81 research outputs found
The Typology of Causative Constructions
Wojcik, Richard H. Translation from Russian of "Tipologiia kauzativnykh konstruktsii (The Typology of Causative Constructions)" by N. Medialkov and G. Silnitskii
State estimation of a dehydration process by interval analysis
This article presents a general methodology of state estimation by interval analysis in a dynamic system modeled by difference equations. The methodology is applied to a pineapple osmotic dehydration process, in order to predict the behavior of the process within a range of allowed perturbation. The paper presents simulations and validations
Optical monitoring of the z=4.40 quasar Q 2203+292
We report Cousins R-band monitoring of the high-redshift (z=4.40) radio quiet
quasar Q 2203+292 from May 1999 to October 2007. The quasar shows maximum
peak-to-peak light curve amplitude of ~0.3 mag during the time of our
monitoring, and ~0.9 mag when combined with older literature data. The rms of a
fit to the light curve with a constant is 0.08 mag and 0.2 mag, respectively.
The detected changes are at ~3-sigma level. The quasar was in a stable state
during the recent years and it might have undergone a brightening event in the
past. The structure function analysis concluded that the object shows
variability properties similar to those of the lower redshift quasars. We set a
lower limit to the Q 2203+292 broad line region mass of 0.3-0.4 M_odot.
Narrow-band imaging search for redshifted Ly_alpha from other emission line
objects at the same redshift shows no emission line objects in the quasar
vicinity.Comment: 9 pages, 8 figures, accepted for publication in MNRA
Making big steps in trajectories
We consider the solution of initial value problems within the context of
hybrid systems and emphasise the use of high precision approximations (in
software for exact real arithmetic). We propose a novel algorithm for the
computation of trajectories up to the area where discontinuous jumps appear,
applicable for holomorphic flow functions. Examples with a prototypical
implementation illustrate that the algorithm might provide results with higher
precision than well-known ODE solvers at a similar computation time
The January 2015 outburst of a red nova in M31
M31N 2015-01a (or M31LRN 2015) is a red nova that erupted in January 2015 --
the first event of this kind observed in M31 since 1988. Very few similar
events have been confirmed as of 2015. Most of them are considered to be
products of stellar mergers. Results of an extensive optical monitoring of the
transient in the period January-March 2015 are presented. Eight optical
telescopes were used for imaging. Spectra were obtained on BTA, GTC and the
Rozhen 2m telescope. We present a highly accurate 70 d lightcurve and
astrometry with a 0.05" uncertainty. The color indices reached a minimum 2-3 d
before peak brightness and rapidly increased afterwards. The spectral type
changed from F5I to F0I in 6 d before the maximum and then to K3I in the next
30 d. The luminosity of the transient was estimated to
during the optical maximum. Both the
photometric and the spectroscopic results confirm that the object is a red
nova, similar to V838 Monocerotis.Comment: 5 pages, 4 figures, 4 tables, accepted for publication in Astronomy
and Astrophysics as a Letter to the Editor; page 5 is online material onl
First optical identification of a suprsoft X-ray source in M31
We propose the first association of an optical counterpart with a luminous
supersoft X-ray source in M31, RX J0044.0+4118, observed with ROSAT in July
1991. The PSPC position is at 1.6" angular distance from a candidate nova in
outburst in September of 1990. This is interesting because the incidence of
classical novae among supersoft X-ray sources is an open question. The proposed
optical counterpart was measured at R~17.7 in September of 1990, and it had
faded to R>19.2 when it was observed again after 70 days.
The light curve was too sparsely monitored for definite conclusions on the
speed class of the nova. No other variable objects with V<23.5 were found in
the ROSAT spatial error box. We evaluate that the probability that a classical
or recurrent nova was in outburst in the ROSAT error box in the few years
preceding the observation is very small, so the proposed identification is
meaningful. We also show evidence that the associated supersoft X-ray source
turned off in the third year after the outburst.Comment: To appear in Astronomy and Astrophysic
Locally Optimal Reach Set Over-approximation for Nonlinear Systems
Safety verification of embedded systems modeled as hybrid systems can be scaled up by employing simulation-guided reach set over-approximation techniques. Existing methods are applicable only to restricted classes of systems, overly conservative, or computationally expensive. We present new techniques to compute a locally optimal bloating factor based on discrepancy functions, which allow construction of reach set over-approximations from simulation traces for general nonlinear systems. The discrepancy functions are critical for tools like C2E2 to verify bounded time safety properties for complex hybrid systems with nonlinear continuous dynamics. The new discrepancy function is computed using local bounds on a matrix measure under an optimal metric such that the exponential change rate of the discrepancy function is minimized. The new technique is less time consuming and less conservative than existing techniques and does not incur significant computational overhead. We demonstrate the effectiveness of our approach by comparing the performance of a prototype implementation with the state-of-the-art reachability analysis tool Flow*.National Science Foundation/CCF 1422798Ope
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