2,978 research outputs found

    The Three Loop Isotopy and Framed Isotopy Invariants of Virtual Knots

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    This paper introduces two virtual knot theory ``analogues'' of a well-known family of invariants for knots in thickened surfaces: the Grishanov-Vassiliev finite-type invariants of order two. The first, called the three loop isotopy invariant, is an invariant of virtual knots while the second, called the three loop framed isotopy invariant, is a regular isotopy invariant of framed virtual knots. The properties of these invariants are investigated at length. In addition, we make precise the informal notion of ``analogue''. Using this formal definition, it is proved that a generalized three loop invariant is a virtual knot theory analogue of a generalization of the Grishanov-Vassiliev invariants of order two

    Using IMPRINT to Guide Experimental Design with Simulated Task Environments

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    Experimental Designs involving Simulated Task Environments aim to explore interesting conditions with human subjects. By using activity simulators such as IMPRINT, it may be possible to identify these conditions of interest without the need for human subjects. This thesis presents research that aims to demonstrate that IMPRINT can be used to predict human performance in a task environment representing the task performed by Network Analysts of the 33rd Network Warfare Squadron. The research is done by examining the task performed by the Network Analysts, and then designing a Simulated Task Environment modeled on this task. A model of the task performed is also built in IMPRINT. With a first iteration, it was found that the IMPRINT model was not able to predict performance in a majority of cases, however the methodology illustrates a starting point that others may use

    Railroading in Iowa Before 1900

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    Railroading in Iowa Before 1900

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    Annual Aboveground Biomass Growth in Temperate Forests of Eastern North America

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    The below dissertation is organized into three individual standalone manuscripts supporting the overarching theme of reconstructing annual aboveground biomass growth in temperate forests of eastern North America using dendrochronological applications. Each manuscript is organized with the intent of submission to a peer-reviewed journal. The first manuscript validated the technique I use throughout my dissertation by comparing tree-ring derived estimates of annual aboveground productivity with estimates from co-located or nearby permanent remeasurement plots at Howland, Maine, Harvard Forest, Massachusetts, and Fernow, West Virginia. The second manuscript investigated the size-related distribution of biomass growth at 16 eastern U.S. forest sites and compared results with United States Forest Service inventory plot data. The goal of this manuscript was to determine where, structurally, biomass was allocated in forests and whether these quantities changed over time and between forests. The third manuscript was inspired by the results of my second chapter. Here, I investigated whether the degree of asymmetry, or the slope of the linear regression between tree diameter and growth, is a useful indicator of total forest productivity. Previous studies linking asymmetry and productivity have been inconclusive, and this chapter evaluates consistency or lack of consistency across the same 16-site eastern U.S. forest network

    Results of phase change paint tests of 0.040 scale 50% forebody models (82-0) of the space shuttle orbiter in the AEDC VKF B hypersonic wind tunnel (OH75)

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    Post-test information and data are presented from phase change paint, aerodynamic heating wind tunnel tests of a Rockwell International space shuttle orbiter forebody model. These tests were conducted in the Arnold Engineering and Development Center von Karman Facility Tunnel B Hypersonic Wind Tunnel. The purpose of these tests was to determine the effect of simulated orbiter protuberances and penetrations (including RCS nozzles) on aerodynamic heating rates during simulated entry conditions

    Heat transfer phase change paint tests of 0.0175-scale models (nos. 21-0 and 46-0) of the Rockwell International space shuttle orbiter in the AEDC tunnel B hypersonic wind tunnel (test OH25A)

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    Tests were conducted in a hypersonic wind tunnel using various truncated space shuttle orbiter configurations in an attempt to establish the optimum model size for other tests examining body shock-wing leading edge interference effects. The tests were conducted at Mach number 8 using the phase change paint technique. A test description, tabulated data, and tracings of isotherms made from photographs taken during the test are presented

    Results of phase change paint heat transfer test utilizing 0.040-scale 50% forebody models (no. 82-0) of the Rockwell International Space Shuttle Orbiter in AEDC VKF hypersonic tunnel B (test OH54B)

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    Aerodynamic heating phase change paint tests for the space shuttle orbiter are reported. The model was a 0.040 scale representation of the forward 50% of the orbiter. Surface roughness effects on boundary layer transition were investigated. The roughness was simulated by steel balls 0.020 and 0.025 inch in diameter and a 0.25 in. diameter hole simulating the forward ET attach socket. A nominal Mach number of was tested with unit Reynolds number varying from 0.75 x 1 million ft through 3.5x 1 million ft. Angle of attack was varied from 20 degrees to 40 degrees

    Results of heat transfer tests on a 0.0175-scale space shuttle orbiter model (56-0) in the AEDC VKF 'B' Hypersonic Wind Tunnel (OH74)

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    The results are presented of aerodynamic heating tests conducted on a 0.0175-scale model of the space shuttle orbiter. The tests were conducted at a nominal Mach number of 8 and model angles of attack varying between 20 deg and 45 deg

    Results of phase change paint thermal mapping test OH46 using the 0.006-scale model 90-0 in the NASA LaRC variable density tunnel

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    Results of a test conducted in the NASA LaRC Mach 8 variable density tunnel to obtain thermal contours on a 0.006 scale model of the configuration 140B Space Shuttle Orbiter are presented using the phase change paint technique. The model was tested at 25 deg, 30 deg, and 35 deg angle of attack at unit Reynolds numbers ranging from 1.0 through 8.0 million per foot. The model was tested with and without a ventral fin mounted on its bottom centerline. Elevon deflections of 0 deg and 10 deg and bodyflap deflections of 0 and 13.75 deg were investigated
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