Modelling of mass and heat transport in planar substrate type SOFCs

A mathematical model is presented that incorporates the mass transport by diffusion in the porous structure of thick substrate type solid oxide fuel cells (SOFCs). On the basis of the mean transport pore model a multidimensional study allows for an optimization of the structural parameters of the substrates with respect to cell performance. Next to the mass transport in the porous substrates the electrochemical kinetics, methane/steam reforming and shift reaction, and energy equations are integrated in the model and boundary as well as operation conditions can be varied. Two-dimensional simulations for both anode as well as cathode substrate type SOFC operating on partially prereformed methane are presented and discussed. (C) 2003 The Electrochemical Society

Good to excellent long-term survival of a single-design condylar constrained knee arthroplasty for primary and revision surgery

Purpose!#!The purpose of the study was to determine the long-term survivorship, functional outcomes of a single-design condylar constrained (CCK) TKA in primary and revision cases as well as to assess specific risk factors for failure. It was hypothesized that primary CCK TKA had a better survival than revision knees.!##!Methods!#!One hundred and forty three patients who underwent revision TKA (n = 119) or complex primary TKA (n = 24) using a single-design condylar constrained knee system (Genesis CCK, Smith & Nephew) performed at a single institution between 1999 and 2008 were retrospectively included. The median follow-up amounted to 11.8 years (IQR 10.3-14.4). Implant survivorship was analyzed using Kaplan-Meier survival estimates and multivariate Cox regression analysis to identify risk factors for failure. Function was determined using the Oxford Knee Score (OKS).!##!Results!#!The implant survival was 86.4% after five, 85.5% after ten and 79.8% at 15 years. A reduced implant survivorship was found in males (HR 5.16, p = 0.001), smokers (HR 6.53, p = 0.004) and in obese patients (HR 2.26, p = 0.095). Patients who underwent primary TKA had a higher revision-free implant survivorship compared to revision TKA at 15 years (100% vs. 76%, p = 0.036). The main cause for re-revision was infection in 10% of all revision TKA performed with the CCK design included, while no case was revised for instability. The median OKS was 39 (IQR 35-44) in 102 patients available for long-term functional outcome.!##!Conclusion!#!CCK implants are associated with excellent long-term survival when used in primary TKA; however, survival was worse when used during revision TKA. Males, smokers, obese patients and are at higher risk for revision. While instability and aseptic loosening were rare, infection remains a major concern.!##!Level of evidence!#!Level IV, retrospective observational study