A new real-time shape acquisition with a laser scanner: first test results

The first results of a new method for real-time shape acquisition with a laser scanner are presented. The new method is essentially based on the use of a laser beam and a web-cam. A digital filter parameters identification was studied for the laser line detection in the image. After this, a model for the reconstruction in real-time of the laser line in the space was developed. The first test rig was just conceived to validate the method; hence, no high resolution cameras were adopted. Nevertheless, the tests have showed encouraging results.     

A Bayesian paradox and its impact on the GUM approach to uncertainty

The paper presents ideas and observations about the use of the frequentist and the Bayesian approach to estimation and uncertainty. The merits and the pitfalls of the Bayesian approach, compared with the frequentist one, are illustrated using a simple example, which gives rise to an instructive paradox. The impact of the paradox on the GUM approach to uncertainty prescribed in Supplement 1 is highlighted and discussed.     

The release into the atmosphere of hazardous volatiles Part II. Release from a slab of contaminated porous particles. The importance of free convection

The release of a volatile organic compound from a slab of porous particles imbued with an immobile oily phase containing the volatile is studied. The most important feature of the model is that it accounts for natural convection besides diffusion. The gas which fills the interparticle porosity of the contaminated slab has a composition, and thus a density, different from that of the surrounding atmosphere. Therefore, a natural convection flux may be established through the slab. The model shows that natural convection indeed plays an important role which increases with the vapor pressure of the component. For benzene it predominates the overall process.     

Theoretical fuel element modelling at CNEA

Computer codes and theoretical developments aiming to model nuclear reactor fuel elements at CNEA are reviewed. The codes PELT, VAINA and BACO for the overall fuel behaviour, as well as the finite element systems ELASTEF, PLASTEF and CTR are described. The influence on the BACO code predictions of including a fuel cracking model is discussed. Also, some examples of the calculated fuel cladding contact pressure are shown for different situations. Applications of the finite element systems to calculate the stress concentration at the skids of the Central Nuclear Atucha fuel rods and to predict local thermal effects of PuO₂ particles in a UO₂ fuel are discussed.     

Low-temperature relaxation processes in cold-worked zirconium

The internal friction and modulus relaxation spectrum of high-purity polycrystalline zirconium has been studied between 77 K and room temperature. Low (1 Hz) and high (50 kHz) frequency measurements are reported after room- and low-temperature tensile deformation. Three relaxation peaks appeared, called P₁, P₂ and P₃. The variation of these with the measuring frequency, amount of cold work and annealing of the specimen at temperatures above that of deformation was investigated. The peak P₁ appeared in the range 80 to 90 K at 1Hz after cold work at 80 K and dissappeared on heating the specimen above 200 K. P₂ appeared either after deformation at room temperature or at low temperature if followed by an annealing process above 200 K: this peak is a very wide one at low frequencies (1 Hz) with its maximum at about 150 K. P₃, generated by cold-working the specimen at 80 K, proved to be very unstable and recovered while being measured at 1 Hz: its physical origin is still uncertain. The recovery of the modulus defect after deformation at 80 K showed three stages, coincident with those of resistivity reported in the literature. The peak p₁ is considered to be due to the relaxation of dislocations against intrinsic lattice barriers, the peak P₂ to the interaction of point defects with dislocations.     

Coexpression of IL-6 and soluble IL-6R causes nodular regenerative hyperplasia and adenomas of the liver

Studies with tumor necrosis factor p55 receptor- and interleukin-6 (IL-6)-deficient mice have shown that IL-6 is required for hepatocyte proliferation and reconstitution of the liver mass after partial hepatectomy. The biological activities of IL-6 are potentiated when this cytokine binds soluble forms of its specific receptor subunit (sIL-6R) and the resulting complex interacts with the transmembrane signaling chain gp130. We show here that double transgenic mice expressing high levels of both human IL-6 and sIL-6R under the control of liver-specific promoters spontaneously develop nodules of hepatocellular hyperplasia around periportal spaces and present signs of sustained hepatocyte proliferation. The resulting picture is identical to that of human nodular regenerative hyperplasia, a condition frequently associated with immunological and myeloproliferative disorders. In high expressors, hyperplastic lesions progress with time into discrete liver adenomas. These data strongly suggest that the IL-6/sIL-6R complex is both a primary stimulus to hepatocyte proliferation and a pathogenic factor of hepatocellular transformation.     

Interpolated smoothed pseudo Wigner-Ville distribution for accuratespectrum analysis

This paper deals with a new application of the time-domain windowed (smoothed version) of the pseudo Wigner-Ville distribution (PWD), that can be easily implemented in a dedicate digital instrument to be used as a spectral analyzer for time-frequency analysis of nonstationary signals. New computational algorithms are studied and developed to attain high time-frequency resolution, accuracy, flexibility and computational efficiency. Particularly, to reduce the negative effects due to leakage during frequency changes, a new interpolation formula is derived by using the windowing theory. The suggested technique allows the users to perform optimal evaluations of the instantaneous amplitudes and frequencies of analyzed signals     

Optimized windows for FIR filter design to perform maximally flatdecimation stages in signal conditioning

New cosine windows, the coefficients of which have been computed through a simple optimization procedure, are proposed to minimize the sidelobe ripples. This allows maximally flat low-pass finite-duration impulse-response (FIR) filter realizations in a multistage-decimation process. In digital measuring devices this strategy is performed in order to limit the amount of data to the storage capabilities of the processor, in conjunction with filtering the data set available after oversampling to remove digitally the noise power produced by quantization. The consequent increase of the number of effective bits improves the dynamic performance of digital instrumentation, especially at lower frequencies