A study based on surface wave dispersion and receiver functions

Madagascar and Sri Lanka are key regions to understand the amalgamation and break-up of Gondwana; both islands were located centrally in the supercontinent and in the Pan-African Orogen. We determined crustal radial seismic anisotropy in southern Madagascar and the crustal velocity structure in Sri Lanka and compared our findings to those derived in other studies of Pan-African regions. We found major similarities, supporting the hypothesis that these once juxtaposed regions experienced major crustal unification through orogenetic processes. We determined radial anisotropy (RA) in the crust of southern Madagascar from the differences between the speeds of vertically and horizontally polarized shear waves (VSV and VSH). The latter we derived from Rayleigh and Love surface wave dispersion determined from seismic ambient noise cross-correlations. The amalgamated Precambrian units in the east and the Phanerozoic Morondava basin in the west of southern Madagascar were shaped by different geodynamic processes: The crystalline basement was strongly deformed and metamorphosed to varying degrees during the assembly of Gondwana and the Pan-African Orogeny, whereas the Morondava basin was formed during the separation of Africa and Madagascar. The different developments are reflected in first order differences in the radial anisotropy structure. In the Precambrian domains, positive RA (VSVVSH) in between. The upper crustal anisotropy may reflect shallowly dipping layering within the Archean units and adjacent imbricated nappe stacks, whereas the lower crustal anisotropy likely represents fossilized crustal flow during the syn- or post-orogenic collapse of the Pan-African Orogen. The layer of negative RA may have preserved vertically oriented large shear zones of late Pan-African age. Within the Morondava basin, negative RA in the uppermost ∼5 km could have been generated by steep normal faults, jointing, and magmatic dike intrusions. The deeper sediments and underlying crustal basement are characterized by positive RA. This is consistent with horizontal bedding in the sediments and with the alignment of fabrics in the basement created by extension during the basin formation. The crust of Sri Lanka mostly consists of Precambrian rocks. We analyzed newly derived data from a temporary seismic network deployed in 2016–2017. Rayleigh wave phase dispersion from ambient noise cross-correlation and receiver functions were jointly inverted for the seismic structure using a transdimensional Bayesian approach. We determined Moho interface depths between 30–40 km, with the thickest crust (38–40 km) beneath the central Highland Complex (HC). The thinnest crust (30–35 km) is along the west coast, which experienced crustal thinning through the formation of the Mannar basin. The majority of VP/VS ratios are within a range of 1.66–1.73 and redominantly favor a felsic bulk crustal composition with intermediate to high silica content. A major intra-crustal (18–27 km), westward dipping (∼4.3°) interface with high VS (∼4 km/s) underneath is prominent in the central HC, continuing into the eastern Vijayan Complex (VC). The dipping discontinuity anda low velocity zone in the upper crust of the central HC can be related to the HC/VC contact zone. They are also in agreement with the well-established amalgamation theory of Sri Lanka, described by a stepwise collision of the arc fragments during Gondwana’s assembly, and deep crustal thrusting processes and a transpressional regime along the suture between HC and VC. We found striking similarities of seismic properties between southern Madagascar and Sri Lanka, and southern India and East Antarctica as once juxtaposed Pan-African terranes. Their crustal thicknesses range between 35–40 km in regions with little to no influence of post-orogenic processes such as rifting or younger orogeny. Pan-African crust of all comparison studies agree to average crustal VP/VS ratios on the lower side (1.65–1.78), indicating felsic to intermediate bulk crustal compositions. Sri Lanka shows higher surface VS (3.1–3.6 km/s) compared to average values in southern Madagascar (3.2–3.4 km/s) and southern India (3.2 km/s), which might be due to different burial depths and metamorphic grade of surface rocks during the Pan-African Orogeny, or different petrological compositions. A low velocity layer in the upper crust as we observe in central Sri Lanka is also present in other Pan-African terranes, and possibly was generated through retrograde metamorphic processes and fluid migration during the transpressive regime. The strong similarities of seismic crustal properties between these regions might be attributed to the region spanning unification of crustal structures through extensive common overprinting during the Pan-African Orogeny. Differences might be seen as consequence of autochtone terrane compositions, positions within the orogen, and individual reworking processes after the orogeny. We developed a software (BayHunter), implementing a Bayesian inversion approach, to estimate a range of models that fit the data and outputs meaningful uncertainty estimations. BayHunter is a Python framework to perform a Markov chain Monte Carlo (McMC) transdimensional Bayesian inversion of surface wave dispersion and receiver functions. The algorithm follows a data-driven strategy and solves for the velocity-depth structure, the number of layers, noise scaling parameters and VP/VS ratio. BayHunter was developed and used for the inversion of seismic data in Sri Lank

Development of an augmented reality guided computer assisted orthopaedic surgery system

Previously held under moratorium from 1st December 2016 until 1st December 2021.This body of work documents the developed of a proof of concept augmented reality guided computer assisted orthopaedic surgery system – ARgCAOS. After initial investigation a visible-spectrum single camera tool-mounted tracking system based upon fiducial planar markers was implemented. The use of visible-spectrum cameras, as opposed to the infra-red cameras typically used by surgical tracking systems, allowed the captured image to be streamed to a display in an intelligible fashion. The tracking information defined the location of physical objects relative to the camera. Therefore, this information allowed virtual models to be overlaid onto the camera image. This produced a convincing augmented experience, whereby the virtual objects appeared to be within the physical world, moving with both the camera and markers as expected of physical objects. Analysis of the first generation system identified both accuracy and graphical inadequacies, prompting the development of a second generation system. This too was based upon a tool-mounted fiducial marker system, and improved performance to near-millimetre probing accuracy. A resection system was incorporated into the system, and utilising the tracking information controlled resection was performed, producing sub-millimetre accuracies. Several complications resulted from the tool-mounted approach. Therefore, a third generation system was developed. This final generation deployed a stereoscopic visible-spectrum camera system affixed to a head-mounted display worn by the user. The system allowed the augmentation of the natural view of the user, providing convincing and immersive three dimensional augmented guidance, with probing and resection accuracies of 0.55±0.04 and 0.34±0.04 mm, respectively.This body of work documents the developed of a proof of concept augmented reality guided computer assisted orthopaedic surgery system – ARgCAOS. After initial investigation a visible-spectrum single camera tool-mounted tracking system based upon fiducial planar markers was implemented. The use of visible-spectrum cameras, as opposed to the infra-red cameras typically used by surgical tracking systems, allowed the captured image to be streamed to a display in an intelligible fashion. The tracking information defined the location of physical objects relative to the camera. Therefore, this information allowed virtual models to be overlaid onto the camera image. This produced a convincing augmented experience, whereby the virtual objects appeared to be within the physical world, moving with both the camera and markers as expected of physical objects. Analysis of the first generation system identified both accuracy and graphical inadequacies, prompting the development of a second generation system. This too was based upon a tool-mounted fiducial marker system, and improved performance to near-millimetre probing accuracy. A resection system was incorporated into the system, and utilising the tracking information controlled resection was performed, producing sub-millimetre accuracies. Several complications resulted from the tool-mounted approach. Therefore, a third generation system was developed. This final generation deployed a stereoscopic visible-spectrum camera system affixed to a head-mounted display worn by the user. The system allowed the augmentation of the natural view of the user, providing convincing and immersive three dimensional augmented guidance, with probing and resection accuracies of 0.55±0.04 and 0.34±0.04 mm, respectively

The geology and geochemistry of the Etendeka Formation quartz latites, Namibia

The Etendeka Formation volcanics of north-western Namibia form part of the Karoo Igneous Province of southern Africa and consist of a series of basalts interbedded with quartz latites and minor volumes of latite. This thesis examines various aspects of the geology and geochemistry of the quartz latites, in particular the volcanological and petrogenetic origin of these rocks . This study has involved the geological mapping of ca. 5000 km² of the southern Etendeka region and the documentation of the field and petrographic characteristics of the quartz latites. 183 whole rock quartz latite samples have been analysed for 32 elements by x-ray fluorescence spectrometry and 17 of these samples were selected for detailed mineral analyses by electron microprobe

Spatio-Temporal Modeling for Action Recognition in Videos

Technological innovation in the field of video action recognition drives the development of video-based real-world applications. This PhD thesis provides a new set of machine learning algorithms for processing videos efficiently, leading to outstanding results in human action recognition in videos. First of all, two video representation extraction methods, Temporal Squeezed Pooling (TSP) and Pixel-Wise Temporal Projection (PWTP), are proposed in order to enhance the discriminative video feature learning abilities of Deep Neural Networks (DNNs). TSP enables spatio-temporal modeling by temporally aggregating the information from long video frame sequences. PWTP is an improved version TSP, which filters out static appearance while performing information aggregation. Secondly, we discuss how to address the long-term dependency modeling problem of video DNNs. To this end, we develop two spatio-temporal attention mechanisms, Region-based Non-local (RNL) and Convolution Pyramid Attention (CPA). We devise an attention chain by connecting the RNL or CPA module to the Squeeze-Excitation (SE) operation. We demonstrate how the attention mechanisms can be embedded into deep networks to alleviate the optimization difficulty. Finally, we are focused on tackling the problem of heavy computational cost in video models. To this end, we introduce the concept of busy-quiet video disentangling for exceedingly fast video modeling. We propose the Motion Band-Pass Module (MBPM) embedded into the Busy-Quiet Net (BQN) architecture to reduce videos’ information redundancy in the spatial and temporal dimensions. The BQN architecture is extremely lightweight while still performing better than other heavier models. Extensive experiments for all the proposed methods are provided on multiple video benchmarks, including UCF101, HMDB51, Kinetics400, Something-Something V1

ADAPTABLES 2006 : proceedings of the joint CIB, Tensinet, IASS international conference on adaptability in design and construction, Volume 3

No abstract

A Study of Technological Innovation in New Zealand

This thesis addresses the research problem of "what are the key underpinning assets or drivers of technological innovation, and how can they be harnessed to create competitive advantage?" Technological change is an evolutionary process. Research and technological innovation creates knowledge and technology that is irreversible in the sense that inventions can be superseded but not "uninvented". Technological innovation creates knowledge and technology that is cumulative because it lays a platform for further knowledge creation, or sets in place another rung in an ascending ladder of new performance characteristics or properties which are demonstrably superior to their antecedents. In turn, the asset specificity and irreversibility of technology and its cumulativeness create barriers to competitive entry. This allows a firm to earn the premiums that create market power and allow further innovation to be financed. The model of technological innovation advanced in this thesis has at its core the strategic governance framework of a firm, within which the dynamics of significant new technology, human capital and social processes are catalysed and made productive by differentiated technological learning processes. No one type of technological learning applies universally, but rather learning is differentiated by variables such as firm size and structure, the past experience and core competencies of the firm, its human capital stocks, social processes, interactions with the external environment, and a host of market, institutional and technological factors. It is argued that the dynamics of significant new technology, human capital and social processes are fundamental and necessary conditions of technological innovation. Technological learning processes underly and provide a connecting thread that integrates these necessary conditions into a model of technological innovation that can be applied by managers to create and sustain competitive advantage. Technological learning both shapes and is shaped by the human capital stocks and social processes of a firm. Learning processes give rise to significant new technology, and the dynamics of that technology in turn helps catalyse and gives rise to further learning. The rate and direction of learning and of technological innovation is also driven by the firm's interaction with external sources of ideas and technology. To create competitive advantage through technological innovation business managers must address a firm's strategy, human capital-related assets, social processes and technological learning abilities. Policy managers must ensure that the public technostructure is in place to foster human capital creation within an economy and to facilitate access to new ideas and sources of stimulus