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41.
Enrico Pisoni Marcello Farina Claudio Carnevale Luigi Piroddi 《Engineering Applications of Artificial Intelligence》2009,22(4-5):593-602
Air pollution has a negative impact on human health. For this reason, it is important to correctly forecast over-threshold events to give timely warnings to the population. Nonlinear models of the nonlinear autoregressive with exogenous variable (NARX) class have been extensively used to forecast air pollution time series, mainly using artificial neural networks (NNs) to model the nonlinearities. This work discusses the possible advantages of using polynomial NARX instead, in combination with suitable model structure selection methods. Furthermore, a suitably weighted mean square error (MSE) (one-step-ahead prediction) cost function is used in the identification/learning process to enhance the model performance in peak estimation, which is the final purpose of this application. The proposed approach is applied to ground-level ozone concentration time series. An extended simulation analysis is provided to compare the two classes of models on a selected case study (Milan metropolitan area) and to investigate the effect of different weighting functions in the identification performance index. Results show that polynomial NARX are able to correctly reconstruct ozone concentrations, with performances similar to NN-based NARX models, but providing additional information, as, e.g., the best set of regressors to describe the studied phenomena. The simulation analysis also demonstrates the potential benefits of using the weighted cost function, especially in increasing the reliability in peak estimation. 相似文献
42.
Yasuhiro Shimizu Elisabetta Di Bartolomeo Enrico Traversa Gualtiero Gusmano Takeo Hyodo Kenji Wada Makoto Egashira 《Sensors and actuators. B, Chemical》1999,60(2-3):118-124
NO2 sensing properties of SnO2-based varistor-type sensors have been investigated in the temperature range of 400-650°C and in the NO2 concentration range of 15–30 ppm. Pure SnO2 exhibited a weak nonlinear I–V characteristic in air, but clear nonlinearity in NO2 at 450°C. The breakdown voltage of SnO2 shifted to a high electric field upon exposure to NO2 and the magnitude of the shift was well correlated with NO2 concentration. Thus, SnO2 exhibited some sensitivity to NO2 as a varistor-type sensor. When SnO2 particles coated with a SiO2 thin film were used as a raw material for fabricating a varistor, the breakdown voltage in air was approximately the double that of pure SnO2 and the sensitivity to 15 ppm NO2 was enhanced slightly. However, the sensitivity to 30 ppm NO2 decreased. The Cr2O3-loading on SnO2 also led to an increase in the breakdown voltage in air, but the Cr2O3 addition was not effective for promoting the NO2 sensitivity under the present experimental conditions. 相似文献
43.
Enrico Giunchiglia Nicola Leone Marco Maratea 《Annals of Mathematics and Artificial Intelligence》2008,53(1-4):169-204
In this paper, we study the relation among Answer Set Programming (ASP) systems from a computational point of view. We consider smodels, dlv, and cmodels ASP systems based on stable model semantics, the first two being native ASP systems and the last being a SAT-based system. We first show that smodels, dlv, and cmodels explore search trees with the same branching nodes (assuming, of course, a same branching heuristic) on the class of tight logic programs. Leveraging on the fact that SAT-based systems rely on the deeply studied Davis–Logemann–Loveland (dll) algorithm, we derive new complexity results for the ASP procedures. We also show that on nontight programs the SAT-based systems are computationally different from native procedures, and the latter have computational advantages. Moreover, we show that native procedures can guarantee the “correctness” of a reported solution when reaching the leaves of the search trees (i.e., no stability check is needed), while this is not the case for SAT-based procedures on nontight programs. A similar advantage holds for dlv in comparison with smodels if the “well-founded” operator is disabled and only Fitting’s operator is used for negative inferences. We finally study the “cost” of achieving such advantages and comment on to what extent the results presented extend to other systems. 相似文献
44.
Ceramic Microtubes from Preceramic Polymers 总被引:2,自引:0,他引:2
Paolo Colombo § Katia Perini Enrico Bernardo Tiziano Capelletti Giorgio Maccagnan 《Journal of the American Ceramic Society》2003,86(6):1025-1027
A novel process for the production of ceramic microtubes involving the microextrusion of preceramic polymers was studied. Microtubes with a wide range of inner and outer diameters and several centimeters long were produced from two silicone resins. A coextrusion approach was also used to extend the forming capability of the technique. The addition of carbon black resulted in electrically conductive silicon oxycarbide (SiOC) ceramic microtubes. SiOC microtubes possessed a high bending strength, ranging from ∼30–1100 MPa. 相似文献
45.
NH3-NO/NO2 SCR for diesel exhausts after treatment: mechanism and modelling of a catalytic converter
Nova Isabella Ciardelli Cristian Tronconi Enrico Chatterjee Daniel Weibel Michel 《Topics in Catalysis》2007,42(1-4):43-46
We review herein the key mechanistic and kinetic features of the reactions involved in the NH3-NO/NO2 SCR system investigated by dynamic reactive experiments over a V-based commercial powdered catalyst, eventually leading to
the proposal of an original redox scheme which accounts for stoichiometry, selectivity and intrinsic kinetics of the global
SCR process. 相似文献
46.
Dr. Blijke S. Kroezen Gabriele Conti Benedetta Girardi Dr. Jonathan Cramer Dr. Xiaohua Jiang Dr. Said Rabbani Jennifer Müller Maja Kokot Enrico Luisoni Prof. Daniel Ricklin Dr. Oliver Schwardt Prof. Beat Ernst 《ChemMedChem》2020,15(18):1706-1719
Siglecs are members of the immunoglobulin gene family containing sialic acid binding N-terminal domains. Among them, Siglec-8 is expressed on various cell types of the immune system such as eosinophils, mast cells and weakly on basophils. Cross-linking of Siglec-8 with monoclonal antibodies triggers apoptosis in eosinophils and inhibits degranulation of mast cells, making Siglec-8 a promising target for the treatment of eosinophil- and mast cell-associated diseases such as asthma. The tetrasaccharide 6’-sulfo-sialyl Lewisx has been identified as a specific Siglec-8 ligand in glycan array screening. Here, we describe an extended study enlightening the pharmacophores of 6’-sulfo-sialyl Lewisx and the successful development of a high-affinity mimetic. Retaining the neuraminic acid core, the introduction of a carbocyclic mimetic of the Gal moiety and a sulfonamide substituent in the 9-position gave a 20-fold improved binding affinity. Finally, the residence time, which usually is the Achilles tendon of carbohydrate/lectin interactions, could be improved. 相似文献
47.
Valentina Nania Guido Enrico Pellegrini Laura Fabrizi Giulio Sesta Patrizia De Sanctis Dario Lucchetti Mauro Di Pasquale Ettore Coni 《Food chemistry》2009
Perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS) are environmental contaminants belonging to a chemical group known as perfluorinated compounds (PCFs). The United States Environmental Protection Agency (US EPA) considers both compounds to be carcinogenic. The goal of the present study was to evaluate the contamination levels of PFOS and PFOA in edible fish of the Mediterranean Sea. Twenty six fish muscles, 17 fish livers, five series of cephalopods (each composed of ten specimens) and thirteen series of bivalves (each composed of about 50 specimens) were used for the investigation. A fast sample treatment, followed by an LC–ESI–MS/MS method is described for the identification, and quantification of PFOA and PFOS in fish. The method was in-house-validated through the determination of precision, accuracy, specificity, calibration curve, decision limit (CCα), and detection capability (CCβ). The results showed PFOA and PFOS levels in fishes and molluscs lower than those reported for analogue matrices in different geographic areas. Therefore, our biomonitoring results did not show that the Mediterranean Sea had any particularly alarming pollution by PFCs, although it is located in a semi-closed basin with scarce water change. Nonetheless, a worrying element is that a few fish showed extremely high contamination by PFOA and PFOS. This finding needs further clarification in order to assess whether such unusual contamination is linked to “dot-like” pollutant release, which could explain the anomaly. 相似文献
48.
The synthesis of oxidised water-soluble fullerenes, prepared by chemically-induced aerobic oxidation, yields functionalised carbon cluster structures, which are oxidised by the covalent insertion of different oxygen units. Their strictly pH-dependent behaviour in aqueous solutions appears to be properly ascribed to the existence of directly attached carboxylic moieties. The presence of these groups, which are usually neglected and underestimated, has been thoroughly investigated. Several concurrent spectral (UV-VIS, XPS, solid-state 13C CPMAS NMR, FT-IR, Raman, EDAX, TGA-MS, ESI-MS) and chemical (acid-base behaviour, salt precipitation by metal-complexation, carboxylic functionalisation) methods have provided a definitive set of consistent evidence, indicating for the first time the direct linkage of carboxylic groups on water-soluble fullerenes prepared in this manner. 相似文献
49.
Luigi Dusonchet Enrico Telaretti 《Electric Power Systems Research》2011,81(7):1308-1316
In this paper the dynamic behaviour of a wind turbine connected to the grid is examined. The model of the fixed speed wind turbine has been developed with the Simulink simulation tool (Matlab Inc.) It is composed of the induction generator, the shaft system, an aerodynamic model of the wind turbine rotor and the pitch control system. Using this model, a three-phase fault is applied close to the wind turbine and cleared by disconnecting the faulty line.The rigorous implementation of the simulink model allowed the authors to evaluate the exact dependence of various electrical parameters for the induction generator on voltage stability. Furthermore, the effects of wind turbine mechanical construction and of grid parameters on voltage stability are also evaluated and discussed.For each parameter, the terminal voltage and the generator rotor speed for different fault-clearing times are drawn. Finally, the terminal voltage and the generator rotor speed obtained for a fifth order model of the induction generator are compared with those obtained for a third order model. The differences between the two models are discussed. The results will help to understand transient stability phenomena in wind farms. 相似文献
50.
Enrico Fabrizi Caterina Giusti Nicola Salvati Nikos Tzavidis 《Papers in Regional Science》2014,93(3):685-701
Measures of economic well‐being are often needed for geographically small areas, as economic indicators may be distributed unevenly among the subsets of relatively small regions. We consider small area estimation of average equivalized income. Disposable household income data are usually available only for a sample of households, typically too small to provide reliable estimates for small regions. We consider a small area estimation technique that is robust to outliers, produces results consistent with design weighted estimates obtained for larger areas and yield maps with approximately no shrinkage. The proposed methodology is applied to the Local Labour Systems in Tuscany (Italy). 相似文献