Wavelet Applications for Flight Flutter Testing

Wavelets present a method for signal processing that may be useful for analyzing responses of dynamical systems. This paper describes several wavelet-based tools that have been developed to improve the efficiency of flight flutter testing. One of the tools uses correlation filtering to identify properties of several modes throughout a flight test for envelope expansion. Another tool uses features in time-frequency representations of responses to characterize nonlinearities in the system dynamics. A third tool uses modulus and phase information from a wavelet transform to estimate modal parameters that can be used to update a linear model and reduce conservatism in robust stability margins

Correlation Filtering of Modal Dynamics using the Laplace Wavelet

Wavelet analysis allows processing of transient response data commonly encountered in vibration health monitoring tasks such as aircraft flutter testing. The Laplace wavelet is formulated as an impulse response of a single mode system to be similar to data features commonly encountered in these health monitoring tasks. A correlation filtering approach is introduced using the Laplace wavelet to decompose a signal into impulse responses of single mode subsystems. Applications using responses from flutter testing of aeroelastic systems demonstrate modal parameters and stability estimates can be estimated by correlation filtering free decay data with a set of Laplace wavelets

Procedural justice and public involvement in natural resource decision making

This thesis examines the application of findings from the social psychological field of procedural justice to public involvement in natural resource decision making. The methodological approach involves examining the literature of each of the fields and developing a synthesis applicable to public involvement. The review of public involvement literature reveals a variety of reasons for involving the public in decision making, but little attention to the effects of procedures on participants. However, a comparison and synthesis of the principle findings of the two disciplines indicates important procedural elements for public participation programs, including (1) procedural justice supports process related goals for public involvement; (2) public participation procedures should be inclusive; (3) public participation procedures should provide for interactive approaches; (4) procedural preferences are situationally specific; (5) decision makers must provide clear justification for their decisions; and (6) decision makers must maintain the appearance of impartiality. These findings lead to a rejection of the positivist ideology that has dominated public involvement literature and the development of a new theory of public involvement that recognizes the importance of both outcomes and procedures. Finally, the thesis discusses issues regarding the application of this theory to public involvement programs, including issues relating to interest groups, non-participants, historical mistrust, the meanings of satisfaction and dissatisfaction, and measures of fairness

A landscape-scale analysis of vegetation recovery at Mount St. Helens

I used satellite remote sensing to examine the key factors controlling the natural revegetation of Mount St. Helens since its eruption in 1980. The study required three stages: determining the amount of vegetation present; characterizing vegetation change; and analyzing the influence of factors affecting vegetation change. To determine the amount of vegetation present, I compared various vegetation indices and multiple regression using raw spectral bands. Reference data were from interpretation of aerial photographs. A model using multiple regression on raw spectral bands provided the best results and explained 75% of the variability in vegetation cover. To characterize vegetation change during the study period, eight Landsat Thematic Mapper satellite scenes from 1984 to 1995 were geometrically and radiometrically corrected to each other. They were then transformed to estimate green vegetation cover for each scene using the model developed in the first stage. I fit growth curves to each pixel using a combination of a non-hierarchical clustering algorithm and polynomial growth curves. To represent response variables, I extracted four parameters from the growth curves: number of years to reach 10% vegetation cover; maximum rate of increase in vegetation cover; time-integrated vegetation cover; and maximum estimated cover reached. Regression tree analysis explained 50%, 31%, 57%, and 51% of the variation in these response variables, respectively. Remaining variability was a function of other variables, stochastic factors and image processing. The most important determinant of revegetation was the presence or absence of biotic legacies, as evidenced by volcanic disturbance impacts. This stratified the study area into primary and secondary succession areas. Under secondary succession conditions, gradients of biotic legacies were evident. Factors affecting the establishment and growth of survivors were important, including original tephra thickness and erosional processes, evidenced by the importance of slope gradient. In primary succession areas, erosional processes were important in mitigating site conditions for colonizing seeds. Distance from seed sources was important primarily near forested edges. Additional topographic variables, including elevation, aspect, and slope curvature, had limited importance. I was not able to detect significant effects of streams, roads, or pre-eruption vegetation conditions

Improved Flight Test Procedures for Flutter Clearance

Flight flutter testing is an integral part of flight envelope clearance. This paper discusses advancements in several areas that are being investigated to improve efficiency and safety of flight test programs. Results are presented from recent flight testing of the F/A-18 Systems Research Aircraft. A wingtip excitation system was used to generate aeroelastic response data. This system worked well for many flight conditions but still displayed some anomalies. Wavelet processing is used to analyze the flight data. Filtered transfer functions are generated that greatly improve system identification. A flutter margin is formulated that accounts for errors between a model and flight data. Worst-case flutter margins are computed to demonstrate the flutter boundary may lie closer to the flight envelope than previously estimated. This paper concludes with developments for a distributed flight analysis environment and on-line health monitoring

Spatiotemporal Variability in Biomass and Forage Quality Across a Temperate Landscape with Heterogeneous Phenology Patterns (Poster)

Although spatial and temporal heterogeneity in grassland biomass and forage quality is well-recognized to play an important role in migratory ungulate population dynamics, attempts to directly quantify biomass and forage quality across temperate landscapes throughout the growing season are limited. It is generally recognized that biomass and forage quality are directly related to phenology, but little is known about how seasonal biomass and forage quality differs across land use and biophysical gradients with varying phenology patterns. This study uses field estimates of biomass, chlorophyll concentration, crude protein, and in vitro dry matter digestibility collected from 20, 250m2 grassland plots throughout the summers of 2013 and 2014 to quantify how biomass and forage quality differ across land uses and biophysical gradients in the migratory elk (Cervus elaphus) range in the Upper Yellowstone River Basin. Key findings were that irrigated agriculture had overall greater and longer available biomass and forage quality throughout the growing season compared to private and public grasslands with natural phenology patterns. And that areas that begin growth later in the season had overall greater biomass and forage quality than areas with mid and early phenology characteristics, but availability was shorter. These results suggest that seasonal patterns of biomass and forage quality differ with phenological characteristics across temperate landscapes. This information should be incorporated in our understanding of spatiotemporal patterns of vegetation important for studying migratory ungulate ecology and predicting the effects of climate change and human land use on vegetation dynamics in temperate landscapes

Spatial Variation in Distribution and Growth Patterns of Old Growth Strip-Bark Pines

Postindustrial rises in CO2 have the potential to confound the interpretation of climatically sensitive tree-ring chronologies. Increased growth rates observed during the 20th century in strip-bark trees have been attributed to CO2 fertilization. Absent in the debate of CO2 effects on tree growth are spatially explicit analyses that examine the proximate mechanisms that lead to changes in rates of tree growth. Twenty-seven pairs of strip-bark and companion entire-bark trees were analyzed in a spatially explicit framework for abiotic environmental correlates. The strip-bark tree locations were not random but correlated to an abiotic proxy for soil moisture. The strip-bark trees showed a characteristic increase in growth rates after about 1875. Furthermore, the difference in growth rates between the strip-bark trees and entire-bark companions increased with increasing soil moisture. A possible mechanism for these findings is that CO2 is affecting water-use efficiency, which in turn affects tree-ring growth. These results point to the importance of accounting for microsite variability in analyzing the potential role of CO2 in governing growth responses

The Temporal Dynamics of Implicit Processing of Non-Letter, Letter, and Word-Forms in the Human Visual Cortex

The decoding of visually presented line segments into letters, and letters into words, is critical to fluent reading abilities. Here we investigate the temporal dynamics of visual orthographic processes, focusing specifically on right hemisphere contributions and interactions between the hemispheres involved in the implicit processing of visually presented words, consonants, false fonts, and symbolic strings. High-density EEG was recorded while participants detected infrequent, simple, perceptual targets (dot strings) embedded amongst a of character strings. Beginning at 130 ms, orthographic and non-orthographic stimuli were distinguished by a sequence of ERP effects over occipital recording sites. These early latency occipital effects were dominated by enhanced right-sided negative-polarity activation for non-orthographic stimuli that peaked at around 180 ms. This right-sided effect was followed by bilateral positive occipital activity for false-fonts, but not symbol strings. Moreover the size of components of this later positive occipital wave was inversely correlated with the right-sided ROcc180 wave, suggesting that subjects who had larger early right-sided activation for non-orthographic stimuli had less need for more extended bilateral (e.g., interhemispheric) processing of those stimuli shortly later. Additional early (130–150 ms) negative-polarity activity over left occipital cortex and longer-latency centrally distributed responses (>300 ms) were present, likely reflecting implicit activation of the previously reported ‘visual-word-form’ area and N400-related responses, respectively. Collectively, these results provide a close look at some relatively unexplored portions of the temporal flow of information processing in the brain related to the implicit processing of potentially linguistic information and provide valuable information about the interactions between hemispheres supporting visual orthographic processing