SearcharxivSearch

arXiv subjects

Junhao Deng

Publications and source records attributed to Junhao Deng.

3 recordsLinked to original sources

APREBot: Active Perception System for Reflexive Evasion Robot

Reliable onboard perception is critical for quadruped robots navigating dynamic environments, where obstacles can emerge from any direction under strict reaction-time constraints. Single-sensor systems face inherent limitations: LiDAR provides omnidirectional coverage but lacks rich texture information, while cameras capture high-resolution detail but suffer from restricted field of view. We introduce APREBot (Active Perception System for Reflexive Evasion Robot), a novel framework that integrates reflexive evasion with active hierarchical perception. APREBot strategically combines LiDAR-based omnidirectional scanning with camera-based active focusing, achieving comprehensive environmental awareness essential for agile obstacle avoidance in quadruped robots. We validate APREBot through extensive sim-to-real experiments on a quadruped platform, evaluating diverse obstacle types, trajectories, and approach directions. Our results demonstrate substantial improvements over state-of-the-art baselines in both safety metrics and operational efficiency, highlighting APREBot's potential for dependable autonomy in safety-critical scenarios. Videos are available at https://sites.google.com/view/aprebot/

cs.RO

A novel reverberation mapping method for blazars

Reverberation mapping (RM) is the most promising method to measure the masses of supermassive black holes in the center of active galaxy nuclei (AGNs). However, the dominant jet component hinders the application of RM method for blazars. In this work, we present a new algorithm to disentangle the contribution of the accretion disk from that of the relativistic jet in blazars by analyzing the spectral break of the optical spectroscopic data. We applied this method to two flat-spectrum radio quasars (FSRQs), PKS 1510-089 and PKS 0736+017. In PKS 1510-089, the variability of the H$\gamma$ line is delayed with respect to the disk emission by approximately 94 days, while the H$\beta$ line shows a lag of about 111 days relative to the disk. In PKS 0736+017, the H$\gamma$ variability is delayed with respect to the disk by roughly 66 days, and the H$\beta$ line exhibits a lag of about 67 days. Based on these measured time lags, we estimate black hole masses of $\sim1.4\times10^{8}\,M_{\odot}$ for PKS 1510-089 and $\sim8.1\times10^{7}\,M_{\odot}$ for PKS 0736+017. This method paves the way to apply the RM method for blazars, and improves the understanding of disk and jet activities.

astro-ph.HE

A sample study on the Fermi-LAT spectral variation behavior of blazars

In this study, we analyze the $\sim 16$ yr Fermi-LAT data of 160 blazars consisting of 92 flat-spectrum radio quasars (FSRQs), 64 BL Lacertae type objects (BL Lacs), and 4 blazar candidates of unknown type objects (BCU), and exhibit their spectral variation. By fitting a linear model ($y = kx + b$) to the monthly binned flux-index plots, we find that most of the FSRQs ($\sim 89\%$) display a harder-when-brighter (HWB) trend ($k>0$), while the majority of BL Lacs ($\sim 64\%$) exhibit a softer-when-brighter (SWB) trend ($k<0$). By plotting their slope ($k$) versus their variability index and inverse Compton (IC) peak frequency, we find a moderate positive correlation between $k$ and the variability index, and we find a moderate negative correlation between $k$ and the IC peak frequency, which we name as the gamma-ray variability sequence of blazars. Additionally, 7 blazars may not follow the linear variation trend, particularly in PKS 0537-441, AP Librae, and PKS 1510-089. Additional very-high-energy gamma-ray emission components may be the cause of the break in the variation trend.

astro-ph.HE