Several theorems on closed (resp. open) covering properties of H-spaces are obtained which improve and generalize the corresponding results of Sperner, Klee, Alexandroff-Pasynkoff, Berge, Ghouila-Houri, Danzer-Grunbau...Several theorems on closed (resp. open) covering properties of H-spaces are obtained which improve and generalize the corresponding results of Sperner, Klee, Alexandroff-Pasynkoff, Berge, Ghouila-Houri, Danzer-Grunbaum-Klee, Ky Fan, Shih-Tan, Horvath and Lassonde. As application an almost fixed point theorem for lower semi-continuous map in l.c.-spaces and a generalization of Tychonoffs fixed point theorem are proved in l.c.-spaces which improve those results of Ky Fan and Horvath.展开更多
The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experie...The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types （irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes）. We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; pH; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon （SOC） storage, decreased in the fol-lowing order： irrigated cropland （5,699 g/m^2） 〉 sandy grassland （3,390 g/m^2） 〉 rainfed cropland （2,411 g/m^2） 〉 fixed dunes （821 g/m^2） 〉 mobile dunes （463 g/m^2）. SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.展开更多
Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 parti...Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.展开更多
A new 3D coordination polymer,namely,[Yb_3（μ_3-OH）_3（μ_2-OH）（DDLA）_（2.5）（BIPY）]（1,H_2DDLA = 2,2-dipyridyl-4,4-dicarboxylic acid,BIPY = 2,2？-bipyridine）,has been synthesized via solvothermal method. The ...A new 3D coordination polymer,namely,[Yb_3（μ_3-OH）_3（μ_2-OH）（DDLA）_（2.5）（BIPY）]（1,H_2DDLA = 2,2-dipyridyl-4,4-dicarboxylic acid,BIPY = 2,2？-bipyridine）,has been synthesized via solvothermal method. The complex crystallizes in triclinic,space group P1 with a = 7.7339（4）,b = 15.6699（8）,c = 17.2221（9） ？,α = 68.8630（10）,β = 88.1890（10）,γ = 88.1740（10）°,V = 1945.27（17） ？~3,Z = 2,D_c = 2.296 g·cm^3,μ（MoKα） = 1.075 mm^（-1）,F（000） = 1268,S = 1.068,R = 0.0263 and wR = 1.067 for 5176 observed reflections with I 〉 2σ（I）. Compound 1 contains a unique alternating double trinucleate {[Yb_3（μ_3-OH）_2OH]_2}_n chain,in which Yb^（3＋） is bridged through μ_3-OH and μ_2-OH two coordination modes. The alternating double trinucleate chains are further extended into a 3D structure through DDLA^（2-） ligands by different coordination modes. The photoluminescence spectra show 1 is highly sensitized by the characteristic emission of Yb^（3＋） in the NIR region.展开更多
For the purpose of summarising the judicial experiencein adjudicating IP-related cases and familarising the readersin China and overseas with the practical situation of
Reclamation of lands abandoned after mining in mountain areas is critical to erosion control,safety from landslides,and ecological protection of mountain ecosystems.However,little is known about alpine coal mine recla...Reclamation of lands abandoned after mining in mountain areas is critical to erosion control,safety from landslides,and ecological protection of mountain ecosystems.However,little is known about alpine coal mine reclamation using the soil seed bank as a potential source for revegetation.We collected samples of persistent soil seed bank for germination experiments from nine reclaimed sites with different soil cover thicknesses and from six control sites in the Qilian Mountains of China.Soil properties of each site were determined(including soil water content,soil available potassium,soil available phosphorus,soil total nitrogen,pH,soil organic matter,soil total phosphorus,and soil total potassium,and soil alkali-hydrolyzable nitrogen),and the relationships of the characteristics of the soil seed bank with soil cover thickness and soil properties were examined.The results showed that the density,number of species,and diversity of the topsoil seed bank were significantly correlated with soil cover thickness,and all increased with the increment of soil cover thickness.Soil cover thickness controlled the soil seed bank by influencing soil properties.With the increase in soil cover thickness,soil properties(e.g.,soil organic matter,soil total nitrogen,etc.)content increased while soil pH decreased.The soil seed bank had the potential to restored the pre-mining habitat at reclaimed sites with approximately 20-cm soil cover thickness.Soil properties of reclaimed sites were lower than that of natural sites.The relationship between the soil seed bank and soil cover thickness determined in this study provides a foundation for improving reclamation measures used in coal mines,as well as for the management and monitoring of reclaimed areas.展开更多
A subgroup H of a group G is said to have the sub-cover-avoidance property in G ffthereis a chief series 1 = G0 ≤ G1 ≤…≤ Gn - G, such that Gi-1（H ∩ Gi） G for every i = 1,2,... ,l. In this paper, we give some...A subgroup H of a group G is said to have the sub-cover-avoidance property in G ffthereis a chief series 1 = G0 ≤ G1 ≤…≤ Gn - G, such that Gi-1（H ∩ Gi） G for every i = 1,2,... ,l. In this paper, we give some characteristic conditions for a group to be solvable under the assumptions that some subgroups of a group satisfy the sub-cover-avoidance property.展开更多
针对现有防篡改方法存在被篡改数据量过大、无法确保知识产权数据安全性的问题,引入区块链与改进密文策略属性基加密(Ciphertext Policy Attribute Based Encryption,CP-ABE)算法,开展对知识产权数据防篡改方法的设计研究。首先,利用区...针对现有防篡改方法存在被篡改数据量过大、无法确保知识产权数据安全性的问题,引入区块链与改进密文策略属性基加密(Ciphertext Policy Attribute Based Encryption,CP-ABE)算法,开展对知识产权数据防篡改方法的设计研究。首先,利用区块链技术创建知识产权数据智能合约,避免非法攻击者对其进行篡改;其次,利用改进CP-ABE算法控制知识产权数据细粒度访问,实现知识产权数据加密防篡改与授权访问;最后,进行实验分析。实验结果表明,应用该方法能够有效控制知识产权数据被篡改量,有利于保障知识产权拥有者的个人权益。展开更多
基金This project partially supported by National Natural Science Foundation of ChinaThis work was partially supported by NSERC of Canada under grant A-8096
文摘Several theorems on closed (resp. open) covering properties of H-spaces are obtained which improve and generalize the corresponding results of Sperner, Klee, Alexandroff-Pasynkoff, Berge, Ghouila-Houri, Danzer-Grunbaum-Klee, Ky Fan, Shih-Tan, Horvath and Lassonde. As application an almost fixed point theorem for lower semi-continuous map in l.c.-spaces and a generalization of Tychonoffs fixed point theorem are proved in l.c.-spaces which improve those results of Ky Fan and Horvath.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41271007, 31260089, and 31560161)the One Hundred Person Project of the Chinese Academy of Sciences (Y551821002)
文摘The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types （irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes）. We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; pH; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon （SOC） storage, decreased in the fol-lowing order： irrigated cropland （5,699 g/m^2） 〉 sandy grassland （3,390 g/m^2） 〉 rainfed cropland （2,411 g/m^2） 〉 fixed dunes （821 g/m^2） 〉 mobile dunes （463 g/m^2）. SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.
基金Funded by Natural National Science Foundation of China(NSFC)(No.11305149)National High-Tech R&D Program(863 Program)(No.2013AA030704)。
文摘Aluminum-matrix boron carbide (B4Cp/Al) is a kind of neutron absorbing material widely used in nuclear spent fuel storage. In order to improve the tensile property of B4Cp/Al composites, a new type of nano-Al2O3 particle (Al2O3np) reinforced B4Cp/Al + Al2O3np composites were prepared by powder metallurgy method. The Monte Carlo particle transport program (MCNP) was used to determine the influence of Al2O3np on the thermal neutron absorptivity of composites. The universal material testing machine and scanning electron microscope (SEM) were used to study the mechanical properties, microstructure and fracture morphology of B4Cp/Al composites. The results indicated that the neutron absorption properties of B4Cp/Al composites were not affected by the addition of nano-Al2O3 particles in the range of 1 wt%-15 wt%. The addition of Al2O3np can obviously reduce the grain size of B4Cp/Al matrix metals thus improve the tensile strength of the composites. The addition threshold of Al2O3np is about 2.5 wt%. Both B4Cp and Al2O3np change the fracture characteristics of the composites from toughness to brittleness, and the latter is more important.
基金financially supported by the National Natural Science Foundation of China(21503183)Dr.Scientific research Foundation of Yanan university(YDBK2015-02)
文摘A new 3D coordination polymer,namely,[Yb_3（μ_3-OH）_3（μ_2-OH）（DDLA）_（2.5）（BIPY）]（1,H_2DDLA = 2,2-dipyridyl-4,4-dicarboxylic acid,BIPY = 2,2？-bipyridine）,has been synthesized via solvothermal method. The complex crystallizes in triclinic,space group P1 with a = 7.7339（4）,b = 15.6699（8）,c = 17.2221（9） ？,α = 68.8630（10）,β = 88.1890（10）,γ = 88.1740（10）°,V = 1945.27（17） ？~3,Z = 2,D_c = 2.296 g·cm^3,μ（MoKα） = 1.075 mm^（-1）,F（000） = 1268,S = 1.068,R = 0.0263 and wR = 1.067 for 5176 observed reflections with I 〉 2σ（I）. Compound 1 contains a unique alternating double trinucleate {[Yb_3（μ_3-OH）_2OH]_2}_n chain,in which Yb^（3＋） is bridged through μ_3-OH and μ_2-OH two coordination modes. The alternating double trinucleate chains are further extended into a 3D structure through DDLA^（2-） ligands by different coordination modes. The photoluminescence spectra show 1 is highly sensitized by the characteristic emission of Yb^（3＋） in the NIR region.
文摘For the purpose of summarising the judicial experiencein adjudicating IP-related cases and familarising the readersin China and overseas with the practical situation of
基金supported by the National Key Research and Development Program of China (2019YFC0507400)
文摘Reclamation of lands abandoned after mining in mountain areas is critical to erosion control,safety from landslides,and ecological protection of mountain ecosystems.However,little is known about alpine coal mine reclamation using the soil seed bank as a potential source for revegetation.We collected samples of persistent soil seed bank for germination experiments from nine reclaimed sites with different soil cover thicknesses and from six control sites in the Qilian Mountains of China.Soil properties of each site were determined(including soil water content,soil available potassium,soil available phosphorus,soil total nitrogen,pH,soil organic matter,soil total phosphorus,and soil total potassium,and soil alkali-hydrolyzable nitrogen),and the relationships of the characteristics of the soil seed bank with soil cover thickness and soil properties were examined.The results showed that the density,number of species,and diversity of the topsoil seed bank were significantly correlated with soil cover thickness,and all increased with the increment of soil cover thickness.Soil cover thickness controlled the soil seed bank by influencing soil properties.With the increase in soil cover thickness,soil properties(e.g.,soil organic matter,soil total nitrogen,etc.)content increased while soil pH decreased.The soil seed bank had the potential to restored the pre-mining habitat at reclaimed sites with approximately 20-cm soil cover thickness.Soil properties of reclaimed sites were lower than that of natural sites.The relationship between the soil seed bank and soil cover thickness determined in this study provides a foundation for improving reclamation measures used in coal mines,as well as for the management and monitoring of reclaimed areas.
基金The NSF(10871210)of Chinathe NSF(06023728)of Guangdong Province
文摘A subgroup H of a group G is said to have the sub-cover-avoidance property in G ffthereis a chief series 1 = G0 ≤ G1 ≤…≤ Gn - G, such that Gi-1（H ∩ Gi） G for every i = 1,2,... ,l. In this paper, we give some characteristic conditions for a group to be solvable under the assumptions that some subgroups of a group satisfy the sub-cover-avoidance property.
文摘针对现有防篡改方法存在被篡改数据量过大、无法确保知识产权数据安全性的问题,引入区块链与改进密文策略属性基加密(Ciphertext Policy Attribute Based Encryption,CP-ABE)算法,开展对知识产权数据防篡改方法的设计研究。首先,利用区块链技术创建知识产权数据智能合约,避免非法攻击者对其进行篡改;其次,利用改进CP-ABE算法控制知识产权数据细粒度访问,实现知识产权数据加密防篡改与授权访问;最后,进行实验分析。实验结果表明,应用该方法能够有效控制知识产权数据被篡改量,有利于保障知识产权拥有者的个人权益。
