963 research outputs found
Bootstrapping Color Constancy
Bootstrapping provides a novel approach to training a neural network to estimate the chromaticity of the illuminant in a scene given image data alone. For initial training, the network requires feedback about the accuracy of the network’s current results. In the case of a network for color constancy, this feedback is the chromaticity of the incident scene illumination. In the past1, perfect feedback has been used, but in the bootstrapping method feedback with a considerable degree of random error can be used to train the network instead. In particular, the grayworld algorithm2, which only provides modest color constancy performance, is used to train a neural network which in the end performs better than the grayworld algorithm used to train it
Ongoing Emergence: A Core Concept in Epigenetic Robotics
We propose ongoing emergence as a core concept in
epigenetic robotics. Ongoing emergence refers to the
continuous development and integration of new skills
and is exhibited when six criteria are satisfied: (1)
continuous skill acquisition, (2) incorporation of new
skills with existing skills, (3) autonomous development
of values and goals, (4) bootstrapping of initial skills, (5)
stability of skills, and (6) reproducibility. In this paper
we: (a) provide a conceptual synthesis of ongoing
emergence based on previous theorizing, (b) review
current research in epigenetic robotics in light of ongoing
emergence, (c) provide prototypical examples of ongoing
emergence from infant development, and (d) outline
computational issues relevant to creating robots
exhibiting ongoing emergence
Ridge Regression Approach to Color Constancy
This thesis presents the work on color constancy and its application in the field of computer vision. Color constancy is a phenomena of representing (visualizing) the reflectance properties of the scene independent of the illumination spectrum. The motivation behind this work is two folds:The primary motivation is to seek ‘consistency and stability’ in color reproduction and algorithm performance respectively because color is used as one of the important features in many computer vision applications; therefore consistency of the color features is essential for high application success. Second motivation is to reduce ‘computational complexity’ without sacrificing the primary motivation.This work presents machine learning approach to color constancy. An empirical model is developed from the training data. Neural network and support vector machine are two prominent nonlinear learning theories. The work on support vector machine based color constancy shows its superior performance over neural networks based color constancy in terms of stability. But support vector machine is time consuming method. Alternative approach to support vectormachine, is a simple, fast and analytically solvable linear modeling technique known as ‘Ridge regression’. It learns the dependency between the surface reflectance and illumination from a presented training sample of data. Ridge regression provides answer to the two fold motivation behind this work, i.e., stable and computationally simple approach. The proposed algorithms, ‘Support vector machine’ and ‘Ridge regression’ involves three step processes: First, an input matrix constructed from the preprocessed training data set is trained toobtain a trained model. Second, test images are presented to the trained model to obtain the chromaticity estimate of the illuminants present in the testing images. Finally, linear diagonal transformation is performed to obtain the color corrected image. The results show the effectiveness of the proposed algorithms on both calibrated and uncalibrated data set in comparison to the methods discussed in literature review. Finally, thesis concludes with a complete discussion and summary on comparison between the proposed approaches and other algorithms
Emerging Linguistic Functions in Early Infancy
This paper presents results from experimental
studies on early language acquisition in infants and
attempts to interpret the experimental results within
the framework of the Ecological Theory of
Language Acquisition (ETLA) recently proposed
by (Lacerda et al., 2004a). From this perspective,
the infant’s first steps in the acquisition of the
ambient language are seen as a consequence of the
infant’s general capacity to represent sensory input
and the infant’s interaction with other actors in its
immediate ecological environment. On the basis of
available experimental evidence, it will be argued
that ETLA offers a productive alternative to
traditional descriptive views of the language
acquisition process by presenting an operative
model of how early linguistic function may emerge
through interaction
Deep CCD Surface Photometry of the Edge-On Spiral NGC 4244
We have obtained deep surface photometry of the edge-on spiral galaxy NGC
4244. Our data reliably reach 27.5 R magnitude arcsec^{-2}, a significant
improvement on our earlier deep CCD surface photometry of other galaxies. NGC
4244 is a nearby Scd galaxy whose total luminosity is approximately one
magnitude fainter than the peak of the Sc luminosity function. We find that it
has a simple structure: a single exponential disk, with a scale height h_Z =
246 +/- 2 pc, a scale length h_R = 1.84 +/- 0.02 kpc and a disk cutoff at a
radius R(max) = 10.0 kpc (5.4 scale lengths). We confirm a strong cutoff in the
stellar disk at R(max), which happens over only 1 kpc. We do not see any
statistically significant evidence for disk flaring with radius. Unlike the
more luminous Sc galaxies NGC 5907 and M 33, NGC 4244 does not show any
evidence for a second component, such as a thick disk or halo, at mu(R) < 27.5
magnitude arcsec^{-2}.Comment: 36 pages, including 12 figures; accepted for publication in Sept 99
A
The star formation history of mass-selected galaxies in the COSMOS field
We explore the evolution of the specific star formation rate (SSFR) for
3.6um-selected galaxies of different M_* in the COSMOS field. The average SFR
for sub-sets of these galaxies is estimated with stacked 1.4GHz radio continuum
emission. We separately consider the total sample and a subset of galaxies (SF)
that shows evidence for substantive recent star formation in the rest-frame
optical SED. At 0.2<z<3 both populations show a strong and M_*-independent
decrease in their SSFR towards z=0.2, best described by a power- law (1+z)^n,
where n~4.3 for all galaxies and n~3.5 for SF sources. The decrease appears to
have started at z>2, at least above 4x10^10M_Sun where our conclusions are most
robust. We find a tight correlation with power-law dependence, SSFR (M_*)^beta,
between SSFR and M_* at all z. It tends to flatten below ~10^10M_Sun if
quiescent galaxies are included; if they are excluded a shallow index beta_SFG
-0.4 fits the correlation. On average, higher M_* objects always have lower
SSFRs, also among SF galaxies. At z>1.5 there is tentative evidence for an
upper SSFR-limit that an average galaxy cannot exceed. It is suggested by a
flattening of the SSFR-M_* relation (also for SF sources), but affects massive
(>10^10M_Sun) galaxies only at the highest z. Below z=1.5 there thus is no
direct evidence that galaxies of higher M_* experience a more rapid waning of
their SSFR than lower M_* SF systems. In this sense, the data rule out any
strong 'downsizing'. We combine our results with recent measurements of the
galaxy (stellar) mass function in order to determine the characteristic mass of
a SF galaxy (M_*=10^(10.6\pm0.4)M_Sun). In this sense, too, there is no
'downsizing'. Our analysis constitutes the most extensive SFR density
determination with a single technique to z=3. Recent Herschel results are
consistent with our results, but rely on far smaller samples.Comment: 37 pages, 14 figures, 7 tables; accepted for publication in the
Astrophysical Journal; High resolution versions of all figures available at
www.mpia-hd.mpg.de/homes/karim/research.htm
Is there a general trait of susceptibility to simultaneous contrast?
Individuals differ in their susceptibility to simultaneous contrast. Are the underlying differences in neural machinery conserved across different stimulus dimensions? We measured the extent to which 101 subjects perceived simultaneous contrast on the dimensions of luminance, colour, luminance contrast, colour contrast, orientation, spatial frequency, motion and numerosity. Individual differences showed re-test reliability for each dimension (0.32ICC(c,1)0.78, p0.05), but susceptibility to simultaneous contrast, with a few exceptions, was not correlated across dimensions. Either susceptibility to contrast arises empirically from an individual's interactions with the environment, or it is genetically determined but independently for different dimensions
Estimating Illumination Chromaticity via Support Vector Regression
The technique of support vector regression is applied to the problem of estimating the chromaticity of the light illuminating a scene from a color histogram of an image of the scene. Illumination estimation is fundamental to white balancing digital color images and to understanding human color constancy. Under controlled experimental conditions, the support vector method is shown to perform better than the neural network and color by correlation methods
Discovery of Rotational Braking in the Magnetic Helium-Strong Star Sigma Orionis E
We present new U-band photometry of the magnetic Helium-strong star Sigma Ori
E, obtained over 2004-2009 using the SMARTS 0.9-m telescope at Cerro Tololo
Inter-American Observatory. When combined with historical measurements, these
data constrain the evolution of the star's 1.19 d rotation period over the past
three decades. We are able to rule out a constant period at the p_null = 0.05%
level, and instead find that the data are well described (p_null = 99.3%) by a
period increasing linearly at a rate of 77 ms per year. This corresponds to a
characteristic spin-down time of 1.34 Myr, in good agreement with theoretical
predictions based on magnetohydrodynamical simulations of angular momentum loss
from magnetic massive stars. We therefore conclude that the observations are
consistent with Sigma Ori E undergoing rotational braking due to its magnetized
line-driven wind.Comment: 6 pages, 3 figures, accepted by ApJ Letters, typos correcte
Detection of a supernova signature associated with GRB 011121
Using observations from an extensive monitoring campaign with the Hubble
Space Telescope we present the detection of an intermediate-time flux excess
which is redder in color relative to the afterglow of GRB 011121, currently
distinguished as the gamma-ray burst with the lowest known redshift. The red
``bump,'' which exhibits a spectral roll-over at ~7200 Angstrom, is well
described by a redshifted Type Ic supernova that occurred approximately at the
same time as the gamma-ray burst event. The inferred luminosity is about half
that of the bright supernova 1998bw. These results serve as compelling evidence
for a massive star origin of long-duration gamma-ray bursts. Models that posit
a supernova explosion weeks to months preceding the gamma-ray burst event are
excluded by these observations. Finally, we discuss the relationship between
spherical core-collapse supernovae and gamma-ray bursts.Comment: Published in the Astrophysical Journal (Letters) on 20 May 2002.
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