629 research outputs found
Evaluating outlet working fluid’s temperature by implementing closed-loop geothermal systems in decommissioned hydrocarbon wells: the case studies of San Benigno and Cinzano wells
No full textAbandoned hydrocarbon wells offer significant potential for extracting geothermal energy from the subsurface if effectively repurposed. Among the discussed geothermal systems, closed-loop wellbore heat exchangers (WBHEs) represent one of the most promising technologies. Simplified methods to assess the exploitable temperature potential of decommissioned wells, using coaxial and U-tube WBHEs and integrating geological and technical considerations, have been developed and are available in the literature. Such solutions are useful tools for evaluating the suitability of a selected well for geothermal repurposing during the preliminary analysis phase. This study focuses on the application of simplified approaches for the preliminary assessment of the extracted temperature following the implementation of coaxial and U-tube WBHEs in the San Benigno and Cinzano wells, leveraging on-site temperature data. These assessments allowed the identification of these wells as economically unsuitable for repurposing, unlike others studied and located within the Italian territory
Comparison of microbiological and fermentation parameters obtained with an improved rumen in vitro technique with those obtained in vivo
No full textThe aim of the present work was to develop and evaluate a rapid in vitro technique to study the activity of rumen micro-organisms and to estimate the nutritive value of feeds. The rumen culture apparatus described here is essentially a batch system, modified in order to obtain conditions of strict anaerobiosis and the balanced growth of all the microbial forms present in the mixed rumen inoculum. Validation of this technique was carried out by comparing studies run simultaneously in vivo and in vitro, analysing microbial flora composition, biochemical parameters of rumen fluid and feed degradability. At the different incubation periods studied, degradability and biochemical parameters had very similar trends in the two systems and the microbiological analysis did not show any significant (P>0.05) differences between the in vivo and the in vitro approaches. The in vitro system described showed the possibility to maintain, for the time studied, a balanced microbial composition, which represents the equilibrium found in the animals. (C) 1998 Elsevier Science B.V
Pin-hole array production and detailed data analysis for advanced single-shot X-ray imaging of laboratory plasmas
No full textLaser produced plasmas offer the unique opportunity to investigate physical mechanisms working at extremely high field in pulsed regime [1] (Gizzi et al., 2009). Future large scale infrastructure like HiPER and ELI may open new frontiers of knowledge in this way. Technologies needed for improving diagnostic in this field have a strong impact on a wide range of multi-disciplinary applications as for compact plasma-based accelerators [1,2] (Gizzi et al., 2009; Betti et al., 2009) laser fusion oriented experiments, three-dimensional microscopy and lithography. As an example the X-ray imaging, being a powerful diagnostic tool for deep investigation on different variety of laser produced plasma, has obtained a grooving effort in recent years. Large scale facilities working in single-pulse regime for laser fusion oriented experiments have evidenced the necessity to obtain spectrally resolved X-ray images of produced plasmas in a single shot. By combining the charge coupled devices (CCD) based single-photon detection technique with a pin-hole array (PHA) a new diagnostic technique was developed, as shown in recent experiments related to the European HiPER project [3] (Labate et al., 2009). Here we qualitatively describe the PHA production process on a heavy metal substrate by means of SEM images that show an internal diameter on the micrometer scale and an aspect ratio of about 20. The characterization of the X-ray contrast up to 90 keV is presented. The data analysis of the X-ray photons interaction on CCD, for spectrum reconstruction up to high energy, is described [4] (Levato et al., 2008). (C) 2010 Elsevier B.V. All rights reserved. RI Gizzi, Leonida/F-4782-201
Muscle fibers conduction velocity in cycling: a cross-correlation based application for dynamic exercise
No full textThe aim of this study was the repeatibility and reliability assessment of a new cross correlation-based algorithm for the estimation of mean muscle fibers conduction velocity in dynamic exercise. Myoelectric signals were recorded with a 4 electrodes linear surface array from left Vastus Lateralis muscle of 18 cyclist subjects (age 26.2+3.5 years, weight 66.5+7.3 kg, height 1.75+0.06m) pedalling at 70 revolutions per minute on a cycloergometer during an incremental test. Conduction velocity was estimated on one window centered around the signal's root mean square peak for each cycle by means of cross correlation method. According to literature, a normalized value for cross correlation integral ranging from 0.7 and 1 demonstrates the presence of the same phenomenon over two distinct acquisition points. In order to carry out the measurements of conduction velocity from surface signals in dynamic contractions, a special care must be observed in the positioning of analysis window. More strictly it's necessary to place the analysis window on the same portion of pedal cycle for each repetition of cycling gesture. From our experiments, and in agreement with literature, we found a substantial repeatability of root mean square peak position from cycle to cycle. We estimated conduction velocity in -5250 pedal cycles obtaining 93.4% cross correlation normalized values .7 and a 0.2 m/s root mean square error in estimation value
Low-frequency oscillations of the neural drive to the muscle are increased with experimental muscle pain
No full textWe investigated the influence of nociceptive stimulation on the accuracy of task execution and motor unit spike trains during low-force isometric contractions. Muscle pain was induced by infusion of hypertonic saline into the abductor digiti minimi muscle of 11 healthy men. Intramuscular EMG signals were recorded from the same muscle during four isometric contractions of 60-s duration at 10% of the maximal force [maximal voluntary contraction (MVC)] performed before injection (baseline), after injection of isotonic (control) or hypertonic saline (pain), and 15 min after pain was no longer reported. Each contraction was preceded by three 3-s ramp contractions from 0% to 10% MVC. The low-frequency oscillations of motor unit spike trains were analyzed by the first principal component of the low-pass filtered spike trains [first common component (FCC)], which represents the effective neural drive to the muscle. Pain decreased the accuracy of task performance [coefficient of variation (CoV) for force: baseline, 2.8 ± 1.8%, pain, 3.9 ± 1.8%; P < 0.05] and reduced motor unit discharge rates [11.6 ± 2.3 pulses per second (pps) vs. 10.7 ± 1.7 pps; P < 0.05]. Motor unit recruitment thresholds (2.2 ± 1.2% MVC vs. 2.4 ± 1.6% MVC), interspike interval variability (18.4 ± 4.9% vs. 19.1 ± 5.4%), strength of motor unit short-term synchronization [common input strength (CIS) 1.02 ± 0.44 vs. 0.83 ± 0.22], and strength of common drive (0.47 ± 0.08 vs. 0.47 ± 0.06) did not change across conditions. The FCC signal was correlated with force (R = 0.45 ± 0.06), and the CoV for FCC increased in the painful condition (5.69 ± 1.29% vs. 7.83 ± 2.61%; P < 0.05). These results indicate that nociceptive stimulation increased the low-frequency variability in synaptic input to motoneurons.</p
Diffraction and polarization properties of POLICRYPS permanent and switchable gratings
No full textAn experimental and theoretical study is presented on a novel class of electrically switchable diffraction gratings, formed by alternated stripes of polymer and liquid crystal (LC) called POLICRYPS (POlimer LIquid CRYstal Polymer Slides) [1]. The measurement of the diffraction efficiency versus the angle of incidence was performed for both p and s polarized probe beams at two wavelengths of 632.8 nm and 1550 nm. In particular infrared diffraction properties are interesting for possible applications of POLICRYPS as optical switches for fiber optic communication systems as demonstrated in a previous work [2]. The sample under test consisted of a 11.5 μm thick cell made of coupled ITO coated glass substrates filled with a mixture of 30%wt of nematic LC (NLC) 5CB and 70%wt of UV curable pre-polymer NOA61. A grating with a period of about 1.38 μm was written by laser curing at wavelength of 351 nm. A strong modulation of the refractive index across the sample is due to the NLC director which is oriented perpendicularly to the polymer stripes on the cell surface, and hence parallel to the wave vector of the impinging optical field. This geometry yields a high mismatch between the refractive index of NOA-61 (nP= 1.56) and the extraordinary refractive index of 5CB (ne= 1.7057) at 632.8 nm and T=25 °C. Diffraction efficiencies of about 95% at 632.8 nm and of about 40% at 1550 nm for a p-polarized beam probe were detected. Diffraction efficiencies below 8% were measured for an s-polarized beam probe. The grating can be switched off by applying an external electric field due to the matching between the refractive index of the liquid crystal and the polymer one. The presence of a threshold voltage for the decrease of the diffraction efficiency is due to the balancing between the dielectric torque and the elastic torque acting on the director of NLC molecules confined among the polymer stripes. At the Bragg angle the grating diffraction efficiency can be switched below 5% by applying an electric field of 5 V/μm at 632.8 nm and of 8 V/μm at 1550 nm. The coupled mode theory extended to thick anisotropic materials [3] has been used to fit the diffraction angular spectra at both wavelengths. Agreement between theoretical and experimental results for both polarizations has been achieved by including a statistical fluctuation of the LC molecule axis orientation with a Gaussianlike distribution respect to the grating vector [4].
References
[1] R. Caputo, A. V. Sukhov, and C. Umeton, Mol. Cryst. Liq. Cryst., Vol. 372, pp. 263-274, 2001.
[2] R. Asquini, A. d’Alessandro, C. Gizzi, P. Maltese, R. Caputo, A. V. Sukhov, C. Umeton, A. Veltri, Mol. Cryst. Liq. Cryst., 2003, in press.
[3] G. Montemezzani and M. Zgonik, Phys. Rev. E, Vol. 55, pp. 1035-1047, 1997.
[4] R. Sutherland, J. Opt. Soc. Am. B, Vol. 19, pp. 2995-3003, 2002
Note: Real-time monitoring via second-harmonic interferometry of a flow gas cell for laser wakefield acceleration
No full textThe use of a gas cell as a target for laser wakefield acceleration (LWFA) offers the possibility to obtain stable and manageable laser-plasma interaction process, a mandatory condition for practical applications of this emerging technique, especially in multi-stage accelerators. In order to obtain full control of the gas particle number density in the interaction region, thus allowing for a long term stable and manageable LWFA, real-time monitoring is necessary. In fact, the ideal gas law cannot be used to estimate the particle density inside the flow cell based on the preset backing pressure and the room temperature because the gas flow depends on several factors like tubing, regulators, and valves in the gas supply system, as well as vacuum chamber volume and vacuum pump speed/throughput. Here, second-harmonic interferometry is applied to measure the particle number density inside a flow gas cell designed for LWFA. The results demonstrate that real-time monitoring is achieved and that using low backing pressure gas (<1 bar) and different cell orifice diameters (<2 mm) it is possible to finely tune the number density up to the 1019 cm-3 range well suited for LWFA
Historical damage pattern and causes of differential damage: an approach based on combining geophysical prospecting, geological and historical-technical data
No full textWe describe a multidisciplinary and interdisciplinary method to analyse the causes of differential macroseismic effects caused by an earthquake in a historical town. We illustrate the method with a case study based on analysing the damage caused by the 1930 Irpinia earthquake (Me=6.7) in Melfi, a town in southern Italy. A damage pattern map was already available for this site. To understand the anomalies of Melfi damage, we used an integrated approach that combines geological surveys, geophysical prospecting and analysis of unpublished technicalhistorical data. Geo-electrical prospecting was adopted to infer the geological set-up and to estimate the thickness of shallow deposits. The results of the geophysical surveys were compared with detailed geological information derived from both in situ surveys and boreholes. Finally, cross-correlation among these data and technical reports coeval to the earthquake allowed us to create a complete picture of the possible causes of uneven damageWe describe a multidisciplinary and interdisciplinary method to analyse the causes of differential macroseismic effects caused by an earthquake in a historical town. We illustrate the method with a case study based on analysing the damage caused by the 1930 Irpinia earthquake (MeCombining double low line6.7) in Melfi, a town in southern Italy. A damage pattern map was already available for this site. To understand the anomalies of Melfi damage, we used an integrated approach that combines geological surveys, geophysical prospecting and analysis of unpublished technical-historical data. Geo-electrical prospecting was adopted to infer the geological set-up and to estimate the thickness of shallow deposits. The results of the geophysical surveys were compared with detailed geological information derived from both in situ surveys and boreholes. Finally, cross-correlation among these data and technical reports coeval to the earthquake allowed us to create a complete picture of the possible ..
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