• Restorative Dentistry and Endodontics
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• v.21 no.2
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• pp.451-469
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• 1996

The purpose of this study was to investigate the effect of calcium hydroxide and glass ionomer cement fillings on the levels of $LTB_4$ and $LTC_4$ in experimentally inflamed rat dental pulp. The dental pulp in the mandibular incisor of wistar rat was irritated by cutting a 5mm deep hole in the dentin with a twist drill bur of 0.5mm diameter, without cooling. The cavities were filled with calcium hydroxide(light-cured) and glass ionomer cement(light cured). The untreated pulp served as control tissue specimen. After cavity preparations, the rat with or without various treatment were sacrificed in various time by decapitation. The dental pulp tissue were carefully removed and the concentrations of $LTB_4$ and $LTC_4$ were determined by radioimmunoassay. And pulps were examined histologically to observe inflammatory feature. The result were obtained as follows : 1. The inflammatory features of pulps were observed microscopically in all experimental groups. And degree of inflammation was decreased with time. 2. The concentrations of $LTB_4$ and $LTC_4$ for all experimental groups were significantly higher than those for control group 6 hours after cavity preparation(p<0.05). 3. The group filled with calcium hydroxide was the lowest, and the group filled with glass ionomer cement, the group of irritation in that order showed increased concentrations of $LTB_4$ and $LTC_4$ 6 hours after cavity preparation. In the concentrations of $LTB_4$, significant differences among 3 groups were noted(p<0.05). 4. The group filled with calcium hydroxide was the lowest, and the group filled with glass ionomer cement, the group of irritation in that order showed increased concentrations of $LTB_4$ and $LTC_4$ 24 hours after cavity preparation. And there were statistically significant difference in concentrations of $LTB_4$ between the group of irritation and the group filled with calcium hydroxide(p<0.05). 5. The group filled with calcium hydroxide was the lowest, and the group filled with glass ionomer cement, the group of irritation in that order showed increased concentrations of $LTB_4$ and $LTC_4$ 48 hours after cavity preparation. But no statistically difference was found (p>0.05). 6. The concentrations of $LTB_4$ and $LTC_4$ in all experimental groups were highest level at 6 hour after experiment and decreased as time progresses(correlation coefficient>0.8).

• Resources Recycling
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• v.8 no.1
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• pp.23-28
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• 1999

Firing characteristics, transverse rupture strength, and heat capacity were studied of the heat-reservoir refractory materials made of red-firing clay, mill scale, and water glass. The firing shrinkage increased with increase of the clay proportion in samples. The volume of fired bodies showed shrinkage by drying up to $300^{\circ}C$, steady expansion in the 300-$700^{\circ}C$ range due to phase transition of iron oxides. and drastic expansion above $1200^{\circ}C$. Flexural strength decreased from 5.6 Mpa to 2.35 Mpa with the decrease of the ratio of clay to mill scale from 1:1 to 1:3 Heat capacities changed from 1.1 Joul/g$^{\circ}$C to 1.35 Joul/g$^{\circ}$C with the ratio of millscale to clay ratio from 1:1 to 1:3. Mill scale in the specimen appears to exist as liquid phase during firing. Firing the specimens in air leads to the eruption of the molten mill scale to the sample surfaces. Contrarily, firing samples in a refractory sagger with a cover suppressed the eruption of the molten mill scale to the surfaces. The addition of mill scale gave rise to porous sintered bodies which would delay cooling rates of heat-reservoir brick.

• Resources Recycling
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• v.26 no.5
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• pp.54-60
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• 2017

In this study, we investigated the effect of $TiCl_4$ injection time on the Kroll reaction at a given weight ratio of $TiCl_4$ and Mg. The reduction reaction was investigated by measuring the temperature change according to $TiCl_4$ injection time and observing the cross section and appearance of the Ti sponge after the reaction. The temperature increment due to Kroll reaction heat generation was found to be linearly proportional to the $TiCl_4$ feed rate. In the graph of $TiCl_4$ injection time and reduction tank temperature, initial temperature peaks were observed irrespective of the injection conditions. This is interpreted to mean a temporary interruption of reaction due to $MgCl_2$ formation after the initial Kroll reaction. In addition, when the cross section of the sponge was observed, a large amount of spherical Mg particles was observed in $MgCl_2$. We can infer that this is the process of continuously feeding the unreacted Mg surface, so that a continuous Kroll reaction takes place. The sponge appearance showed that the coalescence or growth of the Kroll reacted Ti particles can be controlled by the cooling rate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.1
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• pp.160-164
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• 2015

The effects of different ingredient formulations on physicochemical qualities and consumer preferences were investigated using Baikseolgi incorporated with pomegranate concentrate (PC), a healthy food ingredient, as a model system. PC was incorporated into the formulation at five different amounts [0%, 1.6%, 3.3%, 5%, and 6.6% (w/w)] by replacing the equivalent amount of water added. After appropriate mixing, rice cakes were steamed and quality attributes were evaluated after cooling. The pH decreased while moisture content increased significantly with increased PC substitution (P<0.05). Lightness decreased significantly from 82.33 to 65.09 with higher incorporation of PC (P<0.05), indicating that the color of Baikseolgi became darker. Redness and yellowness, on the other hand, increased significantly (P<0.05). Hardness gradually increased as the PC content increased in the formulation (P<0.05). In addition, DPPH and ABTS radical scavenging activities increased significantly (P<0.05), and they were well correlated. The overall consumer acceptance results indicate that incorporation of 1.6% PC in the formulation of Baikseolgi is recommended to take advantage of the health benefits of PC without sacrificing quality acceptance by consumers.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.600-607
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• 1994

Optimum exper~mental conditions were established for the growth of heteroepitaxial GaAs layers on InP using liquid phase epitaxy (LPE) technique. Results showed that the optimum growth temperature was $720^{\circ}C$ at a cooling rate of $0.5^{\circ}C$/min. Surface morphology of the grown layers significantly improved by addition of about 0.005wt% Se to the Ga growth melt, which effectively suppressed melt-back of InP substrates into the melt during the initial stage of growth. It was observed that the quality of GaAs layers also improved substantially when the substrates patterned with grating structure were used, as determined by the (400) double crystal X-ray diffraction. The transmission electron microscopy observation indicated t.hat the misfit dislocations interact with each other at the grating region, resulting in a lower dislocation density in the upper GaAs layer.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.75-80
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• 2000

The positions of Xe atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated Na-A have been determined. Na-A was exposed to 1050atm of xenon gas at 400 $^{\circ}C$ for seven days, followed by cooling at pressure to encapsulate Xe atoms. The resulting crystal structure of Na-A(7Xe) (a = 12.249(1) $\AA$, $R_1$ = 0.065, and $R_2$ = 0.066) were determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1) $^{\circ}C$ and 1 atm. In the crystal structure of Na-A(7Xe), seven Xe atoms per unit cell are distributed over four crystallographically distinct positions: one Xe atom at Xe(1) lies at the center of the sodalite unit, two Xe atoms at Xe(4) are found opposite four-rings in the large cavity, and four Xe atoms, two at Xe(2) and others at Xe(3), respectively, occupy positions opposite and between eight- and six-rings in the large cavity. Relatively strong interactions of Xe atoms at Xe(2) and Xe(3) with $Na^+$ ions of four-, eight-, and six-rings are observed:Na(1)-Xe(2) = 3.09(6), Na(2)-Xe(3) = 3.11(2), and Na(3)-Xe(2) = 3.37(8) $\AA$. In each sodalite unit, one Xe atom is located at its center. In each large cavity, six Xe atoms are found, forming a distorted octahedral arrangement with four Xe atoms, at equatorial positions (each two at Xe(2) and Xe(3)) and the other two at axial positions (at Xe(4)). With various reasonable distances and angles, the existence of $(Xe)_6$ cluster is proposed (Xe(2)-Xe(3) = 4.78(6) and 4.94(7), Xe(2)-Xe(4) = 4.71(6) and 5.06(6), Xe(3)-Xe(4) = 4.11(3) and 5.32(4) $\AA$, Xe(2)-Xe(3)-Xe(2) = 93(1), Xe(3)-Xe(2)-Xe(3) = 87(1), Xe(2)-Xe(4)-Xe(2) = 91(4), Xe(2)-Xe(4)-Xe(3) = 55(2), 59(1), 61(1), and 68(1), and Xe(3)-Xe(4)-Xe(3) = 89($^{\circ}1$)). These arrangements of the encapsulated Xe atoms in the large cavity are stabilized by alternating dipoles induced on Xe(2), Xe(3), and Xe(4) by eight- and six-ring $Na^+$ ions as well as four-ring oxygens, respectively.

• Journal of Radiation Industry
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• v.9 no.4
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• pp.217-221
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• 2015

When reactor coolant leaks occur due to cracks of a steam generator's tube, radioactive materials contained in the primary cooling water in nuclear power plant are forced out toward the secondary systems. At this time the secondary water purification resin in the ion exchange resin tower of the steam generator blowdown system is contaminated by the radioactivity of the leaked radioactive materials, so we pack this in special containers and store temporarily because we could not dispose it by ourselves. If steam generator tube leakage occurs, it produces contaminated spent resins annually about 5,000~7,000 liters. This may increase the amount of nuclear waste productions, a disposal working cost and a unit price of generating electricity in the plant. For this reasons, it is required to develop a decontamination process technique for reducing the radioactive level of these resins enough to handle by the self-disposal method. In this research, First, Investigated the structure and properties of the ion exchange resin used in a steam generator blowdown system. Second, Checked for a occurrence status of contaminated spent resin and a disposal technology. Third, identified the chemical characteristics of the waste radionuclides of the spent resin, and examined ionic bonding and separation mechanism of radioactive nuclear species and a spent resin. Finally, we carried out the decontamination experiment using chemicals, ultrasound, microbubbles, supercritical carbon dioxide to process these spent resin. In the case of the spent resin decontamination method using chemicals, the higher the concentration of the drug decontamination efficiency was higher. In the ultrasound method, foreign matter of the spent resin was removed and was found that the level of radioactivity is below of the MDA. In the microbubbles method, we found that the concentration of the radioactivity decreased after the experiment, so it can be used to the decontamination process of the spent resin. In supercritical carbon dioxide method, we found that it also had a high decontamination efficiency. According to the results of these experiments, almost all decontamination method had a high efficiency, but considering the amounts of the secondary waste productions and work environment of the nuclear power plant, we judged the ultrasound and supercritical carbon dioxide method are suitable for application to the plant and we established the plant applicable decontamination process system on the basis of these two methods.

• Korean Journal of Dental Materials
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• v.44 no.3
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• pp.197-206
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• 2017

The hardening effect by ice-quenching after oxidation of a Pd-Ag-Sn-Au metal-ceramic alloy during porcelain firing simulation was investigated by means of hardness test, field emission scanning electron microscopic observations, and X-ray diffraction analysis. The hardness decreased by ice-quenching after oxidation, which was induced by the homogenization of the ice-quenched specimen. The decreased hardness by ice-quenching after oxidation was recovered from the wash stage which was the first stage of the remaining firing process for bonding porcelain. After wash stage, the hardness of the ice-quenched specimens decreased during the subsequent porcelain firing process. But the final hardness of the ice-quenched specimens after oxidation was higher than that of the specimens cooled at stage 0 after oxidation. The increase in hardness of the specimens during the first firing process was caused by the lattice strains generated at the interface between the face-centered cubic Pd-Ag-rich matrix and the face-centered tetragonal Pd3(Sn, Ga, In) precipitate. The decrease in hardness of the specimens during the remaining firing process was caused by the microstructural coarsening.

• Journal of agriculture & life science
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• v.44 no.4
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• pp.69-77
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• 2010

Fuzzy control is widely used for improving temperature control performance as controlling ventilation in greenhouse because the technique can respond more flexibly to the outside air temperature and wind speed. By pre-studied PID and normal fuzzy control this study was performed to obtain the fundamental data that can be established in better greenhouse ventilation control method. The temperature control error by the simple fuzzy control was $1.2^{\circ}C$. The accumulated operating size of the window and the number of operating were 84% and 13, respectively. These showed equivalent control performance with pre-studied result that control error. The accumulated operating size of the window and the number of operating were 75% and 12, respectively. The proposed fuzzy technique was simple control logic method compared with step and PID control methods, but it showed equivalent performance. Therefore, the proposed simple fuzzy control method could be used in micro controller of small programmable memory size and many applications.

• Bulletin of the Korean Chemical Society
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• v.22 no.9
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• pp.1023-1029
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• 2001

The positions of Kr atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated zeolite A of unit-cell composition Cs3Na8HSi12Al12O48 (Cs3-A) have been determined. Cs3-A was exposed to 1025 atm of krypton gas at 400 $^{\circ}C$ for four days, followed by cooling at pressure to encapsulate Kr atoms. The resulting crystal structure of Cs3-A(6Kr) (a = $12.247(2)\AA$, R1 = 0.078, and R2 = 0.085) has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at $21(1)^{\circ}C$ and 1 atm. In the crystal structure of Cs3-A(6Kr), six Kr atoms per unit cell are distributed over three crystallographically distinct positions: each unit cell contains one Kr atom at Kr(1) on a threefold axis in the sodalite unit, three at Kr(2) opposite four-rings in the large cavity, and two at Kr(3) on threefold axes in the large cavity. Relatively strong interactions of Kr atoms at Kr(1) and Kr(3) with Na+ ions of six-rings are observed: Na-Kr(1) = 3.6(1) $\AA$ and Na-Kr(3) = $3.08(5)\AA.$ In each sodalite unit, one Kr atom at Kr(1) was displaced $0.74\AA$ from the center of the sodalite unit toward a Na+ ion, where it can be polarized by the electrostatic field of the zeolite, avoiding the center of the sodalite unit which by symmetry has no electrostatic field. In each large cavity, five Kr atoms were found, forming a trigonal-bipyramid arrangement with three Kr(2) atoms at equatorial positions and two Kr(3) atoms at axial positions. With various reasonable distances and angles, the existence of Kr5 cluster was proposed (Kr(2)-Kr(3) = $4.78(6)\AA$ and Kr(2)-Kr(2) = $5.94(7)\AA$, Kr(2)-Kr(3)-Kr(2) = 76.9(3), Kr(3)-Kr(2)-Kr(3) = 88(1), and Kr(2)-Kr(2)-Kr(2) = $60^{\circ}).$ These arrangements of the encapsulated Kr atoms in the large cavity are stabilized by alternating dipoles induced on Kr(2) by four-ring oxygens and Kr(3) by six-ring Na+ ions, respectively.