| 1. |
|
|
| 2. |
- Lonardo, F., et al.
(författare)
-
Influence of the Heat Treatment on the Layer JC of Internal-Sn Nb3Sn Wires With Internally Oxidized Nanoparticles
- 2024
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 34:5
-
Tidskriftsartikel (refereegranskat)abstract
- We evaluated various heat treatments (HT) for maximizing the Nb 3 Sn layer thickness while retaining a refined grain microstructure in low filament count internal-Sn Nb 3 Sn Rod-In-Tube wires with internally oxidized nanoparticles. These wires were manufactured in our laboratory using SnO 2 as oxygen source and Nb alloys containing Ta and Zr or Hf. By reacting the wires at 650 °C for 200 hours we obtained relatively thin reaction layers but high layer critical current densities (layer J C ) of ∼3000 A/mm 2 for Hf-containing wires and ∼2700 A/mm 2 for Zr-containing wires, both at 4.2 K and 16 T. Notably, both of these values are over the layer J C threshold of 2500 A/mm 2 , which is estimated to be necessary for attaining the corresponding Future Circular Collider (FCC) target non-Cu J C of 1500 A/mm 2 . Following this heat treatment, the fine-grained Nb 3 Sn area occupies only ∼35% of the filament area for Hf-containing wires and ∼20% for Zr-containing wires. After heat treatments with a reaction step at 700 °C these values increase to 70–80% and ∼60%, respectively, with only a minor increase of the grain size. However, we observed a noticeable decrease in the layer J C for these HT. Magnetic measurements show that the high J C wires exhibit a point defect contribution from precipitates to the pinning force, which is missing in wires with depressed J C values. The higher heat treatment temperatures may have caused excessive coarsening of the oxide precipitates, to sizes unsuitable for flux pinning. Reaction heat treatment temperatures in the range of 650 °C to 700 °C and durations between 50 and 200 hours may provide a better compromise between the Nb 3 Sn layer thickness, its grain size and nanoparticle size.
|
|
| 3. |
- Rossi, L., et al.
(författare)
-
A European Collaboration to Investigate Superconducting Magnets for Next Generation Heavy Ion Therapy
- 2022
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 32:4
-
Tidskriftsartikel (refereegranskat)abstract
- Next generation ion therapy magnets both for gantry and for accelerator (synchrotron) are under investigation in a recently launched European collaboration that, in the frame of the European H2020 HITRIplus and I.FAST programmes, has obtained some funding for work packages on superconducting magnets. Design and technology of superconducting magnets will be developed for ion therapy synchrotron and -especially- gantry, taking as reference beams of 430 MeV/nucleon ions (C-ions) with 10(10) ions/pulse. The magnets are about 60-90 mm diameter, 4 to 5 T peak field with a field change of about 0.3 T/s and good field quality. The paper will illustrate the organization of the collaboration and the technical program. Various superconductor options (LTS, MgB2 or HTS) and different magnet shapes, like classical CosTheta or innovative Canted CosTheta (CCT), with curved multifunction (dipole and quadrupole), are under evaluation, CCT being the baseline. These studies should provide design inputs for a new superconducting gantry design for existing facilities and, on a longer time scale, for a brand-new hadron therapy centre to be placed in the South East Europe (SEEIIST project).
|
|
| 4. |
|
|
| 5. |
- Iagnemma, Karl, et al.
(författare)
-
Terramechanics Modeling of Mars Surface Exploration Rovers for Simulation and Parameter Estimation
- 2011
-
Ingår i: Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference--2011. - New York : ASME Press. - 9780791854815 ; , s. 805-812
-
Konferensbidrag (refereegranskat)abstract
- In 1997 and 2004, small wheeled robots ("rovers") landed on the surface of Mars to conduct scientific experiments focused on understanding the planet's climate history, surface geology, and potential for past or present life. Recently, the Mars Exploration Rover(MER)"Spirit"became deeply embedded in regolith at a site called Troy, ending its mission as a mobile science platform. The difficultyfaced in navigating mobile robots over sloped, rocky, and deformable terrain has highlighted the importance of developing accurate simulation tools for use in a predictive mobility modeling capacity. These simulation tools require accurate knowledge of terrain model parameters.This paperdescribes a terramechanics-based toolfor simulation of rover mobility. It also describes ongoing work toward estimation of terrain parameters of Mars soil. Copyright © 2011 by ASME.
|
|
| 6. |
|
|
| 7. |
- Senatore, C., et al.
(författare)
-
Direct shear behaviour of dry, granular soils for low normal stress with application to lightweight robotic vehicle modelling
- 2011
-
Ingår i: Proceedings of the International Symposium of the International Society of Terrain-Vehicle Systems, 2011. - Rwed Hook, NY : Curran Associates, Inc.. - 9781618395986 ; , s. 1-11
-
Konferensbidrag (refereegranskat)abstract
- Modelling of soil shearing behaviour under wheeled or tracked vehicles requires the knowledge of three soil properties: cohesion, angle of internal friction, and shear modulus. For lightweight robots it is necessary to characterize the soil for small normal stress (<15kPa) while most of the data collected in the literature regards higher stress testing conditions. Soil failure at low stress may diverge from Mohr-Coulomb envelope invalidating the fundamental assumptions behind classical terramechanics approach. Through the analysis of direct shearing performance of a dry, granular, soil, this paper address several issues related to off-road traction mechanics (not necessarily limited to low stress cases). We present an improved approach for shear modulus calculation that overcome the inaccuracies introduced by Wong method. We analyze the importance of density in modifying terrain response. Moreover, we show how erroneous estimation of soil cohesion and angle of internal friction may limit the applicability of Bekker/Wong theory to lightweight tracked vehicles.
|
|
| 8. |
- Senatore, C., et al.
(författare)
-
Investigation of Stress and Failure in Granular Soils For Lightweight Robotic Vehicle Applications
- 2012
-
Ingår i: Proceedings of the 2012 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS). ; , s. 1-12
-
Konferensbidrag (refereegranskat)abstract
- This paper describes novel experimental methods aimed at understanding the fundamental phenomena governing the motion of lightweight vehicles on dry, granular soils. A single-wheel test rig is used to empirically investigate wheel motion under controlled wheel slip and loading conditions on sandy, dry soil. Test conditions can be designed to replicate typical field scenarios for lightweight robots, while key operational parameters such as drawbar force, torque, and sinkage are measured. This test rig enables imposition of velocities, or application of loads, to interchangeable running gears within a confined soil bin of dimensions 1.5 m long, 0.7 m wide, and 0.4 m deep. This allows testing of small-scale wheels, tracks, and cone or plate penetrators. Aside from standard wheel experiments (i.e., measurements of drawbar force, applied torque, and sinkage during controlled slip runs) two additional experimental methodologies have been developed. The first relies on high-speed imaging of the wheel-soil interface and the use of particle image velocimetry (PIV) to measure micro-scale terrain kinematics. The second experimental methodology consists of a custom force sensor array located at the wheel-terrain interface. The sensors allow explicit measurement of normal and shear forces (and, therefore, estimation of normal and shear stresses) at numerous discrete points along the wheel-soil interface. Experimental measurements gathered by these test methodologies are to be compared against well-established semi-empirical models, to validate and understand limitations of the models and propose improvements.
|
|
| 9. |
- Trease, B., et al.
(författare)
-
Dynamic Modeling And Soil Mechanics For Path Planning Of Mars Exploration Rovers
- 2011
-
Ingår i: Proceedings of the ASME International Design Engineering Technical Conference. - New York : ASME Press. - 9780791854839 ; , s. 755-765
-
Konferensbidrag (refereegranskat)abstract
- To help minimize risk of high sinkage and slippage during drives and to better understand soil properties and rover terramechanics from drive data, a multidisciplinary team was formed under the Mars Exploration Rover (MER) project to develop and utilize dynamic computer-based models for rover drives over realistic terrains. The resulting tool, named ARTEMIS (Adams-based Rover Terramechanics and Mobility Interaction Simulator), consists of the dynamic model, a library of terramechanics subroutines, and the high-resolution digital elevation maps of the Mars surface. A 200-element model of the rovers was developed and validated for drop tests before launch, using MSC-Adams dynamic modeling software. Newly modeled terrain-rover interactions include the rut-formation effect of deformable soils, using the classical Bekker-Wong implementation of compaction resistances and bull-dozing effects. The paper presents the details and implementation of the model with two case studies based on actual MER telemetry data. In its final form, ARTEMIS will be used in a predictive manner to assess terrain navigability and will become part of the overall effort in path planning and navigation for both Martian and lunar rovers. Copyright © 2011 by ASME.
|
|
