Presently China mainly relies on the low cost of production factors and introducing advanced foreign technology to create an international competitive edge.Thepresent foreign trade growth mode,which is charaterized of...Presently China mainly relies on the low cost of production factors and introducing advanced foreign technology to create an international competitive edge.Thepresent foreign trade growth mode,which is charaterized of quantitative expansion,labor-intensive and low prices,low e ciency,unsustained,is facing lots ofdifficulties.The problems such as the worsening terms of trade,the huge trade surplus,too much dependence on foreign trade,the rising prices of production factors,difficulties in the introduction of high technology,excessive consumption of resources,environmental pressures exacerbated the situations.Therefore,China mustadopt effective measures into a sustained and high efficiency foreign trade growth mode,which is supposed to be described as optimization of export commoditystructure,market diversification,mainly relying on independent innovation and independent brands,promoting trade with science and technology,rationaliztion ofindustrial structure,focusing on high added value.展开更多
Spatially explicit models have become widely used in today＇s mathematical ecology and epidemiology to study the persistence of populations. For simplicity, population dynamics is often analysed by using ordinary diff...Spatially explicit models have become widely used in today＇s mathematical ecology and epidemiology to study the persistence of populations. For simplicity, population dynamics is often analysed by using ordinary differential equations （ODEs） or partial differential equations （PDEs） in the one-dimensional （1D） space. An important question is to predict species extinction or persistence rate by mean of computer simulation based on the spatial model. Recently, it has been reported that stable turbulent and regular waves are persistent based on the spatial susceptible-infected-resistant-susceptible （SIRS） model by using the cellular automata （CA） method in the two-dimensional （2D） space [Proc. Natl. Acad. Sci. USA 101, 18246 （2004）]. In this paper, we address other important issues relevant to phase transitions of epidemic persistence. We are interested in assessing the significance of the risk of extinction in 1D space. Our results show that the 2D space can considerably increase the possibility of persistence of spread of epidemics when the degree distribution of the individuals is uniform, i.e. the pattern of 2D spatial persistence corresponding to extinction in a 1D system with the same parameters. The trade-offs of extinction and persistence between the infection period and infection rate are observed in the 1D case. Moreover, near the trade-off （phase transition） line, an independent estimation of the dynamic exponent can be performed, and it is in excellent agreement with the result obtained by using the conjectured relationship of directed percolation. We find that the introduction of a short-range diffusion and a long-range diffusion among the neighbourhoods can enhance the persistence and global disease spread in the space.展开更多
分析“三生空间”的转型特征及其碳储量效应,对区域生态环境以及社会经济发有重要意义。运用地理信息系统(Geographic Information System,GIS)技术和生态系统服务和权衡的综合评估(Integrated Valuation of Ecosystem Services and Tra...分析“三生空间”的转型特征及其碳储量效应,对区域生态环境以及社会经济发有重要意义。运用地理信息系统(Geographic Information System,GIS)技术和生态系统服务和权衡的综合评估(Integrated Valuation of Ecosystem Services and Trade-offs,InVEST)模型,以广西壮族自治区(以下简称广西)为例,探讨“三生空间”转型对碳储量的影响。研究结果表明:1990—2020年广西“三生空间”转型变化显著,其中以2010—2020年间变化最为显著;广西“三生空间”碳储量在1990—2020年间总体呈下降趋势,在2010—2020年间下降最为剧烈;林地生态用地转向农业生产用地、草地生态用地,是导致广西“三生空间”碳储量减少主要的空间变迁形式,而碳储量增加的主要空间变迁形式则是农业生产用地和草地生态用地分别向林地生态用地的转变。“三生空间”的转型会对碳储量产生影响,应基于其演变规律,合理利用土地,实施国土空间管控措施。展开更多
文摘Presently China mainly relies on the low cost of production factors and introducing advanced foreign technology to create an international competitive edge.Thepresent foreign trade growth mode,which is charaterized of quantitative expansion,labor-intensive and low prices,low e ciency,unsustained,is facing lots ofdifficulties.The problems such as the worsening terms of trade,the huge trade surplus,too much dependence on foreign trade,the rising prices of production factors,difficulties in the introduction of high technology,excessive consumption of resources,environmental pressures exacerbated the situations.Therefore,China mustadopt effective measures into a sustained and high efficiency foreign trade growth mode,which is supposed to be described as optimization of export commoditystructure,market diversification,mainly relying on independent innovation and independent brands,promoting trade with science and technology,rationaliztion ofindustrial structure,focusing on high added value.
文摘Spatially explicit models have become widely used in today＇s mathematical ecology and epidemiology to study the persistence of populations. For simplicity, population dynamics is often analysed by using ordinary differential equations （ODEs） or partial differential equations （PDEs） in the one-dimensional （1D） space. An important question is to predict species extinction or persistence rate by mean of computer simulation based on the spatial model. Recently, it has been reported that stable turbulent and regular waves are persistent based on the spatial susceptible-infected-resistant-susceptible （SIRS） model by using the cellular automata （CA） method in the two-dimensional （2D） space [Proc. Natl. Acad. Sci. USA 101, 18246 （2004）]. In this paper, we address other important issues relevant to phase transitions of epidemic persistence. We are interested in assessing the significance of the risk of extinction in 1D space. Our results show that the 2D space can considerably increase the possibility of persistence of spread of epidemics when the degree distribution of the individuals is uniform, i.e. the pattern of 2D spatial persistence corresponding to extinction in a 1D system with the same parameters. The trade-offs of extinction and persistence between the infection period and infection rate are observed in the 1D case. Moreover, near the trade-off （phase transition） line, an independent estimation of the dynamic exponent can be performed, and it is in excellent agreement with the result obtained by using the conjectured relationship of directed percolation. We find that the introduction of a short-range diffusion and a long-range diffusion among the neighbourhoods can enhance the persistence and global disease spread in the space.
文摘分析“三生空间”的转型特征及其碳储量效应,对区域生态环境以及社会经济发有重要意义。运用地理信息系统(Geographic Information System,GIS)技术和生态系统服务和权衡的综合评估(Integrated Valuation of Ecosystem Services and Trade-offs,InVEST)模型,以广西壮族自治区(以下简称广西)为例,探讨“三生空间”转型对碳储量的影响。研究结果表明:1990—2020年广西“三生空间”转型变化显著,其中以2010—2020年间变化最为显著;广西“三生空间”碳储量在1990—2020年间总体呈下降趋势,在2010—2020年间下降最为剧烈;林地生态用地转向农业生产用地、草地生态用地,是导致广西“三生空间”碳储量减少主要的空间变迁形式,而碳储量增加的主要空间变迁形式则是农业生产用地和草地生态用地分别向林地生态用地的转变。“三生空间”的转型会对碳储量产生影响,应基于其演变规律,合理利用土地,实施国土空间管控措施。
