Vibration energy scavenging via piezoelectric bimorphs of optimized shapes

Compact autonomous power sources are one of the prerequisites for the development of wireless sensor networks. In this work vibration energy harvesting via piezoelectric resonant bimorph beams is studied. The available analytical approaches for the modeling of the coupled electromechanical behavior are critically evaluated and compared with a finite element (FEM) numerical model. The latter is applied to analyze thoroughly the stress and strain states, as well as to evaluate the resulting voltage and charge distributions in the piezoelectric layers. The aim of increasing the specific power generated per unit of scavenger volume is pursued by optimizing the shape of the scavengers. Two optimized trapezoidal configurations are hence identified and analyzed. An experimental set-up for the validation of the proposed numerical model and of the obtained optimized structures is developed. Results of a preliminary experimental assessment, confirming the improved performances of optimized scavengers, are finally given.     

Numerical Modeling of Electrode Degradation During Resistance Spot Welding Using CuCrZr Electrodes

Resistance spot welding is a technique widely used by the automotive industry to assemble thin steel sheets. The cyclic thermo-mechanical loading associated with the accumulation of weld spots progressively deteriorates the electrodes. This study addresses the development of a comprehensive multi-physical model that describes the sequential deterioration. Welding tests achieved on uncoated and Zn-coated steel sheets are analyzed. Finite element analysis is performed using an electrical-thermal-metallurgical model. A numerical experimental design is carried out to highlight the main process parameters and boundary conditions which affect electrode degradation.     

Structure,electrochemistry and spectroscopy of a new diacylhydrazido-bridged diruthenium complex with a strongly near-infrared absorbing RuIIIRuII intermediate

Reaction of Ru(bpy)₂Cl₂·2 H₂O with 1,2-bis(trifluoroacetyl)hydrazine H₂(adc-CF₃) under basic conditions yields the dinuclear [(μ-adc-CF₃){Ru(bpy)₂}₂]²⁺ ion which was isolated and crystallized for structure determination in the meso diastereoisomer form as the bis(hexafluorophosphate). The Ru ··Ru distance was determined at 5.029(1) Å, and the N–N bond length at 1.463(5) Å reveals a hydrazido(2?) form of the bridge, implying unchanged + II metal oxidation states. Besides bpy-based reduction, the cyclic voltammetric analysis revealed two oxidation waves with a (3+) intermediate. Spectroelectrochemistry demonstrated that this intermediate [(μ-adc-CF₃){Ru(bpy)₂}₂]³⁺ with a comproportionation constant of K_c = 10^8.8 and an absorption at 1680 nm (ε = 9900 M^-1 cm^?1) is a mixed-valent species as evident most convincingly from the EPR parameters at g₁ = 2.239, g₂ = 2.065, g₃ = 1.891 (g_av = 2.101, Δg = g₁ ? g₃ = 0.348).     

Compressive properties of Ti–6Al–4V auxetic mesh structures made by electron beam melting

In this current work, a Ti–6Al–4V 3-D re-entrant lattice auxetic structure is manufactured by the electron beam melting (EBM) process. Four different design configurations (two negative Poisson’s ratio values × two relative densities) were manufactured and tested under compressive stress. Two failure modes were observed whose occurrence appeared to be dependent on the ratio of vertical strut length to re-entrant strut length. A small deflection analytical model is presented that predicts yield strength and modulus for one type of design with good accuracy. Results also show that the re-entrant lattice structure possesses superior mechanical properties compared to regular foam structures. Limitations of the analytical model are also discussed.     

évaluation du traitement des traits perceptifs des concepts vivants et non vivants lors du vieillissement normal et de la maladie d'Alzheimer.

The purpose of this study is to examine whether the way in which adults process animate and inanimate objects is impacted by the distinctiveness of the object and whether processing ability varies with age and with the quality of aging (e.g. normal aging versus pathological aging). We examined the perceptual functioning of young adults, elderly subjects and patients suffering from Alzheimer's disease. Generally, the results do not support the distributed model of conceptual representation. However, they do demonstrate that the ability to recognize objects by their distinctiveness is affected by normal and pathological aging. A gradual deterioration in the ability to correctly perceive animate objects was also observed as pathological aging progressed. These results, as well as our methods of assessing semantic memory, are discussed in terms of their theoretical and practical implications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Model of fracture for the Zry cladding of nuclear fuel rods included in the code DIONISIO 1.0

The DIONISIO code describes most of the main phenomena occurring in a fuel rod during normal operation of a nuclear power reactor. Starting from the irradiation history, the code predicts the temperature distribution, elastic and plastic stress and strain, creep, swelling and densification, release of fission gases, caesium and iodine to the internal rod volume, gas mixing, pressure increase, irradiation growth of the cladding, development of an oxide layer on its surface and hydrogen uptake, restructuring and grain growth in the pellet.This work presents the model of Zircaloy fracture included in the code DIONISIO 1.0. The model of pellet-cladding mechanical interaction (PCMI) provides the forces caused by the solid-solid contact which add to the changing internal pressure and to the constant external pressure. Besides, the program evaluates the effects of a corrosive atmosphere (stress corrosion cracking, SCC) internal or external. With these data, the code calculates the J integral around the tip of an initiated crack, and proceeds to analyze, according to the quantity of corrosive substance dissolved and the cladding stress field, if the crack remains unchanged, if it grows due to the I-SCC mechanism, or if propagation is ductile, following the R curve of the material.Results corresponding to different PHWR and PWR reactors are presented and compared with code results. In particular, good agreement is obtained in the simulation of MOX experiments, where the cladding failed due to propagation of cracks originated in SCC.     

Advantages of graded-channel SOI nMOSFETs for application as source-follower analog buffer

In this work the performance of graded-channel (GC) SOI MOSFETs operating as source-follower buffers is presented. The experimental analysis is performed by comparing the gain and linearity of buffers implemented with GC and standard SOI MOS devices considering the same mask dimensions. It is shown that by using GC devices, buffer gain very close to the theoretical limit can be achieved, with improved linearity, while for standard devices the gain departs from the theoretical value depending on the inversion level imposed by the bias current and input voltage.Two-dimensional numerical simulations were performed in order to confirm some hypotheses proposed to explain the gain behavior observed in the experimental data. By using numerical simulations the channel length has been varied, showing that the gain of buffers implemented with GC devices remains close to the theoretical limit even when short-channel devices are adopted. It has also been shown that the length of a source-follower buffer using GC devices can be reduced by a factor of 5, in comparison with a standard SOI MOSFET, without gain loss or linearity degradation.     

Eye Movements and Word Skipping During Reading Revisited.

The authors examined word skipping in reading in 2 experiments. In Experiment 1, skipping rates were higher for a preview of a predictable word than for a visually similar nonword, indicating there is full recognition in parafoveal vision. In Experiment 2, foveal load was manipulated by varying the frequency of the word preceding either a 3-letter target word or a misspelled preview. There was again a higher skipping rate for a correct preview and a lower skipping rate when there was a high foveal load, but there was no interaction, and the pattern of effects in fixation times was the same as in the skipping data. Experiment 2 also showed significant skipping of nonwords similar to the target word, indicating skipping based on partial information. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Volatile profile and differentiation between Albariño wines from different origins

Commercial Albariño wines from different subzones of Certified Brand of Origin ‘Rías Baixas’ (NW Spain) were analysed over four consecutive harvests. The contents of monoterpenes, volatile phenols, alcohols, sulphur compounds, acetates, fatty acids and ethyl esters were determined by gas chromatography (flame ionisation detector and flame photometric detector) and gas chromatography–mass spectrometry. These white wines presented high concentrations of free monoterpenes, volatile phenols, acetates, and ethyl esters, while the levels of sulphur compounds, known as default compounds, were very low. All the wines were elaborated from Albariño grapes, but they were produced by different enological practices, such as skin contact and by carrying out malolactic fermentation or not. No significant differences were found between wines from the same subzone and from different vintages. The results obtained, and confirmed by Principal component and linear discriminant analysis, showed a differentiation among these wines as a function of the Galician subzone of origin.