• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.812-817
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• 1995

Endodontically treated teeth are usually restored for crown protection, aesthetics, and prevention of root canal recontamination. Restoration of these teeth, however, often requires intracanal posts. Various depths and techniques have been recommended for the preparation of post space. Therefore the purpose of this study was to evaluate the effect that pst preparation has on the coronal seal by linear dye penetration of root canals obturated by lateral condensation, vertical condensation, and thermafil techniques. Forty canals of roots of incisors and canines were cleaned and shaped with the use of a step-back technique. Thirty canals were obturated, 10 each with lateral, vertical, and thermafil techhniques. Five root canals were obturated without a root canal sealer and served as positive controls. Another five root canals were obturated, and their coronal half was sealed with sticky wax and served as negative controls. The apical 5 to 6mm of the filling materials were exposed to india ink for 48 hours. The depth of dye penetration was measured in all groups and statistically analyzed (ANOVA). The results were as follows. 1. The apical plugs in the thermafil groups had the highest degree of coronal dye leakage. 2. The group filled by vertical condensation technique had the lowest degree of coronal dye leakage. 3. No significant statistical difference was found in the amount of coronal dye leakage in canals filled by lateral condensation versus those filled by the veritcal condensation technique. 4. Significant statistical differences in coronal dye penetration were found between the canals filled by thermafil and those filled by the lateral or vertical condensation techniques (p<0.05).

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.182-188
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• 2011

Polysilazane and polymethylsilazane based precursor films were deposited on Si-substrate by spin-coating, subsequently annealed at $150{\sim}850^{\circ}C$, and characterized. Structural analysis, shrink, compositional change, etch rate, and gap-filling were observed. Annealing the precursor films led to formation of spin-on dielectric films. C-containing precursor films showed that less loss of N, H, and C while less gain of O than that of C-free precursor films at $400^{\circ}C$, but more loss of N, H, and C while more gain of O at $850^{\circ}C$. Thus polysilazane based precursor films exhibited less reduction in thickness of 14.5% than silazane based one of 15.6% at $400^{\circ}C$ but more 37.4% than 19.4% at $850^{\circ}C$. FTIR indicated that C induced smaller amount of Si-O bond, non-uniform property, and lower resistance to chemical etching.

• Journal of the Korean Institute of Gas
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• v.28 no.2
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• pp.7-16
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• 2024

This study presents investigation on the technical characteristics and field cases of the salt cavern storage method for large-scale hydrogen storage. The salt cavern storage method enables effective hydrogen storage compared to other methods due to the low porosity and permeability of the rock salt that constitutes the cavern, which is not likely to leak and requires a small amount of cushion gas for operation. In addition, there is no chemical reaction between rock salt and hydrogen, and multiple injection/withdrawl cycles can be performed making it effective for peak shaving and short-term storage. The salt cavern is formed in three stages: leaching, debrining, and filling, and leakage tests are conducted to ensure stable operation. Field applications are currently performing to meet industrial demand in the surrounding area of four sites in the UK and Texas, USA, and salt cavern operation is being prepared for energy storage in European countries such as Germany and France. The investigated results in this study can be utilized as a basic guideline for the design of future hydrogen storage projects.

• Nuclear Engineering and Technology
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• v.56 no.5
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• pp.1584-1602
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• 2024

It is vital to output the required electrical power following various task requirements when the space reactor power supply is operating in orbit. The dynamic performance of the closed Brayton cycle thermoelectric conversion system is initially studied and analyzed. Based on this, a load tracking power regulation method is developed for the liquid metal cooled space reactor power system, which takes into account the inlet temperature of the lithium on the hot side of the intermediate heat exchanger, the filling quantity of helium and xenon, and the input amount of the heat pipe radiator module. After comparing several methods, a power regulation method with fast response speed and strong system stability is obtained. Under various changes in power output, the dynamic response characteristics of the ultra-small liquid metal lithium-cooled space reactor concept scheme are analyzed. The transient operation process of 70 % load power shows that core power variation is within 30 % and core coolant temperature can operate at the set safety temperature. The second loop's helium-xenon working fluid has a 65K temperature change range and a 25 % filling quantity. The lithium at the radiator loop outlet changes by less than ±7 K, and the system's main key parameters change as expected, indicating safety. The core system uses less power during 30 % load power transient operation. According to the response characteristics of various system parameters, under low power operation conditions, the lithium working fluid temperature of the radiator circuit and the high-temperature heat pipe operation temperature are limiting conditions for low-power operation, and multiple system parameters must be coordinated to ensure that the radiator system does not condense the lithium working fluid and the heat pipe.

• Magazine of the Korean Society of Agricultural Engineers
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• v.13 no.3
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• pp.2322-2341
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• 1971

The studies were conducted to determine the methods of irrigation control which is not only able to save the irrigation water as a adaptable measures for the insufficient irrigation water and the drought but also increase the yields of rice, in the paddy field which shows over percolating tendency through the couple years of 1968 and 1969 at Suwon. These experiments were carried with late maturing rice variety, Norim No. 6 and the major treatments in this experiments were filling the clay under surface soil, periodic irrigation and lining the Vinyl under the surface soil and three replicated completely randomized design was employed. Results obtained will be summarzed as follows. 1. Through the couple years, the plots tilled the clay under 15cm of the surface soil saved the irrigation water by 364% to 45% and 78% to 88% respectively. Particulary, the plot of filling the clay with 9cm thick under 15cm of the surface soil, saved the amount of irrigation water by 45% to 88% and also increased yields by 12% to 20% through the couple years. 2. The plots in which amount of 40mm of irrigation water is irrigated periodically from 5 to 8 days at the stages of tillering and ripening, saved theamount of irrigation water by 41% to 55% and also increased yields by 10% to 16% respectively through the couple years. 3. The plot lined the Vinyl under 15cm of the surface soil, saved the amount of irrigation water by 75% to 88% in accordance with the size of hole. The plot of lining the Vinyl with $3cm/m^2$ hole yielded almost same as the check plot, but in the case of lesser hole than above yielded less. 4. The plots inserted the Vinyl paper in 57cm depth and with 6cm height from the soil surface around the plot to prevent the ridge percolation reduced the amount of percolation by 25% to 33%. 5. The plot filled the wheat straw with 6cm thick under 15cm of the surface soil increased yields by 30% in former year but opposite results were gained in later year. 6. Generally, yields and yield components such as number of spikes of spikes per hill and number of grains per spike were decreased in 1969. These faots are considered to depend upon the rainy and cold weather in the stages of vigorous tillering and less sunshine in the stages of ripening. 7. The variation of characters among the plots will be summarized as follows. (1) Tallerplant height was found in the plots of clay filling and irrigation control. (2) longer culm length and higher yields were founds in the plots filled the clay with 9cm thick and controled the irrigation periodically froir 7 to 8 days. (3) Length of spike increased generally with yields but opposite tendency was found also. (4) Number of spikes per hill increased with yields in the plots of irrigation control. (5) Number of grains per spike increased with yields in the plots filled the clay with 9cm thick and controled irrigation periodically from 5 to 8 days. (6) Tendency of variation of 1000 grain weight is similar to Number of grains per spike. (7) Percentage of complete grains increased in the plot of clay filling and irrigation control.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.317-324
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• 2007

The sewage treatment sludge disposal has become a serious environmental problem because of restricted direct land-filling and oceandumping in spite of their large amounts discharged. So the recycling of sewage treatment sludge is very useful alternative for waste management. Here, we studied the feasibility of zeolite synthesis in open system from the sewage treatment sludge incinerator fly ash by means of hydrothermal synthesis. We considered the concentration of NaOH, reaction time, reaction temperature and reaction step as synthesis variables. The phase of zeolite products was identified by X-ray diffractometer(XRD) and ammonium ion exchange test was performed for the raw fly ash and two zeolite products(Z-3 and Z-5). In leaching test of the raw fly ash, hazard metal is detected very low level compared with regulatory leaching test standard. But in total recoverable test, the total contents of the fly ash were very high in terms of the standard for waste-derived fertilizer. Through hydrothermal reaction, small amount of zeolite P was synthesied in 1 N of NaOH solution and relatively large amount of hydroxysodalite was synthesied in 3 N and 5 N of NaOH solution with similar peak intensity. Addition of an aging step in the synthesis didn't increase the amount of zeolite phase. Maximum $NE_4^+-N$ exchange capacity is 1.49 mg $NH_4^+-N/g$ in Z-3 and 1.38 mg $NH_4^+-N/g$ in Z-5. Most of the ammonium ion is exchanged in 30 minutes and disorption did not occur until 5 hours.

• Journal of Nutrition and Health
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• v.40 no.6
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• pp.566-575
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• 2007

The purpose of this research was to understand how individuals reflect on the frequency and quantity of foods that they consume. Participants selected 5 males and 15 females aged 30 years or older were first interviewed on the frequency of their food consumption. Then based on this data, they were given a cognitive interview using the method of verbal proving. The individual cognitive interviews were recorded with consent while being conducted after complete approval by the Seoul National University Institution Review Board. The recorded material was evaluated using a thematic analysis after transcribing them into text. By analyzing stages of reflection, the major barriers to make the device difficult are revealed: 1) More difficulty in remembering events over the course of a full year due to diversification in the types of food that people consume 2) difficulty calculating the average for seasonal foods 3) difficulty estimating the amount of consumption from the photos presented 4) difficulty estimating amount of consumption from the quantity presented 5) difficulty processing foods that people think are healthy and foods are unhealthy simultaneously 6) difficulty having to consider foods where target food goes in as an ingredient; 7) difficulties arising from having to increase frequency when the amount consumed is higher than the quantity that is presented 8) difficulty having to combine the frequency and quantity of each food item when numerous foods are clustered into one category. These findings show that the less participants were involved in cooking, the more diverse their eating habits were, and the more they tried to adhere to rules of filling out the questionnaire, the more it was difficult for them to come up with an answer to the question being asked. It therefore seems necessary to construct a Food Frequency questionnaire that is attentive to these problems that arise from the recall stages.

• 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.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.74-81
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• 2019

In this study, to characterize the application of CSA and dihydrate gypsum Utilizing industrial byproducts, we investigated the characteristics of CSA and dihydrate gypsum to investigate the characteristics of Mine Liner according to the addition amount. As a result of compressive strength, length change and absorption rate of mining lime wastewater according to CSA addition amount, up to 30% of CSA showed a positive effect on shrinkage and absorption reduction effect as well as strength at initial age. However, due to excessive use of CSA 50%, it was reduced by 15% compared to OPC due to increase of absorption rate and decrease of cement amount due to over expansion rather than shrinkage compensation and void filling.

• Journal of Advanced Engineering and Technology
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• v.10 no.3
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• pp.285-290
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• 2017

Molding of body with ribs is the most difficult during flow molding process. The rib area is easy to be deformed at the rear side due to wall thickness variation. In this study, relationships between molding condition and deflection of rib-shaped part is investigated during the compression molding of fiber reinforced plastic composites, and the following results are derived. Polypropylene(PP), Polystyrene(PS), and stampable sheet(SS 40wt%) show the increment of deflection along with releasing temperature. For the correlation between incremental holding pressure load and deflection, stampable sheet exhibits lower deflection along with higher holding pressure, while PS shows significant increase of deflection with higher holding pressure, PP shows completely different characteristic, significant reduction of deflection along with higher holding pressure. Regarding to mold temperature and deflection, deflection amount of SS is the biggest, and PS shows the smallest. In addition, all three kinds shows the highest amount of deflection at 173C. Deflection is reduced when mold closing speed is increased. Amount of deflection in SS is larger and is not highly dependent on molding conditions like holding pressure and cooling parameters, compared with single component material like PP. This can be elucidated by anisotropic and inhomogeneous characteristics of glass fiber during filling process of stampable sheet composite.