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RF 스위치 적용을 위한 박막 PZT 엑추에이터의 d<SUB>31</SUB> 구동과 d<SUB>33</SUB> 구동 특성 비교
신민재(M. J. Shin),서영호(Y. H. Seo),최두선(D-S. Choi),황경현(K-H. Hwang) 한국정밀공학회 2006 한국정밀공학회 학술발표대회 논문집 Vol.2006 No.5월
In this work, we present the comparison between d<SUB>31</SUB> and d<SUB>33</SUB> mode characterization using the PZT micro-actuator for large displacement. The PZT micro-actuator consisted of Si, PZT, and Pt layer on SOI wafer. The electrode shapes were laminated and interdigitated for d<SUB>31</SUB> and d<SUB>33</SUB> mode, respectively. In order to characterize the actuation mode, we measured the displacement using laser interferometer. The maximum displacement of d<SUB>31</SUB> mode was 12.2㎛ at 10V, the actuation characterization of d<SUB>31</SUB> was better than that of d<SUB>33</SUB> mode. We estimated that displacement of d<SUB>33</SUB> mode would be larger than that of d<SUB>31</SUB> above 30V.
d^0 Magnetism in ZnO Thin Film Manifested by the Magnetoresitance
D. F. Wang,J. M. Kim,V. T. T. Thuy,M. S. Seo,이영백 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.51
ZnO thin films with different electron concentrations were deposited on silicon wafers by magnetron sputtering, and the magnetic and the magnetoresistive properties were studied. The magnetic-property measurements showed that the ZnO film was ferromagnetic at room temperature. Through the magnetoresistance (MR) measurements, the MR of ZnO was found to depend strongly on the temperature and the electron concentration. At a high electron concentration, the sample shows a negative MR at all temperatures. For the sample with a low electron concentration, a negative MR is revealed at high temperatures. However, when the temperature was reduced to 2 K, a positive MR as large as 19.8% was observed. Moreover, aging effects of the MR and the magnetization were found when the sample was put in air for a month. The ferromagnetism disappeared, and the MR at 2 K became negative again. This can be explained by a modification of thedefects in ZnO.
Seo, D.,Park, K.W.,Kim, J.,Hong, J.,Kwak, K. Elsevier Scientific Pub. Co 2016 Computational & theoretical chemistry Vol.1081 No.-
<P>The recent improvements in metal-free organic dye-sensitized solar cells (DSSCs) have been attributed to the ability to tune the optical and electronic properties through various structural modifications. Within the donor-pi-conjugated spacer-acceptor (D-pi-A) architecture, the electron-donating and accepting strengths have been proven to be major control variables for increasing the energy conversion efficiency. In the present study, a series of metal-free organic D-pi-A dyes for DSSCs were designed and investigated. In particular, the electron donating strength was modulated by adding electron donating groups to the donor side. The HOMO energy increased with a gradual increase in donor strength which was verified by an investigation of the bond distances between the nitrogen and carbon atom of phenyl ring connected with pi-conjugated spacer. The net electron transfer from the donor to acceptor, calculated from natural bond orbital (NBO) analysis, also showed quantitative correlation with the bond distances. Finally, the absorption peak shifted to a longer wavelength with the increase of donor strength as well as pi-conjugated spacer. Detailed analysis of the results supported that all properties investigated has a strong correlation with the bond distance between the nitrogen and the carbon atom in the phenyl ring attached to the pi-conjugated spacer. Based on this apparent correlation, this bond distance from ground-state DFT calculations may be used as a descriptor for the high throughput screening of DSSC dyes instead of using computationally expensive TDDFT calculations. (C) 2016 Elsevier B.V. All rights reserved.</P>
Seo, K.D.,Choi, I.T.,Kim, H.K. Elsevier Science 2015 ORGANIC ELECTRONICS Vol.25 No.-
SGT dyes containing various amine-typed donors as triphenylamine, bis-fluorenylamine and bis-phenothiazinylamine as the electron donor and a cyanoacrylic acid moiety as electron acceptor in D-π-A system, were developed to use in dye-sensitized solar cells (DSSCs). The SGT-102 dye containing bis-fluorenylamine had a better prevented charge recombination than other SGT dyes; leading to improvement in V<SUB>oc</SUB>. As a result, the conversion efficiency of 7.22% was achieved with a J<SUB>sc</SUB> of 12.1mAcm<SUP>-2</SUP>, V<SUB>oc</SUB> of 865mV and a FF of 69.1 for the DSSC employing a dye containing the bulky bis-fluorenylamine donor unit, while the DSSC based on a dye containing the bulky bis-phenothiazinylamine donor unit showed a lower J<SUB>sc</SUB> and V<SUB>oc</SUB>, leading to a lower efficiency of 5.16%, due to slow charge recombination associated with differently geometric structure orientations.
Lee, D.,Seo, M.W.,Nguyen, T.D.B.,Cho, W.C.,Kim, S.D. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.27
The three-reactor chemical-looping (TRCL) system for high purity hydrogen production and intrinsic CO<SUB>2</SUB> separation is an innovative concept using a circulating oxygen carrier. The process employs iron oxide as an oxygen carrier, via which a redox reaction takes place alternately within three reactors, i.e. a fuel reactor (FR), where the natural gas is combusted to CO<SUB>2</SUB> and H<SUB>2</SUB>O, a steam reactor (SR), where the steam is reduced to hydrogen, and an air reactor (AR), where the oxygen carrier returned to its original form by aeration. As it consists of three reactors (AR, FR, and SR) and a riser, the TRCL system has complicated hydrodynamic characteristics. In this study, a cold mode TRCL system with non-mechanical valve was designed and constructed to investigate the solid circulation characteristics. A series of hydrodynamic tests on the system was performed in which zirconia (d@?ρ=181μm, ρ<SUB>s</SUB> = 3850 kg/m<SUP>3</SUP>) was used as a bed material. The solid flow rate increased up to a maximum value with increasing gas velocity into the loop-seal. The gas leakages between AR and FR, and between FR and SR due to solid circulation were negligible. Furthermore, a two-dimensional (2D) computational fluid dynamics (CFD) simulation using a commercial CFD code was carried out in order to better understand the flow behavior of the gas solid mixture inside the TRCL system.
크롬 코팅 처리된 금형에서 박판의 온간 딥드로잉 성형성에 관한 연구
이재동,공경환,최치수,김헌영,서대교 기계기술연구소 2000 성균관대학교 논문집 기계기술편 Vol.2 No.1
Some deep drawing characteristics to the elevated temperatures were investigated for the SCP1 steel sheets by using the Cr-coated die. For this investigations, six steps of temperature ranges, from room temperature to 250℃, and six kinds of drawing ratio, from 2.4 to 2.9 were adopted. As a result, the limiting drawing ratio, maximum drawing force, and the maximum drawing depth were sensitively affected by the elevated temperatures, and the more stable thickness strain distribution was observed to the elevated temperatures. Some experimental results were compared with analytical results using the DYNA-3D code.
Kim, D.S.,Choi, J.S.,Kim, D.W.,Kim, K.S.,Seo, Y.G.,Cho, K.H.,Kim, J.O.,Yong, C.S.,Youn, Y.S.,Lim, S.J.,Jin, S.G.,Choi, H.G. Elsevier/North Holland 2016 International journal of pharmaceutics Vol.511 No.1
The purpose of this study was to compare the powder properties, solubility, dissolution and oral absorption of solvent@?wetted (SWSD) and kneaded (KNSD) l-sulpiride@?loaded solid dispersions. The SWSD and KNSD were prepared with silicon dioxide, sodium laurylsulfate and D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) using a spray dryer and high shear mixer, respectively. Their powder properties, solubility, dissolution and oral absorption were assessed compared to l-sulpiride powder. The drug in SWSD was in the amorphous state; however, in KNSD, it existed in the crystalline state. The SWSD with a drug/sodium laurylsulphate/TPGS/silicon dioxide ratio of 5/½/12 gave the higher drug solubility and dissolution compared to the KNSD with the same composition. The oral absorption of drug in the SWSD was 1.4 fold higher than the KNSD and 3.0 fold higher than the l-sulpiride powder (p<0.05) owing to better solubility and reduced crystallinity. Furthermore, the SWSD at the half dose was bioequivalent of commercial l-sulpiride@?loaded product in rats. Thus, the SWSD with more improved oral absorption would be recommended as an alternative for the l-sulpiride@?loaded oral administration.