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The solid oxide fuel cell (SOFC) system has emerged as an important technology for automotive and stationary applications. Modeling and simulation of the SOFC system have been utilized as an integral tool in an accelerated joint SOFC system development program. Development of unique modeling approaches and their results are discussed and compared with experimental performance. One dimensional system level analysis using Aspen with an embedded stack electro-chemical model was performed resulting in effective sub-system partitioning and requirements definition. Further, a three-dimensional integrated electro-chemical/thermal/computational fluid dynamics analysis of steady-state operation was employed. The combination of one-dimensional and three-dimensional environments led to effective performance projection at all levels in the system, resulting in optimization of overall system performance early in the design cycle.

In this paper we have established some coupled coincidence and coupled common fixed point theorems on (ψ, )-weakly contractive condition for mapping having the g-mixed monotone property in partially ordered generalized metric spaces which generalize some recent fixed point theorems given in the literature.

A joint study was conducted by Oak Ridge National Laboratory (ORNL) and the Pacific Northwest Laboratory (PNL) for the U.S. Department of Energy-Lightweight Materials (DOE-LWM) Program. the purpose of the study was to assess and benchmark the current modeling capabilities with respect to accuracy of predictions and simulation time. Two modeling capabilities with respect to accuracy of predictions and simulation time. Two simulation platforms were considered in this study, which included the LS-DYNA3D code installed on ORNL`s high- performance computers and the finite element code MARC used at PNL. both ORNL and PNL performed superplastic forming (SPF) analysis on a standard butter-tray geometry, which was defined by PNL, to better understand the capabilities of the respective models. The specific geometry was selected and formed at PNL, and the experimental results, such as forming time and thickness at specific locations, were provided for comparisons with numerical predictions. Furthermore, comparisons between the ORNL simulation results, using elasto-plastic analysis, and PNL`s results, using rigid-plastic flow analysis, were performed.

Fast microstructure reconstruction from statistical information is critical to create high resolution image with large domain for materials property prediction. Large structural data generated from multimodality chemical imaging instrumentation also calls for fast microstructure reconstruction for evaluation and interpretation. Stochastic methods in microstructure reconstruction from two-point correlation function have been applied widely in materials and mechanical engineering community. The main challenge is to increase the efficiency of large data reconstruction and reconstruction. A novel simulated annealing method, adaptive multiple super fast simulated annealing, is proposed for fast solution to improve efficiency. Combining the advantage of very fast cooling schedules, dynamic adaption and parallelisation, the new simulation annealing algorithm increases the efficiencies by several orders of magnitude, making the large domain image fusion feasible.

We present a generalized kinetic model for gas-solid heterogeneous reactions taking place at the interface between two phases. The model studies the reaction kinetics by taking into account the reactions at the interface, as well as the transport process within the product layer. The standard unreacted shrinking core model relies on the assumption of quasi-static diffusion that results in a steady-state concentration profile of gas reactant in the product layer. By relaxing this assumption and resolving the entire problem, general solutions can be obtained for reaction kinetics, including the reaction front velocity and the conversion (volume fraction of reacted solid). The unreacted shrinking core model is shown to be accurate and in agreement with the generalized model for slow reaction (or fast diffusion), low concentration of gas reactant, and small solid size. Otherwise, a generalized kinetic model should be used.

Interstitial loops are one of the principal evolving defects in irradiated materials. The evolution of interstitial loops, including spatial and size distributions, affects both vacancy and interstitial accumulations in the matrix, hence, void formation and volumetric swelling. In this work, a phase-field model describing the growth kinetics of interstitial loops in irradiated materials during aging is developed. The diffusion of vacancies and interstitials and the elastic interaction between interstitial loops and point defects are accounted in the model. The effects of interstitial concentration, chemical potential, and elastic interaction on the growth kinetics and stability of interstitial loops are investigated in two and three dimensions. It is found that the elastic interaction enhances the growth kinetics of interstitial loops. The elastic interaction also affects the stability of a small interstitial loop adjacent to a larger loop. The model predicts linear growth rates for interstitial loops that is in agreement with the previous theoretical predictions and experimental observations.

Using density functional theory, a series of calculations of structural and electronic properties of Si-substituted graphene were conducted. Through substituting C atoms by Si atoms on graphene in the present study, we found that the band gap of graphene can be continuously tuned with differently substitutional concentration. To utilize such substitution-induced band gap changes, we proposed a special design to fabricate graphene-based quantum well device.

In the above titled paper (ibid., vol. 56, no. 8, pp. 1732-1743, Aug. 09), the third author's name was misspelled in the byline. The corrected byline is presented here.

We developed a nondestructive and noncontact method for measuring stress at the midplane of tempered glass plates that uses Bragg scattering from a pair of thermal gratings. These gratings are formed by 1064-nm beams from a seeded Nd:YAG laser, and we measure the polarization state of light from a 532-nm beam that scatters from both thermal gratings. The change in polarization of the doubly scattered light with separation between the two gratings allows measurement of the in-plane stress. A model of the Bragg scattering efficiency, experimental investigations of the scattered beams, and stress measurements are reported.

This paper examines key aspects of the manufacturing process that “Transformation Induced Plasticity” (TRIP) steels would be exposed to, and systematically evaluate how the forming and thermal histories affect final strength and ductility of the material. The paper evaluates in-service temperature variations, such as under hood and hot/cold cyclic conditions, to determine whether these conditions influence final strength, ductility and energy absorption characteristics of several available TRIP steel grades. As part of the manufacturing thermal environment evaluations, stamping process thermal histories are included in the studies. As part of the in-service conditions, different pre-straining levels are also included. Materials from four steel suppliers world wide are examined. The material properties are established over a full range of expected thermal histories and selected loading modes. Establishing these relationships will allow OEM designers to select TRIP steels for proper vehicle applications, and to specify manufacturing process conditions that yield reliable final material property levels.