Metrological approach for permafrost temperature measurements

Permafrost degradation is a growing direct impact of climate change. Detecting permafrost shrinkage, in terms of extension, depth reduction and active layer shift is fundamental to capture the magnitude of trends and address actions and warnings. Temperature profiles in permafrost allow direct understanding of the status of the frozen ground layer and its evolution in time. The Sommeiller Pass permafrost monitoring station, at about 3000 m of elevation, is the key site of the regional network installed in 2009 during the European Project “PermaNET” in the Piedmont Alps (NW Italy). The station consists of three vertical boreholes with different characteristics, equipped with a total of 36 thermistors distributed in three different chains. The collected raw data shows a degradation of the permafrost base at approximately 60 m of depth since 2014, corresponding to about 0.03 °C/yr. In order to verify and better quantify this potential degradation, three on-site sensor calibration campaigns were carried out to understand the reliability of these measurements. By repeating calibrations in different years, two key results have been achieved: the profiles have been corrected for errors and the re-calibration allowed to distinguish the effective change of permafrost temperatures during the years, from possible drifts of the sensors, which can be of the same order of magnitude of the investigated thermal change. The warming of permafrost base at a depth of ∼ 60 m has been confirmed, with a rate of (4.2 ± 0.5)∙10−2 °C/yr. This paper reports the implementation and installation of the on-site metrology laboratory, the dedicated calibration procedure adopted, the calibration results and the resulting adjusted data, profiles and their evolution with time. It is intended as a further contribution to the ongoing studies and definition of best practices, to improve data traceability and comparability, as prescribed by the World Meteorological Organization Global Cryosphere Watch programme

Presentation of the new EPM 23RPT03 project “Metrology for standardised moisture/water content measurement in plant-origin bulk materials in support of International and European food safety and trade – GrainMet”

The EPM Project 23RPT03 GrainMet, aims to develop new measurement technologies, SI traceability paths and certified reference materials (CRMs) for plant origin bulk materials, and to transfer this knowledge to NMIs/DIs with emerging metrology systems. GrainMet intends to build capacity, infrastructure and engage with stakeholders in a coordinated fashion to deliver services at local level based on a common knowledge basis. In particular, GrainMet focuses on the development of a method for the water content determination in plant-origin bulk materials, based on volumetric Karl Fisher titration, which has the potential to become a primary method. A CRM for the water content consisting of grain or a derivative thereof, will be developed. Good practice guides, live and e-trainings will be produced and made available for the project stakeholders (e.g. Georgia, Moldova, Ukraine, Austria) to enhance their capabilities and to promote their participation in international trade

Structural, morphological and optical characterization of CdS-doped silica aerogels synthesized through sol-gel method

Aerogels are highly porous materials characterized by ultra-low density. The incorporation of luminescent materials into silica aerogels results in luminescent aerogels, which have potential applications in light-emitting diodes and optoelectronic devices. In this study, the photoluminescence properties of CdS-doped silica aerogels are reported. The CdS-doped silica aerogels exhibited three distinct emission bands in the blue, green, and red regions. The blue emission is attributed to localized trap states on the CdS surface, while the green emission is associated with sulfur and cation vacancies. The red emission is linked to the substitution of sulfur traps by other counter ions. Supercritical drying of the CdS-doped aerogels resulted in the removal of quantum dots, indicating the non-covalent bonding of CdS nanoparticles to the silica matrix. However, a fraction of the quantum dots remained embedded in the aerogel, as evidenced by weak emission bands and the X-ray diffraction patterns of CdS nanocrystals

Numerical analysis of Josephson junction arrays for multi-order quantum voltage steps

The dynamics of overdamped Josephson junctions under varying microwave-driving conditions have been studied through numerical simulations using the resistively-shunted junction model, with a focus on primary voltage metrology applications, where a significantly high number of series-connected junctions and stringent uniformity of their electrical parameters are required. The aim is to determine the optimal junction characteristics and external microwave (rf) parameters that maximize the width of quantum voltage levels (Shapiro steps) from order n = 0 to n > 1. Both the rf and dc power requirements, along with the junction parameter spread and power attenuation, are analyzed as key factors that need to be optimized for improved performance of the quantum device. This work aims to advance the development of next-generation programmable Josephson voltage standards with logic architectures that surpass the conventional binary and ternary codifications used in present quantum voltage arrays, while significantly reducing the overall number of junctions as well as the number of sub-arrays and bias lines. Existing technologies exploiting n = 0 and n=+/- 1 voltage steps are first discussed and analyzed to verify the validity of the simulation model. They are then further investigated to extend their usability with multi-order quantum steps for n up to 3. From the simulation results, it follows that present junction technologies may be employed with no modifications for the simultaneous operation of quantum steps up to n = 2, although optimal power efficiency would require a retrimming of the junction's electrical parameters. On the contrary, extending the highest step order to n = 3 strictly requires the junction's characteristic parameters to be properly adjusted to maintain sustainable power levels as well as acceptable quantum-locking ranges

Figures of merit of passive daytime radiative cooling materials

Passive daytime radiative cooling (PDRC) materials represent an emerging technology that can provide sub-ambient cooling by dissipating heat as radiation through the long-wave infrared transparency window of the atmosphere. As such, they hold promise to alleviate our growing cooling needs and could find application in a broad range of areas. An increasing number of PDRC materials and applications is reported and tested each year. The fast-paced progress in this field also creates higher demand for reliable and universal methods for comparing the performance of novel materials and predicting their cooling abilities in different environments. However, clear figures of merit and standardised testing methods to evaluate real-world cooling performance are still lacking, so that the cooling performances of various novel PDRC materials presented in literature often cannot be compared. In this work, we review and discuss these issues from the specific viewpoint of the European Partnership on Metrology project PaRaMetriC, which aims at developing a metrological framework to classify and compare these materials

Self‐organized Criticality in Neuromorphic Nanowire Networks With Tunable and Local Dynamics

Self-organized criticality (SOC) has attracted large interest as a key property for the optimization of information processing in biological neural systems. Inspired by this synergy, nanoscale self-organizing devices are demonstrated to emulate critical dynamics due to their complex nature, proving to be ideal candidates for the hardware implementation of brain-inspired unconventional computing paradigms. However, controlling the emerging critical dynamics and understanding its relationship with computing capabilities remains a challenge. Here, it is shown that memristive nanowire networks (NWNs) can be programmed in a critical state through appropriate electrical stimulation. Furthermore, multiterminal electrical characterization reveals that network areas can establish spatial interactions endowing local critical dynamics. The impact of such tunable and local dynamics versus the information processing in the network is experimentally analyzed through in materia implementation of nonlinear transformation (NLT) tasks, in the framework of reservoir computing. As for brain where cortical areas are specialized for a certain function, it is demonstrated that the computing performance of nanowire networks rely on the response of reduced subsets of outputs, which may show critical dynamics or not, depending on the specificity of the task. Such brain-like behavior can lead to neuromorphic systems based on self-organizing networks with reduced hardware complexity by exploiting their local and specialized behavior