• Elastomers and Composites
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• 제36권4호
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• pp.225-236
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• 2001

2원, 3원 공중합 점착제의 물성을 향상시키기 위해 4인 공중합체를 단량체의 종류와 농도, 개시제의 종류와 농도, 반응온도와 반응시간, 용매의 종류 및 단량체와 용매의 혼합비를 변화시켜 합성하여 점착제의 물성인 점도, 분자량, 전환율, 고형분과 구조분석들을 고찰하였다. 합성한 각 중합체에 내하여 가교제의 종류 및 농도를 변화시켜 점착세의 성능인 점착력. 유지력, 내열성, 내후성, 경시변화를 고찰한 결과, 디음과 같은 결론을 얻었다. 4원 공중합체의 최적 혼합비는 BA/2-EHA/MMA/2-HEMA인 경우, 주단량체인 BA/2-EHA가 80%, 공단량체인 MMA가 15%, 관능성 단량체 2-HEMA가 5%. BA/2-EHA/MMA/AA인 경우, 주단량체인 BA, 2-EHA가 80%, 공단량체인 MMA기 15%, 관능성 단량체 AA가 5%이다. 4원으로 합성한 RA/2-EHA/MMA/2-HEMA의 점착제에 가교제로 이소시아네이트가 적합하였으며, BA/2-EHA/MMA/AA인 경우는 가교제로 멜라민계가 적합하고 점착력의 경시변화는 가교제로 이소시아네이트(PTDI)나 멜라민계 모두 균일하있으며, 내후성 시험후에 표면관찰을 하면 멜라민계는 점착제 잔유물이 남아있어 불안정했고, PTDI는 점착제 잔유물이 전혀 없이 안정성이 우수하였다.

• Korean Chemical Engineering Research
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• 제53권1호
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• pp.46-52
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• 2015

A leaching kinetics was conducted for the purpose of recovery of praseodymium in sulfuric acid ($H_2SO_4$) from REE slag concentrated by the smelting reduction process in an arc furnace as a reactant. The concentration of $H_2SO_4$ was fixed at an excess ratio under the condition of slurry density of 1.500 g slag/L, 0.3 mol $H_2SO_4$, and the effect of temperatures was investigated under the condition of 30 to $80^{\circ}C$. As a result, praseodymium oxide ($Pr_6O_{11}$) existing in the slag was completely converted into praseodymium sulfate ($Pr_2(SO_4)_3{\cdot}8H_2O$) after the leaching of 5 h. On the basis of the shrinking core model with a shape of sphere, the first leaching reaction was determined by chemical reaction mechanism. Generally, the solubility of pure REEs decreases with the increase of leaching temperatures in sulfuric acid, but REE slag was oppositely increased with increasing temperatures. It occurs because the ash layer included in the slag is affected as a resistance against the leaching. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction was determined to be $9.195kJmol^{-1}$. In the second stage, the leaching rate is determined by the ash layer diffusion mechanism. The apparent activation energy of the second ash layer diffusion was determined to be $19.106kJmol^{-1}$. These relative low activation energy values were obtained by the existence of unreacted ash layer in the REE slag.

• 산업경영시스템학회지
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• 제39권2호
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• pp.82-87
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• 2016

As contemporary society has become more complicated, specialized, and segmented, people are experiencing more diverse types of stress. In particular, while several factors associated with job stress have been examined among nurses, who belong to a professional group, the existing research has made no quantitative assessments of stress that reflect temporal differences in individuals. Therefore, the aim of this study is to understand the effects of job stress on alpha-amylase with regard to the working hours of nurses, to assess the variations in jobs stress over time, and provide basic data to improve the quality of nursing services. Ninety nurses working in three shifts in general, emergency, and intensive care wards of a university hospital in D City participated in this study. Salivary alpha-amylase (SAA) was extracted and analyzed at two-hour intervals from 07:00 to 15:00 from nurses on the day shift and from 23:00 to 07:00 from those working the night shift. The SAA level was highest between 23:00 and 01:00 for nurses in general wards ($mean{\pm}S.D.\;39.00{\pm}14.88$) and between 11:00 and 13:00 for those in both intensive care units and emergency wards ($mean{\pm}S.D.\;67.50{\pm}62.93$ and $mean{\pm}S.D.\;39.67{\pm}35.96$, respectively). The characteristic variation in SAA was significant between 23:00 and 01:00 (p < 0.01) and for those in their fifties or older (p < 0.01). The activation ratio of alpha-amylase, a stress reactant, showed an increase when the sympathetic nervous system was activated by mental stress; in addition, job stress was manifested with the effect of awakening at different time segments and at different ages among the nurses. With the aim of raising the level of service based on the nurses maintaining their mental health, it is necessary to focus sharply on the time segment for critical control and to conduct repetitive studies to determine the divisions of eustress critical values as well as to expand the population.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.363-363
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• 2014

Ruthenium (Ru) has attractive material properties due to its promising characteristics such as a low resistivity ($7.1{\mu}{\Omega}{\cdot}cm$ in the bulk), a high work function of 4.7 eV, and feasibility for the dry etch process. These properties make Ru films appropriate for various applications in the state-of-art semiconductor device technologies. Thus, it has been widely investigated as an electrode for capacitor in the dynamic random access memory (DRAM), a metal gate for metal-oxide semiconductor field effect transistor (MOSFET), and a seed layer for Cu metallization. Due to the continuous shrinkage of microelectronic devices, better deposition processes for Ru thin films are critically required with excellent step coverages in high aspect ratio (AR) structures. In these respects, atomic layer deposition (ALD) is a viable solution for preparing Ru thin films because it enables atomic-scale control of the film thickness with excellent conformality. A recent investigation reported that the nucleation of ALD-Ru film was enhanced considerably by using a zero-valent metallorganic precursor, compared to the utilization of precursors with higher metal valences. In this study, we will present our research results on the synthesis and characterization of novel ruthenium complexes. The ruthenium compounds were easy synthesized by the reaction of ruthenium halide with appropriate organic ligands in protic solvent, and characterized by NMR, elemental analysis and thermogravimetric analysis. The molecular structures of the complexes were studied by single crystal diffraction. ALD of Ru film was demonstrated using the new Ru metallorganic precursor and O2 as the Ru source and reactant, respectively, at the deposition temperatures of $300-350^{\circ}C$. Self-limited reaction behavior was observed as increasing Ru precursor and O2 pulse time, suggesting that newly developed Ru precursor is applicable for ALD process. Detailed discussions on the chemical and structural properties of Ru thin films as well as its growth behavior using new Ru precursor will be also presented.

• 한국세라믹학회지
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• 제41권7호
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• pp.518-527
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• 2004

본 연구에서는 다공성 알루미나 기판의 기공 형상 개질을 통해서 필터의 집진 효율, 성능 및 내구성 향상을 위한 공정에 대해서 다루었다. 탄화규소 휘스커를 통한 기공 개질을 위해서 모재의 표면뿐만 아니라 기공 내부에까지 균일한 탄화규소 휘스커를 얻고자 화학 기상 침착법(Chemical Vapor Infiltration： CVI)을 사용하여 실험을 진행하였다. 실험결과 증착 온도와 증착 위치 및 입력 기체비와 같은 공정 조건의 변화에 따라 증착 경향에 확연한 차이를 나타내는 것을 알 수 있다. 다시 말해 첫째, 시편의 관찰 위치가 표면에서 내부로 들어갈수록 “반응 기체의 고갈 효과”로 인해 휘스커가 점점 세선화 되는 것을 볼 수 있으며 두 번째로 증착 온도에 따라서 debris, whisker, film등과 같이 증착물의 형상이 변화하게 된다. 이러한 형상의 변화는 여러 가지 물성의 변화를 가져오게 되는데 그 중에서, film이 증착 되는 경우에는 기판의 강도가 박 115.7% 가량 현저하게 증가하는 반면에 비표면적과 기체 투과율은 감소하게 되지만, 휘스커의 경우에는 강도가 95%, 비표면적은 33.5% 정도가 증가하며 기체 투과율 감소를 최소화 할 수 있다. 따라서 다공성 알루미나 기판 내부 기공에 휘스커를 증착 하면 필터로 인한 압력 저하를 최소화하면서 기공의 크기보다 작은 미세 분진들을 걸러 낼 수 있게 되므로 차세대 필터 재료로 기대된다.

• 한국자기학회지
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• 제9권2호
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• pp.78-84
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• 1999

고온연소합성법(self-propagating high temperature synthesis)을 이용하여(Ni, Zn)Fe2O4 분말을 제조하고 초기 분말의 크기와 산소압에 따른 생성물의 미세조직과 자기적 특성을 조사하였다. (Ni, Zn) 페라이트 분체는 다양한 입도의 Fe, Fe2O3, NiO, ZnO의 원료 분말을 n-hexane 용액에서 습식으로 spex mill을 사용하여 5분 혼합하고 12$0^{\circ}C$ 진공로에서 24시간 건조한 후 0.5~10기압의 산소압에서 고온연소합성 반응으로 제조하였다. 성형 압력이 없는 경우 평균 연소온도와 연소속도는 최대 약 125$0^{\circ}C$와 9.8mm/sec였으며 산소압과 ZnO입도가 감소하면 감소하였다. 고온연소합성된 시료는 다공질 구조를 갖고 있으며 X-선 회절 시험으로 시편들의 spinel구조를 관찰하였다. ZnO입도와 산소압이 증가하면 보자력, 최대자화, 잔류자화, 각형비 및 큐리 온도는 각각 13.24Oe, 43.88emu/g, 1.27emu/g, 0.0034emu/gOe, 37.8$^{\circ}C$에서 11.83Oe, 68.87emu/g, 1.23emu/g, 0.00280emu/gOe, 439.$^{\circ}C$와 7.99Oe, 75.84emu/g, 0.791emu/g, 0.001937emu/gOe, 53.8$^{\circ}C$로 변화하였다. 산소압에 따른 겉보기 활성화에너지를 고려하면 페라이트의 연소합성 반응은 ZnO입도와 산소압에 크게 의존한다.