柔性交流输电装置(flexible AC transmission system,FACTS)在提升电网安全稳定和运行效率方面发挥着重要的作用。随着柔性交流输电装置在电力系统中的广泛应用,研究系统中多FACTS的协调控制机理对于实现系统的协调阻尼控制具有重要的...柔性交流输电装置(flexible AC transmission system,FACTS)在提升电网安全稳定和运行效率方面发挥着重要的作用。随着柔性交流输电装置在电力系统中的广泛应用,研究系统中多FACTS的协调控制机理对于实现系统的协调阻尼控制具有重要的理论价值和现实意义。针对实现多FACTS协调控制过程中遇到的交互影响问题,提出基于选择模式分析(selective modal analysis,SMA)和多变量频域控制理论的多FACTS交互作用机理分析方法,通过SMA实现多FACTS交互作用的有效特征量提取,进而通过多变量频域控制理论推导出多FACTS间的交互作用关系和发生条件,并在此基础上揭示多FACTS间交互作用机理。研究结果表明:处于多机系统同一电力区域中的多台FACTS阻尼控制器间存在相互制约的关系,当控制器参数满足负交互条件时会发生比较明显的负交互作用,严重时甚至威胁系统的安全运行,当控制器参数满足协调运行条件时才能保证多FACTS间的协调运行与控制。通过仿真验证了文中机理研究的正确性以及在实际电网中应用的可行性。展开更多
The effects of socio-demographics, land use characteristics and trip attributes on the commute mode choice are studied with a nested logit （NL） model. Based on the random utility maximum theory, the NL model is form...The effects of socio-demographics, land use characteristics and trip attributes on the commute mode choice are studied with a nested logit （NL） model. Based on the random utility maximum theory, the NL model is formulated. The analysis is carried out in the main area of Nanjing. Direct and cross elasticities are calculated to analyze the effects of travel time and travel cost on the selection of travel mode choice. The results reveal that the non-motorized travel modes are more attractive in the areas with higher housing and employment accessibility and car owners are found to be more likely to commute to work by car. The bus and subway choice probabilities are more sensitive to changes in travel times than to changes in travel costs. In conclusion, a comprehensive public transit system and effective integration of land use and transportation policies help to relieve the traffic congestion levels caused by the increasing urban sprawl.展开更多
This study is to investigate what factors and how they affect tours (trip chains) behavior. The key issue is the understanding and definition of tour and tour level mode. Also, these definitions should fit for the dat...This study is to investigate what factors and how they affect tours (trip chains) behavior. The key issue is the understanding and definition of tour and tour level mode. Also, these definitions should fit for the data. A semi-home based tour definition is stated, and a competing mode based tour mode is defined. Based on the definition, this study used Madison Area Data from National Household Survey to estimate a MNL structured model. It is found that travel distance could be a positive factor for car mode. Meanwhile, the number of trips is also a positive factor for choosing car.展开更多
From the view of system theory, modern agriculture in a region embodies elements conformity, structure optimization, multi-functionality and sustainable development. This paper first expounds on the relationship among...From the view of system theory, modern agriculture in a region embodies elements conformity, structure optimization, multi-functionality and sustainable development. This paper first expounds on the relationship among agricultural elements, structure, function and development theoretically, compartmentalizes agriculture types based on human-land elements matching, and depicts the development path of agricultural multi-functionality. it shows that the matching of human-land elements is a key to agricultural types, and the multi-functionality is an indication of agricultural development stages. At last, as a case study of Suzhou in eastern coastal area, the paper analyzes the evolvement situation and developing mechanism and some typical models of modern agriculture which suit to agriculture system evolvement. The results .show that in Suzhou the agriculture productivity, has improved greatly; And along with the agriculture structure optimizing, agriculture function has translated from ＂production ＂ to ＂non- production and production ＂. With simulation of agricultural trend in Suzhou, it is .found that Suzhou has a LP- dependence （labor productivity） on agricultural element, so Suzhou will has much more potential in land productivity. Based on the above analysis on agricultural system, some typical patterns on modern agriculture in Suzhou are brought up, such as export-oriented agriculture, enterprises-leading agriculture, science and technology, parks agriculture, stereoseopic agriculture, and tourism and sightseeing agriculture.展开更多
基金The National Natural Science Foundation of China(No.50908051)
文摘The effects of socio-demographics, land use characteristics and trip attributes on the commute mode choice are studied with a nested logit （NL） model. Based on the random utility maximum theory, the NL model is formulated. The analysis is carried out in the main area of Nanjing. Direct and cross elasticities are calculated to analyze the effects of travel time and travel cost on the selection of travel mode choice. The results reveal that the non-motorized travel modes are more attractive in the areas with higher housing and employment accessibility and car owners are found to be more likely to commute to work by car. The bus and subway choice probabilities are more sensitive to changes in travel times than to changes in travel costs. In conclusion, a comprehensive public transit system and effective integration of land use and transportation policies help to relieve the traffic congestion levels caused by the increasing urban sprawl.
文摘This study is to investigate what factors and how they affect tours (trip chains) behavior. The key issue is the understanding and definition of tour and tour level mode. Also, these definitions should fit for the data. A semi-home based tour definition is stated, and a competing mode based tour mode is defined. Based on the definition, this study used Madison Area Data from National Household Survey to estimate a MNL structured model. It is found that travel distance could be a positive factor for car mode. Meanwhile, the number of trips is also a positive factor for choosing car.
基金supported by Major Program of the National Natural Science Foundation of China (Grant No.40771014)
文摘From the view of system theory, modern agriculture in a region embodies elements conformity, structure optimization, multi-functionality and sustainable development. This paper first expounds on the relationship among agricultural elements, structure, function and development theoretically, compartmentalizes agriculture types based on human-land elements matching, and depicts the development path of agricultural multi-functionality. it shows that the matching of human-land elements is a key to agricultural types, and the multi-functionality is an indication of agricultural development stages. At last, as a case study of Suzhou in eastern coastal area, the paper analyzes the evolvement situation and developing mechanism and some typical models of modern agriculture which suit to agriculture system evolvement. The results .show that in Suzhou the agriculture productivity, has improved greatly; And along with the agriculture structure optimizing, agriculture function has translated from ＂production ＂ to ＂non- production and production ＂. With simulation of agricultural trend in Suzhou, it is .found that Suzhou has a LP- dependence （labor productivity） on agricultural element, so Suzhou will has much more potential in land productivity. Based on the above analysis on agricultural system, some typical patterns on modern agriculture in Suzhou are brought up, such as export-oriented agriculture, enterprises-leading agriculture, science and technology, parks agriculture, stereoseopic agriculture, and tourism and sightseeing agriculture.
