http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
다양한 레이저(CW~FS)를 이용한 폴리머 박막의 탄화현상 해석
안대환(Daehwan Ahn),박병구(Byounggu Bak),김동식(Dongsik Kim) 한국레이저가공학회 2009 한국레이저가공학회지 Vol.12 No.3
The process of thermal-degradation of thin-film polymeris studied in this work for various laser sources from CW to fs. Samples composed of a thin polymer layer sandwiched between two glass plates are irradiated by the lasers and the threshold irradiance of polymer carbonization is experimentally measured. In the numerical analysis, the transient temperature distribution is calculated and the number density of carbonization in the polymer layer is also estimated. It is shown that pulsed lasers can result in more uniform distribution of temperature and carbonization than the CW laser.
안대환(Daehwan Ahn),박성진(Seongjin Park),권영삼(Youngsam Kwon),김동식(Dongsik Kim) 한국레이저가공학회 2010 한국레이저가공학회지 Vol.13 No.1
In this work, the feasibility of using a UV laser for micromachining of powder injection molded parts is examined experimentally. The results, although preliminary, indicate that microfabrication of various parts by laser micromachining of the injection molded parts and then sintering is promising. Particularly, micromachining of a mixture composed of stainless steel particles and polymer binders was studied using a KrF excimer laser
안대환(Daehwan Ahn),김동식(Dongsik Kim) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.1
Water jet impingement cooling is used to remove heat from high-temperature surfaces such as hot steel plates in the steel manufacturing process (thermo-mechanical cooling process; TMCP). In those processes, uniform cooling is the most critical factor to ensure high strength steel and good quality. In this study, experiments are performed to measure the heat transfer coefficient together with the inverse heat conduction problem (IHCP) analysis for a plate cooled by planar water jet. In the inverse heat transfer analysis, spatial and temporal variations of heat transfer coefficient, with no information regarding its functional form, are determined by employing the conjugate gradient method with an adjoint problem. To estimate the two dimensional distribution of heat transfer coefficient and heat flux for planar waterjet cooling, eight thermo-couple are installed inside the plate. The results show that heat transfer coefficient is approximately uniform in the span-wise direction in the early stage of cooling. In the later stage where the forced-convection effect is important, the heat transfer coefficient becomes larger in the edge region. The surface temperature vs. heat flux characteristics are also investigated for the entire boiling regimes. In addition, the heat transfer rate for the two different plate geometries are compared at the same Reynolds number.
Your age is showing : An analysis of identity fraud in online game classification systems
Byungjoon Yoo(유병준),Daehwan Ahn(안대환),Seongmin Jeon(전성민) 한국벤처창업학회 2012 한국벤처창업학회 학술대회 Vol.2012 No.4
Massively Multiplayer Online Role Playing Game (MMORPG) has become a very popular business area to study as it represents new patterns of collaboration and social interaction in the virtual world. In this study, we empirically raise the issues of identity fraud in MMORPGs. In principle, the online game classification system controls the scope of users’ activities with regard to the level of age appropriateness. However, the results from this study cast doubt on the effect of the current classification system in that distinctive behavior differences were not found to exist from one age group to another. Specifically, the econometric and multivariate analyses show that the behaviors of the group whose ages are around 40 is very similar to those of the group whose ages are under 14.