Validity of random microstructures simulation in fiber-reinforced composite materials

This paper establishes a set of criteria to check two microstructures in fiber-reinforced composites for geometrical equivalence. The criteria are based on a combination of a point process, one-point and two-point probability functions; convergence of microstructure size; and equality of fiber radius distribution. The criteria were shown to distinguish different microstructures and identify similar ones. Also, a reconstruction technique is proposed that can efficiently reconstruct a microstructure while satisfying the criteria. Results show the reconstruction technique exceeded the 5% tolerances set by multiple samples of an experimental observation.     

Z-fiber influence on high speed penetration of 3D orthogonal woven fiber composites

In the current work we present a computational investigation of high speed penetration response of 3D orthogonal woven fiber composites (3D OWC) utilizing sub-unit cell, meso-level partitioned damage mechanics with the specific aim of understanding the role of Z-fibers in the mechanical response. In our model, two primary sources of nonlinearities have been addressed – one resulting from the strain rate dependence and large deformation of the composite constituents and the other from evolving failure. We reduce a number of arbitrary parameters typically present in high speed models by taking advantage of specific geometrical properties of 3D OWC which prevent extensive delamination. This property allows us to partition the structure into resin impregnated fibers assumed to be wholly responsible for the progressive damage behavior and bulk resin which is identified as the source of visco-plasticity and strain rate dependence. The fibers are modeled as anisotropic linear elastic with strain rate dependent progressive damage evolution. The resin is modeled using an advanced high strain rate large deformation Mulliken–Boyce polymer model (Mulliken and Boyce 2006) together with a terminal thermo-mechanical failure criterion. The projectile is assumed to be cylindrical, isothermal, rigid and impacting at right angles to the plate. The shape of the damaged area and the extent of penetrative damage compares favorably with experiments. We find that Z-fibers aid in improving penetration and impact resistance by both energy absorption and structural engagement. However, we also find that they are susceptible to localized de-bonding especially around the winding crowns. In addition, we found crucial differences in mechanical response in wave propagation brought about by the interplay of fiber architecture and damage with respect to simplified membrane models.Finally, the Z-fibers were found to influence the shape and nature of the damaged area in the fibers compared to layered composites where the matrix damage is spread more evenly while the fiber damage is restricted towards the fiber axes directions.     

Not all PBILs are the same: Unveiling the different learning mechanisms of PBIL variants

Model-based optimization using probabilistic modeling of the search space is one of the areas where research on evolutionary algorithms (EAs) has considerably advanced in recent years. The population-based incremental algorithm (PBIL) is one of the first algorithms of its kind and it has been extensively applied to many optimization problems. In this paper we show that the different applications of PBIL reported in the literature correspond, in fact, to two essentially different algorithms, which are defined by the way the learning step is implemented. We analytically and empirically study the impact of the learning method on the search behavior of the algorithm. As a result of our research, we show examples in which the choice of a PBIL variant can produce qualitatively different outputs of the search process.     

A critical review on the applications of artificial neural networks in winemaking technology

Since their development in 1943, artificial neural networks were extended into applications in many fields. Last twenty years have brought their introduction into winery, where they were applied following four basic purposes: authenticity assurance systems, electronic sensory devices, production optimization methods, and artificial vision in image treatment tools, with successful and promising results. This work reviews the most significant approaches for neural networks in winemaking technologies with the aim of producing a clear and useful review document.     

Euphorbia tirucalli β-Amyrin Synthase: Critical Roles of Steric Sizes at Val483 and Met729 and the CH–π Interaction between Val483 and Trp534 for Catalytic Action

The functions of Val483, Trp534, and Met729 in Euphorbia tirucalli β-amyrin synthase were revealed by comparing the enzyme activities of site-directed mutants against that of the wild type. The Gly and Ala variants with a smaller bulk size at position 483 predominantly afforded monocyclic camelliol C, which suggested that the orientation of the (3S)-2,3-oxidosqualene substrate was not appropriately arranged in the reaction cavity as a result of the decreased bulk size, leading to failure of its normal folding into the chair–chair–chair–boat–boat conformation. The Ile variant, with a somewhat larger bulk, afforded β-amyrin as the dominant product. Intriguingly, various variants of Trp534 exhibited significantly decreased enzymatic activities and provided no aberrantly cyclized products, although the aromatic Phe and Tyr residues were incorporated and the steric sizes of the aliphatic residues were altered. Therefore, the Trp534 residue does not stabilize the transient cation through a cation–π interaction. Furthermore, the Trp residue, with the largest steric bulk among all natural amino acids, is essential for high enzymatic activity. Robust CH–π complexation between the Val483 and Trp534 residues is proposed herein. Altering the steric bulk at the Met729 position afforded the pentacyclic skeletons. Thus, Met729 is positioned at the E-ring formation site. More detailed insights into the functions of the Val483, Trp534, and Met729 residues are provided by homology modeling.     

Effect of fluorination on haze reduction in transparent polyimide films for flexible substrates

High transmittance is an important parameter for polyimide (PI) films used as flexible display substrates. However, thermal treatment during film fabrication can cause an undesired phenomenon affecting color change in the films, which is called haze. Until now, haze formation in PI films has remained mostly unexplored, suggesting that originates in the composition. In this work, the effect of fluorination on haze reduction was investigated. Both experiments and density functional theory calculations suggest that a high degree of fluorination of PI repeating units results in weaker intra/intermolecular conjugations between polymer chains and higher haze resistance in the following order: one fluorinated group (−1.43 eV) > two fluorinated groups (−0.76 eV) > three fluorinated groups (−0.52 eV) > four fluorinated groups (−0.43 eV). The differences in the haze resistance can influence on haziness in the PI films by thermal gradient inside a lab scale cavity in a furnace. The obtained results indicate that slow heat transfer facilitates the manufacturing process to obtain high transparency in PI films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44375.     

Dynamic kinetic analysis of growth of Listeria monocytogenes in a simulated comminuted,non-cured cooked pork product

The objective of this study was to directly construct a tertiary growth model for Listeria monocytogenes in a simulated comminuted, non-cured cooked pork product and simultaneously determine the kinetic parameters using a combination of dynamic and isothermal growth curves. Growth studies were conducted using a cocktail of 5 strains of L. monocytogenes in cooked pork under both dynamic and isothermal temperature profiles designed to examine the effect of temperature on bacterial growth.A direct kinetic analysis method was used to construct the growth models and determine the kinetic parameters. The bacterial growth was simulated by a set of differential equations, and the temperature effect was evaluated by the cardinal parameters model. A numerical analysis and optimization method was used to simultaneously solve the different equations and search for the best fits of kinetic parameters for the growth curves and models. The estimated minimum, optimum, and maximum growth temperatures were 0, 33.0, and 42.6 °C, matching well with typical growth characteristics of this microorganism. The root-mean-square error (RMSE) of curve-fitting was 0.42 log CFU/g.The growth models and kinetic parameters were validated using both independent dynamic and isothermal growth curves to check the accuracy of the models. The results showed that the RMSE of predicted growth was 0.49 log CFU/g. The residual errors of predictions follow a Laplace distribution, with 80.3% of the residual errors falling within ±0.5 log CFU/g of the observations. This study proves that the one-step dynamic analysis with both dynamic and isothermal temperature profiles can be an effective approach for simultaneously constructing a tertiary model and determining the kinetic parameters.     

Prediction of acceleration length in turbulent gas–solid flows

CFD investigation for gas–solid flows in a horizontal pipe was performed using Euler–Euler approach or two-fluid model and accounting for four-way coupling. Calibration of the numerical model is obtained by confirming the numerical predictions with published experimental data. Based upon the axial profiles of the pressure gradient, the authors investigated the acceleration length for different particle properties and loadings. It is found that acceleration length increases generally with increasing particulate loading and/or decreasing gas phase mean flow velocity. However, the variations of acceleration length with particle diameter are quite different under different operating conditions. Finally, an empirical correlation for acceleration length (L_a) is proposed, which contains two terms: the first-term matches with the entrance length for gas only flow; whereas the second term is regarded as the enhancement due to addition of solids to gas flow. The accuracy of the correlation is approximately ±11%.     

A text-based visual notation for the unit testing of model-driven tools

During the unit testing of model-driven tools, a large number of models and test classes needs to be managed and maintained. Typically, some of these artifacts are specified manually, some are generated automatically. Existing approaches to test management rely on the available visual and textual modeling notations. As these notations are not tailored to unit testing, distinct maintainability trade-offs arise.In this paper, we propose a notation that aims to combine the benefits of visual and text-based approaches. The notation is at the same time visual and text-based, as it uses ASCII characters to emulate the familiar graphical notations. In our evaluation based on real models, we identify problematic model shapes challenging the scalability our notation, while finding that it is well-suited to capture typical test models.