Istituto Nazionale di Ricerca Metrologica
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Relation between fluence rate and mean photons pathlengths: an alternative option for Monte Carlo-based-calculations of fluence
Get PDFUsually, in biomedical optics, the average photon fluence rate, evaluated in a subvolume of a propagating medium, is obtained by Monte Carlo simulations by calculating the power deposited by photons absorbed in the subvolume. We propose an alternative method based on evaluating the average path length traveled by all photons injected within the subvolume. Application examples are given. This method also works for a zero absorption coefficient and for a nonconstant spatial distribution of the absorption coefficient within the subvolume. The proposed approach is a re-visitation of a well-known method applied to nuclear and radiation physics. The results obtained show that a potential advantage of the proposed method is that it can improve the convergence of Monte Carlo simulations. Indeed, when calculating the fluence in a region of interest with the proposed method, all photons passing through the region are considered. Whereas with the traditional approach, only absorbed" photons are considered. In the latter case, this can produce a poorer Monte Carlo statistic for the same number of photons launched
Mesoscopic Modeling and Experimental Validation of Thermal and Mechanical Properties of Polypropylene Nanocomposites Reinforced By Graphene-Based Fillers
Get PDFThe development of nanocomposites relies on structure-property relations, which necessitate multiscale modeling approaches. This study presents a modeling framework that exploits mesoscopic models to predict the thermal and mechanical properties of nanocomposites starting from their molecular structure. In detail, mesoscopic models of polypropylene (PP)- and graphene-based nanofillers (graphene (Gr), graphene oxide (GO), and reduced graphene oxide (rGO)) are considered. The newly developed mesoscopic model for the PP/Gr nanocomposite provides mechanistic information on the thermal and mechanical properties at the filler-matrix interface, which can then be exploited to enhance the prediction accuracy of traditional continuum simulations by calibrating the thermal and mechanical properties of the filler-matrix interface. Once validated through a dedicated experimental campaign, this multiscale model demonstrates that with the modest addition of nanofillers (up to 2 wt %), the Young’s modulus and thermal conductivity show up to 35 and 25% enhancement, respectively, whereas the Poisson’s ratio slightly decreases. Among the different combinations tested, the PP/Gr nanocomposite shows the best mechanical properties, whereas PP/rGO demonstrates the best thermal conductivity. This validated mesoscopic model can contribute to the development of smart materials with enhanced mechanical and thermal properties based on polypropylene, especially for mechanical, energy storage, and sensing applications
Crystal bending in triple-Laue X-ray interferometry. Part I. Theory
Get PDFThe measured value of the (220) lattice-plane spacing of silicon 28 using scanning X-ray interferometry is essential to realize the kilogram by counting Si-28 atoms. An assumption made is that the measured lattice spacing is the bulk value of an unstrained crystal forming the analyser of the interferometer. However, analytical and numerical studies of the X-ray propagation in bent crystals suggest that the measured lattice spacing might refer to the analyser surface. To confirm the result of these studies and to support experimental investigations of the matter by phase-contrast topography, a comprehensive analytical model is given of the operation of a triple-Laue interferometer having the splitting or recombining crystal bent
Effect of mechanical cutting on the energy loss of laser-scribed grain-oriented alloys
Get PDFWe investigate the effect of mechanical cutting on the magnetic properties of high permeability grain-oriented (HGO) laser-scribed Fe-Si sheets. Measurements have been performed on strips of different widths (5 to 60 mm) cut from 0.27 mm thick sheets. Normal magnetization curve and energy loss have been determined by means of a digitally controlled single strip tester from 1 Hz to 1 kHz at peak magnetic polarization values Jp = 1000 mT and 1700 mT. The results fit into a simple phenomenological model regarding the dependence of magnetization curve and energy loss on the strip width, in substantial continuity with the approach originally developed for non-oriented electrical steels. The hysteresis Wh and excess Wexc loss components are shown to depend on the strip width according to a hyperbolic law, with a limiting fully hardened strip predicted to occur for widths around 3.5 mm. It is then consistently observed that the mechanical cutting of standard 30 mm wide HGO Epstein strips is conducive to an increase of the energy loss at 50 Hz and 1.7 T of the order of 13 %
Low noise parametric amplification in DARTWARS
No full textSuperconducting parametric amplifiers (SPAs) are an essential component in the field of quantum computing, providing high-performance amplification of extremely weak signals with low noise levels. As quantum computers scale up in size and complexity, the need for high-fidelity and high bandwidth readout becomes increasingly important. This is where SPAs come into play, providing an alternative to traditional low-temperature amplifiers with the potential to significantly improve the readout performance. Besides quantum computing, SPAs can play a central role also in the field of quantum sensing and in reading out low-temperature detectors.
SPAs are based on the principle of parametric amplification, which allows for the amplification of a signal by exploiting the nonlinearity of a material's response to a driving signal. Superconductors are particularly well-suited for this purpose due to their intrinsic non-linearity. One of the most significant advantages of SPAs is their ability to provide quantum-limited amplification, which means that the noise added by the amplifier is at the level of quantum noise. This is crucial for
quantum computing applications, where even small amounts of added noise can significantly reduce the fidelity of qubit readout.
Two main types of SPAs have emerged so far: Josephson parametric amplifiers (JPAs) and traveling-wave parametric amplifiers (TWPAs). While JPAs have proven to reach the quantum limit, they have limited bandwidth and saturation power, which restricts the number of devices they can read. Conversely, TWPAs have the potential to increase the bandwidth and saturation power to levels comparable to commercial amplifiers.
The DARTWARS (Detector Array Readout with Traveling Wave AmplifieRS) project is dedicated to developing TWPAs. Two approaches are being explored: one is based on Josephson junctions (TWJPA) while the other is based on the kinetic inductance of a high-resistivity superconductor (KITWPA). The goal is to achieve a gain value of around 20 dB, a high saturation power of approximately -50 dBm, and a noise level that is either quantum-limited or nearly quantum-limited
(TN < 600 mK). These features will enable the readout of large arrays of detectors or qubits with virtually no degradation in noise.
DARTWARS is a three-year project with the aim of developing TWPAs to their technical limits. In this contribution, I will present the progress made by the DARTWARS collaboration thus far
Recent Advances and Future Prospects for Memristive Materials, Devices, and Systems
No full textMemristive technology has been rapidly emerging as apotentialalternative to traditional CMOS technology, which is facing fundamentallimitations in its development. Since oxide-based resistive switcheswere demonstrated as memristors in 2008, memristive devices have garneredsignificant attention due to their biomimetic memory properties, whichpromise to significantly improve power consumption in computing applications.Here, we provide a comprehensive overview of recent advances in memristivetechnology, including memristive devices, theory, algorithms, architectures,and systems. In addition, we discuss research directions for variousapplications of memristive technology including hardware acceleratorsfor artificial intelligence, in-sensor computing, and probabilisticcomputing. Finally, we provide a forward-looking perspective on thefuture of memristive technology, outlining the challenges and opportunitiesfor further research and innovation in this field. By providing anup-to-date overview of the state-of-the-art in memristive technology,this review aims to inform and inspire further research in this field
Metrology for marine monitoring: cooperation between INRiM and ENEA
Get PDFThe study of the status of the marine environment is typically carried out by monitoring several parameters, both chemical and physicochemical, classified as Essential Ocean Variables by the Global Climate Observing System. These variables are useful to obtain quantifiable indications to monitor the phenomena occurring in the oceans and to relate them to the changes occurring on the global scale in all the environmental compartments. In this framework, a research collaboration is ongoing between the Italian National Metrology Institute (INRiM) and the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), to support the collection, validation and maintenance of reliable and accurate databases, by applying the concepts of metrology from the laboratory to the field. Among the main Essential Ocean Variables, the dissolved oxygen and the partial pressure of carbon dioxide are key parameters to monitor the changing ocean and are largely measured in stations around the globe. INRiM and ENEA are collaborating in the measurement of these variables, focusing on the metrological traceability issues and the measurement uncertainty evaluation, also exploiting innovative Internet of Underwater Things (IoUT) in situ monitoring systems developed by WSense, spinoff of Sapienza University
In Silico Experiments to Explore the Heating Efficiency of Magnetic Nanoparticles in Hyperthermia Preclinical Tests
Get PDFPerformance evaluation of instrument transformers in power quality measurements: activities and results from 19NRM05 IT4PQ project
No full textTemperature and Frequency Dependence of Magnetic Losses in Fe-Co
Get PDFWe investigate the temperature dependence of the energy loss W(f) of 0.10 and 0.20 mm thick Fe-Co-V sheets (Vacoflux (R) and Vacodur (R)) in the range-50(degrees)C <= T <= 155(degrees)C. The measurements, performed from DC to f = 5 kHz on ring samples and Epstein strips, show that W(f) passes through a minimum value around room temperature at all tested polarization values (1.0 <= J(p) <= 1.9 T). The largest effect occurs under quasi-static regime and declines with frequency, depending on the sheet thickness and the ensuing role of the dynamic loss. The somewhat abnormal increase of the quasi-static loss W-hyst with temperature, which contrasts with a concurrent decrease of the magneto crystalline anisotropy constant, is interpreted in terms of temperature-dependent internal stresses and their change with T. The stresses are assumed to derive from the different thermal expansion coefficients of the ordered and disordered structural phases, a conclusion made plausible by the highly magnetostrictive properties of the material, dwelling in a low anisotropy environment. The AC properties are treated by adapting the loss decomposition to the inception and development of a non-uniform induction profile across the sheet thickness (skin effect) at high frequencies. The classical loss component is calculated via the numerical solution of the Maxwell's diffusion equation, where the magnetic constitutive equation of the material is identified with the normal magnetization curve. It turns out that the so-found W-class(f) and the resulting excess loss W-exc(f) are moderately dependent on temperature and W(f) eventually tends towards a slow monotonical decrease with Tat the highest frequencies