Evolution of contact resistance and coupling loss in prototype ITER PF NbTi conductors under transverse cyclic load

Cyclic energizing of a magnet coil with Cable in Conduit Conductors (CICC), as for fusion applications, results in an anomalous change of the interstrand contact resistance (R/sub c/) and coupling loss (n/spl tau/) due to the alternating transverse forces. Previously, three Nb/sub 3/Sn ITER conductors have been tested in a cryogenic press, up to 40 cycles. Now, for the first time, the behavior of NbTi conductors under cyclic load is investigated and results are presented for three full-size prototype ITER Poloidal Field (PF) Coil conductors. One conductor has bare copper strands and no petal wrapping while the others have a Cr and solder strand surface coating. The press can transmit a maximum transverse force of 800 kN/m directly to a cable section of 400 mm length at 4.2 K. Each conductor is tested up to 220 kN/m and 40,000 full loading cycles. The magnetization of the conductors and the R/sub c/ between combinations of strands and strand bundles is measured at various number of cycles. It appears that the R/sub c/ can vary for up to orders of magnitude during cyclic loading

Electromagnetic Performance of Sub-Size NbTi CICC's Subjected to Transverse Cyclic Loading

It was demonstrated previously that transverse cable loading due to electromagnetic forces in coils has a strong impact on the inter-strand contact resistance R/sub c/ of poloidal field (PF) cable-in-conduit conductors (CICC) for the International Thermonuclear Experimental Reactor (ITER). Continuing the study, two NbTi medium-size CICC's were subjected to cyclic loading up to 40,000 cycles in the Twente Cryogenic Press in order to simulate transversal forces on the strands and to verify their influence on the conductors' contact resistances R/sub c/ and AC loss behavior. The results are presented and compared with the data obtained on the other section of the same conductor lengths in the SULTAN test facility and on full size ITER cables tested in the cryogenic press

Self Field Measurements by Hall Sensors on the SeCRETS Long Sample CICCs in SULTAN

The aim of this work is to determine the existence and degree of the current unbalance of two types of cable-in-conduit conductors (CICC) of the SeCRETS long sample experiment, and its influence on the conductors' performance. The self-field measurements are performed by using six sets of annular Hall sensors, each containing six sensors, and two linear arrays with ten sensors. The change of the self-field is associated with the redistribution of the transport current between the strands inside the conductor during and after a ramp of current, due to changes of the applied magnetic field or temperature of the conductor. During the DC, AC losses and stability tests, the signals from the Hall sensors were recorded. In DC tests, a clear change of the self-field pattern is observed in the high field region when either current or temperature approached their critical (I/sub cs/ and T/sub cs/) values. No change in the self-field pattern is observed in the experiments with pulsed fields. The method requires improvements for a reasonable quantitative assessment of the current unbalance in the conductor

Self field measurements by Hall sensors on the SeCRETS short sample CICC's subjected to cyclic load

An imbalance in the transport current among the strands of a Cable-in-Conduit conductors (CICC) can be associated with the change of their performance. In order to understand and improve the performance of CICC's, it is essential to study the current imbalance. This paper focuses on the study of the current imbalance in two short samples of the SeCRETS (Segregated Copper Ratio Experiment on Transient Stability) conductors subjected to a cyclic load in the SULTAN facility. The self field around the conductors was measured on four locations by 32 miniature Hall sensors for a reconstruction of the current distribution. The results of the self field measurements in the DC tests are presented and discussed

Replacing the Irreplaceable: Fast Algorithms for Team Member Recommendation

In this paper, we study the problem of Team Member Replacement: given a team of people embedded in a social network working on the same task, find a good candidate who can fit in the team after one team member becomes unavailable. We conjecture that a good team member replacement should have good skill matching as well as good structure matching. We formulate this problem using the concept of graph kernel. To tackle the computational challenges, we propose a family of fast algorithms by (a) designing effective pruning strategies, and (b) exploring the smoothness between the existing and the new team structures. We conduct extensive experimental evaluations on real world datasets to demonstrate the effectiveness and efficiency. Our algorithms (a) perform significantly better than the alternative choices in terms of both precision and recall; and (b) scale sub-linearly.Comment: Initially submitted to KDD 201