Istituto Nazionale di Ricerca Metrologica
METRICA Archivio istituzionale della ricerca - INRIMNot a member yet
8322 research outputs found
Sort by
From spectral analysis to hysteresis loops: A breakthrough in the optimization of magnetic nanomaterials for bioapplications
Get PDFAn innovative method is proposed to determine the most important magnetic properties of bioapplication-oriented magnetic nanomaterials exploiting the connection between hysteresis loop and frequency spectrum of magnetization. Owing to conceptual and practical simplicity, the method may result in a substantial advance in the optimization of magnetic nanomaterials for use in precision medicine. The techniques of frequency analysis of the magnetization currently applied to nanomaterials both in vitro and in vivo usually give a limited, qualitative picture of the effects of the active biological environment, and have to be complemented by direct measurement of the hysteresis loop. We show that the very same techniques can be used to convey all the information needed by present-day biomedical applications without the necessity of doing conventional magnetic measurements in the same experimental conditions. The spectral harmonics obtained analysing the response of a magnetic tracer in frequency, as in magnetic particle spectroscopy/imaging, are demonstrated to lead to a precise reconstruction of the hysteresis loop, whose most important parameters (loop's area, magnetic remanence and coercive field) are directly obtained through transformation formulas based on simple manipulation of the harmonics amplitudes and phases. The validity of the method is experimentally verified on various magnetic nanomaterials for bioapplications submitted to ac magnetic fields of different amplitude, frequency and waveform. In all cases, the experimental data taken in the frequency domain exactly reproduce the magnetic properties obtained from conventional magnetic measurements
Cryptomelane nanocrystals: Pseudosymmetry causes anisotropic peak broadening in Rietveld refinement
Get PDFCryptomelane (□2-xKx)[Mn8O16] is an octahedral molecular sieve with the hollandite framework, a strongly correlated electron system with tunnel structure. Rietveld refinement using powder X-ray diffraction patterns of a nanocrystalline sample was undertaken to assess both structural and morphological details which might be tuned for specific applications. The distribution of peak widths was highly anisotropic but successful refinement of the tetragonal structure could be achieved assuming both grain shape and microstrain anisotropy. The microstrain hypothesis appeared flawed from high uncertainties and correlations and was in conflict with the negative slope of a Williamson-Hall plot. As an alternative, lattice desymmetrization from tetragonal to monoclinic was considered. Comparison of calculated and observed hkl dependence of line broadening confirmed that the pseudosymmetry hypothesis was more appropriate, improving results for both structure and particle shape. This is the first time that lattice desymmetrization was used to explain anisotropic diffraction line broadening, a major issue in nanomaterials where peaks are intrinsically broad and the new model helps to abate correlations which afflict Rietveld refinement in these systems
Accurate Parameters Identification of a Supercapacitor Three-Branch Model
Get PDFSupercapacitors are becoming increasingly important storage system components. To effectively control their terminal voltage, even in real time, numerous circuit models capable of faithfully simulating their behavior in energy systems and various applications are being explored. The three-branch supercapacitor model appears to be a good compromise between simplicity and accuracy. Typically, this model lacks accuracy in dynamic cycling and long stand-by periods. In this study, a new model identification method based on the state equations of the circuit is described and tested on a 400 F supercapacitor, and the obtained results are validated by measurements. Such an approach, suitably optimized, provides good agreement with the measurements, with discrepancies below 50 mV even in repeated cycles. In the static identification, after 90 minutes of self-discharge, the discrepancy was approximately 5 mV. The study also discusses the sensitivity of the model output to the circuit parameters, which is useful for choosing the appropriate timespan for parameter optimization and introduces variable leakage resistance and a method for its determination. Through this parameter, good agreement with the measurements is observed during the long self-discharging phases. A discrepancy of less than 50 mV between the measured and computed results is observed after one week. The union of the circuit state equations based model and the nonlinear leakage resistance determination allows the three-branch circuit model to achieve a high accuracy both in real-time simulation and in the presence of long stand-by phases
Decoration of laser induced graphene with MXene and manganese oxide for fabrication of a hybrid supercapacitor
Get PDFDuring the last years, Internet of Things has become a prominent topic of technical, social, and economic importance. One of the main consequences is the high demand for energy and power density from small energy storage devices. In this field the laser induced graphene (LIG) has become a promising material to produce flexible micro-supercapacitors. The issue with this material is that the performances are strongly restrained by its limited surface area and the relatively low conductivity. In this work we improve the performance of a LIG supercapacitor by decorating its surface through electrophoresis: one electrode will be decorated with metal nitrides and metal carbides (MXenes), the other with manganese oxide. These two materials have appreciable conductivity and pseudocapacitance. Electrochemical measurements have been carried out on the two electrodes separately. After a charge balancing, the device has been sealed in pouch and tested
Absolute frequency measurement of a Yb optical clock at the limit of the Cs fountain
Get PDFWe present the new absolute frequency measurement of ytterbium (Yb-171) obtained at INRiM with the optical lattice clock IT-Yb1 against the cryogenic caesium (Cs-133) fountain IT-CsF2, evaluated through a measurement campaign that lasted 14 months. Measurements are performed by either using a hydrogen maser as a transfer oscillator or by synthesizing a low-noise microwave for Cs interrogation using an optical frequency comb. The frequency of the Yb-171 unperturbed clock transition S-1(0)-> P-3(0) results to be 518 295 836 590 863.44(14) Hz, with a total fractional uncertainty of 2.7x10(-16) that is limited by the uncertainty of IT-CsF2. Our measurement is in agreement with the Yb frequency recommended by the Consultative Committee for Time and Frequency. This result confirms the reliability of Yb as a secondary representation of the second and is relevant to the process of redefining the second in the International System of Units on an optical transition
The impact of physicochemical features of carbon electrodes on the capacitive performance of supercapacitors: a machine learning approach
Get PDFHybrid electric vehicles and portable electronic systems use supercapacitors for energy storage owing to their fast charging/discharging rates, long life cycle, and low maintenance. Specific capacitance is regarded as one of the most important performance-related characteristics of a supercapacitor's electrode. In the current study, Machine Learning (ML) algorithms were used to determine the impact of various physicochemical properties of carbon-based materials on the capacitive performance of electric double-layer capacitors. Published experimental datasets from 147 references (4899 data entries) were extracted and then used to train and test the ML models, to determine the relative importance of electrode material features on specific capacitance. These features include current density, pore volume, pore size, presence of defects, potential window, specific surface area, oxygen, and nitrogen content of the carbon-based electrode material. Additionally, categorical variables as the testing method, electrolyte, and carbon structure of the electrodes are considered as well. Among five applied regression models, an extreme gradient boosting model was found to best correlate those features with the capacitive performance, highlighting that the specific surface area, the presence of nitrogen doping, and the potential window are the most significant descriptors for the specific capacitance. These findings are summarized in a modular and open-source application for estimating the capacitance of supercapacitors given, as only inputs, the features of their carbon-based electrodes, the electrolyte and testing method. In perspective, this work introduces a new wide dataset of carbon electrodes for supercapacitors extracted from the experimental literature, also giving an instance of how electrochemical technology can benefit from ML models
Rapporto dell’attività INRIM – Progetto Dynametric INRIM Metrostaff
No full textQuesto rapporto raccoglie i risultati preliminari ottenuti nel progetto Dynametric INRIM Metrostaff. Esso si prefigge di caratterizzare metrologicamente per via dimensionale una macchina di misura a coordinate innovativa. Questa è rivolta ad applicazioni bidimensionali, o tridimensionali in cui la componente verticale è ridotta, a grande velocità. La configurazione innovativa e la grande velocità, cui necessariamente corrispondono grandi accelerazioni, sottopongono i carrelli mobili e la struttura ad importanti forze dinamiche, che si traducono in deformazioni e conseguenti errori di misura a coordinate. Mentre la caratterizzazione statica degli errori di geometria delle macchine a coordinate è materia consolidata in letteratura e nella pratica industriale, quella degli errori dinamici lo è assai meno ed è legata alla specifica configurazione della macchina. Scopo di questo rapporto è di caratterizzare dinamicamente una macchina di misura innovativa per via interferometrica in modo idoneo non solo alla stima degli errori ma anche allo loro futura correzione in tempo reale. I risultati presentati sono preliminari e relativi ad un prototipo perché la macchina di misura definitiva e completa di tutti gli assi di misura non è ancora disponibile alla data di redazione di questo progetto.This technical report summarises the preliminary results of the Dynametric INRIM ASF Metrology project. It aims at the metrological characterisation of an innovative coordinate measuring machine by accelerometry. The machine is intended for high speed bidimensional applications or tri dimensional when the vertical component is small. The innovative set up and the high speed result in strong accelerations and structure and carriages undergo severe dynamic stresses and the consequent deformations and coordinate measurement errors. The characterisation of static geometry errors of coordinate measuring machines is well established in the technical literature and industrial practice; on the contrary, that of dynamic errors is not and is related to the design of the individual machine. This reports aims at the dynamic characterisation of an innovative coordinate measuring machine by interferometry in a way suitable not only to estimate but also to compensate the errors real time. The reported results are preliminary and related to a prototype because the definitive fully equipped machine is not available yet at the publication time of this report
Tomography of memory engrams in self-organizing nanowire connectomes
Get PDFSelf-organizing memristive nanowire connectomes have been exploited for physical (in materia) implementation of brain-inspired computing paradigms. Despite having been shown that the emergent behavior relies on weight plasticity at single junction/synapse level and on wiring plasticity involving topological changes, a shift to multiterminal paradigms is needed to unveil dynamics at the network level. Here, we report on tomographical evidence of memory engrams (or memory traces) in nanowire connectomes, i.e., physicochemical changes in biological neural substrates supposed to endow the representation of experience stored in the brain. An experimental/modeling approach shows that spatially correlated short-term plasticity effects can turn into long-lasting engram memory patterns inherently related to network topology inhomogeneities. The ability to exploit both encoding and consolidation of information on the same physical substrate would open radically new perspectives for in materia computing, while offering to neuroscientists an alternative platform to understand the role of memory in learning and knowledge.Hardware architectures based on self-organized memristive networks of nano objects have attracted a growing attention. Here, nanowire connectomes are experimentally proved to translate spatially correlated short-term plasticity effects into long-lasting topological changes, thus emulating both information encoding and memory consolidation of human brain
