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Photocatalytic enhancement of cesium removal by Prussian blue-deposited TiO<sub>2</sub>
Kim, Hyuncheol,Kim, Minsun,Kim, Wooyul,Lee, Wanno,Kim, Soonhyun Elsevier 2018 Journal of hazardous materials Vol.357 No.-
<P><B>Abstract</B></P> <P>After the Fukushima nuclear accident, tremendous efforts were made to treat radiocesium, radiostrontium, and other radioactive materials. For the first time, we demonstrate that a TiO<SUB>2</SUB> photocatalyst can significantly enhance Cs adsorption by Prussian blue-deposited TiO<SUB>2</SUB> (PB/TiO<SUB>2</SUB>) under UV irradiation. In this study, we synthesized PB/TiO<SUB>2</SUB> using the photodeposition method. After the Cs ions were adsorbed on the PB/TiO<SUB>2</SUB> in darkness, we then exposed the PB/TiO<SUB>2</SUB> to UV light irradiation. This resulted in a further increase in Cs ion adsorption of more than 10 times the amount adsorbed in darkness. This photocatalytic-enhanced adsorption of Cs ions was not observed on PB mixed with SiO<SUB>2</SUB>, nor under visible light irradiation. We investigated the effects of PB concentration, PB/TiO<SUB>2</SUB> concentration, and gas purging on both dark and photocatalytic-enhanced adsorption of Cs ions by PB/TiO<SUB>2</SUB>. Based on the results, we suggest that the photocatalytic-enhanced adsorption of Cs ions on PB/TiO<SUB>2</SUB> is due to photocatalytic reduction of PB, which leads to additional adsorption of Cs ions. The change in solution color before and after the reaction, and the change in solution pH in the dark and during UV irradiation strongly support this suggestion. The photocatalytic-enhanced adsorption of Cs ions was equivalent during radioactive <SUP>137</SUP>Cs removal, indicating important applications for pollutant removal from contaminated water.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Prussian blue (PB)-deposited TiO<SUB>2</SUB> was synthesized using the photodeposition method. </LI> <LI> TiO<SUB>2</SUB> photocatalysts greatly enhance Cs adsorption by PB/TiO<SUB>2</SUB> under UV irradiation. </LI> <LI> Photocatalytic-enhanced Cs adsorption is due to photocatalytic reduction of PB. </LI> <LI> Photocatalysts can be used for radioactive <SUP>137</SUP>Cs removal from contaminated water. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Wonseok,Oh, Jeewhan,Kwon, Soonhyun,Kim, Kihong,Kim, Sung Jae The Royal Society of Chemistry 2019 Lab on a chip Vol.19 No.8
<P>Recently, the ion concentration polarization (ICP) phenomenon has been actively utilized for low abundance biomolecular preconcentration applications. Since ICP significantly rearranges the ion distribution near a permselective membrane, its detailed investigation should be conducted for developing efficient platforms. In particular, proton transport through the membrane critically affects the pH of sample solutions so that continuous monitoring or batch measurement of pH is the priority task to be carried out. Moreover, electrochemical reactions have been overlooked, even though an overpotential is applied to preconcentrate a sample under physiological conditions, and the electrodes are in direct contact with the sample biomolecules. In this work, we experimentally visualized and directly measured how the electrochemical reaction dominated the preconcentration efficiency using two types of electrode configurations; large exposed electrode area (LEEA) and small exposed electrode area (SEEA). Interestingly, significant pH variation was confirmed only in the case of SEEA. As a result, the BSA preconcentration was impeded within a short period in the case of SEEA, but loss-free preconcentration was achieved in the case of LEEA. Therefore, one should pay careful attention to the electrode design of electrokinetic operation, especially when pH-sensitive biomolecules are involved.</P>
Relighting 3D Scenes with a Continuously Moving Camera
Soonhyun Kim,Min-Ho Kyung,Joo-Haeng Lee 한국전자통신연구원 2009 ETRI Journal Vol.31 No.4
This paper proposes a novel technique for 3D scene relighting with interactive viewpoint changes. The proposed technique is based on a deep framebuffer framework for fast relighting computation which adopts image-based techniques to provide arbitrary viewchanging. In the preprocessing stage, the shading parameters required for the surface shaders, such as surface color, normal, depth, ambient/diffuse/specular coefficients, and roughness, are cached into multiple deep framebuffers generated by several caching cameras which are created in an automatic manner. When the user designs the lighting setup, the relighting renderer builds a map to connect a screen pixel for the current rendering camera to the corresponding deep framebuffer pixel and then computes illumination at each pixel with the cache values taken from the deep framebuffers. All the relighting computations except the deep framebuffer precomputation are carried out at interactive rates by the GPU.
CdS-loaded flexible carbon nanofiber mats as a platform for solar hydrogen production
Kim, Young Kwang,Kim, Minsun,Hwang, Sung-Ho,Lim, Sang Kyoo,Park, Hyunwoong,Kim, Soonhyun Elsevier 2015 International journal of hydrogen energy Vol.40 No.1
<P><B>Abstract</B></P> <P>Photocatalysis-based solar hydrogen (H<SUB>2</SUB>) has garnered attention as a renewable energy carrier, yet the technology is still immature. For practical operation of photocatalytic H<SUB>2</SUB> production, we fabricated a novel heterojunction of CdS-loaded flexible carbon nanofiber (CNF) mats. CNF mats were prepared by electrospinning and carbonization. CdS nanoparticles were deposited in alcohol and water solutions by the successive ionic layer adsorption and reaction (SILAR) method. The former solution was found to be more effective in uniformly dispersing CdS particles in the CNF mats. When pristine CNF mats were treated with acid (hereafter CdS/a-CNF), the degree of CdS particle distribution was further enhanced. Moreover, H<SUB>2</SUB> production was improved by a factor of 3 in an aqueous solution of Na<SUB>2</SUB>S (0.1 M) and Na<SUB>2</SUB>SO<SUB>3</SUB> (0.1 M) under visible light (<I>λ</I> > 420 nm). Heat-treatment of CdS/a-CNF mats at 400 °C dramatically increased H<SUB>2</SUB> production by 3.6 times due to the improved crystallinity of the CdS particles. In this heterojunction, the CNF mats have three roles: They work as a multi-scalable support for CdS particles, enhance photogenerated charge transfers, and catalyze H<SUB>2</SUB> evolution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We fabricated for the first time the CdS-loaded flexible carbon nanofiber mats. </LI> <LI> CdS loading was affected by the CNF mat surface and preparation conditions. </LI> <LI> CdS-loaded flexible CNF mats show superior visible-light-induced H<SUB>2</SUB> production. </LI> <LI> CdS-loaded flexible CNF mats are very useful in practical applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
김순현(Soonhyun Kim),이주행(Joo-Haeng Lee),경민호(Min-Ho Kyung) 한국HCI학회 2007 한국HCI학회 논문지 Vol.2 No.1
재조명(relighting) 렌더링은 장면 내에 새로운 광원의 추가 또는 기존 광원 속성의 변경으로 인한 영상의 변화를 효율적으로 계산하는 과정을 말한다. 본 논문에서는 쉐이딩(shading) 계산에서 광원에 독립적인 파라메터를 미리 텍스쳐 이미지 형태로 캐시화하여 재조명 렌더링 과정에서의 계산량을 줄이는 방법을 사용하였다. 이러한 쉐이딩 파라메터들의 캐시 이미지들은 사용자가 카메라 시점을 바꾸고자 할 경우 새로 생성을 하여야 하는데, 이러한 캐시 이미지 생성에는 많은 시간이 소요된다. 본 논문에서는 새로운 시점에서의 캐시 이미지들을 영상 기반 렌더링(image-based rendering) 기법을 이용하여 실시간에 구하는 방법을 제시한다. 이 방법은 먼저 여러 개의 지정된 카메라 시점에 대한 캐시 이미지들을 미리 생성해 둔다. 다음 원하는 시점의 캐시 이미지는 각 픽셀에 투영되는 3차원 표면점을 역시점변환(inverse viewing transform)을 통해 구하고, 이 점을 지정된 카메라 시점으로 다시 투영하여 캐시 이미지에서의 대응 픽셀을 찾는다. 대응 픽셀의 파라메터 값들을 평균하여 새 캐시 이미지에 써준다. 이 과정들은 하드웨어 그래픽 가속기의 단편 쉐이더(fragment shader)를 이용하여 실시간으로 수행된다. We develop an interactive relighting renderer allowing camera view changes based on a deep-frame buffer approach. The renderer first caches the rendering parameters for a given 3D scene in an auxiliary buffer with the same size of the output image. The rendering parameters independent from light changes are selected from the shading models used for shading pixels. Next, as the user interactively edits one light at one time, the relighting renderer instantly re-shades each pixel by updating the contribution of the changed light with the shading parameters cached in the deep-frame buffer. When the camera moves, the cache values should be re-computed because the currently cached values become obsolete. We present a novel method to synthesize them quickly from the cache images of the user specified cameras by using an image-based technique. This computations are all performed on GPU to achieve real-time performance.