Uncertainty assessment for the Bayesian updating process of concrete strength properties

Reassessment of infrastructure buildings has become an essential approach to deal with increasing traffic loads on ageing infrastructure buildings and to verify the service-life of those structures. Good estimation of the actual material properties is highly relevant for reliable structural reassessment. Although this holds for all building materials, the importance of good parameter estimation is of special importance for concrete structures, where the strength properties show relatively high variation and where the nominal strength properties tend to be too conservative. Modern design guidelines allow to make use of scientific methods such as Bayesian Updating of material properties to enable a more realistic consideration of the actual material properties in the reassessment of existing structures. However, guidelines for application and experience with those methods are not yet reported much or are rather vague [1]. The presented study focuses on the effect of the Bayesian Updating process for material parameters with special emphasis on the number and sampling location of test specimens as well as on the accuracy and confidence in the obtained posterior distribution, since sampling also includes a certain margin of uncertainty. The investigation on the methodological potential and on the uncertainty margin in the updating process in this contribution uses a batch of 14 test results on the concrete compressive strength obtained from drill cores along with the inherent measurement uncertainties from the testing procedure. After a short review of Bayes’ Theorem, the Markov Chain Monte Carlo Method (MCMC) and the bootstrap methodology, all combinations of subsamples of size 1, 3 and 5 specimens were built and provided to the Bayes’ updating procedure via MCMC to determine the posterior distributions. The series of obtained posterior distributions for a certain subsample was used to determine the uncertainty in the Bayesian Updating process by evaluation of the scatter in the expected value, the standard deviation and the 5 %-quantile of the updated distribution. The simulations show the importance of an adequate sample size and quantify the uncertainties arising from the limited number of observations

A Flight Simulator Study to Evaluate Manual Flying Skills of Airline Pilots

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.This paper reports an experimental study with the objective to assess pilots’ raw-data-based flight performance which is affected by long-term practice and structured training. Fifty-seven airline pilots with different levels of aviation experience scheduled on an Airbus fleet, representing contrary levels of practice and training, had to fly a simulated 45 minutes approach and landing scenario while flight performance data were objectively recorded. The level of practice and training was found to have a significant influence on manual flying skills. Pilots with low levels of practice and training showed a large variance in manual flight performance; pilots with high levels of practice and training demonstrated high and homogenous performance

Validitätsbedingungen thermozeptiver Maße in der Diagnostik der diabetischen Neuropathie kleiner Nervenfasern

Die Zuverlässigkeit der Thermästhesie in der Diagnostik der SNP (small fibre neuropathy) wurde mehrfach gezeigt. Über die Validität des Verfahrens beim Diabetes mellitus ist noch wenig bekannt. In der vorliegenden Studie wurden mehrere Validitätsaspekte untersucht, insbesondere die Einheitlichkeit des Merkmals "Thermosensibilität" bei Gesunden und Patienten, der Zusammenhang mit anderen Neuropathie-Indikatoren, die diagnostische Sensitivität/Spezifität und die Abhängigkeit von akuter Stoffwechsellage und Testprozedur. Hierzu wurden die Kalt-, Warm- und Hitzeschmerz-Schwellen bei 139 Typ-I-Diabetikern und 88 Kontrollpersonen an Hand und Fuß verglichen. Ein Teil der Diabetespatienten wurde nach verbesserter Blutzuckereinstellung erneut untersucht. Zusätzlich wurden Vibrationsschwellen und Herzfrequenzvariabilität bestimmt. Wichtige Ergebnisse waren: (1) Reliabilität und Stabilität thermozeptiver Schwellen von Patienten und Kontrollpersonen unterschieden sich nicht. (2) Die Korrelationen zwischen den verschiedenen Schwellen und Messorten ergaben eine relative Unabhängigkeit der Hitzeschmerzsensibilität von den Warm-/Kaltschwellen bei den Gesunden, während sie bei den Diabetikern am Fuß enger mit ihnen zusammenhing. Dies könnte ein Effekt der SNP sein, die die längeren dünnen Fasern gleichermaßen trifft. (3) Vibrationsschwellen und Herzfrequenzvariabilität korrelierten nur mäßig mit der Thermosensibilität. (4) Die Kalt- und Warmschwellen am Fuß waren bei den Diabetespatienten am stärksten verändert und von der Erkrankungsdauer abhängig. (5) Die diagnostische Sensitivität der kombinierten Thermästhesiemaße für die Trennung von Diabetespatienten (unausgelesen bezüglich SNP) und Kontrollpersonen betrug 57 Prozent bei einer Spezifität von 5 Prozent. (6) Aktuelle Stoffwechsellage und Prozedurparameter (Reizserienlänge, Reizverzögerung) beeinflussten die thermozeptiven Schwellen und müssen standardisiert werden

The Small Heat Shock Protein Hsp27 Affects Assembly Dynamics and Structure of Keratin Intermediate Filament Networks

AbstractThe mechanical properties of living cells are essential for many processes. They are defined by the cytoskeleton, a composite network of protein fibers. Thus, the precise control of its architecture is of paramount importance. Our knowledge about the molecular and physical mechanisms defining the network structure remains scarce, especially for the intermediate filament cytoskeleton. Here, we investigate the effect of small heat shock proteins on the keratin 8/18 intermediate filament cytoskeleton using a well-controlled model system of reconstituted keratin networks. We demonstrate that Hsp27 severely alters the structure of such networks by changing their assembly dynamics. Furthermore, the C-terminal tail domain of keratin 8 is shown to be essential for this effect. Combining results from fluorescence and electron microscopy with data from analytical ultracentrifugation reveals the crucial role of kinetic trapping in keratin network formation

Tunable Cooperativity in Coupled Spin--Cavity Systems

We experimentally study the tunability of the cooperativity in coupled spin--cavity systems by changing the magnetic state of the spin system via an external control parameter. As model system, we use the skyrmion host material Cu$_2$OSeO$_3$ coupled to a microwave cavity resonator. In the different magnetic phases we measure a dispersive coupling between the resonator and the magnon modes and model our results by using the input--output formalism. Our results show a strong tunability of the normalized coupling rate by magnetic field, allowing us to change the magnon--photon cooperativity from 1 to 60 at the phase boundaries of the skyrmion lattice state

Downregulation of the Hsp90 System Causes Defects in Muscle Cells of Caenorhabditis Elegans

The ATP-dependent molecular chaperone Hsp90 is required for the activation of a variety of client proteins involved in various cellular processes. Despite the abundance of known client proteins, functions of Hsp90 in the organismal context are not fully explored. In Caenorhabditis elegans, Hsp90 (DAF-21) has been implicated in the regulation of the stress-resistant dauer state, in chemosensing and in gonad formation. In a C. elegans strain carrying a DAF-21 mutation with a lower ATP turnover, we observed motility defects. Similarly, a reduction of DAF-21 levels in wild type nematodes leads to reduced motility and induction of the muscular stress response. Furthermore, aggregates of the myosin MYO-3 are visible in muscle cells, if DAF-21 is depleted, implying a role of Hsp90 in the maintenance of muscle cell functionality. Similar defects can also be observed upon knockdown of the Hsp90-cochaperone UNC-45. In life nematodes YFP-DAF-21 localizes to the I-band and the M-line of the muscular ultrastructure, but the protein is not stably attached there. The Hsp90-cofactor UNC-45-CFP contrarily can be found in all bands of the nematode muscle ultrastructure and stably associates with the UNC-54 containing A-band. Thus, despite the physical interaction between DAF-21 and UNC-45, apparently the two proteins are not always localized to the same muscular structures. While UNC-45 can stably bind to myofilaments in the muscular ultrastructure, Hsp90 (DAF-21) appears to participate in the maintenance of muscle structures as a transiently associated diffusible factor

Flying the Needles: Flight Deck Automation Erodes Fine-Motor Flying Skills Among Airline Pilots

Objective: The aim of this study was to evaluate the influence of practice and training on fine-motor flying skills during a manual instrument landing system (ILS) approach. Background: There is an ongoing debate that manual flying skills of long-haul crews suffer from a lack of flight practice due to conducting only a few flights per month and the intensive use of automation. However, objective evidence is rare. Method: One hundred twenty-six randomly selected airline pilots had to perform a manual flight scenario with a raw data precision approach. Pilots were assigned to four equal groups according to their level of practice and training by fleet (short-haul, longhaul) and rank (first officer, captain). Results: Average ILS deviation scores differed significantly in relation to the group assignments. The strongest predictor variable was fleet, indicating degraded performance among long-haul pilots. Conclusion: Manual flying skills are subject to erosion due to a lack of practice on long-haul fleets: All results support the conclusion that recent flight practice is a significantly stronger predictor for fine-motor flying performance than the time period since flight school or even the total or type-specific flight experience. Application: Long-haul crews have to be supported in a timely manner by adequate training tailored to address manual skills or by operational provisions like mixed-fleet flying or more frequent transitions between short-haul and long-haul operation

Pilot Decision Making: Modeling Choices in Go-Around Situations

Pilot decision making is highly influenced by cockpit information displays. Decision quality could benefit from knowledge of temporal and individual influences on decision making under time pressure that suggests leverage points for cockpit or process design. In a recent flight simulator experiment, airline pilots were presented a realistic landing scenario. During the approach phase, instruments indicated weather conditions suggesting a go-around decision to be taken. The alternative decision consists of landing in spite of illegitimate strong tailwind. Gaze tracking analysis identified, whether relevant display information was picked up by the pilots. The time between checking the aircraft’s wind indicator and the moment of decision was taken as predictor of choice to go-around. Modeling of pilots’ choice behavior shows strong influences of the predictor analyzed. A comparison of long-haul captains and short-haul first officers shows dependency of decision-behavior on level of practice and training

Pilots’ Willingness to Report Aviation Incidents

This paper reports results from a survey-based study among eighty-six airline pilots investigating their willingness to report safety-relevant events and incidents. Pilots have been asked to report how many events they have experienced in thirty-five different contextual areas and how often they have reported these cases. Thus, underreporting rates, respectively dark figures, were calculated and listed. These results and the willingness to report are discussed within an aviation operation’s background. Most of these surveyed underreporting rates are very high, which means a substantial source of uncertainty in airlines’ safety reporting databases, and thus for airlines’ safety management systems