6,406 research outputs found

    Preliminary analysis of a downsized advanced gas-turbine engine in a subcompact car

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    Relative fuel economy advantages exist for a ceramic turbine engine when it is downsized for a small car were investigated. A 75 kW (100 hp) single shaft engine under development was analytically downsized to 37 kW (50 hp) and analyzed with a metal belt continuously variable transmission in a synthesized car. With gasoline, a 25% advantage was calculated over that of a current spark ignition engine, scaled to the same power, using the same transmission and car. With diesel fuel, a 21% advantage was calculated over that of a similar diesel engine vehicle

    A class of well-posed parabolic final value problems

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    This paper focuses on parabolic final value problems, and well-posedness is proved for a large class of these. The clarification is obtained from Hilbert spaces that characterise data that give existence, uniqueness and stability of the solutions. The data space is the graph normed domain of an unbounded operator that maps final states to the corresponding initial states. It induces a new compatibility condition, depending crucially on the fact that analytic semigroups always are invertible in the class of closed operators. Lax--Milgram operators in vector distribution spaces constitute the main framework. The final value heat conduction problem on a smooth open set is also proved to be well posed, and non-zero Dirichlet data are shown to require an extended compatibility condition obtained by adding an improper Bochner integral.Comment: 16 pages. To appear in "Applied and numerical harmonic analysis"; a reference update. Conference contribution, based on arXiv:1707.02136, with some further development

    Assessment of a method to detect signals for updating systematic reviews.

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    BackgroundSystematic reviews are a cornerstone of evidence-based medicine but are useful only if up-to-date. Methods for detecting signals of when a systematic review needs updating have face validity, but no proposed method has had an assessment of predictive validity performed.MethodsThe AHRQ Comparative Effectiveness Review program had produced 13 comparative effectiveness reviews (CERs), a subcategory of systematic reviews, by 2009, 11 of which were assessed in 2009 using a surveillance system to determine the degree to which individual conclusions were out of date and to assign a priority for updating each report. Four CERs were judged to be a high priority for updating, four CERs were judged to be medium priority for updating, and three CERs were judged to be low priority for updating. AHRQ then commissioned full update reviews for 9 of these 11 CERs. Where possible, we matched the original conclusions with their corresponding conclusions in the update reports, and compared the congruence between these pairs with our original predictions about which conclusions in each CER remained valid. We then classified the concordance of each pair as good, fair, or poor. We also made a summary determination of the priority for updating each CER based on the actual changes in conclusions in the updated report, and compared these determinations with the earlier assessments of priority.ResultsThe 9 CERs included 149 individual conclusions, 84% with matches in the update reports. Across reports, 83% of matched conclusions had good concordance, and 99% had good or fair concordance. The one instance of poor concordance was partially attributable to the publication of new evidence after the surveillance signal searches had been done. Both CERs originally judged as being low priority for updating had no substantive changes to their conclusions in the actual updated report. The agreement on overall priority for updating between prediction and actual changes to conclusions was Kappa = 0.74.ConclusionsThese results provide some support for the validity of a surveillance system for detecting signals indicating when a systematic review needs updating

    The relationship between readiness for, and involvement in self-directed learning

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    The study examined the following research questions: (1) Are there predictive relationships between readiness for self-directed learning and the extent to which adults are involved in self-directed learning? (2) Which personal readiness factor(s) is(are) the best predictor(s) of high involvement in self-directed learning?;The Self-Directed Learning Readiness Scale (SDLRS) and the Adult Learning Projects Telephone Interview Schedule was administered to a random sample of sixty-five Iowa State University Cooperative Extension Service professional staff;Findings indicate there is a positive, predictive relationship between readiness and the number of self-planned projects conducted, as well as the amount of time spent on them;Self-concept as an effective, independent learner was identified as the readiness factor that best predicted the number of self-planned projects (R(\u272) = .20) and the time spent on them (R(\u272) = .42). After self-concept was accounted for, view of learning as a lifelong, beneficial process was the only other readiness factor which contributed to the prediction. At least five individual items on the SDLRS appear to be very effective (r(\u272) = 1.00) in predicting extent of involvement in self-planned projects;Readiness level did not differ with respect to gender, full versus part-time employment, program area, level of position, educational level beyond a bachelor\u27s degree, or job tenure;Extent of involvement in self-planned projects was found to differ with respect to tenure and level of position. Staff with less than two years and those with 6-10 years tenure engaged in more self-planned projects than their colleagues. Individuals with less than two years tenure also spent significantly more time on self-planned learning than other staff. State level staff devoted significantly more time to self-planned projects than county or area level staff;Findings suggest that the SDLRS can predict involvement in self-planned learning. However, its predictive ability is limited due to the large portion of unexplained variance in the number of self-planned projects and time spent on these projects. Recommendations for further research were identified, including possible revision of the SDLRS

    Relative generalized hamming weights and extended weight polynomials of almost affine codes

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    This is a post-peer-review, pre-copyedit version of an article published in Lecture Notes in Computer Science, International Castle Meeting on Coding Theory and Applications ICMCTA 2017: Coding Theory and Applications, 207-216. The final authenticated version is available online at: http://dx.doi.org/10.1007/978-3-319-66278-7_17 .This paper is devoted to giving a generalization from linear codes to the larger class of almost affine codes of two different results. One such result is how one can express the relative generalized Hamming weights of a pair of codes in terms of intersection properties between the smallest of these codes and subcodes of the largest code. The other result tells how one can find the extended weight polynomials, expressing the number of codewords of each possible weight, for each code in an infinite hierarchy of extensions of a code over a given alphabet. Our tools will be demi-matroids and matroids

    Understanding the effect of cube size on the near wake characteristics in a turbulent boundary layer

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143036/1/6.2017-3640.pd

    Spin-dynamic field coupling in strongly THz driven semiconductors : local inversion symmetry breaking

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    We study theoretically the optics in undoped direct gap semiconductors which are strongly driven in the THz regime. We calculate the optical sideband generation due to nonlinear mixing of the THz field and the near infrared probe. Starting with an inversion symmetric microscopic Hamiltonian we include the THz field nonperturbatively using non-equilibrium Green function techniques. We find that a self induced relativistic spin-THz field coupling locally breaks the inversion symmetry, resulting in the formation of odd sidebands which otherwise are absent.Comment: 8 pages, 6 figure

    A Formal, Resource Consumption-Preserving Translation of Actors to Haskell

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    We present a formal translation of an actor-based language with cooperative scheduling to the functional language Haskell. The translation is proven correct with respect to a formal semantics of the source language and a high-level operational semantics of the target, i.e. a subset of Haskell. The main correctness theorem is expressed in terms of a simulation relation between the operational semantics of actor programs and their translation. This allows us to then prove that the resource consumption is preserved over this translation, as we establish an equivalence of the cost of the original and Haskell-translated execution traces.Comment: Pre-proceedings paper presented at the 26th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2016), Edinburgh, Scotland UK, 6-8 September 2016 (arXiv:1608.02534
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