[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites,...[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites, which had the same vegetation composition （taking Leymus chinensis and Stipa krylovii as main species） and soil type, were chosen as research objects for the VOR and CVOR evaluation of the effect of open grazing and livestock exclusion on the health of typical steppes, and for building the calculation model for VOR and CVOR indices to evaluate the health of typical steppes with different exclusion periods. [ Result] The VOR and CVOR composite indices both could accurately evaluate the health of typical steppes, and the evaluation results from the both indices were quite consistent. Although the condition （C）, vigor（V）, organization （O） and resilience（ R ） indices changed differently in different exclusion periods, the VOR and CVOR composite indices increased gradually with the peri- od of exclusion prolonged, and the health condition of typical steppe changed from ＂alert＂ level （in the open grazing and earlier exclusion period） to ＂healthy＂ level （after 13 to 20 years＇exclusion）. [ Conclusion] The application of exclusion was beneficial to the recovery of degraded grassland ecosystem.展开更多
With the aim of improving parameter identification and, eventually, evaluating driver distraction with changes in gaze direction, we applied a genetic algorithm (GA) method to identify parameters for an existing vesti...With the aim of improving parameter identification and, eventually, evaluating driver distraction with changes in gaze direction, we applied a genetic algorithm (GA) method to identify parameters for an existing vestibulo-ocular reflex (VOR) model. By changing the initial inputs to the GA and fixing two parameters pertaining to the horizontal direction, we achieved improved parameter identification with a lower mean-square error. The influence of driver distraction on eye movement with changes in gaze direction was evaluated from the difference between the predicted and observed VOR in the vertical axis. When a driver was given an additional mental workload, the mean-square error between the measured and simulated values was bigger than that in the absence of the mental workload. This confirmed the relationship between driver distraction and eye movement in the vertical direction. We hope that this method can be applied in evaluating driver distraction.展开更多
该文介绍了仪表着陆系统(Instrument Landing System,ILS)和甚高频全向信标(Very High Frequency Omni directional Range,VOR)的航空导航系统中重要性,以及应用中的工作原理。通过设计原理进行方案设计,提出一种基于FPGA的地面信号发...该文介绍了仪表着陆系统(Instrument Landing System,ILS)和甚高频全向信标(Very High Frequency Omni directional Range,VOR)的航空导航系统中重要性,以及应用中的工作原理。通过设计原理进行方案设计,提出一种基于FPGA的地面信号发生技术,具有资源利用率高、配置灵活高效等特点,能够产生高精度LOC、GS、MB和VOR基带信号。最后进行了仿真实验,得到各种基带信号的波形图,验证了该技术的可靠和有效。展开更多
基金supported by National Key Fundamental Research and Development Fund of China (No.2007CB106800)
文摘[Objective] The aim of this study was to evaluate the effect of livestock exclusion on the health of grassland ecosystem accurately and quantitatively. [Method] One open grazing site and five seasonal exclusion sites, which had the same vegetation composition （taking Leymus chinensis and Stipa krylovii as main species） and soil type, were chosen as research objects for the VOR and CVOR evaluation of the effect of open grazing and livestock exclusion on the health of typical steppes, and for building the calculation model for VOR and CVOR indices to evaluate the health of typical steppes with different exclusion periods. [ Result] The VOR and CVOR composite indices both could accurately evaluate the health of typical steppes, and the evaluation results from the both indices were quite consistent. Although the condition （C）, vigor（V）, organization （O） and resilience（ R ） indices changed differently in different exclusion periods, the VOR and CVOR composite indices increased gradually with the peri- od of exclusion prolonged, and the health condition of typical steppe changed from ＂alert＂ level （in the open grazing and earlier exclusion period） to ＂healthy＂ level （after 13 to 20 years＇exclusion）. [ Conclusion] The application of exclusion was beneficial to the recovery of degraded grassland ecosystem.
文摘With the aim of improving parameter identification and, eventually, evaluating driver distraction with changes in gaze direction, we applied a genetic algorithm (GA) method to identify parameters for an existing vestibulo-ocular reflex (VOR) model. By changing the initial inputs to the GA and fixing two parameters pertaining to the horizontal direction, we achieved improved parameter identification with a lower mean-square error. The influence of driver distraction on eye movement with changes in gaze direction was evaluated from the difference between the predicted and observed VOR in the vertical axis. When a driver was given an additional mental workload, the mean-square error between the measured and simulated values was bigger than that in the absence of the mental workload. This confirmed the relationship between driver distraction and eye movement in the vertical direction. We hope that this method can be applied in evaluating driver distraction.
文摘该文介绍了仪表着陆系统(Instrument Landing System,ILS)和甚高频全向信标(Very High Frequency Omni directional Range,VOR)的航空导航系统中重要性,以及应用中的工作原理。通过设计原理进行方案设计,提出一种基于FPGA的地面信号发生技术,具有资源利用率高、配置灵活高效等特点,能够产生高精度LOC、GS、MB和VOR基带信号。最后进行了仿真实验,得到各种基带信号的波形图,验证了该技术的可靠和有效。
