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In this paper, we propose a new amplitude-only method for pattern synthesis of uniform linear array (ULA) based on genetic algorithm (GA) and artificial neural network (ANN), which can produce a low sidelobe pattern with deep nulls. Unlike existing schemes for pattern synthesis, our method can avoid falling into local optimum and exhibits a faster convergence speed, and is also easy to implement due to its low computational complexity. In complicated and changing environments, the proposed method can quickly and accurately synthesize the desired pattern of the ULA. Numerical results demonstrate the effectiveness of the devised algorithm. [ABSTRACT FROM AUTHOR]

In order to better understand the tempo-spatial characteristics of surface ozone (O3) on the regional scale of Yangtze River Delta (YRD), China, cluster analysis was applied to surface O3 monitored from 2016 to 2017 at 110 state-controlled stations. Eight spatial regions with distinct patterns of O3 variations were identified. The exceedances over the Grade I (100 µg/m3) and Grade II (160 µg/m3) National Ambient Air Quality Standard of maximum daily average 8 h O3 (MDA8 O3) varied within 99 ~ 192 and 1 ~ 41 days, respectively, for different subregions. The central and east YRD were the most polluted subregions with higher incidence of O3 episodes, while the southwest and southeast YRD were relatively clean. The spatial disparity of O3 over YRD was strongly affected by local emissions, with larger precursor emissions contributing to higher frequencies of O3 pollution and larger amplitudes of temporal variations. The regional O3 pollution mainly occurred in spring, with higher peaks of MDA8 O3 being observed during April ~ May for most subregions. While for east YRD, O3 pollution was most serious in summer, when its monthly MDA8 O3 reached the highest value (141.0 µg/m3). During the whole study period, the spatial differences of weekly/monthly amplitudes of MDA8 O3 were similar to those of NO2 among the eight subregions, indicating the significant influence of NO2 on O3 over YRD on the yearly timescale. This influence was especially evident in warm seasons for the coastal subregions, where O3 production was controlled by NOx. While for the west inland subregion, O3 was less affected by NO2 variation, indicating a NOx-saturated characteristic of O3 formation. [ABSTRACT FROM AUTHOR]

Transport of nitrogen compounds to groundwater, especially from agricultural fertilization, is a main problem in aquifer contamination. Ammonium (NH4+-N) is one of the most common nitrogen fertilizer forms. In order to evaluate the risk of agricultural fertilizer pollution to aquifers caused by infiltration, a soil column experiment and breakthrough modeling simulation were employed to study NH4+-N retention by a sandy soil profile (10–60 cm depth). The soil used was collected from an irrigated semi-arid cropland in Bulanghe Town, Yuyang District, Yulin City, Shaanxi Province of China, and recombined in a laboratory soil column. Column experiments were accomplished using aqueous solutions containing various concentrations of NH4+-N and the breakthrough curves were determined. The linear soil-water partition coefficients (Kd) were determined from batch equilibrium experiments, and the retardation factor (Rd) for the saturated sandy soil was computed. The lowest NH4+-N concentrations at the depth range of 10-20 cm suggested the strongest NH4+-N sorption. The chemical nonequilibrium model in Hydrus-1D can better simulate the breakthrough of NH4+-N through the soil column. The soil sorption capacity decreases as the irrigation flow rate increases. The results provide a scientific basis for optimization of fertilizer application in agricultural management under irrigation in desert oasis, and those semi-arid areas with similar soil texture and vadose zones of small thickness. [ABSTRACT FROM AUTHOR]

Fabrication of core-shells on sheets is considered as an effective strategy to explore novel functional composite materials. Herein, a three-component composite was successfully constructed by dispersing and anchoring carbon-coated Fe3O4 nanoparticle core-shell structures onto reduced graphene oxide (rGO) sheets. Carbonization of glucose polymer formed carbon shells existing between the Fe3O4 particles and rGO sheets. The structure of core-shells placed on rGO sheets formed close connections and high structural stability to the Fe3O4@C-rGO (FCG) composite. Reversible specific capacity up to 884 mA h g−1 at 0.2 C with good recyclability was achieved with FCG as an anode material of lithium-ion batteries. These unique three-dimensional structures of core-shells on sheets are beneficial to enhancing lithium-ion battery storage capacity, cycle stability, and rate performances.Fabrication of novel functional materials is an effective strategy to construct core-shells on sheets. Fe3O4@C-rGO (FCG) composites have been successfully prepared by fabricating carbon shell-coated Fe3O4 nanoparticles (NPs) and reduced graphene oxide (rGO) sheets together. Carbonization of glucose formed carbon shells between Fe3O4 NPs and rGO sheets. The synergism between core-shell structures and sheets contributed to the close connection and high structure stability in FCG. As anode material of lithium-ion batteries (LIBs), the reversible specific capacity of FCG still maintained 748 mA h g−1 after 300 cycles at 0.2 C with good recyclability. This three-dimensional core-shell on sheets structure is beneficial to enhancing lithium storage capacity, cycle stability and rate performance. [ABSTRACT FROM AUTHOR]

To enhance denitrification in a process of solute infiltration through a soil, a two-section mixed-medium soil infiltration system (TMSIS) for urban non-point pollution was developed. The artificial aerobic respiration and nitrification took place in the upper aerobic section (AES), while grass powders and sawdust were mixed in the bottom anaerobic section (ANS) to supply organic carbon source for denitrification bacteria, and the reduction was increased by iron addition in the ANS. Measured resident concentrations from the bottom of each ANS column were assumed to represent mean values averaged over the column cross-sectional area. The TMSIS with hydraulic loading rates (HLR) of 0.32, 0.24, and 0.16 m3 m−2 day−1 and with wetting-drying ratio (RWD) of 1.0 showed remarkable removal efficiencies for chemical oxygen demand (COD), NH4+-N, and TP, respectively. The hydraulic loading rate of 0.32 m3 m−2 day−1 was selected as the optimal HLR due to the high contaminated runoff treatment efficiency. When RWD was 1.0, 0.5, or 0.2 with hydraulic loading rate of 0.32 m3 m−2 day−1, the TMSIS could treat synthetic urban runoff contaminants very well. The corresponding effluent water met the China’s national quality standard for class V surface water. The wetting-drying ratio of 0.5 with hydraulic loading of 0.32 m3 m−2 day−1 was selected as the optimal operation conditions for the TMSIS. Aerobic respiration and nitrification mainly took place in the upper AES, in which most of the COD and the NH4+-N were removed. Mixed sawdust and grass powders used as a carbon source and heterotrophic denitrification were put at the bottom of the ANS. The developed TMSIS has the potential to be applied for urban non-point pollution removal. [ABSTRACT FROM AUTHOR]

Manganous oxide (MnO)-based composites have motivated extensive researches as an anode electrode for lithium-ion storage due to the high theoretical capacity. Whereas, low cycling stability is the pivotal problem that retards the application of materials. Herein, a hydrothermal-annealing strategy is exploited to obtain the composite materials. The MnO nanoparticles (5–20 nm) wrapped by carbon shells to form core-shell structure are supported on the surface of reduced graphene oxide (rGO) sheets. The rGO flakes in electrode materials possess higher electrical conductivity, and improve the electro-conductibility and structural stability during charging-discharging process. Used as anode for lithium-ion batteries, the composite exhibits large reversible specific capacity (866 mA h g−1 at 0.2 C after 230 cycles) as well as a good cyclicity with a coulombic efficiency of 96%. The hydrothermal-annealing synthetic pathway opens up possibilities for designing and preparing novel electrode materials of lithium or other metallic ion batteries. [ABSTRACT FROM AUTHOR]