This study semi-quantitatively analyzed the effects of leukoaraiosis.Patients with moderate or severe lacunar infarction were found to exhibit low scores on the Montreal Cognitive Assessment Scale （F=12.02,P=0.000）,...This study semi-quantitatively analyzed the effects of leukoaraiosis.Patients with moderate or severe lacunar infarction were found to exhibit low scores on the Montreal Cognitive Assessment Scale （F=12.02,P=0.000）,and prolonged P300 Cz2.0 latency （F=16.04,P=0.000）.Correlation analysis revealed that the occurrence of leukoaraiosis was negatively correlated with Montreal Cognitive Assessment scores （r=-0.416,P=0.000）,and positively correlated with P300 Cz2.0 latency （r=0.538,P=0.000）.These findings indicate that leukoaraiosis aggravates cognitive impairment in patients with lacunar infarction,such that more severe leukoaraiosis is associated with more severe cognitive decline.展开更多
Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite ...Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO3-ABS （acrylonitrile-butadiene-styrene copolymer） composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate （BA） and styrene （St）. The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO3 surface treatment. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
[Objectives]The paper was to study the toxicity of 9 biocontrol microbial products to adult population of Lasioderrma serricorne.[Methods]Nine biocontrol microbes were used as test materials to study their toxicity to...[Objectives]The paper was to study the toxicity of 9 biocontrol microbial products to adult population of Lasioderrma serricorne.[Methods]Nine biocontrol microbes were used as test materials to study their toxicity to the experimental population of L.serricorne adults.[Results]The toxicities of these biocontrol microbes from low to high at 5 d post spraying were:Luhai Beauveria bassiana powder(LC_(50)=462.752×10^(8) spores/L),Meichongzhi B.bassiana powder(LC_(50)=9713.157×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=11203.321×10^(8)spores/L),Nongbao Bio B.bassiana powder(LC_(50)=12188.866×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=21685.532×10^(8) spores/L);Fatu Bacillus thuringiensis suspension(LC_(50)=1.0844×10^(8) IU/L),Laojite B.thuringiensis suspension(LC_(50)=2.056×10^(8) IU/L),Lujinwa B.thuringiensis powder(LC_(50)=2.273×10^(8) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=18.399×10^(8) spores/L).The toxicities of these biocontrol microbes from low to high at 10 d post spraying were:Nongbao Bio B.bassiana powder(LC_(50)=0.072×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=2.484×10^(8) spores/L),Luhai B.bassiana powder(LC_(50)=44.551×10^(8) spores/L),Meichongzhi B.bassiana powder(LC_(50)=96.447×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=723.347×10^(8) spores/L);Lujinwa B.thuringiensis powder(LC_(50)=0.0001×10^(8) IU/L),Fatu B.thuringiensis suspension(LC_(50)=0.045×10^(8) IU/L),Laojite B.thuringiensis suspension(LC_(50)=0.0644×10^(8) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=1.899×10^(8) spores/L).The toxicities of these biocontrol microbes from low to high at 15 d post spraying were:Meichongzhi B.bassiana powder(LC_(50)=0.001×10^(8) spores/L),Nongbao Bio B.bassiana powder(LC_(50)=0.01×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=0.084×10^(8) spores/L),Luhai B.bassiana powder(LC_(50)=2.370×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=8.915×10^(8)spores/L);Lujinwa B.thuringiensis powder(LC_(50)=0.16×10^(4) IU/L),Laojite B.thuringiensis suspension(LC_(50)=0.185×10^(4) IU/L),Fatu B.thuringiensis suspension(LC_(50)=32.211×10^(4) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=1590×10^(4) spores/L).[Conclusions]According to the three stages of tube rubbing,it is found that the control effects of Lujinwa B.thuringiensis powder and Meichongzhi B.bassiana powder are the best,and the results will provide technical support for the biological control of L.serricorne adults.展开更多
The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fa...The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction,magnetic field and the expansion angle of the electrode are varied.Arc root movement is more likely to occur at the upper electrode.There is a competitive relationship between arc expansion and the transferring effect.The effect of wind on the arc column is greater than the effect on the arc root.The magnetic field has a significant driving effect on both the arc column and the arc root.The research results provide a comprehensive experimental basis for forther probing the method of DC arc suppression,and the improvement of the arcing horn.展开更多
[Objectives]This study was conducted to clarify the differences and abundance or deficiency of various elements in tobacco leaves from different positions of CB-1 in Zhangping City,so as to guide the production of pre...[Objectives]This study was conducted to clarify the differences and abundance or deficiency of various elements in tobacco leaves from different positions of CB-1 in Zhangping City,so as to guide the production of precision fertilization.[Methods]The element contents of CB-1 were determined by an X-ray fluorescence spectrometer.[Results]In terms of the contents of carbon,the upper leaves(45.73%)were significantly higher than the cutters(41.53%),and the lower leaves(43.15%)had no significant differences from both of them.For the content of oxygen element,there was no significant difference between the cutters(44.77%)and the lower leaves(43.40%),both of which were significantly higher than the upper leaves(40.75%).The contents of nitrogen,phosphorus,sulfur,boron and nickel all increased with the increase of the position,and they were significantly higher in the upper leaves than in the cutters and lower leaves.The contents of potassium,calcium,magnesium,chlorine and silicon all decreased with the increase of the position,and the lower leaves were significantly higher than the cutters and upper leaves.The contents of aluminum,titanium and chromium increased significantly with the increase of the position.The contents of strontium,zirconium and arsenic decreased significantly with the increase of the position.The element contents of tobacco leaves had significant or extremely significant differences between different parts of CB-1 in Zhangping City mostly.The contents of nitrogen,potassium,calcium,sulfur,chlorine,molybdenum and nickel in tobacco leaves were appropriate,and the contents of manganese and iron were too high,while the contents of phosphorus and copper were slightly low.The contents of magnesium,silicon,boron and sodium were too low.[Conclusions]This study can guide targeted fertilization and regulation of element contents in the tobacco leaves from different parts in production,and is of great significance to improving the production,quality and industrial availability of CB-1.展开更多
目的系统评价庆大霉素封管液预防血透患者中心静脉导管相关感染的效果。方法检索Cochrane Library、PubMed、Web of Science、Joanna Briggs Institute Library、CINAHL Complete、中国知网、万方及维普数据库,选择血透患者单独应用庆...目的系统评价庆大霉素封管液预防血透患者中心静脉导管相关感染的效果。方法检索Cochrane Library、PubMed、Web of Science、Joanna Briggs Institute Library、CINAHL Complete、中国知网、万方及维普数据库,选择血透患者单独应用庆大霉素或肝素封管液的随机对照试验。根据Cochrane Reviewer′s Handbook 5.0推荐标准进行质量评价,由2位研究者筛选文献,采用RevMan5.3软件进行Meta分析。结果本研究共纳入11项随机对照试验。Meta分析结果显示,单独应用庆大霉素封管的血透患者中心静脉导管相关感染发生率低于单独应用肝素封管(OR=0.34,95%CI:0.23~0.51,I^(2)=18%,P<0.001)。单独应用庆大霉素封管的血透患者中心静脉导管内血栓形成发生率低于单独肝素封管(OR=0.16,95%CI:0.10~0.27,I2=18%,P<0.001)。结论本研究结果提示,庆大霉素封管液可降低血透患者的中心静脉导管相关感染发生率以及导管内血栓形成的风险,对临床工作具有一定的参考价值。展开更多
The Hengduan Mountains Region(HMR) is essential for the future ecological protection, clean energy production,Sichuan-Xizang and Yunnan-Xizang railways, and other major infrastructure projects in China. The distributi...The Hengduan Mountains Region(HMR) is essential for the future ecological protection, clean energy production,Sichuan-Xizang and Yunnan-Xizang railways, and other major infrastructure projects in China. The distributions of climate and vegetation exhibit significant regional differentiation and vertical zonality due to the rugged longitudinal ranges and gorges and the complex disaster-prone environments in HMR. Therefore, it is urgent to develop the climate-vegetation regionalization in HMR to effectively satisfy the national requirements such as agricultural production and ecological protection, mountain disaster risk prevention, and major project construction. We here develop a new scheme of climate-vegetation regionalization with the latest demarcation outcome of HMR, the ground observation from 122 meteorological stations in HMR and its surrounding areas during 1990–2019, and the high-precision remote sensing data of land cover types. The new scheme first constructs the regionalization index system, fully considering the extraordinarily complicated geomorphic pattern of mountains and valleys, the scarcity of meteorological observations, and the remarkable differentiation of climate and vegetation in HMR. The system consists of three primary regionalization indices(i.e., days with daily average temperature steady above 10°C, aridity index, and main vegetation types, dividing the temperature zones, moisture regions, and vegetation subregions, respectively) and three auxiliary indices of the accumulated temperature above 10°C, and the temperatures in January and July. Then, the HMR is divided into five temperature zones, 20 moisture regions, and 55 vegetation subregions. Compared with previous regionalization schemes, the new scheme optimizes the climate spatial interpolation model of thin plate smoothing spline suitable for the unique terrain in HMR. Moreover, the disputed division index threshold between different climatic zones(regions) is scientifically clarified using geographical detectors. Specifically, the stepwise downscaling pane division method is initially proposed to determine the zoning boundary, alleviating the excessive dependence of the traditional zoning method on subjective experience.Besides, the scheme considers the typical regional characteristics of the complex underlying surface and the high gradient zone of climate-vegetation distribution types in HMR. Consequently, the transition zone with quick climate changes between the plateau temperate and mid-subtropical zones is divided into mountainous subtropics, taking into account the spatial distribution characteristics of climate-vegetation regionalization indices. The regionalization scheme will provide practically theoretical support for agricultural production, ecological protection, major project construction, disaster prevention and relief efforts, and other socioeconomic activities in HMR, serving as a classic case of climate-vegetation regionalization for the alpine and canyon regions with intricate underlying surface, striking regional differences, and lack of ground observations.展开更多
[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshi...[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshing and redrying workshop as the survey site,the occurrence regularity of L.serricorne was investigated,and the life history table was inferred according to its biological characteristics.The temperature,humidity and duration of tobacco leaf threshing and redrying were simulated in the laboratory to study the survival rate of all states of L.serricorne in this environment.[Results]The lifecycle of L.serricorne in tobacco leaf threshing and redrying workshop was:the overwintering generation pupated in late February;the pupa began to emerge in early March,and reached its peak in late March.The first-generation eggs started hatching in late March,pupated in late May,emerged in early June,and reached the peak eclosion of the first-generation adults in mid-July.The second-generation eggs began to hatch in late July,pupated in mid-August,emerged in late August,and reached the peak eclosion of the second-generation adults in mid-September.The third-generation eggs began to hatch in mid-September;most of the larvae began to overwinter,some pupated in mid-November and survived the winter as pupae,and some pupae emerged to adults.The survival test results of different states of L.serricorne under simulated temperature,humidity and duration in the tobacco leaf threshing and redrying process showed that the mortality rates of eggs in simulated 1,2 and 3 conditions were about 51.22%,90.24% and 100%,and the mortalities of larvae in simulated 1,2 and 3 conditions were about 18.30%,81.25%and 100%,respectively.The mortalities of pupae in simulated 1,2 and 3 conditions were about 69.39%,100% and 100%,and the mortalities of adults in simulated 1,2 and 3 conditions were about 100%,100% and 100%,respectively.[Conclusions]L.serricorne of different states can be killed by appropriately raising the temperature during threshing and redrying.展开更多
Latitudinal patterns of treeβ-diversity reveal important insights into the biogeographical processes that influence forest ecosystems.Although previous studies have extensively documentedβ-diversity within relativel...Latitudinal patterns of treeβ-diversity reveal important insights into the biogeographical processes that influence forest ecosystems.Although previous studies have extensively documentedβ-diversity within relatively small spatial extents,the potential drivers ofβ-diversity along latitudinal gradients are still not well understood at larger spatial extents.In this study,we determined whether treeβ-diversity is correlated with latitude in forests of southeastern China,and if so,what ecological processes contribute to these patterns of treeβ-diversity.We specifically aimed to disentangle the relative contributions from interspecific aggregation and environmental filtering across various spatial extents.We delineated regional communities comprising multiple nearby national forest inventory(NFI)plots around random focal plots.The number of NFI plots in a regional community served as a surrogate for spatial extent.We also used a null model to simulate randomly assembled communities and quantify the deviation(β-deviation)between observed and expectedβ-diversity.We found thatβ-diversity decreased along a latitudinal gradient and that this pattern was clearer at larger spatial extents.In addition,latitudinal patterns ofβ-deviation were explained by the degree of species spatial aggregation.We also identified environmental factors that driveβ-deviation in these forests,including precipitation,seasonality,and temperature variation.At larger spatial extents,these environmental variables explained up to 84%of theβ-deviation.Our results reinforce that ecological processes are scale-dependent and collectively contribute to theβ-gradient in subtropical forests.We recommend that conservation efforts maintain diverse forests and heterogeneous environments at multiple spatial extents to mitigate the adverse effects of climate change.展开更多
Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understa...Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understanding the compression behavior and failure mechanism of such structures under loading remains a challenge.In this study,considering the correlation between the strut angle and bearing capacity,body-centered tetragonal(BCT)lattice structures with varying angles are designed based on a body-centered cubic(BCC)structure.BCT Al_(2)O_(3) ceramic lattice structures with varying angles are fabricated by vat photopolymerization.The mechanical properties,deformation process,and failure mechanism of the Al_(2)O_(3) ceramic lattice structures are characterized through a combination of ex-and in-situ X-ray computed tomography(X-CT)compression testing and analyzed using a finite element method(FEM)at macro-and micro-levels.The results demonstrate that as the angle increases,the stress concentration gradually expands from the node to the strut,resulting in an increased loadbearing capacity.Additionally,the failure mode of the Al_(2)O_(3) ceramic lattice structures is identified as diagonal slip shear failure.These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.展开更多
Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC c...Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC ceramic products.This article systematically reviews the additive manufacturing technologies of SiC ceramic developed in recent years,including Indirect Additive Manufacturing(Indirect AM)and Direct Additive Manufacturing(Direct AM)technologies.This review also summarizes the key scientific and technological challenges for the additive manufacturing of SiC ceramic,and also forecasts its possible future opportunities.This paper aims to provide a helpful guidance for the additive manufacturing of SiC ceramic and other structural ceramics.展开更多
Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different struc...Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.展开更多
Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufac...Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process.These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics.However,systematic research on defects,including defect geometrical features,quantitative statistics,and formation mechanism,as well as the intrinsic relationship with mechanical properties,need to be studied in depth.In this work,Al2 O3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic(SL)additive manufacturing.The defects,including their sizes and distributions,in both green and sintered bodies were investigated by using scanning electron microscopy(SEM)and X-ray computed tomography(X-CT).Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism.Moreover,the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed.This study can give some fundamental understanding of the defects in additive manufactured ceramics.展开更多
Self-cleaning is the key factor that makes superhydrophobic nanostructured materials have wide applications.The self-cleaning effect,however,strongly depends on formations and movement of water droplets on superhydrop...Self-cleaning is the key factor that makes superhydrophobic nanostructured materials have wide applications.The self-cleaning effect,however,strongly depends on formations and movement of water droplets on superhydrophobic nanostructured surfaces,which is greatly restricted at low humidity(<7.6 g·kg^(-1)).Therefore,we propose a self-cleaning method at low humidity in which the pollution is electro-aggregated and driven in the electric field to achieve the aggregation and cleaning large areas.The cleaning efficiency of this method is much higher than that of water droplet roll-off,and will not produce"pollution bands".A simplified numerical model describing pollution movements is presented.Simulation results are consistent with experimental results.The proposed method realizes the self-cleaning of superhydrophobic nanostructured surfaces above dew point curve for the first time,which extends applications of superhydrophobic nanostructured materials in low humidity,and is expected to solve self-cleaning problems of outdoor objects in low humidity areas(<5.0 g·kg^(-1)).展开更多
Precursor-derived ceramic SiOC(PDC-SiOC)microlattices exhibit excellent oxidation resistance,high-temperature stability,and superior mechanical properties.However,the printing accuracy of the PDC-SiOC microlattices by...Precursor-derived ceramic SiOC(PDC-SiOC)microlattices exhibit excellent oxidation resistance,high-temperature stability,and superior mechanical properties.However,the printing accuracy of the PDC-SiOC microlattices by 3D printing is still limited,and mechanical properties of the PDC-SiOC microlattices have not been studied systematically.Here,PDC-SiOC octet microlattices were fabricated by projection micro stereolithography(PμSL)3D printing,and photoabsorber(Sudan III)’s effect on the accuracy was systematically analyzed.The results showed that the addition of Sudan III improved the printing accuracy significantly.Then,the ceramization process of the green body was analyzed in detail.The order of the green body decreased,and most of their chemical bonds were broken during pyrolysis.After that,the PDC-SiOC microlattices with different truss diameters in the range of 52–220μm were fabricated,and their mechanical properties were investigated.The PDC-SiOC microlattices with a truss diameter of 52μm exhibited higher compression strength(31 MPa)than those with bigger truss diameters.The size effect among the PDC-SiOC microlattices was analyzed.Our work provides a deeper insight into the manufacturing of PDC-SiOC micro-scaled architectures by 3D printing and paves a path to the research of the size effect in ceramic structures.展开更多
Climate change and human activities have increased avalanche risks in alpine mountains.Therefore,strengthening the research on mitigating and controlling avalanche disasters is indispensable for sustainable socio-econ...Climate change and human activities have increased avalanche risks in alpine mountains.Therefore,strengthening the research on mitigating and controlling avalanche disasters is indispensable for sustainable socio-economic development in mountainous areas.Early avalanche warning is an essential means of avalanche disaster prevention.However,the theoretical development and application of avalanche warning strategies remain limited due to the lack of systematic understanding of the triggering mechanisms of avalanches.Based on observational data(2015–2019)of avalanches,snowpack,meteorological parameters,surface soil temperature and moisture,and topography in avalanche-prone areas in the central Tianshan Mountains,we analyzed the characteristics of different types of avalanches under a continental snow climate and the environmental factors(such as meteorological conditions and snowpack)that trigger avalanches,as well as the triggering mechanisms for different types of avalanches under the continental snow climate in terms of snow-layer shear fracture modes.We found that the snowpack parameters,weather conditions,and soil temperature and moisture varied significantly among the stages of snow accumulation,stabilization,and melting,resulting in different avalanches prevailing in different stages of snowpack evolution.Moreover,the snow-layer fractures were driven by single external factors or the combined multiple factors under the continental snow climate.Fifty-four percent of the avalanche events in the study area occurred during or after a snowfall,with 36%related to sudden increases in temperature.Then considering different triggering scenarios,snowpack evolution stages,and the coupling of intrinsic and extrinsic drivers of triggering snow-layer shear failure,we constructed five snow-layer shear fracture modes and twelve avalanche-triggering modes on mountain slopes under a continental snow climate.展开更多
Snow avalanches can repeatedly occur along the same track under diferent snowpack and meteorological conditions during the snow season in areas of snow avalanche activity.The snowfall,air temperature,and snow cover ca...Snow avalanches can repeatedly occur along the same track under diferent snowpack and meteorological conditions during the snow season in areas of snow avalanche activity.The snowfall,air temperature,and snow cover can change dramatically in a warming climate,causing signifcant changes in the snow avalanche risk.But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question.Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate,we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it.The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution,resulting from interactions between the snowfall,air temperature,and snowpack evolution.In addition,the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the frst half of March with climate warming.The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignifcant increase.These fndings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters,and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.展开更多
To overcome the shortcomings of single component carrier supported platinum(Pt)-based catalysts,herein,we demonstrate the fabrication of alumina combined mesoporous carbon to prepare a series of alumina-carbon composi...To overcome the shortcomings of single component carrier supported platinum(Pt)-based catalysts,herein,we demonstrate the fabrication of alumina combined mesoporous carbon to prepare a series of alumina-carbon composites and their corresponding Pt-based catalysts.The alumina-carbon composites Al@PhFC are synthesized by using phloroglucinol-formaldehyde resin as carbon source and aluminum acetylacetone as the aluminum source.Further,the effect of alumina content on the properties of the composites is investigated.The composites and catalysts are characterized by using XRD,XPS,N2 sorption,and TEM.The Pt/Al@PhFC-1.8 composite with appropriate amounts of alumina,pore diameter,and moderate Pt nanoparticle size,resulted in 99.5%of conversion efficiency and 77.4%of optical selectivity in the asymmetric hydrogenation of ethyl 2-oxo-4-phenylbutanoate(EOPB).Intere stingly,this composite can be used more than 20 times without a significant decrease in its performance.展开更多
文摘This study semi-quantitatively analyzed the effects of leukoaraiosis.Patients with moderate or severe lacunar infarction were found to exhibit low scores on the Montreal Cognitive Assessment Scale （F=12.02,P=0.000）,and prolonged P300 Cz2.0 latency （F=16.04,P=0.000）.Correlation analysis revealed that the occurrence of leukoaraiosis was negatively correlated with Montreal Cognitive Assessment scores （r=-0.416,P=0.000）,and positively correlated with P300 Cz2.0 latency （r=0.538,P=0.000）.These findings indicate that leukoaraiosis aggravates cognitive impairment in patients with lacunar infarction,such that more severe leukoaraiosis is associated with more severe cognitive decline.
基金the National Natural Science Foundation of China(No.20236020,20325621)the National R & D Program of China(No.2001BA310A01).
文摘Nano-calcium carbonate composite particles were synthesized by the soapless emulsion polymerization technique of double monomers. The composite particles formation mechanism was investigated. The effects of composite particles on the mechanical properties of nano-CaCO3-ABS （acrylonitrile-butadiene-styrene copolymer） composite material were studied. It was validated that the composite particles are made up of the nano-calcium carbonate cores and the shells of alternating copolymers of butyl acrylate （BA） and styrene （St）. The shells are chemically grafted and physically wrapped on the surface of nano-calcium carbonate particles. When the composite particles were filled in ABS matrix, the CaCO3 particles are homogeneously dispersed in the composite material as nanoscales. The impact strength of the composite material is obviously enhanced after filling appropriate amounts of composite particles. It can be concluded that the soapless emulsion polymerization of double monomers is an effective method for nano-CaCO3 surface treatment. 2008 University of Science and Technology Beijing. All rights reserved.
基金Science and Technology Project of China Tobacco Guizhou Provincial Corporation(201918)Science and Technology Foundation of General Administration of Quality Supervision,Inspection and Quarantine of the People's Republic of China(2017IK257,2017IK261,2016IK075,2014IK022)+3 种基金Science and Technology Foundation of Guizhou Province(J[2013]2149)Humanities and Social Science Research Project of Guizhou Education Department(2022ZC016)Theoretical Innovation Project of Guizhou Province(Joint Project)(GZLCLH-2021-169)Construction of Guizhou Academic Pioneer.
文摘[Objectives]The paper was to study the toxicity of 9 biocontrol microbial products to adult population of Lasioderrma serricorne.[Methods]Nine biocontrol microbes were used as test materials to study their toxicity to the experimental population of L.serricorne adults.[Results]The toxicities of these biocontrol microbes from low to high at 5 d post spraying were:Luhai Beauveria bassiana powder(LC_(50)=462.752×10^(8) spores/L),Meichongzhi B.bassiana powder(LC_(50)=9713.157×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=11203.321×10^(8)spores/L),Nongbao Bio B.bassiana powder(LC_(50)=12188.866×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=21685.532×10^(8) spores/L);Fatu Bacillus thuringiensis suspension(LC_(50)=1.0844×10^(8) IU/L),Laojite B.thuringiensis suspension(LC_(50)=2.056×10^(8) IU/L),Lujinwa B.thuringiensis powder(LC_(50)=2.273×10^(8) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=18.399×10^(8) spores/L).The toxicities of these biocontrol microbes from low to high at 10 d post spraying were:Nongbao Bio B.bassiana powder(LC_(50)=0.072×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=2.484×10^(8) spores/L),Luhai B.bassiana powder(LC_(50)=44.551×10^(8) spores/L),Meichongzhi B.bassiana powder(LC_(50)=96.447×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=723.347×10^(8) spores/L);Lujinwa B.thuringiensis powder(LC_(50)=0.0001×10^(8) IU/L),Fatu B.thuringiensis suspension(LC_(50)=0.045×10^(8) IU/L),Laojite B.thuringiensis suspension(LC_(50)=0.0644×10^(8) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=1.899×10^(8) spores/L).The toxicities of these biocontrol microbes from low to high at 15 d post spraying were:Meichongzhi B.bassiana powder(LC_(50)=0.001×10^(8) spores/L),Nongbao Bio B.bassiana powder(LC_(50)=0.01×10^(8) spores/L),Yiqiang Bio B.bassiana powder(LC_(50)=0.084×10^(8) spores/L),Luhai B.bassiana powder(LC_(50)=2.370×10^(8) spores/L),Yeshengwang B.bassiana powder(LC_(50)=8.915×10^(8)spores/L);Lujinwa B.thuringiensis powder(LC_(50)=0.16×10^(4) IU/L),Laojite B.thuringiensis suspension(LC_(50)=0.185×10^(4) IU/L),Fatu B.thuringiensis suspension(LC_(50)=32.211×10^(4) IU/L),Nongbao Bio B.thuringiensis powder(LC_(50)=1590×10^(4) spores/L).[Conclusions]According to the three stages of tube rubbing,it is found that the control effects of Lujinwa B.thuringiensis powder and Meichongzhi B.bassiana powder are the best,and the results will provide technical support for the biological control of L.serricorne adults.
基金National Natural Science Foundation of China(No.51907168)funded by Sichuan Science and Technology Program(Outstanding Youth Science and Technology Talents)(No.2020JDJQ0039)。
文摘The dynamic physical characteristics of a DC arc on an arcing horn for a high voltage direct current(HVDC)grounding electrode line are significantly different from those of the switching device arc,secondary arc,AC fault arc and pantograph-catenary arc.In this work,an experimental platform for the DC arc on the arcing horn was built,and mechanisms of the arc column short circuit and arc root movement were studied.This work further analyzes the characteristics and mechanisms of the arc motion when wind speed and direction,magnetic field and the expansion angle of the electrode are varied.Arc root movement is more likely to occur at the upper electrode.There is a competitive relationship between arc expansion and the transferring effect.The effect of wind on the arc column is greater than the effect on the arc root.The magnetic field has a significant driving effect on both the arc column and the arc root.The research results provide a comprehensive experimental basis for forther probing the method of DC arc suppression,and the improvement of the arcing horn.
基金Supported by Science and Technology Project of China Tobacco Hebei Industrial Co.Ltd.(2021130000300029).
文摘[Objectives]This study was conducted to clarify the differences and abundance or deficiency of various elements in tobacco leaves from different positions of CB-1 in Zhangping City,so as to guide the production of precision fertilization.[Methods]The element contents of CB-1 were determined by an X-ray fluorescence spectrometer.[Results]In terms of the contents of carbon,the upper leaves(45.73%)were significantly higher than the cutters(41.53%),and the lower leaves(43.15%)had no significant differences from both of them.For the content of oxygen element,there was no significant difference between the cutters(44.77%)and the lower leaves(43.40%),both of which were significantly higher than the upper leaves(40.75%).The contents of nitrogen,phosphorus,sulfur,boron and nickel all increased with the increase of the position,and they were significantly higher in the upper leaves than in the cutters and lower leaves.The contents of potassium,calcium,magnesium,chlorine and silicon all decreased with the increase of the position,and the lower leaves were significantly higher than the cutters and upper leaves.The contents of aluminum,titanium and chromium increased significantly with the increase of the position.The contents of strontium,zirconium and arsenic decreased significantly with the increase of the position.The element contents of tobacco leaves had significant or extremely significant differences between different parts of CB-1 in Zhangping City mostly.The contents of nitrogen,potassium,calcium,sulfur,chlorine,molybdenum and nickel in tobacco leaves were appropriate,and the contents of manganese and iron were too high,while the contents of phosphorus and copper were slightly low.The contents of magnesium,silicon,boron and sodium were too low.[Conclusions]This study can guide targeted fertilization and regulation of element contents in the tobacco leaves from different parts in production,and is of great significance to improving the production,quality and industrial availability of CB-1.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23090302)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0903)。
文摘The Hengduan Mountains Region(HMR) is essential for the future ecological protection, clean energy production,Sichuan-Xizang and Yunnan-Xizang railways, and other major infrastructure projects in China. The distributions of climate and vegetation exhibit significant regional differentiation and vertical zonality due to the rugged longitudinal ranges and gorges and the complex disaster-prone environments in HMR. Therefore, it is urgent to develop the climate-vegetation regionalization in HMR to effectively satisfy the national requirements such as agricultural production and ecological protection, mountain disaster risk prevention, and major project construction. We here develop a new scheme of climate-vegetation regionalization with the latest demarcation outcome of HMR, the ground observation from 122 meteorological stations in HMR and its surrounding areas during 1990–2019, and the high-precision remote sensing data of land cover types. The new scheme first constructs the regionalization index system, fully considering the extraordinarily complicated geomorphic pattern of mountains and valleys, the scarcity of meteorological observations, and the remarkable differentiation of climate and vegetation in HMR. The system consists of three primary regionalization indices(i.e., days with daily average temperature steady above 10°C, aridity index, and main vegetation types, dividing the temperature zones, moisture regions, and vegetation subregions, respectively) and three auxiliary indices of the accumulated temperature above 10°C, and the temperatures in January and July. Then, the HMR is divided into five temperature zones, 20 moisture regions, and 55 vegetation subregions. Compared with previous regionalization schemes, the new scheme optimizes the climate spatial interpolation model of thin plate smoothing spline suitable for the unique terrain in HMR. Moreover, the disputed division index threshold between different climatic zones(regions) is scientifically clarified using geographical detectors. Specifically, the stepwise downscaling pane division method is initially proposed to determine the zoning boundary, alleviating the excessive dependence of the traditional zoning method on subjective experience.Besides, the scheme considers the typical regional characteristics of the complex underlying surface and the high gradient zone of climate-vegetation distribution types in HMR. Consequently, the transition zone with quick climate changes between the plateau temperate and mid-subtropical zones is divided into mountainous subtropics, taking into account the spatial distribution characteristics of climate-vegetation regionalization indices. The regionalization scheme will provide practically theoretical support for agricultural production, ecological protection, major project construction, disaster prevention and relief efforts, and other socioeconomic activities in HMR, serving as a classic case of climate-vegetation regionalization for the alpine and canyon regions with intricate underlying surface, striking regional differences, and lack of ground observations.
基金Supported by Science and Technology Project of China Tobacco Guizhou Provincial Corporation(201918)Guizhou Province Academic Pioneer and Academic Pioneer Construction。
文摘[Objectives]The paper was to study the occurrence regularity and life history of cigarette beetle Lasioderrma serricorne(Fabricius)in tobacco leaf threshing and redrying workshop.[Methods]With the tobacco leaf threshing and redrying workshop as the survey site,the occurrence regularity of L.serricorne was investigated,and the life history table was inferred according to its biological characteristics.The temperature,humidity and duration of tobacco leaf threshing and redrying were simulated in the laboratory to study the survival rate of all states of L.serricorne in this environment.[Results]The lifecycle of L.serricorne in tobacco leaf threshing and redrying workshop was:the overwintering generation pupated in late February;the pupa began to emerge in early March,and reached its peak in late March.The first-generation eggs started hatching in late March,pupated in late May,emerged in early June,and reached the peak eclosion of the first-generation adults in mid-July.The second-generation eggs began to hatch in late July,pupated in mid-August,emerged in late August,and reached the peak eclosion of the second-generation adults in mid-September.The third-generation eggs began to hatch in mid-September;most of the larvae began to overwinter,some pupated in mid-November and survived the winter as pupae,and some pupae emerged to adults.The survival test results of different states of L.serricorne under simulated temperature,humidity and duration in the tobacco leaf threshing and redrying process showed that the mortality rates of eggs in simulated 1,2 and 3 conditions were about 51.22%,90.24% and 100%,and the mortalities of larvae in simulated 1,2 and 3 conditions were about 18.30%,81.25%and 100%,respectively.The mortalities of pupae in simulated 1,2 and 3 conditions were about 69.39%,100% and 100%,and the mortalities of adults in simulated 1,2 and 3 conditions were about 100%,100% and 100%,respectively.[Conclusions]L.serricorne of different states can be killed by appropriately raising the temperature during threshing and redrying.
基金supported by the National Natural Science Foundation of China(42271317)the Innovation Research Team Project of the Natural Science Foundation of Hainan Province(422CXTD515)。
文摘Latitudinal patterns of treeβ-diversity reveal important insights into the biogeographical processes that influence forest ecosystems.Although previous studies have extensively documentedβ-diversity within relatively small spatial extents,the potential drivers ofβ-diversity along latitudinal gradients are still not well understood at larger spatial extents.In this study,we determined whether treeβ-diversity is correlated with latitude in forests of southeastern China,and if so,what ecological processes contribute to these patterns of treeβ-diversity.We specifically aimed to disentangle the relative contributions from interspecific aggregation and environmental filtering across various spatial extents.We delineated regional communities comprising multiple nearby national forest inventory(NFI)plots around random focal plots.The number of NFI plots in a regional community served as a surrogate for spatial extent.We also used a null model to simulate randomly assembled communities and quantify the deviation(β-deviation)between observed and expectedβ-diversity.We found thatβ-diversity decreased along a latitudinal gradient and that this pattern was clearer at larger spatial extents.In addition,latitudinal patterns ofβ-deviation were explained by the degree of species spatial aggregation.We also identified environmental factors that driveβ-deviation in these forests,including precipitation,seasonality,and temperature variation.At larger spatial extents,these environmental variables explained up to 84%of theβ-deviation.Our results reinforce that ecological processes are scale-dependent and collectively contribute to theβ-gradient in subtropical forests.We recommend that conservation efforts maintain diverse forests and heterogeneous environments at multiple spatial extents to mitigate the adverse effects of climate change.
基金supported by National Natural Science Foundation of China(Grant Nos.52275310,52402084)the China Postdoctoral Science Foundation(Grant No.2024M751646).
文摘Vat photopolymerization additive manufacturing produces lightweight load-bearing ceramic lattice structures that have flexibility,time-efficiency,and high precision,compared to conventional technology.However,understanding the compression behavior and failure mechanism of such structures under loading remains a challenge.In this study,considering the correlation between the strut angle and bearing capacity,body-centered tetragonal(BCT)lattice structures with varying angles are designed based on a body-centered cubic(BCC)structure.BCT Al_(2)O_(3) ceramic lattice structures with varying angles are fabricated by vat photopolymerization.The mechanical properties,deformation process,and failure mechanism of the Al_(2)O_(3) ceramic lattice structures are characterized through a combination of ex-and in-situ X-ray computed tomography(X-CT)compression testing and analyzed using a finite element method(FEM)at macro-and micro-levels.The results demonstrate that as the angle increases,the stress concentration gradually expands from the node to the strut,resulting in an increased loadbearing capacity.Additionally,the failure mode of the Al_(2)O_(3) ceramic lattice structures is identified as diagonal slip shear failure.These findings provide a greater understanding of ceramic lattice structure failures and design optimization approaches.
基金supported by the National Natural Science Foundation of China(No.51772028).
文摘Silicon carbide(SiC)ceramic and related materials are widely used in various military and engineering fields.The emergence of additive manufacturing(AM)technologies provides a new approach for the fabrication of SiC ceramic products.This article systematically reviews the additive manufacturing technologies of SiC ceramic developed in recent years,including Indirect Additive Manufacturing(Indirect AM)and Direct Additive Manufacturing(Direct AM)technologies.This review also summarizes the key scientific and technological challenges for the additive manufacturing of SiC ceramic,and also forecasts its possible future opportunities.This paper aims to provide a helpful guidance for the additive manufacturing of SiC ceramic and other structural ceramics.
基金supported by the National Natural Science Foundation of China(Grant No.51772028).
文摘Cellular ceramic structures(CCSs)are promising candidates for structural components in aerospace and modern industry because of their extraordinary physical and chemical properties.Herein,the CCSs with different structural parameters,i.e.,relative density,layer,size of unit cells,and structural configuration,were designed and prepared by digital light processing(DLP)-based additive manufacturing(AM)technology to investigate their responses under compressive loading systematically.It was demonstrated that as the relative density increased and the size of the unit cells decreased,the mechanical properties of one-layer CCSs increased.The mechanical properties of three-layer CCSs were more outstanding than those of the CCSs with one and two layers.In addition,structural configurations also played a vital role in the mechanical properties of the CCSs.Overall,the mechanical properties of the CCSs from superior to inferior were that with the structural configurations of modified body-centered cubic(MBCC),Octet,SchwarzP,IWP,and body-centered cubic(BCC).Furthermore,structural parameters also had significant impacts on the failure mode of the CCSs under compressive loading.As the relative density increased,the failure mode of the one-layer CCSs changed from parallel-vertical-inclined mode to parallel-vertical mode.It was worth noting that the size of the unit cells did not alter the failure mode.Inclined fracture took a greater proportion in the failure mode of the multi-layer CCSs.But it could be suppressed by the increased relative density.Similarly,the proportions of the parallel-vertical mode and the fracture along a specific plane always changed with the variation of the structural configurations.This study will serve as the base for investigating the mechanical properties of the CCSs.
基金financial support from the National Natural Science Foundation of China(No.51772028)the Graduate Technology Innovation Project of Beijing Institute of Technology(No.2019CX10020)。
文摘Ceramics have been widely fabricated by additive manufacturing(AM).Compared to conventional technologies,the strength of additive manufactured ceramic is relatively low owing to the formation of defects during manufacturing process.These defects have significant effects on the microstructure and mechanical properties of additive manufactured ceramics.However,systematic research on defects,including defect geometrical features,quantitative statistics,and formation mechanism,as well as the intrinsic relationship with mechanical properties,need to be studied in depth.In this work,Al2 O3 ceramics were prepared from photosensitive slurries with different solid loadings by using stereolithographic(SL)additive manufacturing.The defects,including their sizes and distributions,in both green and sintered bodies were investigated by using scanning electron microscopy(SEM)and X-ray computed tomography(X-CT).Geometrical features and quantitative statistics of the defects were evaluated and discussed to reveal their formation mechanism.Moreover,the intrinsic relationship between defects and mechanical properties of the additive manufactured ceramic was revealed.This study can give some fundamental understanding of the defects in additive manufactured ceramics.
基金The authors are grateful to the supporting program of the National Natural Science Foundation of China(Nos.51837009 and 51907168).
文摘Self-cleaning is the key factor that makes superhydrophobic nanostructured materials have wide applications.The self-cleaning effect,however,strongly depends on formations and movement of water droplets on superhydrophobic nanostructured surfaces,which is greatly restricted at low humidity(<7.6 g·kg^(-1)).Therefore,we propose a self-cleaning method at low humidity in which the pollution is electro-aggregated and driven in the electric field to achieve the aggregation and cleaning large areas.The cleaning efficiency of this method is much higher than that of water droplet roll-off,and will not produce"pollution bands".A simplified numerical model describing pollution movements is presented.Simulation results are consistent with experimental results.The proposed method realizes the self-cleaning of superhydrophobic nanostructured surfaces above dew point curve for the first time,which extends applications of superhydrophobic nanostructured materials in low humidity,and is expected to solve self-cleaning problems of outdoor objects in low humidity areas(<5.0 g·kg^(-1)).
基金supported by the National Natural Science Foundation of China(No.52275310)the Open Project of State Key Laboratory of Explosion Science and Technology(No.QNKT22-15)the characterization at the Analysis&Testing Center,Beijing Institute of Technology.
文摘Precursor-derived ceramic SiOC(PDC-SiOC)microlattices exhibit excellent oxidation resistance,high-temperature stability,and superior mechanical properties.However,the printing accuracy of the PDC-SiOC microlattices by 3D printing is still limited,and mechanical properties of the PDC-SiOC microlattices have not been studied systematically.Here,PDC-SiOC octet microlattices were fabricated by projection micro stereolithography(PμSL)3D printing,and photoabsorber(Sudan III)’s effect on the accuracy was systematically analyzed.The results showed that the addition of Sudan III improved the printing accuracy significantly.Then,the ceramization process of the green body was analyzed in detail.The order of the green body decreased,and most of their chemical bonds were broken during pyrolysis.After that,the PDC-SiOC microlattices with different truss diameters in the range of 52–220μm were fabricated,and their mechanical properties were investigated.The PDC-SiOC microlattices with a truss diameter of 52μm exhibited higher compression strength(31 MPa)than those with bigger truss diameters.The size effect among the PDC-SiOC microlattices was analyzed.Our work provides a deeper insight into the manufacturing of PDC-SiOC micro-scaled architectures by 3D printing and paves a path to the research of the size effect in ceramic structures.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA23090302)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(Grant No.2019QZKK0906)the National Natural Science Foundation of China(Grant No.42101080).
文摘Climate change and human activities have increased avalanche risks in alpine mountains.Therefore,strengthening the research on mitigating and controlling avalanche disasters is indispensable for sustainable socio-economic development in mountainous areas.Early avalanche warning is an essential means of avalanche disaster prevention.However,the theoretical development and application of avalanche warning strategies remain limited due to the lack of systematic understanding of the triggering mechanisms of avalanches.Based on observational data(2015–2019)of avalanches,snowpack,meteorological parameters,surface soil temperature and moisture,and topography in avalanche-prone areas in the central Tianshan Mountains,we analyzed the characteristics of different types of avalanches under a continental snow climate and the environmental factors(such as meteorological conditions and snowpack)that trigger avalanches,as well as the triggering mechanisms for different types of avalanches under the continental snow climate in terms of snow-layer shear fracture modes.We found that the snowpack parameters,weather conditions,and soil temperature and moisture varied significantly among the stages of snow accumulation,stabilization,and melting,resulting in different avalanches prevailing in different stages of snowpack evolution.Moreover,the snow-layer fractures were driven by single external factors or the combined multiple factors under the continental snow climate.Fifty-four percent of the avalanche events in the study area occurred during or after a snowfall,with 36%related to sudden increases in temperature.Then considering different triggering scenarios,snowpack evolution stages,and the coupling of intrinsic and extrinsic drivers of triggering snow-layer shear failure,we constructed five snow-layer shear fracture modes and twelve avalanche-triggering modes on mountain slopes under a continental snow climate.
基金supported by the Second Tibetan Plateau Scientifc Expedition and Research Program(STEP)(Grant nos.2019QZKK0906,2019QZKK0903)the National Natural Science Foundation of China(Grant no.42101080)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(CAST)(2022QNRC001)。
文摘Snow avalanches can repeatedly occur along the same track under diferent snowpack and meteorological conditions during the snow season in areas of snow avalanche activity.The snowfall,air temperature,and snow cover can change dramatically in a warming climate,causing signifcant changes in the snow avalanche risk.But how the risk of snow avalanche activity during the snow season will change under a warming climate remains an open question.Based on the observed meteorological and snowpack data from 1968 to 2021 and the snow avalanche activity data during the 2011–2021 snow seasons along a transportation corridor in the central Tianshan Mountains that has a typical continental snow climate,we analyzed the temporal distribution of the snow avalanche activity and the impacts of climate change on it.The results indicate that the frequency of the snow avalanche activity is characterized by a Gaussian bimodal distribution,resulting from interactions between the snowfall,air temperature,and snowpack evolution.In addition,the active period of wet snow avalanches triggered by temperature surges and high solar radiation has gradually moved forward from the second half to the frst half of March with climate warming.The frequency and size of snowfall-triggered snow avalanches showed only a slight and insignifcant increase.These fndings are important for rationally arranging snow avalanche relief resources to improve the risk management of snow avalanche disasters,and highlight the necessity to immediately design risk mitigation strategies and disaster risk policies to improve our adaptation to climate change.
基金supported by the National Natural Science Foundation of China(Nos.51603077,21603077)the Natural Science Foundation of Fujian Province(No.2019J01077)+2 种基金Marine High-Tech Industry Development Project of Fujian Province[No.(2016)17]Promotion Program for Young and Middle-AgedTeacher in Science and Technology Research of Huaqiao University(No.ZQN-PY516)Subsidized Project for Postgraduates’Innovative Fund in Scientific Research of Huaqiao University。
文摘To overcome the shortcomings of single component carrier supported platinum(Pt)-based catalysts,herein,we demonstrate the fabrication of alumina combined mesoporous carbon to prepare a series of alumina-carbon composites and their corresponding Pt-based catalysts.The alumina-carbon composites Al@PhFC are synthesized by using phloroglucinol-formaldehyde resin as carbon source and aluminum acetylacetone as the aluminum source.Further,the effect of alumina content on the properties of the composites is investigated.The composites and catalysts are characterized by using XRD,XPS,N2 sorption,and TEM.The Pt/Al@PhFC-1.8 composite with appropriate amounts of alumina,pore diameter,and moderate Pt nanoparticle size,resulted in 99.5%of conversion efficiency and 77.4%of optical selectivity in the asymmetric hydrogenation of ethyl 2-oxo-4-phenylbutanoate(EOPB).Intere stingly,this composite can be used more than 20 times without a significant decrease in its performance.
