Time-Dependent Reliability of Aging Structures: Overview of Assessment Methods

Reliability assessment of engineered structures is a powerful and useful concept to estimate the structural capacity of withstanding hazardous events during their service lives. Taking into account the time variation of both structural resistance and the external load processes, the structural safety level is dependent on the duration of service period of interest, due to the accumulation of hazards by exposure in time. This paper presents an overview on the nonempirical assessment methods for time-dependent reliability of deteriorating structures. Generally, these methods can be classified into two types, namely simulation-based and analytical methods. The former is usually brute, and is especially suitable for solving high-dimensional reliability problems. Conversely, analytical solutions may improve the calculation efficiency significantly, and offer insights into the reliability problem that otherwise could be difficult to achieve through Monte Carlo simulation. Both the simulation-based and analytical methods will be reviewed in this paper. Furthermore, the application of time-dependent reliability methods in practical engineering is discussed. Recommendations for future research efforts are also presented

Evolutionary genomics : statistical and computational methods

This open access book addresses the challenge of analyzing and understanding the evolutionary dynamics of complex biological systems at the genomic level, and elaborates on some promising strategies that would bring us closer to uncovering of the vital relationships between genotype and phenotype. After a few educational primers, the book continues with sections on sequence homology and alignment, phylogenetic methods to study genome evolution, methodologies for evaluating selective pressures on genomic sequences as well as genomic evolution in light of protein domain architecture and transposable elements, population genomics and other omics, and discussions of current bottlenecks in handling and analyzing genomic data. Written for the highly successful Methods in Molecular Biology series, chapters include the kind of detail and expert implementation advice that lead to the best results. Authoritative and comprehensive, Evolutionary Genomics: Statistical and Computational Methods, Second Edition aims to serve both novices in biology with strong statistics and computational skills, and molecular biologists with a good grasp of standard mathematical concepts, in moving this important field of study forward

Nicht Gauß’sche Zeitdomäne Vulnerabilitätsoptimierung von hohen Gebäuden unter dynamischer Windlast

The need to better understand the behavior of tall buildings with complex geometric forms and coupled dynamic systems constituted the first objective of this thesis. The other was the development of automatic design procedures that guarantee both reliability and optimality. The first stage of this work involved wind tunnel tests using simultaneously measured pressure taps on two tall building models characterized by their geometric form. These were used to estimate the forcing functions of two equivalent dynamic systems characterized by their coupled and uncoupled dynamic nature. A complete characterization of the dynamic response was then carried out. In particular the importance of considering higher modes when estimating the root mean square response of coupled systems with complex geometric forms was clearly shown. The assumption that the response of tall buildings is gaussian was then investigated. The results showed in an unequivocal fashion that this hypostasis is not true. Strong non-gaussian features were seen for both systems. This stage concluded with the demonstration of the important role played by the background response of coupled tall buildings with irregular profiles. The second stage of this thesis concerned two main points. Firstly the definition of appropriate models for the rigorous combination of the directional aerodynamics and wind climatological information was investigated. In particular a specific component-wise reliability model was developed. The resolution of this last yields rigorous estimates of the component response levels with specified Mean Recurrence Intervals. Secondly a Reliability-Based Design Optimization procedure for the member size optimization of tall frameworks subject to probabilistic constraints on the member capacity and inter-story drift ratios was developed. The procedure is based on the concept of decoupling the optimization loop from the reliability assessment therefore guaranteeing extreme efficiency.Das erste Ziel dieser Arbeit ist das Verhalten von hohen Gebäuden mit komplexen geometrischen Formen und gekoppelten dynamischen Systemen besser zu verstehen. Darauf aufbauend werden automatische Entwurfsmethoden entwickelt, die sowohl Zuverlässigkeit als auch Optimalität gewährleisten. Hierfür wurden in Windkanaltests durch simultane Druckmessbohrungen Drücke an zwei geometrisch verschiedenen Gebäudemodellen gemessen. Diese wurden verwendet, um die Kräftefunktionen zweier äquivalenter dynamischer Systeme zu schätzen, die sich durch ihre gekoppelte und entkoppelte dynamische Verhaltensweise auszeichnen. Dann wurde die dynamische Antwort vollständig charakterisiert. Hier wurde die Wichtigkeit aufgezeigt, bei der Schätzung der mittleren quadratischen Antwort von gekoppelten Systemen mit komplexer geometrischer Struktur auch höhere Schwingungsmodi mit einzubeziehen. Die Normalverteilungsannahme der Antwort wurde im Anschluss untersucht. Die Ergebnisse zeigten eindeutig, dass die Hypothese nicht gestützt werden kann. Stark nicht-normalverteilte Verhaltensweisen konnten für beide Systeme beobachtet werden. Schließlich wurde die zentrale Rolle der quasistatischen Antwort für hohe gekoppelte Gebäude mit irregulärem Profil demonstriert. Im zweiten Teil wurde nach der Definition geeigneter Modelle gesucht, die direktionelle Aerodynamik und klimatologische Windinformation kombinieren. Speziell wurde hierfür ein spezifisches komponentenweises Zuverlässigkeitsmodell entwickelt, das Schätzungen der Komponentenantworten mit speziellen mittleren Wiederkehrperioden liefert. Zum Anderen wurde eine zuverlässigkeitsbasierte Entwurfsmethode zur Optimierung von Elementgrößen großer Rahmenkonstruktionen entwickelt, die probabilistische Nebenbedingungen bezüglich der Elementkapazitäten und relativen Stockwerksverschiebung erfüllen müssen. Letztere basiert auf dem Konzept, die Optimierungsschleife von der Zuverlässigkeitsbemessung zu entkoppeln und somit eine hohe Effizienz zu garantieren

The role of visual adaptation in cichlid fish speciation

D. Shane Wright (1) , Ole Seehausen (2), Ton G.G. Groothuis (1), Martine E. Maan (1) (1) University of Groningen; GELIFES; EGDB(2) Department of Fish Ecology & Evolution, EAWAG Centre for Ecology, Evolution and Biogeochemistry, Kastanienbaum AND Institute of Ecology and Evolution, Aquatic Ecology, University of Bern.In less than 15,000 years, Lake Victoria cichlid fishes have radiated into as many as 500 different species. Ecological and sexual sel ection are thought to contribute to this ongoing speciation process, but genetic differentiation remains low. However, recent work in visual pigment genes, opsins, has shown more diversity. Unlike neighboring Lakes Malawi and Tanganyika, Lake Victoria is highly turbid, resulting in a long wavelength shift in the light spectrum with increasing depth, providing an environmental gradient for exploring divergent coevolution in sensory systems and colour signals via sensory drive. Pundamilia pundamila and Pundamilia nyererei are two sympatric species found at rocky islands across southern portions of Lake Victoria, differing in male colouration and the depth they reside. Previous work has shown species differentiation in colour discrimination, corresponding to divergent female preferences for conspecific male colouration. A mechanistic link between colour vision and preference would provide a rapid route to reproductive isolation between divergently adapting populations. This link is tested by experimental manip ulation of colour vision - raising both species and their hybrids under light conditions mimicking shallow and deep habitats. We quantify the expression of retinal opsins and test behaviours important for speciation: mate choice, habitat preference, and fo raging performance