3,866 research outputs found

    Angular distribution of photoelectrons at 584A using polarized radiation

    Get PDF
    Photoelectron angular distributions for Ar, Xe, N2, O2, CO, CO2, and NH3 were obtained at 584 A by observing the photoelectrons at a fixed angle and simply rotating the plane of polarization of a highly polarized photon source. The radiation from a helium dc glow discharge source was polarized (84%) using a reflection type polarizer

    Multimedia courseware: Never mind the quality how much will it cost to develop?

    Get PDF
    This paper evaluates multimedia courseware costing techniques such as the US Airforce Interactive Courseware Method (Golas, 1993), CBT Analyst (Kearsley, 1985), CEAC (Schooley, 1988) and MEEM (Marshall, Samson, Dugard, & Scott, 1994) against the data from ten multimedia courseware developments. The Relative Error and Mean Absolute Relative Error (MARE) are calculated to allow comparison of the different methods

    Improved photoionization mass spectrometer

    Get PDF
    Improved spectrometer for gas analysis lessens the intensity problem that occurs in obtaining dispersed ultraviolet radiation. A filter, consisting of a selectively transmitting gas cell, a thin film or mirror, or a predispersing grating, alleviates problems of interference from higher-order spectral lines and from scattered ultraviolet light

    Analytical photoionization mass spectrometer with an argon gas filter between the light source and monochrometer Patent

    Get PDF
    Analytical photoionization mass spectrometer with argon gas filter between light source and monochromete

    On the capacity achieving covariance matrix for Rician MIMO channels: an asymptotic approach

    Get PDF
    The capacity-achieving input covariance matrices for coherent block-fading correlated MIMO Rician channels are determined. In this case, no closed-form expressions for the eigenvectors of the optimum input covariance matrix are available. An approximation of the average mutual information is evaluated in this paper in the asymptotic regime where the number of transmit and receive antennas converge to ++\infty. New results related to the accuracy of the corresponding large system approximation are provided. An attractive optimization algorithm of this approximation is proposed and we establish that it yields an effective way to compute the capacity achieving covariance matrix for the average mutual information. Finally, numerical simulation results show that, even for a moderate number of transmit and receive antennas, the new approach provides the same results as direct maximization approaches of the average mutual information, while being much more computationally attractive.Comment: 56 pp. Extended version of the published article in IEEE Inf. Th. (march 2010) with more proof

    X-56A Structural Dynamics Ground Testing Overview and Lessons Learned

    Get PDF
    The X-56A Multi-Utility Technology Testbed (MUTT) is a subscale, fixed-wing aircraft designed for high-risk aeroelastic flight demonstration and research. Structural dynamics ground testing for model validation was especially important for this vehicle because the structural model was directly used in the development of a flight control system with active flutter suppression capabilities. Structural dynamics ground tests of the X-56A MUTT with coupled rigid-body and structural modes provided a unique set of challenges. An overview of the ground vibration test (GVT) and moment of inertia (MOI) test setup and execution is presented. The series of GVTs included the wing by itself attached to a strongback and complete vehicle at two mass conditions: empty and full fuel. Two boundary conditions for the complete-vehicle test were studied: on landing gear and suspended free-free. Pitch MOI tests were performed using a compound pendulum method and repeated with two different pendulum lengths for independent verification. The original soft-support test configuration for the GVT used multiple bungees, resulting in unforeseen coupling interactions between the soft-support bungees and the vehicle structural modes. To resolve this problem, the soft-support test setup underwent multiple iterations. The various GVT configurations and boundary-condition modifications are highlighted and explained. Lessons learned are captured for future consideration when performing structural dynamics testing with similar vehicles

    EliXR-TIME: A Temporal Knowledge Representation for Clinical Research Eligibility Criteria.

    Get PDF
    Effective clinical text processing requires accurate extraction and representation of temporal expressions. Multiple temporal information extraction models were developed but a similar need for extracting temporal expressions in eligibility criteria (e.g., for eligibility determination) remains. We identified the temporal knowledge representation requirements of eligibility criteria by reviewing 100 temporal criteria. We developed EliXR-TIME, a frame-based representation designed to support semantic annotation for temporal expressions in eligibility criteria by reusing applicable classes from well-known clinical temporal knowledge representations. We used EliXR-TIME to analyze a training set of 50 new temporal eligibility criteria. We evaluated EliXR-TIME using an additional random sample of 20 eligibility criteria with temporal expressions that have no overlap with the training data, yielding 92.7% (76 / 82) inter-coder agreement on sentence chunking and 72% (72 / 100) agreement on semantic annotation. We conclude that this knowledge representation can facilitate semantic annotation of the temporal expressions in eligibility criteria

    Changes in the Characteristics of Typhoons Crossing the Island of Taiwan

    Get PDF
    The article of record as published may be found at http://dx.doi.org/10.1175/1520-0493(1974)1022.0.CO;2Twenty-two typhoons (1960-72) are examined to determine the effect of Taiwan on the intensity and movement of tropical cyclones crossing the island. The results show an average intensity (maicimum surface wind) decrease of over 403 and a distinct northward deflection as the storms approach the island with a southward deflection after passage. Forecast rules for typhoons approaching or crossing Taiwan are presented

    Tropical Cyclone Movement Forecasts Based on Observations from Satellites

    Get PDF
    The article of record as published may be found at http://dx.doi.org/10.1175/1520-0450(1975)0142.0.CO;2A method to predict 24 h movement of tropical cyclones using consecutive daily satellite views is described. The method is based on the observation that changes in the location of major structural features of the storm are correlated with changes in the direction of movement of the storm centers. Major structural features appear to retain the same relative location with respect to the direction of movement of the storm center. The rotation of features noted in comparing satellite views over a 24 h period is frequently found to approximate in sense and value the further deflection the storm will.take in its track during the following 24 h. A test evaluation of the method was conducted by seven individuals using 31 separate data sets of satellite data. For the purposes of the test only direction of movement forecasts were made and storm center displacement was neglected. The results on a post-analysis, nonreal- time, basis compared favorably with official 24 h forecasts
    corecore