Economic clusters have been a central focus of current urban and regional research, policies and practices. However, a methodology to identify and analyze policy-relevant economic cluster dynamics is still not well de...Economic clusters have been a central focus of current urban and regional research, policies and practices. However, a methodology to identify and analyze policy-relevant economic cluster dynamics is still not well developed. Based on input-output(I-O) data of 1987, 1992, 1997, 2002 and 2007 of Beijing, this article presents an adapted principle component analysis for identifying the evolution of local economic cluster patterns. This research addresses the changes of economic interaction of industries with complementary and common activities over time. The identified clusters provide an insight into the reality of economic development in a diversifying urban economy: the increasing importance of services and the growing interaction between service and manufacturing industries. Our method therefore provides the analysts with a better understanding of the emergence, disappearance and development of economic clusters citywide. The results could be used to assist monitoring urban economic development and designing more practical urban economic strategies.展开更多
The key to studying urban sustainable development depends on quantifying stores, efficiencies of urban metabolisms and capturing urban metabolisms′ mechanisms. This paper builds up the metabolic emergy account and qu...The key to studying urban sustainable development depends on quantifying stores, efficiencies of urban metabolisms and capturing urban metabolisms′ mechanisms. This paper builds up the metabolic emergy account and quantifies some important concepts of emergy stores. Emphasis is placed on the urban metabolic model based on the slack based model(SBM) method to measure urban metabolic efficiencies. Urban metabolic mechanisms are discussed by using the regression method. By integrating these models, this paper analyzes the urban metabolic development in Beijing from 2001 to 2010. We conclude that the metabolic emergy stores of Beijing increased significantly from 2001 to 2010, with the emergy imported accounting for most of the increase. The metabolic efficiencies in Beijing have improved since the 2008 Olympic Games. The population, economic growth, industrial structures, and environmental governance positively affect the overall urban metabolism, while the land expansion, urbanization and environmentally technical levels hinder the improving of urban metabolic efficiencies. The SBM metabolic method and the regression model based on the emergy analysis provide insights into the urban metabolic efficiencies and the mechanism. They can promote to integrate such concepts into their sustainability analyses and policy decisions.展开更多
Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing ...Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing the two approaches of ES and SBM, as well as metabolic evolution index, urban metabolic stocks, efficiencies and elasticity of 31 Chinese cities are evaluated in a systematic way. The results imply that over the last decade(2000–2010), most of the cities, such as Chongqing, Nanjing, Shijiazhuang, Hangzhou, were experiencing drastic urban metabolic efficiency decline accompanied with a moderate decrease of industrial outputs. By contrast, metropolises and specialized cities have improved their urban metabolic performances, with higher output-input ratio and fewer undesirable outputs. However, their exported emergy experienced a substantial increase as well. It is concluded that local urban management might develop policies to diversify urban renewable supplies and address the undesirable output problems. The urban emergy of renewable resources should be specified as a prime focus for future research. In addition, mechanisms of different urban metabolic models will also be necessary for researchers.展开更多
The establishment and management of protected areas(PAs)often involve modifying traditional land use rights and changing the production and living activities of locals,which can lead to changes in the factors that dri...The establishment and management of protected areas(PAs)often involve modifying traditional land use rights and changing the production and living activities of locals,which can lead to changes in the factors that drive land use transitions.Our understanding of the spatiotemporal patterns of land use transition and the contributions of social-ecological drivers remains incomplete.In this study,we focused on the Yarlung Zangbu Grand Canyon National Park and examined how social-ecological factors influence land use transitions by developing a theoretical model of land use transitions within PAs.Our findings revealed that cropland,shrubland,grassland,and wetland experienced net losses in area,while forestland,water,ice/snow,barren land,and impervious land exhibited fluctuating growth patterns from 1985 to 2020.The net decrease in grassland was 157425.60 ha,while the net increase in forest was 140709.20 ha.The quality of land habitat increased from 0.5158 to 0.6656.Land use dominant and recessive transitions displayed varying spatial characteristics and scales across different time periods.In particular,the degree of influence of policy factors on land use dominant transition declined from 0.0800 in 1985-1990 to -0.0432 in 2010-2020,while its influence on land use recessive transition declined from 0.00058 in 1985-1990 to 0 in 2010-2020.The results show that social-ecological factors intricately influenced different types of land use transitions,leading to a shift from a balanced state to a new equilibrium.These results enhance our understanding of the spatiotemporal patterns and complex dynamics of land use transitions within PAs,providing insights and practical implications for effective land management in PAs by considering the land-human relationships.展开更多
We propose a density-matrix-formalism based scheme to study polarization mode dispersion(PMD)monitoring and compensation in optical fiber communication systems.Compared to traditional monitoring and compensation schem...We propose a density-matrix-formalism based scheme to study polarization mode dispersion(PMD)monitoring and compensation in optical fiber communication systems.Compared to traditional monitoring and compensation schemes based on the PMD vector in the Stokes space,the scheme we proposed requires no auxiliary matrices and can be handily extended to any higher-dimensional modal space,which is advantageous in mode-division multiplexing(MDM)systems.A 28 GBaud polarization division multiplexing quadrature phase-shift keying(PDM-QPSK)coherent simulation system is built to demonstrate that our scheme can implement the monitoring and compensation of 170 ps large differential-group-delay(DGD)that far exceeds the typical DGDs in practical optical communication systems.The results verify the effectiveness of the density-matrix-formalism based scheme in PMD monitoring and compensation,thus pave the way for further applications of the scheme in more general MDM optical communication systems.展开更多
基金Under the auspices of National Natural Science Foundation of China(No.41371008)
文摘Economic clusters have been a central focus of current urban and regional research, policies and practices. However, a methodology to identify and analyze policy-relevant economic cluster dynamics is still not well developed. Based on input-output(I-O) data of 1987, 1992, 1997, 2002 and 2007 of Beijing, this article presents an adapted principle component analysis for identifying the evolution of local economic cluster patterns. This research addresses the changes of economic interaction of industries with complementary and common activities over time. The identified clusters provide an insight into the reality of economic development in a diversifying urban economy: the increasing importance of services and the growing interaction between service and manufacturing industries. Our method therefore provides the analysts with a better understanding of the emergence, disappearance and development of economic clusters citywide. The results could be used to assist monitoring urban economic development and designing more practical urban economic strategies.
基金Under the auspices of National Natural Science Foundation of China(No.41371008,41101119)New Start Academic Research Projects of Beijing Union University(No.ZK201201)
文摘The key to studying urban sustainable development depends on quantifying stores, efficiencies of urban metabolisms and capturing urban metabolisms′ mechanisms. This paper builds up the metabolic emergy account and quantifies some important concepts of emergy stores. Emphasis is placed on the urban metabolic model based on the slack based model(SBM) method to measure urban metabolic efficiencies. Urban metabolic mechanisms are discussed by using the regression method. By integrating these models, this paper analyzes the urban metabolic development in Beijing from 2001 to 2010. We conclude that the metabolic emergy stores of Beijing increased significantly from 2001 to 2010, with the emergy imported accounting for most of the increase. The metabolic efficiencies in Beijing have improved since the 2008 Olympic Games. The population, economic growth, industrial structures, and environmental governance positively affect the overall urban metabolism, while the land expansion, urbanization and environmentally technical levels hinder the improving of urban metabolic efficiencies. The SBM metabolic method and the regression model based on the emergy analysis provide insights into the urban metabolic efficiencies and the mechanism. They can promote to integrate such concepts into their sustainability analyses and policy decisions.
基金National Natural Science Foundation of China(No.41530634,41530751)Key Consulting Project of the Chinese Academy of Science and Technology Strategic Consulting(No.Y02015001)+1 种基金Open Project Funding of Beijing Modern Industrial New Area Development Research Base in 2015(No.JD2015002)Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2014042)
文摘Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing the two approaches of ES and SBM, as well as metabolic evolution index, urban metabolic stocks, efficiencies and elasticity of 31 Chinese cities are evaluated in a systematic way. The results imply that over the last decade(2000–2010), most of the cities, such as Chongqing, Nanjing, Shijiazhuang, Hangzhou, were experiencing drastic urban metabolic efficiency decline accompanied with a moderate decrease of industrial outputs. By contrast, metropolises and specialized cities have improved their urban metabolic performances, with higher output-input ratio and fewer undesirable outputs. However, their exported emergy experienced a substantial increase as well. It is concluded that local urban management might develop policies to diversify urban renewable supplies and address the undesirable output problems. The urban emergy of renewable resources should be specified as a prime focus for future research. In addition, mechanisms of different urban metabolic models will also be necessary for researchers.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20020302)The Second Tibetan Plateau Scientific Expeditionand Research Program(2019QZKK0406).
文摘The establishment and management of protected areas(PAs)often involve modifying traditional land use rights and changing the production and living activities of locals,which can lead to changes in the factors that drive land use transitions.Our understanding of the spatiotemporal patterns of land use transition and the contributions of social-ecological drivers remains incomplete.In this study,we focused on the Yarlung Zangbu Grand Canyon National Park and examined how social-ecological factors influence land use transitions by developing a theoretical model of land use transitions within PAs.Our findings revealed that cropland,shrubland,grassland,and wetland experienced net losses in area,while forestland,water,ice/snow,barren land,and impervious land exhibited fluctuating growth patterns from 1985 to 2020.The net decrease in grassland was 157425.60 ha,while the net increase in forest was 140709.20 ha.The quality of land habitat increased from 0.5158 to 0.6656.Land use dominant and recessive transitions displayed varying spatial characteristics and scales across different time periods.In particular,the degree of influence of policy factors on land use dominant transition declined from 0.0800 in 1985-1990 to -0.0432 in 2010-2020,while its influence on land use recessive transition declined from 0.00058 in 1985-1990 to 0 in 2010-2020.The results show that social-ecological factors intricately influenced different types of land use transitions,leading to a shift from a balanced state to a new equilibrium.These results enhance our understanding of the spatiotemporal patterns and complex dynamics of land use transitions within PAs,providing insights and practical implications for effective land management in PAs by considering the land-human relationships.
基金supported by the National Natural Science Foundation of China(No.61501214)the Natural Science Foundation of Shandong Province(Nos.ZR2022MF284 and ZR2018MA044).
文摘We propose a density-matrix-formalism based scheme to study polarization mode dispersion(PMD)monitoring and compensation in optical fiber communication systems.Compared to traditional monitoring and compensation schemes based on the PMD vector in the Stokes space,the scheme we proposed requires no auxiliary matrices and can be handily extended to any higher-dimensional modal space,which is advantageous in mode-division multiplexing(MDM)systems.A 28 GBaud polarization division multiplexing quadrature phase-shift keying(PDM-QPSK)coherent simulation system is built to demonstrate that our scheme can implement the monitoring and compensation of 170 ps large differential-group-delay(DGD)that far exceeds the typical DGDs in practical optical communication systems.The results verify the effectiveness of the density-matrix-formalism based scheme in PMD monitoring and compensation,thus pave the way for further applications of the scheme in more general MDM optical communication systems.
