3,853 research outputs found

    Space shuttle main engine hardware simulation

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    The Huntsville Simulation Laboratory (HSL) provides a simulation facility to test and verify the space shuttle main engine (SSME) avionics and software system using a maximum complement of flight type hardware. The HSL permits evaluations and analyses of the SSME avionics hardware, software, control system, and mathematical models. The laboratory has performed a wide spectrum of tests and verified operational procedures to ensure system component compatibility under all operating conditions. It is a test bed for integration of hardware/software/hydraulics. The HSL is and has been an invaluable tool in the design and development of the SSME

    Lifting of D1-D5-P states

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    We consider states of the D1-D5 CFT where only the left-moving sector is excited. As we deform away from the orbifold point, some of these states will remain BPS while others can `lift'. We compute this lifting for a particular family of D1-D5-P states, at second order in the deformation off the orbifold point. We note that the maximally twisted sector of the CFT is special: the covering surface appearing in the correlator can only be genus one while for other sectors there is always a genus zero contribution. We use the results to argue that fuzzball configurations should be studied for the full class including both extremal and near-extremal states; many extremal configurations may be best seen as special limits of near extremal configurations.Comment: 51 pages, 6 figure

    Impregnation and Adsorption of Rare Earth Elements on Amberlite XAD-7

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    Beads were washed then impregnated with an organophosphorous extractant D2EHPA. The washing process, as well as factors in the impregnation process were studied. Water was deemed sufficient to prewash the beads before use over small and large amounts of acid with acetone. The impregnation of beads at an Amberlite D2EHPA ratio of 1:1 was determined to be best. Absorption isotherms of Neodymium were the first to be studied. By testing different concentrations, Amberlite was determined to absorb the max amount at 4000 ppm. The pH values from 2-7 were determined to have no effect on the amount of Neodymium absorbed by Amberlite. The pH values 0 and 1 were not able to be measured by the ICP; possibly due to the large number of ions in the solution. The shaking time of Amberlite to adsorb Neodymium was determined to be over 15 hours. It is recommended to shake Amberlite with the Rare Earth solution overnight. The adsorption isotherm of Lanthanum was also tested and determined to be similar to Neodymium. When a Lanthanum and Neodymium solution was created, the isotherm showed that Neodymium adsorbed much better than Lanthanum. The elution of Neodymium from Amberlite was also achieved and the Amberlite was reloaded successfully with Neodymium

    Lateral-Torsional Instability and Biaxial Flexure of Continuous GFRP Beams Including Warping and Shear Deformations

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    This dissertation presents an experimental and theoretical study of the lateral-torsional instability and biaxial flexure of Glass Fiber Reinforced Polymer (GFRP) beams including warping and shear deformation effects. The theoretical analysis is based on three simultaneous differential equations of equilibrium with new terms added to account for shear deformation effects. To solve these equations, algorithms based upon a central finite-difference approach are then developed. The experimental study is conducted on a series of single- and multi-span beams subjected to concentrated loads. The predicted beam behavior agreed well with that observed experimentally. The investigation revealed that the ASCE-LRFD Prestandard for pultruded GFRP beams can result in seriously unconservative buckling load predictions. The same is found for biaxially loaded beams which can develop very large induced warping normal stresses currently unaccounted for by the ACSE-LRFD Prestandard. A new lateral-torsional buckling load equation is presented which accounts for shear deformation effects

    Forage Seed Quality: Dormancy, Standards and Quarantine

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    There are many dimensions to the concept of seed quality. Viable seed which will not germinate when provided with all the requirements for germination is dormant. Forage grasses mostly exhibit non-deep physiological dormancy (PD), while physical dormancy (PY) is common in forage legumes where imbibition is prevented by the seed coat’s impermeability to water (hard seed). Methods for breaking PD and PY to allow germination testing and/or crop establishment are discussed. In the seed industry seed quality standards are an important feature of quality assurance and may apply for seed production contracts, seed certification, seed sale and seed importing. Standards for these uses are discussed, with a comment on legislated minimum germination standards which may do little to offer protection to the buyer. Exported seed lots must meet the seed quality standards and phytosanitory/biosecurity requirements of the importing country, but while there is an obvious need to protect against the spread of economically important pests, they should not be used as unnecessary barriers to the seed trade

    The Guppy Effect as Interference

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    People use conjunctions and disjunctions of concepts in ways that violate the rules of classical logic, such as the law of compositionality. Specifically, they overextend conjunctions of concepts, a phenomenon referred to as the Guppy Effect. We build on previous efforts to develop a quantum model that explains the Guppy Effect in terms of interference. Using a well-studied data set with 16 exemplars that exhibit the Guppy Effect, we developed a 17-dimensional complex Hilbert space H that models the data and demonstrates the relationship between overextension and interference. We view the interference effect as, not a logical fallacy on the conjunction, but a signal that out of the two constituent concepts, a new concept has emerged.Comment: 10 page

    Chandra observations of the HII complex G5.89-0.39 and TeV gamma-ray source HESSJ1800-240B

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    We present the results of our investigation, using a Chandra X-ray observation, into the stellar population of the massive star formation region G5.89-0.39, and its potential connection to the coincident TeV gamma-ray source HESSJ1800-240B. G5.89-0.39 comprises two separate HII regions G5.89-0.39A and G5.89-0.39B (an ultra-compact HII region). We identified 159 individual X-ray point sources in our observation using the source detection algorithm \texttt{wavdetect}. 35 X-ray sources are associated with the HII complex G5.89-0.39. The 35 X-ray sources represent an average unabsorbed luminosity (0.3-10\,keV) of 1030.5\sim10^{30.5}\,erg/s, typical of B7-B5 type stars. The potential ionising source of G5.89-0.39B known as Feldt's star is possibly identified in our observation with an unabsorbed X-ray luminosity suggestive of a B7-B5 star. The stacked energy spectra of these sources is well-fitted with a single thermal plasma APEC model with kT\sim5\,keV, and column density NH=2.6×1022_{\rm H}=2.6\times10^{22}\,cm2^{-2} (AV10_{\rm V}\sim 10). The residual (source-subtracted) X-ray emission towards G5.89-0.39A and B is about 30\% and 25\% larger than their respective stacked source luminosities. Assuming this residual emission is from unresolved stellar sources, the total B-type-equivalent stellar content in G5.89-0.39A and B would be 75 stars, consistent with an earlier estimate of the total stellar mass of hot stars in G5.89-0.39. We have also looked at the variability of the 35 X-ray sources in G5.89-0.39. Ten of these sources are flagged as being variable. Further studies are needed to determine the exact causes of the variability, however the variability could point towards pre-main sequence stars. Such a stellar population could provide sufficient kinetic energy to account for a part of the GeV to TeV gamma-ray emission in the source HESSJ1800-240B.Comment: 34 pages, 9 figure

    Experimental Evidence for Quantum Structure in Cognition

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    We proof a theorem that shows that a collection of experimental data of membership weights of items with respect to a pair of concepts and its conjunction cannot be modeled within a classical measure theoretic weight structure in case the experimental data contain the effect called overextension. Since the effect of overextension, analogue to the well-known guppy effect for concept combinations, is abundant in all experiments testing weights of items with respect to pairs of concepts and their conjunctions, our theorem constitutes a no-go theorem for classical measure structure for common data of membership weights of items with respect to concepts and their combinations. We put forward a simple geometric criterion that reveals the non classicality of the membership weight structure and use experimentally measured membership weights estimated by subjects in experiments to illustrate our geometrical criterion. The violation of the classical weight structure is similar to the violation of the well-known Bell inequalities studied in quantum mechanics, and hence suggests that the quantum formalism and hence the modeling by quantum membership weights can accomplish what classical membership weights cannot do.Comment: 12 pages, 3 figure

    Developing a Challenging Online Doctoral Course Using Backward and Three-Phase Design Models

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    Current Practices and Future Trends in Aviation (DAV 735)—one of 19 online courses in the Ph.D. in Aviation program at Embry-Riddle Aeronautical University—has run five times since 2011. A team of one instructional designer and one professor were responsible for its initial design, development, and ongoing improvement. This continuity provided the opportunity for a longitudinal, descriptive case study reporting on three wicked instructional design challenges: (a) doctoral student body comprised largely of multidisciplinary aviation professionals, (b) no seminal textbook on the course topics, and (c) unforeseen usability problems with Internet technologies. This case analysis has significance because of the lack of literature reporting on the practices of instructional design teams in terms of how theories are applied. An adapted three-phase design model and the backward design model informed the initial design and ongoing improvement of the course. This approach was successful in addressing needs of the users and was instrumental in the course receiving a Blackboard® Catalyst Exemplary Course award in 2014. Recommendations include: (a) adopting an iterative and collaborative course development and improvement process, (b) using problem-based learning, and (c) empowering students to both define and enhance their learning. Use of a template-based production process, reliance on post-course perceptions to inform major improvements, and lack of generalizability when student enrollments or feedback are limited led to questions as to whether the models need to be extended or elaborated
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