Numerical Analysis of an Intercity Bus Structure: A Simple Unifilar Model Proposal to Assess Frontal and Semifrontal Crash Scenarios

Abstract To improve the safety of the intercity bus structure against impact scenarios and to reduce the injuries and death in traffic accidents it is crucial in a country with continental dimensions like Brazil, where the road transport matrix is fundamental in the traffic of people and goods. In this context in the present article, a numerical model of an intercity bus was built with elastoplastic beam implemented in a commercial software Ls-Dyna. This model was submitted to different frontal and semi frontal impact crash scenarios. With this model were analyzed different accidents which happened in the Brazilian highways, it was also simulated a frontal impact test and the results obtained were compared with the experimental results. Finally two numerical approaches were compared, they are: a simple model made with lumped masses and non-linear springs series connected, and the elastoplastic beam model. The different comparisons carried out let us validate the intercity bus model created using elastoplastic beam elements and propose to use this model as an effective tool to search for more efficient bus structural configurations against impact scenarios

Understanding charge transport in lead iodide perovskite thin-film field-effect transistors

Fundamental understanding of the charge transport physics of hybrid lead halide perovskite semiconductors is important for advancing their use in high-performance optoelectronics. We use field-effect transistors (FETs) to probe the charge transport mechanism in thin films of methylammonium lead iodide (MAPbI$_{3}$). We show that through optimization of thin-film microstructure and source-drain contact modifications, it is possible to significantly minimize instability and hysteresis in FET characteristics and demonstrate an electron field-effect mobility (μ$_{FET}$) of 0.5 cm$^{2}$/Vs at room temperature. Temperature-dependent transport studies revealed a negative coefficient of mobility with three different temperature regimes. On the basis of electrical and spectroscopic studies, we attribute the three different regimes to transport limited by ion migration due to point defects associated with grain boundaries, polarization disorder of the MA$^{+}$ cations, and thermal vibrations of the lead halide inorganic cages.S.P.S. acknowledges funding from the Royal Society London for a Newton Fellowship. B.Y. acknowledges support from China Council Scholarship and Cambridge Overseas Trust. A.S. and R.H.F. acknowledge funding and support from the Engineering and Physical Sciences Research Council (EPSRC) through the India-U.K. APEX project. P.D. acknowledges support from the European Union through the award of a Marie Curie Intra-European Fellowship. X.M. is grateful for the support from the Royal Society. B.N. is grateful for the support from Gates Cambridge and the Winton Program for the Physics of Sustainability. We acknowledge funding from the EPSRC through a program grant (EP/M005143/1). We acknowledge funding from the German Federal Ministry of Education and Research under agreement number 01162525/1. This work was performed in part on the SAXS/WAXS beamline of the Australian Synchrotron, Victoria, Australia (55, 56). C.R.M. acknowledges support from the Australian Research Council (DP13012616)

A simple theory of particle-assisted wetting

Adsorption of solid particles to a fluid/fluid interface can reduce the total interfacial energy of a system of three fluid bulk phases in such a way that the particles induce the wetting of a fluid/fluid interface by a liquid, which does not wet this interface in the absence of particles. This particle-assisted wetting is most prominent if the contact angles at the fluid/fluid/particle contact lines are close to $\pi/2$ and if the spreading coefficient of the wetting liquid is negative but close to zero

Electrical properties of micrometric metallic dots obtained by porous polymeric membranes

We report on the fabrication of micrometric regular metallic arrays obtained by using, as a template, a polymeric membrane with regular pores. The membranes were prepared by embedding hydrophobized silica colloids into a polymer layer and subsequently removing them. We have investigated the electronic transport properties of the metallic arrays as a function of the applied electric field and temperature. Simple current voltage (IV) characteristics present a strong switching behavior with I ON /I OFF ratios up to 10 4. Different temperature dependences of the resistance in the different ranges of the applied electric field have been observed. Finally, the performances of a field effect device (FET), with the conducting channel and insulating layer consisting of a Gold dot array and a STO substrate, respectively, have been investigated. The channel resistivity has been modified at least of two orders of magnitude and a mobility of about 2 cm 2/V*s has been extracted by the analysis of the FET transfer curve. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005