73 research outputs found
Single machine scheduling with job-dependent machine deterioration
We consider the single machine scheduling problem with job-dependent machine
deterioration. In the problem, we are given a single machine with an initial
non-negative maintenance level, and a set of jobs each with a non-preemptive
processing time and a machine deterioration. Such a machine deterioration
quantifies the decrement in the machine maintenance level after processing the
job. To avoid machine breakdown, one should guarantee a non-negative
maintenance level at any time point; and whenever necessary, a maintenance
activity must be allocated for restoring the machine maintenance level. The
goal of the problem is to schedule the jobs and the maintenance activities such
that the total completion time of jobs is minimized. There are two variants of
maintenance activities: in the partial maintenance case each activity can be
allocated to increase the machine maintenance level to any level not exceeding
the maximum; in the full maintenance case every activity must be allocated to
increase the machine maintenance level to the maximum. In a recent work, the
problem in the full maintenance case has been proven NP-hard; several special
cases of the problem in the partial maintenance case were shown solvable in
polynomial time, but the complexity of the general problem is left open. In
this paper we first prove that the problem in the partial maintenance case is
NP-hard, thus settling the open problem; we then design a -approximation
algorithm.Comment: 15 page
X-ray Astronomical Point Sources Recognition Using Granular Binary-tree SVM
The study on point sources in astronomical images is of special importance,
since most energetic celestial objects in the Universe exhibit a point-like
appearance. An approach to recognize the point sources (PS) in the X-ray
astronomical images using our newly designed granular binary-tree support
vector machine (GBT-SVM) classifier is proposed. First, all potential point
sources are located by peak detection on the image. The image and spectral
features of these potential point sources are then extracted. Finally, a
classifier to recognize the true point sources is build through the extracted
features. Experiments and applications of our approach on real X-ray
astronomical images are demonstrated. comparisons between our approach and
other SVM-based classifiers are also carried out by evaluating the precision
and recall rates, which prove that our approach is better and achieves a higher
accuracy of around 89%.Comment: Accepted by ICSP201
Hydrodynamic Collectivity in Proton--Proton Collisions at 13 TeV
In this paper, we investigate the hydrodynamic collectivity in proton--proton
(pp) collisions at 13 TeV, using iEBE-VISHNU hybrid model with HIJING initial
conditions. With properly tuned parameters, our model simulations can
remarkably describe all the measured 2-particle correlations, including
integrated and differential elliptic flow coefficients for all charged and
identified hadrons (, ). However, our model calculations show
positive 4-particle cumulant in high multiplicity pp collisions,
and can not reproduce the negative measured in experiment. Further
investigations on the HIJING initial conditions show that the fluctuations of
the second order anisotropy coefficient increases with the
increase of its mean value, which leads to a similar trend of the flow
fluctuations. For a simultaneous description of the 2- and 4- particle
cumulants within the hydrodynamic framework, it is required to have significant
improvements on initial condition for pp collisions, which is still lacking of
knowledge at the moment.Comment: 7 pages, 6 figures, published versio
MicroRNA-519a promotes proliferation and inhibits apoptosis of hepatocellular carcinoma cells by targeting FOXF2
AbstractRecent studies report that microRNA-519a (miR-519a) is a novel oncomir, which facilitates the onset and progression of human cancers. However, the clinical significance of miR-519a and its functional role and underlying mechanisms in hepatocellular carcinoma (HCC) are poorly investigated. In the present study, elevated expression of miR-519a was observed in HCC tissues compared with adjacent non-tumor tissues. The increased level of miR-519a expression was significantly correlated with adverse clinical features of HCC including hepatitis B virus (HBV) infection, large tumor size, cirrhosis and advanced tumor-node-metastasis tumor stage. Furthermore, high expression of miR-519a was prominently associated with a poorer 5-year overall survival and recurrence-free survival of HCC patients. Gain- and loss-of function experiments showed that miR-519a overexpression enhanced proliferation and reduced apoptosis of Huh7 cells. By contrast, miR-519a knockdown inhibited SMMC-7721 cell proliferation and induced apoptosis. Importantly, up-regulation of miR-519a reduced the expression of FOXF2 mRNA and protein in Huh7 cells, while down-regulation of miR-519a resulted in increased expression of FOXF2 in SMMC-7721 cells. An inverse correlation between mRNA levels of miR-519a and FOXF2 was observed in HCC tissues. Thus, Forkhead box F2 (FOXF2) was identified as a downstream target of miR-519a in HCC. Mechanistically, the effects of miR-519a knockdown on SMMC-7721 cells were abrogated by FOXF2 repression. In conclusion, miR-519a is a novel prognostic predictor for HCC patients and it may potentiate proliferation and inhibits apoptosis of HCC cells by targeting FOXF2
Exploring the Cosmic Reionization Epoch in Frequency Space: An Improved Approach to Remove the Foreground in 21 cm Tomography
Aiming to correctly restore the redshifted 21 cm signals emitted by the
neutral hydrogen during the cosmic reionization processes, we re-examine the
separation approaches based on the quadratic polynomial fitting technique in
frequency space to investigate whether they works satisfactorily with complex
foreground, by quantitatively evaluate the quality of restored 21 cm signals in
terms of sample statistics. We construct the foreground model to characterize
both spatial and spectral substructures of the real sky, and use it to simulate
the observed radio spectra. By comparing between different separation
approaches through statistical analysis of restored 21 cm spectra and
corresponding power spectra, as well as their constraints on the mean halo bias
and average ionization fraction of the reionization processes, at
and the noise level of 60 mK we find that, although the complex
foreground can be well approximated with quadratic polynomial expansion, a
significant part of Mpc-scale components of the 21 cm signals (75% for Mpc scales and 34% for Mpc scales) is lost because
it tends to be mis-identified as part of the foreground when
single-narrow-segment separation approach is applied. The best restoration of
the 21 cm signals and the tightest determination of and can be
obtained with the three-narrow-segment fitting technique as proposed in this
paper. Similar results can be obtained at other redshifts.Comment: 33 pages, 14 figures. Accepted for publication in Ap
A Study of the Merger History of the Galaxy Group HCG 62 Based on X-Ray Observations and SPH Simulations
We choose the bright compact group HCG 62, which was found to exhibit both
excess X-ray emission and high Fe abundance to the southwest of its core, as an
example to study the impact of mergers on chemical enrichment in the intragroup
medium. We first reanalyze the high-quality Chandra and XMM-Newton archive data
to search for the evidence for additional SN II yields, which is expected as a
direct result of the possible merger-induced starburst. We reveal that, similar
to the Fe abundance, the Mg abundance also shows a high value in both the
innermost region and the southwest substructure, forming a high-abundance
plateau, meanwhile all the SN Ia and SN II yields show rather flat
distributions in in favor of an early enrichment. Then we carry
out a series of idealized numerical simulations to model the collision of two
initially isolated galaxy groups by using the TreePM-SPH GADGET-3 code. We find
that the observed X-ray emission and metal distributions, as well as the
relative positions of the two bright central galaxies with reference to the
X-ray peak, can be well reproduced in a major merger with a mass ratio of 3
when the merger-induced starburst is assumed. The `best-match' snapshot is
pinpointed after the third pericentric passage when the southwest substructure
is formed due to gas sloshing. By following the evolution of the simulated
merging system, we conclude that the effects of such a major merger on chemical
enrichment are mostly restricted within the core region when the final relaxed
state is reached.Comment: Accepted for publication in the Astrophysical Journa
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