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基于无人机多光谱数据和氮素空间分异的玉米冠层氮浓度估算

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作物学报 2025年第1期51卷 189-206页

作者：郝琪陈天陆王富贵王振白岚方王永强王志刚内蒙古农业大学农学院内蒙古呼和浩特010010

作物冠层氮素营养的遥感诊断对指导作物精准施氮,提高作物氮效率和产量具有重要意义。本研究针对玉米冠层纵深大影响无人机估算氮浓度精度的问题,基于2022年和2023年不同氮肥运筹处理下田间无人机多光谱数据和氮浓度实测数据,分析玉米... 详细信息

作物冠层氮素营养的遥感诊断对指导作物精准施氮,提高作物氮效率和产量具有重要意义。本研究针对玉米冠层纵深大影响无人机估算氮浓度精度的问题,基于2022年和2023年不同氮肥运筹处理下田间无人机多光谱数据和氮浓度实测数据,分析玉米冠层氮浓度空间分布特征,并利用随机森林算法确定估算冠层氮浓度的有效叶层。进一步结合随机森林算法和多光谱植被指数构建有效叶层氮浓度估算模型,最终将有效叶层氮浓度转换到冠层尺度实现冠层氮浓度的估算。结果表明:(1)九叶展期和大喇叭口期玉米冠层氮浓度表现为上层叶片>中层叶片>下层叶片,吐丝期和乳熟期表现为中层叶片>上层叶片>下层叶片。(2)各时期估算冠层氮浓度的有效叶层分别为下层、中层、中层和中层。与支持向量回归模型相比,随机森林回归估算冠层氮浓度的精度较高。(3)结合随机森林算法,基于有效叶层氮浓度估算冠层氮浓度的平均RMSE、NRMSE和MAE分别为0.10%、4.41%和0.07%,而直接基于植被指数估算冠层氮浓度的平均RMSE、NRMSE和MAE分别为0.19%、9.00%和0.15%。综上,玉米冠层氮浓度存在空间分异特征,估算冠层氮浓度时考虑基于随机森林和植被指数估算的有效叶层氮浓度能明显提高冠层氮浓度的估算精度。本研究确定的考虑空间分异的冠层氮浓度估算框架可为玉米氮素营养实时诊断提供理论支撑。

关键词：玉米冠层氮浓度氮素空间分异多光谱数据机器学习

p-adic Modular Symbols and ∧-adic Modular Forms

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Acta Mathematica Sinica,English Series 2006年第2期22卷 331-338页

作者： fu Zheng wang LMAM&Department of Mathematics.Peking University

A construction of A-adic modular forms from p-adic modular symbols is described. It shows that each A linear map satisfying some certain conditions from the module of p-adic modular symbols to A corresponds to a A-adi... 详细信息

关键词： Modular symbol Manin symbol A-adic modular form

The Affine Complete Hypersurfaces of Constant Gauss-Kronecker Curvature

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Acta Mathematica Sinica,English Series 2009年第8期25卷 1353-1362页

作者： Bao fu wang Department of Mathematics Sichuan University Chengdu 610064 P. R. China

Given a bounded convex domain Ω with C∞ boundary and a function ψ∈C∞（δΩ）, Li-Simon-Chen can construct an Euclidean complete and W-complete convex hypersurface M with constant affine Gauss-Kronecker curvature,... 详细信息

关键词： Gauss-Kronecker curvature affine completeness

Preparation of Al_(72)Ni_8Ti_8Zr_6Nb_3Y_3 amorphous powders and bulk materials

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International Journal of Minerals,Metallurgy and Materials 2016年第10期23卷 1187-1195页

作者： Yu Wu Xin-fu wang fu-sheng Han Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Sciences

Amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were successfully fabricated by mechanical alloying. The microstructure, glass-forming ability, and crystallization behavior of amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were investigated by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, and differential scanning calorimetry（DSC）. The isothermal crystallization kinetics was analyzed by the Johnson-Mehl-Avrami equation. In the results, the supercooled liquid region of the amorphous alloy is as high as 81 K, as determined by-non-isothermal DSC curves. The activation energy for crystallization is as high as 312.6 kJ ·mol1 obtained by Kissinger and Ozawa analyses. The values of Avrami exponent（n） imply that the crystallization is dominated by interface-controlled three-dimensional growth in the early stage and the end stage and by diffusion-controlled two- or three-dimensional growth in the middle stage. In addition, the amorphous Al_（72）Ni_8Ti_8Zr_6Nb_3Y_3 powders were sintered under 2 GPa at temperatures of 673 K and 723 K. The results show that the Vickers hardness of the compacted powders is as high as Hv 1215.

关键词： amorphous alloys mechanical alloying thermal stability pressing Vickers hardness

Electrochemical performance of aluminum niobium oxide as anode for lithium-ion batteries

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Rare Metals 2016年第3期35卷 256-261页

作者： Qi wang fu-Chi wang Xing-wang Cheng School of Material Science and Engineering Beijing Institute of Technology

AlNbO_4,as lithium-ion batteries（LIBs） anode,has a high theoretical capacity of 291.5 m Ah g^-***,AlNbO_4 anode materials were synthesized through a simple solid-state *** structure,morphology and electrochemical performances of AlNbO4 anode were systematically *** results show that AlNbO4 is monoclinic with C2/m space *** scanning electron microscopy（SEM） and transmission electron microscopy（TEM） characterizations reveal the AlNbO_4 particles with the size of 100 nm^–2 *** a lithium-ion batteries anode,AlNbO4 delivers a high reversible capacity and good rate *** discharge capacity is as high as 151.0 m Ah g^-1 after 50 charge and discharge cycles at 0.1 C corresponding to capacity retention of 90.7 %.When the current density increases to 5.0C,AlNbO4 anode displays reversible discharge capacity of 73.6 m Ah g^-1 at the50 th cycle.

关键词： Aluminum niobium oxide Electrochemical performance Anode Lithium-ion batteries

Thermal shock behavior of ZrB2-SiC ceramics with different quenching media

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Frontiers of Materials Science 2013年第2期7卷 184-189页

作者： Chang-An wang Ming-fu wang State Key Lab of New Ceramics and Fine Processing School of Materials Science and Engineering Tsinghua University Beijing 100084 China Science and Technology on Scramjet Laboratory Beijing 100074 China

The thermal shock behavior of ZrB2-SiC ceramics was studied with water, air and methyl silicone oil as quenching media, respectively. The temperature of all coolants was room temperature （25℃） and the residual strength of the ceramics after quenching was tested. The strength of the ceramics after water quenching had an obvious drop when the temperature difference, AT, was about 275℃, while the residual strength of the specimens quenched by air and silicone oil only varied a little and even increased slightly when the temperature difference was higher than 800℃. The different thermal conductive coefficient of the coolants and surface heat transfer coefficient resulted in the differences in the thermal shock behavior. The formation of oxidation layer was beneficial for improving the residual strength of the ceramics after quenching.

关键词： ultra-high temperature ceramic (UHTC) zirconium diboride (ZrB2) siliconcarbide (SIC) thermal shock resistance mechanical property

A continuum damage model for piezoelectric materials

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Acta Mechanica Sinica 2008年第2期24卷 171-179页

作者： Yiming fu X. wang College of Mechanics and Aerospace Hunan University Changsha 410082 China

In this paper, a constitutive model is proposed for piezoelectric material solids containing distributed cracks. The model is formulated in a framework of continuum damage mechanics using second rank tensors as internal variables. The Helrnhotlz free energy of piezoelectric mate- rials with damage is then expressed as a polynomial including the transformed strains, the electric field vector and the tensorial damage variables by using the integrity bases restricted by the initial orthotropic symmetry of the material. By using the Talreja＇s tensor valued internal state damage variables as well as the Helrnhotlz free energy of the piezoelectric material, the constitutive relations of piezoelectric materials with damage are derived. The model is applied to a special case of piezoelectric plate with transverse matrix cracks. With the Kirchhoff hypothesis of plate, the free vibration equations of the piezoelectric rectangular plate considering damage is established. By using Galerkin method, the equations are solved. Numerical results show the effect of the damage on the free vibration of the piezoelectric plate under the close-circuit condition, and the present results are compared with those of the three-dimensional theory.

关键词： Tensor valued internal state variables Continuum damage mechanics Damage constitutiverelations Piezoelectric plate

Numerical investigation of filling transients in small-scale pipelines with submerged outlet

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Journal of Hydrodynamics 2019年第1期31卷 145-151页

作者： Ling wang fu-jun wang Jing Huang College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System China Agricultural UniversityBeijing 100083China Zhuzhou Southern Valve Co. Ltd Zhuzhou 412007China

An elastic model that combines the dead-end and the orifice at the downstream end is proposed in order to study the hydraulic transients during the rapid filling in small-scale pipelines with submerged *** this model,the unsteady water flow is solved by the method of characteristics,the water-air interface is traced by a shock fitting method,and the air phase is controlled by the polytropic *** model is validated by a filling test in a pipeline with *** the proposed model is applied to the filling transient analysis in a small-scale pipeline with submerged ***,the effects of the submerged depth of the downstream reservoir on the filling transients are *** model provides a reasonable approximation of the submerged outlet boundary condition in small-scale pipelines.

关键词： Small-scale pipelines rapid filling submerged outlet elastic model hydraulic transients

Polyethylene glycol derived carbon quantum dots nanofluids:An excellent lubricant for diamond-like carbon film/bearing steel contact

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Friction 2022年第9期10卷 1393-1404页

作者： fu wang Lunlin SHANG Guangan ZHANG Zhaofeng wang State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Polyethylene glycol derived carbon quantum dots nanofluids were synthesized via a slow thermal oxidation *** size of carbon quantum dots was ca.2 nm and had a decreasing trend with the increase of oxidation *** used as lubricant in a diamond-like carbon film/bearing steel interface,the nanofluids achieved an ultra-low friction coefficient(μ≈0.02),much lower than that of original polyethylene glycol(μ=0.12).The worn surface analyses revealed that the nanofluids could effectively inhibit the tribo-oxidation of steel counterpart that occurred under original polyethylene glycol lubrication,and hence reduced the abrasion component of ***,the poly-hydroxyl carbon dots and oxidized polyethylene glycol species in nanofluids induced a hydroxyl-rich sliding interface via their tribochemical reactions with friction surfaces,which promoted the adsorption of polyethylene glycol molecules on sliding *** with the mild corrosion wear of steel counterface,this shifted the boundary lubrication to a mixed/film lubrication regime,thereby achieving an ultra-low friction *** above results suggest that the polyethylene glycol derived carbon quantum dots nanofluids should be a quite excellent candidate lubricant for solid–liquid synergy lubrication based on diamond-like carbon films.

关键词： polyethylene glycol diamond-like carbon films ultra-low friction synergy lubrication