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Yuyang Chen

Publications and source records attributed to Yuyang Chen.

38 records · Page 3Linked to original sources

A New Bayesian Optimization Algorithm for Complex High-Dimensional Disease Epidemic Systems

This paper presents an Improved Bayesian Optimization (IBO) algorithm to solve complex high-dimensional epidemic models' optimal control solution. Evaluating the total objective function value for disease control models with hundreds of thousands of control time periods is a high computational cost. In this paper, we improve the conventional Bayesian Optimization (BO) approach from two parts. The existing BO methods optimize the minimizer step for once time during each acquisition function update process. To find a better solution for each acquisition function update, we do more local minimization steps to tune the algorithm. When the model is high dimensions, and the objective function is complicated, only some update iterations of the acquisition function may not find the global optimal solution. The IBO algorithm adds a series of Adam-based steps at the final stage of the algorithm to increase the solution's accuracy. Comparative simulation experiments using different kernel functions and acquisition functions have shown that the Improved Bayesian Optimization algorithm is effective and suitable for handing large-scale and complex epidemic models under study. The IBO algorithm is then compared with four other global optimization algorithms on three well-known synthetic test functions. The effectiveness and robustness of the IBO algorithm are also demonstrated through some simulation experiments to compare with the Particle Swarm Optimization algorithm and Random Search algorithm. With its reliable convergence behaviors and straightforward implementation, the IBO algorithm has a great potential to solve other complex optimal control problems with high dimensionality.

stat.ME↗

AstroSat UVIT Detections of Chandra X-ray Sources in M31

An ultraviolet survey of M31 has been carried out during 2017-19 with the UVIT instrument onboard the AstroSat Observatory. Here we match the M31 UVIT source catalog (Leahy et al. 2020) with the Chandra source catalog (Vulic et al. 2016). We find 67 UVIT/Chandra sources detected in a varying number of UV and X-ray bands. The UV and X-ray photometry is analyzed using powerlaw and blackbody models. The X-ray types include 15 LMXBs and 5 AGNs. Cross-matches with catalogs of stars, clusters and other source types yield the following. 20 of the UVIT/Chandra sources match with M31 globular clusters and 9 with foreground stars. 3 more globular clusters and 2 more foreground stars are consistent with the UVIT source positions although outside the Chandra match radius of 1 arcsec. The UV emission of the UVIT/Chandra sources associated with globular clusters is consistent with emission from blue horizontal branch stars rather than from the X-ray source. The LMXBs in globular clusters are among the most luminous globular clusters in M31.Comparison with stellar evolutionary tracks shows that the UVIT/Chandra sources with high UV blackbody temperatures are consistent with massive (10 to 30 M$_{\odot}$) stars in M31.

astro-ph.GA↗