Experimental and Numerical Study of the Interaction Between Water Mist and Fire in an Intermediate Test Tunnel

The paper deals with interaction between water mist and hot gases in a longitudinally ventilated tunnel. The work aims at understanding the interaction of mist, smoke and ventilation.The study is based on one intermediate tunnel test and an extensive use of the computational code Fire Dynamics Simulator (FDS, NIST). The approach consists first of reconstructing the test with the CFD code by defining the relevant numerical parameters to accurately model the involved water mist system. Then, it consists of handling from the local data the complicated flows generated by the water mist flooding on the one hand and by fire and ventilation on the other hand. The last stage consists in quantifying each mechanism involved in interaction between water mist and hot gases. There are three main results in this study. Firstly, the CFD code prediction is also evaluated in this configuration, with and without water mist. Before the mist system activation, the agreement is satisfactory for gas temperatures and heat flux. After the activation time, the CFD code predicts well the thermal environment and in particular its stratification. Secondly, water mist plays a strong thermal role since in the test studied, roughly half of the heat released by fire is absorbed by water droplets. Thirdly, heat transfer from gaseous phase to droplets is the main mechanism involved (73%). The remaining heat absorbed by droplets results from tunnel surface cooling which represents (9%) and radiative attenuation (18%).     

Determinants of cross-regional R&D collaboration: some empirical evidence from Europe in biotechnology

In this study, we focus on the pattern of cross-regional R&D collaborations through which voluntary knowledge flows and accompanying spillovers might occur. Our aim is to investigate the processes that give rise to the observed network configuration in order to identify hampering factors of knowledge diffusion, with a particular interest in the role of geographical proximity and differences in territorial features. We make use of the data on project proposals submitted to the 7th Framework Programme in the field of biotechnology. We build a non-valued inter-regional R&D cooperation network among a set of European regions and study its formation through exponential random graph models (Frank and Strauss in J Am Stat Assoc 81(395):832–842, 1986; Wasserman and Pattison in Psychometrika 61(3):401–425, 1996). Besides the role played by absorptive capacities, the empirical results reveal that contiguity affects the pattern of cross-regional collaborations not only via edge formation among neighbours but also through a triadic closure process which links neighbouring regions to non-neighbours. Furthermore, triadic closure is found out to be in play among highly populated regions and regions including capital cities.     

Study of prepolymerization complex formation in the synthesis of steroid-based molecularly imprinted polymers

The preparation of steroid-based molecularly imprinted polymers (MIPs) based upon noncovalent interaction is particularly suited for selective capture of steroid hormones in biological and environmental samples. The success of this method lies in the optimization of the interaction between steroids (template) and methacrylic acid (functional monomer) in the prepolymerization mixture. NMR techniques coupled with DFT calculations were used to evaluate the capacity of the methacrylic acid to bind a steroid for future applications. The androstane derivative steroids considered in the present study have two functional groups at C(3) and C(17), which may interact with the methacrylic acid. These can be hydroxyl or ketone groups. Experimental results show that the steroids can be divided in three groups corresponding to the ketone type at C(3), the H-bond strength increasing with the number of double bonds. DFT calculations are in very good agreement with experimental results, showing increasing binding energy from no bonds, a single bond, and two double bond steroids. For steroids holding a hydroxyl group the binding energy obtained in the solvent model is comparable to the binding energy of single bond ketone steroids.     

Synthesis, electron tomography and single-particle optical response of twisted gold nano-bipyramids

A great number of works focus their interest on the study of gold nanoparticle plasmonic properties. Among those, sharp nanostructures appear to exhibit the more interesting features for further developments. In this paper, a complete study on bipyramidal-like gold nanostructures is presented. The nano-objects are prepared in high yield using an original method. This chemical process enables a precise control of the shape and the size of the particles. The specific photophysical properties of gold bipyramids in suspension are ripened by recording the plasmonic response of single and isolated objects. Resulting extinction spectra are precisely correlated to their geometrical structure by mean of electron tomography at the single-particle level. The interplay between the geometrical structure and the optical properties of twisted gold bipyramids is further discussed on the basis of numerical calculations. The influence of several parameters is explored such as the structural aspect ratio or the tip truncation. In the case of an incident excitation polarized along the particle long axis, this study shows how the plasmon resonance position can be sensitive to these parameters and how it can then be efficiently tuned on a large wavelength range.     

Electron fluctuation induced resonance broadening in nano electromechanical systems: the origin of shear force in vacuum

This article presents a study of the poorly understood "shear-force" used in an important class of near-field instruments that use mechanical resonance feedback detection. In the case of a metallic probe near a metallic surface in vacuum, we show that in the 10-60 nm range there is no such a thing as a shear-force in the sense of the nonconservative friction force. Fluctuations of the oscillator resonance frequency, likely induced by local charge variations, could account for the reported effects in the literature without introducing a dissipative force.     

Stress intensity factors computation for bending plates with extended finite element method

The modelization of bending plates with through‐the‐thickness cracks is investigated. We consider the Kirchhoff–Love plate model, which is valid for very thin plates. Reduced Hsieh–Clough–Tocher triangles and reduced Fraejis de Veubeke–Sanders quadrilaterals are used for the numerical discretization. We apply the eXtended Finite Element Method strategy: enrichment of the finite element space with the asymptotic bending singularities and with the discontinuity across the crack. The main point, addressed in this paper, is the numerical computation of stress intensity factors. For this, two strategies, direct estimate and J‐integral, are described and tested. Some practical rules, dealing with the choice of some numerical parameters, are underlined. Copyright © 2012 John Wiley & Sons, Ltd.     

Potentialities of Raman Imaging for the Analysis of Oxide Scales Formed on Zircaloy-4 and M5® in Air at High Temperature

Micro-Raman imaging was used to investigate oxide scales formed on Zircaloy-4 and M5^® alloys in air, in the 800–1,000 °C temperature range. To create the 2D spectral images, the data were processed by different ways. The results clearly show that a microscopic picture of the scales in terms of microstructure and internal stresses can be developed from Raman spectral maps at the micron scale. Data on the microstructure, crystallography, and composition, are presented. They confirm that the crystallographic phases observed for the Zircaloy-4 and M5^® alloys are different, since, for Zircaloy-4, we clearly observed additional Raman signatures which most probably track the presence of nitrogen in the layers well before the occurrence of the kinetic transition. In particular, they show the presence of cubic zirconia in the layers, and strongly suggest the presence of zirconium nitride and oxynitride. Results also suggest the presence of strong stress gradients in the oxide scales.     

Multitemporal MERIS images for land-cover mapping at a national scale: a case study of Portugal

Medium-spatial-resolution satellite images have already proved to be successful in automatic production of global land-cover maps. However, their operational use for land-cover mapping at a national scale has not yet been well established. We find that the reasons for this are not data-source dependent, but are due to the land-cover nomenclatures properties adopted, regional landscape specificities and the methodological approaches used. The aim of this paper is to evaluate the suitability for national applications of land-cover maps derived from automatic classification of medium-spatial-resolution satellite images. To tackle this issue, we produce a land-cover map of Continental Portugal from multitemporal MEdium Resolution Imaging Spectrometer (MERIS) full-resolution satellite images of 2005 and evaluate its accuracy. For the accuracy assessment of the final map, we compute unbiased estimates of overall, user and producer accuracies using an independent testing sample collected through a stratified random sampling design. The overall accuracy of the final map is 80%, with an absolute precision of 2% at the 95% confidence level. High independent accuracy assessment results demonstrate that medium-spatial-resolution satellite images can be used on an operational basis for annual production of land-cover maps suitable for national applications.     

A new instrument for automated microcontact printing with stamp load adjustment

An instrument for automated microcontact printing (microCP) on microscope slides is described. The movement of the stamp, which is actuated by a computer controlled pneumatic actuator, is precisely guided until it makes contact with the substrate. As a consequence, the absolute position of the microprinted patterns is reproducible over a series of substrates with 1 mum standard deviation. Exchange of substrates and stamps is a quick and simple procedure. This makes possible the microprinting of adjacent or superimposable patterns, with different products, in a reproducible manner. Furthermore, a novel approach is described for adjusting the load on the stamp during contact. Two adjustable screws are set up so that their length (with reference to the substrate holder) limits the stamp compression during contact. The load on the stamp is proportional to the stamp compression and from the experimental point of view, this is controlled by the operator adjusting the screws. This makes possible the microCP with stamps incorporating large surface features as well as stamps with isolated features raised on the surface. For proof of concept, automated microCP of a single parallelepiped polydimethylsiloxane feature, with a surface of 2 cm x 30 microm and a height of 25 mum, is demonstrated inside a microfluidic channel without roof collapse. A second example is provided with a single cross feature, possessing an overall surface of 140 x 140 microm(2) and a height of 14 microm. Potential applications of this versatile, inexpensive and compact instrument are discussed. The machine's potential for high throughput also makes it suitable for mass production applications.