2,754 research outputs found
Common Due-Date Problem: Exact Polynomial Algorithms for a Given Job Sequence
This paper considers the problem of scheduling jobs on single and parallel
machines where all the jobs possess different processing times but a common due
date. There is a penalty involved with each job if it is processed earlier or
later than the due date. The objective of the problem is to find the assignment
of jobs to machines, the processing sequence of jobs and the time at which they
are processed, which minimizes the total penalty incurred due to tardiness or
earliness of the jobs. This work presents exact polynomial algorithms for
optimizing a given job sequence or single and parallel machines with the
run-time complexities of and respectively, where
is the number of jobs and the number of machines. The algorithms take a
sequence consisting of all the jobs as input and
distribute the jobs to machines (for ) along with their best completion
times so as to get the least possible total penalty for this sequence. We prove
the optimality for the single machine case and the runtime complexities of
both. Henceforth, we present the results for the benchmark instances and
compare with previous work for single and parallel machine cases, up to
jobs.Comment: 15th International Symposium on Symbolic and Numeric Algorithms for
Scientific Computin
Cascade Support Vector Machines with Dimensionality Reduction
Cascade support vector machines have been introduced as extension of classic support vector machines that allow a fast training on large data sets. In this work, we combine cascade support vector machines with dimensionality reduction based preprocessing. The cascade principle allows fast learning based on the division of the training set into subsets and the union of cascade learning results based on support vectors in each cascade level. The combination with dimensionality reduction as preprocessing results in a significant speedup, often without loss of classifier accuracies, while considering the high-dimensional pendants of the low-dimensional support vectors in each new cascade level. We analyze and compare various instantiations of dimensionality reduction preprocessing and cascade SVMs with principal component analysis, locally linear embedding, and isometric mapping. The experimental analysis on various artificial and real-world benchmark problems includes various cascade specific parameters like intermediate training set sizes and dimensionalities
IT-basiertes Audit-Management in der Praxis
Mittels Software-Einsatz kann das Audit-Management unterstützt werden. Insbesondere durch die Anbindung an ein ERP-System können Audit-Prozesse effizienter werden, indem Kennzahlen vom ERP System direkt in die Audit-Auswertung einfließen
The Current Ability to Test Theories of Gravity with Black Hole Shadows
Our Galactic Center, Sagittarius A* (Sgr A*), is believed to harbour a
supermassive black hole (BH), as suggested by observations tracking individual
orbiting stars. Upcoming sub-millimetre very-long-baseline-interferometry
(VLBI) images of Sgr A* carried out by the Event-Horizon-Telescope
Collaboration (EHTC) are expected to provide critical evidence for the
existence of this supermassive BH. We assess our present ability to use EHTC
images to determine if they correspond to a Kerr BH as predicted by Einstein's
theory of general relativity (GR) or to a BH in alternative theories of
gravity. To this end, we perform general-relativistic magnetohydrodynamical
(GRMHD) simulations and use general-relativistic radiative transfer (GRRT)
calculations to generate synthetic shadow images of a magnetised accretion flow
onto a Kerr BH. In addition, and for the first time, we perform GRMHD
simulations and GRRT calculations for a dilaton BH, which we take as a
representative solution of an alternative theory of gravity. Adopting the VLBI
configuration from the 2017 EHTC campaign, we find that it could be extremely
difficult to distinguish between BHs from different theories of gravity, thus
highlighting that great caution is needed when interpreting BH images as tests
of GR.Comment: Published in Nature Astronomy on 16.04.18 (including supplementary
information); simulations at https://blackholecam.org/telling_bhs_apart
Detecting Quasars in Large-Scale Astronomical Surveys
We present a classification-based approach to identify quasi-stellar radio
sources (quasars) in the Sloan Digital Sky Survey and evaluate its performance
on a manually labeled training set. While reasonable results can already be
obtained via approaches working only on photometric data, our experiments
indicate that simple but problem-specific features extracted from spectroscopic
data can significantly improve the classification performance. Since our
approach works orthogonal to existing classification schemes used for building
the spectroscopic catalogs, our classification results are well suited for a
mutual assessment of the approaches' accuracies.Comment: 6 pages, 8 figures, published in proceedings of 2010 Ninth
International Conference on Machine Learning and Applications (ICMLA) of the
IEE
How to tell an accreting boson star from a black hole
The capability of the Event Horizon Telescope (EHT) to image the nearest
supermassive black hole candidates at horizon-scale resolutions offers a novel
means to study gravity in its strongest regimes and to test different models
for these objects. Here, we study the observational appearance at 230 GHz of a
surfaceless black hole mimicker, namely a non-rotating boson star, in a
scenario consistent with the properties of the accretion flow onto Sgr A*. To
this end, we perform general relativistic magnetohydrodynamic simulations
followed by general relativistic radiative transfer calculations in the boson
star space-time. Synthetic reconstructed images considering realistic
astronomical observing conditions show that, despite qualitative similarities,
the differences in the appearance of a black hole -- either rotating or not --
and a boson star of the type considered here are large enough to be detectable.
These differences arise from dynamical effects directly related to the absence
of an event horizon, in particular, the accumulation of matter in the form of a
small torus or a spheroidal cloud in the interior of the boson star, and the
absence of an evacuated high-magnetization funnel in the polar regions. The
mechanism behind these effects is general enough to apply to other horizonless
and surfaceless black hole mimickers, strengthening confidence in the ability
of the EHT to identify such objects via radio observations.Comment: 16 pages, 12 figures. Published in MNRAS. Adding more information in
the form of appendices, and a new simulation of a different boson star model.
The conclusions do not chang
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