12,811 research outputs found
Observation of enhanced optical spring damping in a macroscopic mechanical resonator and application for parametric instability control in advanced gravitational-wave detectors
We show that optical spring damping in an optomechanical resonator can be enhanced by injecting a phase delay in the laser frequency-locking servo to rotate the real and imaginary components of the optical spring constant. This enhances damping at the expense of optical rigidity. We demonstrate enhanced parametric damping which reduces the Q factor of a 0.1-kg-scale resonator from 1.3×10^5 to 6.5×10^3. By using this technique adequate optical spring damping can be obtained to damp parametric instability predicted for advanced laser interferometer gravitational-wave detectors
Properties of a highly birefringent photonic crystal fiber
Author name used in this publication: J. JuAuthor name used in this publication: W. JinAuthor name used in this publication: M. S. Demokan2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Design of single-polarization single-mode photonic crystal fiber at 1.30 and 1.55 µm
Author name used in this publication: M. Suleyman Demokan2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Two-mode operation in highly birefringent photonic crystal fiber
Author name used in this publication: J. JuAuthor name used in this publication: W. JinAuthor name used in this publication: M. S. Demokan2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
The Impacts of Climate Change on Chinese Agriculture - Phase II National Level Study final report
Active motions of Brownian particles in a generalized energy-depot model
We present a generalized energy-depot model in which the conversion rate of
the internal energy into motion can be dependent on the position and the
velocity of a particle. When the conversion rate is a general function of the
velocity, the active particle exhibits diverse patterns of motion including a
braking mechanism and a stepping motion. The phase trajectories of the motion
are investigated in a systematic way. With a particular form of the conversion
rate dependent on the position and velocity, the particle shows a spontaneous
oscillation characterizing a negative stiffness. These types of active
behaviors are compared with the similar phenomena observed in biology such as
the stepping motion of molecular motors and the amplification in hearing
mechanism. Hence, our model can provide a generic understanding of the active
motion related to the energy conversion and also a new control mechanism for
nano-robots. We also investigate the noise effect, especially on the stepping
motion and observe the random walk-like behavior as expected.Comment: to appear in New J. Phy
Temperature sensitivity of a two-mode photonic crystal fiber interferometric sensor
Author name used in this publication: M. S. Demokan2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Approximate Minimum Diameter
We study the minimum diameter problem for a set of inexact points. By
inexact, we mean that the precise location of the points is not known. Instead,
the location of each point is restricted to a contineus region (\impre model)
or a finite set of points (\indec model). Given a set of inexact points in
one of \impre or \indec models, we wish to provide a lower-bound on the
diameter of the real points.
In the first part of the paper, we focus on \indec model. We present an
time
approximation algorithm of factor for finding minimum diameter
of a set of points in dimensions. This improves the previously proposed
algorithms for this problem substantially.
Next, we consider the problem in \impre model. In -dimensional space, we
propose a polynomial time -approximation algorithm. In addition, for
, we define the notion of -separability and use our algorithm for
\indec model to obtain -approximation algorithm for a set of
-separable regions in time
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