3,525 research outputs found

    Enabling Data-Driven Transportation Safety Improvements in Rural Alaska

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    Safety improvements require funding. A clear need must be demonstrated to secure funding. For transportation safety, data, especially data about past crashes, is the usual method of demonstrating need. However, in rural locations, such data is often not available, or is not in a form amenable to use in funding applications. This research aids rural entities, often federally recognized tribes and small villages acquire data needed for funding applications. Two aspects of work product are the development of a traffic counting application for an iPad or similar device, and a review of the data requirements of the major transportation funding agencies. The traffic-counting app, UAF Traffic, demonstrated its ability to count traffic and turning movements for cars and trucks, as well as ATVs, snow machines, pedestrians, bicycles, and dog sleds. The review of the major agencies demonstrated that all the likely funders would accept qualitative data and Road Safety Audits. However, quantitative data, if it was available, was helpful

    Excimer laser machining of bisphenol A polycarbonate under closed immersion filtered water with varying flow velocities and the effects on the etch rate

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    Until now, progress in laser ablation micromachining has been significantly limited with respect to feature miniaturization and output yield by ablation-generated debris. Gas-jetting techniques have proven to be inadequate and vacuum environments are unwieldy in an industrial setting. To this end, a controlled geometry for both the optical interfaces of a flowing liquid film can be provided by a closed flowing thick film filtered water immersion technique. This ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on etch rate, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities that are controllable by modifying liquid flowrate. A mean increase in etch rate of 8.5 per cent when using a turbulent flow velocity regime immersed ablation over ablation in ambient air was recorded. However, use of laminar flow velocities resulted in a mean loss of 26.6 per cent in etch rate compared to ablation in ambient air. Plotting the recorded etch rate achieved with respect to flow velocity gives support for previously proposed flow–plume interactions: the primary cause of a 37 per cent variance in etch rate over a 72 per cent change in laminar flow velocity was a shift in the ratio between the refresh rate of liquid volume over the feature and laser repetition rate. The small variance of etch rate achieved by modification of turbulent regime flow velocity indicates that laser etching provided the dominating contribution to the total etch rate measured. This work demonstrates that this technique developed for ablation debris control does not reduce the efficiency of laser etching with respect to that achieved with established gas media laser ablation machining. Therefore, this process shows great promise for industrial implementation development

    Modeling hydrodynamic self-propulsion with Stokesian Dynamics. Or teaching Stokesian Dynamics to swim

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    We develop a general framework for modeling the hydrodynamic self-propulsion (i.e., swimming) of bodies (e.g., microorganisms) at low Reynolds number via Stokesian Dynamics simulations. The swimming body is composed of many spherical particles constrained to form an assembly that deforms via relative motion of its constituent particles. The resistance tensor describing the hydrodynamic interactions among the individual particles maps directly onto that for the assembly. Specifying a particular swimming gait and imposing the condition that the swimming body is force- and torque-free determine the propulsive speed. The body’s translational and rotational velocities computed via this methodology are identical in form to that from the classical theory for the swimming of arbitrary bodies at low Reynolds number. We illustrate the generality of the method through simulations of a wide array of swimming bodies: pushers and pullers, spinners, the Taylor=Purcell swimming toroid, Taylor’s helical swimmer, Purcell’s three-link swimmer, and an amoeba-like body undergoing large-scale deformation. An open source code is a part of the supplementary material and can be used to simulate the swimming of a body with arbitrary geometry and swimming gait

    Security Theorems via Model Theory

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    A model-theoretic approach can establish security theorems for cryptographic protocols. Formulas expressing authentication and non-disclosure properties of protocols have a special form. They are quantified implications for all xs . (phi implies for some ys . psi). Models (interpretations) for these formulas are *skeletons*, partially ordered structures consisting of a number of local protocol behaviors. Realized skeletons contain enough local sessions to explain all the behavior, when combined with some possible adversary behaviors. We show two results. (1) If phi is the antecedent of a security goal, then there is a skeleton A_phi such that, for every skeleton B, phi is satisfied in B iff there is a homomorphism from A_phi to B. (2) A protocol enforces for all xs . (phi implies for some ys . psi) iff every realized homomorphic image of A_phi satisfies psi. Hence, to verify a security goal, one can use the Cryptographic Protocol Shapes Analyzer CPSA (TACAS, 2007) to identify minimal realized skeletons, or "shapes," that are homomorphic images of A_phi. If psi holds in each of these shapes, then the goal holds

    Dimensions and Global Twist of Single-Layer DNA Origami Measured by Small-Angle X-ray Scattering

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    The rational design of complementary DNA sequences can be used to create nanostructures that self-assemble with nanometer precision. DNA nanostructures have been imaged by atomic force microscopy and electron microscopy. Small-angle X-ray scattering (SAXS) provides complementary structural information on the ensemble-averaged state of DNA nanostructures in solution. Here we demonstrate that SAXS can distinguish between different single-layer DNA origami tiles that look identical when immobilized on a mica surface and imaged with atomic force microscopy. We use SAXS to quantify the magnitude of global twist of DNA origami tiles with different crossover periodicities: these measurements highlight the extreme structural sensitivity of single-layer origami to the location of strand crossovers. We also use SAXS to quantify the distance between pairs of gold nanoparticles tethered to specific locations on a DNA origami tile and use this method to measure the overall dimensions and geometry of the DNA nanostructure in solution. Finally, we use indirect Fourier methods, which have long been used for the interpretation of SAXS data from biomolecules, to measure the distance between DNA helix pairs in a DNA origami nanotube. Together, these results provide important methodological advances in the use of SAXS to analyze DNA nanostructures in solution and insights into the structures of single-layer DNA origami

    The Grizzly, October 4, 1985

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    Patterns for the Future Begin the Campaign • Rendell Enforces the Death Penalty • Ursinus: A Good Buy • Letters: Alpha Sigma Nu\u27s Pride Comes Through; WVOU Prints a Schedule • Editorial: How About a Little Help From Some Friends? • Homecoming 1957: Not so Different From Now • Alumni Search for Success: Holly Hayer • There was a Resume Workshop Seniors • Voices to be Performed at Ritter • Field Hockey Team: Leaving Teams in the Dust • Grizzlies Overcome a Ten Year Nemesis! • Cross Country Teams Survive Gloria • Homecoming Events Announced • Campus Security Noteshttps://digitalcommons.ursinus.edu/grizzlynews/1146/thumbnail.jp
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