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This paper is an account of an experiment designed to determine the binding energy of the deuteron by a method which is relatively insensitive to uncertainties in the energy-range relation for protons of low energy. The protons, produced by the disintegration of deuterium by Th C″ gamma-radiation, were observed in a low-pressure cloud chamber in a strong magnetic field. The curvatures of the tracks allowed the calculation of the corresponding kinetic energies. The final value of the binding energy as got by this experiment is VB=2.17+/- 0.05x106 electron-volts, which is in excellent agreement with the values previously got by Bethe (from the data of Chadwick, Feather and Bretscher) and by J. R. Richardson and Emo.

Abstract Not Available.

Studies were performed to determine the mechanism whereby carbon nanotubes form in an electric arc. Various experimental parameters including cathode cooling, composition, and diameter were varied. It was found that tube-tube sintering is a primary reason for tube defects, and that this effect can be minimized by reducing the temperature of the cathode where the tubes grow. The investigations also led to the pseudo-convection growth model, which explains many features of the cathode deposits in which tubes form. Various other means of nanotube growth were studied. Possible uses for these nanotubes were also explored.

In complex robotic operating environments in which robots must cooperate in a flexible and event-driven manner, a cooperative distributed environment for intelligent control is required. We develop a realistic technique for going beyond the model of a central controller for a multi-robot environment and replacing it with a schema of interacting, reconfigurable, cooperating robots. This schema provides the following main features: an open model of cooperation capable of supporting a wide variety of representations and algorithms for planning and executing tasks, a dynamic environment in which physical and reasoning capabilities can be added, removed, and reconfigured while performing tasks to best utilize limited resources, the capability of detecting and correcting errors and failures, a rich interaction model capable of handling the complexity and variety of communications and cooperation necessary between intelligent agents, and a realistic method of achieving global goals from localized actions. We formulate this model of interacting robots as a social system. We define this social system by specifying the members of the society, the interactions of these members, and the fundamental guidelines of the society used to judge the actions of the members. We successfully implement a prototype system that incorporates these concepts, and demonstrate it on some example situations involving multiple cooperating robots. Using the results of these examples, we also develop a qualitative analysis of this model against two other common models of intelligent control for multi-robot systems.

In this thesis we propose methods for preconditioning Krylov subspace methods for solving the integral equation formulation of the Helmholtz partial differential equation for modeling scattered waves. An advantage of using an integral formulation is that only the scattering obstacle is discretized and the outgoing boundary conditions are automatically satisfied. Furthermore, convergence is dictated by the wave number kappa with only a mild dependence on the discretization. However such methods are increasingly computationally expensive for increasing values of kappa. This cost is due to GMRES iteration counts that increase like O(kappa2), for a linear system that is dense with dimension N = O(kappa 4). GMRES is slow due to a small subset of the spectrum that is well separated, a part of which approaches the origin as kappa increases. The troublesome subset corresponds to low frequency eigenfunctions which can be approximated using coarse meshes. We propose a preconditioner based on deflating this subset of the spectrum which we evaluate by interpolating coarse mesh approximations of the spectrum. We show that for discretizations of less than one node per wavelength, we can effectively precondition the full problem over a sufficiently resolved mesh.

The optical properties of plasmon resonant metallic nanoparticles are of great interest because of their ability both to control optical fields on the nanometer scale and to function as sensitive indicators of their local environment. I investigate the relationship between the dielectric function of a metal and the optical properties of the constituent metallic nanoparticle. Using a Drude shell - silica core nanoshell geometry, I examine how systematic changes in the parameters of the Drude dielectric function affect the near and far field properties of the nanoparticle. The nanoshell geometry allows separation of intrinsic properties and extrinsic phase retardation, or finite size, effects.

No description available.