•The ability of CNN to estimate rice grain yield using UAV images is investigated.•The correlation between VI and rice grain yield is low at the ripening stage.•The proposed CNN provides robust yield ...forecast throughout the ripening stage.•RGB images dominate the network training at the ripening stage of paddy rice.•A more robust network can be trained by RGB data from late stage.
Forecasting rice grain yield prior to harvest is essential for crop management, food security evaluation, food trade, and policy-making. Many successful applications have been made in crop yield estimation using remotely sensed products, such as vegetation index (VI) from multispectral imagery. However, VI-based approaches are only suitable for estimating rice grain yield at the middle stage of growth but have limited capability at the ripening stage. In this study, an efficient convolutional neural network (CNN) architecture was proposed to learn the important features related to rice grain yield from low-altitude remotely sensed imagery. In one major region for rice cultivation of Southern China, a 160-hectare site with over 800 management units was chosen to investigate the ability of CNN in rice grain yield estimation. The datasets of RGB and multispectral images were obtained by a fixed-wing, unmanned aerial vehicle (UAV), which was mounted with a digital camera and multispectral sensors. The network was trained with different datasets and compared against the traditional vegetation index-based method. In addition, the temporal and spatial generality of the trained network was investigated. The results showed that the CNNs trained by RGB and multispectral datasets perform much better than VIs-based regression model for rice grain yield estimation at the ripening stage. The RGB imagery of very high spatial resolution contains important spatial features with respect to grain yield distribution, which can be learned by deep CNN. The results highlight the promising potential of deep convolutional neural networks for rice grain yield estimation with excellent spatial and temporal generality, and a wider time window of yield forecasting.
Lithium-ion batteries have become the most promising energy storage devices in recent years. However, the simultaneous increase of energy density and power density is still a huge challenge. ...Ultrafast laser structuring of electrodes is feasible to increase power density of lithium-ion batteries by improving the lithium-ion diffusion kinetics. The influences of laser processing pattern and film thickness on the rate capability and energy density were investigated using Li(Ni0.6Mn0.2Co0.2)O2 (NMC 622) as cathode material. NMC 622 electrodes with thicknesses from 91 µm to 250 µm were prepared, while line patterns with pitch distances varying from 200 µm to 600 µm were applied. The NMC 622 cathodes were assembled opposing lithium using coin cell design. Cells with structured, 91 µm thick film cathodes showed lesser capacity losses with C-rates 3C compared to cells with unstructured cathode. Cells with 250 µm thick film cathode showed higher discharge capacity with low C-rates of up to C/5, and the structured cathodes showed higher discharge capacity, with C-rates of up to 1C. However, the discharge capacity deteriorated with higher C-rate. An appropriate choice of laser generated patterns and electrode thickness depends on the requested battery application scenario; i.e., charge/discharge rate and specific/volumetric energy density.
•The new quantification method of river microhabitat heterogeneity index was proposed.•River microhabitat heterogeneity can support macroinvertebrate species diversity well.•Debris flow weakens the ...ecological role of river microhabitat heterogeneity.•The best interval of river microhabitat heterogeneity index is ≥ 8.0 for protecting water ecology.
Mountain rivers provide habitat or refuges and create migration corridors for diverse aquatic and riparian organisms. River microhabitat heterogeneity (RMH), which plays a key role in ecological restoration, is sensitive to external disturbances in mountain rivers. However, the effects of RMH, induced by hydro-geomorphological processes, on local macroinvertebrates have not been quantitatively studied. To explore the ecological significance of RMH, we proposed a new RMH index (RMHI) for quantitative evaluation of RMH and selected five debris flow-dominated mountain rivers (DMR) and five equilibrium sediment transport mountain rivers (EMR) as contrasting examples based on the richness of sediment supply. We found that RMH supported macroinvertebrate α-diversity and functional richness in both DMR and EMR, but debris flow weakened the ecological role of RMH in DMR. The proposed RMHI should be ≥ 8.0 to maintain the ecological health of mountain rivers. Besides, the macroinvertebrate communities were mainly driven by species turnover in EMR, while species turnover and nestedness were balanced in DMR. And macroinvertebrate community shift from an R-strategy to a K-strategy due to deposition and erosion. According to the research results, we put forward the following suggestions. At the watershed scale, ecological conservation of mountain rivers requires a regional approach focusing on multiple sites in EMR. Priority should be given to protect the river with high macroinvertebrate species richness and close attention needs to be paid to multiple sites of DMR. At the river scale, we can protect the biodiversity of mountain rivers by maintain RMHI above its threshold.
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•Seasonal variations in bacterial community were more obvious than spatial variations.•Planktonic bacterial communities had stronger distance-decay patterns in spring.•Network of the ...mainstem had the lowest modularity.•Bacterial community was strongly affected by deterministic processes between seasons.•Stochastic processes dominated the bacterial community structure within seasons.
The incoming water area of the Central Line Project of the South-to-North Water Diversion comprises the upper reaches of the Han River in China. Bacterioplankton are important members of river ecosystems. However, the mechanisms (deterministic or stochastic processes) regulating planktonic bacterial community structure in the upper Han River are not well understood. Herein, we documented the spatiotemporal patterns, assembly processes, and co-occurrence relationships of the planktonic bacterial communities in the Han River and its tributaries. Seasonal variations in bacterioplankton communities were clearly observed and were more obvious than spatial differences. The planktonic bacterial community showed a significant distance (dendritic distance) decay pattern during the two sampling periods, and the distance decay pattern was stronger in spring than in the other season. Network analysis showed that bacterial community networks displayed non-random co-occurrence patterns, and significant differences in the topological properties of empirical and random networks (average clustering coefficient, average path length, and average degree) were found. Compared to those of the tributaries, the network of the mainstem had the lowest modularity; this may be caused by the significant difference in biodiversity between the mainstem and the tributaries. Redundancy analysis revealed that pH exhibited significant effects on the planktonic bacterial community in both seasons. However, variation partitioning analysis showed that spatial factors (stochastic processes) contributed more to explaining community assembly than environmental factors during the two seasons. In addition, the neutral community model can also explain a large part of the community variation observed during the autumn and spring (R2 = 0.817 and 0.808, respectively). This study shows that seasonal variation in the bacterial community is greatly influenced by seasonal environmental variation. However, stochastic processes dominantly affect the structure of the bacterioplankton community within seasons. In order to effectively manage and protect microbial diversity, managers consider not only local species diversity, but also the effect of regional species dispersal.
•We tested patterns of multi-faceted beta diversity across mountain streams.•All three facets of beta diversities increase from the north slope to south slope.•Spatial variables were most important ...in structuring three facets of beta diversity.•Functional and phylogenetic beta diversity complement to taxonomic beta diversity.•Combining multi-faceted biodiversity is essential for management and conservation.
There is a growing recognition that examining patterns of ecological communities and their underlying determinants is not only feasible based on taxonomic data, but also functional and phylogenetic approaches. This is because these additional facets can enhance the understanding of the relative contribution of multiple processes in shaping biodiversity. However, few studies have focused on multifaceted beta diversities in lotic macroinvertebrates, especially when considering driving factors operating at multiple spatial scales. Here, we examined the spatial patterns of multi-faceted (i.e., taxonomic, functional and phylogenetic) beta diversity and their components (i.e., turnover and nestedness) of macroinvertebrates in 50 sites in 10 streams situated in the north and south slope of the Qinling Mountains, the geographical dividing line of Northern and Southern China. We found that the streams draining the north slope showed significantly lower values of beta diversity based on all three facets than the streams draining the south slope. Such north-to-south increases of beta diversity were caused by the distinct climatic and local environmental conditions between the sides of the mountain range. Moreover, spatial variables generally played the most important role in structuring all facets and components of beta diversity, followed by local environmental and climatic variables, whereas catchment variables were less important. Despite the similar results of relative contribution of explanatory variables on each beta diversity facet, the details of community-environment relationships (e.g., important explanatory variables and explanatory power) were distinct among different diversity facets and their components. In conclusion, measuring functional and phylogenetic beta diversity provides complementary information to traditional taxonomic approach. Therefore, an integrative approach embracing multiple facets of diversity can better reveal the mechanisms shaping biodiversity, which is essential in assessing and valuing aquatic ecosystems for biodiversity management and conservation.
•Soil moisture data from three scales are assimilated into a subsurface model.•Coarse-scale data are useful for finer-scale state-parameter estimation.•Soil spatial heterogeneity affects the data ...assimilation efficiency.•Conflicting multi-scale data can also contain considerably useful information.•The difference information assimilation method is convenient and useful.
This paper assesses the value of multi-scale near-surface (0∼5 cm) soil moisture observations to improve state-only or state-parameter estimation based on the ensemble Kalman filter (EnKF). To the best of our knowledge, studies on assimilating multi-scale soil moisture data into a distributed hydrological model with a series of detailed vertical soil moisture profiles are rare. Our analysis factors include spatial measurement scales, soil spatial heterogeneity, multi-scale data with contrasting information and systematic measurement errors. Results show that coarse-scale soil moisture data are also very useful for identifying finer-scale parameters and states given biased initial parameter fields, but it becomes increasingly difficult to recover the finer-scale spatial heterogeneity of soil property as the observation grids become coarser. In state-only estimation, near-surface soil moisture data result in improvement for shallow soil moisture profiles and degradation for deeper soil moisture profiles, with stronger influences from finer-scale data. With the decrease of background spatial heterogeneity of soil property, the value of coarse-scale data increases notably. Soil moisture data at two scales with contrasting information are found to be both useful. By updating spatially correlated soil hydraulic parameters, deviated observations still contain considerably useful information for finer-scale state-parameter estimation. Eventually, by presenting a difference information assimilation method based on EnKF we successfully extract useful information from soil moisture data containing systematic measurement errors. The current study can be extended to consider more complex atmosphere input and topography, etc.
Conductive hydrogels have garnered wide interest for various promising applications, such as wearable devices, electronic skins, and intelligent robots. However, these hydrogels still suffer from ...weak mechanical properties, poor environmental stability, and low sensitivity. Here, we report a conductive organohydrogel that is easily synthesized by a one-step acrylamide polymerization in the presence of cellulose nanofiber (CNF)-templated carbon nanotube (CNT) hybrids and glycerol-water binary solvent. The uniformly dispersed CNF/CNT nanohybrids act as a reinforced and conductive skeleton, which synergistically endows the organohydrogel with excellent tensile strength (≈ 119.2 kPa) and high electronic conductivity (≈ 2.7 mS cm
−1
). Moreover, the synergy of glycerol-water solvent network and polyacrylamide (PAAm) polymer matrix provides an ultra-stretchability (up to 1343%) and skin-like modulus (≈ 17.7 kPa), which can well match the dynamic human–machine interface. Furthermore, the organohydrogels exhibit excellent flexibility under an extreme temperature (< − 24 °C) and maintain the long-term water-retention capability in an open environment (> 10 days), owing to the glycerol-enhanced H-bonding interface interactions. Benefiting from these high performances, our organohydrogel can be employed for preparing multifunctional sensing devices, which display high sensitivity to external strains (gauge factor = 10.03) and dynamic temperature changes (temperature coefficient of resistance = − 1.081% °C
−1
), superior to the most reported samples. Our results pave the way for simple and practical systems that fulfill the requirements of intelligent electronic devices.
Graphical abstract
The electrochemical performance of lithium-ion batteries is directly influenced by type of active material as well as its morphology. In order to evaluate the impact of particle morphology in ...thick-film electrodes, Li(Ni0.6Mn0.2Co0.2)O2 (NMC 622) cathodes with bilayer structure consisting of two different particle sizes were manufactured and electrochemically characterized in coin cells design. The hierarchical thick-film electrodes were generated by multiple casting using NMC 622 (TA) with small particle size of 6.7 µm and NMC 622 (BA) with large particle size of 12.8 µm. Besides, reference electrodes with one type of active material as well as with two type of materials established during mixing process (BT) were manufactured. The total film thickness of all hierarchical composite electrodes were kept constant at 150 µm, while the thicknesses of TA and BA were set at 1:2, 1:1, and 2:1. Meanwhile, three kinds of thin-film cathodes with 70 µm were applied to represent the state-of-the-art approach. Subsequently, ultrafast laser ablation was applied to generate groove structures inside the electrodes. The results demonstrate that cells with thin-film or thick-film cathode only containing TA, cells with bilayer electrode containing TBA 1:2, and cells with laser-structured electrodes show higher capacity at C/2 to 5C, respectively.
The Weihe River Basin plays an indispensable role in the water environment and water ecological balance in Northwest China and the lower reaches of the Yellow River. In the context of river ...ecosystems being affected by climate change and human activities, phytoplankton, as primary producers in food webs, serve as an important ecological indicator of environmental change. As such, systematic surveys on the water environment and phytoplankton were carried out in the Weihe River mainstem and its five tributaries from the northern foot of the Qinling Mountains from October to November 2017 and April to May 2018. In total, 154 species of phytoplankton belonging to 69 genera were identified in the heavy sediment-laden mainstem, with an average density and biomass of 177.57*10
4
cell L
−1
and 6.53 mg L
−1
, respectively. Furthermore, a total of 207 species of phytoplankton belonging to 81 genera were identified in the five tributaries originating in the Qinling Mountains, with an average density and biomass of 80.98*10
4
cell L
−1
and 1.90 mg L
−1
, respectively. Canonical correspondence analysis (CCA) was employed to analyze the relationship between phytoplankton communities and environmental factors. The results of data screening and Monte Carlo sequencing tests revealed that water temperature (WT), dissolved oxygen (DO), and nitrite nitrogen (NO
2
-
-N) were the primary environmental factors affecting the distribution and abundance of phytoplankton in the Weihe River mainstem. WT, flow velocity (V), pH, conductivity (Cond), and NO
2
-
-N predominantly structured the phytoplankton communities in the Weihe River tributaries. The results of this study are useful for the ecological management and conservation of the mainstem and tributaries of the Weihe River Basin.
A viable solution toward “green” optoelectronics is rooted in our ability to fabricate optoelectronics on transparent nanofibrillated cellulose (NFC) film substrates. However, the flammability of ...transparent NFC film poses a severe fire hazard in optoelectronic devices. Despite many efforts toward enhancing the fire-retardant features of transparent NFC film, making NFC film fire-retardant while maintaining its high transparency (≥90%) remains an ambitious objective. Herein, we combine NFC with NFC-dispersed monolayer clay nanoplatelets as a fire retardant to prepare highly transparent NFC-monolayer clay nanoplatelet hybrid films with a superb self-extinguishing behavior. Homogeneous and stable monolayer clay nanoplatelet dispersion was initially obtained by using NFC as a green dispersing agent with the assistance of ultrasonication and then used to blend with NFC to prepare highly transparent and self-extinguishing hybrid films by a water evaporation-induced self-assembly process. As the content of monolayer clay nanoplatelets increased from 5 wt % to 50 wt %, the obtained hybrid films presented enhanced self-extinguishing behavior (limiting oxygen index sharply increased from 21% to 96.5%) while retaining a ∼90% transparency at 600 nm. More significantly, the underlying mechanisms for the high transparency and excellent self-extinguishing behavior of these hybrid films with a clay nanoplatelet content of over 30 wt % were unveiled by a series of characterizations such as SEM, XRD, TGA, and limiting oxygen index tester. This work offers an alternative environmentally friendly, self-extinguishing, and highly transparent substrate to next-generation optoelectronics, and is aimed at providing a viable solution to environmental concerns that are caused by ever-increasing electronic waste.
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