Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element metho...Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element method,often relied on simplified twodimensional models due to theoretical complexities.Consequently,these simplified models inadequately represent the mechanical properties of nanomaterials and fail to capture the substantial impact of surface effects,particularly the curvature dependence of nanosurfaces.This study applies the principle of minimum energy and leverages the Steigmann-Ogden surface theory of nanomaterials to formulate a novel finite element surface element that comprehensively accounts for surface effects.We conducted an analysis of the stress distribution and deformation characteristics of four typical 2D and 3D nanomaterial models.The accuracy of the developed surface element and finite element calculation method was verified through comparison with established references.The resulting finite element model provides a robust and compelling scientific approach for accurately predicting the mechanical performance of nanomaterials.展开更多
In this study,we performed a systematic analysis of the multiplicity dependence of hadron production at mid-rapidity(|y|<0.5),ranging from the light to the charm sector in proton-proton(pp)collisions at√s=13 TeV.T...In this study,we performed a systematic analysis of the multiplicity dependence of hadron production at mid-rapidity(|y|<0.5),ranging from the light to the charm sector in proton-proton(pp)collisions at√s=13 TeV.This study used a multi-phase transport(AMPT)model coupled with PYTHIA8 initial conditions.We investigated the baryon-to-meson and the strange-to-non-strange meson ratios varying with the charged particle density.By tuning the coalescence parameters,the AMPT model provides a reasonable description of the experimental data for the inclusive production of both light and charm hadrons,comparable to the string fragmentation model calculations with color reconnection effects.Additionally,we analyzed the relative production of hadrons by examining the self-normalized particle ratios as a function of the charged hadron density.Our findings suggest that parton evolution effects and the coalescence hadronization process in the AMPT model result in a strong flavor hierarchy in the multiplicity dependence of the baryon-to-meson ratio.Furthermore,our investigation of the p_(T) differential double ratio of the baryon-to-meson fraction between high-and low-multiplicity events revealed distinct modifications to the flavor associated baryon-to-meson ratio p_(T) shape in high-multiplicity events when comparing the coalescence hadronization model to the color reconnection model.These observations highlight the importance of understanding the hadronization process in high-energy pp collisions through comprehensive multiplicity-dependent multi-flavor analysis.展开更多
OBJECTIVE:To observe the effect of different acupuncture frequencies on the abstinence rate which could be used as a reference for optimizing acupuncture cessation programs.METHODS:From July 2018 to June 2022,a total ...OBJECTIVE:To observe the effect of different acupuncture frequencies on the abstinence rate which could be used as a reference for optimizing acupuncture cessation programs.METHODS:From July 2018 to June 2022,a total of 220 smokers were recruited based on inclusion criteria and randomly divided into the high-frequency acupuncture group(HF group,n=110):5 times a week from the 1st to the 4th week,from weeks 5 to 8,three times a week and the low-frequency acupuncture group(LF group,n=110):3 times a week from the 1st to the 4th week,from weeks 5 to 8,twice a week,then treated for 8 weeks and followup at 1 month in Beijing.RESULTS:In total,162 subjects completed the whole study with a drop-out rate of 20.45%.The expiratory CO point abstinence rate was HF group 53/110(48.18%)vs LF group 41/110(37.27%)in Week 8(P=0.102)and HF group 46/110(41.82%)vs LF group 45/110(40.91%)in Week 12(P=0.891)and the HF acupuncture and LF acupuncture were nearly equal in the 8-week abstinence rate.In addition,both HF and LF acupuncture significantly reduced Fagerstr?m test for nicotine dependence scale(FTND)scores(P<0.05),Minnesota nicotine withdrawal scale(MNWS)scores(P<0.05),and Brief Questionnaire of Smoking Urges scale(QSU-Brief)scores(P<0.05),but HF acupuncture showed some superiority over LF acupuncture in relieving patients'smoking cravings(P<0.05).CONCLUSIONS:The study initially showed that both high-frequency acupuncture and low-frequency acupuncture treatment were safe and effective on smoking cessation for 8 weeks,but high-frequency acupuncture was advantageous in reducing smoking cravings.More accurate acupuncture frequency needs to be validated through larger clinical studies to optimize acupuncture smoking cessation programs.展开更多
Objective:To evaluate the global liter-ature output on the relationship between brain-derived neurotrophic factor(BDNF)and cognitive function in al-cohol dependence syndrome using bibliometric methods and explore the ...Objective:To evaluate the global liter-ature output on the relationship between brain-derived neurotrophic factor(BDNF)and cognitive function in al-cohol dependence syndrome using bibliometric methods and explore the status and trends in this field.Method:The literature on the application of BDNF in cognitive impairment caused by alcohol dependence syndrome published from 1995 to 2023 were retrieved from Web of Science,and the relevant information(publication characteristics,country and institution,author,number of publications,citation,journal and research field,corresponding author,key words,etc.)was recorded.The bibliometrix R package was used for quantitative and qualitative analysis of publication output and author contributions.Result:A total of 99 articles were included.The overall number of publications in this field has increased over time.The countries and institutions that contributed the most to the field were the United States and the Academy of Medical Sciences of Iranian universities,respectively.Most of the authors were from the United States,followed by Spain,China,and Iran.Ceccanti M,Fiore M were the most productive authors.Publications with Ceccanti M had the highest h-index.The most cited reference author is Haenninen H(227 citations),and the number one published journal is Alcohol.Most articles were published in 2020(n=12)and 2022(n=11),followed by 2019 and 2021(n=10).The corresponding author has the largest number of publications from the United States,and more publications from a single country tend to have more cooperation from other countries.BDNF and alcohol appeared more frequently in various keyword clouds.However,significant differences remained in the author keyword cloud,keyword plus word cloud,and paper topic word cloud.Conclusion:BDNF has great potential in the application of cognitive dysfunction caused by alcohol dependence syndrome.Bibliometric methods and data visualization techniques can help understand the current state of research progress and enable relevant scholars and practitioners to predict the development trends in this field.展开更多
The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradua...The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradually increase their mobility, leave their parents, disperse from their natal site, and respond to the challenges of new environments. Characterizing these post-fledging movements and space use is essential for understanding juvenile survival strategies and devising targeted conservation measures. The Crested Ibis (Nipponia nippon), an endangered species and a highly protected animals at the national level in China, has seen limited research on its post-fledging movements and space use. From 2015 to 2023, we utilized biologgers, combined with field surveys, to study the movement and space use characteristics of 37 fledglings in Hanzhong City, Shaanxi Province, China, over a two-month post-fledging period. We quantified changes in activity levels (based on overall dynamic body acceleration), independence timing, onset of post-fledging dispersal, habitat selection, and daily activity rhythms after independence. Our results revealed individuals began independent living 26.23 ± 2.34 days post-fledging and onset of dispersal at 25.58 ± 2.33 days, with a range area at the natal of 2.08 ± 0.56 km^(2). The initial 30 days post-fledging are characterized as an ontogenetic phase marked by a rapid increase in body activity level. Fledglings preferred paddy fields during the independent period rather than the forests they relied on before independence. Interestingly, the daily activity rhythm, particularly foraging behavior, peaked at noon—contrasting with the expected morning and evening activity peaks—likely as an adaptation to avoid periods of peak human activity. Additionally, drowning, collisions, and predation in paddy fields are noteworthy causes of fledgling mortality. Consequently, we recommend protecting a 2-km^(2) area around the nest site for at least two-month post-fledging, implementing safety measures around power lines and cesspools. Additionally, reducing human disturbances near foraging habitats and expanding space within paddy fields would help mitigate survival pressures on fledglings.展开更多
In recent years,skeleton-based action recognition has made great achievements in Computer Vision.A graph convolutional network(GCN)is effective for action recognition,modelling the human skeleton as a spatio-temporal ...In recent years,skeleton-based action recognition has made great achievements in Computer Vision.A graph convolutional network(GCN)is effective for action recognition,modelling the human skeleton as a spatio-temporal graph.Most GCNs define the graph topology by physical relations of the human joints.However,this predefined graph ignores the spatial relationship between non-adjacent joint pairs in special actions and the behavior dependence between joint pairs,resulting in a low recognition rate for specific actions with implicit correlation between joint pairs.In addition,existing methods ignore the trend correlation between adjacent frames within an action and context clues,leading to erroneous action recognition with similar poses.Therefore,this study proposes a learnable GCN based on behavior dependence,which considers implicit joint correlation by constructing a dynamic learnable graph with extraction of specific behavior dependence of joint pairs.By using the weight relationship between the joint pairs,an adaptive model is constructed.It also designs a self-attention module to obtain their inter-frame topological relationship for exploring the context of actions.Combining the shared topology and the multi-head self-attention map,the module obtains the context-based clue topology to update the dynamic graph convolution,achieving accurate recognition of different actions with similar poses.Detailed experiments on public datasets demonstrate that the proposed method achieves better results and realizes higher quality representation of actions under various evaluation protocols compared to state-of-the-art methods.展开更多
Firm entry plays an important role in the industrial transformation of mature resource-based cities.This study describes the industrial evolution of resource-based cities at the firm level and uses kernel density esti...Firm entry plays an important role in the industrial transformation of mature resource-based cities.This study describes the industrial evolution of resource-based cities at the firm level and uses kernel density estimation and econometric models to study the spatiotemporal characteristics and determinants of new firm entry from 2011 to 2019 in four mature resource-based cities.The results are summarized as follows:(1)New resource-based firm entry tends to be natural resource-oriented and path-dependent.The new non-resource-based firms show a high concentration in central urban areas,and the industry types are mainly wholesale and retail of resource products,cultural tourism,and equipment manufacturing.(2)Heterogeneous incumbent firms affect firm entry differently.Affected by competition and agglomeration effects,resource-based and non-resource-based incumbent firms have negative and positive impacts on new resource-based firm entry,respectively.Resourcebased incumbent firm agglomeration positively influences new non-resource-based firm entry.(3)Besides incumbent firms,firm entry can also be affected by multidimensional factors,such as factor costs,economic environment,and institutional environment.Research on new firm entry can better reveal the path dependence and path creation process of the industrial development of resource-based cities from a micro-perspective.展开更多
The recent discovery of field emission devices based on one-dimensional nanostructures has attracted much interest in emerging applications on next-generation flat panel displays,molecule-based sensors,and so forth.To...The recent discovery of field emission devices based on one-dimensional nanostructures has attracted much interest in emerging applications on next-generation flat panel displays,molecule-based sensors,and so forth.To achieve a comprehensive understanding of surface potentials at the nano-emitters during the tunneling process,in this study we systematically investigated the image potentials of single-walled boron nitride nanotubes with different edges,diameters and lengths in the frame of a composite first-principles calculation.The image potentials of zigzag single-walled boron nitride nanotubes are found to be dependent on the non-equivalent sides.Only the image potentials of isolated armchair single-walled boron nitride nanotube can be well fitted with the image potential of an ideal metal sphere of a size comparable to the tube diameter.On the contrary,the image potentials of zigzag and grounded armchair single-walled boron nitride nanotubes exhibit a strong length-dependence characteristic and are significantly different from that of an ideal metal sphere,which originates from the significant axial symmetry breaking of induced charge at the tip for the long tube.The correlation between the testing electron and electronic structure of single-walled boron nitride nanotube has also been discussed.展开更多
In this paper,we study systems of conservation laws in one space dimension.We prove that for classical solutions in Sobolev spaces H^(s),with s>3/2,the data-to-solution map is not uniformly continuous.Our results a...In this paper,we study systems of conservation laws in one space dimension.We prove that for classical solutions in Sobolev spaces H^(s),with s>3/2,the data-to-solution map is not uniformly continuous.Our results apply to all nonlinear scalar conservation laws and to nonlinear hyperbolic systems of two equations.展开更多
Magnesium alloys usually exhibit poor ductility attributed to their intrinsic hexagonal close-packed(hcp)structure,which fails to provide sufficient independent slip systems for homogeneous deformation.Here we demonst...Magnesium alloys usually exhibit poor ductility attributed to their intrinsic hexagonal close-packed(hcp)structure,which fails to provide sufficient independent slip systems for homogeneous deformation.Here we demonstrate that multiple deformation mechanisms can be activated with increasing tensile strain in a fine-grained Mg-3Gd with a weak basal texture.<c+a>slip,tension twinning and compression/double twinning exhibit a high orientation dependence at an early stage of deformation,whereas the orientation dependence becomes less obvious with further increasing strain.The high work hardening rate at the strain of 2%–5%is accompanied by the significant increase of<c+a>slip and tension twinning activities.The fine microstructure strongly restricts the activation and growth of twinning,resulting in a slow exhaust of tension twinning and thin compression twins.The restriction of twinning and the activation of profuse<c+a>slip near grain/twin boundaries,relaxing the stress concentration,sustain the homogeneous deformation to a high strain.展开更多
In the context of the rapidly growing demand for green investments and the need to combat climate change,this study contributes to the emerging literature on green investments by exploring the time-frequency connected...In the context of the rapidly growing demand for green investments and the need to combat climate change,this study contributes to the emerging literature on green investments by exploring the time-frequency connectedness between green bonds(GBs)and green equities.Specifically,we examine the degree of connection between GBs and green equities,the extent to which these markets influence each other,and which one is the primary net transmitter versus the net receiver of shocks under diverse market conditions.To accomplish these objectives,we use the wavelet-based Quantile-on-Quantile(QQ),dynamic conditional correlation(DCC),portfolio implications,and Quantile VAR approaches.The results show that GBs and green equities have a strong positive connection,depending on time and frequency domains.However,a negative association between GBs and green equities is observed during periods of crisis,highlighting GBs’ability to hedge green equity portfolios.The portfolio strategies demonstrate that investors require to invest in the Green Economy equity and S&P GB portfolio to reach the highest level of hedging effectiveness.The findings further imply that the Global Water Equity Index transmits the highest spillover to other green assets,while the Green Economy Equity Index receives the most spillover from other assets.The pairwise volatility connectivity reveals that most pairs have minimal quantile dependence,indicating the potential for diversification across the GB and green equity pairs.These findings have significant implications for investors and policymakers concerned with green investments and climate change mitigation.展开更多
基金supported by the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant No.2023ZB397)the Project funded by China Postdoctoral Science Foundation (Grant No.2023M732986).
文摘Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element method,often relied on simplified twodimensional models due to theoretical complexities.Consequently,these simplified models inadequately represent the mechanical properties of nanomaterials and fail to capture the substantial impact of surface effects,particularly the curvature dependence of nanosurfaces.This study applies the principle of minimum energy and leverages the Steigmann-Ogden surface theory of nanomaterials to formulate a novel finite element surface element that comprehensively accounts for surface effects.We conducted an analysis of the stress distribution and deformation characteristics of four typical 2D and 3D nanomaterial models.The accuracy of the developed surface element and finite element calculation method was verified through comparison with established references.The resulting finite element model provides a robust and compelling scientific approach for accurately predicting the mechanical performance of nanomaterials.
基金supported by the National Natural Science Foundation of China(Nos.12205259 and 12147101)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)with No.G1323523064.
文摘In this study,we performed a systematic analysis of the multiplicity dependence of hadron production at mid-rapidity(|y|<0.5),ranging from the light to the charm sector in proton-proton(pp)collisions at√s=13 TeV.This study used a multi-phase transport(AMPT)model coupled with PYTHIA8 initial conditions.We investigated the baryon-to-meson and the strange-to-non-strange meson ratios varying with the charged particle density.By tuning the coalescence parameters,the AMPT model provides a reasonable description of the experimental data for the inclusive production of both light and charm hadrons,comparable to the string fragmentation model calculations with color reconnection effects.Additionally,we analyzed the relative production of hadrons by examining the self-normalized particle ratios as a function of the charged hadron density.Our findings suggest that parton evolution effects and the coalescence hadronization process in the AMPT model result in a strong flavor hierarchy in the multiplicity dependence of the baryon-to-meson ratio.Furthermore,our investigation of the p_(T) differential double ratio of the baryon-to-meson fraction between high-and low-multiplicity events revealed distinct modifications to the flavor associated baryon-to-meson ratio p_(T) shape in high-multiplicity events when comparing the coalescence hadronization model to the color reconnection model.These observations highlight the importance of understanding the hadronization process in high-energy pp collisions through comprehensive multiplicity-dependent multi-flavor analysis.
基金the Fund of Science and Technology Innovation Project of Chinese Academy of Chinese Medical Sciences Project:Self-service Acupuncture Smoking Cessation Research and Development(No.CI2021A03506)Fund of Capital Health Development Special Research Project:Research on Development and Clinical Applicalion of Wrist Acupuncture Smoking Cessation Instrument(No.2022-1-4281)。
文摘OBJECTIVE:To observe the effect of different acupuncture frequencies on the abstinence rate which could be used as a reference for optimizing acupuncture cessation programs.METHODS:From July 2018 to June 2022,a total of 220 smokers were recruited based on inclusion criteria and randomly divided into the high-frequency acupuncture group(HF group,n=110):5 times a week from the 1st to the 4th week,from weeks 5 to 8,three times a week and the low-frequency acupuncture group(LF group,n=110):3 times a week from the 1st to the 4th week,from weeks 5 to 8,twice a week,then treated for 8 weeks and followup at 1 month in Beijing.RESULTS:In total,162 subjects completed the whole study with a drop-out rate of 20.45%.The expiratory CO point abstinence rate was HF group 53/110(48.18%)vs LF group 41/110(37.27%)in Week 8(P=0.102)and HF group 46/110(41.82%)vs LF group 45/110(40.91%)in Week 12(P=0.891)and the HF acupuncture and LF acupuncture were nearly equal in the 8-week abstinence rate.In addition,both HF and LF acupuncture significantly reduced Fagerstr?m test for nicotine dependence scale(FTND)scores(P<0.05),Minnesota nicotine withdrawal scale(MNWS)scores(P<0.05),and Brief Questionnaire of Smoking Urges scale(QSU-Brief)scores(P<0.05),but HF acupuncture showed some superiority over LF acupuncture in relieving patients'smoking cravings(P<0.05).CONCLUSIONS:The study initially showed that both high-frequency acupuncture and low-frequency acupuncture treatment were safe and effective on smoking cessation for 8 weeks,but high-frequency acupuncture was advantageous in reducing smoking cravings.More accurate acupuncture frequency needs to be validated through larger clinical studies to optimize acupuncture smoking cessation programs.
基金supported by grants from the Scientific Research Fund project of Education Department of Yunnan Province(2024J0314)Joint Special Project on Basic Research of Yunnan Provincial Department of Science and Technology and Kunming Medical University(202501AY070001-206).
文摘Objective:To evaluate the global liter-ature output on the relationship between brain-derived neurotrophic factor(BDNF)and cognitive function in al-cohol dependence syndrome using bibliometric methods and explore the status and trends in this field.Method:The literature on the application of BDNF in cognitive impairment caused by alcohol dependence syndrome published from 1995 to 2023 were retrieved from Web of Science,and the relevant information(publication characteristics,country and institution,author,number of publications,citation,journal and research field,corresponding author,key words,etc.)was recorded.The bibliometrix R package was used for quantitative and qualitative analysis of publication output and author contributions.Result:A total of 99 articles were included.The overall number of publications in this field has increased over time.The countries and institutions that contributed the most to the field were the United States and the Academy of Medical Sciences of Iranian universities,respectively.Most of the authors were from the United States,followed by Spain,China,and Iran.Ceccanti M,Fiore M were the most productive authors.Publications with Ceccanti M had the highest h-index.The most cited reference author is Haenninen H(227 citations),and the number one published journal is Alcohol.Most articles were published in 2020(n=12)and 2022(n=11),followed by 2019 and 2021(n=10).The corresponding author has the largest number of publications from the United States,and more publications from a single country tend to have more cooperation from other countries.BDNF and alcohol appeared more frequently in various keyword clouds.However,significant differences remained in the author keyword cloud,keyword plus word cloud,and paper topic word cloud.Conclusion:BDNF has great potential in the application of cognitive dysfunction caused by alcohol dependence syndrome.Bibliometric methods and data visualization techniques can help understand the current state of research progress and enable relevant scholars and practitioners to predict the development trends in this field.
基金funded by the National Natural Science Foundation of China(No.32270554,32400400).
文摘The post-fledging period, extending from fledging to independence, is a crucial life stage characterized by high mortality due to fledglings' limited mobility and inexperience. During this stage, fledglings gradually increase their mobility, leave their parents, disperse from their natal site, and respond to the challenges of new environments. Characterizing these post-fledging movements and space use is essential for understanding juvenile survival strategies and devising targeted conservation measures. The Crested Ibis (Nipponia nippon), an endangered species and a highly protected animals at the national level in China, has seen limited research on its post-fledging movements and space use. From 2015 to 2023, we utilized biologgers, combined with field surveys, to study the movement and space use characteristics of 37 fledglings in Hanzhong City, Shaanxi Province, China, over a two-month post-fledging period. We quantified changes in activity levels (based on overall dynamic body acceleration), independence timing, onset of post-fledging dispersal, habitat selection, and daily activity rhythms after independence. Our results revealed individuals began independent living 26.23 ± 2.34 days post-fledging and onset of dispersal at 25.58 ± 2.33 days, with a range area at the natal of 2.08 ± 0.56 km^(2). The initial 30 days post-fledging are characterized as an ontogenetic phase marked by a rapid increase in body activity level. Fledglings preferred paddy fields during the independent period rather than the forests they relied on before independence. Interestingly, the daily activity rhythm, particularly foraging behavior, peaked at noon—contrasting with the expected morning and evening activity peaks—likely as an adaptation to avoid periods of peak human activity. Additionally, drowning, collisions, and predation in paddy fields are noteworthy causes of fledgling mortality. Consequently, we recommend protecting a 2-km^(2) area around the nest site for at least two-month post-fledging, implementing safety measures around power lines and cesspools. Additionally, reducing human disturbances near foraging habitats and expanding space within paddy fields would help mitigate survival pressures on fledglings.
基金supported in part by the 2023 Key Supported Project of the 14th Five Year Plan for Education and Science in Hunan Province with No.ND230795.
文摘In recent years,skeleton-based action recognition has made great achievements in Computer Vision.A graph convolutional network(GCN)is effective for action recognition,modelling the human skeleton as a spatio-temporal graph.Most GCNs define the graph topology by physical relations of the human joints.However,this predefined graph ignores the spatial relationship between non-adjacent joint pairs in special actions and the behavior dependence between joint pairs,resulting in a low recognition rate for specific actions with implicit correlation between joint pairs.In addition,existing methods ignore the trend correlation between adjacent frames within an action and context clues,leading to erroneous action recognition with similar poses.Therefore,this study proposes a learnable GCN based on behavior dependence,which considers implicit joint correlation by constructing a dynamic learnable graph with extraction of specific behavior dependence of joint pairs.By using the weight relationship between the joint pairs,an adaptive model is constructed.It also designs a self-attention module to obtain their inter-frame topological relationship for exploring the context of actions.Combining the shared topology and the multi-head self-attention map,the module obtains the context-based clue topology to update the dynamic graph convolution,achieving accurate recognition of different actions with similar poses.Detailed experiments on public datasets demonstrate that the proposed method achieves better results and realizes higher quality representation of actions under various evaluation protocols compared to state-of-the-art methods.
基金National Natural Science Foundation of China,No.72050001。
文摘Firm entry plays an important role in the industrial transformation of mature resource-based cities.This study describes the industrial evolution of resource-based cities at the firm level and uses kernel density estimation and econometric models to study the spatiotemporal characteristics and determinants of new firm entry from 2011 to 2019 in four mature resource-based cities.The results are summarized as follows:(1)New resource-based firm entry tends to be natural resource-oriented and path-dependent.The new non-resource-based firms show a high concentration in central urban areas,and the industry types are mainly wholesale and retail of resource products,cultural tourism,and equipment manufacturing.(2)Heterogeneous incumbent firms affect firm entry differently.Affected by competition and agglomeration effects,resource-based and non-resource-based incumbent firms have negative and positive impacts on new resource-based firm entry,respectively.Resourcebased incumbent firm agglomeration positively influences new non-resource-based firm entry.(3)Besides incumbent firms,firm entry can also be affected by multidimensional factors,such as factor costs,economic environment,and institutional environment.Research on new firm entry can better reveal the path dependence and path creation process of the industrial development of resource-based cities from a micro-perspective.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.12004083 and 51972069)the Science and Technology Projects in Guangzhou(Grant Nos.202102020350 and 202102010470)+7 种基金the National Key R&D Program of China(Grant No.2016YFB0200800)the Opening Project of Joint Laboratory for Planetary Science and Supercomputing(Grant No.CSYYGS-QT-2024-14)the Key-Area Research and Development Program of Guangdong Province(Grant No.2019B030330001)the College Students Innovation and Entrepreneurship Training Program of Guangdong Province(Grant No.S202311078133)Key Discipline of Materials Science and Engineering,Bureau of Education of Guangzhou(Grant No.202255464)the National Supercomputer Center in Guangzhouthe National Supercomputing Center in Chengduthe Network Center of Guangzhou University。
文摘The recent discovery of field emission devices based on one-dimensional nanostructures has attracted much interest in emerging applications on next-generation flat panel displays,molecule-based sensors,and so forth.To achieve a comprehensive understanding of surface potentials at the nano-emitters during the tunneling process,in this study we systematically investigated the image potentials of single-walled boron nitride nanotubes with different edges,diameters and lengths in the frame of a composite first-principles calculation.The image potentials of zigzag single-walled boron nitride nanotubes are found to be dependent on the non-equivalent sides.Only the image potentials of isolated armchair single-walled boron nitride nanotube can be well fitted with the image potential of an ideal metal sphere of a size comparable to the tube diameter.On the contrary,the image potentials of zigzag and grounded armchair single-walled boron nitride nanotubes exhibit a strong length-dependence characteristic and are significantly different from that of an ideal metal sphere,which originates from the significant axial symmetry breaking of induced charge at the tip for the long tube.The correlation between the testing electron and electronic structure of single-walled boron nitride nanotube has also been discussed.
文摘In this paper,we study systems of conservation laws in one space dimension.We prove that for classical solutions in Sobolev spaces H^(s),with s>3/2,the data-to-solution map is not uniformly continuous.Our results apply to all nonlinear scalar conservation laws and to nonlinear hyperbolic systems of two equations.
基金This project has received funding from the National Key Research and Development Program(2021YFB3702100)TY was supported by a research grant(VIL50197)from VILLUM FONDEN。
文摘Magnesium alloys usually exhibit poor ductility attributed to their intrinsic hexagonal close-packed(hcp)structure,which fails to provide sufficient independent slip systems for homogeneous deformation.Here we demonstrate that multiple deformation mechanisms can be activated with increasing tensile strain in a fine-grained Mg-3Gd with a weak basal texture.<c+a>slip,tension twinning and compression/double twinning exhibit a high orientation dependence at an early stage of deformation,whereas the orientation dependence becomes less obvious with further increasing strain.The high work hardening rate at the strain of 2%–5%is accompanied by the significant increase of<c+a>slip and tension twinning activities.The fine microstructure strongly restricts the activation and growth of twinning,resulting in a slow exhaust of tension twinning and thin compression twins.The restriction of twinning and the activation of profuse<c+a>slip near grain/twin boundaries,relaxing the stress concentration,sustain the homogeneous deformation to a high strain.
基金supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea(NRF-2022S1A5A2A01038422).
文摘In the context of the rapidly growing demand for green investments and the need to combat climate change,this study contributes to the emerging literature on green investments by exploring the time-frequency connectedness between green bonds(GBs)and green equities.Specifically,we examine the degree of connection between GBs and green equities,the extent to which these markets influence each other,and which one is the primary net transmitter versus the net receiver of shocks under diverse market conditions.To accomplish these objectives,we use the wavelet-based Quantile-on-Quantile(QQ),dynamic conditional correlation(DCC),portfolio implications,and Quantile VAR approaches.The results show that GBs and green equities have a strong positive connection,depending on time and frequency domains.However,a negative association between GBs and green equities is observed during periods of crisis,highlighting GBs’ability to hedge green equity portfolios.The portfolio strategies demonstrate that investors require to invest in the Green Economy equity and S&P GB portfolio to reach the highest level of hedging effectiveness.The findings further imply that the Global Water Equity Index transmits the highest spillover to other green assets,while the Green Economy Equity Index receives the most spillover from other assets.The pairwise volatility connectivity reveals that most pairs have minimal quantile dependence,indicating the potential for diversification across the GB and green equity pairs.These findings have significant implications for investors and policymakers concerned with green investments and climate change mitigation.
