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심상은,김경희,남정훈,백성현,이강석,박수진 한국고분자학회 2015 Macromolecular Research Vol.23 No.5
Multi-walled carbon nanotubes (MWCNTs) were uniformly coated with silica using polyethyleneimine (PEI) as a coupling agent without subjecting the surfaces of the MWCNTs to chemical modification, such as an amine treatment or chemical oxidation. PEI was physically adsorbed onto the MWCNTs, and the silica coating process was performed through a sol-gel reaction of tetraethyl orthosilicate (TEOS) in ethanol under base catalytic conditions at room temperature. PEI was the best coupling agent for coating silica on MWCNTs among the various amphiphilic polymers and surfactant tested, which included Triton X-100, polyvinylpyrrolidone, polyethylene glycol, and sodium dodecyl sulfate. During the sol-gel process using PEI as a coupling agent, silica could be uniformly formed on MWCNTs without any structural defects. As the amount of TEOS used was increased, the thickness of coated silica layer and electrical resistivity of MWCNTs also increased (up to 5.3×1010 Ω sq-1) owing to the high surface coverage of silica on the MWCNTs.
질화갈륨 기반 청색 고체 발광 다이오드에서의 스트레스 영향 해석
심상균,이준기,김영만 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.6
It was proven that the light outputs of blue GaN-based light-emitting diodes (LEDs) was seriously influenced by the application of external stress. We have simulated the wave function overlap of an electron and hole, which are significantly reduced by the development of stress. Consequently, its internal quantum efficiency decreased from 67.0% to 37.5%. To experimentally investigate the effect of stress, we designed and prepared a special zig system. By applying external tensile stress to compensate for the compressive stress innately developed in Blue LEDs, it was found that the optical output was greatly enhanced from 83.1 mcd to 117.2 mcd at a current of 100 mA, an increase of approximately 41%. In contrast, when the compressive stress is developed more by external compressive stress, we observed that the light output power was reduced from 89.0 mcd to 80.7 mcd, a decrease of approximately 9.3%. 본 논문에서는 질화 갈륨 기반 청색 고체 발광 다이오드가 외부 스트레스에 의해 광출력이 매우 심각하게 저하됨을 명백하게 증명하였다.우리는 전자와 홀의 파동함수 중첩이 스트레스 발달에 의해 현저하게 감소됨에 따라 내부 양자효율이 67.0%에서 37.5%로 감소한다는 것을 시뮬레이션을 통하여 확인하였다. 스트레스의 효과를 실험적으로 확인하기 위해 특수 지그 시스템을 설계하고 제작하였다.질화 갈륨 기반 청색 고체 발광 다이오드에서 발생된 압축응력을 상쇄시키기 위해 인장응력을 외부에서 적용함으로써 광 출력이 100mA 전류에서 83.1mcd에서 117.2mcd로 약 41% 향상된 것으로 나타났다. 반대로 외부에서 압축응력을 적용함에 따라 압축응력이 더 발달할 때 광출력이 89.0mcd에서 80.7mcd로 약 9.3% 감소하는 것을 관찰했다.
심상은,최혁중,강형구,임태호,강보승 대한응급의학회 2010 대한응급의학회지 Vol.21 No.4
Purpose: We use many electronic devices for treating patients in our emergency department. Several studies have reported an association between electromagnetic field exposure and risk of cancer and other diseases. Our purpose was to measure the intensity of power-frequency magnetic fields in the emergency department and evaluate the conditions exceeded regulation guidelines for power-frequency magnetic fields. Methods: Extremely low frequency magnetic fields were measured at 78 ordinary working spots in our tertiary hospital’s emergency department (ED) and evaluated according to national regulatory guidelines and SWEDAC. Each spot was measured four times. During measurement, every electrical device in the emergency department was turned on. Results: The average intensity of the magnetic fields in our emergency department was 0.99±1.27 mG. The maximum intensity was 8.3 mG, which was found in the pediatric section. Conclusion: The power-frequency magnetic field intensities of the various sections of our ED did not exceed national regulatory guidelines. However, pediatric and the minor emergency section showed magnetic fields intensities far above 2 mG. We found these high values outside the pediatric and waiting sections, where the electrical cabinet panel was located. We conclude that the electrical cabinet panel should be shielded and that similar studies are needed for other emergency departments.
Nanosecond Laser Flash Photolysis Study of 5-Styryl-1,3-dimethyluracil
심상철,신은주,채규호,Shim Sang Chul,Shin Eun Ju,Chae Kyu Ho Korean Chemical Society 1985 Bulletin of the Korean Chemical Society Vol.6 No.4
The photoisomerization of 5-styryl-1,3-dimethyluracil is studied with nanosecond laser flash photolysis technique at room temperature. The laser flash photolysis of E-isomer produces the transient absorption spectrum regarded as the triplet-triplet absorption, but the transient absorption of Z-isomer does not show the typical decay curve, probably due to the facile photocyclization reaction during the laser flash photolysis. Using the energy transfer method on nanosecond laser spectroscopy, the energy of the lowest triplet state for E isomer is estimated to lie between 41.8 and 47 kcal/mol. The triplet lifetime for E-isomer obtained from the decay curve of the transient absorption is ca. 93ns. The $S_1 → T_1$ intersystem crossing of E-isomer on direct excitation is relatively inefficient at room temperature supporting the singlet mechanism for direct photoisomerization.