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A statistical approach to radar rainfall estimates using polarimetric variables
You, C.-H.,Kang, M.-Y.,Hwang, Y.,Yee, J.-J.,Jang, M.,Lee, D.-I. Elsevier 2018 Atmospheric research Vol.209 No.-
<P><B>Abstract</B></P> <P>To improve the accuracy of radar rainfall estimates, this study examines rainfall relationships derived from polarimetric variables calculated from Drop Size Distributions (DSDs) measured by POSS (Precipitation Occurrence Sensor System) and PARSIVEL (PARticle Size and VELocity) disdrometers for eight different rainfall events in Korea associated with the Changma front, low pressure systems, typhoons, or the indirect effects of typhoons.</P> <P>Analysis of the correlation coefficients between polarimetric variables as independent parameters shows that multicollinearity is expected for Z–K<SUB>DP</SUB>, Z–A<SUB>H</SUB>, and K<SUB>DP</SUB>–A<SUB>H</SUB>. Of these, R(Z, K<SUB>DP</SUB>) is the only relationship that had too low an accuracy for application to radar rainfall estimation. R(Z, Z<SUB>DR</SUB>, K<SUB>DP</SUB>) and R(Z, K<SUB>DP</SUB>, A<SUB>H</SUB>) were also omitted from this analysis because their intercept coefficients were too large.</P> <P>Analysis of the sensitivity of radar rainfall estimation to DSDs variation shows that the latest observed DSDs perform well, as much as 2.4 mm h<SUP>−1</SUP> for RMSE (Root Mean Square Error) and 0.23 for NE (Normalized Error) in maximum. The statistical scores of each radar rainfall estimator vary between different rainfall events. This paper examines a new approach to radar rainfall estimation that is similar to the ensemble technique widely used in numerical prediction models. The ensemble members were chosen based on the average and standard deviation of their RMSE and NE for eight rainfall events. Two different weighting schemes were applied to each ensemble and the members were weighted equally or, alternatively, weighted based on their statistical scores. The performance of eight ensemble sets was examined using four independent rainfall events. There is little difference in the accuracy of each ensemble with respect to the weighting scheme applied. An ensemble composed of R(Z,Z<SUB>DR</SUB>), R(Z), and R(K<SUB>DP</SUB>), all given an equal weighting, was the most accurate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Calculating all possible rainfall relation using drop size distributions by disdrometer </LI> <LI> Variations of the radar rainfall estimation accuracy with time </LI> <LI> Proposal of the ensemble mean as a new approach on radar rainfall estimation </LI> </UL> </P>
Joo, H.W.,Lee, M.S.,Kim, S.W.,Kim, S.S.,Lee, J.Y.,Baek, J.Y.,You, C.-Y.,Lee, K.A.,Rhee, J.R.,Lee, S.S.,Hwang, D.G. IEEE 2006 IEEE transactions on magnetics Vol.42 No.10
The dependencies of the stack number N on perpendicular exchange-biasing (H<SUB>ex</SUB>) and coercivity H<SUB>c</SUB>) in [Pd/Co]<SUB>N</SUB> and [Pd/Co (or CoFe)]<SUB>N</SUB>/FeMn multilayers were investigated. With the help of the careful designs of layer structures, a series of samples whose surface anisotropies have the linear function N was prepared with constant bulk anisotropies. From the experimental data obtained, it was found that H<SUB>ex</SUB> does not depend on the surface anisotropy, while H<SUB>c</SUB> shows a strong dependence. Therefore, it is possible to tailor wide ranges of H<SUB>c</SUB> (300-600 Oe) without varying H<SUB>ex</SUB>(∼200 Oe) through the single control parameter stack number N.
Solid-state synthesis and thermoelectric properties of Bi-doped Mg<sub>2</sub>Si compounds
You, S.W.,Kim, I.H. Elsevier 2011 Current Applied Physics Vol.11 No.3
Bi-doped Mg<SUB>2</SUB>Si (Mg<SUB>2</SUB>Si:Bi<SUB>m</SUB>, m = 0, 0.005, 0.01, 0.02, 0.03) was prepared by solid-state synthesis. The electronic transport properties (Hall coefficient, mobility and carrier concentration) and thermoelectric properties (Seebeck coefficient, electrical conductivity, thermal conductivity and figure-of-merit) were examined. Mg<SUB>2</SUB>Si was synthesized successfully by a solid-state reaction at 673 K for 6 h and Bi-doped Mg<SUB>2</SUB>Si powders were obtained by mechanical alloying for 24 h. They were fully consolidated by hot pressing at 1073 K for 1 h. All the Mg<SUB>2</SUB>Si:Bi<SUB>m</SUB> samples exhibited an n-type conduction, indicating that the electrical conduction is mainly due to electrons. The electrical conductivity increased significantly and the absolute value of the Seebeck coefficient decreased with increasing Bi content because the electron concentration was increased considerably from 10<SUP>16</SUP> to 10<SUP>20</SUP> cm<SUP>-3</SUP> by Bi doping. The thermal conductivity was not changed significantly by Bi doping due to the much larger contribution of lattice thermal conductivity over electronic thermal conductivity. The thermal conduction in Bi-doped Mg<SUB>2</SUB>Si was attributed dominantly to the lattice vibrations (phonons). A maximum thermoelectric figure-of-merit of 0.7 was obtained for Mg<SUB>2</SUB>Si:Bi<SUB>0.02</SUB> at 823 K.
You, K.E.,Park, J.H.,Kim, Y.C.,Oh, S.G. Elsevier 2014 SOLID STATE SCIENCES Vol.33 No.-
Silica-hematite (α-Fe<SUB>2</SUB>O<SUB>3</SUB>) nanocomposites were synthesized by addition of aqueous solution containing ferrous ions (Fe<SUP>2+</SUP>), cetyltrimethylammonium bromide (CTAB) as a surfactant and tert-butanol (t-butanol) as a cosurfactant into colloidal silica solution. At alkaline atmosphere, silica surface with negative charges electrostatically attracts positively-charged iron hydroxide nuclei or particles which are stabilized by cationic CTAB molecules, and then silica-iron compound composites could be formed. Finally, the silica-hematite composite particles were obtained after calcination at 800 <SUP>o</SUP>C for 4 h. Through these processes, two types of composites having ''core-shell type'' or ''decorated type'' could be achieved. Morphology, BET surface area, crystallinity and magnetic properties of samples were analyzed by using TEM, BET, XRD and VSM, respectively. The ''decorated type'' composites had larger BET surface area and better magnetization. Also, to estimate the application in water treatment, adsorption properties of composites were studied through methylene blue (MB) adsorption which was characterized by UV-vis spectroscopy, involving collection of composites with neodymium magnet.
유상희,김학희 선문대학교 첨단과학기술연구소 1997 첨단과학기술연구소 논문집 Vol.2 No.-
다공성탄소의 전처리 방법에는 여러 가지가 있는데, 그 전처리는 산처리, 함침처리, 열처리 등이 있다. 다중성탄소의 열처리는 가장 일반적인 전처리 방법의 하나이다. 열처리에 의하여 다공성탄소의 비표면적이 증가하는데 이는 흡착성능과 관계되어진다. total pore volume과 평균 pore radius, 비표면적을 volumetic 분석기로 측정하였다. 또한 micropore와 pore surface는 SEM을 통하여 관찰하였다. 다공성탄소의 세공구조의 변화와 그로 인한 흡착성능이 향상되었음을 결론 내릴 수가 있었다. 다공성탄소의 열처리는 약 340℃에서 수행하였다. There are several methods for pretreatments of microporous carbon, those are acid treatment, impregnant treatment and heat-treatment etc. Heat-treatment of microporous carbon is the one of the most general methods in pretreatments. Specific surface area of microporous carbon was increased by heat-treatment, which is related with adsorption capacity. Total pore volume, average pore radius and specific surface area were measured through volumetric adsorption analyzer. Structural change of micropore and pore surface were observed by scanning electron microscope(SEM). It was concluded that improvement of adsorption capacity was resulted in the structural change of porous carbon. Heat treatment of microporous carbon was carried out about 340℃
Han, H.S.,You, J.-M.,Jeong, H.,Jeon, S. American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.6
A simple method has adapted to prepare MWCNT grafted Poly(lactic acid) (MWCNT-g-PLA) by intercalative polymerization of poly(lactic acid) in the presence of multi-wall carbon nanotubes (MWCNT) functionalized with hydroxyl groups. The functionalized MWCNT has obtained from the treatment of methylene diphenyl diisocyanate (MDI) with MWCNT, and then the reaction with 1,4-butanediol (BD) to create functional hydroxyl groups. MWCNT-g-PLA-Pd and MWCNT-g-PLA..Pt have prepared from the MWCNT-g-PLA and metal precursors. The synthesized materials have characterized by H-1-NMR, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The MWCNT-g-PLA-Pd is possibilities for employing to electrochemical detection of hydrogen peroxide. Electrocatalytic activities are verified from cyclic voltammetry (CV) and amperometric response in 0.1 M phosphate buffer solution (PBS). The biosensor provided good stability and selectivity towards interferences such as UA, AA, and glucose.