• 한국재료학회지
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• 제27권10호
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• pp.569-575
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• 2017

To improve photocatalytic performance, a $PbS/ZnO/TiO_2$ nanotube catalyst was synthesized, and its surface characteristics and photocatalytic efficiency were investigated. The hybrid photocatalysts were produced by anodic oxidation and successive ionic layer adsorption and reaction(SILAR). The photocatalytic efficiency was evaluated using the dye degradation rate. The $PbS/ZnO/TiO_2$ photocatalyst significantly enhanced the photocatalytic activity for dye degradation, which was ascribed to the synergistic effect of their better absorption of solar light and a decrease in the rate of excited electron-hole recombination.

• 한국소음진동공학회논문집
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• 제18권2호
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• pp.255-262
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• 2008

In this study, seismic response control performance of decentralized response-dependent MR damper which generates the control force using only the response of damper-installed floor, was experimentally investigated through the tests of a full-scale structure installed with large MR dampers. The performance of the decentralized control algorithm was compared to those of the centralized ones such as Lyapunov, modulated homogeneous friction, and clipped-optimal control. Hybrid mass damper were controlled to induce seismic response of the full-scale structure under El Centro earthquake. Experimental results indicated that the proposed decentralized MR damper provided superior or equivalent performance to centralized one in spite of using damper-installed floor response for calculating input voltage to MR damper.

• 한국철도학회논문집
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• 제10권1호
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• pp.39-44
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• 2007

This rafer explains a durability test of a large train car body made of carbon/epoxy composite material. The composite car body with the length of 23m was manufactured as a sandwich structure composed of an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces. In order to evaluate durability of the composite car body, it was excited by two 500kN capacity hydraulic actuators installed underneath the body bolster. The natural frequency of the composite car body under full weight condition was found to be 4.33Hz. Based on this result, the excitation frequency and displacement of 5Hz and ${\pm}1.0mm$, respectively, were used as inputs for the durability test. The test was conducted for $2{\times}10^6$ cycles. During the test, the nondestructive tests using X-ray radiography and dye penetration method was performed to determine the presence of the cracks. Upon completion of the test, no cracks were found.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.272-272
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• 2013

The attractive features of photosynthetic reaction center proteins for energy application make them useful in solar energy conversion to hydrogen fuel or electrical energy. Almost unity charge separation quantum yield and its rapid speed of ~1ns, absorbance region in visible light (480~740 nm) and high proportion of photosynthetically active solar energy of 48.5% allowed photosystem1 to exploited as a bio-material for photo-energy devices. Directionality of photosystem1 in electron transfer can solve main problem in two-step water splitting process where back reaction deteriorates the overall efficiency. In the study, photosystem1 was extracted from spinach and the photo-induced excited electron in the reaction center was utilized in various field of light energy application. First, hydrogen evolving system realized by photodeposition of platinum at the end of the electron transfer chain, with combining specific semiconductor to oxidize water in the first step of Z-scheme. The evaluation by gas-chromatography demonstrated hydrogen evolution through the system. For the further application of photoelectrical material on electrode, photosystem1 have been controlled by copper ion, which is expected to assemble photosystem in specific orientation followed by maximized photoelectrical ability of film. The research proposed concrete methods for combining natural protein and artificial materials in one system and suggested possibility of designing interface between biological and inorganic materials.

• Smart Structures and Systems
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• 제32권6호
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• pp.393-402
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• 2023

Recently, hybrid and electric vehicles have been actively developed to replace internal combustion engine (ICE) vehicles. However, their vibrations and noise with complex spectra cause discomfort to drivers. To reduce the vibrations transmitted through primary excitation sources such as powertrains, structural changes have been introduced. However, the interference among different parts is a limitation. Thus, active mounting systems based on smart materials have been actively investigated to overcome these limitations. This study focuses on diminishing the source movement when a structure with two active mounting systems is excited to a single sinusoidal and a multi-frequency signal, which were investigated for source movement reduction. The overall structure was modeled based on the lumped parameter method. Active vibration control was implemented based on the modeled structure, and a multi-normalization least mean square (NLMS) algorithm was used to obtain the control input for the active mounting system. Furthermore, the performance of the NLMS algorithm was compared with that of the quantification method to demonstrate the performance of active vibration control. The results demonstrate that the vibration attenuation performance of the source component was improved.

• 한국자기학회지
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• 제23권6호
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• pp.184-187
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• 2013

MgO 기반 스핀소자에 유기장벽 Cu-Phthalocyanine(CuPc)가 삽입된 무기${\backslash}$유기 터널 접합 소자 Fe${\backslash}$MgO(001)${\backslash}$CuPc${\backslash}$Co의 자기 저항 현상과 그 계면 특성의 상관관계에 대한 연구가 진행되었다. 특히 1.6 nm MgO(001)${\backslash}$x nm CuPc(x = 0~5) 계면의 전자기적 특성을 스핀 편극된 준안정상태 He 원자 분광계(Metastable Helium De-excitation Spectroscopy, MDS)를 이용하여 규명하였다. 에피 성장된 MgO(001) 위에 적층된 약 1.6 nm 두께의 CuPc 층상구조의 표면에서, MgO(001) 하지층의 표면과는 달리, up-spin band와 down-spin band의 비대칭성이 현저해지는 것으로 관찰되었다. 이 결과는 실온과 저온(77 K)에서 ~10 %와 30 %로 각각 측정된 자기저항 현상과 복합장벽을 통과하는 스핀거동을 이해하는데 중요한 단초를 제공해 준다.

• 대한토목학회논문집
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• 제26권5A호
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• pp.849-859
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• 2006

본 연구에서는 벤치마크 사장교를 이용해 다양한 불확실성에 대해서 복합시스템에 사용된 ${\mu}$-제어기의 강인성 해석을 수행하였다. 복합 시스템에 추가적으로 사용된 능동제어 장치로 인하여 전체 시스템의 강인성이 저하되거나 불안정성이 발생할 수 있다. 따라서 본 연구에서는 복합 시스템의 강인성을 향상 시키기 위해 기본적으로 신뢰성이 확보되는 수동장치와 함께 불확실성을 포함한 시스템의 성능과 안정성(강인성능)을 보장하는 ${\mu}$-합성법을 능동제어 장치에 사용하였다. 교량상판에 추가적인 질량, 구조물 강성행렬에 대한 섭동, 능동제어 장치의 시간지연, 그리고 이들의 조합을 이용하여 ${\mu}$-합성법의 강인성을 조사하였다. 수치해석 결과 다양한 불확실성에 대해 제안된 시스템은 제어성능의 저하 없이 뛰어난 강인성을 보여 주었다. 또한 제어시스템의 강인성은 다른 불확실성에 비해 구조물의 강성행렬 섭동에 더 큰 영향을 받는다. 따라서 ${\mu}$-합성법으로 제어되는 복합 시스템은 불확실성이 많은 지진하중을 받는 사장교에 개선된 제어기법으로 제안될 수 있다.

• 한국전자파학회논문지
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• 제19권8호
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• pp.927-932
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• 2008

본 논문에서는 두 개의 빔 형성을 위한 $4{\times}1$ 배열 안테나에 급전할 수 있는 새로운 $4{\times}4$ Hadamard 행렬 급전 장치를 제안한다. 만약 배열 안테나의 각 안테나를 Hadamard 행렬의 각 행으로 급전을 하면 두 개의 빔을 형성하게 된다. 두 빔 사이의 각도는 행렬의 적절한 행을 선택함으로써 조절할 수 있다. Hadamard 행렬의 급전 구조는 네 개의 $90^{\circ}$ 하이브리드, 한 개의 크로스오버, 네 개의 $90^{\circ}$ 위상 변위기가 사용된다. 마이크로스트립 표면에 Hadamard 행렬을 포함한 배열 안테나를 제작하였으며, 측정된 안테나의 주 빔 방향은 입력 포트의 선택에 따라 각각 $0^{\circ}$, ${\pm}15^{\circ}$, ${\pm}33^{\circ}$, ${\pm}45^{\circ}$가 되었다.

• Molecules and Cells
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• 제46권8호
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• pp.513-525
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• 2023

Orange carotenoid protein (OCP) of photosynthetic cyanobacteria binds to ketocarotenoids noncovalently and absorbs excess light to protect the host organism from light-induced oxidative damage. Herein, we found that mutating valine 40 in the α3 helix of Gloeocapsa sp. PCC 7513 (GlOCP1) resulted in blue- or red-shifts of 6-20 nm in the absorption maxima of the lit forms. We analyzed the origins of absorption maxima shifts by integrating X-ray crystallography, homology modeling, molecular dynamics simulations, and hybrid quantum mechanics/molecular mechanics calculations. Our analysis suggested that the single residue mutations alter the polar environment surrounding the bound canthaxanthin, thereby modulating the degree of charge transfer in the photoexcited state of the chromophore. Our integrated investigations reveal the mechanism of color adaptation specific to OCPs and suggest a design principle for color-specific photoswitches.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.17-18
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• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.