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A conceptual design tool: Sketch and fuzzy logic based system
A real time sketch and fuzzy logic based prototype system for conceptual design has been developed. This system comprises four phases. In the first one, the system accepts the input of on-line free-hand sketches, and segments them into meaningful parts by using fuzzy knowledge to detect corners and inflection points on the sketched curves. The fuzzy knowledge is applied to capture user’s drawing intention in terms of sketching position, direction, speed and acceleration. During the second phase, each segmented sub-part (curve) can be classified and identified as one of the following 2D primitives: straight lines, circles, circular arcs, ellipses, elliptical arcs or B-spline curves. Then, 2D topology information (connectivity, unitary constraints and pairwise constraints) is extracted dynamically from the identified 2D primitives. From the extracted information, a more accurate 2D geometry can be built up by a 2D geometric constraint solver. The 2D topology and geometry information is then employed to further interpretation of a 3D geometry. The system can not only accept sketched input, but also users’ interactive input of 2D and 3D primitives.
This makes it friendly and easier to use, in comparison with ‘sketched input only’, or ‘interactive input only’ systems.
Finally, examples are given to illustrate the system
Topological Censorship
All three-manifolds are known to occur as Cauchy surfaces of asymptotically
flat vacuum spacetimes and of spacetimes with positive-energy sources. We prove
here the conjecture that general relativity does not allow an observer to probe
the topology of spacetime: any topological structure collapses too quickly to
allow light to traverse it. More precisely, in a globally hyperbolic,
asymptotically flat spacetime satisfying the null energy condition, every
causal curve from \scri^- to {\scri}^+ is homotopic to a topologically
trivial curve from \scri^- to {\scri}^+. (If the Poincar\'e conjecture is
false, the theorem does not prevent one from probing fake 3-spheres).Comment: 12 pages, REVTEX; 1 postscript figure in a separate uuencoded file.
Our earlier version (PRL 71, 1486 (1993)) contained a secondary result,
mistakenly attributed to Schoen and Yau, regarding ``passive topological
censorship'' of a certain class of topologies. As Gregory Burnett has pointed
out (gr-qc/9504012), this secondary result is false. The main topological
censorship theorem is unaffected by the erro
Direct Search for Dark Matter - Striking the Balance - and the Future
Weakly Interacting Massive Particles (WIMPs) are among the main candidates
for the relic dark matter (DM). The idea of the direct DM detection relies on
elastic spin-dependent (SD) and spin-independent (SI) interaction of WIMPs with
target nuclei. In this review paper the relevant formulae for WIMP event rate
calculations are collected. For estimations of the WIMP-proton and WIMP-neutron
SD and SI cross sections the effective low-energy minimal supersymmetric
standard model is used. The traditional one-coupling-dominance approach for
evaluation of the exclusion curves is described. Further, the mixed spin-scalar
coupling approach is discussed. It is demonstrated, taking the high-spin Ge-73
dark matter experiment HDMS as an example, how one can drastically improve the
sensitivity of the exclusion curves within the mixed spin-scalar coupling
approach, as well as due to a new procedure of background subtraction from the
measured spectrum. A general discussion on the information obtained from
exclusion curves is given. The necessity of clear WIMP direct detection
signatures for a solution of the dark matter problem, is pointed out.Comment: LaTeX, 49 pages, 14 figures, 185 reference
Photometric type Ia supernova surveys in narrow band filters
We study the characteristics of a narrow band type Ia supernova survey
through simulations based on the upcoming Javalambre Physics of the
accelerating universe Astrophysical Survey (J-PAS). This unique survey has the
capabilities of obtaining distances, redshifts, and the SN type from a single
experiment thereby circumventing the challenges faced by the resource-intensive
spectroscopic follow-up observations. We analyse the flux measurements
signal-to-noise ratio and bias, the supernova typing performance, the ability
to recover light curve parameters given by the SALT2 model, the photometric
redshift precision from type Ia supernova light curves and the effects of
systematic errors on the data. We show that such a survey is not only feasible
but may yield large type Ia supernova samples (up to 250 supernovae at
per month of search) with low core collapse contamination ( per
cent), good precision on the SALT2 parameters (average ,
and ) and on the distance modulus (average
, assuming an intrinsic scatter
), with identified systematic uncertainties
. Moreover, the
filters are narrow enough to detect most spectral features and obtain excellent
photometric redshift precision of , apart from 2 per
cent of outliers. We also present a few strategies for optimising the survey's
outcome. Together with the detailed host galaxy information, narrow band
surveys can be very valuable for the study of supernova rates, spectral feature
relations, intrinsic colour variations and correlations between supernova and
host galaxy properties, all of which are important information for supernova
cosmological applications.Comment: 20 pages, 12 tables and 26 figures. Version accepted by MNRAS, with
results slightly different from previous on
Detection of Small-Scale Granular Structures in the Quiet Sun with the New Solar Telescope
Results of a statistical analysis of solar granulation are presented. A data
set of 36 images of a quiet Sun area on the solar disk center was used. The
data were obtained with the 1.6 m clear aperture New Solar Telescope (NST) at
Big Bear Solar Observatory (BBSO) and with a broad-band filter centered at the
TiO (705.7 nm) spectral line. The very high spatial resolution of the data
(diffraction limit of 77 km and pixel scale of 0.0375) augmented by the very
high image contrast (15.50.6%) allowed us to detect for the first time a
distinct subpopulation of mini-granular structures. These structures are
dominant on spatial scales below 600 km. Their size is distributed as a power
law with an index of -1.8 (which is close to the Kolmogorov's -5/3 law) and no
predominant scale. The regular granules display a Gaussian (normal) size
distribution with a mean diameter of 1050 km. Mini-granular structures
contribute significantly to the total granular area. They are predominantly
confined to the wide dark lanes between regular granules and often form chains
and clusters, but different from magnetic bright points. A multi-fractality
test reveals that the structures smaller than 600 km represent a multi-fractal,
whereas on larger scales the granulation pattern shows no multi-fractality and
can be considered as a Gaussian random field. The origin, properties and role
of the newly discovered population of mini-granular structures in the solar
magneto-convection are yet to be explored.Comment: 13 pages, 5 figure
Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
We present the discovery of a new, peculiar form of double-periodic pulsation
in RR Lyrae stars. In four, long-period ( d) stars observed by the
Optical Gravitational Lensing Experiment, and classified as fundamental mode
pulsators (RRab), we detect additional, low-amplitude variability, with period
shorter than fundamental mode period. The period ratios fall in a range similar
to double-mode fundamental and first overtone RR Lyrae stars (RRd), with the
exception of one star, in which the period ratio is significantly lower and
nearly exactly equals 0.7. Although period ratios are fairly different for the
four stars, the light curve shapes corresponding to the dominant, fundamental
mode are very similar. The peak-to-peak amplitudes and amplitude ratios
(Fourier parameters and ) are among the highest observed in
RRab stars of similar period, while Fourier phases ( and
) are among the lowest observed in RRab stars.
If the additional variability is interpreted as due to radial first overtone,
then, the four stars are the most extreme RRd variables of the longest
pulsation periods known. Indeed, the observed period ratios can be well
modelled with high metallicity pulsation models. However, at such long
pulsation periods, first overtone is typically damped.
Five other candidates, with weak signature of additional variability, sharing
the same characteristics, were also detected and are briefly discussed.Comment: Accepted for publication in MNRA
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