Evaluation of Joint Resistance Between Bi-2223/Ag Superconducting Tapes
We fabricated Bi-2223/Ag jointed tape and evaluated its current carrying capacity and joint resistance at 77.3 K as a function of the contact length. The tapes were jointed by the conventional resistive joint method with 40Pb-60Sn solder as an insert material and their joint resistance was measured by two different techniques, i.e., the standard four-probe and field decay methods. It was observed that the current carrying capacity and joint resistance were significantly dependent on the contact length. As the contact length increased, the current carrying capacity improved and increased to the level of critical current in the unjoined tape at the contact length of 5 cm. On the other hand, the joint resistance linearly decreased as the contact length increased. In addition, the joint resistances measured by the two methods were similar to each other (7.3times10-9 Omega~8.0times10-9 Omega), indicating that the standard four-probe method maintained a moderate degree of accuracy at the level of resistance of 10-9 Omega
Development of Joints Between Two Parallel SS-Laminated BSCCO/Ag HTS Tapes
Stainless-steel (SS)-laminated high-strength high-temperature superconductor (HTS) BSCCO tapes are now commercially available for different practical applications. These SS-laminated HTS tapes are tolerant to smaller winding diameters, and the pancake winding becomes much easier due to higher tensile strength. However, the joining of two parallel SS-laminated HTS tapes is more complicated because of their limitation in maximum temperature exposure. The joining between the pancakes however becomes resistive due to the SS-laminated layer. We have experimentally studied the performance of the bridge joint between two parallel SS-laminated BSCCO tapes with different numbers of cross bridges of two different types of BSCCO tape. The splices of both SS-laminated BSCCO tape and silver (Ag)-sheathed BSCCO tape have been used as cross bridges at the joint. The current-voltage I-V characteristic curves of the joints were investigated at 77 K, which is liquid nitrogen temperature. Joint resistance has been estimated from the I-V characteristic curve. The lowest joint resistance achieved at 77 K at self-field, with six bridges made of SS-laminated HTS tape, is 0.78 ¿¿, and the lowest joint resistance of six Ag-sheathed HTS bridges is 0.54 ¿¿. The corresponding contact resistances are 0.402 and 0.27 ¿¿·cm2 for both types of joints.
LABORATORY AND FIELD TESTING OF SEED SPACING UNIFORMITY FOR SUGARBEET PLANTERS
Five planter configurations were evaluated for seed spacing uniformity at three field speeds using a seed 
location method in the field and a laboratory method involving an opto-electronic sensor system. Planter seed spacing 
uniformity was described using the Coefficient of Precision (CP3) measure. Results showed that CP3 measures 
determined using the laboratory test method were significantly different from those determined using the field test method. 
This indicated the laboratory test method cannot be used to predict planter seed spacing uniformity in the field. Seed 
spacing uniformity determined in laboratory tests was higher than, or equal to, seed spacing uniformity determined in 
field tests. This indicated the laboratory test method may be useful to screen out planters or planter units with poor 
uniformity of seed metering. Field testing of the planters that perform well in laboratory tests must be conducted to 
adequately determine the seed spacing uniformity of those planters in the field. Results from laboratory and field tests 
could be useful in determining areas for improvement of planters or planter units.