Search results for "Energy engineering"
showing 10 items of 1099 documents
Cover Picture: Direct Metal‐Free Chemical Vapor Deposition of Graphene Films on Insulating Substrates for Micro‐Supercapacitors with High Volumetric …
2019
Optimal Integration of Hybrid Supercapacitor and IPT system for a Free Catenary Tramway
2017
The aim of the presented paper is the study of an optimal integration of Supercapacitor based storage system and Inductive Power Transfer system for the free-catenary operation of a tramway. The paper starts from the definition of the Inductive Power transfer pad system and proposed an optimal integration strategy for the correct size of on-board supercapacitors and the inductive energy transfer.
Resistive state triggered by vortex entry in YBa 2 Cu 3 O 7−δ nanostructures
2014
We have realized YBa2Cu3O7-delta nanowires and nano Superconducting Quantum Interference Devices (nanoSQUID). The measured temperature dependence of the wire resistances below the superconducting transition temperature has been analyzed using a thermally activated vortex entry model valid for wires wider than the superconducting coherence length. The extracted zero temperature values of the London penetration depth, lambda(0) similar or equal to 270 +/- 15 nm, are in good agreement with the value obtained from critical current modulations as a function of an externally applied magnetic field in a nanoSQUID implementing two nanowires.
Effect of boron doping in the microwave surface resistance of neutron irradiated melt-textured Y1.6Ba2.3Cu3.3O7−x samples
2012
We report on the microwave surface resistance of melt-textured Y_1.6Ba_2.3Cu_3.3O_7-x samples, doped with different amount of B_2O_3 and, subsequently, irradiated by thermal neutrons at the fluence of 1.476 \times 10^17 cm^-2. The microwave surface resistance has been measured as a function of temperature and DC magnetic field. The experimental results are quantitatively discussed in the framework of the Coffey and Clem theory, properly adapted to take into account the d-wave nature of cuprate superconductors. By fitting the experimental data at zero DC field, we have highlighted the effects of the induced defects in the general properties of the samples, including the intergranular region.…
Possibility of unconventional superconductivity of SrTiO3−δ
2003
Abstract SrTiO3−δ can show metallic behavior and superconductivity at T It is demonstrated that by variation of the annealing temperature in vacuum the transport properties of SrTiO3−δ can be tuned continuously from semiconducting to metallic. We present measurements of the upper critical field Bc2(T) which show near Tc a positive curvature. This unusual temperature dependence is consistent with a model of weakly interacting charged bosons which condense in the superconducting state (local pairing). However, measurements of current–voltage curves reveal only small critical currents of our samples. This observation is discussed in the framework of doping inhomogeneities.
Preparation and characterization of (Hg0.7Mo0.3)Sr2(Ca0.7Y0.3)Cu2Ox and (Hg0.9Re0.1)Ba2CaCu2Oy superconducting films by laser ablation
2000
Abstract Oriented (Hg 0.7 Mo 0.3 )Sr 2 (Ca 0.7 Y 0.3 )Cu 2 O x and (Hg 0.9 Re 0.1 )Ba 2 CaCu 2 O y superconducting films were prepared on SrTiO 3 substrates using laser ablation and post-Hg-vapor annealing. Due to the stability of Mo 0.3 Sr 2 (Ca 0.7 Y 0.3 )Cu 2 O x and Re 0.1 Ba 2 CaCu 2 O y in air, no special handling was needed during the grinding, mixing and pressing of the precursor targets. The superconductivity of the films was characterized with the temperature dependence of the ac susceptibility ( χ - T ) and the resistance ( R - T ) while the crystallography was probed with x-ray diffraction (XRD) and scanning electron microscopy (SEM).
Effect of film thickness on the transport properties of MgB2 synthesized by spray pyrolysis
2011
Abstract Polycrystalline MgB2 films of different thickness have been prepared by employing spray pyrolysis technique on MgO (1 0 0) substrate. The MgB2 and other phases have been confirmed using X-ray diffraction technique and no trace of impurities phases have been found. The resistivity behavior shows that the superconducting transition temperature lies in the range of 37–39 K with narrow transition width. The transport critical current density vary with films thickness and achieved highest value ∼1.2 × 106 A/cm2 at 20 K for 2.0 μm thick film and its values increase as thickness increases.
Depinning frequency in a heavily neutron-irradiated MgB2 sample
2008
The magnetic-field-induced variations of the microwave surface resistance have been investigated in a heavily neutron-irradiated MgB2 sample, in which the irradiation has caused the merging of the two gaps into a single value. The experimental results have been analyzed in the framework of the Coffey and Clem model. By fitting the experimental data, we have determined the field dependence of the depinning frequency, omega_0, at different values of the temperature. Although the pinning is not particularly effective, the value of omega_0 obtained at low temperatures is considerably higher than that observed in conventional low-temperature superconductors.
Microwave response of a cylindrical cavity made of bulk MgB2 superconductor
2008
We report on the microwave properties of a resonant cylindrical cavity made of bulk MgB2 superconductor, produced by the reactive liquid Mg infiltration process. The frequency response of the cavity has been measured in the range 5-13GHz. Among the various modes, the TE011, resonating at 9.79GHz, exhibits the highest quality factor. For this mode, we have determined the temperature dependence of the quality factor, obtaining values of the order of 10^5 in the temperature range 4.2-30K. The values of the surface resistance deduced from the measurements of the quality factor agree quite well with those independently measured in a small sample of MgB2 extracted from the same specimen from whic…
Microscopic studies of surface morphology of high temperature superconductor thick layers
2004
Abstract The surface morphology and structure of the YBa2Cu3O7−δ superconductor ayers prepared on passive ceramic and single crystal substrates is studied by electron microscopy. The layers reveal features of structure formation.