This doctoral thesis deals with designs and developments of multi(wide)-band multifunctional antennas based on folded dipoles. In the beginning, the concept of Orthogonal Folded Dipoles (OFD) are put forward. Orthogonal folded dipoles are formed by two identical two-port folded dipoles orthogonally joining with each other at the center, and can be fed through different combinations of feed nodes to offer dual- and wide-band modes, respectively. The impedances of the 2 modes are studied both by analytical models and by commercial electromagnetic simulation tools. The properties of the linearly polarized radiation patterns in the two modes vary quite little, except for ±45◦  rotation of two principal planes. In this way, orthogonal folded dipoles can possibly provide pattern reconfigurability in a context of switchable types and orientations of polarizations. Next, the concept of Log-Periodic Folded Dipole Array (LPFDA) is proposed. It stems from the traditional log-periodic dipole array, whereas folded dipoles instead of straight dipoles are applied as the elements of the array. Two configurations, i.e. partly-scaled LPFDA and fully-scaled LPFDA, are studied through simulations and optimizations. The comparison shows that the latter outperforms the former in terms of higher directivity, reduced front-to-back ratio and lower crosspolar level. The key parts of this thesis focus on exploiting Eleven antennas, based on the LPFDAs, in a variety of applications. First, the 4-port L-band lab model for use in satellite terminals demonstrates that the radiation patterns for monopulse tracking can be achieved through different excitation combinations of the multiport Eleven antenna. Second, a decade bandwidth, an unchanged phase center and nearly constant directivities over the whole band can be regarded as the major figure-of-merit of the Eleven antenna, which makes it suitable as feed for prime-fed reflector antennas. Through endeavors of using Genetic Algorithms, the wideband Eleven antennas have been gradually optimized in term of matching as well as efficiencies. Besides, the rotationally symmetric circular Eleven feed is a very promising solution for improving the BOR1 efficiency and therefore the aperture efficiency by a fraction of dB. Last but not least, the two multiport L-band lab models measured in a reverberation chamber demonstrate that the Eleven antenna with MIMO diversity ports can possibly overcome narrowband multipath fading in a real radio link and improve the link quality in terms of a significant diversity gain and high maximum available capacity.

Digitized by Kansas Correctional Industries

Thesis (Ph. D.)--Virginia Polytechnic Institute, 1965. / Vita. Abstract. Includes bibliographical references (leaves 78-79). Also available via the Internet.

No description available.

Over the past few years, many high performance asynchronous transfer mode (ATM) switches have been proposed. The majority of these switches have high performance but also high hardware complexity. Therefore, there is a need for switch designs with low complexity and high performance. This research proposes three new ATM switches based on the folded hypercube network (FHC). The performance of the three architectures are studied using a network model and simulation. The major performance parameters measured are the cell loss rate and cell delay time through the switch under uniform, normal, and bursty traffic patterns. To guarantee faster switching of time-sensitive cells, the routing algorithm of the three switches uses a priority scheme that gives higher precedence to the time-sensitive cells. Also, an output buffer controller is designed to manage the buffers in a fair manner. The three proposed switch architectures have lower complexity while providing equivalent or better switching performance compared to other more complex ATM switches described in the literature. This research shows a new approach to designing ATM switches by using the FHC as the switching fabric for the first time instead of using the crossbar, multi-path, or Banyan-based switching fabrics. / Ph. D.

An experimental and finite element investigation of the behavior of single-span, simply-supported folded plate structures containing rectangular openings is summarized. A seven-plate aluminum model was tested under a uniform load of 40.26 psf. on the horizontal surfaces. Six different cases are analyzed by changing the number, size, and location of the holes. The results of only the two extreme cases, no-hole and 12-hole analyses, are presented. Good agreement is shown between experimental and theoretical solutions, thus the validity of the finite element analysis is established in dealing with cutouts in folded plate structures. A comparison of experimental results and analytical results, obtained by the finite element method of analysis, is made and the effects of the holes on the behavior of the structure are discussed. Recommendations for future research are indicated. / Master of Science

Call number: LD2668 .T4 1985 A35 / Master of Science

Folded almanacs are fascinating manuscripts that display astrological content relevant to the practice of medicine. However, due to the lack of primary evidence demonstrating the almanac in practice, it is difficult to ascertain their actual use. Medieval Scholars have therefore concentrated on the almanac's sources, materiality and contextual evidence of apparent medical purpose. My thesis examines the metaphysical principles within the folded almanac, which exemplify the micro/macrocosm inherent in medieval astro-medicine. I argue that the folded almanac, as a material object and compilation of medical knowledge, situates the physician, patient and constellations within metaphysical ideas of body, time and space. Using the yet unstudied folded almanac from the National Library of Scotland, Acc 12059.3 (the Borthwick almanac) as a primary model, I demonstrate how this physical object, in dealing with the corporeal body, exhibits the unity of body, time and space. This approach reveals that the folded almanac (1) is a performative object that establishes medical authority, (2) tracks the progress of health and illness using Aristotelian and Thomist concepts of time, (3) maps the intersection of celestial and human bodies onto practical textual spaces. The culmination of these findings illustrates that the folded almanac engaged with a very technical but abstract branch of medieval medicine which sought to explain how, why, when and where illness was manifested, and also operated as an interventional tool for aiding in the restoration of health.

In order to perform a specific function, a protein needs to fold into the proper structure. Prediction the protein structure from its amino acid sequence has still been unsolved problem. The main focus of this thesis is to develop new approach on the protein structure modeling by means of differential geometry and integrable theory. The start point is to simplify a protein backbone as a piecewise linear polygonal chain, with vertices recognized as the central alpha carbons of the amino acids. Frenet frame and equations from differential geometry are used to describe the geometric shape of the protein linear chain. Within the framework of integrable theory, we also develop a general geometrical approach, to systematically derive Hamiltonian energy functions for piecewise linear polygonal chains. These theoretical studies is expected to provide a solid basis for the general description of curves in three space dimensions. An efficient algorithm of loop closure has been proposed.

The Discrete Wavelet Transform (DWT) is a popular tool in the field of image and video compression applications. Because of its multi-resolution representation capability, the DWT has been used effectively in applications such as transient signal analysis, computer vision, texture analysis, cell detection, and image compression. Daubechies wavelets are one of the popular transforms in the wavelet family. Daubechies filters provide excellent spatial and spectral locality-properties which make them useful in image compression.<p> In this thesis, we present an efficient implementation of a shared hardware core to compute two 8-point Daubechies wavelet transforms. The architecture is based on a new two-level folded mapping technique, an improved version of the Algebraic Integer Quantization (AIQ). The scheme is developed on the factorization and decomposition of the transform coefficients that exploits the symmetrical and wrapping structure of the matrices. The proposed architecture is parallel, pipelined, and multiplexed. Compared to existing designs, the proposed scheme reduces significantly the hardware cost, critical path delay and power consumption with a higher throughput rate.<p> Later, we have briefly presented a new mapping scheme to error-freely compute the Daubechies-8 tap wavelet transform, which is the next transform of Daubechies-6 in the Daubechies wavelet series. The multidimensional technique maps the irrational transformation basis coefficients with integers and results in considerable reduction in hardware and power consumption, and significant improvement in image reconstruction quality.