Design and implementation of H-inf controller for micro-monocopter

An all rotating platform has been modified with the purpose of having at one's disposal an operative monocopter. The nature of the modifications are described, as well as the control strategy designed and implemented to control the prototype. This strategy corresponds to a H-inf controller in which a nonlinear function has been included to cancel the propeller quadratic force.     

WWER-1000 base metal reference steel and its characterisation

The surveillance programmes of western power reactors include, in many cases, standard reference materials in addition to actual pressure vessel steels. These are specimens cut from standard steel plates (Heavy Section Steel Technology, JRQ, etc.) that are similar in composition and heat treatment to the base material in the respective reactor pressure vessels, and are supposed to serve as a monitor by comparing the radiation embrittlement of the plant-specific material to the reference material, and to detect anomalies in the radiation environment of the surveillance capsules.A correlation monitor material for the eastern WWER-1000 (similar as the JRQ for western reactors) is needed in order to determine the reliability of accelerated data for the validation of reactor pressure vessel surveillance data. Reference materials should be well characterised in terms of irradiation behaviour (transition temperature shift, non-destructive signal, etc.). The magnitude of the sensitivity to irradiation for this material should be measurable for the selected exposures. In this subject the IAEA is launching a new co-ordinated research programme. Material is already manufactured, and the JRC-IE has become its custodian. A detailed plan for characterisation of the reference steel is set up, including irradiation conditions, post-irradiation testing techniques and implementation plan. It is expected the participation of several research institutes worldwide in a round robin, which will allow a better comprehension of WWER-1000 steel's behaviour and will be considered as a benchmarking between different laboratories.The JRC-Institute for Energy in collaboration with the Russian Research Centre – Kurchatov Institute is performing the “as received” material characterisation by both destructive methods and non-destructive techniques.The non-destructive techniques used at the JRC-IE premises are novel methods specially developed for non-destructive assessment of the embrittlement state of materials, as the STEAM method and the measurement of magnetic properties. The STEAM technique (Seebeck and Thomson effects on aged material), is based on the measurement of the Seebeck coefficient. The magnetic properties evaluation is done through Barkhausen noise and permeability measurements.This paper presents a preliminary analysis of the results obtained by all involving laboratories.     

Atmospheric corrosion of zinc induced by runoff

Atmospheric corrosion and runoff of zinc were investigated during two years in humid tropical climate on hot dip galvanized steel and zinc samples. The high zinc mass loss (14.70 g m⁻²) is induced by the intensive zinc release (12.40 g m⁻²). No corrosion phase containing chloride was detected on the zinc surface, while a variety of sulfates not dissolved by rains reveals the sensitivity of zinc to SO₂ pollutant. However, two chloride-containing corrosion products were detected on the galvanized steel. Exponential equation is proposed that fits well the experimental data for zinc mass loss induced by runoff process as a function of the time of wetness. The formula gives possibility to predict the mass loss even before a steady state in the corrosion process has been reached. This equation can converge to a Benarie lineal function (C = At_w), when the coefficient b = 1 for the corrosion which is accelerated with the partial removal of the corrosion layer during the runoff phenomena.     

Analysis of High-Performance Flip-Flops for Submicron Mixed-Signal Applications

This paper presents a detailed analysis of high-performance edge-triggered memory elements for deep submicron mixed-signal applications. The variations of the main parameters (power, delay, peak of supply current) with supply voltage, as well as timing restrictions have been studied. Especial emphasis has been given to switching-noise generation, an aspect of important concern in mixed-signal applications. We have analyzed the sources of switching noise, noticing that, the less noisy flip-flops are those based on differential structures.     

Laser-enhanced plating: A review of its mechanisms and applications

Model calculations are compared with published optical reflectance spectra for thermally oxidized samples of black chrome solar absorbing film on nickel substrates (T ≈ 600 °C). Good agreement between the model calculations and the published reflectance spectra indicates that the diffusion and oxidation of the nickel substrate is the primary cause of reflectance changes in this temperature regime (T ? 500 °C). Auger electron spectroscopy utilizing depth profiling similarly heated black chrome films on nickel substantiates this observation.     

A mathematical model of aluminum depth filtration with ceramic foam filters: Part I. Validation for short-term filtration

This work presents a mathematical model to compute the efficiency of depth filtration of molten aluminum using ceramic foam filters. In the model, the porous structure of foam filters was represented by a unit cell that takes into account the convergent-divergent nature of the flow field. The steady, two-dimensional, and fully developed flow field within the unit cell was obtained from the numerical solution of the continuity and Navier-Stokes equations. The assessment of the proper assumptions for the model was carried out by comparing the computed velocity field with that experimentally determined for a physical model of the unit cell with scale 10:1 and containing an aqueous solution of CaCl₂. The measurements were done using the particle image velocimetry (PIV) technique. The efficiency and the coefficient of initial filtration for foam filters were obtained from the determination of the particle limiting trajectory, resulting from a force balance on a spherical inclusion. This balance included the buoyancy and the viscous drag forces. The last force took into consideration the wall effect on the particle motion. The values of the computed initial filtration coefficient show an excellent agreement with the corresponding measured ones reported for laboratory and plant tests for short-term filtration. This comparison involves several combinations of particle sizes and downward fluid superficial velocities. This model is further extended to study long-term filtration in the second part of the article.     

Assessing glass-ceramic homogeneity and nucleation self-correlation by crystallization statistics

In this work, we implemented and tested a statistical method to evaluate the microstructural uniformity of partially crystallized glasses employing the aggregation index (R-index), a parameter derived from the Poisson distribution function, which has mainly been used in Ecology studies. Since the crystal nucleation rate strongly depends on the chemical composition, the spatial crystal distribution in glass-ceramics can be used to infer their chemical homogeneity. We also tested the hypothesis, advanced by some authors, of preferential secondary nucleation close to preexisting crystals (even in chemically homogeneous samples). To this end, we conducted a nearest-neighbor statistical analysis of the spatial crystal distribution in partially crystallized Li₂Si₂O₅ and Ba₅Si₈O₂₁ glasses, used as model materials, by inspecting optical micrographs obtained at different magnifications. The resultant R-indexes indicate a very high degree of homogeneity of the crystal number distribution, reflecting the uniform distribution of the chemical elements in the parent glasses. Moreover, the results for both glasses refute the suggestion that crystal nucleation is self-correlated. These outcomes allow us to suggest the R-index as a valuable and easily implemented tool to evaluate the chemical homogeneity of glasses that undergo internal nucleation, such as those used for glass-ceramics.     

Blends of PP/PE co‐octene for modified atmosphere packaging applications

The aim of this work was to obtain films of polypropylene (PP)/polyethylene co‐octene (POE) blends and study the influence of their composition and mixing conditions on final morphology and ultimate properties (thermal, mechanical, oxygen and water vapour transmission rates). Scanning electron microscopy showed segregation of POE domains in the PP matrix. Thermal analysis indicated that the addition of POE modified neither the melting temperature nor the crystallinity of PP in the pressed films. It was found that permeabilities of films were mainly related to POE content rather than morphological features. For the maximum POE concentration used (40%), the oxygen permeability increased up to ∼100% from that of neat PP. A similar trend was found for water vapour permeability. Rigidity of blends dropped significantly with the addition of POE although their ductility slightly increased when compared to pure PP. No significant effect of blend preparation conditions on these properties was found. Mechanical and permeability characteristics of films make them very attractive to be used for MAP of fresh produce such as apple, blueberry and mushroom. Copyright © 2011 John Wiley & Sons, Ltd.     

Electrocaloric Effect in Ba(Zr,Ti)O3–(Ba,Ca)TiO3 Ceramics Measured Directly

In this paper, we report on studies of the electrocaloric (EC) effect in lead‐free (1?x)Ba(Zr_0.2Ti_0.8)O₃–x(Ba_0.7Ca_0.3)TiO₃ ceramics with compositions range between 0.32 ≤ x ≤ 0.45. The EC effect was measured directly using a modified differential scanning calorimeter. The maximum EC temperature change, ΔT_direct = 0.33 K under an electric field of 2 kV/mm, was observed for the composition with x = 0.32 at ~63°C. We found that the EC effect peaks not only around the Curie temperature but also at the transition between the ferroelectric phases with different symmetries. A strong discrepancy observed between the results of the direct measurements and indirect estimations points out that using Maxwell's equations is invalid for the thermodynamic nonequilibrium conditions that accompany only partial (incomplete) poling of ceramics. We also observe a nonlinearity of the EC effect above the Curie temperature and in the temperature range corresponding to the tetragonal ferroelectric phase.