Search results for "Pie"
showing 10 items of 4404 documents
Structural Health Monitoring of Cracked Beam by the Dual Reciprocity Boundary Element Method
2012
In this paper a 2D boundary element model is used to characterize the transient response of a piezoelectric based structural health monitoring system for cracked beam. The BE model is written for piezoelectric non-homogeneous problem employing generalized displacements. The dual reciprocity method is used to write the mass matrix in terms of boundary parameters only. The multidomain boundary element technique is implemented to model non-homogeneous and cracked configuration, unilateral interface conditions are also considered to prevent the physical inconsistence of the overlapping between interface nodes belonging to the crack surfaces. To assess the reliability and the effectiveness of th…
Two Methods to Broaden the Bandwidth of a Nonlinear Piezoelectric Bimorph Power Harvester
2017
We propose two methods to broaden the operation bandwidth of a nonlinear pinned–pinned piezoelectric bimorph power harvester. The energy-scavenging structure consists of a properly poled and electroded flexible bimorph with a metallic layer in the middle, and is subjected to flexural vibration. Nonlinear effects at large deformations near resonance are considered by taking the in-plane extension of the bimorph into account. The resulting output powers are multivalued and exhibit jump phenomena. Two methods to broaden the operation bandwidth are proposed: The first method is to extend the operation frequency to the left single-valued region through optimal design. The second method is to exc…
High-velocity Impact Location on Aircraft panels Using Macro-fiber Composite piezoelectric Rosettes
2010
In this article, an approach based on an array of macro-fiber composite (MFC) transducers arranged as rosettes is proposed for high-velocity impact location on isotropic and composite aircraft panels. Each rosette, using the directivity behavior of three MFC sensors, provides the direction of an incoming wave generated by the impact source as a principal strain angle. A minimum of two rosettes is sufficient to determine the impact location by intersecting the wave directions. The piezoelectric rosette approach is easier to implement than the well-known time-of-flight-based triangulation of acoustic emissions because it does not require knowledge of the wave speed in the material. Hence, th…
Self-piercing riveting for aluminium alloys-composites hybrid joints
2008
In the paper, the growing interest on hybrid joints developed between composite panels and aluminium alloys blanks is focused. The self-piercing riveting operation is considered and its feasibility for the proposed joints verified. The most relevant process parameters were investigated in order to determine a suitable process window and, what is more, the mechanical performances of the developed joints were investigated in order to determine process parameters aimed to maximise them. Finally, the failure mechanics of the obtained joints were considered in order to highlight the mechanisms which occur and determine the lost of the load carrying capability of the joints. The developed experim…
On the dynamic behavior of piezoelectric active repair by the boundary element method
2011
The dynamic behavior of piezoelectric active repair bonded on cracked structures is analyzed in this article. The boundary element code used to perform the simulations is implemented in the framework of piezoelectricity in order to model the coupling between the elastic and the electric fields, which represents the most important feature of piezoelectric media. The fracture mechanics problem, i.e. the crack, as well as the bonding layer between the host structure and the active patch is modeled by means of the multidomain technique provided with an interface spring model. More particularly, the spring interface model allows considering the bonding layer as a zero-thickness elastic ply char…
Estats col · lapsats, les administracions internacionals, l'ocupació i els neo-protectorats
2012
Xerrada sobre els estats col · lapsats, les administracions internacionals, l'ocupació i els neo-protectorats.
Bourdieu en la educación científica: consecuencias para la enseñanza y la investigación
2012
Over the last decades, the development and establishment of a sociocultural approach to science education have led to an increasing interest in other theoretical frameworks such as the sociology of science and the sociology of education of Pierre Bourdieu (1930-2002). With the purpose of contributing to the advancement of the appropriation of Bourdieu’s work by research in science education, this paper presents some of the most important ideas of this author and discusses their implications for science education and research. A lo largo de las últimas décadas, el desarrollo y la consolidación de un abordaje sociocultural a la educación científica han dado lugar a un creciente interés por re…
Failure of Cytomegalovirus-Specific CD8+ T Cell Levels at Viral DNAemia Onset to Predict the Eventual Need for Preemptive Antiviral Therapy in Alloge…
2018
Psychological therapies for adolescents with borderline personality disorder (BPD) or BPD features-A systematic review of randomized clinical trials …
2021
Objectives To review the effectiveness of psychological therapies for adolescents with borderline personality disorder (BPD) or BPD features. Methods We included randomized clinical trials on psychological therapies for adolescents with BPD and BPD features. Data were extracted and assessed for quality according to Cochrane guidelines, and summarized as mean difference (MD) with 95% confidence intervals (CI) for continuous data and as Odds ratios (OR) with 95% CI for dichotomous data. Risk of bias was assessed using Cochrane’s risk of bias tool for each domain. When possible, we pooled trials into meta-analyses, and used Trial Sequential Analysis (TSA) to control for random errors. Quality…