In order to remain competitive in the marketplace, all motor vehicle manufacturers face difficult decisions with regard to balancing cost vs. feature. That is to say that the manufacturer must balance the cost of the product to the customer to remain competitive whilst offering appropriate technology and standard features required by that customer. All motor manufacturers are therefore under pressure to keep costs of nonfeature items to a minimum. One of the cost reductions items prevalent on most vehicles is the deletion of the structural member that attaches the rear bumper, known as the bumper beam (RBB), which is researched in this Thesis. This generates average vehicle savings of $20 and, as this is invisible to the customer, should enable the manufacturers to realise a significant saving or allow this revenue to be spent on additional feature without loss of vehicle function. However, in nearly all cases, deletion of the rear bumper beam has the effect of degrading the steering responses of the vehicle by 1 to 1½ rating points (out of 10), which is contrary to the premise of cost reductions; which is to ensure that vehicle function is unaffected. Initial analysis of vehicles with deleted rear bumper beams cannot show an objective measurable difference in any vehicle behaviours with or without the beam fitted, and hence CAE studies using ADAMS models cannot verify the effects of the bumper beam. It was necessary to employ unconventional modelling and testing methods such as rigid body, flexible body model techniques as well as experimental studies included driving robots and expert driver appraisals. The research demonstrated that vehicle modelling methods currently used, cannot establish or predict the complete vehicle ride and handling status. A total vehicle model approach should be used without separating the body CAE model and vehicle dynamics ADAMS model into separate entities. Furthermore, it was concluded that the determination to the effects of body hysteresis rather than pure stiffness is of crucial importance and that the steering attribute could be maintained with the deletion of the RBB analytically.

The energy demand has increased dramatically in the last century, and so to have global CO2 emissions. Two critical challenges for the geo-energy sector are to develop different approaches for harvesting energy and to actively decrease atmospheric CO2 emissions. Addressing these challenges requires efficient, sustainable, and affordable technical solutions. Complex fluids are ubiquitous and offer great potential for geo-engineering applications such as the development of geo-energy, enhanced oil recovery and CO2 geological sequestration and utilization. This thesis will present new results on interfacial phenomena in CO2-fluid-mineral systems, including interfacial tension hysteresis, the effects of surface-active components on interfacial tension (surfactants, nanoparticles, organo-bentonites and asphaltenes), and the interfacial pinning of immiscible fluids on substrates. Pore-scale phenomena come together in the study of the physical properties of CO2 and its implication for both storage and assisted gravity oil drainage. Finally, we provide a better understanding of the interfacial phenomena of complex fluids and their interactions within porous media that can lead to efficient and sustainable geo-energy systems.

With the rise of soft-switched converter topologies which enable high-frequency power conversion, there has been a premise that these converter topologies can help achieve loss-less switching in a power device. However, this theory is not completely true as there even with soft-switching there is some degree of loss associated in the form of output capacitance-related hysteresis loss, channel turn-off loss, and loss during the dead-time period in these converter topologies. The soft-switching converters utilize the existence of the device's output capacitance (COSS), which is charged and discharged consecutively at each switching cycle, and a hysteresis loss exists due to the difference in charging and discharging output capacitance. In order fully utilize the potential of these novel soft-switching topologies, we need to investigate further into the origins of these losses or loss mechanisms, methods to measure or compute these losses, and then devise ways to optimize the loss for a given application. This work focuses on exploring methods to quantify this loss for different operating conditions like device current, switching frequency, dV/dT, etc. In this aspect, some methods have been studied and used to quantify this hysteresis loss for a variety of power devices like SI and GaN. It is reported that only channel turn-off losses exist in devices with ZVS transition, however, we found that the charging and discharging of COSS is not loss-free and thus it is important that we account for this loss in the design process. Finally, the loss data obtained from these tests are compared with each other for five different power devices to validate their applicability, and later these test results are used to get an optimized device selection criterion for the best possible efficiency and minimal losses for a ZVS application. / Master of Science / To eliminate the switch-related losses, soft-switching or zero-voltage switching (ZVS) was introduced which provides a soft transition of voltage and current instead of a sharp transition like in hard-switched converters. Moreover, the output capacitance of the devices is charged/discharged to achieve soft switching, which also possesses a loss (hysteresis loss) due to repeated charging and discharging of output capacitance. Soft-switching converter topologies have gained quite a momentum for almost a decade, and it keeps on increasing in the distant future, to extract the maximum benefits from these topologies is to operate at high switching frequencies to minimize the size and volume of the converter. However, the hysteresis loss can severely impact the converter efficiency on even a few 100 kHz and MHz levels. This work focuses on exploring methods to measure hysteresis loss in output capacitance which has a major share in the overall switching loss. In this regard, some methods have been investigated that deal with the measurement of the output capacitance-related hysteresis loss and are implemented to get the hysteresis loss data for different power devices. Two test methods (calorimetric and non-linear resonance) are implemented on five different power devices (3 SI and 2 GaN) to get the energy loss in the output capacitance; these test results are used to explain the switching loss in an isolated boost resonance DC-DC converter, and a concept of ZVS figure of merit is used to obtain the optimized device. Moreover, a design example of a soft-switched converter is presented to highlight the impact of COSS hysteresis loss in the overall switching loss of primary side devices.

Autostereoscopic 2D/3D (two-dimension/three-dimension) switchable display has been attracting great interest in research and practical applications for several years. Among different autostereoscopic solutions, direction-multiplexed 3D displays based on microlens array or parallax barrier are viewed as the most promising candidates, due to their compatibility with conventional 2D display technologies. These 2D/3D switchable display system designs rely on fast switching display panels and photonics devices, including adaptive focus microlens array and switchable slit array. Polymer-stabilized blue phase liquid crystal (PS-BPLC) material provides a possible solution to meet the aforementioned fast response time requirement. However, present display and photonic devices based on blue phase liquid crystals suffer from several drawbacks, such as low contrast ratio, relatively large hysteresis and short lifetime. In this dissertation, we investigate the material properties of PS-BPLC so as to improve the performance of PS-BPLC devices. Then we propose several PS-BPLC devices for the autostereoscopic 2D/3D switchable display system designs. In the first part we evaluate the optical rotatory power (ORP) of blue phase liquid crystal, which is proven to be the primary reason for causing the low contrast ratio of PS-BPLC display systems. Those material parameters affecting the ORP of PS-BPLC are investigated and an empirical equation is proposed to calculate the polarization rotation angle in a PS-BPLC cell. Then several optical compensation methods are proposed to compensate the impact of ORP and to improve the contrast ratio of a display system. The pros and cons of each solution are discussed accordingly. In the second part, we propose two adaptive focus microlens array structures and a high efficiency switchable slit array based on the PS-BPLC materials. By optimizing the design parameters, these devices can be applied to the 2D/3D switchable display systems. In the last section, we focus on another factor that affects the performance and lifetime of PS-BPLC devices and systems: the UV exposure condition. The impact of UV exposure wavelength, dosage, uniformity, and photo-initiator are investigated. We demonstrate that by optimizing the UV exposure condition, we can reduce the hysteresis of PS-BPLC and improve its long term stability.

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