60 research outputs found
An adaptive large neighborhood search heuristic for the share-a-ride problem
The Share-a-Ride Problem (SARP) aims at maximizing the profit of serving a set of passengers and parcels using a set of homogeneous vehicles. We propose an adaptive large neighborhood search (ALNS) heuristic to address the SARP. Furthermore, we study the problem of determining the time slack in a SARP schedule. Our proposed solution approach is tested on three sets of realistic instances. The performance of our heuristic is benchmarked against a mixed integer programming (MIP) solver and the Dial-a-Ride Problem (DARP) test instances. Compared to the MIP solver, our heuristic is superior in both the solution times and the quality of the obtained solutions if the CPU time is limited. We also report new best results for two out of twenty benchmark DARP instances
Discovery of an unusual bright eclipsing binary with the longest known period: TYC 2505-672-1 / MASTER OT J095310.04+335352.8
We report on the MASTER Global Robotic Net discovery of an eclipsing binary,
MASTER OT J095310.04+335352.8, previously known as unremarkable star TYC
2505-672-1, which displays extreme orbital parameters. The orbital period
P=69.1 yr is more than 2.5 times longer than that of epsilon-Aurigae, which is
the previous record holder. The light curve is characterized by an extremely
deep total eclipse with a depth of more than 4.5 mag, which is symmetrically
shaped and has a total duration of 3.5 yrs. The eclipse is essentially gray.
The spectra acquired with the Russian 6 m BTA telescope both at minimum and
maximum light mainly correspond to an M0-1III--type red giant, but the spectra
taken at the bottom of eclipse show small traces of a sufficiently hot source.
The observed properties of this system can be better explained as the red giant
eclipsed by a large cloud (the disk) of small particles surrounding the
invisible secondary companion.Comment: 8 figures, 9 pages, Astronomy and astrophysics in prin
Dissipative Dynamics of Polymer Phononic Materials
Phononic materials are artificial composites with unprecedented abilities to control acoustic waves in solids. Their performance is mainly governed by their architecture, determining frequency ranges in which wave propagation is inhibited. However, the dynamics of phononic materials also depends on the mechanical and material properties of their constituents. In the case of viscoelastic constituents, such as most polymers, it is challenging to correctly predict the actual dynamic behavior of real phononic structures. Existing studies on this topic either lack experimental evidence or are limited to specific materials and architectures in restricted frequency ranges. A general framework is developed and employed to characterize the dynamics of polymer phononic materials with different architectures made of both thermoset and thermoplastic polymers, presenting qualitatively different viscoelastic behaviors. Through a comparison of experimental results with numerical predictions, the reliability of commonly used elastic and viscoelastic material models is evaluated in broad frequency ranges. Correlations between viscous effects and the two main band-gap formation mechanisms in phononic materials are revealed, and experimentally verified guidelines on how to correctly predict their dissipative response are proposed in a computationally efficient way. Overall, this work provides comprehensive guidelines for the extension of phononics modeling to applications involving dissipative viscoelastic materials.</p
Optical polarization observations with the MASTER robotic net
We present results of optical polarization observations performed with the
MASTER robotic net for three types of objects: gamma-ray bursts, supernovae,
and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A,
polarization observations were obtained during very early stages of optical
emission. For GRB100906A it was the first prompt optical polarization
observation in the world. Photometry in polarizers is presented for Type Ia
Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the
linear polarization of SN 2012bh at the early stage of the envelope expansion
was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3,
QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer
the degree of the linear polarization and polarization angle. The blazars OC
457 and 3C 454.3 were observed during their periods of activity. The results
show that MASTER is able to measure substantially polarized light; at the same
time it is not suitable for determining weak polarization (less than 5%) of dim
objects (fainter than 16). Polarimetric observations of the optical
emission from gamma-ray bursts and supernovae are necessary to investigate the
nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been
correcte
Measurement of the Muon Decay Parameter delta
The muon decay parameter delta has been measured by the TWIST collaboration.
We find delta = 0.74964 +- 0.00066(stat.) +- 0.00112(syst.), consistent with
the Standard Model value of 3/4. This result implies that the product Pmuxi of
the muon polarization in pion decay, Pmu, and the muon decay parameter xi falls
within the 90% confidence interval 0.9960 < Pmuxi < xi < 1.0040. It also has
implications for left-right-symmetric and other extensions of the Standard
Model.Comment: Extended to 5 pages. Referee's comments answere
Supernova search with active learning in ZTF DR3
We provide the first results from the complete SNAD adaptive learning
pipeline in the context of a broad scope of data from large-scale astronomical
surveys. The main goal of this work is to explore the potential of adaptive
learning techniques in application to big data sets. Our SNAD team used Active
Anomaly Discovery (AAD) as a tool to search for new supernova (SN) candidates
in the photometric data from the first 9.4 months of the Zwicky Transient
Facility (ZTF) survey, namely, between March 17 and December 31 2018 (58194 <
MJD < 58483). We analysed 70 ZTF fields at a high galactic latitude and
visually inspected 2100 outliers. This resulted in 104 SN-like objects being
found, 57 of which were reported to the Transient Name Server for the first
time and with 47 having previously been mentioned in other catalogues, either
as SNe with known types or as SN candidates. We visually inspected the
multi-colour light curves of the non-catalogued transients and performed
fittings with different supernova models to assign it to a probable photometric
class: Ia, Ib/c, IIP, IIL, or IIn. Moreover, we also identified unreported
slow-evolving transients that are good superluminous SN candidates, along with
a few other non-catalogued objects, such as red dwarf flares and active
galactic nuclei. Beyond confirming the effectiveness of human-machine
integration underlying the AAD strategy, our results shed light on potential
leaks in currently available pipelines. These findings can help avoid similar
losses in future large-scale astronomical surveys. Furthermore, the algorithm
enables direct searches of any type of data and based on any definition of an
anomaly set by the expert.Comment: 22 pages with appendix, 12 figures, 2 tables, accepted for
publication in Astronomy and Astrophysic
Measurement of the Michel Parameter in Muon Decay
The TWIST Collaboration has measured the Michel parameter in normal
muon decay, . In the Standard Model,
= 3/4. Deviations from this value require mixing of left- and
right-handed muon and electron couplings in the muon-decay Lagrangian. We find
= 0.75080 0.00044(stat.) 0.00093(syst.) 0.00023, where
the last uncertainty represents the dependence of on the Michel
parameter . This result sets new limits on the mixing angle in
left-right symmetric models.Comment: 4 pages, 3 figures, submitted to PR
The MASTER-II network of robotic optical telescopes. First results
The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered. © 2013 Pleiades Publishing, Ltd
Discovery of a young low-mass brown dwarf transiting a fast-rotating F-type star by the Galactic Plane eXoplanet (GPX) survey
We announce the discovery of GPX-1 b, a transiting brown dwarf with a mass of
and a radius of
, the first sub-stellar object discovered by the Galactic
Plane eXoplanet (GPX) survey. The brown dwarf transits a moderately bright (
= 12.3 mag) fast-rotating F-type star with a projected rotational velocity
km/s. We use the isochrone placement algorithm to
characterize the host star, which has effective temperature K,
mass , radius
and approximate age Gyr. GPX-1 b has an orbital period
of 1.75 d, and a transit depth of %. We describe the GPX
transit detection observations, subsequent photometric and
speckle-interferometric follow-up observations, and SOPHIE spectroscopic
measurements, which allowed us to establish the presence of a sub-stellar
object around the host star. GPX-1 was observed at 30-min integrations by TESS
in Sector 18, but the data is affected by blending with a 3.4 mag brighter star
42 arcsec away. GPX-1 b is one of about two dozen transiting brown dwarfs known
to date, with a mass close to the theoretical brown dwarf/gas giant planet mass
transition boundary. Since GPX-1 is a moderately bright and fast-rotating star,
it can be followed-up by the means of Doppler tomography.Comment: 13 pages, 13 figures, accepted to MNRAS in May 202
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