146 research outputs found
Explicit Computation of Input Weights in Extreme Learning Machines
We present a closed form expression for initializing the input weights in a
multi-layer perceptron, which can be used as the first step in synthesis of an
Extreme Learning Ma-chine. The expression is based on the standard function for
a separating hyperplane as computed in multilayer perceptrons and linear
Support Vector Machines; that is, as a linear combination of input data
samples. In the absence of supervised training for the input weights, random
linear combinations of training data samples are used to project the input data
to a higher dimensional hidden layer. The hidden layer weights are solved in
the standard ELM fashion by computing the pseudoinverse of the hidden layer
outputs and multiplying by the desired output values. All weights for this
method can be computed in a single pass, and the resulting networks are more
accurate and more consistent on some standard problems than regular ELM
networks of the same size.Comment: In submission for the ELM 2014 Conferenc
Broadband Photometry of 105 Giant Arcs: Redshift Constraints and Implications for Giant Arc Statistics
We measure the photometric properties of 105 giant arcs that were identified
in systematic searches for galaxy-cluster-scale strong lenses in the Second
Red-Sequence Cluster Survey (RCS-2) and the Sloan Digital Sky Survey (SDSS).
The cluster lenses span 0.2 < z_lens < 1.2 in redshift, with a median z_lens =
0.58. Using broadband color criteria we sort the entire arc sample into
redshift bins based on u-g and g-r colors, and also r-z colors for the ~90% of
arcs that have z-band data. This analysis yields broad redshift constraints
with 71 +5 -4 % of the arcs at z > 1.0, 64 +6 -4 % at z > 1.4, 56 +5 -4 % at z
> 1.9, and 21 +4 -2 % at z > 2.7. The remaining 29 +3 -5 % have z < 1. The
inferred median redshift is z_s = 2.0 +/- 0.1, in good agreement with a
previous determination from a smaller sample of brighter arcs (g < 22.5). This
agreement confirms that z_s = 2.0 +/- 0.1 is the typical redshift for giant
arcs with g < 24 that are produced by cluster-scale strong lenses, and that
there is no evidence for strong evolution in the redshift distribution of arcs
over a wide range of g-band magnitudes (20 < g < 24). Establishing that half of
all giant arcs are at z > 2 contributes significantly toward relieving the
tension between the number of arcs observed and the number expected in a
Lambda-CDM cosmology, but there is considerable evidence to suggest that a
discrepancy persists. Additionally, this work confirms that forthcoming large
samples of giant arcs will supply the observational community with many
magnified galaxies at z > 2.Comment: 16 pages, 8 figures, 3 tables, Accepted to ApJ; University of Chicago
Department of Astronomy & Astrophysics PhD Thesi
Shapes and Alignments of Galaxy Cluster Halos
We present distribution functions and spatial correlations of the shapes of
dark matter halos derived from Hubble Volume simulations of a LambdaCDM
universe. We measure both position and velocity shapes within spheres
encompassing mean density 200 times the critical value, and calibrate small-N
systematic errors using Poisson realizations of isothermal spheres and higher
resolution simulations. For halos more massive than 3x10^{14} Msun/h, the shape
distribution function peaks at (minor/major, intermediate/major) axial ratios
of (0.64,0.76) in position, and is rounder in velocity, peaking at (0.72,0.82).
Halo shapes are rounder at lower mass and/or redshift; the mean minor axis
ratio in position follows (M,z) = c_{15,0} [1-\alpha\ln(M/10^{15}Msun/h)]
(1+z)^{-\epsilon}, with c_{15,0}=0.631 \pm 0.001, \alpha=0.023 \pm 0.002 and
\epsilon=0.086 \pm 0.004. Position and velocity principal axes are well aligned
in direction, with median alignment angle , and the axial ratios in
these spaces are correlated in magnitude. We investigate mark correlations of
halo pair orientations using two measures: a simple scalar product shows alignment extending to 30 \hinv \mpc while a filamentary statistic
exhibits non-random alignment extending to scales \sims 200 \hinv \mpc, ten
times the sample two-point correlation length and well into the regime of
negative two-point correlation. Cluster shapes are unaffected by the
large-scale environment; the shape distribution of supercluster members is
consistent with that of the general population.Comment: 12 pages, 8 figures, submitted to Ap
A sensitivity matrix approach using two-stage optimization for voltage regulation of LV networks with high PV penetration
The occurrence of voltage violations is a major deterrent for absorbing more rooftop solar power into smart Low-Voltage Distribution Grids (LVDGs). Recent studies have focused on decentralized control methods to solve this problem due to the high computational time in performing load flows in centralized control techniques. To address this issue, a novel sensitivity matrix was developed to estimate the voltages of the network by replacing load flow simulations. In this paper, a Centralized Active, Reactive Power Management System (CARPMS) is proposed to optimally utilize the reactive power capability of smart Photovoltaic (PV) inverters with minimal active power curtailment to mitigate the voltage violation problem. The developed sensitivity matrix is able to reduce the time consumed by 55.1% compared to load flow simulations, enabling near-real-time control optimization. Given the large solution space of power systems, a novel two-stage optimization is proposed, where the solution space is narrowed down by a Feasible Region Search (FRS) step, followed by Particle Swarm Optimization (PSO). The failure of standalone PSO to converge to a feasible solution for 34% of the scenarios evaluated further validates the necessity of the two-stage optimization using FRS. The performance of the proposed methodology was analysed in comparison to the load flow method to demonstrate the accuracy and the capability of the optimization algorithm to mitigate voltage violations in near-real time. The deviations of the mean voltages of the proposed methodology from the load flow method were: 6.5Ă10â3 p.u for reactive power control using Q-injection, 1.02Ă10â2 p.u for reactive power control using Q-absorption, and 0 p.u for active power curtailment case
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Confucius computer: a philosophical digital agent for intergenerational philosophical play
Confucianism is commonly defined as â... a system of philosophical, ethical and political thought based on the teachings of Confucius,â which originated through the teachings of Confucius during the sixth-century BCE. It is a way of life or a philosophy of human nature that considers human relationships as the foundation of the society. Confucius teachings had highly influenced the development of several cultures in Asia, making Confucianism an intangible cultural heritage. In this paper, we are re-acquainting users with an intangible heritage that is part of their everyday, by developing a system that permits experiencing Confucius teachings virtually and interactively. The system can measure philosophical intent of the human and generate meaningful philosophical answers. It is also aimed for intergenerational sharing of Confucius heritage through a simple interactive process with the virtual sage making the experience enjoyable and entertaining. Previous research in natural language processing (NLP) mainly focused on the understanding and delivering of human natural language accurately. In this research, we explored how to apply NLP to model the knowledge and teachings of Confucius, through the natural conversation between human and computer. This virtual Confucius, a chat agent that generates outputs based on Confucius teachings, using a series of algorithms and techniques to improve the matching accuracy between user input and computer output, introduces a novel way of interacting with intangible cultures. Our user evaluation results revealed that there is a positive correlation between relevance and enjoyment, finding their experiences interacting with virtual Confucius very encouraging. Adults who participated in experiencing the virtual Confucius together with their children believed that this system has the potential to improve intergenerational interactions through shared play
The 400d Galaxy Cluster Survey Weak Lensing Programme: I: MMT/Megacam Analysis of CL0030+2618 at z=0.50
The mass function of galaxy clusters at high redshifts is a particularly
useful probe to learn about the history of structure formation and constrain
cosmological parameters. We aim at deriving reliable masses for a
high-redshift, high-luminosity sample of clusters of galaxies selected from the
400d survey of X-ray selected clusters. Here, we will focus on a particular
object, CL0030+2618 at z=0.50 Using deep imaging in three passbands with the
MEGACAM instrument at MMT, we show that MEGACAM is well-suited for measuring
gravitational shear. We detect the weak lensing signal of CL0030+2618 at 5.8
sigma significance, using the aperture mass technique. Furthermore, we find
significant tangential alignment of galaxies out to ~10 arcmin or >2r_200
distance from the cluster centre. The weak lensing centre of CL0030+2618 agrees
with several X-ray measurements and the position of the brightest cluster
galaxy. Finally, we infer a weak lensing virial mass of M_200=7.5 10^{14} M_sun
for CL0030+2618. Despite complications by a tentative foreground galaxy group
in the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are
in remarkable agreement. This study paves the way for the largest weak lensing
survey of high-redshift galaxy clusters to date.Comment: 32 pages, 24 figures, submitted to Astronomy & Astrophysics; fixed
some LaTeX issues, now 30 pages v3: Improved version accepted by Astronomy &
Astrophysic
The Bio-Politics of Population Control and Sex Selective Abortion in China and India
China and India, two countries with skewed sex ratios in favor of males, have introduced a wide range of policies over the past few decades to prevent couples from deselecting daughters, including criminalizing sex-selective abortion through legal jurisdiction. This article aims to analyze how such policies are situated within the bio-politics of population control and how some of the outcomes reflect each governmentâs inadequacy in addressing the social dynamics around abortion decision making and the social, physical, and psychological effects on womenâs wellbeing in the face of criminalization of sex-selective abortion. The analysis finds that overall, the criminalization of sex selection has not been successful in these two countries. Further, the broader economic, social, and cultural dynamics which produce bias against females must be a part of the strategy to combat sex selection, rather than a narrow criminalization of abortion which endangers womenâs access to safe reproductive health services and their social, physical, and psychological wellbeing
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