Yuhai Yuan

Guangzhou University

BL Lacertae is a key monitoring target of the 1.26 m National Astronomical Observatory–Guangzhou University Infrared/Optical telescope. Within the monitored duration from 2020 September 4 to 2022 September 28, we report 13,948 observations at the g , r , and i bands ( g band: 4498, r band: 4866, i band: 4584). (1) In the monitored duration, this so...

This study uses a parabolic equation to fit the Inverse Compton (IC) spectral component of 3743 blazars (794 FSRQs, 1432 BL Lacs, and 1517 BCUs) from the 4FGL-DR3 catalog. Some mutual correlations are investigated, and a Bayesian classification is performed to the IC peak frequencies. Our analyses draw the following conclusions: (1) The Bayesian cl...

Based on the database monitored by the 1.26 m National Astronomical Observatory–Guangzhou University Infrared/Optical Telescope, we studied the optical variabilities of FSRQ 3C454.3. The monitoring period was from 2016 October 17 to 2018 December 14, and there were 6701 observations covering the g , r, and i bands (2196 at the g band, 2214 at the r...

In this paper, the multiwavelength data from radio to X-ray bands for 2709 blazars in the 4FGL-DR3 catalog are compiled to calculate their spectral energy distributions using a parabolic equation log ( ν f ν ) = P 1 log ν − P 2 2 + P 3 . Some important parameters including spectral curvature ( P 1 ), synchrotron peak frequency ( P 2 , log ν p ), an...

3C 273 is a well-studied FSRQ. In order to analyze its spectrum variabilities, we make spectroscopic observations of 3C 273 using the 2.16 m telescope at Xinglong Observatory of the National Astronomical Observatories. Based on these observations and some other spectra from the literature, we study the spectrum variabilities and the physical origin...

In this work, we present 8523 pairs of R -band optical photometry observations for the quasar 3C 454.3 made during the period of 2006 October–2018 February on the 70 cm meniscus telescope at Abastumani Observatory, Georgia, to study its intraday variabilities (IDVs) and long-term variations, and we have come to the following results. (1) We detecte...

Active galactic nuclei (AGNs) have been attracting research attention due to their special observable properties. Specifically, a majority of AGNs are detected by Fermi-LAT missions, but not by Fermi-LAT, which raises the question of weather any differences exist between the two. To answer this issue, we compile a sample of 291 superluminal AGNs (1...

In this work, we compiled a sample of 202 Fermi/LAT blazars with available broad line emissions. Out of the 202 sources, 66 have known Doppler factors. The correlation between ($\gamma$-ray) and broad-line emission, and that between radio and broad-line emission are investigated by removing the effects of redshift and beaming boosting for the whole...

Active galactic nuclei (AGNs) have been attracting research attention due to their special observable properties. Specifically, a majority of AGNs are detected by Fermi-LAT missions, but not by Fermi-LAT, which raises the question of whether any differences exist between the two. To answer this issue, we compile a sample of 291 superluminal AGNs (1...

Blazars are a special subclass of active galactic nuclei with extreme observation properties. This subclass can be divided into two further subclasses of flat spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs) according to their emission line features. To compare the spectral properties of FSRQs and BL Lacs, the 1.4 GHz radio, optical...

In this paper, the average energy of the \(\gamma\)-photon (\(E_{\mathrm {a},\mathrm{ph}}\)) is calculated and the correlation between \(\log E_{\mathrm{a},\mathrm{ph}}\) and the logarithm of the synchrotron peak frequency (\(\log\nu_{\mathrm{p}}\)) is discussed for a sample of 620 BL Lac objects. The results show that there exists a positive corre...

Context. Using the 1.56 m telescope at the Shanghai Observatory (ShAO), China, we monitored two sources, BL Lac object S5 0716+714 and flat spectrum radio quasar (FSRQ) 3C 273. For S5 0716+714, we report 4969 sets of CCD (Charge-coupled Device) photometrical optical observations (1369 for V band, 1861 for R band and 1739 for I band) in the monitori...

Variability is one of the extreme observational properties of BL Lacertae objects. AO 0235+164 is a well studied BL Lac through the whole electro-magnetic wavebands. In the present work, we show its optical R band photometric observations carried out during the period of Nov, 2006 to Dec. 2012 using the Ap6E CCD camera attached to the primary focus...

In this work, we present optical R band observations of AO 0235+164 carried out during the period of November 2006 to December 2012 using the Ap6E CCD camera attached to the primary focus of the 70 cm meniscus telescope at Abastumani Observatory, Georgia. It shows a large variation of Δ R = 4.88 mag (14.19–19.07 mag) and a short time scale of Δ T v...

(Abridged) In this paper, multi-wavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, $\log(\nu F_{\nu}) = P_1(\log\nu - P_2)^2 + P_3,$ is used for SED fitting. Synchrotron peak frequency ($\log \nu_p$), spectral curvature ($P_1$), peak flux ($\nu_{\rm p}F_{\rm...

In this paper, we present VRI photometric observations of NGC1275 obtained by using the 1.56 m telescope at Shanghai Observatory (ShAO), China, during the period of Nov. 2005 to Feb. 2014. Our observations show that the maximum variabilities at three bands are ΔmV=1.03±0.09 mag, ΔmR=0.82±0.08 mag and ΔmI=0.95±0.03 mag; and the time scales are Δt1=2...

Blazars are strong γ-ray emitters, the γ-ray emissions are likely strongly beamed, therefore, one should use the intrinsic (de-beamed) emissions to investigate its emission nature. In this work, we compiled a sample of Fermi blazars with available beaming Doppler factors, δR, to investigate the correlation between γ-ray flux density, logfγ, and red...

In this work, we reported the optical photometry monitoring results for two brightest nearby quasars, PHL 1811 and 3C 273 using the ST-6 camera at Abastumani Observatory, Georgia. For PHL 1811, we found 3 microvariability events with time scale of ΔT = 6.0 min. For 3C273, we found that the largest variations are ΔV = 0.369 ± 0.028 mag, ΔR = 0.495 ±...

Variability is one of the extreme observational properties of BL Lacertae objects. AO 0235+164 is a well studied BL Lac through the whole electro-magnetic wavebands, it is violently variable in the optical bands. In the present work, we show its optical R band photometric observations carried out during the period of Nov. 2006 to Dec. 2012 using th...

In this talk, we will show the beaming effect for Fermi/LAT blazars, then we discuss the correlations between γ-ray luminosity and other parameters, such as radio Doppler factors, superluminal motions, and core-dominance parameters. We also compare the Doppler factors determined from the γ-ray luminosity, X-ray emissions, and the short-term time sc...

Using the 1.56 m telescope at Shanghai Observatory, China, we present the photometric results of 1ES 1959+650, which cover from 2006 June 11 to 2014 July 31. The maximum variabilities are DmV max = 1.74 ±0.02 ± mag in the V band, ΔmR max = 0.97 ±0.02 ± mag in the R band, and ΔmI max = 1.15 ±0.03 ± mag in the I band. During the monitoring period, we...

In the radio band, the relationship between the emission spectrum (α) and flux density (F) can demonstrate the emission theory and process. In this paper, we used the radio data of 3C273 and 3C446 from UMRAO (the University of Michigan Radio Observatory) to calculate the spectral indices (α), and analyzed the relationship between spectral indices (...

According to the data of optical observations of the Tuorla Observatory in Finland, using the power spectrum method, DCF (Discrete Correlation Function) method, and Jurkevich method, respectively, we analyzed the periodicity of the long-term light variation of the BL Lac object 1ES 1959+650, and obtained its light period to be P =1.4±0.3 yr. Assumi...

University Michigan RAdio Observatory (UMRAO) supply many radio photometries and polarimetries. We select a sample of 81 blazars from UMRAO and analyse the correlations between their spectral index and polarizations. Out of 35 BL Lacs and 46 FSRQs in the sample, 8 and 15 show strong correlation.

Variability is one of the most observable characteristics of active galactic nuclei, and it is important when considering the emission mechanism. In this paper, we report optical photometry monitoring of two nearby brightest quasars, PHL 1811 and 3C?273, using the ST-6 camera attached to the Newtonian focus and the Ap6E CCD camera attached to the p...

In this work, we analyze the X-ray spectral indices of the 245 Fermi-detected blazars. Relations between the γ-ray emission and the X-ray emission are our research focuses. Our analysis shows that: (1) the X-ray spectral indices of the Fermi/LAT-detected-blazars (α X|Fermi ), have similar distributions with those of non-Fermi-detected blazars (α X|...

In this paper, the preliminary data from University of Michigan Radio Astronomy Observatory database (UMRAO) are used to discuss the radio spectral index properties of 8 BL Lacs. To do so, we calculated the radio spectral index, α (F ∝ ν α ), which was obtained by fitting the averaged flux densities in the bands (4.8 GHZ, 8 GHz, and 14.5 GHz) by bi...

In this paper, we estimated the black hole mass for some blazars with available variability time scales by assuming that the γ-ray emissions are from a distance of 200R g from the center. The results show that the central black hole masses are in the range of log (M/M ⊙) = 6.45 to 8.30.

In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi γ-ray data is compiled to investigate the correlation both between the X-ray spectral index and the γ-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes α...

Treatment-emergent abnormalities in electrocardiogram parameters.

Background The study evaluated efficacy and safety of the 2 mg dose of prucalopride compared to placebo in patients with chronic constipation (CC) from the Asia-Pacific region. Methods Randomized, placebo-controlled, parallel-group, phase III study with 2-week run-in, 12-week treatment phase, and 1-week follow-up. Adult patients with CC (≤2 sponta...

In this paper, a sample including 68 blazars (18 BL Lacs and 50 FSRQs) with known Doppler factors and superluminal velocity from our previous papers is presented. Both the Lorentz factors (Γ) and viewing angles (θ) are estimated for the 68 sources. The relationship between BL Lacs and FSRQs is also revisited using the two variables of gG and θ. The...

Based on the new data from the database of the University of Michigan Radio Astronomy Observatory (UMRAO), we analyze the spectral index and optical variability of OJ287 and 3C279. The main results show that 1) the time delay among three radio bands (4.8, 8, and 14.5 GHz) shows: τ 8−14.5 = 31 d, τ4.8−8 = 41 d for OJ287, but no time delay lying in 3...

Double perovskite YBaCuFeO5+δ samples were prepared by two different sintering procedures. The interstitial oxygen contents of two samples are different which were estimated from thermogravimetric analysis (TGA). The mechanical spectrum below room temperature was measured using the vibrating reed method at kilohertz frequencies. Two internal fricti...

Double perovskite oxide YBaCuFeO5+delta samples (labeled as "as-prepared") were sintered by a solid-state reaction technique. Mechanical spectra of as-prepared sample were measured under vacuum condition from room temperature up to 720K by the reed vibration method. In the first heating run, two internal friction peaks were observed around 380 and...

We extend an experimental procedure to measure the complex Young’s modulus of glycerol from liquid to glassy state, a composite reed vibration method. In this report, a rigorous analysis is obtained to subtract the mechanical spectrum of deposited materials from a composite system consisting of the substrate reed and of materials deposited on it. T...

In this work, we present the analysis results using UMRAO preliminary data base. We used the light curves 1) to get the shortest timescales and then to get the brightness temperature so that we can estimate the Doppler factors; 2) to investigate the periodicity and discuss the variability index. We also used the data base to discuss the polarizatio...

We use the database of University of Michigan Radio Astronomy Observatory (UMRAO) at three radio bands (4.8, 8 and 14.5 GHz) to analyse the long-term polarization variation in search of the possible periodicity. Using the power spectral analysis method (PSA), the Jurkevich method and the discrete correlation function (DCF) method, we find that ther...

The method of time delay correlation function (TDCF) is a new method for calculating the sequential time delays. This method is utilized to calculate the time delays in 3 radio wave bands (4.8GHz, 8GHz and 14.5GHz) of the blazar 0316+413 (NGC 1275) and to make the multi-band correlation analysis for other 7 blazar sources. The calculated result of...

To compare the efficacy and tolerability of oral hyoscine butylbromide tablets and capsules in Chinese patients with recurrent episodes of self-reported gastric or intestinal spasm-like pain and to show non-inferiority of both formulations. 302 patients were entered into a randomized, double-blind, double-dummy, active-controlled 2-arm parallel gro...

The internal friction of partially Sr-substituted Pr(Ba1−xSrx)2Cu3O7−δ (x = 0, 0.05, 0.1, 0.2, 0.3, and 0.4) ceramics was measured by the vibrating-reed method from liquid nitrogen temperature to room temperature at kilohertz frequencies. The intensity of the internal friction peak, which appears around 250 K, decreases upon Sr doping. The result i...

A method was designed to measure the mechanical spectrum of materials from liquid to solid state in a composite reed vibration system. More experiments were performed to check the reliability of this method with the variation of deposited area. Negligible differences in the spectra are found with different deposited areas. However, a clear distinct...

Recently a composite reed vibration method has been designed to measure the mechanical spectra (complex Young's modulus) of materials from liquid to solid state. The mechanical spectra of materials can be obtained from a composite system consisting of a substrate reed and of materials deposited on it. In this report, two sets of formulas to calcula...

Normalized mechanical spectra of glycerol, 1,2-propanediol carbonate and poly(vinyl chloride)/di(2-ethyl-hexyl) phthalate (PVC/DOP) blends were studied in the temperature range from 100 to 300K by a composite method. The dynamic glass transition was observed, which exhibits a peak of temperature-dependent loss modulus. The peak moves toward higher...

Recently a composite reed vibration method has been designed to measure the mechanical spectra (complex Young's modulus) of materials from liquid to solid state. The normalized mechanical spectra of materials can be obtained from a composite system consisting of a substrate reed and of materials deposited on it. In this report, this method has been...

In this work, using the data base at the University of Michigan Radio Astronomy Observatory (UMRAO) at 8 GHz, we investigated the possible periodicity in the radio light curves using Jurkevich analysis method. The results show that the radio sources display a possibly physically significant periodicity in a range of 0.08 to 14.5 years. Besides, the...

In this paper, we used the method to determine the central black mass (M), and the boosting factor (δ), the propagation angle (Φ), and the distance along the axis to the site of the γ-ray production (d) as well for 32 γ-ray loud blazars with available variability timescales. If we take the intrinsic γ-ray luminosity to be λ times the Eddington lumi...

Optically, thin two-temperature accretion flows may be thermally and viscously stable, but acoustically unstable. Here, we propose that the O-mode instability of a cooling-dominated optically thin two-temperature inner disk may explain the 23-day quasi-periodic oscillation (QPO) period observed in the TeV and X-ray light curves of Mkn 501 during it...

The mechanical spectrum of bilayer cuprate La1.82Sr0.18CaCu2O6+delta (La2126) was measured using the vibrating reed method from 30 K to room temperature at kilohertz frequency. A clear modulus softening was observed at 223 K accompanied by a sharp internal friction peak, which evidences a phase transition. Another broad internal friction peak aroun...

In this paper, we used the database of the university of Michigan Radio Astronomy Observatory (UMRAO) at three (4.8 GHz, 8.0 GHZ, and 14.5 GHz) radio frequency to analyze the radio light curves by the power spectral analysis method in search of possible periodicity. The analysis results showed that the radio sources display astrophysically meaningf...

We reported the result of long term optical variability of the blazar 4C 29.45 (QSO 1156+295, Ton 599), carried out optical photometric observations in Johnson V, Cousins RI passbands during April 1997 to March 2002 using the 1.56 meter telescope of the Shanghai Astronomical Observatory (SHAO) at Sheshan, China, compiled the post-1974 optical photo...

A new experimental method describing the determination of the mechanical spectra (complex Young’s modulus Y^*=Y^′+iY^″ versus temperature) of materials from the liquid to the glassy state, including the glass transition, is reported. The conventional vibration-reed method developed for solids is extended to composite s...