Linear and non-linear dynamic response of sandwich panels to blast loading

The problem of the dynamic response of sandwich flat panels exposed to blast loadings is addressed. The sandwich model includes a number of non-classical effects such as the anisotropy and heterogeneity of face sheets, transverse orthotropy of the core layer, the geometrical non-linearities considered in the von Kármán sense, as well as the initial geometric imperfections. As concerns the blast pulses considered in this analysis, these are due to either an underwater/in-air explosion, or are due to a pressure wave traveling across the panel span. Implications of the explosive charge, stand-off distance, directionality property of face sheets material, damping ratio, geometric non-linearity, initial geometric imperfection, and of the characteristics of the blast, on dynamic response and dynamic magnification factor are put into evidence via a parametric study, and pertinent conclusions are outlined.     

Effect of Biaxial Load on Crack Deflection/Penetration at Bi-material Ceramic Interface

The paper investigates the effect of the biaxial loading on crack deflection/penetration at a bi-material ceramic interface. A biaxially loaded geometry was numerically investigated using Finite Element Analysis in order to determine the energy release rate. The obtained results could be used in conjunction with a fracture criteria at interface for estimating the path of the crack after the interface was reached.     

Nonlinear Dynamics of Stiffened Flat Panels under Thermomechanical Loads

This paper investigates the effects of geometrical nonlinearities on dynamics of orthogonally stiffened flat panels featuring initial geometric imperfections and subjected to a temperature and a lateral pressure field. To this end, the equations governing the small finite deflection theory of stiffened flat panels incorporating the dynamic effects are established. Numerical simulations involving simply supported square panels with movable in-plane edge conditions highlighting the frequency-temperature interaction for prescribed lateral load amplitudes are presented, and implications played by stiffening parameters in conjunction with initial geometric imperfections are outlined.     

Global maximum power point tracking based on new extremum seeking control scheme

A new perturbed‐based extremum seeking control (PESC) scheme is proposed in this paper to track the global maximum power point (GMPP). The PESC scheme has two control loops based on power of the photovoltaic (PV) array: the first loop operates as usually to track the maximum power point and the second sweeps all local MPPs to locate the GMPP. Once the GMPP is located based on its uniqueness (after the PV pattern is quickly scanned many times, depending on the PV pattern's profile), the GMPP is accurately tracked based on first control loop. The used PV patterns have the profile of the PV power characteristics obtained for PV array under partially shaded conditions (PSCs). This PESC scheme is proposed to track the GMPP in the PV applications, but also in other multimodal problems from industry, being a good motif to revive the specialists' interest for the extremum seeking control field. The results obtained here are very promising for both search speed and tracking accuracy performances of the GMPP under different PSCs simulated on the PV array. Thus, the energy efficiency of PV array controlled with the proposed PESC scheme will increase with more than 1.2% in comparison with that obtained with the other MPP algorithms because of better performance shown by this PESC scheme. A 99.6% tracking accuracy is obtained here in comparison with a maximum 98.4% tracking accuracy reported in the literature. Furthermore, 100% hit and high search speed are obtained here for the GMPP localization. Copyright © 2015 John Wiley & Sons, Ltd.     

Polyhydrosilane Mediated Synthesis of One-Dimensional Gold Nanostructures

This work presents a solution-phase approach for the “one pot” synthesis of polysilane-gold nanorods. The process starts by the reduction of HAuCl₄ to Au^o with a solution of poly[diphenylsilane-co-methyl(H)silane] cooled to 4 °C. The formed small Au nanoparticles (5–15 nm diameter) serve further as seeds for the heterogeneous nucleation and anisotropic growth that takes place at 25 °C and yields crystalline needle-like polymer–gold nanostructures. The evolution of the small spherical nanoparticles to nanorods with length/width aspect ratios up to 10³ has been proved by UV–Vis spectroscopy, polarized light microscopy and AFM. Further insights on the growth mechanism were obtained by SEM, DLS and TEM.     

Personalization in multimedia retrieval: A survey

With the explosive broadcast of multimedia (text documents, image, video etc.) in our life, how to annotate, search, index, browse and relate various forms of information efficiently becomes more and more important. Combining these challenges by relating them to user preference and customization only complicates the matter further. The goal of this survey is to give an overview of the current situation in the branches of research that are involved in annotation, relation and presentation to a user by preference. This paper will present some current models and techniques being researched to model ontology, preference, context, and presentation and bring them together in a chain of ideas that leads from raw uninformed data to an actual usable user interface that adapts with user preference and customization.     

Nonperiodic flutter of a buckled composite panel

The nonlinear vibrations of a composite panel subjected to uniform edge compression and a high-supersonic coplanar flow is analysed. Third-order piston theory aerodynamics is used and the effects of in-plane edge restraints, small initial geometric imperfections, transverse shear deformation, and transverse normal stress are considered in the structural model. Periodic solutions and their bifurcations are determined using a predictor-corrector type Shooting Technique, in conjunction with the Arclength Continuation Method for the static state. It is demonstrated that third-order aerodynamic nonlinearities are destabilizing, and hard flutter oscillations (both periodic and quasiperiodic) of the buckled panel are obtained. Furthermore, chaotic motions of an uncompressed panel, as well as a buckled-chaotic transition, and chaos via period-doubling are possible, and the associated Lyapunov exponents are computed. A coexistence of the buckled state with flutter motion may also occur. Results indicate that edge restraints parallel to the flow do not significantly affect the immediate post-critical response, and that a higher-order shear deformation theory is required for a moderately thick/flexible-in-transverse-shear composite panel.