In the face of huge amounts of image data, how to let the computer simulate human cognition of images and automatically classify images into different semantic categories have become a key issue in ...image semantic analysis. Image classification is based on some attribute of the image, and it is divided into pre-set categories. For human beings, image classification is not difficult but there is a series of problems in using computers to classify images: (1) images contain a large amount of information, which is complex, diverse, and indescribable; and (2) there is a huge difference between the physical expression of images and the conceptual information known by human beings. The traditional sparse coding method loses the spatial information when classifying images. In this paper, spatial pyramid multi-partition method is used to add spatial information restriction to the feature. The proposed multi-scale spatial latent semantic analysis method based on sparse coding has higher average classification accuracy than many existing methods, which verifies its effectiveness and robustness. Experiments also show that the classification accuracy of this paper is 2.1% higher than that of sparse coding for image classification (ScSPM) and the classification performance is 3.1% higher than that of ScSPM when the number of training images is 40. Compared with other methods, the classification performance of the proposed method is improved significantly.
Surface albedo is widely used in climate and environment applications as an important parameter for controlling the surface energy budget. There is an increasing need for albedo data to be available ...for use in applications that require a fine spatial resolution and for validating coarse-resolution datasets; however, such products with long-term global coverage are not available thus far. Existing algorithms for Landsat albedo estimation all require surface reflectance from explicit and reliable atmospheric correction, which may sometimes be unavailable or carry uncertainties due to saturated visible bands or a lack of dense vegetation. In addition, most of the existing algorithms require concurrent clear-sky observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) for bidirectional reflectance distribution function (BRDF) correction, which limited the data availability for Landsat albedo estimation. To overcome these problems, in this study, we adopt the direct estimation approach previously used with coarser resolution data, such as MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS), and apply it to multiple Landsat data obtained by Multispectral Scanner (MSS), Thematic Mapper (TM), Enhanced Thematic Mapper Plus (ETM+), and Operational Land Imager (OLI). By incorporating Landsat spectral response functions and a database of bidirectional reflectance distribution function (BRDF) into radiative transfer simulations, a unified algorithm is developed to estimate surface albedo directly from the Landsat top-of-atmospheric reflectance data obtained by MSS, TM, ETM+, and OLI with few ancillary inputs. To overcome the saturation problems in the visible bands of TM and ETM+ over very bright surfaces, a refined approach is employed by using only non-saturated bands. The validation results against ground measurements over various land cover types and climate regions show that our algorithm is effective for both snow-free and snow-covered surfaces and can achieve root-mean-square errors (RMSEs) of not more than 0.034. In addition, we show the high potential of the earlier MSS data for producing consistent surface albedo estimations based on inter-comparison with TM-based results with RMSEs of 0.011–0.017 and R2 of 0.858–0.963. This long-term, 30-m resolution surface albedo estimation can date back to the early 1980s, which allows for improved understanding of long-term climate change and land cover change effects.
•A unified approach was applied for albedo estimation for different Landsat sensors.•Explicit corrections for atmospheric and surface BRDF effects are not required.•The proposed approach is designed for both snow-free and snow-covered surfaces.•RMSE vs ground measurements was smaller than 0.034 for snow-free surfaces.•The potential of extending albedo estimation to the MSS-era has been demonstrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The appropriate sizes of scale-breeding industries are causing increasing attention in that rational scale-breeding industries may both meet the meat demand of the market and avoid serious ...environmental problems. In this paper, the appropriate scales of breeding-type family farms were studied from the perspective of quantifying resource losses. The mathematical models about quantifying resource losses were built, and then the evaluation index system of resource losses was established. More than one hundred family farms in Sichuan province and Chongqing city of China located in the subtropics were selected as research cases and were classified as small-, medium- and large-scale family farms, whose unit resource losses and resource loss rates were both evaluated by the index system. Results show that the unit resource losses and the resource loss rate of medium-scale family farms are the lowest among these three kinds of family farms. Therefore, medium-scale farms are moderate, and then are recommended for scale-breeding industries.
Implications: Appropriate sizes are essential for the green development of scale-breeding industries. The external environment factors and internal resource effect should be considered. The unit resource losses and the resource loss rate of medium-scale family farms are the lowest among these three kinds of family farms. Therefore, medium-scale farms are optimistic, and then are recommended for scale-breeding industries. For medium-scale family farms, the scale of 800-999 pigs is optimistic. Furthermore, it is very necessary to adopt green cycle.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
For several decades, long‐term time series data sets of multiple global land surface albedo products have been generated from satellite observations. These data sets have been used as one of the key ...variables in climate change studies. This study aims to assess the surface albedo climatology and to analyze long‐term albedo changes, from nine satellite‐based data sets for the period 1981–2010, on a global basis. Results show that climatological surface albedo data sets derived from satellite observations can be used to validate, calibrate, and further improve surface albedo simulations and parameterizations in current climate models. However, the albedo products derived from the International Satellite Cloud Climatology Project and the Global Energy and Water Exchanges Project have large seasonal biases. At latitudes higher than 50°, the maximal difference in winter zonal albedo ranges from 0.1 to 0.4 among the nine satellite data sets. Satellite‐based albedo data sets agree relatively well during the summer at high latitudes, with a standard deviation of 0.04 for the 70°–80° zone in both hemispheres. The fine‐resolution (0.05°) data sets agree well with each other for all the land cover types in middle to low latitudes; however, large spread was identified for their albedos at middle to high latitudes over land covers with mixed snow and sparse vegetation. By analyzing the time series of satellite‐based albedo products over the past three decades, albedo of the Northern Hemisphere was found to be decreasing in July, likely due to the shrinking snow cover. Meanwhile, albedo in January was found to be increasing, likely because of the expansion of snow cover in northern winter. However, to improve the albedo estimation at high latitudes, and ultimately the climate models used for long‐term climate change studies, a still better understanding of differences between satellite‐based albedo data sets is required.
Key Points
Land albedo climatologies were derived from nine global satellite data setsMost satellite albedos can be used for model calibration and validationLarge differences were found at high latitudes between satellite data sets
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The Li–CO2 battery is a promising energy storage device for wearable electronics due to its long discharge plateau, high energy density, and environmental friendliness. However, its utilization is ...largely hindered by poor cyclability and mechanical rigidity due to the lack of a flexible and durable catalyst electrode. Herein, flexible fiber‐shaped Li–CO2 batteries with ultralong cycle‐life, high rate capability, and large specific capacity are fabricated, employing bamboo‐like N‐doped carbon nanotube fiber (B‐NCNT) as flexible, durable metal‐free catalysts for both CO2 reduction and evolution reactions. Benefiting from high N‐doping with abundant pyridinic groups, rich defects, and active sites of the periodic bamboo‐like nodes, the fabricated Li–CO2 battery shows outstanding electrochemical performance with high full‐discharge capacity of 23 328 mAh g−1, high rate capability with a low potential gap up to 1.96 V at a current density of 1000 mA g−1, stability over 360 cycles, and good flexibility. Meanwhile, the bifunctional B‐NCNT is used as the counter electrode for a fiber‐shaped dye‐sensitized solar cell to fabricate a self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6%. Along with a stable voltage output, this design demonstrates great adaptability and application potentiality in wearable electronics with a breath monitor as an example.
A self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6% is fabricated using bifunctional bamboo‐like N‐doped carbon nanotube fiber as the cathode for the Li–CO2 battery and as the counter electrode for the dye‐sensitized solar cells simultaneously. The fiber‐shaped Li–CO2 batteries show high specific capacity, long cycle life, and high flexibility.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The recent realization of photonic topological insulators has brought the discovery of fundamentally new states of light and revolutionary applications such as nonreciprocal devices for photonic ...diodes and robust waveguides for light routing. The spatially distinguished layer pseudospin has attracted attention in two‐dimensional electronic materials but it is yet to be discovered in topological photonic structures. Here, all‐dielectric layered photonic topological insulators based on bilayer photonic crystal slabs are reported. The introduction of layer pseudospin offers more dispersion engineering capability, leading to the layer‐polarized and layer‐mixed photonic topological insulators. Their phase transition is demonstrated with a model Hamiltonian by considering the nonzero interlayer coupling. Layer‐direction locking behavior of layer‐polarized photonic topological insulators results in the selective light refraction. High transmission is observed in the bilayer domain wall between two layer‐mixed photonic topological insulators, even when a large defect is introduced. Layered photonic topological insulators not only offer a route toward the observation of richer nontrivial phases, but also open a way for device applications in integrated photonics and information processing by using the additional layer pseudospin.
All‐dielectric layered photonic topological insulators are reported based on bilayer photonic crystal slabs. This class of photonic topological insulators is demonstrated in the on‐chip silicon‐on‐insulator platform which is pursued in topological nanophotonics. The introduction of additional layer pseudospin offers more dispersion engineering capability and enriches the nontrivial phases with the finding of layer‐polarized and layer‐mixed photonic topological insulators.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Individual free fatty acids (FAs) play important roles in metabolic homeostasis, many through engagement with more than 40G protein-coupled receptors. Searching for receptors to sense beneficial ...omega-3 FAs of fish oil enabled the identification of GPR120, which is involved in a spectrum of metabolic diseases. Here, we report six cryo-electron microscopy structures of GPR120 in complex with FA hormones or TUG891 and G
or G
trimers. Aromatic residues inside the GPR120 ligand pocket were responsible for recognizing different double-bond positions of these FAs and connect ligand recognition to distinct effector coupling. We also investigated synthetic ligand selectivity and the structural basis of missense single-nucleotide polymorphisms. We reveal how GPR120 differentiates rigid double bonds and flexible single bonds. The knowledge gleaned here may facilitate rational drug design targeting to GPR120.
A methyl group on an arene, despite its small size, can have a profound influence on biologically active molecules. Typical methods to form a methylarene involve strong nucleophiles or strong and ...often toxic electrophiles. We report a strategy for a new, highly efficient, copper and iodide co-catalyzed methylation of aryl- and heteroarylboronic esters with the mild, nontoxic reagent trimethylphosphate, which has not been used previously in coupling reactions. We show that it reacts in all cases tested in yields that are higher than those of analogous copper-catalyzed reactions of MeOTs or MeI. The combination of C-H borylation and this methylation with trimethylphosphate provides a new approach to the functionalization of inert C-H bonds and is illustrated by late-stage methylation of four medicinally active compounds. In addition, reaction on a 200 mmol scale demonstrates reliability of this method. Mechanistic studies show that the reaction occurs by a slow release of methyl iodide by reaction of PO(OMe)
with iodide catalyst, rather than the typical direct oxidative addition to a metal center. The low concentration of the reactive electrophile enables selective reaction with an arylcopper intermediate, rather than nucleophilic groups on the arylboronate, and binding of tert-butoxide to the boronate inhibits reaction of the electrophile with the tert-butoxide activator to form methyl ether.
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Vacancy defects in the porous ZnO nanoplates facilitate separation of charge carriers, and are in favor of adsorption and activation of CO2, resulting in greatly enhanced photocatalytic activity.
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•Porous ZnO nanoplates with VO defects are prepared by annealing precursor in air.•Amount of vacancy defects in ZnO can be tailored by changing heating temperature.•Different amount of defects lead to different performance for CO2 photoreduction.•VO defect can facilitate the separation of photogenerated electrons and holes.•VO defect is in favor of the adsorption and activation of CO2 on ZnO surface.
Photocatalytic conversion of CO2 into hydrocarbons by utilization of the solar energy is considered a promising approach to mitigate energy crisis and the environmental issues. Since the defects in a catalyst play an important role in CO2 reduction, herein, the porous ZnO nanoplates with vacancy defects are synthesized by annealing ZnS(en)0.5 precursor in air at different temperature. The defect amount in ZnO changes with the annealing temperature, resulting in different photocatalytic activity for CO2 reduction. The related mechanism has been studied both experimentally and theoretically. Raman spectra and chemical composition of the obtained catalysts are used to determine the defects. Transient techniques are used to investigate the separation of photogenerated charge carriers. CO2 adsorption capacity for different catalysts is also measured. First-principles calculation is used to study the adsorption and activation of CO2 on the ZnO surface. We envision that this work may afford an efficient approach to develop the semiconductor photocatalysts with superior activity via defects engineering.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Quantifying and attributing the phenological changes in snow cover are essential for meteorological, hydrological, ecological, and societal implications. However, snow cover phenology changes have ...not been well documented. Evidence from multiple satellite and reanalysis data from 2001 to 2014 points out that the snow end date (De) advanced by 5.11 (±2.20) days in northern high latitudes (52-75°N) and was delayed by 3.28 (±2.59) days in northern mid-latitudes (32-52°N) at the 90% confidence level. Dominated by changes in De, snow duration days (Dd) was shorter in duration by 5.57 (±2.55) days in high latitudes and longer by 9.74 (±2.58) days in mid-latitudes. Changes in De during the spring season were consistent with the spatiotemporal pattern of land surface albedo change. Decreased land surface temperature combined with increased precipitation in mid-latitudes and significantly increased land surface temperature in high latitudes, impacted by recent Pacific surface cooling, Arctic amplification and strengthening westerlies, result in contrasting changes in the Northern Hemisphere snow cover phenology. Changes in the snow cover phenology led to contrasting anomalies of snow radiative forcing, which is dominated by De and accounts for 51% of the total shortwave flux anomalies at the top of the atmosphere.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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