[en] It was forecast that from 1986 to the late 1990s the nuclear plus hydraulic baseload generation capability within Ontario Hydro will frequently exceed the total system electrical demand. As a result, nuclear units will increasingly be required to meet changes in demand in order to minimize the operating costs. This paper discusses Ontario Hydro's electrical system requirements regarding nuclear generating stations and the key issues affecting their operation. It summarizes the economic impact of nuclear maneuvering, reviews the operating experience to date, and presents the long-term strategy that is being pursued. The results of our analysis indicate significant savings on fuel replacement costs due to nuclear maneuvering capability. This is achieved by eliminating the need for shutting down baseload nuclear units and then having to replace the required demand load from maneuverable but expensive coal-fired stations. Between 1986 and 1987, Pickering NGS-B and Bruce NGS-B demonstrated the nuclear maneuvering capability of CANDU reactors and saved Ontario Hydro one million dollars in fuel costs. A typical load cycle at Bruce NGS-B consisted of reducing power to 50% FP, holding at that power, then returning to full power when system required it. Deeper nuclear maneuvers, where power is reduced to 20% to 25% FP, have also been successfully demonstrated. A joint work program within Ontario Hydro is being pursued by Operation, Research, Design, and Systems Planning departments to anticipate potential areas of concern during the coming periods of significant unutilized energy. In particular, the potential long-term effects on equipment include a scheme to anticipate, monitor and evaluate the impact on equipment reliability and performance

[en] We report on the preparation and structural characterization of YBa₂Cu₃O₇/La_0.7Ca_0.3MnO₃ and La_0.7Ca_0.3MnO₃/YBa₂Cu₃O₇ bilayers onto (1 0 0) SrTiO₃ substrates. The samples have been fabricated by sequential dc sputtering processes in high oxygen pressure starting from stochiometric targets. The critical temperature of the YBa₂Cu₃O₇ single layer was T_c(ρ=0)=91 K and the metal-insulator transition temperature (T_MI) of the manganite single layer was T_MI=135 K. The structural characterization of the bilayers has been performed by X-ray diffraction analysis revealing highly epitaxial heterostructure with well defined interface for both kind of samples

[en] Epitaxial La_0.7Ca_0.3MnO₃ (LCMO) thin films have been deposited by high pressure DC sputtering technique on SrTiO₃ substrates. As-grown films exhibit metal-insulator transition temperature (T_MI) with values ranging from 131 to 220 K. The maximum value of the magnetoresistance is of about -77% in a magnetic field of 0.5 T for T_MI=131 K. The same films, annealed in a pure oxygen atmosphere, exhibit transitions to a metallic state at temperatures ranging from 210 to 284 K. Transmission electron microscopy analyses show a coherent growth between film and substrate

[en] The KLOE-2 experiment is currently collecting data at DATNE the INFN e+e- collider located in the Frascati National Laboratories. The experiment has a wide physics program ranging from: discrete symmetries test, study of light unflavored mesons, searches for light mass for dark matter candidates. In this contribution the upgrade of the detector will be briefly discussed before starting a more detailed presentation on some results concerning: CPT and Lorentz Invariance tests with neutral kaons, dark forces massive boson mediator searches, hadron structure and low energy mesons interaction. (paper)

[en] We have investigated the structural and electrical properties of La_0.7Ca_0.3MnO₃ thin films grown both by pulsed laser or DC-sputtering deposition techniques on SrTiO₃ (1 0 0) substrates. X-ray diffractograms and pole figures revealed the epitaxial character of the samples. Resistance vs. temperature measurements without applied magnetic field showed the metal-insulator transition temperature (T_MI) in the range of 220-260 K. The magnetoresistance temperature dependence was also investigated and correlated with the thickness of the films, the oxygen annealing treatment and the presence of lattice defects

[en] A solid-state riometer has been installed at Terra Nova Bay (74 degrees 42^' S and 164 degrees 06^' E) during the 9. italian Antarctic expedition (1993/1994) to provide, in the frame of the geophysical observatories, studies on the ionospheric absorption in the lower part of the ionosphere. This kind of measurements will integrate the already existing active vertical ionospheric sounding and the magnetic absolute vector observations, with the objective of investigating the state of the ionosphere-magnetosphere coupling. In order to evaluate the base disturbance to the riometer, a remote campaign has been performed at McCarthy Ridge, rather far from the base station, where no atropic noise is expected. Preliminary data analysis confirms the good quality of the antarctic riometer observations

[en] Highlights: • A novel generalized modelling approach for multiphase flows has been developed. • Suitable closures are selected as a function of the local interface morphology. • The switch between different closure models depends on the local mesh resolution. • Good predictions obtained for multiphase flows with different interfacial scales. Multiphase flows are ubiquitous both in nature and industry. A broad range of interfacial scales, ranging from fine dispersions to large segregated interfaces, is often observed in such flows. Standard multiphase models rely on either the interface-averaging approach, which is suitable for the modelling of dispersed flows, or on the interface-resolving approach, which is ideal for large segregated interfaces. This results in the inability of such models to deal with complex multiscale flows, and different generalized hybrid modelling approaches having been proposed to overcome this shortcoming. This work presents a novel generalized multifluid modelling approach where large segregated interfaces are identified in the multifluid field from the local interface topology and resolution, avoiding the need for a-priori thresholds of the local volume fraction used in the majority of the models available in the literature. Interface compression and suitable modelling closures for drag and surface tension are activated in the large interfaces regions, whilst the model reverts to a standard multifluid formulation in the regions of small/dispersed interfaces. An assessment against different benchmark cases shows that the approach is as accurate as one-fluid interface-resolving techniques for large/segregated interfaces, while successfully recovering the expected multifluid behaviour for fully dispersed flows. Further, a prototypical multiscale flow has been simulated to demonstrate that the model can effectively switch between large-interface and dispersed-interface mode based on the local flow conditions and mesh size. It is concluded that the present approach represents a promising step towards the development of a comprehensive multiphase model capable of simulating complex multiscale flows of industrial interest.

[en] We present conductance characteristics of point contact junctions realized between a normal Pt-Ir tip and YBa₂Cu₃O_7-x/La_0.7Ca_0.3MnO₃ (YBCO/LCMO) bilayers. The point contact characteristics show a zero bias conductance peak, as a consequence of the formation of Andreev bound states at the YBCO Fermi level. The temperature evolution of the spectra reveals a depressed zero bias peak and a reduced superconducting energy gap, both explainable in terms of spin polarization effects due to the LCMO layer

[en] The fabrication and characterization of superconducting and ferromagnetic heterostructures is an open field due to the fundamental interest in the physics of the coexistence of these two competing orders and their possible applications in the spintronics industry. In this paper we present structural, electrical and magnetic characterization for the single La_0.7Ca_0.3MnO₃ (LCMO) thin layer, La_0.7Ca_0.3MnO₃/YBa₂Cu₃O_7-x (LCMO/YBCO) bilayers and the LCMO/YBCO/LCMO trilayers. In particular, we show a detailed magnetic characterization of the LCMO thin films by means of low temperature magnetic force microscopy. We discuss the different dynamics of the magnetic domains observed, depending on the substrate induced strain and on the film thickness.

[en] Highlights: • Assessment and calibration of different turbulent heat flux closures is performed. • Four different turbulent heat flux closures are assessed for low-Prandtl fluids. • This assessment has been performed for all three flow regimes. - Abstract: Thermal-hydraulics is recognized as a key safety challenge in the development of liquid metal cooled reactors. At nominal operating conditions, the Prandtl number of liquid metals which are used as primary coolants, such as lead and sodium, is very low: typically of the order of 0.025–0.001. Obtaining an accurate prediction of the turbulent heat transfer at such a low Prandtl number is not an easy task for the standard turbulence models and has challenged the modellers over several decades. In the framework of the EU SESAME project, an effort has been put forward to assess and/or further develop/calibrate different turbulent heat flux closures. In this regard, the present article reports an assessment of four different turbulent heat flux closures for applications involving low-Prandtl fluids. These closures include: (i) the Reynolds analogy based on a constant turbulent Prandtl number (ii) a four-equation explicit algebraic heat flux model (AHFM) (ii) a three-equation implicit AHFM called AHFM-NRG and (iv) a non-linear second-order heat flux model called Turbulence Model for Buoyant Flows (TMBF). The performance of these turbulence models has been assessed in three different test cases against high-fidelity numerical reference data been generated within the SESAME project. The three test cases are: a natural Rayleigh-Bénard convection flow, a mixed convection planar channel flow and a forced convection impinging jet flow. The shortcomings of the classical Reynolds analogy approach for low-Prandtl fluids in all flow regimes are highlighted; hence, more advanced and well-calibrated closures are recommended.