MgB2 conductors for dc and ac applications

The paper presents discussion on up to date results on MgB2 conductors from the point of view of their future dc and ac applications. Basic physical parameters of MgB2 compound relevant to conductors are introduced. Different conductor preparation methods and conductor architectures are presented and attainable critical current densities discussed. Some numerical results on critical currents and ac losses of future multifilamentary MgB2 conductors with magnetic cladding of their filaments are given. Recently observed anomalous decrease of ac susceptibility at 50 K in copper clad Powder-in-tube, PIT, MgB2 wires is presented.Comment: Paper presented at EUCAS'01 conference, Copenhagen, 26-30 August 200

Effect of Spatial Titration on Task Performance

A spatial titration method was used with a reinforcement schedule to determine task-reinforcement area separation most preferred and effective in producing high task performance. Two third-grade boys were given task contingent reinforcement where the task was solving arithmetic problems. Following shaping to stable response rates, the titration operation was introduced. Errors decreased the task-reinforcement area distance while correct responses increased the distance. With the introduction of Titration Phase 1, both subjects\u27 incorrect responses produced a zero task-reinforcement area separation. In Titration Phase 2, both subjects were started at the opposite extreme of the reinforcement continuum. Repeated errors produced a zero task-reinforcement area spatial separation

Ice volume changes of Ariebreen, Spitsbergen, during 1936-1990-2007

Ariebreen (77º 01' N, 15º 29' E) is a small valley glacier (ca. 0.36 km2 in August 2007) located at Hornsund, Spitsbergen, Svalbard, ca. 2.5 km to the west of Hornsund Polish Polar Station. Many Svalbard glaciers have experienced a significant recession at least since the 1930s, and most likely since the end of Little Ice Age in the early 20th century (Werner, 1993). It has manifested as thinning and retreating of ice fronts, though a simultaneous thickening at the uppermost elevations in many locations has been reported (Bamber et al., 2004; Nuth et al., 2007). Moreover, the thinning rate of western Svalbard glaciers has shown an acceleration during the most recent decades (Kohler et al., 2007). The main aims of this contribution are to determine whether Ariebreen follows such retreat pattern and to quantify the retreat it has experienced, in terms of area, thickness and volume changes, to estimate the average mass balance equivalent to the ice volume change during the period under investigation, and to estimate the volume of ice presently stored in Ariebreen. The main tools to accomplish this will be the analysis of digital terrain models (DTM) of the glacier surface corresponding to different dates, and the radio-echo sounding of the ice body to determine the present ice volume. The latter is described in a separate contribution to this workshop (Navarro et al., 2008)

Niobium based intermetallics as a source of high-current/high-magnetic field superconductors

The article is focused on low temperature intermetallic A15 superconducting wires development for Nuclear Magnetic Resonance, NMR, and Nuclear Magnetic Imaging, MRI, magnets and also on cryogen-free magnets. There are many other applications which would benefit from new development such as future Large Hadron Collider to be built from A15 intermetallic conductors. This paper highlights the current status of development of the niobium based intermetallics with special attention to Nb 3 (Al 1-x, Ge x). Discussion is focused on the materials science aspects of conductor manufacture, such as b-phase (A15) formation, with particular emphasis on the maximisation of the superconducting parameters, such as critical current density, Jc, critical temperature, Tc, and upper critical field, Hc2 . Many successful manufacturing techniques of the potential niobium-aluminide intermetallic superconducting conductors, such as solid-state processing, liquid-solid processing, rapid heating/cooling processes, are described, compared and assessed. Special emphasis has been laid on conditions under which the Jc (B) peak effect occurs in some of the Nb3(Al,Ge) wires. A novel electrodeoxidizing method developed in Cambridge whereby the alloys and intermetallics are produced cheaply making all superconducting electromagnetic devices, using low cost LTCs, more cost effective is presented.This new technique has potential to revolutionise the existing superconducting industry enabling reduction of cost orders of magnitude.Comment: Paper presented at EUCAS'01 conference, Copenhagen, 26-30 August 200