Modeling and model validation of supercapacitors for real-time simulations

Supercapacitors are becoming very important in the automotive and energy and power industry due to their specially characteristics, in particular in the field of hybrid vehicles and hybrid energy storage systems. For this reason, having accurate models that can represent the behavior of such systems is necessary and the main important characteristics of supercapacitor are a high-power density and a long lifetime with low maintenance. This thesis focuses on modeling supercapacitors to the study of their behavior in a short time period. As, their operation often short intense power deliveries. The goal of this thesis is to compare the accuracy of equivalent-circuit models of supercapacitors together with their required execution time for real-time simulations. In the first chapter, the operation of the supercapacitor from the molecular point of view and the principal of storing energy in a supercapacitor is introduced. Common operation modes of supercapacitors are also introduced. Next, equivalent-circuit models of supercapacitors are introduced. The models are implemented in MATLAB/Simulink and their responses are compared with the experimental results. The parameter estimation results. The parameter estimation tool of MATLAB has been used to estimate the model parameters for each model. At the end, the models are compared in terms of inaccurately reproducing the experimental response of a supercapacitor. Lastly, the models are compared in terms of their required execution time for real-time simulations. The models are implemented in RT-LAB software and simulated on the Opal-RT’s OP4510 real-time simulator. Here the execution times of the models compared with the goal of representing a large number of supercapacitor cells

L¿USO DELL¿ISTOLOGIA NEL CONTROLLO DEGLI ALIMENTI DI ORIGINE ANIMALE CON PARTICOLARE RIFERIMENTO AI PRODOTTI ITTICI

Under Council Regulations, authentication of fish as fresh or frozen-thawed is compulsory because of the widespread fraudulent practice of retailing fish products as fresh, when they have actually been frozen. Moreover, in order to satisfy the health requirements of EC Regulations 853/2004 and 1276/2011, the fish intended for raw consumption has to be deep-frozen before usage, to protect consumers against Anisakiasis.. The aim of this study was to apply histological analysis as a method for distinguishing between fresh and frozen-thawed fish, with a view to evaluate its potential use as a routine screening technique in compliance with the requirements of EC Regulation No. 882/2004 on official food and feed controls. In a first experiment, method performance (i.e., accuracy and precision) was evaluated on tissue samples from three common Mediterranean fish species; the evaluation was subsequently extended to include samples from 35 different fish species in a second experiment to test for method robustness. Specifically, method accuracy was tested by comparing histological results against a gold standard obtained from the analysis of frozen and unfrozen fish samples prepared for the study; method precision was evaluated according to inter-rater agreement (i.e., three laboratories with expertise in histopathology in the first experiment, and three expert analysts in the second experiment) by estimating Cohen's kappa (and corresponding 95% confidence intervals) for each pair of labs and experts and combined Cohen\u2019s kappa for all three experts and labs. The observed interrater agreement among the three labs and the three experts showed good method accuracy and precision (high sensitivity and specificity), as well as good method reproducibility. Our results suggest that, besides being a rapid and simple tool, histology is a highly accurate method for distinguishing between fresh and frozen-thawed fish, irrespective of the fish species analysed. Furthermore in a third experiment ten samples obtained both from red and white-meat fish, based on real production of the food business, were designated to evaluate the performance of the histological method in correctly classifying the fish as fresh/frozen as well as the microbiological and chemical safety issues possibly related to the fishery products. All samples were collected and were subjected to histological, microbiological and chemical analyses before and after freezing. For two samples species identification was needed. Based on the histological method, one out of ten fish, all claimed to be fresh by the supplier, was not; all the remaining nine samples following freezing could be characterized microscopically as frozen; microbiological parameters resulted normal, while flesh from a tuna fish (Euthynnus alletteratus) contained mercury residues three times the legally permitted level

Histology as a Valid Tool To Differentiate Fresh from Frozen-Thawed Marinated Fish.

European Commission Regulation (EU) 1276/2011 requires that fishery products intended for raw consumption be frozen at -20°C for not less than 24 h or at -35°C for at least 15 h in order to kill viable parasites other than trematodes. But because marinating processes are not always effective in destroying nematode larvae, raw marinated fish preparations should be frozen before consumption. This study evaluated the performance of a standardized histological method to distinguish between fresh and frozen-thawed raw marinated fish. Sixty anchovy (Engraulis encrasicolus) fillets were sampled: 30 were marinated at +4°C for 24 h, and 30 were frozen at -20°C for 24 h before being marinated for 24 h. All 60 samples were fixed in formalin, processed for paraffin embedding, cut, and stained with hematoxylin and eosin. The slide preparations were examined microscopically by three independent histopathologists and classified as frozen-thawed or negative according to standard operating procedure criteria in use at our laboratory. Performance evaluation of the method showed 100% sensitivity (95% confidence interval [CI], 88.4 to 100%) and 100% specificity (95% CI, 88.4 to 100%), and the interrater agreement (Cohen's kappa) was 1 (95% CI, 0.85 to 1). Histology proved a valid and reliable tool to distinguish fresh from frozen-thawed marinated fish. It can be applied to deliver safe raw fishery products to consumers in order to minimize the risk of anisakidosis

Differentiation between Fresh and Thawed Cephalopods Using NIR Spectroscopy and Multivariate Data Analysis

The sale of frozen–thawed fish and fish products, labeled as fresh, is currently one of the most common and insidious commercial food frauds. For this reason, the demand of reliable tools to identify the storage conditions is increasing. The present study was performed on two species, commonly sold in large-scale distribution: Cuttlefish (Sepia officinalis) and musky octopus (Eledone spp.). Fifty fresh cephalopod specimens were analyzed at refrigeration temperature (2 ± 2°C), then frozen at −20°C for 10 days and finally thawed and analyzed again. The performance of three near-infrared (NIR) instruments in identifying storage conditions were compared: The benchtop NIR Multi Purpose Analyzer (MPA) by Bruker, the portable MicroNIR by VIAVI and the handheld NIR SCiO by Consumer Physics. All collected spectra were processed and analyzed with chemometric methods. The SCiO data were also analyzed using the analytical tools available in the online application provided by the manufacturer to evaluate its performance. NIR spectroscopy, coupled with chemometrics, allowed discriminating between fresh and thawed samples with high accuracy: Cuttlefish between 82.3–94.1%, musky octopus between 91.2–97.1%, global model between 86.8–95.6%. Results show how food frauds could be detected directly in the marketplace, through small, ultra-fast and simplified handheld devices, whereas official control laboratories could use benchtop analytical instruments, coupled with chemometric approaches, to develop accurate and validated methods, suitable for regulatory purposes

Identification of Illicit Conservation Treatments in Fresh Fish by Micro-Raman Spectroscopy and Chemometric Methods

In the field of food control for fresh products, the identification of foods subjected to illicit conservation treatments to extend their shelf life is fundamental. Fresh fish products are particularly subjected to this type of fraud due to their high commercial value and the fact that they often have to be transported over a long distance, keeping their organoleptic characteristics unaltered. Treatments of this type involve, e.g., the bleaching of the meat and/or the momentary abatement of the microbial load, while the degradation process continues. It is therefore important to find rapid methods that allow the identification of illicit treatments. The study presented here was performed on 24 sea bass samples divided into four groups: 12 controls (stored on ice in the fridge for 3 or 24 h), and 12 treated with a Cafodos-like solution for 3 or 24 h. Muscle and skin samples were then characterized using micro-Raman spectroscopy. The data were pre-processed by smoothing and taking the first derivative and then PLS-DA models were built to identify short- and long- term effects on the fish's muscle and skin. All the models provided the perfect classification of the samples both in fitting and cross-validation and an analysis of the bands responsible for the effects was also reported. To the best of the authors' knowledge, this is the first time Raman spectroscopy has been applied for the identification of a Cafodos-like illicit treatment, focusing on both fish muscle and skin evaluation. The procedure could pave the way for a future application directly on the market through the use of a portable device

Chemometric Differentiation of Sole and Plaice Fish Fillets Using Three Near-Infrared Instruments

Fish species substitution is one of the most common forms of fraud all over the world, as fish identification can be very challenging for both consumers and experienced inspectors in the case of fish sold as fillets. The difficulties in distinguishing among different species may generate a “grey area” in which mislabelling can occur. Thus, the development of fast and reliable tools able to detect such frauds in the field is of crucial importance. In this study, we focused on the distinction between two flatfish species largely available on the market, namely the Guinean sole (Synaptura cadenati) and European plaice (Pleuronectes platessa), which are very similar looking. Fifty fillets of each species were analysed using three near-infrared (NIR) instruments: the handheld SCiO (Consumer Physics), the portable MicroNIR (VIAVI), and the benchtop MPA (Bruker). PLS-DA classification models were built using the spectral datasets, and all three instruments provided very good results, showing high accuracy: 94.1% for the SCiO and MicroNIR portable instruments, and 90.1% for the MPA benchtop spectrometer. The good classification results of the approach combining NIR spectroscopy, and simple chemometric classification methods suggest great applicability directly in the context of real-world marketplaces, as well as in official control plans