• 분석과학
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• 제8권4호
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• pp.493-498
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• 1995

PAZO-6 is a new combined type liquid crystalline polymers (LCP) which has two types of mesogens combined non linearly. Ordering of branch mesogen azo group, in PAZO-6 is an important parameter to observe as well as the substitution effect on the backbone. The related small molecules sllch as monomers as well as the polymer itself are studied by solid state NMR techniques. Preliminary $^{13}C$ CP/MAS (cross polarization/ magic angle spinning) spectral results suggest that the azo groups in the monomers are not aligned with themselves. Azo groups in the monomers seem to be poorly ordered between well ordered p-phenylene terephthalate moeities. Similar disordering tendency of the azo group in PAZO-6 is deduced from the overall aromatic carbon peak positions which are not much different from those of the monomer.

• Corrosion Science and Technology
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• 제5권5호
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• pp.181-188
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• 2006

In this study, the characteristics of the experimentally produced high N-high Cr bearing stainless steels are discussed as a part of applications of materials for FGD (Fuel Gas Desulfurization) system of thermal power plants or for power plants using seawater as coolant. Corrosion resistance of developed alloys is especially investigated in detail. Corrosion characteristics of vacuum melted cast are shown to be superior to that of air melted one. From the viewpoint of CPT, It is estimated that the differences of corrosion resistance are $21.8^{\circ}C{\sim}24.6^{\circ}C$ at PRE 40 and $8^{\circ}C{\sim}12.4^{\circ}C$ at PRE 50, and the gaps becomes bigger as the PRE values are lower. In the evaluation of corrosion resistance in alloy A2501, Z3101, and A3301 according to Cr concentration, alloy A3301 shows a deviation from the general tendency in chloride solutions. It has relatively high PRE value as 48.6, but it has relatively poor pitting resistance. It is, however, difficult to observe a specific phase except ferrite in microstructure analysis and neither detects special phase such as sigma phase.

• Journal of Welding and Joining
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• 제25권6호
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• pp.78-83
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• 2007

The wettability of Sn-Xwt%Cu(X=$0{\sim}3wt%$) solder was evaluated with wetting balance tester. And, the intermetallic compounds(IMCs) which were formed at the interface between solders and pads were investigated by using scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The wetting force of Sn-0.7wt%Cu solder was higher than that of 100wt%Sn and Sn-3.0wt%Cu solder. The value of $\gamma_{fl}$ and ($\gamma_{fs}-\gamma_{ls}$) had a tendency to increase with increasing the wetting temperature. The activation energy with bare Cu pad and flux with 15% solid content was increased in the following order: Sn-0.7Cu (68.42 kJ/mol) ; Sn-3.0Cu(72.66 kJ/mol) ; Sn solder(94.53 kJ/mol). It was identified that the Cu6Sn5 phase was formed at the interface between Sn-Xwt%Cu solder and Cu pad.

• 대한금속재료학회지
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• 제48권1호
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• pp.71-76
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• 2010

The use of advanced high-strength steels (AHSS) in automotive applications has steadily increased over the past few years. Two different failure modes are generally observed in shear-tension tests for resistance spot welds of AHSS. interfacial fractures and full button pullout. Despite high load-carrying capacity. the resistance spot welds in AHSS cue prone to interfacial fractures. To improve the load carrying ability of welds during shear-lap and cross tension tests. the tip surface of the electrode was grooved in a round shape. The electrode tip surface was modified so as to concentrate the current now in the central and circumferential portion of the electrode force. The results showed that the interfacial fracture was suppressed in welds using the modified electrode. In a comparison of failure mode during mechanical tests. the welds made with the modified electrode showed a higher tendency to fail via full button pullout fracture.

• 한국분말재료학회지
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• 제26권1호
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• pp.22-27
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• 2019

In this study, the effects of powder size and composition on the reflectance of Al-Si based alloys are presented. First, the reflectance of Al-Si bulk and powder are analyzed to confirm the effect of powder size. Results show that the bulk has a higher reflectance than that of powder because the bulk has lower surface defects. In addition, the larger the particle size, the higher is the reflectance because the interparticle space decreases. Second, the effect of composition on the reflectance by the changing composition of Al-Si-Mg is confirmed. Consequently, the reflectance of the alloy decreases with the addition of Si and Mg because dendrite Si and $Mg_2Si$ are formed, and these have lower reflectance than pure Al. Finally, the reflectance of the alloy is due to the scattering of free electrons, which is closely related to electrical conductivity. Measurements of the electrical conductivity based on the composition of the Al-Si-Mg alloy confirm the same tendency as the reflectance.

• Macromolecular Research
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• 제12권2호
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• pp.156-171
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• 2004

We describe the precision synthesis schemes of siloxane-containing polymers, i.e., the control of their molecular weight, stereoregularity, and higher-order structures. First, we found a new catalytic dehydrocoupling reaction of water with bis(dimethylsilyl)benzene to give poly(phenylene-disiloxane). Together with this reaction, we applied hetero-condensations to the synthesis of thermally stable poly(arylene-siloxane)s. The dehydrocoupling reaction was applied to the synthesis of syndiotactic poly(methylphenylsiloxane) and poly(silsesquioxane)s, which we also prepared by hydrolysis and deaminative condensation reactions. We discuss the tendency for loop formation to occur in the synthesis of poly(silsesquioxane) by hydrolysis, and provide comments on the design of functionality of the polymers produced. By taking advantage of the low energy barrier to rotation in the silicon-oxygen bond, we designed selective oxygen-permeable membrane materials and liquid crystalline materials. The low surface free energy of siloxane-containing systems allows surface modification of a blend film and the design of holographic grating materials.

• Journal of Preventive Medicine and Public Health
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• 제11권1호
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• pp.14-23
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• 1978

This survey was conducted on a total 672 pulmonary tuberculosis patients who were registered at certain health center in Busan, during the period from July 15th to August 31st, 1977, based on Modified Cornell Medical Index(CMI) consisting of 70 questions. Number of 'Yes' response of an individual patients was collected by each large section of Modified CMI. The each number of 'Yes' response was standardized by mean of Z scoring. Z score was obtained by following formula. Z=50+10(Xi-m)/s M : means of 'Yes' response by each section for all subjects s : standard deviation of the mean Xi : number of 'Yes' response by each section in an individual patients The results of obtained were as follows: 1. The number of investigated cases were 672 (459 males and 213 females). The most prevalent group was 20-24 years old group as 18.4% by age, moderate advanced group as 50.8% by radiological diagnosis, INH+PAS+SM group as 34.7% by antituberculotics and unemployed group as 59.9% by occupation. By bacteriological examination of sputum, the rate of negative group was 60.5% and positive group was 39.5%. 2. Z score of complaints by sex was higher in female as 52.4 than in male as 48.9 in general. By radiological diagnosis, there was decreasing tendency with age in male but increasing tendency with age in female. 3. By age group, Z score of complaints was increasing tendency with age in male but there was non-significant differences in female. 4. By bacteriological examination of sputum, the Z score of complaints was increasing tendency with the more discharged bacteria in both sex generally. 5. By antituberculotics, INH group was revealed the highest Z score of complaints as 50.4 in male and INH+PAS group was the highest as 51.21 in female. 6. By occupation, agricultural and fisherman group was the highest as 53.5 and the next group was professional, technical and related workers, unemployed and sales workers in that order.

• 한국지구과학회지
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• 제40권2호
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• pp.188-199
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• 2019

이 연구의 목적은 2013 교육강령의 북한 교과서 중 지구과학 내용의 탐구 경향성을 조사하여 향후 북한 지구과학교육의 이해를 위한 기초 자료로 제공하는 것이다. 연구대상은 초급중학교의 자연과학1 2와 조선지리2, 고급중학교의 지리1 교과서이며, 교과서의 지구과학 내용을 Romey 분석법에 따라 본문 삽화 문제 활동지수 측면에서 분석하였다. 이 연구의 결과는 다음과 같다. 첫째, 대기과학 문제와 천문학 본문은 탐구적 경향을 나타내었다. 둘째, 해양학의 비중은 상대적으로 작았다. 셋째, 비 탐구적 문제가 많거나 탐구적 문제가 과도하여 문제의 균형이 필요하였다. 넷째, 탐구학습을 강조하지 않는 경향을 보였다. 마지막으로 탐구 경향성의 양적 및 질적 수준의 제고가 필요한 것으로 조사되었다. 향후 북한 교과서 중 지구과학 내용의 질적 분석 및 남북한 교과서 중 지구과학 내용의 탐구 경향성 비교 분석 등을 제안하였다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.577-582
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• 2002

The solidification cracking susceptibilities of AI-Mg-Si alloy laser welds were assessed using the self-restraint tapered specimen crack test. The cracking susceptibility of 6061 and 6082 Al-Mg-Si alloy laser welds was substantially reduced when the filler wire containing high Si such as Al-12 wt.% Si (4047A) was used. The amount of eutectic was observed to affect the solidification cracking of Al-Mg-Si alloy laser welds. Abundant eutectic seems to heal the cracking and reduces the cracking susceptibility, while an initial increase in eutectic liquid leads to the increased cracking tendency.

• 한국전산유체공학회지
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• 제6권3호
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• pp.51-56
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• 2001

As IT(Information Technology) has been developing, an application engineering is advanced so quickly. Especially, CFD field that is influenced greatly by Computing Power is an outstanding example. In this paper, it says a research tendency of the KISTI Supercomputing Center that performs the CFD research based on IT. The representative researches are the National Grid Project, TeraCluster Construction and development and a supporting plan for Supercomputer users' parallelization.