•FDTD modeling the channel two of Chang’E-3 Lunar Penetrating Radar.•The scattering effects of numerous rocks could explain the missing reflectors.•The dielectric constant variations agree with the ...density-depth change of regolith.
The thickness of lunar regolith is an important index of evaluating the quantity of lunar resources such as 3He and relative geologic ages. Lunar penetrating radar (LPR) experiment of Chang’E-3 mission provided an opportunity of in situ lunar subsurface structure measurement in the northern mare imbrium area. However, prior work on analyzing LPR data obtained quite different conclusions of lunar regolith structure mainly because of the missing of clear interface reflectors in radar image. In this paper, we utilized finite-difference time-domain (FDTD) method and three models of regolith structures with different rock density, number of layers, shapes of interfaces, and etc. to simulate the LPR signals for the interpretation of radar image. The simulation results demonstrate that the scattering signals caused by numerous buried rocks in the regolith can mask the horizontal reflectors, and the die-out of radar echo does not indicate the bottom of lunar regolith layer and data processing such as migration method could recover some of the subsurface information but also result in fake signals. Based on analysis of simulation results, we conclude that LPR results uncover the subsurface layered structure containing the rework zone with multiple ejecta blankets of small crater, the ejecta blanket of Chang’E-3 crater, and the transition zone and estimate the thickness of the detected layer is about 3.25m.
This morphological study of multi-storied brick pagodas of the Tang Dynasty expands studies of the design theories of traditional masonry towers. Through a comprehensive examination of the formal ...beauty and design principles of ancient Chinese architecture, we identified and verified square-circle patterns (special intersectional relationships between squares and circles in geometry) and the dimensional modulus used in the morphological design of multi-storied brick pagodas of the Tang Dynasty. According to the linear variation characteristics of the geometric shapes of the brick pagodas, a linear regression analysis was conducted to identify the relationships among the dimensions of the most typical Tang multi-storied brick pagoda, the Xuanzang Pagoda in Xi'an. A set of mathematical models was then formulated through parametric abstraction to describe these relationships. These models were confirmed plausible for describing other Tang multi-storied brick pagodas involved in the study. In addition, the use of proportion and modules implies that there is the possibility that the design of multi-storied brick pagodas in the Tang dynasty took other wooden structures as a reference. Our study provides a new scientific research method for the design and protection of pagodas, and is useful for future studies of ancient Chinese multi-storied buildings.
Geological structure of the subsurface of the Moon provides valuable information on lunar evolution. Recently, Chang׳E-3 has utilized lunar penetrating radar (LPR), which is equipped on the lunar ...rover named as Yutu, to detect the lunar geological structure in Northern Imbrium (44.1260N, 19.5014W) for the first time. As an in situ detector, Chang׳E-3 LPR has relative higher horizontal and vertical resolution and less clutter impact compared to spaceborne radars and earth-based radars.
In this work, we analyze the LPR data at 500MHz transmission frequency to obtain the shallow subsurface structure of the landing area of Chang׳E-3 in Mare Imbrium. Filter method and amplitude recovery algorithms are utilized to alleviate the adverse effects of environment and system noises and compensate the amplitude losses during signal propagation. Based on the processed radar image, we observe numerous diffraction hyperbolae, which may be caused by discrete reflectors beneath the lunar surface. Hyperbolae fitting method is utilized to reverse the average dielectric constant to certain depth (ε¯). Overall, the estimated ε¯ increases with the depth and ε¯ could be classified into three categories. Average ε¯ of each category is 2.47, 3.40 and 6.16, respectively. Because of the large gap between the values of ε¯ of neighboring categories, we speculate a three-layered structure of the shallow surface of LPR exploration region.
One possible geological picture of the speculated three-layered structure is presented as follows. The top layer is weathered layer of ejecta blanket with its average thickness and bound on error is 0.95±0.02m. The second layer is the ejecta blanket of the nearby impact crater, and the corresponding average thickness is about 2.30±0.07m, which is in good agreement with the two primary models of ejecta blanket thickness as a function of distance from the crater center. The third layer is regarded as a mixture of stones and soil. The echoes below the third layer are in the same magnitude as the noises, which may indicate that the fourth layer, if it exists, is uniform (no clear reflector) and its thickness is beyond the detection limit of LPR. Hence, we infer the fourth layer is a basalt layer.
•Analyze the Chang׳E-3LPR data at 500MHz.•Observe numerous diffraction hyperbolae and apply hyperbolae fitting method to reverse the average dielectric constant.•Speculate two subsurface interfaces based on the distribution of the estimated dielectric constants.•Present possible geological picture of the speculated three-layered structure.
Geological structure of the subsurface of the Moon provides valuable information on lunar evolution. Recently, Chang super(3)E-3 has utilized lunar penetrating radar (LPR), which is equipped on the ...lunar rover named as Yutu, to detect the lunar geological structure in Northern Imbrium (44.1260N, 19.5014W) for the first time. As an in situ detector, Chang super(3)E-3 LPR has relative higher horizontal and vertical resolution and less clutter impact compared to spaceborne radars and earth-based radars. In this work, we analyze the LPR data at 500MHz transmission frequency to obtain the shallow subsurface structure of the landing area of Chang super(3)E-3 in Mare Imbrium. Filter method and amplitude recovery algorithms are utilized to alleviate the adverse effects of environment and system noises and compensate the amplitude losses during signal propagation. Based on the processed radar image, we observe numerous diffraction hyperbolae, which may be caused by discrete reflectors beneath the lunar surface. Hyperbolae fitting method is utilized to reverse the average dielectric constant to certain depth (). Overall, the estimated increases with the depth and could be classified into three categories. Average of each category is 2.47, 3.40 and 6.16, respectively. Because of the large gap between the values of of neighboring categories, we speculate a three-layered structure of the shallow surface of LPR exploration region. One possible geological picture of the speculated three-layered structure is presented as follows. The top layer is weathered layer of ejecta blanket with its average thickness and bound on error is 0.95 plus or minus 0.02m. The second layer is the ejecta blanket of the nearby impact crater, and the corresponding average thickness is about 2.30 plus or minus 0.07m, which is in good agreement with the two primary models of ejecta blanket thickness as a function of distance from the crater center. The third layer is regarded as a mixture of stones and soil. The echoes below the third layer are in the same magnitude as the noises, which may indicate that the fourth layer, if it exists, is uniform (no clear reflector) and its thickness is beyond the detection limit of LPR. Hence, we infer the fourth layer is a basalt layer.
Nowadays generating electricity continuously in real waves over extended periods is a big challenge due to harsh ocean environment for wave energy converters (WECs). In this study, in order to ...enhance the reliability of WEC, a novel BIWEC which can form an integrated system by combing with existing floating platforms is proposed. This design method provides a robust mechanism for using wave energy efficiently and has been validated through the numerical simulations and physical model experiments of integrated systems. In addition, a comprehensive study and analysis on the coupling dynamic characteristics of the integrated system, as well as the influence of different power take-off (PTO) parameters on the power generation performance of BIWEC are conducted. Furthermore, using the typical wave conditions in the South China Sea (2–10 s wave period and 2 m wave height) as an example, the capture power and capture width ratio of BIWEC under various effective motion strokes and mass ratios are investigated. The research results indicate that the BIWEC has the characteristics of dual resonance frequencies, a wide range of wave frequency capture, and high energy conversion efficiency, and the results of the physical experiments are consistent with those of numerical simulations, validating the reliability of the physical experiments. In the physical experimental tests, the average mechanical efficiency of the BIWEC model is 49.17%. The research results presented in this paper have significant implications for the further promoting of commercialization of WEC.
•A novel BIWEC is proposed, which can be integrated with existing floating platforms to reduce construction costs.•The coupled dynamic response mathematical model between BIWEC and floating platform is established.•Taking typical wave conditions in the South China Sea as an example, the theoretical energy conversion efficiency of BIWEC is studied.•A physical model of BIWEC with scale ratio of 1:8 and the corresponding onshore platform testing system are established.•The research results indicate that BIWEC has high energy conversion efficiency and a wide effective wave frequency capture range.
•Electrochemical activation using graphite electrodes can successfulliy activate periodate (PI) for water decontamination.•1O2 as the primary reactive species is produced in the E-GP/PI system ...through the combination of O2•−.•A dual descriptor model is proposed to reveal the selective oxidation behavior of 1O2.•The E-GP/PI system shows strong pH tolerance, long-lasting performance, and high resistance to aqueous matrices.•BPA degradation mechanism is proposed based on experimental results and DFT calculations.
Advanced oxidation technologies based on periodate (PI, IO4−) have garnered significant attention in water decontamination. In this work, we found that electrochemical activation using graphite electrodes (E-GP) can significantly accelerate the degradation of micropollutants by PI. The E-GP/PI system achieved almost complete removal of bisphenol A (BPA) within 15 min, exhibited unprecedented pH tolerance ranging from pH 3.0 to 9.0, and showed more than 90% BPA depletion after 20 h of continuous operation. Additionally, the E-GP/PI system can realize the stoichiometric transformation of PI into iodate, dramatically decreasing the formation of iodinated disinfection by-products. Mechanistic studies confirmed that singlet oxygen (1O2) is the primary reactive oxygen species in the E-GP/PI system. A comprehensive evaluation of the oxidation kinetics of 1O2 with 15 phenolic compounds revealed a dual descriptor model based on quantitative structure−activity relationship (QSAR) analysis. The model corroborates that pollutants exhibiting strong electron-donating capabilities and high pKa values are more susceptible to attack by 1O2 through a proton transfer mechanism. The unique selectivity induced by 1O2 in the E-GP/PI system allows it to exhibit strong resistance to aqueous matrices. Thus, this study demonstrates a green system for the sustainable and effective elimination of pollutants, while providing mechanistic insights into the selective oxidation behaviour of 1O2.
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•As compared to precipitation, soil moisture greatly influences GPP.•There is a solid spatial agreement among PUE and SWUE with a step-wise gradient from southwest to northeast.•PUE ...and SWUE are relatively low in extremely arid and humid regions.•In relatively moderate areas, PUE and SWUE increase with the abundance of moisture conditions.•Meadow grassland has the highest PUE and SWUE, followed by typical grassland and desert steppe.
Grassland ecosystem dominates in the Mongolian Plateau, mostly located in its arid and semi-arid regions. Although the ecosystem is an important source for agriculture, it is also a fragile system ecologically. This system is one of the most sensitive areas to global climate change. Precipitation (PPT) and soil moisture (SM) are important water sources in the grassland ecosystem, and their changes would greatly affect vegetation growth. This paper generates the precipitation use efficiency (PUE) and soil water use efficiency (SWUE) of Mongolian Plateau grassland based on multi-source remote sensing data to investigate the spatio-temporal distribution pattern and identify the driving factors. Results showed four main findings. Firstly, two water use efficiency (WUE) indicators show a generally increasing trend from 2000 to 2018, with average PUE and SWUE 1.07 gC·m−2·mm−1 and 1.03 gC/kg·H2O, respectively. They have similar spatial distribution patterns, consistent with the available water resources, decreasing from northeast to southwest. However, grassland vegetation growth is more sensitive to soil moisture than precipitation, and the dynamic change of SWUE is smoother and more significant than PUE. Secondly, due to the higher species richness, better vegetation biological characteristics and less severe growth environment, meadow grassland has the highest PUE and SWUE, followed by typical grassland and desert steppe. Thirdly, PUE and SWUE are relatively low in extremely arid and humid regions. In areas with relatively moderate water conditions (PPT in 148–360 mm, SM in 0.14–0.35 cm3/cm3), two indicators increase with the abundance of moisture conditions and reach the maximum. Fourthly, there is a positive linear relationship between PUE (SWUE) with precipitation and a unimodal correlation between PUE (SWUE) with temperature across the entire grassland. However, a varying correlation exists in different grassland ecosystems, especially meadow grassland. Together with analyzing past and future trends, this study provides strong evidence to reflect the impact of global climate change and the management and protection of the grassland ecosystems in arid and semi-arid regions.
Ensuring food safety is crucial for both the national economy and the well-being of individuals, as it forms the foundation of social and economic development. The process of ensuring food safety ...must cover all stages of production, including planting or breeding, processing, packaging, storage, transportation, sales, and consumption. Compliance with national mandatory standards is imperative, and there should be no potential harm to human health. However, effective monitoring and management of food safety necessitate testing technology that is sensitive, precise, efficient, and practical. In the field of biosensing, microfluidic technology has garnered substantial interest due to its capacity for miniaturization, integration, lab-on-a-chip analysis, and multiplex detection. In this review, we thoroughly examine various forms of food pollution and contamination, such as foodborne pathogens, heavy metal ions, viruses, veterinary drugs, illegal additives, and biotoxins. Additionally, we provide a comprehensive review of the most recent technologies based on microfluidics-enhanced biosensors for food safety monitoring, including optical transduction, electrical strategies, and magnetic methods. Finally, we present the critical challenges and future perspectives of developing microfluidics-based biosensing technology for food safety monitoring. We believe that this review will help bridge the gap between food safety and microfluidics-enhanced biosensor technology, providing implications for scientists and engineers in both fields to collaborate and promote the development of new devices and technologies for food safety management.
•Summarizing food pollution and contaminations.•Highlighting recognition elements for microfluidics-based biosensors.•Reviewing food safety biosensors with various transductions.•Discussing challenges and opportunities for next-generation food safety biosensors.
Influenza outbreaks pose a significant threat to global public health. Traditional surveillance systems and simple algorithms often struggle to predict influenza outbreaks in an accurate and timely ...manner. Big data and modern technology have offered new modalities for disease surveillance and prediction. Influenza-like illness can serve as a valuable surveillance tool for emerging respiratory infectious diseases like influenza and COVID-19, especially when reported case data may not fully reflect the actual epidemic curve. This study aimed to develop a predictive model for influenza outbreaks by combining Baidu search query data with traditional virological surveillance data. The goal was to improve early detection and preparedness for influenza outbreaks in both northern and southern China, providing evidence for supplementing modern intelligence epidemic surveillance methods. We collected virological data from the National Influenza Surveillance Network and Baidu search query data from January 2011 to July 2018, totaling 3,691,865 and 1,563,361 respective samples. Relevant search terms related to influenza were identified and analyzed for their correlation with influenza-positive rates using Pearson correlation analysis. A distributed lag nonlinear model was used to assess the lag correlation of the search terms with influenza activity. Subsequently, a predictive model based on the gated recurrent unit and multiple attention mechanisms was developed to forecast the influenza-positive trend. This study revealed a high correlation between specific Baidu search terms and influenza-positive rates in both northern and southern China, except for 1 term. The search terms were categorized into 4 groups: essential facts on influenza, influenza symptoms, influenza treatment and medicine, and influenza prevention, all of which showed correlation with the influenza-positive rate. The influenza prevention and influenza symptom groups had a lag correlation of 1.4-3.2 and 5.0-8.0 days, respectively. The Baidu search terms could help predict the influenza-positive rate 14-22 days in advance in southern China but interfered with influenza surveillance in northern China. Complementing traditional disease surveillance systems with information from web-based data sources can aid in detecting warning signs of influenza outbreaks earlier. However, supplementation of modern surveillance with search engine information should be approached cautiously. This approach provides valuable insights for digital epidemiology and has the potential for broader application in respiratory infectious disease surveillance. Further research should explore the optimization and customization of search terms for different regions and languages to improve the accuracy of influenza prediction models.
Aligned submicron fibers have played an essential role in inducing stem cell proliferation and differentiation. In this study, it is aimed to identify the differential causes of stem cell ...proliferation and differentiation between bone marrow mesenchymal stem cells (BMSCs) on aligned‐random fibers with different elastic modulus, and to change the differential levels through a regulatory mechanism mediated by B‐cell lymphoma 6 protein(BCL‐6) and miRNA‐126‐5p(miR‐126‐5p). The results showed that phosphatidylinositol(4,5)bisphosphate alterations are found in the aligned fibers compared with the random fibers, which has a regular and oriented structure, excellent cytocompatibility, regular cytoskeleton, and high differentiation potential. The same trend is actual for the aligned fibers with a lower elastic modulus. The level of proliferative differentiation genes in cells is altered by BCL‐6 and miR‐126‐5p mediated regulatory mechanisms to make the cell distribution nearly consistent with the cell state on low elastic modulus aligned fibers. This work demonstrates the reason for the difference of cells between the two kinds of fibers and on fibers with different elastic modulus. These findings provide more insights for understanding the gene‐level regulation of cell growth in tissue engineering.
The high expression of PIP2 on the tropic fibers with low elastic modulus is the main reason for the increased potential of stem cell proliferation and differentiation. The cells on random fibers or high elastic modulus aligned fibers were altered by BCL‐6 and miR‐126‐5p mediated regulatory mechanisms to be consistent with cells on low elastic modulus aligned fibers.
