11,961 research outputs found
Fast Load Control with Stochastic Frequency Measurement
Matching demand with supply and regulating frequency
are key issues in power system operations. Flexibility
and local frequency measurement capability of loads offer new regulation mechanisms through load control. We present a
frequency-based fast load control scheme which aims to match
total demand with supply while minimizing the global end-use
disutility. Local frequency measurement enables loads to make decentralized decisions on their power from the estimates of total demand-supply mismatch. To resolve the errors in such estimates caused by stochastic frequency measurement errors, loads communicate via a neighborhood area network. Case studies show that the proposed load control can balance demand with supply and restore the frequency at the timescale faster than AGC, even when the loads use a highly simplified system model in their algorithms. Moreover, we discuss the tradeoff between communication and performance, and show with experiments that a moderate amount of communication significantly improves the performance
A sound card based multi-channel frequency measurement system
For physical processes which express themselves as a frequency, for example
magnetic field measurements using optically-pumped alkali-vapor magnetometers,
the precise extraction of the frequency from the noisy signal is a classical
problem. We describe herein a frequency measurement system based on an
inexpensive commercially available computer sound card coupled with a software
single-tone estimator which reaches Cram\'er--Rao limited performance, a
feature which commercial frequency counters often lack. Characterization of the
system and examples of its successful application to magnetometry are
presented.Comment: 4 pages, 3 figures, 1 tabl
Absolute Frequency Measurement of Rubidium 5S-7S Two-Photon Transitions
We report the absolute frequency measurements of rubidium 5S-7S two-photon
transitions with a cw laser digitally locked to an atomic transition and
referenced to an optical frequency comb. The narrow, two-photon transition,
5S-7S (760 nm) insensitive to first order in a magnetic field, is a promising
candidate for frequency reference. The performed tests yield the transition
frequency with accuracy better than reported previously.Comment: This paper was published in Optics Letters and is made available as
an electronic reprint with the permission of OSA. The paper can be found at
http://dx.doi.org/10.1364/OL.38.004581. Systematic or multiple reproduction
or distribution to multiple locations via electronic or other means is
prohibited and is subject to penalties under la
Absolute frequency measurement of the 1S0 - 3P0 transition of 171Yb
We report the absolute frequency measurement of the unperturbed transition
1S0 - 3P0 at 578 nm in 171Yb realized in an optical lattice frequency standard.
The absolute frequency is measured 518 295 836 590 863.55(28) Hz relative to a
cryogenic caesium fountain with a fractional uncertainty of 5.4x10-16 . This
value is in agreement with the ytterbium frequency recommended as a secondary
representation of the second in the International System of Units.Comment: This is an author-created, un-copyedited version of an article
accepted for publication/published in Metrologia. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The Version of Record is available online at
http://dx.doi.org/10.1088/1681-7575/aa4e62. It is published under a CC BY
licenc
Experimental determination of liquid oscillation frequency in an inclined right circular cylinder
Liquid oscillation frequency measurement in inclined right circular cylinde
Relativistic general-order coupled-cluster method for high-precision calculations: Application to Al+ atomic clock
We report the implementation of a general-order relativistic coupled-cluster
method for performing high-precision calculations of atomic and molecular
properties. As a first application, the static dipole polarizabilities of the
ground and first excited states of Al+ have been determined to precisely
estimate the uncertainty associated with the BBR shift of its clock frequency
measurement. The obtained relative BBR shift is -3.66+-0.44 for the 3s^2
^1S_0^0 --> 3s3p ^3P_0^0 transition in Al+ in contrast to the value obtained in
the latest clock frequency measurement, -9+-3 [Phys. Rev. Lett. 104, 070802
(2010)]. The method developed in the present work can be employed to study a
variety of subtle effects such as fundamental symmetry violations in atoms.Comment: 4 pages, 3 tables, submitte
- …