121,913 research outputs found
Spectroscopic measurement of volatile organic compounds as biomarkers for human breath analysis
No full textI composti BTEX - benzene, toluene, etilbenzene e xileni - sono tra i composti organici volatili (COV) più pericolosi, pertanto il loro rilevamento altamente sensibile e selettivo può fornire informazioni chiave in molte applicazioni, dal monitoraggio ambientale all'analisi dell'espirato. I sensori ottici basati su tecniche di spettroscopia di assorbimento laser (LAS) possono rappresentare una soluzione per il rilevamento di BTEX poiché questi composti mostrano caratteristiche di assorbimento forti e distinte nella regione spettrale 13 - 15 μm. Tra queste tecniche, la spettroscopia fotoacustica a diapason di quarzo (QEPAS) e la spettroscopia termoelastica indotta dalla luce (LITES) rappresentano due tecniche efficaci. L'attività di ricerca svolta durante il mio dottorato di ricerca in Industria 4.0 presso il Politecnico di Bari si è concentrato sullo sviluppo di sensori ottici basati su tecniche QEPAS e LITES per il rilevamento di benzene, mirando la banda di assorbimento target centrata a 14,85 μm utilizzando un Laser a cascata quantica (QCL) non commerciale. I sensori QEPAS e LITES sviluppati hanno mostrato un'eccellente risposta lineare e sono stati ottenuti limiti di rilevamento minimi stimati (MDL), rispettivamente di 13 ppb e 105 ppb, con una costante di tempo del lock-in amplifier di 100 ms.BTEX compounds - benzene, toluene, ethylbenzene, and xylenes - are among the most hazardous Volatile Organic Compounds (VOCs), thus their highly sensitive and selective detection can provide key information in many applications, ranging from environmental monitoring to breath analysis. Optical sensors based on laser absorption spectroscopy (LAS) techniques can represent a viable solution for BTEX detection since these compounds show strong and distinct absorption features in the spectral region 13 - 15 μm. Among these techniques, Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS) and Light-Induced Thermoelastic Spectroscopy (LITES) represent two effective techniques. The research activity carried out during my Ph.D. program in Industry 4.0 at the Polytechnique University of Bari was focused on the development of optical sensors based on QEPAS and LITES techniques for benzene detection, targeting the absorption band centred at 14.85 μm using a non-commercial Quantum Cascade Laser (QCL) source. The developed QEPAS and LITES sensors showed an excellent linear response and estimated minimum detection limits (MDL) of 13 ppb and 105 ppb, respectively, were obtained with a lock-in time constant of 100 ms
Time continuous two-source energy-water balance modelling of heterogeneous crops: FEST-2-EWB
No full textAn accurate knowledge of the water and energy exchanges in the soil-crop-atmosphere system is critical for a precise and aware control of all agricultural operations, from field management to irrigation and harvest. This concern is more complex to address in heterogeneous systems, with the presence of bare soil or simple grass in between the main crop. In this work, a two-source energy-water balance model is developed, joining the advantages of the single-source FEST-EWB model (internal computation of surface temperature and time-continuous modelling) and those of two-source approaches (employing two surface temperatures to accurately characterize the intra-pixel heterogeneity). In order to validate the model results, a laboratory experiment has been designed over a lysimeter, with the target of obtaining partitioned estimates of Evaporation and Transpiration over a heterogeneous grass crop. These partitioned fluxes were supported by a safe error margin in the scaling procedure (less than +/- 1 mm/d). The FEST-EWB and FEST-2-EWB models were first calibrated using surface temperature obtained from thermal camera observations (with roughly 1.7 degrees C of average bias). Then, they were validated against the partitioned estimated. The single-source modelling showed a consistent overestimation of the estimated Transpiration, by an amount roughly 20% of the average irrigation event. On the other hand, the two-source model shows much lower (6%) errors, portraying more accurately the Transpired water volume. Such an improvement in crop water consumption estimation can provide a successful reference to optimize the use of the irrigation water resource, with consistent water savings
Impact of aerodynamic temperature on ET estimates of Mediterranean irrigated crops from an energy-water balance model
No full textThe aerodynamic temperature identifies the temperature at an effective depth within the vegetation canopy, where sensible heat flux is originated, thus regulating the surface energy balance partitioning between latent and sensible heat. As it cannot be directly measured, a common practice in thermal infrared based retrieval of evapotranspiration is to substitute it with the radiometric temperature. However, numerous works have proven the two temperatures to be quite different, with peak differences as high as & PLUSMN;10 degrees C, with direct consequences in evapotranspiration modelling over complex landscapes. In this work, the main focus is on the integration of aerodynamic temperature within a hydrological modelling scheme, in order to identify possible improvements in the latent heat (and, thus, evapotranspiration) estimation. A first part of the analysis centres on comparing the differences between indirect estimates of aerodynamic temperature and measurements of radiometric surface temperature, showing divergences sometimes exceeding 10-15 degrees C. In a second step, a sensitivity analysis of the variable with respect to some environmental parameters was conducted. Meteorological parameters were found to be influential, whereas vegetation parameters played a relatively lesser role. In order to plug the aerodynamic temperature within the selected hydrological model (FEST-EWB), a test models was developed, testing the impact of the (measured) variable within the different turbulent fluxes. As the final aim was to continuously integrate the aerodynamic temperature within the hydrological model, possible parametrizations were scruti-nised, using the meteorological dependencies already investigated in the first part of the study. The newly-developed FEST-AeroT model, with a continuous parametrization of aerodynamic temperature, produced mild improvements in sensible and latent heat estimation and virtually no gain in net radiation. The model and parametrization uncertainties may be the reason why such a high a priori temperature divergence produced so small differences in final energy flux modelling
Improved Thermal Management of Li-Ion Batteries with Phase-Change Materials and Metal Fins
No full textThe continuing increase in pollutant emissions requires the use of alternative power sources. This includes the use of electric or hybrid vehicles whose energy storage system is based on batteries of various types, including lithium-ion batteries. The optimum operating temperature is between 15 °C and 35 °C. Too high temperatures can lead to catastrophic phenomena such as thermal runaway. The thermal gradient within the system should not exceed 5 °C. An effective Battery Thermal Management System can mitigate this problem. This study analysed a lithium-ion battery with a bag structure. Temperature control was evaluated using a passive (low-cost) system with phase-change materials (PCMs). The material chosen was n-octadecane (paraffin) due to its thermophysical properties and market price. Four different cooling methods were analysed, including air, fins, pure PCM, and a mixed system of single cells and small battery packs. The results show that an undesirable temperature peak around 50 °C (323.15 K) can occur at hot spots. The best system for containing the temperature inside the battery pack is the PCM cooling system with fins. The optimum fin thickness is 1.5 mm. To contain the temperature inside the battery pack, the number of fins studied is 10, while the best temperature containment is achieved with n+ 1 plates, where n is the number of cells
A double two-sources energy-water balance model for improving evapotranspiration estimates and irrigation management in fruit trees fields
No full textImproving the use of water in irrigated agriculture is meaningful in a period of increasing water scarcity conditions. A more accurate estimate of evapotranspiration (ET) and its components thus becomes fundamental to better quantify the irrigation water volumes. Many existing models, based on different remote sensing data, provide daily estimates of latent heat flux (LE) from correlation between net radiation and instantaneous estimates of LE, computed as residual component of the energy balance equation or from a correlation of land surface temperature (LST) with vegetation indices., However, they mainly lack of solutions which are continuous in time (e.g. hourly), independent from satellite LST availability and a simultaneous estimation of soil moisture. Addressing this gap, a double two-sources energy-water balance model (FEST‐2×2‐EWB) is developed based on the decoupling of both water and energy fluxes between the bare soil or grass interrow and the trees rows. This novel parameterization approach enables the differentiation of water uptake from the root zone, which varies between tall trees and grass, considering the dynamics of soil moisture (SM) in the superficial and deep layers. Additionally, it provides partitioned values for transpiration and evaporation. The new model has been evaluated in two irrigated trees fields in the North of Italy, a walnut trees field from 2019 to 2021 and a pear trees field, for the year 2022. Results of the study showcased a root-mean-square-error (RMSE) of about 55 W m− 2 and a bias of about 40 W m− 2 for hourly latent and sensible heat fluxes when compared to the eddy covariance stations located in the fields, while a RMSE of 2 °C (bias of 1.5 °C) for LST and of 0.04 for SM. The FEST‐2×2‐EWB model significantly enhances the accuracy of ET simulation in fruits trees areas in respect to the original one source and one-layer version of the same model. Finally, the application of an irrigation optimization strategy with this new model, allowed to demonstrate its potentiality in water saving (about 90 mm in a year) in respect to farmers applied irrigation, and with a difference of about 60 mm between using the double two-sources model and single source one
ON THE PROBLEM OF THE MACHINERY CHOICE AND HULL WEIGHT ASSESSMENT FOR THE DESIGN OF HIGH-SPEED VESSELS
No full textIn the last decades an increase of interest of high-speed ferries has been registered and, as a consequence, new problems have arisen as regards the request of data and adequate procedures for conceptual and preliminary design analysis. In particular, the request of increasing speed and large vessels is a continual challenge to designers to choose propulsions systems, to estimate the principal components of propulsion machinery and hull weights. At the same time, there is a lack of published systematic data and techniques suitable for both, conceptual and preliminary analysis.
Firstly, a large of database has been presented that considers new designs and high speed ferries in the world; the regression analysis of which permits rapidly to estimate the main parameters (Displacement, Length, Breadth etc etc).
Successively, a new parametric procedure has been developed to estimate hull weight of both monohull and catamaran fast ferries, including steel and/or aluminum materials. The procedure has been consequently calibrated in order to evaluate reliable parameters which permitting the hull weight estimation.
Finally a database for the machinery choice is presented, which includes medium and high-speed diesels and gas turbines, the regression of which has been particularly discussed
Proximal-sensing-powered modelling of energy-water fluxes in a vineyard: A spatial resolution analysis
No full textSpatial resolution is a key parameter in energy–water surface flux modelling. In this research, scale effects are analyzed on fluxes modelled with the FEST-EWB model, by upscaling both its inputs and outputs separately. The main questions are: (a) if high-resolution remote sensing images are necessary to accurately model a heterogeneous area; and (b) whether and to what extent low-resolution modelling provides worse/better results than the upscaled results of high-resolution modelling. The study area is an experimental vineyard field where proximal sensing images were obtained by an airborne platform and verification fluxes were measured via a flux tower. Modelled fluxes are in line with those from alternative energy-balance models, and quite accurate (NSE = 0.78) with respect to those measured in situ. Field-scale evapotranspiration has resulted in both the tested upscaling approaches (with relative error within ±30%), although fewer pixels available for low-resolution calibration may produce some differences. When working at low resolutions, the model has produced higher relative errors (20% on average), but is still within acceptable bounds. This means that the model can produce high-quality results, partially compensating for the loss in spatial heterogeneity associated with low-resolution images
Analisi di alcuni parametri di qualità in germogli di Glicine max (L.) Merr. e Vigna radiata (L.) R. Wilczek, cresciuti al buio e in condizioni di luce bianca e blu
No full textContenuto e distribuzione di alcuni importanti metaboliti in germogli di soia verde cresciuti a diversa qualità di luce
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