RC Autonomous Circuits with Chaotic Behavior

The paper presents obtained results with applying the "Semi-systematic procedure for producing the chaos from quasi-sinusoidal oscillators". We applied this procedure to RC autonomous circuit and obtained two new autonomous circuits with chaotic behaviour. The two obtained circuits are presented. The usage of various non-linear devices is examined

A new treatment process to recover magnetite, zinc and lead from iron and steelmaking dusts and sludges

Steelmaking dusts are frequently classified as hazardous residues, due to their eco-toxicity characteristics. This derives mainly from the presence of heavy metals like zinc, lead and cadmium in their compositions, in forms that are easily leachable by water or slightly acidic or alkaline media. Following the most employed eco-toxicity standard tests, like DIN 38414-S41) from Germany, and TCLP (Toxicity Characteristic Leaching Procedure)2) from the United States, steelmaking dusts present a high level of mobility of heavy metals, what is relevant for the evaluation of their environmental impact, when disposed in controlled landfills. In the present project (contract number ERB IC 15CT97-0704), a new process is being developed to recover valuable metals and products from steelmaking dusts and sludges. Two different process routes are being evaluated, both from the technical and from the economic points of view. A pre-treatment stage, based on water leaching of the dusts, is, in both cases, studied, to remove alkalis present in the wastes

A statistical study of the performance of the Hakamada-Akasofu-Fry version 2 numerical model in predicting solar shock arrival times at Earth during different phases of solar cycle 23

The performance of the Hakamada Akasofu-Fry, version 2 (HAFv.2) numerical model, which provides predictions of solar shock arrival times at Earth, was subjected to a statistical study to investigate those solar/interplanetary circumstances under which the model performed well/poorly during key phases (rise/maximum/decay) of solar cycle 23. In addition to analyzing elements of the overall data set (584 selected events) associated with particular cycle phases, subsets were formed such that those events making up a particular sub-set showed common characteristics. The statistical significance of the results obtained using the various sets/subsets was generally very low and these results were not significant as compared with the hit by chance rate (50%). This implies a low level of confidence in the predictions of the model with no compelling result encouraging its use. However, the data suggested that the success rates of HAFv.2 were higher when the background solar wind speed at the time of shock initiation was relatively fast. Thus, in scenarios where the background solar wind speed is elevated and the calculated success rate significantly exceeds the rate by chance, the forecasts could provide potential value to the customer. With the composite statistics available for solar cycle 23, the calculated success rate at high solar wind speed, although clearly above 50%, was indicative rather than conclusive. The RMS error estimated for shock arrival times for every cycle phase and for the composite sample was in each case significantly better than would be expected for a random data set. Also, the parameter "Probability of Detection, yes" (PODy) which presents the Proportion of Yes observations that were correctly forecast (i.e. the ratio between the shocks correctly predicted and all the shocks observed), yielded values for the rise/maximum/decay phases of the cycle and using the composite sample of 0.85, 0.64, 0.79 and 0.77, respectively. The statistical results obtained through detailed analysis of the available data provided insights into how changing circumstances on the Sun and in interplanetary space can affect the performance of the model. Since shock arrival predictions are widely utilized in making commercially significant decisions re. protecting space assets, the present detailed archival studies can be useful in future operational decision making during solar cycle 24. It would be of added value in this context to use Briggs-Rupert methodology to estimate the cost to an operator of acting on an incorrect forecast

Iterative inversion of global magnetospheric ion distributions using energetic neutral atom (ENA) images recorded by the NUADU/TC2 instrument

A method has been developed for extracting magnetospheric ion distributions from Energetic Neutral Atom (ENA) measurements made by the NUADU instrument on the TC-2 spacecraft. Based on a constrained linear inversion, this iterative technique is suitable for use in the case of an ENA image measurement, featuring a sharply peaked spatial distribution. The method allows for magnetospheric ion distributions to be extracted from a low-count ENA image recorded over a short integration time (5 min). The technique is demonstrated through its application to a set of representative ENA images recorded in energy Channel~2 (hydrogen: 50–81 keV, oxygen: 138–185 keV) of the NUADU instrument during a geomagnetic storm. It is demonstrated that this inversion method provides a useful tool for extracting ion distribution information from ENA data that are characterized by high temporal and spatial resolution. The recovered ENA images obtained from inverted ion fluxes match most effectively the measurements made at maximum ENA intensity

Bismuth Doping in Nanostructured Tetrahedrite: Scalable Synthesis and Thermoelectric Performance

In this study, we demonstrate the feasibility of Bi-doped tetrahedrite Cu12Sb4−xBixS13 (x = 0.02–0.20) synthesis in an industrial eccentric vibratory mill using Cu, Sb, Bi and S elemental precursors. High-energy milling was followed by spark plasma sintering. In all the samples, the prevailing content of tetrahedrite Cu12Sb4S13 (71–87%) and famatinite Cu3SbS4 (13–21%), together with small amounts of skinnerite Cu3SbS3, have been detected. The occurrence of the individual Cu-Sb-S phases and oxidation states of bismuth identified as Bi0 and Bi3+ are correlated. The most prominent effect of the simultaneous milling and doping on the thermoelectric properties is a decrease in the total thermal conductivity (κ) with increasing Bi content, in relation with the increasing amount of famatinite and skinnerite contents. The lowest value of κ was achieved for x = 0.2 (1.1 W m−1 K −1 at 675 K). However, this sample also manifests the lowest electrical conductivity σ, combined with relatively unchanged values for the Seebeck coefficient (S) compared with the un-doped sample. Overall, the lowered electrical performances outweigh the benefits from the decrease in thermal conductivity and the resulting figure-of-merit values illustrate a degradation effect of Bi doping on the thermoelectric properties of tetrahedrite in these synthesis conditions

Characterization and pre-treatment of steelmaking dusts in order to recover valuable products

Steelmaking dusts are frequently classified as hazardous residues, due to their eco-toxicity characteristics. This derives mainly from the presence of heavy metals like zinc, lead and cadmium in their compositions, in forms that are easily leachable by water or slightly acidic or alkaline media. Following the most employed eco-toxicity standard tests, like DIN 38414-S41) from Germany, and TCLP (Toxicity Characteristic Leaching Procedure)2) from the United States, steelmaking dusts present a high level of mobility of heavy metals, what is relevant for the evaluation of their environmental impact, when disposed in controlled landfills. By this work, financed by the European Communities COPERNICUS Programme, a characterisation of the dusts generated in different steelmaking plants has been done. Also, the behaviour of the dusts when washed with cold water has been evaluated, giving some informations on the mobility of metals and on the prospects for pre- treatment of the residues to recover valuable products