arXiv subjects

Bingqiang Qiao

Publications and source records attributed to Bingqiang Qiao.

3 recordsLinked to original sources

arXiv2022

Prospective Study on Observations of γ-Ray Sources in the Galaxy Using the HADAR Experiment

The High Altitude Detection of Astronomical Radiation (HADAR) experiment is a refracting terrestrial telescope array based on the atmospheric Cherenkov imaging technique. It focuses the Cherenkov light emitted by extensive air showers through a large aperture water-lens system for observing very-high-energy-rays and cosmic rays. With the advantages of a large field-of-view (FOV) and low energy threshold, the HADAR experiment operates in a large-scale sky scanning mode to observe galactic sources. This study presents the prospects of using the HADAR experiment for the sky survey of TeV γ-ray sources from TeVCat and provids a one-year survey of statistical significance. Results from the simulation show that a total of 23 galactic point sources, including five supernova remnant sources and superbubbles, four pulsar wind nebula sources, and 14 unidentified sources, were detected in the HADAR FOV with a significance greater than 5 standard deviations (σ). The statistical significance for the Crab Nebula during one year of operation reached 346.0 σ and the one-year integral sensitivity of HADAR above 1TeV was ~1.3%-2.4% of the flux from the Crab Nebula.

astro-ph.HE↗

arXiv2015

Limitation of the Least Square Method in the Evaluation of Dimension of Fractal Brownian Motions

With the standard deviation for the logarithm of the re-scaled range $\langle |F(t+τ)-F(t)|\rangle$ of simulated fractal Brownian motions $F(t)$ given in a previous paper \cite{q14}, the method of least squares is adopted to determine the slope, $S$, and intercept, $I$, of the log$(\langle |F(t+τ)-F(t)|\rangle)$ vs $\rm{log}(τ)$ plot to investigate the limitation of this procedure. It is found that the reduced $χ^2$ of the fitting decreases with the increase of the Hurst index, $H$ (the expectation value of $S$), which may be attributed to the correlation among the re-scaled ranges. Similarly, it is found that the errors of the fitting parameters $S$ and $I$ are usually smaller than their corresponding standard deviations. These results show the limitation of using the simple least square method to determine the dimension of a fractal time series. Nevertheless, they may be used to reinterpret the fitting results of the least square method to determine the dimension of fractal Brownian motions more self-consistently. The currency exchange rate between Euro and Dollar is used as an example to demonstrate this procedure and a fractal dimension of 1.511 is obtained for spans greater than 30 transactions.

physics.data-an↗

arXiv2013

Error Assessment in Modeling with Fractal Brownian Motions

To model a given time series $F(t)$ with fractal Brownian motions (fBms), it is necessary to have appropriate error assessment for related quantities. Usually the fractal dimension $D$ is derived from the Hurst exponent $H$ via the relation $D=2-H$, and the Hurst exponent can be evaluated by analyzing the dependence of the rescaled range $\langle|F(t+τ)-F(t)|\rangle$ on the time span $τ$. For fBms, the error of the rescaled range not only depends on data sampling but also varies with $H$ due to the presence of long term memory. This error for a given time series then can not be assessed without knowing the fractal dimension. We carry out extensive numerical simulations to explore the error of rescaled range of fBms and find that for $0<H<0.5$, $|F(t+τ)-F(t)|$ can be treated as independent for time spans without overlap; for $0.5<H<1$, the long term memory makes $|F(t+τ)-F(t)|$ correlated and an approximate method is given to evaluate the error of $\langle|F(t+τ)-F(t)|\rangle$. The error and fractal dimension can then be determined self-consistently in the modeling of a time series with fBms.

physics.data-an↗