M-sequenze based ultra-wideband radar and its application to crack detection in salt mines

Die vorliegende Dissertation beschreibt einen innovativen ultra-breitband (UWB)elektromagnetischen Sensor basierend auf einem Pseudo-Rauschverfahren.Der Sensor wurde für zerstörungsfreies Testen in zivilen Anwendungen entwickelt.Zerstörungsfreies Testen entwickelt sich zu einem immer wichtiger werdenden Bereich in Forschung und Entwicklung. Neben unzähligen weiteren Anwendungen und Technologien, besteht ein primäres Aufgabenfeld in der Überwachung und Untersuchung von Bauwerken und Baumaterialien durch berührungslose Messung aus der Ferne.Diese Arbeit konzentriert sich auf das Beispiel der Auflockerungszone im Salzgestein.Der Hintergrund und die Notwendigkeit, den Zustand der oberflächennahen Salzschichten in Salzminen kennen zu müssen, werden beleuchtet und die Messaufgabe anhand einfacher theoretischer Überlegungen beschrieben. Daraus werden die Anforderungen für geeignete UWB Sensoren abgeleitet. Die wichtigsten Eigenschaften sind eine sehr hohe Messband breite sowie eine sehr saubere Systemimpulsantwort frei von systematischen Gerätefehlern. Beide Eigenschaften sind notwendig, um die schwachen Rückstreuungen der Auflockerungen trotz der unvermeidlichen starken Oberflächenreflexion detektieren zu können.Da systematische Fehler bei UWB Geräten technisch nicht von vorne herein komplett vermeidbar sind, muss der Sensor eine Gerätekalibrierung erlauben, um solche Fehler möglichst gut zu unterdrücken.Aufgrund der genannten Anforderungen und den Nebenbedingungen der Messumgebung unter Tage, wurde aus den verschiedenen UWB-Technologien ein Prinzip ausgewählt, welches pseudozufällige Maximalfolgen als Anregungssignal benutzt. Das M-Sequenzkonzept dient als Ausgangpunkt für zahlreiche Weiterentwicklungen. Ein neues Sendemodul erweitert dabei die Messbandbreite auf 12~GHz. Die äquivalente Abtastrate wird um den Faktor vier auf 36~GHz erhöht, ohne den geringen Abtastjitter des ursprünglichen Konzepts zu vergrössern.Weiterhin wird die Umsetzung eines Zweitormesskopfes zur Erfassung von S-Parametern sowie einer automatische Kalibriereinheit beschrieben. Etablierte Kalibrierverfahren aus dem Bereich der Netzwerkanalyse werden kurz rekapituliert und die Adaption des 8-Term Verfahrens mit unbekanntem Transmissionsnormal für das M-Sequenzsystem beschrieben. Dabei werden Kennwerte vorgeschlagen, die dem Bediener unter Tage einfach erlauben, die Kalibrierqualität einzuschätzen und Hinweise auf mögliche Gerätefehler oder andere Probleme zu bekommen. Die Kalibriergenauigkeit des neuen Sensors im Labor wird mit der eines Netzwerkanalysators verglichen. Beide Geräte erreichen eine störungsfreie Dynamik von mehr als 60~dB in den Systemimpulsantworten für Reflexion und Transmission.Der neu entwickelte UWB Sensor wurde in zahlreichen Messungen in Salzminen in Deutschland getestet. Zwei Messbeispiele werden vorgestellt - ein sehr alter, kreisrunder Tunnel sowie ein ovaler Tunnelstumpf, welcher kurz vor den Messungen erst aufgefahren wurde. Messaufbauten und Datenverarbeitung werden beschrieben. Schließlich werden Schlussfolgerungen und Vorschläge für zukünftige Arbeiten mit dem neuen M-Sequenzsensor sowie der Messung von Auflockerungen im Salzgestein diskutiert.This dissertation describes an innovative ultra-wideband (UWB) electromagnetic sensor device based on a pseudo-noise principle developed in the context of non-destructive testing in civil engineering.Non-destructive testing is becoming a more and more important fieldfor researchers and engineers alike. Besides the vast field of possibleapplications and testing technologies, a prime and therefore typical topic is the inspection and monitoringof constructions and materials by means of contactless remote sensing techniques.This work focuses on one example the assessment of the disaggregation zone in salt rock tunnels.The background and relevance of knowing the state of salt rock layers near a tunnel's surface are explainedand simple theoretical considerations for requirements of suitable UWB sensor devices are shown. The most important sensor parameters are a very large measurement bandwidth and a very clean impulse response. The latterparameter translates into the mandatory application of calibration techniques to remove systematic errors of the sensor system itself. This enables detection of weak scattering responses from near-surface disaggregation despite the presence of a strong surface reflection.According to the mentioned requirements and other side conditions in salt mine environments an UWB sensor principlebased on pseudo-noise stimuli namely M-Sequences is selected as a starting point for system development. A newtransmitter frontend for extending the stimulus bandwidth up to 12~GHz is presented. Furthermore, a technique for increasing the (equivalent) sampling rate while keeping the stable and low-jitter sampling regime of the M-Sequencesapproach is introduced and its implementation is shown. Moreover, an automatic calibration unit for full two-port coaxial calibration of the new UWB sensor has been developed. Common calibration techniques from the area of vector network analysers are shortly reviewed and a reasonablealgorithm the 8-term method with an unknown line standard - is selected for the M-Sequences device. The 8-term method is defined in the frequency domain and is adapted for use with time domain devices. Some performance figures and comparisonwith calibration results from network analysers are discussed to show the effectiveness of the calibration.A spurious-free dynamic range of the time domain impulse responses in excess of 60~dB has been achieved for reflection as well as transmission measurements.The new UWB sensor was used in various real world measurements in different salt mines throughout Germany. Two measurementexamples are described and results from the disaggregation zone of a very old and a freshly cut tunnel will be presented. Measurement setup and data processing are discussed and finally some conclusions for future work on this topic are drawn

Efficient Q-Learning by Division of Labor

Q-learning as well as other learning paradigms depend strongly on the representation of the underlying state space. As a special case of the hidden state problem we investigate the effect of a self-organizing discretization of the state space in a simple control problem. We apply the neural gas algorithm with adaptation of learning rate and neighborhood range to a simulated cart-pole problem. The learning parameters are determined by the ambiguity of successful actions inside each cell

Self-adjusting reinforcement learning

We present a variant of the Q-learning algorithm with automatic control of the exploration rate by a competition scheme. The theoretical approach is accompanied by systematic simulations of a chaos control task. Finally, we give interpretations of the algorithm in the context of computational ecology and neural networks

Building nonlinear data models with self-organizing maps

We study the extraction of nonlinear data models in high dimensional spaces with modified self-organizing maps. Our algorithm maps lower dimensional lattice into a high dimensional space without topology violations by tuning the neighborhood widths locally. The approach is based on a new principle exploiting the specific dynamical properties of the first order phase transition induced by the noise of the data. The performance of the algorithm is demonstrated for one- and two-dimensional principal manifolds and for sparse data sets

Simulation und Regelung von Resonanzversuchsständen zur Untersuchung der Bauteilermüdung

[no abstract

Phylogeny of the nematode genus Pristionchus and implications for biodiversity, biogeography and the evolution of hermaphroditism

<p>Abstract</p> <p>Background</p> <p>The nematode <it>Pristionchus pacificus </it>has originally been developed as a satellite organism for comparison to <it>Caenorhabditis elegans</it>. A 10X coverage of the whole genome of <it>P. pacificus </it>is available, making <it>P. pacificus </it>the first non-<it>Caenorhabditis </it>nematode with a fully sequenced genome. The macroevolutionary comparison between <it>P. pacificus </it>and <it>C. elegans </it>has been complemented by microevolutionary studies of closely related strains and species within the genus <it>Pristionchus</it>. In addition, new understanding of the biology of <it>Pristionchus </it>from field studies, demonstrating a close association with various scarab beetles and the Colorado potato beetle, supports consideration of this nematode in studies of ecosystems. In the course of field studies on four continents more than 1,200 isolates were established from 15,000 beetle specimens representing 18 <it>Pristionchus </it>species. Two remarkable features of the <it>Pristionchus </it>– beetle association are the high species specificity of the interaction and the interception of the beetle's sex communication system for host recognition by the nematodes, as suggested by chemotaxis studies. Evolutionary interpretations of differences in developmental, behavioral and ecological patterns require a phylogenetic framework of the genus <it>Pristionchus</it>.</p> <p>Results</p> <p>Here, we provide a robust phylogeny of all 18 available <it>Pristionchus </it>species based on a set of 27 ribosomal protein genes encompassing a total of 10,971 bp. The phylogenetic tree provides evidence for North American and European clades, which are embedded in a deeper clade that includes Asian species. It also indicates putative invasion events. Of the 18 <it>Pristionchus </it>species, 13 are gonochoristic and five are hermaphroditic. The phylogeny indicates that all hermaphroditic species have arisen independently within the genus <it>Pristionchus</it>.</p> <p>Conclusion</p> <p>Combined ribosomal protein cDNA data can provide the basis for reconstruction of a robust phylogenetic framework for microevolutionary and biogeographic analyses. An additional major implication of our studies is the use of <it>Pristionchus </it>for nematode biodiversity assessments. While some species are represented by more than 100 isolates, others were found less than four times. Such patterns were observed on all continents and in all phylogenetic clades indicating that species asymmetry is a widespread phenomenon, which can now be further investigated by molecular tools.</p

Sex, bugs and Haldane's rule: the nematode genus Pristionchus in the United States

BACKGROUND: The nematode Pristionchus pacificus has been developed as a satellite organism in evolutionary developmental biology for comparison to Caenorhabditis elegans. Comparative studies have revealed major differences in the regulation of developmental processes between P. pacificus and C. elegans. To place evolutionary developmental biology and the observed developmental differences between species in a comprehensive evolutionary context, such studies have to be complemented with ecological aspects. Knowledge about the ecology of the organism in question might indicate specific environmental conditions that can result in developmental adaptations and could account for species differences in development. To this end, we have started to investigate the ecology of Pristionchus nematodes. In recent field studies in Western Europe we found six Pristionchus species that are closely associated with scarab beetles and the Colorado potato beetle. This Pristionchus – beetle association provides the unique opportunity to combine research in evolutionary developmental biology with ecology. However, it remains unknown how general these findings from Europe are on a global scale. RESULTS: Here, we describe the Pristionchus species associated with scarab and Colorado potato beetles in the Eastern United States and show striking transatlantic differences and unexpected evolutionary and ecological patterns. Twohundredeighty of 285 (98%) isolates from American scarab beetles belong to five Pristionchus species, all of which are different from the European species. We describe four of them as novel Pristionchus species. The five American Pristionchus species fall into a single phylogenetic clade and have a male-female (gonochoristic) mode of reproduction, whereas the majority of European isolates are hermaphroditic. Crosses between the two most closely related species, P. aerivorus and P. pseudaerivorus n. sp., follow Haldane's rule in that heterogametic F1 males are inviable. We observed P. aerivorus and P. pseudaerivorus n. sp. coexisting on the same scarab beetle and obtained two cases of F1 hybrids from wild beetles. Finally, the Colorado potato beetle is associated with the same nematode, P. uniformis in the United States and Europe. Given the introduction of the Colorado potato beetle to Europe in 1877, our results suggest that P. uniformis was introduced together with its beetle vector. CONCLUSION: Taken together, the Pristionchus – beetle association provides a powerful tool for studying biodiversity, biogeography, speciation and species invasion on a global scale