7,040 research outputs found
Measurements of the global distribution of carbon monoxide in the troposphere
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
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
Lunar atmosphere data and postulated theory of its structur
Perturbations to observed ambient neutral densities due to presence of an Orbiting Geophysical Observatory
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
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
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
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
- …