No abstract

Owing to the presence of joint resistance and flux creep, high-temperature superconducting (HTS) coils without a power supply inevitably suffer from current decay. A flux pump is a voltage supply that requires connections with smaller footprints and a lower heat load than traditional current leads. In this study, we explain the principle of the upper limit for the output current of the traveling wave flux pumps. Based on this principle, a miniaturized linear flux pump device was developed. With narrow and misaligned iron teeth, elaborate 3D geometry of the iron pieces, and optimized driving current waveform, the miniaturized flux pump can support more than 120 A output current with only a 10 mm wide HTS tape and a compact size of 4.6 × 4.6 × 3.4 cm. Our experimental results show that the critical current of the HTS tape has a significant effect on the flux pump output. An HTS tape with a larger critical current supports a higher maximum transport current, whereas an HTS tape with a smaller critical current requires less applied current for positive output. Finally, excitation tests on HTS coils were performed. Charge/active discharge and field supplement experiments were done on a maglev HTS racetrack coil of 0.4 H, where charging/field supplement capbility of the miniaturized flux pump were demonstrated up to 46.8 A (close to the critical current of the coil). It has also been proved that the flux pump can work together with an external power supply with persistent current switch. The miniaturized flux pump can also independently charge an HTS coil of 60 μH to 91.6 A, which is the critical current of the coil at a low voltage criterion.

Abstract-Frequency-domain anti-jamming (FDAJ) algorithms achieve prominent performance on interference suppression with simple calculations; and hence they are widely used in many applications. The interference suppression threshold plays a key role in the algorithm and affects system performance greatly. In this paper, the initial interference threshold is derived theoretically and then a novel FDAJ algorithm is proposed based on the iterative calculation of the threshold. With the iterative process, the optimal threshold for the interference suppression can be approached with little loss of valid signals; and the antijamming performance can be further improved. The simulation results validate well that our proposed iterative algorithm has superior performance for interference suppression. Finally, two FPGA-based implementations are presented: pipeline scheme and iterative scheme. After analysing the different characteristics of each implementation, we discuss the suitable applications for these schemes.

In this paper we consider the problem of estimating lower and upper bounds for approximate cycle matching in homogeneous symmetric publish/subscribe system. The approximate cycle matching aims to find cycle matchings as many as possible with limited space, where a probability threshold is used to prune the space used to store the intermediate results of the approximate cycle matching. It is necessary to estimate the lower and upper bounds of the space to be saved according to the probability threshold.The existing method partitions a 2d space of possible subscriptions into rectangle zones by the probability threshold. The possible subscriptions in different zones are counted to estimate the lower and upper bounds. In order to get tighter bounds, we propose an estimation method based on the space partition with curves and prove that there exist such kind of curves, and then propose an estimation method based on dimension reduction in the case that the data distribution is previously known.The proposed methods are evaluated in a simulated environment.The results show that the proposed methods estimate the bounds tighter than the existing method, and the estimation is improved by nearly 20% in the best case.Keywords-publish/subscribe; approximate cycle matching; estimation of lower and upper bounds

No abstract