Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozo...Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozone in North America. The aim of this study was to research the nitrogen (N) and phosphorous (P) content and nutrient limitation (defined as N and P limitation) of growth of cyanobacteria in a northern prairies reservoir (Lake Diefenbaker [LD], SK, Canada). A combination of concentration balance analysis for N and P, controlled bioassays with the natural consortium of phytoplankton or defined monocultures of cyanobacteria, and satellite imagery was applied to address this aim. The current trophic status of Lake Diefenbaker is one of moderate eutrophication. Primary production in the lake is P-limited, and N did not represent a limiting factor for algal production. There was no significant increase in TP con- centrations between the upper and lower portions of the reservoir, indicating that most of the phosphorus in LD comes from upstream sites in Alberta. Anabaena circinalis, a species that has the potential to seriously degrade lake ecosys- tems, was identified as the predominant cyanobacteria in LD. Together with the fact that TP influxes into the reservoir primarily originate from upstream sources, these results suggest the need for remedial measures in the upstream reach of the South Saskatchewan River. Satellite imaging represented a promising approach in support of monitoring for po- tential algal blooms in LD;however, due to limited sensitivity and issues associated with atmosphere interference this methodology should only be used in combination with in situ water quality monitoring. In summary, while this study indicated that Lake Diefenbaker is potentially at risk with cyanobacteria blooms (some of which such as Anabena sp. that can produce toxins) during late summer and fall, development of clear causal relationships and risk assessment strategies is currently limited due to lack of monitori展开更多
针对卫星上相机成像噪音高、灵敏度低以及国外垄断的问题,提出一种基于FPGA和国产CMOS图像传感器的空间相机成像系统设计,应用于小卫星的空间成像。系统采用高分辨率的国产CMOS图像传感器作为成像元件,使用Spartan-6系列的FPGA作为主控...针对卫星上相机成像噪音高、灵敏度低以及国外垄断的问题,提出一种基于FPGA和国产CMOS图像传感器的空间相机成像系统设计,应用于小卫星的空间成像。系统采用高分辨率的国产CMOS图像传感器作为成像元件,使用Spartan-6系列的FPGA作为主控芯片,CMOS输出图像信号进入FPGA进行缓存和排序,再通过Camera Link接口发送到上位机。实验结果表明,系统能采集到2 048×1 024像素大小的图片,图像信噪比高于36 d B,优于CMOS传感器技术手册提供的参考值31 d B,成像效果良好,能满足小卫星的空间成像要求。展开更多
文摘Harmful algae blooms have become an increasing concern in context with the safety of water resources around the globe;however, little is known about the dynamics and specific causes of such blooms in the prairie ecozone in North America. The aim of this study was to research the nitrogen (N) and phosphorous (P) content and nutrient limitation (defined as N and P limitation) of growth of cyanobacteria in a northern prairies reservoir (Lake Diefenbaker [LD], SK, Canada). A combination of concentration balance analysis for N and P, controlled bioassays with the natural consortium of phytoplankton or defined monocultures of cyanobacteria, and satellite imagery was applied to address this aim. The current trophic status of Lake Diefenbaker is one of moderate eutrophication. Primary production in the lake is P-limited, and N did not represent a limiting factor for algal production. There was no significant increase in TP con- centrations between the upper and lower portions of the reservoir, indicating that most of the phosphorus in LD comes from upstream sites in Alberta. Anabaena circinalis, a species that has the potential to seriously degrade lake ecosys- tems, was identified as the predominant cyanobacteria in LD. Together with the fact that TP influxes into the reservoir primarily originate from upstream sources, these results suggest the need for remedial measures in the upstream reach of the South Saskatchewan River. Satellite imaging represented a promising approach in support of monitoring for po- tential algal blooms in LD;however, due to limited sensitivity and issues associated with atmosphere interference this methodology should only be used in combination with in situ water quality monitoring. In summary, while this study indicated that Lake Diefenbaker is potentially at risk with cyanobacteria blooms (some of which such as Anabena sp. that can produce toxins) during late summer and fall, development of clear causal relationships and risk assessment strategies is currently limited due to lack of monitori
文摘针对卫星上相机成像噪音高、灵敏度低以及国外垄断的问题,提出一种基于FPGA和国产CMOS图像传感器的空间相机成像系统设计,应用于小卫星的空间成像。系统采用高分辨率的国产CMOS图像传感器作为成像元件,使用Spartan-6系列的FPGA作为主控芯片,CMOS输出图像信号进入FPGA进行缓存和排序,再通过Camera Link接口发送到上位机。实验结果表明,系统能采集到2 048×1 024像素大小的图片,图像信噪比高于36 d B,优于CMOS传感器技术手册提供的参考值31 d B,成像效果良好,能满足小卫星的空间成像要求。
