• Journal of Oral Medicine and Pain
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• v.31 no.3
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• pp.223-229
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• 2006

The objectives of this study was to investigate the amount of tooth ablation and the change of intrapulpal temperature by Er:YAG laser as it relates to pulse energy and pulse repetition rate at the identical power and, thereby, to reveal which of the two parameters strongly relates with ablation efficiency and intrapulpal temperature. Extracted healthy human molar teeth were sectioned into two pieces and each specimen was irradiated within the combination of pulse energy and pulse repetition time at the same power of 3W; $300mJy{\times}10Hz$ group, $200mJy{\times}15Hz$ group, and $150mJy{\times}20Hz$ group. Each specimen comprised ten tooth specimens. A laser beam with conjunction of a water flow rate of 1.6 ml/min was applied over enamel surfaces of the specimens during 3 seconds and the ablation amount was determined by difference in weight before and after irradiation. To investigate the temperature change in the pulp according to the above groups, another five extracted healthy human molar teeth were prepared. Each tooth was embedded into resin block and the temperature-measuring probes were kept on the irradiated and the opposite walls in the dental pulp during lasing. When the power was kept constant at 3W, ablation amount increased with pulse energy rather than pulse repetition rate (p=0.000). Although intrapulpal temperature increased with pulse repetition rate, there were no significant differences among the groups and between the irradiated and the opposite pulpal walls, except at a condition of $150y{\times}20Hz$ (p=0.033). Conclusively, it is suggested that ablation efficacy is influenced by pulse energy rather than pulse repetition rate.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.1
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• pp.39-50
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• 2014

This paper reviews the results of recent observations in the Yeonsuri valley of Mt. Youngmun during springtime (March to May) in 2012. Automated weather stations were installed at twelve sites in the valley to measure temperature and 2, 3 dimensional wind. We examined temporal and spatial characteristics of temperatures and wind data. The Yeonsuri valley springtime average temperature lapse rate between the top and bottom of the entire period is $-0.44^{\circ}C/100$ m. It can be changed by the synoptic weather conditions, the lapse rates is greatest in order of clear days ($-0.48^{\circ}C/100$ m), rainy ($-0.41^{\circ}C/100$ m) and cloudy days ($-0.40^{\circ}C/100$ m). In the night, the temperature inversion layer (thermal belt) and the cold pool are formed within the valley. In addition, we measured temperature and wind distribution from the bottom to 3.5 m, the cold layers existed up to 1.5 m, which were affected by ground mixed layer. The results will provide useful guidance on agricultural practices as well as model simulations.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.2
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• pp.81-88
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• 2016

This study was conducted to find out the effects of Improvement of Botanical Composition Technology (IBCT) on the forage production and ecological characteristics in a Rumex acetosella-dominated hilly pasture in Pyeongchang, in a period from August 2013 to the end of growing season in October 2015. $2MT\;ha^{-1}$ limestone was applied in August 2013 and April 2014. Liming significantly increased soil pH from 4.69 to 5.47 and then the soil pH consistently hovered at 4.91~4.98. For every grazing time, plant height was found to be higher with the application of IBCT as compared with the control. After grazing, no significant difference in plant height was found between the IBCT group and the control. Changes in the botanical composition of grassland can be affected by a lot of circumstances, but application of IBCT decreased Rumex acetosella from 12% to 2%, while also increasing the proportion of pasture. In relation to the botanical composition of grass, orchardgrass and timothy showed the highest percentages throughout the whole study period. The proportion of Kentucky bluegrass increased over time while tall fescue steadily decreased. The totals for grazing days were 58 in 2014 and 55 in 2015. Average herbage dry matter intake was $7,848kg\;ha^{-1}$ in 2014 and $6,941kg\;ha^{-1}$ in 2015. Due to the application of IBCT, dry matter productivity showed a significant increase of 59% during the first grazing period in 2014 (3,437 kg ha and 5,460 kg ha in control and IBCT). In 2015, the total dry matter yield of the IBCT group was 51% greater than the control ($5,742kg\;ha^{-1}$ and $8,685kg\;ha^{-1}$ in control and IBCT). Under acidic soil conditions, red sorrel can grow more strongly than grasses because it has better tolerance in dry and acidic conditions. Therefore, constant management is required in order to keep red sorrel from dominating the hilly pasture. In this study, the application of IBCT was able to effectively control weeds at all points. As a result, total management, including improvement of soil, overseeding, and application of selective herbicide and fertilizer, is needed to maintain excellent grassland conditions due to the limiting effects of environmental factors on grassland productivity.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.4
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• pp.359-365
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• 1985

The four rice varieties, Kwanak, Nongbaek, Pungsan and Nampung-byo were cultivated to examine the growth conditions and grain yield in a Gyuam SiL paddy field irrigated with cold water around $17^{\circ}C$. Water temperatures for various distances from the inlet were measured. The results were summerized as follows. 1. Culm length, panicle exertion, diameter of the 3rd internode stem, heading date, fertilization rate, ripeness rate, no. of grains per panicle and grain yield were sensitive to water temperature. Panicle length, flag-leaf length, diameter of spike-neck and no. of panicles, however, were negligibly sensitive and there were no differences among varieties. 2. Elongations of the 2nd and 3rd internode steam were unsensitive to water temperature. 1st internode elongation and 4th internode development, however, were sensitive which was major factor in the culm length. 3. Ratios of partial dry weight to total dry weight were closely correlated with water temperature, Therefore, dry weight of grain was increased with water temperature while that of plant and root decreased. 4. Chlorophyll contents were decreased with the increment of water temperature and the highest at $20^{\circ}C$. 5. There was no grain yield at $17^{\circ}C$, Increases of grain yield to water temperature per unit were order at Pungsan > Kwanak > Nongbaek > Nampung. 6. The critical temperature in grain yield was $21^{\circ}C$. Optimum temperatures of Japonica ${\times}$ Indica types were higher than those of Japonica types.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.14 no.4
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• pp.113-132
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• 2019

The degree of females' participation in corporate activity has been recently increased over the world and females' participation in economic activity may be new dynamic fuel for the Korean economy that falls into the vicious cycle of low growth. Start-up, therefore, has increasingly taken attention as an opportunity for females whose careers were interrupted to re-enter the labor market. The need for studies that examine factors influencing the decision of start-up is also increased along with the increase of the ratio of females' start-up. This study aims to verify effects of the women's characteristics(women discrimination, women's role conflict) and the human networks of females whose careers were interrupted, with the intention for entrepreneurial intention, which are mediated by personal attitudes and subjective norm suggested by Ajzen's Theory of Reasoned Action, based on an empirical research. The findings show that the human networks of females have an effect on attitudes toward start-up activity and subjective norm and the woman discrimination influence the personal attitudes. In contrast, the women's role conflict have no effect on both personal attitude toward start-up activity and subjective norm. This can be supposed as an outcome resulted from the subjects' low level of conflict caused by their sex roles, on their age distribution. The relation between subjective norm and entrepreneurial Intention seemed to be moderated by their perceived strong entrepreneurial supporting policy. Their attitudes toward start-up activity were found to have a mediating effect on the relation between the women discrimination, human networks and entrepreneurial Intention, while the subjective norm only mediated the relation between human networks and entrepreneurial Intention. Based on such results, this study attempts to suggest theoretical suggestions and the direction of various entrepreneurial supporting policy for the increase and the growth of start-up of females whose careers were interrupted, in Korea.

• Korean Journal of Ichthyology
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• v.30 no.4
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• pp.194-204
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• 2018

In order to minimize the damage on the red sea bream Pagrus major by a harmful dinoflagellate Cochlodinium polykrikoides, we investigated the effect of feeding, starvation and stocking density on the survival rate, growth, growth restoration and physiological response of P. major exposure to C. polykrikoides. The experimental groups were divided into three groups such as F-HD (feeding and high density with $6.4kg/m^3$), S-HD (starvation and high density with $6.4kg/m^3$) and S-LD (starvation and low density with $3.2kg/m^3$) according to stocking density and starvation in marine cage ($11m{\times}11m{\times}5m$). The F-HD was fed throughout the experiment for 9 weeks, whereas S-HD and S-LD were not fed for 5 weeks and then refeeding for 4 weeks. Survival rate was the lowest in F-HD (85.5%) and S-LD was the highest (97.3%). The growth rates of S-HD and S-LD were significantly lower than F-HD during starvation period for 4 weeks, but rapidly recovered after feeding. The nutritional status such as ALB, TP, TCH, TG were similar to tendency of growth data. Ht, Hb, AST, ALT and GLU levels were significantly higher in the F-HD than in the starvation groups at the same time (in 3 week) during starvation period. But starvation groups did not differ during starvation period. As a result, F-HD is more sensitive to stress than S-HD and S-LD. Thus, during C. polykrikoides bloom period, starvation and stocking density control can help survival and growth restoration of the red sea bream.

• Composites Research
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• v.35 no.4
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• pp.248-254
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• 2022

In this study, TiB₂-steel composite with high-fractional TiB₂ reinforcement was fabricated by gas pressure infiltration process and the microstructure analysis and compressive strength and hardness were evaluated. To elucidate the correlation between microstructure and mechanical properties for fabricated composite, after the compression test of TiB₂-steel composite, the fracture surface was analyzed and the fracture behavior on compression test was predicted. As a result of the compression fracture surface analysis, interfacial failure trace between the steel matrix and the reinforcement was observed, and the interface between the steel matrix and the reinforcement was analyzed using TEM. From the result of microstructure analysis on the fabricated composite, it was confirmed that, in addition to TiB₂ reinforcement and steel matrix, TiC phase and coarse (Fe,M)₂B (M=Cr,Mn) phase were formed. Throughout the thermodynamic calculation, it was confirmed that TiC and (Fe,M)₂B can be formed as a stable phase under the process condition. The fabricated TiB₂-steel composite had a significantly increased hardness, and the compressive strength and Young's modulus were improved by 3.07 times and 1.95 times, respectively, compared to steel matrix. It seems that the coarse (Fe,M)₂B (M=Cr,Mn) phase formed throughout the composite causes the deterioration of mechanical properties, and by controlling the formation of the (Fe,M)₂B (M=Cr,Mn) phase, it is judged that the mechanical properties of the TiB₂-steel composite can be further improved.

• 한국노년학
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• v.29 no.4
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• pp.1247-1259
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• 2009

Muscle mass is reduced by aging. There seems to be no direct relationship between sarcopenia(muscle loss) and medical cost in the elderly, but lowering muscle mass results in increase risk of fall and decrease of strength, fitness, physical activity, and independent life. This is coupled with physical trouble and chronic degenerative disease such as diabetes, obesity, hyperlipidemia, and hypertension. Thus, sarcopenia is potential risk factor increasing mortality. The purpose of this study was to investigate the effects of elastic band exercise and detraining on sarcopenia prevention related variables, body composition and fitness. The subject of this study was 60~70 aged 14 seniors who participated in exercise program in J-welfare senior center at J-gu in S-city. Elastic band exercise was performed twice per week for 12 weeks. The body composition and fitness variables were measured before 12 weeks of control, after control(before exercise), after 12 weeks of exercise(before detraining), and after 12 weeks of detraining. There was no significant difference in body composition and fitness variables before and after 12 weeks of control, but elastic band exercise before and after 12 weeks has effect on body composition variables such as weight (t=2.978, p=0.001), body mass index (t=3.502, p=0.004), percent body fat (t=2.216, p=0.045), muscle mass (t=-3.837, p=0.002), visceral fat area (t=5.186, p<0.001), and waist-hip ratio (t=3.045, p=0.009) and on fitness variables such as 2-minutes step (t=-6.891 p<0.001), arm curl (t=-4.702, p<0.001), chair stand (t=-4.860, p<0.001), chair sit and reach (t=-5.910, p<0.001), back scratch (t=-3.835, p=0.002), and 8-ft up and go (t=7.560, p<0.001). This exercise effect was continued after 12 weeks of detraining on body composition variables such as weight (t=2.323, p=0.037), body mass index (t=2.503, p=0.026), muscle mass (t=-3.137, p=0.008) and on fitness variables such as 2-minutes step (t=-6.489 p<0.001), chair stand (t=-4.694, p<0.001), chair sit and reach (t=-3.690, p=0.003), and 8-ft up and go (t=7.539, p<0.001). It was found that the elastic band exercise has positive effect on body composition and fitness in the elderly and the effect was maintained over 12 weeks of detraining.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.69 no.1
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• pp.34-48
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• 2024

The objective of this study was to evaluate the safety of biodegradable mulching films in soybean (Glycine max) cultivation by measuring their effects on crop growth and yield, film decomposition and soil chemical and physical properties. In 2022 and 2023, plant height, branch number, chlorophyll contents, yield components, and yield of soybean did not vary significantly in areas using PE films and biodegradable mulching films. The light transmission rate of the biodegradable mulching films ranged from 6.4 to 15.8% when measured 112 days after soybean transplanting, and was higher, on average, in 2023 than in 2022. In both years, degradation of the biodegradable mulching films began 20 days after soybean transplantation and increased over time. In addition, remains of biodegradable mulching films were present in fields at soybean harvest and remained until 50 days after harvest. Decomposition rates of the biodegradable mulching films at 112 days after soybean transplanting ranged from 9.8 to 26.7% in 2022 and 13 to 36% in 2023. Although soil pH and EC varied based on the year and timing of measurements, there was no significant difference between areas that used biodegradable mulching films and PE films. Soil organic matter, nitrate and exchangeable cation contents such as Ca, Mg, and K were not significantly different in areas that used both PE films and biodegradable films. However, significantly higher levels of available phosphoric acid content were measured in areas that used biodegradable mulch films E, S, and T. Regardless of which films were used, there were no significant differences in the soil's physical properties. In 2022 and 2023, there was no difference between areas that used biodegradable mulch films and PE films. However, soil temperature in mulched areas was 2℃ higher and soil moisture was 5-15% higher than in non-mulched areas. Barley growth was not affected by being planted in soil that had been used for soybean cultivation with biodegradable films. Therefore, the biodegradable mulch films used in this study can be used without negatively affecting the growth, yield, and soil environment of soybeans.

• Journal of Korean Society of Disaster and Security
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• v.16 no.4
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• pp.45-59
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• 2023

The global focus on mitigating climate change has traditionally centered on carbon dioxide, but recent attention has shifted towards methane as a crucial factor in climate change adaptation. Natural settings, particularly aquatic environments such as wetlands, reservoirs, and lakes, play a significant role as sources of greenhouse gases. The accumulation of organic contaminants on the lake and reservoir beds can lead to the microbial decomposition of sedimentary material, generating greenhouse gases, notably methane, under anaerobic conditions. The escalation of methane emissions in freshwater is attributed to the growing impact of non-point sources, alterations in water bodies for diverse purposes, and the introduction of structures such as river crossings that disrupt natural flow patterns. Furthermore, the effects of climate change, including rising water temperatures and ensuing hydrological and water quality challenges, contribute to an acceleration in methane emissions into the atmosphere. Methane emissions occur through various pathways, with ebullition fluxes-where methane bubbles are formed and released from bed sediments-recognized as a major mechanism. This study employs Biochemical Methane Potential (BMP) tests to analyze and quantify the factors influencing methane gas emissions. Methane production rates are measured under diverse conditions, including temperature, substrate type (glucose), shear velocity, and sediment properties. Additionally, numerical simulations are conducted to analyze the relationship between fluid shear stress on the sand bed and methane ebullition rates. The findings reveal that biochemical factors significantly influence methane production, whereas shear velocity primarily affects methane ebullition. Sediment properties are identified as influential factors impacting both methane production and ebullition. Overall, this study establishes empirical relationships between bubble dynamics, the Weber number, and methane emissions, presenting a formula to estimate methane ebullition flux. Future research, incorporating specific conditions such as water depth, effective shear stress beneath the sediment's tensile strength, and organic matter, is expected to contribute to the development of biogeochemical and hydro-environmental impact assessment methods suitable for in-situ applications.