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Effects of tree size and organ age on variations in carbon,nitrogen,and phosphorus stoichiometry in Pinus koraiensis

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Journal of Forestry Research 2024年第3期35卷 155-165页

作者： yanjun wang Guangze Jin Zhili Liu Center for Ecological Research Northeast Forestry UniversityHarbin 150040People's Republic of China Key Laboratory of Sustainable Forest Ecosystem Management-Ministry of Education Northeast Forestry UniversityHarbin 150040People's Republic of China Northeast Asia Biodiversity Research Center Northeast Forestry UniversityHarbin 150040People's Republic of China

Carbon(C),nitrogen(N),and phosphorus(P)are of fundamental importance for growth and nutrient dynamics within plant organs and deserve more attention at regional to global ***,our knowledge of how these nutrients vary with tree size,organ age,or root order at the individual level remains *** determined C,N,and P contents and their stoichiometric ratios(i.e.,nutrient traits)in needles,branches,and fine roots at different organ ages(0-3-year-old needles and branches)and root orders(1st-4th order roots)from 64 Pinus koraiensis of varying size(Diameter at breast height ranged from 0.3 to 100 cm)in northeast *** factors were also *** results show that nutrient traits were regulated by tree size,organ age,or root order rather than soil *** a whole-plant level,nutrient traits decreased in needles and fine roots but increased in branches with tree *** the organ level,age or root order had a negative effect on C,N,and P and a positive effect on stoichiometric *** results demonstrate that nutrient variations are closely related to organ-specific functions and ecophysiological processes at an individual *** is suggested that the nutrient acquisition strategy by younger trees and organ fractions with higher nutrient content is for ***,nutrient storage strategy in older trees and organ fractions are mainly for steady *** results clarified the nutrient utilization strategies during tree and organ ontogeny and suggest that tree size and organ age or root order should be simultaneously considered to understand the complexities of nutrient variations.

关键词： Tree size Organ age(or root order) Carbon(C) Nitrogen(N) Phosphorus(P) Pinus koraiensis

Secondary trading of airport slots:Issues and challenges

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Chinese Journal of Aeronautics 2023年第12期36卷 1-12页

作者： yanjun wang Mengyin wang Weishan XU Mark HANSEN College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 210016China Adam Smith Businesses School University of GlasgowGlasgow G128QQUK Department of Civil and Environmental Engineering University of CaliforniaBerkeley 94720USA

Most Level 3 airports around the world suffer severe congestion and flight *** have to obtain airport slots in order to schedule flights at such *** main way for airlines to acquire slots is primary slot allocation,in which a slot coordinator distributes slots to airlines according to certain rules and *** to excessive demand for slots and restrictions on allocation rules,it is difficult for some airlines to obtain the desired slots in this *** way for airlines to obtain slots is through secondary slot trading,in which slots can be redistributed among airlines without being returned to slot *** secondary trading of airport slots has played a positive role in promoting the efficient utilization of slot resources,but systematic studies are *** paper discusses the reasons for the existence of slot secondary trading,sorts out the main policies and rules governing the mechanism,investigates its impacts on the industry and society,and points out the major problems and *** paper provides a reference for subsequent research and practical application of airport slot secondary trading in the future.

关键词： Air traffic management Airport capacity Airport slot allocation Market-based mechanism Secondary slot trading

A Hierarchical unsupervised method for power line classification from airborne LiDAR data

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International Journal of Digital Earth 2019年第12期12卷 1406-1422页

作者： yanjun wang Qi Chen Lin Liu Kai Li National-local Joint Engineering Laboratory of Geo-spatial Information Technology Hunan University of Science and TechnologyXiangtanPeople’s Republic of China School of Resource Environment and Safety Engineering Hunan University of Science and TechnologyXiangtanPeople’s Republic of China Department of Geography and Environment University of Hawai’i at MānoaHonoluluHIUSA Department of Geography University of CincinnatiCincinnatiOHUSA School of Geographic Science Center of Geo-Informatics for Public SecurityGuangzhou UniversityGuangzhouPeople’s Republic of China

The automatic classification of power lines from airborne light detection and ranging(LiDAR)data is a crucial task for power supply *** methods for power line classification can be either supervised or *** methods might achieve high accuracy for small areas,but it is time consuming to collect training data over areas of different conditions and ***,unsupervised methods that can automatically work over different areas without sophisticated parameter tuning are in great *** this paper,we presented a hierarchical unsupervised LiDAR-based power line classification method that first screened the power line candidate points(including the power line corridor direction detection based on a layered Hough transform,connectivity analysis,and Douglas–Peucker simplification algorithm),followed by the extraction of contextual linear and angular features for each candidate laser points,and finally by setting the feature threshold values to identify the power line *** tested the method over both forest and urban areas and found that the precision,recall and quality rates were up to 96.7%,88.8%and 78.3%,respectively,for the test datasets and were higher than the ones from a previously developed supervised classification ***,our approach has the advantages of achieving relatively high accuracy and being relatively fast.

关键词： Airborne LiDAR data power lines unsupervised classification feature extraction

Air route network optimization in fragmented airspace based on cellular automata

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Chinese Journal of Aeronautics 2017年第3期30卷 1184-1195页

作者： Shijin wang Xi CAO Haiyun LI Qingyun LI Xu HANG yanjun wang College of Civil Aviation Nanjing University of Aeronautics and Astronautics Air Traffic Control Division Central-south Regional Air Traffic Management Bureau

Air route network optimization,one of the essential parts of the airspace planning,is an effective way to optimize airspace resources,increase airspace capacity,and alleviate air traffic ***,little has been done on the optimization of air route network in the fragmented airspace caused by prohibited,restricted,and dangerous areas（PRDs）.In this paper,an air route network optimization model is developed with the total operational cost as the objective function while airspace restriction,air route network capacity,and non-straight-line factors（NSLF） are taken as major constraints.A square grid cellular space,Moore neighbors,a fixed boundary,together with a set of rules for solving the route network optimization model are designed based on cellular *** empirical traffic of airports with the largest traffic volume in each of the 9 flight information regions in China's Mainland is collected as the origin-destination（OD） airport pair *** on traffic patterns,the model generates 35 air routes which successfully avoids 144 *** with the current air route network structure,the number of nodes decreases by 41.67%,while the total length of flight segments and air routes drop by 32.03% and 5.82% *** NSLF decreases by 5.82% with changes in the total length of the air route *** importantly,the total operational cost of the whole network decreases by 6.22%.The computational results show the potential benefits of the model and the advantage of the *** of air route network can significantly reduce operational cost while ensuring operation safety.

关键词： Air route network planning Airspace restriction Cellular automata Network capacity Optimization of nodes

EFFECT OF Z-PINS’ DIAMETER,SPACING AND OVERLAP LENGTH ON CONNECTING PERFORMANCE OF CMC SINGLE LAP JOINT

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Acta Mechanica Solida Sinica 2008年第5期21卷 461-471页

作者： Yongqiang Tao Guiqiong Jiao Bo wang yanjun Chang School of Mechanics and Civil Construction Northwest Polytechnical University Xi＇an 710072 China

The effect of through-thickness reinforcement by composite pins （Z-pins） on the static tensile strength and failure mechanisms of the joints made from ceramic matrix composite （CMC） is investigated. Overlap length of the single lap joint is 15 mm, 20 mm, 23 mm, 37 mm, and 60 mm, respectively. The experimental results indicate that the final failure modes of the joints can be divided into two groups, （a） the bond-line stops debonding until crack encounters Z-pins; and then the adherends break at the location of Z-pins, when overlap length is more than 20 mm; （b） the bond-line detaches entirely and Z-pins are drawn from adherends, when overlap length is equal to 15 mm. A simple efficient computational approach is presented for analyzing the benefit of through-thickness pins for restricting failure in the single lap joints. Here, the mechanics problem is simplified by representing the effect of the pins by tractions acting on the fracture surfaces of the cracked bond-line. The tractions are prescribed as functions of the crack displacement, which are available in simple forms that summarize the complex deformations to a reasonable accuracy. The resulting model can be used to track the evolution of complete failure mechanisms, for example, bond-line initial delamination and ultimate failure associated with Z-pin pullout, ultimate failure of the adherends. The paper simulates connecting performance of the single lap joints with different Z-pins＇ diameter, spacing and overlap length; the numerical results agree with the experimental results; the numerical results indicate enlarging diameter and decreasing spacing of Z-pins are in favor of improving the connecting performance of the joints. By numerical analysis method, the critical overlap length that lies between two final failure modes is between 18 mm and 19 mm, when Z-pins＇ diameter and spacing are 0.4 mm, 5 mm, respectively.

关键词： ceramic matrix composite (CMC) single lap joint Z-pins connecting performance,overlap length diameter spacing

Empirical analysis of airport network and critical airports

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Chinese Journal of Aeronautics 2016年第2期29卷 512-519页

作者： Cong Wei Hu Minghua Dong Bin wang yanjun Feng Cheng College of Civil Aviation Nanjing University of Aeronautics and Astronautics Nanjing 211106 China National Key Laboratory of Air Traffic Flow Management Nanjing 211106 China The 28th Research Institute of China Electronics Technology Group Corporation Nanjing 210000 China

Air transport network, or airport network, is a complex network involving numerous airports. Effective management of the air transport system requires an in-depth understanding of the roles of airports in the network. Whereas knowledge on air transport network properties has been improved greatly, methods to find critical airports in the network are still lacking. In this paper, we present methods to investigate network properties and to identify critical airports in the network. A novel network model is proposed with airports as nodes and the correlations between traffic flow of airports as edges. Spectral clustering algorithm is developed to classify air- ports. Spatial distribution characteristics and intraclass correlation of different categories of air- ports are carefully analyzed. The analyses based on the fluctuation trend of distance-correlation and power spectrum of time series are performed to examine the self-organized criticality of the net- work. The results indicate that there is one category of airports which dominates the self-organized critical state of the network. Six airports in this category are found to be the most important ones in the Chinese air transport network. The flights delay occurred in these six airports can propagate to the other airports, having huge impact on the operation characteristics of the entire network. The methods proposed here taking traffic dynamics into account are capable of identifying critical air- ports in the whole air transport network.

关键词： Airport network Critical airport Spatial correlation Spectral clustering Power-law distributionPower spectra

Simulating cross-sectional geometry of the main channel in response to changes in water and sediment in Lower Yellow River

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Journal of Geographical Sciences 2020年第12期30卷 2033-2052页

作者： wang yanjun WU Baosheng ZHONG Deyu Key Laboratory of River Regulation and Flood Control of Ministry of Water Resources Yangtze River Scientific Research InstituteWuhan 430010China State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China

To understand the non-equilibrium morphological adjustment of a river in response to environmental changes,it is essential to(i)accurately identify how past conditions of water and sediment have impacted current morphological adjustment of the river,and(ii)establish a corresponding simulation for non-equilibrium *** on discharge and suspended sediment concentration(SSC)as well as 82 cross-sectional data items for the Huayuankou-Lijin reach of the Lower Yellow River in the period 1965-2015,the process of adjustment of the geometry of the main channel(area,width,depth,and geomorphic coefficient),and its responses to changes in discharge and SSC for different reaches are statistically *** this,a delayed response model(DRM)of the geometry of the main channel subjected to variations in discharge and SSC is established using a multi-step analytical model,with the discharge and SSC as the main controlling *** results show that the area,width,and depth of the main channel decreased initially,then increased,decreased again,and finally increased *** features of the geometry of the channel were positively correlated with the 4-year moving average discharge and negatively with the 4-year moving average *** geomorphic coefficient for the Huayuankou-Sunkou reach exhibited a trend of decrease,whereas that of the Sunkou-Lijin reach decreased initially,then increased,decreased again,and finally increased *** for the Huayuankou-Gaocun reach in 1965-1999,the coefficient was negatively correlated with the 4-year moving average discharge and positively with *** simulated values of the morphological parameters of the main channel for all sub-reaches obtained using the DRM agreed well with the measured *** indicates that the DRM can be used to simulate the process of response of the cross-sectional geometry of the main channel to variations in the water and *** results of the model show that the adjustment of th

关键词： Lower Yellow River water and sediment changes cross-sectional geometry of the main channel delayed response model

Removal of carbonyl sulfide from CO_2 stream using AgNO_3-modified NaZSM-5

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Journal of Energy Chemistry 2013年第6期22卷 902-906页

作者： yanjun wang Shaoyun Chen Heng Chen Xingzhou Yuan Yongchun Zhang State Key Laboratory of Fine Chemicals School of Chemical Engineering Dalian University of Technology

Removal of carbonyl sulfide(COS) from CO2 stream is significant for the production and utilization of food grade CO2. This study investigates the adsorption performance of Ag/NaZSM-5 as adsorbent prepared by incipient wetness impregnation for the removal of COS from a CO2 stream in a fixed-bed adsorption apparatus. Effects of various conditions on the preparation of adsorbent, adsorption and desorption were intensively examined. The results revealed that COS can be removed to below 1×10-9from a CO2stream(1000 ppm COS/CO2) using Ag/NaZSM-5(10 wt% AgNO3) with an adsorption capacity of 12.86 mg·g-1. The adsorbent can be fully regenerated using hot air at 450 C. The adsorption ability remained stable even after eight cycles of regeneration.

关键词： carbonyl sulfide adsorption π-complexation completely regeneration Ag-modified adsorbents

Wear Behavior of Cold Pressed and Sintered Al_2O_3/TiC/CaF_2-Al_2O_3/TiC Laminated Ceramic Composite

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Acta Metallurgica Sinica(English Letters) 2013年第2期26卷 157-166页

作者： Xuefeng YANG Jian CHENG Peilong SONG Shouren wang Liying YANG yanjun wang Ken MAO School of Mechanical Engineering University of Jinan Key Laboratory for Anisotropy and Texture of Materials of the Ministry of Education Northeastern University School of Engineering Warwick University

A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure. Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear. Al2O3/TiC ceramic was also cold pressed and sintered for comparison. Friction analysis of the two ceramics was then conducted via a wear-and-tear machine. Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum, respectively. Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite. Under the friction load, the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits. This process formed a smooth, self-lubricating film, which led to better anti-wear properties. Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.

关键词： Friction and wear characteristics Wear property Ceramic-matrix compos-ites Layer manufacture Surface appearance Sliding