On evaluating stream learning algorithms

Most streaming decision models evolve continuously over time, run in resource-aware environments, and detect and react to changes in the environment generating data. One important issue, not yet convincingly addressed, is the design of experimental work to evaluate and compare decision models that evolve over time. This paper proposes a general framework for assessing predictive stream learning algorithms. We defend the use of prequential error with forgetting mechanisms to provide reliable error estimators. We prove that, in stationary data and for consistent learning algorithms, the holdout estimator, the prequential error and the prequential error estimated over a sliding window or using fading factors, all converge to the Bayes error. The use of prequential error with forgetting mechanisms reveals to be advantageous in assessing performance and in comparing stream learning algorithms. It is also worthwhile to use the proposed methods for hypothesis testing and for change detection. In a set of experiments in drift scenarios, we evaluate the ability of a standard change detection algorithm to detect change using three prequential error estimators. These experiments point out that the use of forgetting mechanisms (sliding windows or fading factors) are required for fast and efficient change detection. In comparison to sliding windows, fading factors are faster and memoryless, both important requirements for streaming applications. Overall, this paper is a contribution to a discussion on best practice for performance assessment when learning is a continuous process, and the decision models are dynamic and evolve over time.     

Laser synthesis and luminescence properties of SrAl2O4:Eu2+, Dy3+ phosphors

A laser melting method has been developed for the synthesis of highly luminescent, long-lasting SrAl₂O₄:Eu²⁺, Dy³⁺ phosphors. The high temperature achieved in high-power density CO₂ laser irradiation of mixtures of SrCO₃, Al₂O₃, Eu₂O₃, and Dy₂O₃ enabled the one-step, fast synthesis of these phosphors in air at atmospheric pressure. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy characterization studies reveal that the produced materials consist of monoclinic SrAl₂O₄ grains extensively surrounded by rare-earth ion-enriched grain boundaries. The photoluminescence properties of laser-produced SrAl₂O₄:Eu²⁺, Dy³⁺ materials are discussed. The results reported here suggest that this laser melting method is a promising route for the synthesis of ceramic phosphors. It is presented as an alternative to the conventional sol–gel and solid-state methods, which require the use of high-temperature furnaces, flux additives, and reducing atmospheres.     

Effect of pH and Temperature on the Activity of Enzymatic Extracts from Pineapple Peel

This study was carried out to characterize a crude extract from pineapple peel after precipitation by three methods with the aim of obtaining an enzymatic extract from agro-industrial waste. The characterization of these extracts involved the determination of both protein content and specific protease activities. The effects of pH and temperature on specific protease activity and on the stability of the extracts were also evaluated. The optimal values of specific activity for the crude extract (CE) were pH 6.0 (5.76 U mg⁻¹ protein) and 7.0 (5.71 U mg⁻¹ protein) and a temperature of 70 °C (16 U mg⁻¹ protein). The average values for the relative specific activity were 17.4% (pH 3.0 to 9.0) and 42.7% (at 30, 50, and 70 °C). The ethanolic extract had the highest specific activity (10.7 U mg⁻¹ protein) in comparison to the best results obtained for the isoelectric precipitation (7.7 U mg⁻¹ protein) and the ammonium sulfate precipitation (4.7 U mg⁻¹ protein). Moreover, the ethanolic extract was more stable than the CE, retaining 60.9% and 53.7% of the initial specific activity during the evaluation of the stability at different pH and temperature values, respectively. The optimal values of pH and temperature were almost the same for the crude and the ethanolic extracts. In addition, the ethanolic extract was more stable than the CE in the experimental conditions tested in this work.     

Continuous flow carbamoylation of aniline by dimethyl carbonate using a microreactor coated with a thin film of ceria supported gold nanoparticles

Selective carbamoylation of aniline by dimethyl carbonate has been performed under continuous flow using a microreactor having 10 μm microchannels and 4 ml of total volume. Nanoparticulated ceria and gold nanoparticles supported on nanoparticulated ceria that have proved to be highly selective in batch reactions were tested as catalysts. The catalyst coating was deposited as thin film on the stainless steel microreactor plate that was previously activated by heating at 700 °C for 2 h. It was observed that at 120 °C and 5 bar pressure, both catalysts were stable over long times on stream reaching maximum conversions about 35%.     

Analyzing Mobility in Peripheral Regions of the European Union: The Case of Canarias-Madeira-Azores

We analyze the principal factors that determine mobility in a context of airline choice in the main domestic routes connecting the archipelagos of Azores, Madeira and the Canary Islands with the mainland and among them. With that purpose we conducted several stated preference (SP) experiments facing individuals with the choice between two virtual airlines which differed in terms of a group of service attributes that include price, frequency, comfort and compensation for delay among others. We found different multinomial logit specifications that allowed us to estimate the relative importance of each attribute in the decision-making process. We conclude that the price, the flight frequency, the quality (or availability) of food, the penalty imposed for making changes in the ticket, receiving some compensation in case of delay as well as having more leg room in the plane seat are among the most important factors that represent the global service. We also obtained the willingness to pay for improvements in the level of service. We found very interesting the dual interpretation of the vehicle considered to compensate travelers in case of delay. Finally, our results shed evidence of the existence of systematic taste variation explained in terms of some socioeconomic characteristics interacting with service attributes.     

Understanding medicinal taste and odour formation in drinking waters.

The formation of bromophenols during chlorination of phenol- and bromide-containing waters can be critical for taste and odour problems in drinking waters. The work performed has confirmed that flavour threshold concentrations of some bromophenols are in the ng/L range. In addition, under typical drinking water conditions, kinetic experiments and model simulations performed have shown that (1) bromination is the predominant reaction pathway, (2) bromophenol reaction kinetics are rapid leading to taste-and-odour episodes that last for short periods of 10-20 min, (3) increasing phenol concentration and pH tends to increase taste and odour intensity, (4) increasing chlorine or bromide concentrations tends to shorten the duration of the taste-and-odour episode.     

Towards a Phosgene-Free Synthesis of Aryl Isocyanates: Alcoholysis of <Emphasis Type="Italic">N-</Emphasis>phenylurea to <Emphasis Type="Italic">N-</Emphasis>phenyl-<Emphasis Type="Italic">O-</Emphasis>methyl Carbamate Promoted by Basic Metal Oxide Nanoparticles and Organocatalysts

There is an urgent need to develop new processes for the synthesis of polyurethanes and polycarbonates different from the current technology based on the use of phosgene. In the case of polyurethanes, the reaction of phosgene with aromatic amines renders N-aryl isocyanates that are the co-monomers for these polymers. In the search for a phosgene-free process for the synthesis of N-aryl isocyanates, N-aryl carbamates could play a key role of synthetic precursors. N-Aryl carbamates can be prepared in turn by alcoholysis of N-aryl ureas. Herein, we compare the catalytic activity of three homogeneous catalysts and four heterogeneous metal oxides for the methanolysis of N-phenylurea as a model probe for other aromatic ureas. In the present work we have carried out this reaction in the presence of KOH, 1,8-diaminonaphthalene (a protonic sponge), a dimeric phosphazene (strong, neutral soluble base) and nanometric ZnO, MgO, CaO and a mixed Mg/Al metal oxide derived from hydrotalcite calcination. Besides the target N-phenyl O-methyl carbamate, N-phenyl isocyanate and undesired aniline were also formed. It was observed that using KOH and diaminonaphthalene, aniline was formed preferentially with respect to the desired carbamate. In contrast, dimeric phosphazene forms the target N-phenyl O-methyl carbamate with 90% selectivity at 99% N-phenylurea conversion. In the case of the metal oxides, the best-performing solid catalyst was CaO that exhibits similar activity (99% N-phenylurea conversion) and carbamate selectivity (89%) as phosphazene. CaO performs as a truly heterogeneous catalyst and could be reused for a second run with only a 4 and 2% decrease in conversion and selectivity, respectively.     

Present and future of wastewater reuse in Spain

This article contains an analysis of the current situation in Spain with respect to the reuse of treated effluent, outlining the different experiences obtained together with the future prospects. In matters concerning reuse, Spanish Law places particular emphasis on the planning of basic State regulations that are now being drawn up by the Ministry of Environment, as well as developing other supplementary tools for hazard control and the breakthroughs that are in the process of being made in the planning area. Finally, an account is given of a series of observations that the authors believe to be relevant with respect to achieving sustainable progress for reuse in Spain.     

TOTAL MERCURY DETERMINATION IN NAPHTHAS BY EITHER ATOMIC FLUORESCENCE OR ABSORPTION SPECTROSCOPY

Mercury determination in light hydrocarbon fractions and natural gas condensates, has long been an important issue in the oil industry. Mercury has to be monitored, because of the many problems encountered with this metal in reforming and processing. The main objective of this study was to develop a fast reliable methodology to quantify total mercury in naphtha fractions.

Since there is no certified standard analysis procedure for Hg in naphtha, two methodologies with different operating principles were implemented, namely: atomic fluorescence spectroscopy with thermal desorption (AFS-TD) and atomic absorption spectroscopy with electrothermal atomization (AAS-ETA). The statistical treatment applied was paired t-test (95% confidence level), which showed that both techniques are statistically equivalent.