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Corn Yield Forecasting in Northeast China Using Remotely Sensed Spectral Indices and Crop Phenology Metrics

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Journal of Integrative Agriculture 2014年第7期13卷 1538-1545页

作者： WANG meng TAO Fu-lu SHI Wen-jiao Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences University of Chinese Academy of Sciences

Early crop yield forecasting is important for food safety as well as large-scale food related planning. The phenology-adjusted spectral indices derived from Moderate Resolution Imaging Spectroradiometer （MODIS） data were used to develop liner regression models with the county-level corn yield data in Northeast China. We also compared the different spectral indices in predicting yield. The results showed that, using Enhanced Vegetation Index （EVI）, Normalized Difference Water Index （NDWI） and Land Surface Water Index （LSWI）, the best time to predict corn yields was 55-60 days after green-up date. LSWI showed the strongest correlation （R2=0.568）, followed by EVI （R2=0.497） and NDWI （R2=0.495）. The peak correlation between Wide Dynamic Range Vegetation Index （WDRVI） and yield was detected 85 days after green-up date （RZ=0.506）. The correlation was generally low for Normalized Difference Vegetation Index （NDVI）（R2=0.385） and no obvious peak correlation existed for NDVI. The coefficients of determination of the different spectral indices varied from year to year, which were greater in 2001 and 2004 than in other years. Leave-one-year-out approach was used to test the performance of the model. Normalized root mean square error （NRMSE） ranged from 7.3 to 16.9% for different spectral indices. Overall, our results showed that crop phenology-tuned spectral indices were feasible and helpful for regional corn yield forecasting.

关键词： remote sensing yield corn MODIS phenology

Hydrogen and helium shell burning during white dwarf accretion

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Research in Astronomy and Astrophysics 2018年第5期18卷 111-118页

作者： Xiao Cui Xiang-Cun meng Zhan-Wen Han Yunnan Observatories Chinese Academy of Sciences Kunming 650216 China Key Laboratory for the Structure and Evolution of Celestial Objects Chinese Academy of Sciences Kunming 650216 China University of Chinese Academy of Sciences Beijing 100049 China

Type Ia supernovae（SNe Ia） are believed to be thermonuclear explosions of carbon oxygen（CO） white dwarfs（WDs） with masses close to the Chandrasekhar mass limit. How a CO WD accretes matter and grows in mass to this limit is not well understood, hindering our understanding of SN Ia explosions and the reliability of using SNe Ia as a cosmological distance indicator. In this work, we employed the stellar evolution code MESA to simulate the accretion process of hydrogen-rich material onto a 1.0 M⊙CO WD at a high rate（over the Eddington limit） of 4.3 × 10^-7 M⊙yr^-1. The simulation demonstrates the characteristics of the double shell burning on top of the WD, with a hydrogen shell burning on top of a helium burning shell. The results show that helium shell burning is not steady（*** flashes）. Flashes from the helium shell are weaker than those in the case of accretion of helium-rich material onto a CO WD. The carbon to oxygen mass ratio resulting from the helium shell burning is higher than what was previously thought. Interestingly, the CO WD growing due to accretion has an outer part containing a small fraction of helium in addition to carbon and oxygen. The flashes become weaker and weaker as the accretion continues.

关键词： stars evolution - supernovae general - white dwarfs

Spatial and temporal effects on seed dispersal and seed predation of Musa acuminata in southern Yunnan, China

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Integrative Zoology 2012年第1期7卷 30-40页

作者： Lingzeng meng xiuxia GAO Jin CHEN Konrad MARTIN Xishuangbanna Tropical Botanical Garden Chinese Academy of SciencesMenglunChina University of Hohenheim Institute of Plant Production and Agroecology in the Tropics and SubtropicsStuttgartGermany

Wild bananas are abundant in tropical areas and many ecologists have observed that the succession process is quicker following increased *** study was conducted to analyze animal–seed interactions and their effects on the seed fate of a wild banana species(Musa acuminata)in tropical southern Yunnan(China)through experiments considering spatial(site and habitat)and temporal(seasons)*** largest proportion of fruits(81%)was removed by frugivorous seed dispersers,especially by bats at *** 13%of the fruits were removed by climbing seed predators(different species of rats).In the exclosure treatment,rodents accounted for a significantly higher total artificially exposed seed removal number than ants,but with spatial and temporal *** highest seed predation rate by rodents(70%)was found in forest with wild banana stands,corresponding with the highest rodent diversity(species numbers and abundance)among the habitat *** contrast,the seed removal number by ants(57%)was highest in the open land habitats,but there was no close correlation with ant *** removal numbers by ants were significantly higher in the dry compared to the rainy season,but rodent activity showed no differences between *** overall results suggest that the largest proportion of seeds produced by wild banana are primarily dispersed by *** seed dispersal by bats at nighttime is essential for wild banana seeds to escape seed predation.

关键词： bats Musa acuminata seed dispersal seed predation tropical forest

Simulation on Helicopter Scissors Tail-Rotor Noise Based on N-S Equations and F1A Formulas

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Transactions of Nanjing University of Aeronautics and Astronautics 2017年第6期34卷 710-719页

作者： meng Xiaowei Xu Guohua Shi Yongjie Wang Liangquan National Key Laboratory of Rotorcraft Aeromechanics Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China

Aiming at the noise of helicopter scissors tail-rotor,an advanced numerical method is established by combining computational fluid dynamics(CFD)model with Farassat 1 A(F1 A)*** this method,Navier-tokes(N-S)equations are used as governing equations,and the flow field is solved at quasi-steady and unsteady states in hover and forward fight,respectively,based on two different types of embedded grid systems.A simple and effective solution approach is provided for the generation difficulty of donor cells caused by the close gap among scissors tail-rotor *** the CFD calculation results as input,the thickness noise,loading noise and total noise of tail-rotor are calculated by F1 *** the method,numerical examples on rotor flowfield and noise are performed and the results are compared with available ***,aerodynamic and acoustic characteristics of scissors tail-rotor are emphatically calculated in both hover and forward ***,the research on the effects of blade-tip shape parameters on scissors tail-rotor noise is carried ***,the scissors tail-rotor is compared with the conventional tail-rotor,and the results show that in hover,the noise of a scissors tail-rotor is not always the smaller one.

关键词： FW-H equation scissors tail rotor thickness noise loading noise helicopter computational fluid dynamics(CFD)

A Distributed Cell Outage Compensation Mechanism Based on RS Power Adjustment in LTE Networks

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China Communications 2014年第A01期11卷 40-47页

作者： LI Wenjing YU Peng YIN mengjun meng Luoming StateKeyLaboratoryofNetworkingandSwitchingTechnology BeijingUniversityofPostsandTelecommunicationsBeijing100876China

To solve the coverage and quality problems caused by cell outage in LTE networks, this paper proposes a distributed self-organizing networks management architecture and a distributed cell outage compensation management mechanism. After detecting and analyzing the outage, a cell outage compensation algorithm based on reference signal power adjustment is proposed. The simulation results show that the proposed mechanism can mitigate the performance degradation significantly. Compared with other algorithms, the proposed scheme is more effective in compensating the coverage gap induced by cell outage

关键词： LTE cell outage compensation (COC) reference signal power PSO

Numerical Optimization on Aerodynamic/Stealth Characteristics of Airfoil Based on CFD/CEM Coupling Method

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第3期33卷 274-284页

作者： Jiang Xiangwen Zhao Qijun Zhao Guoqing meng Chen National Key Laboratory of Science and Technology on Rotorcraft Aeromechanics Nanjing University of Aeronautics and Astronautics

Based on computational fluid dynamics （CFD）/computational eleetromagnetics method （CEM） coupling method and surrogate model optimization techniques, an integration design method about aerodynamic/stealth characteristics of airfoil is established. The O-type body-fitted and orthogonal grid around airfoil is first generated by using the Poisson equations, in which the points per wave and the normal range satisfy the aerodynamic and electromagnetic calculation accuracy requirement. Then the aerodynamic performance of airfoil is calculated by sol- ving the Navier-Stokes （N-S） equations with Baldwin-Lomax （B-L） turbulence model. The stealth characteristics of airfoil are simulated by using finite volume time domain （FVTD） method based on the Maxwell＇s equations, Steger-Warming flux splitting and the third-order MUSCL scheme. In addition, based upon the surrogate model optimization technique with full factorial design （FFD） and radial basis function （RBF）, an integration design about aerodynamic/stealth characteristics of rotor airfoil is conducted by employing the CFD/CEM coupling meth- od. The aerodynamic/stealth characteristics of NACA series airfoils with different maximum thickness and camber combinations are discussed. Finally, by choosing suitable lift-to-drag ratio and radar cross section （RCS） ampli- tudes of rotor airfoil in four important scattering regions as the objective function and constraint, the compromised airfoil with high lift-to-drag ratio and low scattering characteristics is designed via systemic and comprehensive ana- lyses.

关键词： rotor airfoil aerodynamic characteristics stealth characteristics CFD/CEM coupling surrogate modle

prpf4 is essential for cell survival and posterior lateral line primordium migration in zebrafish

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Journal of Genetics and Genomics 2018年第8期45卷 443-453页

作者： Yixia Wang Yanchao Han Pengfei Xu Shihui Ding Guangyuan Li Hongbin Jin Yaping meng Anming meng Shunji Jia State Key Laboratory of Membrane Biology Tsinghua-Peking Center for Life Sciences School of Life Sciences Tsinghua University

Prpf4 （pre-mRNA processing factor 4）, a key component of spliceosome, plays critical roles in pre-mRNA splicing and its mutations result in retinitis pigmentosa due to photoreceptor defects. In this study, we characterized a zebrafish prpf4t243 mutant harboring a Tol2 transposon-based gene trap cassette in the third intron of the prpf4 gene. Cells in the brain and spinal cord gradually undergo p53-dependent apoptosis after 28 hpf in prpf4t243 mutants, suggesting that a widespread function of prpf4 in neural cell survival. In addition, prpf4 is essential for survival of posterior lateral line primordial （pLLP） cells, prpf4 deficiency perturbs Fgf, Wnt/β-catenin and chemokine signaling pathways and impairs pLLP migration. RNA-Seq analysis suggests that prpf4 deficiency may impair spliceosome assembly, leading to compensatory upregulation of core spliceosomal genes and alteration of pre-mRNA splicing. Taken together, our studies uncover an essential role of prpf4 in pre-mRNA splicing, cell survival and pLLP migration.

关键词： prpf4 Splicing Apoptosisp LLP Zebrafish

Mechanical Behavior of Light Trusses Made of Poplar Laminated Veneer Lumber and Connected with Bolts and Tooth Plates

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Journal of Renewable Materials 2020年第9期8卷 1111-1127页

作者： Yan Liu Yanfei Guo Xufeng Sun meng Gong College of Civil Engineering Yangzhou UniversityYangzhouChina Wood Science and Technology Center University of New BrunswickFrederictonCanada

Poplar Laminated Veneer Lumber(Poplar LVL)is a new type of engineering materials with high strength,good reliability and small *** LVL is manufactured from the fast-growing poplar,which is widely used in packaging,furniture and others,however,is rarely adopted in *** order to explore the feasibility of poplar LVL trusses in construction of roof,four 4.5-m-span Fink-and-Howe trusses were designed and assembled,which were made of poplar LVL with bolted-and tooth-plated *** static loading on the upper chord joints of a truss was imposed by self-balancing test *** mechanical properties of trusses were *** ultimate load,deformation character and failure mode of each truss were measured,observed and ***,four types of analytical models with different joint connection assumptions were used to estimate the ultimate load and *** results showed that the poplar LVL trusses were basically in elastic stage before the design load was reached,showing good working performance under the action of design *** bearing capacity of the trusses of bolted connections was greater than that of the tooth-plated *** for the same joint connection type,the bearing capacity of Fink trusses exceeded that of Howe *** poplar LVL light trusses of both types of connections showed good structural performance,which could be reasonably used for building roof systems.

关键词： Poplar LVL truss mechanical properties bearing capacity bolted connection truss plate connections model

Correlation mechanism between force chains and friction mechanism during powder compaction

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Chinese Physics B 2022年第2期31卷 423-433页

作者： ning Zhang Shuai Zhang Jian-Jun Tan Wei Zhang School of Mechanical&Automotive Engineering Fujian University of TechnologyFuzhou 350118China

The relation between friction mechanism and force chains characteristics has not yet been fully studied in the powder metallurgy research *** this work,a uniaxial compression discrete element model is established based on the compaction process of ferrous ***,the correlation mechanism between force chains and the friction mechanism during powder compaction is *** simulation results reveal a strong correlation between the variation of the friction coefficient and the evolution of force *** the powder compaction,the friction coefficient would eventually tend to be stable,a feature which is also closely related to the slip ratio between *** side wall friction and the friction between particles would have an important effect on the direction of force chain growth in about one-third of the area near the side *** research results provide theoretical guidance for improving the densification process of the powder according to the force chain and friction.

关键词： powder compaction force chains granular matter discrete element method