7,040 research outputs found

    Measurements of the global distribution of carbon monoxide in the troposphere

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    Carbon monoxide and methane grab samples were obtained simultaneously with ozone, aerosol, nitric oxide and DACOM CO measurements. Eighty grab samples were collected at various altitudes up to 19,000 ft. along a north-south flight path from Wallops Flight Center, VA to 11 N. CO and CH were analyzed by flame ionization gas chromatography with cryogenic preconcentration. The relationship between CO and O3 concentrated is examined. A comparative analysis between trends in aerosol and CO concentration is performed

    A Monte Carlo Template based analysis for Air-Cherenkov Arrays

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    We present a high-performance event reconstruction algorithm: an Image Pixel-wise fit for Atmospheric Cherenkov Telescopes (ImPACT). The reconstruction algorithm is based around the likelihood fitting of camera pixel amplitudes to an expected image template. A maximum likelihood fit is performed to find the best-fit shower parameters. A related reconstruction algorithm has already been shown to provide significant improvements over traditional reconstruction for both the CAT and H.E.S.S. experiments. We demonstrate a significant improvement to the template generation step of the procedure, by the use of a full Monte Carlo air shower simulation in combination with a ray-tracing optics simulation to more accurately model the expected camera images. This reconstruction step is combined with an MVA-based background rejection. Examples are shown of the performance of the ImPACT analysis on both simulated and measured (from a strong VHE source) gamma-ray data from the H.E.S.S. array, demonstrating an improvement in sensitivity of more than a factor two in observation time over traditional image moments-fitting methods, with comparable performance to previous likelihood fitting analyses. ImPACT is a particularly promising approach for future large arrays such as the Cherenkov Telescope Array (CTA) due to its improved high-energy performance and suitability for arrays of mixed telescope types.Comment: 13 pages, 10 figure

    The lunar atmosphere Scientific report

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    Lunar atmosphere data and postulated theory of its structur

    Perturbations to observed ambient neutral densities due to presence of an Orbiting Geophysical Observatory

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    Perturbations in density of ions and neutral particles in upper atmosphere due to OG

    An investigation of surface albedo variations during the recent sahel drought

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    Applications Technology Satellite 3 green sensor data were used to measure surface reflectance variations in the Sahara/Sahel during the recent drought period; 1967 to 1974. The magnitude of the seasonal reflectance change is shown to be as much as 80% for years of normal precipitation and less than 50% for drought years. Year to year comparisons during both wet and dry seasons reveal the existence of a surface reflectance cycle coincident with the drought intensity. The relationship between the green reflectance and solar albedo is examined and estimated to be about 0.6 times the reflectance change observed by the green channel

    The experimental determination of tyre model parameters

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    SUMMARY This report describes the analysis of a series of experiments on pneumatic tyres which were designed to test the various hypotheses: regarding the deformed shape of a tyre during the steering process. The experiments consisted of several separate tests first described in Ref. 1 and 2. a) The application of a point lateral force or a moment at one position on the tread band which is restrained at the centre of the wheel, and the measurement of the resulting lateral deflection of each point of the tyre perimeter. b) The application of a uniform force around the tyre perimeter on a hollow cylindrical former and applying a load at the centre of the wheel. c) Direct determination of tread band tension by cutting the tread band and bridging the cut by a dynamometer. d) Estimation of the bending modulus of the tread band by test on sections cut from the tread band. The analysis of the experiments is carried out by first transforming the test results into a Fourier series and determining the spectral content of the bending line with an harmonic analysis. Transfer functions of beam and string models are derived and applied to the test results. A method of considering a three parameter model is described

    Modeling Documents with Deep Boltzmann Machines

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    We introduce a Deep Boltzmann Machine model suitable for modeling and extracting latent semantic representations from a large unstructured collection of documents. We overcome the apparent difficulty of training a DBM with judicious parameter tying. This parameter tying enables an efficient pretraining algorithm and a state initialization scheme that aids inference. The model can be trained just as efficiently as a standard Restricted Boltzmann Machine. Our experiments show that the model assigns better log probability to unseen data than the Replicated Softmax model. Features extracted from our model outperform LDA, Replicated Softmax, and DocNADE models on document retrieval and document classification tasks.Comment: Appears in Proceedings of the Twenty-Ninth Conference on Uncertainty in Artificial Intelligence (UAI2013
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