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
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 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
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
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
This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and inte...This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and integration.This novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and asymmetry.The four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic,geometric and quadratic mean radius.Comparisons were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of means.The sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative measure.With a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most accurate.Calculating CPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of underestimation.For the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown asymmetry.This study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awareness among researchers and practitioners on the existence of bias in their CPA calculations and for the need to use an unbiased method in the future.Our new method is recommended for calculating CPA where at least four crown radius measurements per tree are available because that is the minimum number required for its use.展开更多
Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes.The circadian clock mechanisms in brain and peripheral tissues can osc...Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes.The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli.Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown.Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms.Teeth enamel is formed by enamel-forming cells known as ameloblasts,which are regulated and orchestrated by the circadian clock during amelogenesis.This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis.Several physiological processes are involved,including gene expression,cell morphology,metabolic changes,matrix deposition,ion transportation,and mineralization.Next,the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed.Circadian rhythm disruption can directly lead to Enamel Hypoplasia,which might also be a potential causative mechanism of amelogenesis imperfecta.Finally,future research trajectory in this field is extrapolated.It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.展开更多
In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an ...In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an approach that not only rectifies lead leakage but also places paramount importance on the attainment of rigorous interfacial passivation.Crown ethers,notably benzo-18-crown-6-ether(B18C6),were strategically integrated at the perovskite-hole transport material interface.Crown ethers exhibit a dual role:efficiently sequestering and immobilizing Pb^(2+)ions through host-vip complexation and simultaneously establishing a robust interfacial passivation layer.Selected crown ether candidates,guided by density functional theory(DFT)calculations,demonstrated proficiency in binding Pb2+ions and optimizing interfacial energetics.Photovoltaic devices incorporating these materials achieved exceptional power conversion efficiency(PCE),notably 21.7%for B18C6,underscoring their efficacy in lead binding and interfacial passivation.Analytical techniques,including time-of-flight secondary ion mass spectrometry(ToF-SIMS),ultraviolet photoelectron spectroscopy(UPS),time-resolved photoluminescence(TRPL),and transient absorption spectroscopy(TAS),unequivocally affirmed Pb^(2+)ion capture and suppression of non-radiative recombination.Notably,these PSCs maintained efficiency even after enduring 300 h of exposure to 85%relative humidity.This research underscores the transformative potential of crown ethers,simultaneously addressing lead binding and stringent interfacial passivation for sustainable PSCs poised to commercialize and advance renewable energy applications.展开更多
Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required abo...Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required about the acclimation of the crown and its effects on the basal area growth of trees at the edge of a gap.Methods This work compared trees'growth and crown structure at the edge of a transient gap,with a gap size of more than 80m^(2),with trees in the stand that were at least 30m away from the gap.A total of 249 European beeches(Fagus sylvatica L.),Norway spruces(Picea abies L.Karst),Scots pines(Pinus sylvestris L.),oaks(Quercus spp.;Quercus petraea(Matt.)Liebl.,Quercus robur L.),and silver firs(Abies alba Mill.)were examined on long-term experimental plots in southern Germany.Various crown measures were developed and calculated using high-resolution terrestrial laser scanning(TLiDAR)to capture the three-dimensional crown structures.Growth responses to edge conditions were measured based on tree rings.Using linear mixed models,we predict the basal area increment of edge trees relative to trees in the stand under wet and dry soil moisture conditions after the gap formation.Results We identified i)species-specific acclimation of the crown of edge trees after the gap formation,ii)under wet soil moisture conditions a growth increase of 25%–45%for beech,pine,and oak edge trees and growth losses of 5%–60%for spruce and fir and iii)coniferous tree species benefited from the edge position regarding their basal area increment under dry soil moisture conditions and deciduous tree species grew regardless of the soil moisture conditions at the edge of a gap.Conclusion Gaps have a species-specific effect on the habitus and growth of edge trees and can have both positive and negative impacts on silviculture.展开更多
A series of novel crown aldoxime ethers were synthesized,demonstrating notable thermal and hydrolysis stability.The showcased acid-catalyzed and photo-induced cis/trans isomerization,which enables orthogonal control o...A series of novel crown aldoxime ethers were synthesized,demonstrating notable thermal and hydrolysis stability.The showcased acid-catalyzed and photo-induced cis/trans isomerization,which enables orthogonal control over both vip complexation and the chiroptical effects of these crown aldoxime ethers,manifesting a regulation of complexation through isomerization at binding heteroatoms.展开更多
Fusarium crown rot,mainly caused by Fusarium pseudograminearum,is a destructive disease in wheat production.To establish a rapid and reliable detection method for F.peasudeograminearum,the specific PCR primer pair(Fpg...Fusarium crown rot,mainly caused by Fusarium pseudograminearum,is a destructive disease in wheat production.To establish a rapid and reliable detection method for F.peasudeograminearum,the specific PCR primer pair(Fpg-F1;R2)was designed based on the RPB sequence,and real-time fluorescence quantitative PCR(qPCR)was used to validate the efficiency of the primer.The results showed that the primer pair had high specificity and sensitivity of 100 pg of DNA.Furthermore,the qPCR system for early and rapid detection of F.peasudeograminearum had an amplification efficiency of 87.5%and correlation coefficient of 0.99,and the pathologic threshold of F.pseudograminearum in soil was determined by using this detection system.It was found that F.pseudograminearum could cause Fusarium crown rot when the DNA concentration of F.pseudograminearum in field soil exceeded 213 pg·g^(-1).Hence,the qPCR-based method we developed for F.pseudograminearum detection has the advantages of high specificity and sensitivity,and can be used for rapid and early detection of F.pseudograminearum even in field soils.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.
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.
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supported by the Natural Science Foundation of China (32071758)the Fundamental Research Funds for the Central Universities of China (No. 2572020BA01)
文摘This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and integration.This novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and asymmetry.The four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic,geometric and quadratic mean radius.Comparisons were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of means.The sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative measure.With a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most accurate.Calculating CPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of underestimation.For the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown asymmetry.This study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awareness among researchers and practitioners on the existence of bias in their CPA calculations and for the need to use an unbiased method in the future.Our new method is recommended for calculating CPA where at least four crown radius measurements per tree are available because that is the minimum number required for its use.
基金supported by grants from the National Key R&D Program of China(2022YFC2401803)the National Natural Science Foundation of China(51973004)+1 种基金the China Postdoctoral Science Foundation(2023M730116)the Peking University Medicine Sailing Program for YoungScholars’Scientific&Technological Innovation(BMU2023YFJHPY012).
文摘Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes.The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli.Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown.Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms.Teeth enamel is formed by enamel-forming cells known as ameloblasts,which are regulated and orchestrated by the circadian clock during amelogenesis.This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis.Several physiological processes are involved,including gene expression,cell morphology,metabolic changes,matrix deposition,ion transportation,and mineralization.Next,the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed.Circadian rhythm disruption can directly lead to Enamel Hypoplasia,which might also be a potential causative mechanism of amelogenesis imperfecta.Finally,future research trajectory in this field is extrapolated.It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1F1A1047203)financially supported by the Ministry of Trade,Industry and Energy(MOTIE)and Korea Institute for Advancement of Technology(KIAT)through the International Cooperative R&D program(P0026100)+1 种基金the NRF grant funded by the Korea government(MSIT)(2021R1I1A1A01061036)financial support from the NRF grant funded by the Korea government(MSIT)(RS-2023-00213920)。
文摘In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an approach that not only rectifies lead leakage but also places paramount importance on the attainment of rigorous interfacial passivation.Crown ethers,notably benzo-18-crown-6-ether(B18C6),were strategically integrated at the perovskite-hole transport material interface.Crown ethers exhibit a dual role:efficiently sequestering and immobilizing Pb^(2+)ions through host-vip complexation and simultaneously establishing a robust interfacial passivation layer.Selected crown ether candidates,guided by density functional theory(DFT)calculations,demonstrated proficiency in binding Pb2+ions and optimizing interfacial energetics.Photovoltaic devices incorporating these materials achieved exceptional power conversion efficiency(PCE),notably 21.7%for B18C6,underscoring their efficacy in lead binding and interfacial passivation.Analytical techniques,including time-of-flight secondary ion mass spectrometry(ToF-SIMS),ultraviolet photoelectron spectroscopy(UPS),time-resolved photoluminescence(TRPL),and transient absorption spectroscopy(TAS),unequivocally affirmed Pb^(2+)ion capture and suppression of non-radiative recombination.Notably,these PSCs maintained efficiency even after enduring 300 h of exposure to 85%relative humidity.This research underscores the transformative potential of crown ethers,simultaneously addressing lead binding and stringent interfacial passivation for sustainable PSCs poised to commercialize and advance renewable energy applications.
基金funded by the Bavarian Ministry of Nutrition,Agriculture and Forestry through the projects“Acclimation of Forest Trees”(grant#kliffw006)“Maintenance and Monitoring of long term experiments”(W007,grant#Gz:7831-1/874).
文摘Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required about the acclimation of the crown and its effects on the basal area growth of trees at the edge of a gap.Methods This work compared trees'growth and crown structure at the edge of a transient gap,with a gap size of more than 80m^(2),with trees in the stand that were at least 30m away from the gap.A total of 249 European beeches(Fagus sylvatica L.),Norway spruces(Picea abies L.Karst),Scots pines(Pinus sylvestris L.),oaks(Quercus spp.;Quercus petraea(Matt.)Liebl.,Quercus robur L.),and silver firs(Abies alba Mill.)were examined on long-term experimental plots in southern Germany.Various crown measures were developed and calculated using high-resolution terrestrial laser scanning(TLiDAR)to capture the three-dimensional crown structures.Growth responses to edge conditions were measured based on tree rings.Using linear mixed models,we predict the basal area increment of edge trees relative to trees in the stand under wet and dry soil moisture conditions after the gap formation.Results We identified i)species-specific acclimation of the crown of edge trees after the gap formation,ii)under wet soil moisture conditions a growth increase of 25%–45%for beech,pine,and oak edge trees and growth losses of 5%–60%for spruce and fir and iii)coniferous tree species benefited from the edge position regarding their basal area increment under dry soil moisture conditions and deciduous tree species grew regardless of the soil moisture conditions at the edge of a gap.Conclusion Gaps have a species-specific effect on the habitus and growth of edge trees and can have both positive and negative impacts on silviculture.
基金support of the National Natural Science Foundation of China (Nos.22271201,92056116,22171194,22201194)the Science & Technology Department of Sichuan Province (Nos.2022YFH0095 and 2021ZYD0052)the Fundamental Research Funds for the Central Universities (No.20826041D4117)。
文摘A series of novel crown aldoxime ethers were synthesized,demonstrating notable thermal and hydrolysis stability.The showcased acid-catalyzed and photo-induced cis/trans isomerization,which enables orthogonal control over both vip complexation and the chiroptical effects of these crown aldoxime ethers,manifesting a regulation of complexation through isomerization at binding heteroatoms.
基金Yong Science and Technology Talent of AAAS(QNYC-201911)。
文摘Fusarium crown rot,mainly caused by Fusarium pseudograminearum,is a destructive disease in wheat production.To establish a rapid and reliable detection method for F.peasudeograminearum,the specific PCR primer pair(Fpg-F1;R2)was designed based on the RPB sequence,and real-time fluorescence quantitative PCR(qPCR)was used to validate the efficiency of the primer.The results showed that the primer pair had high specificity and sensitivity of 100 pg of DNA.Furthermore,the qPCR system for early and rapid detection of F.peasudeograminearum had an amplification efficiency of 87.5%and correlation coefficient of 0.99,and the pathologic threshold of F.pseudograminearum in soil was determined by using this detection system.It was found that F.pseudograminearum could cause Fusarium crown rot when the DNA concentration of F.pseudograminearum in field soil exceeded 213 pg·g^(-1).Hence,the qPCR-based method we developed for F.pseudograminearum detection has the advantages of high specificity and sensitivity,and can be used for rapid and early detection of F.pseudograminearum even in field soils.
