Adaptive Modeling of Details for Physically-based Sound Synthesis and Propagation

In order to create an immersive virtual world, it is crucial to incorporate a realistic aural experience that complements the visual sense. Physically-based sound simulation is a method to achieve this goal and automatically provides audio-visual correspondence. It simulates the physical process of sound: the pressure variations of a medium originated from some vibrating surface (sound synthesis), propagating as waves in space and reaching human ears (sound propagation). The perceived realism of simulated sounds depends on the accuracy of the computation methods and the computational resource available, and oftentimes it is not feasible to use the most accurate technique for all simulation targets. I propose techniques that model the general sense of sounds and their details separately and adaptively to balance the realism and computational costs of sound simulations. For synthesizing liquid sounds, I present a novel approach that generate sounds due to the vibration of resonating bubbles. My approach uses three levels of bubble modeling to control the trade-offs between quality and efficiency: statistical generation from liquid surface configuration,explicitly tracking of spherical bubbles, and decomposition of non-spherical bubbles to spherical harmonics. For synthesizing rigid-body contact sounds, I propose to improve the realism in two levels using example recordings: first, material parameters that preserve the inherent quality of the recorded material are estimated; then extra details from the example recording that are not fully captured by the material parameters are computed and added. For simulating sound propagation in large, complex scenes, I present a novel hybrid approach that couples numerical and geometric acoustic techniques. By decomposing the spatial domain of a scene and applying the more accurate and expensive numerical acoustic techniques only in limited regions, a user is able to allocate computation resources on where it matters most.Doctor of Philosoph

Seismic observation of the Earth’s small-scale structure

The Earth’s mantle is chemically and thermally heterogeneous varying in 3-dimensions and on many length-scales. Subduction introduces slabs into the mantle while interactions with the core may enrich the mantle in iron. The lower mantle demonstrates the strongest seismic anomalies outside of the crust. The Large Low Shear Velocity Provinces (LLSVPs), two volumes 1000s km across with seismic velocity reductions of 1-3 %, are likely thermally and chemically distinct from the surrounding mantle. Smaller velocity anomalies are detected close to the Core-Mantle Boundary (CMB) such as velocity increases ∼100 km thick often related to subducted slabs, and strong velocity decreases 10-100 km thick called Ultra Low Velocity Zones. Array analysis of signals arriving before PKP demonstrates that they are waves scattered from volumes of anomalous material with 10 km scale-lengths in the lowermost mantle under South Africa. The data image a heterogeneous 80 km tall ridge at the CMB likely related to the edge of the African LLSVP. Scattering is likely caused by heterogeneities with strongly reduced velocities and increased densities probably elevated above the CMB by entrainment into the LLSVP. Scattered PKKP waves (PK•KP) reveal heterogeneities irregularly distributed in the lowermost 300 km of the mantle. Scattering is also seen under South Africa, co-located with PKP observations. Anomalies are preferentially located towards the edges of the LLSVPs and regions of subducted material. The predisposition of small-scale anomalies towards the edge of the large-scale structure suggests control by dynamic processes. P(Pdiff )-travel-times are used to resolve the boundary of the Pacific LLSVP. The east of the LLSVP displays a sharp (60 km wide) transition and is traced steeply upwards sloping at 70◦. The transition at the northern edge is broader (120 km wide) and shallower (30◦slope). The proximity to active subduction may sharpen and steepen the boundary of the LLSVP, providing insight into the dynamics of the lowermost mantle

NASA thesaurus. Volume 3: Definitions

Publication of NASA Thesaurus definitions began with Supplement 1 to the 1985 NASA Thesaurus. The definitions given here represent the complete file of over 3,200 definitions, complimented by nearly 1,000 use references. Definitions of more common or general scientific terms are given a NASA slant if one exists. Certain terms are not defined as a matter of policy: common names, chemical elements, specific models of computers, and nontechnical terms. The NASA Thesaurus predates by a number of years the systematic effort to define terms, therefore not all Thesaurus terms have been defined. Nevertheless, definitions of older terms are continually being added. The following data are provided for each entry: term in uppercase/lowercase form, definition, source, and year the term (not the definition) was added to the NASA Thesaurus. The NASA History Office is the authority for capitalization in satellite and spacecraft names. Definitions with no source given were constructed by lexicographers at the NASA Scientific and Technical Information (STI) Facility who rely on the following sources for their information: experts in the field, literature searches from the NASA STI database, and specialized references

Drilling Fluid Additives for Wellbore Strengthening and Reservoir Protection

The objective of the research was to optimise drilling fluid additives for wellbore strengthening, preventing lost circulation and avoiding drilling fluid induced formation damage. Industry standard testing, such as HTHP fluid loss tests following API 13B, yield limited insight into important areas such as wellbore strengthening and formation damage. Therefore, new testing methodologies were developed and evaluated. These provided new insight into important areas for designing and evaluating drilling fluids and drilling fluid additives for wellbore strengthening and reservoir protection. Key conclusions were that exposing particles to mechanical wear significantly impacted the relative performance of materials used for preventative treatments. Oil-based fluids were found to create a high-degree of internal formation plugging, whereas water-based fluids more predominantly isolated the wellbore pressure from the pore-pressure though an external filter-cake. Inclusion of cellulose based fibres where the D90 value value ⪞ 3/2 the median pore size was shown to reduce internal plugging and reduce formation damage, in both water-based fluids and oil-based fluids. Particle degradation studies showed that CaCO3 degraded rapidly for particles > 23 μm and that the most wear resistant particles were selected cellulose-based materials. Combinations of fine CaCO3 and slightly coarser cellulose mixtures were found to be effective for creating low-permeability filter-cakes and preventing formation damage. For preventative treatment in drilling conditions with large differences between the matrix pore-size and the aperture of natural or induced fractures, a dual mode particle size distribution was found to be effective in both laboratory studies and field applications. In such situations, the fine mode of the PSD provided low filter-cake permeabilities when the particles followed an Andreasen distribution with a packing factor of around 0.08-0.10. Natural and induced fractures were most effectively sealed when granular cellulose particles made up the coarse mode of the PSD and these particles were sized similar to or slightly larger than the fracture aperture

The Architecture of Soft Machines

This thesis speculates about the possibility of softening architecture through machines. In deviating from traditional mechanical conceptions of machines based on autonomous, functional and purely operational notions, the thesis proposes to conceive of machines as corporeal media in co-constituting relationships with human bodies. As machines become corporeal (robots) and human bodies take on qualities of machines (cyborgs) the thesis investigates their relations to architecture through readings of William S. Burroughs’ proto-cyborgian novel The Soft Machine (1961) and Georges Teyssot’s essay ‘Hybrid Architecture: An Environment for the Prosthetic Body’ (2005) arguing for a revision of architecture’s anthropocentric mandate in favour of technologically co-constituting body ideas. The conceptual shift in man-machine relations is also demonstrated by discussion of two installations shown at the Venice Biennale, Daniel Libeskind’s mechanical Three Lessons in Architecture (1985) and Philip Beesely’s responsive Hylozoic Ground (2010). As the purely mechanical model has been superseded by a model that incorporates digital sensing and embedded actuation, as well as soft and compliant materiality, the promise of softer, more sensitive and corporeal conceptions of technology shines onto architecture. Following Nicholas Negroponte’s ambition for a ‘humanism through machines,’ stated in his groundbreaking work, Soft Architecture Machines (1975), and inspired by recent developments in the emerging field of soft robotics, I have developed a series of practical design experiments, ranging from soft mechanical hybrids to soft machines made entirely from silicone and actuated by embedded pneumatics, to speculate about architectural environments capable of interacting with humans. In a radical departure from traditional mechanical conceptions based on modalities of assembly, the design of these types of soft machines is derived from soft organisms such as molluscs (octopi, snails, jellyfish) in order to infuse them with notions of flexibility, compliance, sensitivity, passive dynamics and spatial variability. Challenging architecture’s alliance with notions of permanence and monumentality, the thesis finally formulates a critique of static typologisation of space with walls, floors, columns or windows. In proposing an embodied architecture the thesis concludes by speculating about architecture as a capacitated, sensitive and sensual body informed by reciprocal conditioning of constituent systems, materials, morphologies and behaviours