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This paper presents the design, manufacturing and test results of HTS coils for single-phase resistive current limiters using two different Bi-2223/Ag tapes. Two coils were separately wound on cylindrical G-10 tubes with helical path. One of the coil was wound in a bifilar conductor arrangement aiming at reducing the self-inductance. The maximum flux density is 40 mT on the HTS tape for both coils and the calculated inductance is 5.76 μH for the noninductively wound coil and 28.3 μH for the conventional one. The two coils were individually tested under DC and AC currents. The DC power loss was calculated from the measured voltage-current values product and the AC power loss was determined by the liquid nitrogen mass boil-off measurement. The acquired voltage AC waveforms were analyzed through the separation of distinct contributions due to magnetic flux and to a resistive component in-phase with the current. It was observed an inflection point common to the DC and AC power losses curves close to Ic attributed to the AC transition current. [ABSTRACT FROM AUTHOR]

A very accurate mathematical method, named Helicoidal Method, to calculate the flux density vector B produced by the current circulating in the resistive single-phase superconductor electrical current limiter (RSCL) coils, at any point of the its whole space, using the Biot-Savart's Law is presented in this paper. It is very important to remember that these coils are single layer concentric cylindrical coils with voids (free space) between its neighbor turns which turns present helicoidal form. The calculation of the vector B, at any point of the space of the coils, is used in the dynamic simulation of the RSCL for design and operation purposes, but it is also used to calculate the self-inductance of each electrical current limiter coil and the mutual inductance between each pair of coils, which are necessary to determine the equivalent impedance of the RSCL. To verify the proposed method accuracy the self-inductance of three different coils, made with copper wire, are calculated, measured and the results are compared. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical method to quickly calculate the flux density vector B produced by the current circulating in a resistive single-phase superconducting electrical current limiter (RSCL), at any point of its whole space, using the Biot-Savart's Law. As the calculation using the exact form of the turns of each coil (single layer cylindrical coil with helicoidal form presenting voids (free space) between neighbor turns) is computationally very cumbersome to be used in a RSCL dynamic simulator, it is proposed in this paper to substitute the real coil, only for the subject of the calculation, by an imaginary coil formed by plane closed circular turns with the same number of turns, the same height and radius as the real coil. Each turn of the imaginary coil is placed exactly in the medium position between successive turns of the actual coil and will carry the same current. The coil self-inductance is also calculated to verify the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

The present work investigates the impact on financial intermediation of distributed ledger technology (DLT), which is usually associated with the blockchain technology and is at the base of the cryptocurrencies' development. "Bitcoin" is the expression of its main application since it was the first new currency that gained popularity some years after its release date and it is still the major cryptocurrency in the market. For this reason, the present analysis is focused on studying its price determination, which seems to be still almost unpredictable. We carry out an empirical analysis based on a cost of production model, trying to detect whether the Bitcoin price could be justified by and connected to the profits and costs associated with the mining effort. We construct a sample model, composed of the hardware devices employed in the mining process. After collecting the technical information required and computing a cost and a profit function for each period, an implied price for the Bitcoin value is derived. The interconnection between this price and the historical one is analyzed, adopting a Vector Autoregression (VAR) model. Our main results put on evidence that there aren't ultimate drivers for Bitcoin price; probably many factors should be expressed and studied at the same time, taking into account their variability and different relevance over time. It seems that the historical price fluctuated around the model (or implied) price until 2017, when the Bitcoin price significantly increased. During the last months of 2018, the prices seem to converge again, following a common path. In detail, we focus on the time window in which Bitcoin experienced its higher price volatility; the results suggest that it is disconnected from the one predicted by the model. These findings may depend on the particular features of the new cryptocurrencies, which have not been completely understood yet. In our opinion, there is not enough knowledge on cryptocurrencies to assert that Bitcoin price is (or is not) based on the profit and cost derived by the mining process, but these intrinsic characteristics must be considered, including other possible Bitcoin price drivers., (Copyright © 2020 Baldan and Zen.)

A morphological study of the budgerigar vas deferens was conducted to demonstrate the electron-microscopic features of its epithelial lining. The analysis showed that the vas deferens of the budgerigar was found to be of a tubular and serpentine structure, continuous with the epididymal region and lined with stereo ciliated pseudostratified epithelium, which contained folds projecting into the tubular lumen and a characteristic brush border. The epithelium consists of ciliated and non-ciliated cells with different electron densities. Ciliated cells were characterized by two morphologically distinct configurations: some cells were columnar and other ciliated cells were longer, thinner and dark. Non-ciliated cells showed apical cytoplasmic expansions, which projected into the tubular lumen as protrusions.