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김현기,김준형,안상현 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.72 No.-
High oxygen-vacancy ratio has been recognized as an important criterion for oxygen evolvingelectrocatalysts to achieve high catalytic performance. Herein, we report changes in the oxygen-vacancyratio during long-term stability tests. NiFe-based electrocatalysts containing various anions wereprepared by a simple electrodeposition. After the fabrication procedure was optimized, the S-doped NiFeoxide electrocatalyst exhibited higher intrinsic activity than others in an alkaline electrolyte because ithad the highest oxygen-vacancy ratio. During oxygen evolution at a constant positive potential, theintrinsic activity of the S-doped NiFe oxide electrocatalyst showed a significant correlation with theoxygen-vacancy ratio and surface morphology as a function of time.
김현기,김은혜,김성수 한국고분자학회 2018 Macromolecular Research Vol.26 No.5
Clay platelets have been used to make clay polymer nanocomposite (CPN) in order to enhance the barrier properties of plastic substrates and sputtered barrier films. Clay platelets tend to be randomly dispersed and should be oriented in the film direction to achieve effective barrier properties. In this work, well-oriented nanocomposites were prepared on substrates by adopting a dry lamination process between two heated rubber rolls during the curing step. Dry lamination enabled the clay platelets to be oriented upon application before the sample was completely cured, and the final curing step froze the structure to maintain the orientation. The dry lamination time was optimized at a maximum peak of isothermal curing reaction using DSC. Through characterization via XRD and TEM, it was confirmed that clay platelets are well dispersed and exfoliated in the CPN. The CPN with highly oriented clay platelets enhanced the barrier properties to reach a water vapor transmittance rate of 5.5×10-4 g/m2/day, while maintaining optical properties.
Electrodeposited rhenium–cobalt alloy with high activity for acidic hydrogen evolution reaction
김현기,김준형,한경호,Wenwu Guo,홍석진,박주혜,안상현 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.95 No.-
The development of high-performance electrodes for hydrogen evolution reaction (HER) is essential forcommercialization of water electrolyzers. Among the promising candidate for HER catalyst, Re and itsoxide display an optimal hydrogen binding energy to that of Pt. Nevertheless, only a few studies havereported the acidic HER catalysts with the high overpotentials (>100 mV at –10 mA cm–2). Furthermore,Re transition metal alloy for the acidic HER catalyst have rarely been reported. Herein, we report a CoRealloy catalyst for the acidic HER, which was fabricated by electrodeposition on carbon paper (CP) bycontrolling the electrodeposition. The optimized CoRe/CP electrode exhibited a higher HER activity thanthose of the other Re-based catalysts with an overpotential of 45.1 mV at10 mA cm–2. The activationenergy for the HER of CoRe/CP, which was calculated from the Arrhenius plot, demonstrated a lower valueof 8.99 kJ mol–1 K–1.
데이터마이닝의 베이지안 망 기법을 이용한 교통수단선택 모형의 설계 및 구축
김현기,김강수,이상민 대한교통학회 2004 대한교통학회지 Vol.22 No.2
데이터마이닝 (Data Mining)은 대용량의 데이터에 존재하는 관계, 패턴, 규칙 등을 효율적으로 탐색하여 이를 모형화함으로써, 유용한 정보로 추출·변환하는 일련의 과정이다. 특히 베이지안 망 (Bayesian Network)은 신경망, 유전자알고리즘, 퍼지이론 등과 더불어 데이터마이닝의 중요한 기법 중의 하나로서, 베이지안 통계 이론 (Bayesian Statistics Theory)를 적용하여 변수들간의 확률적인 관계를 기호화함으로써, 설명변수들과 종속변수들간의 인과관계를 파악할 수 있다.이 연구는 기존에 적용된 바가 없는 데이터마이닝의 베이지안 망을 이용하여 수도권 교통수단선택 모형을 구축한다. 2002년도 수도권 가구통행실태조사 자료의 사회·경제적 특성과 교통체계 특성을 반영하여 베이지안 망을 이용한 교통수단선택 모형을 설계·구축하여, 각 변수들간의 상관관계와 인과관계를 분석함으로써, 설명변수인 성과 연령의 구성비가 변하였을 때, 교통수단선택의 변화율(확률)을 예측한다.이 연구를 통해 현실에서는 내재하나 설명변수간의 복잡한 상관성을 배제하고 설명변수들과 교통수단선택간의 단순한 직선관계를 가정하는 기존 교통수단선택 모형의 한계를 극복할 수 있는 가능성을 제시한다. 또한 선택되지 않은 교통수단에 대한 정보의 부족으로 인한 교통수단선택 모형 구축의 어려움을 극복한다. 또한 다양한 교통정책에 따른 교통수단선택의 변화를 실시간으로 시뮬레이션 할 수 있는 방법론을 개발한다.
스테로이드 치료로 호전된 COVID-19 (BNT162b) 백신 후 세포독성뇌들보병터 환자
김현기,김낙훈,최새미,김아영,최호진 대한신경과학회 2022 대한신경과학회지 Vol.40 No.3
Cytotoxic lesions of the corpus callosum (CLOCC) are secondary lesions on corpus callosum caused by cytokinopathy of callosal neurons and microglia. Fever, headache, and digestive disturbances are common symptoms. Reversible and hyperintense signals on fluid‐attenuated inversion recovery imaging, diffusion‐weighted imaging (DWI) and decreased apparent diffusion coefficient are typical features of magnetic resonance imaging. Herein, we report a rare case of CLOCC caused by COVID19 vaccination (BNT162b) and discharged without no neurologic symptoms due to prompt treatment.
김현기,이현주,임태호,안상현 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.66 No.-
Porous Sn and Sn-based binary catalysts are facilely fabricated by an electrodeposition method. Varying conditions for Sn electrodeposition enables a control of Sn roughness, which exhibits a significant effect on catalytic performance for electrochemical CO2 reduction. At a specific applied potential, the porous Sn catalyst with relative roughness factor of 56.5 demonstrates a HCOOH Faradaic efficiency of 40.7% with a H2/CO ratio of 2.2. Further improvement of the HCOOH Faradaic efficiency to 59.2% is achieved by using a porous Sn0.29In0.71 catalyst. This catalyst also achieves a H2/CO ratio of 2.2, which can be used as syngas to produce value-added hydrocarbons.
Improved Continuous Positive Airway Pressure Adherence with Pillow Height Change: A Case Report
김현기,이정주,김혜윤 대한수면연구학회 2019 Journal of sleep medicine Vol.16 No.2
In this case report, we tried to see the relationship between the continuous positive airway pressure (CPAP) adherence of obstructive sleep apnea (OSA) patient and the height of pillow. The patient was 41-year old female with OSA and had trouble adjusting to CPAP therapy due to the high pressure of the CPAP. We performed a overnight polysomnography for 8 hours in hospital and compared the apnea-hypopnea index (AHI) score and optimal CPAP pressure after changing the height of the pillow. The lower pillow setting had lower AHI score and lower optimal CPAP pressure which made the patient to feel more comfortable while sleeping. In conclusion, height of the pillow deserves consideration as a factor to promote CPAP adherence with lowering pressure, especially in the patients who are suffering with high pressure CPAP therapy.