Mit TZI und Grüner Pädagogik lernen, mehrdeutig zu leben

Das Angebot, das der Autor entwickelt, eröffnet neue Perspektiven auf den Aspekt der Ambiguitätstoleranz und weist den Weg hin zu Lösungsansätzen, die mit BNE verbunden werden können. (DIPF/Orig.

Stereoscopic Measurements of Blade Deformation on a Shrouded Prop-Fan with Boundary Layer Ingestion by means of Image Pattern Correlation Technique

The material presented herein describes the implementation of optical blade deformation measurements based on the image pattern correlation technique (IPCT) in a stereoscopic imaging configuration applied to the first rotor of a counter-rotating shrouded fan stage (CRISPMulti) which has a diameter of about 1m. The correlation-based stereoscopic image analysis is discussed, as well as the difficulties with regard to the correlation-based stereomatching of two camera views for the highly curved blade surface involving pattern displacements up to 12% of the image height. Cross-correlation of speckle images at reference positionwith images of the displaced positions recovered the full 3c displacement field in the optically assessable area of the suction side. The three-dimensional displacements could be evaluated with triangulation errors below 0.5mm at blade tip velocities exceeding 250m/s (4830rpm). Comparative measurements using a third camera imaging the blade tip match the stereo IPCT results within deviations of 0.5mm for the axial component whereby the circumference component matches closely

TRANSMISSION OF SIGNALS FROM RATS RECEIVING HIGH DOSES OF MICROBEAM RADIATION TO CAGE MATES: AN INTER-MAMMAL BYSTANDER EFFECT

Inter-animal signaling from irradiated to non-irradiated organisms has been demonstrated for whole body irradiated mice and also for fish. The aim of the current study was to look at radiotherapy style limited exposure to part of the body using doses relevant in preclinical therapy. High dose homogenous field irradiation and the use of irradiation in the microbeam radiation therapy mode at the European Synchrotron Radiation Facility (ESRF) at Grenoble was tested by giving high doses to the right brain hemisphere of the rat. The right and left cerebral hemispheres and the urinary bladder were later removed to determine whether abscopal effects could be produced in the animals and also whether effects occurred in cage mates housed with them. The results show strong bystander signal production in the contra-lateral brain hemisphere and weaker effects in the distant bladder of the irradiated rats. Signal strength was similar or greater in each tissue in the cage mates housed for 48hrs with the irradiated rats. Our results support the hypothesis that proximity to an irradiated animal induces signalling changes in an unirradiated partner. If similar signaling occurs between humans, the results could have implications for caregivers and hospital staff treating radiotherapy patients

Experimental and Numerical Investigation of a Multi-Jet Impingement Cooling Configuration

In order to protect turbine blades from thermal damage or thermally induced aging, internal impingement cooling has found common use throughout engine design, both in stationary gas turbines as well as aircraft engines, but also finds applications in other areas requiring cooling. The present investigation is focused on a generic impingement cooling configuration that can be easily modelled with computational fluid dynamics (CFD) and at the same time can be studied in detail experimentally. The acquired experimental data can be directly used for the validation of the CFD simulations, ultimately allowing their application in more complex, realistic configurations where experimental investigations become prohibitively expensive or otherwise impossible. The investigated configuration consists of 9 evenly spaced jets of Reynolds number Re D = 10000 issuing into a square channel that is sealed at one end. The jets directly impinge on a uniformly heated target plate. With previous work on similar configurations well described in literature, the focus of the present contribution is to further exploit the potentials offered by snap-shot based and time-resolved measurements. The flow field within the channel is characterized with both conventional, snap-shot particle image velocimetry (PIV) as well as with high-speed, time-resolved PIV (TR-PIV) to, respectively, capture overview data as well as detailed information on temporally evolving flow structures. In addition, measurements of the unsteady surface temperature distribution on the heated channel wall are performed by means of a newly developed unsteady temperature sensitive paint (iTSP) measurement technique. The interaction of the turbulent jets with the wall and with its neighbors is studied in detail using correlation and spectral analysis as well as modal decomposition. Where possible, this is supplemented with corresponding data obtained from numerical modelling. None of the applied postprocessing methods reveal a significant interaction between jets suggesting that the jet-driven dynamics of heat transfer at the wall are restricted to their immediate vicinity which may simplify the requirements on numerical models of similar cooling configurations

Multi-Resolution, Time-Resolved PIV Measurements of a Decelerating Turbulent Boundary Layer near Separation

We report on measurements of the time-evolving velocity profile of a turbulent boundary layer subjected to a strong adverse pressure gradient (APG) at Reynolds numbers up to Re_theta ~55000 with an upstream friction Reynolds number exceeding Re_tau ~10000. Near the point of flow separation high-resolution imaging at high camera frame rates captured the time evolving velocity profile using the so-called "profile-PIV" technique in a nested imaging configuration of two cameras operating at different image magnifications. One camera used an image magnification better than unity to resolve the viscous scales directly at the wall while the remainder of the roughly 200 mm thick boundary layer is simultaneous captured by the second camera. In the APG the variance of the stream-wise velocity exhibits no "inner peak" commonly found in turbulent boundary layers without pressure gradient influence. Spectral analysis further shows that the peak energy within the boundary layer shifts away from the wall toward lower frequencies. The overlap between the simultaneously imaged areas allows to assess and, to first order, correct for the effect of spatial smoothing on statistical quantities, spectra and related quantities. A multi-frame cross-correlation algorithm was used to process the extensive database. In addition, a newly developed 2D-2C "Shake-The-Box" algorithm(STB) provided highly resolved particle tracking data beyond the reach of conventional PIV processing

Measurement of Aerodynamically Induced Blade Distortion on a Shrouded Counter-Rotating Prop-Fan

Blade deformation on a 1 m diameter composite fan rotor is measured simultaneously using stereoscopic image pattern correlation technique (IPCT) and blade-tip imaging. Absolute referencing of the blades is made possible by simultaneously tracking a marker on the hub using a fourth camera. Illumination is provided by microsecond pulses of high-power LEDs. Rise and fall time in the 100ns regime are achieved using a self-designed high-current drive circuit. A high-speed microcontroller provides accurate, speed-independent angular delays to enable phase-locked triggering of cameras and LEDs. Mean and RMS deformation of the blade are acquired for different aerodynamic loading conditions induced by imposing a non-uniformity upstream of the rotor aimed at mimicking boundary layer ingestion

Multi-resolution, time-resolved particle image velocimetry of a turbulent boundary layer approaching separation

The evolution and characteristics of turbulent boundary layers subjected to a positive pressure gradient are common in many flows of industrial relevance and appear, for instance, on the suction side of high-lift wing sections or turbomachinery blading. The pressure gradient is associated with a deceleration of the external flow which results in a thickening of the boundary layer and reduction of the wall friction. Under strong adverse pressure gradient conditions, the wall friction reduces to zero as the flow begins to separate. From a numerical perspective these flows are difficult to model with methods of engineering relevance, such as Reynolds averaged Navier-Stokes simulations (RANS) and motivate experiments such as the one presented here to provide relevant validation data

Modification of turbulence models for pressure-induced separation on smooth surfaces using the DLR VicToria experiment

A new experiment of a turbulent boundary layer flow at a large adverse pressure gradient at a high Reynolds number is presented. The strong pressure gradient leads to pressure-induced separation on the smooth surface of the geometry model with a thin separation bubble. The experiment was performed within the DLR internal project VicToria. First, the design of the test case, the set-up in the wind tunnel, and the measurement technique using both large-scale and high-magnification particle imaging and Lagrangian particle tracking are described. Then the experimental results for the mean velocity are described as the flow evolves downstream from the zero-pressure gradient region into the adverse pressure gradient region. From the measurement data a wall law for the mean velocity with a thin log-law region and a half-power law region above the log-law is observed in the adverse pressure gradient region. Then the differential Reynolds stress transport model SSG/LRR-omega is considered. Based on the observation that the length-scale equation is not consistent with the assumed wall laws at adverse-pressure gradient, a modification of the equation for the dissipation rate omega in the model is proposed, so that the modified model can predict the observed wall law at adverse-pressure gradient. Finally, the numerical results using the modified SSG/LRR-omega model are shown. The modification causes a reduction of the mean velocity in the inner part of the boundary layer at adverse-pressure gradients, making the modified model more susceptible for flow separation. The numerical predictions of the modified model are found to be in good agreement with the experimental data

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Decoherence and correlations in systems of trapped ultra-cold quantum gases

Since the achievement of Bose-Einstein condensation (BEC), the progress in matterwave physics has been immense. Among the many recent achievements there is the miniaturization of atom traps, demonstration of the superfluid-Mott insulator quantum-phase transition in optical lattices and the experimental demonstration of the BEC-BCS crossover in ultra-cold gases. Miniaturization of atom traps using micro-structured wires on a chip is one important step towards an on-chip cold-atom device. These so-called \atom chips" provide high control and versatility for trapping and guiding the ultra-cold atomic clouds. Particularly interesting is the use of these microchips to build mesoscopic devices for cold atomic clouds as, for instance, in the case of an atom-cloud interferometer. However, these mesoscopic devices require coherent transport of the atom cloud. A general method to treat decoherence due to current fluctuations in multi-wire atomchip traps is presented in the rst part of this thesis. The decoherence rate Γ shows a strong dependence on the distance between the wire and the atom cloud, r0, scaling as Γ ~ r-4 0 for a single atom waveguide. Considering an interferometer device, a strong dependence of the decoherence rate on the trap geometry is found. Studying many-body eects in ultra-cold quantum gases is another important research eld. Experiments using ultra-cold quantum gases in optical lattices have demonstrated the superuid-Mott insulator quantum phase transition and manybody entanglement. Optical lattices are based on a periodic modulation of the light intensity, generated by retro-reected laser beams. Correlations of the atomic cloud between dierent lattice sites of the optical lattice play a central role in these manybody experiments. The dierent phases of the superuid-Mott insulator system can be characterized by the dierent behavior of the inter-lattice site correlations. There are several numerical methods such as Quantum Monte Carlo (QMC) simulations, Density Matrix Renormalization Group (DMRG) simulations, exact-diagonalization, or the Gutzwiller ansatz, to investigate the dynamics of an ultra-cold gas in an optical lattice theoretically. The Gutzwiller method, corresponding to the mean-eld solution, allows for the treatment of large lattice sizes. Mean-eld approaches have proven to be very useful to describe many-body physics. However, diculties arise in the correct description of the behavior of the decay of inter-lattice site correlations. Based on the Gutzwiller approach, we have developed a method which allows the successive inclusion of inter-lattice site correlations. Comparing the results for the particle-number uctuations and the correlation function obtained from pure Gutzwiller calculations, to calculations which perturbatively include short-range correlations and calculations using \quasi-exact methods", showed a considerable improvement relative to the pure Gutzwiller results due to the inclusion of short-range correlations. Many-body eects do not only arise in periodic potentials, but become increasingly important at ultra-low temperatures. The formation of Bose-Einstein condensates requires an overlap of the atom wavefunctions and, hence, the formation of a single condensate wavefunction. Another example of a many-body state is the superuid-BCS state, commonly used as a description of superconductivity. Here, fermions in dierent hyperne states form Cooper pairs. Experiments with ultracold quantum gases enable a variation of the interparticle interaction, e.g. , by using a Feshbach resonance. Using Feshbach resonances to tune the interaction strength has enabled the experimental observation of the crossover from a superuid-BCS state to a Bose-Einstein condensate of molecules. A useful way to characterize the dierent states of ultra-cold quantum gases is to investigate the particle-number uctuations. In this thesis we suggest to divide the atomic cloud into bins and consider the atom-number uctuations in these bins. We calculate the full counting statistics for dierent physical systems of ultra-cold gases (e.g. bosonic gases, fermionic gases, and spin mixtures). In particular, we consider the BCS-state as a rst trial example to show that there is a strong variation in the particle-number statistics at the crossover from a superuid-BCS state to a Bose-Einstein condensate of molecules