122,066 research outputs found
Design of Integrated Micro-Fluxgate Magnetic Sensors: Advantages and Challenges of Numerical Analyses
No full textMiniaturization and on-chip integration are major lines of research in many branches of science and technology developments, undoubtedly in sensor technology. Fluxgate magnetometers are very sensitive, and accurate magnetic sensors able to detect weak fields both AC and DC, which in recent years saw a great effort in minimizing their dimensions, weight, and power consumption. The physics behind the fluxgate principle is rather complex and makes simulations difficult and only partially used in the literature. The limited physical access to micro sensors for measurements and the need to optimize the entire integrated system, including the sensor geometry and the excitation and readout circuits, make numerical analyses particularly useful in the design of miniaturized sensors. After a thorough review of the miniaturized solutions proposed so far, the present paper examines in detail the possibility of adopting a model based approach for designing miniaturized fluxgate sensors. The model of the fluxgate effect of two different technologies proposed in the literature has been implemented to benchmark simulation results with real data. In addition to the advantages for an optimized design, the implementation and computational challenges of the numerical analyses are precisely outlined
Accelerating the charge inversion algorithm with hierarchical matrices for gas insulated systems
No full textSurface charges accumulating on dielectrics during long-time operation of Gas Insulated High Voltage Direct Current (HVDC-GIS) equipments may affect the stable operation and could possibly trigger surface flashovers. In industrial applications, to quantify and identify the location of the surface charge accumulation from experimental measurements, the surface potential distribution is evaluated using, e.g., electrostatic probes, then the charge density is determined by solving an electrostatic problem based on an inversion procedure known as Charge Inversion Algorithm. The major practical limitation of such procedure is the inversion and the storage of the fully dense matrix arising from the representation via Integral Equations of the electrostatic phenomenon, resulting in O(N3) computational complexity and O(N2) memory requirement. In this paper it is shown how hierarchical matrices can be efficiently used to accelerate the charge inversion algorithm and, more importantly, reduce the..
A comparison between current-based integral equations approaches for eddy current problems
No full textIn this paper, a comparison between two current-based Integral Equations approaches for eddy current problems is presented. In particular, the very well-known and widely adopted loop-current formulation (or electric vector potential formulation) is compared to the less common J–φ formulation. Pros and cons of the two formulations with respect to the problem size are discussed, as well as the adoption of low-rank approximation techniques. Although rarely considered in the literature, it is shown that the J–φ formulation may offer some useful advantages when large problems are considered. Indeed, for large–scale problems, while the computational efforts required by the two formulations are comparable, the J–φ formulation does not require any particular attention when non-simply connected domains are considered
Application of FFT-PEEC method for nonlinear inductance extraction
No full textThis paper shows how the recently proposed Partial Element Equivalent Circuit (PEEC) method accelerated by the Fast Fourier Transform (FFT) (i.e., the FFT-PEEC method) can be efficiently adopted for the extraction of inductances when nonlinear ferromagnetic materials are involved. An efficient and simplified strategy for the inductance extraction by means of FFT-PEEC is proposed in order to speed-up the parameter extraction for many coil-current values. Such tool finds practical applications in the modelling of electromagnetic devices where the magnetic saturation of ferromagnetic media may be an undesirable phenomenon which, however, cannot be neglected, e.g., in power electronics or integrated inductors. Moreover, such tool can be particularly useful during the design of electronic devices which exploit saturation effects, such as voltage regulators, tunable core inductors, magnetic amplifiers, and fluxgate magnetometers
Mechanism of action of an autovaccine against cancer cells associating autologous tumor proteins to hydroxylapatite micro/nanoparticles.
No full textToxicity and outcome in cats with oral squamous cell carcinoma after accelerated hypofractionated radiotherapy and concurrent systemic treatment
No full textRecently, a multimodal approach to oral squamous cell carcinoma (SCC) in cats, combining medical treatment and accelerated radiation therapy, showed a substantial outcome improvement in a small pilot study. Herein we retrospectively review 51 cats with unresectable, histologically confirmed oral SCC and a complete initial staging work-up: cats in group A (n = 24) received medical anti-angiogenic treatment consisting of bleomycin, piroxicam and thalidomide, cats in group B (n = 27) received the anti-angiogenic treatment and concurrent accelerated hypofractionated radiation therapy with 48Gy delivered in 10 fractions. Overall median progression-free interval (PFI) was poor with 70 days (95% CI: 48;93). In the irradiated cats (group B), however, PFI was significantly longer with 179 days (95% CI: 58;301) days, vs 30 days (95% CI: 23;38) in medically only treated cats (P <.001). Overall median overall survival (OS) was 89 days (95% CI: 55;124), again significantly longer in the irradiated cats (group B) with 136 (95% CI: 40;233) vs 38 days (95% CI: 23;54) (P <.001). In 8 of the 27 (29.6%) cats in group B, however, severe toxicity (grade 3) occurred. Neither onset nor severity of toxicity could be associated with any of the tested variables, including anatomic site, tumour size, clinical stage and duration of neoadjuvant medical treatment. Given the potential severe acute effects and the impact on quality of life after chemo-radiotherapy, owners must be clearly informed about the risks of treatment. With the overall poor outcome and high occurrence of acute toxicity, we cannot recommend the use of this accelerated radiation protocol combined with anti-angiogenic therapy for oral SCC in cats
Simulation, Code Benchmarking and Optimization of the Magnetic Field Configuration in a Negative Ion Accelerator
No full textSPIDER is a full-size Negative Ion Source and a multi-beamlet 100 kV accelerator, presently under con-
struction in Padova and is part of PRIMA, the test bed for the full development of the Heating Neutral
Beam system for ITER. During the final design, the SPIDER extractor and accelerator system has been
improved with respect to the original configuration. In particular, the magnetic configuration has been
optimized in order to improve the performances in terms of ion beam optics and aiming, and to obtain
an efficient filter for the extracted electrons
Accurate magnetic sensor system integrated design
No full textInductive measurement of magnetic fields is a diagnostic technique widely used in several scientific fields, such as magnetically confined fusion, plasma thrusters and particle accelerators, where real time control and detailed characterization of physics phenomena are required. The accuracy of the measured data strongly influences the machine controllability and the scientific results. In the framework of the assembly modifications of the RFX-mod experiment, a complete renew and improvement of the magnetic diagnostic system, from the probes moved inside the vacuum vessel to the integrator modules, has been carried out. In this paper, the whole system making up the magnetic diagnostics is described, following the acquisition chain from the probe to the streamed data and illustrating the requirements and conflicting limitations which affect the different components, in order to provide a comprehensive overview useful for an integrated design of any new systems. The characterization of a prototypical implementation of the whole acquisition chain is presented, focusing on the flexible ADC architecture adopted for providing a purely numerical signal integration, highlighting the advantages that this technology offers in terms of flexibility, compactness and cost effectiveness, along with the limitations found in existing implementation in terms of ADC noise characteristics and their possible solutions
Sperimentazione di un sistema per la compensazione del campo magnetico con trasmissione wireless
No full textPrediction of lightning impulse voltage induced breakdown in vacuum interrupters
No full textA concept to predict the Lightning Impulse Voltage (LIV) breakdown probability of medium voltage Vacuum Interrupter (VI) tubes has been developed and tested for the first time employing the Voltage Holding Prediction Model (VHPM) originally formulated at Consorzio RFX. The VHPM is capable to calculate the Weibull breakdown probability curve of any multi-electrode multi-voltage system insulated in vacuum under dc voltage. Even though the possibility to employ the VHPM in the prediction of voltage breakdown under LIV conditions is not straightforward, the potential benefits of the VHPM usage in VI tube technology with regard to development, design and testing at medium and high voltage levels, strongly recommend the assessment of VHPM under LIV conditions. The paper aims to describe the methodology adopted to identify experimentally the VHPM parameters to be employed in such a novel application to assess its prediction capability. The measurements have been done in the Siemens Berlin VI tube factory test stand for LIV, compliant with the IEC standard. Different vacuum tube types manufactured by Siemens were investigated. The main difficulty was to obtain, with such a test bed, voltage breakdown distributions well fitted by a Weibull Distribution - upon which the VHPM is based - primarily due to the difficulty to reach a well-defined end of the conditioning test sequence preceding the relevant voltage breakdown test sequence suitable to be analyzed by the VHPM. Nevertheless, the VHPM prediction resulted in reasonable agreement with the measured probability curves. Finally, investigating VI tubes with spiral-type Radial Magnetic Field (RMF) contacts, characterized by a geometry strongly deviating from axial 2-D symmetry, the first implementation of a full 3-D version of the VHPM has been tested. © 1994-2012 IEEE
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