In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investi...In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investigates an experimental laboratory smoke environment using an ammonium chloride smoke agent.The particle size distribution,composition,and mass flow distribution of the smoke were studied.Based on a discrete phase model and a kεturbulence model,a numerical simulation was developed to model the smoke generation and diffusion processes of the smoke agent in a confined space.The temporal and spatial distribution characteristics of the smoke mass concentration,velocity,and temperature in the space after smoke generation were analyzed,and the motion law governing the smoke diffusion throughout the entire space was summarized.Combined with the experimental verification of the smoke environment laboratory,the results showed that the smoke plume changed from fan-shaped to umbrella-shaped during smoke generation,and then continued to spread around.Meanwhile,the mass concentration of smoke in the space decreased from the middle outward;the changes in temperature and velocity were small and stable.In the diffusion stage(after 900 s),the mass concentration of smoke above 0.8 m was relatively uniform across an area of smoke that was 12 m thick.The concentration decreased over time,following a consistent decreasing trend,and the attenuation was negligible in a very short time.Therefore,this system was suitable for conducting experimental research on laser fuzes in a smoke environment.Owing to the stability of the equipment and facilities,the setup could reproduce the same experimental smoke environment by artificially controlling the smoke emission of the smoke agent.Overall,this work provides a theoretical reference for subsequent research efforts regarding the construction of uniform smoke environments and evaluating laser transmission characteristics in smoky environments.展开更多
The contamination and environmental risk assessment of the toxic elements in sediments from the middle-downstream (Zhuzhou-Changsha section) of the Xiangjiang River in Hunan Province of China were studied. The results...The contamination and environmental risk assessment of the toxic elements in sediments from the middle-downstream (Zhuzhou-Changsha section) of the Xiangjiang River in Hunan Province of China were studied. The results show that As, Cd, Pb and Zn are major contaminants in sediments, and average concentrations of these elements significantly exceed both the Control Standards for Pollutants in Sludge of China (GB4284-84) for agricultural use in acidic soils and the effect range median (ERM) values. The average concentrations of As, Cd and Pb in the river water slightly exceed the limit of Surface Water Environment Quality Standard (GB3838-2002). The concentrations of As and Cr in depth profiles extensively change, but slight changes are observed in Pb and Zn. Cd and Zn in most sediment samples can easily enter the food-chain and bring possible ecotoxicological risk to organisms living in sediments according to the risk assessment code.展开更多
The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiogr...The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiography combined with an experimental witness plate test method was used,and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was erployed to model the perforation process.The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate,respectlvely.Threedimensional numerical simulations of EFP's penetration under various impact conditions were conducted.The results show that,an ellipsoidal debris cloud,with the major-to-minor axis radio(a/b)smaller than that caused by shaped charge jets,was formed behind the target.With the increase of target thickness(h) and decrease of impact velocity(v_0) and obliquity(θ),the value of a/b decreases.The number of debris ejected from target is significantly higher than that from EFP.Based on the statistical analysis of the spatial distribution of the BAD,An engineering calculation model was established considering the influence of h,v_0 and θ.The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.展开更多
Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional c...Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.展开更多
PCG2 （Preconditioned Conjugate-Gradient Method 2）, the most popular mothod used in groundwater field, was used to solve the distributed model of large-scale groundwater system. Its principle and effect was analyzed ...PCG2 （Preconditioned Conjugate-Gradient Method 2）, the most popular mothod used in groundwater field, was used to solve the distributed model of large-scale groundwater system. Its principle and effect was analyzed mathematically, and verified by some specific examples. Numerical results acquired by PCG2 are accurate, it demonstrates that PCG2 is effective on methodology itself and man-ralated operation. So PCG2 is worthy of popularizing in the area of groundwater system for numerical analysis.展开更多
Studies in tobacco fields were conducted in 1993. The results showed that the distribution pattern of the larva was aggregative,and the aggregation did not change with the densities of population of the larva. The cha...Studies in tobacco fields were conducted in 1993. The results showed that the distribution pattern of the larva was aggregative,and the aggregation did not change with the densities of population of the larva. The characteristics of the vertical distribution of the larva on tobacco plants was more in the lower leaves than in the upper. The difference of population density among the tobacco fields with an elevation of 490 meters and 900 meters was not significant. The number of sampling was given under different precisions by using two-stage sampling technique. The average of leaf area loss caused by the larva in tobacco fields was 12.654 cm2.展开更多
This study aimed at gaining the cultivated land quality and the situation of soil pollution, taking Nehe City in Heilongjiang Province as an example, used ordinary Kriging interpolation of geostatistics, investigated ...This study aimed at gaining the cultivated land quality and the situation of soil pollution, taking Nehe City in Heilongjiang Province as an example, used ordinary Kriging interpolation of geostatistics, investigated the content and spatial distribution of eight kinds of heavy metal elements（namely Cd, Cr, Pb, Cu, Zn, Ni, Hg and As） in farming land soil, then analyzed the distinction and potential source of these heavy metal elements. The result showed that（1） all these elements had a certain amount of accumulation compared with those in the background of Heilongjiang Province, among which the accumulated levels of Cu and As were the highest.（2） Through statistic analyses, it showed that the spatial autocorrelation degrees of these four elements（namely Cd, Cr, Cu and Zn） were higher.（3） The pollution of Cd and Cu was relatively severe.（4） The spatial distribution features of these eight kinds of heavy metal elements were different, and the soil parent material and the human activity played double roles in the content distribution of heavy metal elements in farming land soil.展开更多
Five trace elements including Zn, Cu, Cd, Cr and As were investigated in surface water from ten typical sampling sites in Honghu Lake. The consequence indicated that all of the detected trace element levels were withi...Five trace elements including Zn, Cu, Cd, Cr and As were investigated in surface water from ten typical sampling sites in Honghu Lake. The consequence indicated that all of the detected trace element levels were within the allowed standard of China’s safe water guideline. The hazard quotients （HQ） and the hazard index （HI） value levels of all the five heavy metals in all sampling sites did not exceed the acceptable risk limits of non-carcinogenic value through the selected assessment method. Pearson’s correlation analysis and principal component analysis （PCA） indicated that Zn and Cu mainly originated from the natural alluviation and non-point agricultural sources, whereas Cr and As were mainly derived from industrial effluents. Moreover, Cd mainly originated from both non-point agricultural and industrial pollution sources. In addition, cluster analysis （CA） implied that cluster 1 （including S3, S5, S6 and S10） was considered the set of high pollution sites and cluster 2 （including S4 and S9） was identified as the set of moderate pollution sites.展开更多
remote sensing of woody vegetation in savannas has been inhibited by its complex stand structure and abundant vegetation species.An understanding of the distribution and spatial variation in savanna vegetation is crit...remote sensing of woody vegetation in savannas has been inhibited by its complex stand structure and abundant vegetation species.An understanding of the distribution and spatial variation in savanna vegetation is critical for making timely assessments of the ecosystem conditions.This study investigated the possibility of improving the prediction of woody vegetation in tropical savannas using an approach that integrates spatial statistics and remote sensing.展开更多
Electrical conductivity(EC)is considered as the most important indicator for assessment of groundwater quality.Determination of suitable interpolation method for derivation of groundwater quality variables map such as...Electrical conductivity(EC)is considered as the most important indicator for assessment of groundwater quality.Determination of suitable interpolation method for derivation of groundwater quality variables map such as EC is dependent on region conditions and existence of enough data.For determining groundwater EC,341 groundwater samples were randomly collected from the central regions of Guilan province,paddy soils,in northern Iran.Interpolation methods including inverse distance weighting(IDW),global polynomial interpolation(GPI),local polynomial interpolation(LPI),radial basis function(RBF),ordinary kriging(OK)and empirical Bayesian Kriging(EBK)were used to generate spatial distribution of groundwater EC.The results indicate that EBK is a superior method with the least RMSE,MAE and the highest R 2.The generated maps can be used to identify the regions in the studied area where groundwater could be allowed to be extracted and utilized by farmers to reduce adverse effect of the scarcity of surface water.展开更多
基金the Central University Special Funding for Basic Scientific Research(Grant No.30918012201)the Foundation of JWKJW Field(Grant 2020-JCJQ-JJ-392)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX20_0315).
文摘In response to the demand for short-range detection of anti-smoke environment interference by laser fuzes,this study proposes a smoke environment simulation of non-uniform continuous point source diffusion and investigates an experimental laboratory smoke environment using an ammonium chloride smoke agent.The particle size distribution,composition,and mass flow distribution of the smoke were studied.Based on a discrete phase model and a kεturbulence model,a numerical simulation was developed to model the smoke generation and diffusion processes of the smoke agent in a confined space.The temporal and spatial distribution characteristics of the smoke mass concentration,velocity,and temperature in the space after smoke generation were analyzed,and the motion law governing the smoke diffusion throughout the entire space was summarized.Combined with the experimental verification of the smoke environment laboratory,the results showed that the smoke plume changed from fan-shaped to umbrella-shaped during smoke generation,and then continued to spread around.Meanwhile,the mass concentration of smoke in the space decreased from the middle outward;the changes in temperature and velocity were small and stable.In the diffusion stage(after 900 s),the mass concentration of smoke above 0.8 m was relatively uniform across an area of smoke that was 12 m thick.The concentration decreased over time,following a consistent decreasing trend,and the attenuation was negligible in a very short time.Therefore,this system was suitable for conducting experimental research on laser fuzes in a smoke environment.Owing to the stability of the equipment and facilities,the setup could reproduce the same experimental smoke environment by artificially controlling the smoke emission of the smoke agent.Overall,this work provides a theoretical reference for subsequent research efforts regarding the construction of uniform smoke environments and evaluating laser transmission characteristics in smoky environments.
基金Project (20507022) supported by the National Natural Science Foundation of ChinaProject (EREH050303) supported by the Foundation of Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health
文摘The contamination and environmental risk assessment of the toxic elements in sediments from the middle-downstream (Zhuzhou-Changsha section) of the Xiangjiang River in Hunan Province of China were studied. The results show that As, Cd, Pb and Zn are major contaminants in sediments, and average concentrations of these elements significantly exceed both the Control Standards for Pollutants in Sludge of China (GB4284-84) for agricultural use in acidic soils and the effect range median (ERM) values. The average concentrations of As, Cd and Pb in the river water slightly exceed the limit of Surface Water Environment Quality Standard (GB3838-2002). The concentrations of As and Cr in depth profiles extensively change, but slight changes are observed in Pb and Zn. Cd and Zn in most sediment samples can easily enter the food-chain and bring possible ecotoxicological risk to organisms living in sediments according to the risk assessment code.
基金supported by National Natural Science Foundation of China(Grant no.11872123)。
文摘The behind-armor debris(BAD) formed by the perforation of an EFP is the main damage factor for the secondary destruction to the behind-armor components.Aiming at investigating the BAD caused by EFP,flash X-ray radiography combined with an experimental witness plate test method was used,and the FEM-SPH adaptive conversion algorithm in LS-DYNA software was erployed to model the perforation process.The simulation results of the debris cloud shape and number of debris were in good agreement with the flash X-ray radiographs and perforated holes on the witness plate,respectlvely.Threedimensional numerical simulations of EFP's penetration under various impact conditions were conducted.The results show that,an ellipsoidal debris cloud,with the major-to-minor axis radio(a/b)smaller than that caused by shaped charge jets,was formed behind the target.With the increase of target thickness(h) and decrease of impact velocity(v_0) and obliquity(θ),the value of a/b decreases.The number of debris ejected from target is significantly higher than that from EFP.Based on the statistical analysis of the spatial distribution of the BAD,An engineering calculation model was established considering the influence of h,v_0 and θ.The model can with reasonable accuracy predict the quantity and velocity distribution characteristics of BAD formed by EFP.
基金supported by the National Natural Science Foundation of China(Grant No.11822203and 11702026)。
文摘Non-cylindrical casings filled with explosives have undergone rapid development in warhead design and explosion control.The fragment spatial distribution of prismatic casings is more complex than that of traditional cylindrical casings.In this study,numerical and experimental investigations into the fragment spatial distribution of a prismatic casing were conducted.A new numerical method,which adds the Lagrangian marker points to the Eulerian grid,was proposed to track the multi-material interfaces and material dynamic fractures.Physical quantity mappings between the Lagrangian marker points and Eulerian grid were achieved by their topological relationship.Thereafter,the fragment spatial distributions of the prismatic casing with different fragment sizes,fragment shapes,and casing geometries were obtained using the numerical method.Moreover,fragment spatial distribution experiments were conducted on the prismatic casing with different fragment sizes and shapes,and the experimental data were compared with the numerical results.The effects of the fragment and casing geometry on the fragment spatial distributions were determined by analyzing the numerical results and experimental data.Finally,a formula including the casing geometry parameters was fitted to predict the fragment spatial distribution of the prismatic casing under internal explosive loading.
基金Supported by National Natural Science Foundation (30370825)
文摘PCG2 （Preconditioned Conjugate-Gradient Method 2）, the most popular mothod used in groundwater field, was used to solve the distributed model of large-scale groundwater system. Its principle and effect was analyzed mathematically, and verified by some specific examples. Numerical results acquired by PCG2 are accurate, it demonstrates that PCG2 is effective on methodology itself and man-ralated operation. So PCG2 is worthy of popularizing in the area of groundwater system for numerical analysis.
文摘Studies in tobacco fields were conducted in 1993. The results showed that the distribution pattern of the larva was aggregative,and the aggregation did not change with the densities of population of the larva. The characteristics of the vertical distribution of the larva on tobacco plants was more in the lower leaves than in the upper. The difference of population density among the tobacco fields with an elevation of 490 meters and 900 meters was not significant. The number of sampling was given under different precisions by using two-stage sampling technique. The average of leaf area loss caused by the larva in tobacco fields was 12.654 cm2.
基金Supported by the National Natural Science Foundation of China(D201401)the Natural Science Foundation of Heilongjiang Province of China
文摘This study aimed at gaining the cultivated land quality and the situation of soil pollution, taking Nehe City in Heilongjiang Province as an example, used ordinary Kriging interpolation of geostatistics, investigated the content and spatial distribution of eight kinds of heavy metal elements（namely Cd, Cr, Pb, Cu, Zn, Ni, Hg and As） in farming land soil, then analyzed the distinction and potential source of these heavy metal elements. The result showed that（1） all these elements had a certain amount of accumulation compared with those in the background of Heilongjiang Province, among which the accumulated levels of Cu and As were the highest.（2） Through statistic analyses, it showed that the spatial autocorrelation degrees of these four elements（namely Cd, Cr, Cu and Zn） were higher.（3） The pollution of Cd and Cu was relatively severe.（4） The spatial distribution features of these eight kinds of heavy metal elements were different, and the soil parent material and the human activity played double roles in the content distribution of heavy metal elements in farming land soil.
基金Projects(51578222,51178172) supported by the National Natural Science Foundation of ChinaProjects(17Z017,17G025) supported by the Humanities and Social Science Project of Hubei Provincial Education Department,China+1 种基金Project(1718WT15) supported by the Hubei College Student Affairs Research Institute,ChinaProjects(2016J1410,2016J1411) supported by the Graduate Innovative Education Program of Zhongnan University of Economics and Law,China
文摘Five trace elements including Zn, Cu, Cd, Cr and As were investigated in surface water from ten typical sampling sites in Honghu Lake. The consequence indicated that all of the detected trace element levels were within the allowed standard of China’s safe water guideline. The hazard quotients （HQ） and the hazard index （HI） value levels of all the five heavy metals in all sampling sites did not exceed the acceptable risk limits of non-carcinogenic value through the selected assessment method. Pearson’s correlation analysis and principal component analysis （PCA） indicated that Zn and Cu mainly originated from the natural alluviation and non-point agricultural sources, whereas Cr and As were mainly derived from industrial effluents. Moreover, Cd mainly originated from both non-point agricultural and industrial pollution sources. In addition, cluster analysis （CA） implied that cluster 1 （including S3, S5, S6 and S10） was considered the set of high pollution sites and cluster 2 （including S4 and S9） was identified as the set of moderate pollution sites.
文摘remote sensing of woody vegetation in savannas has been inhibited by its complex stand structure and abundant vegetation species.An understanding of the distribution and spatial variation in savanna vegetation is critical for making timely assessments of the ecosystem conditions.This study investigated the possibility of improving the prediction of woody vegetation in tropical savannas using an approach that integrates spatial statistics and remote sensing.
文摘Electrical conductivity(EC)is considered as the most important indicator for assessment of groundwater quality.Determination of suitable interpolation method for derivation of groundwater quality variables map such as EC is dependent on region conditions and existence of enough data.For determining groundwater EC,341 groundwater samples were randomly collected from the central regions of Guilan province,paddy soils,in northern Iran.Interpolation methods including inverse distance weighting(IDW),global polynomial interpolation(GPI),local polynomial interpolation(LPI),radial basis function(RBF),ordinary kriging(OK)and empirical Bayesian Kriging(EBK)were used to generate spatial distribution of groundwater EC.The results indicate that EBK is a superior method with the least RMSE,MAE and the highest R 2.The generated maps can be used to identify the regions in the studied area where groundwater could be allowed to be extracted and utilized by farmers to reduce adverse effect of the scarcity of surface water.
