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            Optimization-based approach for strategic design and operation of a biomass-to-hydrogen supply chain

            Woo, Y.b.,Cho, S.,Kim, J.,Kim, B.S. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.12

            <P>We present a new optimization-based approach for design and operation of a renewable hydrogen system from various types of biomass. To achieve this goal, we develop an optimization model (mixed integer linear programming) which determines the optimal logistics decision-making to minimize the total annual cost for a comprehensive biomass to -hydrogen (B2H2) supply chain with import and inventory strategies. With the proposed approach we can identify the optimal design of the supply chain and main cost-drivers, manage logistics operations against fluctuations of biomass availability and hydrogen demand, and make strategic decisions for planning the B2H2 system such as capital investment and energy import planning. To validate the model, a case study of an upcoming B2H2 supply chain for the transportation sector at Jeju Island, Korea, is analyzed. Finally, a sensitivity analysis is conducted to provide insights into the efficient management of the B2H2 supply chain. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

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            Design of Mg-Ni alloys for fast hydrogen generation from seawater and their application in polymer electrolyte membrane fuel cells

            Oh, S.,Kim, M.,Eom, K.,Kyung, J.,Kim, D.,Cho, E.,Kwon, H. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.10

            <P>Mg and its alloys are very attractive for hydrogen generation via hydrolysis because their hydrolysis reaction occurs in neutral seawater instead of the alkaline water necessary for the hydrolysis of Al and its alloys. The hydrogen generation rate from the hydrolysis of Mg is proportional to the corrosion rate of Mg to Mg2+. Mg powder, though producing a high reaction rate in the hydrolysis, causes explosive dangers when in contact with air or moisture. However, Bulk Mg such as plate and sheet exhibits an extremely low hydrogen generation rate. To overcome the disadvantage, Mg-Ni alloys were designed to form an electrochemically noble phase (Mg2Ni) along grain boundaries (G.B.), and hence to significantly accelerate the hydrolysis rate by causing a galvanic and intergranular corrosion between the noble Mg2Ni and Mg matrix. In particular, the Mg-2.7Ni alloy among the designed Mg-Ni alloys exhibits the highest hydrogen generation rate (23.8 ml min(-1) g(-1)) that is 1300 times faster than that of pure Mg. Furthermore, it was demonstrated that PEMFC stably produced 7.3 W for 20 min when it is operated by the hydrogen generated from the hydrolysis of 2 g Mg-2.7Ni alloy, that is, equivalent to 1.215 KWh/Kg-Mg-2.7Ni alloy. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

          • Effect of solvents on photonic crystallinity in graphene oxide dispersions

            Ekanayaka, T.K.,Hong, S.H.,Shen, T.Z.,Song, J.K. Pergamon Press ; Elsevier Science Ltd 2017 Carbon Vol.123 No.-

            <P>Structural color reflections from graphene oxide (GO) dispersions in binary mixtures of deionized water and organic solvents were obtained, and they were investigated at varying GO concentrations using three organic solvents: 1,4-dioxane, N-methyl-2-pyrrolidone (NMP), and dimethylformamide (DMF). Adding organic solvents in the aqueous GO dispersion changes the peak wavelength of the reflection spectrum and the purity of the reflection color, and in particular, the dependence of the peak wavelength on the GO concentration was more sensitive in the binary organic solvents than in pure water. This phenomenon can be explained by considering both the variations of the reflective index and the electrical screening effect in the binary solvents. However, only weak structural coloration based on the second order Bragg reflection was obtained in GO dispersions in pure DMF solvent, and even no structural coloration was observed in organic GO dispersions prepared using dried GO powder. These phenomena are related to the gelation at low concentration and the geometrical deformation of GO particles. Electrical switching of the structural color reflection was also demonstrated. (C) 2017 Elsevier Ltd. All rights reserved.</P>

          • Learning to segment and unfold polyhedral mesh from failures

            Xi, Z.,Kim, Y.h.,Kim, Y.J.,Lien, J.M. Pergamon Press ; Elsevier Science Ltd 2016 Computers & graphics Vol.58 No.-

            <P>Folding planar sheets to make 3D shapes from is an ancient practice with many new applications, ranging from personal fabrication of customized items to design of surgical instruments for minimally invasive surgery in self-folding machines. Given a polyhedral mesh, unfolding is an operation of cutting and flattening the mesh. The flattened polyhedral nets are then cut out of planar materials and folded back to 3D. Unfolding a polyhedral mesh into planar nets usually require segmentation. Either used as a preprocessing step to simplify the mesh and provide semantics or as the result of unfolding to avoid overlapping, the segmentation and the unfolding operations are decoupled. Consequently, segmented components may not be unfoldable and unfolded nets usually provide no semantic meaning and make folding difficult. In this paper, we propose a strategy that tightly couples unfolding and segmentation. We show that the proposed method produces unfoldable segmentation that resembles carefully designed paper craft. The key idea that enables this capability is an algorithm that learns from failed unfoldings. (C) 2016 Elsevier Ltd. All rights reserved.</P>

          • Graphene/poly(3,4-ethylenedioxythiophene)/Fe<sub>3</sub>O<sub>4</sub> nanocomposite - An efficient oxygen reduction catalyst for the continuous electricity production from wastewater treatment microbial fuel cells

            Gnana kumar, G.,Joseph Kirubaharan, C.,Yoo, D.J.,Kim, A.R. Pergamon Press ; Elsevier Science Ltd 2016 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY - Vol.41 No.30

            <P>The ternary composite comprising reduced graphene oxide (rGO), poly(3,4-ethylenedioxythiophene) (PEDOT) and iron oxide (Fe3O4) nanorods is developed and its substantial contribution toward the green energy generation of air cathode microbial fuel cells (ACMFC) as an efficient oxygen reduction reaction (ORR) catalyst is evaluated by using the different electrochemical techniques under various regimes and conditions. The effectual distribution of needle like and cubic inverse spinel structured Fe3O4 nanorods over the PEDOT enveloped graphene sheets are elucidated from the electron micrographs and the growth and composite formation mechanisms of Fe3O4 and rGO/PEDOT/Fe3O4, respectively, are enunciated from the detailed structural characterizations. The extended surface area, high electrical conductivity, and large oxygen adsorption sites of rGO/PEDOT/Fe3O4 nanocomposite facilitate the excellent ORR kinetics, which yields the maximum ACMFC power density with the superior durability of more than 600 h. Thus the proposed strategy extends a new approach in bringing the advantages of active carbon, conductive polymer and nanomaterials in a single tool, which constructs the prepared ternary composite as a potential ORR contender to the commercially available catalysts. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

          • A complete characterization of nonlinear absorption for the evolution p-Laplacian equations to have positive or extinctive solutions

            Chung, S.Y.,Park, J.H. Pergamon Press ; Elsevier Science Ltd 2016 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.71 No.8

            <P>This paper is concerned with long time behaviors of solutions to the initial-boundary value problem of the evolution p-Laplacian equations with nonlinear absorption. A long time behavior of solutions to these equations has been studied so far for particular types of nonlinear absorption term. The purpose of this paper is to give a complete characterization of the nonlinear absorption term, according to the parameter p in p-Laplacian operator and the growth of the nonlinear absorption term near the origin, in order to determine whether the solution to the equations is extinctive or positive. In addition, we also give upper bounds for extinction times of solutions. (C) 2016 Elsevier Ltd. All rights reserved.</P>

          • Structure and tribological properties of plasma-treated carbide derived carbon layer

            Lee, E.S.,Chun, Y.S.,Lee, C.H.,Lim, D.S. Pergamon Press ; Elsevier Science Ltd 2016 Carbon Vol.96 No.-

            <P>The effect of hydrogen plasma treatment on the nanocrystal structure and tribological properties of carbide derived carbon (CDC) was investigated. The CDC layer was formed on a SiC substrate using chlorine gas at 1000 degrees C. The plasma treatment was performed on the CDC layer via plasma-enhanced chemical vapor deposition (PECVD) and plasma exposure times of 1, 3, 5, 10 and 15 h were used. Raman spectra and transmission electron microscopy measurements revealed that the carbon layer of the 5 h-treated CDC layer consisted of nanocrystal phases; prior to the treatment, the carbon layer was mainly composed of amorphous carbon structures. Furthermore, the effect of the plasma treatment on the tribological properties of the CDC layer was investigated. The optimum friction coefficient value of 0.09 and a slightly enhanced wear rate were obtained after the 5 h plasma treatment. These results showed that the plasma treatment transformed the carbon structure of the CDC and increased the amount of sp(3)-bonded nanocrystal structures. As a result, the tribological properties of the CDC layer were optimized by using the plasma treatment. (C) 2015 Elsevier Ltd. All rights reserved.</P>

          • Synthesis of integrated graphene films with self-assembled single-layer channels and multi-layer electrodes via a single process

            Jung, D.,Jung, M.W.,Kim, S.H.,Song, W.,Kim, Y.,Lee, S.S.,Lee, J.O.,Park, C.Y.,An, K.S. Pergamon Press ; Elsevier Science Ltd 2016 Carbon Vol.107 No.-

            <P>Integrated graphene films (IGFs) with self-assembled single-layer graphene as a channel and multi-layer graphene as an electrode material were synthesized simultaneously using a one-step process by thermal chemical vapor deposition. The prominent difference in graphene growth rate between Ni and Cu catalytic substrates made enable to synthesize the IGFs with self-assembled single-layer and multi-layer graphene on a Cu foil with pre-patterned Ni films. The thickness of multi-layer graphene for IGFs was precisely controlled by optimizing conditions including the injection temperature of carbon feedstock and the surface concentration of Ni atoms affected by the inter-diffusion related to the growth temperature and time. The thickness and crystallinity of synthesized IGFs were evaluated by resonant Raman spectroscopy. We fabricated the IGFs-based field effect transistors (FETs) to examine electrical transport properties of the films. These results suggest that the synthesis technique for IGFs could lead to mass fabrication of wearable graphene-based FETs in the near future. (C) 2016 Published by Elsevier Ltd.</P>

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            Low-temperature co-firing process of solid oxide fuel cells by a trace of copper

            Jeon, O.S.,Jang, J.,Lee, J.G.,Lee, Y.,Shul, Y.G. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.8

            <P>8 mol % yttria stabilized zirconia (8 YSZ) is widely used as an electrolyte material for solid oxide fuel cells (SOFCs) at high temperatures, but its poor sinterability causes complications of the cell fabrication processes, increasing manufacturing costs significantly. In this study, a low-temperature co-firing process for the YSZ-based SOFCs is developed by adding the small amount of Cu to each of YSZ electrolytes and anodes. The cells are successfully fabricated without any distortions or cracks. The cell is about 1.011 V at 850 degrees C in open circuit voltage (OCV), which is reasonable despite of the co-firing process even at 1250 degrees C. The maximum power density is 0.71 W cm(-2) at 850 degrees C, which has similar performance of a conventional cell fabricated by multi-step process. Overall, the co-firing process using Cu can become promising for cost-effective fabrication process of the SOFCs except the problems related to the cathode. Copyright (c) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

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            Rapid compression machine studies on ignition delay changes in a methyl butanoate/n-heptane mixture by hydrogen addition

            Lee, S.,Song, S. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.42

            <P>The use of alternative energy is increasing with the concerns about global warming and the dwindling reserves of fossil fuels. Biodiesel and hydrogen are promising alternative fuels, and engine research has investigated the use of biodiesel/hydrogen mixtures. However, no study has examined the chemical kinetics of biodiesel and hydrogen mixtures. This study investigated the effects of hydrogen on the ignition delay of a methyl butanoate/n-heptane mixture. An experiment was conducted using a rapid compression machine (RCM) at 15 bar while varying the temperature (716-858 K) and hydrogen fraction in the fuel mixture (0, 25, 50, and 75%), and a numerical analysis was performed using CHEMKIN-PRO software to understand how the combustion process changes. The experimental and numerical analyses showed that, with hydrogen addition, the ignition delay increased. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

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