<p>Implantable wireless devices are used to treat a variety of diseases that are not able to be treated with pharmaceuticals or traditional surgery, These implantable devices have use in the treatment of neurological disorders like epilepsy, optical disorders such as glaucoma, or injury related issues such as targeted muscle reinnervation. These devices can rely upon harvesting power from an inductive wireless power source and batteries. Improvements to how well the devices utilize this power directly increase the efficacy of the device operation as well as the device's lifetime, reducing the need for future surgeries or implantations. </p> <p> I have designed an improvement to cavity resonator based wireless power by designing a dynamic impedance matching implantable power supply, capable of tracking with device motion throughout a changing magnetic field and tracking with changing powering frequencies. This cavity resonator based system presents further challenges practically in the turn-on cycle of the improved device. </p> <p> I further design a coil-to-coil based wireless power system, capable of dynamically impedance matching a high quality factor coil to optimize power transfer during steady state, while also reducing turn-on transient power required in dynamic systems by utilizing a second low quality factor coil. This second coil has a broadband response and is capable of turning on at lower powers than that of the high quality factor coil. The low quality factor coil powers the circuitry that dynamically matches the impedance of the high quality factor coil, allowing for low power turn on while maintaining high power transfer at all operating frequencies to the implantable device. </p> <p> Finally, an integrated circuit is designed, fabricated, and tested that is capable of smoothly providing regulated DC power to the implantable device by stepping up from wireless power to a reasonable voltage level or stepping down from a battery to a reasonable voltage level for the device. The chip is fabricated in 0.18um CMOS process and is capable of providing power to the "Bionode" implantable device. </p>

In the built environment, human activities such as railway and road traffic, constructionworks or industrial manufacturing can give rise to ground borne vibrations. Such vibrations become a concern in urban areas as they can cause human discomfort or disruption of vibration sensitive equipment in buildings. In Sweden, geological formations of soft clay soils overlying till and a high quality bedrock are encountered in densely populated areas, which are soil conditions that are prone to high levels of ground borne vibrations. Under such soil conditions, end-bearing piles are often used in the design of building foundations. The dynamic response of a building is governed by the interaction between the soil and the foundation. It is therefore essential that models used for vibration predictions are able to capture the dynamic soil-structure interaction of pile foundations. The purpose of this thesis is to experimentally and numerically investigate dynamic soil-structure interaction of an end-bearing pile group in clay by constructing a test foundation of realistic dimensions. The small-strain properties in a shallow clay deposit are estimated using different site investigation and laboratory methods. The results are synthesised into a representative soil model to compute the free-field surface response, which is validated with vibration measurements performed at the site. It is found that detailed information regarding material damping in the clay and the topmost soil layer both have a profound influence on the predicted surface response, especially with an increasing distance from the source. Dynamic impedances of four end-bearing concrete piles driven at the site are measured. Pile-soil-pile interaction is investigated by measuring the response of the neighbour piles when one of the piles in the group is excited. The square pile group is subsequently joined in a concrete cap and measurements of the impedances of the pilegroup and acceleration measurements within the piles at depth are performed. A numerical model based on the identified soil properties is implemented and validated by the measurements. A good agreement between the predicted and measured responses and impedances of the pile group foundation is found, establishing confidence in the ability to predict the dynamic characteristics of end-bearing pile foundations under the studied soil conditions. / Mänsklig verksamhet i urbana miljöer så som väg- och järnvägstrafik, byggnation eller maskindrift inom industri kan ge upphov till vibrationer som sprider sig via marken i närområdet. Dessa vibrationer kan ge upphov till kännbara vibrationer eller påverka vibrationskänslig utrustning i byggnader. I Sverige förekommer ofta mjuka lerjordar ovanpå berg, och inte sällan i tätbebyggda områden. Under sådana jordförhållanden används ofta spetsbärande pålar för grundläggning av byggnader. Det dynamiska verkningssättet för byggnader är beroende av interaktionen mellan jorden och byggnadens grund. Det är därför viktigt att modeller som används för vibrationsanalys i byggnader kan beskriva denna interaktion mellan jord och byggnadsfundament. Syftet med denna avhandling är att experimentellt och via numeriska modeller studera dynamisk jord-struktur-interaktion av ett spetsbärande pålfundament i lera. Jordensmekaniska egenskaper vid små töjningar utvärderas för en lerjord som är avsatt på morän och berg genom både fältförsök och laboratorieanalyser av prover. Informationen kombineras för att konstruera en lagerförd jordmodell av platsen för att beräkna jordens dynamiska respons till följd av en punktlast. Modellen valideras med vibrationsmätningar som utförts på platsen. Studien visar att detaljerad information angående lerans materialdämpning och de mekaniska egenskaperna av jordens översta lager har en stor inverkan på förutsägelser av jordens dynamiska respons vid ytan, speciellt vid stora avstånd från vibrationskällan. Experimentella tester utförs för att mäta dynamiska impedanser av fyra slagna spetsbärande betongpålar. Interaktionen mellan pålarna utvärderas genom att utföra mätningarav de omgivande pålarnas respons till följd av excitering av en påle. Pålgruppen sammanfogas därefter i ett betongfundament och impedanserna samt accelerationer inuti pålarna uppmäts. En numerisk modell baserad på de identifierade mekaniska egenskaperna av jorden upprättas och valideras genom mätningarna. De numeriska resultaten är i god överensstämmelse med de uppmätta vilket styrker användningen av numeriska modeller för att förutsäga interaktionen mellan jord och spetsbärandepålar under de studerade jordförhållandena. / <p>QC 20210302</p>

The interconversion of α- and β-Ni(OH)₂ was studied using cyclic voltammetry and dynamic electrochemical impedance (dEIS). Holding experiments were done at 0.5 V, 0.6 V, 0.8 V and 1.0 V while subsequent cathodic holds were applied in selected experiments at -0.1, -0.2, -0.25 V. The number of thickness of Ni(OH)₂ formed increased with increasing anodic potential. After α-Ni(OH)₂ was formed (< 0.5 V), it was easily reduced by sweeping down to -0.15 V. However, sweeping further (> 0.5 V) resulted in its "irreversible" conversion to β-Ni(OH)₂. Since β-Ni(OH)₂ was not reduced by sweeping to -0.15 V, the current, capacitance and the conductance at the α-Ni(OH)₂ peak (at 0.2 V) decreased as a result. However, β-Ni(OH)₂ was shown to be reducible during potential holds at -0.2 V or lower. In contrast, holding at -0.1 V only resulted in partial reduction. Eventually, a link was established between the reduction of β-Ni(OH)₂ and hydrogen evolution. The relatively slow reduction of the β-Ni(OH)₂ to metallic nickel appears to inhibit the capacitance increase at -0.15 V which occurs when the potential is kept under 0.5 V. The retention of a low capacitance while β-Ni(OH)₂ persists suggests a blocking mechanism. A concerted adsorption-desorption step which generates adsorbed hydrogen prior to hydrogen evolution was proposed. An exponential increase in current and capacitance occurred during the potential hold at -0.2 V. The capacitance increase suggests a reversal of the blocking (low capacitance at -0.15 V) caused by the persistence of β-Ni(OH)₂. Additionally, the exponential current decay during the hold at -0.2 V was significantly slower than the conversion of α- to β-Ni(OH)₂ at 0.8 V. This further demonstrates the possibility of a slow step involving surface blocking during the reduction of β-Ni(OH)₂. These observations provide new information on the mechanism and kinetics of the interconversion of α-Ni(OH)₂ into β-Ni(OH)₂ and the interaction of the latter in the hydrogen evolution reaction. / Graduate