1,651 research outputs found
A synchrotron computed tomography dataset for validation of longitudinal tensile failure models based on fibre break and cluster development
No full textWe performed in-situ tensile tests on two carbon fibre/epoxy composites with continuous scanning using synchrotron computed tomography (CT). Both composites were cross-ply laminates, and two specimens were tested for each composite. The voxel size was sufficiently small to recognize individual fibres and fibre breaks. For each test, 16-19 volumes were reconstructed, cropped down to the 0° plies and analysed to track fibre break and cluster development. This dataset provides the last CT volume before failure for each of the four specimens as well as the individual fibre break locations in all reconstructed volumes. These data are then plotted against predictions from six state-of-the-art strength models. The target is that these data become a benchmark for the development of new models, inspiring researchers to set up refined experiments and develop improved models
Fibre-direction strain measurement in a composite ply under quasi-static tensile loading using digital volume correlation and in situ synchrotron radiation computed tomography
No full textDigital Volume Correlation (DVC), in concert with in situ Synchrotron Radiation Computed Tomography (SRCT), has been applied to Carbon-Fibre Reinforced Polymers (CFRPs) under quasi-static tensile loading. DVC represents a relatively novel tool for quantifying full-field volumetric displacements and implicit strain fields. The highly anisotropic and somewhat regular/self-similar microstructures found in well-aligned unidirectional (UD) materials at high volume fractions are shown to be intrinsically challenging for DVC, especially along the fibre direction. To permit the application of DVC to displacement and/or strain measurements parallel to the fibre orientation, the matrix was doped with a sparse population of sub-micrometre barium titanate particles to act as displacement trackers (i.e. fiducial markers). For the novel materials systems we have developed, measurement noise is considered along with the spatial filtering intrinsic to DVC data processing. Compared to volume images acquired through Micro-focus Computed Tomography (μCT), hold-at-load artefacts are mitigated through scan times on the order of ∼seconds using SRCT, as opposed to ∼hours. Instances of individually fractured fibres evolving into clusters of breaks are presented, together with the associated strain redistribution (imaged at a voxel resolution of 0.65 μm). It is shown that the distance over which strain is recovered in the broken fibres not only increases with the applied force, but also with the number of broken fibres, delineating aspects of the load shedding phenomenon. The study demonstrates that unprecedented, mechanistically-consistent three-dimensional (3D) strain measurements may be made in relation to fibre failure events, that can be used to validate micromechanical models for predicting UD tensile failure. We believe this work presents the first application of DVC to the SRCT imaging of failure in CFRPs, achieving significantly higher resolution than reported previously within the literature.<br/
A novel particle-filled Carbon-Fibre Reinforced Polymer model composite tailored for the application of Digital Volume Correlation and Computed Tomography
No full textThis paper presents the development of novel Carbon-Fibre Reinforced Polymer (CFRP) laminates, tailored for the application of Digital Volume Correlation (DVC) and Computed Tomography (CT) to experimental mechanics analyses of these materials. Analogous to surface-based Digital Image Correlation (DIC), DVC is a relatively novel volumetric method that utilizes CT data to quantify internal three-dimensional (3D) displacements and implicit strain fields. The highly anisotropic and somewhat regular/self-similar microstructures found in well-aligned unidirectional (UD) materials at high fibre volume fractions are intrinsically challenging for DVC, especially along the fibre direction at microstructural length-scales on the order of a few fibre diameters. To permit the application of DVC to displacement and/or strain measurements parallel to the fibre orientation, the matrix was doped with a sparse population of sub-micrometre particles to act as displacement trackers (i.e. fiducial markers). Barium titanate particles (400 nm, ∼1.44 vol. %) were found to offer the most favourable compromise between contrast in CT images and the ability to obtain a homogeneous distribution in 3D space with sufficient particle compactness for local DVC analyses. This property combination was selected following an extensive Micro-focus Computed Tomography (µCT)-based qualitative assessment on a wide test matrix, that included 38 materials manufactured with a range of possible particle compositions, mean sizes and concentrations. By comparing the tensile behaviour of the particle-adapted material alongside its particle-free counterpart, we demonstrate through the application of in situ Synchrotron Radiation Computed Tomography (SRCT) that the macro- and micromechanical responses of the newly developed CFRP are consistent with standard production materials indicating its suitability as a model system for mechanistic investigations
Three dimensional flow structures in journal bearings
No full textThis paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.In general, the fluid flow in journal bearings can be described by the Navier-Stokes Equations and the conservation of mass. The application of the small gap criterion allows a simplification of these equations yielding the Reynolds Equation, which links the local gap size with the pressure gradient resulting in a powerful tool for the designing process of journal bearings. Typically, the Reynolds Equation is used in EHD-design software based on FE-methods, which is used to compute pressure distributions, forces, deformations and many more parameters needed for the selection of the right bearing geometry. However, there are regions in the journal bearing where the Reynolds Equation must fail, because either the small gap criterion or the Couette flow assumption is violated. There are pockets, grooves and holes, which are necessary to distribute the oil supply across the gap. Moreover, the oil feed represents a cross flow perpendicular to the circumferential main flow. In these regions three dimensional flow structures replace the
undisturbed Couette flow, which are strongly affected by vortices, but are non-turbulent due to the Re-scale. This work presents experimental data obtained from a cylinder apparatus with moderate gap sizes, which
features independently rotating cylinders and a cross flow through a hole in the sidewall. LDV-measurements of velocity profiles and visualization methods to animate the three dimensional nature of the
flow are presented. The experimental data are used to validate 3D-CFD calculations, which are expanded towards smaller gap sizes in the range of typical journal bearings in automotive applications
Bestimmung der Masse und Breite des W-Bosons im semileptonischen Zerfallskanal mit dem OPAL Detektor bei LEP
No full textDiese Arbeit ist eine Weiterentwicklung der beim OPAL-Experiment verwendeten
Faltungsmethode zur Bestimmung der Masse des geladenen Eichbosons der
schwachen Wechselwirkung. Die Methode wurde ausgeweitet auf eine
gleichzeitige Bestimmung der Masse Mw und der Zerfallsbreite Gw des W-Boson
genannten Eichbosons. Analysiert wurden dazu Daten, die mit dem
OPAL-Experiment in den Jahren 1997 bis 2000 aufgezeichnet wurden. Von den
möglichen Zerfällen der erzeugten W-Bosonpaare werden nur
semileptonische betrachtet, bei denen ein W-Boson hadronisch in ein
Quark-Antiquark-Paar zerfällt und das andere in ein geladenes Lepton und ein
Neutrino.
In der Faltungsmethode werden die aus der Detektorauflösung resultierenden
Fehler der einzelnen Ereignisse berücksichtigt. Dazu wird eine Funktion P(m)
für jedes Ereignis ermittelt, welche die Wahrscheinlichkeit angibt, daß die
produzierten W-Bosonen eine mittlere Masse m haben. Diese sogenannte
Ereigniswahrscheinlichkeitsdichte wird mit einer Physikfunktion
PF(m;Mw,Gw) gefaltet, die von den Parametern Masse Mw und Zerfallsbreite
Gw des W-Bosons abhängt. Sie beschreibt die Erzeugungswahrscheinlichkeit der
W-Bosonpaare unter Berücksichtigung von Photonabstrahlung im
Anfangszustand. Aus dieser Faltung erhält man eine von Mw und Gw abhängige
Ereignis-Likelihoodfunktion, die ein Wahrscheinlichkeitsmaß dafür ist, daß
dieses Ereignis von einem W-Boson mit den Parametern Mw und Gw herrührt.
Aus allen selektierten semileptonischen W-Bosonereignissen wird eine
Gesamt-Likelihood-Funktion L(Mw,Gw) berechnet. Durch Maximierung dieser
Funktion bezüglich Mw und Gw ist erstmals bei OPAL eine gleichzeitige
Bestimmung der Masse und Breite des W-Bosons möglich.
Mit einer integrierten Gesamtluminosität von 683.84 pb^-1, die in den Jahren
1997 bis 2000 bei Schwerpunktsenergien von 183 bis 208 GeV vom
OPAL-Experiment aufgezeichnet wurden, ergibt sich aus den semileptonischen
Zerfällen von W-Bosonpaaren ein Wert für die Masse Mw und Breite Gw des
W-Bosons zu:
Mw = 80.424 +- 0.077 GeV/c^2
Gw = 2.126 +- 0.130 GeV/c^2
Die gemessenen Parameter befinden sich in guter Übereinstimmung mit
den Vorhersagen des Standardmodells der Teilchenphysik
Standardized Oral Care Regimen
No full text-Purpose/goal statement: In medical surgical hospitalized patients, how does nursing staff education on the importance of a standardized oral care regimen in the prevention of non-ventilator hospital acquired pneumonia, compared to no oral care education, affect the documentation rates of oral care in a 23-day period? -Relevance to conference themes and objectives: Oral care is considered a routine part of daily care for patients in acute care settings. However, education and implementation of standardized oral care regimens can be lacking (Lounsbury & Munro, 2020). Additionally, documentation of oral care is often overlooked and omitted in the acute care environment (Meehan & McKenna, 2020). This is an issue for hospitalized adults and may lead to poor outcomes, such as non-ventilator hospital acquired pneumonia (Giuliano et al., 2021). Nursing staff should be educated about the importance of oral care and have standardized oral care regimens. Giuliano, K. K., Penoyer, D., Middleton, A., & Baker, D. (2021). Original research: Oral care as prevention for nonventilator hospital-acquired pneumonia a four-unit cluster randomized study. American Journal of Nursing, 121(6), 24-33. https://doi.org/10.1097/01.NAJ.0000753468.99321.93 Lounsbury, O. & Munro, S. (2020). Oral care for non-ventilator associated hospital-acquired pneumonia prophylaxis: Optimizing clinical outcomes and organizational effectiveness. Patient Safety, 2(4), 78-81. https://doi.org/10.33940/U.S.%20Department%20of%20Veterans%20Affairs Meehan, C. D. & McKenna, C. (2020). Preventing hospital acquired pneumonia implementing a fundamental nursing skills bundle can reduce risk. American Nurse Journal, 15(2). -Methods, Results, and Recommendations: Methods: A total of eleven nurses and patient care assistants on a medical-surgical floor in a Kentucky hospital attended a 10-minute face-to-face educational session about the importance of oral care in preventing non-ventilator hospital acquired pneumonia. The significance of having a standardized oral care regimen with patients brushing their teeth three times per day was also included. The documentation of oral care in the electronic charting system, which included brushing teeth with a toothbrush and toothpaste, was assessed for 23 days after the educational session. Results: Of the total 474 patients during the project implementation, 210 patients had oral care documented. A two proportions z-test was conducted to assess whether there was a significant difference between the proportions of oral care documentation rates before and after the oral care educational session. It showed that the results were statistically significant. Recommendations: An implication for nursing practice is to have a standardized oral care regimen with a pre-educational session on the importance of oral care in non-ventilated hospitalized patients. Having oral care completed twice per day may help increase compliance due to the nursing staff’s busy schedule. Furthermore, daily task reminders of completing and documenting oral care should be included in the electronic charting system to help with consistency
New design tools for lightweight aerospace structures
No full textThis paper presents two new design tools for lightweight aerospace structures. The first tool is the Tailored Fibre Placement (TFP) design tool TACO. It is used to optimize the fibre orientations of structures made of Carbon Fibre Reinforcement Plastics (CFRP). The optimization concept is explained and results are given for a horizontal tail plane connection beam of an aircraft. The second tool, iBuck, is a fast, semi-analytical local buckling and post-buckling tool for stiffened panels that are loaded in-plane. The panels are assumed to be representative for an aircraft fuselage and are stiffened in axial and circumferential direction. Results are presented for axially loaded panels and compared to FE-results
Ludwik Fleck: Denkstile und Tatsachen. Gesammelte Schriften und Zeugnisse
No full textDer polnische Mikrobiologe und Wissenschaftstheoretiker Ludwik Fleck gilt seit langem als Klassiker der Wissenschaftstheorie und erlebt derzeit eine Renaissance, die sich durch die verschiedenen Disziplinen zieht. Die neue kommentierte Studienausgabe trägt dem Rechnung und versammelt bekannte und unbekannte Texte Flecks – zum Teil erstmals in deutscher Übersetzung – sowie biographisches Material und Briefe. Dokumentiert wird die ganze Breite von Flecks Denken und Wirken, wodurch nicht zuletzt der politische Hintergrund seiner Wissenschaftstheorie und medizinischen Praxis sichtbar wird
The bare necessities? a comparative study of the material evidence for Roman medical practice in urban domestic and army spheres
No full textThe study of medicine in the Roman world is, in many areas, hampered by lack of evidence yet, despite this, valuable research has been done in the areas of urban domestic and army medicine. The aim of this thesis is not to reproduce that research but to examine the material evidence for medicine and medical practice used in it, in particular the instruments and buildings where medicine might have been practiced and, through comparison of the data, to see what similarities and differences there were between medicine in the domestic and army spheres. At the same time this data will be placed in context through an examination of the general levels of health in the ancient world and the status of doctors. In the domestic chapter we shall see that the evidence for the status of doctors is sketchy and confusing while the evidence for the health of people is drawn mainly from the skeletons found at Herculaneum. The examination of the instruments from the Naples museum and the provenance of those to which it could be assigned, will shed light on the types of medicine practiced and where doctors might have seen their patients. Throughout this chapter the argument looks forward to the comparison with army medicine in the following chapter. The evidence for health in the army comes mainly from literary sources and that for the status of doctors comes from inscriptions. It appears that doctors had ranks in the army with equivalent levels of pay as the soldiers. While there are fewer finds of instruments from forts, they raise some interesting points. The debate about valetudinaria is addressed and I argue that, while they existed, there is evidence to suggest that the buildings identified as valetudinaria were not in fact hospitals and that each case must be examined on its own merits. The conclusions are more numerous than might have been expected. There are obvious differences in levels of health between the army and the urban population but there are significant overlaps between doctors in the army and the domestic spheres. The instruments in the two spheres are the same in design with some surprising types turning up. The question of where medicine was practiced remains hazy with the conclusion that in the domestic sphere there is no definite evidence while in the army sphere the buildings identified as valetudinaria may not have been hospitals
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