• 한국분말재료학회지
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• 제25권2호
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• pp.99-103
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• 2018

Spherical monosized pure aluminum (Al) particles are successfully fabricated by the pulsated orifice ejection method (POEM). The surface reaction between Al and the graphite crucible is investigated by analysing the microstructure and chemical composition of the materials. No significant chemical reaction occurs between Al and the graphite owing to the crystalline Al oxide (${\gamma}-Al_2O_3$) layer generated in the initial state. The ${\gamma}-Al_2O_3$ layer is clearly observed in all regions between the Al particles and graphite via transmission electron microscopy and confirmed by the selected area diffraction pattern. The morphology of the ${\gamma}-Al_2O_3$ layer perfectly follows the surface morphology of the graphite crucible, which showed nanoscale roughness. This implies that molten Al could not directly contact graphite even though the surface of the crucible became rough to some extent. However, this passivation phenomenon allowed the successful fabrication of monosized pure Al particles. Therefore, POEM is a useful process at least to manufacture monosized pure Al particles.

• 한국분말재료학회지
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• 제24권4호
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• pp.285-291
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• 2017

We propose a custom analysis technique for the dark field (DF) image based on transmission electron microscopy (TEM). The custom analysis technique is developed based on the $DigitalMicrograph^{(R)}$ (DM) script language embedded in the Gatan digital microscopy software, which is used as the operational software for most TEM instruments. The developed software automatically scans an electron beam across a TEM sample and records a series of electron diffraction patterns. The recorded electron diffraction patterns provide DF and ADF images based on digital image processing. An experimental electron diffraction pattern is recorded from a IrMn polycrystal consisting of fine nanograins in order to test the proposed software. We demonstrate that the developed image processing technique well resolves nanograins of ~ 5 nm in diameter.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.576-577
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• 2006

This study was conducted to improve the durability and decrease the friction of the sintered bushing used in the joints of construction equipment. Research was carried out to examine the effects of the groove pattern on the inner surface. The following results were obtained: (1) The bushing (EK Bush) with grooves on the inner diameter showed increased durability as compared to a non-grooved bushing. (2) The helical-grooved bushing showed the least amount of wear; it was １/10 of the wear of the non-grooved bushing. (3) If the distance between grooves was decreased, then the coefficient of friction also decreased.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.28-29
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• 2006

High-Speed Centrifugal Compaction Process (HCP) is a wet compacting method, in which powders are compacted under a huge centrifugal force. The HCP was well applied to small alumina specimens, but the compact easily cracked when we applied the HCP to other materials. We clarified how the cracks introduced and found that the formation of such a flow pattern was related to the Colioli's force in the centrifugal field.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.405-406
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• 2006

Raw materials from different sources, produced by a given process and having equal chemical composition, are supposed to be equivalent. The differences in sintering behavior have been investigated on P/M steels obtained from four diffusion-bonded powders (Fe + Ni + Cu + Mo) on atomized iron base, at the same alloy contents. Two levels of carbon and two sintering conditions have been investigated. Dimensional changes, C content, hardness, microhardness pattern, universal hardness, fractal analysis, pore features, microstructure features, and rupture strength have been compared to characterize different raw materials. The results show that the claimed equivalence is not confirmed by experimental data.

• 한국분말재료학회지
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• 제11권3호
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• pp.242-246
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• 2004

FePt nanoparticles for high-density magnetic recording media were synthesized by the simultaneous chemical reduction of Fe(acac) $_2$ and Pt(acac) $_2$ with 1,2-hexadecanediol as the reducing reagent. TEM images showed that the shape of as-synthesized FePt nanoparticle was spherical and average particle size was 3 nm. Also, SAD pattern showed that crystal structure was disordered FCC (face centered cubic). These FCC structured nanoparticles were transformed FCT (face centered tetragonal) structure by annealing at 55$0^{\circ}C$ for 30 min in Ar atmosphere. XRD analysis revealed that as-synthesized FePt nanoparticles were transformed from disordered FCC to ordered FCT. Finally, the coercivity of 2 kOe for FePt nanoparticles with FCT structure was obtained by VSM measurement.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 추계학술발표대회 개요집
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• pp.220-222
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• 2001

The average grain size, the grain-size distribution, the morphology and the microstructure are fundamental characteristics of a spraying powder. Now that the significance of the grain size for the pattern of properties of the powder has been recognised, greater consideration is also being given to it in standards and regulations. However, unfortunately, the processes according to which the grain size and the grain-size distribution must be determined are specified in the rarest of cases. The contribution therefore dealt with the comparison of different particle-size measuring techniques, such as diffraction spectroscopy, sedimentation, sieving and microscopic measurement. The comparability of the measured results was investigated on twelve plasma spraying powders with different compositions, nominal sizes and morphologies.

• Bulletin of the Korean Chemical Society
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• 제20권5호
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• pp.517-524
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• 1999

By heating the magnesiumsilicate (Mg2SiO4:forsterite) xerogel in carbon dioxide, carbonaceous component was intentionally introduced into the amorphous solid precursor. Carbon was introduced homogeneously as unidentate carbonate. Upon being heated at 800 。C in carbon dioxide, the xerogel which had homogeneously distributed carbonaceous component in it crystallized into a single phase product of a new crystalline material, which had approximate composition of Mg8Si4Ol8C. The powder X-ray diffraction pattern of the new crystalline material did not match with any known crystalline compound registered in the powder diffraction file. Crystallization from amorphous xeroget to the new crystalline phase occurred in a very narrow range of temperature, from 750 。C to 850 。C in carbon dioxide, or in dty oxygen. Upon being heated above 850 。C, carbonaceous component was expelled from the product, accompanied by irreversible transition from the new crystalline material to forsterite.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.609-614
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• 2018

인터넷 기술의 급격한 성장으로 우리들은 언제 어디에서나 다양한 장치를 이용하여 온라인에 접속할 수 있으며, 실시간, 대용량의 영상 및 사진들이 인터넷상에 올려지고 있다. 이러한 영상들의 대부분은 영상에 관련된, 영상을 인식할 수 있는 간단한 주석을 갖는다. 그럼에도 아직도 주석이 없는 단일 영상이나 잘못된 주석이나 태그 정보 때문에 우리가 원하는 영상을 찾는데 문제점이 있어 이러한 문제해결을 위해서는 영상의 올바른 정보를 태깅하는 것이 필수적이다. 대부분의 태그는 문서나 주석의 형태를 가지므로 주석이나 문서의 정보가 올바르지 않으면 원하는 영상을 찾는데 많은 어려움이 따른다. 그리하여 더 나은 영상 탐색 결과와 올바른 영상 주석을 위해서 작가에 의한 주석뿐만 아니라 올바른 영상분석 또한 아주 중요하다. 영상 특징을 추출하는 것은 신뢰성 있는 영상 주석을 위해 필수 불가결한 요소이다. 따라서 본 논문에서는 다양한 불특정 영상으로 부터 계층적 텍스트 추출 방법을 사용하여 신뢰성 있는 영상 주석을 얻는다. 다양한 영상으로 부터 영상이나 사진 속에 포함된 텍스트 정보를 추출하는 방법을 제안하였으며, 실험결과 제안한 텍스트 추출기법이 대부분의 영상으로부터 정확하게 텍스트 특징을 추출하는 결과를 보여주었고, 성능 평가 결과 최소 0.04부터 최대 0.52의 높은 평가결과를 보여주었다. 또한 정확도 측면에서도 다른 기법들 보다 최소 18.1%부터 최대 37.9%의 높은 정확도를 보여주었다.

• 한국식품영양과학회지
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• 제41권6호
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• pp.834-839
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• 2012

민들레 뿌리분말의 첨가비율(0, 5, 10, 15%)을 달리하여 제조한 민들레 약주의 이화학적 및 관능적 특성을 조사하였다. 민들레 뿌리분말 첨가량의 증가에 따른 pH 변화는 미미하였고, 산도와 당도는 15% 첨가구가 각각 가장 높은 함량을 나타났다. 환원당 함량은 민들레 뿌리분말 15% 첨가구가 발효 3일째에 다른 시료구에 비하여 가장 높았으며, 그 이후에는 급격하게 감소하여 다른 시험구와 비슷한 함량을 나타내었고, 알코올 함량은 발효가 진행됨에 따라 시험구 모두 증가하였다. 민들레 뿌리분말 첨가 비율을 달리하여 제조한 약주의 관능적 특성은 첨가 비율이 10, 15%로 증가할수록 종합적 기호도가 좋지 않았으며, 첨가 비율이 5%인 시험구가 색, 향, 맛, 목넘김, 종합적 기호도가 우수하였다. 이와같이 민들레 뿌리분말의 첨가 비율을 달리하여 제조한 약주의 이화학적 및 관능적 특성을 검토한 결과, 민들레 뿌리분말 5%를 첨가하여 제조한 약주가 가장 우수한 것으로 나타났다. 위의 실험 결과, 민들레 뿌리분말로 약주를 제조할 경우, 민들레 뿌리분말 5%를 첨가하는 것이 가장 적합함을 알 수 있었다.