No description available.

Electrically conductive polymer composites, i.e. polymers filled with conductive fillers, may display a broad range of electrical properties. A rational design of fillers, filler surface chemistry and filler loading can tune the electrical properties of the composites to meet the requirements of specific applications. In this dissertation, two studies were discussed. In the first study, highly conductive composites with electrical conductivity close to that of pure metals were developed as environmentally-friendly alternatives to tin/lead solder in electronic packaging. Conventional conductive composites with silver fillers have an electrical conductivity 1~2 orders of magnitude lower than that of pure, even at filler loadings as high as 80-90 wt.%. It is found that the low conductivity of the polymer composites mainly results from the thin layer of insulating lubricant on commercial silver flakes. In this work, by modifying the functional groups in polymer backbones, the lubricant layer on silver could be chemically reduced in-situ to generate silver nanoparticles. Furthermore, these nanoparticles could sinter to form metallurgical bonds during the curing of the polymer matrix. This resulted in a significant electrical conductivity enhancement up to 10 times, without sacrificing the processability of the composite or adding extraneous steps. This method was also applied to develop highly flexible/stretchable conductors as building block for flexible/stretchable electronics. In the second study, a moderately conductive carbon/polymer composite was developed for use in sensors to monitor the thermal aging of insulation components in nuclear power plants. During thermal aging, the polymer matrix of this composite shrank while the carbon fillers remained intact, leading to a slight increase in filler loading and a substantial decrease in the resistivity of the sensors. The resistivity change was used to correlate with the aging time and to predict the need for maintenance of the insulation component according to Arrhenius’ equation. This aging sensor realized real-time, non-destructive monitoring capability for the aging of the target insulation component for the first time.

Sensorless control strategies were first suggested well over a decade ago with the aim of reducing the size, weight and unit cost of electrically actuated servo systems. The resulting algorithms have been successfully applied to the induction and synchronous motor families in applications where control of armature speeds above approximately one hundred revolutions per minute is desired. However, sensorless position control remains problematic. This thesis provides an in depth investigation into sensorless motor control strategies for high precision motion control applications. Specifically, methods of achieving control of position and very low speed thresholds are investigated. The developed grey box identification techniques are shown to perform better than their traditional white or black box counterparts. Further, fuzzy model based sliding mode control is implemented and results demonstrate its improved robustness to certain classes of disturbance. Attempts to reject uncertainty within the developed models using the sliding mode are discussed. Novel controllers, which enhance the performance of the sliding mode are presented. Finally, algorithms that achieve control without a primary feedback sensor are successfully demonstrated. Sensorless position control is achieved with resolutions equivalent to those of existing stepper motor technology. The successful control of armature speeds below sixty revolutions per minute is achieved and problems typically associated with motor starting are circumvented.

No description available.

"A small “spiralpole” antenna – the hybrid structure where one dipole wing is kept, but another wing is replaced by a coaxial single-arm spiral, is studied both theoretically and experimentally. Such a structure implies the implementation of an impedance-matching network (an inductor in series with a small dipole) directly as a part of the antenna body. The antenna impedance behavior thus resembles the impedance behavior of a small dipole in series with an extra inductance, which is that of the spiral. However, there are two improvements compared to the case when an equivalent small dipole is matched with an extra lumped inductor. First, the spiralpole antenna has a significantly larger radiation resistance – the radiation resistance increases by a factor of two or more. This is because the volume of the enclosing sphere is used more efficiently. Second, a potentially lower loss is expected since we only need a few turns of a greater radius. The radiation pattern of a small spiralpole antenna is that of a small dipole, so is the first (series) resonance. The Q-factor of the antenna has been verified against the standard curves. The antenna is convenient in construction and is appealing when used in conjunction with passive RFID tags such as SAW temperature sensors. "

The microwave near-field detection technique is of interest to many researchers for characterizing materials because of its high sensitivity. It is based on sensing buried objects by producing an evanescent field.The advantage of evanescent fields is their capability to interrogate electrically small objects. In the past, near-field probes have been designed to sense magnetic materials. For dielectric materials, a near-field probe that senses the permittivity of the materials is important. This work presents a novel design of a near-field probe that generates a dominant electric eld. The probe is an electrically small dipole measuring approximately 0.07?? in length operating at 216.3 MHz. The antenna is matched to a 50??? system using two chip inductors distributed symmetrically on the dipole. The numerical and measurement results show that the proposed design is highly sensitive and capable of sensing subsurface object. The proposed design is compact, lightweight and applicable for microwave applications.

Part A of two Project Reports; Part B can be found at: http://hdl.handle.net/11375/17691 / <p>The annealing behaviour of 15N implanted, aluminum doped-SiC has been studied by measuring the differential capacitance as a function of applied bias. The samples were doubly implanted at 450°c with 45 Kev and 25 Kev ions, for a dose of 10^16/cm^2 at each energy.</p> <p> An n-i-p structure with a thick insulator region was found after annealing at 1000°c. The thickness of this i region could be substantially reduced with additional annealing at higher temperatures, and a fairly good n-p junction was obtained after 1480°c anneal.</p> <p> About 20-30% of the implanted nitrogen ions were found to be electrically active.</p> <p> The C-V behaviour was found to have large variations with the a.c. measuring frequency.</p> / Thesis / Master of Engineering (MEngr)

Electrical control over propellant combustion has the opportunity to improve the functionality and performance of various propulsion systems. In solid rocket motors, active burn rate modulation has the potential to enable throttling. In spacecraft propulsion systems, electrolysis of propellants may provide a means to reduce energy requirements and eliminate the need for expensive catalysts. The work presented in this thesis is concerned with fundamental science related to propellant electrolysis and the performance of rocket propulsion systems using electrolytic ignition. Specifically, the present research is concerned with the effect of conductive and energetic additives on the ignition, combustion, and extinction characteristics of lithium perchlorate-based propellants. Particular attention is paid to the relative importance of electrochemistry and ohmic heating during ignition and steady-state combustion as well as the relative influence of pressure and voltage during steady combustion. Research into the development of an electrically initiated propellant and its integration into a rocket motor is presented as well. This work focused primarily on surveying propellants based on ammonium perchlorate, lithium perchlorate, and hydroxylammonium nitrate for use in a small rocket motor. The decomposition processes of propellants based on ionic liquids and gel polymer electrolytes are detailed. Finally, data from motor firings is presented and parameters influencing the motor's performance and consistency are identified for future improvement. / Master of Science / The principal disadvantage of solid rocket motors is the lack of an active throttling and restart capability. Put simply, once a motor is ignited, it will burn until all of the propellant is consumed and there currently isn't a good method to speed up or slow down a solid rocket on command after it has been launched. As a result, the situations in which solid rocket motors can be used are limited. For example, solid rockets are not used in satellite propulsion because satellites need periodic adjustments to attitude and altitude, not a single boost. But solid rockets are relatively cheap, simple, and reliable and so various means of throttling solid propellants are being investigated. The method relevant to this work is throttling by using an electrical stimulus. By applying voltage across a propellant, the propellant can be ignited and the burning rate can be changed. The research here investigates what materials can be added to these propellants to make them ignite and burn faster as well as the development of novel propellants for applications in a small rocket motor.

Electrically controllable propellants (ECPs) provide a new method to increase the control and functionality of rocket motors in particular solid rockets. Traditional solid rockets do not have the capability to modify the burning rate on demand during operation, which greatly limits operational capabilities. The research outlined in this dissertation explores the fundamentals in the creation of ECPs to enable increased control in the burning rate of solid rockets. The research is organized into four studies which step through the fundamentals of ECPs, starting with a focus on the solid oxidizers, then moving into the creation of electrically controllable gel propellants (ECGPs). Next, electrically controllable solid propellants (ECSPs) were explored under atmospheric conditions, and then finally under elevated pressures. The first study explores the ability to electrically control the decomposition characteristics of various solid oxidizers. Typical composite solid propellants are composed of solid fuels and oxidizers and isolating the oxidizer in this study enables the ability to characterize critical components of ECSPs individually. This study discovered that certain solid oxidizers respond differently to applied voltages, but generally the decomposition rate of the solid oxidizers is greatly increased when voltage is applied using metal electrodes. The melt layer formed in the decomposition of the solid oxidizers was observed to be critical in the ability to manipulate the decomposition rate of the oxidizers. The second study built upon the knowledge that the melt layer was critical in the functionality of ECPs and explored the utilization of ECGPs which combined a viscous liquid polymer fuel in which solid oxidizers were dissolved. The ECGPs used in this study readily decomposed and ignited when a voltage potential was applied. The composition of the ECGPs along with the magnitude of the voltage being applied greatly impacted the ignition delay and overall burning characteristics of the propellants. This study illustrated the potential to create ECPs that enable increased control over the burning characteristics compared to conventional propellants. The third study utilized a solid polymer binder along with the solid oxidizers to create ECSPs that would readily decompose and ignite when a voltage potential was applied. Compositional changes in the propellant along with the magnitude of the applied voltage potential were observed to impact the regression rate of the ECSPs utilized in this study. The electrochemical decomposition characteristics of the ECSPs were explored to better characterize the contribution of the electrochemical reactions and how they differ from the more conventional thermochemical decomposition. The fourth and final study builds upon the prior ECSP study, but now experiments utilize compositions with electrically conductive additives to increase the responsiveness of the ECSPs to the applied voltage. This enabled the creation of ECSPs which ignite much more readily and with a higher degree of consistency. Experiments were also conducted at elevated pressures to analyze the combined impact that voltage and pressure play on the regression rate of the ECSPs. / Doctor of Philosophy / Solid rockets have many applications in both the civilian and defense industries due to their relatively low costs and long-term storage capabilities. However, traditional solid rockets have a limited degree of control as a result of the fuel and oxidizer being combined in the propellant and the combustion of the propellant being self-sustaining. The ability to change the thrust of the solid rocket motor on demand is something not currently possible without greatly increasing the complexity of the rocket motor, and even then the thrust control is limited. The addition of a simple method to vary the thrust of the rocket motor would drastically improve the functional capabilities and safety of the rocket. The method explored in this study to enable the creation of controllable solid rockets is through the use of electrically controllable propellants. These are propellants whose burning characteristics can be modified when subjected to an electric field. The work outlined in this dissertation develops a fundamental understanding of the methods to create electrically controllable solid and gel propellants. The electrically controllable propellants in this study demonstrated the capability to have their burning rate greatly increase or decrease by increasing or decreasing the voltage being applied to them. In addition to changing the burning rate, several compositions developed in this study were able to have their burning extinguished by removing the voltage and reignited by reapplying the voltage. These capabilities and the fundamentals behind their development enable the creation of much more functional rocket motors that overcome the limitations of current systems.

Implanted Devices are important components of the Wireless Body Area Network (WBAN) as a promising technology in biotelemetry, e-health care and hyperthermia applications. The design of WBAN faces many challenges, such as frequency band selection, channel modeling, antenna design, physical layer (PHY) protocol design, medium access control (MAC) protocol design and power source. This research focuses on the design of implanted antennas, channel modeling between implanted devices and Wireless Power Transfer (WPT) for implanted devices. An implanted antenna needs to be small while it maintains Specific Absorption Rate (SAR) and is able to cope with the detuning effect due to the electrical properties of human body tissues. Most of the proposed antennas for implanted applications are electric field antennas, which have a high near-zone electric field and, therefore, a high SAR and are sensitive to the detuning effect. This work is devoted to designing a miniaturized magnetic field antenna to overcome the above limitations. The proposed Electrically Coupled Loop Antenna (ECLA) has a low electric field in the near-zone and, therefore, has a small SAR and is less sensitive to the detuning effect. The performance of ECLA, channel model between implanted devices using Path Loss (PL) and WPT for implanted devices are studied inside different human body models using simulation software and validated using experimental work. The study is done at different frequency bands: Medical Implanted Communication Services (MICS) band, Industrial Scientific and Medical (ISM) band and 3.5 GHz band using ECLA. It was found that the proposed ECLA has a better performance compared to the previous designs of implanted antennas. Based on our study, the MICS band has the best propagation channel inside the human body model among the allowed frequency bands. The maximum PL inside the human body between an implanted antenna and a base station on the surface is about 90 dB. WPT for implanted devices has been investigated as well, and it has been shown that for a device located at 2 cm inside the human body with an antenna radius of 1 cm an efficiency of 63% can be achieved using the proposed ECLA. / Ph. D.