Urbanization is a complex process reflecting the growth, formation and develop- ment of cities and their systems. Measuring regional urbanization levels within a long time series may ensure healthy and harmonious urba...Urbanization is a complex process reflecting the growth, formation and develop- ment of cities and their systems. Measuring regional urbanization levels within a long time series may ensure healthy and harmonious urban development. Based on DMSP/OLS night- time light data, a human-computer interactive boundary correction method was used to ob- tain information about built-up urban areas in the Bohai Rim region from 1992 to 2012. Con- sequently, a method was proposed and applied to measure urbanization levels using four measurement scale units： administrative division, land-sea location, terrain feature, and geomorphological types. Our conclusions are： 1） The extraction results based on DMSP/OLS nighttime light data showed substantial agreement with those obtained using Landsat TM/ETM＋ data on spatial patterns. The overall accuracy was 97.70% on average, with an average Kappa of 0.79, indicating that the results extracted from DMSP/OLS nighttime light data were reliable and could well reflect the actual status of built-up urban areas. 2） Bohai Rim＇s urbanization level has increased significantly, demonstrating a high annual growth rate from 1998 to 2006. Areas with high urbanization levels have relocated evidently from capital to coastal cities. 3） The distribution of built-up urban areas showed a certain degree of zonal variation. The urbanization level was negatively correlated with relief amplitude and altitude. A high level of urbanization was found in low altitude platforms and low altitude plains, with a gradual narrowing of the gap between these two geomorphological types. 4） The measure- ment method presented in this study is fast, convenient, and incorporates multiple perspec- tives. It would offer various directions for urban construction and provide reference values for measuring national-level urbanization.展开更多
大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵...大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵列(field programmable gate array,FPGA)微秒级小步长并行仿真能力,提出一种面向双馈风电场站的发电单元FPGA并行仿真方法。首先,进行双馈感应电机微秒级高并行度离散化建模与换流器受控源建模;接着,对节点导纳矩阵分块降维以实现发电单元内部分网并行,并从整体电路解算层面提出单元级并行仿真框架;最后,考虑实时数字仿真器(real time digital simulator,RTDS)与FPGA仿真平台特点,分配发电单元的微秒级小步长仿真任务并搭建联合仿真硬件框架;通过对比RTDS标准模型与RTDS+FPGA联合仿真模型,验证所提并行仿真方法的准确性。展开更多
Polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM) are implicated in plants’ responses under conditions of abiotic stress. Previous research in other crops has indicated that polyamines and changes in ...Polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM) are implicated in plants’ responses under conditions of abiotic stress. Previous research in other crops has indicated that polyamines and changes in their concentrations are associated with drought tolerance under conditions of water-deficit stress;however, no information exists on cotton (Gossypium hirsutum L.). Growth chamber experiments were conducted with two cotton cultivars differing in drought tolerance, ST5288B2F (drought-sensitive) and Siokra L23 (drought-tolerant) in order to investigate the distribution of free polyamines, the effect of water-deficit stress on the polyamine metabolism of cotton reproductive units and their subtending leaves as well as the possible relationship between polyamines and drought tolerance in cotton. Our results showed that cotton ovaries contained significantly higher levels of total free polyamines compared to their subtending leaves under both control and water stress conditions. Water-deficit stress significantly increased PUT concentrations in ST5288B2F, while SPM levels significantly decreased in Siokra L23. The results indicated that water-deficit stress significantly affected cotton polyamine metabolism in reproductive structures and their subtending leaves;however, no clear relationship between drought-tolerance and changes in polyamine accumulation was established. Further research is needed to elucidate the mechanism according to which water-deficit stress affects polyamine metabolism.展开更多
In this article, we designed and synthesized a series of 5-（2,6-dimethyl-4H-pyran-4-ylidene）-1,3-diethyl-2-thioxodihydropyrimidine-4,6（1H, 5H）-dione（PD） unit based polymers（PFTDT, CZTDT, PHTDT and THTDT） for t...In this article, we designed and synthesized a series of 5-（2,6-dimethyl-4H-pyran-4-ylidene）-1,3-diethyl-2-thioxodihydropyrimidine-4,6（1H, 5H）-dione（PD） unit based polymers（PFTDT, CZTDT, PHTDT and THTDT） for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability（all above 377 °C）. Very broad absorption spectrum was also obtained from the polymer THTDT（300？850 nm）. CV characterization found that these polymers owned low highest occupied molecular orbital（HOMO） energy levels（？5.39 e V for THTDT, ？5.49 e V for CZTDT and ？5.78 e V for PFTDT） except for PHTDT（？5.17 e V）. The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.展开更多
基金Surveying and Mapping Geoinformation Nonprofit Specific Project,No.201512033National Natural Science Foundation of China,No.41171332+1 种基金Major State Basic Research Development Program of China,No.2015CB954101National Science Technology Basic Special Project,No.2011FY110400-2
文摘Urbanization is a complex process reflecting the growth, formation and develop- ment of cities and their systems. Measuring regional urbanization levels within a long time series may ensure healthy and harmonious urban development. Based on DMSP/OLS night- time light data, a human-computer interactive boundary correction method was used to ob- tain information about built-up urban areas in the Bohai Rim region from 1992 to 2012. Con- sequently, a method was proposed and applied to measure urbanization levels using four measurement scale units： administrative division, land-sea location, terrain feature, and geomorphological types. Our conclusions are： 1） The extraction results based on DMSP/OLS nighttime light data showed substantial agreement with those obtained using Landsat TM/ETM＋ data on spatial patterns. The overall accuracy was 97.70% on average, with an average Kappa of 0.79, indicating that the results extracted from DMSP/OLS nighttime light data were reliable and could well reflect the actual status of built-up urban areas. 2） Bohai Rim＇s urbanization level has increased significantly, demonstrating a high annual growth rate from 1998 to 2006. Areas with high urbanization levels have relocated evidently from capital to coastal cities. 3） The distribution of built-up urban areas showed a certain degree of zonal variation. The urbanization level was negatively correlated with relief amplitude and altitude. A high level of urbanization was found in low altitude platforms and low altitude plains, with a gradual narrowing of the gap between these two geomorphological types. 4） The measure- ment method presented in this study is fast, convenient, and incorporates multiple perspec- tives. It would offer various directions for urban construction and provide reference values for measuring national-level urbanization.
文摘大规模双馈风电场作为实现我国“双碳”目标的陆上风电主力,其高比例电力电子设备的接入对电力系统电磁暂态高精度仿真技术提出日益严苛的要求,面向上百台发电单元的双馈场站全拓扑精细化微秒级仿真研究仍相对空白。基于现场可编程门阵列(field programmable gate array,FPGA)微秒级小步长并行仿真能力,提出一种面向双馈风电场站的发电单元FPGA并行仿真方法。首先,进行双馈感应电机微秒级高并行度离散化建模与换流器受控源建模;接着,对节点导纳矩阵分块降维以实现发电单元内部分网并行,并从整体电路解算层面提出单元级并行仿真框架;最后,考虑实时数字仿真器(real time digital simulator,RTDS)与FPGA仿真平台特点,分配发电单元的微秒级小步长仿真任务并搭建联合仿真硬件框架;通过对比RTDS标准模型与RTDS+FPGA联合仿真模型,验证所提并行仿真方法的准确性。
文摘Polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM) are implicated in plants’ responses under conditions of abiotic stress. Previous research in other crops has indicated that polyamines and changes in their concentrations are associated with drought tolerance under conditions of water-deficit stress;however, no information exists on cotton (Gossypium hirsutum L.). Growth chamber experiments were conducted with two cotton cultivars differing in drought tolerance, ST5288B2F (drought-sensitive) and Siokra L23 (drought-tolerant) in order to investigate the distribution of free polyamines, the effect of water-deficit stress on the polyamine metabolism of cotton reproductive units and their subtending leaves as well as the possible relationship between polyamines and drought tolerance in cotton. Our results showed that cotton ovaries contained significantly higher levels of total free polyamines compared to their subtending leaves under both control and water stress conditions. Water-deficit stress significantly increased PUT concentrations in ST5288B2F, while SPM levels significantly decreased in Siokra L23. The results indicated that water-deficit stress significantly affected cotton polyamine metabolism in reproductive structures and their subtending leaves;however, no clear relationship between drought-tolerance and changes in polyamine accumulation was established. Further research is needed to elucidate the mechanism according to which water-deficit stress affects polyamine metabolism.
基金financially supported by the Research Program of 973 Program(No.2014CB643506)the National Natural Science Foundation of China(No.21401053)+2 种基金Project of Scientific Research and Development of Xiangyang(Year of 2013)Open Foundation of Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices(HLOM141003)Opening Project of Guangxi Colleges and Universities Key Laboratory of Beibu Gulf Oil and Natural Gas Resource Effective Utilization(No.2014KLOG03)
文摘In this article, we designed and synthesized a series of 5-（2,6-dimethyl-4H-pyran-4-ylidene）-1,3-diethyl-2-thioxodihydropyrimidine-4,6（1H, 5H）-dione（PD） unit based polymers（PFTDT, CZTDT, PHTDT and THTDT） for the first time. In these polymers, fluorene, 2,7-carbazole, phenothiazine and thiophene are employed as electron-donating groups and PD as electron-withdrawing group. TGA measurements demonstrated that these polymers possess good thermal stability（all above 377 °C）. Very broad absorption spectrum was also obtained from the polymer THTDT（300？850 nm）. CV characterization found that these polymers owned low highest occupied molecular orbital（HOMO） energy levels（？5.39 e V for THTDT, ？5.49 e V for CZTDT and ？5.78 e V for PFTDT） except for PHTDT（？5.17 e V）. The geometry and electronic properties of PFTDT, CZTDT, PHTDT and THTDT were investigated by means of theoretical calculation. All the above advantages demonstrate that PD based polymers could be candidates for electronic devices.
