Highly reliable relative navigation for multi-UAV formation flight in urban environments

Formation flight of multiple Unmanned Aerial Vehicles(UAVs)is expected to bring significant benefits to a wide range of applications.Accurate and reliable relative position information is a prerequisite to safely maintain a fairly close distance between UAVs and to achieve inner-system collision avoidance.However,Global Navigation Satellite System(GNSS)measurements are vulnerable to erroneous signals in urban canyons,which could potentially lead to catastrophic consequences.Accordingly,on the basis of performing relative positioning with double differenced pseudoranges,this paper develops an integrity monitoring framework to improve navigation integrity(a measure of reliability)in urban environments.On the one hand,this framework includes a fault detection and exclusion scheme to protect against measurement faults.To accommodate urban scenarios,spatial dependence in the faults are taken into consideration by this scheme.On the other hand,relative protection level is rigorously derived to describe the probabilistic error bound of the navigation output.This indicator can be used to evaluate collision risk and to warn collision danger in real time.The proposed algorithms are validated by both simulations and flight experiments.Simulation results quantitatively reveal the sensitivity of navigation performance to receiver configurations and environmental conditions.And experimental results suggest high efficiency and effectiveness of the new integrity monitoring framework.

LncPheDB:a genome-wide lncRNAs regulated phenotypes database in plants

LncPheDB(https://www.lncphedb.com/)is a systematic resource of genome-wide long non-coding RNAs(lncRNAs)-phenotypes associations for multiple species.It was established to display the genome-wide lncRNA annotations,target genes prediction,variant-trait associations,gene-phenotype correlations,lncRNA-phenotype correlations,and the similar non-coding regions of the queried sequence in multiple species.LncPheDB sorted out a total of 203,391 lncRNA sequences,2000 phenotypes,and 120,271 variants of nine species(Zea mays L.,Gossypium barbadense L.,Triticum aestivum L.,Lycopersicon esculentum Mille,Oryza sativa L.,Hordeum vulgare L.,Sorghum bicolor L.,Glycine max L.,and Cucumis sativus L.).By exploring the relationship between lncRNAs and the genomic position of variants in genome-wide association analysis,a total of 68,862 lncRNAs were found to be related to the diversity of agronomic traits.More importantly,to facilitate the study of the functions of lncRNAs,we analyzed the possible target genes of lncRNAs,constructed a blast tool for performing similar fragmentation studies in all species,linked the pages of phenotypic studies related to lncRNAs that possess similar fragments and constructed their regulatory networks.In addition,LncPheDB also provides a user-friendly interface,a genome visualization platform,and multi-level and multi-modal convenient data search engine.We believe that LncPheDB plays a crucial role in mining lncRNA-related plant data.