This paper describes a general approach to the specification the stable regime speed-flow function, for motorways, as a part of the stable regime Stochastic Fundamental Diagram consistent with main assumptions of Transportation Systems Theory. Main original elements are: • Specification of speed-flow functions consistent with travel time function, such as BPR-like functions; • Calibration from disaggregate data, say data from single vehicle trajectories; • Specification of the speed r. v. distribution consistent with those used in RUT for route choice behavior modelling, such as Gamma, Inv-Gamma.

Given the increasing consciousness toward the environmental footprint of mobility, accommodating environmental objectives in existing transport planning strategies is imperative for research and practice. In this paper, we use the link macroscopic fundamental diagram (MFD) model to develop optimal routing strategies that minimize total system emissions (TSE) in multiple origin-destination (OD) networks. Piecewise linear (PWL) functions are used to approximate MFD for individual links, and to define link-level emissions. Dynamic network constraints, non-vehicle holding constraints, and convex formulations of the PWL functions are considered. Thus, the system-optimum dynamic traffic assignment (SO-DTA) problem with environmental objectives is formulated as a mixed integer linear program (MILP). Finally, on a synthetic network, numerical examples demonstrate the performance of the proposed framework.

Spin-vortices in vertically spaced pairs of thin elliptical Permalloy nanoparticles are investigated. The two vortex cores with parallel out-of-plane magnetization exhibit a strong monopole-like attraction through the spacer much thinner than the core length, thus forming a bound core-core pair. The material of the spacer is designed to suppress both direct and indirect exchange interactions, so the remaining inter-vortex coupling is purely dipolar. In the investigated vortex pairs, the in-plane magnetization in the vortex periphery, outside the vortex cores, curl in opposite directions (have opposite chirality). As a result, the two cores move in opposite directions in response to an in-plane magnetic field, the Zeeman effect of which acts to decouple the core-core pair. This leads to unique dynamics of the spin-vortex parallel-core/antiparallel-chirality pair, which strongly depend on whether the pair is coupled or decoupled. In the coupled state, the cores are held close together by the core-core attraction, which results in short-radius oscillations and a resonance frequency of about 2 GHz for the main rotational eigen-mode. In the decoupled state, the cores are separated by a distance much greater than the core length and gyrate independently with a resonance frequency of the order of 100 MHz. The dynamics of the vortex pair are investigated at 77 K, where there is a bistability between the coupled and decoupled core states. Resonant excitations are used to decouple the cores with pulses of ∼10 Oe in amplitude and ∼100 ps in duration. The ability to decouple a vortex pair using such fast low-power pulses can be useful for multifrequency oscillators and vortex based memory. A search for quantum effects is undertaken at sub-Kelvin temperatures using a dilution refrigerator. Square pulses of 100 ns duration and amplitudes of the order of 1 Oe are applied in-plane to bring the system closer to decoupling, giving the cores a chance to tunnel through the barrier between the coupled and decoupled states. The amplitude required for decoupling is measured as a function of temperature and a leveling off in the decoupling probability is seen below 400 mK, giving some indication of core tunneling. Macroscopic quantum tunneling of magnetization is interesting from the fundamental physics point of view, e.g., as a model system for studying the measurement paradox in quantum mechanics, as well as for current and future computer technology in terms of understanding the ultimate limitations of miniaturizing magnetic memory elements. / I detta arbete studeras spinnvirvlar i elliptiska skivor av Permalloy ordnade i vertikala par. Kärnor av parallell vertikal magnetisering attraherar varandra likt monopoler genom en film mycket tunnare än kärnorna och bildar därmed ett sammankopplat par. Materialet i filmen mellan virvlarna är designat för att förhindra både direkt och indirekt utbytesväxelverkan och lämnar endast kärnornas dipolväxelverkan. I de virvelpar som studeras går den plana magnetiseringen i virvlarnas periferi runt kärnorna åt olika håll (de har motsatt kiralitet). På grund av detta rör sig kärnorna åt olika håll vid applikation av magnetfält i planet (Zeeman effekten) vilket kan leda till att de kopplas isär. Detta ger virvelpar med parallella kärnor och antiparallell kiralitet unika dynamiska egenskaper som ändras med deras tillstånd, sammankopplade eller isärkopplade. I det sammankopplade tillståndet hålls kärnorna ihop av monopolattraktionen vilket gör att de bara kan röra sig i små banor kring sitt magnetiska masscentrum, med en resonansfrekvens på circa 2 GHz. I det isärkopplade tillståndet är kärnorna separerade med ett avstånd som är mycket större än kärnornas diameter, och de rör sig oberoende av varandra med en resonansfrekvens i storleksordningen 100 MHz. Virvelparets dynamik undersöks vid 77 K, där det finns en bistabilitet mellan det sammankopplade och det isärkopplade tillståndet. Pulser med längd ∼100 ps och styrka ∼10 Oe i resonans med det sammankopplade tillståndet används för att koppla isär kärnorna. Att kunna koppla isär dem med så korta lågeffektspulser kan vara användbart för virvelbaserade minnen och multifrekvensoscillatorer. Ett sökande efter kvanteffekter påbörjas vid temperaturer under 1 K med hjälp av en utspädningskyl. Fyrkantsvågor med en längd på 100 ns och en styrka i storleksordningen 1 Oe, orienterade i planet, används för att ge kärnorna en chans att tunnla genom barriären mellan det sammankopplade och det isärkopplade tillståndet. Den vågamplitud som krävs för att koppla isär kärnorna plottas mot temperaturen och kan ses plana ut under 400 mK, vilket ger viss indikation av tunnling. Dessa undersökningar av makroskopisk kvanttunnling av magnetisering kan vara användbar i grundforskning för att studera mätparadoxen i kvantmekanik, men också i modern datorteknologi för att förstå de absoluta begränsningarna i hur små magnetiska minneselement kan göras.

Due to the escalating demand for traffic information and management, the significance of traffic state estimation, which involves the assessment of traffic conditions on road segments with limited measurement data, is increasing. Two primary estimation methods are model-driven and data-driven. The former uses traffic flow models, while the latter relies on extensive historical data to explore relationships between traffic states. Due to the uninterrupted nature of highway traffic flow, conventional model-driven approach is adopted in the study to estimate traffic information from sensing data. Data-driven approach is applied to enhance the estimation results. The project mainly focuses on comparing the estimation performance between the Particle Filter and the commonly used Extended Kalman Filter. These two methods are implemented in combination with two typical traffic flow models: Cell Transmission Model and METANET. Moreover, the project investigates the potential of using vehicle-to-everything (V2X) data in traffic state estimation, either alone or combined with traditional inductive loop detector (ILD) data. Being an emerging traffic data source, V2X communication has been recently installed and tested on the motorways near Stockholm. This study provides essential insights into how V2X data can benefit existing traffic information estimation and its performance. To evaluate the models mentioned above, the estimation algorithms and traffic flow models are implemented in a self-developed platform, which may be useful for further work. Results from simulation experiments show that Particle Filter can carry out traffic state estimation with comparable accuracy to Extended Kalman Filter. While standalone V2X speed data falls short, effective fusion methods are implemented to combine both data types, ultimately achieving the desired accuracy. These fusion methods encompass direct filtering, weighted averaging, and linear regression. Future investigations could broaden their scope to include new data sources, such as unmanned aerial vehicles (UAVs), and delve into advanced data fusion techniques, such as deep learning. / På grund av den ökande efterfrågan på trafikinformation och trafikhantering ökar betydelsen av trafiklägesuppskattning, vilket innebär bedömning av trafikförhållandena på vägsegment med begränsade mätningsdata. Två primära uppskattningsmetoder är modellbaserade och datadrivna metoder. Den förra använder trafikflödesmodeller, medan den senare förlitar sig på omfattande historiska data för att utforska samband mellan trafiklägen. På grund av det oavbrutna vägtrafikflödet antas en konventionell modellbaserad metod i studien för att uppskatta trafikinformation från sensordata. Den datadrivna metoden används för att förbättra estimatresultaten. Projektet fokuserar främst på att jämföra prestandan i uppskattningen mellan Partikelfiltret och den vanligtvis använda Extended Kalman Filter. Dessa två metoder implementeras i kombination med två typiska trafikflödesmodeller: Cell Transmission Model och METANET. Dessutom undersöker projektet möjligheterna att använda fordons-till-allt (V2X) data i trafiklägesuppskattning, antingen ensamt eller i kombination med data från traditionella induktiva slingdetektorer (ILD). Som en framväxande källa till trafikdata har V2X-kommunikation nyligen installerats och testats på motorvägarna nära Stockholm. Denna studie ger väsentlig inblick i hur V2X-data kan gynna befintlig uppskattning av trafikinformation och dess prestanda. För att utvärdera ovan nämnda modeller implementeras uppskattningsalgoritmerna och trafikflödesmodellerna i en självutvecklad plattform, vilket kan vara användbart för framtida arbete. Resultaten från simuleringsexperiment visar att Partikelfiltret kan utföra trafiklägesuppskattning med jämförbar noggrannhet jämfört med Extended Kalman Filter. Medan fristående V2X-hastighetsdata inte når hela vägen fram implementeras effektiva sammanslagningsmetoder för att kombinera båda datatyperna och slutligen uppnå önskad noggrannhet. Dessa sammanslagningsmetoder omfattar direkt filtrering, viktad medelvärdesbildning och linjär regression. Framtida undersökningar kan utvidga deras omfattning för att inkludera nya datakällor, såsom obemannade flygfordon (UAV:er), och utforska avancerade tekniker för datafusion, såsom djupinlärning.

The Aw-Rascle-Zhang (ARZ) model has become a favorable ``second order" macroscopic traffic model, which corrects several shortcomings of the Payne-Whitham (PW) model. The ARZ model possesses a family of flow rate versus density (FD) curves, rather than a single one as in the ``first order" Lighthill-Whitham-Richards (LWR) model. This is more realistic especially during congested traffic state, where the historic fundamental diagram data points are observed to be set-valued. However, the ARZ model also possesses some obvious shortcomings, e.g., it assumes multiple maximum traffic densities which should be a ``property" of road. Instead, we propose a Generalized ARZ (GARZ) model under the generic framework of ``second order" macroscopic models to overcome the drawbacks of the ARZ model. A systematic approach is presented to design generic ``second order" models from historic data, e.g., we construct a family of flow rate curves by fitting with data. Based on the GARZ model, we then propose a phase-transition-like model that allows the flow rate curves to coincide in the free flow regime. The resulting model is called Collapsed GARZ (CGARZ) model. The CGARZ model keeps the flavor of phase transition models in the sense that it assume a single FD function in the free-flow phase. However, one should note that there is no real phase transition in the CGARZ model. To investigate to which extent the new generic ``second order" models (GARZ, CGARZ) improve the prediction accuracy of macroscopic models, we perform a comparison of the proposed models with two types of LWR models and their ``second order" generalizations, given by the ARZ model, via a three-detector problem test. In this test framework, the initial and boundary conditions are derived from real traffic data. In terms of using historic traffic data, a statistical technique, the so-called kernel density estimation, is applied to obtain density and velocity distributions from trajectory data, and a cubic interpolation is employed to formulate boundary condition from single-loop sensor data. Moreover, a relaxation term is added to the momentum equation of selected ``second order" models to address further unrealistic aspects of homogeneous models. Using these inhomogeneous ``second order" models, we study which choices of the relaxation term &tau are realistic. / Mathematics

Travel-time information is essential in Advanced Traveler Information Systems (ATISs) and Advanced Traffic Management Systems (ATMSs). A key component of these systems is the prediction of the spatiotemporal evolution of roadway traffic state and travel time. From the perspective of travelers, such information can result in better traveler route choice and departure time decisions. From the transportation agency perspective, such data provide enhanced information with which to better manage and control the transportation system to reduce congestion, enhance safety, and reduce the carbon footprint of the transportation system. The objective of the research presented in this dissertation is to develop a framework that includes three major categories of methodologies to predict the spatiotemporal evolution of the traffic state. The proposed methodologies include macroscopic traffic modeling, computer vision and recursive probabilistic algorithms. Each developed method attempts to predict traffic state, including roadway travel times, for different prediction horizons. In total, the developed multi-tool framework produces traffic state prediction algorithms ranging from short – (0~5 minutes) to medium-term (1~4 hours) considering departure times up to an hour into the future. The dissertation first develops a particle filter approach for use in short-term traffic state prediction. The flow continuity equation is combined with the Van Aerde fundamental diagram to derive a time series model that can accurately describe the spatiotemporal evolution of traffic state. The developed model is applied within a particle filter approach to provide multi-step traffic state prediction. The testing of the algorithm on a simulated section of I-66 demonstrates that the proposed algorithm can accurately predict the propagation of shockwaves up to five minutes into the future. The developed algorithm is further improved by incorporating on- and off-ramp effects and more realistic boundary conditions. Furthermore, the case study demonstrates that the improved algorithm produces a 50 percent reduction in the prediction error compared to the classic LWR density formulation. Considering the fact that the prediction accuracy deteriorates significantly for longer prediction horizons, historical data are integrated and considered in the measurement update in the developed particle filter approach to extend the prediction horizon up to half an hour into the future. The dissertation then develops a travel time prediction framework using pattern recognition techniques to match historical data with real-time traffic conditions. The Euclidean distance is initially used as the measure of similarity between current and historical traffic patterns. This method is further improved using a dynamic template matching technique developed as part of this research effort. Unlike previous approaches, which use fixed template sizes, the proposed method uses a dynamic template size that is updated each time interval based on the spatiotemporal shape of the congestion upstream of a bottleneck. In addition, the computational cost is reduced using a Fast Fourier Transform instead of a Euclidean distance measure. Subsequently, the historical candidates that are similar to the current conditions are used to predict the experienced travel times. Test results demonstrate that the proposed dynamic template matching method produces significantly better and more stable prediction results for prediction horizons up to 30 minutes into the future for a two hour trip (prediction horizon of two and a half hours) compared to other state-of-the-practice and state-of-the-art methods. Finally, the dissertation develops recursive probabilistic approaches including particle filtering and agent-based modeling methods to predict travel times further into the future. Given the challenges in defining the particle filter time update process, the proposed particle filtering algorithm selects particles from a historical dataset and propagates particles using data trends of past experiences as opposed to using a state-transition model. A partial resampling strategy is then developed to address the degeneracy problem in the particle filtering process. INRIX probe data along I-64 and I-264 from Richmond to Virginia Beach are used to test the proposed algorithm. The results demonstrate that the particle filtering approach produces less than a 10 percent prediction error for trip departures up to one hour into the future for a two hour trip. Furthermore, the dissertation develops an agent-based modeling approach to predict travel times using real-time and historical spatiotemporal traffic data. At the microscopic level, each agent represents an expert in the decision making system, which predicts the travel time for each time interval according to past experiences from a historical dataset. A set of agent interactions are developed to preserve agents that correspond to traffic patterns similar to the real-time measurements and replace invalid agents or agents with negligible weights with new agents. Consequently, the aggregation of each agent's recommendation (predicted travel time with associated weight) provides a macroscopic level of output – predicted travel time distribution. The case study demonstrated that the agent-based model produces less than a 9 percent prediction error for prediction horizons up to one hour into the future. / Ph. D.

In der Humanmedizin wird zur Beurteilung der Magenschleimhautproben das aktualisierte Sydney-System nach STOLTE (1997) angewendet. Das Ziel war es herauszufinden, ob das histologische Grading System auch in der Veterinärmedizin, für die Beurteilung von Pferdemagenschleimhautpräparaten, genutzt werden kann und ob daraus neue Erkenntnisse erwachsen. Von 60 Pferden wurden direkt post mortem Schleimhautproben aus der Pars glandularis (Drüsenschleimhaut), im Bereich der großen Kurvatur und dem Pylorus, entnommen. Die Patienten wurden in 4 Gruppen, 10 operierte (Kolik)pferde, 36 Pferde mit Kolik und infauster Prognose, 6 Pferde mit hochgradigen Magenulzera und 8 Pferde, die nicht auf Grund einer Kolik euthanasiert wurden, eingeteilt. Die makroskopische Beurteilung der 60 Pferdemägen erfolgte nach MURRAY et al. (1989) und MACALLISTER et al. (1995). Die histopathologische Beurteilung erfolgt in der Humanmedizin anhand der Helicobacter-like-Organismen Dichte, dem Grad der chronischen Entzündung, der Aktivität der Gastritis, der Atrophie und der intestinalen Metaplasie. Nach diesen Beurteilungsvariablen wurden die 120 Proben aus den 60 Pferdemägen beurteilt. Die ätiologischen Diagnosen sind in der Humanmedizin das Ergebnis jahrzehntelanger Forschung. Beim Pferd liegen dagegen zur Ätiologie der Gastritis noch keine gesicherten Erkenntnisse vor. Beim Pferd gibt es bestimmte Gastritisformen, die denen des Menschen ähnlich sind. Doch können die morphologischen Befunde in der Veterinärmedizin, nach den jetzigen Erkenntnissen, keinen Ätiologien zugeordnet werden. Die ätiologischen Diagnosen in dieser veterinärmedizinischen Studie beruhen auf der Diagnostik am Menschen und wurden noch nicht auf ihre Richtigkeit beim Pferd überprüft. Von den 60 untersuchten Pferdemägen wiesen 31 makroskopisch Läsionen in der Magenschleimhaut auf. 20 Pferde mit Veränderungen hatten diese in der Pars glandularis. Bei 44 der Pferde bestätigt der histologische Befund, nach dem aktualisierten Sydney- System, das makroskopische Grading. 13 der Pferde hatten nach dem aktualisierten Sydney-System histologisch einen pathologischen Befund, obwohl makroskopisch die Schleimhaut keine Auffälligkeiten aufwies. Bei nur 3 von den 60 Pferden konnte der histologische den makroskopischen Befund nicht bestätigen. Ätiologisch wurde, nach humanmedizinischen Beurteilungskriterien, bei 18 Pferden im Bereich der großen Kurvatur der Pars glandularis und, oder im Bereich des Pylorus eine C-Gastritis (chemische Gastritis), bei 11 Pferden eine like B-Gastritis (bakterielle Gastritis ohne den Nachweis von Helicobacter-like-Organismen), 3 Pferden eine B-Gastritis (bakterielle Gastritis mit dem Nachweis von Helicobacter-like-Organismen) und bei 9 Pferden eine Sonderform der Gastritis diagnostiziert. 6 Pferde bekamen die Diagnose: zur Zeit nicht klassifizierbar und 7 Pferde die deskriptive Diagnose erosive oder ulzerative Gastritis gestellt. 24 Pferde hatten keinen pathologischen Befund in einem der oben genannten Bereiche der Schleimhaut. Die histopathologischen Befunde der Pferde mit einer like-B-Gastritis oder einer B-Gastritis entsprachen nach humanmedizinischen Gesichtspunkten dem Bild einer Helicobacter-pylori-Gastritis beim Menschen. Bandartige Anordnung der Lymphozyten in der Lamina propria mucosae und neutrophile Granulozyten in Verbindung mit einer Atrophie des Drüsenkörpers, intestinaler Metaplasie und Erosionen. Bei drei Pferden konnte in der Warthin–Starry-Färbung und in der IHC-Reaktion Helicobacter-like-Organismen nachgewiesen werden. Die Pylorusschleimhaut war doppelt so häufig, im Vergleich zur Drüsenschleimhaut der großen Kurvatur, von einer like-B-Gastritis oder B-Gastritis betroffen. Die histologische Auswertung von Magenschleimhautbioptaten, in dieser Studie nach dem aktualisierten Sydney-System aus der Humanmedizin, komplettiert die makroskopische (endoskopische) Diagnostik. Nach den Ergebnissen der vorliegenden Studie gehört in der Pferdemedizin zu jeder Gastroskopie die Bioptatentnahme. Das aktualisierte Sydney-System kann in Zukunft in der Veterinärmedizin als Arbeitsgrundlage für die weitere wissenschaftliche Forschung genutzt werden. / Stolte’s updated Sydney system is used in the field of human medicine for grading the gastric mucosa (STOLTE 1997). The goal of this study was to determine whether this system could also be applied for histological parameter grading in veterinary medicine, in order to gain new insights into medications for treating equine gastric mucosa. Post mortem biopsies of mucosa were taken from 60 equines along the greater curve and pylorus of the pars glandularis. The test animals were divided into four groups: 10 post-colic surgery equines, 36 with colic and an infaust prognosis, six with chronic EGUS (equine gastric ulcer syndrome), and eight equines not euthanized for reasons other than colic. Macroscopic grading of the 60 equine stomachs was performed in accordance with MURRAY et al. (1989) and MACALLISTER et al. (1995). In human medicine, histological scoring is based on the following five parameters: density of Helicobacter-like organisms, grade of the chronic inflammation, level of gastric activity, atrophy, and intestinal metaplasia. A total of 120 biopsies taken from the 60 equines were graded according to these parameters. Etiologic diagnoses for humans are the outcome of decades of research, but the etiology of equine gastritis lacks an equivalent foundation. Equines exhibit forms of gastritis similar to those in humans, but their morphology cannot be classified into any specific etiology. In this study, the etiological diagnoses were based on human diagnostics, but their validity for equines has yet to be substantiated. Of the 60 equine stomachs examined, 31 showed lesions in the gastric mucosa, while 20 of those with changes had lesions in the pars glandularis. Histological findings of 44 equines confirmed the macroscopic grading according to the updated Sydney system. Thirteen equines exhibited pathological findings based on the updated Sydney system histology, although no abnormalities were discovered in the macroscopic examination. The histological diagnosis did not confirm the macroscopic grading for only three of the 60 subjects. The following etiological findings were reached in terms of human medicine: 18 equines with type C gastritis (chemical gastritis) along the greater curve of the pars glandularis and/or pylorus, 11 equines with type B-like gastritis (bacterial gastritis without evidence of H-like organisms), three equines with type B gastritis (bacterial gastritis with evidence of H-like organisms), and nine with a special form of gastritis. Six of the equines could not be classified, while seven showed erosive gastritis or ulceration. A total of 24 equines exhibited no pathological findings along any of the above-mentioned mucosae. The histopathological findings of the equines with either type B-like gastritis or type B gastritis corresponded with H pylori gastritis seen in humans, as ligamental lymphocytes in the lamina propria mucosae and neutrophilic granulocytes associated with atrophy of the glandular corpus, intestinal metaplasia, and erosion. Warthin-Starry staining and the IHC reaction confirmed H-like organisms in three of the equines. The frequency of type B-like gastritis or type B gastritis was observed to be twice as high in the pylorus mucosa as along the glandular mucosa of the greater curve. This study has demonstrated that histological analysis of gastric mucosa biopsies graded according to the updated Sydney system for human medicine significantly complements veterinary gastroscopy, which should therefore always include a biopsy. The updated Sydney system can thus serve as a platform for future scientific research in the field of veterinary medicine.

The study investigated South African Grade 10 Physical science learners’ reasoning about basic chemical phenomena at sub-microscopic level. The study adopted a non-experimental, exploratory and descriptive method and was principally guided by the ex-post facto research design using a concurrent embedded strategy of mixed qualitative and qualitative approach. A total of 280 grade 10 physical science learners in their intact classes and six of their teachers participated in the study. The 280 physical science learners comprised of 100 students from two top performing schools, 100 learners from two middle performing schools and the last 80 learners were drawn from two poor performing schools in Gauteng Department of Education’s Tshwane North District. A two-tier multiple-choice paper and pencil Test of Basic Chemistry Knowledge (TBCK) based on the three levels of chemical representation of matter was administered to the 280 physical science learners in their Grade 11 first term to collect both quantitative and qualitative data. In addition to the TBCK, focus group discussions (FGDs) with learners, teacher interviews and document analysis were used to triangulate data. The results revealed that most Grade 10 learners find it easy to identify pure elements and the solid state but find it difficult to negotiate between the three levels (macroscopic, sub-microscopic and symbolic) of chemical representation of matter. It became clear that learners experienced more difficulties in the concepts of basic solutions, acidic solutions, concentration and ionic compounds in solution. It also became apparent that some learners could not tell differences between a diatomic element and a compound indicating conceptual problems when they reason at particle level, and as a result they could not identify a mixture of elements. The results also indicated that the concepts of pure compounds and mixtures of compounds were not easy to comprehend as most learners took a pure compound for a mixture of atoms and a mixture of compounds for a mixture of elements. It is therefore concluded that learners find it difficult negotiating the three levels of chemical representation of matter. However, it is not clear whether the misconceptions the learners showed could be completely attributable to the concepts involved or the nature of the sub-microscopic models that were used in the test as it was also revealed that most teachers were not using sub-microscopic representations during instruction to enable learners to think at particle level. Furthermore, justifications to the multiple-choice tasks revealed lack of understanding of basic chemical concepts as well as language problems amongst learners as they could not clearly express their reasoning. Based on the results, some recommendations to educators, chemistry curriculum planners, teacher education and the chemistry education research field are suggested. / Science and Technology Education / D. Phil. ((Philosophy in Mathematics, Science and Technology Education)

Coal seam gas has been recognised as a new, potential energy resource in New Zealand. Exploration and assessment programmes carried out by various companies have evaluated the resource and indicated that this unconventional gas may form a part of New Zealand's future energy supply. This study has delineated some of the controls between coal properties and gas content in coal seams in selected New Zealand locations. Four coal cores, one from Huntly (Eocene), two from Ohai (Cretaceous) and one from Greymouth (Cretaceous), have been sampled and analysed in terms of gas content and coal properties. Methods used include proximate, sulphur and calorifc value analyses; ash constituent determination; rank assessment; macroscopic analysis; mineralogical analysis; maceral analysis; and gas analyses (desorption, adsorption, gas quality and gas isotopes). Coal cores varied in rank from sub-bituminous B-A (Huntly); sub-bituminous C-A (Ohai); and high volatile bituminous A (Greymouth). All locations contained high vitrinite content (~85 %) with overall relatively low mineral matter observed in most samples. Mineral matter consisted of both detrital grains (quartz in matrix material) and infilling pores and fractures (clays in fusinite pores; carbonates in fractures). Average gas contents were 1.6 m3/t in the Huntly core, 4.7 m3/t in the Ohai cores, and 2.35 m3/t in the Greymouth core. The Ohai core contained more gas and was more saturated than the other cores. Carbon isotopes indicated that the Ohai gas composition was more mature, containing heavier 13C isotopes than either the Huntly or Greymouth gas samples. This indicates the gas was derived from a mixed biogenic and thermogenic source. The Huntly and Greymouth gases appear to be derived from a biogenic (by CO2 reduction) source. The ash yield proved to be the dominant control on gas volume in all locations when the ash yield was above 10 %. Below 10 % the amount of gas variation is unrelated to ash yield. Although organic content had some influence on gas volume, associations were basin and /or rank dependant. In the Huntly core total gas content and structured vitrinite increased together. Although this relationship did not appear in the other cores, in the Ohai SC3 core lost gas and fusinite are associated with each other, while desmocollinite (unstructured vitrinite) correlated positively with residual gas in the Greymouth core. Although it is generally accepted that higher rank coals will have higher adsorption capacities, this was not seen in this data set. Although the lowest rank coal (Huntly) contains the lowest adsorption capacity, the highest adsorption capacity was not seen in the highest rank coal (Greymouth), but in the Ohai coal instead. The Ohai core acted like a higher rank coal with respect to the Greymouth coal, in terms of adsorption capacity, isotopic signatures and gas volume. Two hypothesis can be used to explain these results: (1) That a thermogenically derived gas migrated from down-dip of the SC3 and SC1 drill holes and saturated the section. (2) Rank measurements (e.g. proximate analyses) have a fairly wide variance in both the Greymouth and Ohai coal cores, thus it maybe feasible that the Ohai cores may be higher rank coal than the Greymouth coal core. Although the second hypothesis may explain the adsorption capacity, isotopic signatures and the gas volume, when the data is plotted on a Suggate rank curve, the Ohai coal core is clearly lower rank than the Greymouth core. Thus, pending additional data, the first hypothesis is favoured.

This thesis considers the problem of determining Casimir-Lifshitz forces in inhomogeneous media. The ground-state energy of the electromagnetic field in a piston-geometry is discussed. When the cavity is empty, the Casimir pressure on the piston is finite and independent of the small-scale physics of the media that compose the mirrors. However, it is demonstrated that, when the cavity is filled with an inhomogeneous dielectric medium, the Casimir energy is cut-off dependent. The local behavior of the stress tensor commonly used in calculations of Casimir forces is also determined. It is shown that the usual expression for the stress tensor is not finite anywhere within such a medium, whatever the temporal dispersion or index profile, and that this divergence is unlikely to be removed by modifying the regularisation. These findings suggest that the value of the Casimir pressure may be inextricably dependent on the detailed behavior of the mirror and the medium at large wave vectors. This thesis also examines two exceptions to this rule: first, the case of an idealised metamaterial is considered which, when introduced into a cavity, reduces the magnitude of the Casimir force. It is shown that, although the medium is inhomogeneous, it does not contribute additional scattering events but simply modifies the effective length of the cavity, so the predicted force is finite and can be stated exactly. Secondly, a geometric argument is presented for determining a Casimir stress in a spherical mirror filled with the inhomogeneous medium of Maxwell's fish-eye. This solution questions the idea that the Casimir force of a spherical mirror is repulsive, but prompts additional questions concerning regularisation and the role of non-local effects in determining Casimir forces.