1,773 research outputs found
AC Loss and Contact Resistance In Copper-Stabilized Nb3Al Rutherford Cables with and without a Stainless Steel Core
Calorimetric measurements of AC loss and hence interstrand contact resistance
(ICR), were measured on three samples of Rutherford cable wound with
Cu-stabilized jelly-roll type unplated Nb3Al strand. One of the cable types was
furnished with a thin core of AISI 316L stainless steel and the other two were
both uncored but insulated in different ways. The cables were subjected to a
room-temperature-applied uniaxial pressure of 12 MPa that was maintained during
the reaction heat treatment (RHT), then vacuum impregnated with CTD 101 epoxy,
and repressurized to 100 MPa during AC-loss measurement. The measurements were
performed at 4.2 K in a sinusoidal field of amplitude 400 mT at frequencies of
1 to 90 mHz (no DC-bias field) that was applied both perpendicular and parallel
to the face of the cable (the face-on, FO, and edge-on, EO, directions,
respectively). For the cored cable the FO-measured effective ICR (FO-ICR), was
5.27 . Those for the uncored cables were less than 0.08
. As shown previously for NbTi- and Nb3Sn-based Rutherford
cables, the FO-ICR can be significantly increased by the insertion of a core,
although in this case it is still below the range recommended for
accelerator-magnet use. Post-measurement dissection of one of the cables showed
that the impregnating resin had permeated between the strands and coated the
core with a thin, insulating layer excepting for some sintered points of
contact. In the uncored cables the strands were coated with resin except for
the points of interstrand contact. It is suggested that in the latter case this
tendency for partial coating leads to a processing-sensitive FO-ICR.Comment: Four pages, with two figure
Valuation of measurement data for low voltage network expansion planning
The introduction of electric vehicles and photovoltaics is changing the residential electricity consumption. Distribution network operators (DNO) are investing in an advanced metering infrastructure (AMI) to enable cost reduction through smart grid applications. The DNO also benefits from the additional measurement data the AMI gives for the network planning process. The availability of AMI data can be limited by the cost of communication and by privacy concerns. To determine the social welfare of an AMI, the economic gains should be estimated. For the planning of the low voltage (LV) network, a method for determining the value of an AMI still needs to be developed. Therefore, a planning methodology which allows various levels of measurement data availability has been developed. By applying this approach the value of different levels of AMI from an LV-network planning perspective can be determined. To illustrated the application of this approach a case study for the LV-network of a Dutch DNO is performed. The results show that an increase in measurement data can lead to €49-254 lower LV-network reinforcement costs. A detailed analysis of the results shows that already 50% of the possible cost reduction can be achieved if only 65% of the households have AMI data available.</p
Valuation of measurement data for low voltage network expansion planning
The introduction of electric vehicles and photovoltaics is changing the residential electricity consumption. Distribution network operators (DNO) are investing in an advanced metering infrastructure (AMI) to enable cost reduction through smart grid applications. The DNO also benefits from the additional measurement data the AMI gives for the network planning process. The availability of AMI data can be limited by the cost of communication and by privacy concerns. To determine the social welfare of an AMI, the economic gains should be estimated. For the planning of the low voltage (LV) network, a method for determining the value of an AMI still needs to be developed. Therefore, a planning methodology which allows various levels of measurement data availability has been developed. By applying this approach the value of different levels of AMI from an LV-network planning perspective can be determined. To illustrated the application of this approach a case study for the LV-network of a Dutch DNO is performed. The results show that an increase in measurement data can lead to €49-254 lower LV-network reinforcement costs. A detailed analysis of the results shows that already 50% of the possible cost reduction can be achieved if only 65% of the households have AMI data available.</p
Optimisation of ITER Nb3Sn CICCs for coupling loss, transverse electromagnetic load and axial thermal contraction
The ITER cable-in-conduit conductors (CICCs) are built up from sub-cable
bundles, wound in different stages, which are twisted to counter coupling loss
caused by time-changing external magnet fields. The selection of the twist
pitch lengths has major implications for the performance of the cable in the
case of strain sensitive superconductors, i.e. Nb3Sn, as the electromagnetic
and thermal contraction loads are large but also for the heat load from the AC
coupling loss. Reduction of the transverse load and warm-up cool-down
degradation can be reached by applying longer twist pitches in a particular
sequence for the sub-stages, offering a large cable transverse stiffness,
adequate axial flexibility and maximum allowed lateral strand support. Analysis
of short sample (TF conductor) data reveals that increasing the twist pitch can
lead to a gain of the effective axial compressive strain of more than 0.3 %
with practically no degradation from bending. For reduction of the coupling
loss, specific choices of the cabling twist sequence are needed with the aim to
minimize the area of linked strands and bundles that are coupled and form loops
with the applied changing magnetic field, instead of simply avoiding longer
pitches. In addition we recommend increasing the wrap coverage of the CS
conductor from 50 % to at least 70 %. The models predict significant
improvement against strain sensitivity and substantial decrease of the AC
coupling loss in Nb3Sn CICCs, but also for NbTi CICCs minimization of the
coupling loss can be achieved. Although the success of long pitches to
transverse load degradation was already demonstrated, the prediction of the
combination with low coupling loss needs to be validated by a short sample
test.Comment: to be published in Supercond Sci Techno
PCN210 G-Ba Assessments of Oncology Trials: Is Increased Overall Survival a “Must Have”?
The influence of knee rigidity on balance corrections: a comparison with responses of cerebellar ataxia patients
Knee rigidity due to aging or disease is associated with falls. A causal relationship between instability and knee rigidity has not been established. Here, we examined whether insufficient knee movement due to knee rigidity could underlie poor balance control in patients. We addressed this by examining the effect of artificially "locking” the knees on balance control in 18 healthy subjects, tested with and without individually fitted knee casts on both legs. Subjects were exposed to sudden rotations of a support surface in six different directions. The primary outcome measure was body centre of mass (COM) movement, and secondary outcome measures included biomechanical responses of the legs, pelvis and trunk. Knee casts caused increased backward COM movement for backward perturbations and decreased vertical COM movement for forward perturbations, and caused little change in lateral COM movement. At the ankles, dorsiflexion was reduced for backward perturbations. With knee casts, there was less uphill hip flexion and more downhill hip flexion. A major difference with knee casts was a reversed pelvis pitch movement and an increased forward trunk motion. These alterations in pitch movement strategies and COM displacements were similar to those we have observed previously in patients with knee rigidity, specifically those with spinocerebellar ataxia (SCA). Pelvis roll and uphill arm abduction were also increased with the casts. This roll movement strategy and minor changes in lateral COM movement were not similar to observations in patients. We conclude that artificial knee rigidity increases instability, as reflected by greater posterior COM displacement following support surface tilts. Healthy controls with knee casts used a pitch movement strategy similar to that of SCA patients to offset their lack of knee movement in regaining balance following multidirectional perturbations. This similarity suggests that reduced knee movements due to knee rigidity may contribute to sagittal plane postural instability in SCA patients and possibly in other patient groups. However in the roll plane, healthy controls rapidly compensate by adjusting arm movements and hip flexion to offset the effects of knee rigidit
Influence of fatigue on superconducting REBCO tapes under repeated cyclic tensile, bending and twisting loads:A simulation-based investigation
The effect of repeated cyclic loading on the superconducting REBCO tape under tensile, bending, and torsional loadings is investigated. The Fatigue Usage Factor (FUS) is calculated for each cyclic loading condition to identify degradation using the Matake criterion. The thicknesses of the tapes' constituent layers are also varied to identify the relative influence of each layer on overall fatigue performance. When the tape was subjected to fatigue-type loading, the thickness of the copper and Hastelloy layers was found to play a significant role. This holds true under tensile, bending, and twisting loading conditions. However, out of the three loading conditions, bending exhibits the greatest variation in FUS value with changes in Hastelloy and copper layer thickness. The maximum value of the fatigue usage factor is observed in the edges of the Hastelloy layer in all three loading cases. It has been found that the properties of the layer material, as well as the adjacent layer, play an important role in determining the fatigue strength of the tape.</p
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