40,765 research outputs found
Living in the Milky Way
It’s finally here. Today, June 20 at 6:34 p.m., is the the summer solstice, also known as the first day of summer and, confusingly enough, midsummer’s eve. From a scientific perspective, it marks the moment the sun reaches its northernmost point in our sky. As a result of that position, it’s the shortest night and longest day if you live north of the equator. [excerpt
Very Large Spectroscopic Surveys with the VLT
Recently, it has been recognised that very large spectroscopic surveys
(several million spectra) are required to advance our understanding of Dark
Energy (via baryonic wiggles) and the detailed history of our Local Group of
galaxies (via Galactic Archeology or near-field cosmology). In this paper I
make a preliminary exploration of how this might be done by putting a wide
field, optical, prime-focus fibre-fed spectroscopic facility on one of the
VLT's UTs.Comment: 6 pages. To be published in the proceedings "Science with the VLT in
the ELT era
Quantum Popov robust stability analysis of an optical cavity containing a saturated Kerr medium
This paper applies results on the robust stability of nonlinear quantum
systems to a system consisting an optical cavity containing a saturated Kerr
medium. The system is characterized by a Hamiltonian operator which contains a
non-quadratic term involving a quartic function of the annihilation and
creation operators. A saturated version of the Kerr nonlinearity leads to a
sector bounded nonlinearity which enables a quantum small gain theorem to be
applied to this system in order to analyze its stability. Also, a non-quadratic
version of a quantum Popov stability criterion is presented and applied to
analyze the stability of this system.Comment: A shortened version will appear in the Proceedings of the 2013
European Control Conferenc
Quantum Robust Stability of a Small Josephson Junction in a Resonant Cavity
This paper applies recent results on the robust stability of nonlinear
quantum systems to the case of a Josephson junction in a resonant cavity. The
Josephson junction is characterized by a Hamiltonian operator which contains a
non-quadratic term involving a cosine function. This leads to a sector bounded
nonlinearity which enables the previously developed theory to be applied to
this system in order to analyze its stability.Comment: A version of this paper appeared in the proceedings of the 2012 IEEE
Multi-conference on Systems and Contro
Education in Nazi Germany
This essay investigates the sweeping educational reforms that the Nazi government implemented to use elementary education to further its political goals. Along with the major laws concerned, it concentrates on several personal accounts of families and students during this era to better understand how these educational reforms affected Germans. Additionally, it analyzes the Hitler Youth and other such recreational organizations that the Nazis created to continue to mold students’ ideologies. It examines the stories of several people who were children in these organizations and what their impressions were of the groups. Finally, it places these Nazi reforms in the context of the post-1945 period of denazification and reconstruction
Input Design for System Identification via Convex Relaxation
This paper proposes a new framework for the optimization of excitation inputs
for system identification. The optimization problem considered is to maximize a
reduced Fisher information matrix in any of the classical D-, E-, or A-optimal
senses. In contrast to the majority of published work on this topic, we
consider the problem in the time domain and subject to constraints on the
amplitude of the input signal. This optimization problem is nonconvex. The main
result of the paper is a convex relaxation that gives an upper bound accurate
to within of the true maximum. A randomized algorithm is presented for
finding a feasible solution which, in a certain sense is expected to be at
least as informative as the globally optimal input signal. In the case
of a single constraint on input power, the proposed approach recovers the true
global optimum exactly. Extensions to situations with both power and amplitude
constraints on both inputs and outputs are given. A simple simulation example
illustrates the technique.Comment: Preprint submitted for journal publication, extended version of a
paper at 2010 IEEE Conference on Decision and Contro
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