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The aqueous-phase chemistry of glyoxal (GL) with reduced nitrogen compounds (RNCs) is a significant source for secondary brown carbon (SBrC), which is one of the largest uncertainties in climate predictions. However, a few studies have revealed that SBrC formation is affected by multifunctional RNCs, which have a non-negligible atmospheric abundance. Hence, we assessed theoretical and experimental approaches to investigate the reaction mechanisms and kinetics of the mixtures for ammonium sulfate (AS), multifunctional amine monoethanolamine (MEA), and GL. Our experiments indicate that light absorption and growth rate are enhanced more efficiently in the MEA–GL mixture relative to AS–GL and MEA–AS–GL mixtures and MEA reactions of the chromophores than in the analogous AS reactions. Quantum chemical calculations show that the formation and propagation of oligomers proceed via four-step nucleophilic addition reactions in three reaction systems. The presence of MEA provides the two extra branched chains that affect the natural charges and steric hindrance of intermediates, facilitating the formation of chromophores. Molecule dynamics simulations reveal that the interfacial and interior attraction on the aqueous aerosols with MEA is more pronounced for small α -dicarbonyls to facilitate further engagement in the aqueous-phase reactions. Our results show a possible missing source for SBrC formation on urban, regional, and global scales. [ABSTRACT FROM AUTHOR]

In order to achieve high precision of the time and frequency synchronization of pseudolite automatic network，a pseudolite time and frequency synchronization system using the structure of Self-Calibrating Pseudolite Array(SCPA) is designed. The system takes FPGA+DSP as the core processor, and integrates high-speed A/D, D/A conversion circuit and up and down converter circuit. The design and implementation of pseudolite two-way pseudo distance measurement technology and the time and frequency synchronization scheme are introduced in detail. The test results show that the phase synchronization error of carrier phase is less than 0.1 Hz and the time synchronization accuracy is better than 2 ns, which provids a significant guarantee for the positioning and timing accuracy of the pseudolite automatic system.

In order to achieve high-precision indoor positioning and overcome the limitations of GPS navigation system indoor or other complex environments, a high-precision indoor positioning scheme based on pseudo satellite is proposed. FPGA+DSP are used as the core processor, and high-speed A/D conversion circuit and up and down converter circuit are integrated. The design and implementation of pseudo satellite signal clock synchronization method and near-far effect elimination are introduced in detail. Through the system test, the results show that the indoor static positioning accuracy and dynamic positioning accuracy are both within 3 cm, and the high-precision indoor positioning is realized. The implementation of this scheme is of great significance for indoor and outdoor seamless positioning.

Aqueous-phase chemistry of glyoxal (GL) with reduced nitrogen compounds (RNCs) plays a significant source of secondary brown carbon (SBrC), which is one of the largest uncertainties in climate predictions. However, few studies have revealed that SBrC formation is affected by multifunctional RNCs, which has a non-negligible atmospheric abundance. Hence, we performed theoretical and experimental approaches to investigate the reaction mechanisms and kinetics of the mixtures for ammonium sulfate (AS), multifunctional amine (monoethanolamine, MEA) and GL. Our experiments indicate that the light-absorption and the growth rate are enhanced in MEA-GL mixture relative to AS-GL and MEA-AS-GL mixtures, and MEA reactions of the chromophores by more efficiently than the analogous AS reactions. Quantum chemical calculations show that the formation and propagation of oligomers proceed via four-step nucleophilic addition reactions in three reaction systems. The presence of MEA provides the extra two branched chains to affect the natural charges and steric hindrance of intermediates, facilitated the formation of chromophores. Molecule dynamics simulations reveal that the interfacial and interior attraction on the aqueous aerosols with MEA is more pronounced for small α-dicarbonyls, to facilitate the further engagement in the aqueous-phase reactions. Our results show a possible missing source for SBrC formation on urban, regional and global scales. [ABSTRACT FROM AUTHOR]

An ionospheric positive disturbance during a moderate geomagnetic storm on October 13, 2016 was studied with total electron content (TEC) from a chain of GNSS receivers and F2 layer peak parameters from two ionosondes at the Greenwich meridian. During a slow decrease of Dst, a large enhancement of the daytime TEC was observed from high to middle latitudes successively while there was small disturbance observed in low latitudes. The occurrence of TEC peak delayed with decreasing latitude. Similarly, positive disturbance of hmF2 and foF2 was recorded and their onsets were earlier in high latitude than middle latitude. These observations indicated that the ionospheric positive disturbance propagated equatorward which denied the dominant effect of prompt penetration eastward electric field (PPEF). Using the latitudinal and temporal variations of TEC peaks, the propagation velocity of the disturbance was estimated and found to decrease with decreasing latitude. Two available Fabry‐Perot interferometers (FPI) at the meridian 70°W of the Greenwich showed that nighttime equatorward wind in middle latitude increased significantly after the storm sudden commencement (SSC), while no change of that was observed in low latitude. The coincidence of the directional and latitudinal features between the ionospheric disturbance and the wind observation suggested the impact of the positive storm was most likely the equatorward wind surge which raised the ionosphere to higher altitude where lower chemical loss led to increase of electron density in the daytime. Key Points: The ionospheric storm exhibited a large enhancement of TEC in middle and high latitudesThe disturbances of hmF2 and foF2 at 51°N were earlier than that of at 41°NThe positive disturbance was caused most likely by the equatorward wind surge rather than the prompt penetrating eastward electric field [ABSTRACT FROM AUTHOR]