197,123 research outputs found
An SPWD-Based Instrument for Accurate Spectral Analyses
No full textThe Wigner-Ville distribution (WD) is particularly used for time-frequency analysis of nonstationary signals. This paper proposes the application of the smoothed version of the WD to design an innovative virtual instrument (VI) which can be used as a spectral analyzer. Our work focuses on the computational algorithms that meet several essential requirements for implementation, such as high time-frequency resolution, precision, flexibility, and computational efficiency. An original interpolation formula is derived, to overcome the negative effects due to leakage. Following this, a simple WD implementation on the designed VI is proposed and a series of numerical checks is show, to suitably characterize the new instrument
High prevalence of bla(CTX-M-1)-group extended-spectrum beta-lactamase genes in Enterobacteriaceae isolates from Emilia-Romagna, Italy.
No full textThe production of extended-spectrum beta-lactamase (ESBL) by Enterobacteriaceae is an increasing challenge in the treatment of infections. The ESBL type most frequently detected in the last few years is CTX-M, which also has the particular ability to spread in the community (Pitout & Laupland, 2008). In Emilia-Romagna, a northern Italian region with a population of about 4 million, the rate of resistance to beta-lactamase due to ESBL grew rapidly in the period 2003-2006 (Gagliotti et al., 2008a). No data on type of circulating ESBL is available at regional level. This study aims to describe the epidemiology of ESBL by testing a sample of clinical strains of ESBL-producers that were isolated in Emilia-Romagna
Una poco nota lettera di Laudivio Zacchia a Giovanni Pontano (cod. Urb. Lat. 1401, C. 2V)
No full textTrace elements in daily collected aerosol: levels characterization and source identification in a four-year study
No full textAtmospheric particulate concentrations were measured at an industrial site in southern Italy from September 2001 to December 2004. In this period, we collected 741 daily samples of PM2.5 by means of a low-volume gravimetric automatic sequential sampler. The 24-h PM2.5 samples were analysed for heavy metal content (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn). We also measured temperature, relative humidity, wind speed and wind direction. Data analysis was performed with univariate and multivariate statistical methods. Principal component analysis and cluster analysis were applied in order to point out the correlation structure among particulate concentrations and heavy metal content and to highlight source profile characterization. In order to discriminate between natural and anthropogenic origin of the trace elements, we also applied the enrichment factor method. In the investigated period, PM2.5 concentrations ranged from 0.04 μg m− 3 to 117 μg m− 3, with a mean value of 13 μg m− 3 and a median value of 10 μg m− 3. A mix of different source emissions and different meteorological conditions may determine this large variation in PM2.5 values. Regarding heavy metal levels, we observed that they decreased during the four years assuming the lowest values in 2004. All the measured elements, except Mn, showed high values of the enrichment factor, suggesting a prevailing anthropogenic origin. The analysis of the relationships among pollutant concentrations and meteorological parameters showed that they were influenced by wind speed and relative humidity. The multivariate analysis allowed us to identify two source profiles for heavy metals. The first profile was characterized both by elements typical of soil dust and crustal material (Fe, Mn) and by elements typical of industrial processes (Ni, Cr and Cu). The second profile was characterized by Pb, Zn and Cd and it may be mainly related to exhaust emissions from both gasoline and diesel fuelled road vehicles
Online monitoring of MBR fouling by transmembrane pressure and permeability over a long-term experiment
No full textSeveral methods have been proposed over the last decade for the monitoring of fouling processes in membrane bioreactors (MBRs). Many of these methods aim to acquire information measuring the transmembrane pressure (TMP) and permeability (K) directly on the membrane modules used in wastewater treatment plants. This study assessed in a critical light the use of TMP and K for membrane fouling monitoring. TMP and K were directly measured on a pilot-scale submerged MBR operated continuously for approximately 450 d at different solids retention times and fed with real municipal wastewater. The results showed that under standard operating conditions such as those usually applied in full-scale MBR and with the monitoring instruments typically employed in industrial applications, the identification of specific TMP trends within a filtration phase was often problematic and the results were unreliable, mainly because of the noise and the variability of real wastewater and environmental conditions. Moreover, a non-linear trend of the pressure behaviour within a filtration phase was observed when fouling phenomena were taking place. This study also proposes the use of the ratio between filtration and backwash permeability in order to assess whether the membrane flux is deviating from the "pressure controlled region" and, consequently, fouling processes are occurring. © 2013 Elsevier B.V. All rights reserved
Effect of solid retention time on sludge filterability and biomass activity: Long-term experiment on a pilot-scale membrane bioreactor treating municipal wastewater
No full textA membrane bioreactor (MBR) pilot-plant fed by municipal wastewater, was continuously operated for 450d at different solid retention times (SRT: 25, 50 and 75d) with the aim of identifying possible relations between transmembrane pressure (TMP) evolution and a set of parameters describing physico-chemical sludge characteristics such as capillary suction time (CST), soluble microbial products (SMP), extracellular polymeric substances, critical flux (Jc), oxygen diffusion, biomass kinetic and stoichiometric coefficients (measured by respirometric techniques). Data analysis confirms that MBRs can operate with high SRT ensuring good treatment performances and, from the biological point of view, no effective loss of biodegradation activities. During the study changes in sludge filterability properties for the different operating conditions were observed. Among the different microbial products that characterise the colloidal materials of the mixed liquor, only the carbohydrate fraction of the SMP was correlated with CST and Jc and showed a clear dependence on SRTs. However, the same information can be obtained by a much simpler analysis such as the chemical oxygen demand (COD) fine fraction (defined as the difference between the mixed liquor soluble COD and the effluent COD). TMP trend showed the typical evolution proposed in the local flux theory. Jc and CST trends can be used to predict sludge filterability. Higher sludge fouling propensity was observed at operating conditions when the highest sludge activity was also observed, suggesting a direct relation between fouling and microbial metabolism. Moreover, the addition of the anoxic process seemed to deteriorate the sludge filterability. © 2013 Elsevier B.V
T4I2016 - Draffan, EA; Wald , M; Ahmad, A.I.; Kadous, A.; Zeinoun, N; Banes , D.; Sabia, O.; Lawand, D.: Personalise, Localise and Globalise: Symbols to enhance independent Communication
No full textDraffan, EA; Wald
, M; Ahmad, A.I.; Kadous, A.; Zeinoun, N; Banes , D.; Sabia, O.; Lawand, D.: Personalise,
Localise and Globalise: Symbols to enhance independent Communication. T4I Communications 1, T4I2016 –
Academic/Research, Nov 2016. Figshare.
This research explored the
personal preferences of AAC users and those supporting them, in their need to
have localised, cultural and religious symbols, that could be used alongside
those already found on communication charts in certain multilingual settings.</p
A comprehensive kinetic modeling of ignition of syngas/air mixtures at low temperatures and high pressures
No full textSyngas has gained increasing attention due to the possibility that it is produced by coal and biomass. In order to develop more efficient processes suitable for different combustion conditions, a study of the kinetic of syngas ignition was carried out. Several kinetic mechanisms present in the literature were compared with experimental data. Different conditions were investigated, including various parameters such as temperature, pressure, and composition. H2O2+M=OH+OH+M and H+H2O2=HO2+H2 have been found to be dominant in the prediction of ignition times by a sensitivity analysis. Enhancements to the kinetic mechanism have been carried out by splitting the reactions in forward and backward reactions, and by adjusting values of the rate constants in the range of confidence of their evaluation. The new mechanism is able to predict quite well the behavior of syngas in all conditions examined, particularly in gas turbine conditions. Moreover, the influence of pressure and of CO concentration have been investigated with the new enhanced kinetic mechanism
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