5 research outputs found
Multi Scale Modelling of Friction Induced Vibrations at the Example of a Disc Brake System
Friction induced vibrations such as brake squealing, or juddering are still challenging topics in product engineering processes. So far, this topic was particularly relevant for the automobile industry because they were the main market for disc brake systems. However, since mobility habits change, disc brake system are more often to be found on bikes or e-scooters. In all of these systems, vibrations are excited in contacts on the micro scale but affect the user comfort and safety on the macro scale. Therefore, the aim of this cross-scale method is to analyze a system on a micro scale and to transfer the excitation mechanisms on a macro scale system. To address both scales, the current work presents a finite element model on the micro scale for the determination of the coefficient of friction, which is transferred to the macro scale and used in a multi-body simulation. Finally, a finite element modal analysis is conducted, which allowed us to evaluate the brake system behavior on base of an excitation
Multi Scale Modelling of Friction Induced Vibrations at the Example of a Disc Brake System
Friction induced vibrations such as brake squealing, or juddering are still challenging topics in product engineering processes. So far, this topic was particularly relevant for the automobile industry because they were the main market for disc brake systems. However, since mobility habits change, disc brake system are more often to be found on bikes or e-scooters. In all of these systems, vibrations are excited in contacts on the micro scale but affect the user comfort and safety on the macro scale. Therefore, the aim of this cross-scale method is to analyze a system on a micro scale and to transfer the excitation mechanisms on a macro scale system. To address both scales, the current work presents a finite element model on the micro scale for the determination of the coefficient of friction, which is transferred to the macro scale and used in a multi-body simulation. Finally, a finite element modal analysis is conducted, which allowed us to evaluate the brake system behavior on base of an excitation
Rapid clinical-scale propagation of mesenchymal stem cells using cultures initiated with immunoselected bone marrow CD105(+) cells
Current clinical protocols used for isolation and purification of
mesenchymal stem cells (MSC) are based on long-term cultures starting
with bone marrow (BM) mononuclear cells. Using a commercially available
immunoselection kit for enrichment of MSC, we investigated whether
culture of enriched BM-CD105(+) cells could provide an adequate number
of pure MSC in a short time for clinical use in the context of graft
versus host disease and graft failure/rejection. We isolated a mean of
5.4 x 10(5) +/- 0.9 x 10(5) CD105(+) cells from 10 small volume (10-25
ml) BM samples achieving an enrichment > 100-fold in MSC. Seeding 2 x
10(3) immunoselected cells/cm(2) we were able to produce 2.5 x 10(8) +/-
0.7 x 10(8) MSC from cultures with autologous serum enriched medium
within 3 weeks. Neither haematopoietic nor endothelial cells were
detectable even in the primary culture cell product. Expanded cells
fulfilled both phenotypic and functional current criteria for MSC; they
were CD29(+), CD90(+), CD73(+), CD105(+), CD45(-); they suppressed
allogeneic T-cell reaction in mixed lymphocyte cultures and retained in
vitro differentiation potential. Moreover, comparative genomic
hybridization analysis revealed chromosomal stability of the cultured
MSC. Our data indicate that adequate numbers of pure MSC suitable for
clinical applications can be generated within a short time using
enriched BM-CD105(+) cells