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Assessment of ecological quality in Northwest China(2000-2020)using the Google Earth Engine platform:Climate factors and land use/land cover contribute to ecological quality

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Journal of Arid Land 2022年第11期14卷 1196-1211页

作者： WANG Jinjie DING Jianli ge xiangyu QIN Shaofeng ZHANG Zhe College of geography and Remote Sensing Science Xinjiang UniversityUrumqi 800046China Xinjiang Key Laboratory of Oasis Ecology Xinjiang UniversityUrumqi 830046China Key Laboratory of Smart City and Environment Modelling of Higher Education Institute Xinjiang UniversityUrumqi 830046China

The ecological quality of inland areas is an important aspect of the United Nations Sustainable Development Goals(UN SDGs).The ecological environment of Northwest China is vulnerable to changes in climate and land use/land cover,and the changes in ecological quality in this arid region over the last two decades are not well understood.This makes it more difficult to advance the UN SDGs and develop appropriate measures at the regional level.In this study,we used the Moderate Resolution Imaging Spectroradiometer(MODIS)products to generate remote sensing ecological index(RSEI)on the Google Earth Engine(geE)platform to examine the relationship between ecological quality and environment in Xinjiang during the last two decades(from 2000 to 2020).We analyzed a 21-year time series of the trends and spatial characteristics of ecological quality.We further assessed the importance of different environmental factors affecting ecological quality through the random forest algorithm using data from statistical yearbooks and land use products.Our results show that the RSEI constructed using the geE platform can accurately reflect the ecological quality information in Xinjiang because the contribution of the first principal component was higher than 90.00%.The ecological quality in Xinjiang has increased significantly over the last two decades,with the northern part of this region having a better ecological quality than the southern part.The areas with slightly improved ecological quality accounted for 31.26%of the total land area of Xinjiang,whereas only 3.55%of the land area was classified as having a slightly worsen(3.16%)or worsen(0.39%)ecological quality.The vast majority of the deterioration in ecological quality mainly occurred in the barren areas Temperature,precipitation,closed shrublands,grasslands and savannas were the top five environmental factors affecting the changes in RSEI.Environmental factors were allocated different weights for different RSEI categories.In general,the recovery of ecological quality in Xinjiang

关键词： ecological quality land use/land cover spatiotemporal change remote sensing ecological index(RSEI) Google Earth Engine Xinjiang

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Asymmetric Thermally Activated Delayed Fluorescence Materials Rendering High-performance OLEDs Through both Thermal Evaporation and Solution-processing

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Chemical Research in Chinese Universities 2022年第6期38卷 1526-1531页

作者： GAO Shiyuan CHEN Xiaojie ge xiangyu CHEN Zhu ZHAO Juan CHI Zhenguo State Key Laboratory of OEMT School of Materials Science and EngineeringSun Yat-sen UniversityGuangzhou510275P.R.China State Key Laboratory of OEMT School of ChemistrySun Yat-sen UniversityGuangzhou510275P.R.China

Exploring high-efficiency thermally activated delayed fluorescence(TADF)materials is of great importance regarding to organic light-emitting diode(OLED).Herein,we present a design strategy for developing asymmetric TADF materials based on a diphenyl sulfone-phenoxazine structure,resulting in efficient TADF emitters(CzPXZ and t-CzPXZ)with aggregation-induced emission properties,while t-CzPXZ is modified with tert-butyl groups.The two compounds exhibit high solid-state luminescence,efficient TADF,and significantly impressive device performances by both thermal evaporation and solution processing.For an instance,CzPXZ and t-CzPXZ enable the thermally-evaporated OLEDs with high external quantum efficiencies(EQEs)of over 20%.Meanwhile,t-CzPXZ allows the solution-processed device with a high EQE of 16.3%with low-efficiency roll-off,attributing to the enhanced molecular solubility and suppressed excitons quenching through tert-butyl modification on t-CzPXZ.The results reveal that the proposed asymmetric structure is a promising approach for developing high-efficiency TADF materials and OLEDs.

关键词： Thermally activated delayed fluorescence Asymmetric strategy Organic light-emitting diode Thermal evaporation Solution processing

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Estimation of soil organic matter in the Ogan-Kuqa River Oasis, Northwest China, based on visible and near-infrared spectroscopy and machine learning

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Journal of Arid Land 2023年第2期15卷 191-204页

作者： ZHOU Qian DING Jianli ge xiangyu LI Ke ZHANG Zipeng GU Yongsheng College of geography and Remote Sensing Science Xinjiang UniversityUrumqi 830046China Xinjiang Key Laboratory of Oasis Ecology Xinjiang UniversityUrumqi 830046China Key Laboratory of Smart City and Environment Modelling of Higher Education Institute Xinjiang UniversityUrumqi 830046China

Visible and near-infrared(vis-NIR)spectroscopy technique allows for fast and efficient determination of soil organic matter(SOM).However,a prior requirement for the vis-NIR spectroscopy technique to predict SOM is the effective removal of redundant information.Therefore,this study aims to select three wavelength selection strategies for obtaining the spectral response characteristics of SOM.The SOM content and spectral information of 110 soil samples from the Ogan-Kuqa River Oasis were measured under laboratory conditions in July 2017.Pearson correlation analysis was introduced to preselect spectral wavelengths from the preprocessed spectra that passed the 0.01 level significance test.The successive projection algorithm(SPA),competitive adaptive reweighted sampling(CARS),and Boruta algorithm were used to detect the optimal variables from the preselected wavelengths.Finally,partial least squares regression(PLSR)and random forest(RF)models combined with the optimal wavelengths were applied to develop a quantitative estimation model of the SOM content.The results demonstrate that the optimal variables selected were mainly located near the range of spectral absorption features(i.e.,1400.0,1900.0,and 2200.0 nm),and the CARS and Boruta algorithm also selected a few visible wavelengths located in the range of 480.0–510.0 nm.Both models can achieve a more satisfactory prediction of the SOM content,and the RF model had better accuracy than the PLSR model.The SOM content prediction model established by Boruta algorithm combined with the RF model performed best with 23 variables and the model achieved the coefficient of determination(R2)of 0.78 and the residual prediction deviation(RPD)of 2.38.The Boruta algorithm effectively removed redundant information and optimized the optimal wavelengths to improve the prediction accuracy of the estimated SOM content.Therefore,combining vis-NIR spectroscopy with machine learning to estimate SOM content is an important method to improve the accuracy of SOM prediction in arid land.

关键词： soil organic matter content vis-NIR spectroscopy random forest Boruta algorithm machine learning

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基于投影相关的超高维生存数据的特征筛选新方法

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中国科学：数学 2024年第2期54卷 211-230页

作者：潘莹丽葛翔宇周艳丽湖北大学数学与统计学学院应用数学湖北省重点实验室武汉430062 中南财经政法大学统计与数学学院武汉430073 中南财经政法大学金融学院武汉430073

本文对超高维右删失生存数据的特征筛选提出一种基于投影相关且具有确定独立筛选(projection correlation sure independent screening, PC-SIS)的新方法.一方面, PC-SIS方法并不需要指定任何模型,也不需要对生存函数进行非参数估计,且... 详细信息

本文对超高维右删失生存数据的特征筛选提出一种基于投影相关且具有确定独立筛选(projection correlation sure independent screening, PC-SIS)的新方法.一方面, PC-SIS方法并不需要指定任何模型,也不需要对生存函数进行非参数估计,且对矩条件和次指数条件不敏感,适用于对异常值或厚尾数据的分析.另一方面,在一定的正则化条件下, PC-SIS方法具有确定筛选性和秩相合性.模拟和实证研究表明, PC-SIS方法能在保留所有重要特征的前提下剔除与响应变量相关程度较弱的特征,以实现降维的目的.

关键词：投影相关秩相合性确定筛选生存数据超高维

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有机钼和多元醇酯对轮毂轴承聚脲润滑脂摩擦性能的影响

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石油炼制与化工 2024年第2期55卷 193-199页

作者：胡强胜石秋雨葛翔宇赵自强北京理工大学机械与车辆学院北京100081 国网智能电网研究院有限公司

为了进一步提升电动汽车用轮毂轴承聚脲润滑脂的摩擦学性能,利用多功能摩擦磨损试验机和自主设计搭建的滚动轴承摩擦测量试验台,分别在纯滑动工况和实际轴承运行工况下考察了有机钼855和多元醇酯3970对商用聚脲润滑脂摩擦学性能的影响,... 详细信息

为了进一步提升电动汽车用轮毂轴承聚脲润滑脂的摩擦学性能,利用多功能摩擦磨损试验机和自主设计搭建的滚动轴承摩擦测量试验台,分别在纯滑动工况和实际轴承运行工况下考察了有机钼855和多元醇酯3970对商用聚脲润滑脂摩擦学性能的影响,并利用显微镜、扫描电子显微镜和三维白光干涉仪表征了试验钢球磨损表面的形貌和表面粗糙度。结果表明:单独添加有机钼855并不能明显改善商用聚脲润滑脂的减摩抗磨性能;而单独添加多元醇酯3970以及二者复配使用,均可明显提升聚脲润滑脂的承载能力、减摩性能和抗磨性能;特别是二者复配使用时聚脲润滑脂的摩擦学性能显著改善,在多种轴承实际运行工况下,添加(855+3970)的聚脲润滑脂样品的摩擦因数降幅均超过20%,最大降幅达38.8%。

关键词：有机钼多元醇酯轮毂轴承润滑脂摩擦磨损

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滚动轴承润滑膜厚及保持架转速的超声测量

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轴承 2024年第2期 46-54页

作者：薛梓涵赵自强葛翔宇王文中北京理工大学机械与车辆学院北京100081

滚动轴承的运行稳定性与钢球和内外圈之间的润滑状态密切相关,膜厚则是表征轴承润滑性能的重要参数。基于超声弹簧模型建立了膜厚测量模型并搭建了试验台,通过试验台模拟球轴承的运行状态并测量钢球周围以及沿滚动方向的膜厚分布,分析... 详细信息

滚动轴承的运行稳定性与钢球和内外圈之间的润滑状态密切相关,膜厚则是表征轴承润滑性能的重要参数。基于超声弹簧模型建立了膜厚测量模型并搭建了试验台,通过试验台模拟球轴承的运行状态并测量钢球周围以及沿滚动方向的膜厚分布,分析了转速对最小膜厚的影响;同时,根据连续2个钢球通过探头正下方的时间间隔计算保持架转速,分析得到了不同重复频率所能测量的保持架转速范围。试验结果表明,膜厚的实际测量值与理论值吻合较好,保持架转速的实际测量值与纯滚动条件下的理论转速一致性良好,可用于轴承打滑状态的评估。

关键词：滚动轴承润滑超声最小油膜厚度保持架转速脉冲重复频率

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Effects of pore size on the lubrication properties of porous polyimide retainer material

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Friction 2023年第8期11卷 1419-1429页

作者： Wenbin CHEN Wenzhong WANG Pengzhe ZHU xiangyu ge School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China

An oil-impregnated porous polyimide(PI)retainer is used in space rolling bearings to improve the lubrication performance,which depends on the release of lubricant from the pores,and therefore is closely related to the pore size.To study the effect of pore size,in this work,PI materials with different pore sizes were prepared by preheating the retainer tube billet during the limit pressing process,and then the friction tests were conducted with the ball-on-ring mode.The results show that the applied load deforms the pores,allowing the lubricant to be squeezed out from the pore;the centrifugal effect induced by rotation also makes the lubricant migrate out of the pore.Therefore,for the same pore sizes,the friction coefficients decrease with the increasing loads and rotation speeds.In addition,it was found that there exists an optimal pore size for the best lubrication properties of porous PI material.Furthermore,the optimal pore size should be larger for lubricants with high viscosity.The microscopic mechanism for lubricant outflow from pores is clarified by molecular dynamic simulations.The insights gained in this study can guide the preparation of oil-impregnated porous retainers under different working conditions.

关键词： porous polyimide(PI)material oil-impregnated material lubrication property pore size

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Graphene superlubricity:A review

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摩擦:英文版 2023年第11期11卷 1953-1973页

作者： xiangyu ge Zhiyuan CHAI Qiuyu SHI Yanfei LIU Wenzhong WANG School of Mechanical Engineering Beijing Institute of TechnologyBeijing 100081China State Grid Smart Grid Research Institute Co. Ltd.Beijing 102209China

Superlubricity has drawn substantial attention worldwide while the energy crisis is challenging human beings.Hence,numerous endeavors are bestowed to design materials for superlubricity achievement at multiple scales.Developments in graphene-family materials,such as graphene,graphene oxide,and graphene quantum dots,initiated an epoch for atomically thin solid lubricants.Nevertheless,superlubricity achieved with graphene-family materials still needs fundamental understanding for being applied in engineering in the future.In this review,the fundamental mechanisms for superlubricity that are achieved with graphene-family materials are outlined in detail,and the problems concerning graphene superlubricity and future progress in superlubricity are proposed.This review concludes the fundamental mechanisms for graphene superlubricity and offers guidance for utilizing graphene-family materials in superlubricity systems.

关键词： superlubricity graphene graphene-family materials two-dimensional(2D)materials friction

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基于多种降水数据产品的黄河源区径流模拟研究

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高原气象 2024年第3期43卷 570-582页

作者：李晓玥文军谢琰陈亚玲陈怡璇葛翔宇成都信息工程大学大气科学学院/高原大气与环境四川省重点实验室四川成都610225 宜宾学院四川宜宾644000

黄河源区位于青藏高原的东北部,该流域气象站点分布稀疏,水文过程研究存在很大的局限性,研究多种降水数据产品在流域的适用性对水文模型研究具有重要的推动作用。本文以黄河源区作为研究区域,基于中国气象同化驱动数据集(China Meteorol... 详细信息

黄河源区位于青藏高原的东北部,该流域气象站点分布稀疏,水文过程研究存在很大的局限性,研究多种降水数据产品在流域的适用性对水文模型研究具有重要的推动作用。本文以黄河源区作为研究区域,基于中国气象同化驱动数据集(China Meteorological Assimilation Datasets for SWAT model Version1.1,CMADS V1.1)、热带降雨测量卫星(Tropical Rainfall Measurement Mission,TRMM)降水数据集(3B42 Version7)和气象站观测降水数据分别驱动土壤水文评估工具分布式水文模型(Soil and Water Assessment Tool,SWAT),同时利用SWAT-CUP(SWAT Calibration and Uncertainty Program)和SUFI-2(Sequential Uncertainty Fitting2)算法对27个敏感性参数进行率定,模拟黄河源区多年月平均径流量的变化规律,并将模拟结果与观测值进行对比分析,评估了CMADS和TRMM 3B42降水数据产品在该流域的精度以及SWAT模型在黄河源区的适用性。结果表明:(1)由3种降水数据获得的降水空间分布为由西向东递增的趋势,TRMM 3B42与实测降水在年和月变化上一致性好于CMADS数据集。(2)参数敏感性分析结果表明:SCS(Soil Conservation Service)径流曲线数、地下水滞后系数、土壤蒸发补偿系数对径流模拟的敏感性程度较强。(3)利用CMADS和TRMM 3B42降水数据集模拟的径流结果均优于实测降水数据,流域内3个水文站在率定期的相关系数R分别是0.93,0.92和0.88;TRMM 3B42模拟结果次之,率定期和验证期的相关系数R均在0.80以上,纳什系数(Nash-Sutcliffe efficiency coefficient,NSE)在0.50以上。本研究证明了CMADS数据集和SWAT模型在地貌类型复杂、气候变化敏感的高海拔地区的径流模拟方面具有较好的适用性,为气象站点稀缺的地区提供了建立水文模型的替换方案。

关键词：黄河源区 SWAT水文模型径流模拟再分析降水数据

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Energy consumption optimization for edge computing-supported cellular networks based on optimal transport theory

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Science China(Information Sciences) 2024年第2期67卷 201-218页

作者： xiangyu LV Xiaohu ge Yi ZHONG Qiang LI Yong XIAO School of Electronic Information and Communications Huazhong University of Science and Technology

With advancements in mobile communication technologies, there have been multiple user device(UD) connections to cellular networks. Because of changes in the spatial distribution of UDs and application requirements, the traditional offloading mechanism based on the nearest distance will result in heavy loads for some base stations(BSs). Because there is a high-order relationship between the energy consumption of the BS processing tasks and the number of computing tasks, the traditional offloading mechanism will result in high energy consumption, and UD’s offloading decision must be dynamically adjusted. The offloading decision of UDs is optimized based on detailed information about various parameters associated with a network from the standpoint of distribution. This information includes details regarding the spatial distribution of UDs,application requirements, and the offloading period of computing tasks. Based on optimal transport theory,an energy consumption optimization algorithm is suggested to lower the total amount of energy consumed by the offloading process of UDs’ computing tasks by reasonably planning the offloading BSs of the UDs in the networks. The simulation results show that the proposed offloading mechanism based on energy consumption optimization reduces the total energy consumption of the offloading process by 28.09% when compared to the traditional offloading mechanism, and the traffic managed by each BS is balanced.

关键词： optimal transport theory edge computing energy consumption reduction dynamic voltage frequency scaling

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