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김민상,이동윤,한천구 청주대학교 산업과학연구소 2017 産業科學硏究 Vol.35 No.1
This study aimed to analyzed the refining methods and replacement ratios of desulfurized gypsum from high volume blast furnace slag mortar and the engineering characteristics of cement mortar in relation to aggregate kinds. As factors of the experiment, in case of desulfurized gypsum depending on the refining method Raw material, 0.3 mm Sieving, 500℃ Heating were used, and the replacement ratios were set at 5 levels of 0, 5, 10, 15, and 20 %. For aggregate kinds, natural fine aggregate and recycled fine aggregate were used and compared, respectively. Overall, the best refining method of desulfurized gypsum was found to be 0.3 mm sieving analysis and within 5 % of replacement ratios the aggregate was best for natural fine aggregate considering flow, air contents, and compressive strength
측정 데이터를 이용한 빔형성기의 적용에 의한 수중 채널 환경에서의 상관 대역폭 분석
김민상,조대영,김계원,이태석,박종원,임용곤,고학림,Kim, Min-Sang,Cho, Dae-Young,Kim, Kye-Won,Lee, Tae-Seok,Park, Jong-Won,Lim, Yong-Gon,Ko, Hak-Lim 한국융합신호처리학회 2014 융합신호처리학회 논문지 (JISPS) Vol.15 No.4
수중 채널 환경에서 고속의 데이터를 신뢰성 있게 전송하기 위한 OFDM 시스템에 대한 연구가 활발히 진행 중이다. 또한, OFDM 통신 시스템에서는 각 부반송파의 대역폭을 채널의 상관 대역폭 보다 작게 설정해야지만 수중 채널 환경에 OFDM 통신의 적용에 의한 성능 향상을 기대할 수 있다. 하지만 실제의 수중 채널 환경에서의 상관 대역폭은 수십 Hz로 매우 작기 때문에, 수중 OFDM 통신 시스템 구성 시에 OFDM을 위한 FFT의 크기가 증가하고, 각 부반송파에 실효 지연 확산 이상의 길이를 갖는 주기적 전치 부호를 추가해야하기 때문에 시스템의 복잡도가 증가하고 데이터의 효율이 저하된다. 따라서 본 연구에서는 수중 채널 환경에서 빔형성기의 적용에 의한 상관 대역폭의 증가를 연구하였다. 이를 위해 실제의 수중 채널 환경에서 측정을 수행하고, 측정 데이터를 분석해 봄으로써 수중 채널 환경에서 빔형성기의 적용에 의한 상관 대역폭의 증가 정도를 분석하였다. 분석 결과 수중 채널 환경에 빔형성기를 적용하는 경우 상관대역폭이 단일 센서를 사용하는 경우에 비해 크게 증가함을 알 수 있었다. The OFDM system have been widely studied for the purpose of increasing data rate with more reliable communications in underwater channel environments. And it is possible only when the sub-carrier's bandwidth is smaller than the coherence bandwidth of channel in the underwater OFDM communication system. However, the size of the FFT for the OFDM system will be increased because the coherence bandwidth is as small as several tens of Hz in real underwater channel environments. Also, It is necessary to add a CP having a length longer than the rms delay spread of a channel. So the complexity of the system is increased and the data efficiency is reduced. Therefore, in this paper, we have studied the increase of the coherence bandwidth by adapting the beamforming technologies. To do this, we have collected data from real underwater channel environments and analyzed the coherence bandwidth when adapting the beamforming technologies. Analyzing the experimental data show that the coherence bandwidth by the beamforming technologies in underwater channel environments was greatly increased compared to that of a single sensor.
GOCI-II 태양광 보정시스템을 활용한가시 채널 복사 보정 개선 및 센서 안정성 분석
김민상,박명숙,안재현,강금실 대한원격탐사학회 2023 大韓遠隔探査學會誌 Vol.39 No.6
Radiometric calibration is a fundamental step in ocean color remote sensing since the step toderive solar radiance spectrum in visible to near-infrared wavelengths from the sensor-observedelectromagnetic signals. Generally, satellite sensor suffers from degradation over the mission period, whichresults in biases/uncertainties in radiometric calibration and the final ocean products such as water-leavingradiance, chlorophyll-a concentration, and colored dissolved organic matter. Therefore, the importance ofradiometric calibration for the continuity of ocean color satellites has been emphasized internationally. Thisstudy introduces an approach to improve the radiometric calibration algorithm for the visible bands of theGeostationary Ocean Color Imager-II (GOCI-II) satellite with a focus on stability. Solar Diffuser (SD)measurements were employed as an on-orbit radiometric calibration reference, to obtain the continuousmonitoring of absolute gain values. Time series analysis of GOCI-II absolute gains revealed seasonalvariations depending on the azimuth angle, as well as long-term trends by possible sensor degradationeffects. To resolve the complexities in gain variability, an azimuth angle correction model was developedto eliminate seasonal periodicity, and a sensor degradation correction model was applied to estimate nonlineartrends in the absolute gain parameters. The results demonstrate the effects of the azimuth anglecorrection and sensor degradation correction model on the spectrum of Top of Atmosphere (TOA) radiance,confirming the capability for improving the long-term stability of GOCI-II data.
Endosomal pH-destabilized PGA-PCL block copolymer micelle
김민상,카살라,Guang Jin Im,김봉섭,Doo Sung Lee 한국생체재료학회 2009 생체재료학회지 Vol.13 No.3
Poly(L-glutamic acid)-poly(ε-caprolactone) diblock copolymers were prepared using ring opening polymerization. The diblock copolymers were characterized by 1H-NMR, gel permeation chromatography and FT-IR. Endosomal pH-destabilized nanoparticles were prepared from dialysis method and their micellar structure was confirmed by dynamic light scattering and transmission electron microscopy. In this study, the method of fabrication and pHdependent structural changes of the diblock copolymer were investigated. pH-Dependent changeable nanoparticles may be helpful for intracellular delivery in drug delivery systems.