Search results for "Energy engineering"
showing 10 items of 1099 documents
Geometric quantum computation with Josephson qubits
2001
The quest for large scale integrability and flexibility has stimulated an increasing interest in designing quantum computing devices. A proposal based on small-capacitance Josephson junctions in the charge regime in which quantum gates are implemented by means of adiabatic geometric phases was discussed. The proposed works, are in the charge regime where the qubit is realized by two nearly degenerate charge states of a single electron box.
Status of delayed-neutron precursor data: half-lives and neutron emission probabilities
2002
Abstract We present in this paper a compilation of the present status of experimental delayed-neutron precursor data; i.e. β-decay half-lives ( T 1/2 ) and neutron emission probabilities ( P n ) in the fission-product region (27 ≤ Z ≤ 57). These data are compared to two model predictions of substantially different sophistication: (i) an update of the empirical Kratz-Herrmann formula (KHF), and (ii) a unified macroscopic-microscopic model within the quasi-particle random-phase approximation (QRPA). Both models are also used to calculate so far unknown T 1/2 and P n values up to Z = 63. A number of possible refinements in the microscopic calculations are suggested to further improve the nucle…
The origin of the Ca–Ti–Cr–Fe–Ni isotopic anomalies in the inclusion EK-1-4-1 of the Allende meteorite
2003
The origin of the correlated Ca-Ti-Cr-Fe-Ni isotopic anomalies in the Ca-Al-rich inclusion of the EK-1-4-1 of the Allende is a longstanding puzzle. The search for a stellar environment which could explain the enrichment of neutron-rich stable Ca-...-Ni isotopes in a self-consistent way requires nuclear physics data far from stability. Recent experimental data have been obtained in the region of the shell closures N = 28 and N = 40, where the possible progenitors of these nuclei are found. Astrophysical network calculations have been updated by including the new beta-decay properties and microscopic predictions of neutron-capture cross sections. Interplay between nuclear structure far from s…
Effect of Acoustic Wave Reflections on Space Charge Measurements with PEA Method
2018
The Pulsed Electro-Acoustic (PEA) method is the most used technique for space charge detection in solid dielectrics. The methodology is largely employed in the field of High Voltage Direct Current (HVDC) transmission and is based on the detection of acoustic waves generated by charges vibration. One of the most common problems arising during the detection is the presence of multiple reflections taking place due to the presence of means discontinuity in the different PEA cell components. This reflection phenomenon, if not well taken into account, could cause incorrect interpretation of the PEA output signal. It is easy to understand that a simulation model is a basic tool to understand the w…
Solar Nanoantennas energy based characterization
2016
Solar nanoantennas appear a very interesting solution to exploit solar radiation, as a matter of fact, their operating principle allows heat losses to be lessened compared to traditional photovoltaic cells and efficiency to be increased. Anyway, some technological issues are to be overcome. Literature often proposes a characterization by radiation efficiency typical of traditional antennas. Since the aim of solar nanoantennas is to harvest energy, in this paper the most promising devices are characterized by the upper bound of deliverable power density calculated in the whole operating wavelengths range.
Analysis of Torque Developed in Axial Flux, Single-Phase Brushless DC Motor With Salient-Pole Stator
2004
An analysis of the torque developed by a single-phase disc brushless permanent magnet motor with salient-pole stator is presented. The machine represents a new family of brushless disc motors with the starting torque issue appearing to be most challenging. To produce a starting torque, the permanent magnets on one of the rotor discs are distributed nonuniformly. However, this significantly distorts a shape of the cogging torque versus rotational angle characteristic which, in turn, affects a waveform of the overall torque. A three-dimensional (3-D) finite-element model is used for the purpose of determining of angular variations of the torque developed by the motor. To find how the torque v…
Thermalization efficiency of superconducting absorbers for thermal X-ray microcalorimeters
2004
The persistence of long living quasiparticles created in the energy thermalization process can affect the performances of a thermal X-ray microcalorimeter with superconducting absorber. Numerical simulations indicate that in an ab- sorber made of high-purity Sn, operated at temperatures lower than 100 mK, up to 60% of the deposited energy can remain trapped in the quasiparticle system for a time much longer than the time scale of the thermal sensor response, producing a reduction of the SNR of the detector. Other pure superconductors can present the same problem and therefore a microscopic analysis of the physical properties can be useful to identify suitable absorbing materials and optimiz…
Guided vortex motion in Nb films on facetted substrate surfaces
2003
Abstract Anisotropy of the pinning force in a superconductor can cause a guiding effect on the vortices, which leads to the appearance of new components in the galvanomagnetic quantities of the sample. In this case one can observe an additional odd magnetoresistive component with respect to magnetic field reversal. Furthermore, an even contribution to the Hall voltage is observed. Guided motion of vortices in Nb films on facetted α-Al2O3 (1 0 1 0) was found by measuring the longitudinal and transversal resistivities of three films with transport current directed parallel, perpendicular and at an angle of 45° with respect to the facet ridges. Field inversion was used to separate the even and…
Negative magnetoresistance of ultra-narrow superconducting nanowires in the resistive state
2008
We present a phenomenological model qualitatively explaining negative magnetoresistance in quasi-one-dimensional superconducting channels in the resistive state. The model is based on the assumption that fluctuations of the order parameter (phase slips) are responsible for the finite effective resistance of a narrow superconducting wire sufficiently close to the critical temperature. Each fluctuation is accompanied by an instant formation of a quasi-normal region of the order of the non-equilibrium quasiparticle relaxation length 'pinned' to the core of the phase slip. The effective time-averaged voltage measured in experiment is a sum of two terms. First one is the conventional contributio…
Performances of a three-phase five-level cascaded H-bridge inverter with phase shifted B-spline based modulation techniques
2017
This paper presents a novel study of the performances of a five-level three-phase Cascaded H-Bridge Multilevel Inverter with Phase Shifted B-Spline based modulation techniques. The study has been focused on the use of B-Spline functions as carrier signals in order to evaluate the performances of the converter in terms of harmonic content on the output voltage. In the first step of this analysis the THD% has been taken into account to compare the voltage waveforms. Interesting results have been found on the fundamental amplitude of the phase and line voltage. Moreover, harmonic spectra has been compared to evaluate the different harmonic distribution in the voltage waveforms. In this work th…