Variationally consistent computational homogenization of transient heat flow

A framework for variationally consistent homogenization, combined with a generalized macro‐homogeneity condition, is exploited for the analysis of non‐linear transient heat conduction. Within this framework the classical approach of (model‐based) first‐order homogenization for stationary problems is extended to transient problems. Homogenization is then carried out in the spatial domain on representative volume elements (RVE), which are (in practice) introduced in quadrature points in standard fashion. Along with the classical averages, a higher order conservation quantity is obtained. An iterative FE²‐algorithm is devised for the case of non‐linear diffusion and storage coefficients, and it is applied to transient heat conduction in a strongly heterogeneous particle composite. Parametric studies are carried out, in particular with respect to the influence of the ‘internal length’ associated with the second‐order conservation quantity. Copyright © 2009 John Wiley & Sons, Ltd.     

The Family Almost Perfect Scale: Development, psychometric properties, and comparing Asian and European Americans.

This article describes two studies related to the development and psychometric evaluation of the Family Almost Perfect Scale (FAPS), which measures the perceived level of perfectionistic standards and evaluation from one's family. In Study 1 (N = 283), exploratory factor analysis was used to determine the FAPS scale items. In Study 2, the FAPS was cross-validated through confirmatory factor analyses with an Asian/Asian American sample (N = 252) and a European American sample (N = 386). These two samples were compared on study variables and Asians/Asian Americans reported modestly higher personal and family discrepancy and lower self-esteem. Participants were also grouped into different perceived perfectionistic family types. Those that perceived having maladaptively perfectionistic families reported greater depression and lower self-esteem. Implications for counseling and future directions for research are also discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A model of reduced oxidation kinetics using constituents and species: Iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane

A previously described methodology for deriving a reduced kinetic mechanism for alkane oxidation and tested for n-heptane is here shown to be valid, in a slightly modified version, for iso-octane and its mixtures with n-pentane, iso-hexane and n-heptane. The model is still based on partitioning the species into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement in the species ensemble, and mathematically decomposing the heavy species into constituents which are radicals. For the same similarity variable found from examining the n-heptane LLNL mechanism in conjunction with CHEMKIN II, the appropriately scaled total constituent molar density still exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures in the cold ignition regime. When extended to larger initial temperatures than for cold ignition, the self-similar behavior becomes initial temperature dependent, which indicates that rather than using functional fits for the enthalpy generation due to the heavy species’ oxidation, an ideal model based on tabular information extracted from the complete LLNL kinetics should be used instead. Similarly to n-heptane, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable, but here their slope variation is no longer fitted and instead, their rate equations are used with the ideal model to calculate them. As in the original model, the light species ensemble is partitioned into quasi-steady and unsteady species; the quasi-steady light species mole fractions are computed using the ideal model and the unsteady species are calculated as progress variables using rates extracted from the ideal model. Results are presented comparing the performance of the model with that of the LLNL mechanism using CHEMKIN II. The model reproduces excellently the temperature and species evolution versus time or versus the similarity variable, with the exception of very rich mixtures, where the predictions are still very good but the multivalued aspect of these functions at the end of oxidation is not captured in the reduction. The ignition time is predicted within percentages of the LLNL values over a wide range of equivalence ratios, initial pressures and initial temperatures.     

Elevated temperature cycling stability and electrochemical impedance of LiMn2O4 cathodes with nanoporous ZrO2 and TiO2 coatings

In this study, nanoporous zirconia (ZrO₂) and titania (TiO₂) coatings are shown to stabilize the cycling performance of lithium-ion batteries with LiMn₂O₄ spinel cathodes. The effect of firing temperature on the coating pore size is discussed and the resulting performance of the coated cathodes is evaluated. Stabilization mechanisms, such as neutralization of acidic electrolytes by ZrO₂ and TiO₂ coatings, are examined. It is proposed that the establishment of a complex nanoporous network for lithium-ion transport results in a more uniform current distribution at the particle surface, thereby suppressing capacity fade that may be associated with surface instabilities of the spinel electrode.     

Toward implantable devices for angle-sensitive,lens-less,multifluorescent, single-photon lifetime imaging in the brain using Fabry–Perot and absorptive color filters

Implantable image sensors have the potential to revolutionize neuroscience. Due to their small form factor requirements;however, conventional filters and optics...     

Sequence-dependent batch chemical scheduling with earliness and tardiness penalties

Production volume in the specialized agricultural chemical industry is typically too small to justify the capital expenditure required for continuous processing. As such, there is a trend towards building chemical processing plants for this market segment that are batch plants. Scheduling of this type of chemical plant under just-in-time operations, where both earliness and lateness penalties are included, is critical to the efficient operation of these plants. In this paper, a heuristic scheduling procedure is developed for the problem of minimizing the total weighted earliness and tardiness costs as well as the total set-up cost for the single-stage batch chemical manufacturing environment.