• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2503-2508
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• 2010

ZnO thin films were grown on Si or $SiO_2$/Si substrates, at growth temperatures ranging from 150 to $400^{\circ}C$, by atomic layer deposition (ALD) using diethylzinc and water. Despite the large band gap of 3.3 eV, the ALD ZnO films show high n-type conductivity, i.e. low resistivity in the order of $10^{-3}\;{\Omega}cm$. In order to understand the high conductivity of ALD ZnO films, the films were characterized with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, elastic recoil detection, Rutherford backscattering, Photoluminescence, and Raman spectroscopy. In addition, the various analytical data of the ZnO films were compared with those of ZnO single crystal. According to our analytical data, metallic zinc plays an important role for the high conductivity in ALD ZnO films. Therefore when the metallic zinc was additionally oxidized with ozone by a modified ALD sequence, the resistivity of ZnO films could be adjusted in a range of $3.8{\times}10^{-3}\;{\sim}\;19.0\;{\Omega}cm$ depending on the exposure time of ozone.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.97-108
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• 2016

Thermally sprayed metals or organic coatings is often used in corrosion protection of steel structures. Duplex coating systems of thermally sprayed metal in combination with organic coating are selected as a new generic type of coatings on steel structures under the highly corrosive environments. In this study, three types of corrosion tests were carried out on four types of thermal sprayed specimens with sealing: zinc, zinc-15%aluminum alloy, aluminum and aluminum-5%magnesium alloy, four types of duplex coated specimens; thermally sprayed metals in combination with paint of acrylic urethane, and painted specimens. NORSOK M-501, Wet/dry cyclic seawater tests and outdoor exposure tests of nine types of specimens were conducted. From the corrosion test results, weathering performance of them were presented.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.5
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• pp.257-262
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• 2006

To evaluate the change in protective levels of zinc oxide (ZnO) varistors after the surge absorption, this paper investigated the effects of the number of injection and amplitude of lightning surges on the life of ZnO varistors for low voltages. Leakage currents flowing through ZnO varistors subjected to the $8/20{\mu}s$ impulse currents under 60 Hz AC voltages were measured. The surge simulator system ECAT that can generate $8/20{\mu}s$ impulse currents with a peak short-circuit of 5 $[kA_p]$ was used. The ZnO varistor leakage current increases with exposure to impulse current, and the number of injection of $8/20{\mu}s$ impulse currents to breakdown was inversely proportional to the amplitude of the test current. Behaviors of ZnO varistor leakage currents were strongly dependent on the number of injection and amplitude of $8/20{\mu}s$ impulse currents. ZnO varistors degrade gradually when subjected to impulse current, and the resistive leakage current flowing through ZnO varistors subjected to the $8/20{\mu}s$ impulse currents under 60 Hz AC voltages was significantly increased after a certain number of injection that is dependent on the amplitude of the test impulse current. As a result, the life of ZnO varistors mainly depends on the amplitude and occurrence frequency of lightning surges.

• The Korean Journal of Ecology
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• v.26 no.3
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• pp.91-96
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• 2003

To monitor the heavy metal exposure conditions of Feral Pigeons Columba livia, we collected them at commercial area, industrial area, park area and resident area in Seoul. In feathers, iron concentrations were significantly different among habitats(ANOVA, p<0.05), and were the highest at park area. Manganese concentrations were relatively higher at industrial and park area than other areas(ANOVA, p<0.05). In case of copper levels were the significantly highest at park area(ANOVA, p<0.05). Zinc, lead and cadmium had no difference among habitats. Correlation between livers and feathers concentrations were highly significant to copper(r²=0.983, p<0.01) and cadmium(r²=0.632, p<0.01), but iron, zinc, manganese and lead were not significantly different.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.658-663
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• 2017

Urchin-structured zinc oxide(ZnO) nanorod(NR) gas sensors were successfully demonstrated on a polyimide(PI) substrate, using single wall carbon nanotubes(SWCNTs) as the electrode. The ZnO NRs were grown with ZnO shells arranged at regular intervals to form a network structure with maximized surface area. The high surface area and numerous junctions of the NR network structure was the key to excellent gas sensing performance. Moreover, the SWCNTs formed a junction barrier with the ZnO which further improved sensor characteristics. The fabricated urchin-structured ZnO NR gas sensors exhibited superior performance upon $NO_2$ exposure with a stable response of 110, fast rise and decay times of 38 and 24 sec, respectively. Comparative analyses revealed that the high performance of the sensors was due to a combination of high surface area, numerous active junction points, and the use of the SWCNTs electrode. Furthermore, the urchin-structured ZnO NR gas sensors showed sustainable mechanical stability. Although degradation of the devices progressed during repeated flexibility tests, the sensors were still operational even after 10000 cycles of a bending test with a radius of curvature of 5 mm.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.979-985
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• 2020

A wide range of techniques have been developed to separate X or Y- chromosome-bearing sperm. In particular, bovine semen sex-sorted by using flow cytometry based on differences in the amount of DNA between X and Y chromosome bearing sperm is used in dairy farms. The first piglets were produced using sex-sorted sperm 30 years ago. However, sexed sperm have not been commercially available in pigs because the flow cytometry technique is not capable of sorting the high number of sperm required for porcine artificial insemination (AI), and the prolonged exposure to an electrical filed might damage to the DNA in sperm. The purpose of this study was to evaluate a boar sperm sorting method based on magnetic nanoparticles. A flow cytometer assay verified the efficacy of the magnetic nanoparticles (> 90% of sex-sorted sperm). In addition, a duplex polymerase chain reaction (PCR) assay using sex chromosome specific genes including SRY (sex-determining region Y; male), ZFY (zinc finger protein Y-linked; male), and ZFX (zinc finger protein X-linked; female) showed that in vitro fertilized porcine embryos by X and Y-chromosome bearing sperm were 100% female (40/40) and 72% female (35/48), respectively, at 8-cell or morula stages, suggesting that the sex-sorted sperm were fertile. In conclusion, our findings suggest that the sex-sorted method based on magnetic nanoparticles can be utilized for porcine sex-sorted AI.

• Journal of Preventive Medicine and Public Health
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• v.22 no.1 s.25
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• pp.125-135
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• 1989

This paper was carried out to study on correlation between mentally retardation and lead and zinc. The subjects were 297 mentally retarded children: 132 of Bomyung special school and Sunmyung, which were located in Taegu city of Korea. The former had their parents but the latter had not. The control group 63 children were randomly seleted from the Dong-in primary school near to Medical School of Kyungpook National University. Atomic absorption spectrophotometer, model IL-551 connected with CTF atomizer(IL. 655) was used for the analysis of lead and zinc. The mean value of lead in hair of mentally retarded children was $14.97{\pm}3.71ppm$ which is significantly higher than that of control group, $11.36{\pm}2.83ppm$. But the content of zinc was not significant in both groups. In the lead there was no significant correlation to age but significant negative correlation to IQ. Zinc showed significant correlation to age but not to IQ. Among the handicapped children, no signigicant correlation between orphan group and non orphan group. Handicaps of mentally-retarded children were speech impairment, emotional disturbance, double and triple handicaps, sensory impairment and abnormal dietary patterns. There were significantly higher contents of lead compared with normal group, except the latter two groups. The disease conditions of mentally retarded children were mongolism, autism, cerebral palsy, epilepsy and microcephaly. In comparing with mongolism, significant difference were existent only on the cerebral palsy and group of unknown etiology. We attempted to divide their past history into external etiology and internal etiology, but could not find significant difference. In view of the whole results, the relationship between mentally-retarded children and lead was presumed to be the early time exposure rather than long interval exposure during growth and the contact opportunity was considered important subject in maternal and child health care.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.2
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• pp.141-151
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• 1993

Blood samples obtained from 200 adults who had visited the "S" general hospital were analyzed to compare the zinc protoporphyrin (ZPP) levels quantified by high performance liquid chromatograph (HPLC) and by hematofluorometer (HF) to investigate the methodological difference if any and the relationship between the levels of blood lead and ZPP among no-lead exposed adults. Also investigated were the distribution of ZPP and protoporphyrin IX (PPIX) concentrations, the establishment of normal levels of blood ZPP and blood lead, and the contribution of age and sex factors to these values. These subjects had no previous occupational exposure to lead. The results obtained were as follows : 1. The mean values of blood lead for male and female subjects were $9.46{\pm}2.44{\mu}g/dl$ and $8.09{\pm}2.17{\mu}g/dl$, respectively. The difference observed in the mean concentrations between male and female subjects was statistically very significant. 2. The mean values of blood ZPP by HPLC for male and female subjects were $15.94{\pm}4.55{\mu}g/dl$ and $22.26{\pm}6.61{\mu}g/dl$, respectively. The difference observed in the mean concentrations between male and female subjects was statistically not significant. The mean values of blood PPIX by HPLC for male and female subjects were $2.51{\pm}1.78{\mu}g/dl$ and $2.81{\pm}1.56{\mu}g/dl$, respectively. The difference observed in the mean concentrations between male and female subjects was statistically not significant. 3. The mean values of blood ZPP by HF for male and female subjects were $28.44{\pm}7.11{\mu}g/dl$ and $37.77{\pm}8.04{\mu}g/dl$, respectively. The difference observed in the mean concentrations between male and female subjects was statistically very significant. 4. No statistically significant correlation was found between the levels of blood ZPP and blood lead. 5. The ratio of ZPP and protoporphyrin IX (PPIX) concentration to erythrocyte protoporphyrin (EP, EP=ZPP+PPIX) concentration was 87.4% and 12.6%, respectively. 6. A statistically very significant correlation was found between the ZPP concentrations determined by HPLC and the values by HF (r=0.7565). The ZPP concentraitons quantified by HF were 1.75 times as high as the values obtained by HPLC. 7. The blood ZPP concentrations quantified by HPLC, HF, and spectrofluorometer (SF) from the blood samples obtained from 14 lead-exposed workers and from 16 no-lead exposed adults showed wide variations. The ZPP concentrations by HF were the highest followed by the levels obtained by SF and by HPLC. In the exposed group, no statistically significant difference was found among three methods of quantifying blood ZPP levels. In the no-lead exposed group, however, statistically significant difference was observed among these methods. The ZPP concentrations by HF were about twice as high as those of by HPLC or by SF. Among three methods of quantifying blood ZPP (HPLC, SF and HF), the results revealed significant difference. Therefore it is suggested that objective methods of quantifying blood ZPP and a system of correcting different ZPP levels be developed by the ministry of Labor.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.296-301
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• 2009

An inductively coupled plasma assisted atomic layer deposition(ICP-ALD) system has been constructed for the deposition of ZnO thin films, and various experiments of ZnO thin films on p-type Si(100) substrates have been carried out to find the self-limiting reaction conditions for the ICP-ALD system under non-plasma circumstances. Diethyl zinc[$Zn(C_2H_5)_2$, DEZn] was used as the zinc precursor, $H_2O$ as the oxidant, and Ar as the carrier and purge gas. At the substrate temperature of $150^{\circ}C$, atomic layer deposition conditions based on self-limiting surface reaction were successfully obtained by series of experiments through the variation of exposure times for DEZn, $H_2O$, and Ar. ZnO deposition was repeated at different substrate temperatures of $90{\sim}210^{\circ}C$. As a result, the thermal process window(ALD window) for ZnO thin films was observed to be $110{\sim}190^{\circ}C$ and the average growth rate was measured to be constant of 0.29 nm/cycle. Properties of the film's microstructure and composition(Zn, O, etc.) were also studied. As the substrate temperature increases, the crystallinity was improved and ZnO(002) peak became dominant. The films deposited at all temperatures were high purity, and the films deposited at high temperatures had the composition ratio between Zn and O closer to one of a stable hexagonal wurtzite structure.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.147-154
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• 2020

In this study, four types of composite added filtration (aluminum, nickel, copper, and zinc) were combined for each thickness to evaluate dose reduction and optimal images due to X-ray attenuation. To evaluate dose and image quality. X-ray generators, Dose Area Product(DAP) and ICY programs with RQR9 standard quality were used. In the image quality evaluation element (PSNR, RMSE, SSIM), only images with PSNR value of 30 dB or more were analyzed. As a result, the best combination in dose evaluation was 3 mmAl + 0.6 mmNi (0.16µGy㎡), and the best filter in image quality evaluation was 0.9 mmAl (PSNR 34.24dB, RMSE 79.52, SSIM 0.24). In this study, the dose aspect and the image quality aspect are mentioned, So it is considered that further studies on patient's exposure dose and optimal image will be needed in the future.