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Park, Cheolwoo,Park, Jeesu,Park, Jaehoon,Heo, Iljeong,Kim, Wooyul,Kim, Jungwon Elsevier 2019 CATALYSIS TODAY - Vol.335 No.-
<P><B>Abstract</B></P> <P>Most Ru(II) complex-sensitized TiO<SUB>2</SUB> systems for hydrogen (H<SUB>2</SUB>) production suffer from instability of the photosensitized system because the anchoring groups of Ru(II) dyes, which are required for their adsorption on TiO<SUB>2</SUB>, are intrinsically vulnerable to chemical and photochemical cleavage. In this study, a new method that enables the use of a Ru(II) dye without any anchoring groups (Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP>) was developed and investigated. The stable photocatalytic efficiency in repeated H<SUB>2</SUB> production cycles under visible-light irradiation indicates that the Ru(II) dye without anchoring groups is highly stable during dye-sensitized H<SUB>2</SUB> production. The dye-sensitized H<SUB>2</SUB> production in the Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP>-sensitized TiO<SUB>2</SUB> system comprising Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP> as a photosensitizer, platinized TiO<SUB>2</SUB> (Pt-TiO<SUB>2</SUB>) as a cocatalyst-electron mediator, and ethylenediaminetetraacetic acid as an electron donor was negligible. However, the addition of phosphate (PO<SUB>4</SUB> <SUP>3–</SUP>) to the Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP>-sensitized TiO<SUB>2</SUB> system enabled the production of H<SUB>2</SUB> via dye sensitization in the absence of any anchoring groups on the dye. The adsorption of PO<SUB>4</SUB> <SUP>3–</SUP> changed the surface charge of Pt-TiO<SUB>2</SUB> from positive to negative under acidic conditions, thereby inducing adsorption of cationic Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP> on the surface of Pt-TiO<SUB>2</SUB> and facilitating electron transfer from excited Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP> to the conduction band of TiO<SUB>2</SUB>. The PO<SUB>4</SUB> <SUP>3–</SUP> adsorption-induced change in the surface charge and the subsequent adsorption of Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP> on the surface of PO<SUB>4</SUB> <SUP>3–</SUP>-adsorbed Pt-TiO<SUB>2</SUB> were confirmed by zeta potential measurements and Fourier transform infrared spectroscopy, respectively. In contrast with H<SUB>2</SUB> production, the presence of PO<SUB>4</SUB> <SUP>3–</SUP> had little effect on the kinetics of anionic chromate (CrO<SUB>4</SUB> <SUP>2–</SUP>) reduction in the Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP>-sensitized TiO<SUB>2</SUB> system. This result indicates that electron transfer from Pt to the electron acceptor on PO<SUB>4</SUB> <SUP>3–</SUP>-adsorbed Pt-TiO<SUB>2</SUB> is highly dependent on the charge character of the electron acceptor (i.e., electron transfer to the cationic electron acceptor is more favored). The negative charge on the surface of Pt-TiO<SUB>2</SUB> induced by the adsorption of PO<SUB>4</SUB> <SUP>3–</SUP> attracts the positively charged protons to the surface, which kinetically enhanced electron transfer from Pt to the protons. The (photo)electrochemical data demonstrate that PO<SUB>4</SUB> <SUP>3–</SUP> adsorbed on Pt-TiO<SUB>2</SUB> facilitates the interfacial electron transfer processes by enhancing the adsorption of Ru(bpy)<SUB>3</SUB> <SUP>2+</SUP> and attracting protons to the surface. The positive effect of PO<SUB>4</SUB> <SUP>3–</SUP> on H<SUB>2</SUB> production increased with increasing PO<SUB>4</SUB> <SUP>3–</SUP> concentration and decreasing pH, where the conditions are more favorable for PO<SUB>4</SUB> <SUP>3–</SUP> and proton adsorption on the surface of Pt-TiO<SUB>2</SUB>. Among the five anions evaluated in this study (PO<SUB>4</SUB> <SUP>3–</SUP>, AsO<SUB>4</SUB> <SUP>3–</SUP>, F<SUP>–</SUP>, NO<SUB>3</SUB> <SUP>–</SUP>, and SO<SUB>4</SUB> <SUP>2–</SUP>), PO<SUB>4</SUB> <SUP>3–</SUP> was most efficient and facilitated stable H<SUB>2</SUB> production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Adsorption of PO<SUB>4</SUB> <SUP>3–</SUP> changes the surface charge of TiO<SUB>2</SUB> from positive to negative. </LI> <LI> PO<SUB>4</SUB> <SUP>3
양생직후 초기재령의 콘크리트 내부 온도와 상대습도의 측정 및 분석
박철우(Park Cheolwoo),박영훈(Park Young-Hoon),박용걸(Park Yong-Gul) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
Concrete is still one most common construction materials even in railway structures. As structures become massive and mega-sized, the importance of early age concrete quality control becomes more significant. Among various factors, relative humidity and temperature are the primary factors governing the early age quality. Temperature raise due to cement hydration causes stress, which can develop to cracking with internal and/or external restraints. Exposure conditions including ambient temperature, humidity and wind also significantly affect the cracking behavior of early age concrete. Among many of studies on the early age concrete behavior, investigation on the variation of temperature and relative humidity internal of concrete is not common. That is in part because the difficulties in measuring the relative humidity and temperature inside the concrete. This study used a digital sensor with an appropriate logger to measure internal temperature and relative humidity. This direct measuring method is expected to provide more reliable and comprehensive data acquisition on the early age behavior of concrete.
An exploratory data analysis in scale-space for interval-valued data
Park, Cheolwoo,Jeon, Yongho,Kang, Kee-Hoon Informa UK (TaylorFrancis) 2016 Journal of applied statistics Vol.43 No.14
<P>We propose an exploratory data analysis approach when data are observed as intervals in a nonparametric regression setting. The interval-valued data contain richer information than single-valued data in the sense that they provide both center and range information of the underlying structure. Conventionally, these two attributes have been studied separately as traditional tools can be readily used for single-valued data analysis. We propose a unified data analysis tool that attempts to capture the relationship between response and covariate by simultaneously accounting for variability present in the data. It utilizes a kernel smoothing approach, which is conducted in scale-space so that it considers a wide range of smoothing parameters rather than selecting an optimal value. It also visually summarizes the significance of trends in the data as a color map across multiple locations and scales. We demonstrate its effectiveness as an exploratory data analysis tool for interval-valued data using simulated and real examples.</P>
The temperature effect on the production of liquid and solid fuel via wood pellet torrefaction
Park Cheolwoo,Jang Eun-Suk,Kim Young-Min 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.6
The effects of temperature on the product quality of wood pellet torrefaction were examined by performing experiments, proximate analysis, ultimate analysis, heating value measurement, thermogravimetric analysis, and moisture absorption of torrefied wood pellets at 250, 300, 350, and 400 °C. The liquids produced during torrefaction and high-temperature pyrolysis of torrefied wood pellet at 800 °C were also analyzed. By increasing the torrefaction temperature to 400 °C, the yield of the solid was decreased to 30.32%, with an increase in gas (17.53%) and liquid (52.16%) yield caused by the partial elimination and decomposition of hemicellulose, cellulose, and lignin of wood pellet. The higher heating value of wood pellets was increased from 4,670 kcal/kg for raw wood pellets to 7,480 kcal/kg for torrefied wood pellets at 400 °C with the carbon concentration during torrefaction. Although the carbon density and heating value of the wood pellets were improved, overall energy recovery efficiency was decreased because of the decrease in solid yield by torrefaction. Thermogravimetric analysis results suggested that thermally stable wood pellet formation is formed by the elimination and structural changes to hemicellulose, cellulose, and lignin. The hydrophobicity of wood pellets was increased by torrefaction leading to the elimination of the hydrophilic functional groups of wood pellets. The moisture absorption of wood pellets (14.95%) was also decreased to 5.09% for torrefied wood pellets. Low-temperature torrefaction between 250 and 300 °C produced the typical pyrolyzates of hemicellulose and cellulose, such as furans and acids. The amount of lignin pyrolyzates, such as guaiacol, eugenol, and other phenolics, was increased by applying high-temperature torrefaction at 400 °C. The solid fuel produced by the high-temperature torrefaction of wood pellets also provided a potential decreasing tar content during gasification, indicating the improved process efficiency of torrefied wood pellets.
Fundamental Property of Chloride Inhibiting and Low Heat Cement for Marine Concrete Structures
Park, Cheolwoo,Sim, Jongsung,Lee, Jongryul Japan Concrete Institute 2009 Journal of advanced concrete technology Vol.7 No.1
<P>As the construction of marine concrete structures become more common, durability issues are gaining importance. This study introduces a newly developed chloride-inhibiting low-heat cement that is a quaternary blended cement. The primary target application of the newly developed cement is massive marine concrete structures. The adiabatic temperature rise of the newly developed cement was about 30% and 28% lower than for ordinary Portland cement and blast furnace slag cement, respectively, and resistance to chloride ion penetration was much higher compared to blast furnace slag cement. Based on the ASTM C1202 guidelines, the adiabatic temperature rise of the new cement could be considered very low at 28 days, while that of the blast furnace slag cement was in low range. Thus the primary purposes of the newly developed cement can be said to have been successfully attained. In addition, the developed chloride-inhibiting and low-heat cement may satisfy the strength requirement of general-purpose marine concrete applications without significant concerns regarding early-age strength. The developed cement was shown to provide sufficient resistance to freezing-thawing attack as long as proper air content is obtained.</P>