18,430 research outputs found

    Effects of noise upon human information processing

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    Studies of noise effects upon human information processing are described which investigated whether or not effects of noise upon performance are dependent upon specific characteristics of noise stimulation and their interaction with task conditions. The difficulty of predicting noise effects was emphasized. Arousal theory was considered to have explanatory value in interpreting the findings of all the studies. Performance under noise was found to involve a psychophysiological cost, measured by vasoconstriction response, with the degree of response cost being related to scores on a noise annoyance sensitivity scale. Noise sensitive subjects showed a greater autonomic response under noise stimulation

    Dynamic stability of a flexible booster subjected to a gimbled, periodically-varying end thrust Technical memorandum no. 104

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    Dynamic structural behavior of large rocket booster synthesized by two thin-walled cylinders and subjected to periodically varying end thrus

    Control of Raman Lasing in the Nonimpulsive Regime

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    We explore coherent control of stimulated Raman scattering in the nonimpulsive regime. Optical pulse shaping of the coherent pump field leads to control over the stimulated Raman output. A model of the control mechanism is investigated.Comment: 4 pages, 5 figure

    Co-reading: investigating collaborative group reading.

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    Collaborative reading, or co-reading as we call it, is ubiquitous—it occurs, for instance, in classrooms, book-clubs, and in less coordinated ways through mass media. While individual digital reading has been the subject of much investigation, research into co-reading is scarce. We report a two-phase field study of group reading to identify an initial set of user requirements. A co-reading interface is then designed that facilitates the coordination of group reading by providing temporary ‘Point-out’ markers to indicate specific locations within documents. A user study compared this new system with collaborative reading on paper, with a positive outcome; the differences in user behavior between paper and the new interface reveal intriguing insights into user needs and the potential benefits of digital media for co-reading

    Principal Component Analysis with Noisy and/or Missing Data

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    We present a method for performing Principal Component Analysis (PCA) on noisy datasets with missing values. Estimates of the measurement error are used to weight the input data such that compared to classic PCA, the resulting eigenvectors are more sensitive to the true underlying signal variations rather than being pulled by heteroskedastic measurement noise. Missing data is simply the limiting case of weight=0. The underlying algorithm is a noise weighted Expectation Maximization (EM) PCA, which has additional benefits of implementation speed and flexibility for smoothing eigenvectors to reduce the noise contribution. We present applications of this method on simulated data and QSO spectra from the Sloan Digital Sky Survey.Comment: Accepted for publication in PASP; v2 with minor updates, mostly to bibliograph

    Torsion–rotation global analysis of the first three torsional states (νt = 0, 1, 2) and terahertz database for methanol

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    Stimulated by recent THz measurements of the methanol spectrum in one of our laboratories, undertaken in support of NASA programs related to the Herschel Space Observatory (HSO) and the Atacama Large Millimeter Array (ALMA), we have carried out a global analysis of available microwave and high-resolution infrared data for the first three torsional states (νt = 0, 1, 2), and for J values up to 30. This global fit of approximately 5600 frequency measurements and 19 000 Fourier transform far infrared (FTFIR) wavenumber measurements to 119 parameters reaches the estimated experimental measurement accuracy for the FTFIR transitions, and about twice the estimated experimental measurement accuracy for the microwave, submillimeter-wave, and terahertz transitions. The present fit is essentially a continuation of our earlier work, but we have greatly expanded our previous data set and have added a large number of new torsion–rotation interaction terms to the Hamiltonian in our previously used computer program. The results, together with a number of calculated (but unmeasured) transitions, including their line strength, estimated uncertainty, and lower state energy, are made available in the supplementary material as a database formatted to be useful for astronomical searches. Some discussion of several open spectroscopic problems, e.g., (i) an improved notation for the numerous parameters in the torsion–rotation Hamiltonian, (ii) possible causes of the failure to fit frequency measurements to the estimated measurement uncertainty, and (iii) pitfalls to be avoided when intercomparing apparently identical parameters from the internal axis method and the rho axis method are also given
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