995 resultados para Viseu - PA
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A medical cyclotron accelerating H- ions to 18 MeV is in operation at the Bern University Hospital (Inselspital). It is the commercial IBA 18/18 cyclotron equipped with a specifically conceived 6 m long external beam line ending in a separate bunker. This feature is unique for a hospital-based facility and makes it possible to conduct routine radioisotope production for PET diagnostics in parallel with multidisciplinary research activities, among which are novel particle detectors, radiation biophysics, radioprotection, radiochemistry and radiopharmacy developments. Several of these activities, such as radiobiology experiments for example, require low current beams down to the pA range, while medical cyclotrons are designed for high current operation above 10 μA. In this paper, we present the first results on the low current performance of a PET medical cyclotron obtained by ion source, radio-frequency and main coil tuning. With this method, stable beam currents down to (1.5+/- 0.5 ) pA were obtained and measured with a high-sensitivity Faraday cup located at the end of the beam transport line.
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In this paper, filter design methodology and application of GaN HEMTs for high efficiency Envelope Amplifier in RF transmitters are proposed. The main objectives of the filter design are generation of the envelope reference with the minimum possible distortion and high efficiency of the amplifier obtained by the optimum trade-off between conduction and switching losses. This optimum point was determined using power losses model for synchronous buck with sinusoidal output voltage and experimental results showed good correspondence with the model and verified the proposed methodology. On the other hand, comparing to Si MOSFETs, GaN HEMTs can provide higher efficiency of the envelope amplifier, due to superior conductivity and switching characteristics. Experimental results verified benefits of GaN devices comparing to the appliance of Si switching devices with very good Figure Of Merit, for this particular application
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Early propagation effect (EPE) is a critical problem in conventional dual-rail logic implementations against Side Channel Attacks (SCAs). Among previous EPE-resistant architectures, PA-DPL logic offers EPE-free capability at relatively low cost. However, its separate dual core structure is a weakness when facing concentrated EM attacks where a tiny EM probe can be precisely positioned closer to one of the two cores. In this paper, we present an PA-DPL dual-core interleaved structure to strengthen resistance against sophisticated EM attacks on Xilinx FPGA implementations. The main merit of the proposed structure is that every two routing in each signal pair are kept identical even the dual cores are interleaved together. By minimizing the distance between the complementary routings and instances of both cores, even the concentrated EM measurement cannot easily distinguish the minor EM field unbalance. In PA- DPL, EPE is avoided by compressing the evaluation phase to a small portion of the clock period, therefore, the speed is inevitably limited. Regarding this, we made an improvement to extend the duty cycle of evaluation phase to more than 40 percent, yielding a larger maximum working frequency. The detailed design flow is also presented. We validate the security improvement against EM attack by implementing a simplified AES co-processor in Virtex-5 FPGA.
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
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Recurso electrónico. Valencia: BVNP, 2014
