Compliant bistable mechanisms are mechanisms that have two stable equilibrium positions within their range of motion. Their bistability is mainly due to the elasticity of their members. This thesis introduces a new type of bistable micromechanisms, the Bistable, Spherical, Compliant, four-bar Micromechanism (BSCM). Theory to predict bistable positions and configurations is also developed. Bistabilty was demonstrated through testing done on micro-prototypes. Compared to the mathematical model of the BSCM, Finite element models of the BSCM indicated important qualitative differences in the mechanism's stability behavior and its input-angle-input torque relation. The BSCM has many valuable features, such as: Two stable positions that require power only when moving from one stable position to the other, accurate and repeatable out-of-plane motion with resistance to small perturbations. The BSCM may be useful in several applications such as active Braille systems and Digital Light Processing (DLP) chips.

<p>Image rendering is the process of creating realistic computer images from  geometric models and physical laws of light and reflection. This master thesis deals mainly with the numerical intricacies of implementing an image renderer using spherical harmonics. It investigates how to calculate the reflection of light in a surface using the Phong model, and employs ray tracing to create a realistic image of a geometric model. Further, it investigates different ways of calculating the spherical harmonic representation of a function defined on the sphere. The thesis also deals with the implementation of self-shadowing, and the effects of adding this component to the rendering equation.</p>

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.

Image rendering is the process of creating realistic computer images from  geometric models and physical laws of light and reflection. This master thesis deals mainly with the numerical intricacies of implementing an image renderer using spherical harmonics. It investigates how to calculate the reflection of light in a surface using the Phong model, and employs ray tracing to create a realistic image of a geometric model. Further, it investigates different ways of calculating the spherical harmonic representation of a function defined on the sphere. The thesis also deals with the implementation of self-shadowing, and the effects of adding this component to the rendering equation.

Tissue equivalent proportional counters (TEPC) are used for medical and space activities whenever a combination of high and low LET (lineal energy transfer) radiations are present. With the frequency and duration of space activities increasing, exposure to fast heavy ions from galactic cosmic radiation and solar events is a major concern. The optimum detector geometry is spherical; to obtain an isotropic response, but simple spherical detectors have the disadvantage of a non-uniform electric field. In order to achieve a uniform electric field along the detector axis, spherical tissue equivalent proportional counters have been designed with different structures to modify the electric field. Some detectors use a cylindrical coil that is coaxial with the anode, but they are not reliable because of their sensitivity to microphonic noise and insufficient mechanical strength. In this work a new spherical TEPC was developed. The approach used was to divide the cathode in several rings with different thicknesses, and adjust the potential difference between each ring and the anode to produce an electric field that is nearly constant along the length of the anode. A-150 tissue equivalent plastic is used for the detector walls, the insulator material between the cathode rings is low density polyethylene, and the gas inside the detector is propane. The detector, along with the charge sensitive preamplifier, is encased in a stainless steel vacuum chamber. The gas gain was found to be 497.5 at 782 volts and the response to neutrons as a function of angle was constant ±7%. This spherical tissue equivalent proportional counter detector system will improve the accuracy of dosimetry in space, and as a result improve radiation safety for astronauts.

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2008. / Includes bibliographical references (p. 79-82).

No description available.

A novel compacted, torrefied, spherical biomass pellet, known as the "Q'Pellet", is aimed at overcoming the challenges of modern biomass pellets by building on the bene fits of torrefaction and utilizing the durability of a sphere. Pellets were made from both untreated hybrid poplar sawdust and material that had been partially torrefied at 250 C, allowing the torrefaction and pelletizing stages to be decoupled. A pelletizing die pre-heated to 280 C was successfully used to heat and torrefy room temperature raw and pre-torrefi ed material, greatly reducing the time required to produce each pellet. All Q'Pellets demonstrated 100% mechanical durability, and did not abrade during a tumbling can test or fracture during an impact resistance (drop) test. The gross calori fic value (GCV), ash and nitrogen content of pellets produced from raw hybrid poplar were 21.29+/-0.08 MJ/kg, 2.42+/-0.23 wt%, and <0.01 wt%, respectively. The GCV, ash and nitrogen content of pellets produced from pre-torre ed material were 21.25+/-0.34 MJ/kg, 3.58+/-1.11 wt%, and 0.42+/-0.03 wt%, respectively. The Q'Pellet was compared to biomass fuel speci fications in Europe and North America. The experiments performed herein provided an understanding of the material and process properties and limitations. Design speci fications for the development of a continuous pelletizing process were outlined. BGM Metalworks Inc has been hired by Queen's University to assist in the design and to fabricate the continuous pelletizing apparatus. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2014-05-06 14:04:54.059

This thesis will focus on spherical near-field antenna measurements and the methods developed or modified for the work of this thesis to estimate the uncertainty in a particular far-field radiation pattern. We will discuss the need for error assessment in spherical near-field antenna measurements. A procedure will be proposed that, in an automated fashion, can be used to determine the overall uncertainty in the measured far-field radiation pattern of a particular antenna. This overall uncertainty will be the result of a combination of several known sources of error common to SNF measurements. This procedure will consist of several standard SNF measurements, some newly developed tests, and several stages of post-processing of the measured data. The automated procedure will be tested on four antennas of various operating frequencies and directivities to verify its functionality. Finally, total uncertainty data will be presented to the reader in several formats.