Time-varying volume visualization

Volume rendering is a very active research field in Computer Graphics because of its wide range of applications in various sciences, from medicine to flow mechanics. In this report, we survey a state-of-the-art on time-varying volume rendering. We state several basic concepts and then we establish several criteria to classify the studied works: IVR versus DVR, 4D versus 3D+time, compression techniques, involved architectures, use of parallelism and image-space versus object-space coherence. We also address other related problems as transfer functions and 2D cross-sections computation of time-varying volume data. All the papers reviewed are classified into several tables based on the mentioned classification and, finally, several conclusions are presented.Preprin

Models for designing pipe-grade polyethylenes to resist rapid crack propagation

Plastic pipeline systems have now become dominant for fuel-gas and water distribution networks. Although they have an impressive service record failures do occur, with Rapid Crack Propagation being characterised as the least probable but most potentially catastrophic one. This study investigates the effect of structural morphology and bulk residual strains on the RCP performance of polyethylene pipes, and proposes a new methodology for predicting a safe service envelope. During crack propagation in PE pipes, the fracture surface has two distinct regions; plane strain and plane stress. In addition to the Instrumented Charpy, Reversed Charpy, High Speed Double Torsion, Dynamic Mechanical Analysis and uniaxial tensile testing, S4 tests of extruded pipe specimens were employed in order to evaluate the structural and fracture parameters of pipe grade resins in these two fracture modes on pipe. A new experimental technique, which modified the pipe bore crystallinity without altering the residual strain field (as evaluated from slit ring tests) showed that the bore surface layer properties had much less influence on RCP than previously thought. Parallel with the experimental work, modeling of the fracture mechanisms was also undertaken. Using previous models in the field, such as the adiabatic decohesion model, the plane strain fracture toughness was evaluated while the plane stress fracture toughness was evaluated either from the Reversed Charpy or from the stability of adiabatic drawing in a tensile test. A mixed mode, temperature sensitive toughness was finally evaluated, leading to an overall fracture properties assessment for polyethylene pipes which could be compared directly to the crack driving force during RCP in pipe. By employing a new mathematical approach, which incorporated both the effects of residual strains and pipe stiffness behind the pressure decay length, a previous basic analytical RCP model was further developed and compared to more elaborate finite element and finite volume solutions. The new results were also compared to S4 experiments using high-speed photography and showed that the new methodology could be employed by the end user even when testing facilities are not directly availabl

The compounding of short fibre reinforced thermoplastic composites

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.It is generally accepted that the mechanical properties of short fibre reinforced thermoplastics do not correspond with the high mechanical properties of fibres used to reinforce them. A study is made into the methods of compounding reinforcing fibres into thermoplastics to produce short fibre reinforced thermoplastics of enhanced properties. The initial method chosen for investigation is the twin screw extrusion compounding process. Variables such as fibre feeding arrangement and extrusion screw design are found to be factors influencing the properties of carbon and glass reinforced nylon 6,6. Use is made of computer programs to predict properties, assess compound quality and estimate fibre-matrix bond strength. Investigations indicate that the presence of reinforcing fibres with enhanced lengths does not result in the predicted property increases. The reasons for this shortfall are believed to lie in unfavourable fibre orientation in injection mouldings and the reduced strain to break of these materials. Short Kevlar reinforced thermoplastics are compounded and their mechanical properties assessed. The reasons for the poor mechanical properties for these materials are identified as a poor bond strength between fibre and matrix, the formation of points of weakness within the fibres by the compounding and moulding processes and the coiled arrangement of fibres present in injection mouldings. A method suitable for the routine assessment of fibre-matrix bond strength is used to examine combinations of fibre and thermoplastic matrix. A comparison is made of the values derived from this method with values calculated from stress-strain curves of injection mouldings. This allows an understanding of the nature of the fibre-matrix bond yielded by compounding and injection moulding steps. A description is given of a novel method designed to overcome the limitations of conventional compounding routes to produce long fibre reinforced injection moulding feedstock. Further work is necessary before this method is a feasible production technique

Multiphase flows in polymer microfluidic systems

Continuous delivery of segmented reagents using pressure-driven multiphase flow in microchannels is a promising technology for high throughput microfluidic bioassays. Separation and encapsulation of the target reagents with another inert fluid provide many advantages over single phase flow in microfluidic applications of biotechnology. In order to achieve these advantages and control these multiphase flows, it is necessary to understand their generation and transport characteristics as influenced by geometrical miniaturization, channel wall properties, the effects of surfactants and operating conditions. For gas-liquid two-phase flow, dry air and deionized water were driven into hot embossed PMMA microchannels with 200 μm square test microchannels. Flow regimes, flow maps and the lengths of the gas bubbles and liquid plugs in terms of the liquid volumetric flow ratio (βL) were determined. Continuous generation of regular segmented flow was also discussed. Three sub-regimes of the Segmented flow were identified based on the statistical phase length scales observed over a substantial test channel length. For the liquid-liquid segmented flow, deionized water and perfluorocarbon with a surfactant were used as test fluids in the hot embossed polycarbonate microchannels. The effects of three expansion ratios from the injection to the test channels of 2, 4, and 16 were investigated comparing the flow regimes, transitions and maps in terms of a fixed carrier fluid volumetric flow ratio. The length of the dispersed fluids and the distance between consecutive droplets or plugs in terms of the carrier fluid volumetric flow ratio (βC) were determined. Velocities of the dispersed droplets and plugs were measured using double-pulsed laser illumination and were found to be 1.46 ± 0.08 and 1.25 ± 0.05 times faster than the superficial velocity of the segmented flow, respectively. The multiphase flow pressure drops were measured for all of the flow regimes in gas-liquid two-phase and liquid-liquid segmented flows. Each flow regime identified on the basis of topological observations, including the length scale of each fluid phase and the number of the gas bubbles or dispersed droplets in unit length with respect to the volumetric flow ratio, was associated with different trends in the pressure drop variation

Efficient rendering of large 3-D and 4-D scalar fields

Rendering volumetric data, as a compute/communication intensive and highly parallel application, represents the characteristics of future workloads for desktop computers. Interactively rendering volumetric data has been a challenging problem due to its high computational and communication requirements. With the consistent trend toward high resolution data, it has remained a difficult problem despite the continuous increase in processing power, because of the increasing performance gap between computation and communication. On the other hand, the new multi-core architecture trend in computational units in PC, which can be characterized by parallelism and heterogeneity, provides both opportunities and challenges. While the new on-chip parallel architectures offer opportunities for extremely high performance, widespread use of those parallel processors requires extensive changes in previous algorithms to take advantage of the new architectures. In this dissertation, we develop new methods and techniques to support interactive rendering of large volumetric data. In particular, we present a novel method to layout data on disk for efficiently performing an out-of-core axis-aligned slicing of large multidimensional scalar fields. We also present a new method to efficiently build an out-of-core indexing structure for n-dimensional volumetric data. Then, we describe a streaming model for efficiently implementing volume ray casting on a heterogeneous compute resource environment. We describe how we implement the model on SONY/TOSHIBA/IBM Cell Broadband Engine and on NVIDIA CUDA architecture. Our results show that our out-of-core techniques significantly reduce the communication bandwidth requirements and that our streaming model very effectively makes use of the strengths of those heterogeneous parallel compute resource environment for volume rendering. In all cases, we achieve scalability and load balancing, while hiding memory latency

Magmatic Cu-Ni-PGE-Au sulfide mineralisation in alkaline igneous systems: An example from the Sron Garbh intrusion, Tyndrum, Scotland

Magmatic sulfide deposits typically occur in ultramafic-mafic systems, however, mineralisation can occur in more intermediate and alkaline magmas. Sron Garbh is an appinite-diorite intrusion emplaced into Dalradian metasediments in the Tyndrum area of Scotland that hosts magmatic Cu-Ni-PGE-Au sulfide mineralisation in the appinitic portion. It is thus an example of magmatic sulfide mineralisation hosted by alkaline rocks, and is the most significantly mineralised appinitic intrusion known in the British Isles. The intrusion is irregularly shaped, with an appinite rim, comprising amphibole cumulates classed as vogesites. The central portion of the intrusion is comprised of unmineralised, but pyrite-bearing, diorites. Both appinites and diorites have similar trace element geochemistry that suggests the diorite is a more fractionated differentiate of the appinite from a common source that can be classed with the high Ba-Sr intrusions of the Scottish Caledonides. Mineralisation is present as a disseminated, primary chalcopyrite-pyrite-PGM assemblage and a blebby, pyrite-chalcopyrite assemblage with significant Co-As-rich pyrite. Both assemblages contain minor millerite and Ni-Co-As-sulfides. The mineralisation is Cu-, PPGE-, and Au-rich and IPGE-poor and the platinum group mineral assemblage is overwhelmingly dominated by Pd minerals; however, the bulk rock Pt/Pd ratio is around 0.8. Laser ablation analysis of the sulfides reveals that pyrite and the Ni-Co-sulfides are the primary host for Pt, which is present in solid solution in concentrations of up to 22 ppm in pyrite. Good correlations between all base and precious metals indicate very little hydrothermal remobilisation of metals despite some evidence of secondary pyrite and PGM. Sulfur isotope data indicate some crustal S in the magmatic sulfide assemblages. The source of this is unlikely to have been the local quartzites, but S-rich Dalradian sediments present at depth. The generation of magmatic Cu-Ni-PGE-Au mineralisation at Sron Garbh can be attributed to post-collisional slab drop off that allowed hydrous, low-degree partial melting to take place that produced a Cu-PPGE-Au-enriched melt, which ascended through the crust, assimilating crustal S from the Dalradian sediments. The presence of a number of PGE-enriched sulfide occurrences in appinitic intrusions across the Scottish Caledonides indicates that the region contains certain features that make it more prospective than other alkaline provinces worldwide, which may be linked the post-Caledonian slab drop off event. We propose that the incongruent melting of pre-existing magmatic sulfides or ‘refertilised’ mantle in low-degree partial melts can produce characteristically fractionated, Cu-PPGE-Au-semi metal bearing, hydrous, alkali melts, which, if they undergo sulfide saturation, have the potential to produce alkaline-hosted magmatic sulfide deposits

Efficient Algorithms for Large-Scale Image Analysis

This work develops highly efficient algorithms for analyzing large images. Applications include object-based change detection and screening. The algorithms are 10-100 times as fast as existing software, sometimes even outperforming FGPA/GPU hardware, because they are designed to suit the computer architecture. This thesis describes the implementation details and the underlying algorithm engineering methodology, so that both may also be applied to other applications

Spectral Interpolation on 3 x 3 Stencils for Prediction and Compression

Many scientific, imaging, and geospatial applications produce large high-precision scalar fields sampled on a regular grid. Lossless compression of such data is commonly done using predictive coding, in which weighted combinations of previously coded samples known to both encoder and decoder are used to predict subsequent nearby samples. In hierarchical, incremental, or selective transmission, the spatial pattern of the known neighbors is often irregular and varies from one sample to the next, which precludes prediction based on a single stencil and fixed set of weights. To handle such situations and make the best use of available neighboring samples, we propose a local spectral predictor that offers optimal prediction by tailoring the weights to each configuration of known nearby samples. These weights may be precomputed and stored in a small lookup table. We show through several applications that predictive coding using our spectral predictor improves compression for various sources of high-precision data

Metamorphic zircon formation in gabbroic rocks – the tale of microtextures

Dating of metamorphic events is crucial for the understanding and reconstruction of large-scale geological processes such as orogenesis. Zircon is one of the most commonly used minerals for dating of igneous and metamorphic events. Zircon incorporates uranium and excludes lead during crystallization, and with time the uranium decays to lead. The diffusion rates of both elements are slow, making zircon resilient to isotopic resetting. However, in order to date geological events, it is imperative to know exactly by which process the dated zircon formed. For example, regional metamorphism is a dynamic process taking place over millions of years. During tectonic burial and heating the rock gradually responds to the increasing temperature and pressure, giving rise to prograde mineral assemblages, whereas retrograde metamorphism takes place during cooling and exhumation. So, in a regionally metamorphosed rock, does the zircon age date the tectonic burial or the exhumation? The interpretation of how zircon formed has direct influence on the tectonic interpretation. Zircon can form or recrystallize within a wide range of metamorphic pressures and temperatures and by several different processes. This means that, for meaningful interpretation of a metamorphic zircon age, the zircon growth needs to be linked to the mineral reactions in the rock. Due to the high closure temperature of zircon (the temperature below which zircon will not undergo isotope diffusion), zircon ages have traditionally been assigned to date the peak of metamorphism (the highest temperature). On the other hand, mass balance models suggest that, in mafic rocks, zircon dissolves during prograde and grows during retrograde mineral reactions and therefore generally dates cooling and exhumation.If hydrous fluids are not present, mafic igneous rocks may remain largely unaffected during a metamorphic event. Coarse-grained mafic rocks such as gabbro are the least permeable, and may record the gradual transition from pristine gabbro to its completely metamorphic recrystallized equivalent. Such metamorphic transitions zones provide information about how metamorphic zircon formed. Two different metamorphic transition zones have been investigated in detail in this thesis: a) a gabbro to eclogite transition at Vinddøldalen in south-central Norway and, b) a gabbro to garnet amphibolite transition at Herrestad in South-central Sweden. The aim has been to link reaction textures to zircon growth and to obtain a direct U-Pb age of the metamorphic process. A third study investigates and reviews the zircon-forming textures in a number of metagabbro and metadolerite bodies metamorphosed at different pressures and temperatures. The results in this thesis show that zircon formation is remarkably similar in all of the investigated metagabbroic rocks, and that zircon is mainly produced by the breakdown of igneous baddeleyite during prograde mineral reactions. The metamorphic mineral reactions and the associated zircon formation in gabbroic rocks are tightly linked to deformation and infiltration of hydrous fluids, and to a lesser extent dependent of variations in pressure and temperature. Therefore, in most gabbroic rocks, zircon formation will take place at the earliest stage of metamorphic recrystallization