Fingerprint of Galactic Loop I on polarized microwave foregrounds

Context: Currently, detection of the primordial gravitational waves by the B-mode of Cosmic Microwave Background (CMB) is primarily limited by our knowledge of the polarized microwave foreground emissions. Thus improvements of the foreground analysis are necessary. As revealed in~\cite{2018arXiv180410382L}, the E-mode and B-mode of the polarized foreground have noticeable different properties, both in morphology and frequency spectrum, suggesting that they arise from different physical processes, and need to be studied separately. Aims: I will study the polarized emission from Galactic loops, especially Loop I, and mainly focus on the following issues: Does it contribute predominantly to the E-mode or B-mode? In which frequency bands and in which sky regions can it be identified? Methods: Based on a well known result about the magnetic field alignment in supernova explosions, a theoretical expectation is established that the loop polarizations should be predominantly E-mode. In particular, the expected polarization angles of Loop I are compared with those from the real microwave band data of WMAP and Planck. Results and conclusions: The comparison between model and data shows remarkable consistency between data and expectation at all bands and for a large area of the sky. This result suggests that the polarized emission of Galactic Loop I is a major polarized component in all microwave bands from 23 to 353 GHz, and a considerable part of the polarized foreground is likely originated from a local bubble associated with Loop I, instead of the far more distant Galactic emission. The result also provides a possible way to explain the reported E-to-B excess~\citep{2016A&A...586A.133P} by contribution of the loops. Finally, this work may also provide the first geometrical evidence that the Earth was hit by a supernova explosion.Comment: Updated using the Planck 2018 data, and the main conclusion is now even better supporte

Traffic signal control using queueing theory

Traffic signal control has drawn considerable attention in the literatures thanks to its ability to improve the mobility of urban networks. Queueing models are capable of capturing performance or effectiveness of a queueing system. In this report, SOCPs (second order cone program) are proposed based on different queueing models as pre-timed signal control techniques to minimize total travel delay. Stochastic programs are developed in order to handle the uncertainties in the arrival rates. In addition, the superiority of the proposed model over Webster’s model has been validated in a microscopic traffic simulation software named CORSIM.Statistic