Bangsakong, Hill, Paldalkong, Danyupkong, Baegwun-kong. Kwangkyokong, Changyupkong and Hwangkeumkong] were measured at two temperatures (15 and 30$^{\circ}C$) and four polyethylene glycol 10,000 (PEG) solutions (0, 20, 30 and 35g/100g-H$_2$O). Adjustments of PEG solution were based on water potentials of 0.0, -0.5, -1.1 and -1.5 MPa at room temperature. Observations were made at 3, 6, 9 and 12 days for 15$^{\circ}C$ and 1, 2, 3 and 4 days for 30$^{\circ}C$. Fifteen seeds of each cultivar were placed on Whatman No. 1 (9cm) filter paper in plastic pertridishes, and adjusted to 15 ml of the proper PEG solution supplemented with 0.2 percent thiram using automatic syringe. The dishes were covered with cap. The seeds were germinated at a continuous temperature of 15 or 30$^{\circ}C$ under dark conditions for programmed period. Seedling moisture content and seedling length of eight soybean cultivars decreased as PEG concentration increased both at 15 and 30$^{\circ}C$. Cultivar differences in seedling moisture content and seedling length were found among eight soybean cultivars at temperatures of 15 and 30$^{\circ}C$. Larger sized cultivar absorbed more moisture than samller sized cultivar. However, reverse results were obtained on the seedling moisture content of each of eight soybean cultivars. Cultiver Hill and Paldalkong showed greater seedling length than the other six cultivars from 20 to 30g/100g water of PEG concentrations both at 15 and 30$^{\circ}C$. The results of this study indicated that germination test of soybean seeds in aqueous solutions of PEG has potential for screening soybean cultivars for improved emergence during moisture stress.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.2
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• pp.185-194
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• 2018

The objective of this study was to compare the shear bonding strength of zirconia after cleaning the crown contaminated by saliva or blood and determine the effect of thermocycling. 180 specimens were embedded in acrylic resin. 20 Specimens in the positive control group were bonded with resin cement without contamination. 20 Specimens in the negative control group were washed with water for 20 seconds and then dried for 10 seconds. 120 Specimens contaminated by saliva or blood were cleaned by using three cleaning methods: 37% phosphoric acid gel, commercial cleanse, and 2.5% NaOCl. All samples were bonded with resin cement and divided into two subgroups: One was not aged, and the other was tested with 30,000 thermocycling. In both groups contamination by saliva and blood, no statistically significant difference was not found in control, groups cleansed by commercial cleanser and 2.5% NaOCl. When the groups cleansed with water and 37% phosphate gel were compared with the control, significantly low shear bond strength was shown. Thermocycling group showed statistically significantly low shear bond stress compared to the groups without thermocycling. When zirconia was contaminated by saliva or blood, its original shear bond strength could be obtained if it was cleaned with commercial cleanser or 2.5% NaOCl.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.12
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• pp.1663-1670
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• 2012

The inhibitory effects of rose hip (Rosa canina L.) water extracts from two different manufactures on osteoarthritis was comparatively investigated in primary cultures of rat cartilage cells. To identify the effects of rose hip extracts against $H_2O_2$ (300 ${\mu}M$, 2 hr) treatment, cell survival was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell survival increased by rose hip extracts in the range of 100 to 600 ${\mu}g/mL$ of $H_2O_2$ treatment. To determine the anti-inflammatory effects of rose hip extracts, tumor necrosis factor alpha (TNF-${\alpha}$), nitric oxide (NO), and Cox-2 expression were measured after lipopolysaccharide (LPS) activation. TNF-${\alpha}$ level with rose hip extract treatment was decreased by 27.4% and 31.9% at 600 ${\mu}g/mL$ of $H_2O_2$ treatment. Nitric oxide was inhibited by rose hip extract at 100~600 ${\mu}g/mL$ of $H_2O_2$ treatment in a dose-dependent manner. In addition, Cox-2 protein expression was dose-dependently decreased while Cox-1 had no change in expression level. The severity of osteoarthritis is controlled by a balance between anabolic and catobolic factors in an articulation, therefore the expression of these factors plays a critical role in preventing osteoarthritis. In measuring anabolic factors, the genetic expression of collagen type I increased with rose hip treatment, while the genetic expression of collagen II did not change. In addition, the genetic expression of aggrecan (proteoglycan core protein) was significantly increased. while the genetic expression of matrix metalloproteinase (MMP) 3, 7 and 13, known catabolic factors, was significantly inhibited by treatment with rose hip extract. The expression of MMP13 was especially highly influenced. In conclusion, rose hip water extracts show inhibitory effects on cell death by $H_2O_2$ mediated oxidative stress, which is related to inhibitory effects on inflammation due to TNF-${\alpha}$, NO, and Cox-2. The ability of rose hip extracts to ameliorate inflammation in primary cultures of cartilage cells seems to associate with an increased genetic expression of specific anabolic factors, collagen type I and aggrecan, and a decreased expression of catabolic factors, MMPs (3, 7, and 13). However, there were no significant differences between rose hip extracts from the two manufacturers.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.2
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• pp.79-89
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• 2009

For preliminary diagnosis on current fishing ground environment and basic information for establishment of effective and rational management policy in fisheries resources protection area, water and sediment quality and changes of total area in the 10 marine protection areas designated for fisheries resources management in Korea were assessed. Results showed that environmental quality in these areas has been degraded by pollution sources, coastal utilization and development stress, etc. The pattern and degree of contamination differed by protection areas, suggesting that it is necessary for optimum environmental management plan considering the regional characteristics. The total designated area of protection areas in 2003 changed by $-22.9{\sim}2.4%$, on average -6.4%, compared with the first year of designation; Wando-Doam Bay showd the highest increase rate (2.4%), and Hansan Bay has the highest decrease rate (-22.9%) Decrease rate of land and sea in total area showd 6.1% and 6.6%. An integrated management of environmental data in protection areas is required for systematic assessment. Therefore, the suitable environmental and information management is needed specifically considering the environment characteristics such as development and utilization conditions of land and sea area Furthermore, bemuse urbanization and industrialization threats the junctions of the protection areas, authorized ministry (MIFAFF) should develope and establish monitoring and management procedures based on the related laws.

• Journal of Korean Society of Forest Science
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• v.98 no.6
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• pp.733-739
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• 2009

This study was carried out to analyze the relationship between major climatic factors (monthly temperature, precipitation) and radial growth of Korean Pine (Pinus koraiensis) in Inje-gun(Mt. Seorak), Sanchung-gun and Namwon-si(Mt. Jiri). Radial growth measurements were crossdated and correlated with climate variables. The climatic factors used were monthly mean temperature and monthly precipitation from August of previous year to September of the current year. In Inje-gun, radial growth was negatively correlated with monthly mean temperature in April, May, June, and August of the current year and was positively correlated with precipitation in August, October of the previous year and in April, August of the current year. Sanchung-gun showed a negative correlation with monthly mean temperature in September of the previous year and August of the current year but positive correlation in January of the current year. In contrast, precipitation in September of the previous year and August of the current year showed a positive influence. The results suggest that high temperature together with low precipitation may thus cause water stress and thereby limit radial growth in this region. In Namwon-si, the climategrowth relationships show that radial growth was negatively correlated with monthly mean temperature in August, October of the previous year and June of the current year. But August of the previous year and May, August of the current year in precipitation was positively correlated with radial growth. In the study areas, precipitation plays an important role for the radial growth of Kroean Pine (Pinus koraiensis). The results suggest that precipitation is important in the radial growth because water deficit in trees would take place in response to high temperature in the study area. Also there was some differences with study areas in the effects of both climatic variables probably as a result of different stand structure and geographical conditions and micro-climate.