1,721,097 research outputs found
Furfural (C5H4O2) encapsulation and release by ZSM-5 zeolite for sustainable treatment in agriculture
No full textAcceleration and wall pressure fluctuations generated by an incompressible jet in installed configuration
No full textIn this work, the cross-statistics of acceleration and wall pressure fluctuations generated by an incompressible jet interacting with a tangential flat-plate are presented. The results are derived from an experimental test campaign on a laboratory-scale model involving simultaneous velocity and wall pressure measurements. The pressure footprint of the jet on the surface was measured through a cavity-mounted microphone array, whereas pointwise velocity measurements were carried out by a hot wire anemometer. The time derivative of the velocity signal has been taken as an estimation of the local acceleration of the jet. The multivariate statistics between acceleration and wall pressure are achieved through cross-correlations and cross-spectra, highlighting that the causality relation is more significant in the potential core where the Kelvin–Helmholtz instability is dominant. The application of a conditional sampling procedure based on wavelet transform allowed us to educe the acceleration flow structures related to the energetic wall-pressure events. The analysis revealed that, unlike the velocity, the acceleration signatures were detected only for positions where the jet had not yet impinged on the plate, their shape being related to a convected wavepacket structure
An experimental investigation of the wall pressure field induced by a low and moderate mach numbers jet on a tangential flat plate
No full textIn this work an experimental analysis of the wall pressure field generated by the interaction between a subsonic jet and a flat plate parallel to the nozzle axis is performed. The analysis is the continuation of previous studies carried out by the same authors on the interaction between a jet and a flat plate in an incompressible jet facility. In the present work a similar installed configuration has been analyzed exploiting a compressible jet facility in order to address the effect of the transition from incompressible to low/moderate compressible flow conditions. The pressure footprint on the flat plate was measured in both the streamwise and spanwise directions through a flush-mounted microphone array for different radial distances of the surface from the jet. Wall pressure fluctuations have been characterized in terms of statistical and spectral quantities. Implications for modelling of the wall pressure fluctuations are considered by the application of the Corcos’ model to the coherence functions in both the streamwise and spanwise directions. Specifically, the Corcos’ model was verified for all the jet flow velocities, the increase of the jet Mach number having the effect to enhance the jet flow development over the plate and to speed up the approach of a quasi-equilibrium turbulent boundary layer
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A statistical investigation on the relationships among financial disclosure, sociodemographic variables, financial literacy and retail investors’ risk assessment ability
No full textThis research focuses on disclosure of information about the uncertain
future performance of non-equity financial products. In particular, it looks at two
schemes, namely What-if and Probabilistic scenarios. For this purpose, a consumer
testing experiment was conducted on a sample of 1,130 potential investors stratified
according to ISTAT standard WRH[SORUHKRZGLIIHUHQWVFKHPHVLQIOXHQFHLQYHVWRU¶V
risk perception and whether financial literacy and sociodemographic variables are
drivers of risk assessment. The analysis was performed using multilevel regression
model
Jet-plate interaction in a supersonic screeching jet
No full textThis work presents an experimental investigation of the effect of a flat plate on the generation of axisymmetric A1 and A2 screech modes. The plate is installed parallel to the nozzle axis of an under-expanded supersonic jet issuing from a convergent nozzle at a radial distance of 0.7 nozzle diameters from the nozzle axis. The impact of the plate on the screech generation is assessed via acoustic measurements in the far field of the jet. We show that the surface presence drastically modifies the usual staging between A1 and A2 modes. Specifically, the plate induces the disappearance of the A2 mode and an extension of the A1 mode to the jet flow conditions for which A2 mode is usually supported in the free-jet case. Schlieren measurements are carried out to assess whether the modifications of the screech mode appearance might be related to modifications of the shock-cell structure within the jet
An experimental investigation of the resonance appearance in an impinging jet
No full textThis work presents an experimental investigation of the resonance generated by a subsonic and supersonic jet issuing from a convergent nozzle and impinging on a flat plate normal to the nozzle axis. The tonal behaviour of jet impingement is explored in a systematic fashion as a function of the jet flow conditions and the nozzle-to-plate distance via acoustic measurements in the far field of the jet. Specifically, the fully expanded jet Mach number is varied in the range 0.4-1.5 and the nozzle-to-plate distance in the range 2-10 nozzle diameters. The resonance appearance and the staging dynamics between the different tones are found to be strongly dependent on the jet-plate distance as well as the jet Mach number, particularly in the supersonic flow regime. Specifically, competition between two resonant dynamics associated with jet impingement and screech is observed for small and intermediate nozzle-plate spacings. For larger distances, resonances disappear in the subsonic regime and the jet dynamics reproduces the behaviour of a free screeching jet in the supersonic regime. Non-linear spectral analysis is finally exploited to characterise the non-linearities associated with the resonance generation
Atropostatin: Design and Total Synthesis of an Atropisomeric Lactone–Atorvastatin Prodrug
Full text linkAtorvastatins play an important role in the inhibition of HMG-CoA reductase, an enzyme present in the liver that takes part in the biosynthesis of cholesterol. In this article, we report the total synthesis of a lactone–atorvastatin prodrug with additional atropisomeric features. Conformational and experimental studies of model compounds were designed to test the stability of the chiral axis. Docking calculations were performed to evaluate the constant inhibition of a library of atorvastatins. Full synthesis of the best candidate was achieved and thermally stable atropisomeric lactone–atorvastatin was obtained. The absolute configuration of the chiral axis of the atropisomers was assigned by means of chiroptical ECD spectroscopy coupled with TD-DFT calculations
Real-Time Estimation of Jet-Surface Interaction Noise
No full textMotivated by the growing concerns for the noise emissions generated by the interaction between the engine jet and the airframe surfaces consequent to the progressive increase of the engine by-pass ratio in commercial aircraft architectures, we study the estimation of the far-field noise radiated by a jet in an installed configuration based on sensor readings in the near field of the jet. We carry out an experimental investigation of the jet-surface interaction phenomena in a simplified set-up where a flat plate is installed parallel to the nozzle axis of a subsonic jet. Real-time estimation is performed using empirical linear transfer functions identified between near-field sensors and far-field observers. The transfer function and the accuracy of the noise estimation performed are characterised as a function of jet flow conditions, type and streamwise position of near-field sensors and radial distance between the jet and the edge. This analysis can guide the positioning of near-field sensors for the implementation of closed-loop control strategies for the jet-surface interaction noise
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