<p>By using flexible and stretchable materials in place of fixed components, soft robots can materially adapt or change to their environment, providing built-in safeties for robotic operation around humans or fragile, delicate objects. And yet, building a robot out of only soft and flexible materials can be a significant challenge depending on the tasks that the robot needs to perform, for example if the robot were to need to exert higher forces (even temporarily) or self-report its current state (as it deforms unexpectedly around external objects). Thus, the appeal of multifunctional materials for soft robots, wherein the materials used to build the body of the robot also provide actuation, sensing, or even simply electrical connections, all while maintaining the original vision of environmental adaptability or safe interactions. Multifunctional material systems are explored throughout the body of this dissertation in three ways: (1) Sensor integration into high strain actuators for state estimation and closed-loop control. (2) Simplified control of multifunctional material systems by enabling multiple functions through a single input stimulus (<i>i.e.</i>, only requiring one source of input power). (3) Presenting a solution for the open challenge of controlling both well established and newly developed thermally-responsive soft robotic materials through an on-body, high strain, uniform, Joule-heating energy source. Notably, these explorations are not isolated from each other as, for example, work towards creating a new material for thermal control also facilitated embedded sensory feedback. The work presented in this dissertation paves a way forward for multifunctional material integration, towards the end-goal of full-functioning soft robots, as well as (more broadly) design methodologies for other safety-forward or adaptability-forward technologies.</p>

Les tenants et aboutissants du modèle phénoménologique de percolation (multi-mode par liaison) développé sur site pour la compréhension de base des spectres de vibration Raman et infrarouges des alliages semi-conducteurs de structure zincblende (II-VI et III-V) et diamant (IV-IV) sont explorés plus avant dans des registres novateurs avec les systèmes Ge1-xSix (diamant), Zn1-xBexSe (zincblende) et ZnSe1-xSx (zincblende). La version du modèle de percolation élaborée pour l’alliage GeSi de structure diamant (3 liaisons, 6 modes/phonons), plus élaborée que la version standard originellement développée pour les alliages zincblende (2 liaisons, 3 phonons), est utilisée comme version modèle pour formaliser à travers l’introduction d’un paramètre d’ordre k ad hoc, une aptitude intrinsèque des spectres de vibration, révélée par le modèle de percolation, à ‘mesurer’ la nature du désordre d’alliage, en termes de substitution aléatoire, ségrégation locale ou dispersion locale. L’alliage de percolation Zn0.67Be0.33Se est utilisé comme système modèle pour étudier, à l’aide d’un montage inhabituel de diffusion Raman en avant, la dispersion des phonons transverses optique au tout proche voisinage du centre tau de la zone de Brillouin. A cette limite, ces modes acquièrent un champ électrique semblable à celui d’une onde électromagnétique pure, i.e. un photon, et se voient désignés sous la terminologie de phonon-polaritons. Une spécificité inexplorée des phonon-polariton d’alliage, à savoir leur renforcement à l’approche de tau, est étudiée plus avant avec les alliages Zn0.47Be0.53Se et ZnSe0.68S0.32, et effectivement observée avec le second alliage. Une étude infrarouge a récemment révélé dans la littérature un comportement vibrationnel multi-mode déconcertant pour la liaison courte (Zn-S) de l’alliage ZnSeS. Nous montrons que ce comportement peut être expliqué dans le cadre d’une version généralisée du modèle de percolation, plus élaborée que la version standard, qui prend en compte l’effet de la dispersion phonon en plus de l’effet de la contrainte locale. Par ailleurs l’étude fine du comportement phonon-polariton de la liaison longue (Zn-Se) de l’alliage représentatif ZnSe0.68S0.32 par diffusion Raman en avant révèle un comportement bimodal insoupçonné, qui fait écho à celui de la liaison courte (Zn-S). Cela établit expérimentalement que le schéma de percolation (multi-phonon par liaison) est générique et s’applique à toutes les liaisons d’un alliage donné, en principe. Enfin, nous explorons le comportement du doublet Zn-S de l’alliage ZnSeS à l’approche de la transition de phase zincblende->rocksalt (~14 GPa) par diffusion Raman en avant sous pression, i.e. dans le régime phonon-polariton. Le mode Zn-S basse fréquence s’affaiblit et converge vers le mode haute fréquence sous pression, comme observé plus tôt en rétrodiffusion pour le doublet Be-Se de l’alliage ZnBeSe. Il semble s’agir d’un comportement intrinsèque du doublet de percolation pour la transition de phase considérée, celui-ci reflèterait une sensibilité aux instabilités locales des liaisons hôtes (Zn-Se) à l’approche de leur transition de phase naturelle, caractéristiques composé pur (ZnSe). Ces comportements sont discutés sur la base d’une modélisation des spectres Raman enregistrés pour des processus de diffusion en arrière (géométrie usuelle) et en avant (en fonction de l’angle de diffusion) dans le cadre du formalisme de la réponse diélectrique linéaire. L’attribution des modes Raman est réalisée via des calculs ab initio (code SIESTA) menés sur site avec des motifs d’impureté prototypes. Les prédictions du modèle de percolation concernant la dépendance du spectre Raman de GeSi vs. k sont confrontées à un calcul ab initio direct des spectres Raman (code AIMPRO), mené en collaboration à partir de supercellules couvrant une série représentative de valeurs de k / The ins and outs of the phenomenological percolation model (multi-mode per bond) developed by the team for the basic understanding of the Raman and infrared spectra of semiconductor alloys with zincblende (II-VI & III-V) and diamond (IV-IV) structure are further explored in novel areas with the Ge1-xSix (diamant), Zn1-xBexSe (zincblende) and ZnSe1-xSx (zincblende) alloys. The version of the percolation worked out for the GeSi diamond alloy (3 bonds, 6 modes/phonons), more refined than the current one for zincblende alloys (2 bonds, 3 phonons), is used as a model version to formalize, via the introduction of a relevant order parameter k, an intrinsic ability behind the vibration spectra, to ‘measure’ the nature of the alloy disorder, as to whether this reflects a random substitution, or a trend towards local clustering or local anticlustering. The percolation-type Zn0.67Be0.33Se alloy is used as a model system to study, by using an unconventional Raman setup corresponding to forward scattering, the dispersion of the transverse optic phonons on approaching of tau, the centre of the Brillouin zone. At this limit such modes become equipped with a macroscopic electric field similar in every point to that carried by a pure electromagnetic wave, namely a photon, being then identified as phonon-polaritons. A specificity of the alloy-related phonon-polaritons, namely their reinforcement approaching of tau ,unexplored so far, is further investigated experimentally with the Zn0.47Be0.53Se et ZnSe0.68S0.32 alloys, selected on purpose, and was indeed confirmed in the latter alloy. A recent infrared study of ZnSeS in the literature has revealed a disconcerting multi-phonon pattern for its shorter bond species (Zn-S). We show that such pattern can be explained within a generalized version of the percolation scheme, a more sophisticated one than the standard version, taking into account the effect of the phonon dispersion in addition to the effect of the local strain. Besides, a refined study of the phonon-polariton regime related to the long Zn-Se bond reveals an unsuspected bimodal pattern, which echoes that earlier evidenced for the short (Zn-S) species. This establishes on an experimental basis that the percolation scheme (multi-phonon per bond) is generic and applies as well to any bond species in an alloy, in principle. Last, we explore the behavior of the Zn-S doublet of ZnSeS at the approach of the zincblende->rocksalt (~14 GPa) transition, by near-forward Raman scattering under pressure, i.e. in the phonon-polariton regime. The low-frequency Zn-S mode appears to weakens and converges onto the high-frequency Zn-S mode under pressure, as earlier observed for the Be-Se doublet of ZnBeSe in backscattering. Such behavior seems to be intrinsic to the percolation-type doublet for the considered structural phase transition. This would reflect a sensitivity to the local instabilities of the host bonds (Zn-Se) at the approach of their natural structure phase transitions characteristic of the related pure compound (ZnSe). The above mentioned behaviors are discussed on the basis of a detailed contour modeling of the Raman spectra taken in backscattering (usual geometry) and forward scattering (depending on the scattering angle then) within the scope of the linear dielectric response. The assignment of the Raman modes is achieved via ab initio phonon calculations done within the SIESTA code using prototype impurity motifs. The predictions of the percolation scheme concerning the k-dependence of the GeSi Raman spectra are confronted with direct ab initio calculations of the GeSi Raman spectra done in collaboration (with V.J.B. Torres) using the AIMPRO code on supercells covering a selection of representative k values

Choral ensembles often operate as hierarchical institutions where the conductor maintains a position of control over the musical, educational, and social aspects of singing with little or no input from singers. This dissertation reconceptualizes the choral experience as a dialogical process where conventional boundaries between conductor and singers blur. This study was conducted online with a vocal ensemble of ten experienced adult avocational singers and asks how a collaborative spirit may transform the ensemble, individual singers, and the conductor. Using a critical participatory action research approach, we engaged in dialogue and group problem solving as we created collective and individual musical projects over the course of ten rehearsals. The research design emphasized collective reflection and democratic decision making. This research journey is presented through a collection of multimodal data fragments such as musical recordings, practitioner reflections and collated singer reflections, rehearsal transcriptions and narratives, photographs, and poetry. Informed by decolonizing and post-qualitative methodologies, this dissertation highlights the ethical dilemmas, rewards, and uncertainties of both collaborative research and learner-centered approaches to education. In investigating how singers might increase their influence within the ensemble setting, we discovered that singers talking back to the conductor set in motion conditions for a choral paradigm that I describe as back talk choral pedagogy. This pedagogical orientation draws on critical and relational perspectives and is characterized by four interconnected commitments: (a) relational accountability; (b) mutual recognition of knowledge; (c) cultivation of a public square; and (d) responsiveness to input. Singer back talk manifested itself in myriad ways, including the reporting of information or observations, sharing opinions and suggestions, directly contesting the conductor, storytelling, and silence. Singer back talk produced noticeable fruits—a culture of shared vulnerability and trust, unique singer contributions, role fluidity between conductor and singers, and choral communion—which positively impacted the learning environment. This inquiry suggests that by centering relational and ethical aspects of musical collaboration, back talk choral pedagogy has the potential to build flourishing, dynamic musical spaces, increase singer ownership, and challenge conductors to expand their teaching practice.

L'objectif principal de ce travail était l'étude systématique de plusieurs groupes de matériaux conducteurs protoniques: Gd₃₋ₓMeₓGaO₆₋₅ (Me = Ca²+, Sr²+), Ba₂Nb₁₋ₓY₁₊ₓO₆₋₅, et BaZr₀.₈₅Y₀.₁₅O₃₋₅ (BZY15). Nous avons développé une voie de synthèse pour chaque groupe de matériaux tels que le procédé de combustion sol-gel, la synthèse lyophilisation et le procédé de complexation de citrate-EDTA modifié des nanopoudres pures et des céramiques denses ont été obtenus après ces synthèses suives d'un processus de frittage classique. La structure et la composition des produits obtenues ont été caractérisées par diffraction des rayons X (XRD) et microscopie électronique à balayage (MEB). La variation de la conductivité en fonction de la température a été étudiée par spectroscopie d'impédance, ainsi que la dépendance en fonction de pO₂ et pH₂O. Pour la famille de Gd₃₋ₓMeₓGaO₆₋₅ (Me = Ca²+, Sr²+), nous avons étudié l'influence de la nature et la quantité de dopant sur les propriétés structurales et électriques. Les résultats indiquent une solution solide possible jusqu'à 10% de taux du substituant. Selon les observations au MEB, la taille des grains est augmente le taux de substitution. En ce qui concerne les propriétés électriques, nous avons constaté une augmentation de la conduction avec le taux de substitution. Tous les composés présentent une bonne stabilité en milieu humide, sous hydrogène et CO₂. Dans le cas des matériaux Ba₂Y₁₊ₓNb₁₋ₓO₆₋₅, les propriétés physico-chimiques des matériaux synthétisés ont été caractérisées par la diffraction des rayons X et par MEB. La taille moyenne des grains a considérablement augmenté avec l'augmentation du taux de Y³⁺. Les propriétés de conduction ont été légèrement améliorées avec la substitution partielle de niobium par l'yttrium. La stabilité de Ba₂Y₁₊ₓNb₁₋ₓO₆₋₅ composés a été étudiée sous différentes atmosphères et conditions. Les propriétés de conduction ionique restent modestes ce qui a été explique par des simulations de dynamique moléculaire. Enfin, nous avons étudié l'influence d'emploi d'un additif ZnO et NiO lors de la synthèse de BZY15, les adjuvants de frittage pouvant être utilisés pour abaisser la température de frittage. L'oxyde de zinc comme un adjuvant de frittage permet de diminuer de 300 °C la température de frittage et d'augmenter légèrement la conduction ionique. / The main objective of the present work was the systematic study of several groups of materials: Gd₃₋ₓMeₓGaO₆₋₅ (Me = Ca²+, Sr²+), Ba₂Nb₁₋ₓY₁₊ₓO₆₋₅, and BaZr₀.₈₅Y₀.₁₅O₃₋₅ (BZY15) as proton conductors. We developed a synthesis route for each group of materials such as sol-gel combustion method, freeze-drying synthesis and modified citrate-EDTA complexing method. Pure nanopowders and dense ceramics were obtained after these syntheses plus a classical sintering process. The structure and composition of the obtained products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The temperature dependences of the conductivity were investigated by impedance spectroscopy as a function of pO₂ and pH₂O. For the family of Gd₃₋ₓMeₓGaO₆₋₅ (Me = Ca²+, Sr²+), we studied the influence of dopant nature and content on the structural and electrical properties. Results indicate that the substitution possible till 10 % of doping content. According to the SEM observations, the grain size is increased with increasing dopant content. Concerning electrical properties, we found an increase of conduction with increasing dopant content. All compounds present a good stability in humid, hydrogen and CO₂ containing atmosphere. In case of Ba₂Y₁₊ₓNb₁₋ₓO₆₋₅ materials, the physico-chemical properties of synthesized materials have been characterized by the XRD and SEM techniques. The average grain size increased significantly with increasing amount of Y³⁺. Conduction properties were slightly improved with the partial substitution of niobium by yttrium. The stability of Ba₂Y₁₊ₓNb₁₋ₓO₆₋₅ compounds was investigated under different atmospheres and conditions. The ionic conduction in this case is quite low, which has been explained by futher molecular dynamics simulations. Finally, we studied the influence of an ZnO and NiO additives on the sintering of BZY15, being these sintering aids used to lower the sintering temperature. Zinc oxide as a sintering aid lowers the sintering temperature by 300 °C and slightly increases the bulk and total conductivity of BZY15.

This report aims to study the degradation of poly(trimethylene carbonate) (PTMC) caused by the enzyme carboxylesterase in vitro. As well as to characterise polymer blends of f-BTI2g-TVTCN and poly(3-hydroxybutyric acid) as core components for organic electrochemical transistors (OETCs). This is to assess the suitability of these polymers in biodegradable biosensors. The degradation study of PTMC showed a lack of degradation in contrast to previous studies performed on the material; previous studies recorded a mass loss of between (5-8)% after two months. The cause for this discrepancy is still unknown but the evidence points to both systematic faults in the gravimetric analysis as well as random errors found in the equipment. The OECT showed that increasing the PHB fraction in the polymer blend resulted in a higher output. The most stable device consisted of a 1:6 blend of f-BTI2g-TVTCN to PHB. Fewer tests were conducted on the 1:10 blend because two devices were damaged during the experiment. The statistical impact of the smaller sample size cannot be overstated so further testing should be conducted to verify the results.

No description available.

In Deutschland nehmen die Fahrgastzahlen und die Verkehrsleistung im Schienenpersonennah- und -fernverkehr in den letzten Jahrzehnten stetig zu. So stieg beispielsweise die Zahl der beförderten Fahrgäste im Schienenpersonennahverkehr von 1,96 Milliarden im Jahr 2004 auf 2,72 Milliarden im Jahr 2018. Dies entspricht einer Zunahme von fast 39%. Allerdings wird es für die Eisenbahnverkehrsunternehmen aufgrund des Fachkräftemangels immer schwieriger, die erforderlichen Transportleistungen durch Triebfahrzeugführer und Zugbegleiter abzudecken. Dies bedeutet, dass mit weniger Ressourcen mehr Transportleistung erbracht werden muss, so dass eine ressourcenschonende und gleichzeitig kosteneffiziente Personalplanung unerlässlich ist. Ziel dieser Arbeit ist die Entwicklung eines Lösungskonzepts zur optimierten und automatisierten Planung des Bahnpersonals, insbesondere zur Sicherstellung der Zugbegleitquoten von Zugbegleitern in Regionalzügen. Da es bereits eine Vielzahl von Publikationen zu Modellierungsansätzen und Lösungsmethoden im Zusammenhang mit der Schichtplanung des Bahnpersonals gibt, wird in einem ersten Schritt die relevante Literatur identifiziert und klassifiziert. Dies ist notwendig, um geeignete mathematische Formulierungen und Lösungsansätze zu ermitteln, die auch für den Spezialfall der Schichtplanungsprobleme für Zugbegleiter mit Zugbegleitquoten angewendet oder weiter modifiziert werden können. Durch die Systematisierung der relevanten Artikel nach Modellformulierungen, Zielsetzungen, betrachteten Rahmenbedingungen und Lösungsmethoden können Forschungslücken leicht identifiziert und Möglichkeiten für weitere Forschungen aufgezeigt werden. Nach einer Analyse der gegebenen rechtlichen Anforderungen, Regelungen aus Tarifverträgen, operativen Bedingungen und der Forderungen aus Verkehrsverträgen ist ein erstes Ziel dieser Arbeit die Entwicklung eines mathematischen Modells, das das gegebene Schichtplanungsproblem für Zugbegleiter mit Zugbegleitquoten darstellt. Um zunächst die Auswirkungen der neuen Restriktionen für die Zugbegleitquoten zu analysieren, können weitere in der Praxis notwendige Anforderungen (z.B. Personalkapazität an den Einsatzstellen) weggelassen und der Planungshorizont auf einen Tag begrenzt werden. Nach der Modellierung des Problems mit weiteren Restriktionen soll in dieser Arbeit ein geeigneter Lösungsansatz entwickelt werden, der vor allem die Lösbarkeit großer realer Instanzen gewährleistet. Die generierten Schichtpläne müssen den gesetzlichen, vertraglichen und betrieblichen Anforderungen genügen und die dadurch entstehenden Kosten minimieren. Da in der Praxis ein Planungszeitraum von einem Tag weder betriebswirtschaftlich sinnvoll noch kosteneffizient ist, wird als nächstes Ziel die Ausdehnung des Planungszeitraums auf mehrere Tage angestrebt. Diese Ausdehnung sollte sich sowohl auf das Modell als auch auf den entwickelten Lösungsansatz auswirken. So können weitere mehrtägige Restriktionen integriert werden, wie z.B. die gleichmäßige Verteilung der von einem Zugbegleiter besetzten Fahrten. In der Forschung ist es wichtig, eine Vergleichbarkeit bzw. eine Bewertung der Qualität des Modells oder des Lösungsansatzes herzustellen. Aus diesem Grund sollte eine Arc-Flow-Formulierung des Schichtplanungsproblems für Zugbegleiter mit Zugbegleitquoten formuliert werden, um kleine Instanzen optimal zu lösen und untere Schranken für reale Instanzen zu setzen. Um die Lösung der Arc-Flow-Formulierung zu beschleunigen und zu verbessern, wird die Anwendung von gültigen Ungleichungen validiert. Der Zweck dieser Arbeit, der sich aus den oben genannten Zielen ableitet, lässt sich in fünf Forschungsfragen zur Schichtplanung für Zugbegleiter mit Zugbegleitquoten zusammenfassen: Q1 Wie ist der aktuelle Forschungsstand zu Schichtplanungsproblemen für das Bahnpersonal und welche Forschungslücken können identifiziert werden? F2 Wie können Schichtplanungsprobleme für Zugbegleiter mit Zugbegleitquoten modelliert werden? F3 Wie können Instanzen von Schichtplanungsprobleme für Zugbegleiter mit Zugbegleitquoten im Hinblick auf die Anforderungen der Praxis gelöst werden? F4 Wie kann das entwickelte mathematische Modell und der hybride Lösungsansatz auf einen mehrtägigen Zeitraum ausgedehnt werden? Was ist das Potenzial eines integrierten Ansatzes im Gegensatz zum sequenziellen, tageweisen Ansatz? F5 Kann eine Arc-Flow-Formulierung des Schichtplanungsproblems für Zugbegleiter mit Zugbegleitquoten verwendet werden, um die Lösungsqualität des bisherigen Ansatzes zu bewerten oder sogar zu verbessern? Können gültige Ungleichungen das Verhalten der Arc-Flow-Formulierung in Bezug auf Rechenzeiten und untere Schranken verbessern?:List of Figures IV List of Tables V List of Algorithms VII List of Abbreviations VIII List of Symbols X 1 Introduction 1 1.1 Motivation 1 1.2 Basics of railway crew scheduling 3 1.3 Purpose and research questions 5 1.4 Structure of this work 6 1.5 Research design 10 2 Large-scale optimization techniques 16 2.1 Column generation 16 2.2 Dantzig-Wolfe decomposition for linear programs 18 3 Railway crew scheduling: models, methods and applications 22 3.1 Introduction 23 3.2 Crew planning in railway operations 25 3.2.1 Crew management in strategic and tactical planning 25 3.2.2 Crew scheduling in operational planning 25 3.2.3 Real-time crew re-scheduling in disruption management 27 3.2.4 Technical terms of crew scheduling 28 3.2.5 Special characteristics of transportation modes 29 3.3 Overview of RCSP literature 32 3.3.1 Planning stage 32 3.3.2 Mode 33 3.3.3 Crew type 33 3.3.4 Model 34 3.3.5 Objective 34 3.3.6 Solution method 34 3.3.7 Country 35 3.4 Model formulations, objectives and constraints of RCSP 40 3.4.1 Model formulations 40 3.4.2 Objectives 44 3.4.3 Constraints 48 3.5 Solution methods 50 3.5.1 Integer programming methods 51 3.5.2 Heuristics 54 3.5.3 Column generation 56 3.5.4 Meta-heuristics 64 3.6 Conclusion and further research opportunities 67 3.7 Decision support tools and railway crew scheduling in practice 69 4 Schichtplanung von Zugbegleitpersonal unter Berücksichtigung von Prüfquoten 74 4.1 Einleitung 75 4.2 Planungsprozesse im Schienenpersonennahverkehr 76 4.3 Problembeschreibung 78 4.3.1 Klassifikation 79 4.3.2 Betriebliche und rechtliche Rahmenbedingungen 80 4.4 Modellierung als Set-Covering-Problem 81 4.5 Modellierung der Schichtplanung der Zugbegleiter mit Prüfquoten 83 4.6 Beispiel 84 4.7 Zusammenfassung und Ausblick 88 5 A hybrid solution approach for railway crew scheduling problems with attendance rates 89 5.1 Introduction 90 5.2 Crew scheduling problem with attendance rates 90 5.3 Hybrid solution approach 92 5.4 Computational results 94 5.5 Conclusions and further research 95 6 Solving practical railway crew scheduling problems with attendance rates 97 6.1 Introduction 98 6.2 Related work 100 6.3 The crew scheduling problem with attendance rates 102 6.3.1 Analytics-based design 102 6.3.2 Problem description and practical requirements 103 6.3.3 Problem formulation 104 6.4 Solution approaches for the MCSPAR 107 6.4.1 A multi-period column generation algorithm 107 6.4.2 Solving the pricing problem 109 6.5 Artifact evaluation 112 6.5.1 Considered transport networks and experimental design 112 6.5.2 Evaluation and comparison of algorithms 114 6.6 Conclusions and further research 116 7 Valid inequalities for the arc flow formulation of the railway crew scheduling problem with attendance rates 118 7.1 Introduction 119 7.2 Related work 121 7.3 Problem description and practical requirements 122 7.4 Arc flow formulation 124 7.5 Valid inequalities 130 7.5.1 Model specic valid inequalities 130 7.5.2 Symmetry breaking constraints 131 7.5.3 Parallel arcs 132 7.5.4 Fixed arcs 132 7.6 Computational results 133 7.6.1 Small-sized instances 134 7.6.2 Bounds for real-world instances 138 7.6.3 Improve heuristic solution 139 7.7 Conclusion 140 8 Conclusion 144 8.1 Summary 144 8.2 Future research 148 A Declarations of authorship 151 Bibliography 155 / In Germany, the number of passengers and the transport performance in regional and long-distance rail passenger transport increase constantly over the last decades. For example, the number of passengers carried in regional rail passenger transport rose from 1.96 billion in 2004 to 2.72 billion in 2018. This represents an increase of almost 39%. However, it is becoming increasingly difficult for railway companies to cover the required transport services by drivers and conductors due to the shortage of skilled workers. This implies that a greater transport performance must be achieved with fewer resources, thus resource-saving and at the same time cost-efficient planning of personnel is essential. This work aims to develop a solution concept for optimized and automated railway crew scheduling, especially ensuring attendance rates for conductors in regional trains. Since there already exists a variety of publications concerning modeling approaches and solution methods related to railway crew scheduling, the first step is to identify and classify relevant literature. This is necessary to determine suitable mathematical formulations and solution approaches which can also be used or further modified for the special case of railway crew scheduling problems with attendance rates for conductors. By systematizing the reviewed articles according to model formulations, objectives, constraints and solution methods, research gaps can easily be identified and opportunities for further research can be revealed. After an analysis of the given legal requirements, regulations from labor contracts, operating conditions and claims under transportation contracts, a first goal of this work is the development of a mathematical model which represents the given problem with attendance rates for conductors. In order to first analyze the effect of the new constraints on attendance rates, further requirements necessary in practice can be omitted (e.g. personnel capacity at crew bases) and the planning horizon can be limited to one day. After modeling the problem with further requirements, this work aims to develop a suitable solution approach which, above all, guarantees the solvability of large real-world instances. The generated shift schedules have to meet legal, contractual and operational requirements and thereby minimize the resulting costs. Since in practice a planning period of one day is neither operationally reasonable nor cost-efficient, the next goal is to extend the planning period to several days. This extension should affect both the model and the developed solution approach. This allows further restrictions concerning several days to be integrated, such as the uniform distribution of attended trips. In research, it is important to establish comparability or an assessment of the quality of the model or solution method. For this reason, an arc-flow formulation of the crew scheduling problem with attendance rates should be formulated to solve small-sized instances optimally and provide lower bounds for real-world instances. To accelerate and improve the arc-flow formulation solution, the application of valid inequalities will be validated. The purpose of this work derived from the above mentioned objectives can be summarized into five research questions on railway crew scheduling with and without attendance rates for conductors: Q1 What is the current state of research for railway crew scheduling problems and which research gaps can be identified? Q2 How can railway crew scheduling problems with attendance rates for conductors be modeled? Q3 How can instances of railway crew scheduling problems with attendance rates be solved with regard to real-world requirements? Q4 How can the developed mathematical model and hybrid solution approach be extended to a multiple day period? What is the potential of an integrated approach in contrast to the sequential day-by-day approach? Q5 Can an arc-flow formulation of the railway crew scheduling problem with attendance rates be used to evaluate or even enhance the solution quality of the previous approach? Can valid inequalities improve the performance of the arc-flow formulation concerning computing times and lower bounds?:List of Figures IV List of Tables V List of Algorithms VII List of Abbreviations VIII List of Symbols X 1 Introduction 1 1.1 Motivation 1 1.2 Basics of railway crew scheduling 3 1.3 Purpose and research questions 5 1.4 Structure of this work 6 1.5 Research design 10 2 Large-scale optimization techniques 16 2.1 Column generation 16 2.2 Dantzig-Wolfe decomposition for linear programs 18 3 Railway crew scheduling: models, methods and applications 22 3.1 Introduction 23 3.2 Crew planning in railway operations 25 3.2.1 Crew management in strategic and tactical planning 25 3.2.2 Crew scheduling in operational planning 25 3.2.3 Real-time crew re-scheduling in disruption management 27 3.2.4 Technical terms of crew scheduling 28 3.2.5 Special characteristics of transportation modes 29 3.3 Overview of RCSP literature 32 3.3.1 Planning stage 32 3.3.2 Mode 33 3.3.3 Crew type 33 3.3.4 Model 34 3.3.5 Objective 34 3.3.6 Solution method 34 3.3.7 Country 35 3.4 Model formulations, objectives and constraints of RCSP 40 3.4.1 Model formulations 40 3.4.2 Objectives 44 3.4.3 Constraints 48 3.5 Solution methods 50 3.5.1 Integer programming methods 51 3.5.2 Heuristics 54 3.5.3 Column generation 56 3.5.4 Meta-heuristics 64 3.6 Conclusion and further research opportunities 67 3.7 Decision support tools and railway crew scheduling in practice 69 4 Schichtplanung von Zugbegleitpersonal unter Berücksichtigung von Prüfquoten 74 4.1 Einleitung 75 4.2 Planungsprozesse im Schienenpersonennahverkehr 76 4.3 Problembeschreibung 78 4.3.1 Klassifikation 79 4.3.2 Betriebliche und rechtliche Rahmenbedingungen 80 4.4 Modellierung als Set-Covering-Problem 81 4.5 Modellierung der Schichtplanung der Zugbegleiter mit Prüfquoten 83 4.6 Beispiel 84 4.7 Zusammenfassung und Ausblick 88 5 A hybrid solution approach for railway crew scheduling problems with attendance rates 89 5.1 Introduction 90 5.2 Crew scheduling problem with attendance rates 90 5.3 Hybrid solution approach 92 5.4 Computational results 94 5.5 Conclusions and further research 95 6 Solving practical railway crew scheduling problems with attendance rates 97 6.1 Introduction 98 6.2 Related work 100 6.3 The crew scheduling problem with attendance rates 102 6.3.1 Analytics-based design 102 6.3.2 Problem description and practical requirements 103 6.3.3 Problem formulation 104 6.4 Solution approaches for the MCSPAR 107 6.4.1 A multi-period column generation algorithm 107 6.4.2 Solving the pricing problem 109 6.5 Artifact evaluation 112 6.5.1 Considered transport networks and experimental design 112 6.5.2 Evaluation and comparison of algorithms 114 6.6 Conclusions and further research 116 7 Valid inequalities for the arc flow formulation of the railway crew scheduling problem with attendance rates 118 7.1 Introduction 119 7.2 Related work 121 7.3 Problem description and practical requirements 122 7.4 Arc flow formulation 124 7.5 Valid inequalities 130 7.5.1 Model specic valid inequalities 130 7.5.2 Symmetry breaking constraints 131 7.5.3 Parallel arcs 132 7.5.4 Fixed arcs 132 7.6 Computational results 133 7.6.1 Small-sized instances 134 7.6.2 Bounds for real-world instances 138 7.6.3 Improve heuristic solution 139 7.7 Conclusion 140 8 Conclusion 144 8.1 Summary 144 8.2 Future research 148 A Declarations of authorship 151 Bibliography 155

Thesis (M. Tech.) - Central University of Technology, Free State, 2011 / The objectives of this research were to investigate and establish a procedure to determine the self-damping characteristics of transmission line conductors subjected to free and forced vibrations. The TERN and Aero-Z IEC62219-REV240609 conductor cables were the transmission line conductors that were readily available at the Vibration Research and Testing Centre (VTRC) of the University of KwaZulu-Natal (UKZN). The question to be answered was whether the self-damping characteristics of the TERN and Aero-Z IEC62219-REV240609 conductors were adequate to suppress Aeolian or wake-induced vibrations. In other words, is it necessary for external damping mechanisms to be used with these conductors? This study confirmed that the self-damping characteristics of conductors are not adequate to suppress Aeolian or wake-induced vibrations. Governing partial differential equations describing the characteristics of the catenary and parabolic cable conductors were developed to validate the experimental results. The experimental tests involved both conductors being subjected to an impulse function (a free vibration method) and also to a harmonic function (a forced vibration method). Measurements were carried out using accelerometers, and the recording equipment consisted of oscilloscopes and the PUMA system. With both the free and forced vibration methods, the damping factor of the TERN conductor was confirmed to be ζ ≤ 0.05, whereas the damping factor of the Aero-Z IEC62219-REV240609 was confirmed to be ζ ≤ 0.2. A procedure for determining the self-damping characteristics of the TERN and Aero-Z IEC62219-REV240609 conductors was developed, with the damping factor found to be ζ ≤ 0.2 for both conductors. These methods can assist in the implementation of procedural analysis of the self-damping behaviour of different types of transmission conductors and in finding the most suitable mass absorber (damper) to use in reducing the rate of failure of transmission line conductors. The results of this study can be used to improve the mathematical modelling of Aeolian and wind-induced vibrations where both self-damping properties and a mass absorber are incorporated.

This study concerned the preparation, characterisation and evaluation of different proton conductors for the Reverse Water Gas Shift Reaction (RWGS) and their evaluation as electrolytes for Solid Oxide Fuel Cells (SOFC) under H₂ and O₂. Materials with both catalytic and conductive properties are of a great interest, as their use in electrocatalytical systems may be very important. Sr₃CaZr₀.₅Ta₁.₅O₈.₇₅ (SCZT), BaCe₀.₉Y₀.₁O₂.₉₅ (BCY10) and Ba₃Ca₁.₁₈Nb₁.₈₂O₈.₇₃ (BCN18), were the initial materials in this study. Thermogravimetric analysis under different atmospheres (5%H₂/Ar, Ar, 5%CO₂, etc), were performed on SCZT and BCN18; with both materials being shown to be stable under reducing and oxidising conditions. Conductivity measurements by two terminal a.c. impedance were also conducted on SCZT and BCN18 under oxidising and reducing atmospheres. As found in literature, BCN18 showed mixed conductivity; with electronic conductivity at high temperatures and pure ionic conductivity below 550ºC, This behaviour was shown in chapter 3, where the change on conduction process was observed upon different gas feeds. Its maximum conductivity values for the different atmospheres were: 8.50x10⁻⁵ S/cm (Dry 5%H₂/Ar at 200ºC), 4.24x10⁻⁴ S/cm (Wet 5%H₂/Ar at 500ºC) and 4.48x10⁻³ S/cm (Air at 900ºC). SCZT proton conducting behaviour was also measured (wet and dry 5%H₂/Ar). Exhibiting an order of magnitude higher in total conductivity upon hydration of the gas feed (σdry=1.01x10⁻⁶ and σwet=1.07x10⁻⁵ at 450ºC). The doping of barium cerate with Zr and Zn by Tao and Irvine, lead to a more stable and easily sinterable BaCe₀.₅Zr₀.₃Y₀.₁₆Zn₀.₀₄O₃ (BCZYZ). Following this work, the introduction of ZnO as a sintering aid to SCZT and BCN18 resulted in Sr₃CaZr₀.₄Ta₁.₅Zn₀.₁O₈.₇₅ (SCZTZ), and Ba₃(Ca₁.₁₈Nb₁.₇₀Zn₀.₁₂)O₈.₅₅ (BCNZ); with higher final densities (above 90% dense). As with BCN18, BCNZ also exhibited mixed conductivity; with higher total conductivity values than BCN18. A maximum of total conductivity of 1.85x10⁻³ S/cm at 900ºC for BCNZ was measured against 6.99x10⁻⁴ S/cm at 900ºC for BCN18. A change in conductivity process was observed when using air or wet 5%H₂/Ar, achieving a maximum of 3.85x10⁻⁴ S/cm at 400ºC when under wet hydrogen. All materials (as powders) have shown catalytic activity for the reverse water gas shift (RWGS) reaction, with the lowest conversion temperature onset at 400ºC for SCZT and a maximum conversion of CO₂ to CO of 42%, with circa 0.52 and 0.59 mmol/s.m² of CO produced at 900ºC by BCN18 and BCZYZ, respectively. No relation between mechanisms for the RWGS and σ for these materials were expected below 10% conversion, as no correlation was found between their activation energies. BCY10 as shown a partial decomposition when exposed to the RWGS reaction, for what BCZYZ After fuel cell testing under H₂ and O₂ both SCZTZ and BCNZ showed mixed conductivity. SCZTZ under different hydrogen partial pressures, exhibited a behaviour close to a pure proton conductor, however, when exposed to both reducing and oxidising conditions, its behaviour did not follow the theoretical values. On the other hand, BCNZ behaves as a pure ionic conductor below 500ºC; with increasing influence of the electronic conductivity on temperature increase. However, as seen for BCNZ conductivity data from 2 terminal a.c. impedance, below 650ºC wet 5%H₂ exhibited the highest conductivity values. This, in additions to the pure ionic conductive behaviour below 400ºC (from the effective ionic transport number), suggests that BCNZ becomes closer to a pure proton conductor with temperature decrease.

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