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Mutual Inductance Measurement in Wireless Power Transfer Systems Operating in the MHz Range
No full textThis tutorial focuses on the problem of the experimental measurement of the mutual inductance (or, equivalently, of the coupling factor) of two coupled coils designed for a Wireless Power Transfer (WPT) system. Although many instruments and techniques are available for this purpose, in the literature, no clear guidelines defining the most reliable technique exist, and the vast majority of papers propose ad-hoc measurement approaches without clearly explaining pros and cons of each specific choice. The contribution of this brief is to fill this gap by ) reviewing the available methodologies that can be used to measure the mutual inductance, ) highlighting the issues that may arise, and ) identifying the most suitable technique for a particular use case. More specifically, to increase the impact of our analysis, we focus on the case of a couple of WPT coils for biomedical applications designed to work at 6.78 MHz, which is a setting both very common and quite tricky for the direct measurement
Power Grids and Instrument Transformers up to 150 kHz: A Review of Literature and Standards
No full textThe phenomenon of high-frequency distortion (HFD) in the electric grids, at both low-voltage (LV) and medium-voltage (MV) levels, is gaining increasing interest within the scientific and technical community due to its growing occurrence and the associated impact. These disturbances are mainly injected into the grid by new installed devices, essential for achieving decentralized generation based on renewable sources. In fact, these generation systems are connected to the grid through power converters, whose switching frequencies are significantly increasing, leading to a corresponding rise in the frequency of the injected disturbances. HFD represents a quite recent issue, but numerous scientific papers have been published in recent years on this topic. Furthermore, various international standards have also covered it, to provide guidance on instrumentation and related algorithms and indices for the measurement of these phenomena. When measuring HFD in MV grids, it is necessary to use instrument transformers (ITs) to scale voltages and currents to levels fitting with the input stages of power quality (PQ) instruments. In this respect, the recently released Edition 2 of the IEC 61869-1 standard extends the concept of the IT accuracy class up to 500 kHz; however, the IEC 61869 standard family provides guidelines on how to test ITs only at power frequency. This paper provides an extensive review of literature, standards, and the main outputs of European research projects focusing on HFD and ITs. This preliminary study of the state-of-the-art represents an essential starting point for defining significant waveforms to test ITs and, more generally, to achieve a comprehensive understanding of HFD. In this framework, this paper provides a summary of the most common ranges of amplitude and frequency variations of actual HFD found in real grids, the currently adopted measurement methods, and the normative open challenges to be addressed
Adaptive Scalpel Scanning Probe Microscopy for Enhanced Volumetric Sensing in Tomographic Analysis
No full textControlling nanoscale tip-induced material removal is crucial for achieving atomic-level precision in tomographic sensing with atomic force microscopy (AFM). While advances have enabled volumetric probing of conductive features with nanometer accuracy in solid-state devices, materials, and photovoltaics, limitations in spatial resolution and volumetric sensitivity persist. This work identifies and addresses in-plane and vertical tip-sample junction leakage as sources of parasitic contrast in tomographic AFM, hindering real-space 3D reconstructions. Novel strategies are proposed to overcome these limitations. First, the contrast mechanisms analyzing nanosized conductive features are explored when confining current collection purely to in-plane transport, thus allowing reconstruction with a reduction in the overestimation of the lateral dimensions. Furthermore, an adaptive tip-sample biasing scheme is demonstrated for the mitigation of a class of artefacts induced by the high electric field inside the thin oxide when volumetrically reduced. This significantly enhances vertical sensitivity by approaching the intrinsic limits set by quantum tunneling processes, allowing detailed depth analysis in thin dielectrics. The effectiveness of these methods is showcased in tomographic reconstructions of conductive filaments in valence change memory, highlighting the potential for application in nanoelectronics devices and bulk materials and unlocking new limits for tomographic AFM
Experimental determination of molar polarizability of nitrogen by a multi-reflection inteferometric technique
Get PDFA novel optical pressure standard, based on a multi-reflection interferometric technique, has been recently developed. It is based on the measurement of the refractive index of a gas through an unbalanced homodyne interferometer (UINT) and is able to measure pressure with a relative standard uncertainty of 10 ppm at 100 kPa [1]. In this work, the interferometer was used to measure the molar polarizability of nitrogen, which resulted in agreement with recent previous determinations, paving the way for using photonic pressure standards as accurate and fast transfer standards of the pascal
Standard Operating Procedure to Optimize Resazurin-Based Viability Assays
Get PDFThe resazurin assay, also known as the Alamar Blue assay, stands as a cornerstone technique in cell biology, microbiology, and drug development. It assesses the viability of cells through the conversion of resazurin into highly fluorescent resorufin. The resulting fluorescence intensity provides a reliable estimate of viable cell numbers. Cytotoxicity assays, such as the resazurin-based method, play a crucial role in the screening of potential drug candidates and in the assessment of pharmaceutical and chemical toxicity. In recent years, inconsistencies have arisen in pharmacogenomic studies, often due to poorly optimized laboratory protocols. These inconsistencies hinder progress in understanding how substances affect cell health, leading to unreliable findings. Thus, the need for standardized and rigorously optimized protocols is evident to ensure consistent and accurate results in cytotoxicity studies. This manuscript describes a standardized procedure for optimizing resazurin-based viability assays to improve the reliability of cytotoxicity data. This optimization approach focuses on critical experimental parameters and data quality, aiming to achieve a level of measurement imprecision of less than 20%. In conclusion, to address the critical issues of reproducibility and reliability, protocol standardization, such as the one described in this manuscript, can greatly enhance the credibility of cytotoxicity studies, ultimately advancing drug safety assessments
Quantum sampling AC standard for electrical power metrology based on programmable Josephson junction series array
Get PDFInsights on the firing temperature of ancient ceramic coffins through a multi-analytical approach: The case of the Sada Nishizuka Kofun, Japan
No full textInvestigating the heating temperatures of ancient ceramic artifacts can offer information about their production technology and enrich our knowledge about the fire control skills in ancient times. We present here the results of a multi-analytical approach, including magnetic, X-Ray Powder Diffraction (XRPD) and thermoluminescence (TL) analyses, applied on the investigation of the equivalent firing temperature of the ceramic coffin (No 2) found in the well-known Sada Nishizuka Kofun, Japan. Monitoring of the magnetic properties of the studied fragments versus laboratory heating showed clear magnetic enhancement at relatively low temperatures around 350-500 degrees C. The magnetic results were compared with independent data obtained from XRPD and TL analyses. The XRPD patterns showed the presence of quartz, plagioclases and clay minerals such as muscovite and smectite, which indicate firing temperatures lower than 850-950 degrees C. The presence of kaolinite in almost all the studied samples lower the estimate temperature below 550 degrees C. Such data were further confirmed by the TL analysis which suggest firing temperature lower than 525 degrees C. The results obtained indicate that the coffin was most probably produced in an open or covered kiln, following the Japanese Haji-type traditional production, reaching maximum firing temperature lower than 550 degrees C. This study offers the first archaeometric experimental data to better understand the production strategy of ceramic coffins during the Kofun period in Japan and highlights the potential of non-conventional archaeometric analyses, such as magnetic and thermoluminescence investigations, to obtain information on firing procedures for ancient ceramic artifacts. (c) 2023 Consiglio Nazionale delle Ricerche (CNR). Published by Elsevier Masson SAS. All rights reserved
