1,325 research outputs found

    Faculty Recital

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    CLVTOPS Liftoff and Separation Analysis Validation Using Ares I-X Flight Data

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    CLVTOPS is a multi-body time domain flight dynamics simulation tool developed by NASA s Marshall Space Flight Center (MSFC) for a space launch vehicle and is based on the TREETOPS simulation tool. CLVTOPS is currently used to simulate the flight dynamics and separation/jettison events of the Ares I launch vehicle including liftoff and staging separation. In order for CLVTOPS to become an accredited tool, validation against other independent simulations and real world data is needed. The launch of the Ares I-X vehicle (first Ares I test flight) on October 28, 2009 presented a great opportunity to provide validation evidence for CLVTOPS. In order to simulate the Ares I-X flight, specific models were implemented into CLVTOPS. These models include the flight day environment, reconstructed thrust, reconstructed mass properties, aerodynamics, and the Ares I-X guidance, navigation and control models. The resulting simulation output was compared to Ares I-X flight data. During the liftoff region of flight, trajectory states from the simulation and flight data were compared. The CLVTOPS results were used to make a semi-transparent animation of the vehicle that was overlaid directly on top of the flight video to provide a qualitative measure of the agreement between the simulation and the actual flight. During ascent, the trajectory states of the vehicle were compared with flight data. For the stage separation event, the trajectory states of the two stages were compared to available flight data. Since no quantitative rotational state data for the upper stage was available, the CLVTOPS results were used to make an animation of the two stages to show a side-by-side comparison with flight video. All of the comparisons between CLVTOPS and the flight data show good agreement. This paper documents comparisons between CLVTOPS and Ares I-X flight data which serve as validation evidence for the eventual accreditation of CLVTOPS

    Creek College

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    Creek College is a project bridging art and environmental conservation. We offer a range of art classes and experiences in exchange for activities that aid in the restoration of watersheds suffering from environmental degradation.https://pdxscholar.library.pdx.edu/creek_college/1000/thumbnail.jp

    Excessive Hospitalizations and Its Associated Economic Burden among People with Diabetes in the United States

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    AbstractObjectivesWe conducted this study to estimate the excessive hospital admission among people with diabetes and the associated economic burden in the USA.MethodsThe study was based on the 2005 Nationwide Inpatient Sample (NIS), a nationally representative probability sample conducted annually by the Agency of Health Research and Quality. Nearly 8 million records were sampled from over 1000 community hospitals in the 2005 NIS.ResultsExcluding childbirth-related admissions, the estimated US hospitalizations numbered approximately 30.8 million; individuals with diabetes accounted for over 6.4 million (20.9%) of these admissions. For every 1000 individuals without diabetes, with type 1 diabetes, and with type 2 diabetes, the numbers of hospitalizations were 89, 418, and 303, respectively. The rates of hospitalization increased greatly by the presence of diabetes for all age groups and sex. During 2005, the national bill of hospital charges and costs for individuals with diabetes exceeded US171billionandUS171 billion and US90 billion, respectively. If the prevalence of diabetes increases to 7.5% from 7.0%, the total number of hospitalizations made by individuals with diabetes will be 7.5 million in 2015.ConclusionsAlthough approximately 7% of the population had diabetes in the USA, nearly 20.9% of hospitalizations were made by individuals with this condition. Due to the excessive hospitalizations incurred by patients with diabetes, a small increase in the number of people with diabetes will amplify the number of hospitalizations. Health-care communities should anticipate this possible increased demand of hospitalizations and the associated economic burden

    Tensile Properties of Inkjet 3D Printed Parts: Critical Process Parameters and Their Efficient Analysis

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    To design and optimize for capabilities of additive manufacturing processes it is also necessary to understand and model their variations in geometric and mechanical properties. In this paper, such variations of inkjet 3D printed parts are systematically investigated by analyzing parameters of the whole process, i.e. storage of the material, printing, testing, and storage of finished parts. The goal is to both understand the process and determine the parameters that lead to the best mechanical properties and the most accurate geometric properties. Using models based on this understanding, we can design and optimize parts, and fabricate and test them successfully, thus closing the loop. Since AM materials change rapidly and this process will have to be repeated, it is shown how to create a cost and time efficient experimental design with the one-factor-at-a-time and design of experiments methods, yielding high statistical accuracies for both main and interaction effects. The results show that the number of intersections between layers and nozzles along the load-direction has the strongest impact on the mechanical properties followed by the UV exposure time, which is investigated by part spacing, the position on the printing table and the expiry date of the material. Minor effects are found for the storage time and the surface roughness is not affected by any factor. Nozzle blockage, which leads to a smaller flow-rate of printing material, significantly affected the width and waviness of the printed product. Furthermore, the machine’s warm-up time is found to be an important factor

    The Performance Puzzle: Understanding the Factors Influencing Alternative Dimensions and Views of Performance

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    There is a large literature on the determinants of organizational performance, and its multidimensional nature is well recognized. However, little research has examined how different organizational and environmental factors influence different stakeholders’ performance assessments of the same service. We address this gap by comparing the factors influencing performance evaluations by different constituencies of child care centers in Ohio. We operationalize performance using (1) regulatory violations documented during state licensing inspections, (2) satisfaction with the center’s quality reported by center directors, (3) satisfaction with the center’s quality reported by teachers, and (4) satisfaction with care quality reported by parents. Our findings suggest that different organizational and environmental factors are associated with the performance assessments of different constituencies. In addition, some of these constituency assessments appear to influence each other

    Do Relationships Matter? Assessing the Association Between Relationship Design and Contractor Performance

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    Contracting relationships vary in the extent to which they are complete and involve formal contract specification as well as the extent to which they are based on strong relationships and rely on cooperation and trust. Where a contracting arrangement falls on these two continuums constitutes what this paper refers to as relationship design and is likely to impact contractor performance. We use data from a survey of child-care centers and Head Start agencies in Ohio to examine the association between the design of contracting relationships and contractor performance. Contractor performance is assessed in two ways: an objective measure of violations identified by government inspectors and a perceptual self-rated measure of performance reported by the contracted service providers. Measures of relationship design are constructed using multiple survey items and are included in multivariate regression analyses while controlling for a variety of organizational characteristics. Findings suggest that contracts involving stronger relationships are positively associated with child-care center performance, and more complete contracts are negatively associated with performance when performance is measured using contractor self-reports
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