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화염증 CO<sub>2</sub> Laser를 이용한 입자의 크기 및 형상 제어
이동근,이선재,최만수,Lee, Donggeun,Lee, Seonjae,Choi, Mansoo 대한기계학회 1999 大韓機械學會論文集B Vol.23 No.11
A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.
On the Generalized Mean Square Error and its Applications
Donggeun Lee(이동근),Chanseok Park(박찬석) 대한산업공학회 2018 대한산업공학회지 Vol.44 No.2
There are several evaluation methods for parameter estimation. For example, the mean squared error (MSE), the Euclidean distance, the Mahalanobis distance and etc. But, when statistical methods have two or more parameter, it is difficult to evaluate whether they are good or not. In this paper we focus on defining the generalized bias (gBias) and the generalized mean squared error (gMSE) related to the generalized variance (gVar) applying to MSE concept to evaluate the parameter estimates. Moreover we will prove this concept beyond the three-dimensional, that is, hyper dimensional. Also we will check the applications of these terms. We will consider the robust estimates such as MAD, Hodges Lehmann estimator compared to other evaluation methods. We will use nuclear area data and find efficient method to predict Weibull distribution in some condition.
이동근(Donggeun Lee),주효상(Hyosang Ju),박지상(Jisang Park),길용성(Yong-Sung Kil),김상효(Sang-Hyo Kim) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2
극부호는 우수한 복호 성능을 위해 큰 크기의 리스트 복호를 수행할 수 있지만, 필연적으로 복호 복잡도가 증가하게 된다. 이를 위하여 복호실패 시 일부 수신신호를 변형하여 재복호를 수행하는 임펄스 섭동 복호가 제안된 바 있다. 본 논문에서는 섭동 비트선정 방식에 따른 성능을 확인하고, LLR 크기에 따른 섭동 우선순위를 적용했을 때 제한된 반복 횟수 내에서 더 큰 성능이득을 가짐을 확인하였다.