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.

No description available.

The objective of this research is to build a prototype of a carbon nanotube (CNT)-based micro X-ray tube array, which can be used in a real-time cone-beam computed tomography (CT) scanner for cancer research. The X-ray tube array consists of an electron source, control grids, focusing electrodes, and an anode plate. All the experiments have been executed in an ultra high vacuum environment at a pressure of 10⁻⁷ Torr. A thin film consisting of multi-wall carbon nanotubes (MWNTs) was used as the electron source. A diode configuration was employed to test the field emission performance of the CNT thin film. The current density achieved was 1mA/cm² at 10V/µm. After the initial burn-in process, a relatively steady emission current was obtained for duration of 170 hours. The control grid was made of 25% opening space stainless steels mesh. Meshes with different wire diameters were tested in a triode structure, and some differences were observed. Multi-anode field emission tests and multi-tube electric field simulations were executed. Experiments and simulations have revealed crosstalk between pixels during field emission. Based on the above experiments and simulations, a signal pixel prototype has been fabricated and is being tested. Moreover, some potential optimizations that will be used in the second prototype are also discussed

A practical problem in computer graphics is that of representing a textured surface at arbitrary scales. I consider the underlying mathematical problem to be that of interpolating autoregressive random fields under arbitrary coordinate transformations. I examine the theoretical basis for the transformations that autoregressive parameters exhibit when the associated stationary random fields are scaled or rotated. The basic result is that the transform takes place in the continuous autocovariance domain, and that the spectral density and associated autoregressive parameters proceed directly from sampling the continuous autocovariance on a transformed grid. I show some real-world applications of these ideas, and explore how they allow us to interpolate into a random field. Along the way, I develop interesting ways to estimate simultaneous autoregressive parameters, to calculate the distorting effects of linear interpolation algorithms, and to interpolate random fields without altering their statistics.

No description available.

The effects of feed processing, pea cultivar and their interaction on the nutritional value of field pea (Pisum sativum L.) for poultry were evaluated in regard to its apparent metabolizable energy (AMEn), apparent protein digestibility (APD), and rate and extent of starch digestion. Amino acid sparing as affected by the rate of starch digestion was studied in laying hens and broiler chickens. Also, the effects of feeding a slowly digested starch (SDS) from pea on performance and metabolism of broiler–breeder pullets were investigated. The first objective of this research was to evaluate the effects of screen–hole size, cold pelleting, and pre–pelleting conditioning temperature on nutrient digestibility of pea. There was no interaction between dietary treatments on all studied parameters. Small hammer–mill screen–hole size (3.2–mm) increased AMEn, APD, and extent of starch digestion values compared with coarse screen–hole size (6.4–mm). The AMEn and extent of protein digestion were not affected by cold pelleting, but the site of protein digestion was affected. In contrast, cold pelleting increased the rate and extent of starch digestion. Pre–pelleting conditioning temperature affected AMEn of pea in a quadratic fashion but had no positive effect on starch digestibility. The 70°C of pre–pelleting conditioning temperature maximized pea AMEn. Increasing pre–pelleting conditioning temperature decreased APD in a linear fashion. The second objective of this research was to study the effects of feed processing, pea cultivar and their interaction on AMEn, APD, and rate and extent of starch digestion. In vitro and in vivo experiments were conducted. An in vitro procedure simulating the gastric and small intestine conditions of chickens was developed to predict the rate and extent of starch digestion as affected by pea cultivar and sieve–hole size (0.5–, 1.0–, 2.0–mm). The rate and extent of starch digestion of cereal grain samples (barley, corn, and wheat) was also compared to pea starch. No interactions were found between pea cultivar and sieve–hole size on the kinetics of starch digestion. Pea cultivar affected the rate and extent of starch digestion. The small sieve–hole size in the in vitro assay resulted in a higher rate and extent of starch digestion. Pea starch was slowly digested in comparison with cereal grains. The in vivo experiment confirmed that fine grinding and pelleting improves AMEn and APD. Cultivar effects on AMEn and APD were observed, but no interaction was found between pea cultivar and feed processing. The third objective of this research was to investigate whether feeding SDS from pea would have sparing effect on amino acid utilization in chickens. In the first experiment, the effects of three levels of pea inclusion 0, 150, 300 g/kg on the response of laying hens to three levels of lysine intake (700, 780, and 860 mg per day) were evaluated using performance and production criteria. This experiment revealed that pea inclusion up to 300 g/kg in laying hen diets was well tolerated by laying hens and improved energy retention as indicated by increased body weight and egg weight. However, this experiment did not confirm the hypothesis that SDS from pea spared amino acids for laying hens. The second experiment investigated the interaction between SDS derived from pea and amino acid levels on the performance and carcass quality of broiler chickens. Six levels of pea inclusion (0, 150, 300, 450, 600, and 750 g/kg) and two levels of amino acids (100 and 85% of Ross × Ross 308 requirement) were examined in a broiler trial (0 – 35 d). The maximum level of pea inclusion recommended in diets increased with broiler age, but the effect of SDS from pea on amino acid sparing could not be confirmed. In the third experiment, the effects of feeding SDS from pea on growth performance and metabolism of broiler breeder pullets were investigated. Body weight and uniformity of pullets fed pea–based diet were similar to that of a wheat–based diet. Target body weight and uniformity of pullets were not affected by feeding a diet containing 890 g/kg of pea. Mean blood glucose levels and relative liver weight were markedly lower in broiler pullets fed pea–based diet compared with those fed a wheat–based diet. In conclusion, feed processing independently had a significant effect on the availability of pea nutrients. Pea is a good source of both energy and protein and that it can be partially or completely included to replace wheat and soybean meal in poultry diets. However, the effect of SDS on amino acid sparing could not be confirmed. Further research is needed to examine other feed processing techniques, pea cultivars, level of inclusion, and to understand other metabolism responses to feeding SDS from pea.

In this paper we consider optimal design of experiments in the case of correlated observations, when no replications are possible. This situation is typical when observing a random process or random field with known covariance structure. We present a theorem which demonstrates that the computation of optimum exact designs corresponds to solving minimization problems in terms of design measures. (author's abstract) / Series: Forschungsberichte / Institut für Statistik

Simultaneous Localization and Mapping (SLAM) is a recursive probabilistic inferencing process used for robot navigation when Global Positioning Systems (GPS) are unavailable. SLAM operates by building a map of the robot environment, while concurrently localizing the robot within this map. The ultimate goal of SLAM is to operate anywhere using the environment's natural features as landmarks. Such a goal is difficult to achieve for several reasons. Firstly, different environments contain different types of natural features, each exhibiting large variance in its shape and appearance. Secondly, objects look differently from different viewpoints and it is therefore difficult to always recognize them. Thirdly, in most outdoor environments it is not possible to predict the motion of a vehicle using wheel encoders because of errors caused by slippage. Finally, the design of a SLAM system to operate in a large-scale outdoor setting is in itself a challenge. <br /><br /> The above issues are addressed as follows. Firstly, a camera is used to recognize the environmental context (e. g. , indoor office, outdoor park) by analyzing the holistic spectral content of images of the robot's surroundings. A type of feature (e. g. , trees for a park) is then chosen for SLAM that is likely observable in the recognized setting. A novel tree detection system is introduced, which is based on perceptually organizing the content of images into quasi-vertical structures and marking those structures that intersect ground level as tree trunks. Secondly, a new tree recognition system is proposed, which is based on extracting Scale Invariant Feature Transform (SIFT) features on each tree trunk region and matching trees in feature space. Thirdly, dead-reckoning is performed via an Inertial Navigation System (INS), bounded by non-holonomic constraints. INS are insensitive to slippage and varying ground conditions. Finally, the developed Computer Vision and Inertial systems are integrated within the framework of an Extended Kalman Filter into a working Vision-INS SLAM system, named VisSLAM. <br /><br /> VisSLAM is tested on data collected during a real test run in an outdoor unstructured environment. Three test scenarios are proposed, ranging from semi-automatic detection, recognition, and initialization to a fully automated SLAM system. The first two scenarios are used to verify the presented inertial and Computer Vision algorithms in the context of localization, where results indicate accurate vehicle pose estimation for the majority of its journey. The final scenario evaluates the application of the proposed systems for SLAM, where results indicate successful operation for a long portion of the vehicle journey. Although the scope of this thesis is to operate in an outdoor park setting using tree trunks as landmarks, the developed techniques lend themselves to other environments using different natural objects as landmarks.

The objective of this research is to build a prototype of a carbon nanotube (CNT)-based micro X-ray tube array, which can be used in a real-time cone-beam computed tomography (CT) scanner for cancer research. The X-ray tube array consists of an electron source, control grids, focusing electrodes, and an anode plate. All the experiments have been executed in an ultra high vacuum environment at a pressure of 10⁻⁷ Torr. A thin film consisting of multi-wall carbon nanotubes (MWNTs) was used as the electron source. A diode configuration was employed to test the field emission performance of the CNT thin film. The current density achieved was 1mA/cm² at 10V/µm. After the initial burn-in process, a relatively steady emission current was obtained for duration of 170 hours. The control grid was made of 25% opening space stainless steels mesh. Meshes with different wire diameters were tested in a triode structure, and some differences were observed. Multi-anode field emission tests and multi-tube electric field simulations were executed. Experiments and simulations have revealed crosstalk between pixels during field emission. Based on the above experiments and simulations, a signal pixel prototype has been fabricated and is being tested. Moreover, some potential optimizations that will be used in the second prototype are also discussed

A practical problem in computer graphics is that of representing a textured surface at arbitrary scales. I consider the underlying mathematical problem to be that of interpolating autoregressive random fields under arbitrary coordinate transformations. I examine the theoretical basis for the transformations that autoregressive parameters exhibit when the associated stationary random fields are scaled or rotated. The basic result is that the transform takes place in the continuous autocovariance domain, and that the spectral density and associated autoregressive parameters proceed directly from sampling the continuous autocovariance on a transformed grid. I show some real-world applications of these ideas, and explore how they allow us to interpolate into a random field. Along the way, I develop interesting ways to estimate simultaneous autoregressive parameters, to calculate the distorting effects of linear interpolation algorithms, and to interpolate random fields without altering their statistics.