9,811 research outputs found

    The Investigation of Cold-mix Asphalt Creep Stiffness Testing Using Multiple Test Apparatuses and Gradations

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    Many current methods of designing and testing Cold In-Place Recycled (CIR) asphalt are undesirable because they require large amounts of material and significant preparation. In an effort to lessen the cost and time of materials testing, this research utilizes several different methods of small scale testing of creep stiffness. These methods include using a Discovery Hybrid Rheometer (DHR) and a three point bending test to find the creep stiffness of emulsion based CIR. The new testing methods utilized samples on the scale of up to a hundredth the size of what the traditional methods of testing require. The two smaller scale tests were compared to the traditional Indirect Tension Test (IDT) testing. In order to fully evaluate the two reduced sample size test methods, this research observed the effect of gradation, temperature, emulsifier type, and Recycled Asphalt Pavement (RAP) content on creep stiffness. If successful, the use of these new test methods could significantly decrease the damage done to roads, and reduce the cost of material management incurred through the quality control testing methods for pavement. Results showed very good correlation between DHR and IDT testing with a proportional difference between the samples. The standard deviations between the DHR and IDT testing were 18.6% and 19.2% of the mean values respectively, indicating similar accuracies of tests. The tests were also able to distinguish between types of material. The proportional difference between the IDT and DHR is expected and is due to the difference of sample and loading configuration. This research begins the validation of using smaller scale DHR tests for CIR stiffness testing

    Are knowledge ascriptions sensitive to social context?

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    Plausibly, how much is at stake in some salient practical task can affect how generously people ascribe knowledge of task-relevant facts. There is a metaphysical puzzle about this phenomenon, and an empirical puzzle. Metaphysically: there are competing theories about when and how practical stakes affect whether it is correct to ascribe knowledge. Which of these theories is the right one? Empirically: experimental philosophy has struggled to find a stakes-effect on people’s knowledge ascriptions. Is the alleged phenomenon just a philosopher’s fantasy? I propose a new psychological account of when and why people’s knowledge ascriptions are sensitive to stakes. My hypothesis is motivated by empirical research on how people’s judgements are sensitive to their social context. Specifically, people’s evaluations are sensitive to their ‘psychological distance’ from the scenarios they are considering. When using ‘fixed-evidence probes’, experimental philosophy has found that what’s at stake for a fictional character in a made-up scenario has little or no effect on how participants ascribe knowledge to them. My hypothesis predicts this finding: the scenarios are too ‘psychologically distant’ to participants. Our empirical puzzle is resolved: the stakes-effect often present in the wild won’t be present in vignette studies. (This illustrates a widespread problem with X-phi vignette studies: if people might judge differently in other social contexts, we can’t generalize from the results of these experiments. That is, vignette studies are of doubtful ‘external validity’.) The hypothesis also resolves our metaphysical puzzle. It predicts that people do not ascribe knowledge in a way deemed correct by any of the standard philosophical views, namely classical invariantism, interest-relative invariantism, and contextualism. Our knowledge ascriptions shift around in the way that’s most useful for social beings like us, and this pattern in our judgements can only be endorsed by a genuinely relativist metaphysics for knowledge

    Rapid rotation of a Bose-Einstein condensate in a harmonic plus quartic trap

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    A two-dimensional rapidly rotating Bose-Einstein condensate in an anharmonic trap with quadratic and quartic radial confinement is studied analytically with the Thomas-Fermi approximation and numerically with the full time-independent Gross-Pitaevskii equation. The quartic trap potential allows the rotation speed Ω\Omega to exceed the radial harmonic frequency ω\omega_\perp. In the regime Ωω\Omega \gtrsim \omega_\perp, the condensate contains a dense vortex array (approximated as solid-body rotation for the analytical studies). At a critical angular velocity Ωh\Omega_h, a central hole appears in the condensate. Numerical studies confirm the predicted value of Ωh\Omega_h, even for interaction parameters that are not in the Thomas-Fermi limit. The behavior is also investigated at larger angular velocities, where the system is expected to undergo a transition to a giant vortex (with pure irrotational flow).Comment: 14 pages, 5 figure

    Full Depth Reclamation: Compaction and Moisture Content

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    Many times a road will fail and will be in need of both a structural increase and a repair. Full Depth Reclamation (FDR) is a road rehabilitation technique able to offer both. This method also has a lower total cost and significantly lower material usage than traditional overlaying repair methods. FDR is a road repair method which mills up the current road down into the subgrade, and then stabilizes and compacts the milled material. This is also useful for correcting deeper problems in the road structure which are not addressed by traditional methods. In this study, three different suggestions of mix designs for this repair method were observed, and the strengths and weaknesses of each were compared. A consistent problem with the more thorough mix designs was that there is a large amount of equipment required from different fields of engineering: many of the tests required equipment from both a soils and a pavements laboratory. In an effort to streamline testing equipment, the results of a modified Proctor test were compared to the results of densities of samples tested in a gyratory compactor at varying water contents. The Proctor and gyratory compactor both gave similar trends between water content and dry density. The gyratory compactor testing was also much quicker, and the data had a tighter fit line. This is an important step in simplifying FDR mix design in order to make it more widely available. Samples with binder contents of 2%, 3%, and 4% and water contents varying from 2%-6% were created in a slotted gyratory compactor. These samples were tested for density and for compressive strength after Ndesign of 75 Gyrations. It was observed that higher water contents were correlated with higher density, and higher compressive strengths. Higher binder contents had no noticeable bearing on the density of the sample, but did increase the compressive strength of the sample. In the future, the adsorption of coarse aggregate will be observed, and samples will be tested at higher water contents

    A Precessing Ferromagnetic Needle Magnetometer

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    A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency Ω\Omega under conditions where its intrinsic spin dominates over its rotational angular momentum, NIΩN\hbar \gg I\Omega (II is the moment of inertia of the needle about the precession axis and NN is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin NN\hbar maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of NN spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum uncertainty, the sensitivity of a precessing needle magnetometer can far surpass that of magnetometers based on spin precession of atoms in the gas phase. Under conditions where noise from coupling to the environment is subdominant, the scaling with measurement time tt of the quantum- and detection-limited magnetometric sensitivity is t3/2t^{-3/2}. The phenomenon of ferromagnetic needle precession may be of particular interest for precision measurements testing fundamental physics.Comment: Main text: 6 pages, 2 figures; Supplementary material: 3 pages, 1 figur

    From Relative Truth to Finean Non-Factualism

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    This paper compares two ‘relativist’ theories about deliciousness: truth-relativism, and Kit Fine’s non-factualism about a subject-matter. Contemporary truth-relativism is presented as a linguistic thesis; its metaphysical underpinning is often neglected. I distinguish three views about the obtaining of worldly states of affairs concerning deliciousness, and argue that none yields a satisfactory version of truth-relativism. Finean non-factualism about deliciousness is not subject to the problems with truth-relativism. I conclude that Finean non- factualism is the better relativist theory. As I explain, non-facualism about deliciousness is happily combined with an invariantist semantics for the word “delicious”. On this approach, relativism is a matter for a metaphysical theory, not a linguistic one

    How to Formulate Arguments from Easy Knowledge, and Maybe How to Resist Them

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    Arguments from “easy knowledge” are meant to refute a class of epistemological views, including foundationalism about perceptual knowledge. I present arguments from easy knowledge in their strongest form, and explain why other formulations in the literature are inferior. I criticize two features of Stewart Cohen’s presentation (2002, 2005), namely his focus on knowing that one’s faculties are reliable, and his use of a Williamson-style closure principle. Rather, the issue around easy knowledge must be understood using a notion of epistemic priority. Roger White’s presentation (2006) is contaminated by the so-called lottery puzzle, which is best kept separate. Distinguishing basic from non-basic visual contents limits the force of the examples discussed by Cohen, White, and Crispin Wright (2007). Finally I present a new strategy for resisting even the best-formulated arguments from easy knowledge

    Appearances, Rationality, and Justified Belief

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    One might think that its seeming to you that p makes you justified in believing that p. After all, when you have no defeating beliefs, it would be irrational to have it seem to you that p but not believe it. That view is plausible for perceptual justification, problematic in the case of memory, and clearly wrong for inferential justification. I propose a view of rationality and justified belief that deals happily with inference and memory. Appearances are to be evaluated as ‘sound’ or ‘unsound.’ Only a sound appearance can give rise to a justified belief, yet even an unsound appearance can ‘rationally require’ the subject to form the belief. Some of our intuitions mistake that rational requirement for the belief’s being justified. The resulting picture makes it plausible that there are also unsound perceptual appearances. I suggest that to have a sound perceptually basic appearance that p, one must see that p
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