• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• 제3권3호
• /
• pp.183-192
• /
• 2005

Natural ventilation in radioactive waste repositories is considered to be less efficient than mechanically forced ventilation for the repository working environment and hygiene & safety of the public at large, for example, controlling the exposure of airborne radioactive particulate matter. It is, however, considered to play an important role and may be fairly efficient for maintaining environmental conditions of the repository over the duration of its lifetime, for example, moisture content and radon (Rn) gas elimination in repository. This paper describes the feasibility of using natural ventilation which can be generated in the repository itself, depending on the conditions of the natural environment during the periods of repository construction and operation. Evidences from natural cave analogues, actual measurements of natural ventilation pressures in mountain traffic tunnels with vertical shafts, and calculations of airflow rates with given natural ventilation pressures indicate possible benefits from passive ventilation for the prospective Korean radioactive waste repository. Natural ventilation may provide engineers with a cost-efficient method for heat and moisture transfer, and radon (Rn) gas elimination in a radioactive waste repository. The overall thermal performance of the repository may be improved. The dry-out period may be extended, and the seepage flux likely would be decreased.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• 제21권8호
• /
• pp.195-204
• /
• 2020

The purpose of this study was to explore factors associated with smartphone dependence among adults in their 20s. The data were derived from the 2017 Survey on Smartphone Over-dependence conducted by the Ministry of Science and ICT and the National Information Society Agency. There were 3,684 participants. The data were analyzed by frequency, percentage, mean, standard deviation, independent t-test, Pearson's correlation coefficient, and weighted hierarchical multiple regression analysis. For the results, factors related with higher smartphone dependence of participants were duration (β=.18, p=.000) and frequency (β=.04, p=.000) of usage, gaming (β=.15, p=.000), watching videos (β=.09, p=.000), mobile shopping (β=.05, p=.000), working (β=.05, p=.010), e-mailing (β=.13, p=.000), and sports betting (β=.07, p=.000). Music (β=-.07, p=.000) and adult content (β=-.07, p=.000) significantly reduced their smartphone dependence. SNS (Social Networking Services) (β=.01, p=.358) and instant messengers (β=-.02, p=.330) were not factors related to smartphone dependence. However, instant messengers were the most used by participants and had a strong correlation with working (r=.55, p=.000). This study shows that smartphone usage patterns related with smartphone dependence among adults in their 20s are different from those of children and adolescents. These results could be used to more deeply understand smartphone dependence among adults in their 20s and plan early detection and prevention and care of dependence.

• The korean journal of orthodontics
• /
• 제38권6호
• /
• pp.407-415
• /
• 2008

Objective: The aim of this study was to evaluate the remineralization of interdentally stripped teeth after fluoride gel or hydroxyapatite paste application. Methods: After interdental stripping, 1.23% fluoride gel or 10% hydroxyapatite paste was applied three times a day, with a duration of four minutes, for a week. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were used to compare the change of surface contents and crystal structures before and after the application of fluoride gel or hydroxyapatite paste. Results: EDS analysis indicated that calcium contents were increased after 10% HAp paste application on stripped enamel (p < 0.01). SEM view showed that enamel surfaces in groups of 1.23% APF gel or 10% HAp paste application were smoother than those of control group, which was regarded as filling of the pore structure. And pores between crystal structures in groups treated with 1.23%, APF gel or 10% HAp paste were smaller than those of control group. Conclusions: Application of APF or HAp on stripped enamel could positively influence on the surface contents or crystal structure.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제31권6호
• /
• pp.478-484
• /
• 2009

Three-dimensional porous scaffolds play an important role in tissue engineering strategies. They provide a void volume in which vascularization, new tissue formation, and remodeling can occur. Like any grafted materials, the ideal scaffold for bone tissue engineering should be biocompatible without causing an inflammatory response. It should also possess biodegradability, which provides a suitable three-dimensional environment for the cell function together with the capacity for gradual resorption and replacement by host bone tissue. Various scaffolds have already been developed for bone tissue engineering applications, including naturally derived materials, bioceramics, and synthetic polymers. The advantages of biodegradable synthetic polymers include the ability to tailor specific functions. The purpose of this study was to examine the osteogenic activity of periosteal-derived cells in a polydioxanone/pluronic F127 scaffold. Periosteal-derived cells were successfully differentiated into osteoblasts in the polydioxanone/pluronic F127 scaffold. ALP activity showed its peak level at 2 weeks of culture, followed by decreased activity during the culture period. Similar to biochemical data, the level of ALP mRNA in the periosteal-derived cells was also largely elevated at 2 weeks of culture. The level of osteocalcin mRNA was gradually increased during entire culture period. Calcium content was detactable at 1 week and increased in a time-dependent manner up to the entire duration of culture. Our results suggest that polydioxanone/pluronic F127 could be a suitable scaffold of periosteal-derived cells for bone tissue engineering.

• Journal of Oral Medicine and Pain
• /
• 제32권1호
• /
• pp.35-43
• /
• 2007

This study was conducted to investigate the preventing effects of OPB (water extracts of Rehmannia glutinosa Libosch and Eleutherococcus senticosus Max) on bone loss in ovariectomized rats. Twenty Sprague Dawley rats of 13 week-old were divided into two groups: control group (ovariectomized, OVX)) and experimental group (OVX + OPB). The preventing effects of OPB on bone loss, OPB were fed with 100 mg OPB/kg body weight from 3 days after ovariectomization. The duration of the treatment period was 8 weeks. All bone mineral density, bone mineral content indices and bone strength indices measured by peripheral quantitative computerized tomography (pQCT) and serum bone marker assessment were carried out at end of experiment. pQCT scanning showed that OVX induced a significant decrease in cancellous bone mineral density in the proximal tibia ($-29.8{\pm}3.0%$). These decreases were significantly prevented by the administration of OPB 100 mg/kg ($-21.4{\pm}2.3%$. p<0.05). Bone strength indices showed significant difference between OVX and OPB treated rats (anti-fracture, anti-twisting, p<0.05). These data suggested that administration of OPB inhibited the loss of bone in OVX rats. CTx level were lower than in the OPB-treated animals compared with OVX. However there was no significant difference between OVX and OPB treated OVX rat. Our results suggest that OPB is effective in preventing the development of bone loss induced by ovariectomy in rats.

• Journal of Bio-Environment Control
• /
• 제9권3호
• /
• pp.141-145
• /
• 2000

This experiment was carried out to investigate the influence of flooding on the quality and yield of an oriental melon. Waterlogging for four periods, 0(not flooded), 5, 10 or 15h, were applied to 30cm depth from the soil surface. The soluble solids content of fruit flesh measured at 7 days after waterlogging was 12.6 Brix in not-flooded plot, but it decreased by 4.7-5.6 Brix in plots flooded 5, 10 or 15h, respectively. Difference in fruit hardness between the no-flooded and 5h-flooded plots was not observed, while a significant decrease in fruit hardness was observed in 10 or 15 h-flooded plots at 7 days after waterlogging. Decrease in fruit hardness in all plots except control plot was observed at 13 days after waterlogging. The percent decayed fruits at 7 days after waterlogging was not observed, but at 13 days after waterlogging it gradually increased as duration of flooding increased. The incidence of downy or powdery mildews increased is significantly in plots flooded for 5, 10 or 15h as compared to the not-flooded control. However, population of cotton caterpillar decreased in the flooded plots. Marketable fruits yield per 10a was 616.2kg in no-flooded plot, but it decreased by 33%, 45% and 66%, respectively, in plots flooded for 5, 10 or 15h. The waterlogging during fruit enlargement stage significantly deteriorated fruit quality and decreased marketable fruit yield.

• Journal of Bio-Environment Control
• /
• 제25권4호
• /
• pp.262-269
• /
• 2016

The objective of this study was to evaluate the effect of storage temperature on fruit quality attributes and physiological disorders including peel blackening in 'Sangjudungsi' persimmon (Diospyros kaki Thunb.) fruit stored in air at -1, 0.5 or $3^{\circ}C$ for up to 3 months. Higher storage temperature reduced ethylene production but not respiration rate, compared with lower storage temperature. Flesh firmness decreased continuously as storage time passed but firmness was reduced rapidly in the fruits stored at higher storage temperature. Fresh weight loss increased at higher storage temperatures. Soluble solids content was higher at lower storage temperature than at higher storage temperature. All color variables ($L^*$, $a^*$, $b^*$) were reduced by lower storage temperature, compared with higher storage temperature, regardless of tissue regions. Fruit softening increased as storage duration advanced and with the increase in storage temperature. Results indicated that the 'Sangjudungsi' persimmon fruits stored at higher storage temperature ($3^{\circ}C$) could not retain fruit quality properly on account of lower flesh firmness and higher incidence of peel blackening and fruit decay, compared with lower storage temperature.

• Asian-Australasian Journal of Animal Sciences
• /
• 제13권12호
• /
• pp.1717-1725
• /
• 2000

The objective was to determine the relationship between feed intake levels and patterns, and growth performance and body composition of barrows and gilts using automatic feed intake recording equipment (F.I.R.E.). This system records the time of visits to the feeder and the duration and size of meals for individual animals housed in groups. Ninety-six crossbred pigs were grown from $33.4{\pm}0.51$ to $109.7{\pm}1.39kg$ live weight over a 13-week period. Eight mixed-sex groups of 12 pigs were used and 4 dietary treatments were compared giving 2 pens per treatment. The dietary treatments consisted of corn-soybean meal diets with differing protein levels which ranged from 14.7% to 19% between 30 to 55 kg, from 13.3% to 16.9% between 56 and 85 kg, and from 12.3% to 16.8% for the remainder of the study. Animals were ultrasonically scanned to measure loin-eye area and backfat thickness to estimate carcass fat-free lean content at the beginning and end of the study. Barrows had higher daily feed intake than gilts (2.67 vs. 2.46 kg resp. p<0.05) which was the result of a longer feeder occupation time per visit (4.77 vs. 4.54 min, resp. p<0.05), higher feed consumption rates (30.4 vs. 29.0 g/min, resp. p<0.05), and higher feed intakes per visit (136.9 vs. 126.8 g, resp. p<0.01). Gilts had less backfat and greater loin-eye area than barrows (p<0.05). Diet had no significant effect on growth performance and had limited impact on feeding patterns. Body weight showed high correlations with ADG (r=0.74), feed intake per visit (r=0.51) and feed consumption rate (r=0.69). Positive correlation were also found between daily feed intake and feed intake per visit (r=0.45), feeder occupation time per day (r=0.56), and feed consumption rate (r=0.55), and between daily feed intake and backfat thickness (r=0.32) and feed consumption rate and loin-eye area (r=0.32). There were negative correlations between number of feeder visit per day and daily feed intake (r=-0.54), and between feed intake per visit and number of feeder visits per day (r=-0.43). However, correlations between feed intake traits and carcass traits were generally low. Visits to the feeder were greatest during the morning (0700 to 1100 h) and lowest during the evening and nighttime. These results highlight limited variation among the sexes in feeding patterns and suggest important relationships between feeding behavior and feed intake.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• 제50권spc1호
• /
• pp.99-103
• /
• 2005

Nitrogen content of liquid manures varies from $3g\;kg^{-1}\;to\;7g\;kg^{-1}$ according to the collecting seasons. The application effects of liquid manure on the yield of rice are the best in LPM+LPM treatment, although the lodging of crops increased and the quality of rice is deteriorated. When application with LPM+CF treatment and CF+LPM treatment showed no difference in rice yield and quality, compared with CE+CF treatment. Therefore, use of liquid manure on farmland should be limited as once per year during cultivation duration and liquid manure is fully fermented during 6 months at least in order to decrease the damage of crops by application of unmatured liquid manure. Also, application amount of liquid manure should be carefully determined by considering the mineral (especially nitrogen) contents of liquid manure and the recommended fertilizer levels for various crops.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• 제31권1호
• /
• pp.43-48
• /
• 1986

The experiment was conducted to know the varietal difference in changing aspect of daily filling sink during of rice using three cultivars; ‘Suweon 295’ (japonica), ‘Suwoen 264’ and ‘IR 1317-70-1’ (semi-dwarf indica) cultivated in the field and green house of the Crop Experiment Station in 1983. There was not significant varietal difference in flowering habit and duration of flowering period each panicle. Semi-dwarf indica cultivars showed shorter days to physiological maturity of rice kernel than the japonica one. The former also displayed earlier decrease in water content of rice grain during ripening than the latter. Japonica variety revealed larger difference in ripening advancement between vigorous florets and inferior one than semi-dwarf indica varieties. The semi-dwarf indica rice cultivars expressed significantly shrewder parabola of daily filling of sink per panicle during ripening than the japonica one. The time showing maximum capacity of daily filling of sink per panicle during ripening was 10-12 days after anthesis. The filling capacity of daily sink filling per panicle for 'IR 1317-70-1', 'Suweon 264' and 'Suweon 265' at this time were about 240 mg, 165 mg and 145 mg, respectively. Pattern of sink filling per panicle during ripening was slightly changed by the cultural environment. ‘Suweon 295’ showed slightly sharper parabola and 2-3 days earlier time showing maximum capcity of daily sink demand per panicle during ripening in the field than those in the green house.