Robust UKF algorithm with motion constraint in BDS navigation

In a complex urban environment,navigation based on single BeiDou navigation satellite system (BDS) will be interfered by multipath (MP) and non-line-of-sight (NLOS) signals, which degrades the accuracy of positioning. In order to solve this problem, a robust unscented Kalman filter (UKF) with motion constraint is proposed. The algorithm constructs an equivalent weight function based on the innovation vector, which will overcome the problem of performance degradation of conventional robust method caused by inaccurate initial values of the position and receiver clock offset. In addition, the approximate moving direction and elevation of the carrier are used to further enhance the filtering solution. The actual on-board experiment results show that this method can effectively suppress the interference of MP and NLOS signals, and improve the accuracy of BDS navigation in urban environments

Application of aptamer-functionalized nanomaterials in molecular imaging of tumors

Elaborated AFNs used in molecular imagin

Higher-order optical rabi oscillations

Rabi oscillations express a phenomenon of periodic conversion between two wave states in a coupled system. The finding of Rabi oscillation has led to important applications in many different disciplines. Despite great progress, it is still unknown whether the Rabi oscillating state can be excited in the framework of the higher-order vector vortex regime. Here, we demonstrate in theory that the higher-order vector vortex light beams can be Rabi oscillating during evolution in an optical coupling system. This new classical oscillating state of light is characterized by a topologically shaped wavefront and coupled with spatially varying polarization. The vector vortex state exhibits a harmonic oscillatory property in the resonant and nonresonant conditions but differs greatly in Rabi oscillating frequencies. During Rabi oscillation, the complex state maintains its topology and intensity profile, while its intrinsic polarization pattern varies adiabatically in a periodic manner. We present an interpretation of the Rabi oscillation of the higher-order wave states in terms of the coupled-mode theory. Furthermore, we reveal a symmetry-protected transition between two Rabi oscillating modes, driven by a slowly varying phase mismatch. This Rabi transition has not been reported in either quantum mechanics or any other physical setting. This work advances the research of Rabi oscillation into the higher-order regime, and it may lead to novel applications in classical and quantum optics

Multifunctional Optical Crystals for All-Solid-State Raman Lasers

In the past few decades, the multifunctional optical crystals for all-solid-state Raman lasers have been widely studied by many scholars due to their compactness, convenience and excellent performance. In this review, we briefly show two kinds of multifunctional Raman crystals: self-Raman (laser and Raman effects) crystals and self-frequency-doubled Raman (frequency-doubling and Raman effects) crystals. We firstly introduce the properties of the self-Raman laser crystals, including vanadate, tungstate, molybdate and silicate doped with rare earth ions, as well as self-frequency-doubled Raman crystals, including KTiOAsO4 (KTA) and BaTeMo2O9 (BTM). Additionally, the domestic and international progress in research on multifunctional Raman crystals is summarized in the continuous wave, passively Q-switched, actively Q-switched and mode-locked regimes. Finally, we present the bottleneck in multifunctional Raman crystals and the outlook for future development. Through this review, we contribute to a general understanding of multifunctional Raman crystals