In order to study the internal flow field characteristics and optimization feasibility of different upper crown flow channel structures of Francis turbines with scuppers, taking the No. 4 unit of ...Xinjiang Hongshanzui First-Stage Hydropower Station as an example, three types of pressure-reducing structures of different upper crown channels scuppers are taken as the research object. Based on the CFD technology, using the SST turbulence model controlled by the
k
–
ω
equation, numerical simulations were carried out for 3 different upper crown flow channel pressure-reducing structures under 7 working conditions, with a total of 21 simulation conditions. The research indicators are the drainage volume of the runner cone, the drainage capacity of drainage holes, the pressure of the main shaft sealing and the flow regime distribution of the leaked water. The results show that there are certain differences in the flow field characteristics of different upper crown flow channel structures; the purpose of depressurization optimization of the upper crown flow channel can be achieved by adding a top cover drain pipe and a runner pump; compared with other structures, the pressure-reducing structure with the runner pump has a significant effect on improving the water discharge performance of the drainage holes, reducing the water mass flow rate of the runner cone and reducing the pressure of the main shaft sealing; in view of the problem of water leakage of the main shaft seal of this unit, it is recommended to use a pressure reduction structure with a runner pump, which can reduce the water mass flow rate of the runner cone by 48.22%, improve the performance of the drainage holes by 17.12% and reduce the pressure on the underside of the main shaft seal by 15.98%. The study can provide a reference for the design and reconstruction of the upper crown flow channel of the medium- and high-head Francis turbine.
Invertebrate herbivory is suggested to modulate community shifts caused by climate warming in grasslands. However, experimental evidence is lacking, especially in high elevation areas. We examined ...the interactive effect of experimental warming and the grassland caterpillar Gynaephora alpherakjj, a typical invertebrate herbivorous insect with sedge preference, on the structure of plant community in a sedge‐dominated alpine meadow in the Tibetan Plateau. We manipulated both herbivore and temperature in a full factorial field experiment using passive warming chambers over one plant‐growing season. Results show that simulated warming significantly increased the aboveground plant biomass (APB) of forbs and total APB, while the presence of caterpillars significantly decreased sedge APB and total APB. The increase in consumption of sedges by caterpillars under warmed conditions can largely be ascribed to the increase in feeding time of caterpillars. Importantly, the presence of caterpillars significantly decreased the APB ratio of sedges to forbs in the warmed but not in the unwarmed chambers. These results suggest that with a warming climate, invertebrate herbivory could accelerate community shifts from sedge dominance to forb dominance in only one plant‐growing season in the Tibetan alpine meadow. This shift would reduce the biomass of high‐quality forage and further threaten animal husbandry in this area. Considering the harm of G. alpherakjj to grasslands, its population should be controlled more strictly under the global warming scenario.
Satellite stereo mapping, together with laser altimetry, can be used to obtain three-dimensional geospatial information. Spaceborne laser altimeter can provide high-accuracy elevation information; ...however, due to the lack of detailed intensity information, its planimetric accuracy is usually worse than the ranging accuracy. The Chinese Gaofen-7 (GF-7) satellite, which was designed for civilian mapping application, was launched on November 3, 2019. The GF-7 satellite's main payloads are a laser altimeter system (with footprint camera) and a dual-linear charge-coupled device (CCD) mapping camera. According to the pixel coordinate of the laser footprint in the stereo image, the laser altimeter together with the footprint camera can provide planimetric geodetic coordinates for the control points of a higher accuracy than the other traditional satellite laser altimeters, and represents a new technology for satellite mapping. In this article, a laser footprint planimetric location method for the GF-7 satellite is proposed. The method is designed based on the main payload characteristics of GF-7 and the working modes of the laser altimeter by the combined use of subpixel phase correlation image matching and four types of laser spot center detection methods. The planimetric positioning accuracies of the laser spots in urban, suburban, farmland, forest, mountainous, and ice sheet areas were also analyzed. The experimental results show that the accuracy of planimetric location relative to stereo image for the laser footprint is 0.3-1.0 m (except for ice sheets ~12 m) when the footprint camera works under the synchronous mode, and 0.2-0.4 m when the footprint camera works under asynchronous mode (AM).
Next-generation communication networks can provide high capacity, low latency, and massive connections; however, they introduce novel challenges of management complexity, and traditional mathematical ...methods cannot well characterize the rational behavior of users. In this article, we pay attention to the methods of artificial intelligence (AI) and game theory. We first review the applications of machine learning (ML) and game theory models in wireless communications and summarize their advantages and disadvantages. After surveying the state of the art, in this article we propose a novel framework combining ML and game theory, which explores and exploits the benefits of the two disciplines. Finally, we apply our novel framework to solve the network selection problem in a 5G ultra-dense and heterogeneous network. Simulation results confirm the advantage of our presented framework on reducing the average delay of users.
At present, the acquisition of seismic data is developing toward high-precision and high-density methods. However, complex natural environments and cultural factors in many exploration areas cause ...difficulties in achieving uniform and intensive acquisition, which makes complete seismic data collection impossible. Therefore, data reconstruction is required in the processing link to ensure imaging accuracy. Deep learning, as a new field in rapid development, presents clear advantages in feature extraction and modeling. In this study, the convolutional neural network deep learning algorithm is applied to seismic data reconstruction. Based on the convolutional neural network algorithm and combined with the characteristics of seismic data acquisition, two training strategies of supervised and unsupervised learning are designed to reconstruct sparse acquisition seismic records. First, a supervised learning strategy is proposed for labeled data, wherein the complete seismic data are segmented as the input of the training set and are randomly sampled before each training, thereby increasing the number of samples and the richness of features. Second, an unsupervised learning strategy based on large samples is proposed for unlabeled data, and the rolling segmentation method is used to update (pseudo) labels and training parameters in the training process. Through the reconstruction test of simulated and actual data, the deep learning algorithm based on a convolutional neural network shows better reconstruction quality and higher accuracy than compressed sensing based on Curvelet transform.
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•Estrogen deficiency promotes M1 polarization and thus alters profiling of small extracellular vesicles (sEVs).•sEVs involve in the cross-talk between macrophages and mesenchymal stem ...cells.•M1-sEVs inhibit osteogenesis of mesenchymal stem cells and aggravate periodontitis.•A cluster of miR-30-5p miRNAs in M1-sEVs are predicted to inhibit osteogenesis.•Treatment of sEVs with miR-30e-5p inhibitor prevents periodontitis in OVX mice.
Emerging evidence indicates that postmenopausal women with periodontitis have aggravated inflammation and prolonged course, with the detailed mechanisms largely unknown. This study aimed to determine the pathogenic role of aberrant extracellular vesicles due to imbalanced-polarized macrophages and explore the therapeutic approach for periodontitis in postmenopausal individuals. Periodontitis in ovariectomized (OVX) mouse models were established to simulate the aggravated periodontitis in postmenopausal women. Small extracellular vesicles (sEVs) derived from macrophages were isolated, characterized and tracked. Both in vitro and in vivo experiments were applied to compare the effects of M1-sEVs and M2-sEVs on osteogenesis. RNA-Seq was performed to find out up-regulated miRNAs in M1-sEVs. As data shown, compared with the Sham control mice, estrogen deficiency in the OVX-periodontitis mice, significantly increased the ratio of M1 macrophages and thus change the profile of sEVs. The sEVs could be uptaken by mesenchymal stem cells (MSCs). Furthermore, M1-sEVs inhibited the osteogenesis of MSCs and aggravated bone loss in periodontitis. Up-regulated miR-30-5p cluster were found in M1-sEVs. Prevention of the communication aberrance using miR-30e-5p inhibitor loaded sEVs in the OVX mice at least partially restores the aggravated periodontitis. Collectively, this study suggests that the increased M1-sEVs in the estrogen-deficiency context aggravate bone loss in periodontitis via negatively regulating osteogenesis of MSCs, and therapeutically targeting the process holds promise for better prognosis.
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► 3DOM-structure and bulk Co3O4, Eu0.6Sr0.4FeO3, and Co3O4/Eu0.6Sr0.4FeO3 are prepared. ► Porous samples are higher than bulk samples in Oads content and better reducibility. ► The ...porous samples exhibit higher catalytic performance than the bulk samples. ► There is a synergistic effect between Co3O4 and Eu0.6Sr0.4FeO3. ► Catalytic activity is governed by Oads content, reducibility, and synergistic action.
Three-dimensionally ordered macroporous (3DOM) and bulk Co3O4, Eu0.6Sr0.4FeO3 (ESFO), and 3 wt% Co3O4/Eu0.6Sr0.4FeO3 (3Co3O4/ESFO) were fabricated using the PMMA-templating (3DOM-Co3O4 and 3DOM-ESFO), citric acid-assisted hydrothermal (Co3O4-bulk and ESFO-bulk), and incipient wetness impregnation (3Co3O4/3DOM-ESFO and 3Co3O4/ESFO-bulk) methods, respectively. Physicochemical properties of these materials were characterized by means of various techniques, and their catalytic activities were evaluated for toluene combustion. Compared to the nonporous Co3O4 and ESFO samples, the 3DOM-Co3O4, 3DOM-ESFO, and 3Co3O4/3DOM-ESFO samples exhibited higher oxygen adspecies concentrations and better low-temperature reducibility. The 3Co3O4/3DOM-ESFO sample showed the best catalytic activity for toluene combustion, giving the T50% and T90% of 251 and 269°C at 20,000mL/(gh), respectively. The apparent activation energies of these samples were in the range of 72–88kJ/mol. We believe that the higher oxygen adspecies concentration, better low-temperature reducibility, and synergistic action between Co3O4 and 3DOM-structured ESFO were responsible for the excellent catalytic performance of 3Co3O4/3DOM-ESFO.
