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오수환,이철욱,김기수,고현성,박상기,박문호,이지면,Oh Su Hwan,Lee Chul-Wook,Kim Ki Soo,Ko Hyunsung,Park Sahnggi,Park Moon-Ho,Lee Ji-Myon 한국광학회 2004 한국광학회지 Vol.15 No.5
본 논문에서는 저 전류 및 고 효율로 동작하는 planar buried heterostructure(PBH) 구조로 sampled grating(SG) distributed bragg reflector(DBR) laser diode(LD)를 처음으로 설계하고 제작하였다. 특히 활성층과 도파로층의 높은 결합 효율을 얻기 위해 건식 식각과 습식 식각을 같이 사용하여 결함이 거의 없는 butt-coupling(BT) 계면을 형성하였다. 제작된 파장 가변레이저의 평균 발진 임계전류는 약 12 mA로 ridged waveguide(RWG)와 buried ridge stripe(BRS) 구조로 제작된 결과 보다 두 배 정도 낮게 나타났으며, 광 출력은 200 mA에서 약 20 mW 정도로 RWG 와 BRS 보다 각각 9 mW, 13 mW 더 우수하게 나타났다. 그리고 파장 가변 영역을 측정한 결과 44 nm로 설계결과와 일치하였으며, 최대 파장 가변 영역 안에서 출력 변화 폭이 5 dB 이내로서 RWG 구조의 9 dB보다 출력변화 폭이 4 dB 적게 나타났다. 전체 파장 가변 영역에서 SMSR이 35 dB 이상으로 나타났다. We have fabricated and designed wavelength-tunable sampled grating distributed Bragg reflector laser diodes(SGDBR-LD) by using, for the first time, planar buried heterostructures(PBH). The diodes have low threshold current values and high-performance of laser operation. Growth condition using metal organic chemical vapor deposition(MOCVD) was optimized for the formation of a good butt-coupling at the interface. A maximum output power of the fabricated device was 20 mW under 200 mA continuous wave(CW) operation at $25^{\circ}C$. Average threshold current and voltage were 12 mA and 0.8 V, approximately. This output power is higher than those of ridge waveguide(RWG) and buried ridge stripe(BRS) structures by amounts of 9 mW and 13 mW, respectively. We obtained a tuning range of 44.4nm which is well matched with the target value of our design. The side mode suppression ratio of more than 35 dB was obtained for the whole tuning range. Optical output power variation was less than 5 dB, which is 4 dB smaller than that of RWG structures.
주의력결핍 과잉행동장애 환아들의 인지 행동적 특성과 정량 뇌파와의 관계 : 후향적 단면 연구
오수환(Soohwan Oh),정유숙(Yoo Sook Joung),윤희준(Hee Joon Yoon),이동익(Dong Ik Lee),김병욱(Byung Wook Kim),박정아(Jung Ah Park),이서지(Suzie Lee),이빛나(Bitna Lee) 대한신경정신의학회 2018 신경정신의학 Vol.57 No.3
Objective This study examined the association between the wave form in quantitative electroencephalography (QEEG) and the cognitive and behavioral characteristics measured by the Korean version of Wechsler Intelligence Scale for Children 4th edition (K-WISC-IV), Korean version of the attention deficit/hyperactivity disorder Rating Scale (K-ARS), and Korean version of Child Behavior Checklist (K-CBCL) in children diagnosed with ADHD. Method A retrospective cross-sectional study was performed on children aged 8 to 13 years, who were diagnosed with ADHD at Samsung Medical Center from November 2011 to March 2017. A total of 57 ADHD children were selected by a medical chart review. Their QEEG findings and psychological test results, including K-WISC-IV, K-CBCL, and K-ARS (n=42), were collected. The QEEG was analyzed by the ranges of Hz: delta (1 - 4 Hz), theta (4 - 8 Hz), alpha (8 - 12 Hz), and beta (12 - 25 Hz) and transformed to the z-scored relative power. The collected data were analyzed using Pearson and Partial correlation analysis. Results The Letter-Number Sequencing scores of K-WISC was positively correlated with fronto- central alpha. The hyperactivity/impulsivity scores of K-ARS were positively correlated with the theta/beta ratio. Among the items of K-CBCL, social immaturity was positively correlated with delta and theta, and negatively correlated with alpha. Social competence was negatively correlated delta and theta, and positively correlated with alpha. Conclusion These results suggest that the resting state QEEG results of children with ADHD may reflect their cognitive and behavioral characteristics, especially in working memory/executive function, hyperactivity/impulsivity, and sociality.
멜론(Cucumis melo L.) 수확 후 관리기술 최근 연구 동향
오수환 ( Su Hwan Oh ),배로나 ( Ro Na Bae ),이승구 ( Seung Koo Lee ) 한국식품저장유통학회(구 한국농산물저장유통학회) 2011 한국식품저장유통학회지 Vol.18 No.4
Among Cucubitaceae, melon (Cucumis melo) is one of the most diversified fruits, with various forms, sizes, pulps, and peel colors. In addition, it is a commercially important crop because of its high sweetness, deep flavor, and abundant juice. In the species, there are both climacteric and non-climacteric melons depending on the respiration and ethylene production patterns after harvest. Ethylene is also considered a crucial hormone for determining sex expression. Phytohormones other than ethylene interact and regulate ripening. There are some indices that can be used to evaluate the optimum harvest maturity. The harvest time can be estimated after the pollination time, which is the most commonly used method of determining the harvest maturity of the fruit. Besides the physiological aspects, the biochemical alterations, including those of sweetness, firmness, flavor, color, and rind, contribute to the overall fruit quality. These changes can be categorized based on the ethylene-dependent and ethylene-independent phenomena due to the ethylene-suppressed transgenic melon. After harvest, the fruits are precooled to 10℃ to reduce the field heat, after which they are sized and packed. The fruits can be treated with hot water (60℃ for 60 min) to prevent the softening of the enzyme activity and microorganisms, and with calcium to maintain their firmness. 1-methylenecyclopropene (1-MCP) treatment also maintains their storability by inhibiting respiration and ethylene production. The shelf life of melon is very short even under cold storage, like other cucurbits, and it is prone to obtaining chilling injury under 10℃. In South Korea, low-temperature (10℃) storage is known to be the best storage condition for the fruit. For long-time transport, CA storage is a good method of maintaining the quality of the fruit by reducing the respiration and ethylene. For fresh-cut processing, washing with a sanitizing agent and packing with plastic-film processing are needed, and low-temperature storage is necessary. The consumer need and demand for fresh-cut melon are growing, but preserving the quality of fresh-cut melon is more challenging than preserving the quality of the whole fruit.