38,566 research outputs found
Irrigation system performance assessment and diagnosis
Performance evaluation / Irrigation programs / Irrigation management / Irrigation systems / Case studies / Hydraulics / Management / Environmental effects / Asia / Africa / South America
A decentralized motion coordination strategy for dynamic target tracking
This paper presents a decentralized motion planning
algorithm for the distributed sensing of a noisy dynamical
process by multiple cooperating mobile sensor agents. This
problem is motivated by localization and tracking tasks of
dynamic targets. Our gradient-descent method is based on a
cost function that measures the overall quality of sensing. We
also investigate the role of imperfect communication between
sensor agents in this framework, and examine the trade-offs in
performance between sensing and communication. Simulations
illustrate the basic characteristics of the algorithms
Polarization Structures in the Thomson-Scattered Emission Lines in Active Galactic Nuclei
A line photon incident in an electron-scattering medium is transferred in a
diffusive way both in real space and in frequency space, and the mean number of
scatterings changes as the wavelength shifts from the line center. This leads
to the profile broadening and polarization dependence on the wavelength shift
as a function of the Thomson optical depth . We find that the
polarization of the Thomson-scattered emission lines has a dip around the line
center when does not exceed a few. Various structures such as the
polarization flip are also seen. An application to an ionized halo component
surrounding the broad emission line region in active galactic nuclei is
considered and it is found that the polarization structures may still persist.
Brief discussions on observational implications are given.Comment: 14 pages, 3 figures, accepted for publication in ApJ Letter
Compression of Deep Neural Networks on the Fly
Thanks to their state-of-the-art performance, deep neural networks are
increasingly used for object recognition. To achieve these results, they use
millions of parameters to be trained. However, when targeting embedded
applications the size of these models becomes problematic. As a consequence,
their usage on smartphones or other resource limited devices is prohibited. In
this paper we introduce a novel compression method for deep neural networks
that is performed during the learning phase. It consists in adding an extra
regularization term to the cost function of fully-connected layers. We combine
this method with Product Quantization (PQ) of the trained weights for higher
savings in storage consumption. We evaluate our method on two data sets (MNIST
and CIFAR10), on which we achieve significantly larger compression rates than
state-of-the-art methods
Internal agent states : experiments using the swarm leader concept
In recent years, an understanding of the operating principles and stability of natural swarms has proven to be a useful tool for the design and control of artificial robotic agents. Many robotic systems, whose design or control principals are inspired by behavioural aspects of real biological systems such as leader-follower relationship, have been developed. We introduced an algorithm which successfully enhances the navigation performance of a swarm of robots using the swarm leader concept. This paper presents some applications based on that work using the simulations and experimental implementation using a swarming behaviour test-bed at the University of Strathclyde. Experimental and simulation results match closely in a way that confirms the efficiency of the algorithm as well as its applicability
Matrix partitioning and EOF/principal component analysis of Antarctic Sea ice brightness temperatures
A field of measured anomalies of some physical variable relative to their time averages, is partitioned in either the space domain or the time domain. Eigenvectors and corresponding principal components of the smaller dimensioned covariance matrices associated with the partitioned data sets are calculated independently, then joined to approximate the eigenstructure of the larger covariance matrix associated with the unpartitioned data set. The accuracy of the approximation (fraction of the total variance in the field) and the magnitudes of the largest eigenvalues from the partitioned covariance matrices together determine the number of local EOF's and principal components to be joined by any particular level. The space-time distribution of Nimbus-5 ESMR sea ice measurement is analyzed
Influence of environmental factors during seed development and after full-ripeness on pre-harvest sprouting in wheat
Results on environmental and genotypic factors influencing preharvest sprouting of wheat are summarized. Other possible areas where additional research is needed is suggested
Spontaneous ÎłH2AX Foci in Human Solid Tumor-Derived Cell Lines in Relation to p21WAF1 and WIP1 Expression.
Phosphorylation of H2AX on Ser139 (ÎłH2AX) after exposure to ionizing radiation produces nuclear foci that are detectable by immunofluorescence microscopy. These so-called ÎłH2AX foci have been adopted as quantitative markers for DNA double-strand breaks. High numbers of spontaneous ÎłH2AX foci have also been reported for some human solid tumor-derived cell lines, but the molecular mechanism(s) for this response remains elusive. Here we show that cancer cells (e.g., HCT116; MCF7) that constitutively express detectable levels of p21WAF1 (p21) exhibit low numbers of ÎłH2AX foci (<3/nucleus), whereas p21 knockout cells (HCT116p21-/-) and constitutively low p21-expressing cells (e.g., MDA-MB-231) exhibit high numbers of foci (e.g., >50/nucleus), and that these foci are not associated with apoptosis. The majority (>95%) of cells within HCT116p21-/- and MDA-MB-231 cultures contain high levels of phosphorylated p53, which is localized in the nucleus. We further show an inverse relationship between ÎłH2AX foci and nuclear accumulation of WIP1, an oncogenic phosphatase. Our studies suggest that: (i) p21 deficiency might provide a selective pressure for the emergence of apoptosis-resistant progeny exhibiting genomic instability, manifested as spontaneous ÎłH2AX foci coupled with phosphorylation and nuclear accumulation of p53; and (ii) p21 might contribute to positive regulation of WIP1, resulting in dephosphorylation of ÎłH2AX
Density Matrix Renormalization for Model Reduction in Nonlinear Dynamics
We present a novel approach for model reduction of nonlinear dynamical
systems based on proper orthogonal decomposition (POD). Our method, derived
from Density Matrix Renormalization Group (DMRG), provides a significant
reduction in computational effort for the calculation of the reduced system,
compared to a POD. The efficiency of the algorithm is tested on the one
dimensional Burgers equations and a one dimensional equation of the Fisher type
as nonlinear model systems.Comment: 12 pages, 12 figure
Direct constraints on the dark matter self-interaction cross-section from the merging galaxy cluster 1E0657-56
We compare new maps of the hot gas, dark matter, and galaxies for 1E0657-56,
a cluster with a rare, high-velocity merger occurring nearly in the plane of
the sky. The X-ray observations reveal a bullet-like gas subcluster just
exiting the collision site. A prominent bow shock gives an estimate of the
subcluster velocity, 4500 km/s, which lies mostly in the plane of the sky. The
optical image shows that the gas lags behind the subcluster galaxies. The
weak-lensing mass map reveals a dark matter clump lying ahead of the
collisional gas bullet, but coincident with the effectively collisionless
galaxies. From these observations, one can directly estimate the cross-section
of the dark matter self-interaction. That the dark matter is not fluid-like is
seen directly in the X-ray -- lensing mass overlay; more quantitative limits
can be derived from three simple independent arguments. The most sensitive
constraint, sigma/m<1 cm^2/g, comes from the consistency of the subcluster
mass-to-light ratio with the main cluster (and universal) value, which rules
out a significant mass loss due to dark matter particle collisions. This limit
excludes most of the 0.5-5 cm^2/g interval proposed to explain the flat mass
profiles in galaxies. Our result is only an order-of-magnitude estimate which
involves a number of simplifying, but always conservative, assumptions;
stronger constraints may be derived using hydrodynamic simulations of this
cluster.Comment: Text clarified; some numbers changed slightly for consistency with
final version of the accompanying lensing paper. 6 pages, uses emulateapj.
ApJ in pres
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