An Enhanced Tire Model for Dynamic Simulation based on Geometrically Exact Shells

In the present work, a tire model is derived based on geometrically exact shells. The discretization is done with the help of isoparametric quadrilateral finite elements. The interpolation is performed with bilinear Lagrangian polynomials for the midsurface as well as for the director field. As time stepping method for the resulting differential algebraic equation a backward differentiation formula is chosen. A multilayer material model for geometrically exact shells is introduced, to describe the anisotropic behavior of the tire material. To handle the interaction with a rigid road surface, a unilateral frictional contact formulation is introduced. Therein a special surface to surface contact element is developed, which rebuilds the shape of the tire

An energy-momentum consistent time integration scheme based on a mixed framework for non-linear electro-elastodynamics

The objective of the present work is the introduction of new mixed variational principles for EM time integrators in electromechanics, hence bridging the gap between the previous work presented by the authors in References [11] and [1], opening up the possibility to a variety of new Finite Element implementations

Treatment of Joint Prosthesis Infection in Accordance with Current Recommendations Improves Outcome

Background. Recently recommended treatment modalities for prosthetic joint infection (PJI) were evaluated. Methods. A retrospective cohort analysis of 68 patients with PJI of hip or knee who were treated from 1995 through 2004 was conducted at the University Hospital Bern (Bern, Switzerland). Results. A 2-stage exchange was the most frequent (75.0%) surgical strategy, followed by retention and/or debridement (17.6%), 1-stage exchange (5.9%), and resection arthroplasty or suppressive antimicrobial treatment (1.5%). The chosen strategy was in 88% agreement with the recommendations. Adherence was only 17% for retention and/or debridement and was 0% for 1-stage exchange. Most PJIs (84%) were treated with an adequate or partially adequate antimicrobial regimen. Recurrence-free survival was observed in 51.5% of PJI episodes after 24 months of follow-up. The risk of treatment failure was significantly higher for PJI treated with a surgical strategy other than that recommended (hazard ratio, 2.34; 95% confidence interval, 1.10-4.70; P=.01) and for PJIs treated with antibiotics not corresponding to recommendations (hazard ratio, 3.45; confidence interval, 1.50-7.60; P=.002). Other risk factors associated with lack of healing were a high infection score at the time of diagnosis (hazard ratio, 1.29; 95% confidence interval, 1.10-1.40; P<.001) and presence of a sinus tract (hazard ratio, 2.35; 95% confidence interval, 1.10-5.0; P=.02). Conclusions. Our study demonstrates the value of current treatment recommendations. Inappropriate choice of conservative surgical strategies (such as debridement and retention) and inadequate antibiotic treatment are associated with failur

Konzepte der Numerik endlicher Rotationen

Algorithmen zur Berechnung endlicher Rotation, die typischer Weise bei Finite Element Simulationen Anwendung finden, können in zwei allgemeine Kategorien unterteilt werden: Im Rahmen der ersten Kategorie werden iterative Rotationsfreiheitsgrade betrachtet, wohingegen der zweiten Kategorie totale Rotationsfreiheitsgrade zugrunde liegen. Diese Freiheitsgrade konnen auf drei unterschiedliche Konfigurationen bezogen werden: Den letzten Iterationsschritt, den letzten inkrementellen Lastschritt&nbsp; oder den unrotierten Ausgangszustand. Unabhänging von der gew¨ahlten Parametrisierung endlicher Rotationen&nbsp; weisen diese Formulierungen unterschiedliche numerische Eigenschaften in Bezug auf Robustheit und Stabilität sowie den erforderlichen zus ¨atzlichen Speicherplatzbedarf auf. Diese allgemein zu klassifizierenden Merkmale werden in diesem Beitrag diskutiert

Hydrogen production by chemical-looping reforming in a circulating fluidized bed reactor using Ni-based oxygen carriers

7 pages, 11 figures,.- Available online November 18, 2008.This work presents the experimental results obtained during auto-thermal chemical-looping reforming (CLR) in a 900 Wth circulating fluidized bed reactor under continuous operation using methane as fuel. Two oxygen carriers based on NiO and supported on γ-Al2O3 and α-Al2O3 were used during more than 50 h of operation with each oxygen carrier. During operation the effect of different operating variables, like fuel reactor temperature, H2O/CH4 molar ratio and solid circulation rate, on CH4 conversion and gas product distribution was analyzed. It was found that in all operating conditions CH4 conversion was very high (>98%) and the most important variable affecting to the gas product distribution was the solid circulation rate, that is, NiO/CH4 molar ratio. Similar gas product distribution was obtained working with both oxygen carriers although at different NiO/CH4 molar ratios. The oxygen carrier of NiO on α-Al2O3 needed lower NiO/CH4 molar ratio to reach the same gas product composition than the oxygen carrier of NiO on γ-Al2O3. Working at optimal operating conditions, 2.5 moles of H2 per mol of CH4 could be obtained in this process. During operation the oxygen carrier particles maintained their physical and chemical properties. These results suggest that these oxygen carriers could have a high durability, being suitable oxygen carriers for a CLR system. © 2008 Elsevier B.V. All rights reserved.This work was partially supported by the European Commission, under the 6th Framework Programme (CACHET Project, Contract no. 019972), and from the CCP2 (CO2 Capture Project), a partnership of BP, Chevron, Conoco-Phillips, Eni Technology, Norsk Hydro, Shell, Suncor, and Petrobras. M. Ortiz thanks Diputación General de Aragon for the F.P.I. fellowship.Peer Reviewe

Sintered alumina with low dielectric loss

Published versio

Observation of strong final-state effects in pi+ production in pp collisions at 400 MeV

Differential cross sections of the reactions $pp \to d\pi^+$ and $pp \to pn\pi^+$ have been measured at $T_p = 400$ MeV by detecting the charged ejectiles in the angular range $4^0 \leq \Theta_{Lab} \leq 21^\circ$. The deduced total cross sections agree well with those published previously for neighbouring energies. The invariant mass spectra are observed to be strongly affected by $\Delta$ production and $NN$ final-state interaction. The data are well described by Monte Carlo simulations including both these effects. The ratio of $pp \to pn\pi^+$ and $pp \to d\pi^+$ cross sections also compares favourably to a recent theoretical prediction which suggests a dominance of $np$-production in the relative $^3S_1$-state.Comment: 17 pages, 5 figure