1,708 research outputs found
Optimal Estimation of Several Linear Parameters in the Presence of Lorentzian Thermal Noise
In a previous article we developed an approach to the optimal (minimum
variance, unbiased) statistical estimation technique for the equilibrium
displacement of a damped, harmonic oscillator in the presence of thermal noise.
Here, we expand that work to include the optimal estimation of several linear
parameters from a continuous time series. We show that working in the basis of
the thermal driving force both simplifies the calculations and provides
additional insight to why various approximate (not optimal) estimation
techniques perform as they do. To illustrate this point, we compare the
variance in the optimal estimator that we derive for thermal noise with those
of two approximate methods which, like the optimal estimator, suppress the
contribution to the variance that would come from the irrelevant, resonant
motion of the oscillator. We discuss how these methods fare when the dominant
noise process is either white displacement noise or noise with power spectral
density that is inversely proportional to the frequency ( noise). We also
construct, in the basis of the driving force, an estimator that performs well
for a mixture of white noise and thermal noise. To find the optimal
multi-parameter estimators for thermal noise, we derive and illustrate a
generalization of traditional matrix methods for parameter estimation that can
accommodate continuous data. We discuss how this approach may help refine the
design of experiments as they allow an exact, quantitative comparison of the
precision of estimated parameters under various data acquisition and data
analysis strategies.Comment: 16 pages, 10 figures. Accepted for publication in Classical and
Quantum Gravit
First U.S. manned six-pass orbital mission /Mercury-Atlas 8, spacecraft 16/
Description and performance analysis of manned six-pass orbital mission /Mercury-Atlas 8
Second United States manned three-pass orbital mission/Mercury-Atlas 7, spacecraft 18/. Description and performance analysis
Orbital mission Mercury-Atlas 7, spacecraft 18 - prelaunch and launch, flight control, recovery, aeromedical analysis, astronaut activities, and spacecraft performance and descriptio
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Itqiy: II. a short story about its noble gases and oxygen isotopes
Bulk, rare earth and other trace elements in Apollo 14 and 15 and Luna 16 samples
The chemical abundances were measured by instrumental and radiochemical neutron activation analysis in a variety of lunar specimens. Apollo 14 soils are characterized by significant enrichments of Al2O3, Na2O and K2O and depletions of TiO2, FeO, MnO and Cr2O3 relative to Apollo 11 and to most of Apollo 12 soils. The uniform abundances in 14230 core tube soils and three other Apollo 14 soils indicate that the regolith is uniform to at least 22 cm depth and within approximately 200 m from the lunar module. Two Luna 16 breccias are similar in composition to Luna 16 soils. Four Apollo 15 soils (LM, STA 4, 9, and 9a) have variable compositions. Interelement correlations between MnO-FeO, Sc-FeO, V-Cr2O3 and K2O-Hf negate the hypothesis that howardite achondrites may be primitive lunar matter, argue against the fission hypothesis for the origin of the moon, and precludes any selective large scale volatilization of alkalies during lunar magmatic events
Effect of tip clearance on performance of small axial hydraulic turbine
The first two stages of a six stage liquid oxygen turbine were tested in water. One and two stage performance was determined for one shrouded and two unshrouded blade end configurations over ranges of clearance and blade-jet speed ratio. First stage, two stage, and second stage efficiencies are included as well as the effect of clearance on mass flow for two stage operation
A New Version of Reimers' law of Mass Loss Based on a Physical Approach
We present a new semi-empirical relation for the mass loss of cool stellar
winds, which so far has frequently been described by "Reimers' law".
Originally, this relation was based solely on dimensional scaling arguments
without any physical interpretation. In our approach, the wind is assumed to
result from the spill-over of the extended chromosphere, possibly associated
with the action of waves, especially Alfven waves, which are used as guidance
in the derivation of the new formula. We obtain a relation akin to the original
Reimers law, but which includes two new factors. They reflect how the
chromospheric height depends on gravity and how the mechanical energy flux
depends, mainly, on effective temperature. The new relation is tested and
sensitively calibrated by modelling the blue end of the Horizontal Branch of
globular clusters. The most significant difference from mass loss rates
predicted by the Reimers relation is an increase by up to a factor of 3 for
luminous late-type (super-)giants, in good agreement with observations.Comment: 12 pages, 4 figures, accepted by ApJ Letter
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