Analysis of running unlubricated friction pairings under permanent slip with an emphasis on advanced ceramic-steel pairings

Running clutches under permanent slip offers multiple applications regarding vibration damping or torque distribution in powertrains, for instance. Advanced engineering ceramics show specific benefits in wear behaviour and thermal resistance and are therefore representing an interesting chance for running unlubricated clutches under permanent slip conditions, as well. The emphasis of this analysis is the characterization of the tribological behaviour of the non-oxide ceramic/steel friction pairing SSiC/C45E regarding friction coefficient and wear. As to influencing factors, the sliding speed and contact pressure between the friction surfaces, as well as the specific energy dissipation are varied and analysed. The analysis results of running advanced engineering ceramics under permanent slip are very promising concerning system based friction coefficient level and stability as well as wear behaviour

Split Analysis Methods and Parametric Bootstrapping in Molecular Phylogenetics : Taking a closer look at model adequacy

Even though the size of datasets in molecular analyses increased rapidly during the last years, undetected systematic errors as well as unsolved problems concerning the evaluation of data quality and adequate substitution model selection still persist. This not only hampers the correct analysis of these datasets but leads to undetectable effects in phylogenetic tree reconstruction. Model-based tree reconstruction methods like maximum likelihood estimation and Bayesian inference have become the methods of choice for reconstruction of phylogenetic trees. Although maximum likelihood methods are known to be consistent if all necessary conditions are met, it depends strongly on the quality of the multiple sequence alignment and the ability of the chosen evolutionary model to reflect the underlying historical processes. This thesis addresses the assessment of model adequacy of estimated evolutionary models to multiple sequence alignments in the light of parametric bootstrapping and aims to find new methods for detection of model misspecifications with the help of split analyses. The second chapter focuses on the influence of the number of gamma rate categories used in modelling among-site rate variation when trying to assess model adequacy using an absolute goodness-of-fit test. The analyses of simulated alignments show that the Goldmann-Cox test rejects models which were only approximated by four discrete gamma rate categories for various tree shapes and branch length setups, if they were simulated with a continuous gamma distribution. Increasing the number of discrete rate categories leads to an acceptance of model adequacy for stationary datasets and a correct detection of non-stationarity and inhomogenetity in simulated data. The results illustrate that the application of the proposed Goldmann-Cox test to evaluate model adequacy might be too strict and rigorous with empirical data, in particular for large phylogenomic datasets. Approaches such as the Goldman-Cox test evaluate the absolute fit of data and model but, do not deliver a deeper insight into the structure of the misfit. The third chapter presents the visualisation of overrepresented splits within splits graphs, which provides a good tool for gaining an overview of possible patterns and contradictory signal or noise within datasets. The analysis of these split residuals, observed by comparison to parametric bootstrap datasets based on the estimated models can help to gain a deeper insight into model adequacy. Highly overrepresented splits can give hints whether heterotachy applies or non symmetric substitution processes. The fourth chapter aims to define a new split weighting scheme by formalising aspects like 'contrast of character states' or 'character state homogeneity' within split subsets. Splits which are detected by the proposed SAMS (Splits Analysis MethodS) algorithm are re-evaluated for a more objective and formal split weighting. A comparison of the published and the new approach showed that the developed weighting scheme delivers reasonable results but needs further improvement. The development of a new GUI offers a much more capable tool to perform a split analysis and visualise the results. The shape of a visualised split spectra can indicate, whether a dataset delivers a clear split signal or if there is a lot of noise present

Moralische Erzählung und anthropologische Fallgeschichte

Sowohl Schubart als auch Lenz beziehen sich in ihren Erzählungen auf das Vorbild Marmontels. Sie verbinden Familien- mit Erziehungsthemen und nähern die moralische Erzählung der anthropologischen Fallgeschichte an. Während Schubart, geleitet von kulturpatriotischen Erwägungen, eine Eingemeindung des Genres anstrebt, setzt Lenz dem Eudaimonismus Marmontels eine komplexe anthropologische Versuchsanordnung entgegen, die den Erziehungsoptimismus der Aufklärung konterkariert und zugleich das Genre hin zu einer Metareflexion der Aufklärung transformiert.Schubart et Lenz font tous deux référence au modèle de Marmontel. Dans leurs contes, ils combinent des thèmes familiaux avec des sujets éducatifs et rapprochent le conte moral de l’histoire anthropologique. Alors que Schubart, guidé par des considérations patriotiques culturelles, s’efforce de germaniser le genre, Lenz confronte l’eudémonisme de Marmontel à un dispositif expérimental anthropologique complexe qui contrecarre l’optimisme éducatif des Lumières et transforme en même temps le genre vers une métaréflexion des Lumières.Both Schubart and Lenz refer to Marmontel’s model. In their tales, they combine family themes with educational topics and bring the moral narrative closer to the anthropological case history. While Schubart, guided by cultural patriotic considerations, strives to ‚germanise‘ the genre, Lenz contrasts Marmontel’s eudaimonism with a complex anthropological experimental arrangement that counteracts the educational optimism of the Enlightenment and at the same time transforms the genre towards a meta-reflection of the Enlightenment

Einfluss der Mikrostruktur auf das Ermüdungsverhalten einkristalliner Nickelbasis-Superlegierungen bei Hochtemperatur

In dieser Arbeit wird der Einfluss von mikrostrukturellen Defekten und Inhomogenitäten auf das Ermüdungsverhalten einer einkristallinen Nickelbasis-Superlegierung bei Hochtemperatur untersucht. Ermöglicht wird dies durch eine miniaturisierte Versuchstechnik, die im Rahmen dieser Arbeit entwickelt und erfolgreich erprobt wurde. Es wurden Low Cycle Fatigue Versuche (lastgesteuert, T=950°C, R≈0,6) an drei Materialvarianten mit verschiedenen Defektgrößen und -verteilungen durchgeführt. Bei entlang der -Richtung orientierten Proben entstehen Risse an Defekten, wie z.B. Erstarrungsporen. Die Porenanordnung in Bezug zur Lastrichtung hat bei äquivalenter kristallographischer Orientierung und gleichem Porenvolumen einen Einfluss auf die Lebensdauer. Bei vergleichbaren Porenvolumengehalten führen kleinere Poren zu einer längeren Lebensdauer als große Poren. Proben, in denen Porengehalt und -größe durch heiß-isostatisches Pressen reduziert wurden, zeigen die längste Lebensdauer

Changes in prescribed medicines in older patients with multimorbidity and polypharmacy in general practice

Background: Treatment complexity rises in line with the number of drugs, single doses, and administration methods, thereby threatening patient adherence. Patients with multimorbidity often need flexible, individualised treatment regimens, but alterations during the course of treatment may further increase complexity. The objective of our study was to explore medication changes in older patients with multimorbidity and polypharmacy in general practice. Methods: We retrospectively analysed data from the cluster-randomised PRIMUM trial (PRIoritisation of MUltimedication in Multimorbidity) conducted in 72 general practices. We developed an algorithm for active pharmaceutical ingredients (API), strength, dosage, and administration method to assess changes in physician-reported medication data during two intervals (baseline to six-months: ∆1; six- to nine-months: ∆2), analysed them descriptively at prescription and patient levels, and checked for intervention effects. Results: Of 502 patients (median age 72 years, 52% female), 464 completed the study. Changes occurred in 98.6% of patients (changes were 19% more likely in the intervention group): API changes during ∆1 and ∆2 occurred in 414 (82.5%) and 338 (67.3%) of patients, dosage alterations in 372 (74.1%) and 296 (59.2%), and changes in API strength in 158 (31.5%) and 138 (27.5%) respectively. Administration method changed in 79 (16%) of patients in both ∆1 and ∆2. Simvastatin, metformin and aspirin were most frequently subject to alterations. Conclusion: Medication regimens in older patients with multimorbidity and polypharmacy changed frequently. These are mostly due to discontinuations and dosage alterations, followed by additions and restarts. These findings cast doubt on the effectiveness of cross-sectional assessments of medication and support longitudinal assessments where possible. Trial registration.: 1. Prospective registration: Trial registration number: NCT01171339 ; Name of registry: ClinicalTrials.gov; Date of registration: July 27, 2010; Date of enrolment of the first participant to the trial: August 12, 2010. 2. Peer reviewed trial registration: Trial registration number: ISRCTN99526053 ; Name of registry: Controlled Trials; Date of registration: August 31, 2010; Date of enrolment of the first participant to the trial: August 12, 2010

Capturing the Competing Influence of Thermal and Mechanical Loads on the Strain of Turbine Blade Coatings via High Energy X-rays

This paper presents findings of synchrotron diffraction measurements on tubular specimens with a thermal barrier coating (TBC) system applied by electron beam physical vapor deposition (EB-PVD), having a thermally grown oxide (TGO) layer due to aging in hot air. The diffraction measurements were in situ while applying a thermal cycle with high temperature holds at 1000 °C and varying internal air cooling mass flow and mechanical load. It was observed that, during high temperature holds at 1000 °C, the TGO strain approached zero if no mechanical load or internal cooling was applied. When applying a mechanical load, the TGO in-plane strain (e22) changed to tensile and the out of plane TGO strain (e11) became compressive. The addition of internal cooling induced a thermal gradient, yielding a competing effect, driving the e22 strain to compressive and e11 strain to tensile. Quantifying TGO strain variations in response to competing factors will provide a path to controlling the TGO strain, and further improving the lifetime assessment and durability design strategies for TBC systems

Impact of the re-envisioned academic library on interlibrary loan services : the case of the Department of Library Services, University of Pretoria

Years ago librarians had the monopoly on providing access to information for teaching, learning and research. With developments in information and communication technology, the internet and the rise of the network society, information is more freely available today and information consumers are not necessarily library users anymore. Yet, information needs of researchers and students at academic libraries did not become less, in fact, it became more sophisticated. Decreasing collection development budgets and limited resources put even more pressure on libraries to effectively and efficiently address these dynamic information needs of users. In order to adapt to all these challenges, the traditional role of librarians as custodians of owned information resources evolved into new opportunities for facilitating access to the information universe. Centrally to this re-envisioned landscape, is the interlibrary loans department, which has become one of the most valuable assets in directing library support services. This presentation will address current trends in the research and academic library environment, with special emphasis on the role and importance of interlibrary loans in providing information need support services. Based on a case study at the Jotello F Soga Library at the Faculty of Veterinary Science, University of Pretoria, the importance of collaboration as well as national and international networks will be highlighted. Quantitative and qualitative evidence will be provided to demonstrate how interlibrary loans contribute to a high standard of service delivery to researchers and other users. It will conclude with a brief discussion on the authors’ opinions on the impact of future directions in the research and academic library environments with special reference to the role and functions of interlibrary loans and how it will influence information need support in future.Presentation presented at the 18th Annual LIASA Conference : 'Re-envisioning the role of library and information services',Birchwood Conference Centre, Gauteng , October 2-6, 2017.ab201

Evaluating deformation behavior of a TBC-System during thermal gradient mechanical fatigue by means of high energy X-ray diffraction

Applications of TBC-systems involve complex thermal mechanical loading pattern including transient thermal gradients across the coated system, which result in multiaxial stresses and stress gradients affecting the damage behavior. In an ongoing research, starting more than 10 years ago, the authors developed laboratory test facilities for evaluating the damage behavior of TBC-systems for gas turbine blades in aeroengines under realistic thermal mechanical loading conditions [1]. Fatigue tests involving thermal gradients have been conducted and damage behavior in dependence of load pattern and pre heat treatment has been intensively investigated on TBC-systems comprising a partially yttria stabilized zirconia (YSZ) topcoat and a MCrAlY bond coat both applied by electron physical vapor deposition (EB-PVD) onto nickel based super alloys serving as substrate [2]. Numerical analyses by means of FE-calculations did provide hypotheses explaining the observed damage behavior [3], but even though the results are plausible they did depend on reasonable assumptions on materials properties since reliable data on the properties of the thin coating layers are still lacking, especially for high temperatures. High energy X-ray diffraction can provide the requested information since it is possible to achieve information on the local deformation processes in each layer with high spatial resolution, and short acquisition times allow for in situ investigation of time dependent deformation processes. A new test facility based on concepts after [1] for cyclic thermal loading of tubular specimens and applying a controlled thermal gradient across the coated specimen’s wall has been developed for implementation into an electro-mechanical test machine at the advanced photon source (APS) at Argonne National Laboratory. A precision positioning rig allows for exact µm-positioning of the entire test machine with respect to the focused X-ray beam, and X-ray diffraction patterns were taken using a 2D detector, giving accurate 360° lattice parameter data [4]. Tests have been performed with varying thermal and mechanical load schemata intending to determine material properties from the respective strain response. The beam energy was 65 keV, and throughout all experiments the beam scanned through the coating layers with a window and step size of 30 µm. Strain data were acquired in plane parallel to the specimen’s length axis and out of plane. Results of the strain data evaluation will be presented and discussed. Exemplary results are: - Elastic properties of the YSZ showed a gradient across the coating thickness reflecting the microstructure gradient of the YSZ resulting from the EB-PVD process. - The YSZ strain was – below the deposition temperature - in plane compressive and out of plane tensile, which is a consequence of (i) the higher thermal expansion coefficient of YSZ with respect to the substrate and (ii) the cylindrical specimen geometry with the YSZ at the outer surface. [1] M. Bartsch, G. Marci, K. Mull, C. Sick, Adv. Eng. Mater. (1999), 1(2), 127–9 [2] M. Bartsch, B. Baufeld, S. Dalkilic, L. Chernova, M. Heinzelmann, Int. J. Fatigue (2008) 30, 211–8 [3] M. T. Hernandez, A. M. Karlsson, M. Bartsch, Surf. Coat. Technol. (2009) 203, 3549–58 [4] S.F. Siddiqui, K. Knipe, A. Manero, C. Meid, J. Wischek, J. Okasinski, J. Almer, A.M. Karlsson, M. Bartsch, S. Raghavan, Review of Scientific Instruments (2013) 84, 08390