Rejection of randomly coinciding events in ZnMoO4_4 scintillating bolometers

Random coincidence of events (particularly from two neutrino double beta decay) could be one of the main sources of background in the search for neutrinoless double beta decay with cryogenic bolometers due to their poor time resolution. Pulse-shape discrimination by using front edge analysis, mean-time and $\chi^2$ methods was applied to discriminate randomly coinciding events in ZnMoO$_4$ cryogenic scintillating bolometers. These events can be effectively rejected at the level of 99% by the analysis of the heat signals with rise-time of about 14 ms and signal-to-noise ratio of 900, and at the level of 92% by the analysis of the light signals with rise-time of about 3 ms and signal-to-noise ratio of 30, under the requirement to detect 95% of single events. These rejection efficiencies are compatible with extremely low background levels in the region of interest of neutrinoless double beta decay of $^{100}$Mo for enriched ZnMoO$_4$ detectors, of the order of $10^{-4}$ counts/(y keV kg). Pulse-shape parameters have been chosen on the basis of the performance of a real massive ZnMoO$_4$ scintillating bolometer. Importance of the signal-to-noise ratio, correct finding of the signal start and choice of an appropriate sampling frequency are discussed

H-Bridge Converter as Basic Switching Topology Workbench in Power Electronics Teaching

This article deals with an effective power electronics learning setup based on a Full-Bridge converter used to teach electrical energy conversion experimentally. In the proposed learning by doing methodology, the hardware and the software are properly mixed in order to obtain an easy-to-use experimental learning environment. In this paper, the H-Bridge is the fundamental brick to build students’ knowledge on the main topics of power electronics converter circuit in different operative conditions. This H-Bridge comes with a reconfigurable output LCL to achieve several basic DC-DC powerconverters topologies. Converter current and voltage switching behavior can be investigated using the proposed setup. Furthermore, the friendly hardware and software set-up allows studying the converter modulation and control techniques of the different power electronics circuits

Superconductivity and its Application in the Field of Electrical Machines

This paper provides a review on the most recent applications of superconductors in rotating electrical machines. The main types of superconductors for the present-day electrical applications are shown to highlight their main features. The main characteristics of superconducting synchronous machines, DC machines and induction machines for marine and vehicle propulsion, future electric aircraft, wind energy and industrial applications are discussed by presenting data of prototypes and demonstrators. The paper aims to raise awareness among researchers and engineers on the importance of superconductivity to enhance the performance of conventional electrical machines

Approaches for Improving Lumped Parameter Thermal Networks for Outer Rotor SPM Machines

This work is about the transient modeling of the thermal characteristics of outer rotor SPM machines by considering a lumped parameter thermal network based approach. The machine considered here poses particular challenges for the modeling, e.g., due to the semi-closed stator surrounded by a rotor bell that provides a speed-dependent cooling of the stator coils. Starting from a simpler basic network configuration, model extensions and refinements are presented and discussed. The subsequent parameter identification is done by means of an initial design of experiments based sampling, and a subsequent single-objective and also a multi-objective optimization of error functions for the components' temperatures. Analyzing the therefrom derived Pareto fronts and the consequent tradeoff regarding achievable minimum modeling errors for different system's components gives insights into where and how the modeling can be further improved. All the investigations are based on experimental results obtained through operating a particularly developed test setup

A test-rig to evaluate a dual-3-phase induction motor drive

The potential advantages of multi-phase solutions over the conventional 3-phase ones have been widely described in the literature. However, their feasibilities and performances have been poorly described and proven. The main goal of this paper is the design and implementation of a test rig to evaluate some control policies for a double-3-phase induction motor drive, a multiphase drive with interest in Electric Vehicle (EV) applications

Measurement-Based Identification of Lumped Parameter Thermal Networks for sub-Kw Outer Rotor PM Machines

This work is on deriving precise lumped parameter thermal networks for modeling the transient thermal characteristics of electric machines under variable load conditions. The goal is to facilitate an accurate estimation of the temperatures of critical machines' components and to allow for running the derived model in real time to adapt the motor control based on the load history and maximum permissible temperatures. Consequently, the machine's capabilities can be exhausted at best considering a highly-utilized drive. The model shall be as simple as possible without sacrificing the exactness of the predicted temperatures. Accordingly, a specific lumped parameter thermal network topology was selected and its characteristics are explained in detail. The measurement data based optimization of its critical parameters through an evolutionary optimization strategy, and the therefore utilized experimental setup will be described in detail here. Measurement cycles were recorded for modeling and verification purposes including both static and dynamic test cycles with changing load torque and speed requirements. Applying the proposed hybrid approach for determining the model's parameters through involving physics-based equations as well as numerical optimization followed a significant improvement of the preciseness of the predicted motor temperatures compared to solely determining the networks's coefficients based on expert knowledge. Thereby, the validation included both the original measurement data as well as extra measurement runs. The proposed and applied strategy provides an excellent basis for future thermal modeling of electric machines

A Comparison of Cryogenic-Cooled and Superconducting Electrical Machines

This paper compares the steady-state operation of air-cooled, cryogenic-cooled and superconducting induction machines. The aim is to investigate the impact of a very low temperature and the influence of a superconducting rotor cage on the performances of standard designed, air-cooled machines. The research work includes a review of the state of the art of cryogenic-cooled and superconducting induction machines for various applications. The performances of the machines are assessed analytically by solving the single-phase equivalent circuit and considering the influence of the temperature, the skin-effect and the nonlinear behavior of superconductors. The analytical results are validated by experiments on a fractional kilowatt induction motor. The experimental activities include the characterization of the core losses at cryogenic temperature

Modeling Approach for Superconducting AC Windings: Case Study on Axial Flux PM Machines

This paper aims to analyze the modeling of superconducting tapes when used for the realization of AC windings in rotating electrical machines. The model is based on literature formulations that describe the non-linear resistivity of superconducting materials, including the effects of external AC magnetic fields. An axial flux permanent magnet machine is considered as case study for applying the provided formulations. The 3D FEM machine model is solved considering both a conventional copper stator winding and superconducting counterpart, with the aim to verify the equivalence of these two winding solutions. Then, a 2D modeling approach of a single-slot is proposed for time-efficient investigations of the superconductor’s behavior in the presence of the slot leakage flux

Direct flux and current vector control for induction motor drives using model predictive control theory

The study presents the direct flux and current vector control of an induction motor (IM) drive, which is a relatively newer and promising control strategy, through the use of model predictive control (MPC) techniques. The results highlight that the fast flux control nature of direct flux control strategy is further enhanced by MPC. Predictive control is applied in two of its variants, namely the finite control set and modulated MPC, and the advantages and limitations of the two are underlined. This work also highlights, through experimental results, the importance of prioritising the flux part of the cost function which is particularly significant in the case of an IM drive. The performance of the MPC-based approach is compared with the proportional-integral controller, which also prioritises the flux control loop, under various operating regions of the drive such as in the flux-weakening regime. Simulations show the performance expected with different control strategies which is then verified through experiments

Molecular and Functional Characterization of Three Different Postzygotic Mutations in PIK3CA-Related Overgrowth Spectrum (PROS) Patients: Effects on PI3K/AKT/mTOR Signaling and Sensitivity to PIK3 Inhibitors

BACKGROUND PIK3CA-related overgrowth spectrum (PROS) include a group of disorders that affect only the terminal portion of a limb, such as type I macrodactyly, and conditions like fibroadipose overgrowth (FAO), megalencephaly-capillary malformation (MCAP) syndrome, congenital lipomatous asymmetric overgrowth of the trunk, lymphatic, capillary, venous, and combined-type vascular malformations, epidermal nevi, skeletal and spinal anomalies (CLOVES) syndrome and Hemihyperplasia Multiple Lipomatosis (HHML). Heterozygous postzygotic PIK3CA mutations are frequently identified in these syndromes, while timing and tissue specificity of the mutational event are likely responsible for the extreme phenotypic variability observed. METHODS: We carried out a combination of Sanger sequencing and targeted deep sequencing of genes involved in the PI3K/AKT/mTOR pathway in three patients (1 MCAP and 2 FAO) to identify causative mutations, and performed immunoblot analyses to assay the phosphorylation status of AKT and P70S6K in affected dermal fibroblasts. In addition, we evaluated their ability to grow in the absence of serum and their response to the PI3K inhibitors wortmannin and LY294002 in vitro. RESULTS AND CONCLUSION: Our data indicate that patients' cells showed constitutive activation of the PI3K/Akt pathway. Of note, PI3K pharmacological blockade resulted in a significant reduction of the proliferation rate in culture, suggesting that inhibition of PI3K might prove beneficial in future therapies for PROS patients