Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening pa...Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.展开更多
Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage.Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed.A Gl...Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage.Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed.A Global Positioning System(GPS)device and softwares required to simultaneously acquire gamma signals and geographical positions during scanning operations were added to an existing measurement system.The reliability of soil carbon measurements in scanning mode was demonstrated to be in agreement with results acquired from static mode.The error analysis indicated that scanning measurements can be conducted with the same accuracy as static measurements in approximately one fourth the time.To obtain results suitable for mapping analogous to traditional chemical analyses(i.e.,±0.5 in weight percent or±0.5 w%),scanning time over a given site should be ca.15 min using the current measurement system configuration.Based on this measurement time,a reasonable towing speed of 3–5 km h^-1,the necessity for complete site coverage during scanning,the number of sites(within the surveyed field),and the required total measurement time can be estimated.Soil carbon measurements for 28 field sites(total area ca.2.5 ha)were conducted in ca.8 h.Based on acquired data,a soil carbon distribution map was constructed utilizing various softwares.The surveyed field area included an asphalt road that had carbon readings higher than the surrounding land.The clarity with which these carbon-rich zones were delineated on the constructed map represents evidence supporting the veracity of this method.Neutron-gamma analysis technology can greatly facilitate timely construction of soil carbon maps.展开更多
Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and...Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and modulation of evapotranspiration. It also plays an important role filtering urban water systems and reducing storm water runoff.Methods: We investigate the capacity of ALS data to individually detect, map and characterize large(taller than15 m) trees within the City of Vancouver. Large trees are critical for the function and character of Vancouver’s urban forest. We used an object-based approach for individual tree detection and segmentation to determine tree locations(position of the stem), to delineate the shape of the crowns and to categorize the latter either as coniferous or deciduous.Results: Results indicate a detection rate of 76.6% for trees > 15 m with a positioning error of 2.11 m(stem location). Extracted tree heights possessed a RMSE of 2.60 m and a bias of-1.87 m, whereas crown diameter was derived with a RMSE of 3.85 m and a bias of-2.06 m. Missed trees are principally a result of undetected treetops occurring in dense, overlapping canopies with more accurate detection and delineation of trees in open areas.Conclusion: By identifying key structural trees across Vancouver’s urban forests, we can better understand their role in providing ecosystem goods and services for city residents.展开更多
High-density linkage maps are essential tools for genome analysis of various biological traits. Our developed compact multi-gel system, HEGS （high efficiency genome scanning） is a high-throughput and high-cost-perfo...High-density linkage maps are essential tools for genome analysis of various biological traits. Our developed compact multi-gel system, HEGS （high efficiency genome scanning） is a high-throughput and high-cost-performance electrophoresis apparatus. Using this system, a high-density （average interval 2.3 cM） map with 1 065 AFLP and 63 SSR markers was constructed from recombinant inbred lines of a japonica and indica hybrid in just two months of electrophoreses by a single person. More than 50% of the mapped AFLP markers were commonly polymorphic for several combinations between japonica and indica rice and 15% were applicable for genetically closer crosses between upland and lowland types of japonica rice. This system can be used for rapid analyses of all kinds of markers.展开更多
Background:The Norwegian forest resource map(SR16)maps forest attributes by combining national forest inventory(NFI),airborne laser scanning(ALS)and other remotely sensed data.While the ALS data were acquired over a t...Background:The Norwegian forest resource map(SR16)maps forest attributes by combining national forest inventory(NFI),airborne laser scanning(ALS)and other remotely sensed data.While the ALS data were acquired over a time interval of 10 years using various sensors and settings,the NFI data are continuously collected.Aims of this study were to analyze the effects of stratification on models linking remotely sensed and field data,and assess the accuracy overall and at the ALS project level.Materials and methods:The model dataset consisted of 9203 NFI field plots and data from 367 ALS projects,covering 17 Mha and 2/3 of the productive forest in Norway.Mixed-effects regression models were used to account for differences among ALS projects.Two types of stratification were used to fit models:1)stratification by the three main tree species groups spruce,pine and deciduous resulted in species-specific models that can utilize a satellite-based species map for improving predictions,and 2)stratification by species and maturity class resulted in stratum-specific models that can be used in forest management inventories where each stand regularly is visually stratified accordingly.Stratified models were compared to general models that were fit without stratifying the data.Results:The species-specific models had relative root-mean-squared errors(RMSEs)of 35%,34%,31%,and 12% for volume,aboveground biomass,basal area,and Lorey’s height,respectively.These RMSEs were 2-7 percentage points(pp)smaller than those of general models.When validating using predicted species,RMSEs were 0-4 pp.smaller than those of general models.Models stratified by main species and maturity class further improved RMSEs compared to species-specific models by up to 1.8 pp.Using mixed-effects models over ordinary least squares models resulted in a decrease of RMSE for timber volume of 1.0-3.9 pp.,depending on the main tree species.RMSEs for timber volume ranged between 19%-59% among individual ALS projects.Conclusions:The stratification by tree species considerably improved models of forest structural variables.A further stratification by maturity class improved these models only moderately.The accuracy of the models utilized in SR16 were within the range reported from other ALS-based forest inventories,but local variations are apparent.展开更多
Static assignment of IP addresses or identifiers can be exploited by an adversary to attack a network. However, existing dynamic IP address assignment approaches suffer from two limitations, namely: participation of t...Static assignment of IP addresses or identifiers can be exploited by an adversary to attack a network. However, existing dynamic IP address assignment approaches suffer from two limitations, namely: participation of terminals in the assignment and inadequate network server management. Thus, in this paper, we propose an Overall-transparent Dynamic Identifier-mapping Mechanism(ODIM) to manage the identifier of network nodes to defend against scanning and worm propagation in the Smart Identifier NETwork(SINET). We establish the selection and allocation constraints, and present selection and allocation algorithms to determine the constraints. The non-repetition probability and cover cycle allow us to evaluate the defense efficiency against scanning. We propose the probability for routing identifiers and derive the defense efficiency of ODIM against worm propagation. Simulation results and theoretical analysis show that the proposed method effectively reduces the detection probability of Routing IDentifiers(RIDs) and thus improves defense capabilities against worm propagation.展开更多
Elucidating the structure-activity relationship in electrocatalysis is of fundamental interest for electrochemical energy conversion and storage.However,the heterogeneity in the surface structure of electrocatalysts,i...Elucidating the structure-activity relationship in electrocatalysis is of fundamental interest for electrochemical energy conversion and storage.However,the heterogeneity in the surface structure of electrocatalysts,including the presence of various facets,poses an analytical challenge in revealing the true structure-activity relationship because the activity is conventionally measured on ensemble,resulting in an averaged activity that cannot be unequivocally associated with a single structural motif.Scanning electrochemical cell microscopy(SECCM)[1]combined with colocalized electron backscatter diffraction(EBSD)offers a direct way to reveal the correlative local electrochemical and structural information.Herein,we measured the hydrogen evolution reaction(HER)activity on Ag and its dependence on the crystal orientation.From the combined EBSD and SECCM mapping,it is found that Ag grains closer to{111}show a higher exchange current density,while those closer to{110}show a lower Tafel slope.The Tafel slope is also found to decrease with the step density increase.The ability to measure the electrocatalytic activity under a high mass-transfer rate allows us to reveal the activity difference at a high current density(up to 200 mA/cm^(2)).The approach reported here can be expanded to other systems to reveal the nature of active sites of electrocatalysis.展开更多
In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning prob...In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.展开更多
目的基于T2^(*)mapping定量分析业余马拉松运动员足踝部关节软骨的T2^(*)值,并分析其与性别、年龄、身体质量指数(body mass index,BMI)、跑龄、跑量之间的相关性。材料与方法于2023年7月份至2023年9月份招募重庆市长跑运动爱好者48名,...目的基于T2^(*)mapping定量分析业余马拉松运动员足踝部关节软骨的T2^(*)值,并分析其与性别、年龄、身体质量指数(body mass index,BMI)、跑龄、跑量之间的相关性。材料与方法于2023年7月份至2023年9月份招募重庆市长跑运动爱好者48名,其中跑量<300 km/月的36例(中低跑量组),跑量≥300 km/月的12例(高跑量组)。所有受试者均进行单侧无症状踝关节的MRI扫描,扫描序列包括T2^(*)mapping多回波自旋回波(spin echo,SE)序列矢状位、质子密度加权成像脂肪抑制(proton density-weighted imaging fat-saturated,PDWI-FS)序列矢状位、冠状位、横轴位以及T1加权脂肪抑制成像(T1-weighted imaging fat-saturated,T1WI-FS)序列横轴位。沿关节软骨轮廓边缘勾画距骨穹窿、跟骰关节跟骨面、骰骨面及后距下关节跟骨面、距骨面软骨作为感兴趣区(region of interest,ROI),获得相应的T2^(*)值。采用线性回归分析软骨T2^(*)值与年龄、BMI、跑龄的相关性,采用独立样本t检验分析不同跑量及不同性别间的软骨T2^(*)值差异。结果(1)距骨穹窿、跟骰关节跟骨面及骰骨面、后距下关节跟骨面及距骨面软骨T2^(*)值在性别上的差异均具有统计学意义(P=0.001、P<0.001、P=0.002、P=0.008、P=0.004);(2)高跑量组的距骨穹窿、后距下关节跟骨面软骨T2^(*)值高于中低跑量组(P=0.014、0.023),不同跑量的跟骰关节跟骨面及骰骨面、后距下关节距骨面软骨T2^(*)值的差异均无统计学意义(P=0.987、0.072、0.724);(3)距骨穹窿、跟骰关节跟骨面及骰骨面、后距下关节跟骨面、距骨面软骨T2^(*)值均与BMI呈正相关(r=0.376、0.384、0.300、0.422、0.455,P=0.005、0.004、0.019、0.001、0.001)。结论在业余马拉松运动员这一跑步群体中,与中低跑量相比,高跑量更有可能导致距骨穹窿、后距下关节跟骨面软骨损伤;而与较低的BMI相比,高BMI增加了距骨穹窿、跟骰关节跟骨面、骰骨面及后距下关节跟骨面、距骨面软骨损伤的风险。展开更多
Based on the study of the application of three-dimensional laser scanning technology in ancient building surveying and mapping,this paper briefly describes the working principle and flow of three-dimensional laser sca...Based on the study of the application of three-dimensional laser scanning technology in ancient building surveying and mapping,this paper briefly describes the working principle and flow of three-dimensional laser scanning technology.Based on the practical application,this paper puts forward the discussion of related problems and matters needing attention.This has a certain reference significance for the study of new technology in surveying and mapping of ancient buildings.展开更多
基金financial support of the National Natural Science Foundation of China(No.52371103)the Fundamental Research Funds for the Central Universities,China(No.2242023K40028)+1 种基金the Open Research Fund of Jiangsu Key Laboratory for Advanced Metallic Materials,China(No.AMM2023B01).financial support of the Research Fund of Shihezi Key Laboratory of AluminumBased Advanced Materials,China(No.2023PT02)financial support of Guangdong Province Science and Technology Major Project,China(No.2021B0301030005)。
文摘Oxide dispersion strengthened(ODS)alloys are extensively used owing to high thermostability and creep strength contributed from uniformly dispersed fine oxides particles.However,the existence of these strengthening particles also deteriorates the processability and it is of great importance to establish accurate processing maps to guide the thermomechanical processes to enhance the formability.In this study,we performed particle swarm optimization-based back propagation artificial neural network model to predict the high temperature flow behavior of 0.25wt%Al2O3 particle-reinforced Cu alloys,and compared the accuracy with that of derived by Arrhenius-type constitutive model and back propagation artificial neural network model.To train these models,we obtained the raw data by fabricating ODS Cu alloys using the internal oxidation and reduction method,and conducting systematic hot compression tests between 400 and800℃with strain rates of 10^(-2)-10 S^(-1).At last,processing maps for ODS Cu alloys were proposed by combining processing parameters,mechanical behavior,microstructure characterization,and the modeling results achieved a coefficient of determination higher than>99%.
基金supported by the National Institute of Food and Agriculture(NIFA)Research Grant(No.ALA2016-67021-24417)“Precision geospatial mapping of soil carbon content for agricultural productivity and lifecycle management”
文摘Soil carbon mapping is extremely useful in assessing the effect of land management practices on soil carbon storage.Applications of neutron-gamma analysis in scanning mode for mapping of soil carbon are discussed.A Global Positioning System(GPS)device and softwares required to simultaneously acquire gamma signals and geographical positions during scanning operations were added to an existing measurement system.The reliability of soil carbon measurements in scanning mode was demonstrated to be in agreement with results acquired from static mode.The error analysis indicated that scanning measurements can be conducted with the same accuracy as static measurements in approximately one fourth the time.To obtain results suitable for mapping analogous to traditional chemical analyses(i.e.,±0.5 in weight percent or±0.5 w%),scanning time over a given site should be ca.15 min using the current measurement system configuration.Based on this measurement time,a reasonable towing speed of 3–5 km h^-1,the necessity for complete site coverage during scanning,the number of sites(within the surveyed field),and the required total measurement time can be estimated.Soil carbon measurements for 28 field sites(total area ca.2.5 ha)were conducted in ca.8 h.Based on acquired data,a soil carbon distribution map was constructed utilizing various softwares.The surveyed field area included an asphalt road that had carbon readings higher than the surrounding land.The clarity with which these carbon-rich zones were delineated on the constructed map represents evidence supporting the veracity of this method.Neutron-gamma analysis technology can greatly facilitate timely construction of soil carbon maps.
文摘Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and modulation of evapotranspiration. It also plays an important role filtering urban water systems and reducing storm water runoff.Methods: We investigate the capacity of ALS data to individually detect, map and characterize large(taller than15 m) trees within the City of Vancouver. Large trees are critical for the function and character of Vancouver’s urban forest. We used an object-based approach for individual tree detection and segmentation to determine tree locations(position of the stem), to delineate the shape of the crowns and to categorize the latter either as coniferous or deciduous.Results: Results indicate a detection rate of 76.6% for trees > 15 m with a positioning error of 2.11 m(stem location). Extracted tree heights possessed a RMSE of 2.60 m and a bias of-1.87 m, whereas crown diameter was derived with a RMSE of 3.85 m and a bias of-2.06 m. Missed trees are principally a result of undetected treetops occurring in dense, overlapping canopies with more accurate detection and delineation of trees in open areas.Conclusion: By identifying key structural trees across Vancouver’s urban forests, we can better understand their role in providing ecosystem goods and services for city residents.
文摘High-density linkage maps are essential tools for genome analysis of various biological traits. Our developed compact multi-gel system, HEGS （high efficiency genome scanning） is a high-throughput and high-cost-performance electrophoresis apparatus. Using this system, a high-density （average interval 2.3 cM） map with 1 065 AFLP and 63 SSR markers was constructed from recombinant inbred lines of a japonica and indica hybrid in just two months of electrophoreses by a single person. More than 50% of the mapped AFLP markers were commonly polymorphic for several combinations between japonica and indica rice and 15% were applicable for genetically closer crosses between upland and lowland types of japonica rice. This system can be used for rapid analyses of all kinds of markers.
基金supported by the Norwegian Institute of Bioeconomy Research(NIBIO).
文摘Background:The Norwegian forest resource map(SR16)maps forest attributes by combining national forest inventory(NFI),airborne laser scanning(ALS)and other remotely sensed data.While the ALS data were acquired over a time interval of 10 years using various sensors and settings,the NFI data are continuously collected.Aims of this study were to analyze the effects of stratification on models linking remotely sensed and field data,and assess the accuracy overall and at the ALS project level.Materials and methods:The model dataset consisted of 9203 NFI field plots and data from 367 ALS projects,covering 17 Mha and 2/3 of the productive forest in Norway.Mixed-effects regression models were used to account for differences among ALS projects.Two types of stratification were used to fit models:1)stratification by the three main tree species groups spruce,pine and deciduous resulted in species-specific models that can utilize a satellite-based species map for improving predictions,and 2)stratification by species and maturity class resulted in stratum-specific models that can be used in forest management inventories where each stand regularly is visually stratified accordingly.Stratified models were compared to general models that were fit without stratifying the data.Results:The species-specific models had relative root-mean-squared errors(RMSEs)of 35%,34%,31%,and 12% for volume,aboveground biomass,basal area,and Lorey’s height,respectively.These RMSEs were 2-7 percentage points(pp)smaller than those of general models.When validating using predicted species,RMSEs were 0-4 pp.smaller than those of general models.Models stratified by main species and maturity class further improved RMSEs compared to species-specific models by up to 1.8 pp.Using mixed-effects models over ordinary least squares models resulted in a decrease of RMSE for timber volume of 1.0-3.9 pp.,depending on the main tree species.RMSEs for timber volume ranged between 19%-59% among individual ALS projects.Conclusions:The stratification by tree species considerably improved models of forest structural variables.A further stratification by maturity class improved these models only moderately.The accuracy of the models utilized in SR16 were within the range reported from other ALS-based forest inventories,but local variations are apparent.
文摘Static assignment of IP addresses or identifiers can be exploited by an adversary to attack a network. However, existing dynamic IP address assignment approaches suffer from two limitations, namely: participation of terminals in the assignment and inadequate network server management. Thus, in this paper, we propose an Overall-transparent Dynamic Identifier-mapping Mechanism(ODIM) to manage the identifier of network nodes to defend against scanning and worm propagation in the Smart Identifier NETwork(SINET). We establish the selection and allocation constraints, and present selection and allocation algorithms to determine the constraints. The non-repetition probability and cover cycle allow us to evaluate the defense efficiency against scanning. We propose the probability for routing identifiers and derive the defense efficiency of ODIM against worm propagation. Simulation results and theoretical analysis show that the proposed method effectively reduces the detection probability of Routing IDentifiers(RIDs) and thus improves defense capabilities against worm propagation.
基金sponsored by the Defense Advanced Research Project Agency (DARPA) and the Army Research Office and was accomplished under Grant Number W911NF-20-1-0304
文摘Elucidating the structure-activity relationship in electrocatalysis is of fundamental interest for electrochemical energy conversion and storage.However,the heterogeneity in the surface structure of electrocatalysts,including the presence of various facets,poses an analytical challenge in revealing the true structure-activity relationship because the activity is conventionally measured on ensemble,resulting in an averaged activity that cannot be unequivocally associated with a single structural motif.Scanning electrochemical cell microscopy(SECCM)[1]combined with colocalized electron backscatter diffraction(EBSD)offers a direct way to reveal the correlative local electrochemical and structural information.Herein,we measured the hydrogen evolution reaction(HER)activity on Ag and its dependence on the crystal orientation.From the combined EBSD and SECCM mapping,it is found that Ag grains closer to{111}show a higher exchange current density,while those closer to{110}show a lower Tafel slope.The Tafel slope is also found to decrease with the step density increase.The ability to measure the electrocatalytic activity under a high mass-transfer rate allows us to reveal the activity difference at a high current density(up to 200 mA/cm^(2)).The approach reported here can be expanded to other systems to reveal the nature of active sites of electrocatalysis.
基金supported by the National Key Research and Development Program of China(No.2017YFA0303500)the National Natural Science Foundation of China(No.11674302)。
文摘In this work,electron energy spectroscopic mapping of surface plasmon of Ag nanostructures on highly oriented pyrolytic graphite is reported.Benefitting from the angular dispersive feature of the present scanning probe electron energy spectrometer,a multi-channel detection mode is developed.By scanning along one direction,the two-dimensional intensity distribution of Ag surface plasmon excitation due to the collision of electron emitted from the tip can be obtained in parallel.The spectroscopic spatial resolution is determined to be around 80 nm.
基金Jiangxi Social Science Planning Project:Research on the Activation of Traditional Villages in Jiangxi Province from the Perspective of Cultural Conservation:A Case Study of Fuhe River Basin(Grant No.17BJ16).
文摘Based on the study of the application of three-dimensional laser scanning technology in ancient building surveying and mapping,this paper briefly describes the working principle and flow of three-dimensional laser scanning technology.Based on the practical application,this paper puts forward the discussion of related problems and matters needing attention.This has a certain reference significance for the study of new technology in surveying and mapping of ancient buildings.
