3,094 research outputs found
Improvements in ERBS attitude determination without gyros
Previous papers have described the modification of the Earth Radiation Budget Satellite (ERBS) Attitude Determination System (ADS) to overcome the impact of on board gyro degradation and failure on attitude ground support of the mission. Two approaches were taken: implementing a Kalman filter in place of the batch-least-squares attitude estimator to account for the propagation error produced by high-noise gyro data, and modeling the ERBS attitude dynamics to restore rate information in the case of gyro failure. Both of these methods had shortcomings. In practice, the filter attitude diverged without complete sensor observability, and accurate dynamics modeling required knowledge of disturbance torque parameters that had to be determined manually. These difficulties have been overcome by improved tuning of the filter and by incorporating dynamics parameter estimation into the ERBS ADS
1943-09-08, Harold to Frances
https://digitalcommons.chapman.edu/hjglickman_collection/1001/thumbnail.jp
1943-12-02, Harold to Frances
https://digitalcommons.chapman.edu/hjglickman_collection/1002/thumbnail.jp
1943-08-09, Harold to Frances
https://digitalcommons.chapman.edu/hjglickman_collection/1000/thumbnail.jp
1943-12-12, Harold to Frances
https://digitalcommons.chapman.edu/hjglickman_collection/1003/thumbnail.jp
Molecular Dynamics Simulation of Ga Penetration along Grain Boundaries in Al: a Dislocation Climb Mechanism
Many systems where a liquid metal is in contact with a polycrystalline solid
exhibit deep liquid grooves where the grain boundary meets the solid-liquid
interface. For example, liquid Ga quickly penetrates deep into grain boundaries
in Al, leading to intergranular fracture under very small stresses. We report
on a series of molecular dynamics simulations of liquid Ga in contact with an
Al bicrystal. We identify the mechanism for liquid metal embrittlement, develop
a new model for it, and show that is in excellent agreement with both
simulation and experimental data
A core genetic module : the Mixed Feedback Loop
The so-called Mixed Feedback Loop (MFL) is a small two-gene network where
protein A regulates the transcription of protein B and the two proteins form a
heterodimer. It has been found to be statistically over-represented in
statistical analyses of gene and protein interaction databases and to lie at
the core of several computer-generated genetic networks. Here, we propose and
mathematically study a model of the MFL and show that, by itself, it can serve
both as a bistable switch and as a clock (an oscillator) depending on kinetic
parameters. The MFL phase diagram as well as a detailed description of the
nonlinear oscillation regime are presented and some biological examples are
discussed. The results emphasize the role of protein interactions in the
function of genetic modules and the usefulness of modelling RNA dynamics
explicitly.Comment: To be published in Physical Review
High-fidelity state detection and tomography of a single ion Zeeman qubit
We demonstrate high-fidelity Zeeman qubit state detection in a single trapped
88 Sr+ ion. Qubit readout is performed by shelving one of the qubit states to a
metastable level using a narrow linewidth diode laser at 674 nm followed by
state-selective fluorescence detection. The average fidelity reached for the
readout of the qubit state is 0.9989(1). We then measure the fidelity of state
tomography, averaged over all possible single-qubit states, which is 0.9979(2).
We also fully characterize the detection process using quantum process
tomography. This readout fidelity is compatible with recent estimates of the
detection error-threshold required for fault-tolerant computation, whereas
high-fidelity state tomography opens the way for high-precision quantum process
tomography
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