124,807 research outputs found
Hot Molecular Cores and High-Mass Star Formation
This review covers hot cores in the context of high-mass star formation.
After giving an overview of chemical processes and diversity during high-mass
star formation, it reviews the `warm envelope' phase which probably precedes
the formation of hot cores. Some recent determinations of the cosmic-ray
ionization rate are discussed, as well as recent evidence for hot cores around
low-mass stars. Routes for future hot core research are outlined.Comment: 8 pages, 1 figure; to appear in the Proceeding of IAU Symposium 221,
Star Formation at High Angular Resolution, Editors M. Burton, R. Jayawardhana
& T. Bourke, Astronomical Society of the Pacifi
Consistency checks for particle filters
An "inconsistent" particle filter produces - in a statistical sense - larger estimation errors than predicted by the model on which the filter is based. Two test variables are introduced that allow the detection of inconsistent behavior. The statistical properties of the variables are analyzed. Experiments confirm their suitability for inconsistency detection
Context dependent learning in neural networks
In this paper an extension to the standard error backpropagation learning rule for multi-layer feed forward neural networks is proposed, that enables them to be trained for context dependent information. The context dependent learning is realised by using a different error function (called Average Risk: AVR) in stead of the sum of squared errors (SQE) normally used in error backpropagation and by adapting the update rules. It is shown that for applications where this context dependent information is important, a major improvement in performance is obtained
Evolution and dynamics of cusped light-like Wilson loops
We discuss the possible relation between the singular structure of TMDs on
the light-cone and the geometrical behaviour of rectangular Wilson loops.Comment: 6 pages, proceedings for the 3rd Workshop on the QCD Structure of the
Nucleon (QCD-N'12
Temporal dynamics of travelling theta wave activity in infants responding to visual looming
A fundamental property of most animals is the ability to see whether an object is approaching on a direct collision course and, if so, when it will collide. Using high-density electroencephalography in 5- to 11-month-old infants and a looming stimulus approaching under three different accelerations, we investigated how the young human nervous system extracts and processes information for impending collision. Here we show that infants' looming related brain activity is characterized by theta oscillations. Source analyses reveal clear localised activity in the visual cortex. Analysing the temporal dynamics of the source waveform, we provide evidence that the temporal structure of different looming stimuli is sustained during processing in the more mature infant brain, providing infants with increasingly veridical time-to-collision information about looming danger as they grow older and become mobile
Towards automated visual flexible endoscope navigation
Background:\ud
The design of flexible endoscopes has not changed significantly in the past 50 years. A trend is observed towards a wider application of flexible endoscopes with an increasing role in complex intraluminal therapeutic procedures. The nonintuitive and nonergonomical steering mechanism now forms a barrier in the extension of flexible endoscope applications. Automating the navigation of endoscopes could be a solution for this problem. This paper summarizes the current state of the art in image-based navigation algorithms. The objectives are to find the most promising navigation system(s) to date and to indicate fields for further research.\ud
Methods:\ud
A systematic literature search was performed using three general search terms in two medicalâtechnological literature databases. Papers were included according to the inclusion criteria. A total of 135 papers were analyzed. Ultimately, 26 were included.\ud
Results:\ud
Navigation often is based on visual information, which means steering the endoscope using the images that the endoscope produces. Two main techniques are described: lumen centralization and visual odometry. Although the research results are promising, no successful, commercially available automated flexible endoscopy system exists to date.\ud
Conclusions:\ud
Automated systems that employ conventional flexible endoscopes show the most promising prospects in terms of cost and applicability. To produce such a system, the research focus should lie on finding low-cost mechatronics and technologically robust steering algorithms. Additional functionality and increased efficiency can be obtained through software development. The first priority is to find real-time, robust steering algorithms. These algorithms need to handle bubbles, motion blur, and other image artifacts without disrupting the steering process
Working With Wilson Lines
We present an algorithm to express Wilson lines that are defined on piecewise
linear paths in function of their individual segments, reducing the number of
diagrams needed to be calculated. The important step lies in the observation
that different linear path topologies can be related to each other using their
color structure. This framework allows one to easily switch results between
different Wilson line topologies, which is helpful when testing different
structures against each other.Comment: Proceedings for SPIN 2014, 6 page
Space-time discontinuous Galerkin method for the compressible Navier-Stokes equations on deforming meshes
An overview is given of a space-time discontinuous Galerkin finite element method for the compressible Navier-Stokes equations. This method is well suited for problems with moving (free) boundaries which require the use of deforming elements. In addition, due to the local discretization, the space-time discontinuous Galerkin method is well suited for mesh adaptation and parallel computing. The algorithm is demonstrated with computations of the unsteady \ud
ow field about a delta wing and a NACA0012 airfoil in rapid pitch up motion
Piecewise Linear Wilson lines
Wilson lines, being comparators that render non-local operator products gauge
invariant, are extensively used in QCD calculations, especially in small-
calculations, calculations concerning validation of factorisation schemes and
in calculations for constructing or modelling parton density functions. We
develop an algorithm to express piecewise path ordered exponentials as path
ordered integrals over the separate segments, and apply it on linear segments,
reducing the number of diagrams needed to be calculated. We show how different
linear path topologies can be related using their colour structure. This
framework allows one to easily switch results between different Wilson line
structures, which is especially useful when testing different structures
against each other, e.g. when checking universality properties of
non-perturbative objects.Comment: Proceedings for Transversity 2014, 6 page
- âŠ