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리튬이차전지용 정극활물질 LiNi1-xCoxO2 의 제조 공정에 따른 전기화학적 특성
고영욱,김현중,이철태,김홍철,엄의흠 한국공업화학회 2000 응용화학 Vol.4 No.2
To improve the electrochemical characteristics of positive electrode in lithium secondary battery, synthesized LiNi_(1-x)Co_xO₂ by sol-gel method and emulsion-drying method. The optimal synthesis conditions and the electrochemical characteristics of LiNi_(1-x)Co_xO₂ with variation of x were studied. Synthesized by sol-gel and emulsion-drying method at the optimal conditions, the hexagonal lattice parameter c increased with increasement of x. Therefore, Ni rich samples showed good cycle-life characteristics and high coulomb efficiency than Co rich samples and Co rich samples showed higher initial discharge capacity than Ni rich sample.
고영욱,염승호 한국생물공학회 2017 Biotechnology and Bioprocess Engineering Vol.22 No.4
Biodiesel was produced using waste coffee grounds (WCGs) via a two-step process comprising lipid extraction and subsequent transesterification steps. Each step was statistically analyzed, and optimum conditions for each step were suggested. WCGs were found to have 16.4% lipid content with 1.9% free fatty acid (FFA) content. The liquid-solid ratio (LSR) significantly influenced lipid extraction from WCGs, while extraction time and temperature did not; 92.7% of lipid extraction efficiency was achieved at 13.7 mL-hexane/g-WCGs, 30 min of extraction time, and 25°C. Owing to the relatively low FFA content, an alkaline catalyst (NaOH) reaction was used that requires less amount of catalyst, methanol, and shorter reaction time compared to an acid catalyst reaction. Reaction time and temperature were the major factors affecting biodiesel conversion, and 94.0% of biodiesel conversion was obtained at optimum conditions for transesterification: 0.5% catalyst, 1.5 mLmethanol/ g-lipid, 45°C, and 9 h of reaction time. With the use of statistical analysis tools, high lipid extraction efficiency and biodiesel conversion were achieved at relatively mild conditions, which would reduce biodiesel production cost substantially.
고영욱,성건희,김정하,Ko, Young-Wook,Sung, Gun-Hee,Kim, Jeong-Ha 한국조류학회(藻類) 2008 ALGAE Vol.23 No.4
To estimate seaweed biomass or standing crop, a nondestructive sampling can be beneficial because of not much destroying living plants and saving time in field works. We suggest a methodological procedure to estimate seaweed biomass per unit area in marine benthic habitats by using species-specific regression equations. Percent cover data are required from the field samplings for most species to convert them to weight data. However, for tall macroalgae such as kelps we need density data and their size (e.g., size class for subtidal kelps) of individuals. We propose that the field sampling should be done with 5 replicates of 50 cm x 50 cm quadrat at three zones of intertidals (upper, middle, lower) and three depth points (1, 5, 10 m) in subtidals. To obtain a reliable regression equation for a species, a substantial number of replicate is necessary from destructive samplings. The regression equation of a species can be further specified by different locality and different season, especially for the species with variable morphology temporally and spatially. Example estimation carried out in Onpyung, Jeju Island, Korea is provided to compare estimated values with real weight data.
Biodiesel production from the mixture of renewable biomass
고영욱,염승호 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.0
Biodiesel is a renewable and carbon-neural fuel. As the production of biodiesel grows, the price of feedstock has risen continuously. Microalgae, sewage sludge and waste coffee ground are considered as alternative feedstock of biodiesel. The two-step process, lipid extraction followed by the transesterification of the lipid with methanol, was adopted in this study for biodiesel production. The lipid compositions of these feedstock were very similar. Alkali catalyst was better than acid one in the biodiesel production from waste coffee ground while acid catalyst was better for microalgae and sewage sludge. The biodiesel production from the mixture of two or three biomass was also investigated under alkali or acid catalyst. The mixing ratio of these biomass was found to influence biodiesel conversion. The sequential reaction under alkali and acid catalyst (or reverse order) resulted in an slight increase in biodiesel conversion. We finally suggested the optimal reaction condition with respect to the mixing ratio of these biomass.
언더필이 적용된 $\mu$p BGA 솔더 접합부의 열피로특성
고영욱,김종민,이준환,신영의 대한용접접합학회 2003 대한용접·접합학회지 Vol.21 No.4
There have been many researches for small scale packages such as CSP, BGA, and Flipchip. Underfill encapsulant technology is one of the latest assembly technologies. The underfill encapsulant could enhance the reliability of the packages by flowing into the gap between die and substrate. In this paper, the effects of underfill packages by both aspects of thermal and mechanical reliabilities are studied. Especially, it is focused to value board-level reliability whether by the underfill is applied or not. First of all, The predicted thermal fatigue lifes of underfilled and no underfilled $\mu$ BGA solder joints are performed by Coffin-Manson's equation and FEA program, ANSYS(version 5.62). Also, the thermal fatigue lifes of $\mu$ BGA solder joints are experimented by thermal cycle test during the temperature, 218K to 423k. Consequently, both experimental and numerical study show that $\mu$ BGA with underfill has over ten times better fatigue lift than $\mu$ BGA without underfill.
고영욱,김성곤,김환용 한국음향학회 1999 韓國音響學會誌 Vol.18 No.1
본 논문에서는 HDTV 비디오 신호를 처리함에 있어 신호의 병목현상을 없애주고 신호의 원활한 처리를 위해 새로운 알고리듬을 적용하여 54MHz의 동작 주파수를 갖는 패커를 제안하고 설계하였다. 또한 제안된 패커의 성능을 검증하기 위해 조합논리를 이용한 ROM 테이블 구조를 갖는 DCT 계수 부호화부를 함께 설계하므로써 DCT 계수 부호화부의 출력을 제안된 패커의 입력 데이타로 사용하였다. 본 논문의 회로는 VHDL 코드를 이용하였고 SYNOPSYS tool의 $0.65{\mu}m$ 공정을 이용한 모델링과 시뮬레이션을 수행하였다. In this thesis, a packer is proposed and designed for removing the bottle-neck effect and easy signal processing using a new algorithm with the operation frequency of 54MHz. To verify the performance of the proposed packer, DCT coefficient encoding block with ROM table using a combinational logic is designed and its output data are used the input data of the packer. Circuits in this thesis are designed by using VHDL code and its modeling and simulation are performed by SYNOPSYS tool using $0.65{\mu}m$ rule.
한국연안 해조류 생물량의 연간 변동 양상: 제주도 문섬지역
고영욱,성건희,이창호,김현희,최동문,고용덕,이욱재,고형범,옥정현,정익교,김정하,Ko, Young-Wook,Sung, Gun-Hee,Yi, Chang-Ho,Kim, Hyun-Hee,Choi, Dong-Mun,Ko, Yong-Deok,Lee, Wook-Jae,Koh, Hyoung-Bum,Oak, Jung-Hyun,Chung, Ik-Kyo,Kim, Jeong-H 한국조류학회(藻類) 2008 ALGAE Vol.23 No.4
Seaweed biomass was estimated using a nondestructive method in the rocky subtidal zones in Munseom, Jeju Island, Korea from July 2006 to April 2008. Seasonal samplings were done at the depth of 1, 5, 10 m using 50 x 50 cm quadrat. Mean biomass was comprised of 2,784 g wet wt m$^{-2}$ and the biomass values varied seasonally from 1,176 g wet wt m$^{-2}$ to 4,217 g wet wt m$^{-2}$ with the highest point in April. Biomass reached maximum at 5 m depth in spring, but was shifted to 10 m depth in summer. Common seaweeds appeared year round in Munseom were Codium minus, Ecklonia cava, Sargassum spp., articulated corallines and Plocamium telfairiae. Among them, E. cava showed the highest biomass (average of 1,288 g wet wt m$^{-2}$), comprising 4% of total biomass. Only 12 species’' biomass covered 98% of total value, which indicated the contribution of few common species to algal community. Seaweed biomass in Munseom represented one of the highest values in coastal regions in Korea.