104,652 research outputs found
Progressive surface modeling scheme from unorganised curves
This paper presents a novel surface modelling scheme to construct a freeform surface
progressively from unorganised curves representing the boundary and interior characteristic curves.
The approach can construct a base surface model from four ordinary or composite boundary curves
and support incremental surface updating from interior characteristic curves, some of which may not
be on the final surface. The base surface is first constructed as a regular Coons surface and upon receiving an interior curve sketch, it is then updated. With this progressive modelling scheme, a final
surface with multiple sub-surfaces can be obtained from a set of unorganised curves and transferred
to commercial surface modelling software for detailed modification. The approach has been tested
with examples based on 3D motion sketches; it is capable of dealing with unorganised design curves
for surface modelling in conceptual design. Its limitations have been discussed
Unsupervised Learning of Complex Articulated Kinematic Structures combining Motion and Skeleton Information
In this paper we present a novel framework for unsupervised kinematic structure learning of complex articulated objects from a single-view image sequence. In contrast to prior motion information based methods, which estimate relatively simple articulations, our method can generate arbitrarily complex kinematic structures with skeletal topology by a successive iterative merge process. The iterative merge process is guided by a skeleton distance function which is generated from a novel object boundary generation method from sparse points. Our main contributions can be summarised as follows: (i) Unsupervised complex articulated kinematic structure learning by combining motion and skeleton information. (ii) Iterative fine-to-coarse merging strategy for adaptive motion segmentation and structure smoothing. (iii) Skeleton estimation from sparse feature points. (iv) A new highly articulated object dataset containing multi-stage complexity with ground truth. Our experiments show that the proposed method out-performs state-of-the-art methods both quantitatively and qualitatively
A Symplectic Integrator for Hill's Equations
Hill's equations are an approximation that is useful in a number of areas of
astrophysics including planetary rings and planetesimal disks. We derive a
symplectic method for integrating Hill's equations based on a generalized
leapfrog. This method is implemented in the parallel N-body code, PKDGRAV and
tested on some simple orbits. The method demonstrates a lack of secular changes
in orbital elements, making it a very useful technique for integrating Hill's
equations over many dynamical times. Furthermore, the method allows for
efficient collision searching using linear extrapolation of particle positions.Comment: 15 pages, 2 figures; minor revisions; accepted for publication in the
Astronomical Journa
Non-destructive cavity QED probe of Bloch oscillations in a gas of ultracold atoms
We describe a scheme for probing a gas of ultracold atoms trapped in an
optical lattice and moving in the presence of an external potential. The probe
is non-destructive and uses the existing lattice fields as the measurement
device. Two counter-propagating cavity fields simultaneously set up a
conservative lattice potential and a weak quantum probe of the atomic motion.
Balanced heterodyne detection of the probe field at the cavity output along
with integration in time and across the atomic cloud yield information about
the atomic dynamics in a single run. The scheme is applied to a measurement of
the Bloch oscillation frequency for atoms moving in the presence of the local
gravitational potential. Signal-to-noise ratios are estimated to be as high as
.Comment: 8 pages, 6 figures, submitted to Phys. Rev.
Microwave apparatus for gravitational waves observation
In this report the theoretical and experimental activities for the
development of superconducting microwave cavities for the detection of
gravitational waves are presented.Comment: 42 pages, 28 figure
Simulations of driven overdamped frictionless hard spheres
We introduce an event-driven simulation scheme for overdamped dynamics of
frictionless hard spheres subjected to external forces, neglecting hydrodynamic
interactions. Our event-driven approach is based on an exact equation of motion
which relates the driving force to the resulting velocities through the
geometric information characterizing the underlying network of contacts between
the hard spheres. Our method allows for a robust extraction of the
instantaneous coordination of the particles as well as contact force statistics
and dynamics, under any chosen driving force, in addition to shear flow and
compression. It can also be used for generating high-precision jammed packings
under shear, compression, or both. We present a number of additional
applications of our method.Comment: 12 pages, 9 figure
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