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This paper investigates a passive fault tolerant control to aircraft that suffers from vertical tail damage. A novel notion of damage degree is introduced to parameterize the damaged flight dynamics model. It is applied to seek the maximum allowable damage degree (tolerance capacity) stabilizable by the proposed passive fault tolerant and backup control under a linearized model. The design algorithms are presented and illustrated through numerical simulations on a Boeing-747 100/200 model. Furthermore, the impact of potential control saturation is taken into account in the proposed design and a set of design parameters are tuned such that the maximum allowable damage degree is bounded, represented as the so-called critical damage degree. [ABSTRACT FROM AUTHOR]

The lifetimes of the first electronically excited state of (H2O)n···Na and (D2O)n···Na clusters up to n= 40 have been measured by two-color pump−probe spectroscopy (800 and 400 nm) with 35 fs laser pulses. The excited-state lifetime decreases rapidly from 1.2 ps at n= 2 to approximately 100 fs at n≥ 10. For (D2O)n···Na, the average lifetime is about 3.6 times longer. The fast energy redistribution is explained by conversion of the electronic excitation into vibrations of the ground state. A simple model based on Fermi’s Golden Rule predicts the observed trends but fails to reproduce the observed lifetimes quantitatively. The longer lifetimes for deuterated clusters are discussed in the framework of the famous energy gap law and indicate that the stretching modes of water play an important role in the energy-transfer process. [ABSTRACT FROM AUTHOR]

In order to study short timescale optical variability of γ-ray blazar S5 0716+714, quasi-simultaneous spectroscopic and multiband photometric observations were performed from 2018 November to 2019 March with the 2.4 m optical telescope located at Lijiang Observatory of Yunnan Observatories. The observed spectra are well fitted with a power law Fλ = Aλ−α (spectral index α > 0). Correlations found between , , , , and are consistent with the trend of bluer-when-brighter (BWB). It is the same case for colors, magnitudes, color variation rates, and magnitude variation rates of photometric observations. The variations of α lead those of Fλ. Also, the color variations lead magnitude variations. The observational data are mostly distributed in the I(+,+) and III(−,−) quadrants of the coordinate system. Both spectroscopic and photometric observations show BWB behaviors in S5 0716+714. The observed BWB may be explained by the shock-jet model, and its appearance may depend on the relative position of the observational frequency ranges with respect to the synchrotron peak frequencies, e.g., at the left of the peak frequencies. Fractional variability amplitudes are Fvar ∼ 40% for both spectroscopic and photometric observations. Variations of α indicate variations of relativistic electron distribution producing the optical spectra. [ABSTRACT FROM AUTHOR]

We present the photometric observations of blazars S5 0716+714 and 3C 273 with high temporal resolution (30–60 s) in the I or R bands. The observations were performed with a 1.02 m optical telescope from 2007 March 7 to 2012 May 16. The F-test, one-way analysis of variance (ANOVA) test, and z-transformed discrete correlation function (ZDCF) cross-correlation zero lag test are used to search for intra-day variability (IDV). Four and five reliable IDVs survive three tests for S5 0716+714 and 3C 273, respectively. IDVs are found for S5 0716+714 and 3C 273. A flare on 2008 May 8 has ΔI ≈ 0.06 ± 0.01 mag in a duration of 0.54 hr for S5 0716+714. A flare on 2011 May 10 shows ΔR ≈ 0.05 ± 0.01 mag in a duration of 0.40 hr for 3C 273. Sharp dips appear on 2011 May 9 for 3C 273 and show ΔR ≈ 0.05 ± 0.01 mag. Under the assumptions that the IDV is tightly connected to black hole mass, M•, and that the flare durations are representative of the minimum characteristic timescales, we can estimate upper bounds to M•. In the case of the Kerr black holes, M• ≲ 108.91M⊙ and M• ≲ 109.02M⊙ are given for S5 0716+714 and 3C 273, respectively. These mass measurements are consistent with those measurements reported in the literature. Also, we discuss the origins of optical variations found in this work. [ABSTRACT FROM AUTHOR]

We present our observations of the optical intra-day variability (IDV) in γ-ray BL Lac object Mrk 501. The observations were run with the 1.02 m and 2.4 m optical telescopes at Yunnan Observatories from 2005 April to 2012 May. The light curve at the R band on 2010 May 15 passes both variability tests (the F-test and the ANOVA test). A flare within the light curve on 2010 May 15 has a magnitude change of mag, a darkening timescale of minutes, and an amplitude of IDV . A decline described by 11 consecutive flux measurements within the flare can be fitted linearly with a Pearson’s correlation coefficient r = 0.945 at the confidence level of . Under the assumptions that the IDV is tightly connected to the mass of the black hole, and that the flare duration, being two times , is representative of the minimum characteristic timescale, we can derive upper bounds to the mass of the black hole. In the case of the Kerr black hole, the timescale of hr gives , which is consistent with measurements reported in the literature. This agreement indicates that the hypothesis about and is consistent with the measurements/data. [ABSTRACT FROM AUTHOR]