Context-Aware Adaptive Opportunistic Routing in Mobile Ad-hoc and Sensor Networks

Mobile ad-hoc networks (MANETs) and wireless sensor networks (WSNs) have been attracting increasing attention for decades due to their broad civilian and military applications. Basically, a MANET or WSN is a network of nodes connected by wireless communication links. Due to the limited transmission range of the radio, many pairs of nodes in MANETs or WSNs may not be able to communicate directly, hence they need other intermediate nodes to forward packets for them. Routing in such types of networks is an important issue and it poses great challenges due to the dynamic nature of MANETs or WSNs. On the one hand, the open-air nature of wireless environments brings many difficulties when an efficient routing solution is required. The wireless channel is unreliable due to fading and interferences, which makes it impossible to maintain a quality path from a source node to a destination node. Additionally, node mobility aggravates network dynamics, which causes frequent topology changes and brings significant overheads for maintaining and recalculating paths. Furthermore, mobile devices and sensors are usually constrained by battery capacity, computing and communication resources, which impose limitations on the functionalities of routing protocols. On the other hand, the wireless medium possesses inherent unique characteristics, which can be exploited to enhance transmission reliability and routing performance. Opportunistic routing (OR) is one promising technique that takes advantage of the spatial diversity and broadcast nature of the wireless medium to improve packet forwarding reliability in multihop wireless communication. OR combats the unreliable wireless links by involving multiple neighboring nodes (forwarding candidates) to choose packet forwarders. In opportunistic routing, a source node does not require an end-to-end path to transmit packets. The packet forwarding decision is made hop-by-hop in a fully distributed fashion. Motivated by the deficiencies of existing opportunistic routing protocols in dynamic environments such as mobile ad-hoc networks or wireless sensor networks, this thesis proposes a novel context-aware adaptive opportunistic routing scheme. Our proposal selects packet forwarders by simultaneously exploiting multiple types of cross-layer context information of nodes and environments. Our approach significantly outperforms other routing protocols that rely solely on a single metric. The adaptivity feature of our proposal enables network nodes to adjust their behaviors at run-time according to network conditions. To accommodate the strict energy constraints in WSNs, this thesis integrates adaptive duty-cycling mechanism to opportunistic routing for wireless sensor nodes. Our approach dynamically adjusts the sleeping intervals of sensor nodes according to the monitored traffic load and the estimated energy consumption rate. Through the integration of duty cycling of sensor nodes and opportunistic routing, our protocol is able to provide a satisfactory balance between good routing performance and energy efficiency for WSNs.

Jüdischer Professor der Theologie auf christlicher Universität : eine Aufgabe f. christl. Staaten

Wiss. bearb., gemeinfasslich vorgetragen u. gewidmet Juden u. Christen von J. G. Diefenbach

Water–montmorillonite systems: Neutron scattering and tracer throughdiffusion studies

Designs for deep geological respositories of nuclear waste include bentonite as a hydraulic and chemisorption buffer material to protect the biosphere from leakage of radionuclides. Bentonite is chosen because it is a cheap, naturally occurring material with the required properties. It consists essentially of montmorillonite, a swelling clay mineral. Upon contact with groundwater such clays can seal the repository by incorporating water in the interlayers of their crystalline structure. The intercalated water exhibits significantly different properties to bulk water in the surrounding interparticle pores, such as lower diffusion coefficients (González Sánchez et. al. 2008). This doctoral thesis presents water distribution and diffusion behavior on various time and space scales in montmorillonite. Experimental results are presented for Na- and Cs-montmorillonite samples with a range of bulk dry densities (0.8 to 1.7 g/cm3). The experimental methods employed were neutron scattering (backscattering, diffraction, time-of-flight), adsorption measurements (water, nitrogen) and tracer-through diffusion. For the tracer experiments the samples were fully saturated via the liquid phase under volume-constrained conditions. In contrast, for the neutron scattering experiments, the samples were hydrated via the vapor phase and subsequently compacted, leaving a significant fraction of interparticle pores unfilled with water. Owing to these differences in saturation, the water contents of the samples for neutron scattering were characterized by gravimetry whereas those for the tracer experiments were obtained from the bulk dry density. The amount of surface water in interlayer pores could be successfully discriminated from the amount of bulk-like water in interparticle pores in Na- and Csmontmorillonite using neutron spectroscopy. For the first time in the literature, the distribution of water between these two pore environments was deciphered as a function of gravimetric water content. The amount was compared to a geometrical estimation of the amount of interlayer and interparticle water determined by neutron diffraction and adsorption measurements. The relative abundances of the 1 to 4 molecular water layers in the interlayer were determined from the area ratios of the (001)-diffraction peaks. Depending on the characterization method, different fractions of surface water and interlayer water were obtained. Only surface and interlayer water exists in amontmorillonite with water contents up to 0.18 g/g according to spectroscopic measurements and up to 0.32 g/g according to geometrical estimations, respectively. At higher water contents, bulk-like and interparticle water also exists. The amounts increase monotonically, but not linearly, from zero to 0.33 g/g for bulk-like water and to 0.43 g/g for interparticle water. It was found that water most likely redistributes between the surface and interlayer sites during the spectroscopic measurements and therefore the reported fraction is relevant only below about -10 ºC (Anderson, 1967). The redistribution effect can explain the discrepancy in fractions between the methods. In a novel approach the fractions of water in different pore environments were treated as a fixed parameter to derive local diffusion coefficients for water from quasielastic neutron scattering data, in particular for samples with high water contents. Local diffusion coefficients were obtained for the 1 to 4 molecular water layers in the interlayer of 0.5·10–9, 0.9·10–9, 1.5·10–9 and 1.4·10–9 m²/s, respectively, taking account of the different water fractions (molecular water layer, bulk-like water). The diffusive transport of 22Na and HTO through Na-montmorillonite was measured on the laboratory experimental scale (i.e. cm, days) by tracer through-diffusion experiments. We confirmed that diffusion of HTO is independent of the ionic strength of the external solution in contact with the clay sample but dependent on the bulk dry density. In contrast, the diffusion of 22Na was found to depend on both the ionic strength of the pore solution and on the bulk dry density. The ratio of the pore and surface diffusion could be experimentally determined for 22Na from the dependence of the diffusion coefficient on the ionic strength. Activation energies were derived from the temperaturedependent diffusion coefficients via the Arrhenius relation. In samples with high bulk dry density the activation energies are slightly higher than those of bulk water whereas in low density samples they are lower. The activation energies as a function of ionic strengths of the pore solutions are similar for 22Na and HTO. The facts that (i) the slope of the logarithmic effective diffusion coefficients as a function of the logarithmic ionic strength is less than unity for low bulk dry densities and (ii) two water populations can be observed for high gravimetric water contents (low bulk dry densities) support the interlayer and interparticle porosity model proposed by Glaus et al. (2007), Bourg et al. (2006, 2007) and Gimmi and Kosakowski (2011).

Transformative deliberative moments among ex-combattants in Colombia

This dissertation presents the concept of Deliberative Transformative Moment and the instrument to identify it, in a further attempt to bridge the gap between deliberation theory and practice. A transformative moment in the deliberative process occurs when the level of deliberation is either lifted from low to high or drops from high to low. In order to identify such a moment, one has to look at the context and dynamics of the group discussion. This broadening of the unit of analysis is a big difference from other existing instruments to measure the level of deliberation, such as the Deliberative Quality Index –DQI, which focuses primarily on the individual speech acts. Consistent with the theoretical framework of consociational and deliberation approaches, the observed discussions took place among two deeply divided groups, Colombian ex-combatants from both the extreme left and the extreme right. Moving beyond a pure Habermasian perspective, this study finds that besides pure rational arguments, there are some contexts in which personal stories, jokes and self-interests, acting as justification of arguments, have either a positive or a negative impact on deliberative transformative moments. Although this research has a strongly qualitative orientation, reliability tests scored high, giving it strength as a reliable and valid research method that shedding some light on the sort of speech acts that enhance deliberation and those that detract from it.

Laufbahnen von ehemaligen Schweizer Nachwuchs-Elite-Athleten unter dem Aspekt des Erfolgs

Die vorliegende Dissertation verfolgt das Ziel, zu untersuchen, wie sich ehemalige Schweizer Nachwuchs-Elite-Athleten unter dem Aspekt des sportlichen Erfolgs entwickelt haben und wie sich ihre heutige Lebenssituation präsentiert. Zudem will die Arbeit ergründen, inwiefern der sportliche Erfolg durch ausgewählte institutionelle, sportwissenschaftliche und individuelle Parameter vorhergesagt werden kann. Zu diesem Zweck wurden alle deutschsprachigen Nachwuchs-Elite-Athleten untersucht (N = 221), welche im Jahre 1999 Inhaber einer Swiss Olympic Talent-Card waren. Die Prädiktoren stammen teilweise aus einer ersten schriftlichen Befragung, welche 1999 durchgeführt wurde (Rücklauf: 79%). Die Daten für die Beschreibung der Laufbahn sowie der heutigen Situation wurden im Sommer 2011 durch eine weitere schriftliche Befragung erhoben (Rücklauf: 48%). Die Daten wurden mit deskriptiven, inferenzstatistischen, cluster- sowie regressionsanalytischen Verfahren ausgewertet. Die Resultate zeichnen insgesamt ein positives Bild. Trotz verschiedener Hürden im Nachwuchsalter schafften die meisten befragten Athleten den Sprung in die Elite-Stufe. Knapp ein Drittel von ihnen konnte dabei grosse Erfolge (Medaillengewinn) an bedeutenden internationalen Wettkämpfen erringen. Die bereits zurückgetretenen Athleten scheinen das Laufbahnende grösstenteils gut bewältigt zu haben, was wohl damit zusammenhängt, dass die Mehrheit von ihnen freiwillig zurückgetretenen ist und konkrete Pläne für die nachsportliche Laufbahn hatte. Insgesamt deuten die Ergebnisse darauf hin, dass sich ein Engagement im Leistungssport nicht negativ auf die Entwicklung in anderen Lebensbereichen auszuwirken scheint. So zeigte sich, dass sich die heutige Situation der ehemaligen Nachwuchs-Elite-Athleten in gesundheitlicher, psychologischer, sozialer, beruflicher und finanzieller Hinsicht durchwegs positiv präsentiert – in gesundheitlicher, beruflicher und finanzieller Hinsicht sogar besser als jene von gleichaltrigen Vergleichspersonen der Schweizer Bevölkerung. Bei der Vorhersage des sportlichen Erfolgs zeigte sich, dass Athleten aus weniger geförderten und weniger bedeutenden Sportarten später insgesamt erfolgreicher sind an bedeutenden internationalen Wettkämpfen. Darüber hinaus erwies sich die mentale Stärke als langfristiger Erfolgsfaktor. Die Ergebnisse erweitern das bestehende Wissen über Laufbahnen von Leistungssportlern sowie über Determinanten von sportlichem Erfolg generell, besonders aber hinsichtlich des Schweizer Sportsystems. Athleten und ihr Umfeld erhalten dadurch einen vertieften Einblick in die Chancen und Risiken eines Engagements im Leistungssport. Swiss Olympic und die Verbände gewinnen ein besseres Verständnis darüber, wie sich Nachwuchs-Elite-Athleten in ihrer sportlichen Entwicklung noch besser unterstützen lassen. Bund, Kantone und Gemeinden können anhand der Ergebnisse besser abschätzen, inwiefern sich die Förderung des Spitzensports durch öffentliche Gelder rechtfertigen lässt.

Rede beim Schluß der ersten israelitischen Synode zu Leipzig am 4. Juli 1869

geh. von M. Lazarus. Nebst d. Ansprache d. Löw