• Journal of Environmental Health Sciences
• /
• v.44 no.4
• /
• pp.340-347
• /
• 2018

Objectives: This study was performed to determine environmental hazard factors and provide more eco-friendly child activity spaces within children's playgrounds installed in Gyeonggi-do Province. Methods: Basic (XRF) and precise (ICP, UV) inspections were conducted. The test items examined were heavy metals and parasite eggs. As a sampling point, painted finish materials (180), synthetic rubber (50), and sand (50) were selected. Results: The total excess rate of heavy metals in the XRF was found to be 7.4% (17/230 points). In a comparison between the basic and precise inspections with 17 excess points, the concentration deviation between the two tests was found to be from 0.01 to 7.7 times, resulting in a large difference. Furthermore, all the excess samples were dual samples. However, the contribution rates of Pb and $Cr^{6+}$ to combined concentration were found to be 85.1 and 14.9% for basic inspection and 91.9 and 8.1% for precise inspections, so there is a similar tendency between the two tests. The excess rate of parasite eggs in sand was expressed at 6%. The excess rate of heavy metals in synthetic rubber was found to be 0%. Conclusion: The reliability of the XRF is low. However, considering the contribution rate of Pb and $Cr^{6+}$ between the two tests, it is likely to be applicable for screening. Dual samples provided high concentrations and excess samples and care should be taken when managing them.

• The Journal of Advanced Prosthodontics
• /
• v.7 no.1
• /
• pp.56-61
• /
• 2015

PURPOSE. The purpose of this study was to evaluate the effects of the surface treatment and shape of the dental alloy on the composition of the prosthetic work and its metallic ion release in a corrosive medium after casting. MATERIALS AND METHODS. Orion Argos (Pd-Ag) and Orion Vesta (Pd-Cu) were used to cast two crowns and two disks. One of each was polished while the other was not. Two as-received alloys were also studied making a total of 5 specimens per alloy type. The specimens were submersed for 7 days in a lactic acid/sodium chloride solution (ISO standard 10271) and evaluated for surface structure characterization using SEM/EDAX. The solutions were quantitatively analysed for the presence of metal ions using ICP-MS and the results were statistically analysed with one-way ANOVA and a Tukey post-hoc test. RESULTS. Palladium is released from all specimens studied (range $0.06-7.08{\mu}g{\cdot}cm^{-2}{\cdot}week^{-1}$), with the Pd-Cu alloy releasing the highest amounts. For both types of alloys, ion release of both disk and crown pairs were statistically different from the as-received alloy except for the Pd-Ag polished crown (P>.05). For both alloy type, disk-shaped pairs and unpolished specimens released the highest amounts of Pd ions (range $0.34-7.08{\mu}g{\cdot}cm^{-2}{\cdot}week^{-1}$). Interestingly, in solutions submerged with cast alloys trace amounts of unexpected elements were measured. CONCLUSION. Shape and surface treatment influence ion release from dental alloys; polishing is a determinant factor. The release rate of cast and polished Pd alloys is between $0.06-0.69{\mu}g{\cdot}cm^{-2}{\cdot}week^{-1}$, which is close to or exceeding the EU Nickel Directive 94/27/EC compensated for the molecular mass of Pd ($0.4{\mu}g{\cdot}cm^{-2}{\cdot}week^{-1}$). The composition of the alloy does not represent the element release, therefore we recommend manufacturers to report element release after ISO standard corrosion tests beside the original composition.

• The Journal of Korean Academy of Prosthodontics
• /
• v.32 no.2
• /
• pp.281-295
• /
• 1994

It is very important for the ideal restorations of anterior openbite patients to record the mandibular movement and to harmonize mandibular movement with other organs in stomatognathic systems. This study was designed to compare the mandibular movement of anterior openbite patients with that of normal bite(Angle Class I) patients, to ascertain which components of mandibular movement have differences between two groups, and to use for occlusal treatment of mandibular movement. Saphon Visi-trainer Model 3(Tokyo Shizaisha Co. Japan) and Denar Pantronic(Denar Corp.,U.S.A.) were used to record mandibular movement. Pantronic survey was peformed by using an arbitrary hinge axis according to manufacturer's direction. Twenty-eight adult who have physiologically normal occlusion(Angle Class I) and are free of TM dysfunction were selected as a control group(Group 1). Fifteen adult who are anterior openbite patient and have not anterior guidance function and have posterior interference at protrusion were selected as a experimental group(Group 2). The results are as follows : 1. There was no statistically significant difference between the average immediate and progressive side shift of anterior openbite patients(0.54mm, $7.57^{\circ}$) and those of normal group(0.49mm, $5.96^{\circ}$). 2. The average protrusive and orbiting condylar inclination of anterior openbite patient$(30.87^{\circ},\;32.27^{\circ})$ were significantly lower than those of normal group$(36.11^{\circ},\;39.04^{\circ})$ (P<0.05). 3. In the results of Visi-trainer recordings, the mean for the maximum protrusion, the maximum laterotrusion, the angle of laterotrusion and the angle of protrusion in the horizontal trajectory between group 1 and 2 did not differ significantly. 4. The mean for the angle of protrusion, the maximum opening in the frontal trajectory, the ICP-RCP(A-P) distance and the angle of protrusion in the sagittal trajectory differ significantly(P<0.05). 5. The significant correlation was found between orbiting condylar inclination and protrusive condylar inclination.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.45 no.1
• /
• pp.137-142
• /
• 2016

We investigated the anti-proliferative effects of solar salt and purified salt (PS) on HepG2 human hepatocellular cancer cells as well as their effects on mRNA and protein expression of apoptosis- and cell cycle-related genes, including Bcl-2, Bax, p53, and p21. Each salt sample suppressed cancer cell proliferation when treated at a concentration of 0.5% or 1%. Especially solar salt from T salt field (SS-T) and solar salt from Y salt field (SS-Y) significantly suppressed proliferation of cancer cells in comparison with PS. Treatment of HepG2 cells with salt samples at a concentration of 1% suppressed expression of Bcl-2 and promoted expression of Bax, p53, and p21 at the mRNA and protein levels in comparison with the control group. Inductively coupled plasma optical emission spectrometry (ICP-OES) showed that SS-T and SS-Y had higher concentrations of Ca, Mg, S, and K than PS, and SS-T contained higher concentrations of these minerals than SS-Y. It seems that Na and mineral contents in solar salt may contribute to regulation of the genes. Taken together, salt, especially mineral rich solar salt, inhibits cancer cell growth by regulating apoptosis and cell cycle-related genes.

• Journal of The Korean Association For Science Education
• /
• v.18 no.1
• /
• pp.71-82
• /
• 1998

The main purpose of Iowa Chautauqua Program(ICP) and Iowa-Scope, Sequence. and Coordination (Iowa-SS&C) was to educate K-12 science teachers so that they could teach science in a human context using the constructivist strategies. The major task for the participating teachers to perform was to develop modules with the emphasis on STS and constructivist approach. which were supposed to be taught in the respective classrooms. Teachers worked together for two weeks for the development of modules during the summer, and attempted the modules with their students. The participating teachers met regularly during the autumn semester to share and reflect their experiences and obtain additional information on science education reform and its implications. During the winter break. the teachers improved and extended the STS modules. The Iowa Chautauqua Program and Iowa-SS&C had two important implications for Korean science education. First, they made the most of the resources they had in order to provide the practicing teachers with recent research findings on the nature of science. science learning and teaching, that is. the constructivist approach. Second, they emphasized both cooperation of teachers and long-term training to realize the reform in school science education.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.11
• /
• pp.18-24
• /
• 2000

(Ba,Sr)$TiO_3$ thin films have attracted great interest as new dielectric materials of capacitors for ultra-large-scale integrated dynamic random access memories (ULSI-DRAMs) such as 1 Gbit or 4 Gbit. In this study, inductively coupled $BCl_3/Cl_2/Ar$ plasmas was used to etch (Ba,Sr)$TiO_3$ thin films. RF power/dc bias voltage=600 W/-250 V and chamber pressure was 10 mTorr. The $Cl_2/(Cl_2+Ar)$ was fixed at 0.2 the (Ba,Sr)$TiO_3$ thin films were etched adding $BCl_3$. The highest (Ba,Sr)$TiO_3$ etch rate is $480{\AA}/min$ at 10 % $BCl_3$ to $Cl_2/Ar$. The change of Cl, B radical density measured by optical emission spectroscopy(OES) as a function of $BCl_3$ percentage in $Cl_2/Ar$. The highest Cl radical density was shown at the addition of 10% $BCl_3$ to $Cl_2/Ar$. To study on the surface reaction of (Ba, Sr)$TiO_3$ thin films was investigated by XPS analysis. Ion bombardment etching is necessary to break Ba-O bond and to remove $BaCl_2$. There is a little chemical reaction between Sr and Cl, but Sr is removed by physical sputtering. There is a chemical reaction between Ti and Cl, and $TiCl_4$ is removed with ease. The cross-sectional of (Ba,Sr)$TiO_3$ thin film was investigated by scanning electron microscopy (SEM), the etch slope is about 65~70$^{\circ}$.

• Journal of the Korean Chemical Society
• /
• v.45 no.4
• /
• pp.304-311
• /
• 2001

A study has been carried out on the extraction chromatographic separation of fission products from spent pressurized water reactor (PWR) fuels for inductively coupled plasma atomic emission spectrometric analysis. Impregnation capacity of tri-n-butyl phosphate (TBP), which is well known as an extractant in the field of uranium separation from various nuclear grade materials, on Amberlite XAD polymeric macroporous support materials was measured. Amberlite XAD-16 of which the surface area is the highest was selected as a support material because its TBP impregnation capacity was the largest in Amberlite XADs. Sorption behaviour of this TBP impregnated resin was investigated for the fission product elements using acidic solutions simulated for dissolver solutions of spent PWR fuels. The parameters affecting the performance of the separation system were optimized. The fission product elements studied excluding Pd and Ru were quantitatively recovered with the precision of less than 3.1%.

• Tribology and Lubricants
• /
• v.30 no.5
• /
• pp.278-283
• /
• 2014

Carbon nanotubes (CNTs) are used in various composite materials to enhance electrical, thermal and mechanical properties of composite materials. In this study, we investigate the wear characteristics of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends containing multi-walled carbon nanotubes (MWCNTs). PC/ABS blends are commonly used in many industrial applications such as cellular phones and display cases and MWCNTs have been added to the PC/ABS blends to improve their electromagnetic interference shielding (EMS). We performed wear tests on PC/ABS blends containing MWCNTs under reciprocating linear sliding conditions with chrome steel balls as a counterpart material. The normal loads were 10, 30, 50, 70, 100 N, the sliding speed was 10 mm/s, the stroke length was 15 mm, and the tests lasted 900 s. The MWCNTs included in the PC/ABS blends lower the wear volume and friction coefficient of the composites. We analyzed the wear debris collected from the composites during the tests in terms of the MWCNT concentration using inductively coupled plasma optical emission spectroscopy. The results show that the quantity of MWCNTs in the debris is proportional to the concentration of MWCNTs in the composite, indicating that the exposure of the MWCNTs to environments by wear could be increased with their concentration in the composite.

• Journal of Korean Society on Water Environment
• /
• v.33 no.4
• /
• pp.416-423
• /
• 2017

The subject samples include 150 and 170 samples collected from intake holes in the former and latter half of 2015, respectively. They were analyzed with ICP-MS. The average concentration of detected barium was $10.54{\mu}g/L$ ($0.23{\sim}168.22{\mu}g/L$) and $8.21{\mu}g/L$ ($0{\sim}255.65{\mu}g/L$) for the former and latter halves of 2015, respectively. The concentration distribution was the highest for the precambrian era at $19.07{\mu}g/L$ and the lowest Cenozoic era at $4.92{\mu}g/L$. The average value for sedimentary, metamorphic, and igneous rocks was $7.84{\mu}g/L$, $20.84{\mu}g/L$, and $9.47{\mu}g/L$, respectively, which indicates that it was the highest for metamorphic rocks. The study also analyzed correlations between barium and other minerals and found that magnesium recorded 0.44 and 0.71 for the former and latter half of 2015, respectively. As for barium concentration according to depth, it was relatively low in shallow groundwater (under 200 m) with its average concentration at $14.33{\mu}g/L$ and $14.71{\mu}g/L$ for the former and latter half of 2015, respectively. It was $8.53{\mu}g/L$ and $4.04{\mu}g/L$ in deep groundwater (over 200 m) for the two periods, respectively, The risk assessment results show that its average risk was HQ 0.00139 and HQ 0.00163 for the former and latter half of 2015, respectively, being considerably lower than "1", which suggests that barium poses few possibilities of consumption risk.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.3
• /
• pp.67-71
• /
• 2014

An attempt to grow high quality GaN on silicon substrate using metal organic chemical vapor deposition (MOCVD), herein GaN epitaxial layers were grown on various Si(111) substrates. Thin Platinum layer was deposited on Si(111) substrate using sputtering, followed by thermal annealing to form Pt nano-clusters which act as masking layer during dry-etched with inductively coupled plasma-reactive ion etching to generate nano-patterned Si(111) substrate. In addition, micro-patterned Si(111) substrate with circle shape was also fabricated by using conventional photo-lithography technique. GaN epitaxial layers were subsequently grown on micro-, nano-patterned and conventional Si (111) substrate under identical growth conditions for comparison. The GaN layer grown on nano-patterned Si (111) substrate shows the lowest crack density with mirror-like surface morphology. The FWHM values of XRD rocking curve measured from symmetry (002) and asymmetry (102) planes are 576 arcsec and 828 arcsec, respectively. To corroborate an enhancement of the growth quality, the FWHM value achieved from the photoluminescence spectra also shows the lowest value (46.5 meV) as compare to other grown samples.