SMA Numerical Modeling Versus Experimental Results: Parameter Identification and Model Prediction Capabilities

In this work, we briefly review the one-dimensional version of a well-known phenomenological shape memory alloy (SMA) constitutive model able to represent the main macroscopic SMA macroscopic behaviors (i.e., superelasticity and shape-memory effect). We then show how to identify the needed parameters from experimental results and, in particular, from strain-temperature tests. We finally use the obtained material parameters to test the prediction properties of the model, comparing numerical results with some experiments (different from those used for the identification), and we discuss model capabilities and further required enhancements.     

Numerical analysis of a three‐dimensional super‐elastic constitutive model

This note deals with the efficient approximation of a non‐linear constitutive relation arising in the study of the three‐dimensional mechanical behaviour of shape memory alloys at constant temperature. In particular, a variable time‐step discretization is investigated. For such an algorithm we prove sharp error estimates of optimal order and exactness for a class of experimentally relevant situations. We also report numerical results relative to proportional and non‐proportional loading tests which fully confirm the theoretical analysis. Copyright © 2004 John Wiley & Sons, Ltd.     

A GIS-based method for multi-objective evaluation of park vegetation

In this paper we describe a method for evaluating the concordance between a set of mapped landscape attributes and a set of quantitatively expressed management priorities. The method has proved to be useful in planning urban green areas, allowing objectively documented decisions and helping the resolution of opinion conflicts among decision makers. A case study, involving the evaluation of the vegetation component of a suburban park, is described in detail. The analysis of the case study highlights the power of the method, and of geographical information systems- (GIS-) based decision support methods in general, as a planning aid for green park areas. Their use allowed us not only to propose interesting reorganization plans, but also to give decision makers a better understanding of their own priorities.     

Linked interpolation for Reissner-Mindlin plate elements: Part II—A simple triangle

The formulation and shape functions given in Part I are extended to develop a simple plate bending triangle with good performance in both thin and thick situations. Indeed, its performance is better than that of other nine DOF elements and its computer implementation simpler. When used with selective reduced integration, the element produces identical results as that of Xu.^1,2 To save space, details given in Part I are not repeated and some results are also presented in the figures of Part I.     

A simple and effective method to form metallic nanoparticles onto composites made up of organic polymers and layered inorganic ion exchangers as fillers

A new easy method for the preparation of polymeric nanocomposites supporting metal nanoparticles is presented. The method concerns the use of a layered inorganic ion exchanger converted in the proper metallic form and exfoliated to act as filler of organic polymers with twofold aim of obtaining a composite (or nanocomposite) and to have metal ions that can be suitably reduced with a proper reducing agent to form metal nanoparticles. This strategy has been applied to the system polyvinylidene fluoride (PVDF) filled with layered a-zirconium phosphate in copper form. Several physical techniques (X-ray powder diffraction, atomic force microscopy, high resolution transmission electron microscopy) have been used to characterize the Cu-nanoparticles, whose dimensions range from 5 to 200 nm for those placed inside or on the surface of the polymeric matrix respectively, depending on the dispersion degree of the inorganic filler. The method is simple and can be used for different polymeric matrices and/or metal ions in order to produce metal/polymer systems with promising technological application.     

Drug-beta-cyclodextrin containing pellets prepared with a high-shear mixer

This work was aimed at investigating the preparation of β-cyclodextrin-microcrystalline cellulose pellets by means of a high-shear mixer, both in the absence or in the presence of ibuprofen as model drug. Drug loading of pellets was accomplished by means of two alternative techniques: 1) solution layering or 2) powder layering. The prepared pellets were characterised in terms of size distribution, shape factor, friability and dissolution rate. The interaction between ibuprofen and β-cyclodextrin was monitored by Differential Scanning Calorimetry (DSC). Micro Fourier Transform Infrared spectroscopy (MicroFTIR) was applied to determine the distribution of components within each pellet on a micro scale. Pellets with narrow size distribution and containing up to about 90% of BCD were prepared using water as binder. The process yield resulted around 84 and 63% for drug-free and medicate pellets respectively. Drug loaded pellets with favourable technological and biopharmaceutical characteristics can be obtained both by powder or solution layering techniques. The latter proved to be more suitable for producing pellets with high drug contents, reduced friability and high drug dissolution rates.     

Principal component analysis as a method to facilitate fast detection of transient-evoked otoacoustic emissions

Transient-evoked otoacoustic emissions (TEOAE) are acoustic signals coming from the inner ear (outer hair cells of the cochlea) after acoustic stimulation by clicks. They can be used to investigate the status of the peripheral hearing system. Some of their potential applications (e.g., their use as a tool in newborn hearing screening programs) are deeply related to the duration of each recording session. This duration can be strongly reduced by applying a principal component analysis approach to a set of TEOAE recorded from the same ear at different stimulus levels averaging only a few sweeps (a maximum of 100 versus the classical 260). The PCA approach is shown to be able to enhance the signal-to-noise ratio and, in turn, to allow a correct detection of the responses. Results of the application of this approach in comparison with responses recorded from the same subjects with the classical technique will be shown.     

Chemical cues from Murgantia histrionica eliciting host location and recognition in the egg parasitoid Trissolcus brochymenae

Host location and recognition by the egg parasitoid Trissolcus brochymenae were analyzed in terms of response to kairomones from several stages of its host, Murgantia histrionica. In a Y-tube olfactometer, parasitoid females responded by increasing residence time and/or reducing linear speed to chemical cues from gravid females, virgin females and males, fifth and third instars, and eggs. In an open arena, T. brochymenae females also responded to patches contaminated by chemicals from the host in the same stages, sexes, and/or physiological conditions as those tested in the olfactometer. The parasitoid displayed arrestment behavior, increased residence time, changed walking pattern, and intense substrate examination. When host egg clusters or glass dummies with a chemical egg extract were placed on the host-contaminated open arena, these elicited an orientation response in the parasitoid. In addition, the chemical egg extract without dummies elicited the same response, whereas dummies without extract did not influence parasitoid behavior. In a closed arena, the parasitoid females recognized and attempted to probe glass beads treated with chemical extracts of host eggs. There were no significant differences compared with their response to the host eggs, and they did not respond to untreated beads. Host recognition was elicited by chemicals from the follicular secretion used by the host to glue the eggs on the substrate. These results are discussed in relation to the level of the host selection sequence influenced by these cues.