Inspired by the locomotion method of cephalopods such as squids, we propose a novel concept of underwater propeller that utilizes pulsed jet for thrust generation. A squid-inspired robot is expected to possess multiple advantages such as mechanical simplicity, high swimming speed, and low environmental footprint. To understand the physical mechanisms of squid-like jet propulsion, computational simulations are conducted to explore the underlying fluid dynamics and fluid-structure interaction problems.

A two-dimensional fluid-structure numerical model is firstly developed by usingthe Immersed Boundary Method (IBM), which avoids the complexity of body-fitted grid regeneration, and is thus suitable for problems involving large body deformations. Through systematic simulations we demonstrate that the 2D squid-inspired swimmer is capable of long-distance swimming through cyclic deflation-inflation shape change. Through parametric studies, it is found that the body oscillation frequency is the most important parameter determining the hydrodynamics of the swimmer.

The 2D IBM-based model is then extended to an axi-symmetric numerical rendition.Based on control volume analysis, a thrust-drag decoupling strategy and a thrust decomposition method are proposed. In the thrust decomposition method the jet-related thrust is calculated as the summation of three components, the jet flux force, the exit normal stress and the flow momentum force inside the chamber. This method allows us to understand the underlying physics of force generation, e.g. the effects of jet speed profile, jet acceleration, background flow and nozzle geometry. Moreover, it enables the separation of thrust and drag forces on the body (a classical problem in free-swimming bodies) so that it leads to a novel method to calculate the propulsive efficiency.

Finally, a potential-flow-based rendition of a 3D squid-inspired propulsion systemis developed to explore the swimming process and the dynamic characteristics. The results show that in the bursting phase its peak speed depends on the size of the body, the deformation time, the amount of volume change during the deformation, and the size of the nozzle. The optimal speed is found to coincide with the critical formation number, indicating that the formation of vortex rings in the wake plays a pivotal role in the dynamics of the system.

Initiatives such as the Google Print Library Project and the Million Book Project have already archived more than fifteen million books in digital format, over 11% of all the books ever published, and within the next decade the majority of world's books will be online. While this digitized collection will be an invaluable resource for researchers to browse and search, we feel that the additional step of mining these manuscripts will reveal new insights, knowledge and historical context. Although most of the data will naturally be text, there will also be tens of millions of pages of images, many in color. In this dissertation, we introduce a simple color measure which both addresses and exploits typical features of historical manuscripts. To enable the efficient mining of massive archives, we propose a tight lower bound to the measure. Beyond the fast similarity search, we show how this lower bound allows us to build several higher-level data mining tools, including motif discovery and link analyses. We demonstrate our ideas in several data mining tasks on manuscripts dating back to the fifteenth century.

Compared to the well preserved or already digitized historical manuscripts, there is another category of cultural heritage, rock art, which requires urgent action in order to be explored and archived for prosperity. Rock art is an archaeological term for human-made markings on stone, including carvings into stone surfaces (petroglyphs) and paintings on stone (pictographs). It is believed that there are millions of petroglyphs in North America alone, and the study of this valued cultural resource has implications even beyond anthropology and history. Surprisingly, although image processing, information retrieval and data mining have had large impacts on many human endeavors, they have had essentially zero impact on the study of rock art. In this dissertation, we consider, for the first time, the problem of data mining large collections of rock art. We propose a robust distance measure for unconstrained and complex shapes, a cheap-to-compute tight lower bound, and algorithms based on these two ideas which enable very fast query-by-content and make the otherwise intractable data mining tasks in large collections of rock art tenable.

Compared with land-based wind turbines, offshore ones have two clear advantages: the access to steady and strong offshore wind resources, and the proximity to heavily populated coastal areas, so that the loss from transportation of electricity is diminished. Structurally, offshore floating wind turbines are different from their land-based counter parts and existing offshore structures. Thus, current design guidelines cannot be applied for offshore floating wind turbines, and extensive numerical studies are required to predict the dynamic behavior of these novel structures. In this research, a fully coupled time domain hydrodynamic, aerodynamic and mooring cables model is developed to study the transient response of offshore floating wind turbines.

In hydrodynamic module of the coupled model, Boundary Element Method is employed to solve the boundary-value problem, and the 4th order Runge–Kutta time marching technique is used to update the position of the free surface. An unsteady wind-blade interaction model based on boundary elements has been developed to calculate the aerodynamic forces. This method achieves fully-3D and fully-unsteady simulations of the wind-blade interactions. A fully nonlinear cable dynamics model which accounts for bending, stretching, and torsional stiffnesses of the cables is employed to simulate the dynamics of the mooring system. Compared to current quasi-static approaches used in cable modeling, the fully nonlinear cable model proves a higher fidelity as it captures all the dynamics of the mooring cables. The information from the aerodynamic, hydrodynamic, and mooring system modules are passed to the dynamic equation of motion in each time step to calculate the responses of a 5MW offshore floating wind turbine.

Various relaxation tests have been carried out to investigate the dissipation effects. For the floating turbine we studied, the relaxation tests indicate that in the pitching mode there is no sufficient damping effects to dissipate disturbances (caused by gusts etc.), even if the aerodynamic damping is counted for. However, by approximately including the viscous damping through a Morison-type approach, the decaying rate in pitch motion is significantly increased (indeed, it becomes comparable to the decaying rate in heave motion). Therefore, we conclude that viscosity is the most important source of damping in pitch motion.

The response of the 5MW system to an incoming wave train generated by a pulsating pressure distribution on the free surface nearby is studied. This wave train causes responses in surge, heave and pitch directions. However, after it leaves the vicinity of the system the only remaining motion is in the heave direction, which will quickly decay due to the damping effects according to relaxation tests.