• Journal of Korea Foundry Society
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• v.28 no.6
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• pp.273-281
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• 2008

Effects of alloying elements on the mechanical properties of hardened and austempered 3.60wt%C - 2.50wt%C ductile cast iron were investigated. Strength and hardness were increased and ductility was decreased as the amount of alloying element increased. The increasing effect of copper addition on the strength was the most pronounced. The strength and hardness were greatly increased and ductility was decreased by hardening. The effect of alloying element on the mechanical properties of the hardened ductile cast iron was not so pronounced due to the high contents of C and Si. The strength and hardness of austempered ductile cast iron were greatly increased, meanwhile the difference of strength from that of hardened one was not so big. The ductility of the former was higher than that of the latter. The strength and ductility of austempered ductile cast iron with 0.25%Mn were the maximum of all Mn added ones. The maximum strength of that was obtained with the addition of 0.80wt%Cu or 2.00wt%Ni along with this amount of Mn added.

• Journal of Sericultural and Entomological Science
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• v.41 no.2
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• pp.116-121
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• 1999

This study was aimed to explain the essence of Hydroxylammonium hydrochloride(H.A.) effect on degummed silk fiber increasing the colour sites due to oxime generating reaction. H.A. in aqueous solution caues to increase the amount of [H+] and reduce pH values as the concentration of H.A. increases. The rate of [H+] absorption of silk fiker in acidic solution differs on the basic of solution pH and shows a specific uptake in each pH, the lower the pH of solution, the higher the amount [H+] absorption. The pH of solution after treating of silk fiber in H.A. and HCl, showed more remaining [H+] in H.A. solution due to [H+] releasing under the procedure of oxime production. Also it was revealed that in higher concentration of H.A. the reaction for oxime fixation in silk fiber carried out stonger and as a result the bigger gap with acid uptake curve appeared. FT-IR analysis of silk fiber treated with H.A. revealed the creating of intermolecular H-bond at the 2,981-2.930 cm-1, which was not appeared for nontraeted silk fibers and shows H-bond between N-OH group in oue chain and C=) group in another chain of silk protein. Colourimetry of dyed silk fiber after H.A. tratment showed that the silk fiber treated with the high concentration of H.A. compare to low concentration, absorbed more dyeing molecules and so Showed less percontage of Whiteness.

• Human Ecology Research
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• v.57 no.4
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• pp.473-483
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• 2019

Smartphones are representative multimedia devices capable of various functions that have emerged due to the development of information communication technologies (ICTs). The popularization of smartphones has changed the way ICTs media is used; consequnetly, it is expected that smartphones will influence family life by changing family communications and time use. However, there is a gap between the empirical research on ICTs media and family. This study explores any correlations in the amount of time spent on smartphones between a husband and wife. We marged 1,444 married couples' media diaries from the 8th Korean Media Panel Survey (2017) to analyze the average amount of time spent on communications and leisure shopping using smartphones. The results show that husbands' time use for communication has increased similarly to wives' time use. In addition, husbands' time use for leisure and shopping was positively related to wives' time spent on communications and leisure shopping. The findings show that the use of smartphones is interrelated within the family and suggested that a family systems approach is needed in ICTs media research. Future studies will provide a deeper understanding of the impact of ICTs media and how families are using a variety of ICTs media devices such as smartphones.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.1
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• pp.148-172
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• 1997

Sixty human premolar teeth were used for this in vitro study. After each tooth was sectioned mesiodistally, one half was used for the experimental group and the other half for the control. Three groups were made for each fluoride applying method and twenthy teeth were assigned to each group. Ten teeth were used for evaluating total fluoride amount and the other ten were used for firmly-bound fluoride. Fluorshield was used for fluoride-releasing sealant and 1.23% APF, 0.05% NaF were used for topical application fluorides. Each tooth was cleaned with a tooth brush using nonfluoride containing pumice before the experiment. In the sealant group, fluoroshield was applied to the enamel surface without etching procedure and stored in $37^{\circ}C$ saline for 30 days. After 30 days, sealant was removed with explorer without scratching the enamel surface and washed with distilled water and dried. In the APF group, each tooth was immersed in 1.23% APF for 30 min then washed and dried in the same manner. In the NaF group, each tooth was immersed in 0.05% NaF for 24 hours then washed and dried as described above. After each fluoride regimen was applied, ten teeth were randomly selected from each group and immersed in 1M KOH solution for 24 hours to remove loosely-bound fluoride possibly deposited by the three different fluorides applied. In each group, total fluoride amount deposited and the amount of enamel removed by acid biopsy were calculated. After loosely-bound fluoride was removed, firmly-bound fluoride deposited and the amount of enamel removed by acid biopsy were also calculated. Total fluoride amount deposition was significantly increased in the APF and NaF groups, but not in the sealant group. Amount of enamel removed by acid-biopsy was also significantly diminished in the APF and NaF groups, but not in the sealant groups. After loosely-bound fluoride was removed from each groups, no statistical difference was found in the amount of firmly-bound fluoride in any groups. Also no effect of firmly-bound fluoride on enamel dissolution was shown in any groups after loosely-bound fluoride was removed from each group. In conclusion, topical application method of APF or NaF is more effective than fluoride-releasing sealant application to make $CaF_2$ coating on enamel surface and $CaF_2$ coating is the main source for anticariogenic effect of fluoride. However, longterm anticariogenic effect of fluoride-releasing sealant should be further evaluated.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.19-31
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• 1994

The objective of this study is to conduct a thermal-hydraulic analysis on the spent fuel pool and to evaluate a parametric effect for the thermal-hydraulic analysis of spent fuel pool. The selected parameters are the Reynolds Number and the gap flow through the oater gap between fuel cell and fuel bundle. The simplified flow network for a path of fuel cells is used to analyze the natural circulation phenomenon. In the flow network analysis, the pressure drop for each assembly from the entrance of the fuel rack to the exit of the fuel assembly is balanced by the driving head due to the density difference between the pool fluid and the average fluid in each spent fuel assembly. The governing equations ore developed using this relation. But, since the parameters(flow rate, pressure loss coefficient, decay heat, density)are coupled each other, iteration method is used to obtain the solution. For the analysis of the YGN 3&4 spent fuel rack, 12 channels are considered and the inputs such as decay heat and pressure loss coefficient are determined conservatively. The results show the thermal-hydraulic characteristics(void fraction, density, boiling height)of the YGN 3&4 spent fuel rack. There occurs small amount of boiling in the cells. Fuel cladding temperature is lower than 343.3$^{\circ}C$. The evaluation of parametric effect indicates that flow resistances by geometric effect are very sensitive to Reynolds number in the transition region and the gap flow is negligible because of the larger flow resistance in the gap flow path than in the fuel bundle.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.267-276
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• 2020

Poly(epichlorohydrin) copolyol series (PECH copolyols) were synthesized via cationic ring-opening copolymerization (ROCP) of oxirane-based monomers and effects of reaction temperature, solvent type, and initiator were studied. As a comonomer, two types of alkylene oxides were used, and polymerization conditions were conducted both with diethylene glycol (DEG) as an initiator in methylene chloride (MC) solvent and tripropylene glycol (TPG) in toluene solvent. In order to induce the active monomer (AM) mechanism in the ring-opening copolymerization reaction, the monomer was injected by an incremental monomer addition (IMA) method using a syringe pump, and the polymerization was performed at -5 ℃. PECH copolyol, a synthesized ephichorohydrin (ECH)-based copolyol, was converted to glycidyl azide-based energy-containing copolyol (GAP copolyol) by azadizing the ECH unit through a substitution reaction. It was confirmed that the synthesized azide copolyol had little effects on changes of the solvent and the initiator. Also, the molecular weight increased 500 after the azide reaction, thereby the GAP copolyol was polymerized as designed. As the content of the comonomer increased, both the T_g and viscosity tended to decrease due to the influence of the alkyl chain length. It is possible to fundamentally prevent CH₃N₃ amount produced in the azide reaction process, and it is expected that a large-scale process could be achievable.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.815-820
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• 2005

ZnO varistor ceramics were fabricated with variation of addition of glass-frit amount and the sintering temperature was $1100^{\circ}C$. The average grain sizes were showed increased from $8.6{\mu}m\;to\;10{\mu}m$, and varistor voltages were decreased from 506V to 460V by added amount of glass-frit. Nonlinear coefficient $\alpha$, of all were with increasing the amount of glass-frit more than 70, in case of added on $0.03wt\%$ glass-frit was 83. And leakage current were less than $1{\mu}A$ with applied at $82\%$ of varistor voltage. The clamping voltage ratio of the specimens added $0.03wt\%$ glass-frit was 1.41 at applied 25A $[8/20\;{\mu}s]$. In the specimen added $0.03wt\%$ glass-frit, endurance of surge current and deviation of varistor voltage were $6200A/cm^2,\;\Delta-1.67\%$, respectively and clamping voltage ratio was 2.33. In the Specimen added $0.03wt\%$ glass-frit were superior to any other compositions on High Temperature Load Test(HTLT) for 1000 hr at $85^{\circ}C$, and deviation of the varistor voltage were $\Delta-1.29\%$.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.119-120
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• 2000

Influences of sustain voltage on wall charges and wall voltages are experimentally investigated in surface AC plasma display panels(AC-PDPs), in which electrode gap and width are $80\;{\mu}m$ and $270\;{\mu}m$, respectively. The filling gas is Ne-Xe gas mixture, and total pressures 300 Torr. Also it is found that the more amount of Xe mixing ratio makes the less wall charge and voltage for sustain voltage ranged from 140 V to 222 V. The response time has been delayed by adding a small amount of Xe to Ne in comparison with that without Xe. It is also found that the wall charge and voltage are reduced by adding a small amount of Xe to Ne in comparison with those without Xe.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.8
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• pp.419-428
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• 2017

In this study, energy loss due to ventilation load in the dock system was analyzed through simulation. Also, flow generated in the dock system of the warehouse was measured using manufactured measuring devices. Numerical simulation was conducted by simulating the most common picking tasks by examining the actual working environment. Incompressible and unsteady turbulent flows were assumed, and the turbulence model was the k-e standard model. Proper grid was selected through grid dependency test. Measurement was conducted using Honeywell and Vaisala sensors, and flow and temperature inside the warehouse were measured and compared with simulation results to validate simulation. When comparing amount of loss occurring in two hours and amount of loss occurring in 15 minutes, docking time of the former was eight times longer but energy loss was 3.8 times lower. Ventilation load occurring during the initial period after opening docking system accounted for a large proportion of total ventilation load. Also, comparing the load when the dock was closed and the load when the truck was parked, ventilation load was significantly higher than load due to heat conduction from the wall. Therefore, in improving the docking system, it is effective to reduce the gap by improving compatibility of the docking system and truck, rather than wall material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.6
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• pp.1087-1093
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• 2017

The purpose of this study is to present an empirical analysis of determinants of the amount of orders received in construction technology engineering industry sector. Regression model was applied for 5 years from 2010 to 2014 to find out how the factors affecting the amount of orders received each year are different and what trends are observed. Although common significant variables were identified that there is a difference in the impact on their orders received. Specifically, the increase in the number of orders received while reducing the impact on orders received from 2010 to 2013, 2014 showed a slight tendency to increase. And increase in the number of employees shows that the influence of order received is higher in 2014 than in 2010. In addition, the gap between the metropolitan area and the non-metropolitan area has doubled in 2014 compared to 2010, but it is also confirmed that the metropolitan area is still strong. On the other hand, in the case of licensed technology, the only statistically significant variable was the negative correlation between the amount of orders received. Although the influence declined in 2014 compared to 2011, it still had a large impact on the amount of orders received.