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The dielectric constant or relative static permittivity of a material represents the capacitance of the material relative to a vacuum and is important in many industrial applications. Nevertheless, accurate experimental values are often unavailable and current prediction methods lack accuracy and are often unreliable. A new QSPR (quantitative structure-property relation) correlation of dielectric constant for pure organic chemicals is developed and tested. The average absolute percent error is expected to be less than 3% when applied to hydrocarbons and non-polar compounds and less than 18% when applied to polar compounds with dielectric constant values ranging from 1.0 to 50.0. A local composition model is developed for mixture dielectric constants based on the Nonrandom-Two-Liquid (NRTL) model commonly used for correlating activity coefficients in vapor-liquid equilibrium data regression. It is predictive in that no mixture dielectric constant data are used and there are no adjustable parameters. Predictions made on 16 binary and six ternary systems at various compositions and temperatures compare favorably to extant correlations data that require experimental values to fit an adjustable parameter in the mixing rule and are significantly improved over values predicted by Oster's equation that also has no adjustable parameters. In addition, molecular dynamics (MD) simulations provide an alternative to analytic relations. Results suggest that MD simulations require very accurate force field models, particularly with respect to the charge distribution within the molecules, to yield accurate pure chemical values of dielectric constant, but with the development of more accurate pure chemical force fields, it appears that mixture simulations of any number of components are likely possible. Using MD simulations, the impact of different portions of the force field on the calculated dielectric constant were examined. The results obtained suggest that rotational polarization arising from the permanent dipole moments makes the dominant contribution to dielectric constant. Changes in the dipole moment due to angle bending and bond stretching (distortion polarization) have less impact on dielectric constant than rotational polarization due to permanent dipole alignment, with angle bending being more significant than bond stretching.

<p>  </p> <p>In the time after their conception, Dielectric Barrier Discharge (DBD) systems have become highly utilized in the field of plasma research, with applications ranging from medicine to water treatments to airfoil design. One of the more recent applications for DBD systems has been the plasma treatment of polymers, overcoming the deficits of previously used chemical treatment systems such as environmental hazards, high cost, and other complexities. A novel development occurring within the past three years was the use of a DBD system to treat the inner surface of small-diameter polymer tubing to improve the wettability and adhesion characteristics as compared to untreated polymer tubing. This work is interested in improving that DBD system.</p> <p>This thesis focuses on the development and implementation of two additional systems for an atmospheric pressure DBD system that treats the inner surface of narrow-diameter polymer tubes. The first, a pulsed-DC HV generator, will improve the plasma treatment. The fast rise times of the applied voltage prevent any stochastic behavior in plasma ignition and reignition, the resulting homogeneity of the plasma means that the plasma conditions of the treatment are more easily reproduced, and the increase in plasma intensity allows for quicker treatment of the tubing, the feed rates can reach the level of industrial production without lessening the effects induced by the treatment. The second, a Capstan-driven spooling system, will also improve the industrial capabilities of the DBD system. The higher feed rates that the spooling system reaches provide a means to rapidly produce treated tubing at a continuous rate, and the user-friendly interface means that system operation increases to a broader range of potential personnel. </p> <p>Investigation of the effect that tube feed rate (plasma exposure time) has on surface wettability was performed for the feed rates of the spooling systems. Feed rates of 2.5, 10, 50, 200, and 800 mm/min were performed on tubing samples for a 100% Helium plasma at a power level of 5 mW and a 98%He-2%O2 plasma at a power level of 20 mW. The temporal evolution of wettability was determined by taking the water contact angle (θ) of the treated tubing surface 0, 1, 2, 4, 16, 24, and 120 hours after plasma treatment. The resulting water contact angles initially fluctuate but eventually decay to reach a steady-state hydrophilicity that remains up to five days. The steady-state contact angles ranged from 42.3o < θss < 70.2o for a Helium plasma and 39.9o < θss < 62.7o for a Helium-Oxygen plasma. </p> <p>Investigation of the plasma power achieved with a pulsed-DC HV generator was also performed. The pulsed DC-driven plasma, which has a characteristic rise time of ~300 ns, ignites at Vbd = 4.5 kV. This breakdown voltage is 1.3 times higher than the minimum for the system, Vbd,min = 3.45 kV, so the resulting overvoltage of the pulsed-DC generator is approximately 1.3 times the minimum breakdown voltage. The electrical power deposited to the discharge for the pulsed-DC driven discharge (133.2 mW) is 6 times the power of the previous AC-driven discharge (21.4 mW). Resulting surface wettability was also calculated for the two generators. The stronger plasma treatment of the pulsed-DC HV generator resulted in a steady-state contact angle 11.4o more hydrophilic than the AC HV generator (θss = 44.6o for pulsed-DC-driven discharge compared to θss = 56o for AC-driven discharge).</p>

With the increasing demand for high performance communication networks and the proliferation of mobile devices, significant advances in antenna design are essential. In recent years the rising demands of the mobile wireless communication industry have forced antennas to have increased performance while being limited to an ever decreasing footprint. Such design constraints have forced antenna designers to consider frequency agile antennas so that their behavior can adapt with changing system requirements or environmental conditions. Frequency agile antennas used for mobile handset applications must also be inexpensive, robust, and make use of electronic switching with reasonable DC power consumption. Previous works have addressed a number of these requirements but relatively little work has been performed on frequency agile dielectric resonator antennas (DRAs). The objective of this thesis is to investigate the use of DRAs for frequency reconfigurability. DRAs are an attractive option due to their compactness, very low losses leading to high radiation efficiencies (better than 95%) and fairly wide bandwidths compared to alternatives. DRA’s are also well suited for mobile communications since they can be placed on a ground plane and are by nature low gain antennas whose radiation patterns typically resemble those of short electric or magnetic dipoles. One way to electronically reconfigure a DRA, in the sense of altering the frequency band over which the input reflection coefficient of the antenna is below some threshold, is to partially load one face of the DRA with a conducting surface. By altering the way in which this surface connects to the groundplane on which the DRA is mounted, the DRA can be reconfigured due to changes in its mode structure. This connection was first made using several conducting tabs which resulted in a tuning range of 69% while having poor cross polarization performance. In order to address the poor cross polarization performance a second conducting surface was placed on the opposing DRA wall. This technique significantly reduced the cross polarization levels while obtaining a tuning range of 83%. The dual-wall conductively loaded DRA was then extended to include a full electronic implementation using PIN diodes and varactor diodes in order to achieve discrete and continuous tuning respectively. The two techniques both achieved discrete tuning ranges of 95% while the varactor implementation also had a continuous tuning range of 59% while both maintaining an acceptable cross polarization level.

This dissertation explores CMOS RF design and reliability for portable wireless receivers. The objective behind this research is to achieve an increase in integration level, and gain more understanding for RF reliability. The fields covered include device, circuit and system. What is under investigation is a multi-band multi-mode receiver with GSM, DCS-1800 and CDMA compatibility. To my understanding, GSM and CDMA dual-mode mobile phones are progressively investigated in industries, and few commercial products are available. The receiver adopts direct conversion architecture. Some improved circuit design methods are proposed, for example, for low noise amplifier (LNA). Except for band filters, local oscillators, and analog-digital converters which are usually implemented by COTS SAW filters and ICs, all the remaining blocks such as switch, LNA, mixer, and local oscillator are designed in MOSIS TSMC 0.35[micro]m technology in one chip. Meanwhile, this work discusses related circuit reliability issues, which are gaining more and more attention. Breakdown (BD) and hot carrier (HC) effects are important issues in semiconductor industry. Soft-breakdown (SBD) and HC effects on device and RF performance has been reported. Hard-breakdown (HBD) effects on digital circuits have also been investigated. This work uniquely address HBD effects on the RF device and circuit performance, taking low noise amplifier and power amplifier as targets.

This thesis reports the development, synthesis and characterization of a ceramic-ceramic nanocomposite system for its possible application as structural and electronic biomaterial in the biomedical industry. The study selected and synthesized alumina-aluminum titanate-titania (Al2O3-Al2TiO5-TiO2) nanoceramic composite using a simple Sol-Gel technique, which can be easily reproduced. Aluminum propoxide and titanium propoxide were used as precursor chemicals. Propanol and 2- methoxy ethanol were used as solvent and stabilizer, respectively. Thermal analyses were performed for a systematic understanding of phase evolution from the synthesized gel. X-Ray diffraction technique was used to confirm the phase evolution, phase purity, crystallite size and crystal structure(s) of the phase(s). Calcination of the powder at low temperatures (700°C) leads to formation of Al2O3-TiO2 nanocomposite and at higher temperatures into Al2O3-Al2TiO5-TiO2 nanocomposite confirmed by XRD analysis. Electron microscopic techniques were used to investigate powder morphology, crystallite size and inter-planner spacing. High Resolution Transmission Electron Microscopy images of the calcined powder showed agglomerates of powder particles with particle size in 15-20 nm range. As-synthesized powder was uniaxially pressed into cylindrical pellets and sintered at elevated temperatures (1000-1400oC) to study the sintering behavior, densification characteristics, and measurement of mechanical and electrical properties and assessment of bioactivity. Phase transformation induced by the sintering process was analyzed by X-ray powder diffraction technique. The effects of nanosize of powder particles and multi-phases on densification, and mechanical and electrical properties were investigated. Vickers hardness and biaxial flexural strength tests were used to determine mechanical properties. Bioactivity of the nanocomposite was assessed in Simulated Body Fluid (SBF), which has the same ionic concentration as that of human plasma. Effects of biodegradation and change in mechanical properties of the composite when kept in SBF and maintained in a static condition were studied in terms of weight loss, change in the pH of the acellular solution and change in mechanical properties (hardness and biaxial strength). Scanning Electron Microscopy was used to observe the formation of apatite crystals on the surface of the nanocomposite specimens soaked in SBF. The results obtained throw light on biocompatibility and bioactivity of Al2TiO5 phase, which has not been reported so far in the literature to the best of our knowledge. Dielectric constant and dissipation factor of the sintered nanocomposite pellets were measured using HP 4284A impedance-capacitance-resistance meter and 16451 B dielectric test fixture at 1 MHz frequency. The effects of sintering time, temperature and phases present on the electrical properties were studied and are reported in the thesis.