Submitted master’s thesis deals with rotary draw bending of tubes as a subprocess of automobile’s stabilizer bar production. The main goal of the thesis is to clarify the influence of the process parameters of the bend on the resulting shape and properties of the product. Submitted thesis includes theoretical description of the chosen tube bending technology, description of defects and possibilities of their removal. The description of the bending machine used for stabilizer bars production is done afterwards. Practical part of the thesis includes experiments clarifying influence of parameters on the resulting shape of the stabilizer bar.

In integrated optics, there are many adiabatic dielectric waveguides. Examples include bending waveguides, multi-mode interferometers (MMI), taper waveguides, grating assisted directional couplers (GADC), etc. Among these waveguide devices, adiabatic bending waveguides are the most important basic devices. They are used to connect various vertical or horizontally displaced waveguides. There are many approximate methods such as the beam propagation method (BPM), finite-difference time-domain, (FD-TD) and finite-difference frequency-domain (FD-FD) methods that have been used to analyze and optimize the waveguide designs. BPM can not calculate wide angle optical traffic due to its intrinsic paraxial limitation. Both FD-TD, FD-FD handle wide-angle bi-directional traffic but both demand tremendous computational resources. In this thesis, we develop a new formulation called full eigen-mode expansion technique (FEMET) that considers only forward propagating but all wide-angle traffic. It is a simplified version of our existing bidirectional, coupled transverse-mode integral-equation (CTMIE) formulation. FEMET includes all forward propagating, high-order mode field but neglects reflection at the dielectric discontinuities. Since FEMET uses no matrix equations, it is much faster than CTMIE. To verify the accuracy of FEMET we consider the titled straight waveguide (TSR) as our test example. TSR has an exact solution in its natural coordinate system which allows us to study computational characteristics of FEMET. The two FEMET computational control parameters are the total number of waveguide sections and the number of modes used in each section. Together they control the speed and accuracy of FEMET. We use FEMET to analyze radiation and mode interference of both S-bend waveguides and two-corner bends. These results compare well with result computed by other methods.

Abstract A buried hybrid waveguide with large angle bend utilizing Fresnel refraction is presented. The waveguide device consists of a polymer core buried in SiO2 cladding on a Si substrate. Large angle bend of the waveguide is achieved based on Fresnel refraction by inserting a low index region into the bend structure. The buried hybrid waveguide was fabricate by dry etching a trench into the SiO2 cladding using Cr as the etch mask. Benzocyclobutene (BCB) polymer was then coated on to the sample to planarize the surface and was used as the guiding core. Etch back was performed to remove the polymer outside the guiding region. The device was completed by passivating the surface with a thin layer of spin on glass (SOG). The normalized transmission loss of the hybrid waveguide with two 8¢X angle bends is 75%. The propagation loss of the waveguide is 0.6 dB/cm. In addition, a theoretical model of the bend waveguide is proposed. BPM-CAD is used to calculate the bending loss of the waveguide with different bending angles. The calculated results suggest that a large angle bend can be obtained for a large index different the core and the cladding.

Thesis (M. S.)--Architecture, Georgia Institute of Technology, 2008. / Committee Chair: Spuybroek, Lars; Committee Member: Reither, Gernot; Committee Member: Young, Kevin. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1960. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The interaction of light with small designed particles and structures gives rise to an increasing number of phenomena of potentially dramatic technological importance, such as metamaterials, superlens focusing, and enhanced spectroscopy. Metallic nanostructures with their geometry-dependent optical resonances are a topic of intense current interest due to their ability to manipulate light in ways not possible with conventional optical materials. A particularly fascinating aspect of these systems is the recently realized possibility of creating optical frequency “magnetic plasmon” responses of comparable magnitude to the “electric plasmon” response. Au nanocups at their magnetoinductive resonance have the unique ability to redirect scattered light in a direction dependent on cup orientation, as a true three-dimensional nanoantenna. As optical frequency nanoantennas, reduced-symmetry plasmonic nanoparticles have light-scattering properties that depend strongly on geometry, orientation, and variations in dielectric environment. Here we investigate how these factors influence the spectral and angular dependence of light scattered by Au nanocups. A simple dielectric substrate causes the axial, electric dipole mode of the nanocup to deviate substantially from its characteristic cos square free space scattering profile, while the transverse, magnetic dipole mode remains remarkably insensitive to the presence of the substrate. Nanoscale irregularities of the nanocup rim and the local substrate permittivity have a surprisingly large effect on the spectral- and angle-dependent light-scattering properties of these structures. The different angular scattering and wavelength response from the axial and transverse nanocup modes make the nanocup an interesting particle for the nanoscale manipulation of light in three dimensions. The sensitivity of this system to geometric and environmental factors may present opportunities for active, substrate-mediated control of light scattering.

The interaction of light with small designed particles and structures gives rise to an increasing number of phenomena of potentially dramatic technological importance, such as metamaterials, superlens focusing, and enhanced spectroscopy. Metallic nanostructures with their geometry-dependent optical resonances are a topic of intense current interest due to their ability to manipulate light in ways not possible with conventional optical materials. A particularly fascinating aspect of these systems is the recently realized possibility of creating optical frequency “magnetic plasmon” responses of comparable magnitude to the “electric plasmon” response. Au nanocups at their magnetoinductive resonance have the unique ability to redirect scattered light in a direction dependent on cup orientation, as a true three-dimensional nanoantenna. As optical frequency nanoantennas, reduced-symmetry plasmonic nanoparticles have light-scattering properties that depend strongly on geometry, orientation, and variations in dielectric environment. Here we investigate how these factors influence the spectral and angular dependence of light scattered by Au nanocups. A simple dielectric substrate causes the axial, electric dipole mode of the nanocup to deviate substantially from its characteristic cos square free space scattering profile, while the transverse, magnetic dipole mode remains remarkably insensitive to the presence of the substrate. Nanoscale irregularities of the nanocup rim and the local substrate permittivity have a surprisingly large effect on the spectral- and angle-dependent light-scattering properties of these structures. The different angular scattering and wavelength response from the axial and transverse nanocup modes make the nanocup an interesting particle for the nanoscale manipulation of light in three dimensions. The sensitivity of this system to geometric and environmental factors may present opportunities for active, substrate-mediated control of light scattering.

Plastic  deformation of tubes can be achieved in numerous ways. One of the most useful type is CNC tube bending machines which is used in many industries such as aerospace, automotive, HVAC systems and so on. It is important that all components of system should mate properly after producing and because of this bend shaping requires sensitive operation on each components to ensure regularity of production processes with high quality end-product. Thus, the CNC tube bending industry to become widespread. However it brings some troubleshooting like wrinkling, springback, breakage and ovalisation. This failures depends on geometry of the material such as bending radius, tube thickness and also friction factor between dies and the tube. Effects of all parameters should be examined before generating the theory for a best solution. Therefore, prediction of the required moment for the proper bending process with low cost and shortened production time is needed. All of these requirements can be achieved through a C++ form application program.

Elasticity of α-helices and coiled coils have often been described by a linear response to local bending with bending stiffness (Kb) and persistence length (Lp) describing their flexibility. However, we observed that the non-bonded forces along the length of these structures are not screened at physiological conditions and introduce a buckling instability. For α-helical systems of same composition, but different lengths, this is identified by a drop in Kb for longer helices and the length where this drop is triggered is referred to as the critical buckling length. When shorter than their critical buckling length they behave linearly, and Kb calculated using normal mode analysis in this regime is about (3.0−3.4)×10-28 Nm2 for α-helices with varying compositions, and about (1.9 − 2.1) × 10−27 Nm2 for coiled coils with leucine zipper periodicity. Beyond the critical buckling length, normal mode solutions turn imaginary, leading to an eventual disappearance of bending modes. Investigations with one dimensional (1-D) linear chains of beads (a simplistic representation of bio-filaments) show that non-bonded forces have a reciprocal relation with the critical buckling length (no buckling instability existed in the absence of non-bonded forces). Critical buckling length is 115.3 ± 2.9 °A for α-helices and 695.1 ± 44.8 Å for coiled coils with leucine zipper periodicity, which is much smaller than their Lp (~ 800 Å for α-helices and ~ 3000 Å for coiled coils).