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김대식,김민국,김대식 한국연소학회 2023 한국연소학회지 Vol.28 No.3
The fuel conversion for a stationary gas turbine from conventional LNG to hydrogen is recognized as a key technology for carbon neutrality in power generation. However, the present NOx reporting method does not properly evaluate NOx generated from hydrogen combustion. The current standard uses NOx, which has been corrected to the reference oxygen concentration(15%) after complete extraction of H2O from the exhaust gas. For a hydrogen combustion, the concentration of H2O and O2 in the exhaust gas increases more than that of hydrocarbon fuels, resulting in over-reporting the actual NOx emission. In this study, under the operating conditions of hydrogen turbines currently being developed, NOx is calculated to be 39.6% over actual emissions affecting the environment. Therefore, it is very important and urgent to establish a new and appropriate NOx reporting method to accurately consider the characteristics of hydrogen combustion.
Occurrence and Prognosis of Symptomatic Venous Thromboembolism in Colorectal Cancer Surgery Patients
김대식,박근명,원용성,김장용,이진권,김준기,오승택,정상설,강원경 대한혈관외과학회 2014 Vascular Specialist International Vol.30 No.2
Purpose: Colorectal cancer (CRC) has a high risk for postoperative thromboembolic complications such as venous thromboembolism (VTE) compared to other surgical diseases, but the relationship between VTE and CRC in Asian patients remains poorly understood. The present study examined the incidence of symptomatic VTE in Korean patients who underwent surgery for CRC. We also identified risk factors, incidence and survival rate for VTE in these patients Materials and Methods: The patients were identified from the CRC database treated from January 2011 to December 2012 in a single institution. These patients were classified into VTE and non-VTE groups, their demographic features were compared, and the factors which had significant effects on VTE and mortality between the two groups were analyzed. Results: We analyzed retrospectively a total of 840 patients and the incidence of VTE was 3.7% (31 patients) during the follow-up period (mean, 17.2 months). Histologic subtype (mucinous adenocarcinoma) and previous history of VTE affected the incidence of VTE on multivariate analysis. There was a statistically significant difference in survival rate between the VTE and non-VTE group, but VTE wasn’t the factor affecting survival rate on multivariate analysis. Comparing differences in survival rate for each pathologic stage, there was only a significant difference in stage II patients. Conclusion: Among CRC patients after surgery, the incidence of VTE was approximately 3% within 1 year and development of VTE wasn’t a significant risk factor for death in our study but these findings are not conclusive due to our small sample size.
김대식,Dohan Lee,Je-Haeng Lee,변동진 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10
A multi-dimensional zinc oxide (ZnO) hybrid structure was successfully grown on a glass substrateby using metal organic chemical vapor deposition (MOCVD). The ZnO hybrid structure wascomposed of nanorods grown continuously on the ZnO film without any catalysts. The growthmode could be changed from a two-dimensional (2D) film to one-dimensional (1D) nanorods bysimply controlling the substrate’s temperature. The ZnO with a hybrid structure showed improvedelectrical and optical properties. The ZnO hybrid structure grown by using MOCVD has excellentpotential for applications in opto-electronic devices and solar cells as anti-reflection coatings(ARCs), transparent conductive oxides (TCOs) and transparent thin-film transistors (TTFTs).
김대식,김천식,이용석,조천웅 대한임상검사과학회 2011 대한임상검사과학회지(KJCLS) Vol.43 No.2
Mandibular advancement devices (MAD) are therapeutic options for obstructive sleep apnea (OSA). The aim of study was to investigate treatment outcomes of before and after insertion of MAD in OSA patients. We retrospectively selected a total of 13 patients who were diagnosed with OSA syndrome. All sleep-related parameters including apnea-hypopnea index (AHI), oxygen desaturation index (ODI), wake after sleep onset (WASO), total arousal were measured by before and after MAD. The use of MAD proves to be efficient in reducing snoring, apnea-hypopne index (17.2±14.6 vs 20.9±14.6), WASO (27.4±28.8 vs 47.9±43.6 ), oxygen desaturation index (9.0±11.6 vs 16.4±11.7), stage N3 (54.8±45.2 vs 36.6±22.0), REM sleep times (73.3±19.4 vs 66.0±31.0) and increases sleep efficiency (92.6±6.6 vs 87.2±11.2). The decreases in apnea index based on a reduction in the overall and supine AHI values after MAD therapy were significantly greater for the positional OSA than nonpositional OSA patients. The use of MAD proves to be efficient in snoring, WASO, sleep efficiency, reduced AHI and associated with good compliance of patients. .
유기금속화학증착법으로 유리기판 위에 성장된 산화아연 하이브리드 구조의 광학적 전기적 특성
김대식,강병훈,이창민,변동진,Kim, Dae-Sik,Kang, Byung Hoon,Lee, Chang-Min,Byun, Dongjin 한국재료학회 2014 한국재료학회지 Vol.24 No.10
A zinc oxide (ZnO) hybrid structure was successfully fabricated on a glass substrate by metal organic chemical vapor deposition (MOCVD). In-situ growth of a multi-dimensional ZnO hybrid structure was achieved by adjusting the growth temperature to determine the morphologies of either film or nanorods without any catalysts such as Au, Cu, Co, or Sn. The ZnO hybrid structure was composed of one-dimensional (1D) nanorods grown continuously on the two-dimensional (2D) ZnO film. The ZnO film of 2D mode was grown at a relatively low temperature, whereas the ZnO nanorods of 1D mode were grown at a higher temperature. The change of the morphologies of these materials led to improvements of the electrical and optical properties. The ZnO hybrid structure was characterized using various analytical tools. Scanning electron microscopy (SEM) was used to determine the surface morphology of the nanorods, which had grown well on the thin film. The structural characteristics of the polycrystalline ZnO hybrid grown on amorphous glass substrate were investigated by X-ray diffraction (XRD). Hall-effect measurement and a four-point probe were used to characterize the electrical properties. The hybrid structure was shown to be very effective at improving the electrical and the optical properties, decreasing the sheet resistance and the reflectance, and increasing the transmittance via refractive index (RI) engineering. The ZnO hybrid structure grown by MOCVD is very promising for opto-electronic devices as Photoconductive UV Detectors, anti-reflection coatings (ARC), and transparent conductive oxides (TCO).
김대식 교육사학회 2007 교육사학연구 Vol.17 No.1
본 고는 조선후기 공적 사적 기록에 등장하는 塾師라는 이들의 존재 양태와 역할을 규명하는 것을 목적으로 한다. 조선후기 문집과 실록 등에서 사용된 숙사의 의미를 검토하여 그들이 교육기관에 소속된 이들만이 아니라, 개인적으로 가르치던 이들에 대한 호칭이기도 하였음을 확인할 수 있었다. 이 시기 숙사는 교육기관에 소속되어 있는가와는 상관없이 초보적 수준의 유학교육을 담당하는 이들에게 사용되는 호칭이었다. 숙사들은 동몽들의 가장 가까이에서 가르치는 친근한 교사들이었다고 할 수 있다. 교육기관과 무관한 숙사들이 존재했다는 것은 조선후기의 유학교육을 이해할 때 교육기관과 그 역할에만 주목할 것이 아니라 교육 행위자에도 초점을 두고 접근할 필요가 있음을 시사한다. temp