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This paper investigates the distributed event-triggered control problems of second-order nonlinear multi-agent systems (MASs) with directed graph. Firstly, an event-triggered consensus algorithm is developed for second-order nonlinear MASs. It is proved that MASs reach practical consensus and Zeno-behavior doesn't occur. Secondly, for leader–follower MASs, an event-triggered tracking algorithm is presented, which ensures that follower agents track leader agent even when leader agent has a nonzero input. Finally, a numerical simulation is given to show effectiveness of the proposed consensus algorithm. [ABSTRACT FROM AUTHOR]

Heterogeneous chemistry and aerosol-radiation interaction (ARI) are considered two of the key mechanisms affecting haze formation and their reasonable parameterizations in atmospherically chemical models play an important role in accurate haze or air quality prediction. However, until the present, their relative contributions to severe haze have rarely been evaluated. Using the double-way atmospherically chemical model GRAPES_Meso5.1/CUACE CW, the relative contributions of heterogeneous chemistry and ARI to PM 2.5 are investigated under different pollution levels in Middle-Eastern China (MEC) during December 2016. Study results show that the combined effects of heterogeneous chemistry and ARI generate 29.7% of total PM 2.5 mass in MEC of December 2016, of which ARI contributes 19.7%, much higher than heterogeneous chemistry (6.1%). However, heterogeneous chemistry is important for reasonable reproduction of the proportion of secondary inorganic aerosols (SIA) of PM 2.5 , especially during heavy haze. Both the contributions of heterogeneous chemistry and ARI to PM 2.5 increase with the haze pollution aggravation but to different degrees. The contribution of heterogeneous chemistry to modeled PM 2.5 concentration rises from 4.0% on clean days to 6.6% under moderate pollution and 7.8% under heavy haze. And that of ARI increases rapidly from 9.1% on clean days to 21.0% under moderate pollution and 29.1% during heavy pollution. It is worth noticing that there is an additional contribution to PM 2.5 caused by the combination of heterogeneous chemistry and ARI except for their respective contributions, which reaches up to 7.3% of PM 2.5 mass and 18.5% of SIA generation under heavily polluted conditions. This is because ARI further promotes heterogeneous oxidation of SO 2 and NO x by increasing the aerosol surface area concentration (SAC), causing additional SIA production via heterogeneous pathways. This work indicates the contribution of ARI to severe haze formation not only by altering meteorological conditions but also by reforming the chemical processes in the model. (a) The interaction mechanism between heterogeneous chemistry and ARI in atmospheric chemistry model GRAPES_Meso5.1/CUACE; (b) Percentage contributions of the combined effects of heterogeneous chemistry and ARI (Δ1), heterogeneous chemistry alone (Δ2), ARI alone (Δ3), and the interaction between the two (Δ4) to PM 2.5 mass concentration in MEC. [Display omitted] • Relative contributions of heterogeneous chemistry and ARI to PM 2.5 are evaluated under different pollution levels. • ARI contributes much more to extreme PM 2.5 during severe haze than heterogeneous chemistry. • Their combined effects exceed the sum of the two because ARI further promotes the heterogeneous oxidation of SO 2 and NO x. [ABSTRACT FROM AUTHOR]

• We synthesized high-quality single crystals of bridgmanite up to 300 μm in size. • Bridgmanite crystals contain less than 50 ppm wt. H 2 O at the uppermost lower mantle. • The majority of the top of a pyrolitic lower mantle is nearly dry. Water solubility in the dominant lower-mantle bridgmanite phase remains controversial. Discrepancies between previous results highlight the importance of the growth high-quality single crystals of bridgmanite under high-pressure and high-temperature conditions corresponding to the top of the lower mantle. Here we synthesized high-quality single crystals of aluminous bridgmanite up to 300 μm in size that were saturated with hydrous melt at 24–26 GPa and 1700–1900 K using both stoichiometric and MgO-rich non-stoichiometric hydrous starting materials in a multi-anvil press. Fourier-transform infrared spectroscopy measurements on clear and pure spots of the single-crystal bridgmanites did not detect any pronounced OH-stretching bands, which were prominent in some earlier studies. The present results support that the lower-mantle dominated bridgmanite is nearly dry, at least at the top of the lower mantle, and that Al3+ and Fe3+ cannot enhance water incorporation into the crystal structure even in the presence of oxygen vacancies. Large partition coefficients of water between transition-zone minerals and dry lower-mantle dominated bridgmanite further support dehydration melting at the top of the lower mantle. We suggest that the majority of the top of a pyrolitic lower mantle is nearly dry based on the dry principal minerals and stability of hydrous phases in this region. [ABSTRACT FROM AUTHOR]

Speciation of thallium (Tl) controls its fate and biogeochemical behaviors. Thus, a sensitive and accurately approach for Tl monitoring is of great demand due to its ultra-low concentration and sensitivity to redox change. In this study, diffusive gradients in thin-films technique (DGT) assembled with novel titanium peroxide (TP) binding gels (TP-DGT) was developed for in situ measurement of dissolved Tl(I) and Tl(III) in waters and sediments. Laboratory test showed a linear mass accumulation of Tl(I) and Tl(III) on the TP binding gels with the deployment time from 4 to 72 h. A fascinating performance of this novel DGT was achieved in a pH range of 4–9, ionic strength range of 0.1–200 mmol L−1, and humic acid concentration of 0–30 mg L−1 with a low detection limit of 0.3 ng L−1 for Tl(I) and 0.6 ng L−1 for Tl(III). The TP binding gels own excellent stability (1–365 d) and high capacity (73.5 μg Tl disc−1) which are suitable for long-term monitoring. Field application in a river indicated that TP-DGT could work effectively, comparable to the grab sampling in waters. For the first time, the TP-DGT coupled with oxygen optode was successfully applied to map 2D distribution patterns of Tl and oxygen simultaneously in the rhizosphere of M. verticillatum L. This study confirms TP-DGT is a promising tool for routine monitoring of Tl in waters and for investigating biogeochemical processes of Tl in sediments. [Display omitted] • A novel TP-DGT is developed for in situ measuring Tl in waters and sediments. • TP-DGT can work well in normal environmental conditions. • TP-DGT coupled with oxygen optode can map 2D distribution patterns of Tl and O 2. • The novel TP-DGT can be applied in aquatic systems as a promising monitoring tool. [ABSTRACT FROM AUTHOR]

In this work, (Bi 0.65-0.65 x Ba 0.35-0.35 x Nd x)(Fe 0.65-0.65 x Ti 0.35-0.35 x Nb x)O 3+ x (abbreviated as: BFBT- x NN, x = 0, 0.04, 0.08 and 0.12) ceramics were fabricated through a solid-state reaction method, aiming to obtain high-performance capacitor materials. BFBT ceramics have attracted increasing attention as potential energy storage materials because of their excellent dielectric and ferroelectric properties. However, two handicaps limit the large improvement of their energy storage performance (ESP). One is the large hysteresis of their polarization (P)-electric field (E) loops; the other is the low dielectric breakdown strength (E b), which has a close correlation with the inevitable defects present in BF-based ceramics. Herein, we designed a co-doping strategy to overcome the two handicaps in order to achieve high ESP in BFBT ceramics. In this strategy, the trivalent rare earth Nd3+ ions and high valence Nb5+ ions are simultaneously introduced at the perovskite A- and B-sites of BFBT ceramics, which is called NN co-doping. The NN co-doping enhances the relaxor properties of BFBT ceramics due to the enhanced composition and charge fluctuations and promotes the formation of the Bi-rich phases, which contribute to the appearance of a slim P - E loop. Meanwhile, the E b of BFBT ceramics is enhanced, which is ascribed to the significantly decreased oxygen vacancy concentration, the reduced grain size and the Bi-rich phases. Benefitting from these factors, a high recoverable energy storage density (W rec) of 3.64 J/cm3 and energy storage efficiency (η) of 88% are simultaneously obtained under an enhanced E b of 330 kV/cm in BFBT-0.08NN ceramics. Moreover, the ESP of BFBT-0.08NN ceramics shows good thermal stability (30–150 °C) and charge-discharge properties. These results indicate that BFBT-0.08NN ceramics could be a promising capacitor material. [ABSTRACT FROM AUTHOR]

(1- x)(0.75(Na 0.5 Bi 0.5)TiO 3 -0.25SrTiO 3)- x NdGaO 3 ceramics (NBST- x NG, x = 0–0.06) were fabricated through a solid-state reaction method. High-valent Nd3+ ions enter the perovskite A-site to occupy Bi vacancies resulting from the volatilization of Bi, inhibiting the formation of oxygen vacancies and contributing to an enhanced breakdown electric field (E b). Low-valent Ga3+ ions enter the B-site to substitute for Ti4+ ions, resulting in the formation of random electric fields (REFs) at the B-site due to co-occupying hetero-valence ions of Ga3+/Ti4+, which significantly reduces ferroelectric hysteresis. Therefore, a synergic effect of A- and B-sites co-doping was realized in NBST- x NG ceramics. Benefitting from this synergic effect, an enhanced recoverable energy storage density (W rec) of 2.88 J/cm3 and an efficiency (η) of 83% are simultaneously obtained in NBST-0.04NG ceramics under a moderate electric field (E) of 200 kV/cm. Compared with most NBT-based ceramics, the values of (η vs W rec / E 2) for NBST-0.04NG ceramics show an obvious advantage, indicating excellent potential for application as an energy storage material. Moreover, W rec and η of NBST-0.04NG ceramics exhibit excellent temperature stability from 30 °C to 200 °C due to the enhanced correlation strength of polar nanoregions (PNRs) and local structural stability. This work provides a potential strategy to improve the energy storage performance of NBT-based ceramics via the synergic effect of A- and B-site co-doping. [ABSTRACT FROM AUTHOR]

Low visibility event, as a disastrous weather, has great impacts on traffic and transportation, aircraft, and people's daily life, etc. Timely and accurate forecasts of low visibility events are urgently needed and meaningful. The reasonable algorithm of atmospheric extinction in atmospheric chemistry models is the basis for quantitatively predicting low visibility. The revised IMPROVE algorithm (RIMP) of atmospheric extinction is incorporated into the chemistry-weather interacted model GRAPES_Meso5.1/CUACE CW V1 to improve the prediction of low visibility events (LVEs) in the urban agglomerations in eastern China, which is compared with the original IMPROVE algorithm (OIMP) used in this model. The study results show that the RIMP effectively reduces the overestimation of low visibility prediction by OIMP in general, leading to a decrease of root-mean-square errors (RMSEs) and an increase of Threat Score (TS) of visibility <3 km, 5 km, and 10 km overall both at regional and city scales in varying degrees due to its more detailed processing of aerosols' size, optical feature and hygroscopic growth; The improvements of visibility prediction of LVEs by RIMP depends on the combined contribution of high relative humidity (RH) and PM 2.5 instead of single high RH or PM 2.5. The relative contributions of RH and PM 2.5 concentration on different levels of low visibility are different in Beijing-Tianjin-Hebei (BTH) and Yangtze River Delta (YRD) regions due to their different RH and PM 2.5 , which leads to the different improvement of RIMP in the two regions. The larger improvements by RIMP occur for visibility <5 km in BTH, while in YRD, the larger improvements by RIMP occur for visibility <10 km and >5 km. Moreover, the improvements by RIMP were more evident with higher RH conditions in both regions. The uncertainty created by the extinction algorithm is one important factor of the multiple factors affecting LVEs prediction; accurate modeling of high RH near saturation is also very important for LVEs prediction. • The revised IMPROVE (RIMP) algorithm is applicated to the atmospheric chemistry model to improve low visibility prediction. • RIMP generally improves low visibility prediction than the original IMPROVE algorithm (OIMP). • The improvements in low visibility prediction by RIMP vary depending on different aerosol and humidity conditions. [ABSTRACT FROM AUTHOR]

Compared with climate models, the role of aerosol-cloud interaction (ACI) in mesoscale numerical weather prediction (NWP) models still needs to be better understood, especially in haze regions with relatively high aerosol concentration. Here, we perform two sensitivity experiments with and without ACI (ACI and NO-ACI) in the atmospheric chemistry model GRAPES_Meso5.1/CUACE to investigate the impact of ACI on mesoscale NWP during the low-cloud period in winter 2016 over varying haze regions (severe polluted Jing-Jin-Ji (JJJ), polluted Yangtze River Delta (YRD), and weak polluted Pearl River Delta (PRD)) in China. The study results show that the real-time ACI improves underestimated cloud optical thickness (COT) and cloud water liquid path (CLWP) in haze regions, with the mean bias of simulated COT (CLWP) decreased by 27% (3%), 60% (14%), and 55% (3%) in JJJ, YRD, and PRD, respectively. The increased COT and CLWP lead to a decrease of 6.8, 21, and 13 W m−2 in daytime surface downward shortwave radiation (SDSR) in JJJ, YRD, and PRD, helping to reduce the mean bias of daytime SDSR by 6%, 13%, and 9%. In addition, ACI mitigates the warm bias of temperature at 2 m and dry bias of relative humidity (RH) at 2 m to a certain extent in haze regions, particularly in YRD with the mean absolute bias improved by 13% and 6%. The simulated vertical structure of temperature and RH in the ACI experiment is more consistent with observations than in the NO-ACI experiment. Further investigations find that the ACI effects on mesoscale NWP strongly depend on COT and CLWP magnitude over varying haze regions. Higher COT and CLWP, hence more significant meteorology changes due to ACI, occur in YRD, followed by PRD and JJJ. This study demonstrates the importance and complexity of ACI in modifying mesoscale NWP over varying haze regions of China, which promotes the further understanding of ACI in operational NWP models and bridges the gap with climate models. •ACI increases COT and CLWP when low-cloud and haze coexist. • ACI further leads to decreased SDSR, lower temperature, and higher RH. • ACI-induced changes improve mesoscale NWP to a certain extent. • The ACI effects on mesoscale NWP strongly depend on COT and CLWP magnitude. [ABSTRACT FROM AUTHOR]

The aerosol-radiation interaction mechanism (ARI) is important for air quality modeling, and its absence in atmospheric chemistry models may cause considerable uncertainties. In this study, the real-time calculated aerosol optical parameters, i.e., mass extinction coefficient (K ext), single scattering albedo (ω), and asymmetry factor (g) from the simulated aerosol concentrations are introduced into the Global/Regional Assimilation and Prediction System 5.1 version coupled with the Chinese Unified Atmospheric Chemistry Environment model (GRAPES_Meso5.1/CUACE) to establish the ARI mechanism for the two-way feedback between aerosols and weather processes. Focusing on Beijing-Tianjin-Hebei (BTH), China, in January 2017, ARI impacts on meteorology and haze-fog are simulated by using this atmospheric chemistry model. The results show that during the severe pollution, ARI can significantly alter the meteorology, especially for the heavily polluted central and southern BTH: The surface solar radiation (SSR), the temperature at 2 m (T2), the vertical diffusion coefficient (VDC), and the planetary boundary layer height (PBLH) are reduced by up to 50 W m−2, 2.5°C, 4 m2 s−1, and 100 m, respectively. In addition to surface meteorology, ARI affects the vertical structure of the planetary boundary layer (PBL), by cooling and humidifying the lower air and heating and drying the higher air. These modifications stabilize the PBL, resulting in an increase of 8% in relative humidity at 2 m (RH2), a key factor influencing secondary aerosol generation and aerosol hygroscopic growth. Stabilized PBL and increased RH2 ultimately result in a 100 μg m−3 increase in PM 2.5 concentrations and a 1.5 km reduction in atmospheric visibility (VIS). By considering the ARI, the model generally improves numerical weather prediction (NWP) and haze-fog prediction. For the entire BTH region, the mean biases for T2 and RH2 are reduced by up to 2°C and 4% respectively. This more accurate NWP will lead to an overall improvement in haze-fog prediction, particularly in a heavily polluted city like Shijiazhuang (SJZ), the biases for PM 2.5 and VIS are reduced by 28% and 125% respectively. The results show the positive feedback between meteorology and haze-fog, and demonstrate the importance of ARI in NWP and haze-fog prediction. • Aerosol-radiation interaction (ARI) has a critical influence on the outbreak of severe haze-fog. • The ARI mechanism is achieved in GRAPES_Meso5.1/CUACE. • The two-way coupled model considering ARI significantly improves the prediction of both meteorology and haze-fog. [ABSTRACT FROM AUTHOR]

Concerning the practical applications, dielectric capacitors with simultaneously high recoverable energy density (W rec) and large energy storage efficiency (η) under a low electric field is imperative and challenging. Herein, a strategy of complex ions substitution is proposed to achieve the goal. The (1- x)(0.75Na 0.5 Bi 0.5 TiO 3 -0.25SrTiO 3)- x La(Mg 2/3 Ta 1/3)O 3 (NBST- x LMT) ceramics were fabricated through a solid-state reaction method. A significantly enhanced breakdown electric field (E b) of 246.03 kV/cm is obtained in NBST-0.06LMT ceramics due to the refined average grain size (AGS), the enhanced band gap width and the inhibited oxygen vacancies by LMT doping. Furthermore, a high W rec of 3.18 J/cm3and large η of 86% are concurrently achieved in NBST-0.06LMT ceramics under a relatively low electric field of 246 kV/cm. Meanwhile, the variations of (W rec , η) under 170 kV/cm are less than 10% from 30 ℃ to 200 ℃, indicating an excellent thermal stability. Besides, the ceramics show a fast discharge rate of 155 ns by a charge-discharge measuring. In general, our results demonstrate the strategy of complex ions substitution is an effective way to achieve high energy storage performance under a relatively low electric field in NBT-based ceramics. [Display omitted] • Complex ions (La3+, Mg2+ and Ta5+) substitution was proposed to achieve high energy storage performance. • An enhanced Eb (246.03 kV/cm) was realized in NBST ceramics. • A high Wrec of 3.18 J/cm3and large η of 86% were concurrently obtained under 246 kV/cm. • The (Wrec, η) exhibits excellent thermal stability from 30 ℃ to 200 ℃. [ABSTRACT FROM AUTHOR]