2,083 research outputs found
Trajectory Synthesis for Fisher Information Maximization
Estimation of model parameters in a dynamic system can be significantly
improved with the choice of experimental trajectory. For general, nonlinear
dynamic systems, finding globally "best" trajectories is typically not
feasible; however, given an initial estimate of the model parameters and an
initial trajectory, we present a continuous-time optimization method that
produces a locally optimal trajectory for parameter estimation in the presence
of measurement noise. The optimization algorithm is formulated to find system
trajectories that improve a norm on the Fisher information matrix. A
double-pendulum cart apparatus is used to numerically and experimentally
validate this technique. In simulation, the optimized trajectory increases the
minimum eigenvalue of the Fisher information matrix by three orders of
magnitude compared to the initial trajectory. Experimental results show that
this optimized trajectory translates to an order of magnitude improvement in
the parameter estimate error in practice.Comment: 12 page
A Calibrated Time Domain Envelope Measurement System for the Behavioral Modeling of Power Amplifiers
This paper presents a set-up which enables the generation and the calibrated time domain measurements of complex envelopes of modulated signals at both ports of non linear microwave power amplifiers. The architecture of the characterization tool is given. Examples of error corrected time domain envelopes at the input / output RF ports of a 36 dBm output power â 30dB power gain L-band SSPA are shown. Futhermore, the use of this characterization tool and a suitable processing of measurement data are applied to a novel measurement based behavioral modeling approach of non linear devices accounting for memory effects
Investigating correlates of self-regulation in early childhood with a representative sample of English-speaking American families
Children who possess less self-regulatory skill are at a disadvantage when compared to children who demonstrate greater skill at regulating their emotions, cognitions and behavior. Children with these regulatory deficits have difficulty connecting with peers, generating relationships with teachers, negotiating their social world, and succeeding academically. By understanding the correlates of self-regulatory abilities, interventions can be developed to ensure that children at-risk for poor self-regulation receive the support necessary to enhance their regulatory skills. Using data from a nationally representative survey of English-speaking American parents with children between the ages of two and eight (n = 1,141), we evaluated a host of demographic and parenting variables to isolate the correlates of self-regulation. Older children were found to have fewer regulatory problems than younger children while children from low-income homes and male children were found to have greater problems with self-regulation. Minority status, household composition (single vs multi-parent), and parental education were not significant correlates of self-regulation. Findings also illustrate the powerful relationship between parenting style and self-regulation. Parents who rely on nurturing parenting practices that reinforce the childâs sense of autonomy while still maintaining a consistent parenting presence (i.e., authoritative parenting) have children who demonstrate stronger self-regulatory skills. Parents who exert an excess of parental control (i.e., authoritarian parents) have children with weaker self-regulatory skills. And lastly, parents who have notable absence of control (i.e., permissive parents) are more likely to have children with considerable regulatory deficits. Results offer implications for both practitioners and scholars
Limit on the Temporal Variation of the Fine-Structure Constant Using Atomic Dysprosium
Over a period of eight months, we have monitored transition frequencies
between nearly degenerate, opposite-parity levels in two isotopes of atomic
dysprosium (Dy). These transition frequencies are highly sensitive to temporal
variation of the fine-structure constant () due to relativistic
corrections of large and opposite sign for the opposite-parity levels. In this
unique system, in contrast to atomic-clock comparisons, the difference of the
electronic energies of the opposite-parity levels can be monitored directly
utilizing a radio-frequency (rf) electric-dipole transition between them. Our
measurements show that the frequency variation of the 3.1-MHz transition in
Dy and the 235-MHz transition in Dy are 9.06.7 Hz/yr and
-0.66.5 Hz/yr, respectively. These results provide a value for the rate of
fractional variation of of yr (1
) without any assumptions on the constancy of other fundamental
constants, indicating absence of significant variation at the present level of
sensitivity.Comment: 4 pages, 2 figure
Filling the gaps in the genomic landscape
Sequencing of genomes from many different bacterial and archaeal groups is broadening the picture of the prokaryotic pan-genome
Magnetic-dipole transition probabilities in B-like and Be-like ions
The magnetic-dipole transition probabilities between the fine-structure
levels (1s^2 2s^2 2p) ^2P_1/2 - ^2P_3/2 for B-like ions and (1s^2 2s 2p) ^3P_1
- ^3P_2 for Be-like ions are calculated. The configuration-interaction method
in the Dirac-Fock-Sturm basis is employed for the evaluation of the
interelectronic-interaction correction with negative-continuum spectrum being
taken into account. The 1/Z interelectronic-interaction contribution is derived
within a rigorous QED approach employing the two-time Green function method.
The one-electron QED correction is evaluated within framework of the anomalous
magnetic-moment approximation. A comparison with the theoretical results of
other authors and with available experimental data is presented
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