The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL) problem of Lundberg&...The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL) problem of Lundberg's profiled cylindrical roller under the conditions of flooded state, moderate load and material parameter. It shows clearly the effects of crowning value on the variations of oil film shape and thickness. The agreement between numerical analysis and experiment results is very good. The results indicate there must be an optimum crowning value that will induce the thickest and most even oil film in EHL state for a given working condition, and this value is larger than the design value in dry contact state for the same working conditions.展开更多
Gear crowning takes an important part in alleviating the concentration of local stresses when misalignment of the flanks exists. It is known that an excessive crowning will lead to a high local stress while an insuffi...Gear crowning takes an important part in alleviating the concentration of local stresses when misalignment of the flanks exists. It is known that an excessive crowning will lead to a high local stress while an insufficient value will not be able to compensate the alignment error resulting in concentration. The selection of the crowning value is always based on empirical estimation. This paper deals with a theoretical method to determine the crowning value. The distribution forms of contact stresses on the flanks of a crowned pinion and a gear are treated as a series of complete or portions of semi-ellipsoids with the same size. The total volume of which equals the whole contact load. From this point of view a series of equations for the computation of the maximum stress is obtained. The calculation of contact stresses considering the existence of alignment errors gives insight into the selection ora proper crowning value for a gear drive.展开更多
Tree plantations are globally significant,and therefore,growth-related challenges cannot be ignored.Canopy structure and light environment influence the growth of plantations,but the precise relationship remains uncle...Tree plantations are globally significant,and therefore,growth-related challenges cannot be ignored.Canopy structure and light environment influence the growth of plantations,but the precise relationship remains unclear.We selected seven-year-old poplar plantations of varying cultivars planted various densities and measured their growth,canopy structure,and light environment.The findings indicate that poplar plantations of different cultivars and at different planting densities showed variations in leaf area index(LAI),average leaf angle(ALA),crown length(CL),length ratio(CLR),roundness(CR)and surface area(CSA),which directly or indirectly affect growth,resulting in disparities in their growing conditions.Crown roundness directly impacted growth,while LAI,CLR and ALA influenced growth indirectly by affecting intercellular carbon dioxide concentration.LAI and CLR had a positive effect;ALA had a negative one.Crown length and surface area directly and indirectly influenced growth by affecting photo synthetically active radiation and net photo synthetic rate,with direct impacts being more pronounced.This research has clarified the regulatory role of canopy structure in plantations growth,providing valuable insights for developing more effective management strategies.展开更多
Allometric equations are fundamental tools in ecological research and forestry management,widely used for estimating above-ground biomass and production,serving as the core foundations of dynamic vegetation models.Usi...Allometric equations are fundamental tools in ecological research and forestry management,widely used for estimating above-ground biomass and production,serving as the core foundations of dynamic vegetation models.Using global datasets from Tallo(a tree allometry and crown architecture database encompassing thousands of species)and TRY(a plant traits database),we fit B ayesian hierarchical models with three alternative functional forms(powerlaw,generalized Michaelis-Menten(gMM),and Weibull)to characterize how diameter at breast height(DBH),tree height(H),and crown radius(CR)scale with and without wood density as a species-level predictor.Our analysis revealed that the saturating Weibull function best captured the relationship between tree height and DBH in both functional groups,whereas the CR-DBH relationship was best predicted by a power-law function in angiosperms and by the gMM function in gymnosperms.Although including wood density did not significantly improve predictive performance,it revealed important ecological trade-offs:lighter-wood angiosperms achieve taller mature heights more rapidly,and denser wood promotes wider crown expansion across clades.We also found that accurately estimating DBH required considering both height and crown size,highlighting how these variables together distinguish trees of similar height but differing trunk diameters.Our results emphasize the importance of applying saturating functions for large trees to improve forest biomass estimates and show that wood density,though not always predictive at broad scales,helps illuminate the biomechanical and ecological constraints underlying diverse tree architectures.These findings offer practical pathways for integrating height-and crown-based metrics into existing carbon monitoring programs worldwide.展开更多
Accurate crown control is paramount for ensuring the quality of hot-rolled strip products.Given the multitude of influencing parameters and the intricate coupling and genetic relationships among them,the conventional ...Accurate crown control is paramount for ensuring the quality of hot-rolled strip products.Given the multitude of influencing parameters and the intricate coupling and genetic relationships among them,the conventional crown control method is no longer sufficient to meet the precision requirements of schedule-free rolling.To address this limitation,an optimization framework for hot-rolled strip crown control was developed based on model-driven digital twin(MDDT).This framework enhances the strip crown control precision by facilitating collaborative operations among physical entities,virtual models,and functional application layers.In virtual modeling,a data-driven approach that integrates the extreme gradient boosting and the improved Harris hawk optimization algorithm was firstly proposed to fit the relationship between key process parameters and strip crown,and a global-local collaborative training strategy was proposed to enhance the model adaptability to diverse working conditions.Subsequently,the influence of crucial process factors on the virtual model was examined through model responses.Furthermore,a novel optimization mode for crown control based on MDDT was established by aligning and reconstructing both the physical and virtual models,thereby enhancing the crown control precision.Finally,data trials were conducted to validate the effectiveness of the proposed framework.The results indicated that the proposed method exhibited satisfactory performance and could be effectively utilized to improve the crown control precision.展开更多
Boom in creative cultural products is boosting Chinese museums.The National Museum of China’s phoenix crown magnet,considered the jewel in the crown of the country’s cultural souvenirs,hit a milestone on 25 March,se...Boom in creative cultural products is boosting Chinese museums.The National Museum of China’s phoenix crown magnet,considered the jewel in the crown of the country’s cultural souvenirs,hit a milestone on 25 March,selling over 1 million units in just eight months and six days.Since last autumn,visitors have been queuing before dawn to get their hands on this star product whenever the museum is open.展开更多
The separation of lithium isotopes (^(6)Li and ^(7)Li) is of great importance for the nuclear industry.The lithium amalgam method is the only lithium isotopes separation process in industry,and the extensive use of me...The separation of lithium isotopes (^(6)Li and ^(7)Li) is of great importance for the nuclear industry.The lithium amalgam method is the only lithium isotopes separation process in industry,and the extensive use of mercury has raised concerns about its potential environmental hazards,which have prompted the search for more efficient and environmentally friendly alternatives.Crown ethers can bind lithium ions highly selectively and separate lithium isotopes effectively.A chemical exchange-based lithium isotopes separation method using crown ether decorated materials could be a viable and cost-effective alternative to the lithium amalgam method.In this review,we provide a systematic summary of the recent advances in lithium isotopes separation using crown ethers decorated materials.展开更多
The authors regret that the declaration of Acknowledgement as below is missing in the paper:AcknowledgementWe are grateful to the Department of Biology and Postgraduate Sciences-Biology of the Universidad del Valle,Ca...The authors regret that the declaration of Acknowledgement as below is missing in the paper:AcknowledgementWe are grateful to the Department of Biology and Postgraduate Sciences-Biology of the Universidad del Valle,Cali-Colombia for their support of the project;to Wilmar Torres MSc.for his statistical advice;to the biologist Helen Burnham MSc.for the translation of the document;to Isabel Castro and all the members of the Ornithology and Animal Behaviour Laboratory-OYCA of Universidad del Valle for their invaluable support in the field.We sincerely thank the anonymous re-viewers for their invaluable feedback and contributions to our manuscript.展开更多
Anion exchange membrane(AEM)fuel cells require membranes with a balance of high conductivity and durability.In this work,a novel bi-crown-ether modified piperidine structure was designed and synthesized,which was then...Anion exchange membrane(AEM)fuel cells require membranes with a balance of high conductivity and durability.In this work,a novel bi-crown-ether modified piperidine structure was designed and synthesized,which was then introduced into the side chain of poly(arylene piperidinium),making a unique bi-crown-ether modified bi-piperidinium side chain grafted polymer for AEM fabrication.The double crown ether units enhanced cation–water interactions and promoted microphase separation,thereby forming efficient hydroxide ion transport channels.The resulting membrane exhibited high water uptake,well-defined ion clusters,and a hydroxide conductivity of 123 mS cm^(-1) at 80℃ with an ion exchange capacity(IEC)of 1.56 mmol g^(-1).After alkaline treatment in 1 M NaOH at 80℃ for 960 h,the membrane retained~85%of its initial conductivity,demonstrating excellent chemical stability.In H2/O2 fuel cell tests at 60℃ ,the membrane achieved a peak power density of 558 mW cm-2 at 1040 mA cm-2.These findings highlight the potential of bi-crown-ether modified piperidinium side chain grafting as an effective strategy to enhance ion conduction properties of AEMs for fuel cell applications.展开更多
In permanently uneven-aged forests, continuous ingrowth of recruitment into higher stand layers is a critical process for the formation and maintenance of differentiated stand structures. This study analyses the abund...In permanently uneven-aged forests, continuous ingrowth of recruitment into higher stand layers is a critical process for the formation and maintenance of differentiated stand structures. This study analyses the abundance and diversity of recruitment(diameter at breast high(DBH) 0.1–4 cm) across 241 research plots in 11 structurally differentiated Norway spruce(silver fir)-dominated forest stands distributed at altitudes between 500 and 1,440 m a.s.l. The influence of light conditions and lateral competition characteristics on the height increment and crown architecture of recruitment was investigated in detail for 352 Norway spruce and 361 silver fir trees. Light-related variables were confirmed to directly affect the recruitment distribution only to a limited extent. Under relatively low light conditions in montane stands, silver fir reached higher height increments than Norway spruce. The better adaptation of silver fir to shaded conditions was reflected also in its higher apical dominance ratio compared to Norway spruce. The height increment and apical dominance ratio of Norway spruce and silver fir recruitment were positively correlated with indirect radiation, DBH, and relative crown length(RCL), but not with lateral competition. These results confirm that the regulation of light conditions in permanently unevenaged stands is crucial for the growth dynamics of recruitment, as well as for the future proportions of Norway spruce and silver fir in mixed, structurally diverse stands.展开更多
Branch size is a crucial characteristic,closely linked to both tree growth and wood quality.A review of existing branch size models reveals various approaches,but the ability to estimate branch diameter and length wit...Branch size is a crucial characteristic,closely linked to both tree growth and wood quality.A review of existing branch size models reveals various approaches,but the ability to estimate branch diameter and length within the same whorl remains underexplored.In this study,a total of 77 trees were sampled from Northeast China to model the vertical distribution of branch diameter and length within each whorl along the crown.Several commonly used functions were taken as the alternative model forms,and the quantile regression method was employed and compared with the classical two-step modeling approach.The analysis incorporated stand,tree,and competition factors,with a particular focus on how these factors influence branches of varying sizes.The modified Weibull function was chosen as the optimal model,due to its excellent performance across all quantiles.Eight quantile regression curves(ranging from 0.20 to 0.85)were combined to predict branch diameter,while seven curves(ranging from 0.20 to 0.80)were used for branch length.The results showed that the quantile regression method outperformed the classical approach at model fitting and validation,likely due to its ability to estimate different rates of change across the entire branch size distribution.Lager branches in each whorl were more sensitive to changes in DBH,crown length(CL),crown ratio(CR)and dominant tree height(H_(dom)),while slenderness(HDR)more effectively influenced small and medium-sized branches.The effect of stand basal area(BAS)was relatively consistent across different branch sizes.The findings indicate that quantile regression is a good way not only a more accurate method for predicting branch size but also a valuable tool for understanding how branch growth responds to stand and tree factors.The models developed in this study are prepared to be further integrated into tree growth and yield simulation system,contributing to the assessment and promotion of wood quality.展开更多
In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.In...In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.Instead of building univariate models for each response variable,we employed a multivariate approach using seemingly unrelated mixed-effects models.These models incorporated variables related to species mixture,tree and stand size,competition,and stand structure.With the inclusion of additional variables in the multivariate seemingly unrelated mixed-effects models,the accuracy of the height prediction models improved by over 10% for all species,whereas the improvement in the crown length models was considerably smaller.Our findings indicate that trees in mixed stands tend to have shorter heights but longer crowns than those in pure stands.We also observed that trees in homogeneous stand structures have shorter crown lengths than those in heterogeneous stands.By employing a multivariate mixed-effects modelling framework,we were able to perform cross-model random-effect predictions,leading to a significant increase in accuracy when both responses were used to calibrate the model.In contrast,the improvement in accuracy was marginal when only height was used for calibration.We demonstrate how multivariate mixed-effects models can be effectively used to develop multi-response allometric models that can be easily calibrated with a limited number of observations while simultaneously achieving better-aligned projections.展开更多
An online subsection cooling method for hot rolling silicon steel was designed to achieve local adjustment of transverse roll gap.Particularly,it was able to meet the requirements of edge drop of the strip by using th...An online subsection cooling method for hot rolling silicon steel was designed to achieve local adjustment of transverse roll gap.Particularly,it was able to meet the requirements of edge drop of the strip by using the features of online thermal crown.First,after the new subsection spray beam was installed at the exit of mill,the special local cooling rules were analyzed for altering the thermal crown of roll according to rolling process parameters.Meanwhile,the dynamic impact of subsection cooling on the local thermal crown could just be obtained according to the measured data.Obviously,the heat transfer coefficient was determined by different subsection cooling curves under varied rolling conditions.Secondly,the rolling rhythm and variable conditions were important dynamic factors of transient roll temperature in practical rolling process.Therefore,real-time calculation and presetting of the thermal crown were carried out to maximize special requirements of load roll gap on local strip crown.By this new method,the transient temperature and the thermal crown of roll could be quantitatively controlled online.And the practical results showed that the predicted temperature was able to match the measured value by more than 95%.Meanwhile,the adjustable range of thermal crown increased by more than 2.5 times.Finally,the qualification rate of strip edge crown has increased from the original 30%to over 70%.展开更多
Rapid urbanization has caused significant changes along the urban-rural gradient,leading to a variety of landscapes that are mainly shaped by human activities.This dynamic interplay also influences the distribution an...Rapid urbanization has caused significant changes along the urban-rural gradient,leading to a variety of landscapes that are mainly shaped by human activities.This dynamic interplay also influences the distribution and characteristics of trees outside forests(TOF).Understanding the pattern of these trees will support informed decision-making in urban planning,in conservation strategies,and altogether in sustainable land management practices in the urban context.In this study,we employed a deep learning-based object detection model and high resolution satellite imagery to identify 1.3 million trees with bounding boxes within a 250 km^(2)research transect spanning the urban-rural gradient of Bengaluru,a megacity in Southern India.Additionally,we developed an allometric equation to estimate diameter at breast height(DBH)from the tree crown diameter(CD)derived from the detected bounding boxes.Our study focused on analyzing variations in tree density and tree size along this gradient.The findings revealed distinct patterns:the urban domain displayed larger tree crown diameters(mean:8.87 m)and DBH(mean:43.78 cm)but having relatively low tree density(32 trees per hectare).Furthermore,with increasing distance from the city center,tree density increased,while the mean tree crown diameter and mean tree basal area decreased,showing clear differences of tree density and size between the urban and rural domains in Bengaluru.This study offers an efficient methodology that helps generating instructive insights into the dynamics of TOF along the urban-rural gradient.This may inform urban planning and management strategies for enhancing green infrastructure and biodiversity conservation in rapidly urbanizing cities like Bengaluru.展开更多
CdSe nanoplatelets(NPLs)are promising candidates for on-chip light sources,yet their performance is hindered by surface defects and inefficient optical gain.Herein,we demonstrate that CdSeS crown passivation significa...CdSe nanoplatelets(NPLs)are promising candidates for on-chip light sources,yet their performance is hindered by surface defects and inefficient optical gain.Herein,we demonstrate that CdSeS crown passivation significantly enhances the photophysical property of CdSe NPLs.Laser spectroscopy techniques reveal suppressed electronic and hole trapping at lateral surfaces,leading to a 4.2-fold increase in photoluminescence quantum yield and a shortened emission lifetime from13.5 to 4.8 ns.In addition,amplified spontaneous emission is achieved under nanosecond pulse pumping,with thresholds of0.75 to 0.16 mJ/cm^(2)for CdSe and CdSe/CdSeS NPLs,respectively.By integrating CdSe/CdSeS NPLs with high-refractiveindex SiO2scatters,coherent random lasing is realized at a threshold of 0.21 mJ/cm^(2).These findings highlight the critical role of lateral surface passivation in optimizing optical gain and pave the way for low-cost,multifunctional nanophotonic devices.展开更多
The ring has been a romantic fascination throughout the ages,embodying not only beauty and order but also harboring numerous undisclosed properties awaiting discovery.In the realm of supramolecular chemistry,macrocycl...The ring has been a romantic fascination throughout the ages,embodying not only beauty and order but also harboring numerous undisclosed properties awaiting discovery.In the realm of supramolecular chemistry,macrocycles,with a cyclic structure and a central cavity like a doughnut,captivate the attention of scientists[1].In 1967,Pedersen's groundbreaking revelation that alkali metal ions could"fall into"the cavities of a cyclic ether named crown ether,even in organic solvents,unveiled a novel universe of macrocycle chemistry.Since then,numerous macrocyclic structures in nature have been discovered,isolated,and scrutinized.Drawing inspiration from nature,chemists endeavor to explore the vast potential of macrocyclic compounds by designing and synthesizing artificial macrocycles with diverse structural features and recognition properties.展开更多
The growth of Sakhalin fir(Abies sachalinen-sis)seedlings,an important forest tree species in northern Hokkaido,Japan,is significantly affected by competition from surrounding vegetation,especially evergreen dwarf bam...The growth of Sakhalin fir(Abies sachalinen-sis)seedlings,an important forest tree species in northern Hokkaido,Japan,is significantly affected by competition from surrounding vegetation,especially evergreen dwarf bamboo.In this study,we investigated the height and root collar diameter(RCD)growth of Sakhalin fir seedlings under various degrees of cover by deciduous vegetation and evergreen dwarf bamboo.Generalized additive models were used to quantify the effects of canopy cover and forest floor cover on the relative growth rates of these two parameters.The canopy cover of Sakhalin fir seedlings had a nonlin-ear negative effect on both the height growth of seedlings in the subsequent year and the RCD growth in the current year,given the general growth pattern in this species,where height growth ceases in early summer and RCD growth con-tinues until autumn.Height growth declined sharply after the canopy cover rate exceeded 50%,while RCD growth declined rapidly between 0 and 50%canopy cover rate.The forest floor cover had a greater negative impact on RCD growth than on height growth.These results suggested that Sakhalin fir seedlings respond to vegetative competition by prioritizing height growth for light acquisition at the expense of diameter growth and possibly root growth for below-ground competition.The cover of evergreen dwarf bamboo reduced the height growth of fir seedlings significantly more than the cover of deciduous vegetation.This difference is likely due to the timing of light availability.When competing with deciduous vegetation,Sakhalin fir seedlings exposed to light during the post-snow melt and early spring before the development of the deciduous vegetation canopy can photosynthesize more effectively,leading to greater height growth.The results of this study highlighted the importance of vegetation control considering the type of vegetation for successful Sakhalin fir reforestation.Adjusting the intensity and timing of weeding based on the presence and abundance of dwarf bamboo and other competing vegetation could potentially reduce weeding costs and increase biodiversity in reforested areas.展开更多
In recent years,with the rapid developme nt of the econo my and society,pollution of valuable metal ions in wastewater has become a major challenge to environmental sustainability.In order to solve the pollution cause...In recent years,with the rapid developme nt of the econo my and society,pollution of valuable metal ions in wastewater has become a major challenge to environmental sustainability.In order to solve the pollution caused by metal ions,researchers have conducted continuous re searches and explored various re mediation methods.Crown ether has attracted great attention because of its ionic radius and cavity size matching well with metal ions,which makes it have the ability to selectively complex metal ions.This unique property enables the directed removal and recovery of metal ions and makes crown ethers increasingly popular in extraction and separation processes.In this paper,the research progress of crown ethers in the extraction and separation of valuable metal ions was reviewed,with emphasis on the principles,extraction systems and the key factors affecting the extraction process.This study can provide some technical support for the application of separation and extraction of valuable metal ions by crown ether.展开更多
在网格环境中,多数节点希望能够更多地使用其他节点的资源,而不愿共享本地的资源.每个理性的用户在追求自身利益最大化的同时,严重影响了协作整体的运行效率.在实际应用中,要吸引资源的拥有者加入资源协作,就必须保证其利益和安全.讨论...在网格环境中,多数节点希望能够更多地使用其他节点的资源,而不愿共享本地的资源.每个理性的用户在追求自身利益最大化的同时,严重影响了协作整体的运行效率.在实际应用中,要吸引资源的拥有者加入资源协作,就必须保证其利益和安全.讨论了资源激励机制和分配机制之间的依赖与制约关系,从经济、信任角度提出自适应的信任-激励相容的资源分配机制.在网格环境中,资源供需的变化会引发价格的浮动,基于经济学的一般均衡理论,给出了资源提供者的动态价格调整策略.提供者可根据当前资源的供需和负载状况,制定自适应的信任-激励相容的分配策略ATIM(adaptive trust-incentive compatible resource allocation),遵循多贡献多分配的原则,激励节点共享出有价值的资源,最大化资源的聚合效用.在CROWN(China research and development environment over wider-area network)平台中评估了ATIM机制的效率和性能.展开更多
文摘The purpose of this paper is to present a comparison of numerical calculations and experiment results of optical interferometry in finite line contact for the elastohydrodynamic lubrication(EHL) problem of Lundberg's profiled cylindrical roller under the conditions of flooded state, moderate load and material parameter. It shows clearly the effects of crowning value on the variations of oil film shape and thickness. The agreement between numerical analysis and experiment results is very good. The results indicate there must be an optimum crowning value that will induce the thickest and most even oil film in EHL state for a given working condition, and this value is larger than the design value in dry contact state for the same working conditions.
文摘Gear crowning takes an important part in alleviating the concentration of local stresses when misalignment of the flanks exists. It is known that an excessive crowning will lead to a high local stress while an insufficient value will not be able to compensate the alignment error resulting in concentration. The selection of the crowning value is always based on empirical estimation. This paper deals with a theoretical method to determine the crowning value. The distribution forms of contact stresses on the flanks of a crowned pinion and a gear are treated as a series of complete or portions of semi-ellipsoids with the same size. The total volume of which equals the whole contact load. From this point of view a series of equations for the computation of the maximum stress is obtained. The calculation of contact stresses considering the existence of alignment errors gives insight into the selection ora proper crowning value for a gear drive.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFD2201203)the financial support of the National Natural Science Foundation of China(32001311)。
文摘Tree plantations are globally significant,and therefore,growth-related challenges cannot be ignored.Canopy structure and light environment influence the growth of plantations,but the precise relationship remains unclear.We selected seven-year-old poplar plantations of varying cultivars planted various densities and measured their growth,canopy structure,and light environment.The findings indicate that poplar plantations of different cultivars and at different planting densities showed variations in leaf area index(LAI),average leaf angle(ALA),crown length(CL),length ratio(CLR),roundness(CR)and surface area(CSA),which directly or indirectly affect growth,resulting in disparities in their growing conditions.Crown roundness directly impacted growth,while LAI,CLR and ALA influenced growth indirectly by affecting intercellular carbon dioxide concentration.LAI and CLR had a positive effect;ALA had a negative one.Crown length and surface area directly and indirectly influenced growth by affecting photo synthetically active radiation and net photo synthetic rate,with direct impacts being more pronounced.This research has clarified the regulatory role of canopy structure in plantations growth,providing valuable insights for developing more effective management strategies.
基金supported by the Xingdian Talent Support Program of Yunnan Province(E5YNR03B01)the Xishuangbanna State Rainforest Talent Support Program(E4BN041B01)the CAS President’s International Fellowship Initiative(2020FYB0003)。
文摘Allometric equations are fundamental tools in ecological research and forestry management,widely used for estimating above-ground biomass and production,serving as the core foundations of dynamic vegetation models.Using global datasets from Tallo(a tree allometry and crown architecture database encompassing thousands of species)and TRY(a plant traits database),we fit B ayesian hierarchical models with three alternative functional forms(powerlaw,generalized Michaelis-Menten(gMM),and Weibull)to characterize how diameter at breast height(DBH),tree height(H),and crown radius(CR)scale with and without wood density as a species-level predictor.Our analysis revealed that the saturating Weibull function best captured the relationship between tree height and DBH in both functional groups,whereas the CR-DBH relationship was best predicted by a power-law function in angiosperms and by the gMM function in gymnosperms.Although including wood density did not significantly improve predictive performance,it revealed important ecological trade-offs:lighter-wood angiosperms achieve taller mature heights more rapidly,and denser wood promotes wider crown expansion across clades.We also found that accurately estimating DBH required considering both height and crown size,highlighting how these variables together distinguish trees of similar height but differing trunk diameters.Our results emphasize the importance of applying saturating functions for large trees to improve forest biomass estimates and show that wood density,though not always predictive at broad scales,helps illuminate the biomechanical and ecological constraints underlying diverse tree architectures.These findings offer practical pathways for integrating height-and crown-based metrics into existing carbon monitoring programs worldwide.
基金financially supported by the National Key Research and Development Program of China(Grant No.2023YFB3710204)Guangxi Science and Technology Major Program(Grant No.AA23023028-1)+1 种基金Natural Science Foundation of Heilongjiang Province of China for Distinguished Young Scientists(Grant No.JQ2022E007)Xinjiang Production and Construction Corps Science and Technology Plan(Grant No.2023AA003).
文摘Accurate crown control is paramount for ensuring the quality of hot-rolled strip products.Given the multitude of influencing parameters and the intricate coupling and genetic relationships among them,the conventional crown control method is no longer sufficient to meet the precision requirements of schedule-free rolling.To address this limitation,an optimization framework for hot-rolled strip crown control was developed based on model-driven digital twin(MDDT).This framework enhances the strip crown control precision by facilitating collaborative operations among physical entities,virtual models,and functional application layers.In virtual modeling,a data-driven approach that integrates the extreme gradient boosting and the improved Harris hawk optimization algorithm was firstly proposed to fit the relationship between key process parameters and strip crown,and a global-local collaborative training strategy was proposed to enhance the model adaptability to diverse working conditions.Subsequently,the influence of crucial process factors on the virtual model was examined through model responses.Furthermore,a novel optimization mode for crown control based on MDDT was established by aligning and reconstructing both the physical and virtual models,thereby enhancing the crown control precision.Finally,data trials were conducted to validate the effectiveness of the proposed framework.The results indicated that the proposed method exhibited satisfactory performance and could be effectively utilized to improve the crown control precision.
文摘Boom in creative cultural products is boosting Chinese museums.The National Museum of China’s phoenix crown magnet,considered the jewel in the crown of the country’s cultural souvenirs,hit a milestone on 25 March,selling over 1 million units in just eight months and six days.Since last autumn,visitors have been queuing before dawn to get their hands on this star product whenever the museum is open.
基金support from the National Natural Science Foundation of China (Grant No.U21B2094 and Grant No.U2067212)。
文摘The separation of lithium isotopes (^(6)Li and ^(7)Li) is of great importance for the nuclear industry.The lithium amalgam method is the only lithium isotopes separation process in industry,and the extensive use of mercury has raised concerns about its potential environmental hazards,which have prompted the search for more efficient and environmentally friendly alternatives.Crown ethers can bind lithium ions highly selectively and separate lithium isotopes effectively.A chemical exchange-based lithium isotopes separation method using crown ether decorated materials could be a viable and cost-effective alternative to the lithium amalgam method.In this review,we provide a systematic summary of the recent advances in lithium isotopes separation using crown ethers decorated materials.
文摘The authors regret that the declaration of Acknowledgement as below is missing in the paper:AcknowledgementWe are grateful to the Department of Biology and Postgraduate Sciences-Biology of the Universidad del Valle,Cali-Colombia for their support of the project;to Wilmar Torres MSc.for his statistical advice;to the biologist Helen Burnham MSc.for the translation of the document;to Isabel Castro and all the members of the Ornithology and Animal Behaviour Laboratory-OYCA of Universidad del Valle for their invaluable support in the field.We sincerely thank the anonymous re-viewers for their invaluable feedback and contributions to our manuscript.
基金supported by the following research grant.The Creative Group Fund of National Natural Science Foundation of China(Grant no.22021005)the Fund of National Natural Science Foundation of China(Grant no.22075037)HEC for National Research Program for Universities(NRPU)Project no.14840.
文摘Anion exchange membrane(AEM)fuel cells require membranes with a balance of high conductivity and durability.In this work,a novel bi-crown-ether modified piperidine structure was designed and synthesized,which was then introduced into the side chain of poly(arylene piperidinium),making a unique bi-crown-ether modified bi-piperidinium side chain grafted polymer for AEM fabrication.The double crown ether units enhanced cation–water interactions and promoted microphase separation,thereby forming efficient hydroxide ion transport channels.The resulting membrane exhibited high water uptake,well-defined ion clusters,and a hydroxide conductivity of 123 mS cm^(-1) at 80℃ with an ion exchange capacity(IEC)of 1.56 mmol g^(-1).After alkaline treatment in 1 M NaOH at 80℃ for 960 h,the membrane retained~85%of its initial conductivity,demonstrating excellent chemical stability.In H2/O2 fuel cell tests at 60℃ ,the membrane achieved a peak power density of 558 mW cm-2 at 1040 mA cm-2.These findings highlight the potential of bi-crown-ether modified piperidinium side chain grafting as an effective strategy to enhance ion conduction properties of AEMs for fuel cell applications.
基金supported by the Scientific Grant Agency of Ministry of Education,Science,Research and Sport of the Slovak Republic (project VEGA 1/0183/25)by the Slovak Research and Development Agency under the Contract No. APVV-21-0199 and APVV-19-0183
文摘In permanently uneven-aged forests, continuous ingrowth of recruitment into higher stand layers is a critical process for the formation and maintenance of differentiated stand structures. This study analyses the abundance and diversity of recruitment(diameter at breast high(DBH) 0.1–4 cm) across 241 research plots in 11 structurally differentiated Norway spruce(silver fir)-dominated forest stands distributed at altitudes between 500 and 1,440 m a.s.l. The influence of light conditions and lateral competition characteristics on the height increment and crown architecture of recruitment was investigated in detail for 352 Norway spruce and 361 silver fir trees. Light-related variables were confirmed to directly affect the recruitment distribution only to a limited extent. Under relatively low light conditions in montane stands, silver fir reached higher height increments than Norway spruce. The better adaptation of silver fir to shaded conditions was reflected also in its higher apical dominance ratio compared to Norway spruce. The height increment and apical dominance ratio of Norway spruce and silver fir recruitment were positively correlated with indirect radiation, DBH, and relative crown length(RCL), but not with lateral competition. These results confirm that the regulation of light conditions in permanently unevenaged stands is crucial for the growth dynamics of recruitment, as well as for the future proportions of Norway spruce and silver fir in mixed, structurally diverse stands.
基金supported by the Young Scientists Fund of the National Key R&D Program of China(No.2022YFD2201800)the Youth Science Fund Program of National Natural Science Foundation of China(No.32301581)+2 种基金the Joint Funds for Regional Innovation and Development of the National Natural Science Foundation of China(No.U21A20244)the China Postdoctoral Science Foundation(No.2024M750383)the Heilongjiang Touyan Innovation Team Program(Technology Development Team for High-Efficiency Silviculture of Forest Resources).
文摘Branch size is a crucial characteristic,closely linked to both tree growth and wood quality.A review of existing branch size models reveals various approaches,but the ability to estimate branch diameter and length within the same whorl remains underexplored.In this study,a total of 77 trees were sampled from Northeast China to model the vertical distribution of branch diameter and length within each whorl along the crown.Several commonly used functions were taken as the alternative model forms,and the quantile regression method was employed and compared with the classical two-step modeling approach.The analysis incorporated stand,tree,and competition factors,with a particular focus on how these factors influence branches of varying sizes.The modified Weibull function was chosen as the optimal model,due to its excellent performance across all quantiles.Eight quantile regression curves(ranging from 0.20 to 0.85)were combined to predict branch diameter,while seven curves(ranging from 0.20 to 0.80)were used for branch length.The results showed that the quantile regression method outperformed the classical approach at model fitting and validation,likely due to its ability to estimate different rates of change across the entire branch size distribution.Lager branches in each whorl were more sensitive to changes in DBH,crown length(CL),crown ratio(CR)and dominant tree height(H_(dom)),while slenderness(HDR)more effectively influenced small and medium-sized branches.The effect of stand basal area(BAS)was relatively consistent across different branch sizes.The findings indicate that quantile regression is a good way not only a more accurate method for predicting branch size but also a valuable tool for understanding how branch growth responds to stand and tree factors.The models developed in this study are prepared to be further integrated into tree growth and yield simulation system,contributing to the assessment and promotion of wood quality.
基金supported by the European Union and the Romanian Government through the Competitiveness Operational Programme 2014–2020, under the project“Increasing the economic competitiveness of the forestry sector and the quality of life through knowledge transfer,technology and CDI skills”(CRESFORLIFE),ID P 40 380/105506, subsidiary contract no. 17/2020partially by the FORCLIMSOC Nucleu Programme (Contract 12N/2023)+2 种基金project PN 23090101CresPerfInst project (Contract 34PFE/December 30, 2021)“Increasing the institutional capacity and performance of INCDS ‘Marin Drǎcea’in RDI activities-CresPer”LM was financially supported by the Research Council of Finland's flagship ecosystem for Forest-Human-Machine Interplay–Building Resilience, Redefining Value Networks and Enabling Meaningful Experiences (UNITE)(decision number 357909)
文摘In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.Instead of building univariate models for each response variable,we employed a multivariate approach using seemingly unrelated mixed-effects models.These models incorporated variables related to species mixture,tree and stand size,competition,and stand structure.With the inclusion of additional variables in the multivariate seemingly unrelated mixed-effects models,the accuracy of the height prediction models improved by over 10% for all species,whereas the improvement in the crown length models was considerably smaller.Our findings indicate that trees in mixed stands tend to have shorter heights but longer crowns than those in pure stands.We also observed that trees in homogeneous stand structures have shorter crown lengths than those in heterogeneous stands.By employing a multivariate mixed-effects modelling framework,we were able to perform cross-model random-effect predictions,leading to a significant increase in accuracy when both responses were used to calibrate the model.In contrast,the improvement in accuracy was marginal when only height was used for calibration.We demonstrate how multivariate mixed-effects models can be effectively used to develop multi-response allometric models that can be easily calibrated with a limited number of observations while simultaneously achieving better-aligned projections.
基金supported by Returned Overseas Scholar Foundation of Hebei Province(Grant No.C20210321)Natural Science Foundation of Hebei Province(Grant No.E2021203106)S&T Program of Hebei(Grant No.236Z1019G)。
文摘An online subsection cooling method for hot rolling silicon steel was designed to achieve local adjustment of transverse roll gap.Particularly,it was able to meet the requirements of edge drop of the strip by using the features of online thermal crown.First,after the new subsection spray beam was installed at the exit of mill,the special local cooling rules were analyzed for altering the thermal crown of roll according to rolling process parameters.Meanwhile,the dynamic impact of subsection cooling on the local thermal crown could just be obtained according to the measured data.Obviously,the heat transfer coefficient was determined by different subsection cooling curves under varied rolling conditions.Secondly,the rolling rhythm and variable conditions were important dynamic factors of transient roll temperature in practical rolling process.Therefore,real-time calculation and presetting of the thermal crown were carried out to maximize special requirements of load roll gap on local strip crown.By this new method,the transient temperature and the thermal crown of roll could be quantitatively controlled online.And the practical results showed that the predicted temperature was able to match the measured value by more than 95%.Meanwhile,the adjustable range of thermal crown increased by more than 2.5 times.Finally,the qualification rate of strip edge crown has increased from the original 30%to over 70%.
基金financial support provided by the German Research Foundation,DFG,through grant number KL894/23-2 and NO 1444/1-2 as part of the Research Unit FOR2432/2the China Scholarship Council(CSC)that supports the first author with a Ph D scholarshipsupport provided by Indian partners at the Institute of Wood Science and Technology(IWST),Bengaluru。
文摘Rapid urbanization has caused significant changes along the urban-rural gradient,leading to a variety of landscapes that are mainly shaped by human activities.This dynamic interplay also influences the distribution and characteristics of trees outside forests(TOF).Understanding the pattern of these trees will support informed decision-making in urban planning,in conservation strategies,and altogether in sustainable land management practices in the urban context.In this study,we employed a deep learning-based object detection model and high resolution satellite imagery to identify 1.3 million trees with bounding boxes within a 250 km^(2)research transect spanning the urban-rural gradient of Bengaluru,a megacity in Southern India.Additionally,we developed an allometric equation to estimate diameter at breast height(DBH)from the tree crown diameter(CD)derived from the detected bounding boxes.Our study focused on analyzing variations in tree density and tree size along this gradient.The findings revealed distinct patterns:the urban domain displayed larger tree crown diameters(mean:8.87 m)and DBH(mean:43.78 cm)but having relatively low tree density(32 trees per hectare).Furthermore,with increasing distance from the city center,tree density increased,while the mean tree crown diameter and mean tree basal area decreased,showing clear differences of tree density and size between the urban and rural domains in Bengaluru.This study offers an efficient methodology that helps generating instructive insights into the dynamics of TOF along the urban-rural gradient.This may inform urban planning and management strategies for enhancing green infrastructure and biodiversity conservation in rapidly urbanizing cities like Bengaluru.
基金supported by the National Natural Science Foundation of China(Grant No.62174079)Guangdong Provincial Quantum Science Strategic Initiative(Grant No.GDZX2404006)Science,Technology and Innovation Commission of Shenzhen Municipality(Grant No.JCYJ20220530113015035)。
文摘CdSe nanoplatelets(NPLs)are promising candidates for on-chip light sources,yet their performance is hindered by surface defects and inefficient optical gain.Herein,we demonstrate that CdSeS crown passivation significantly enhances the photophysical property of CdSe NPLs.Laser spectroscopy techniques reveal suppressed electronic and hole trapping at lateral surfaces,leading to a 4.2-fold increase in photoluminescence quantum yield and a shortened emission lifetime from13.5 to 4.8 ns.In addition,amplified spontaneous emission is achieved under nanosecond pulse pumping,with thresholds of0.75 to 0.16 mJ/cm^(2)for CdSe and CdSe/CdSeS NPLs,respectively.By integrating CdSe/CdSeS NPLs with high-refractiveindex SiO2scatters,coherent random lasing is realized at a threshold of 0.21 mJ/cm^(2).These findings highlight the critical role of lateral surface passivation in optimizing optical gain and pave the way for low-cost,multifunctional nanophotonic devices.
文摘The ring has been a romantic fascination throughout the ages,embodying not only beauty and order but also harboring numerous undisclosed properties awaiting discovery.In the realm of supramolecular chemistry,macrocycles,with a cyclic structure and a central cavity like a doughnut,captivate the attention of scientists[1].In 1967,Pedersen's groundbreaking revelation that alkali metal ions could"fall into"the cavities of a cyclic ether named crown ether,even in organic solvents,unveiled a novel universe of macrocycle chemistry.Since then,numerous macrocyclic structures in nature have been discovered,isolated,and scrutinized.Drawing inspiration from nature,chemists endeavor to explore the vast potential of macrocyclic compounds by designing and synthesizing artificial macrocycles with diverse structural features and recognition properties.
基金supported by the Ministry of Agriculture,Forestry,and Fisheries of Japan (25093 C)JSPS KAKENHI (JP23H02262)
文摘The growth of Sakhalin fir(Abies sachalinen-sis)seedlings,an important forest tree species in northern Hokkaido,Japan,is significantly affected by competition from surrounding vegetation,especially evergreen dwarf bamboo.In this study,we investigated the height and root collar diameter(RCD)growth of Sakhalin fir seedlings under various degrees of cover by deciduous vegetation and evergreen dwarf bamboo.Generalized additive models were used to quantify the effects of canopy cover and forest floor cover on the relative growth rates of these two parameters.The canopy cover of Sakhalin fir seedlings had a nonlin-ear negative effect on both the height growth of seedlings in the subsequent year and the RCD growth in the current year,given the general growth pattern in this species,where height growth ceases in early summer and RCD growth con-tinues until autumn.Height growth declined sharply after the canopy cover rate exceeded 50%,while RCD growth declined rapidly between 0 and 50%canopy cover rate.The forest floor cover had a greater negative impact on RCD growth than on height growth.These results suggested that Sakhalin fir seedlings respond to vegetative competition by prioritizing height growth for light acquisition at the expense of diameter growth and possibly root growth for below-ground competition.The cover of evergreen dwarf bamboo reduced the height growth of fir seedlings significantly more than the cover of deciduous vegetation.This difference is likely due to the timing of light availability.When competing with deciduous vegetation,Sakhalin fir seedlings exposed to light during the post-snow melt and early spring before the development of the deciduous vegetation canopy can photosynthesize more effectively,leading to greater height growth.The results of this study highlighted the importance of vegetation control considering the type of vegetation for successful Sakhalin fir reforestation.Adjusting the intensity and timing of weeding based on the presence and abundance of dwarf bamboo and other competing vegetation could potentially reduce weeding costs and increase biodiversity in reforested areas.
基金financially supported by the National Natural Science Foundation of China (52174336)the Natural Science Foundation of Shandong Province (ZR2021MB051)。
文摘In recent years,with the rapid developme nt of the econo my and society,pollution of valuable metal ions in wastewater has become a major challenge to environmental sustainability.In order to solve the pollution caused by metal ions,researchers have conducted continuous re searches and explored various re mediation methods.Crown ether has attracted great attention because of its ionic radius and cavity size matching well with metal ions,which makes it have the ability to selectively complex metal ions.This unique property enables the directed removal and recovery of metal ions and makes crown ethers increasingly popular in extraction and separation processes.In this paper,the research progress of crown ethers in the extraction and separation of valuable metal ions was reviewed,with emphasis on the principles,extraction systems and the key factors affecting the extraction process.This study can provide some technical support for the application of separation and extraction of valuable metal ions by crown ether.
文摘在网格环境中,多数节点希望能够更多地使用其他节点的资源,而不愿共享本地的资源.每个理性的用户在追求自身利益最大化的同时,严重影响了协作整体的运行效率.在实际应用中,要吸引资源的拥有者加入资源协作,就必须保证其利益和安全.讨论了资源激励机制和分配机制之间的依赖与制约关系,从经济、信任角度提出自适应的信任-激励相容的资源分配机制.在网格环境中,资源供需的变化会引发价格的浮动,基于经济学的一般均衡理论,给出了资源提供者的动态价格调整策略.提供者可根据当前资源的供需和负载状况,制定自适应的信任-激励相容的分配策略ATIM(adaptive trust-incentive compatible resource allocation),遵循多贡献多分配的原则,激励节点共享出有价值的资源,最大化资源的聚合效用.在CROWN(China research and development environment over wider-area network)平台中评估了ATIM机制的效率和性能.
