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121.
An algorithm for considering time-correlated errors in a Kalman filter is presented. The algorithm differs from previous implementations
in that it does not suffer from numerical problems; does not contain inherent time latency or require reinterpretation of
Kalman filter parameters, and gives full consideration to additive white noise that is often still present but ignored in
previous implementations. Simulation results indicate that the application of the new algorithm yields more realistic and
therefore useful state and covariance information than the standard implementation. Results from a field test of the algorithm
applied to the problem of kinematic differential GPS demonstrate that the algorithm provides slightly pessimistic covariance
estimates whereas the standard Kalman filter provides optimistic covariance estimates. 相似文献
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We present results from a new simulation code that accounts for the evolution of the reservoirs of carbon dioxide on Mars, from its early years to the present. We establish a baseline model parameter set that produces results compatible with the present (i.e., Patm?6.5 mbar with permanent CO2 ice cap) for a wide range of initial inventories. We find that the initial inventory of CO2 broadly determines the evolutionary course of the reservoirs of CO2. The reservoirs include the atmosphere, ice cap, adsorbed CO2 in the regolith, and carbonate rocks. We track the evolution of the free inventory: the atmosphere, ice cap and regolith. Simulations begin at 4.53 Gyr before present with a rapid loss of free inventory to space in the early Noachian. Models that assume a relatively small initial inventory (?5 bar) have pronounced minima in the free inventory of CO2 toward the end of the Noachian. Under baseline parameters, initial inventories below ∼4.5 bar result in a catastrophic loss of the free inventory to space. The current free inventory would be then determined by the balance between outgassing, sputtering losses and chemical weathering following the end of the late bombardment. We call these “thin” models. They generically predict small current free inventories in line with expectations of a small present CO2 ice cap. For “thick” models, with initial inventories ?5 bar, a surplus of 300-700 mbar of free CO2 remains during the late-Noachian. The histories of free inventory in time for thick models tend to converge within the last 3.5 Gyr toward a present with an ice cap plus atmospheric inventory of about 100 mbar. For thick models, the convergence is largely due to the effects of chemical weathering, which draws down higher free inventories more rapidly than the low. Thus, thick models have ?450 mbar carbonate reservoirs, while thin models have ?200 mbar. Though both thick and thin scenarios can reproduce the current atmospheric pressure, the thick models imply a relatively large current CO2 ice cap and thin models, little or none. While the sublimation of a massive cap at a high obliquity would create a climate swing of greenhouse warming for thick models, under the thin model, mean temperatures and pressures would be essentially unaffected by increases in obliquity. 相似文献
125.
V. Berezinsky 《Astroparticle Physics》2002,17(4):575-514
Comparison of solar-neutrino signals in SNO [Phys. Rev. Lett. 87 (2001) 071301] and Super-Kamiokande (SK) [Phys. Rev. Lett. 86 (2001) 5651] detectors results in discovery of νe→νμ,τ oscillations at level 3.1–3.3σ [Phys. Rev. Lett. 87 (2001) 071301]. This comparison involves the assumption of neutrino spectrum and a choice for the thresholds of detection in both experiments. In this paper we obtain an exact formula for the comparison of the signals which is valid for arbitrary spectra and thresholds. We find that the no-oscillation hypothesis (astrophysical solutions) is excluded at 3.3σ. If the energy-dependent component of the survival probability for electron neutrinos is small as compared with the average value, i.e. in the case of small distortion of the observed spectrum, the oscillation hypothesis can also be tested to similar accuracy. The oscillation to sterile neutrino only, is excluded at 3.3σ level, and oscillation to active neutrinos is confirmed at 2.8σ. 相似文献
126.
Carlos J.A.P. Martins 《Astrophysics and Space Science》2003,283(4):439-444
I briefly present the Organizing Committee's and my own motivation for organizing this workshop, and I suggest a few key questions
for which we will try to find possible answers in the coming days.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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