Extended framework of Hamilton's principle for thermoelastic continua

Pergamon Press ; Elsevier Science Ltd 2017 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.73 No.7

<P>Based upon the extended framework of Hamilton's principle, a variational formulation for fully coupled thermoelasticity is presented. The resulting formulation can properly account for all the governing differential equations as well as initial boundary conditions. Thus, it provides the basis for a class of unified space time finite element methods. By employing bar elements in one-dimensional space along with linear shape functions temporally, the simplest space time finite element method is presented herein with representative examples for its validity. (C) 2017 Elsevier Ltd. All rights reserved.</P>

Molecular dynamics simulations of modified PEEK polymeric membrane for fuel cell application

Kim, D.J.,Park, C.H.,Nam, S.Y. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.18

<P>In this study, we synthesize a novel poly(ether ether ketone) (PEEK) polymer with sulfonic acid and ammonium moiety, and then tested the properties of the polymeric membrane for fuel cell applications. Furthermore, we investigate the effect of the functional groups on the hydronium and hydroxide ions in hydrated PEEK using molecular dynamics simulations using the COMPASS force field. The amount of functional group is controlled to be from 0 to 40 mol% in both the simulation and experimental processes. The ion diffusivity of the PEEK membranes increases with increasing amounts of functional groups and water molecules. Furthermore, when a large amount of water is added to the simulated cell, the polymer density of the functional group is reduced due to the salvation effect of water. According to the diffusion coefficient results, the simulation data are in good agreement with the experimental ion conductivity. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

Transient behavior of proton exchange membrane fuel cells over a cobalt-phosphorous/nickel foam catalyst with sodium borohydride

Gang, B.G.,Jung, W.,Kwon, S. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.1

<P>In this research, a fuel cell system is operated for 30 min and then stopped for 30 min, followed by re-operation for another 30 min to examine its restart characteristics. In this way, potential hybrid power sources, such as solar cells, can be utilized during the inoperational mode of fuel cell systems. However, such operation shows that the concentration of sodium hydroxide in sodium borohydride solutions and the durability of Co-P/Ni foam catalysts play important roles in restarting the proton exchange membrane fuel cell after the 30-min break. Thus, this article describes the catalytic hydrolysis performance of NaBH4 solutions and the operation of PEM fuel cells to characterize the discontinuous mode of fuel cell systems. Moreover, the byproduct is removed from the byproduct storage while operating the fuel cell system, reducing the total system's weight. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

Graphene/poly(3,4-ethylenedioxythiophene)/Fe₃O₄ 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>

Oxidative stress-mediated mouse liver lesions caused by Clonorchis sinensis infection

Maeng, S.,Lee, H.W.,Bashir, Q.,Kim, T.I.,Hong, S.J.,Lee, T.J.,Sohn, W.M.,Na, B.K.,Kim, T.S.,Pak, J.H. Pergamon Press ; Elsevier Science Ltd 2016 International journal for parasitology Vol.46 No.3

<P>Clonorchis sinensis is a high-risk pathogenic helminth that strongly provokes inflammation, epithelial hyperplasia, periductal fibrosis, and even cholangiocarcinoma in chronically infected individuals. Chronic inflammation is associated with an increased risk of various cancers due to the disruption of redox homeostasis. Accordingly, the present study was conducted to examine the time course relationship between histopathological changes and the appearance of oxidative stress markers, including lipid peroxidation, enzymes involved in lipid peroxidation, and mutagenic DNA adducts in the livers of mice infected with C. sinensis, as well as proinflammatory cytokines in infected mouse sera. Histopathological phenotypes such as bile duct epithelial hyperplasia, periductal fibrosis, edema and inflammatory infiltration increased in infected livers in a time-dependent manner. Intense immunoreactivity of lipid peroxidation products (4-hydroxy-2-nonenal; malondialdehyde), cyclooxygenase-2, 5-lipoxygenase and 8-oxo-7,8-dihydro-2'-deoxyguanosine were concomitantly observed in these injured regions. We also found elevated expressions of cyclooxygenase-2 and 5-lipoxygenase in C sinensis excretory-secretory product-treated cholangiocarcinoma cells. Moreover, the levels of proinflammatory cytokines such as TNF-alpha, IL beta-1 and IL-6 were differentially upregulated in infected sera. With regard to oxidative stress-mediated carcinogenesis, our findings suggest that C sinensis infestation may disrupt host redox homeostasis, creating a damaging environment that favors the development of advanced hepatobiliary diseases such as clonorchiasis-associated cholangiocarcinoma. (C) 2015 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.</P>

Effect of cathode geometry on the electrochemical performance of flat tubular segmented-in-series(SIS) solid oxide fuel cell

Mushtaq, U.,Kim, D.W.,Yun, U.J.,Lee, J.W.,Lee, S.B.,Park, S.J.,Song, R.H.,Kim, G.,Lim, T.H. Pergamon Press ; Elsevier Science Ltd 2015 International journal of hydrogen energy Vol.40 No.18

<P>A flat tubular segmented in series (SIS)-SOFC was fabricated with variable cathode thicknesses and the performance characteristics were analyzed. Vacuum slurry dip coating and screen printing technique were employed to coat the NiO-Ce(1)ScSZ(10) anode, Ce(1)ScSZ(10) electrolyte, and La0.6Sr0.4Co0.2Fe0.8 cathode on the extruded 3YSZ ceramic support. A sub module consisting of 5-cell with a total active electrode area of 4 cm(2) was interconnected in series using Ag-glass composite. Electrochemical performance analysis was conducted between 600 and 800 degrees C using 300 CC/min. 3 vol.% humidified hydrogen fuel and 1500 CC/mm air as oxidant. The results obtained from electrochemical impedance spectroscopy and current voltage polarization curves revealed a 57 mu m thick cathode layer as the optimum thickness. An application of LSCo as the cathode current collector on the surface of the cathode enhanced the performance by approximately 30% at 750 degrees C. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.</P>

Parametric study on interaction of blower and back pressure control valve for a 80-kW class PEM fuel cell vehicle

Kim, D.K.,Min, H.E.,Kong, I.M.,Lee, M.K.,Lee, C.H.,Kim, M.S.,Song, H.H. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.39

<P>Numerical study on the performance of the polymer electrolyte membrane (PEM) fuel cell vehicle with variable operating pressure was conducted to investigate the effect of blower and backpressure control valve. We conducted system level modeling for PEM fuel cell vehicle to predict its performance, where the model is based on the commercial fuel cell vehicle manufactured by Hyundai-Kia Motors and thus is validated against the real driving data. We considered most parts of PEM fuel cell vehicle powertrain, i.e. blower, membrane humidifier, and backpressure control valve at cathode, hydrogen recirculation system using ejector at anode, and the system for refrigeration and air conditioning. In building such a large system model, most of the sub system models were developed based on either zero- or one-dimensional approach, but still capturing critical physical phenomena in each device. Among these components, we focused on the effect of blower and backpressure control valve in cathode side, since these are the main control parameters in the aforementioned vehicle to influence the operating characteristics of the fuel cell stack and thus the performance of the vehicle. From the system modeling results, as the rotation speed of the blower increases, the stoichiometric number for cathodic air becomes higher and the relative humidity becomes lower. When pressure is higher, power generation from stack is proportional to stoichiometric number, however, it has greatly influence on relative humidity, and the variation of system performance is similar to that of stack. In case of the backpressure control valve, the stoichiometric number is higher and the relative humidity is lower, when back pressure is low. This change begins to reduce system power. In the end, we developed the performance curve based on the blower RPM and the valve angle, at various vehicle speeds. The proposed performance curve could provide a useful means to understand overall operating characteristics of the fuel cell vehicle. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Creep failure simulations of 316H at 550^oC: Part II - Effects of specimen geometry and loading mode

Kim, N.H.,Oh, C.S.,Kim, Y.J.,Davies, C.M.,Nikbin, K.,Dean, D.W. Pergamon Press ; Elsevier Science Ltd 2013 Engineering fracture mechanics Vol.105 No.-

<P>In this paper, the FE damage analysis method, proposed in Part I, is applied to simulate creep crack growth in six different types of cracked specimens of 316H at 550 degrees C. Comparison with experimental results shows that simulated creep crack growth rates agree well with experimental data. Shortcomings of the present method to predict creep crack initiation is briefly discussed. (C) 2013 Elsevier Ltd. All rights reserved.</P>

Sustainable harvesting of aqueous phase fatty acids by expanded graphite and isopropyl alcohol

Do, Q.C.,Kim, M.S.,Kim, D.,Ko, S.O.,Kang, S. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.46

<P>Fatty acids (FA) from organic wastes are environmentally friendly raw materials with high economic value ranging from fuels to oleo-chemicals for growing diversity of products. In this study, expanded graphite (EG) and isopropyl alcohol have been used to adsorb and concentrate the low content of FA in aqueous solution to replace the existing solid-phase extraction methods. The results showed that the maximum adsorption capacity of EG was more than 8.2 g-FA/g due to the inter-latticed structure of graphene sheets, and subsequent coalescence of FA droplets. The extraction efficiency of isopropyl alcohol was always higher than those of dichloromethane and ethanol for the recovery of absorbed FA due to the lower surface tension and higher miscibility with water. After 5 times of recycle, although the specific FA adsorption was decreased 42% of raw EG, extraction efficiencies by isopropyl alcohol were not changed. In conclusion, our study suggested that the EG and isopropyl alcohol could achieve the efficient and environmentally friendly harvesting of low concentration of FA in aqueous solutions during the biological conversion of organic matters in food waste. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Brief review of removal effect of hydrogen-plasma arc melting on refining of pure titanium and titanium alloys

Oh, J.M.,Roh, K.M.,Lim, J.W. Pergamon Press ; Elsevier Science Ltd 2016 International journal of hydrogen energy Vol.41 No.48

<P>In this study, the effect of hydrogen-plasma arc melting (HPAM) on the removal of metallic and gaseous impurities from pure titanium and titanium alloys is briefly reviewed according to the previous results and a newly added experiment. The highest removal degree (RD) of metallic impurities from pure titanium by HPAM with an Ar-20 vol.% of H-2 gas is 84.8%. In the titanium alloys, the RD values of the metallic impurities of the Ti-Ni, Ti-Mo, Ti-Al, and Ti-6A1-4V alloys regarding HPAM with an Ar-20 vol.% of H-2 gas are 82.6%, 86.2%, 49.1%, and 76.6%, respectively. The total amount of gaseous impurities such as O, N, C, and H was decreased to 962 ppm from 2697 ppm, whereby a high RD value of 64.6% is shown despite the strong affinity of titanium regarding gaseous elements. It is suggested that HPAM exerts a dramatic effect on the removal of metallic impurities from pure titanium and titanium alloys, and it is appropriate for the refining of titanium alloys whereby a significant weight loss needs to be avoided. Thereby, HPAM process can be applied to industrial refining of commercial titanium and titanium alloys. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>