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Metrological traceability for the absolute gravity Italian network
Get PDFThe Absolute Gravity Italian Network project aims to update the Italian gravity network that nowadays is framed to IGSN71, established in 1971. The focal point of the project is to define a new reference for gravity with absolute gravity observations performed according to the international standardised methodology detailed in the document “CCM-IAG Strategy for Metrology in Absolute Gravimetry” (2015). IAG resolution No. 2 and subsequent, moreover establish the need to satisfy the metrological traceability also for Absolute Gravity measurements. This can be exploited by different methods such as reference sites, international comparisons of absolute gravimeters and calibration by comparison. Measurements have been performed in appropriate sites distributed across the Italian country. The collected and validated data will be stored in an open database, as the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt fuer Kartographie und Geodaesie when will be operative, contributing to feed the new International Terrestrial Gravity Reference System. All the gravimeters used in the measurements participated to the international comparisons organised by CCM and/or EURAMET TC-M obtaining compatible results. However, in order to validate the results and to ensure traceability to the SI, additional comparisons between the absolute gravimeters used in the measurements have been performed just before the measurement campaign. The primary Italian reference instrument is the absolute gravimeter IMGC-02, developed and maintained by INRiM with an expanded measurement uncertainty of 8.5 μGal. The comparison sites are both located at INRiM and are provided with solid basements that guarantee good measurement repeatability and low floor noise which could ensure the final uncertainty. This paper shows the results of these measurements
The absolute gravity network of Italy in the framework of the ITGRS/ITGRF
Get PDFThe activities for establishing the Italian Reference Gravity Network started in 2022. This is in line with the actions promoted by the International Association of Geodesy that during its 2015 General Assembly approved a resolution on the establishment of the new global gravity network the so-called International Terrestrial Gravity Reference System/Frame that will replace IGSN71. An initial set of 30 stations has been defined over the peninsular part of Italy and the two main islands of Sicily and Sardinia. Particularly, the GGOS core station of Matera (the Agenzia Spaziale Italiana Center for Space Geodesy “Bepi” Colombo) is one of the network points as required in the documents of the GGOS-Bureau of Networks and Observations. Thus, this station will provide one link between the Italian national absolute gravity network and the GGOS observation system of IAG. In order to ensure the measurements traceability, as required by the international standards on gravity measurements, the absolute gravimeters used in the measurements participated in international comparison campaigns. Absolute gravity measurements have been supplemented with direct measurements of the local value of the vertical gravity gradient, in order to reduce the absolute values, measured by different instruments at different heights, to an intermediate and common reference height and to the ground reference level to transport it to an external associated station. The gravity field campaigns have been assisted by topographic survey campaigns, allowing a centimetric georeferencing of the gravity stations to the current ITRF. The collected data will be then validated and reduced following the internationally accepted standards and finally published through a dedicate web page of the project. These data will also be submitted to the absolute gravity database maintained by the Bureau Gravimétrique International/Bundesamt fuer Kartographie und Geodaesie where the absolute gravity data that will contribute to the new global absolute gravity reference system are collected
Enhancing ReaxFF for molecular dynamics simulations of lithium-ion batteries: an interactive reparameterization protocol
Get PDFLithium-ion batteries (LIBs) have become an essential technology for the green economy transition, as they are widely used in portable electronics, electric vehicles, and renewable energy systems. The solid-electrolyte interphase (SEI) is a key component for the correct operation, performance, and safety of LIBs. The SEI arises from the initial thermal metastability of the anode-electrolyte interface, and the resulting electrolyte reduction products stabilize the interface by forming an electrochemical buffer window. This article aims to make a first—but important—step towards enhancing the parametrization of a widely-used reactive force field (ReaxFF) for accurate molecular dynamics (MD) simulations of SEI components in LIBs. To this end, we focus on Lithium Fluoride (LiF), an inorganic salt of great interest due to its beneficial properties in the passivation layer. The protocol relies heavily on various Python libraries designed to work with atomistic simulations allowing robust automation of all the reparameterization steps. The proposed set of configurations, and the resulting dataset, allow the new ReaxFF to recover the solid nature of the inorganic salt and improve the mass transport properties prediction from MD simulation. The optimized ReaxFF surpasses the previously available force field by accurately adjusting the diffusivity of lithium in the solid lattice, resulting in a two-order-of-magnitude improvement in its prediction at room temperature. However, our comprehensive investigation of the simulation shows the strong sensitivity of the ReaxFF to the training set, making its ability to interpolate the potential energy surface challenging. Consequently, the current formulation of ReaxFF can be effectively employed to model specific and well-defined phenomena by utilizing the proposed interactive reparameterization protocol to construct the dataset. Overall, this work represents a significant initial step towards refining ReaxFF for precise reactive MD simulations, shedding light on the challenges and limitations of ReaxFF force field parametrization. The demonstrated limitations emphasize the potential for developing more versatile and advanced force fields to upscale ab initio simulation through our interactive reparameterization protocol, enabling more accurate and comprehensive MD simulations in the future
Magnetic nanoparticle hyperthermia enhanced by a rotating field
Get PDFThe heating efficiency of magnetite nanoparticles for therapeutic hyperthermia is shown to be substantially enhanced by applying a uniformly rotating magnetic field in place of a field directed along an axis, when all other factors are held constant. Optimization of the heating efficiency is actively pursued in order to keep the volume fraction of nanoparticles as low as possible, reducing the adverse effects emerging from nanoparticle accumulation in organs. The effect of a rotating magnetic field is calculated by solving rate equations for the magnetic moments of magnetite nanoparticles with predominant N & eacute;el relaxation and pictured as double-well systems. The model results in a simple expression for the power density generated by nanoparticles with random easy-axis directions. A thermal model of a tissue simulant is used to show that applying a rotating instead of a linear field permits us to more than halve the dose of nanoparticles needed to attain the target temperature in the tissue
Evaluation of reliability and use of data from sensors on board of vehicles in meteorology and environmental observations
No full textDetection of low-energy electrons with transition-edge sensors
Get PDFWe present the detection of electrons with kinetic energy in the 100 eV range with transition-edge sensors (TESs). This has been achieved with a (100 x 100)-mu m2 Ti/Au bilayer TES, with a critical temperature of about 84 mK. The electrons are produced directly in the cryostat by an innovative cold source based on field emission from vertically aligned multiwall carbon nanotubes. We obtain a Gaussian energy resolution between 0.8 and 1.8 eV for fully absorbed electrons in the (90-101) eV energy range, which is found to be compatible with the resolution of this same device for photons in the same energy range. This work opens possibilities for high-precision energy measurements of low-energy electrons
Modeling Amorphous-Core Inductors up to Magnetic Saturation
Get PDFIn power supplies, inductors operating in partial magnetic saturation are increasingly exploited, to increase power density and efficiency. The design and simulation of converters exploiting nonlinear magnetic components require accurate models, able to predict their voltage/current characteristics and power losses under different operating conditions. In practical applications, inductors are subjected to either square-wave or sinusoidal voltages with different amplitude, frequency, and duty cycle. We focus on amorphous-core inductors, characterized by an extremely soft magnetic behavior and reduced magnetic losses, with a weak temperature dependence. We propose a novel behavioral circuit model with some temperature-dependent parameters, composed of two coupled nonlinear inductors and linear resistors; a capacitor is also included to account for parasitic capacitances occurring at higher frequencies for the winding. The model is tested on two amorphous-core inductors. Good accuracy is obtained in reproducing the inductor current (with different DC biases) and power loss, for sinusoidal, square, and triangular voltages with different amplitudes (also leading to magnetic saturation), frequencies (from 25 to 200 kHz), and temperatures (from 23 to 100 °C)
Molecular surface coverage standards by reference-free GIXRF supporting SERS and SEIRA substrate benchmarking
Get PDFNon-destructive reference-free grazing incidence X-ray fluorescence (RF-GIXRF) is proposed as a highly effective analytical technique for extracting molecular arrangement density in self-assembled monolayers. The establishment of surface density standards through RF-GIXRF impacts various applications, from calibrating laboratory XRF setups to expanding its applicability in materials science, particularly in surface coating scenarios with molecular assemblies. Accurate determination of coverage density is crucial for proper functionalization and interaction, such as in assessing the surface concentration of probes on plasmonic nanostructures. However, limited synchrotron radiation access hinders widespread use, prompting the need for molecular surface density standards, especially for benchmarking substrates for surface-enhanced Raman and infrared absorption spectroscopies (SERS and SEIRA) as well as associated surface-enhanced techniques. Using reproducible densities on gold ensures a solid evaluation of the number of molecules contributing to enhanced signals, facilitating comparability across substrates. The research discusses the importance of employing molecular surface density standards for advancing the field of surface-enhanced spectroscopies, encouraging collaborative efforts in protocol development and benchmarking in surface science
Optimizing the Marangoni effect towards enhanced salt rejection in thermal passive desalination
Get PDFAmid escalating water scarcity and rising energy prices, the scientific community strives to propose innovative and efficient water treatment solutions. In this context, solar passive technologies have attracted much attention. Furthermore, recent studies have experimentally revealed that the Marangoni effect, when leveraged in well-designed passive devices, may be a promising pathway towards long-term stable performance. This study presents a comprehensive numerical exploration of applying the Marangoni effect to mitigate salt accumulation, a challenge in long-term system operation. Through an extensive sensitivity analysis, we evaluate the solute molar outflow induced by the Marangoni effect, as different parameters vary. Specifically, the Marangoni effect induces enhanced mass transport, outperforming pure diffusive flow by over three orders of magnitude, under nighttime isothermal conditions. Furthermore, we provide a semi-empirical equation describing accurately the mass transfer versus the Marangoni number. Hence, nighttime brine discharge simulations show rapid salt reduction from the evaporator, reaching seawater-like salinity levels within two hours, setting stage for optimal daytime performance. To the best of our knowledge, this discharge time is the lowest reported in the literature under equivalent conditions. In conclusion we believe that the still poorly explored Marangoni effect may offer a durable mean of providing freshwater, particularly in emergencies