With the escalating number of vehicles on the road, great concerns are drawn to the large amount of fossil fuels they use and the detrimental environmental impacts from their emissions. A lot of research and development have been conducted to explore the alternative energy sources. The fuel cell has been widely considered as one of the most promising solutions in automobile applications due to its high energy density, zero emissions and sustainable fuels it employs. However, the cost and low power density of the fuel cell are the major obstacles for its commercialization. This thesis designs a novel converter topology and proposes the control method applied in the Fuel Cell Hybrid Vehicles (FCHVs) to minimize the fuel cell's cost and optimize the system's efficiency. Unlike the previous work, the converters presented in the thesis greatly reduce the costs of hardware and energy losses during switching. They need only three Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) to smoothly accomplish the energy management in the cold start, acceleration, steady state and braking modes. In the converter design, a boost converter connects the fuel cell to the DC bus because the fuel cell's voltage is usually lower than the rating voltage of the motor. In this way, the fuel cell's size can be reduced. So is the cost. With the same reason, the bidirectional converter connected to the ultracapacitor works at the buck pattern when the power is delivered from the DC bus to the ultracapacitor, and the boost converter is selected when the ultracapacitor provides the peaking power to the load. Therefore, the two switches of the bi-directional converter don't work complementarily but in different modes according to the power flow's direction. Due to the converters' simple structure, the switches' duty cycles are mathematically analyzed and the forward control method is described. The fuel cell is designed to work in its most efficient range producing the average power, while the ultracapacitor provides the peaking power and recaptures the braking power. The simulation results are presented to verify the feasibility of the converter design and control algorithm.

Recent advances in wireless communication and micro-electro-mechanical systems (MEMS) have led to the development of implementation of low-cost, low power, multifunctional sensor nodes. These sensor node are small in size and communicate untethered in short distances. The nodes in sensor networks have limited battery power and it is not feasible or possible to recharge or replace the batteries, therefore power consumption should be minimized so that overall network lifetime will be increased. In order to minimize power consumed during idle listening, some nodes, which can be considered redundant, can be put to sleep. In this thesis study, basic routing algorithms and duty cycle control algorithms for WSNs in the literature are studied. One of the duty cycle control algorithms, Role Alternating, Coverage Preserving, and Coordinated Sleep algorithm (RACP) is examined and simulated using the ns2 simulation environment. A novel duty cycle control algorithm, Sink Initiated Path Formation (SIPF) is proposed and compared to RACP in terms of sleep sensor ratio and time averaged coverage.

The shortage of clean water has become a significant global problem, and capacitive deionization (CDI) is a technology that can be used to help relieve the problem. A Ćuk converter system that can recover energy from CDI cells is described. This converter transfers energy between two CDI cells when a cell is in its desorption period, allowing energy that would otherwise be lost to be recovered and improving overall system efficiency. In order to control the states of the MOSFET switches in the converter, a self boost charge pump is used. In this way, the microcontroller can control system duty cycle and optimize energy efficiency. A design method of reducing ripple losses caused by passive elements is presented. Several sensor circuits and their design methods that can minimize power losses are shown. The influence of initial voltage drop and voltage ramp time is also examined. This Ćuk converter system is tested using a dummy cell and a real CDI cell. The converter system shows promising performance experimentally.

My thesis will demonstrate that Rate Adaptive Runlength Limited encoding (RA-RLL) achieves high data rates with acceptable error rate over a wide range of signal distortion/attenuation, and background noise. RA-RLL has performance superior to other infrared modulation schemes in terms of bandwidth efficiency, duty cycle control, and synchronization frequency. Rate adaptive techniques allow for quick convergence of RA-RLL parameters to acceptable values. RA-RLL may be feasibly implemented on systems with non-ideal timing and digital synchronization.