The Dynamics of Ventilated Partial Cavities over a Wide Range of Reynolds Numbers and Quantitative 2D X-ray Densitometry for Multiphase Flow.

Ventilated partial cavity drag reduction is a technique that could potentially enable reduction of a ship's frictional drag, leading to a 5 to 20% net fuel savings, and thus providing economic and environmental benefits. Ventilated partial cavity drag reduction experiments were conducted using two geometrically similar experimental setups. First, experiments were performed at the world's largest re-circulating water channel, the U.S. Navy's Large Cavitation Channel (LCC), at Reynolds numbers to 80 million. For these experiments the LCC was adapted to allow free surface testing, which in itself was a major effort. The effect of the cavity closure geometry, and the cavity's robustness in the presence of global flow perturbations mimicking the effect of ambient waves were studied. Next, the experiments were reproduced at 1:14th size scale at Reynolds numbers of the order of one million, and in these small scale experiments the effect of Weber number was also investigated by reducing the surface tension by a factor of two. Results from these two sets of experiments were compared, and a potential scaling of required ventilation gas flux discussed. In addition the energy economics of the partial cavity drag reduction technique were analyzed. We can note that for partial cavities, the air entrainment is dominated by the cavity closure dynamics. To gain a better understanding of these dynamics, knowing the void fraction distribution, both spatially and temporally, would be very useful. In the cavity's closure region, as well as in most cavitating flows, any intrusive probe would perturb the flow greatly. X-ray densitometry offers a way to obtain a two dimensional time-resolved projection of the void fraction distribution, and a quantitative measure of the void fraction along the beam paths. An x-ray densitometry system was developed for use with a pre-existing cavitation tunnel. The limitations of the x-ray system were investigated, methods to contend with the imaging artifacts found, and the measured void fraction profiles compared against those obtained employing dual fiber optical probes and high speed video.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91443/1/smakihar_1.pd

Advances in Grid Computing

This book approaches the grid computing with a perspective on the latest achievements in the field, providing an insight into the current research trends and advances, and presenting a large range of innovative research papers. The topics covered in this book include resource and data management, grid architectures and development, and grid-enabled applications. New ideas employing heuristic methods from swarm intelligence or genetic algorithm and quantum encryption are considered in order to explain two main aspects of grid computing: resource management and data management. The book addresses also some aspects of grid computing that regard architecture and development, and includes a diverse range of applications for grid computing, including possible human grid computing system, simulation of the fusion reaction, ubiquitous healthcare service provisioning and complex water systems

Investigating human-perceptual properties of "shapes" using 3D shapes and 2D fonts

Shapes are generally used to convey meaning. They are used in video games, films and other multimedia, in diverse ways. 3D shapes may be destined for virtual scenes or represent objects to be constructed in the real-world. Fonts add character to an otherwise plain block of text, allowing the writer to make important points more visually prominent or distinct from other text. They can indicate the structure of a document, at a glance. Rather than studying shapes through traditional geometric shape descriptors, we provide alternative methods to describe and analyse shapes, from a lens of human perception. This is done via the concepts of Schelling Points and Image Specificity. Schelling Points are choices people make when they aim to match with what they expect others to choose but cannot communicate with others to determine an answer. We study whole mesh selections in this setting, where Schelling Meshes are the most frequently selected shapes. The key idea behind image Specificity is that different images evoke different descriptions; but ‘Specific’ images yield more consistent descriptions than others. We apply Specificity to 2D fonts. We show that each concept can be learned and predict them for fonts and 3D shapes, respectively, using a depth image-based convolutional neural network. Results are shown for a range of fonts and 3D shapes and we demonstrate that font Specificity and the Schelling meshes concept are useful for visualisation, clustering, and search applications. Overall, we find that each concept represents similarities between their respective type of shape, even when there are discontinuities between the shape geometries themselves. The ‘context’ of these similarities is in some kind of abstract or subjective meaning which is consistent among different people

Painterly interfaces for audiovisual performance

Thesis (S.M.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 2000.Includes bibliographical references (p. 145-149).This thesis presents a new computer interface metaphor for the real-time and simultaneous performance of dynamic imagery and sound. This metaphor is based on the idea of an inexhaustible, infinitely variable, time-based, audiovisual "substance" which can be gesturally created, deposited, manipulated and deleted in a free-form, non-diagrammatic image space. The interface metaphor is exemplified by five interactive audiovisual synthesis systems whose visual and aural dimensions are deeply plastic, commensurately malleable, and tightly connected by perceptually- motivated mappings. The principles, patterns and challenges which structured the design of these five software systems are extracted and discussed, after which the expressive capacities of the five systems are compared and evaluated.Golan Levin.S.M

Alfvén waves underlying ionospheric destabilization: ground-based observations

During geomagnetic storms, terawatts of power in the million mile-per-hour solar wind pierce the Earth’s magnetosphere. Geomagnetic storms and substorms create transverse magnetic waves known as Alfvén waves. In the auroral acceleration region, Alfvén waves accelerate electrons up to one-tenth the speed of light via wave-particle interactions. These inertial Alfvén wave (IAW) accelerated electrons are imbued with sub-100 meter structure perpendicular to geomagnetic field B. The IAW electric field parallel to B accelerates electrons up to about 10 keV along B. The IAW dispersion relation quantifies the precipitating electron striation observed with high-speed cameras as spatiotemporally dynamic fine structured aurora. A network of tightly synchronized tomographic auroral observatories using model based iterative reconstruction (MBIR) techniques were developed in this dissertation. The TRANSCAR electron penetration model creates a basis set of monoenergetic electron beam eigenprofiles of auroral volume emission rate for the given location and ionospheric conditions. Each eigenprofile consists of nearly 200 broadband line spectra modulated by atmospheric attenuation, bandstop filter and imager quantum efficiency. The L-BFGS-B minimization routine combined with sub-pixel registered electron multiplying CCD video stream at order 10 ms cadence yields estimates of electron differential number flux at the top of the ionosphere. Our automatic data curation algorithm reduces one terabyte/camera/day into accurate MBIR-processed estimates of IAW-driven electron precipitation microstructure. This computer vision structured auroral discrimination algorithm was developed using a multiscale dual-camera system observing a 175 km and 14 km swath of sky simultaneously. This collective behavior algorithm exploits the “swarm” behavior of aurora, detectable even as video SNR approaches zero. A modified version of the algorithm is applied to topside ionospheric radar at Mars and broadcast FM passive radar. The fusion of data from coherent radar backscatter and optical data at order 10 ms cadence confirms and further quantifies the relation of strong Langmuir turbulence and streaming plasma upflows in the ionosphere with the finest spatiotemporal auroral dynamics associated with IAW acceleration. The software programs developed in this dissertation solve the century-old problem of automatically discriminating finely structured aurora from other forms and pushes the observational wave-particle science frontiers forward