Multifilament niobium-tin conductors

A new Nb3Sn wire fabrication method has been developed, improving wire drawing workability and superconducting properties, such as stability and ac losses. A cross section of the single filament wire consists of a niobium tube with a copper sheathed tin rod inside and high conductivity copper tube outside. These constituents show scarcely any workhardening. Wires with 54 to 295 filaments were drawn down to 0.2 mm to 1.0 mm diameter. Heat-treatment conditions to obtain the highest critical current were clarified as a function of the tin content inside the niobium tube. The effect of bend strain in Nb3Sn on the critical current was also examined for samples with different wire diameters and Nb3Sn layer thickness. Losses were measured for twisted and non-twisted samples by means of magnetization experiments. Results were compared with calculated values. It was found that the effective resistivity between Nb3Sn filaments was one order of magnitude higher than that of pure copper. A coil was constructed using a 1 km long Nb3Sn composite having 258 filaments with 1 × 2 mm cross section. The maximum field obtained was 10.65T at 236A in the 6T backing field by NbTi solenoid.     

Heat transfer from plates to conductors: from toroidal field model coil tests analysis to ITER model

During a safety discharge of toroidal field type magnets, eddy currents and associated heat generation are induced in the plates. A model has been developed from the thermohydraulic code Gandalf with introduction of the equations of the heat diffusion from plates to conductors through the steel and insulation. The comparison of calculation and experimental results for the ITER toroidal field model coil is presented.Preliminary analysis for the ITER toroidal field coils is also presented, taking into account the conductor parameters, the magnetic field and the external hydraulic circuit. The possible quench of the magnetic system is discussed.     

Analysis of a fork-shaped rectangular coil facing moving sheet conductors

The electromagnetic induction method utilising eddy current plays an important role in a non-destructive material test. In testing slab-type material by electromotive force method, there is the fork-shaped coil method, which has two coils placed on both sides of the test piece. In most studies, circular coils have been analysed. However, it has been pointed out quantitatively that a rectangular coil is more useful than a circular coil for a non-destructive test. The authors derive a rigid theoretical formula with a test theory experiment.     

Image reconstruction of buried multiple conductors by genetic algorithms

This paper presents an inverse scattering problem for recovering the shapes of multiple conducting cylinders with the immersed targets in a half‐space by genetic algorithm. Two separate perfectly conducting cylinders of unknown shapes are buried in one half‐space and illuminated by transverse magnetic (TM) plane wave from the other half‐space. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations are derived, and the electromagnetic imaging problem is reformulated into an optimization problem. The improved steady state genetic algorithm is used to find out the global extreme solution. Numerical results are given to demonstrate the performance of the inverse algorithm. Good reconstruction can be obtained even when the initial guesses are far different from the exact shapes, and then the multiple scattered fields between two conductors are serious. In addition, the effect of Gaussian noise on the reconstruction is investigated. We can find that the effect of noise is negligible for the normalized standard deviations below 0.01. © 2008 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 18, 276–281, 2008; Published online in Wiley InterScience (www.interscience.wiley.com).     

High-throughput nuclear magnetic resonance analysis using a multiple coil flow probe

An automated method for high-throughput nuclear magnetic resonance (NMR) spectroscopy has been developed using a four-coil Multiplex NMR probe. The probe is constructed with solenoidal microcoils optimized for detection of small volume, mass-limited samples and a flow-through design. Four samples can be simultaneously injected into the Multiplex probe with a robotics liquid handler and then analyzed in rapid succession using a selective excitation experiment. Due to the simultaneous injection of four samples and the reduced analysis time with rapid selective excitation, the analysis rate achieved thus far is as low as 1 sample/34 s for 1D 1H NMR.     

New fluorine ion conductors with tysonite-type structure

New fluorine fast ion conductors with tysonite-type structure have been obtained within the BiF₃1bBF₂ (B = Ba, Pb) systems: Bi_1?yBa_yF_3?y (0.05 ? y ? 0.17) and Bi_1?yPb_yF_3?y (0.075 ? y ? 0.175). The good electrical performances due to high polarizability cations set them among the best so far known fast anion conductors. Correlations between transport properties and structural data have been established.     

A new procedure of statistical approach characterization of ceramic filament fracture strength by bending tests

A procedure of ceramic filaments characterization has been proposed on the base of bending tests performed on continuous filaments. Using a specific bending device, fracture strength σ^R and Weibull modulus m related to commonly used tensile test procedure, can be derived from bending results thanks to a simple relation depending on the related Weibull’s modulus. The proposed new procedure is very rapid to perform and allows easy ceramic filaments acceptance testing in industrial contexts. The procedure has been validated by comparing fracture results obtained with the new procedure with those resulting from tensile tests.     

Mesoscopic transport of InAs-based conductors with superconducting electrodes

We summarize recent experimental results on transport of diffusive and ballistic InAs-based (2-dimensional electron gas) submicron sized conductors connected to superconducting niobium contacts. Both ensemble-averaged and sample-specific transport is shown to depend on the difference in the superconducting phases tuned by a magnetic field. The ballistic case can be understood using a simple model based on phase-conjugated trajectories. The results summarized here are based on research done with S.G. den Hartog, P.H.C. Magnée, A.F.Morpurgo, and B.J. van Wees. C.M.A.Kapteyn and S.Holl contributed as ERASMUS students. InAs heterostructures were provided by G.Borghs from IMEC, Leuven.     

Problems with conductors and dielectrics for cryogenic cables

The most important problems which need to be solved if superconducting power cables are to be used on a large scale are connected with the superconducting cable materials and the dielectrics used for insulation.Research work on superconducting materials for ac and dc cables is briefly reviewed together with stabilization problems for these materials. Three types of insulation are considered - vacuum, subcooled or supercritical helium, and foil wound insulation. The merits and problems encountered in each case are discussed.     

Silver nanowires with semiconducting ligands for low-temperature transparent conductors

Metal nanowire networks represent a promising candidate for the rapid fabrication of transparent electrodes with high transmission and low sheet-resistance values at very low deposition temperatures. A commonly encountered challenge in the formation of conductive nanowire electrodes is establishing high-quality electronic contact between nanowires to facilitate long-range current transport through the network. A new system involving nanowire ligand removal and replacement with a semiconducting sol-gel tin oxide matrix has enabled the fabrication of high-performance transparent electrodes at dramatically reduced temperatures with minimal need for post-deposition treatment.

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Small-Sized Hybrid Magnet with Pulsed Field Magnetization

Small-sized hybrid magnet (HM) operated in liquid nitrogen was constructed. It consists of two superconducting Y-Ba-Cu-O annuli, placed on soft magnetic cores made of permenduire. The magnetization of the superconducting annuli was realized by a pulsed method using two copper coils installed near the annuli. The trapped field value of 2.2 T with the radial (r ≈ 5 mm) homogeneity of 0.1 % can be achieved in the gap of 2 mm between magnetic cores. The magnetization procedure and time evolution of the trapped field are also discussed. The magnets of similar type are promising for application in compact electron spin resonance (ESR) spectrometers.     

The mechanical properties and microstructures of copper and brass joints soldered with eutectic tin-bismuth solder

The mechanical properties and microstructures ofcopper and brass soldered with eutectic tin-bismuth solder have been determined and the joints examined using metallographic techniques. Joints made with copper were stronger than those made with brass. At the copper/solder interface a uniform layer 2m thick of Cu_5.2Sn₅ was formed and at the brass/solder interface a uniform layer 2 m thick of (Cu, Zn)_2.9Sn and an irregular layer 2 to 5m thick of (Cu, Zn)_5.7Sn₅ were formed. Copper joints fractured etthocopper/solder interface and brass joints fractured in the internmetalic layer. Copper joints soldered with eutectic Sn-Bi were stronger than copper joints soldered with eutectic Sn-Pb and the reverse was true for brass joints. Results are also given for the effect of thermal shock on copper and brass joints soldered with Sn-Bi and Sn-Pb solders, and also for We fatigue and creep behaviour of joints soldered with eutectic Sn-Bi solder.     

Strength of filament wound GRP pipes with surface crack

In this work, the effect of surface cracks on strength has been investigated theoretically and experimentally for glass/epoxy filament wound pipes, which are mainly used for bazooka launchers. The pipes with surface crack which have several notch-aspect ratios a/c and notch-to-thickness ratios a/t in the axial direction were exposed to open-ended internal pressure. Critical stress intensity factors were determined experimentally for several winding angles by tensile tests with center notched ring specimens. The strength values of pipes with surface cracks are compared with internal pressure test results and theoretical results.     

Serviceability of glass and ceramic shells with soldered joints subjected to external pressure and marine conditions

Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 2, pp. 95–101, February, 1988.     

Sufficient conditions for the exponential stability in linear conductors with memory

A model describing a linear homogeneous conductor with memory is presented. The dissipativity due to the memory allows to establish some estimates on the asymptotic behavior and prove the exponential decay of the solution of the system in the absence of external sources.     

Resonant tunneling and perpendicular conduction in cuprate conductors with varying O-content

Anisotropy is inherent to layered cuprates with conduction mainly confined to the CuO₂-planes, claimed to be the source of superconductivity. Resonant tunnel exchange for conduction parallel and perpendicular to the CuO₂-planes shows different normal and superconducting properties by charging energies and localizations at the in-plane perturbations being atomic-like and between the CuO₂-planes, being extended. By overdoping the wave function overlap in perpendicular direction via the extended states grows, especially in the superconducting state. The counteraction of overlap and charging energies yield activated resonant tunneling, i.e. the pseudo gap, in the normal state and Josephson tunneling in the superconducting state.     

Stability of uniform temperature fields in linear heat conductors with memory

In this paper we consider the asymptotic behavior of temperature fields in linear heat conductors with memory. Using the method of energy integrals, we establish stability for the history problem both in the case when the governing heat equation is parabolic in character and when the heat equation is hyperbolic and predicts finite wave speeds.     

Modal analysis for filament wound pressure vessels filled with fluid

Filament wound pressure vessels have been extensively used in many engineering fields, especially aerospace industry. Vibration-based damage detection methods have the potential to be employed to monitor the health status of the structures based on the fact that damage occurred in a structure would result in changes in its structural dynamic characteristics. However the presence of fluid will affect the dynamic response of this type of vessel structures. Due to the liquid mass decrease during its service, the whole system is considered a time-variant system in terms of its dynamic response even the structure itself remains free of damage, which cause problems for vibration-based damage detection method that utilized dynamic response change to identify damage. Therefore it is critical to understand how the change of the liquid height level influences the dynamic response of the coupled fluid–structure system. This work describes the FEM analysis and an experimental study on the dynamic response of filament wound pressure vessels filled with liquid of different heights and provides the primary information that can be used for vibration-based damage detection.