• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.25-32
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• 2008

[ $^{169}Yb$ ] industrial NDT sealed sources were developed by using $Yb_2O_3$ pellets as the target and demonstrated for their performance. To produce the pellets, optimal compacting and sintering conditions were determined experimentally. Source holders for $^{169}Yb$ were designed and fabricated. After assembling an active source produced from HANARO with the developed source holder, a demonstration experiment was performed to compare the quality of the radiographs from $^{192}Ir$ and soft X-rays. This demonstration study showed that the developed $^{169}Yb$ produced better radiographs than $^{192}Ir$ for a carbon steel with less than a 4 mm thickness.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.309-316
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• 2014

A large particle accelerator requires an ultrahigh vacuum (UHV) system of average pressure under $1{\times}10^{-7}$ Pa for mitigating the impact of beam scattering from the residual gas molecules. The surface inside the beam ducts should be controlled with an extremely low thermal outgassing rate under $1{\times}10^{-9}Pa{\cdot}m^3/(s{\cdot}m^2)$ for the sake of the insufficient pumping speed. To fulfil the requirements, the aluminum alloys were adopted as the materials of the beam ducts for large accelerator that thanks to the good features of higher thermal conductivity, non-radioactivity, non-magnetism, precise machining capability, et al. To put the aluminum into the large accelerator vacuum systems, several key technologies have been developed will be introduced. The concepts contain the precise computer numerical control (CNC) machining process for the large aluminum ducts and parts in pure alcohol and in an oil-free environment, surface cleaning with ozonized water, stringent welding process control manually or automatically to form a large sector of aluminum ducts, ex-situ baking process to reach UHV and sealed for transportation and installation, UHV pumping with the sputtering ion pumps and the non-evaporable getters (NEG), et al. The developed UHV technologies have been applied to the 3 GeV Taiwan Photon Source (TPS) and revealed good results as the expectation. The problems of leakage encountered during the assembling were most associated with the vacuum baking which result in the consequent trouble shootings and more times of baking. Then the installation of the well-sealed UHV systems is recommended.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.1-8
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• 2003

Two types of ground-water sampling techniques for CFCs (chlorofluorocarbons) analysis, the cold-welded copper tube method and flame-sealed borosilicate glass ampule method, were compared and evaluated. CFCs concentrations by the copper tube method showed a poor reproducibility among triplicates whereas those by the glass ampule method showed a good agreement and relative standard deviations of triplicates were less than 5%. The poor reproducibility of the copper tube method appears to be attributed to the incomplete sealing in connection between faucets of wellhead and the sampling apparatus. The copper tube method also showed higher CFCs concentrations than the glass ampule method, which is more pronounced for CFC-11 than for CFC-12. The plastic tubings and rubber gasket of faucets in case of the copper tube method possibly contaminated the samples with CFC-11 and CFC-12. The potential of CFCs contamination for the glass ampule method was eliminated by using stainless steel and Nylon only and by connecting the sampling equipment directly to the main discharge pipe of wellhead. The validity of the glass ampule method were also verified by detecting very low level of CFCs for the ground-water sample which is old enough to have negligible CFCs.

• Journal of the Korean institute of surface engineering
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• v.50 no.1
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• pp.29-34
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• 2017

Chloride plating solution was fabricated by dissolving metal Ni powders in a mixed solution with HCl and de-ionized water. Effects of $Ni^{2+}$ and saccharin concentrations in the plating baths on current efficiency, residual stress, surface morphology and microstructure of Ni films were studied. In the case of $0.2M\;Ni^{2+}$ concentration, current efficiency was decreased to about 65 % with increasing saccharin concentration, but, in the case of $0.7M\;Ni^{2+}$ concentration, it was shown more than 90 % with the increase of saccharin concentration. Residual stress of Ni thin film was appeared to be about 400 MPa up to 0.0244 M saccharin concentration at the $0.2M\;Ni^{2+}$ concentration and surface morphology with severe cracks was observed in the range of 0.0487~0.0975 M saccharin concentration. Residual stress of Ni thin films was measured to be about 750 MPa without saccharin addition and 114~148 MPa at the range of 0.0097~0.0975 M saccharin concentration for the $0.7M\;Ni^{2+}$ concentration. Relatively low residual stress values (114~148 MPa) of the Ni films at the range of 0.0097~0.0975 M saccharin concentration may be resulted from codeposition of S from saccharin. Ni films at $0.7M\;Ni^{2+}$ concentration showed smooth surface morphology and were independent of saccharin concentration. Ni films at $0.7M\;Ni^{2+}$ concentration consist of FCC(111), FCC(200), FCC(220) and FCC(311) peaks and the intensities of FCC(111) and FCC(200) peaks increased with increasing saccharin concentration. Also, the average grain size decreased with increasing saccharin concentration from about 30 nm to about 15 nm.

• 보존과학연구
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• s.14
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• pp.94-108
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• 1993

The cultural properties of cloth are of animal orgin (silk), or of vegetable orgin(cotton, hemp, ramie). As clothes are of an orginic material, they were subjected to damage by chemical, phisigical or biological factors, viz, moulds insects, lights, humidity and temperature changes, etc. And these factors promote that clothes generally result from various types of deterioration. In 1992, We were performed the conservation treatments for total 9 pieces of cloth, such as 3 pieces of General PAK SHIN-RYONG(Important Folklore Material No.110) 3 pieces of Madam Jung(Important Folklore Material No.115) and 1 piece of King Se-jo(Important Folklore Material No.219). The procedure of the conservation treatment for clothes describe the following below. 1) The washing and dry-cleaning to remove the contaminated substances from cloth was used 0.2% stearyl potassium soap solution and the mixture solution compound of n-Hexane, C6H14. and n-Decane, C10H22. And after the washing and dry-cleaning, the dry of clothes was carried out in a warm condition. These steps were repeated in 2 times over for each cloth. 2) The repair of clothes was attached the similar textiles to stronger fabric linings by needlework.3) The reprodution was made for cloth of King Se-jo to equalize the type, color, quality and skill of materials. 4) After these above procedures, all clothes fumigated to prevent the biodeterioration by using the mixed gas of methyl bromide and ethylene oxide as insecticide and fungicide. 5) Finally for the purpose to keep in a safety long-term condition, the treated clothes sealed with Biaxially Oriented Polyvinylacohol Film(BO-PVA film) and Helium, purity 99.999%, filled up in sealed BO-PVA film bag.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.411-416
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• 2004

In the international temperature scale of 1990 (ITS-90), standard platinum resistance thermometer (SPRT) is a defining standard thermometer used in the temperature range from 13.8033 K to $961^{\circ}C$. Uncertainty of SPRT is about several mK and uncertainty of defining fixed points of the ITS-90 which is used for calibrating SPRT is about several tenth of mK. Above $0^{\circ}C$. the defining fixed points are gallium melting point and indium, tin, zinc, aluminium and silver freezing points which are all realized using an electric furnace or a liquid bath. To realize freezing point of tin ($231.928^{\circ}C$) and zinc ($419.527^{\cir}C$), two 3-zone furnaces which have 3 electric heaters were manufactured. Temperature gradient of the constructed furnaces were tested. Uncertainty caused by temperature gradient of furnace and immersion effect of SPRT in the sealed-type freezing point cells were evaluated 0.038 mK for tin freezing point and 0.036 mK for zinc freezing point.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.710-719
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• 1997

Aucubin, an iridoid glucoside, which is isolated from Aucuba japonica, has some biological effects. This study was to investigate the effect of aucubin on the remainig pulp tissues after pulpotomy. Mongrel dog's coronal pulps were mechanically exposed with a sterile round bur and excised with sterile sharp excarvator. After bleeding was controlled, in control group, $Ca(OH)_2$ powder was applied on the remaining pulps and the cavities were sealed with Z.O.E. cement. In experimental group 1, mixed powder with $Ca(OH)_2$ and aucubin(l : 1 by weight) was applied on the pulpotomized pulp surfaces. After the cavities were covered with sterile aluminum foil, they were sealed with Z.O.E. cement. In experimental group 2, only aucubin powder was applied on the remaining pulps and then they were treated the same as experimental group 1. In the all groups, the pulps were histopathologically observed by light microscope at the time intervals of 1, 2 and 4 weeks after experiment. The results were as follows : 1. In control and experimental groups, mild vascular congestion and bleeding were found in most of the specimens. Less inflammatory infiltration was observed in experimental groups than in control group. 2. Dentin bridge formation was found after 1 week at both control and experimental group 1. Dentin birdge had discontinuous osteodentin like appearance or contained some dentin chips. In experimental group 2, dentin bridge was not seen. 3. The coagulation necrosis layer on the remaining pulp tissues was seen in all groups. In experimental group 2, the thickest layer was observed. And in control group, coagulation necrosis layer was similar as in experimental group 1.

• Restorative Dentistry and Endodontics
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• v.42 no.1
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• pp.27-33
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• 2017

Objectives: To determine the optimal timing for post space preparation of root canals sealed with epoxy resin-based AH Plus sealer in terms of its polymerization and influence on apical leakage. Materials and Methods: The epoxy polymerization of AH Plus (Dentsply DeTrey) as a function of time after mixing (8, 24, and 72 hours, and 1 week) was evaluated using Fourier transform infrared (FTIR) spectroscopy and microhardness measurements. The change in the glass transition temperature ($T_g$) of the material with time was also investigated using differential scanning calorimetry (DSC). Fifty extracted human single-rooted premolars were filled with gutta-percha and AH Plus, and randomly separated into five groups (n = 10) based on post space preparation timing (immediately after root canal obturation and 8, 24, and 72 hours, and 1 week after root canal obturation). The extent of apical leakage (mm) of the five groups was compared using a dye leakage test. Each dataset was statistically analyzed by one-way analysis of variance and Tukey's post hoc test (${\alpha}=0.05$). Results: Continuous epoxy polymerization of the material with time was observed. Although the $T_g$ values of the material gradually increased with time, the specimens presented no clear $T_g$ value at 1 week after mixing. When the post space was prepared 1 week after root canal obturation, the leakage was significantly higher than in the other groups (p < 0.05), among which there was no significant difference in leakage. Conclusions: Poor apical seal was detected when post space preparation was delayed until 1 week after root canal obturation.

• Journal of Radiation Industry
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• v.9 no.2
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• pp.91-102
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• 2015

The iridium disc, generally used in industrial radiography, is examined to find the fracture morphology and fine particles remaining on the shear blank surface. Randomly selected 1,200 discs were observed under a scanning electron microscope tilted more than $45^{\circ}$. Fracture surfaces are classified into three groups: (1) surface fall-out, (2) fracture on the edge and (3) multi-step brittle fracture, which shows the mutual relationship between the fracture morphology and remaining particles. Fracture particles were removed by cleaning the discs in a ultrasonic bath with acetone and collected at the bottom. Removed number of the particles were counted for each different group of fracture surfaces. Followings are conclusions: (1) About 80.5% of discs (966/1,200), have sound plastic shear surfaces with particles remained. (2) About 2% discs accompany surface fall-out's having large particles tens of ${\mu}m$, which is stable not to be pulled out even after the considerably long time of ultrasonic cleaning. (3) About 5% discs contain the fractures on the edge and the particles are removed thoroughly within 30 minutes. (4) 234 discs out of 1,200 discs have multi-step fracture surfaces whose particles never removed in a short period of time but come out very slowly. Such a disc having multiple-step fracture is attributed to the promate cause to the 'leaker'. It is noted here that the discs having mutiple-step fractures should be treated separately with special care, and it is need to study how to treat them.

• Journal of Korean Academy of Oral Health
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• v.41 no.4
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• pp.231-236
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• 2017

Objectives: The objectives of this study were to investigate the changes in bisphenol A (BPA) concentrations in urine from before to after sealant filling and the relationship between BPA and the number of teeth with sealed surfaces. Methods: Thirty-one children aged 6 and 7 years from three elementary schools in Daegu city who did not have any sealant and resin filling were selected as subjects. Urine samples were collected before and after sealant filling until 24 hours, with informed consent from their caregivers. The BPA concentration in all the collected urine samples was analyzed at Seegene Medical. Statistical analysis was performed using the Friedman test, Scheirer-Ray-Hope test, and the repeated-measures generalized linear mixed model of SPSS version 22.0. Results: The BPA concentrations increased from $3.49-{\mu}g/g$ creatinine before to $4.91-{\mu}g/g$ creatinine 2-3 hours later and to $4.15-{\mu}g/g$ creatinine after 24 hours. The more teeth with sealed surfaces, the higher the BPA concentration in children, but the difference was not statistically significant (P>0.05). Conclusions: The BPA concentrations were highest at 2-3 hours after sealant filling and decreased at 24 hours. Exposure to the sealant appears to have a meaningful correlation with the concentration of BPA in the urine of children.