• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.301-301
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• 2003

In current study, Nanocomposites are reinforced with carbon nanofiber, carbon nanotube and SiC, etc. Since the nano reinforcements have the excellent mechanical, thermal and electrical properties compared with that of existing composites, it has lately attracted considerable attention in the various areas. Cu have been widely used as signal transmission materials for electrical electronic components owing to its high electrical conductivity. However, it's size have been limited to small ones due to its poor mechanical properties. Until now, strengthening of the copper alloy was obtained either by the solid solution and precipitation hardening by adding alloy elements or the work hardening by deformation process. Adding the alloy elements lead to reduction of electrical conductivity. In this aspect, if carbon nanofiber is used as reinforcement which have outstanding mechanical strength and electric conductivity, it is possible to develope Cu matrix nanocomposite having almost no loss of electric conductivity. It is expected to be innovative in electric conducting material market. The unidirectional alignment of carbon nanofiber is the most challenging task developing the cooer matrix composites of high strength and electric conductivity. In this study, the unidirectional alignment of carbon nanofibers which is used reinforced material are controlled by drawing process and align mechanism as well as optimized drawing process parameter are verified via numerical analysis. The materials used in this study were pure copper and the nanofibers of 150nm in diameter and of 10∼20$\mu\textrm{m}$ in length. The materials have been tested and the tensile strength was 75MPa with the elongation of 44% for the copper. it is assumed that carbon nanofiber behave like porous elasto-plastic materials. Compaction test was conducted to obtain constitutive properties of carbon nanofiber Optimal parameter for drawing process was obtained by analytical and numerical analysis considering the various drawing angles, reduction areas, friction coefficient, etc. The lower drawing angles and lower reduction areas provides the less rupture of co tube is noticed during the drawing process and the better alignment of carbon nanofiber is obtained.

• 한국치위생학회지
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• 제12권2호
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• pp.251-260
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• 2012

Objectives : The purpose of this study was to examine the knowledge of people in general about orthodontic treatment and their attitude to that by conducting a survey in a bid to provide information on the improvement of their incorrect awareness of orthodontics and on the development of clinical orthodontic treatment. Methods and Results : The subjects in this study were 389 people in general who resided in Seoul and Gyeonggi Province. A self-administered survey was conducted, and the findings of the study were as follows: 1. As for awareness of orthodontic treatment among the people in general by gender, the women knew better about orthodontic treatment than the men, and the gender gap was significant(p<0.05). 2. Concerning satisfaction with the shape and arrangement of the teeth by age, those who were in their 20s were most satisfied, and the teens were satisfied the least. There were significant gaps according to age (p<0.05). 3. As a result of checking the degree of their inconvenience about the use of chewing teeth by age, the people who were in their 30s felt the most inconvenience, and the gap between them and the others was significant(p<0.01). 4. As a result of asking them whether they had an intention to receive orthodontic treatment, the women had a more intention to do that than the men(p<0.001). By age, the younger respondents had a more intention, and the gaps between them and the others were significant(p<0.001). 5. As a result of analyzing their perception of the positives of orthodontics by gender, the women took a more positive view of it than the men, and their gap was significant(p<0.01). Conclusions : When orthodontic treatment or orthodontic treatment counseling is provided to orthodontic treatment patients or people in general in the field of clinical dentistry, it should be noted that the way patients and people in general look at orthodontic treatment is different according to their age and gender, and they should be informed of the positives of orthodontic treatment to step up the development of orthodontic treatment.

• 대한환경공학회지
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• 제32권5호
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• pp.455-460
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• 2010

본 연구에서는 프탈레이트 화합물 측정 시 시료채취 및 분석과정 증에서 야기될 수 있는 공시료의 오염여부를 평가하고 clean-up 절차와 같은 적절한 개선 방안을 제시하였다. 실험도구 및 시료채취 매체에 대한 공시료를 평가한 결과 많은 종류의 실험기구 및 장치에서 DBP와 DEHP가 잔존하는 것으로 나타났다. 따라서 실험도구는 반드시 전처리하여 사용해야 하며, 이후 공시료 보정이 수반되어야 한다. 또한 본 연구에서 제시한 clean-up 방법을 통해 불순물이 많이 제거되었으며, GC/MS를 이용한 정성?정량분석에서 정도개선에 효과적인 것으로 나타났다.

• Corrosion Science and Technology
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• 제6권6호
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• pp.282-285
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• 2007

Smaller size and higher integration of electronic systems make narrower interconnect pitch not only in chip-level but also in package-level. Moreover electronic systems are required to operate in harsher conditions, that is, higher current / voltage, elevated temperature / humidity, and complex chemical contaminants. Under these severe circumstances, electronic components respond to applied voltages by electrochemically ionization of metals and conducting filament forms between anode and cathode across a nonmetallic medium. This phenomenon is called as the electrochemical migration. Many kinds of metal (Cu, Ag, SnPb, Sn etc) using in electronic packages are failed by ECM. Eutectic SnPb which is used in various electronic packaging structures, that is, printed circuit boards, plastic-encapsulated packages, organic display panels, and tape chip carriers, chip-on-films etc. And the material for soldering (eutectic SnPb) using in electronic package easily makes insulation failure by ECM. In real PCB system, not only metals but also many chemical species are included. And these chemical species act as resources of contamination. Model test systems were developed to characterize the migration phenomena without contamination effect. The serpentine-shape pattern was developed for analyzing relationship of applied voltage bias and failure lifetime by the temperature / humidity biased(THB) test.

• 한국강구조학회 논문집
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• 제20권6호
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• pp.691-700
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• 2008

최근 건축구조물의 구조는 다양한 형태의 복잡한 건축물이 구현되고 있다. 이러한 건축구조물의 복합 다양성은 수평저항력에 효과적 으로 저항하기 위해 강재와 접합부의 요구성능이 점차 중요시되고 있다. 접합부는 형상의 불연속과 응력집중 및 다축응력 등이 발생되는 부분으로 골조전체의 변형능력에 큰 영향을 미치고 강성과 인성을 결정하는 중요부위이다. 본 연구에서는 고강도 고성능강 적용에 대한 인성평가를 위해 구조체의 기둥-보 접합부를 빌트업 H형강의 T형 기둥-보 용접접합부로 제작하여 실대실험을 수행하였다. 실험변수는 응력집중 및 형상의 불연속이 발생되는 보 스캘럽을 중심으로 논스캘럽(Non-Scallop)과 종래형 스캘럽, 개량형 스캘럽으로 제작하여 스캘럽 형상이 접합부의 인성에 미치는 영향과 고강도 고성능강의 건축구조물 적용성을 평가하였다. 기존의 기둥-보 용접접합부에 대한 평가방법을 기초로 최근 개발된 고강도 고성능강의 초고층 건축물 적용을 위한 내진설계 자료를 제시하였다.

• 한국재료학회지
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• 제11권2호
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• pp.82-87
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• 2001

Ti-6Al-2Sn-4Zr-6Mo(Ti6246) 합금의 고온 변형거동을 조사하기 위하여 $\alpha$+$\beta$ 영역 및 $\beta$영역의 온도에서 $10^0s^{-1}$에서 $10^{-3}s^{-1}$의 변형속도로 압축시험을 수행하였다. 유동응력은 변형속도가 증가하고 시험 온도가 감소함에 따라 증가하였다 90$0^{\circ}C$ 이하에서 시험한 결과로부터 얻어진 유동곡선은 가공연화 현상을 나타내었으나, 이 합금의$\beta$영역인 95$0^{\circ}C$ 이상에서는 유동응력이 지속적으로 증가하다가 정상 상태를 나타냈다. 압축시험 결과로부터 얻은 유동곡선 분석을 통하여 유동응력의 변형량, 변형속도 및 온도에 대한 관계로부터 이 합금에 대한 구성방정식을 구하였다.

• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.453-461
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• 2022

A chemically sintered and binder-free paste of TiO₂ nanoparticles (NPs) was prepared using a binary-liquid mixture of 1-octanol and CCl₄. The 1:1 (v/v) complex of CCl₄ and 1-octanol easily interacted chemically with the TiO₂ NPs and induced the formation of a highly viscous paste. The as-prepared binary-liquid paste (P_BL)-based TiO₂ film exhibited the complete removal of the binary-liquid and residuals with the subsequent low-temperature sintering (~150℃) and UV-O₃ treatment. This facilitated the fabrication of TiO₂ photoanodes for flexible dye-sensitized solar cells (f-DSSCs). For comparison purposes, pure 1-octanol-based TiO₂ paste (P_O) with moderate viscosity was prepared. The P_BL-based TiO₂ film exhibited strong adhesion and high mechanical stability with the conducting oxide coated glass and plastic substrates compared to the P_O-based film. The corresponding low-temperature sintered P_BL-based f-DSSC showed a power conversion efficiency (PCE) of 3.5%, while it was 2.0% for P_O-based f-DSSC. The P_BL-based low- and high-temperature (500℃) sintered glass-based rigid DSSCs exhibited the PCE of 6.0 and 6.3%, respectively, while this value was 7.1% for a 500℃ sintered rigid DSSC based on a commercial (or conventional) paste.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.1009-1020
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• 1996

Direct-seeded rice can have comparable yield with transplanted rice if its inherent problems can be solved. It is a labor-saving technology and can significantly reduce production cost because seedling nursery , pulling , and transplanting are omitted. Turnaround time between cropping is reduced hence the possibility of a third annual crop. But direct-seeded rice is very vulnerable to pest attack (by birds, rats, and golden snails), desiccation, weed infestation, and prone to lodging resulting to unstable crop establishment and inconsistent yield. These problems can be solved by anaerobic seeding (sowing pre-germinated seeds under the soil). It requires precise seed placement into the soil to optimize its benefits. We developed a four-row anaerobic direct seeder (US $ 200 commercial price) for this purpose . It consist of a structural framework mounted with a drum -hopper metering device, flotation type drivewheels, spring-loaded and adjustable furrow closers, and furrow open rs, and a plastic rainguard. It can sow in line pre-germinated seeds into the soil thus permitting the use of mechanical weeders for a chemical-free weed control. Its performance was comparable with the Japanese two-row anaerobic seeder (costing US$400) in terms of seed placement and crop establishment. It was tested with five cultivars. Seeding rate varied from 38 kg/ha to 80kg/ha. Crop establishment ranged from 64 to 99 percent while grain yield varied from 3.0 t/ha to 5.4t/ha. A six-row anaerobic seeder was also developed and adapted to a powertiller for increased capacity , field efficiency , and easier operation. The anaerobic seeder is useful to farmers shifting to direct seeding to reduce rice production cost and to researchers conducting agronomic studies in direct-seeded rice. Blueprint of the machine is available free of charge from IRRI.

• 한국화재소방학회논문지
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• 제34권1호
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• pp.11-17
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• 2020

성능위주설계의 설계화원 정보는 피난안전성 평가에 직접적인 영향을 미치기 때문에, 실물화재 실험에 근거한 설계화원의 설정이 매우 중요하다. 복합영상관에 대한 성능위주설계의 신뢰성을 개선시키기 위하여, 상영관 의자에 대한 화재실험을 통해 열발생률과 화재확산속도 등의 화재거동에 관한 정보를 제공한다. 이를 위하여 실제 상영관과 유사하게 배열된 다수의 객석 의자가 적용되었다. 주요 결과로서, 객석의자 1개에 대하여 최대 열발생률과 단위 질량당 발열량은 각각 415~988 kW와 15.2~23.8 MJ/kg의 범위를 갖는다. 신형과 구형 객석의자의 평균 단위 질량당 발열량은 각각 23.6 MJ/kg과 16.7 MJ/kg으로 측정되었다. 즉, 신형의자의 증가된 플라스틱 및 쿠션재의 함량으로 인하여, 신형이 구형에 비해 화재위험성이 높은 것으로 확인되었다. 추가로 객석의자가 일렬로 배치될 때, 점화위치와 상관없이 0.39~0.42 m/min의 화재확산속도가 관찰되었다. 마지막으로 복합영상관의 성능위주설계를 위하여 객석의자의 최대 열발생률과 화재성장률로 구성된 화재성장곡선이 제안되었다.

• 대한화학회지
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• 제57권1호
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• pp.40-51
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• 2013

전기전자 부품 및 제품상에서 주로 사용되는 Plastic 중 함유된 Perfluorooctanesulfonic acid (PFOS)의 정량 분석법을 개발하기 위해 LDPE 시료를 대상으로 soxhlet 용매추출과 액체크로마토그래피/질량분석법(LC/MS)을 사용하여 시험방법 유효화를 진행하였다. 그 결과 검출한계(LOD)와 정량한계(LOQ)는 각각 $2.58{\mu}g/L$, $7.82{\mu}g/L$였으며, 회수율은 96-102%를 나타내었다. LC/MS의 검량선은 $7.82-100{\mu}g/L$ 농도범위에서 $r^2$값 0.9992의 직선성을 확인하였다. 또한 EU 환경규제 대응을 위한 전기전자 제품 중의 PFOS 분석법 표준화를 위해서 국내외 시험기관을 대상으로 비교숙련도 시험을 실시하였다. 그 결과 참여한 10개 시험기관 중 3개 시험기관이 이상값을 제출하였다. 이에 $^{19}F$ 핵자기공명분광분석법($^{19}F$ NMR)을 사용하여 이상값의 원인을 규명한 결과 그 주요 원인이 표준시약 및 시료 중에 존재하는 PFOS 이성질체들에 대한 결과처리의 오류였음을 확인하였다.