629 research outputs found

    Radiation and magnetic field effects on new semiconductor power devices for HL-LHC experiments

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    The radiation hardness of commercial Silicon Carbide and Gallium Nitride power MOSFETs is presented in this paper, for Total Ionizing Dose effects and Single Event Effects, under gamma, neutrons, protons and heavy ions. Similar tests are discussed for commercial DC-DC converters, also tested in operation under magnetic field

    A New Smart Grid Hybrid DC–DC Converter with Improved Voltage Gain and Synchronized Multiple Outputs

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    This paper introduces a new hybrid DC-DC converter with enhanced voltage gain and synchronized multiple output capabilities, specifically tailored for smart grid applications. The proposed converter is based on the integration of non-isolated Zeta and Mahafzah converters, comprising a single controlled switch, two diodes, three inductors, and two coupling capacitors. The primary objective of this novel hybrid converter is to improve voltage gain as compared to conventional Zeta and Mahafzah topologies. By achieving higher voltage gain at lower duty cycles, the converter effectively reduces voltage stress on semiconductor switches and output diodes, thereby enhancing overall performance and reliability. A comprehensive examination of the hybrid converter's operating principle is presented, along with detailed calculations of duty cycle and switching losses. The paper also explores the converter's application in smart grids, specifically in the context of renewable energy systems and electric vehicles. Two distinct scenarios are analyzed to evaluate the converter's efficacy. Firstly, the converter is assessed as a DC-DC converter for renewable energy systems, highlighting its relevance in sustainable energy applications. Secondly, the converter is evaluated as an electric vehicle adapter, showcasing its potential in the transportation sector. To validate the converter's performance, extensive simulations are carried out using MATLAB/SIMULINK with parameters set at 25 kW, 200 V, and 130 A. The simulation results demonstrate the converter's ability to efficiently supply multiple loads with opposing energy flows, making it a promising technology for optimized grid management and energy distribution. Moreover, the paper investigates the total harmonic distortion (THD) of the grid current, focusing on its impact in smart grid environments. Notably, the new hybrid converter topology achieves a THD of 21.11% for the grid current, indicating its ability to effectively mitigate harmonics and improve power quality. Overall, this research introduces a cutting-edge hybrid DC-DC converter that enhances voltage gain and synchronizes multiple outputs, specifically catering to the requirements of smart grid applications. The findings underscore the converter's potential to significantly contribute to the advancement of efficient and resilient power conversion technologies for smart grids, enabling seamless integration of renewable energy systems and electric vehicles into the grid

    Accuracy of emergency physicians\u27 self-estimates of CT scan utilization and its potential effect on an audit and feedback intervention: a randomized trial

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    BACKGROUND: Audit and feedback (AandF) has been used as a strategy to modify clinician behavior with moderate success. Although AandF is theorized to work by improving the accuracy of clinicians\u27 estimates of their own behavior, few interventions have included assessment of clinicians\u27 estimates at baseline to examine whether they account for intervention success or failure. We tested an AandF intervention to reduce computed tomography (CT) ordering by emergency physicians, while also examining the physicians\u27 baseline estimates of their own behavior compared to peers. METHODS: Our study was a prospective, multi-site, 20-month, randomized trial to examine the effect of an AandF intervention on CT ordering rates, overall and by test subtype. From the electronic health record, we obtained 12 months of baseline CT ordering per 100 patients treated for every physician from four emergency departments. Those who were randomized to receive AandF were shown a de-identified graph of the group\u27s baseline CT utilization, asked to estimate wherein the distribution of their own CT order practices fell, and then shown their actual performance. All participants also received a brief educational intervention. CT ordering rates were collected for all physicians for 6 months after the intervention. Pre-post ordering rates were compared using independent and repeated measures t tests. RESULTS: Fifty-one of 52 eligible physicians participated. The mean CT ordering rate increased significantly in both experimental conditions after the intervention (intervention pre = 35.7, post = 40.3, t = 4.13, p \u3c 0.001; control pre = 33.9, post = 38.9, t = 3.94, p = 0.001), with no significant between-group difference observed at follow-up (t = 0.43, p = 0.67). Within the intervention group, physicians had poor accuracy in estimating their own ordering behavior at baseline: most overestimated and all guessed that they were in the upper half of the distribution of their peers. CT ordering increased regardless of self-estimate accuracy. CONCLUSIONS: Our AandF intervention failed to reduce physician CT ordering: our feedback to the physicians showed most of them that they had overestimated their CT ordering behavior, and they were therefore unlikely to reduce it as a result. After audit, it may be prudent to assess baseline clinician awareness of behavior before moving toward a feedback intervention

    HBIM MODELLING FOR THE ARCHITECTURAL VALORISATION VIA A MAINTENANCE DIGITAL ECO-SYSTEM

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    The present contribution falls within the framework of the actions envisaged by the "SMART Bethlehem – Sustainable Management And Renewal of Technology in the City of Bethlehem" (2022 – ongoing) research project, scientifically coordinated by the University of Pavia and co-founded by the Italian Agency for Cooperation and Development (AICS). Among the main objectives of the cooperation project is the sustainable urban and territorial development of the Bethlehem area by means of multi-scalar activities, mainly focusing on refurbishment and energy optimisation of a few relevant municipality buildings. A test case implementation of the HBIM methodology was then carried out on the Peace Center, an iconic building facing the "Manger Square" in close proximity to the "Nativity Church", aiming to validate the proposed systematisation of a scan-to-BIM approach focused on the development of an optimised data repository for the planned operation and maintenance activities. An ECO-Systemic workflow is presented, organised in five recursive steps. Starting from a SLAM-TLS integrated digital survey (3DS), the federated sub-models that comprise the overall project are geo-referenced (GEO) within a shared coordinate system (FSC) environment, thereby providing the basis for the subsequent architectural modelling of the built asset (ARC) and the associated enhancement of the level of information (LOI)

    The industrial applicability of PEA space charge measurements, for performance optimization of HVDC power cables

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    Cable manufacturing industries are constantly trying to improve the electrical performance of power cables. During the years, it was found that one of the most relevant degradation factors influencing the cable lifetime is the presence of space charge in the insulation layer. To detect the accumulated charge, the pulsed electro-acoustic (PEA) method is the most used technique. Despite the wide use of the PEA cell, several issues are still present. In particular, the PEA output signal is strongly disturbed by the acoustic waves reflections within the PEA cell. This causes the distortion of the output signal and therefore the misinterpretation of the charge profiles. This, in turn, may result in an incorrect cable characterization from the space charge phenomenon point of view. In 2017, due to the proved degradation effect of the space charge accumulation phenomenon, the IEEE Std 1732 was developed. This standard describes the steps to be followed for the space charge measurement in cables specimens during pre-qualification or type tests. Therefore, cable manufacturing industries started to take a particular interest in these measures. In the light of this, the aim of the present work is to highlight that the enacted standard is not easily applicable since various problems are still present in the PEA method for cables. In particular, in this work, the effect of multiple reflected signals due to the different interfaces involved, but also the effect of the signal attenuation due to cable dielectric thickness, as well as the effect of the PEA cell ground electrode thickness in the output charge profile, are reported. These issues have been demonstrated by means of an experimental test carried out on a full-size cable in the Prysmian Group High Voltage laboratory. To better understand the PEA cell output signal formation, a PEA cell model was developed in a previous work and it has been experimentally validated here. In particular, simulations have been useful to highlight the effect of the reflection phenomena due to the PEA cell ground electrode thickness on the basis of the specimen under test features. Moreover, by analyzing the simulation results, it was possible to separate the main signal from the reflected waves and, in turn, to calculate the suitable ground electrode thickness for the cable specimen under test

    Surface Periodic Poling in Lithium Niobate and Lithium Tantalate

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    Periodic Poling of Lithium Niobate crystals (PPLN) by means of electric field has revealed the best technique for finely tailoring PPLN structures and parameters, which play a central role in many current researches in the field of nonlinear integrated optics. Besides the most studied technique of bulk poling, recently a novel technique where domain inversion occurs just in a surface layer using photoresist or silica masks has been devised and studied. This surface periodic poling (SPP) approach is best suited when light is confined in a thin surface guiding layer or stripe, as in the case of optical waveguide devices. Also, we found that SPP respect to bulk poling offers two orders of magnitude reduction on the scale of periodicity, so that even nanostructures can be obtained provided an high resolution holographic mask writing technique is adopted. We were able to demonstrate 200 nm domain size, and also good compatibility with alpha-phase proton exchange channel waveguide fabrication. Our first experiments on Lithium Tantalate have also shown that the SPP technology appears to be applicable to this crystal (SPPLT), whose properties can allow to overcome limitations such as optical damage or UV absorption still present in PPLN devices. Finally, the issue of SPP compatibility with proton exchange waveguide fabrication will be addresse

    Hierarchical-power-flow-based energy management for alternative/direct current hybrid microgrids

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    Modern microgrids are systems comprising both Alternative Current (AC) and Direct Current (DC) subgrids, integrated with Distributed Generations (DGs), storage systems, and Electric Vehicles (EVs) parking facilities. Achieving stable and reliable load flow control amidst varying load, generation, and charging/discharging strategies requires a hierarchical control scheme. This paper proposes an hourly power flow (PF) analysis within an Energy Management System (EMS) for AC/DC Hybrid Microgrids interconnected via an Interlinking Converter (IC) in both grid-connected and islanded modes. The framework operates within a two-level hierarchically controlled platform. Tertiary control at the top level optimizes DGs' reference power for generation and consumption, minimizing power purchase costs and load shedding in grid-connected and islanded modes, respectively. DG converters employ current control mode to share their power references as the primary controller. While no secondary controller is adopted in this scheme, the Battery Energy Storage System (BESS) in islanded mode utilizes P/Q droop control to maintain voltage and frequency in the AC subsystem. Power sharing between AC and DC subgrids through IC is determined by the difference between AC grid frequency and DC link voltage. Integration of controlled converters’ buses into PF equations enables solving the unified system using the traditional Newton-Raphson (NR) method. A segment of a real distribution grid planned for installation in Italy under the HYPERRIDE project serves as a case study. Comparison with MATLAB/Simulink results confirms the effectiveness, precision, and convergence speed of the proposed model and control schemes, demonstrating efficient load distribution and voltage/frequency restoration in islanded mode

    Relation between flood pulse and functional composition of the macroinvertebrate benthic fauna in the lower Rio Negro, Amazonas, Brazil

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    In a twelve-month study carried out at the archipelago of Anavilhanas, lower Rio Negro, State of Amazonas, Brazil, the macroinvertebrate fauna was sampled from the margins of a lake (Redondo lake) permanently connected to the river. The total biomass of the macroinvertebrates sampled during this period was 9,985.5 mg (dry weight) and 19,314 specimens were collected. Decapods (52.9 %) were the most important group regarding biomass while dipterans (21.1 %), ostracods (20.0%), cladocerans (14.0 %), and oligochaetes (13.4%) were the most abundant macroinvertebrates. All taxa showed frequency variations related to the high-low water cycle of Rio Negro and the substrate at the lake margins varied in quantity as well as in composition and structure. The greatest amounts of litter occurred in the flood period, with a higher proportion of new and whole leaves. The degree of litter fragmentation increased towards the low water period. The functional structure of the macroinvertebrate community showed adaptation to the available substrate in each season. A gradient of dominance between the functional categories, related to the distance from the central area of the water body, was observed. Shredders were sampled mainly inside the "igapó" (high water period), in a similar proportion to collectors. On the other hand, collectors were clearly predominant in the dry period. Scrapers were limited to the rising and falling water periods. The same trend is probably found in all the corresponding sections of the Rio Negro
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