1,226 research outputs found

    WISP information display system user's manual

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    The wind shears program (WISP) supports the collection of data on magnetic tape for permanent storage or analysis. The document structure provides: (1) the hardware and software configuration required to execute the WISP system and start up procedure from a power down condition; (2) data collection task, calculations performed on the incoming data, and a description of the magnetic tape format; (3) the data display task and examples of displays obtained from execution of the real time simulation program; and (4) the raw data dump task and examples of operator actions required to obtained the desired format. The procedures outlines herein will allow continuous data collection at the expense of real time visual displays

    Study of software application of airborne laser doppler system for severe storms measurement

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    Significant considerations are described for performing a Severe Storms Measurement program in real time. Particular emphasis is placed on the sizing and timing requirements for a minicomputer-based system. Analyses of several factors which could impact the effectiveness of the system are presented. The analyses encompass the problems of data acquisition, data storage, data registration, correlation, and flow field computation, and error induced by aircraft motion, moment estimation, and pulse integration

    Cosmological test of the Yilmaz theory of gravity

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    We test the Yilmaz theory of gravitation by working out the corresponding Friedmann-type equations generated by assuming the Friedmann-Robertson-Walker cosmological metrics. In the case that space is flat the theory is consistent only with either a completely empty universe or a negative energy vacuum that decays to produce a constant density of matter. In both cases the total energy remains zero at all times, and in the latter case the acceleration of the expansion is always negative. To obtain a more flexible and potentially more realistic cosmology, the equation of state relating the pressure and energy density of the matter creation process must be different from the vacuum, as for example is the case in the steady-state models of Gold, Bondi, Hoyle and others. The theory does not support the cosmological principle for curved space K =/= 0 cosmological metrics

    Diffusion, Fragmentation and Coagulation Processes: Analytical and Numerical Results

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    We formulate dynamical rate equations for physical processes driven by a combination of diffusive growth, size fragmentation and fragment coagulation. Initially, we consider processes where coagulation is absent. In this case we solve the rate equation exactly leading to size distributions of Bessel type which fall off as exp(x3/2)\exp(-x^{3/2}) for large xx-values. Moreover, we provide explicit formulas for the expansion coefficients in terms of Airy functions. Introducing the coagulation term, the full non-linear model is mapped exactly onto a Riccati equation that enables us to derive various asymptotic solutions for the distribution function. In particular, we find a standard exponential decay, exp(x)\exp(-x), for large xx, and observe a crossover from the Bessel function for intermediate values of xx. These findings are checked by numerical simulations and we find perfect agreement between the theoretical predictions and numerical results.Comment: (28 pages, 6 figures, v2+v3 minor corrections

    A Mandated Minimum Competency Testing Program and Its Impact on Learning Disabled Students: Curricular Validity and Comparative Performances

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    This research was published by the KU Center for Research on Learning, formerly known as the University of Kansas Institute for Research in Learning Disabilities.In this study, LD specialists, regular class teachers, and parents of LD students judged that the objectives of the Kansas Minimum Competency Specifications prescribed for nonhandicapped students were applicable to LD students. In addition, the Kansas Minimal Competency Test was administered to LD students under standard and oral conditions. Results showed that they did not perform as well as their nonhandicapped peers at any of the five grade levels. The test was then administered under two modified conditions. Learning disabled students' performance on some objectives at every grade level was not improved by either administering items orally or administering the test one grade level above that designated for nonhandicapped students

    Complex fabric development revealed by englacial seismic reflectivity: Jakobshavn Isbræ, Greenland

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    This is the published version. Copyright 2008 American Geophysical Union. All Rights Reserved.High-resolution reflection seismic data from Jakobshavn Isbræ, Greenland, reveal complex fabric development. Abundant englacial reflectivity occurs for approximately half the thickness of the ice (the lower half), and disruption of the englacial reflectors occurs in the lower 10–15% of the ice-thickness. These depths correspond to the higher impurity-content, and more easily deformed, ice from the Younger Dryas and Last Glacial Maximum to Stage-3. We conclude that the reflectivity results from contrasting seismic velocities due to changes in the crystal orientation fabric of the ice, and suggest that these fabric changes are caused by variations in impurity loading and subsequent deformation history. These findings emphasize the difference between ice-divide and ice-stream crystal orientation fabrics and have implications for predictive ice sheet modeling

    A 1400-Year Oxygen Isotope History from the Ross Sea Area, Antarctica

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    Four ice cores from the Ross Sea drainage, Antarctica, show patterns of δ18O variations on a time scale of decades to centuries over the last 1400 years without change in the long-term average δ18O. Century scale δ18O fluctuations in the two cores drilled in the Ross Ice Shelf at Station J-9 (82° 23\u27 S, 168° 38\u27 W, elevation 60 m) are highly correlated (P \u3c 2 x 10-4). The long isotope record (\u3e30 000 a) of the 1978 1-9 core thus represents local conditions over at least 102 m and on time scales of 100 years and longer. Regional correlations between the 1-9 δ18O records and those from Ridge BC (82 ° 54\u27S, 136 ° 40\u27W, elevation 509 m) and the Dominion Range (85 ° 15\u27 S, 166 ° 10\u27 E, elevation 2700 m) are barely significant (P ≈ 0.05 for J-9 \u2776 and Dominion Range, δ18O to 1400 years ago) or absent. The failure to find clear regional isotope trends related to climate fluctuations may reflect the finding that between 1957 and 1982 the area was in the transition zone between areas with opposite temperature trends, and showed little or no temperature change. The fact that the records nevertheless show significant δ18O fluctuations highlights the need to base regional climate reconstructions on a regional suite of ice-core records

    Bell State Preparation using Pulsed Non-Degenerate Two-Photon Entanglement

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    We report a novel Bell state preparation experiment. High-purity Bell states are prepared by using femtosecond pulse pumped \emph{nondegenerate} collinear spontaneous parametric down-conversion. The use of femtosecond pump pulse {\em does not} result in reduction of quantum interference visibility in our scheme in which post-selection of amplitudes and other traditional mechanisms, such as, using thin nonlinear crystals or narrow-band spectral filters are not used. Another distinct feature of this scheme is that the pump, the signal, and the idler wavelengths are all distinguishable, which is very useful for quantum communications.Comment: 4 pages, submitted to PR

    Effects of thermal fluctuation and the receptor-receptor interaction in bacterial chemotactic signalling and adaptation

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    Bacterial chemotaxis is controlled by the conformational changes of the receptors, in response to the change of the ambient chemical concentration. In a statistical mechanical approach, the signalling due to the conformational changes is a thermodynamic average quantity, dependent on the temperature and the total energy of the system, including both ligand-receptor interaction and receptor-receptor interaction. This physical theory suggests to biology a new understanding of cooperation in ligand binding and receptor signalling problems. How much experimental support of this approach can be obtained from the currently available data? What are the parameter values? What is the practical information for experiments? Here we make comparisons between the theory and recent experimental results. Although currently comparisons can only be semi-quantitative or qualitative, consistency is clearly shown. The theory also helps to sort a variety of data.Comment: 26 pages, revtex. Journal version. Analysis on another set of data on adaptation time is adde

    Nonlinear Hydrodynamics of a Hard Sphere Fluid Near the Glass Transition

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    We conduct a numerical study of the dynamic behavior of a dense hard sphere fluid by deriving and integrating a set of Langevin equations. The statics of the system is described by a free energy functional of the Ramakrishnan-Yussouff form. We find that the system exhibits glassy behavior as evidenced through stretched exponential decay and two-stage relaxation of the density correlation function. The characteristic times grow with increasing density according to the Vogel-Fulcher law. The wavenumber dependence of the kinetics is extensively explored. The connection of our results with experiment, mode coupling theory, and molecular dynamics results is discussed.Comment: 34 Pages, Plain TeX, 12 PostScript Figures (not included, available on request
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