Hierarchical Communication Diagrams

Formal modelling languages range from strictly textual ones like process algebra scripts to visual modelling languages based on hierarchical graphs like coloured Petri nets. Approaches equipped with visual modelling capabilities make developing process easier and help users to cope with more complex systems. Alvis is a modelling language that combines possibilities of formal models verification with flexibility and simplicity of practical programming languages. The paper deals with hierarchical communication diagrams - the visual layer of the Alvis modelling language. It provides all necessary information to model system structure with Alvis, to manipulate a model hierarchy and to understand a model semantics. All considered concepts are discussed using illustrative examples

A formal framework for heterogeneous systems semantics

Cyber physical systems are usually complex systems which are often critical, meaning their failure can have significant negative impacts on human lives. A key point in their development is the verification and validation (V & V) activities which are used to assess their correctness towards user requirements and the associated specifications. This process aims at avoiding failure cases, thus preventing any incident or accident. In order to conduct these V & V steps on such complex systems, separations of concerns of various nature are used. In that purpose, the system is modeled using heterogeneous models that have to be combined together. The nature of these separations of concerns can be as follows: horizontal, which corresponds to a structural decomposition of the system; vertical, which corresponds to the different steps leading from the abstract specification to the concrete implementation; and transversal, which consists in gathering together the parts that are thematically identical (function, performance, security, safety...). These parts are usually expressed using domain specific modeling languages, while the V & V activities are historically conducted using testing and proofreading, and more and more often, using formal methods, which is advocated in our approach. In all these cases, the V & V activities must take into account these separations in order to provide confidence in the global system from the confidence of its sub-parts bound to the separation in question. In other words, to ensure the correctness of the system, a behavioral semantics is needed which has to rely on the ad-hoc semantics of the subsystems. In order to define it, these semantics must be successfully combined in a single formalism. This thesis stems from the GEMOC project a workbench that allows the definition of various languages along with their coordination properties, and target the formal modeling of the GEMOC core through the association of trace semantics to each preoccupation and the expression of constraints between them to encode the correct behavior of the system. This thesis follows several other works conducted under the TOPCASED, OPEES, QuarteFt, P and GEMOC projects, and provides four contributions in that global context: the first one proposes a methodology to give an operational semantics to executable models illustrated through two case studies: Petri nets and models of processes. The second one proposes a formal context on which refinement can be expressed to tackle vertical separation. The third one gives a denotational semantics to CCSL which is the language that is currently used in the GEMOC projects to express behavioural properties between events from one or several models, possibly heterogeneous. Finally, the fourth one proposes an investigation on how to extend CCSL with the notion of refinement we proposed. All these contribution are mechanized in the Agda proof assistant, and thus have been modeled and proven in a formal manner

Tagungsband Mechatronik 2011: Dresden 31. März – 1. April 2011

Mit dieser sechsten Auflage der Tagung MECHATRONIK 2011 verbindet sich neben dem 10-jährigen Tagungsjubiläum (die erste Tagung fand im Jahre 2001 statt) auch gleichzeitig eine Premiere. Nachdem die ersten fünf Tagungen erfolgreich unter den Fittichen des VDI bzw. des VDI-Wissensforums stattgefunden hatten, beginnt das zweite MECHATRONIK-Dezennium in einem geänderten Format und mit neuen Verantwortlichkeiten und wird dennoch die bewährten Traditionen der deutschsprachigen Mechatronik-Fachgemeinde weiter pflegen. Academia trifft Industrie — Mechatronik und mechatronische Produkte sind seit jeher geprägt durch die Verknüpfung von interdisziplinärem methodenorientierten Wissen und nutzerorientierter Produktgestaltung. Diese Verknüpfung bildet sich höchst erfolgreich speziell in der deutschsprachigen Mechatronik-Fachgemeinde ab, nicht zuletzt deshalb haben deutsche Mechatronikprodukte weltweit eine exzellente Marktpräsenz. Diese enge Verzahnung ist aber ebenso im Tagungsgeschehen etabliert, wo seit vielen Jahren, im Gegensatz zu vielen anderen Ländern und internationalen Tagungen, eine gute Balance zwischen Teilnehmern aus Hochschulen und Industrie gegeben ist. Dies trifft auch auf die MECHATRONIK 2011 zu, mit 47 (70 %) Beiträgen aus Hochschulen und 20 (30 %) Beiträgen aus der Industrie bzw. Industriebeteiligung. Academia trifft Industrie — Dieser Sachverhalt wird zukünftig auch ganz transparent an den Tagungsorten und dem Tagungsumfeld sichtbar sein. Ab diesem Jahr 2011 wird die Organisation und Ausrichtung durch akademische Tagungsveranstalter durchgeführt werden. Die bisherigen wissenschaftlichen Tagungsleiter Prof. Burkhard Corves (Rheinisch- Westfälische Technische Hochschule - RWTH Aachen) und Prof. Klaus Janschek (Technische Universität Dresden) werden zukünftig gemeinsam mit Prof. Torsten Bertram (Technische Universität Dortmund) für die Ausrichtung und Durchführung verantwortlich zeichnen. Als Veranstaltungsort sind entsprechende Räumlichkeiten an den beteiligten Universitäten geplant (2011 in Dresden, 2013 in Aachen, 2015 in Dortmund). Neben einer Kostenersparnis erwarten sich die Veranstalter durch das gegenüber Kongresszentren doch intimere Umfeld einen lebendigen Gedankenaustausch zwischen Wissenschaftlern, Industrievertretern und nicht zuletzt mit dem wissenschaftlichen Nachwuchs. Speziell Studierenden soll damit ein einfacherer Zugang in die Welt des wissenschaftlichen Diskurses mit Experten aus der Industrie und Praxis ermöglicht werden. Academia trifft Industrie — Eine Stärke der bisherigen MECHATRONIK-Tagungen war immer die breite fachliche Verankerung durch die verantwortliche Trägerschaft der VDI-Gesellschaft Produkt- und Prozessgestaltung (VDI-GPP) und VDI/VDE-Gesellschaft Mess- und Automatisierungstechnik (VDI/VDEGMA). Im Selbstverständnis dieser Fachgesellschaften spielt die Bereitstellung von Kommunikationsplattformen zwischen Hochschulen und Industrie eine zentrale Rolle. In den verschiedenen Fachausschüssen von VDI-GPP und VDI/VDE-GMA findet dieser Meinungs- und Informationsaustausch regelmäßig statt. Um eine breitere Fachöffentlichkeit in diese Diskussionen einzubeziehen, ist eine gemeinsame Tagung zum Thema Mechatronik eine logische und fruchtbare Konsequenz. Auch zukünftig wird der enge fachliche und institutionelle Kontakt der Tagung MECAHTRONIK zu den Fachgesellschaften aufgrund der personellen Verankerung der Tagungsveranstalter in den Fachgesellschaften VDI-GPP und VDI/VDE-GMA erhalten bleiben. Das Tagungsprogramm 2011 bietet ein breit gefächertes Angebot an aktuellen und innovativen Fragestellungen zur Mechatronik: mechatronische Produkte, Serienfertigung mechatronischer Produkte, Ressourceneffizienz, Nutzerfreundlichkeit und Akzeptanz, Entwicklungsmethoden und -werkzeuge sowie innovative Konzepte

Understanding eruption dynamics: insights from volcanic seismicity in Ecuador

Persistently active volcanoes in close proximity to society can pose a huge danger to infrastructure, lives and the economy. Careful monitoring of volcanic seismicity is integral to successful hazard assessment and risk management. Geophysical monitoring at active volcanoes can provide rich datasets to examine internal systems. Specifically, seismic monitoring offers the potential to develop real time analysis and forecasts. The generation of volcanic seismicity has been linked to processes such as magma ascent, degassing and rock fracturing. However, studies are often limited to individual volcanoes or specific episodes of unrest, and so it is difficult to compare interpretations. This aim of this thesis is twofold: to develop methodologies to better quantify and characterise volcanic seismicity, and to use these to provide new understanding of volcanic systems, the hazards they might pose and how we can better forecast and monitor unrest. First, I present an extensive literature review of our current understanding of volcanic seismicity. As there is no standardised procedure for the analysis of volcanic earthquakes, there are inconsistent uses of techniques and ambiguous terminology. Existing studies also tend to focus on a handful of well monitored volcanoes where dense arrays can be used to calculate source mechanisms and depths to interpret seismic swarms. In order to address this, I develop a thorough signal processing routine which generates a suite of metrics to characterise a single earthquake event. These metrics can be used across a sequence of earthquakes to track changes in the behaviour of seismicity, and distinguish different types of earthquakes. It is developed with poorly monitored volcanoes in mind, as metrics can be determined for signal from a single station, and even a single component instrument. I use parameters in the time domain including amplitude, duration and cross correlation, and compare three different approaches to calculate the quality (Q) factor, in the frequency domain. I then present two candidate volcanoes to apply the methodology and attempt to describe the internal processes at each. Tungurahua and Cayambe are two relatively understudied volcanoes and yet they are potentially the most dangerous natural hazards in Ecuador. Tungurahua’s most recent eruptive phase (1999-2016) was explosive and persistent. In contrast, Cayambe volcano has not erupted in over 200 years and yet has been seismically restless in recent years. This presents an opportunity to compare the seismicity associated with ongoing, and reawakening volcanic processes. In chapter 4, I characterise the seismicity atTungurahua between 2012 and the final explosions in 2016. Seismicity at Tungurahua was dominated by long-period (LP) earthquakes, particularly episodes of highly periodic, repeating LP seismicity, known as drumbeats. In this chapter, I show that persistent drumbeats occur in phase with cyclical Vulcanian eruptions. These events are attributed to the initial failure and subsequent resealing of an upper conduit plug. In each explosive episode, the signal metrics are able to distinguish a shift in the signal properties of drumbeat LPs. In chapter 5, I focus specifically on accelerating rates of drumbeat LPs, often considered precursors to eruptions. I use temporal statistics and a Markov chain Monte Carlo (MCMC) approach to model three episodes of drumbeats. In one significant episode, the last ever recorded drumbeats at Tungurahua, I show these events are precursors to a ‘failed’ attempt at an explosion. In chapter 6 I then compare these findings at Tungurahua, with the 2016 seismic crisis at Cayambe. Here I demonstrate the repeating LP seismicity is likely a result of shallow hydrothermal systems, rather than surficial ‘icequakes’ or magmatic ascent. However, swarms of volcano-tectonic events (VTs) in 2016, are likely attributed to stresses on regional faults and ascent of a new pulse of magma. Finally, I begin to explore the complex volcano-tectonic interactions at both Tungurahua and Cayambe. Where there are high rates of tectonic events globally, and high rates of eruptions, it is important to distinguish causality and coincidence. VT swarms at Cayambe occur two months after the Mw7.8 Pedernales earthquake, 200km west. Using models of static stress change I suggest the crust at Cayambe was subject to a dilational regime, prompting resumed activity in 2016. However, the Pedernales earthquake occurs just two months after the final eruption at Tungurahua and yet does not appear to promote or restrict further explosive activity. This thesis presents case studies of two active volcanoes that are subject to limited seismic monitoring. These methods are not computationally intensive and could be readily adopted into routine volcano monitoring, to further inform hazard assessment. Although Cayambe and Tungurahua are neighbouring volcanoes, comparable in their rheology, they are very different in their current dynamic state, and this is evident in the seismicity. An enhanced understanding of these systems should inform further assessment of seismicity at intermediate-composition, arc volcanoes

Doctors' perspective on obstetric ultrasound: concept, knowledge and practice

Problems arise when women attend for obstetric ultrasound scans, not always fully aware of the purpose of the examinations they have chosen to opt for and sometimes experience anxiety, as their expectations are not met. This study has explored, through in- depth interviews and ‘framework’ analysis, whether doctors are actively engaged in unbiased information sharing with pregnant women during their consultations. Through exploration of the literature on women’s and health professionals’ perspective on the use of obstetric ultrasound, a gap is seen in the knowledge regarding the medical perspective on ultrasound use in pregnancy. Results of this study revealed three themes relating to the doctor’s experiences of offering obstetric ultrasound: doctors’ knowledge and understanding, their views on the practice of obstetric ultrasound use and their ideas on the concept of ultrasound. These themes been considered alongside the writings on power/knowledge, govemmentality and self-surveillance through risk theory, by the philosopher Michel Foucault (1926-84), as his ideas have been central to this research question. The conclusion reached is that, although making changes to doctors’ in house training may increase their knowledge of obstetric ultrasound, it may still be the case that their professional position within society will still create a barrier to women making informed decisions when requiring to consider opting for ultrasound scans during their pregnancy