城市轨道交通信号系统在风险、可靠性和安全评价等方面的研究很多,在脆弱性方面的研究较少。笔者通过建立城市轨道交通信号系统面向对象的Petri网模型,提出信号系统脆弱性的定量分析方法。首先,提出了城市轨道交通信号系统的脆弱性概念...城市轨道交通信号系统在风险、可靠性和安全评价等方面的研究很多,在脆弱性方面的研究较少。笔者通过建立城市轨道交通信号系统面向对象的Petri网模型,提出信号系统脆弱性的定量分析方法。首先,提出了城市轨道交通信号系统的脆弱性概念,辨识了信号系统脆弱性程度的影响要素。其次,依据某地铁对信号设备的运营维护分工,把信号设备按照空间布局分为正线轨旁类信号设备、车载类信号设备、控制中心类信号设备和车辆段类信号设备,采取基于对象的有色Petri网(Objects Oriented Colored Petri Net,OOCPN)方法为信号系统建立分析模型,并利用OOCPN运行特征提出脆弱性影响要素的攻击路径搜索算法。最后,阐述了信号系统脆弱性分析的量化计算方法与步骤,并进行了实例验证,实现信号系统的脆弱性量化分析。展开更多
In a field experiment, the populations of major soil fauna groups including earthworms, enchytraeids,arthropods and nematodes were examined in conventional tillage (CT) and no-tillage (NT) red soil ecosystems to evalu...In a field experiment, the populations of major soil fauna groups including earthworms, enchytraeids,arthropods and nematodes were examined in conventional tillage (CT) and no-tillage (NT) red soil ecosystems to evaluate their responses to tillage disturbance. Earthworms, macrry and micro-arthropods were stimulated under NT with earthworms showing the highest population increase by four times, while enchytraeids and nematodes favored CT system, predicting certain adaptability of these animals to plow-disturbed soil environment. On the basis of relative response index it was found that soil fauna was more sensitive to tillage than soil resource base (C and N pools) and microflora. The population structure of soil fauna was also affected by tillage treatments. Analysis on nematode trophic groups showed that bacteria-feeding and plant parasitic nematodes were more abundant in CT soil whereas the proportions of fungivores and omnivorepredators increased in NT soil. Possible reasons for the differentiation in both size and structure of the fauna population were discussed and the ecological significance involved in these changes was emphasized.展开更多
The urban vulnerability poses a serious challenge to achieving sustainable devel- opment. With the concentration of the population and the economy, cities must manage the higher frequencies and risks of various hazard...The urban vulnerability poses a serious challenge to achieving sustainable devel- opment. With the concentration of the population and the economy, cities must manage the higher frequencies and risks of various hazards and are becoming more vulnerable. Re- search on the assessment and regulatory control of urban vulnerability is of great significance for both urbanization quality improvement and sustainable development in China or other countries in the world. Because of the complexity of cities and vulnerability concepts, existing studies have focused on different aspects of urban vulnerability. And the research content of urban vulnerability is scattered and relatively independent, leading to a lack of comparability among the research data and resulting in tremendous difficulties in summarizing the conclu- sions through comparison of independent research data. Therefore the goal of this study was to construct urban vulnerability index （UV/） from the perspective of sustainable development that could assess urban vulnerability comprehensively. In this study, we selected 10 subin- dexes involving 36 specific parameters from four aspects （resources, eco-environmental sys- tems, economics, and social development） to construct a comprehensive index system. We also established the standard values of measurements. Then we take 288 prefecture-level cities in China as a study area and evaluate its overall urban vulnerability and its spatial differentiation. Results indicate that urban vulnerability of China has a remarkable spatial differentiation of both ＂gradient distribution＂ and ＂clustered distribution＂; the extent of urban vulnerability corresponds to city size, the bigger the city, the lower its vulnerability; re- source-based cities are more vulnerable than comprehensive cities; a city＇s economic growth rate does not reflect the extent of its urban vulnerability. Further, we offer a few suggestions to cope with urban vulnerability in China.展开更多
文摘城市轨道交通信号系统在风险、可靠性和安全评价等方面的研究很多,在脆弱性方面的研究较少。笔者通过建立城市轨道交通信号系统面向对象的Petri网模型,提出信号系统脆弱性的定量分析方法。首先,提出了城市轨道交通信号系统的脆弱性概念,辨识了信号系统脆弱性程度的影响要素。其次,依据某地铁对信号设备的运营维护分工,把信号设备按照空间布局分为正线轨旁类信号设备、车载类信号设备、控制中心类信号设备和车辆段类信号设备,采取基于对象的有色Petri网(Objects Oriented Colored Petri Net,OOCPN)方法为信号系统建立分析模型,并利用OOCPN运行特征提出脆弱性影响要素的攻击路径搜索算法。最后,阐述了信号系统脆弱性分析的量化计算方法与步骤,并进行了实例验证,实现信号系统的脆弱性量化分析。
文摘In a field experiment, the populations of major soil fauna groups including earthworms, enchytraeids,arthropods and nematodes were examined in conventional tillage (CT) and no-tillage (NT) red soil ecosystems to evaluate their responses to tillage disturbance. Earthworms, macrry and micro-arthropods were stimulated under NT with earthworms showing the highest population increase by four times, while enchytraeids and nematodes favored CT system, predicting certain adaptability of these animals to plow-disturbed soil environment. On the basis of relative response index it was found that soil fauna was more sensitive to tillage than soil resource base (C and N pools) and microflora. The population structure of soil fauna was also affected by tillage treatments. Analysis on nematode trophic groups showed that bacteria-feeding and plant parasitic nematodes were more abundant in CT soil whereas the proportions of fungivores and omnivorepredators increased in NT soil. Possible reasons for the differentiation in both size and structure of the fauna population were discussed and the ecological significance involved in these changes was emphasized.
基金National Natural Science Foundation of ChinaNo.41371177
文摘The urban vulnerability poses a serious challenge to achieving sustainable devel- opment. With the concentration of the population and the economy, cities must manage the higher frequencies and risks of various hazards and are becoming more vulnerable. Re- search on the assessment and regulatory control of urban vulnerability is of great significance for both urbanization quality improvement and sustainable development in China or other countries in the world. Because of the complexity of cities and vulnerability concepts, existing studies have focused on different aspects of urban vulnerability. And the research content of urban vulnerability is scattered and relatively independent, leading to a lack of comparability among the research data and resulting in tremendous difficulties in summarizing the conclu- sions through comparison of independent research data. Therefore the goal of this study was to construct urban vulnerability index （UV/） from the perspective of sustainable development that could assess urban vulnerability comprehensively. In this study, we selected 10 subin- dexes involving 36 specific parameters from four aspects （resources, eco-environmental sys- tems, economics, and social development） to construct a comprehensive index system. We also established the standard values of measurements. Then we take 288 prefecture-level cities in China as a study area and evaluate its overall urban vulnerability and its spatial differentiation. Results indicate that urban vulnerability of China has a remarkable spatial differentiation of both ＂gradient distribution＂ and ＂clustered distribution＂; the extent of urban vulnerability corresponds to city size, the bigger the city, the lower its vulnerability; re- source-based cities are more vulnerable than comprehensive cities; a city＇s economic growth rate does not reflect the extent of its urban vulnerability. Further, we offer a few suggestions to cope with urban vulnerability in China.
