Ultra-Wideband (UWB) wireless communication systems employ large bandwidths and low transmitted power spectral densities, and are suitable for operation as underlay systems which reuse allocated spectrum. The subject of this dissertation is Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB for high data-rate communication. We address four main questions: (1) What are the theoretical performance limits and practical system performance of MB-OFDM? (2) What extensions can be used to increase the system power efficiency and range? (3) Is it possible to estimate the system error rate without resorting to time-consuming simulations? and (4) What is the effect of interference from narrowband systems on MB-OFDM, and can this interference be mitigated? As for questions 1 and 2, we investigate the MB-OFDM performance, and propose system enhancements consisting of advanced error correcting codes and OFDM bit-loading. Our methodology includes the development of information-theoretic performance measures and the comparison of these measures with performance results for MB-OFDM and our proposed extensions, which improve the power efficiency by over 6 dB at a data rate of 480 Mbps. To address question 3, we develop novel analytical methods for bit error rate (BER) estimation for a general class of coded multicarrier systems (of which MB-OFDM is one example) operating over quasi-static fading channels. One method calculates system performance for each channel realization. The other method assumes Rayleigh distributed subcarrier channel gains, and leads directly to the average BER. Both methods are also able to account for sum-of-tones narrowband interference. As for question 4, we first present an exact analysis of the uncoded BER of MB-OFDM in the presence of interference from incumbent systems such as IEEE 802.16 ("WiMAX"). We also present a Gaussian approximation for WiMAX interference, and establish its accuracy through comparison with exact analysis and simulations. We then propose a two-stage interference mitigation technique for coded MB-OFDM, consisting of interference estimation during silent periods, followed by metric weighting during decoding, which provides substantial gains in performance in return for modest increases in complexity, and without requiring any modifications to the MB-OFDM transmitter.

 This thesis focuses on three research topics on the design about planar ultrawide-band (UWB) monopole antennas, namely, the design of band notches for UWB monopole antennas, the ground-plane and cable effects on the measurement of compact UWB monopole antennas, and the design of a chipless UWB radio-frequency-identification (UWB-RFID) system. The designs of single, dual, triple and quadruple band-notched UWB monopole antennas using coplanar waveguide (CPW) resonators, quarter-wavelength (λ/4)-resonators and meander lines (MLs) are presented. The center frequencies and bandwidths of the individual notches in all these designs can be adjusted independently by varying the dimensions of the resonators. Studies of the designs are carried out by computer simulations using the EM software tool, CST MWS. For verification of the simulation results, these antennas are fabricated and measured using the antenna measurement system, Satimo Starlab. The frequency-domain performances, in terms of return loss, peak gain, efficiency and radiation pattern, and the time-domain performances, in terms of pulse responses and fidelity, are investigated by simulation and measurement. Results show that these UWB antennas have approximately omnidirectional radiation patterns with good band-notched characteristics and fidelities of more than 85% in the pulse responses. Results of studies show that, using a small ground plane in the design of the compact UWB antennas, there will be larger discrepancies between the measured and simulated radiation patterns, radiation efficiencies and peak gains at low frequencies. The discrepancies are due to diffraction of the electric fields at the edges of the small ground plane, which leads to currents flowing back to the measuring cable and hence secondary radiation. Computer simulation and measurement are used to study the ground-plane effects using a group of nine UWB antennas. These antennas have the same radiator but with rectangular ground planes of different sizes. Results show that the width of the ground plane affects the efficiency more than the length, while the length affects the lower cut-off frequency. The cable effects are further studied by modeling the measuring cables. Results show that, by using the cable model, the simulation and measurement efficiencies agree extremely well. The design of a novel chipless UWB-RFID system is presented. The system employs uniplanar chipless tags and a pair of high-gain reader antennas. The chipless tag is composed of two UWB monopole antennas connected by a CPW. Tag identification (ID) is represented by a spectral signature in the UWB and created by using a multi-resonator embedded on the CPW. Detection of spectral signature is based on only the amplitude of the spectral signature. Vertically and horizontally polarized signals are used to reduce mutual coupling between the uplink and downlink signals. Further reduction of the mutual coupling is achieved by using a copper plate in the reader to separate the uplink and downlink signals. Results of studies in an anechoic chamber show that the proposed RFID system can achieve a read range larger than 30 cm, indicating that the proposed system has great potentials for short-range item tracking at low-cost. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Ultra-Wideband (UWB) wireless communication systems employ large bandwidths and low transmitted power spectral densities, and are suitable for operation as underlay systems which reuse allocated spectrum. The subject of this dissertation is Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB for high data-rate communication. We address four main questions: (1) What are the theoretical performance limits and practical system performance of MB-OFDM? (2) What extensions can be used to increase the system power efficiency and range? (3) Is it possible to estimate the system error rate without resorting to time-consuming simulations? and (4) What is the effect of interference from narrowband systems on MB-OFDM, and can this interference be mitigated? As for questions 1 and 2, we investigate the MB-OFDM performance, and propose system enhancements consisting of advanced error correcting codes and OFDM bit-loading. Our methodology includes the development of information-theoretic performance measures and the comparison of these measures with performance results for MB-OFDM and our proposed extensions, which improve the power efficiency by over 6 dB at a data rate of 480 Mbps. To address question 3, we develop novel analytical methods for bit error rate (BER) estimation for a general class of coded multicarrier systems (of which MB-OFDM is one example) operating over quasi-static fading channels. One method calculates system performance for each channel realization. The other method assumes Rayleigh distributed subcarrier channel gains, and leads directly to the average BER. Both methods are also able to account for sum-of-tones narrowband interference. As for question 4, we first present an exact analysis of the uncoded BER of MB-OFDM in the presence of interference from incumbent systems such as IEEE 802.16 ("WiMAX"). We also present a Gaussian approximation for WiMAX interference, and establish its accuracy through comparison with exact analysis and simulations. We then propose a two-stage interference mitigation technique for coded MB-OFDM, consisting of interference estimation during silent periods, followed by metric weighting during decoding, which provides substantial gains in performance in return for modest increases in complexity, and without requiring any modifications to the MB-OFDM transmitter.

The application of nanoparticles (NPs) in different technologies has led to tremendous advancement in those fields.  Moreover, there is growing interest in application of ultra-small NPs (USNPs) at 1-3 nm due to their distinct molecule like features. Parallel to these promises, there is a growing concern regarding their safety. The main goal of this thesis was to investigate the toxicity and underlying mechanisms following exposure to different metal and metal oxide NPs as well as USNPs. Their effects were studied on Saccharomyces cerevisiae, on hepatocytes and endothelial cells and finally in vivo on zebrafish embryos (Danio rerio). By selecting the rutile form of titanium dioxide (TiO2-USNPs) without intrinsic or intracellular reactive oxygen species (ROS) production, we could study biological impacts solely due to size and direct interaction with the cells. We showed that TiO2-USNPs were not cytotoxic but induced DNA damage. They had anti-angiogenic effects both in vitro and in vivo. Also, at high concentrations they caused complete mortality in zebrafish embryos exposed in water, while at lower concentrations induced delay in hatching. When injected they caused malformations. They specifically induced the differential overexpression of transcripts involved in lipid and cholesterol metabolism in endothelial cells. In hepatocytes they induced the overexpression of proteins in the electron transport chain and decreased lipids in lipid rafts. At 30 nm, TiO2-NPs, were also not cytotoxic but were genotoxic. They had no effects in vivo or on angiogenesis. However, they induced differential expression of transcripts involved in endoplasmic reticulum (ER) stress and heat shock response as well as cholesterol metabolism. This suggests a more toxic response in the cells compared to TiO2-USNPs.  Single walled carbon nanotubes (SWCNTs) despite having the highest oxidative activity among the NPs studied, were not severely cyto- or genotoxic but induced expression of transcripts involved in early ER stress response. Copper oxide (CuO-NPs) was the most toxic NPs studied due to both ion release and ROS production, affecting lipid metabolism of the cells. Silver (Ag-NPs) were also cytotoxic and caused the disruption of cellular components and lipids. ZnO-NPs were not cytotoxic, did not affect cellular lipids but they increased the size of vacuoles in yeast cells. Finally by using superparamagnetic iron oxide NPs (SPIONs) with different coatings, and using a mathematical model, a nano impact index (INI) was developed as a tool to enable the comparison of nanotoxicology data. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.</p>

A new Ultra-Wideband (UWB) pattern diversity antenna is proposed, designed and investigated in this thesis. The antenna is capable of radiating in directive and omni-directional modes. Three different versions of the design are studied to show the performance for different applications. The first design consists of a single radiating element fed from two sides by coaxial probes over a shaped ground plane. In-phase excitation of the ports produces omni-directional radiation patterns and out-of-phase excitation results in directive radiation in the boresight of the antenna. The shape of the radiator is a disk, which is modified in geometry to improve the isolation of the ports. The antenna shows impedance bandwidth from 6.8 GHz to more than 15 GHz. The second design is a dual-element version of the same antenna to equalize the radiation patterns in the E- and H-planes. The antenna requires four ports and has an impedance bandwidth from 7.4 GHz to more than 15 GHz. A microstrip power divider is then included, in the third design, which in addition to decreasing the number of extra circuits for feeding, decreases the lower frequency to 4.5 GHz, without changing the radiation patterns significantly throughout the bandwidth. A prototype of this antenna was fabricated and measured, and the results are presented. In the fifth chapter, an electromagnetic polarization filter is designed for the single element UWB antenna, to reduce the cross-polarization level. 7 dB reduction in the maximum level of cross-polarization is achieved, throughout the frequency band 8 - 11 GHz. The following chapter is dedicated to the study and performance of the microstrip-fed UWB antenna, when used as a feed for prime-focus reflectors. It is shown that the designed antenna is capable of feeding the reflector with efficiency as high as 75%, and more than 60%, over a wide bandwidth of 5.5 - 9 GHz.

Exposure to UV radiation is known to result in the development of skin cancer and the use of protectants m the form of topically applied sunscreens is becoming widespread. The compounds used within sunscreen formulations are subject to stringent tests and must be approved for use by such bodies as COLIPA (EC), or the FDA (U.S.). Despite these testing procedures the photochemical and photophysical properties of many of the active ingredients are poorly understood and not well documented. This study presents the results of detailed photophysical investigations of two sunscreen agents. Menthyl anthranilate is currently approved for use m commercially available formulations by the FDA, and N-acetyl-menthyl anthranilate has been synthesised as an analogue of N-acetyl-homomenthyl anthranilate, a compound approved for use by COLIPA until 1989. This work has highlighted some disturbing properties of these compounds. Following absorption of light both compounds fluoresce m UV-A region. Population of the triplet state also occurs to a significant extent, producing long lived species which are readily quenched by oxygen generating singlet oxygen, a potentially damaging species that has been linked to DNA damage. Furthermore, the triplet state energy of N-acetyl-menthyl anthranilate has been shown to be -315 kJmol(^-1)"', high enough to sensitise the formation of thymine dimers m the skin, another potential source of DNA damage. A thorough understanding of the behaviour of sunscreen formulations m contact with skin is vital. In vivo studies are made difficult due to restrictions in the sampling methods for currently used spectroscopic techniques such as UV and fluorescence. This work demonstrates the use of infixed spectroscopy, utilising an ATR probe and a flat ATR crystal, to analyse sunscreen formulations present on skin at normal usage levels. The technique has been used successfully to identify the individual active components within the formulations, probe the water-resistance properties and monitor changes that occur within the formulations following irradiation. A relationship between the IR absorbance values and Sun Protection Factor (SPF) values of any given formulation has been demonstrated and this has been used to test the water resistance claims of the manufacturers.

No description available.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Richard Wolff. Includes bibliographical references (leaves 109-112).

La radiogoniométrie consiste à mesurer l’angle d’incidence de signaux électromagnétiques. Elle a pour applications principales le contrôle du spectre et la guerre électronique. Dans le domaine des réseaux d’antennes pour la radiogoniométrie, de nouvelles problématiques sont apparues alors que les algorithmes de traitement d’antenne se perfectionnent. Ces dernières concernent la largeur de bande, la compacité et la diversité de polarisation. De précédents travaux ont initié la démarche de conception de telles antennes et réseaux pour la radiogoniométrie. L’objectif de ce travail de recherche a consiste en premier lieu a proposer une antenne de dimensions réduites opérant dans les bandes V/UHF et présentant une diversité de polarisation. Par la suite, il s’est agi de concevoir un réseau fonctionnel de radiogoniométrie intégrant l’antenne développe. Une antenne planaire de dimensions 150mm x 150mm (λ/4 x λ/4) a alors été conçue et réalisée entre 500 MHz et 3000 MHz. Sa mise en réseau permet des performances angulaires de l’ordre de 2° et moins sur la même bande pour des dimensions de 260mm (diamètre) x 150mm (hauteur) soit λ/2,3 x λ/4. Par la même occasion, un absorbant de faible épaisseur (25mm soit λ/24) a été développé et mesuré. Il permet une augmentation du rapport avant/arrière d’au moins 10dB de l’antenne développe sur sa bande de fonctionnement. / Radio direction finding (DF) allows for the measurement of the direction of arrival of incoming electromagnetic signals. Its main applications include spectrum monitoring and electronic warfare. DF antennas and arrays are subject to new problematics (bandwidth, compactness and polarization diversity) while DF algorithms have kept on improving. Previous works have initiated the design of such antennas and arrays. This work aims at designing an antenna with reduced dimensions for the VHF and UHF frequency bands and with a polarization diversity. This antenna shall then be integrated in a functional DF array. For this purpose, a planar antenna has been designed and measured in the 500-3000 MHz frequency band. Its final dimensions are 150mm x 150mm (λ/4 x λ/4). This antenna has then been integrated in the final DF array whose accuracy on the same frequency band is of the order of 2° for a final size of 260mm (diameter) x 150mm (height), that is λ/2,3 x λ/4. This study has also allowed for the design of a low-profile absorber (with a height of 25mm, that is λ/24 at its lowest frequency of operation). An increase of 10dB in the front to back ratio of the proposed antenna has been enabled by this absorber on its whole frequency band.

Resumo não disponível.