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한창석,천창환,한승오,Han, Chang-Suk,Chun, Chang-Hwan,Han, Seung-Oh 한국재료학회 2009 한국재료학회지 Vol.19 No.6
The deposition behavior and structural and magnetic properties of electroless Co-B and Co-Fe-B deposits, as well as the amorphous ribbon substrates, were investigated. These Co-based alloy deposits exhibited characteristic polycrystalline structures and surface morphology and magnetic properties that were dependent on the type of amorphous substrates. The catalytic activity sequence of the amorphous ribbon electrodes for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath that did not contain the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of the substrates. The deposition rate linearly varied against the deposition time. The initial deposition potential may have also determined the structural and magnetic properties of the deposit based on the thickness of ${\mu}m$ order. Furthermore, a basic study of the electroless deposition processes on an amorphous ribbon substrate has been carried out in connection with the structural and magnetic properties of the deposits.
열전 냉각기를 포함하는 볼로미터 패키지의 SPICE 등가 모델링
한창석 ( Chang Suk Han ),박승만 ( Seung Man Park ),김남환 ( Nam Hwan Kim ),한승오 ( Seung Oh Han ) 한국센서학회 2013 센서학회지 Vol.22 No.1
For a successful commercialization of microbolometer, it is required to develop a robust package including thermal stabilizing mechanism. In order to regulate the temperature within some operating range, thermoelectric cooler is generally used but it`s not easy to model the whole package due to the coupled physics nature of thermoelectric cooler. In this paper, SPICE-compatible modeling methodology of a microbolometer package is presented, whose steady-state results matched well with FEM results at the maximum difference of 5.95%. Although the time constant difference was considerable as 15.7%, it can be offset by the quite short simulation time compared to FEM simulation. The developed model was also proven to be useful for designing the thermal stabilizer through parametric and transient analyses under the various working conditions.
In-X(X=Pb, Sn) 합금의 마르텐사이트변태거동 특성에 관한 연구
한창석 ( Chang Suk Han ),한승오 ( Seung Oh Han ) 한국열처리공학회 2010 熱處理工學會誌 Vol.23 No.5
The phase transformations and the shape memory effect in In-rich Pb alloys and In rich-Sn alloys have been studied by means of X-ray diffractometry supplemented by metallographic observations. The alloys containing 12~15 at.%Pb transform from the α2 (fct) phase to the α1 (fct) phase by way of an intermediate phase (m phase) on cooling. The results of X-ray diffraction show that the metastable intermediate phase is observed both on cooling and heating, and has a face-centered orthorhombic (fco) structure. It is concluded that the α1 →/← α2 transformation is expressed by the α1 →/← m →/← α2 transformation both on usual cooling and heating with the rate more than 8 × 10(-3) K/s. The m →/← a2 transformation takes place with a mechanism involving macroscopic shear and are of diffusionless (martensitic) type. The temperature hysteresis in the two transformations is 10~13 K between the heating and cooling transformations. The alloys containing 0~11 at.%Sn are -phase solid solutions with a face centered tetragonal structure (c/a> 1) at room temperature, the axial ratio increasing continuously with tin content. The In-(11~15) at.%Sn alloys are mixtures of α and β phases, the β phase having a f. c. tetragonal structure (c/a < 1). The alloys containing more than 15 at.%Sn are β-phase solid solutions. The In-(12.9~15.0) at.%Sn alloys show a shape memory effect only when quenched to the temperature of liquid nitrogen, although their effect becomes weak and finally disappears after keeping at room temperature for a long time. The β → α` phase transformation is of the diffusionless (martensitic) type, and takes place between 330 K at 12.9 at.%Sn and 150 K at 14.5 at.%Sn. The hysteresis of transformation temperatures on heating and cooling is considerably large (29~40 K), depending on the composition. Both In-Pb and In-Sn alloys showed distinct the shape memory effects.
압전형 에너지 수확장치를 위한 통합 해석환경의 적용 및 검증
( Jian Liu ),( Chris Welham ),한승오 ( Seung Oh Han ) 한국센서학회 2013 센서학회지 Vol.22 No.5
Vibrational energy harvester based on piezoelectricity has been expected to be the dominant energy harvesting technology due to the advantages of high conversion efficiency, light weight and small size, night operation, etc. Its commercialization is just around the corner but the integration with power management electronics should be solved in advance. In this paper, therefore, fully-integrated design environment for piezoelectric energy harvesting systems is presented to assist co-design with the power management electronics. The proposed design environment is capable of analyzing the energy harvester including the package-induced damping effects and simulating the device and its power management electronics simultaneously. When the developed design environment was applied to the fabricated device, the simulated resonant frequency matched well with the experimental result with a difference of 2.97% only. Also, the complex transient response was completed in short simulation time of 3,001 seconds including the displacement distribution over the device geometry. Furthermore, a full-bridge power management circuit was modeled and simulated with the energy harvester simultaneously. Therefore the proposed, fully-integrated design environment is accurate and fast enough for the contribution on successful commercialization of piezoelectric energy harvester.
실내 공기질 향상을 위한 비분산 적외선 이산화탄소 가스센서
이승환,박정민,박영환,한승오,Yi, Seung-Hwan,Park, Jeong-Min,Park, Young-Hwan,Han, Seung-Oh 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.7
We have simulated and proposed novel optical cavity, which has two elliptical mirrors, for NDIR gas sensor module and have tested it from 0 ppm to 2,000 ppm $CO_2$ concentration. The proposed sensor module shows the maximum peak voltage at 500 ms pulse modulation time, however, it shows a maximum voltage changes at 200 ms pulse duration with 18,000 times amplification gain. From 0 ppm to 2,000 ppm, the voltage difference of sensor module $({\Delta}V)$ shows 360 mV at 200 ms pulse duration and 3 sec turn-off time. The response time of designed sensor module is about 30 seconds.