Dependence of the exchange bias and coercivity of [Pd/Ferromagnet]_N/FeMn multilayers on the stack number N

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.

Oxide-free Sb₂S₃ sensitized solar cells fabricated by spin and heat-treatment of Sb(III)(thioacetamide)₂Cl₃

You, M.S.,Lim, C.S.,Kwon, D.H.,Heo, J.H.,Im, S.H.,Chae, K.J. Elsevier Science 2015 ORGANIC ELECTRONICS Vol.21 No.-

Pure Sb<SUB>2</SUB>S<SUB>3</SUB> without oxide impurities was formed by thermal decomposition of Sb(thioacetamide: TA)<SUB>2</SUB>Cl<SUB>3</SUB> precursor. From the analysis of thermal properties of Sb(TA)<SUB>2</SUB>Cl<SUB>3</SUB>, we developed a spin-coating and heat-treatment process to form pure Sb<SUB>2</SUB>S<SUB>3</SUB> thin-films with controllable thickness due to the formation of insoluble Sb<SUB>2</SUB>S<SUB>3</SUB> by heat-treatment. Through the spin-coating and heat-treatment process, we could fabricate oxide-free Sb<SUB>2</SUB>S<SUB>3</SUB> planar type sensitized solar cell with 8.12mA/cm<SUP>2</SUP> of short circuit current density (J<SUB>sc</SUB>), 0.616V of open circuit voltage (V<SUB>oc</SUB>), 45.9% of fill factor (F.F), and overall power conversion efficiency (η) of 2.3% at 1 sun condition.

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>

SOL Parameters, and Particle and Heat Fluxes at Divertor Targets from Electric Probe Measurements in KSTAR

J. G. Bak,H. S. Kim,J. Kim,K. I. You,S. H. Hong,M. K. Bae 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8

The plasma parameters in the scrape-off layer (SOL) region and the particle flux at the divertortarget are measured by using a fast reciprocating Langmuir probe assembly (FRLPA) and a fixededge Langmuir probe array (ELPA) in the KSTAR. The e-folding lengths of the plasma density (ne)and the electron temperature (Te), ne and Te, are obtained from the radial profile measurementusing the FRLPA at the outboard mid-plane during ohmic and H-mode discharges. Particle fluxesmeasured by using the ELPA at the divertor target are mapped to the outboard mid-plane, and thefluxes are quite well matched to the radial profile of the particle flux from the FRLPA measurement. Finally, the peak heat flux at the divertor target during edge localized modes (ELMs) can beestimated to be up to 1.0 MWm−2 for the neutral beam power of 2.7 MW by using Te at theseparatrix and Te from the FRLPA measurements. In this work, the experimental results fromthe probe measurements in the KSTAR are presented.

ZnIn₂S₄단결정 박막의 성장과 광학적 특성

홍광준,유상하,방진주,김소형,여희숙,양혜정,김현수 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

Perpendicular magnetic anisotropy properties of tetragonal Mn₃Ga films under various deposition conditions

Bang, H.W.,Yoo, W.,Choi, Y.,You, C.Y.,Hong, J.I.,Dolinsek, J.,Jung, M.H. Elsevier 2016 Current Applied Physics Vol.16 No.1

<P>The tetragonal Mn3Ga films exhibited high perpendicular magnetic anisotropy, low saturation magnetization, and high spin polarization, which satisfy the criteria of spin-transfer-torque based devices. For practical device applications, it is necessary to improve the interface nature and optimize the deposition conditions. We fabricated thin films of tetragonal Mn3Ga directly on MgO(100) without any buffer layer by using DC/RF magnetron sputtering method. We investigated the crystallinity, microstructure, and magnetic properties with varying the deposition conditions; such as deposition temperature (350 -450 degrees C), RF power (25-40 W), and Ar gas pressure (2-7 mTorr). X-ray diffraction data revealed that the growth direction is perpendicular to the film plane, i.e., the c axis. Scanning electron microscope images showed that the top surface is flat with a maximum thickness of 290 nm. The optimal deposition conditions are 400 degrees C, 35 W, and 5 mTorr in our sputtering system. For the field perpendicular to the film plane, clear hysteresis loop was observed with the saturation magnetization M-S - 100 emu/cc at room temperature. By extrapolating the hard magnetization data for the field parallel to the film plane, the anisotropic energy was estimated about K-1 = 1 x 10(6) J/m(3). (C) 2015 Elsevier B.V. All rights reserved.</P>

소결과정에서 Fe_2O_3-CaO-Al_2O_3-SiO_2계로부터 Calcium-Ferrite 생성거동에 미치는 염기도의 영향

黃熙鎭,車榮宰,兪炳敦,韓晶煥,李始衡,許完旭 대한금속재료학회 2002 대한금속·재료학회지 Vol.40 No.5

The effect of the basicity on the formation behaviour of calcium ferrites was investigated in the sintering process of Fe_2O_3-CaO-Al_2O_3-SiO_2 system. In the system of Fe_2O_3-CaO-Al_2O_3, the mineral structure consists of iron oxide particles and matrix phase, which is likely to be CF(calcium ferrite). When SiO_2 is added into Fe_2O_3-CaO-Al_2O_3 system, the area fraction of CF decreases sharply. When the basicity(CaO/SiO_2) decreases below the unity, CF does not form, and the mineral structure is composed of iron oxide particles and the silicate slag. The iron oxide particles are mainly magnetite in the temperature range higher than 1300℃, while they consist of both magnetite and hematite at the temperatures below 1250℃. When SiO_2 is added into Fe_2O_3-CaO-Al_2O_3 system, the formation of hematite is promoted in the lower temperature range. The increase of SiO_2 content tends to change the composition of CF from hemi-CF to mono-CF. The solubility of solutes such as CaO, Al_2O_3 and SiO_2 in CF increase with the increase of SiO_2 content in the system.

Electrochemical Sensing of H₂O₂ by the Modified Electrode with Pd Nanoparticles on Multi-Walled Carbon Nanotubes-g-Poly(Lactic Acid)

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.

Chemical Bath Deposition 방법으로 제작한 CdSe 박막의 특성

홍광준,이상열,유상하,서상석,문종대,신영진,정태수,신현길,김택성,송정훈,유기수 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.16 No.-

Chemical bath deposition 방법으로 다결정 CdSe 박막을 세라믹 기판 위에 성장시킨 다음 온도를 변화시켜 열처리하고 X-선 회절무늬를 측정하여 결정구조를 밝혔다. 450℃로 열처리한 시료가 X-선 회절무늬로 부터 외삽법에 의해 a_o와 c_o 는 각각 4.302 Å과 7.014 Å인 육방정계임을 알았다. 이 때 낱알크기는 약 0.3㎛이었다. Van der Pauw 방법으로 Hall 효과를 측정하여 운반자 농도와 이동도의 온도의존성을 연구하였다. 이동도는 33 K 에서 200 K 까지는 압전산란에 의하여, 200 k 에서 293 K 까지는 극성광학산란에 의하여 감소하는 경향이 나타냈다. 광전도 셀의 특성으로 스텍트럼 응답, 감도(γ), 최대허용소비전력 및 응답 시간을 측정하였다. Polycrystalline CdSe thin films were grown on creamic substrate using a chemical bath deposition (CBD) method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdSe polycrystal structure. Using extrapolation method of X-ray diffraction patterns for the CdSe samples annealed in N_2 gas at 450℃ it was found hexagonal structure whose lattice parameters a_o and c_o were 4.302 Å and 7.014 Å, respectively. It grain size was about 0.3 ㎛. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by piezo electric scattering at temperature range of 33 K and 200 K, and by polar optical potical scattering at temperature range of 200 K and 293 K. We measured also spectral response, sensitivily (γ), maximum allowable power dissipation and response time on these samples.

수정된 화학전이 NMR 영상법에 의한 수분과 지질의 비율 측정에 관한 연구

신용진,장차익,홍광준,유상하,이관교,양경승,백창현,김남수,정준우 조선대학교 기초과학연구소 1996 自然科學硏究 Vol.19 No.1

다양한 화학종(化學種)의 선택적인 핵자기공명(nuclear magnetic resonance, NMR) 영상(imaging)을 얻기 위한 몇몇 기술들이 가장 일반적인 Dixon's, CHESS, SECSI 등 3가지 방법들과 함께 발전해 왔다. 모든 화학전이 영상법(chemical shift imaging method)에 있어서 가장 큰 문제점은 정자기장의 균일성과 RF(radiofrequency) 코일에 대전된 시료가 인가되었을 때 나타나는 자기장의 찌그러짐이다. 만약 자기장의 shimming이 없다면, 약 3.5ppm으로 분리된 수분(water)과 지질(fat)의 선택적 양성자 영상을 얻는데 위 세 가지 방법들은 이용될 수 없다. 2.5ppm에서 3.5ppm의 선폭(linewidth)을 가진 시료(phantom)를 이용한 실험으로 위의 세 가지 기술과 새로운 화학전이 영상기술을 정량적으로 분석할 수 있었다. 본 연구에서는 선택적인 포화(saturation)와 재집중(refocusing) pulse가 포함된 새로운 화학전이 영상기술(modified CHESS+SECSI technique)이 다양한 시료에서 수분과 지질의 정량적 비율을 측정하는데 이용될 수 있도록 개발되었다. There are several methods developed to achieve selective NMR image of differing chemical species with the three most popular being Dixon's, CHESS, and SECSI, A major problem common to all chemical shift imaging methods is the uniformity of the static magnetic field and distortions introduced when RF coils are loaded with a conducting specimen. Without magnetic field shimming, these methods cannot be used to selectively image protons in fat and water which are separated by approximately 3.5ppm. Experiments with a phantom, with linewidths of 2.5 to 3.5ppm, were quantitatively evaluated for the above three methods and a new chemical shift imaging method. In this study the new chemical shift imaging method (modified CHESS+SECSI technique) which included a selective saturation and refocusing pulse, was developed to determine the ratio of water and fat in different samples.