A GNSS Anti-Spoofing Technique Based on the Spatial Distribution Characteristic of the Residual Vectors

Anti-spoofing is becoming a crucial technique for applications with high navigation accuracy and reliability requirements.Anti-spoofing technique based on Receiver Autonomous Integrity Monitoring(RAIM)is a good choice for most Global Navigation Satellite System(GNSS)receivers because it does not require any change to the hardware of the receiver.However,the conventional RAIM method can only detect and mitigate a single spoofing signal.Some improved RAIM methods can deal with more spoofing signals,but the computational complexity increases dramatically when the number of satellites in view increase or need additional information.This paper proposes a new RAIM method,called the SRV-RAIM method,which has a very low computation complexity regardless of the number of satellites in view and can deal with any number of spoofing signals.The key to the new method is the spatial distribution characteristic of the Satellites'Residual Vectors(SRV).In replay or generative spoofing scenarios,the pseudorange measurements of spoofing signals are consistent,the residual vectors of real satellites and those of spoofing satellites have good separation characteristics in spatial distribution.Based on this characteristic,the SRV-RAIM method is proposed,and the simulation results show that the method can separate the real signals and the spoofing signals with an average probability of 86.55%in the case of 12 visible satellites,regardless of the number of spoofing signals.Compared to the conventional traversal-RAIM method,the performance is only reduced by 3.59%,but the computational cost is reduced by 98.3%,so most of the GNSS receivers can run the SRV-RAIM algorithm in time.

Bionic peptide scaffold in situ polarization and recruitment of M2 macrophages to promote peripheral nerve regeneration

Tissue regeneration requires exogenous and endogenous signals,and there is increasing evidence that the exogenous microenvironment may play an even more dominant role in the complex process of coordinated multiple cells.The short-distance peripheral nerve showed a spontaneous regenerative phenomenon,which was initiated by the guiding role of macrophages.However,it cannot sufficiently restore long-distance nerve injury by itself.Based on this principle,we firstly constructed a proinflammatory model to prove that abnormal M2 expression reduce the guidance and repair effect of long-distance nerves.Furthermore,a bionic peptide hydrogel scaffold based on self-assembly was developed to envelop M2-derived regenerative cytokines and extracellular vesicles(EVs).The cytokines and EVs were quantified to mimic the guidance and regenerative microenvironment in a direct and mild manner.The bionic scaffold promoted M2 transformation in situ and led to proliferation and migration of Schwann cells,neuron growth and motor function recovery.Meanwhile,the peptide scaffold combined with CX3CL1 recruited more blood-derived M2 macrophages to promote long-distance nerve reconstruction.Overall,we systematically confirmed the important role of M2 in regulating and restoring the injury peripheral nerve.This bionic peptide hydrogel scaffold mimicked and remodeled the local environment for M2 transformation and recruitment,favoring long-distance peripheral nerve regeneration.It can help to explicate regulative effect of M2 may be a cause not just a consequence in nerve repair and tissue integration,which facilitating the development of pro-regenerative biomaterials.