Flood Forecasting and Decision Making in the new Millennium. Where are We?

This paper reviews the development of real time flood forecasting systems from the early 1970 approaches to the recent probabilistic ones. A preliminary discussion on the motivations for developing real time flood forecasting systems is introduced to explain their evolution in the last four to five decades. It will be shown how recent probabilistic flood forecasts are more robust and effective than the traditional deterministic ones. In particular, when combined with Bayesian decision approaches, probabilistic forecasts are the most appropriate tools for rational decision making in flood warning and flood management.Moreover, they allow taking into account the information from several models to be taken into account by combining into a unique predictive density the deterministic predictions of several hydrological or hydraulic models of a different nature, while in the multi-temporal forecasting extensions, they provide to answers questions such as: Which is the probability of overtopping a dyke in the next 24 h? When will this event be more likely to occur during the next 24 h?The work concludes with a discussion on the still unresolved problems, namely how decisions makers can fully take advantage of the probabilistic forecasts and how these forecasts must be communicated to them in order to meet this objective.     

Absolute rate constants for radical-monomer reactions

Summary A method is described for determining the absolute rate constants for the first few propagation steps in radical polymerization. The procedure involves a product analysis of the oligomeric alkoxyamines formed when an initiator is decomposed in monomer containing a very low concentration of a nitroxide radical scavenger. The method is illustrated with analysis of data for methyl acrylate. The rate constants for the first two propagation steps for polymerization of this monomer,k _p(1) andk _p(2), are at least an order of magnitude greater thank _p(average). Values of the absolute rate constants for reactions of phenyl and primary alkyl radicals with methyl acrylate are also estimated.     

2 1/2 D Visual Servoing with Respect to Unknown Objects Through a New Estimation Scheme of Camera Displacement

Classical visual servoing techniques need a strong a priori knowledge of the shape and the dimensions of the observed objects. In this paper, we present how the 2 1/2 D visual servoing scheme we have recently developed, can be used with unknown objects characterized by a set of points. Our scheme is based on the estimation of the camera displacement from two views, given by the current and desired images. Since vision-based robotics tasks generally necessitate to be performed at video rate, we focus only on linear algorithms. Classical linear methods are based on the computation of the essential matrix. In this paper, we propose a different method, based on the estimation of the homography matrix related to a virtual plane attached to the object. We show that our method provides a more stable estimation when the epipolar geometry degenerates. This is particularly important in visual servoing to obtain a stable control law, especially near the convergence of the system. Finally, experimental results confirm the improvement in the stability, robustness, and behaviour of our scheme with respect to classical methods.     

Physical,dynamic-mechanical and thermogravimetric analysis of aromatic and cycloaliphatic-based poly(urethaneurea)s

Experimental batches of linear rubber-like polyurethanes characterized by the presence of chemically different hard segments are studied and their thermal and dynamic-mechanical properties are related to the differences in chemical compositions. Interesting correlations are found between the development of crystallinity in such elastomeric poly(urethaneurea)s and the aromatic or alicyclic nature of the diisocyanate. Moreover, for a fixed ratio between hard and soft segments, and for a given composition of the soft segment, the results seem to indicate a better degree of phase separation in cycloaliphatic-based hard segment poly(urethaneurea)s than in aromatic-based hard segment poly(urethaneurea)s.     

High Performance, Low-Dose Radiography Systems for Space and Remote Site Applications

Medical imaging applications using X- and gamma-rays have reached outstanding levels of complexity and performance, thanks to technology achievements in the fields of radiography, tomography and high resolution synchrotron devices. The operability of the related instrumentation resides in the availability of highly qualified specialists, as well as of medical doctors for diagnoses and treatment. This is a problem for personnel working in difficult ambient conditions as can be found in remote sites like Arctica, Antarctica and under-populated, desolated or mountainous regions on Earth. Astronauts, during long permanence at the Space Station or on future mission to Mars are potentially subject to risks such as traumas, fractures or diseases which would require semi-automated, easy-to-handle application of X-ray radiographic devices. For this purpose, the possible use of imaging instrumentation based on solid state detectors is discussed with special regard to CdZnTe pixel devices, now available with sub-mm resolution. The use of these semiconductor detectors will also allow to perform image diagnostics at much lower doses compared to the current plate-based radiographic techniques.     

Dielectrophoresis of Lossy Dielectrics

Dielectrophoresis of a solid particle in a liquid medium is usually studied under the assumption that the dielectrics are ideal. Real dielectrics, however, exhibit nonzero conductivities, and the results are sometimes unpredictable. The particular case of a lossy dielectric sphere in a lossy dielectric liquid is considered. The dielectrophoretic motion following the application of a dc field is studied, and it is shown that the motion is strongly affected by conductivities. From the results it can be deduced, for instance, that the separation of solid particles in liquid media can be based on differences of conductivities rather than differences of permitivities of the two media.     

Influence of high power diode laser surface melting on the pitting corrosion resistance of type 316L stainless steel

High Power Diode Lasers (HPDL) are becoming more and more attractive for industrial materials processing because of their high efficiency, low running costs, small sizes and low weight. Surface melting experiments have been carried out on 316L steel with a 1 kW HPDL, with application to modify its pitting corrosion resistance in NaCl 0.05 M. Surface modifications have been investigated with optical microscopy for the microstructure, microprobe analysis for the chemical content and X Ray Diffraction for phase transformations and residual stresses. Heat conduction characteristics, analysed with a 2D Finite element code, have driven to a 28% calculated absorption of the laser light generating nearly 400 m melted depth. A refinement and homogenization of structure together with -ferrite transformation and the dissolution of inclusions was found in the melted thickness, driving to enhanced pitting resistance (nearly + 0.2 V on the pitting potential values, and factor 2 decrease of the passive current density). This pitting resistance, investigated at different depths below the surface, was found to be little affected by the ferrite content (6% estimated value), and the fineness of the microstructure, but depreciated by the surface state without post-polishing. Therefore, it is believed that localized corrosion improvements can be mainly attributed to the dissolution of Al-base and Mn-base detrimental inclusions, despite the generation of up to 6% ferrite susceptible to drive to enhanced galvanic couplings with phase.