목 적: 하드코팅과 광변색 코팅을 동시에 실시하여 제조한 광변색 렌즈에 대한 퇴색속도 중심으로 광학 적 특성을 조사하여 비교하고자 하였다. 방 법: Tetraethyl orthosilicate와 3-glycidoxypropyltrimethoxysilane로 조성된 하드코팅 액에 적, 황, 청색의 광변색 물질을 각각 혼합하고, 플라스틱 안경렌즈 표면에 플로우 코팅 후 열경화하였다. 코팅된 광변색 렌즈의 표면 물성과 광학적 특성을 평가하였다. 결 과: 광변색 코팅 렌즈는 우수한 부착력과 무코팅 렌즈보다 강한 표면 경도로 하드코팅의 특성을 보였 다. 광변색 코팅 렌즈의 최대흡광도(λmax)는 적색, 황색, 청색 렌즈에서 각각 499, 418, 606 nm이었으며, 이를 기준으로 반감기에 의한 퇴색속도는 청, 적, 황색의 변색 렌즈 순으로 각각 204, 416, 670 sec이었다. 코팅 렌즈의 퇴색속도는 spironaphthoxazine계인 청색이 naphthopyran계인 적색과 황색보다 빨랐고, 동일 계열에서도 폐환상태의 열적 안전성이 클수록 빠르게 평가되었다. 결 론: 광변색 코팅 렌즈의 퇴색속도는 열적으로 안정한 상태로 가역하려는 광변색 물질의 특성에 따라 달라진다. 따라서 광변색 코팅에서 코팅 성분보다 광변색 물질이 갖는 고유의 퇴색속도를 우선적으로 고려 하여야 할 것이다.

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

A magenta azomethine dye(D) was synthesized from the reaction of 3-methyl-1-phenyl-2-pyrazoline-5-one with N,N-diethyl-1,4-phenylenediamine. The magenta azomethine dye was identified on the basis of elemental analysis, 13C-NMR, infrared, and GC/MS studies. The magenta azomethine dye was decomposed in a basic solution. Rate constants of the fading reaction of magenta azomethine dye in ethanol-water solvent were measured spectrophotometrically at 540 nm. Reaction rate was increased with the increase of [OH-] and [H2O] in the region of [H2O]= 11～40 M. The reaction was governed by the following rate law. -d[D]/dt = {ko + kOH[OH-][H2O]}[D] A possible mechanism consistent with the empirical rate law has been proposed.