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Lee, Junggoo,Lee, Joonho,Tanaka, Toshihiro,Mori, Hirotaro IOP Pub 2009 Nanotechnology Vol.20 No.47
<P>Phase stabilities of nanometer-sized materials are quite different from those of the corresponding bulk materials. Among the phase stabilities, melting point suppression is one of the most fundamentally important issues. In this work, real-time, atomic-scale direct observation of melting point suppression in nanometer-sized Au particles, along with simple size reduction, was carried out by means of <I>in situ</I> high resolution electron microscopy. Namely, it was confirmed in real space on an atomic scale that a solid-to-liquid transition occurred when the size of a particle, placed on a graphite substrate maintained at 1100 K, decreased to 5 nm during diminution. Furthermore, a monolayer-thick hole was formed on the substrate at the position of the liquid Au particle, probably due to carbon dissolution into the liquid Au particle.</P>
Sangjun Lee,Jeehye Kwon,Hee-Ryoung Cha,Kyung Min Kim,Hae-Woong Kwon,Junggoo Lee,Dongyun Lee 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.2
We report an enhancement in the coercivity of sintered Dy free Nd-Fe-B magnets from 11.84 to 14.26 kOe by the grain-boundary diffusion of electrochemically deposited Cu-Nd. In the optimized electrochemical deposition and heat treatment conditions, a distinct Nd-rich grain-boundary phase was observed after the diffusion process; distributions of each element was carefully mapped by scanning electron microscopy equipped with backscattered electron detector. X-ray diffraction patterns indicated that Nd2Fe14B was oxidized by the inward diffusion of oxygen, which might be formed during the electrodeposition of Cu-Nd, forming antiferromagnetic Fe2O3 that might degrade the overall coercivity. A mechanism underlying the enhancement of coercivity is basically the same as the well-known proposed mechanism, distribution of a thin Nd-rich phase by grain-boundary diffusion process. In this study, electrochemical deposition process has been extensively investigated, and then the process was demonstrated to be successful and economically useful method to improve coercivity of the magnet.
Urea-SCR 시스템 적용을 위한 스월 인젝터의 분무특성
홍정구(Junggoo Hong),구건우(Kunwoo Ku),김성열(Sungyoul Kim),이충원(Choongwon Lee),강명권(Myungkweon Kang),김경남(Kyungnam Kim),김재경(Jaekyoung Kim) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.4
??In this study, a swirl hollow cone injector, which has a good atomization performance at the low injection pressure relatively, was designed to apply the Urea-SCR. In order to investigate the spray pattern and SMD of a swirl injector, the spray visualization was conducted by using the simple swirl injector, and the images of the spray cross-section were obtained from a sheet beam of Nd-Yag laser and CCD camera. The SMD of the swirl injector was measured with the axial of stance from the nozzle exit. The shape of the spray was converted from the hollow cone to solid cone along the distance from the injector exit. The spray angle is increased and the SMD is decreased with increasing injection pressure respectively.
한국 노인에서 맥압과 관상동맥질환의 연관성 : 제 7기 한국 국민건강영양조사(2016-2018)
Yoojeong Lee,Geeyon Seo,Jiae Heo,Junggoo Kim,Hyojin Park,Jean Shin,Byoungduck Han,Joung Sik Son,Seon Mee Kim 대한임상노인의학회 2021 대한임상노인의학회지 Vol.22 No.2
Background: Although the pulse pressure (PP) is an independent predictor of coronary heart disease (CHD), many physicians disregard its importance and there have been no recent studies on Korean elderly. We investigated the association between PP and CHD in Korean elderly through the nationwide, observational study. Methods: This study included 4100 subjects aged ≥65 years from the 7th Korean National Health and Nutrition Examination Survey (2016-2018). Pulse pressure was calculated as the difference between the systolic blood pressure (SBP) and the diastolic blood pressure (DBP), and high PP was defined as ≥60 mmHg. Subjects diagnosed with angina pectoris or myocardial infarction were classified into the CHD group. Multivariate logistic regression analysis was performed to evaluate the association between PP and CHD. Results: Among the subjects, the incidence of high PP was higher in women, while CHD was higher in men. Subjects with high PP were older, had higher SBP, lower DBP and higher FBG compared to subjects with normal PP. After adjustment for multiple covariates, participants with high PP had a higher risk for incidence of CHD with an OR of 1.361 (95% of CI: 1.077-1.719). Conclusions: In this study, we found the significant association between PP and CHD in Korean elderly.
Urea-SCR 시스템 적용을 위한 스월 인젝터의 분무특성
홍정구(Junggoo Hong),구건우(Kunwoo Ku),김성열(Sungryoul Kim),이충원(Choongwon Lee),강명권(Myungkweon Kang),김경남(Kyungnam Kim),김재경(Jaekyoung Kim) 한국자동차공학회 2011 한국자동차공학회 지부 학술대회 논문집 Vol.2011 No.4
In this study, a swirl hollow cone injector, which has a good atomization performance at the low injection pressure relatively, was designed to apply the Urea-SCR. In order to investigate the spray pattern and SMD of a swirl injector, the spray visualization was conducted by using the simple swirl injector, and the images of the axial of stance from the nozzle exit. The shape of the spray was converted from the hollow cone to solid cone along the distance from the injector exit. The spray angle is increased and the SMD is decreased with increasing injection pressure respectively.
열처리로 직화버너에서 연료-공기 혼합에 따른 화염 영향
이철우(Cheolwoo Lee),김영호(Youngho Kim),김인수(Insu Kim),홍정구(Junggoo Hong) 한국연소학회 2014 KOSCOSYMPOSIUM논문집 Vol.2014 No.11
Experiments have been performed for the burners used in the non-oxidizing direct fired furnaces for the cold rolled plate to investigate the effect of fuel/air mixing patterns of the burner nozzle on flame shape, temperature and combustion gas concentration. CFD simulation has also been performed to investigate the mixing state of air-fuel for a nozzle mixing burner and a partially pre-mixing burner. A partially pre-mixing burner showed that flame temperature increased up to 26℃ on average compared than that of the nozzle mixing. It also showed that the mixing distance is important at the partially pre-mixing burner. Test results for a partially pre-mixing burner showed that the residual oxygen concentration and the volume ratio of CO/CO2 of the flame were applicable to be used in field furnaces.
Structural and Magnetic Properties of the Gas Atomized Mn-Al Alloy Powders
Xiaolei Wang,Junggoo Lee,Jooho Lee,Hwijun Kim,Chuljin Choi,Zhidong Zhang 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.4
Ferromagnetic Mn-Al powders were produced by a gas-atomization method followed by heating treatment. The gas-atomized powders were ε-phase, which is a high temperature phase in the Mn-Al system. The ε-τ phase transformation took place by subsequent heat treatment at temperatures from 500 to 700 °C. The gas-atomized powders with a smaller particle size formed the τ-phase faster and thus exhibited better magnetic properties. On the other hand, the annealing temperature and time similarly played important roles in determining the magnetic properties of the products. The Mn-Al powders of 25-38 μm annealed at 550 °C for 120 min exhibited a high coercivity of 3.2 kOe with a remanence of 38 emu/g.