894 research outputs found
Study of state-of-the-art static inverter design Final report, 6 Jan. - 6 Jun. 1966
Multiple purpose inverter design based on phase demodulated inverter circuit selected from state-of-the-art assessment of ten inverter circuit
Sample size determination for at test given at value from a previous study: A FORTRAN 77 program
Experimental feedback control of quantum systems using weak measurements
A goal of the emerging field of quantum control is to develop methods for
quantum technologies to function robustly in the presence of noise. Central
issues are the fundamental limitations on the available information about
quantum systems and the disturbance they suffer in the process of measurement.
In the context of a simple quantum control scenario--the stabilization of
non-orthogonal states of a qubit against dephasing--we experimentally explore
the use of weak measurements in feedback control. We find that, despite the
intrinsic difficultly of implementing them, weak measurements allow us to
control the qubit better in practice than is even theoretically possible
without them. Our work shows that these more general quantum measurements can
play an important role for feedback control of quantum systems.Comment: 4 pages, 3 figures. v2 Added extra citation, journal reference and
DOI. Minor typographic correction
Thirty Meter Telescope Site Testing I: Overview
As part of the conceptual and preliminary design processes of the Thirty
Meter Telescope (TMT), the TMT site testing team has spent the last five years
measuring the atmospheric properties of five candidate mountains in North and
South America with an unprecedented array of instrumentation. The site testing
period was preceded by several years of analyses selecting the five candidates,
Cerros Tolar, Armazones and Tolonchar in northern Chile; San Pedro Martir in
Baja California, Mexico and the 13 North (13N) site on Mauna Kea, Hawaii. Site
testing was concluded by the selection of two remaining sites for further
consideration, Armazones and Mauna Kea 13N. It showed that all five candidates
are excellent sites for an extremely large astronomical observatory and that
none of the sites stands out as the obvious and only logical choice based on
its combined properties. This is the first article in a series discussing the
TMT site testing project.Comment: Accepted for publication in PASP, April 2009 issu
Determination of the Nature of the Tetragonal to Orthorhombic Phase Transition in SrFe_2As_2 by Measurement of the Local Order Parameter
SrFe2As2 is the end-member for a series of iron-pnictide superconductors and
has a tetragonal-to-orthorhombic phase transition near 200 K. Previous
macroscopic measurements to determine the nature of the transition gave
seemingly inconsistent results so we use electron microscopy to monitor the
local order parameter showing that the transformation is first order and that
the orthorhombic phase grows as needle domains. This suggests the transition
occurs via the passage of transformation dislocations, explaining the apparent
inconsistencies. This mechanism may be common to similar transitions.Comment: 4 pages, 4 figures submitted to Physical Review Letters.
Supplementary information can be found at
http://cook.msm.cam.ac.uk/~supp_info/ An extra sentence in the second last
paragraph and reference 16 has been adde
Detection of Orbital Fluctuations Above the Structural Transition Temperature in the Iron-Pnictides and Chalcogenides
We use point contact spectroscopy to probe () and . For we detect orbital
fluctuations above while for AE=Ca these fluctuations start below .
Co doping preserves the orbital fluctuations while K doping suppresses it. The
fluctuations are only seen at those dopings and temperatures where an in-plane
resistive anisotropy is known to exist. We predict an in-plane resistive
anisotropy of above . Our data are examined in light of
the recent work by W.-C. Lee and P. Phillips (arXiv:1110.5917v2). We also study
how joule heating in the PCS junctions impacts the spectra. Spectroscopic
information is only obtained from those PCS junctions that are free of heating
effects while those PCS junctions that are in the thermal regime display bulk
resistivity phenomenon.Comment: Accepted for publication in Physical Review
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