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Micro-electro-mechanical systems (MEMS) switches for radio-frequency (RF) signals have certain advantages over solid-state switches, such as lower insertion loss, higher isolation, and lower static power dissipation. Mechanical dynamics can be a determining factor for the reliability of RF MEMS. The RF MEMS ohmic switch discussed in this paper consists of a plate suspended over an actuation pad by four double-cantilever springs. Closing the switch with a simple step actuation voltage typically causes the plate to rebound from its electrical contacts. The rebound interrupts the signal continuity and degrades the performance, reliability and durability of the switch. The switching dynamics are complicated by a nonlinear, electrostatic pull-in instability that causes high accelerations. Slow actuation and tailored voltage control signals can mitigate switch bouncing and effects of the pull-in instability; however, slow switching speed and overly-complex input signals can significantly penalize overall system-level performance. Examination of a balanced and optimized alternative switching solution is sought. A step toward one solution is to consider a pull-in-free switch design. In this paper, determine how simple RC-circuit drive signals and particular structural properties influence the mechanical dynamics of an RF MEMS switch designed without a pull-in instability. The approach is to develop a validated modeling capability and subsequently study switch behavior for variable drive signals and switch design parameters.In support of project development, specifiable design parameters and constraints will be provided. Moreover, transient data of RF MEMS switches from laser Doppler velocimetry will be provided for model validation tasks. Analysis showed that a RF MEMS switch could feasibly be designed with a single pulse waveform and no pull-in instability and achieve comparable results to previous waveform designs. The switch design could reliably close in a timely manner, with small contact velocity, usually with little to no rebound even when considering manufacturing variability.

The ability to accurately determine in-service deterioration of concrete remains an important facet of research. This research aims to develop more reliable laboratory testing methods to better replicate in-service conditions. Two concrete deterioration modes were studied; Salt Scaling (SS) and Alkali-Silica Reaction (ASR). For SS, wrapping slabs in plastic was adopted to provide the same curing environment as curing compound for comparison to standard moist curing. Slabs with and without supplementary cementing materials were tested. The two curing methods produced different scaling results; however, results of tested samples did not change in terms of meeting or failing the acceptance limit. For ASR, modified tests focused on changing sample size to attempt to reduce alkali leaching during testing, and hence produce results that mimic long term performance of actual structures. Cube moulds were designed, manufactured, and used rather than standard prisms. Increase of specimen dimension appear to reduce leaching at 38°C.