• 한국재료학회지
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• 제1권2호
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• pp.86-92
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• 1991

Morse potential을 변형한 2체항(2-body tem)과 Axilrod-Teller potential을 변형한 3체항(3-body tem)으로 구성된 포텐셜에너지 함수를 사용하여 $C_2-C_6$ cluster 동소체들의 에너지들의 에너지를 3체항 세기인자(3-body intensity factor)의 함수로 나타냄으로써 3체 인력의 기여도의 증가함에 따라 carbon cluster들의 구조는 open structure로부터 closed structure로, 또한 복잡한 구조로부터 단순한 구조, 즉 3차원적인 형태로부터 2차원 및 1차원적인 형태로 변해감을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제23권8호
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• pp.1163-1165
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• 2002

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.309-314
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• 2002

The ablation dynamics and cluster formation of $C_n^+$ ions ejected from 355 nm laser ablation of a graphite target in vacuum are investigated using a reflectron time-of-flight (RTOF) mass spectrometer. At low laser fluence, odd-numbered cluster ions with $3{\leq}n{\leq}15$ are predominantly produced. Increasing the laser fluence shifts the maximum size distribution towards small cluster ions, implying the fragmentation of larger clusters within the hot plume. The temporal evolution of $C_n^+$ ions was measured by varying the delay time of the ion extraction pulse with respect to the laser irradiation, providing significant information on the characteristics of the ablated plume. Above a laser fluence of $0.2J/cm^2$ , large cluster ions ($n{\geq}30$) are produced at relatively long delay times, indicating that atoms or small carbon clusters aggregate during plume propagation. The dependence of the intensity of ablated $C_n^+$ ions on delay time after laser irradiation shows that the most probable velocity of each cluster ion decreases with cluster size.

• Bulletin of the Korean Chemical Society
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• 제28권11호
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• pp.1996-2002
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• 2007

The redox behavior of a [Ni6(μ3-Se)2(μ4-Se)3(Fe(η 5-C5H4P-Ph2)2)3] (= [Ni-Se-dppf], dppf = 1,1-bis(diphenylphosphino) ferrocene) cluster was studied using platinum (Pt) and glassy carbon electrodes (GCE) in nonaqueous media. The cluster showed electrochemical activity at the potential range between +1.6 and ?1.6 V. In the negative region (0 to ?1.6 V), the cluster exhibited two-step reductions. The first step was one-electron reversible, while the second step was a five-electron quasi-reversible process. On the other hand, in the positive region (0 to +1.6 V), the first step involved one-electron quasi-reversible process. The applicability of the cluster was found towards the electrocatalytic reduction of CO2 and was evaluated by experiments using rotating ring disc electrode (RRDE). RRDE experiments demonstrated that two electrons were involved in the electrocatalytic reduction of CO2 to CO at the Se-Ni-dppf-modified electrode.

• 대한금속재료학회지
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• 제47권6호
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• pp.331-337
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• 2009

To lower the annealing temperature and the deviation of the mechanical properties of bake hardening steels, high purity steels were investigated. The steels were characterized by treating at low recrystallization temperature. It was confirmed that the strengthening originated from the solid solution of carbon and the ferrite grain refinement by fine MnS precipitates as carbon and sulfur contents increased in high purity steels. However, it was observed that there was no more increase of strength in steels containing over 40 ppm of carbon. It was considered that the excess carbon formed either the carbon cluster or the low temperature unstable carbides which had the negligible effect on the strengthening because they were reported to be highly coherent with the matrix. The carbon cluster and unstable carbides could be transformed to the stable cementite during bake hardening treatment. MnS was not observed in the high purity steel containing 5 ppm S, resulting in very coarse recrystallized grains and good ductility. As sulfur content increased, the recrystallized grain size decreased due to the formation of the fine MnS precipitates.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2071-2078
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• 2024

The precipitation of solutes is a major cause of irradiation hardening and embrittlement limiting the service life of reactor pressure vessel (RPV) steels. Impurities play a significant role in the formation of precipitation in RPV materials. In this study, the effects of carbon on cluster formation and irradiation hardening were investigated in an RPV alloy Fe-1.35Mn-0.75Ni using C and Fe ions irradiation at 290 ℃. Nanoindentation results showed that C ion irradiation led to less hardening below 1.0 dpa, with hardening continuing to increase gradually at higher doses, while it was saturated under Fe ion irradiation. Atom probe tomography revealed a broad size distribution of Ni-Mn clusters under Fe ion irradiation, contrasting a narrower size distribution of small Ni-Mn clusters under C ion irradiation. Further analysis indicated the influence of carbon on the cluster formation, with solute-precipitated defects dominating under C ion irradiation but interstitial clusters dominating under Fe ion irradiation. Simulations suggested that carbon significantly affected solute nucleation, with defect clusters displaying smaller size and higher density as carbon concentration increased. The higher hardening at doses above 1.0 dpa was attributed to a substantial increase in the number density of defect clusters when carbon was present in the matrix.

• 천문학회지
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• 제14권1호
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• pp.13-17
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• 1981

The observed radial UBV colour variations (both B-V and U-B) of some globular clusters are examined for correlations with radial variations in the integrated spectra. The results show that the presence of a radial colour gradient is correlated with the presence of a gradient of the CN (and possibly the G-band) line strength, in the sense that the CN (and possibly the G-band) is stronger in the centre (where the cluster is redder) and becomes weaker in the outer region of the cluster (where the cluster is bluer). This may suggest that a primordial abundance, possibly nitrogen and carbon gradient was set up in the early stage of cluster formation.

• 한국컴퓨터정보학회논문지
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• 제28권7호
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• pp.189-198
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• 2023

최근 지구온난화로 인한 폭염, 태풍, 폭설 등 기후변화를 급증하고 있다. 미국 뉴욕에서 개최된 제 25차 '기후변화 당사국총회(COP25)'에 따른 세계 각국은 '탄소중립' 달성하기 위한 협상을 진행했다. 도시는 경제발전뿐만 아니라 탄소중립 과정에서도 중요한 역할을 수행한다. 본 연구는 이산화탄소와 관계되는 경제요인 및 환경요인을 고려하여 엘보우 규칙 (Elbow method) 과 K-means 군집 알고리즘을 활용하여 한국 63개 도시의 탄소배출 현황을 분석하였다. 연구결과에 따른 한국 도시는 기술집약 도시, 경공업 도시, 미래 혁신도시, 중공업 도시, 서비스 집약도시 및 농촌, 가정생산집약도시로 구분될 수 있고 향후 시도별 탄소중립 목표를 실천하기 위해 구체적인 제안을 제시하였다.

• Journal of Microbiology and Biotechnology
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• 제7권1호
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• pp.68-74
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• 1997

One hundred and eighty two lactic acid bacteria, isolated mainly from kimchi, including reference strains were examined for their ability to utilize 95 carbon sources. The test strains were assigned to 5 major, 1 minor and 12 single-membered clusters based on the $S_{SM}$, UPGMA algorithm (at similarity of $80{\%}$). These aggregate clusters were equivalent to the genus Leuconostoc (aggregate cluster M and N), the genus Lactobacillus (aggregate cluster Q and R), and the genera Lactobacillus and Leuconostoc (aggregate cluster O and P) according to the database of the Biolog system. This study demonstrates that rapid identification and classification of isolates originating from kimchi can be achieved on the basis of such carbon source utilization tests.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.113.2-113.2
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• 2007