甚高频数据交换系统(Very high frequency Data Exchange System,VDES)作为新一代船舶通信系统,具有广阔的应用前景。由于卫星相对船舶的高速运动,VDES中上行应用特定消息(Application-specific Message,ASM)链路会产生较大的多普勒频移...甚高频数据交换系统(Very high frequency Data Exchange System,VDES)作为新一代船舶通信系统,具有广阔的应用前景。由于卫星相对船舶的高速运动,VDES中上行应用特定消息(Application-specific Message,ASM)链路会产生较大的多普勒频移,在接收端仅依靠已知训练序列估计的频偏等信道参数无法满足正确解调的性能要求。为此提出一种基于判决反馈的解调方法,通过分段解调,缩短每次解调的数据长度,提高解调时对频偏的容忍度,并利用每段解调的结果作为下一段未解调数据的导频,估计出当前数据中的信道参数。仿真结果表明,所提算法相较于无反馈相干解调算法性能大大提升。在上述研究的基础上,在可编程逻辑器件上实现了对ASM无导频上行链路的正确解调。展开更多
Prevailing agricultural systems dominated by annual crop monocultures,and the landscapes that contain them,lack resilience and multifunctionality.They are vulnerable to extreme weather events,contribute to degradation...Prevailing agricultural systems dominated by annual crop monocultures,and the landscapes that contain them,lack resilience and multifunctionality.They are vulnerable to extreme weather events,contribute to degradation of soil,water,and air quality,reduce biodiversity,and negatively impact human health,social engagement,and equity.To achieve greater resilience,stability,and multiple ecosystem services therein,and to improve socioeconomic outcomes,we propose a practical framework to gain multifunctionality at multiple scales.This framework includes forages within agroecosystems that have the essential structural features of diversity,perenniality,and circularity.These three structural features are associated with increased resilience,stability,and provision of several ecosystem services,which in turn improve human health and socioeconomic outcomes.This framework improves understanding of,and access to,tools and materials for promoting the adoption of diverse circular agroecosystems with perennial forages.Application of this framework can result in land transformations that solve sustainability challenges in agriculture if policy,economic,and social barriers can be overcome by a transdisciplinary process of equitable knowledge production.展开更多
Numerous studies have unequivocally demonstrated that biochar and,to a lesser degree,earthworms can independently improve soil fertility and crop productivity,although information about their co-application effects on...Numerous studies have unequivocally demonstrated that biochar and,to a lesser degree,earthworms can independently improve soil fertility and crop productivity,although information about their co-application effects on soil characteristics is limited.In this review,(1)earthworm biomarkers and underlying influencing factors,as well as the changes in the amended soil quality in response to co-application of earthworms and biochar are presented,(2)the functional interactions between earthworms and biochar in soil are summarized;(3)the principles governing the synergetic effects of biochar and earthworms on soil quality enhancement are probed;and(4)alternative strategies to optimize the efficacy of earthworm and biochar amendments are provided.It is noteworthy that while low doses of biochar can have a positive effect on various earthworm biomarkers,including growth and reproduction,restoration of the intestinal environment,and the mitigation of cellular organelle toxicity and genetic damage,high biochar dosages can yield adverse effects.Conversely,earthworms play a crucial role in distributing biochar particles deeper into the soil matrix,bolstering carbon sequestration potential,and enhancing the persistence and efficiency of biochar utilization.Moreover,earthworms stimulate the production of soil extracellular enzymes by microorganisms,which are pivotal to the processing,stabilization,and decomposition of soil organic matter,as well as nutrient cycling in terrestrial ecosystems.Additionally,they enhance the binding affinities of these enzymes to biochar.Significantly,changes in earthworm biomarkers in response to biochar integration are predominately governed by biochar properties and dosage,contact time,and soil type.展开更多
文摘甚高频数据交换系统(Very high frequency Data Exchange System,VDES)作为新一代船舶通信系统,具有广阔的应用前景。由于卫星相对船舶的高速运动,VDES中上行应用特定消息(Application-specific Message,ASM)链路会产生较大的多普勒频移,在接收端仅依靠已知训练序列估计的频偏等信道参数无法满足正确解调的性能要求。为此提出一种基于判决反馈的解调方法,通过分段解调,缩短每次解调的数据长度,提高解调时对频偏的容忍度,并利用每段解调的结果作为下一段未解调数据的导频,估计出当前数据中的信道参数。仿真结果表明,所提算法相较于无反馈相干解调算法性能大大提升。在上述研究的基础上,在可编程逻辑器件上实现了对ASM无导频上行链路的正确解调。
基金funded by USDA NIFA Sustainable Agricultural Systems Coordinated Agricultural Project grant#2021‐68012‐35917.
文摘Prevailing agricultural systems dominated by annual crop monocultures,and the landscapes that contain them,lack resilience and multifunctionality.They are vulnerable to extreme weather events,contribute to degradation of soil,water,and air quality,reduce biodiversity,and negatively impact human health,social engagement,and equity.To achieve greater resilience,stability,and multiple ecosystem services therein,and to improve socioeconomic outcomes,we propose a practical framework to gain multifunctionality at multiple scales.This framework includes forages within agroecosystems that have the essential structural features of diversity,perenniality,and circularity.These three structural features are associated with increased resilience,stability,and provision of several ecosystem services,which in turn improve human health and socioeconomic outcomes.This framework improves understanding of,and access to,tools and materials for promoting the adoption of diverse circular agroecosystems with perennial forages.Application of this framework can result in land transformations that solve sustainability challenges in agriculture if policy,economic,and social barriers can be overcome by a transdisciplinary process of equitable knowledge production.
基金National Key Agricultural Science and Technology Project of China(NK2022180104)National Key Research and Development Program of China(2021YFD1500202,2019YFC1803403).
文摘Numerous studies have unequivocally demonstrated that biochar and,to a lesser degree,earthworms can independently improve soil fertility and crop productivity,although information about their co-application effects on soil characteristics is limited.In this review,(1)earthworm biomarkers and underlying influencing factors,as well as the changes in the amended soil quality in response to co-application of earthworms and biochar are presented,(2)the functional interactions between earthworms and biochar in soil are summarized;(3)the principles governing the synergetic effects of biochar and earthworms on soil quality enhancement are probed;and(4)alternative strategies to optimize the efficacy of earthworm and biochar amendments are provided.It is noteworthy that while low doses of biochar can have a positive effect on various earthworm biomarkers,including growth and reproduction,restoration of the intestinal environment,and the mitigation of cellular organelle toxicity and genetic damage,high biochar dosages can yield adverse effects.Conversely,earthworms play a crucial role in distributing biochar particles deeper into the soil matrix,bolstering carbon sequestration potential,and enhancing the persistence and efficiency of biochar utilization.Moreover,earthworms stimulate the production of soil extracellular enzymes by microorganisms,which are pivotal to the processing,stabilization,and decomposition of soil organic matter,as well as nutrient cycling in terrestrial ecosystems.Additionally,they enhance the binding affinities of these enzymes to biochar.Significantly,changes in earthworm biomarkers in response to biochar integration are predominately governed by biochar properties and dosage,contact time,and soil type.
