• 한국세라믹학회지
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• 제39권2호
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• pp.184-189
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• 2002

본 연구는, PbO-base 유리계의 정보와의 비교 등을 통해 Bi-base 조성 PDP rib으로의 새로운 유리조성 설계를 위한 기초연구의 일환이다. PbO와 유사한 밀도값 및 작업 용이성을 갖고 있는 Bi를 도입한 $Bi_2O_3-B_2O_3-ZnO$ 조성계에 대해, 연화점, 열팽창계수, 에칭성, 유전율 등의 특성측정 및 XPS로 조성에 따른 구조변화 등을 조사하였다. $Bi_2O_3$를 50∼80 wt%까지 폭넓게 첨가된 $Bi_2O_3-B_2O_3-ZnO$계 유리들은 조성에 따라 연화점이 400∼480$^{\circ}C$, 열팽창계수가 $68{\sim}72{\times}10^{-7}/^{\circ}C$, 유전상수는 13∼25으로서 동조성의 Pb-base 조성계와 유사한 물성치를 나타내었다. 특히, Bi의 함유량이 70∼65 wt%의 조성의 경우, 성분 및 물성의 미세조정 등을 통해 rib 재료의 출발조성으로서 적용가능성이 확인되었다. $Bi_2O_3$의 양이 감소함에 따라 $O_{1s}$ peak에서의 결합에너지의 증가와 반가폭(FWHM)이 감소하였는데, 이는 비가교산소의 증가에 기인하였다.

• Journal of Korean Society for Atmospheric Environment
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• 제16권E호
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• pp.39-46
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• 2000

Volatile Organic Compounds (VOCs) are considered as the precursors of atmospheric ozone and photochemical smog formation. In particular, chemical plants have produced a lot of VOCs and thus they have been forced to reduce or remove air emissions from the on-site chemical facilities. For the effective removal of VOCs produced in the chemical plants, the authors employed a titanium oxide(TiO$_2$) mediated photo-catalytic oxidation method. The initiation methods employed in this study to produce oxygen radicals for th photo-catalytic oxidation of the VOCs were Ultra-Violet(UV), Non-Thermal Plasma(NTS), and a combination of Uv and NTP. This study focused on a comparison of the removal efficiencies of VOCs as a function of the initiation method such as NTP and/or UV techniques. Removal efficiency change of VOCs as was investigated as a function of the wavelength of the UV lamp(254, 302, and 365 nm) and the degree of TiO$_2$ coating (10 and 30%). In this study, it was identified that removal efficiencies if the VOCs under the normal air environment were much better than those under the nitrogen gas environment containing small amount of oxygen. Removal efficiency by NTP technique was much better than the UV or the combination of UV and NTP techniques. In a comparison if UV wavelengths employed, it was found that shorter wavelength showed better removal efficiency, compared with longer ones. When the removal efficiencies of VOCs were compared in terms of the degree of TiO$_2$ coating, the higher TiO$_2$coating showed better removal efficiency that the lower TiO$_2$ coating

• 한국항공우주학회지
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• 제43권12호
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• pp.1048-1053
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• 2015

고온 환경에 노출되는 열 보호 시스템의 삭마 현상에 의한 표면 침식은 주로 재료의 두께 방향으로 진행된다. 본 논문에서는 0.4MW 아크 가열 풍동을 통한 삭마 실험을 수행하고 삼차원 표면 측정기를 이용하여 삭마 재료의 표면 상태를 측정하였다. 특히, 정밀한 삼차원 이미지 데이터를 획득하여 고온 플라즈마 환경에서 진행된 삭마 재료의 표면 거칠기와 침식량을 산출하였다. 이와 같은 삭마 실험 전후에 발생된 시편의 질량 감소도 함께 측정함으로써 표면 특성의 변화를 정량적으로 비교 및 분석하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.622-622
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• 2013

Piezoelectric energy harvesting (PEH) device refers to a power device for acquiring mechanical energy from the environment surrounding us which would otherwise be wasted and for converting it into usable electrical energy. While much work has been done on developing ZnO nanogenerator (NG) with nanowire arrays, there are some issues of not only scaling up its output power but also optimizing structure for operating feasibly in various conditions. Efficiency of NG is highly dependent on fixed orientation. But in many cases, it is not easy to predict where the pressure and vibration may come from. Furthermore, the direction of the applied mechanical stress is usually non-stationary and can be random in various practical applications. Therefore an omnidirectional PEH is needed.In this work, we investigate an omnidirectional PEH device consisting ZnO nanowires. We deposited spiral patterned ZnO seed layer on Kapton film. We deposited thin Cr layer on the ZnO seed layer using DC-sputter to form a passivation layer to retard un-expected growth of ZnO nanowires. We grew ZnO nanowires along the spiral arms using hydrothermal method. ZnO nanowires have been selectively grown from the ZnO sidewall without Cr layer and have the average length of$5{\mu}m$ and the average diameter of 40nm. We reduced the defect in the as-grown ZnO nanowires by O2 plasma using asher and by thermal treatment using RTA. Consequently, each nanowire has different directions to each other. This isotropic design can lead to the omnidirectional power generation. The morphology of NG is characterized with FESEM. Maximum output power of the device is measured by using a picoammeter and a nanovoltmeter.

• Journal of Microbiology and Biotechnology
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• 제30권5호
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• pp.662-667
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• 2020

Epidermal growth factor receptor (EGFR) mutations are not only genetic markers for diagnosis but also biomarkers of clinical-response against tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC). Among the EGFR mutations, the in-frame deletion mutation in EGFR exon 19 kinase domain (EGFR exon 19-del) is the most frequent mutation, accounting for about 45% of EGFR mutations in NSCLCs. Development of sensitive method for detecting the EGFR mutation is highly required to make a better screening for drug-response in the treatment of NSCLC patients. Here, we developed a fluorometric tandem gene amplification assay for sensitive detection of low-abundance EGFR exon 19-del mutant genomic DNA. The method consists of pre-amplification with PCR, thermal cycling of ligation by Taq ligase, and subsequent rolling circle amplification (RCA). PCR-amplified DNA from genomic DNA samples was used as splint DNA to conjugate both ends of linear padlock DNA, generating circular padlock DNA template for RCA. Long stretches of ssDNA harboring multiple copies of G-quadruplex structure was generated in RCA and detected by thioflavin T (ThT) fluorescence, which is specifically intercalated into the G-quadruplex, emitting strong fluorescence. Sensitivity of tandem gene amplification assay for detection of the EGFR exon 19-del from gDNA was as low as 3.6 pg, and mutant gDNA present in the pooled normal plasma was readily detected as low as 1% fraction. Hence, fluorometric detection of low-abundance EGFR exon 19 deletion mutation using tandem gene amplification may be applicable to clinical diagnosis of NSCLC patients with appropriate TKI treatment.

• 한국재료학회지
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• 제30권7호
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• pp.350-358
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• 2020

A variety of composite powders having different aluminum and carbon contents are prepared using various organic solvents having different amounts of carbon atoms in unit volume as ball milling agents for titanium and aluminum ball milling. The effects of substrate temperature and post-heat treatment on the texture and hardness of the coating are investigated by spraying with this reduced pressure plasma spray. The aluminum part of the composite powder evaporates during spraying, so that the film aluminum content is 30.9 mass%~37.4 mass% and the carbon content is 0.64 mass%~1.69 mass%. The main constituent phase of the coating formed on the water-cooled substrate is a non-planar α₂ phase, obtained by supersaturated carbon regardless of the alloy composition. When these films are heat-treated at 1123 K, the main constituent phase becomes γ phase, and fine Ti₂AlC precipitates to increase the film hardness. However, when heat treatment is performed at a higher temperature, the hardness is lowered. The main constitutional phase of the coating formed on the preheated substrate is an equilibrium gamma phase, and fine Ti₂AlC precipitates. The hardness of this coating is much higher than the hardness of the coating in the sprayed state formed on the water-cooled substrate. When hot pressing is applied to the coating, the porosity decreases but hardness also decreases because Ti₂AlC grows. The amount of Ti₂AlC in the hot-pressed film is 4.9 vol% to 15.3 vol%, depending on the carbon content of the film.

• 한국표면공학회지
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• 제56권6호
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• pp.401-411
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• 2023

This study investigates the synthesis, characterization, and application of zinc oxide (ZnO) nanoparticles for corrosion resistance and stress corrosion cracking (SCC) mitigation in high-temperature and high-pressure environments. The ZnO nanoparticles are synthesized using plasma discharge in water, resulting in rod-shaped particles with a hexagonal crystal structure. The ZnO nanoparticles are applied to Alloy 600 tubes in simulated nuclear power plant atmospheres to evaluate their effectiveness. X-ray diffraction and X-ray photoelectron spectroscopy analysis reveals the formation of thermodynamically stable ZnCr₂O₄and ZnFe₂O₄ spinel phases with a depth of approximately 35 nm on the surface after 240 hours of treatment. Stress corrosion cracking (SCC) mitigation experiments reveal that ZnO treatment enhances thermal and mechanical stability. The ZnO-treated specimens exhibit increased maximum temperature tolerance up to 310 ℃ and higher-pressure resistance up to 60 bar compared to non-treated ZnO samples. Measurements of crack length indicate reduced crack propagation in ZnO-treated specimens. The formation of thermodynamically stable Zn spinel structures on the surface of Alloy 600 and the subsequent improvements in surface properties contribute to the enhanced durability and performance of the material in challenging high-temperature and high-pressure environments. These findings have significant implications for the development of corrosion-resistant materials and the mitigation of stress corrosion cracking in various industries.

• 공업화학
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• 제28권6호
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• pp.607-618
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• 2017

석탄화력발전소를 포함한 다양한 산업설비에서 유해 대기오염물질이 배출되고 있으며, 이러한 오염물질은 인체 건강과 자연 생태계에 영향을 준다. 특히, 질소산화물($NO_x$)와 이산화황($SO_2$)은 인체 건강에 악영향을 주는 미세먼지($PM_{2.5}$) 형성에 원인물질로 알려져 있다. 이러한 $NO_x$와 $SO_2$ 배출을 저감하기 위해서 선택적 촉매 환원(SCR)과 습식 탈황 공정(WFGD)으로 결합된 혼합 시스템이 사용되고 있으나, 높은 설치비용 및 운전비용을 필요로 하며, 유지보수의 문제점, 기술적인 한계점을 가지고 있다. 최근에 이러한 혼합 시스템을 대체하기 위한 $NO_x$, $SO_2$ 동시 저감 기술이 연구되고 있으며, 제안된 기술들은 흡수, 고도 산화(AOPs), 저온 플라즈마(NTP), 전자 빔(EB) 등이 있다. 이러한 기술들은 강한 수용성 산화제 및 산화력을 가진 화학활성종에 의한 $NO_x$, $SO_2$를 $HNO_3$, $H2SO_4$ 형태로의 산화 반응, 기-액 계면에서 $HNO_3$와 $H2SO_4$ 흡수 반응, 화학 첨가제에 의한 중화 반응을 기본으로 하고 있다. 본 논문에서는 각각의 동시 저감공정에 대한 기술적인 특징과 대용량 처리 공정 응용을 위한 향후 전망을 정리하였다.

• Biomolecules & Therapeutics
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• 제15권1호
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• pp.58-64
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• 2007

The previous study reported the biological effect of magnetic field exerted by acting on endocrine and anti-oxidant system. The present study aims to study whether ELF-MF (extremely low frequency magnetic field) affects the physiological endocrine systems such as thyroid and whether ELF-MF affects the defense system against oxidative stress when it alters the function of thyroid. Finally, we correlate the effects of MF on oxidative stress, and adrenal and thyroid with an environmental stress factor. We exposed sham or MF to rats for 5 or 25 days. After the exposure, we determined pain sensitivity, level of TSH, $T_3$ and free $T_4$ in plasma. We also assayed in whole brain, lipid peroxidation, the activity of enzymatic anti-oxidant defense including superoxide dismutase(SOD) and glutathione peroxidase (GPx), and non enzymatic defense such as reduced or oxidized glutathione contents. MF induced the hypersensitivity to thermal stimuli with the reduction of latency. $T_3$ and $T_4$ levels were also increased by the exposure of MF. In addition, we observed the rise of MDA level in rat brain by MF although the MF did not change superoxide dismutase and glutathione peroxidase activity. The effect of MF on both reduced and oxidized glutathione results in decrease in reduced or oxidized glutathione in whole brain. In every experiment, there was no significant difference in MF influence between short term (5 days) and long term (25 days) exposure. Taken together, MF exposure affects the thyroid hormonal control in brain. The elevated thyroid hormone acts on brain, leading to hyper-utilization of oxygen. This phenomenon may be correlated with oxidative stress resulting from MF exposure. In conclusion, we suggest that MF exposure may be an environmental stress by exerting oxidative stress.

• 한국식품과학회지
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• 제48권5호
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• pp.525-529
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• 2016

시중에서 판매되고 있는 후추 29종을 수거하여 오염도를 조사한 결과, 전통시장에서 구입한 후추는 일반세균 $10^6-10^7$, Bacillus $10^4-10^5$, 효모와 곰팡이 $10^2$ 이하의 오염도를 보였고, 유기농 제품으로 판매되는 후추의 경우에는 일반세균 $10^4$, Bacillus $10^2-10^3$, 효모는 $10^1$ 이하의 오염도를 나타내었다. 대형마트에서 판매되고 있는 후추는 낮은 오염도를 나타내었으나 일부에서는 일반세균이 $10^3$ 정도의 오염도를 보였다. 전압 1,000 V, 펄스수 5 pps, 시료와 램프사이의 거리 4 cm의 조건에서 10분간 광펄스 처리하였을 경우 통후추는 1.45-1.55 log, 흑후추분말과 백후추분말은 0.8-0.85 log의 사멸율을 나타내었다. 살균 용기의 차이에 따른 살균율에는 유의적인 차이를 나타내지 않았다. 광펄스에 의한 후추의 살균율은 오존처리나 감압방전프라즈마 살균 등 다른 비가열 살균방법에 비해서는 높은 사멸율을 보여 산업적 적용 가능성을 보였으나, 추가적인 연구를 통해 살균 효과를 높일 수 있는 방법이 제시되어야 할 것으로 판단된다.