123 research outputs found

    A residual based snapshot location strategy for POD in distributed optimal control of linear parabolic equations

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    In this paper we study the approximation of a distributed optimal control problem for linear para\-bolic PDEs with model order reduction based on Proper Orthogonal Decomposition (POD-MOR). POD-MOR is a Galerkin approach where the basis functions are obtained upon information contained in time snapshots of the parabolic PDE related to given input data. In the present work we show that for POD-MOR in optimal control of parabolic equations it is important to have knowledge about the controlled system at the right time instances. For the determination of the time instances (snapshot locations) we propose an a-posteriori error control concept which is based on a reformulation of the optimality system of the underlying optimal control problem as a second order in time and fourth order in space elliptic system which is approximated by a space-time finite element method. Finally, we present numerical tests to illustrate our approach and to show the effectiveness of the method in comparison to existing approaches

    THE USE OF TECHNOLOGY TO IMPLEMENT PEER MEDIATED INTERVENTION: STUDENTS WITH AUTISM AS TUTORS AND TUTEES

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    Peer mediated interventions have been effective in teaching academic and social skills to students with disabilities. The present study assesses the effectiveness of students with autism spectrum disorder serving as the tutor and tutee. Four peer mediators and four students with autism spectrum disorder used technology and the simultaneous prompting procedure to teach acquisition of social studies vocabulary. Results indicate that both students with and without autism spectrum disorder effectively delivered instruction using technology and all students learned a portion of the vocabulary taught by a same-aged peer

    Performance Report: A timeline for the synchrotron calibration of AXAF

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    Presented herein are the known elements of the timeline for synchrotron reflectance calibrations of HRMA witness samples (Section 2). In Section 3, lists of measurements to be done on each witness flat are developed. The elements are then arranged into timelines for the three beamlines we expect to employ in covering the full 50-12,000 eV energy range (Section 4). Although the required AXAF operational range is only 0.1-10 keV, we must calibrate the extent to which radiation just outside this band may contaminate our in-band response. In Section 5, we describe the working relationships which exist with each of the beamlines, and estimate the time available for AXAF measurements on each. From the timelines and the available time, we calculate the number of flats which could be measured in full detail over the duration of the program for each beamline. A suggestion is made regarding a minimum required baselines of witness flats from each element coating run or qualification run to be used in the calibration. We intend that this suggestion open discussion of the issue of witness flat deployment

    Measurement of transmission loss using an inexpensive mobile source on the Upper Slope of the South China Sea

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    During the 2014 South China Sea Upper-Slope Sand Dunes Experiment, an inexpensive, expendable mobile sound source was deployed to investigate potential use of such a device to acquire quality transmission loss (TL) data and yield additional spatial information of the complex acoustic environment. The mobile source was programmed to maintain depth, speed, and to transmit a tonal signal followed by a short linear-sweep timing/ranging pulse every minute. A vertical hydrophone array and other receivers recorded the signals. The methodology and related mathematical tools to analyze the received acoustic data for coherence time (optimum integration time) and consequently TL were developebcd. Specifically, coherence times were estimated based on a tolerance of one-dB degradation in the measured SPL of the tone. It is shown that a time segment is coherent when 50% of the segment has phase fluctuations within ± 45° about the linear trend of the phase. The optimum integration time was applied to the data to obtain TL estimates versus range using spectral estimation techniques. Measured coherence time and TL were compared to model results from the National Taiwan University to gain insights into the quality, limitations, and attainable future advances of this measurement method.http://archive.org/details/measurementoftra1094547264Lieutenant, United States NavyApproved for public release; distribution is unlimited

    A Technique of Direct Tension Measurement of a Strung Fine Wire

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    We present a new technique of direct measurement of wire tensions in wire chambers. A specially designed circuit plucks the wire using the Lorentz force and measures the frequency of damped transverse oscillations of the wire. The technique avoids the usual time-consuming necessity of tuning circuit parameter to a resonance. It allows a fast and convenient determination of tensions and is straightforward to implement.Comment: 15 pages with 9 figure

    The x ray reflectivity of the AXAF VETA-I optics

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    The x-ray reflectivity of the VETA-I optic, the outermost shell of the AXAF x-ray telescope, with a bare Zerodur surface, is measured and compared with theoretical predictions. Measurements made at energies of 0.28, 0.9, 1.5, 2.1, and 2.3 keV are compared with predictions based on ray trace calculations. The data were obtained at the x-ray calibrations facility at Marshall Space Flight Center with an electron impact x-ray source located 528 m from the grazing incidence mirror. The source used photoelectric absorption filters to eliminate bremsstrahlung continuum. The mirror has a diameter of 1.2 m and a focal length of 10 m. The incident and reflected x-ray flux are detected using two proportional counters, one located in the incident beam of x-rays at the entrance aperture of the VETA-I, and the other in the focal plane behind an aperture of variable size. Results on the variation of the reflectivity with energy as well as the absolute value of the reflectivity are presented. We also present a synchrotron reflectivity measurement with high energy resolution over the range 0.26 to 1.8 keV on a flat Zerodur sample, done at NSLS. We present evidence for contamination of the flat by a thin layer of carbon on the surface, and the possibility of alteration of the surface composition of the VETA-I mirror perhaps by the polishing technique. The overall agreement between the measured and calculated effective area of VETA-I is between 2.6 percent and 10 percent, depending on which model for the surface composition is adopted. Measurements at individual energies deviate from the best-fitting calculation to 0.3 to 0.8 percent, averaging 0.6 percent at energies below the high energy cutoff of the mirror reflectivity, and are as high as 20.7 percent at the cutoff. We also discuss the approach to the final preflight calibration of the full AXAF flight mirror

    Personalized And Situation-Aware Recommendations For Runners

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    The project uService investigates the transformation of a mobile user into a service super prosumer, i.e., a producer, provider and consumer of services at the same time. The goal is to develop a platform which enables a user to create, discover and consume mobile services anywhere and at any time on the mobile device. uRun is an application scenario of the project in the field of mobile health and fitness. The uRun framework provides a mobile assistance system particularly for runners, which combines Web 2.0 and Web 3.0 technologies and personalized and situation-aware recommendation mechanisms. The ability to create individual and mobile health and fitness services as well as a personalized and situation-aware assistance system based on a semantic knowledge base are considered to provide an edge over existing consumer-centric health care systems. In this article, we describe the recommendation mechanism and the incorporation of semantic knowledge for the uService platform and the uRun framework

    A straw drift chamber spectrometer for studies of rare kaon decays

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    We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5 mm diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-intensity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds
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