Scholarship & Research
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Item Characterization of the effects of hygrothermal-aging on mechanical performance and damage progression of fiberglass epoxy composite(Montana State University - Bozeman, College of Engineering, 2018) Voth, Michael Mark; Chairperson, Graduate Committee: David A. MillerMarine Hydro-Kinetic Devices (MHK) are a developing renewable energy technology that allows energy to be harvested from the natural flow of water due to tides, currents, and waves. Fiber Reinforced Polymers (FRP), which have been extensively used in wind energy applications, offer favorable mechanical properties as well as low costs and manufacturability making them a viable option for construction of MHK devices. However, exposure to a harsh marine environment results in moisture uptake into the FRP, often degrading mechanical properties. A study of a fiberglass-epoxy FRP was conducted to characterize the effects of moisture on mechanical properties and damage behavior of the material as well as classify the degradation mechanisms responsible for changes in performance. Environmental exposure was simulated through hygrothermal aging, exposing the FRP samples to distilled water and elevated temperature (50 °C) to accelerate the environmental effects. Quasi-static tension tests of both unidirectional and cross-ply laminates were conducted to classify the effects of moisture on mechanical properties of constituent and multi-angle laminates. Cross-ply laminates experienced 54% reduction in strengths due to moisture absorption, while unidirectional laminates strengths were reduced by 40%. Constitutive stress-strain response in conjunction with Acoustic Emission (AE) monitoring describe changes in damage behavior due to hygrothermal aging. This work also characterizes hygrothermal effects on pure/neat epoxy material to aid in interpreting hygrothermal degradation mechanisms in the composite as well as guided ultrasonic evaluation of composite specimens to characterize effects of moisture on AE signals.Item Definition of alarm fatigue and its influence on staff performance(Montana State University - Bozeman, College of Engineering, 2014) Deb, Shuchisnigdha; Chairperson, Graduate Committee: David ClaudioAn alarm is a warning of an approaching situation which requires a response. This study considered the influences of alarms in the clinical health environment. The Emergency Care Research Institute considered alarm hazard as the number one health technology hazard for the years 2012 through 2014. The Joint Commission set a standard for all hospitals in the US to assess alarm fatigue in their monitoring process and to develop a systematic, coordinated approach to clinical alarm system management. In order to comply with this requirement, a working definition of alarm fatigue is necessary. To the very best of our knowledge, there have been no studies proposing a quantitative definition of alarm fatigue, a way to measure it, or exploring the influence of alarm fatigue on performance deterioration. This observational study undertook the objective of defining alarm fatigue and its role on performance deterioration in a quantitative way. A survey using a questionnaire proposed by the American College of Clinical Engineering Healthcare Technology Foundation was conducted before the observations to assess the attitude of nurses toward the existing alarm monitoring system at the hospital where the research took place. An extensive literature review and Hierarchical Task Analyses were conducted in order to reveal all the possible influencing factors behind alarm fatigue. From these, alarm fatigue was defined and measured in terms of mental workload and three types of affect: boredom, apathy, and distrust. A conceptual model was developed considering the significance of working conditions and staff individuality on alarm fatigue and, consequently, alarm fatigue on staff performance. Staff performance was measured in terms of response (yes/no), response time and number of ignored alarms. Several analytical approaches were performed to find association between alarm fatigue and staff performance. The results show that, in general, performance deterioration is actually influenced by a combination of alarm fatigue with working conditions and staff individuality. In the case of nurses and response time, alarm fatigue plays no role, only working conditions and staff individuality. These findings suggest that the role of alarm fatigue as a health hazard in the clinical environment should be reevaluated.