[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
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
Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been mad...Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been made on the application of PV.In recent decades there has been a substantial amount of work done on PV in a gen-eral moist atmosphere.In this paper PV and the general-ized moist potential vorticity (GMPV) and their applica-tion in the tropical cyclones and mesoscale meteorologi-cal field are reviewed.The GMPV is derived for a real atmosphere (neither totally dry nor saturated) by intro-ducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature.Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere.A new convective vorticity vector (CVV) is introduced in connection with GMPV in order to diagnose the devel-opment of tropical deep convections.展开更多
文摘探究广西北部湾经济区(以下简称“研究区”)2001-2020年生态系统健康时空动态变化特征,可为研究区生态系统健康和社会经济可持续发展提供数据支持与理论参考。耦合“活力组织弹性”(Vigor Organization Resilience,VOR)模型、生态系统服务和权衡的综合评估(Integrated Valuation of Ecosystem Services and Trade offs,InVEST)模型构建生态系统健康多指标评价体系,并建立最小二乘法优化赋权模型对各评价指标进行优化赋权,对研究区生态系统健康状况进行评价与分析。结果表明:①研究区近20年来生态系统健康等级为三级的区域面积占研究区总面积的85%左右,且处于相对较为稳定的变化状态,研究区生态系统健康整体处于一般健康水平以上;②研究区生态系统健康状况总体上呈现北部、西部和南部地区优于中部和东部地区的空间分布差异;③研究区生态系统健康等级转移呈现以稳定型为主、退化型面积略大于改善型面积的空间变化特征,生态系统健康状况总体呈现轻微恶化趋势;④对研究区6个城市的生态系统健康从时间尺度和空间尺度对比分析发现,崇左、防城港、钦州3市生态系统健康状况变化较为明显,而南宁、玉林、北海3市相对较为平缓,但各市健康等级空间分布变化趋势较为吻合。本研究结果对推动广西北部湾经济区生态文明建设协调发展具有实际意义。
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。
文摘Potential vorticity (PV) has been served as a powerful and useful dynamic tracer for the understanding of the large-scale dynamics and synoptic variations in the atmosphere and oceans.Significant progress has been made on the application of PV.In recent decades there has been a substantial amount of work done on PV in a gen-eral moist atmosphere.In this paper PV and the general-ized moist potential vorticity (GMPV) and their applica-tion in the tropical cyclones and mesoscale meteorologi-cal field are reviewed.The GMPV is derived for a real atmosphere (neither totally dry nor saturated) by intro-ducing a generalized potential temperature instead of the potential temperature or equivalent potential temperature.Such a generalization can depict the moist effect on PV anomaly in the non-uniformly saturated atmosphere.A new convective vorticity vector (CVV) is introduced in connection with GMPV in order to diagnose the devel-opment of tropical deep convections.
