Physical Dissipation and the Method of Controlled Lagrangians

We describe the effect of physical dissipation on stability of equilibria which have been stabilized, in the absence of damping, using the method of controlled Lagrangians. This method applies to a class of underactuated mechanical systems including “balance” systems such as the pendulum on a cart. Since the method involves modifying a system’s kinetic energy metric through feedback, the effect of dissipation is obscured. In particular, it is not generally true that damping makes a feedback-stabilized equilibrium asymptotically stable. Damping in the unactuated directions does tend to enhance stability, however damping in the controlled directions must be “reversed” through feedback. In this paper, we suggest a choice of feedback dissipation to locally exponentially stabilize a class of controlled Lagrangian systems

Dissipation and Controlled Euler-Poincaré Systems

The method of controlled Lagrangians is a technique for stabilizing underactuated mechanical systems which involves modifying a system’s energy and dynamic structure through feedback. These modifications can obscure the effect of physical dissipation in the closed-loop. For example, generic damping can destabilize an equilibrium which is closed-loop stable for a conservative system model. In this paper, we consider the effect of damping on Euler-Poincaré (special reduced Lagrangian) systems which have been stabilized about an equilibrium using the method of controlled Lagrangians. We describe a choice of feed-back dissipation which asymptotically stabilizes a sub-class of controlled Euler-Poincaré systems subject to physical damping. As an example, we consider intermediate axis rotation of a damped rigid body with a single internal rotor

Time dependence in perpendicular media with a soft underlayer

In this paper we describe measurements of magnetic viscosity or time dependence in magnetic thin films suitable for use as perpendicular recording media. Generally, such effects cannot be measured using conventional magnetometry techniques due to the presence of a thin (0.1 mum) soft underlayer (SUL) in the media necessary to focus the head field. To achieve our results we have developed an ultrastable MOKE magnetometer, the construction of which is described. This has enabled us to measure nominally identical films with and without the presence of the SUL. We find that the presence of the SUL narrows the energy barrier distribution in the perpendicular film increasing the nucleation field (H-n), reducing the coercivity (H-c) and results in an increase in the squareness of the loop. This in turn results in an increase in the magnitude of the viscosity in the region of the H-c but that the range of fields over which the viscosity occurs is reduced

An examination of the relationship between teacher characteristics, socioeconomic factors and statewide test performance of students with individual education plans

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (March 1. 2007)Vita.Thesis (Ed.D.) University of Missouri-Columbia 2006.Testing results from 2004 indicated that two of Missouri's 96 middle schools with a reportable number of students with IEPs met the math proficiency goal for adequate yearly progress. The purpose of this study was to examine the relationship between the performance of students with and without IEPs on the MAP mathematics examinations, socioeconomic factors, and teacher characteristics. Findings indicated that teachers' average years of experience and mean household income failed to demonstrate a significant correlation to student achievement. Correlations demonstrated a significantly negative correlation between achievement for students with IEPs and per pupil expenditures for students with and without IEPs. There was a significantly negative correlation between the percent of student receiving free or reduced-price lunch and achievement for students both with and without IEPs. Findings indicated a significantly positive relationship between the percent of teachers with advanced degrees and achievement for students both with and without IEPs.Includes bibliographical reference

Effects of Climate Change on the Probability of Urban Tree Failures from Wind Gusts

Trees grown in urban environments provide environmental, economic and psychological benefits to their surrounding communities. However, urban trees also pose significant risks since damaged trees can cause serious harm to people, housing, and infrastructure by falling on sidewalks, roads, houses or power lines. To better understand the risk posed to trees by wind, models have been developed that estimates the required wind speed needed to damage a tree or group of trees, and the likelihood that such a wind speed is met or exceeded annually. The importance of such models is rising each year as the associated risk grows as well, due to an increase in urbanization, frequency and intensity of wind storms increasing with global warming and growing evidence that elevated atmospheric CO2 concentrations, driven by climate change, cause trees to grow faster and larger, likely increasing their fragility to wind. In this thesis, a model was created to consider the impacts of climate change on trees’ risk using analysis of wind trends globally and locally in the Toronto region, and by considering the impact of the steadily increasing concentration of CO2 in the atmosphere. The CO2 increase impact on trees has been inferred based on meta-analysis data from 219 papers studying the impact of elevated CO2 growing conditions on 293 tree samples of varying age and species. The model functions by estimating the return period of wind storms that can damage an individual tree via trunk rupture or overturning. Meta-analysis data indicates that the density of leaves in tree crowns is likely to change with elevated CO2 concentrations. The aerodynamic impact of this change is currently not well understood. In an effort to improve the model further, experimental wind testing was conducted at the Wind Engineering, Energy and Environment Dome (WindEEE) at Western University, where a 9-year-old, 1.9 m tall red maple (Acer rubrum) was subjected to wind speeds from 6-12 m/s. The testing was repeated 5 times, between each repetition the crown was thinned by 25% to simulate varying crown leaf densities of the tree, and to analyze the relationship between the density of leaves in the crown and the drag coefficient

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Psoas Abscess in Inflammatory Bowel Disease

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72133/1/j.1572-0241.1985.tb02023.x.pd

Fresh fruit, vegetables, and mushrooms as transmission vehicles for <i>Echinococcus multilocularis</i> in Europe:inferences and concerns from sample analysis data from Poland

Fresh fruit, vegetables, mushrooms, and other fresh produce are recognised as important vehicles of infection for several foodborne parasites, particularly those with a faecal-oral transmission route and robust environmental transmission stages. Nevertheless, analysis of such foods for parasite transmission stages, even during outbreaks, tends to show only low contamination. Echinococcus multilocularis is considered one of the most important foodborne parasites, but there are few studies in which fresh produce or like foods collected in their natural habitat is analysed for contamination with E. multilocularis eggs. In this article, we question a recent study from Poland reporting over 23 % of fresh berries, vegetables, and mushroom being highly contaminated with E. multilocularis eggs. In particular, it appears unlikely that 20 % of raspberries, which are elevated from ground level, should be exposed to faecal contamination. Additionally, the similar egg contamination of vegetation in forest and plantation environments is surprising considering the preference of the parasite’s most competent intermediate hosts for the latter environment. Furthermore, a lack of specific temporal information is concerning due to the varying infection pressure (and therefore environmental contamination) occurring in definitive hosts over the course of the year. Several important aspects of the study seem to us to have been neglected, and we are concerned that the published data might, if not questioned, lead to incorrect interpretation, and unnecessary losses in the agricultural sector

The effect of grading the atomic number at resistive guide element interface on magnetic collimation

Using 3 dimensional numerical simulations, this paper shows that grading the atomic number and thus the resistivity at the interface between an embedded high atomic number guide element and a lower atomic number substrate enhances the growth of a resistive magnetic field. This can lead to a large integrated magnetic flux density, which is fundamental to confining higher energy fast electrons. This results in significant improvements in both magnetic collimation and fast-electron-temperature uniformity across the guiding. The graded interface target provides a method for resistive guiding that is tolerant to laser pointing