• Tribology and Lubricants
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• 제35권2호
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• pp.106-113
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• 2019

We investigated the application of tetrahedral amorphous carbon (ta-C) coatings to fabricate a glass lens manufactured using a glass molding process (GMP). In this work, ta-C coatings with different thickness (50, 100, 150 and 200 nm) were deposited on a tungsten carbide (WC-Co) mold using the X-bend filter of a filtered cathode vacuum arc. The effects of thickness on mechanical and tribological properties of the coating were studied. These ta-C coatings were characterized by atomic force microscopy, scanning electron microscopy, nano-indentation measurements, Raman spectrometry, Rockwell-C tests, scratch tests and ball on disc tribometer tests. The nano-indentation measurements showed that hardness increased with an increase in coating thickness. In addition, the G-peak position in the Raman spectra analysis was right shifted from 1520 to $1586cm^{-1}$, indicating that the $sp^3$ content increased with increasing thickness of ta-C coatings. The scratch test showed that, compared to other coatings, the 100-nm-thick ta-C coating displayed excellent adhesion strength without delamination. The friction test was carried out in a nitrogen environment using a ball-on-disk tribometer. The 100-nm-thick ta-C coating showed a low friction coefficient of 0.078. When this coating was applied to a GMP, the life time, i.e., shot counts, dramatically increased up to 2,500 counts, in comparison with Ir-Re coating.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1026-1029
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• 2006

Particulate reinforced titanium composites were produced by PM rout. Differents volumetric percentages of TiN reinforcements were used, 5,10,15 vol%. Samples were uniaxial pressed and vacuum sintered at differents temperatures between $1200-1300^{\circ}C$. Density, porosity, shrinkage, mechanical properties and microstructure were studied. Elastic properties and strength resistance were analysed by flexural strength and tension tests, and after the test, fractured samples were analysed too, obtaining a correlation between the fracture, interparticulated or intraparticulated, and the reinforcement addition.. Hardness and microhardness test were applied too, in order to complete the study about mechanical properties. In order to study wear resistance pin-on-disc test were used. In addition, the temperature influence, the reactivity between matrix and reinforcement, and the microstructures developed were observed by optical and electron microscopy.

• 한국식품과학회지
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• 제37권3호
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• pp.405-411
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• 2005

본 연구에서는 항균활성을 지니는 기능성 생고분자 필름을 제조하기 위한 전 단계로 키토산과 젤라틴을 이용하여 혼합비율별로 키토산/젤라틴 혼합용액의 항균활성을 측정하였다. 사용된 균주는 그램양성(Bacillus cereus ATCC 14579, Listeria monecytogenes ATCC 15313) 및 그램음성(Escherichia coli ATCC 25922, Salmonella enteritidis IFO 3313) 세균 4종류이고, paper diffusion method와 optical density method로 항균효과를 나타내는 키토산/젤라틴 혼합용액의 최적 혼합비율 및 키토산의 최소저해농도를 측정하였다. 또한 키토산의 용매로 사용된 2%(v/v) 초산의 항균효과를 측정하였다. 혼합비율별로 제조된 키토산/젤라틴 혼합용액을 이용하여 paper diffusion method로 paper disc(8 mm)에 $50\;{\mu}L$, $75\;{\mu}L$씩 분주시켜 항균활성을 측정한 결과, 저해환의 크기는 8 mm에서 18.07 mm로 측정되었다. 키토산의 농도가 0%에서 10%(B. cereus, E. coli, E. enteritidis), 20%(L. monocytogenes)까지는 전혀 항균활성을 나타내지 않았지만, 그 농도가 20%(B. cereus, E. coli, S. enteritidis), 30%(L. moncytogenes) 이상으로 높아질수록 항균활성이 서서히 증가하는 경향을 보였다. L. monocytogenes는 키토산의 농도가 30%에서 항균활성을 나타내었지만, 그 저해환의 크기가 뚜렷하지 않았다. 따라서 B. cereus. E. coli 및 S. enteritidis 균주들에 대하여 항균환성을 나타내는 혼합용액의 혼합비율은 chitosan/gelatin=2/8이였고, 그 때 항균활성을 나타내는 키토산의 절대량은 0.3 mg으로 측정되었다. 또한 L. monocytogenes에 대해서는 혼합비율이 chitosan/gelatin=4/6이였고, 항균활성을 나타내는 키토산의 절대량은 0.6 mg이었다. 혼합비율별로 제조된 키토산/젤라틴 혼합용액을 이용하여 항균활성을 나타내는 키토산의 최소저해농도를 optical density method로 측정하였다. 그 결과, B. cereus, L. monocytogenes, E. coli 및 S. enteritidis에 대한 키토산의 최소저해농도는 각각 0.1461 mg/mL, 0.2419 mg/mL, 0.0980 mg/mL 및 0.0490 mg/mL로 측정되었다. 또한 2%(v/v) 초산 자체의 최소저해농도를 측정한 결과, B. cereus, L. mosocytogenes, E. eoli에 대해서는 control과 비교시 유의적인 항균효과는 나타나지 않았다. 반면에 S. enteritidis의 경우는 배양시간 4시간까지는 항균활성을 나타내었지만, 8시간 이후부터는 S. enteritidis의 성장이 control 보다 높아져 배양시간 20시간에서는 control 보다 약 2배 이상 균주의 성장을 촉진시켰다.

• 한국식품과학회지
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• 제31권3호
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• pp.764-770
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• 1999

41종의 약용식물을 열수추출하여 위궤양 원인균으로 보고된 Helicobacter pylori에 대해 항균활성을 탐색하였다. 2-fold dilution 방법에 의해서는 백련초, 어성초, 방기, 황련은 100 ppm이하, 백두옹, 연교, 종대황, 소엽은 200 ppm 이하, 사간, 우방자, 결명자, 귤피, 희침, 소목은 300 ppm 이하와 농도에서 H. pylori에 대해 항균활성을 나타냈다. 이중 3가지 추출물만이 disc 방법을 통해 항균활성이 재확인되었으며, 소목, 황련, 소엽의 순으로 강한 항균활성을 나타냈다. 항균활성이 확인된 3가지 추출물을 chloroform, ethyl acetate, butanol로 순차 분획하여 H. pylori에 대한 항균활성을 확인하였다. 소목의 경우는 ethyl acetate 분획물에서, 소엽의 경우는 butanol 분획물에서, 황련의 경우는 butanol과 chloroform 분획물에서 가장 강한 항균활성을 나타내었다. 추출물의 분획에 따른 항균활성의 상승효과는 모든 추출물에서 확인할 수 있었다. H. pylori의 crude-urease를 분리하여 urea R broth에서 흡광도와 pH를 조사한 결과, 반응 2시간 후 pH가 8.15까지, 560 nm에서의 흡광도는 1.7까지 증가하는 것으로 나타났다. H. pylori의 urease 활성은 소목, 소엽, 황련에 의해 80%이상 억제되었으며, 이중 소목은 urease 활성을 95%이상 억제시켰다.

• 한국수산과학회지
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• 제42권2호
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• pp.171-178
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• 2009

The purpose of this study was the development of a digital water color measurement system using a CCD optical device. Photographs of the standard medium of Forel and Ule water color scales in the laboratory, and one of sea surface above a Secchi disc (Z=SD/2) immersed in seawater were taken. The colors of these pictures were estimated with the value of CIE $L^*a^*b^*$. Water color assessment was conducted with a digital photo-image. In the case of the Forel scale (No. 1-11), the $b^*$ value was so high that the water color number was large. In the Ule scale (No.11-21), the $a^*$ value became high, which is why the number on the water color scale was large. The color of these pictures showed that the $a^*$ value in the Forel scale and the $b^*$ value in the Ule scale increase with the increase of the F value. The $a^*$ value of seawater color was always lower than the one on the Forel and Ule water color scales. This indicates that the color of the scales differs from actual seawater color. It was concluded that water color number can more effectively be assessed by estimating the ${\Delta}Eab^*$ color difference between the water scales and actual seawater color.

• 한국대기환경학회지
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• 제34권3호
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• pp.493-507
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• 2018

Due to high spatio-temporal variability of amount and optical/microphysical properties of atmospheric aerosols, satellite-based observations have been demanded for spatiotemporal monitoring the major aerosols. Observations of the heavy aerosol episodes and determination on the dominant aerosol types from a geostationary satellite can provide a chance to prepare in advance for harmful aerosol episodes as it can repeatedly monitor the temporal evolution. A new geostationary observation sensor, namely the Advanced Himawari Imager (AHI), onboard the Himawari-8 platform, has been observing high spatial and temporal images at sixteen wavelengths from 2016. Using observed spectral visible reflectance and infrared brightness temperature (BT), the algorithm to find major aerosol type such as volcanic ash (VA), desert dust (DD), polluted aerosol (PA), and clean aerosol (CA), was developed. RGB color composite image shows dusty, hazy, and cloudy area then it can be applied for comparing aerosol detection product (ADP). The CALIPSO level 2 vertical feature mask (VFM) data and MODIS level 2 aerosol product are used to be compared with the Himawari-8/AHI ADP. The VFM products can deliver nearly coincident dataset, but not many match-ups can be returned due to presence of clouds and very narrow swath. From the case study, the percent correct (PC) values acquired from this comparisons are 0.76 for DD, 0.99 for PA, 0.87 for CA, respectively. The MODIS L2 Aerosol products can deliver nearly coincident dataset with many collocated locations over ocean and land. Increased accuracy values were acquired in Asian region as POD=0.96 over land and 0.69 over ocean, which were comparable to full disc region as POD=0.93 over land and 0.48 over ocean. The Himawari-8/AHI ADP algorithm is going to be improved continuously as well as the validation efforts will be processed by comparing the larger number of collocation data with another satellite or ground based observation data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.203-206
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• 2004

For the realization of PRAM, $Ge_2Sb_2Te_5$ (GST) has been employed for the phase transition between the crystal and amorphous states by electrical joule heating. Although there has been a vast amount of results concerning the GST in material aspect for the laser-induced optical storage disc applications, the process-related issues of GST for the PRAM applications have not been reported. In this work, the etching behaviors of GST were investigated when the processing conditions were varied in the high-density helicon plasma. The etching parameters of RF main power, RF bias power, and chamber pressure were fixed at 600 W, 150 W, and 5 mTorr, respectively. For the etching processes, gas mixtures of $Ar/Cl_2$, $Ar/CF_4$, and $Ar/CHF_3$ were employed, in which the etching rates and etching selectivities of GST thin film in given gas mixtures were evaluated. From obtained results, it is found that we can arbitrarily design the etching process according to given cell structures and material combinations for PRAM cell fabrications.

• 대한전자공학회논문지TC
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• 제47권2호
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• pp.18-24
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• 2010

신뢰성 있는 채널 모델은 다양한 데이터 검출 알고리즘의 개발과 성능 평가에 중요한 척도가 되므로 정확한 모델링이 요구된다. 본 논문에서는 Super-RENS (Super-Resolution Near-field Structure) 시스템의 비선형 모델링을 위해 정규 구간선형 모델 (canonical piecewise-linear; PWL)과 2차 볼테라 (second-order Volterra) 모델을 적용하고자 한다. 또한 이를 바탕으로 비선형 심볼간 간섭 (Inter-Symbol Interference; ISI)을 제거하기 위해 새로운 비선형 등화기를 제안한다. Super-RENS 디스크로부터 획득한 RF 신호 샘플들을 사용하여 모의실험을 수행한 결과, Super-RENS 시스템의 비선형 모델링을 위해 정규 구간선형 모델과 2차 볼테라 모델이 유용하게 활용될 수 있다는 가능성을 확인하였고 제안된 비선형 등화기의 성능은 비트오율 측면에서 등화기가 없는 경우보다 우수한 성능을 나타내었다.

• 한국융합학회논문지
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• 제9권10호
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• pp.315-324
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• 2018

본 논문은 지식 조합과 기술 변화 간의 상호 작용이 발명 유용성에 미치는 영향을 분석한다. 본 연구는 기술 변화에 따라 외부 주체들이 현 기술 환경에 적합하다고 판단하는 지식 요소가 달라져 선행 기술 대비 새로운 지식 요소나 다양한 기술 분야의 지식 요소를 조합한 발명의 유용성이 변함을 주장한다. 1992년부터 2000년까지 미국에 출원된 광학 디스크 등록 특허들을 분석한 결과는 선행 기술 대비 새로운 지식 요소를 많이 가지는 발명의 유용성은 낮음을 보였다. 그러나 다각화된 지식 요소를 가지는 발명의 유용성은 높았다. 또한, 실증 분석 결과는 선행 기술 대비 새로운 지식 요소와 발명 유용성 간의 부의 관계는 지배적 디자인이 나타난 이후 강화됨을 보였다.

• 한국축산식품학회지
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• 제37권4호
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• pp.502-510
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• 2017

This study investigated bacterial growth-inhibitory effect of 69 therapeutic herbal plants extracts on 9 bacterial strains using a disc diffusion assay. Especially, the antimicrobial activity of Psoraleae semen, which showed different activity on pathogenic Gram-positive and Gram-negative bacteria, was evaluated by MIC (minimal inhibition concentration) and biofilm formation assay. The effect of Psoraleae semen extract on bacterial cell membranes was examined by measurement of protein leakage (optical density at 280 nm) and scanning electron microscope (SEM). No clear zone was formed on discs containing Gram-negative bacteria, but Gram-positive bacteria exhibited clear zones. The MICs of Psoraleae semen extract were $8{\mu}g/mL$ for Streptococcus mutans, and $16{\mu}g/mL$ for Enterococci and Staphylococcus aureus. In addition, biofilm formation was inhibited at concentration $8-16{\mu}g/mL$. Protein leakage values and SEM images revealed that cell membranes of Gram-positive bacteria were impaired following exposure to the extract. Further, the extract inhibited the growth of Listeria monocytogenes in sausages. These results indicate that Psoraleae semen extract could be utilized as a natural antimicrobial agent against Gram-positive bacteria.