Rice farmers occupy a potentially important intersection between economics and hydrology in Northern California. While drought makes water an increasingly precious commodity across California, the monetary worth of wa...Rice farmers occupy a potentially important intersection between economics and hydrology in Northern California. While drought makes water an increasingly precious commodity across California, the monetary worth of water is not uniform across different localities and uses. As a result, circumstances have given many Sacramento Valley rice farmers the option to sell their water to users elsewhere, in lieu of using it themselves. Because the sold water is typically surface water that would normally help recharge local aquifers when applied to a field;it is reasonable to suspect that transferring that water elsewhere could adversely affect local aquifers since that recharge would be reduced. This study performs numerical experiments using the United States Geological Survey’s Central Valley Hydrologic Model (CVHM) to better understand the temporal effects of a set of land idling scenarios. CVHM is capable of modeling the entire Central Valley, which encompasses the Sacramento and San Joaquin Valleys, and of representing rice field idling on a large scale. These experiments were executed using historical data to contrast recently typical amounts of rice field idling with scenarios reflecting varying degrees of hypothetical, increased idling. In doing so, this study aims to characterize the nature and potential magnitude of idling rice fields on groundwater storage in the Sacramento Valley. The impact of these scenarios on groundwater storage was quantified relative to an unaltered baseline model scenario. The results of this research show rice field idling will reduce recharge and groundwater storage levels;these results may provide useful information for future policy decisions and provide a basis for future study.展开更多
The relocity and sirain-rate .field which are different from Avilzur's have beenestablished in Caitesian coordinates. Using the integral as a function of the upper limitand integration depending on a parameler, an...The relocity and sirain-rate .field which are different from Avilzur's have beenestablished in Caitesian coordinates. Using the integral as a function of the upper limitand integration depending on a parameler, an analylical upper-bound solution todrawing stress through idling rolls has been obtained in this paper.展开更多
The intake air control system of a gasoline engine is a typical nonlinear system, and included among the adverse fac-tors that always induce poor idle-speed control stability are dead time and disturbances in the inta...The intake air control system of a gasoline engine is a typical nonlinear system, and included among the adverse fac-tors that always induce poor idle-speed control stability are dead time and disturbances in the intake air control process. In this paper, to improve the responsiveness when idling with regard to disturbances, a mean-value engine model (MVEM) with dead time was constructed as the control object, and the two servo structures of sliding mode control (SMC) were studied for better idle control performance, especially in transient process of speed change. The simulation results confirmed that under the constraint condition of control input, the robustness of idle speed control that is being subjected to torque disturbances and noise disturbances can be greatly improved by use of the servo structure II.展开更多
When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is...When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.展开更多
With the acceleration of urban and rural development,the problem of rural idle residential land has become increasingly prominent,and its effective revitalization and utilization is of great significance for optimizin...With the acceleration of urban and rural development,the problem of rural idle residential land has become increasingly prominent,and its effective revitalization and utilization is of great significance for optimizing the allocation of land resources and promoting the sustainable development of rural economy.Based on the performance evaluation of the revitalization and utilization of rural idle residential land in previous studies,this paper discusses the theoretical framework and method system of the current evaluation system.This study first defines the concept connotations of rural idle residential land and their revitalization and utilization.It then summarizes the progress of domestic and international research on performance evaluation,and sorts out and explores the existing relevant research methods for land performance performance by domestic scholars,thereby making the reflective summary of the performance evaluation on the revitalization and utilization of rural idle residential land,and pointing out the possible future research direction.展开更多
秸秆焚烧容易污染空气,影响交通。常规秸秆焚烧监测难度较大,而卫星遥感数据具有覆盖面广,时效性强、分辨率高等优点,有利于秸秆焚烧监测工作的进展。本文将介绍如何使用MODIS数据提取秸秆焚烧火点的算法。在算法实现上采用交互式数据语...秸秆焚烧容易污染空气,影响交通。常规秸秆焚烧监测难度较大,而卫星遥感数据具有覆盖面广,时效性强、分辨率高等优点,有利于秸秆焚烧监测工作的进展。本文将介绍如何使用MODIS数据提取秸秆焚烧火点的算法。在算法实现上采用交互式数据语言IDL(Interactive Data Language)进行实现,大大缩短了人机交互时间,提高了秸秆焚烧点自动提取的响应速度,从而提高工作效率,促进秸秆焚烧监测工作的开展。展开更多
MODIS数据具有高时相分辨率、高光谱分辨率和中等地面分辨率的特征,利用MODIS数据来监测和提取旱情严重地区的水体信息已经成为一个重要的研究方向.本文利用各类地物在MODIS各个波段上的波谱特征差异性进行水体提取,但与以往水体信息提...MODIS数据具有高时相分辨率、高光谱分辨率和中等地面分辨率的特征,利用MODIS数据来监测和提取旱情严重地区的水体信息已经成为一个重要的研究方向.本文利用各类地物在MODIS各个波段上的波谱特征差异性进行水体提取,但与以往水体信息提取方法有创新之处在于:本文借助于非线性的指数函数对低反射的水体的反射率进行了拉伸而对高反射的非水体地物的反射率进行了压缩,从而提高了水体在短波红外上的反射率而抑制了非水体在红波段上的反射率,通过波段间的归一化处理进而构建出EXPWI(EXP Water Index)方法 .为了更进一步地提高水体信息提取的自动化程度,本文用ENVI/IDL编写了EXPWI模型.研究表明利用IDL编写的EXPWI法快速实现了中等分辨率遥感影像中水体信息的自动提取,能有效的抑制背景地物的干扰而清晰的识别出湖泊、河道和地表的微弱水体信息,而且能有效降低云对水体信息提取的干扰,更重要的是在抑制大气噪音对提取结果的干扰方面,EXPWI法的效果很好.展开更多
利用大气激光后向散射垂直剖面图与消偏振度相结合的方法,分析CALIPSO卫星偏振激光雷达的后向散射信号。以2008年11月23日和24日的CALIPSO卫星数据为例,研究了北京地区大气中云层在可见光和红外光波段的垂直和水平分布特征。利用交互式...利用大气激光后向散射垂直剖面图与消偏振度相结合的方法,分析CALIPSO卫星偏振激光雷达的后向散射信号。以2008年11月23日和24日的CALIPSO卫星数据为例,研究了北京地区大气中云层在可见光和红外光波段的垂直和水平分布特征。利用交互式数据语言IDL(interactive data language)得到大气后向散射强度的垂直分布及其消偏振度,根据垂直剖面图可以直观地观测大气中各成分(如气溶胶、低空云和卷云等)的空间分布情况,并且能清楚地显示大气边界层的高度,由消偏振度可准确获得云层的分布高度及厚度。观测数据的处理结果表明:在海拔高度3km～7km存在厚度为2km～2.5km的云,其消偏振度约为0.2。展开更多
文摘Rice farmers occupy a potentially important intersection between economics and hydrology in Northern California. While drought makes water an increasingly precious commodity across California, the monetary worth of water is not uniform across different localities and uses. As a result, circumstances have given many Sacramento Valley rice farmers the option to sell their water to users elsewhere, in lieu of using it themselves. Because the sold water is typically surface water that would normally help recharge local aquifers when applied to a field;it is reasonable to suspect that transferring that water elsewhere could adversely affect local aquifers since that recharge would be reduced. This study performs numerical experiments using the United States Geological Survey’s Central Valley Hydrologic Model (CVHM) to better understand the temporal effects of a set of land idling scenarios. CVHM is capable of modeling the entire Central Valley, which encompasses the Sacramento and San Joaquin Valleys, and of representing rice field idling on a large scale. These experiments were executed using historical data to contrast recently typical amounts of rice field idling with scenarios reflecting varying degrees of hypothetical, increased idling. In doing so, this study aims to characterize the nature and potential magnitude of idling rice fields on groundwater storage in the Sacramento Valley. The impact of these scenarios on groundwater storage was quantified relative to an unaltered baseline model scenario. The results of this research show rice field idling will reduce recharge and groundwater storage levels;these results may provide useful information for future policy decisions and provide a basis for future study.
文摘The relocity and sirain-rate .field which are different from Avilzur's have beenestablished in Caitesian coordinates. Using the integral as a function of the upper limitand integration depending on a parameler, an analylical upper-bound solution todrawing stress through idling rolls has been obtained in this paper.
文摘The intake air control system of a gasoline engine is a typical nonlinear system, and included among the adverse fac-tors that always induce poor idle-speed control stability are dead time and disturbances in the intake air control process. In this paper, to improve the responsiveness when idling with regard to disturbances, a mean-value engine model (MVEM) with dead time was constructed as the control object, and the two servo structures of sliding mode control (SMC) were studied for better idle control performance, especially in transient process of speed change. The simulation results confirmed that under the constraint condition of control input, the robustness of idle speed control that is being subjected to torque disturbances and noise disturbances can be greatly improved by use of the servo structure II.
基金Supported by the Major Science and Technology Projects in Jilin Province and Changchun City(20220301010GX).
文摘When the proton exchange membrane fuel cell(PEMFC)system is running,there will be a condition that does not require power output for a short time.In order to achieve zero power output under low power consumption,it is necessary to consider the diversity of control targets and the complexity of dynamic models,which brings the challenge of high-precision tracking control of the stack output power and cathode intake flow.For system idle speed control,a modelbased nonlinear control framework is constructed in this paper.Firstly,the nonlinear dynamic model of output power and cathode intake flow is derived.Secondly,a control scheme combining nonlinear extended Kalman filter observer and state feedback controller is designed.Finally,the control scheme is verified on the PEMFC experimental platform and compared with the proportion-integration-differentiation(PID)controller.The experimental results show that the control strategy proposed in this paper can realize the idle speed control of the fuel cell system and achieve the purpose of zero power output.Compared with PID controller,it has faster response speed and better system dynamics.
文摘With the acceleration of urban and rural development,the problem of rural idle residential land has become increasingly prominent,and its effective revitalization and utilization is of great significance for optimizing the allocation of land resources and promoting the sustainable development of rural economy.Based on the performance evaluation of the revitalization and utilization of rural idle residential land in previous studies,this paper discusses the theoretical framework and method system of the current evaluation system.This study first defines the concept connotations of rural idle residential land and their revitalization and utilization.It then summarizes the progress of domestic and international research on performance evaluation,and sorts out and explores the existing relevant research methods for land performance performance by domestic scholars,thereby making the reflective summary of the performance evaluation on the revitalization and utilization of rural idle residential land,and pointing out the possible future research direction.
文摘秸秆焚烧容易污染空气,影响交通。常规秸秆焚烧监测难度较大,而卫星遥感数据具有覆盖面广,时效性强、分辨率高等优点,有利于秸秆焚烧监测工作的进展。本文将介绍如何使用MODIS数据提取秸秆焚烧火点的算法。在算法实现上采用交互式数据语言IDL(Interactive Data Language)进行实现,大大缩短了人机交互时间,提高了秸秆焚烧点自动提取的响应速度,从而提高工作效率,促进秸秆焚烧监测工作的开展。
文摘MODIS数据具有高时相分辨率、高光谱分辨率和中等地面分辨率的特征,利用MODIS数据来监测和提取旱情严重地区的水体信息已经成为一个重要的研究方向.本文利用各类地物在MODIS各个波段上的波谱特征差异性进行水体提取,但与以往水体信息提取方法有创新之处在于:本文借助于非线性的指数函数对低反射的水体的反射率进行了拉伸而对高反射的非水体地物的反射率进行了压缩,从而提高了水体在短波红外上的反射率而抑制了非水体在红波段上的反射率,通过波段间的归一化处理进而构建出EXPWI(EXP Water Index)方法 .为了更进一步地提高水体信息提取的自动化程度,本文用ENVI/IDL编写了EXPWI模型.研究表明利用IDL编写的EXPWI法快速实现了中等分辨率遥感影像中水体信息的自动提取,能有效的抑制背景地物的干扰而清晰的识别出湖泊、河道和地表的微弱水体信息,而且能有效降低云对水体信息提取的干扰,更重要的是在抑制大气噪音对提取结果的干扰方面,EXPWI法的效果很好.
文摘利用大气激光后向散射垂直剖面图与消偏振度相结合的方法,分析CALIPSO卫星偏振激光雷达的后向散射信号。以2008年11月23日和24日的CALIPSO卫星数据为例,研究了北京地区大气中云层在可见光和红外光波段的垂直和水平分布特征。利用交互式数据语言IDL(interactive data language)得到大气后向散射强度的垂直分布及其消偏振度,根据垂直剖面图可以直观地观测大气中各成分(如气溶胶、低空云和卷云等)的空间分布情况,并且能清楚地显示大气边界层的高度,由消偏振度可准确获得云层的分布高度及厚度。观测数据的处理结果表明:在海拔高度3km～7km存在厚度为2km～2.5km的云,其消偏振度约为0.2。
