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관 유동과 Blasius 유동에서 가장 불안정한 교란에 관하여
최상규,정명균,Choi, Sang-Kyu,Chung, Myung-Kyoon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.6
The pseudospectral method for stability analysis was used to find the most influential disturbance mode for transition of plane channel flows and Blasius flow at their critical Reynolds numbers. A number of various oblique disturbance waves were investigated for their pseudospectra and resolvent norm contours in each flow, and an exhaustive search method was employed to find the disturbing waves to which the flows become most unstable. In plane Poiseuille flow an oblique disturbance with a wavelength of 3.59h (where h is the half channel width) at an angle $28.7^{\circ}$ was found to be the most influential for the flow transition to turbulence, and in plane Couette flow it is an oblique wave with a wavelength of 3.49h at an angle of $19.4^{\circ}$. But in Blasius flow it was found that the most influential mode is a normal wave with a wavelength of $3.44{\delta}_{999}$. These results imply that the most influential disturbance mode is closely related to the fundamental acoustic wave with a certain shear sheltering in the respective flow geometry.
재활용 산화철 및 알루미늄 분말을 활용한 철도레일 이음용 테르밋 분말 개발
최상규,박성상,백응률,Choi, Sang-Kyu,Park, Sung-Sang,Baek, Eung-Ryul 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.5
Nowadays in Republic of Korea, whole amount of the thermite welding powder for rail joinning is dependent on import. However the demand of the thermite welding powder would be enlarge because some constructing high-speed train and city metro projects are currently in progress. In addition this is the main reason why we should develop the thermite welding powder, domestically. This study is focused on utilizing the recyclable materials like Al powders from cans and iron oxide scales from wire rods as the main components of the thermite welding powder. By minimizing Al content in weld zone by controlling the mixing ratio of the Al powder in the thermite welding powder, the excessive dissolution of the Si and Mn components came from the Al powders could be controled. The tensile strength of welding zone in welded rail was 740 MPa, with that the developed thermite welding powder.
차세대 군용전원용 500W급 마이크로 터빈 발전기 시스템 설계
최상규,최범석,한용식,우병철,송인혁,민성기,임진식,Choi, Sang-Kyu,Choi, Bum-Suk,Han, Yong-Shik,Woo, Byung-Chul,Song, In-Hyuck,Min, Seong-Ki,Lim, Jin-Sik 한국군사과학기술학회 2011 한국군사과학기술학회지 Vol.14 No.6
Recent developments of small-size unmanned or manned mobile systems such as autonomous robots, exoskeleton or armored suits, micro air vehicles, and unmanned armored vehicles require long-lasting independent power sources of high energy and power density to support the systems' operation for up to 72 hours in the fields. Chemical batteries such as Ni-MH, Li-Ion, the current primary power sources for mobile devices, however, are not capable of providing enough power and energy density for the next generation high power mobile machines. For this reason, KIMM along with KERI and KIMS has been carrying out a 500W MTG development project under the DAPA's "Next generation military power source R&D program" since 2009. In this paper, a design process for a 500W MTG system currently being developed at KIMM is briefly described and the technical issues related to its development are addressed.
최상규(Sang-Kyu Choi),최혜선(Hye-Seon Choi) 한국식품영양과학회 2004 한국식품영양과학회지 Vol.33 No.8
한약재의 재료로 사용되는 옥발에서 항응고물질(anticoagulant)을 추출하여 정제하였다. 정제된 항응고물질의 분자량은 135 kDa으로 측정되었고 옥발로부터 정제된 항응고 물질의 회수율은 11%이고, 24배 농축되었다. 옥발의 항응고 물질은 열에 안정하고 비특이적 단백질 가수분해 효소 처리후에도 활성을 유지하였으나, periodate 산화 처리 시 현저하게 활성이 소실되어 항응고물질의 성분은 당류인 것으로 추정된다. 옥발의 항응고물질을 thin layer chromatography (TLC)와 Bio-LC로 구성당을 분석한 결과 galactose, glucose, mannose, glucosamine, galactosamine, fucose로 구성되어있고, IR을 통하여 확인된 OH, N-H bond가 확인되어 항응고물질이 중성당과 아미노당으로 구성된 것을 뒷받침해주고 있다. 옥발의 항응고물질은 thrombin time(TT)에 가장 민감하고, TT에서 항응고 활성을 2배, 3배 지연시키는 농도는 60 nM와 88 nM이었다. Prothrombin time(PT)에도 민감하였지만, snake venom activity와 activated partial thromboplastin time(APTT)의 clotting activity에는 상대적으로 별영향을 끼치지 않았다. 옥발의 항응고물질을 정제된 fibrinogen을 이용하여 thrombin과의 반응 시 fibrinogen의 농도가 증가함에 따라 응고 저해 정도가 감소하여 thrombin에 대해 fibrinogen과 결합자리를 경쟁하고, 이 때 Ki 값은 23 nM이다. An anticoagulant was purified from corn silk which has been used in Oriental Medicine. The anticoagulant from corn silk has a molecular mass of 135 kDa, and purified by 24 folds with a recovery of 11%. It was not sensitive to heat and protease treatment. However, periodate oxidation of the anticoagulant resulted in loss of activity significantly, implying that a carbohydrate was responsible for an anticoagulant activity. Galactose, glucose, mannose, fucose, glucosamine, and galactosamine were detected after acid hydrolysis by thin layer chromatography (TLC) and Bio-LC. It was confirmed that anticoagulant had OH and NH bonds by IR, supporting that the anticoagulant is composed of neutrosugar and aminosugar. Its anticoagulating activity was measured by delay in thrombin time (TT) and prothrombin time (PT) without affecting clotting by snake venom and delay in activated partial thromboplastin time (APTT). TT was more sensitive than PT, and was delayed two and three times at the concentration of 60 and 88 nM, respectively. The anticoagulating activity was reduced in the thrombin-induced clotting assay using purified fibrinogen according to the increase of fibrinogen concentration with the apparent Ki value of 23 nM.
최상규 ( Sang Kyu Choi ),이영애 ( Young Ae Lee ),이종익 ( Jong Ik Lee ) 대한임상검사과학회 1982 대한임상검사과학회지(KJCLS) Vol.14 No.1
In criminal investigations, the detection of human blood stains, particularly of an extremely small quantity of blood is the most important routine work. The authors have applied the fibrin plate method to detect the human blood from the washed, diluted and 01d b100d stains. It \vas possible to detect human blood of very smal1 quantity and to identify it``s blood types Therefore, this method can be recognized as a very sensitive one for identification of the human blood from the points of legal medicine.
급속열분해를 통하여 생산된 바이오오일 액적의 증발 특성에 관한 수치해석적 연구
최상규 ( Sang Kyu Choi ),최연석 ( Yeon Seok Choi ),김석준 ( Seock Joon Kim ),한소영 ( So Young Han ) 한국공업화학회 2016 공업화학 Vol.27 No.6
바이오매스는 최근 화석연료의 고갈 및 지구온난화 등의 문제에 대응하기 위한 신재생에너지원으로 많은 관심을 받고 있다. 바이오오일은 폐목재, 농업 및 임업 부산물 등의 바이오매스로부터 급속열분해 과정을 통하여 생산되는 액체연료이다. 바이오오일은 일반적인 석유 계통의 연료에 비하여 점도가 매우 높고 고체상의 불순물을 포함하고 있어 버너 적용시 스프레이 분무 특성이 저하된다. 또한, 바이오오일은 셀룰로오스, 헤미셀룰로오스, 리그닌으로부터 유래되는 수백 종류의 화학종들로 이루어져 있어 일반적인 액체연료와는 액적의 증발 특성이 뚜렷하게 구분된다. 본 연구에서는, 바이오오일의 구성 성분을 아세트산, 레보글루코산, 페놀, 수분으로 단순화하여 액적의 증발 특성에 관한 수치해석적 연구를 수행하였다. 다양한 주위공기 온도, 액적의 초기 지름, 에탄올 혼합 비율에 대하여 액적의 증발 특성을 비교하였다. 주위공기 온도가 높아질수록 바이오오일 액적의 증발 시간은 짧아졌으며, 특히 낮은 온도 범위에서는 증발 시간이 공기온도에 매우 민감하였다. 또한 액적의 지름이 감소할수록, 에탄올 혼합 비율이 증가할수록 증발 시간이 단축됨을 알 수 있었다. Biomass is regarded as one of the promising energy sources to deal with the depletion of fossil fuels and the global warming issue. Biocrude-oil can be produced through the fast pyrolysis of biomass feedstocks such as wood, crops, agricultural and forestry residues. It has significantly higher viscosity than that of conventional petroleum fuel and contains solid residues, which can lower the spray and atomization characteristics when applied to the burner. In addition, biocrude-oil consists of hundreds of chemical species derived from cellulose, hemicellulose and lignin, and evaporation characteristics of the bio-crude- oil droplet are distinct from the conventional fuels. In the present study, a numerical study was performed to investigate the evaporation characteristics of biocrude-oil droplet using a simplified composition of the model biocrude-oil which consists of acetic acid, levoglucosan, phenol, and water. The evaporation characteristics of droplets were compared at various surround-ing air temperatures, initial droplet diameters, and ethanol mixing ratios. The evaporation time becomes shorter with increasing air temperature, and it is much sensitive to the air temperature particularly in low temperature ranges. It was also found that the biocrude-oil droplet evaporates faster in cases of the smaller initial droplet diameter and larger ethanol mixing ratio.