1,333 research outputs found
Navega??o de m?ltiplos agentes sobre superf?cies arbitr?rias utilizando planariza??o din?mica
Path planning of multiple agents on arbitrary surfaces is a recent research topic. The
quality of the paths generated to arbitrary surface is poor compared to method proposed to planar
surfaces. A major limitation to improve the quality is related to the computational cost of
computing distances over arbitrary surface. Traditional path planning algorithms designed to
planar surface use Euclidian distance with has constant computational cost, in the other hand,
arbitrary surfaces require Geodesic distances with in turn has a considerable higher computational
cost. This project proposes novel dynamic planarization around each agent with will
allow the use of Eucledian distance during the local navigation, that way, classic path planning
algorithms designed for planar surface can be used over arbitrary surface. The main benefit is
the increased quality of paths for agents. The proposed solution uses geodesic distance in the
global navigation, responsible for defining the initial path. However, for the local navigation, or
obstacle avoidance, our solution allows the use of classic techniques. To allow the use of these
methods we propose a planarization of the surface adjacent to the agent in order to replace the
use of geodesic distance with Euclidean distance in the local navigation. Additionally, the algorithm
is massively parallel and implemented in the CPU and GPU to explore the best features
of each.Navega??o de m?ltiplos agentes em superf?cies arbitr?rias ? um t?pico de pesquisa recente que
tem atra?do crescente aten??o, entretanto, estes trabalhos n?o s?o capazes de realizar a navega-
??o em tempo real com a mesma qualidade dos trabalhos focados em superf?cies planares. Um
dos principais fatores limitantes ? o custo computacional do c?lculo de dist?ncia entre dois pontos
sobre uma superf?cie arbitr?ria, o que em superf?cies planares pode ser realizado em tempo
constante atrav?s do c?lculo de dist?ncia euclidiana. Neste trabalho ? proposta uma abordagem
para realizar a navega??o de m?ltiplos agentes sobre superf?cies arbitr?rias, e ao contr?rio dos
trabalhos anteriores, permitindo a utiliza??o de t?cnicas de navega??o sobre superf?cies planares,
por exemplo, Reciprocal Velocity Obstacles. A solu??o proposta utiliza o c?lculo da
dist?ncia geod?sica na navega??o global, respons?vel pela defini??o do caminho inicial. Para o
desvio dos obst?culos din?micos s?o utilizadas t?cnicas consolidadas, criadas para superf?cies
planares, com comprovada qualidade. Para permitir a utiliza??o desses m?todos ? proposta uma
planariza??o da superf?cie pr?xima do agente de modo a substituir o uso de dist?ncia geod?sica
por dist?ncia euclidiana na navega??o local. Al?m disso, ? implementado um algoritmo h?brido
CPU/GPU e assim explorando as melhores qualidades de cada processador
First Results from Pb+Pb collisions at the LHC
At the end of 2010, the CERN Large Hadron Collider started operation with
heavy ion beams, colliding lead nuclei at a centre-of-mass energy of 2.76
TeV/nucleon and opening a new era in ultra-relativistic heavy ion physics at
energies exceeding previous accelerators by more than an order of magnitude.
This review summarizes the results from the first year of heavy ion physics at
LHC obtained by the three experiments participating in the heavy ion program,
ALICE, ATLAS, and CMS.Comment: To appear in Annual Review of Nuclear and Particle Scienc
N=2 Boundary conditions for non-linear sigma models and Landau-Ginzburg models
We study N=2 nonlinear two dimensional sigma models with boundaries and their
massive generalizations (the Landau-Ginzburg models). These models are defined
over either Kahler or bihermitian target space manifolds. We determine the most
general local N=2 superconformal boundary conditions (D-branes) for these sigma
models. In the Kahler case we reproduce the known results in a systematic
fashion including interesting results concerning the coisotropic A-type branes.
We further analyse the N=2 superconformal boundary conditions for sigma models
defined over a bihermitian manifold with torsion. We interpret the boundary
conditions in terms of different types of submanifolds of the target space. We
point out how the open sigma models correspond to new types of target space
geometry. For the massive Landau-Ginzburg models (both Kahler and bihermitian)
we discuss an important class of supersymmetric boundary conditions which
admits a nice geometrical interpretation.Comment: 48 pages, latex, references and minor comments added, the version to
appear in JHE
Light emission from a scanning tunneling microscope: Fully retarded calculation
The light emission rate from a scanning tunneling microscope (STM) scanning a
noble metal surface is calculated taking retardation effects into account. As
in our previous, non-retarded theory [Johansson, Monreal, and Apell, Phys. Rev.
B 42, 9210 (1990)], the STM tip is modeled by a sphere, and the dielectric
properties of tip and sample are described by experimentally measured
dielectric functions. The calculations are based on exact diffraction theory
through the vector equivalent of the Kirchoff integral. The present results are
qualitatively similar to those of the non-retarded calculations. The light
emission spectra have pronounced resonance peaks due to the formation of a
tip-induced plasmon mode localized to the cavity between the tip and the
sample. At a quantitative level, the effects of retardation are rather small as
long as the sample material is Au or Cu, and the tip consists of W or Ir.
However, for Ag samples, in which the resistive losses are smaller, the
inclusion of retardation effects in the calculation leads to larger changes:
the resonance energy decreases by 0.2-0.3 eV, and the resonance broadens. These
changes improve the agreement with experiment. For a Ag sample and an Ir tip,
the quantum efficiency is 10 emitted photons in the visible
frequency range per tunneling electron. A study of the energy dissipation into
the tip and sample shows that in total about 1 % of the electrons undergo
inelastic processes while tunneling.Comment: 16 pages, 10 figures (1 ps, 9 tex, automatically included); To appear
in Phys. Rev. B (15 October 1998
Towards the Rosetta Stone of planet formation
Transiting exoplanets (TEPs) observed just about 10 Myrs after formation of
their host systems may serve as the Rosetta Stone for planet formation
theories. They would give strong constraints on several aspects of planet
formation, e.g. time-scales (planet formation would then be possible within 10
Myrs), the radius of the planet could indicate whether planets form by
gravitational collapse (being larger when young) or accretion growth (being
smaller when young). We present a survey, the main goal of which is to find and
then characterise TEPs in very young open clusters.Comment: Poster contribution to Detection and Dynamics of Transiting
Exoplanets (Haute Provence Observatory Colloquium, 23-27 August 2010
Transport Theoretical Description of Collisional Energy Loss in Infinite Quark-Gluon Matter
We study the time evolution of a high-momentum gluon or quark propagating
through an infinite, thermalized, partonic medium utilizing a Boltzmann
equation approach. We calculate the collisional energy loss of the parton,
study its temperature and flavor dependence as well as the the momentum
broadening incurred through multiple interactions. Our transport calculations
agree well with analytic calculations of collisional energy-loss where
available, but offer the unique opportunity to address the medium response as
well in a consistent fashion.Comment: 12 pages, updated with additional references and typos correcte
Bucket Fuser: Statistical Signal Extraction for 1D 1H NMR Metabolomic Data
Untargeted metabolomics is a promising tool for identifying novel disease biomarkers and unraveling underlying pathomechanisms. Nuclear magnetic resonance (NMR) spectroscopy is particularly suited for large-scale untargeted metabolomics studies due to its high reproducibility and cost effectiveness. Here, one-dimensional (1D) 1H NMR experiments offer good sensitivity at reasonable measurement times. Their subsequent data analysis requires sophisticated data preprocessing steps, including the extraction of NMR features corresponding to specific metabolites. We developed a novel 1D NMR feature extraction procedure, called Bucket Fuser (BF), which is based on a regularized regression framework with fused group LASSO terms. The performance of the BF procedure was demonstrated using three independent NMR datasets and was benchmarked against existing state-of-the-art NMR feature extraction methods. BF dynamically constructs NMR metabolite features, the widths of which can be adjusted via a regularization parameter. BF consistently improved metabolite signal extraction, as demonstrated by our correlation analyses with absolutely quantified metabolites. It also yielded a higher proportion of statistically significant metabolite features in our differential metabolite analyses. The BF algorithm is computationally efficient and it can deal with small sample sizes. In summary, the Bucket Fuser algorithm, which is available as a supplementary python code, facilitates the fast and dynamic extraction of 1D NMR signals for the improved detection of metabolic biomarker
CMTr mediated 2`-O-ribose methylation status of cap adjacent-nucleotides across animals
ACKNOWLEDGMENTS We thank Mark Carrington and Nancy Standard for T. brucei total RNA, Jane Nimmo for honeybees, Caroline Chadwick for mouse tissue, Pawel Grzechnik for HEK293T cells, Roland Arnold for HCT116 cells, Rupert Fray for plasmids, and the National BioResource Project, Tokyo, Japan for the C. elegans CMTr2 strain. M.S. acknowledges funding from the Leverhulme Trust and the Biotechnology and Biological Sciences Research Council (BBSRC) (BB/R002932/1), J.P. and B.M. from BBSRC (BB/T002859/1), and F.M. from the Wellcome Trust (106955/Z/15/Z).Peer reviewedPublisher PD
Automorphisms of associative algebras and noncommutative geometry
A class of differential calculi is explored which is determined by a set of
automorphisms of the underlying associative algebra. Several examples are
presented. In particular, differential calculi on the quantum plane, the
-deformed plane and the quantum group GLpq(2) are recovered in this way.
Geometric structures like metrics and compatible linear connections are
introduced.Comment: 28 pages, some references added, several amendments of minor
importance, remark on modular group in section 8 omitted, to appear in J.
Phys.
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