豇豆Vigna unguiculata喜温喜光,是一种适合在我国南方种植的豆科蔬菜。长期以来,豇豆病虫害多发重发,其中,蓟马是豇豆上最主要和最顽固的害虫之一。传统的化学防治方法对蓟马的防治效果常常不理想,并易造成农药残留问题。本文概述了我...豇豆Vigna unguiculata喜温喜光,是一种适合在我国南方种植的豆科蔬菜。长期以来,豇豆病虫害多发重发,其中,蓟马是豇豆上最主要和最顽固的害虫之一。传统的化学防治方法对蓟马的防治效果常常不理想,并易造成农药残留问题。本文概述了我国豇豆产业的种植情况和以蓟马为主的病虫害问题及豇豆蓟马研究现状,并从农艺措施、理化诱控、生物防治、化学防治和抗性治理角度总结了豇豆蓟马的综合防治技术。最后,从构建豇豆蓟马的有害生物综合治理(integrated pest management,IPM)技术体系、加强基础研究和防控技术产品开发、建立科学用药和农药监管制度3个方面提出建议,以期为我国豇豆产业的绿色可持续发展提供参考。展开更多
本研究根据 IPM 策略,将所提出的模型以害虫数量作为阁值指标,以此来刻画只有当害虫数量达 到阁值时才对其进行综合害虫治理的策略,通过化学和生物防治相结合,将 Leslie-Gower 模型扩 展为非光滑 Filippov 系统。 为了使害虫种群保持在...本研究根据 IPM 策略,将所提出的模型以害虫数量作为阁值指标,以此来刻画只有当害虫数量达 到阁值时才对其进行综合害虫治理的策略,通过化学和生物防治相结合,将 Leslie-Gower 模型扩 展为非光滑 Filippov 系统。 为了使害虫种群保持在给定的经济阁值 ET 或以下,利用 Filippov 凸方法和 Filippov 系统相关的定性分析理论,分析了模型在不同阁值的全局动力学,得到实平衡 点和伪平衡点的全局稳定性。 研究表明,在不同阁值范围下,增加自然天敌的释放量以及减少杀 虫剂的用量能有效避免害虫数量爆发,从而为综合害虫治理提供策略和方法。In this study, based on the IPM strategy, the proposed model uses the pest popu- lation as a threshold indicator to depict the strategy of integrated pest management only when the pest population reaches the threshold, and extends the Leslie-Gower model to a non-smooth Filippov system by combining chemical and biological control. In order to keep the pest population at or below a given economic threshold ET, the global dynamics of the model at different thresholds were analyzed by using the Filippov convex method and the qualitative analysis theory related to the Filippov system to obtain the global stability of the inner equilibrium and pseudo-equilibrium points. The study shows that increasing the release of natural enemies and decreasing the amount of insecticides can effectively avoid the outbreak of pest population in different threshold ranges, thus providing strategies and methods for integrated pest management.展开更多
The Internet is believed to bring more technological dividends to vulnerable farmers during the green agriculture transformation.However,this is different from the theory of skill-biased technological change,which emp...The Internet is believed to bring more technological dividends to vulnerable farmers during the green agriculture transformation.However,this is different from the theory of skill-biased technological change,which emphasizes that individuals with higher levels of human capital and more technological endowments benefit more.This study investigates the effects of Internet use on farmers'adoption of integrated pest management(IPM),theoretically and empirically,based on a dataset containing 1015 farmers in China's Shandong Province.By exploring the perspective of rational inattention,the reasons for the heterogeneity of the effects across farmers with different endowments,i.e.,education and land size,are analyzed.The potential endogeneity issues are addressed using the endogenous switching probit model.The results reveal that:(1)although Internet use significantly positively affects farmers'adoption of IPM,vulnerable farmers do not benefit more from it.Considerable selection bias leads to an overestimation of technological dividends for vulnerable farmers;(2)different sources of technology information lead to the difference in the degree of farmers'rational inattention toward Internet information,which plays a crucial role in the heterogeneous effect of Internet use;and(3)excessive dependence on strong-tie social network information sources entraps vulnerable farmers in information cocoons,hindering their ability to reap the benefits of Internet use fully.Therefore,it is essential to promote services geared towards elderly-oriented Internet agricultural technology information and encourage farmers with strong Internet utilization skills to share technology information with other farmers actively.展开更多
This paper explores some design parameters of an interior permanent magnet synchronous motor that contribute to enhancing motor performance.Various geometry parameters such as magnet dimension,machine diameter,stator ...This paper explores some design parameters of an interior permanent magnet synchronous motor that contribute to enhancing motor performance.Various geometry parameters such as magnet dimension,machine diameter,stator teeth height,and number of poles are analyzed to compare overall torque,power,and torque ripples in order to select the best design parameters and their ranges.Pyleecan,an open-source software,is used to design and optimize the motor for electric vehicle applications.Following optimization with Non-dominated Sorting Genetic Algorithm(NSGA-Ⅱ),two designs A and B were obtained for two objective functions and the corresponding torque ripples values of the design A and B were later reduced by 32%and 77%.Additionally,the impact of different magnet grades on the output performances is analyzed.展开更多
针对现有浅地层电磁探测设备受现场各种大型用电设备干扰强,导致信号失真严重,系统整体零件分散导致稳定性及使用维护不便,且体积较大不利于运输携带等问题,采用了一种智能功率管理模块(Intelligent Power Module,IPM)的电源功率组和抗...针对现有浅地层电磁探测设备受现场各种大型用电设备干扰强,导致信号失真严重,系统整体零件分散导致稳定性及使用维护不便,且体积较大不利于运输携带等问题,采用了一种智能功率管理模块(Intelligent Power Module,IPM)的电源功率组和抗噪性能优越的人工编码源伪随机码相结合设计的伪随机电磁发射机系统进行优化。文中从伪随机恒流方波脉冲电磁发射系统的原理、系统整体结构设计、硬件软件组成、样机实物形体描述以及实验结果方面进行了介绍,设计完成后整体体积较现有设备缩减了30%以上,经室外实验验证设计的发射机在抗噪性、稳定性、整装集成度以及后续维保便捷性方面都有较大程度的改善。展开更多
文摘豇豆Vigna unguiculata喜温喜光,是一种适合在我国南方种植的豆科蔬菜。长期以来,豇豆病虫害多发重发,其中,蓟马是豇豆上最主要和最顽固的害虫之一。传统的化学防治方法对蓟马的防治效果常常不理想,并易造成农药残留问题。本文概述了我国豇豆产业的种植情况和以蓟马为主的病虫害问题及豇豆蓟马研究现状,并从农艺措施、理化诱控、生物防治、化学防治和抗性治理角度总结了豇豆蓟马的综合防治技术。最后,从构建豇豆蓟马的有害生物综合治理(integrated pest management,IPM)技术体系、加强基础研究和防控技术产品开发、建立科学用药和农药监管制度3个方面提出建议,以期为我国豇豆产业的绿色可持续发展提供参考。
文摘本研究根据 IPM 策略,将所提出的模型以害虫数量作为阁值指标,以此来刻画只有当害虫数量达 到阁值时才对其进行综合害虫治理的策略,通过化学和生物防治相结合,将 Leslie-Gower 模型扩 展为非光滑 Filippov 系统。 为了使害虫种群保持在给定的经济阁值 ET 或以下,利用 Filippov 凸方法和 Filippov 系统相关的定性分析理论,分析了模型在不同阁值的全局动力学,得到实平衡 点和伪平衡点的全局稳定性。 研究表明,在不同阁值范围下,增加自然天敌的释放量以及减少杀 虫剂的用量能有效避免害虫数量爆发,从而为综合害虫治理提供策略和方法。In this study, based on the IPM strategy, the proposed model uses the pest popu- lation as a threshold indicator to depict the strategy of integrated pest management only when the pest population reaches the threshold, and extends the Leslie-Gower model to a non-smooth Filippov system by combining chemical and biological control. In order to keep the pest population at or below a given economic threshold ET, the global dynamics of the model at different thresholds were analyzed by using the Filippov convex method and the qualitative analysis theory related to the Filippov system to obtain the global stability of the inner equilibrium and pseudo-equilibrium points. The study shows that increasing the release of natural enemies and decreasing the amount of insecticides can effectively avoid the outbreak of pest population in different threshold ranges, thus providing strategies and methods for integrated pest management.
基金the National Social Science Fund of China(20CGL027)。
文摘The Internet is believed to bring more technological dividends to vulnerable farmers during the green agriculture transformation.However,this is different from the theory of skill-biased technological change,which emphasizes that individuals with higher levels of human capital and more technological endowments benefit more.This study investigates the effects of Internet use on farmers'adoption of integrated pest management(IPM),theoretically and empirically,based on a dataset containing 1015 farmers in China's Shandong Province.By exploring the perspective of rational inattention,the reasons for the heterogeneity of the effects across farmers with different endowments,i.e.,education and land size,are analyzed.The potential endogeneity issues are addressed using the endogenous switching probit model.The results reveal that:(1)although Internet use significantly positively affects farmers'adoption of IPM,vulnerable farmers do not benefit more from it.Considerable selection bias leads to an overestimation of technological dividends for vulnerable farmers;(2)different sources of technology information lead to the difference in the degree of farmers'rational inattention toward Internet information,which plays a crucial role in the heterogeneous effect of Internet use;and(3)excessive dependence on strong-tie social network information sources entraps vulnerable farmers in information cocoons,hindering their ability to reap the benefits of Internet use fully.Therefore,it is essential to promote services geared towards elderly-oriented Internet agricultural technology information and encourage farmers with strong Internet utilization skills to share technology information with other farmers actively.
基金funded by the Advanced Sustainable Manufacturing Technologies(ASTUTE2020)operation supporting manufacturing companies across Wales,which has been part-funded by the European Regional Development Fund through the Welsh Government and the participating Higher Education Institutions。
文摘This paper explores some design parameters of an interior permanent magnet synchronous motor that contribute to enhancing motor performance.Various geometry parameters such as magnet dimension,machine diameter,stator teeth height,and number of poles are analyzed to compare overall torque,power,and torque ripples in order to select the best design parameters and their ranges.Pyleecan,an open-source software,is used to design and optimize the motor for electric vehicle applications.Following optimization with Non-dominated Sorting Genetic Algorithm(NSGA-Ⅱ),two designs A and B were obtained for two objective functions and the corresponding torque ripples values of the design A and B were later reduced by 32%and 77%.Additionally,the impact of different magnet grades on the output performances is analyzed.
文摘针对现有浅地层电磁探测设备受现场各种大型用电设备干扰强,导致信号失真严重,系统整体零件分散导致稳定性及使用维护不便,且体积较大不利于运输携带等问题,采用了一种智能功率管理模块(Intelligent Power Module,IPM)的电源功率组和抗噪性能优越的人工编码源伪随机码相结合设计的伪随机电磁发射机系统进行优化。文中从伪随机恒流方波脉冲电磁发射系统的原理、系统整体结构设计、硬件软件组成、样机实物形体描述以及实验结果方面进行了介绍,设计完成后整体体积较现有设备缩减了30%以上,经室外实验验证设计的发射机在抗噪性、稳定性、整装集成度以及后续维保便捷性方面都有较大程度的改善。
