1,235 results on '"Lei, Wang"'
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2. CSST Strong-lensing Preparation: A Framework for Detecting Strong Lenses in the Multicolor Imaging Survey by the China Survey Space Telescope (CSST)
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Xu Li, Ruiqi Sun, Jiameng Lv, Peng Jia, Nan Li, Chengliang Wei, Hu Zou, Xinzhong Er, Yun Chen, Zhang Ban, Yuedong Fang, Qi Guo, Dezi Liu, Guoliang Li, Lin Lin, Ming Li, Ran Li, Xiaobo Li, Yu Luo, Xianmin Meng, Jundan Nie, Zhaoxiang Qi, Yisheng Qiu, Li Shao, Hao Tian, Lei Wang, Wei Wang, Jingtian Xian, Youhua Xu, Tianmeng Zhang, Xin Zhang, and Zhimin Zhou
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Strong gravitational lensing ,Astronomy image processing ,Neural networks ,Space telescopes ,Astronomy ,QB1-991 - Abstract
Strong gravitational lensing is a powerful tool for investigating dark matter and dark energy properties. With the advent of large-scale sky surveys, we can discover strong-lensing systems on an unprecedented scale, which requires efficient tools to extract them from billions of astronomical objects. The existing mainstream lens-finding tools are based on machine-learning algorithms and applied to cutout-centered galaxies. However, according to the design and survey strategy of optical surveys by the China Space Station Telescope (CSST), preparing cutouts with multiple bands requires considerable efforts. To overcome these challenges, we have developed a framework based on a hierarchical visual transformer with a sliding window technique to search for strong-lensing systems within entire images. Moreover, given that multicolor images of strong-lensing systems can provide insights into their physical characteristics, our framework is specifically crafted to identify strong-lensing systems in images with any number of channels. As evaluated using CSST mock data based on a semianalytic model named CosmoDC2, our framework achieves precision and recall rates of 0.98 and 0.90, respectively. To evaluate the effectiveness of our method in real observations, we have applied it to a subset of images from the DESI Legacy Imaging Surveys and media images from Euclid Early Release Observations. A total of 61 new strong-lensing system candidates are discovered by our method. However, we also identified false positives arising primarily from the simplified galaxy morphology assumptions within the simulation. This underscores the practical limitations of our approach while simultaneously highlighting potential avenues for future improvements.
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- 2024
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3. Interannual synchronization of the North American summer monsoon and the North Atlantic tropical cyclone genesis frequency
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Jianzhou Luo, Jinwen Weng, Weijian Luo, and Lei Wang
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monsoon–tropical cyclone relationship ,North Atlantic tropical cyclone ,North American monsoon ,tropical Pacific–Atlantic interbasin SST ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Variations of the North American summer monsoon (NASM) and North Atlantic tropical cyclone (NATC) activities strongly influence climate anomalies in North America, with serious potential risk to life and property. Despite the scientific importance of this topic, the possible linkage between the NASM and the NATC genesis frequency remains unexplored. Here, we aim to examine the relationship between interannual variations of the NASM intensity and the NATC genesis frequency based on observations and Coupled Model Intercomparison Project Phase 6 (CMIP6) models. Our results show a strong association between the NASM intensity and the NATC genesis frequency during the extended boreal summer, with a good synchronization between their interannual variations. In years with stronger (weaker) NASM intensity, the NATC genesis frequency tends to be higher (lower). The observed NASM–NATC synchronization may be explained by two pathways: tropical-ocean-driven pathway and monsoon-heating-driven pathway. In the tropical-ocean-driven pathway, the tropical Pacific and Atlantic interbasin sea surface temperature (SST) anomalies play a critical role in bridging the NASM and NATC, by modulating the cross-Central American wind. Simulations of the tropical Pacific–Atlantic interbasin SST anomalies are critical for CMIP6 models to capture the observed linkage between the NASM and the vertical wind shear over the NATC main development region (MDR). In the monsoon-heating-driven pathway, the heating source due to the rainfall anomalies associated with the NASM can trigger atmospheric circulation anomalies through the Gill-type response, thereby affecting the NATC by changing the vertical wind shear over the MDR. This study demonstrates a connection between interannual variations of the NASM and the NATC genesis frequency, results of which can be used to advance our understanding of the monsoon–TC relationship and increase research focus on the interannual NASM–NATC synchronization in climate prediction.
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- 2024
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4. Comparative analysis of indices in capturing the onset and withdrawal of the South Asian Summer Monsoon
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Xiuping Li, Lei Wang, Shiyuan Zhong, and Liu Liu
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South Asian summer monsoon ,rainfall ,withdrawal ,onset ,Tibetan Plateau ,Environmental sciences ,GE1-350 ,Meteorology. Climatology ,QC851-999 - Abstract
The South Asian summer monsoon (SASM) exerts a profound influence on South Asia and the southern Tibetan Plateau. The timing of its onset and withdrawal significantly impacts regional rainfall, a critical water source for agriculture and the economy. Various SASM indices, employing different variables, have been employed to gauge monsoon onset and withdrawal, each demonstrating distinct characteristics. This study provides a comprehensive comparison of prominent SASM indices related to onset and withdrawal, revealing similar timing but varying magnitudes. Across nearly all indices, a consistent pattern emerges, indicating a trend towards earlier onset and delayed retreat during 1979–2018, marked by pronounced interdecadal variability, with a notable turning point around 1997. The earlier onset and later retreat are likely to enhance rainfall and potential water resources for South Asia and the Tibetan Plateau. Delving into the mechanisms revealed a delayed connection between the SASM onset to the large-scale sea surface temperature (SST) anomalies characterized by the Oceanic Niño Index (ONI) in the preceding spring, but a simultaneous connection between SASM withdrawl and ONI in autumn. Current index definitions, relying on single or dual variables, may fall short in accurately depicting monsoon onset and withdrawal. To address this, we introduce a novel monsoon index derived from multiple large-scale circulation variables, offering improved trend capture and enhanced representation of interannual variability in SASM onset and withdrawal. This study advances our understanding of SASM indices and their correlation with monsoon rainfall, providing insights into the dynamics of SASM onset and withdrawal.
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- 2024
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5. 3D printing in space: from mechanical structures to living tissues
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Mao Mao, Zijie Meng, Xinxin Huang, Hui Zhu, Lei Wang, Xiaoyong Tian, Jiankang He, Dichen Li, and Bingheng Lu
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3D printing in space ,space manufacturing ,microgravity ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Industrial engineering. Management engineering ,T55.4-60.8 ,Physics ,QC1-999 - Abstract
3D printing stands at the forefront of transforming space exploration, offering unprecedented on-demand and rapid manufacturing capabilities. It adeptly addresses challenges such as mass reduction, intricate component fabrication, and resource constraints. Despite the obstacles posed by microgravity and extreme environments, continual advancements underscore the pivotal role of 3D printing in aerospace science. Beyond its primary function of producing space structures, 3D printing contributes significantly to progress in electronics, biomedicine, and resource optimization. This perspective delves into the technological advantages, environmental challenges, development status, and opportunities of 3D printing in space. Envisioning its crucial impact, we anticipate that 3D printing will unlock innovative solutions, reshape manufacturing practices, and foster self-sufficiency in future space endeavors.
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- 2024
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6. Study of Iron and Stony Meteorite Ablation Based on Simulation Experiments in an Arc Heater
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Lei Wang, Lei Ning Dang, Ling Wei Yang, Jin Bo Liu, Jie Huang, Zhen Jun Huang, Jing Kang Yang, and Yue Luo
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Meteorites ,Astrophysics ,QB460-466 - Abstract
To observe meteorite ablation, simulation experiments were conducted on the L5 ordinary chondrite and IAB-MG iron meteorites in an arc-heated facility and three flight conditions were reproduced. To mimic the high heating rates and the significant shear stress that meteorites experience during Earth entry, the samples were machined into 9° spherical cones with a 20 mm nose radius. High-quality video, the surface temperature, a time-resolved spectrum, and infrared video were recorded. The atom species were determined via spectroscopy to analyze the ablation products. Due to the electrode erosion and dissociation of air, the atomic lines of copper, nitrogen, and oxygen were detected in all the tests. Although the copper atom is a pollutant to the flow field, the five copper lines were used to determine the flow-field temperature. The ablation rates and effective heat of ablation of both the samples were measured under different conditions. The results indicate that shear stress is the dominant factor influencing meteorite ablation. Furthermore, the diversity between stony and iron meteorites suggests that the mass loss of stony meteorites depends on the fragmentation of the main body and that of iron meteorites depends on the shearing loss of the molten layer. Then, the fusion crusts were analyzed, the microstructures of the samples were obtained, the crust thicknesses were measured, and the elemental distribution of the stony meteorites was determined via energy dispersion spectroscopy. The study results explain the differences in the ablation and recrystallization process between stony and iron meteorites.
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- 2024
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7. HybPSF: Hybrid Point-spread Function Reconstruction for the Observed JWST NIRCam Image
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Lin Nie, Huanyuan Shan, Guoliang Li, Lei Wang, Cheng Cheng, Charling Tao, Qifan Cui, Yushan Xie, Dezi Liu, and Zekang Zhang
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Gravitational lensing ,Galaxy clusters ,Astronomy data analysis ,Astronomy ,QB1-991 - Abstract
The James Webb Space Telescope (JWST) marks a new era of astronomical observation and discovery, providing unrivaled precision in various measurements, including photometry, morphology, and shear measurement. Accurate point-spread function (PSF) models are essential for many of these measurements. In this paper, we introduce HybPSF, a hybrid PSF construction method for JWST NIRCam imaging data that combines the WebbPSF software, which simulates the PSF for JWST, with observed data to produce more accurate and reliable PSF models. We apply this method to the SMACS J0723 imaging data and construct supplementary structures from residuals obtained by subtracting the WebbPSF PSF model from the data. Our results show that HybPSF significantly reduces discrepancies between the PSF model and the data compared to WebbPSF. Specifically, the PSF shape parameter ellipticity and size comparisons indicate that HybPSF improves precision by approximately 10 times for R ^2 and 50% for e . This improvement has important implications for astronomical measurements using JWST NIRCam imaging data.
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- 2024
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8. Magnetic Field Signatures of Intermediate-sized Impact Craters on Mars
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Kuixiang Zhang, Aimin Du, Can Huang, Hao Luo, Lin Tian, Yasong Ge, Jipeng Qin, and Lei Wang
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Mars ,Impact phenomena ,Planetary dynamics ,Magnetic fields ,Astrophysics ,QB460-466 - Abstract
Magnetic field signatures over impact craters provide constraints for the history of the Martian dynamo. Due to limitations of the spatial resolution of magnetic field models, previous studies primarily focused on large impact craters (mostly ≥ 500 km in diameter). To fill the impact crater age gaps of previous studies, we investigate the magnetic field signature of 23 intermediate-sized craters (150–500 km in diameter) on Mars using both MAVEN data and a magnetic field model. Ten impact craters located in the South Province, the unmagnetized primordial crust, exhibit no or weak magnetic field signatures. The other 13 impact craters produce stronger magnetic anomalies, with the ratio of the averaged magnetic field inside and outside the craters ( B _in / B _out ) ranging from 0.4 to 1.2. The B _in / B _out values exhibit correlation coefficients of −0.54, −0.57, and −0.69 with the diameters of craters, calculated from the MAVEN data, the crustal field model at the surface, and 150 km altitude, respectively. A B _in / B _out larger than 1.0 usually appears in craters with smaller diameters, which is also demonstrated by the forward modeling in this study. Furthermore, the results of the forward modeling indicate that the craters of stronger magnetizations show a larger B _in / B _out . According to this, the Martian dynamo can be associated with the magnetization of craters of different ages, and the characteristic time of the dynamo can be limited. Our study supports the hypothesis that the Martian dynamo weakened or ceased at ∼4.0 Ga and a late dynamo was perhaps active at ∼3.7 Ga.
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- 2023
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9. Importance of realistic zonal currents in depicting the evolution of tropical central Pacific sea surface temperature
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Da Pang, Xianghui Fang, and Lei Wang
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El Niño ,equatorial central Pacific ,zonal currents ,zonal current residual term ,statistical model ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Classical El Niño–Southern Oscillation (ENSO) theories mainly consider the vertical process-related Ekman and thermocline feedbacks. However, the zonal current-related zonal advective feedback has been suggested to play a crucial role in the evolution of central Pacific (CP) El Niño and La Niña events. Also, the simulation of a realistic current is complex and not the focus of the classical ENSO theories. Using reanalysis datasets and a statistical model, this study emphasizes the importance of the zonal currents in the sea surface temperature anomaly (SSTA) evolution in the Niño4 region (160° E–150° W, 5° S–5° N). Specifically, in addition to the widely used predictors for the ENSO evolution, i.e. the equatorial Pacific mean thermocline depth anomaly (D20) and the zonal wind stress anomaly (ZWS), the zonal current anomaly (ZCA) averaged in the CP is first extracted to construct a statistical model to predict the SSTA of the Niño4 region. The results show that this model has improved overall prediction skill and accuracy for several CP El Niño and La Niña events during 1980–2020, compared with the benchmark linear regression model based on D20 and ZWS. By further removing the components related to the equatorial Kelvin and first symmetric meridional ( $m = 1$ ) Rossby waves (namely, the principal part of the traditional ENSO mechanism) from the ZCA, the remainder, which contains higher-order Rossby waves and other nonlinear components and is called the zonal current anomaly residual (ZCA_RSD), is found to be the key part of the improvements in the prediction skill. This suggests that to better simulate and predict the complex ENSO events, more vertical and meridional modes of the tropical Pacific need to be included to obtain a realistic anomalous zonal current.
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- 2023
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10. Diagnosing observed extratropical stationary wave changes in boreal winter
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Wanying Sun and Lei Wang
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stationary waves ,stationary wave modeling ,diabatic heating ,climate change ,extratropical dynamics ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Stationary waves are time-averaged zonally asymmetric component of the climatological mean atmospheric circulation, primarily due to the unevenly distributed topography and diabatic heating. Stationary waves are subject to influence from long-term external forcing. In this study, the temporal evolution of the winter (January) Northern Hemisphere stationary waves during 1961–2020 is diagnosed with the fifth generation European Centre for Medium-range Weather Forecasts reanalysis data (ERA5), which shows an overall strengthening in amplitude and an eastward shift in phase. A stationary wave model is used to attribute the stationary wave response to changes in the zonal mean basic state (Δ ZM ) and the zonally asymmetric diabatic heating forcing ( $\Delta {q^*}$ ). The pattern of stationary wave changes is well captured by the response to Δ ZM alone, whereas the contribution of $\Delta {q^*}$ to the amplitude increases in height and becomes dominant in the stratosphere. $\Delta {q^*}$ is also found to be important in driving stationary wave changes in the North Pacific and Western Europe regions. Furthermore, changes in tropospheric stationary waves are probably a result of internal variability, whereas stratospheric changes are more likely to be driven by external forcing.
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- 2023
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11. Temporal and spatial changes in hydrological wet extremes of the largest river basin on the Tibetan Plateau
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Yuanwei Wang, Suheng Wang, Lei Wang, Xiaoyu Guo, Jing Zhou, Chenhao Chai, Jie Xu, Xiangfei Li, Mengtian Fan, Shengfeng Wang, and Lin Zhao
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extreme discharges ,spatial-temporal variability ,hydrological modeling ,upper Brahmaputra ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Global warming accelerates the rate of inter-regional hydrological cycles, leading to a significant increase in the frequency and intensity of hydrological wet extremes. The Tibetan Plateau (TP) has been experiencing a rapid warming and wetting trend for decades. This trend is especially strong for the upper Brahmaputra basin (UBB) in the southern TP. The UBB is the largest river on the TP, and these changes are likely to impact the water security of local and downstream inhabitants. This study explores the spatial-temporal variability of wet extremes in the UBB from 1981–2019 using a water- and energy-budget distributed hydrological model (WEB-DHM) to simulate river discharge. The simulated results were validated against observed discharge from the Ministry of Water Resources at a mid-stream location and our observations downstream. The major findings are as follows: (1) the WEB-DHM model adequately describes land-atmosphere interactions (slight underestimation of −0.26 K in simulated annual mean land surface temperature) and can accurately reproduce daily and monthly discharge (Nash-Sutcliffe efficiency is 0.662 and 0.796 respectively for Nuxia station); (2) although extreme discharge generally occurs in July and is concentrated in the southeastern TP, extreme wet events in the UBB are becoming increasingly frequent (after 1998, the number of extreme days per year increased by 13% compared to before) and intense (maximum daily discharge increased with a significant trend of 444 (m ^3 s ^−1 ) yr ^−1 ), and are occurring across a wider region; (3) Precipitation is more likely to affect the intensity and spatial distribution of wet extremes, while the air temperature is more correlated with the frequency. Our wet extreme analysis in the UBB provides valuable insight into strategies to manage regional water resources and prevent hydrological disasters.
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- 2023
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12. Isotopic composition and emission characteristics of CO2 and CH4 in glacial lakes of the Tibetan Plateau
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Fangping Yan, Zhiheng Du, Tao Pu, Qian Xu, Lei Wang, Ruifang Ma, Chao Zhang, Zhengliang Yu, Chaoliu Li, and Shichang Kang
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carbon dioxide ,methane ,emission characteristics ,sources and sinks ,Tibetan Plateau ,glacial lakes ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Carbon dioxide (CO _2 ) and methane (CH _4 ) emissions from freshwater ecosystems are predicted to increase under climate warming. However, freshwater ecosystems in glacierized regions differ critically from those in non-glacierized regions. The potential emissions of CO _2 and CH _4 from glacierized environments in the Tibetan Plateau (TP) were only recently recognized. Here, the first direct measurement of CO _2 and CH _4 emission fluxes and isotopic composition during the spring of 2022 in 13 glacial lakes of the TP revealed that glacial lakes were the previously overlooked CO _2 sinks due to chemical weathering in glacierized regions. The daily average CO _2 flux was −5.1 ± 4.4 mmol m ^−2 d ^−1 , and the CO _2 consumption could reach 38.9 Gg C-CO _2 yr ^−1 by all glacial lakes in the TP. This consumption might be larger during summer when glaciers experience intensive melting, highlighting the importance of CO _2 uptake by glacial lakes on the global carbon cycle. However, the studied glacial lakes were CH _4 sources with total emission flux ranging from 4.4 ± 3.3 to 4082.5 ± 795.6 μ mol m ^−2 d ^−1 . The large CH _4 range was attributed to ebullition found in three of the glacial lakes. Low dissolved organic carbon concentrations and CH _4 oxidation might be responsible for the low CH _4 diffusive fluxes of glacial lakes without ebullition. In addition, groundwater input could alter CO _2 and CH _4 emissions from glacial lakes. CH _4 in glacial lakes probably had a thermogenic source; whereas CO _2 was influenced mainly by atmospheric input, as well as organic matter remineralization and CH _4 oxidation. Overall, glacial lakes in the TP play an important role in the global carbon cycle and budget, and more detailed isotopic and microbial studies are needed to constrain the contributions of different pathways to CO _2 and CH _4 production, consumption and emissions.
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- 2023
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13. MAVEN Observations of the Interloop Magnetic Reconnections at Mars
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Guo Chen, Can Huang, Ying Zhang, Yasong Ge, Aimin Du, Rongsheng Wang, Lei Wang, Lican Shan, Christian Mazelle, and Hao Luo
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Mars ,Magnetic fields ,Plasma physics ,Astrophysics ,QB460-466 - Abstract
Magnetic reconnection between neighboring magnetic field loops, the so-called interloop reconnection, is a common process to drive flares in the solar atmosphere. However, there is no direct evidence that a similar but less explosive process can take place on planets. The strong crustal fields on Mars generate plenty of magnetic loops in the near-Mars regions, providing a unique environment to research the interloop reconnection on a planet. Here, we report magnetic reconnection events between crustal field loops in the Martian ionosphere observed by Mars Atmosphere and Volatile EvolutioN (MAVEN) for the first time. During the current layer crossing, MAVEN recorded the characteristic signals of collisionless magnetic reconnection, including the Hall magnetic field, Alfvénic outflow, and electron energization. This finding implies that the interloop reconnection in the Martian ionosphere could contribute to the localized energy deposition and particle energization, which provides the seed source for aurora in the Martian atmosphere.
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- 2023
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14. Large-scale circulation dominated precipitation variation and its effect on potential water availability across the Tibetan Plateau
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Xiuping Li, Lei Wang, Deliang Chen, Lonnie Thompson, Kun Yang, Shiyuan Zhong, Liu Liu, Zongxue Xu, and Lei Song
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large-scale circulation ,duration ,intensity ,precipitation ,surface runoff ,Tibetan Plateau ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
The large-scale circulation, Indian summer monsoon (ISM), has a strong influence on the Tibetan Plateau (TP) since its onset and intensity have profound impacts on regional precipitation, which then can supply water for glaciers, lakes, rivers and social demands. Weakening monsoon intensity and longer monsoon duration seem contradictory, as a weaker monsoon tends to produce less precipitation, while a longer duration increases the probability of precipitation. Past research has focused on how ISM’s intensity affects precipitation, with little consideration of the impacts of ISM duration. Here, we investigate the long-term (1979–2100) variability in the ISM’s duration and intensity. We find a prolonged ISM from 1979 to 2018, accompanied by monsoon weakening. Different combinations of duration and intensity have resulted in different spatial patterns of precipitation across the southeastern TP. Weakening and prolonged ISM is helpful to produce more precipitation around the southeastern TP, with intensity acting as a dominant control. Afterwards, an obvious impact can be found on potential water availability. Climate projections suggest that the ISM will weaken and lengthen until 2100, thereby increasing precipitation and potential water availability across the southeastern TP. This long-term trend should receive more attentions as increased regional extreme precipitation will increase the probability of flood risks until the end of this century.
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- 2023
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15. Kelvin–Helmholtz Instability at Mars: In Situ Observations and Kinetic Simulations
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Lei Wang, Can Huang, Aimin Du, Yasong Ge, Guo Chen, Zhongwei Yang, Songyan Li, and Kuixiang Zhang
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Mars ,Planetary boundary layers ,Solar-planetary interactions ,Space plasmas ,Astrophysics ,QB460-466 - Abstract
Kelvin–Helmholtz (K-H) instability is a fundamental boundary instability between two fluids with different speeds, exchanging the mass, momentum, and energy across the boundary. Although the K-H instability has been suggested to play a critical role in atmospheric ion loss on Mars, the knowledge about its formation and evolution is still poor, due to the limitation of spacecraft missions and a dearth of dedicated simulation codes. In this study, we combine observations from the Mars Atmosphere and Volatile EvolutioN mission and global 3D kinetic simulations to investigate the solar wind–Mars interaction. For the first time, it is found that K-H waves prominently appear in the −E hemisphere, which is attributed to the stronger proton velocity shear therein associated with the asymmetric diamagnetic drift motion of protons. The K-H instability is mainly excited in the −E hemisphere and propagates downstream along the boundary, with the waves also able to be generated near the subsolar point. The K-H waves produce plasma clouds with a net oxygen ion escape rate of about 1.5 × 10 ^24 s ^−1 , contributing to almost half of the global loss on present-day Mars. This heavy ion escape pattern associated with K-H instability is cyclic and could occur on other nonmagnetized planets, potentially influencing planetary atmosphere evolution and habitability.
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- 2023
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16. Weakening seasonality of Indo-Pacific warm pool size in a warming world since 1950
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Qiuying Gan, Jeremy Cheuk-Hin Leung, Lei Wang, and Banglin Zhang
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Indo-Pacific warm pool ,seasonality ,global warming ,capacity for change ,expansion ,climatological SST pattern ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Seasonal variation of the Indo-Pacific warm pool (IPWP) plays an important role in oceanographic and climatological processes. While expansion of the IPWP under greenhouse warming has been widely discussed, the response of IPWP seasonality to climate change has received limited attention. In this study, we found an obvious seasonal diversity in expansion of the IPWP from 1950 to 2020, with a maximum (minimum) expansion trend of 0.28 $ \times $ 10 ^7 km ^2 /decade in winter (0.17 $ \times $ 10 ^7 km ^2 /decade in spring), which consequently reduces the seasonality amplitude of the variation in IPWP size. This is primarily attributed to the seasonal difference in the climatological spatial sea surface temperature (SST) pattern over the Indo-Pacific Ocean, especially that over the tropical Indian Ocean, which determines the capacity for IPWP expansion. Heat budget analyses show that the seasonal shortwave radiation and latent heat fluxes are the major factors controlling the capacity for change in IPWP size across seasons. The presented analyses emphasize the significant weakening of the seasonality of IPWP size, which may have great impacts on the ecological environment of the IPWP and the tropical climate system, and remind us that the intrinsic properties of the climate background of Indo-Pacific SST hold important clues about IPWP expansion under climate change.
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- 2023
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17. In-situ growth of CeO2/Ce(OH)CO3 composites with enhanced photocatalytic activity by the incomplete conversion of CeO2 to Ce(OH)CO3
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Xinhao Wu, Jianping Tang, Yuan Li, Yujun Chen, Guiwen Huang, Lei Wang, and Shengliang Zhong
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In-situ growth ,CeO2/Ce(OH)CO3 ,incomplete conversion ,ethylene glycol ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
In this paper, a novel strategy was used to grow CeO _2 /Ce(OH)CO _3 composite in situ by the incomplete conversion of CeO _2 to Ce(OH)CO _3 using ethylene glycol (EG) as CO _3 ^2− source and solvent. Interestingly, the content of Ce(OH)CO _3 in CeO _2 /Ce(OH)CO _3 composite can be controlled by changing the solvent composition. The obtained CeO _2 /Ce(OH)CO _3 composite all exhibited enhanced photocatalytic performance for methylene blue (MB) degradation. The CeO _2 /Ce(OH)CO _3 composite prepared at 200 °C for 24 h with a H _2 O/EG volume ratio of 0.5 showed the best visible-light activity with a degradation efficiency of 98.84% within 120 min. This work provided a novel method to fabricate basic rare Earth carbonates and their composites for environmental purification.
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- 2023
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18. Optimization of Centrifugal Pump Impeller Based on Neural Network and NSGA-II Algorithm.
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Wei, Chen, Wensheng, Ma, Lei, Wang, Meng, Zhang, Qiang, Zhang, and Kaizi, Huo
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- 2024
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19. ENSO and QBO modulation of the relationship between Arctic sea ice loss and Eurasian winter climate
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Xuan Ma, Lei Wang, Doug Smith, Leon Hermanson, Rosie Eade, Nick Dunstone, Steven Hardiman, and Jiankai Zhang
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Barents–Kara Sea sea ice ,Eurasian winter climate ,ENSO ,QBO ,stratosphere–troposphere coupling ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
The causality between Arctic sea ice decline and cold boreal winters has been widely debated recently and remains controversial. A major source of uncertainty in the sea ice-cold winter relationship originates from that the stratosphere polar vortex (SPV) is not only affected by Arctic sea ice anomaly but can also be modulated by El Niño-Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO). Using reanalysis data and hindcasts from the decadal prediction system version 4, here we show that both cold and warm winters occur over Eurasia when the Barents–Kara Sea sea ice is abnormally low. Warm winters occur during the La Niña-easterly QBO-low sea ice (LANINA-EQBO-LICE) years and cold winters during the neutral ENSO-neutral QBO (NENSO-NQBO)-LICE and El Niño (ELNINO)-NQBO-LICE years. During the LANINA-EQBO-LICE years, weakened upward-propagating planetary waves from the troposphere to the stratosphere strengthen the Arctic SPV and then weaken the Aleutian low and Siberian high, creating conditions favorable for Eurasian warming. The atmospheric responses are opposite in the NENSO-NQBO-LICE and ELNINO-NQBO-LICE years. This implies that care should be taken in using Arctic sea ice alone as the precursor to predict boreal winter climate.
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- 2022
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20. Divergent runoff impacts of permafrost and seasonally frozen ground at a large river basin of Tibetan Plateau during 1960–2019
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Lei Song, Lei Wang, Jing Zhou, Dongliang Luo, and Xiuping Li
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cryosphere-hydrology model ,frozen ground ,runoff ,soil temperature and moisture ,upper Yellow River basin ,Tibetan Plateau ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Since the 20th century, due to global warming, permafrost areas have undergone significant changes. The degradation of permafrost has complicated water cycle processes. Taking the upper Yellow River basin (UYRB) as a demonstration, this study discusses the long-term (1960–2019) changes in frozen ground and their hydrological effects with a cryosphere-hydrology model, in particular a permafrost version of the water and energy budget-based distributed hydrological model. The permafrost at the UYRB, with thickening active layer and lengthening thawing duration, has degraded by 10.8%. The seasonally frozen ground has a more pronounced intra-annual regulation that replenishes surface runoff in the warm season, while the degradation of permafrost leads to a runoff increase. The occurrence of extreme events at the UYRB has gradually decreased with the degradation of frozen ground, but spring droughts and autumn floods become more serious. The results may help better understand the hydrological impacts of permafrost degradation in the Tibetan Plateau.
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- 2022
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21. Economic growth dominates rising potential flood risk in the Yangtze River and benefits of raising dikes from 1991 to 2015
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Wei Qi, Lian Feng, Hong Yang, Junguo Liu, Yi Zheng, Haiyun Shi, Lei Wang, and Deliang Chen
- Subjects
flood risk ,yangtze river ,economic exposure ,hydrological extreme ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Flooding in the Yangtze River Basin could severely damage socio-economic development, river ecosystems, food security, hydropower production and transportation in China. The Yangtze River Basin accounts for approximately 30% of China’s gross domestic product (GDP) and is an engine for the country’s rapid economic growth. One commonly held belief is that climate change has intensified extreme flood events, leading to increasing economic damage in the Yangtze River. Here, we quantitatively attributed economic exposure to climate change (i.e. climate-induced changes in weather-related events) and GDP growth, and assessed benefits, i.e. the reduction in economic exposure, from flood defence dikes of varying heights. To do this, we developed a framework by combing a large scale hydrological model, a hydraulic model, and long-term GDP data. We find that climate-induced changes in flood inundation area and resulted economic exposure were decreasing overall, whereas GDP growth drove the increases of potential economic exposure to floods. We also reveal that the basin average flood defence dikes should be at least approximately 3.5 m high to achieve an about ten-year average flood occurrence. Our results have significant policy and socioeconomic development implications.
- Published
- 2022
- Full Text
- View/download PDF
22. Synergistic effects of Y and Nd on grain refinement of Mg-Y-Nd-Al alloy
- Author
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Lili Zhao, Liping Wang, Lei Wang, Yicheng Feng, Rui Fan, Sicong Zhao, and Yuanke Fu
- Subjects
Mg alloy ,microstructure ,nucleation particle ,grain refinement ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
In this study, the synergistic effects of Y and Nd on the grain refinement of the as-cast Mg-Y-Nd-Al alloy was investigated by varying Y and Nd contents while fixing their total content (Y + Nd) at 7%. When the contents of Y and Nd were 3% and 4%, respectively, the refinement was most effective and the smallest grain size of 49 ± 5 μ m was achieved. The grain refinement process was primarily controlled by the heterogeneous nucleation and the growth restriction factor (Q value). Y could only form Al _2 RE phase with Al, while both Al _2 RE and Al _11 RE _3 were formed between Nd and Al. The Al _2 RE phase acted as nucleation particles of α -Mg and facilitated heterogeneous nucleation; however, Al _11 RE _3 was an unfavorable phase for heterogeneous nucleation. When the Y content was less than 3%, the quantity of Al _2 RE phase increased when more Y was available, which resulted in more active nucleation particles and better refinement. When the Y content exceeded 3%, the Q value (growth limiting factor) of the alloy decreased, while the quantity of Al _2 RE phase remained unchanged. This would lead to a decreased number of active nucleation particles and a less effective grain refinement.
- Published
- 2022
- Full Text
- View/download PDF
23. Systematic investigation of a NbTi-Bi2223 hybrid low-resistive joint
- Author
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Zili Zhang, Wanshuo Sun, Yaohui Wang, Xiaolong Zhang, Lei Wang, Junsheng Cheng, HongLi Suo, and Qiuliang Wang
- Subjects
Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,Electrical and Electronic Engineering ,Condensed Matter Physics - Abstract
In this study, a NbTi-Bi2223 hybrid low-resistive joint fabricated by the superconducting solder method was systematically investigated. The joint is a necessary component of gigahertz nuclear magnetic resonance (NMR) with Bi2223 as the insert coil. The joint resistance and current capability under different applied magnetic fields were measured, and the resistance exhibited a near-linear relationship with the applied field. Beyond the superconducting properties, the allowed mechanical criteria for the Bi2223 tape in the joint were also briefly studied. Based on the above two properties, a 1.3-GHz NMR design with a NbTi-Bi2223 hybrid low-resistive joint was shown as an application demonstration. Although the current resistance can fit the magnetic-field decay criteria, obtaining a lower resistance value was attempted by extending the joint length but failed. The main source of the resistance in NbTi-Bi2223 was studied. We attempt to show an engineering-feasible NbTi-Bi2223 hybrid low-resistive joint to help improve the development of gigahertz NMR.
- Published
- 2023
24. Assessing High-Energy X-ray and Proton Irradiation Effects on Electrical Properties of P-GaN and N-GaN Thin Films
- Author
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Aoxue Zhong, Lei Wang, Yun Tang, Yongtao Yang, Jinjin Wang, Huiping Zhu, Zhenping Wu, Weihua Tang, and Bo Li
- Subjects
General Physics and Astronomy - Abstract
The effects of ionizing and displacement irradiation of high-energy X-ray and 2 MeV proton on GaN thin films were investigated and compared in this study. The electrical properties of both P-GaN and N-GaN, separated from power devices, were gauged for fundamental analysis. It was found that the electrical properties of P-GaN were improved as a consequence of the disruption of the Mg-H bond induced by high-dose X-ray irradiation, as indicated by the Hall and circular transmission line model. Specifically, under a 100 Mrad(Si) X-ray dose, the specific contact resistance ρc of P-GaN decreased by 30%, and the hole carrier concentration increased significantly. Additionally, the atom displacement damage effect of a 2 MeV proton of 1×1013 p/cm2 led to a significant degradation of the electrical properties of P-GaN, while those of N-GaN remained unchanged. P-GaN was found to be more sensitive to irradiation than N-GaN thin film. The effectiveness of X-ray irradiation in enhancing the electrical properties of P-GaN thin films was demonstrated in this study.
- Published
- 2023
25. Multisource electrohydraulic servo valve fault status diagnostic algorithm based on a message propagation mechanism
- Author
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Wei, Gao, primary, Pengfei, Sun, additional, Chao, Ai, additional, Lei, Wang, additional, Lijuan, Chen, additional, Wenting, Chen, additional, Shuwei, Zheng, additional, and Dong, Yang, additional
- Published
- 2023
- Full Text
- View/download PDF
26. CyberKnife® in abdominal stereotactic body radiosurgery
- Author
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Lei Wang, Nataliya Kovachuk, and Erqi Pollom
- Published
- 2023
27. Modulation of winter precipitation associated with tropical cyclone of the western North Pacific by the stratospheric Quasi-Biennial oscillation
- Author
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Lei Wang, Lin Wang, Wen Chen, and Jingliang Huangfu
- Subjects
tropical cyclone ,precipitation ,Quasi-Biennial oscillation ,western North Pacific ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Tropical cyclone precipitation (TCP) has increasing impacts on many coastal regions under global warming. Causes of TCP variation have been principally explored in the troposphere. This study identifies the significant modulation of the stratosphere Quasi-Biennial oscillation (QBO) on the winter TCP in the coastal regions of the western North Pacific (WNP). In the westerly QBO winter, the zonal wind vertical shear anomalies in the stratosphere strengthen (weaken) convective activities around the East China Sea (the Philippines) and cause middle-level easterly (westerly) anomalies of the middle (low) latitudes in the troposphere, leading to more (less) TC activities around the East China Sea (the Philippines). Consequently, a TCP dipole pattern can be observed. The TCP increases in East China, Korean peninsula, Japan and Russian Far East, but decreases in Indo–China Peninsula, South China and the Philippines. These results not only improve the knowledge of QBO-TCP relationship but also provide a potential indicator for the seasonal prediction of the TCP in the coastal regions of the WNP due to the high predictability of the QBO.
- Published
- 2021
- Full Text
- View/download PDF
28. Analysis of variation in reference evapotranspiration and its driving factors in mainland China from 1960 to 2016
- Author
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Dong Wu, Shibo Fang, Xingyuan Tong, Lei Wang, Wen Zhuo, Zhifang Pei, Yingjie Wu, Ju Zhang, and Mengqian Li
- Subjects
reference evapotranspiration ,spatiotemporal variation ,abrupt change ,driving factor ,mainland China ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Understanding the variation in reference evapotranspiration (ET _o ) is vital for hydrological cycles, drought monitoring, and water resource management. With 1507 meteorological stations and 130 radiation-measured stations, the annual and seasonal ET _o were calculated at each site from 1960 to 2016 in mainland China. The phenomenon of coefficient ‘ a ’ being less than 0.25 and coefficient ‘ b ’ being greater than 0.50 in the Angstrom–Prescott model occurred in almost the whole country, except for a small area of western and northeastern China. Moreover, the Xiao’s method was more applicable to calculate the net longwave radiation ( R _nl ) and then improve the estimation accuracy of ET _o . The annual ET _o varied from 538.8 to 1559.8 mm and had a high-value center located in the plateau and desert of northwestern China and a low-value center located in Northeast China and near the Sichuan Basin. The spatial distribution of seasonal ET _o was roughly similar to that of annual ET _o , except for that in winter when ET _o was high in the south and low in the north. In mainland China, the annual ET _o decreased by 21.2 mm decade ^−1 because of the declining sunshine duration before 1993 and increased by 21.1 mm decade ^−1 due to the decreased relative humidity (RH) after 1993. Generally, the abrupt change of ET _o mainly occurred in the southern China rather than northern China (except for Qinghai Tibet Plateau). Basically, the dominant driving factors of annual and seasonal ET _o were RH and/or T _max after the abrupt change in most parts of China.
- Published
- 2021
- Full Text
- View/download PDF
29. An exploration of the connection between quasi-biennial oscillation and Madden-Julian oscillation
- Author
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Feiyang Wang and Lei Wang
- Subjects
quasi-biennial oscillation ,Madden-Julian oscillation ,subseasonal-to-seasonal prediction ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental sciences ,GE1-350 ,Science ,Physics ,QC1-999 - Abstract
Recent studies have shown arguments about the connection between stratospheric quasi‐biennial oscillation (QBO) and activities of Madden‐Julian oscillation (MJO) during boreal winter on interannual timescale, especially for the question of which aspects of MJO, amplitude or occurrence frequency, can really be modulated by QBO. This study re-examines the interannual variability of the seasonally averaged amplitude and the occurrence of both ‘active’ (amplitude > 1.0) and ‘inactive’ (amplitude < 1.0) MJO days in boreal winter December–January–February (DJF), and their relation to QBO variation. Significant correlations between the QBO index and the indicators of MJO activity reveal that wintertime amplitude of ‘active’ and ‘inactive’ MJO days are typically larger in QBO easterly phase (EQBO) than in QBO westerly phase (WQBO). More importantly, we can also expect more ‘active’ MJO days and simultaneously less ‘inactive’ MJO days in EQBO winter as a consequence of more days in winter shifting from ‘inactive’ to ‘active’ due to larger MJO amplitudes. The significantly positive (negative) correlation between the time series of averaged amplitude and occurrence of ‘active’ (‘inactive’) MJO days can as well be interpreted as evidence that QBO is closely connected to the occurrence of MJO days via modulating MJO amplitudes. These results update our current understanding of the QBO-MJO connection, which is helpful to advance the MJO prediction.
- Published
- 2021
- Full Text
- View/download PDF
30. Experimental characterization of friction and wear behavior of textured Titanium alloy (Ti-6Al-4V) for enhanced tribological performance
- Author
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Dawit Zenebe Segu, Lei-Lei Wang, Pyung Hwang, and Seok-Won Kang
- Subjects
dry friction ,laser micro-texture ,ANOVA ,titanium alloy ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
Laser surface texturing (LST) is an effective surface engineering technique that can improve the efficiency and reliability of a tribosystem. In this study, surface textures with combined dimple patterns were prepared on a Ti-6Al-4V alloy surface using a Nd:YAG pulsed laser. Sliding dry and MoS _2 solid-lubricated experiments were performed to assess the tribological characteristics of these specimens using a ball-on-disk mode. An L _9 (3 ^4 ) orthogonal array table was used to prepare an experimental plan, which contained three parameters: the sliding speed, applied load, and the area density of dimple on the friction properties. The results show that the MoS _2 -added textured surface effectively decreased the coefficient of friction and reduced adhesion wear compared to an untextured surface. Analysis of variance (ANOVA) suggested that the texture area density has a major effect on the friction coefficient at a confidence level of 99%, followed by the applied load and sliding speed. Scanning electron microscopy (SEM) revealed that the wear mechanisms were adhesive and abrasive wear, and a transfer layer from the Ti-6Al-4V alloy was obtained on the counterpart ceramic ball. In conclusion, a higher texture area density is advantageous to increase the friction and wear performance of the Ti-6Al-4V alloy surface.
- Published
- 2021
- Full Text
- View/download PDF
31. Synthesis of yttrium aluminum garnet (Y3Al5O12, YAG) powder with nano and submicro size and high infrared transmittance using flame aerosol synthesis method
- Author
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Hui Tian, Lei Wang, Taisheng Yang, and Zili Zhang
- Subjects
YAG ,flame aerosol synthesis ,infrared transmittance ,hollow sphere ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
In this study, the flame aerosol synthesis (FAS) method was used to synthesize a yttrium aluminum garnet (Y _3 Al _5 O _12 , YAG) nanopowder. The dominant reaction route in the FAS method is the liquid route; this shaped the primary morphology of the YAG nanopowder into hollow and solid spheres. The effects of precursor concentration and annealing parameters were systematically investigated. At a precursor concentration of 0.4 mol L ^−1 and an annealing temperature of 1400 °C, the YAG nanopowder exhibited excellent infrared transmittance. Compared to other conventional synthesis methods, the FAS method has the advantages of high yield, low cost, and ease of obtaining a nanosized powder. The FAS method is thought to be one of the best choices for the large-scale production of YAG powders.
- Published
- 2021
- Full Text
- View/download PDF
32. Reaction mechanism of metakaolin materials prepared by calcining coal gangue
- Author
-
Shaowu Jiu, Simeng Cheng, Hui Li, and Lei Wang
- Subjects
coal gangue ,metakaolin ,reaction mechanism ,activity ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
Metakaolin-based auxiliary cementitious materials fabricated by coal gangue were achieved. The temperature and time required for the preparation of metakaolin materials from the calcination of coal gangue were optimized based on the analysis of the reaction characteristics and kinetics during the calcination of coal gangue. The phase, microstructures, and activity analysis of the products were performed, and the effect of calcination conditions on the activity of the product was ascertained. The results of thermal analysis-infrared spectra combined experiments indicated that the dehydroxylation of kaolinite was a one-step reaction during the calcination of coal gangue within a temperature range of 379.8 °C–737.3 °C. According to the General Integration, Flynn-Wall-Ozawa and Kissinger methods, the activation energy E of dehydroxylation of kaolinite is 181.62 kJ·mol ^−1 and pre-index factor A is 10 ^9.27 s ^−1 for calculating the calcination time of metakaolin. The experimental results show that high-activity metakaolin products, that with a dissolution rate of 64.79–71.57 wt% of activated alumina and with an effective dissolution rate of 68.82–94.35 wt% of activated silica, are prepared under the condition of calcination for 15 min and the temperature of 700 °C–825 °C. The kinetic model simulation results for the calcination time at different temperatures correspond to the experimental results.
- Published
- 2021
- Full Text
- View/download PDF
33. Study of gadolinium aluminate nanoparticles with perovskite structure prepared by citric acid chelation method
- Author
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Shiyu Dai, Gang Wang, Pengyuan Qi, Xiaochen Xu, Lili Jiang, Jingyu Zhong, Shuo Yuan, and Lei Wang
- Subjects
citric acid ,sol-gel ,perovskite structure ,GAP nanoparticles ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
Gadolinium aluminate (GdAlO _3 , GAP) is a rare earth compound with perovskite structure. Its optical isotropic structure prevents the defects of refractive index difference in any direction. GAP has unique and excellent properties in electricity, magnetism, luminescence and catalysis, especially as a high-quality luminescent matrix material. Sol-gel method has the advantages of accurate control of chemical composition, particle size and purity of products. The main preparation parameters include chelating agent concentration, alcohol water ratio, calcination temperature and so on. In this paper, the citric acid chelating agent was used to prepare gadolinium aluminate nanoparticles by sol-gel method, thermogravimetry-differential thermal analysis (TG-DTA), x-ray diffraction (XRD) and scanning electron microscope (SEM) were employed to analyze the effects of chelating agent, dispersant, solvent and calcination temperature on the phase and morphology changing in precursor and final product. The results show that GAP nanoparticles with high degree of crystallinity, nearly spherical morphology and 60–100 nm particle size can be obtained at the molar ratio of citric acid to cationic of 1:1, the ammonium citrate to citric acid of 1.5:1 and the calcination temperature of 900 °C for 4 h. When the calcination temperature is higher than 1100 °C, a new phase of Gd _3 Al _5 O _12 (GdAG) will be formed with calcination neck shape.
- Published
- 2020
- Full Text
- View/download PDF
34. High-performance aramid fabric in infrared shielding by magnetron sputtering method
- Author
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Leilei Jia, Binhe Fu, Matthew Lee Lu, Hui-e Liang, and Lei Wang
- Subjects
functional garment ,infrared stealth ,aramid fabric ,magnetron sputtering technology ,surfaces ,thermal properties ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
In addition to providing basic protective functions, modern military uniforms are also being designed to provide special functions, such as infrared shielding. In this study, a nanoscale copper film was deposited on Kevlar para-1414 aramid fabric by magnetron sputtering technology to significantly enhance infrared shielding. The deposition of a uniform nano-copper film on the surface of the aramid fabric enhanced infrared shielding, tensile strain, and conductivity, which is of guiding significance for the development of infrared shielding garments.
- Published
- 2020
- Full Text
- View/download PDF
35. Phase evolution of a novel Al–Zn–Mg–Cu–Zr–Sm alloy during homogenization annealing treatment
- Author
-
Fenglong Zhai, Liping Wang, Xin Gao, Yicheng Feng, Sicong Zhao, and Lei Wang
- Subjects
Al–Zn–Mg–Cu–Zr–Sm alloy ,pretreatment ,homogenization ,microstructure ,dendritic segregation ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
The effects of pretreatment and homogenization on the microstructure of a new Al-6.7Zn-2.6Mg-2.0Cu-0.1Zr-0.3Sm alloy were investigated. The results show that severe dendritic segregation is visible at the grain boundaries of the as-cast microstructure, which consists of the η (Mg (Zn, Cu, Al) _2 ), Al _10 Cu _7 Sm _2 and Fe-rich phases. Besides, some small η and needle-shaped θ (Al _2 Cu) phases are distributed inside of the grains. After pretreatment at 400 °C for 10 h, the η phase and θ phase in the grains are dissolved, and Al _3 Zr particles are precipitated inside of the grains by homogeneous nucleation. However, dendritic segregation still exists at the grain boundaries. After homogenization annealing, the η phase present at the grain boundaries completely dissolves, and only a small number of Al _10 Cu _7 Sm _2 and Fe-rich phases remain. The alloy microstructure becomes more uniform and the volume fraction of residual eutectic decreases to 0.70% after homogenization annealing. The optimal homogenization processing is determined as 400 °C/10 h + 470 °C/24 h, which is in perfect accordance with the results obtained via homogenizing kinetic analysis.
- Published
- 2020
- Full Text
- View/download PDF
36. Synthesis of a novel magnetic nano-zeolite and its application as an efficient heavy metal adsorbent
- Author
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Xiao Zhang, Ting Cheng, Chen Chen, Lei Wang, Qin Deng, Gang Chen, and Chenhao Ye
- Subjects
nano-zeolite ,magnetic ,magnetic sphere ,adsorbent ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
A novel magnetic nano-zeolite (MNZ@MS) is successfully synthesized, characterized and applied to adsorp heavy metals from solution. In the synthesis of MNZ@MS, the fly ash magnetic sphere (MS) and [C _18 H _37 (CH _3 ) _2 -N ^+ -(CH _2 ) _3 -N ^+ -(CH _3 ) _2 C _18 H _37 ] Cl _2 is used as carrier and directing agent, respectively. The characterization results of XRD, XRF, XPS and SEM demonstrate that the nano-scale (200–600 nm) Linde F(K) zeolite completely wraps the magnetic spherical fly ash particle, and the saturation magnetization value of MNZ@MS is around 17.7 emu g ^−1 . MNZ@MS exhibits a favorable and efficient adsorption performances on heavy metals, and the maximum adsorption capacity of Cu, Cd and Pb on MNZ@MS is 59.9 mg g ^−1 , 188 .6 mg g ^−1 and 909.1 mg g ^−1 , respectively. The higher pH value in solution is more conducive to the adsorption process of heavy metals on MNZ@MS. The adsorption is a fast process, well represented by the pseudo-second-order model. Concerning the equilibrium behavior, Langmuir isotherm model are more suitable for describing the adsorption. Furthermore, in competitive adsorption system, the adsorption process of Pb is the most difficult to be interfered, and the order of adsorption advantage is Pb>Cu>Cd. MNZ@MS may be applied as a low-cost and efficient magnetic adsorbent for wastewater treatment to remove heavy metals.
- Published
- 2020
- Full Text
- View/download PDF
37. Experimental research based on a C-band compact transit-time oscillator with a novel diode loading an embedded soft magnetic material and shielding structure
- Author
-
Yufang He, Juntao He, Junpu Ling, Lei Wang, and Lili Song
- Subjects
General Physics and Astronomy - Abstract
In order to reduce the external magnetic field and improve the conversion efficiency of high-power microwave generation devices with low external magnetic field, a novel diode with embedded soft magnetic and shielding structure is proposed. The soft magnetic material is designed to enhance the local magnetic field in the diode region. Besides, the diode applies a shielding structure which can reduce the radial electric field. From simulation research, it is found that the emission and transmission quality of the electron beam with low magnetic field is greatly improved when loading this diode. Through simulation research, it is verified that the diode can increase the conversion efficiency of the TTO from 30% to 36.7%. In our experimental study, under the conditions of a diode voltage of 540kV and a current of 10.5kA, the output microwave power is 1.51GW when loading the novel diode and the microwave frequency is 4.27GHz when an external guiding magnetic field of 0.3T is applied. The corresponding conversion efficiency is improved from 20.0% to 26.6%, which is 6.6% higher than the device loaded with a conventional diode. Our experiments have verified that this novel diode can effectively improve the conversion efficiency of high-power microwave sources operating with low magnetic field, and contribute to the miniaturization and compactness of high-power microwaves.
- Published
- 2022
38. Design and Workspace Analysis of Drilling Arm of Mining Anchor Drilling Robot
- Author
-
Jun, Zhang, primary, Jiguo, Wang, additional, Qianyi, Zhang, additional, Ning, Wang, additional, Chaofan, Wang, additional, and Lei, Wang, additional
- Published
- 2022
- Full Text
- View/download PDF
39. Effects of the magnetic field intensity on pole erosion of low-power Hall thrusters
- Author
-
Lei Wang, Yi Li, Zekai Wang, Zijian Liu, Hong Li, Liqiu Wei, and Yongjie Ding
- Subjects
Acoustics and Ultrasonics ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Magnetic pole erosion is a key life-limiting factor of low-power Hall thrusters. In this study, the effects of the magnetic field intensity near the inner magnetic pole on the pole erosion of a 100 W permanent-magnet Hall thruster at rated operating point were investigated using magnetic field intensity adjustment technology. The experimental results indicate that the erosion rate of the inner magnetic pole decreased considerably with a decrease in the magnetic field intensity near the inner magnetic pole, and the erosion rate can be decreased by over 37.5% when the magnetic field intensity decreased by 20%. Further analysis indicates that the decrease of magnetic field intensity reduces the number of electrons moving along the magnetic field lines to the magnetic pole, and increases the surface potential of the magnetic pole. The reduction of the potential difference between the channel outlet and the magnetic pole leads to a decrease in the current density and energy of the ions sputtered to the magnetic pole, which contributes greatly to the decrease in pole erosion rate. This study provides a reference for the protection of magnetic pole erosion.
- Published
- 2023
40. Cavitation erosion-corrosion behaviour of Fe-19Cr-15Mn-0.66 N high nitrogen austenitic stainless steel in sodium chloride solution
- Author
-
Liang Li, Yanxin Qiao, Huiling Zhou, Xin Li, Lei Huang, Lanlan Yang, and Lei Wang
- Subjects
Condensed Matter Physics ,Mathematical Physics ,Atomic and Molecular Physics, and Optics - Abstract
In this work, the cavitation erosion (CE)-corrosion behaviors of high nitrogen austenitic stainless steel (HNSS) Fe-19Cr-15Mn-0.66 N were investigated under both static and CE conditions in 0.5 mol l−1 NaCl solution. For the sample after 8 h CE, the cumulative mass loss increased by 15% in 0.5 mol l−1 NaCl solution compared to distilled water, indicating that the corrosive media promoted mass loss. The corrosion behavior of the samples under static and CE conditions was evaluated using electrochemical techniques. The results showed that compared with the samples under static conditions, the samples under CE had a higher corrosion rate, and the corrosion resistance of the samples gradually decreased with the prolongation of C E time.The open circuit potential and potentiodynamic polarization tests showed a higher corrosion rate under CE conditions. The electrochemical impedance spectroscopy results revealed a decrease in corrosion resistance with increasing CE time. The XPS results showed that CE has a significant effect on the composition of the passive film, promoting a notable increase in Cr2O3 and Fe2O3.
- Published
- 2023
41. Optimizing the morphology of all-polymer solar cells for enhanced photovoltaic performance and thermal stability
- Author
-
Kang An, Wenkai Zhong, Chunguang Zhu, Feng Peng, Lei Xu, Zhiwei Lin, Lei Wang, Cheng Zhou, Lei Ying, Ning Li, and Fei Huang
- Subjects
Materials Chemistry ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Abstract
Due to the complicated film formation kinetics, morphology control remains a major challenge for the development of efficient and stable all-polymer solar cells (all-PSCs). To overcome this obstacle, the sequential deposition method is used to fabricate the photoactive layers of all-PSCs comprising a polymer donor PTzBI-oF and a polymer acceptor PS1. The film morphology can be manipulated by incorporating amounts of a dibenzyl ether additive into the PS1 layer. Detailed morphology investigations by grazing incidence wide-angle X-ray scattering and a transmission electron microscope reveal that the combination merits of sequential deposition and DBE additive can render favorable crystalline properties as well as phase separation for PTzBI-oF:PS1 blends. Consequently, the optimized all-PSCs delivered an enhanced power conversion efficiency (PCE) of 15.21% along with improved carrier extraction and suppressed charge recombination. More importantly, the optimized all-PSCs remain over 90% of their initial PCEs under continuous thermal stress at 65 °C for over 500 h. This work validates that control over microstructure morphology via a sequential deposition process is a promising strategy for fabricating highly efficient and stable all-PSCs.
- Published
- 2023
42. Research on roughness prediction model of robotic sanding carbon fiber reinforced plastics
- Author
-
Guo Lei Wang, Cun Ning Lin, Su Ming Chen, Shan Yue, Hong Ming Xue, and Xiang Lin Gao
- Subjects
History ,Computer Science Applications ,Education - Abstract
By taking a pneumatic eccentric grinder and round sandpapers as research objects, the modeling method is proposed to accurately predict the surface roughness of robotic sanding carbon fiber reinforced plastic parts. A four-factor, the four-level orthogonal experiment was conducted which took four process parameters into account: pressing force, feeding speed, grit size, and supply air pressure. The multiple linear regression analysis method was then applied to create a roughness prediction model. Furthermore, accuracy validation results show that the model’s prediction error is within ±9%.
- Published
- 2023
43. Analysis and Research on Lightning Inrush Wave Overvoltage in EHV GIS Substation transformation project
- Author
-
Ruming Feng, Lei Zhao, Chuanqiang Che, Qiong Wang, null Tianyu, Jun Zhao, and Lei Wang
- Subjects
History ,Computer Science Applications ,Education - Abstract
When lightning intrudes into the over-voltage in the 500 kV substation, the lightning wave will be introduced into the substation along the line, which will seriously affect the insulation level of the equipment. In this paper, firstly, the working principle, characteristics, and lightning current simulation of the ZnO arrester are described. Then, the electromagnetic transient program (EMTP-ATP) used in a 500 kV GIS substation carried out the simulation research to the lightning over-voltage, specifically studied the lightning protection effect of metal oxide arrester, compared the lightning over-voltage under the different lightning locations and operation mode, and calculated the 500kV GIS Substation under the single in single out operation mode, 500kV. The influence of different positions of lightning arresters in GIS on the magnitude of lightning over-voltage and the lightning over-voltage on the substation equipment in GIS is also described.
- Published
- 2023
44. R&D of on-board metal-insulation REBCO superconducting magnet for electrodynamic suspension system
- Author
-
Shixian Liu, Lei Wang, Yong Chen, Luzhong Wang, Benzhe Zhou, Xinning Hu, Junsheng Cheng, and Qiuliang Wang
- Subjects
Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,Electrical and Electronic Engineering ,Condensed Matter Physics - Abstract
Metal-insulation (MI) REBCO high-temperature superconducting (HTS) magnet has the advantages of short charging delay, low contact losses, and self-protection abilities, which shows important application prospects in many fields. Recently, Institute of Electrical Engineering, Chinese Academy of Sciences developed a prototype on-board MI HTS coil used for electrodynamic suspension (EDS) system working with an acceleration of beyond 8 g. To design a reliable engineering on-board magnet, specific Ic angle dependence data of short sample under different fields were fully considered to estimate the operating margin and losses accurately of the on-board magnet. A semi-analytical method, combination of the dynamic circuit method and finite element method, was used to analyze the dynamic electromagnetic force distribution inside the on-board magnet under motion state, in which the effect of the propulsion coils and the figure-eight-shaped coils were taken into considerations. Finally, a full-size MI double pancake racetrack coil was fabricated and tested in a liquid nitrogen bath. The test results meet the design requirements and verify the feasibility of the design, which provides an important reference for the experiment of on-board EDS with high acceleration in the future.
- Published
- 2023
45. MHD effects of liquid metal flows through multiple electrically coupling ducts with U-turn bends in fusion blankets
- Author
-
Xinting Lv, Xiujie Zhang, and Lei Wang
- Subjects
Condensed Matter Physics ,Mathematical Physics ,Atomic and Molecular Physics, and Optics - Abstract
The investigation of liquid metal (LM) magnetohydrodynamic (MHD) flows through multiple electrically coupling ducts with U-turn bends is of crucial importance for accurately predicting the thermal-hydraulic performance of LM blankets in fusion reactors. Moreover, this duct configuration is often adopted in liquid blanket designs. Here, the combination effects of the MHD coupling, 3D MHD and inclined external magnetic fields on LM MHD flows through the multiple coupling ducts with different aspect ratios and wall conductance ratios are systematically investigated by numerical simulations. The results indicate that the MHD pressure gradient caused by MHD coupling effect decreases but the 3D MHD pressure gradient increases firstly and then decreases as the inclined angles of external magnetic fields increase. In addition, the results also indicate that the normalized pressure gradient can be reduced by increasing the wall conductance ratio ( C w ) through the increase of the wall thickness. Furthermore, an important finding is that the pressure gradients caused by the MHD coupling decrease with the increases of aspect ratios (b/a) of ducts, while the 3D MHD pressure gradient when b/a = 16 increases to an excessive large degree about 40 times of the pressure gradient in a single conductive duct. The related investigation results will provide a theoretical support for the liquid blanket designs in fusion reactors and deepen our understanding on the LM MHD effects.
- Published
- 2023
46. Transition mechanisms of breather molecules in the Hirota equation
- Author
-
Jun-Fei Zhao, Lei Wang, Shuo Zhou, and Yin-Chuan Zhao
- Subjects
Condensed Matter Physics ,Mathematical Physics ,Atomic and Molecular Physics, and Optics - Abstract
The transition dynamics of the breather molecules are investigated for the Hirota equation, which describes the propagation of ultrashort optical pulses in optical fibers. Based on the two-breather solution, the breather molecules and breather complexes are obtained. The half-transition mechanism of the breather molecules is unveiled and a series of the transformed wave molecules and the corresponding complexes are generated. The superposition mechanisms of breather molecules and transformed wave molecules are explained through the nonlinear superposition principle. It should be noted that the full transition of the breather molecules does not exist in the Hirota equation. The effects of the phase parameters on the transformed wave molecules are discussed. Besides, the collisions for breather molecules and transformed wave molecules are investigated. The distances between atoms in the molecules and the shapes of the transformed waves are changed after the collisions. By means of the phase shift analysis, the nature of shape-changed collisions is shed light on. Finally, the stability of the propagation of molecule waves under small perturbations is performed.
- Published
- 2023
47. Bivariate polynomial for time-dependent dielectric properties of ex-vivo porcine and human liver tissue at frequencies below 100 MHz
- Author
-
Lei Wang, Jianbo Li, Zhenyu Ji, Xiuzhen Dong, and Xuetao Shi
- Subjects
Applied Mathematics ,Instrumentation ,Engineering (miscellaneous) - Abstract
Time-dependent dielectric properties of ex vivo tissue are important for biological viability assessment, successful organ transplantation and finding the optimal substitute for the in vivo tissue. However, there are relatively few studies on the time dependence of dielectric properties and especially the mathematical models related to it. This study mathematically describes the time-dependent dielectric properties of excised liver tissues at frequencies below 100 MHz. A bivariate high-order polynomial was used to reflect the mathematical correlation of dielectric properties (relative permittivity ε and conductivity σ ) with frequency and ex vivo time under controlled temperature and humidity. Statistical analysis, cross validation and error analysis were used to assess the fitting performance and prediction ability of the bivariate high-order polynomial fitting model. The results showed that the dielectric properties of excised porcine liver tissues and human liver tissues could be well fitted and predicted by the bivariate high-order polynomial fitting model at frequencies below 100 MHz. Encouragingly, the dielectric properties can be calculated at a given frequency and ex vivo time at controlled temperature and humidity. This presents a new way of obtaining accurate dielectric properties of ex vivo biological tissues in a specific outer environment. It is also possible to extrapolate back the ex vivo time after excision from the body using the dielectric properties.
- Published
- 2023
48. High Voltage Cable Fault Location Technology Based on Traveling Wave
- Author
-
Lei Wang, Zhe Wang, Lin Niu, Lijuan Guo, Ying Pei, Hongbo Li, Zhiguang Ma, Zhenhai Zhang, and Lina Chen
- Subjects
History ,Computer Science Applications ,Education - Abstract
High voltage cable line is an important part of power grid; its stable operation is of great significance to urban power system. This paper proposed a high voltage cable insulation monitoring system using traveling wave. The travelling wave data are collected by high precision satellite timing signal and an on-line fault location system for high voltage cable is designed.
- Published
- 2023
49. Restoration Strategy of Distributed Power Supply in Distribution Network Based on Genetic Algorithm
- Author
-
Lei Wang, Lin Niu, Zhiguang Ma, Hongbo Li, Li Wang, Tao Wang, Zhenhai Zhang, and Lina Chen
- Subjects
History ,Computer Science Applications ,Education - Abstract
Nowadays, the penetration of distributed power in distribution network increases the complexity of power supply restoration. For the recovery of the traditional method in the field of distributed power supply system restore deficiency, the improving measures are put forward based on the many kinds of operation constraints, proposes the mathematical model of multi-objective optimization. In addition to conventional constraints in the mathematical model, will also be the network structure and branch power flow constraints into consideration. In view of the model, using the rough set theory, a multi-objective optimization problem into a single objective problem, and on this basis, considering the characteristic of radial network and the characteristics of the different load, by using genetic algorithm to reconstruct network, finally through the corresponding example recovery strategy is feasible and efficient.
- Published
- 2023
50. A Novel Compound Fault Recovery and Control Techniques in Electric Distribution Network
- Author
-
Wandeng Mao, Shaoguang Yuan, Yangyang Tian, Zhimin Guo, Hao Liu, and Lei Wang
- Subjects
History ,Computer Science Applications ,Education - Abstract
When the distribution network is affected by natural disasters or deliberately damaged, failure may cause a large area power outage, which will seriously impact the national economy, social stability, people’s normal life, etc. This paper proposes a composite fault recovery method for the distribution networks based on the maximum-flow method. A service flow model, an information link recovery model, and a multi-objective optimization model are established to effectively solve communication power’s composite fault recovery problem in the distribution network.
- Published
- 2023
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