• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.8 no.2
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• pp.196-208
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• 1998

To improve the quality of environmental measurements and evaluation of the workplace air in the pigment manufacturing industries, we analyzed metal(chromium, cadmium, lead, iron, cobalt, manganese, antimony, titanium, arsenic, and selenium) concentrations by ICP-AES in sixty seven samples of inorganic bulk pigments which are produced and/or used in Korea. We also collected MSDS which has to be supplied by manufacturer and/or supplier and posted in the workplace according to the Hazard Communication Standards, and compared the number of metals listed in each MSDS with the number of metals determined by ICP-AES. Results were as followed; 1. Among seventeen yellowish-colored samples, chromium(2~19%) and lead(0.1~61%) were the two major metals. In thirteen reddish-colored samples, iron was the major component with 37~81%. Cobalt and manganese were detected in blue-colored samples with less than 1%, while antimony and titanium were the major two metals in white-colored pigments with 178~300 ppm and with 36~65%, respectively. 2. In area samples collected in workplace air(one pigments producing factory and five retailer stores), iron and manganese were detected but the concentrations not exceeded the TLVs(1 and $5mg/m^3$, respectively). In three of fifteen samples, the concentrations of lead exceeded the TLV ($0.05mg/m^3$). 3. Two out of seven companies provided MSDS, and the average provision rate was 22.4%. And the coincidence rate of the number of metals referenced in MSDS and determined by ICP-AES mostly accorded, but in one sample, different metal was detected from MSDS. In summary, metals have to be concerned in evaluation of the workplace air dealing with compounds of inorganic pigments dust are cobalt, chromium, iron, manganese, lead and antimony, and these are simultaneously determined by ICP-AES. Taking this opportunity, it is needed to reinforce that the personnel is to be concerned about prevention of workers' ill health regarding to provision of MSDS.

• Journal of Veterinary Clinics
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• v.32 no.6
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• pp.504-507
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• 2015

Coxiella burnetii is an obligate intracellular rickettsial organism and the causative agent of Query fever, a zoonosis that occurs worldwide. In Korea, C. burnetii infection had occurred in humans and animals. However, the studies were only conducted in geographically limited area for detection of C. burnetii. The objective of this study was to detect C. burnetii in Korean native cattle and dairy cattle nationwide by real-time PCR. The total of 807 blood samples from 622 Korean native cattle and 185 dairy cows, 170 individual milk samples of dairy cows, and 348 bulk tank milk samples of dairy herds were collected nationwide. From blood samples, C. burnetii was detected in 17 (2.7%) out of 622 Korean native cattle and 2 (1.1%) of 185 dairy cows. From milk samples, C. burnetii was detected in 27 (15.9%) out of 170 individual milk samples of dairy cows. And C. burnetii was detected in 84 (24.1%) of 348 bulk tank milk samples. In conclusion, this study revealed that the detection rates are considerably high in cattle and the infection of C. burnetii has been continuously occurring in cattle of Korea. In order to prevent the hazards of a zoonosis Q-fever that occur both humans and domestic animals, further studies are needed to clarify the epidemiology of Q-fever of domestic animals and humans in Korea.

• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.609-615
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• 1999

From July of 1997 to June of 1998, total 279 raw milk samples over withdrawal period after mastitis treatment from dairy farms located in the provinces of Kyonggi and Choongchung were collected to test drug residues. Each sample was tested by TTC- II test and Delvotest SP. Among the total 152 raw milk samples of cow treated by ${\beta}$-lactams, 32 samples(21.2%) were positive on the Delvotest and 15 samples(9.9%) showed positive on the TTC-II test. Also, from the total 37 samples treated by sulfonamides, 5 samples(13.5%) were positive on the Delvotest and 3 samples(8.1%) showed positive on the TTC-II test. For the total 55 raw milk samples of cow treated by tetracyclines, 9 samples(16.4%) were positive on the Delvotest and 5 samples(9.1%) showed positive on the TTC-II test. In addition, from the total 35 samples treated by aminoglycosides, 7 samples(20.0%) were positive on the Delvotest and 5 samples(14.3%) showed positive on the TTC-II test. Our study shows that it is possible that drugs are to be detected by the drug residues test of an individual raw milk even over the withdrawal period after mastitis treatment and the raw milk of bulk tank.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1220-1228
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• 2003

The mirage technique is proved to be powerful in measuring the thermal diffusivity of materials. In particular, its contactless nature makes it suitable for delicate samples and microscale structures. In this study, thermal-wave-coupling method is developed in a general form for both thermally thin and thick samples. In the suggested measuring scheme, the probe beam can be positioned close to the pump beam and the absolute position need not be measured. Therefore the new scheme provides a relatively simple yet effective way to determine the thermal diffusivity of thermally thick samples. Thermal diffusivities of bulk samples like Ni and Al were measured and the characteristics of mirage signal for a thin film were observed by using the mirage experimental setup. The apparent thermal diffusivity was measured by varying such parameters as probe beam height, size of pump beam, power of pump beam, and surface condition of sample. From the practical standpoint, it is shown that the size of the pump beam is the most important factor for accurate thermaldiffusivity measurement. Experiments using thin-film samples show that the thermal diffusivity of a substrate covered with thin film can be measured by photothermal mirage signals.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.249-259
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• 2009

The objective of this research was to find out the physical properties, such as dispersion and coagulation, of soil minerals depending on the types and concentrations of the cations in aqueous solution. Hwangto samples were obtained from 90 to 130 cm from surface at Jangdong-ri, Donggang-Myon, Naju, Chonnam Province. The clay fraction (< $2\;{\mu}m$) was separated by sedimentation method from the bulk soils. Both Hwangto and clay fractions, and the same samples after removal of amorphous and crystalline iron oxides were used in this experiment. The effect of 4 cations ($Na^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$) and their concentrations on settling speed and basal spacing of the minerals were observed to examine the physical properties of the soil and clay minerals. Hwangto mainly consisted of quartz, and the clay fractions consisted of kaolinite, illite, and vermiculite. The bulk soils contained 16.3 mg/kg of amorphous iron oxides and 436 mg/kg of crystalline iron oxides. Clay fractions were dispersed better than bulk soils due to their smaller particle size than that of the bulk samples in the aqueous solution. The bulk and clay samples were dispersed better when iron oxides were removed because of coating of minerals by the iron oxides. Clay minerals were settled faster as the charge and the concentration of cations added increased. The d-spacing of kaolinite and illite did not change when 4 types of cations were added. The d-spacing of vermiculite showed $14.04\;{\AA}$ when divalent cations were added while that of vermiculite showed $13.9\;{\AA}$ when monovalent cations were added. It may be attributed to the hydration radii of cations. This study indicated that both coating of iron oxides on minerals and types and concentrations of cations affect dispersion of minerals in solution and d-spacing of expanding clay minerals such as vermiculite.

• Restorative Dentistry and Endodontics
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• v.44 no.4
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• pp.37.1-37.10
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• 2019

Objectives: This study evaluated the bond strength of various fiberglass post cementation techniques using different resin-based composites. Materials and Methods: The roots from a total of 100 bovine incisors were randomly assigned to 5 treatment groups: G1, post + Scotchbond Multi-Purpose (SBMP) + RelyX ARC luting agent; G2, relined post (Filtek Z250) + SBMP + RelyX ARC; G3, individualized post (Filtek Z250) + SBMP; G4, individualized post (Filtek Bulk-Fill) + SBMP; G5, individualized post (Filtek Bulk-Fill Flow) + SBMP. The samples were subjected to the push-out (n = 10) and pull-out (n = 10) bond strength tests. Data from the push-out bond strength test were analyzed using 2-way analysis of variance (ANOVA) with the Bonferroni post hoc test, and data from the pull-out bond strength test were analyzed using 1-way ANOVA. Results: The data for push-out bond strength presented higher values for G2 and G5, mainly in the cervical and middle thirds, and the data from the apical third showed a lower mean push-out bond strength in all groups. No significant difference was noted for pull-out bond strength among all groups. The most frequent failure modes observed were adhesive failure between dentine and resin and mixed failure. Conclusions: Fiberglass post cementation using restorative and flowable bulk-fill composites with the individualization technique may be a promising alternative to existing methods of post cementation.

• Journal of Korea Water Resources Association
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• v.31 no.2
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• pp.123-132
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• 1998

Monitoring solute transport has been known to be difficult especially for the unsaturated soil. The object of this study is to investigate the TDR application to monitoring solute concentration in the vadose zone. The TDR calibration test was conducted for soil samples with various water contents and concentrations. The voltage attenuation of electromagnetic wave of TDR was used to estimate the bulk electrical conductivity of a soil. The relationship between the bulk soil electrical conductivity and the solute concentration was assumed to be linear at a constant volumetric soil water content. In this study four proposed relationships were compared using data obtained from KCI solution at three different concentrations. Relationships given by Topp, Daltaon, Yanuka showed the linearity between the bulk soil electrical conductivity and the solute concentration, which were more pronounced than Zegelin's. The three relationships were found to be useful to measure the solute concentration in the vadose zone. In addition, TDR method was proven to be a viable technique in monitoring solute transport through unsaturated soils in transient flow condition.

• Journal of Surface Science and Engineering
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• v.42 no.2
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• pp.95-101
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• 2009

This study is the research on the thermal emissivity depending on the bulk graphite's alignment degree. Bulk graphites were manufactured by uni-axial pressing and subsequent heat treatment of natural graphite flakes with organic binder. The samples were prepared to be $0^{\circ}$ (relative to the 002 c-face), $45^{\circ}$, and $90^{\circ}$ (relative to the 100 a-face) for measuring alignment degree. The alignment degree of the sample was measured by XRD. The thermal emissivity was measured by infrared thermal image camera at $100^{\circ}C$ and compared with the value obtained by Infrared spectroscopy. The alignment degree and thermal emissivity of $0^{\circ}$ sample were measured to be 0 and 0.70 respectively. And those of $90^{\circ}$ sample were 0.73 and 0.80 respectively. The emissivity value was correlated with obtained by IR spectroscopy. Therefore it was considered that the thermal emissivity of the bulk graphite is correlated with the alignment degree.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.93-93
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• 2003

Photoluminescence(PL) properties of Silicon nanocrystals (nc-Si) as a function of temperature is reported to consider the mechanism of PL. Nc-Si has been made by $Si^+$ ion-implantation into thermal $SiO_2$ and subsequent annealing. And after gold had been diffused at the same samples above, the resultant PL spectra has been compared to the PL spectra from the non-gold doped nc-Si. PL peak energy variation from nc-Si is same with the variation of energy bandgap of bulk silicon as temperature changes from 6 K to room temperature. This result may mean nc-Si is still indirect transition material like bulk silicon. Gold doped nc-Si reveals short peak wavelength of PL spectrum than gold undoped one. PL peak shift through gold doing process shows clearly the PL mechanism is not from defect or interface states. PL intensity increases from 6K to a certain temperature and then decrease to room temperature. This characteristic with temperature shows that phonon have a role for the luminescence as theory explains that electron and hole can be recombined radiatively by phonon's assist in nc-Si, which is almost impossible in bulk silicon. Therefore luminescence is observed in nc-Si constructed less than a few of unit cell and the peak energy of luminescence can be higher than the bulk bandgap energy by the bandgap widening effect occurs in nanostructure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.407-411
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• 2022

Bulk-sized PbTiO₃ (PT), which is widely known as a high-performance ferroelectric oxide but cannot be fabricated into a monolithic ceramic due to its high c/a ratio, was successfully prepared with a high tetragonality by partially substituting Ni ions for Pb ions using a solid-state reaction method. We found that Ni-doped PT was well-fabricated as a bulk monolith with a significant c/a ratio of ~1.06. X-ray diffraction on as-sintered and crushed samples revealed that NiTiO₃ secondary phase was present at the doping level of more than 2 at.%. Scanning electron microscopic study showed that NiTiO₃ secondary phase grew on the surface of PT specimens regardless of the doping level possibly due to the evaporation of Pb during sintering. We demonstrated that an unconventional introduction of Ni ions into A-site plays a key role on the fabrication of bulk PT, though how Ni ion functions should be studied further. We expect that this study contributes to a further development of displacive ferroelectric oxides with a high c/a ratio.