16,483 research outputs found

    Dose of colistin. a work in progress?

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    We thank Rashid and colleagues [1] and Honoré and colleagues [2] for their comments regarding our article on risk factors for acute kidney injury in pa- tients receiving colistin or other nephrotoxic antimi- crobials [3]. It is correct that we did not specifically report urine output in the text, but it was obviously included in the RIFLE (Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease) criteria reported in Table two [3]

    Automotive Stirling Engine Development Program

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    Mod I engine testing and test results, the test of a Mod I engine in the United States, Mod I engine characterization and analysis, Mod I Transient Test Bed fuel economy, Mod I-A engine performance are discussed. Stirling engine reference engine manufacturing and reduced size studies, components and subsystems, and the study and test of low-cost casting alloys are also covered. The overall program philosophy is outlined, and data and results are presented

    an experimental and numerical analysis of the performances of a wankel steam expander

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    Abstract In the last decades, the energy market increased its interest towards the smart grids and electrically isolated systems. These systems utilize small size power generators in which volumetric expanders may be employed for a wide range of operative conditions, because of their robustness and reliability. In this work a study on a volumetric expander based on the Wankel mechanism was carried out. The aim of this study was to develop a lumped parameters numerical model able to predict the brake effective torque and working fluid consumption of the expander. This model was validated by comparison with experimental results obtained using steam as working fluid. This model allowed to trace the trends of mechanical and thermal losses versus rotating speed and inlet pressure. The experimental results encouraged the need for a further development of this expander, and showed the capability of the numerical model to predict the effective performances of the device

    cfd optimization of cpc solar collectors

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    Abstract The use of solar energy for industrial purpose at medium-low temperature is receiving attention. As a matter of fact, this temperature range, usually between 80-200°C, requires low cost devices to convert solar energy into useful heat. In particular, the use of CPCs collectors has been suggested in literature because they can be operated without the use of a tracking system, at least within certain limits. The thermal losses of these devices are often reduced by using an evacuated pipe, but this solution increases the manufacturing costs and reduces the reliability and the optical efficiency of the receiver. A series of alternative methods for the thermal losses reduction has been proposed in this paper, for working temperature up to 200°C. Their effectiveness was evaluated by means of a previously validated CFD model. A cylindrical receiver and a concentration ratio of 2 were taken into account. The results were analyzed in terms of temperature contours and thermal efficiency. In particular, the optical efficiency was focused as a key parameter in the performances of a CPC. As conclusion, it was found that a proper arrangement of the absorber with a baffle may entail an improvement of the thermal efficiency without significantly increasing the complexity of the system

    Extinction properties of the X-ray bright/optically faint afterglow of GRB 020405

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    We present an optical-to-X-ray spectral analysis of the afterglow of GRB 020405. The optical spectral energy distribution not corrected for the extragalactic extinction is significantly below the X-ray extrapolation of the single powerlaw spectral model suggested by multiwavelength studies. We investigate whether considerable extinction could explain the observed spectral ``mismatch'' by testing several types of extinction curves. For the first time we test extinction curves computed with time-dependent numerical simulations of dust grains destruction by the burst radiation. We find that an extinction law weakly depen dent on wavelength can reconcile the unabsorbed optical and X-ray data with the expected synchrotron spectrum. A gray extinction law can be provided by a dust grain size distribution biased toward large grains.Comment: 6 pages, 5 figures, accepted for publication on A&

    Automotive Stirling Engine Development Program

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    Program status and plans are discussed for component and technology development; reference engine system design, the upgraded Mod 1 engine; industry test and evaluation; and product assurance. Four current Mod 1 engines reached a total of 2523 operational hours, while two upgraded engines accumulated 166 hours

    Source to tap investigation of natural organic matter in non-disinfected drinking water distribution systems

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    Despite being reduced by treatment, natural organic matter (NOM) is ubiquitous in drinking water distribution systems (DWDSs) from sources to consumers' taps where it can potentially have negative impacts on drinking water quality. While a few studies have investigated its behaviour in disinfected and NOM-rich DWDSs, its dynamics in non-disinfected systems, characterized by low NOM content, have not yet been explored. In this study, we monitored the NOM variations occurring between groundwater sources and consumers' taps of a non-disinfected DWDS, including three drinking water treatment plants, using both fluorescence and absorbance, selected due to their increasing adoption by water utilities. PARAFAC analysis of fluorescence data, combined with absorbance indices, highlighted how NOM characteristics in groundwater vary due to the combination of multiple factors (e.g., well depth, pumping rate), especially in the case of shallower aquifers. The treatment processes display different effects on NOM when monitored by fluorescence and absorbance, due to the differences among fluorophores and between fluorescent and chromophoric molecules. Variations of the NOM characteristics between the treatment plant outlets and sampling locations within the network were detected only in few locations, suggesting the importance of the processes occurring in specific sections of the network and the last meter before consumption. These findings highlight the overall stability of water quality within non- disinfected NOM-poor DWDSs, but they stress the importance of (i) properly selecting the analytical method to be used for monitoring and (ii) localized water quality variations mainly related to pipe materials, suggesting several implications for DWDS monitoring and management

    experimental results of a wankel type expander fuelled by compressed air and saturated steam

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    Abstract The work presented in this paper deals with the experimental tests which were carried out on a prototype of a rotary volumetric expansion device based on the Wankel mechanism. This expansion device is addressed to small size power plants (in the range 5-50 kW) for distributed micro-generation using various sources of thermal energy, such as sun, biomass and waste heat. The prototype was built using an internal combustion Wankel engine, employing the shaft, the rotor, the bearings, while the statoric case was newly built on the design of the University of Pisa. Firstly, the tests were carried out with the compressed air produced by a compressor, then the prototype was fed with the saturated steam produced by a biomass boiler. In the first case, the exhaust back-pressure was the atmospheric one, in the second case vacuum conditions were employed thanks to a condenser. The inlet pressure was between 4 and 8 bar. The results showed the capability of the prototype to rotate regularly at 3000 rpm, and allowed the validation of numerical models presented in previous papers. Moreover, the expansion device showed the capability of developing the expected power

    The resummed thrust distribution in DIS

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    We present preliminary results on the resummation of leading and next-to-leading logarithms for the thrust distribution in deep inelastic scattering. Our predictions, expanded to O(alpha_s^2), are compared to corresponding results from the Monte Carlo programs DISASTER++ and DISENT.Comment: 5 pages; talk presented by V. Antonelli at the UK Phenomenology Workshop on Collider Physics, September 1999, St. John's College, Durha
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