生物完整性指数(index of biotic integrity,IBI)是用以度量区域生物集群维持物种组成、多样性、结构和功能稳态能力的量化指标,经过30多年的发展,已成为水生态健康定量评价的热门方法。IBI是将具有不同敏感性的多项度量指标复合而得的...生物完整性指数(index of biotic integrity,IBI)是用以度量区域生物集群维持物种组成、多样性、结构和功能稳态能力的量化指标,经过30多年的发展,已成为水生态健康定量评价的热门方法。IBI是将具有不同敏感性的多项度量指标复合而得的一个数值,其理论基础是生态学与数学,涉及生物学和环境科学等其他多门学科。IBI作为一种定量分析方法,其理论技术体系仍在不断发展演化,关键技术环节为参照位点选取、度量指标筛选以及指标赋权和复合,各环节的实现存在多种观点和方法。基于大量监测数据的预测模型研究是目前国际学界的研究热点,但我国学界尚未见IBI预测模型的研究报道。除了传统的F-IBI(鱼类IBI)、B-IBI(底栖动物IBI)、A-IBI(固着藻类IBI)、P-IBI(浮游生物IBI)和AP-IBI(水生植物IBI),已有学者提出M-IBI(微生物IBI),基于上述单类群IBI(s-IBI)的研究成果,多类群IBI(m-IBI)将成为今后重要的研究方向。IBI的应用目的可分为水生态健康定量评价、水生态对人类干扰响应的定量分析和预测水生态健康状况。认为IBI具有定量化、对象依赖性、学科交叉性、标准化趋势和系统误差性的特点,IBI在农村河道、灌区和农田生态健康评价领域是一种极具前景的方法。展开更多
为了解阿勒泰地区额尔齐斯河和乌伦古河流域的鱼类多样性现状和历史演变,本研究于2013–2016年间在该流域的鱼类多样性进行了连续调查,并结合历史资料和标本,以Margalef丰富度指数、Shannon-Wiener多样性指数、Pielou均匀度指数分析评...为了解阿勒泰地区额尔齐斯河和乌伦古河流域的鱼类多样性现状和历史演变,本研究于2013–2016年间在该流域的鱼类多样性进行了连续调查,并结合历史资料和标本,以Margalef丰富度指数、Shannon-Wiener多样性指数、Pielou均匀度指数分析评估了流域内鱼类的多样性水平和时空变化。该流域历史上分布有土著鱼类23种,当前记录到19种,流域内还有外来鱼类15种。阿勒泰鱼类的区系组成以鲤科种类为主,其中特有和珍稀濒危物种占比高,具有重要的保护价值。多样性指数计算结果显示,2013–2016年鱼类多样性情况整体稳定,额尔齐斯河鱼类物种数多于乌伦古河。研究还基于鱼类生物完整性指数(Fish Index of Biological Integrity,F-IBI)对34个采集点的河流健康状况进行了评价,结果显示额尔齐斯河流域大多数调查点的健康状况处于"亚健康"或"一般"水平,乌伦古河流域多数调查点的健康状况处于"健康"水平。水利工程、外来物种、过度捕捞是影响阿勒泰地区鱼类多样性的重要因素。未来应通过水利工程的联合调度、下泄合理生态流量、布设鱼类通道、规范养殖渔业、严控外来物种、本地土著鱼类的人工增殖放流,以及合理的就地保护措施对阿勒泰地区的鱼类多样性加以保护,提升水体健康程度。展开更多
地面沉降是由于地表高程降低所诱发的区域环境地质灾害.城市快速发展带来的载荷的增加影响地面沉降的发展.选取覆盖北京平原区的TM遥感影像,以北京典型地下水漏斗区为研究区,在NDBI、MNDWI、SAVI指数基础上,计算遥感建筑用地指数(IBI),...地面沉降是由于地表高程降低所诱发的区域环境地质灾害.城市快速发展带来的载荷的增加影响地面沉降的发展.选取覆盖北京平原区的TM遥感影像,以北京典型地下水漏斗区为研究区,在NDBI、MNDWI、SAVI指数基础上,计算遥感建筑用地指数(IBI),获取建筑用地(载荷)时空密度差异信息;结合永久散射体干涉测量(Persistent Scatterers for SAR Interferometry,PS-InSAR)监测结果,基于GIS空间分析技术和统计分析方法,从3种不同的空间采样角度,分析载荷密度差异与地面沉降的相关性.结论显示,(1)地面沉降的不均匀性与载荷密度的正相关性表现为:沉降速率值越大,Spearman秩相关系数越大;(2)动静载荷的共同作用相对于单纯的静载荷对地面沉降的影响更明显;(3)在较短时间周期内,相对于地下水开采,载荷对地面沉降的影响较小,但仍旧是不容忽视的问题,需要长期系统性的研究.展开更多
Indices of Biological Integrity (IBIs) are being increasingly used as useful and direct tools for assessing general health of aquatic ecosystems. Although such ecosystems in Iraq, especially the southern marshes, unde...Indices of Biological Integrity (IBIs) are being increasingly used as useful and direct tools for assessing general health of aquatic ecosystems. Although such ecosystems in Iraq, especially the southern marshes, underwent severe alterations during the last two decades, including extensive desiccation in the 1990s, such tools are largely lacking. Phytoplankton Index of Biological Integrity (P-IBI) was developed from data collected seasonally from 2005 up to 2007 in different sites of the southern marshes of Iraq to evaluate the trend of these ecosystems based on phytoplankton data. Ten metrics were selected for measuring P-IBI for the first time in Iraq as a proposed project from Nature Iraq and Twin Rivers Institute, American University of Iraq-Sulaimani. Although generally fluctuated both spatially and temporally, mean P-IBI scores showed better conditions in Al Hawizeh marsh (Good) as compared to the Central and West & East Al Hammar marshes (Fair to Good). However, the results generally indicated evidence of improvement at the Central and West & East Al Hammar marshes, whereas no recovery of the status of water was evident throughout the data obtained at Al Hawizeh marsh. Values were generally higher in winter. These observations clearly reflect the relative stability of the Hawizeh marsh ecosystem which was not subject to the desiccation process in the 1990s, while the severely dried systems of the Central and Hammar marshes are showing positive responses to the restoration efforts that were started after 2003. Among the ten metrics comprising the index, relative abundance of diatoms had the most prominent effect on the P-IBI value in the three marshes. Metrics such as chlorophyll- a concentration and relative abundance of Cyanophyta and Chlorophyta also played a significant role in determining the index value. Continuous monitoring based on the selection of the most suitable metrics is recommended.展开更多
正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是一种高效的多载波宽带数字调制技术,在无线通信系统中有较广泛的应用。通过对OFDM系统的基本原理以及该系统中各个模块的特点进行研究,用Simulink构建数字电视地面广播...正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是一种高效的多载波宽带数字调制技术,在无线通信系统中有较广泛的应用。通过对OFDM系统的基本原理以及该系统中各个模块的特点进行研究,用Simulink构建数字电视地面广播(Digital Television Terrestrial Broadcasting,DTTB)中的TDS-OFDM系统仿真模型。仿真结果表明,TDS-OFDM系统的误码率较低,具有较强的抗多径衰落和频率选择性衰落能力。展开更多
文摘生物完整性指数(index of biotic integrity,IBI)是用以度量区域生物集群维持物种组成、多样性、结构和功能稳态能力的量化指标,经过30多年的发展,已成为水生态健康定量评价的热门方法。IBI是将具有不同敏感性的多项度量指标复合而得的一个数值,其理论基础是生态学与数学,涉及生物学和环境科学等其他多门学科。IBI作为一种定量分析方法,其理论技术体系仍在不断发展演化,关键技术环节为参照位点选取、度量指标筛选以及指标赋权和复合,各环节的实现存在多种观点和方法。基于大量监测数据的预测模型研究是目前国际学界的研究热点,但我国学界尚未见IBI预测模型的研究报道。除了传统的F-IBI(鱼类IBI)、B-IBI(底栖动物IBI)、A-IBI(固着藻类IBI)、P-IBI(浮游生物IBI)和AP-IBI(水生植物IBI),已有学者提出M-IBI(微生物IBI),基于上述单类群IBI(s-IBI)的研究成果,多类群IBI(m-IBI)将成为今后重要的研究方向。IBI的应用目的可分为水生态健康定量评价、水生态对人类干扰响应的定量分析和预测水生态健康状况。认为IBI具有定量化、对象依赖性、学科交叉性、标准化趋势和系统误差性的特点,IBI在农村河道、灌区和农田生态健康评价领域是一种极具前景的方法。
文摘为了解阿勒泰地区额尔齐斯河和乌伦古河流域的鱼类多样性现状和历史演变,本研究于2013–2016年间在该流域的鱼类多样性进行了连续调查,并结合历史资料和标本,以Margalef丰富度指数、Shannon-Wiener多样性指数、Pielou均匀度指数分析评估了流域内鱼类的多样性水平和时空变化。该流域历史上分布有土著鱼类23种,当前记录到19种,流域内还有外来鱼类15种。阿勒泰鱼类的区系组成以鲤科种类为主,其中特有和珍稀濒危物种占比高,具有重要的保护价值。多样性指数计算结果显示,2013–2016年鱼类多样性情况整体稳定,额尔齐斯河鱼类物种数多于乌伦古河。研究还基于鱼类生物完整性指数(Fish Index of Biological Integrity,F-IBI)对34个采集点的河流健康状况进行了评价,结果显示额尔齐斯河流域大多数调查点的健康状况处于"亚健康"或"一般"水平,乌伦古河流域多数调查点的健康状况处于"健康"水平。水利工程、外来物种、过度捕捞是影响阿勒泰地区鱼类多样性的重要因素。未来应通过水利工程的联合调度、下泄合理生态流量、布设鱼类通道、规范养殖渔业、严控外来物种、本地土著鱼类的人工增殖放流,以及合理的就地保护措施对阿勒泰地区的鱼类多样性加以保护,提升水体健康程度。
文摘地面沉降是由于地表高程降低所诱发的区域环境地质灾害.城市快速发展带来的载荷的增加影响地面沉降的发展.选取覆盖北京平原区的TM遥感影像,以北京典型地下水漏斗区为研究区,在NDBI、MNDWI、SAVI指数基础上,计算遥感建筑用地指数(IBI),获取建筑用地(载荷)时空密度差异信息;结合永久散射体干涉测量(Persistent Scatterers for SAR Interferometry,PS-InSAR)监测结果,基于GIS空间分析技术和统计分析方法,从3种不同的空间采样角度,分析载荷密度差异与地面沉降的相关性.结论显示,(1)地面沉降的不均匀性与载荷密度的正相关性表现为:沉降速率值越大,Spearman秩相关系数越大;(2)动静载荷的共同作用相对于单纯的静载荷对地面沉降的影响更明显;(3)在较短时间周期内,相对于地下水开采,载荷对地面沉降的影响较小,但仍旧是不容忽视的问题,需要长期系统性的研究.
文摘Indices of Biological Integrity (IBIs) are being increasingly used as useful and direct tools for assessing general health of aquatic ecosystems. Although such ecosystems in Iraq, especially the southern marshes, underwent severe alterations during the last two decades, including extensive desiccation in the 1990s, such tools are largely lacking. Phytoplankton Index of Biological Integrity (P-IBI) was developed from data collected seasonally from 2005 up to 2007 in different sites of the southern marshes of Iraq to evaluate the trend of these ecosystems based on phytoplankton data. Ten metrics were selected for measuring P-IBI for the first time in Iraq as a proposed project from Nature Iraq and Twin Rivers Institute, American University of Iraq-Sulaimani. Although generally fluctuated both spatially and temporally, mean P-IBI scores showed better conditions in Al Hawizeh marsh (Good) as compared to the Central and West & East Al Hammar marshes (Fair to Good). However, the results generally indicated evidence of improvement at the Central and West & East Al Hammar marshes, whereas no recovery of the status of water was evident throughout the data obtained at Al Hawizeh marsh. Values were generally higher in winter. These observations clearly reflect the relative stability of the Hawizeh marsh ecosystem which was not subject to the desiccation process in the 1990s, while the severely dried systems of the Central and Hammar marshes are showing positive responses to the restoration efforts that were started after 2003. Among the ten metrics comprising the index, relative abundance of diatoms had the most prominent effect on the P-IBI value in the three marshes. Metrics such as chlorophyll- a concentration and relative abundance of Cyanophyta and Chlorophyta also played a significant role in determining the index value. Continuous monitoring based on the selection of the most suitable metrics is recommended.
文摘正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)是一种高效的多载波宽带数字调制技术,在无线通信系统中有较广泛的应用。通过对OFDM系统的基本原理以及该系统中各个模块的特点进行研究,用Simulink构建数字电视地面广播(Digital Television Terrestrial Broadcasting,DTTB)中的TDS-OFDM系统仿真模型。仿真结果表明,TDS-OFDM系统的误码率较低,具有较强的抗多径衰落和频率选择性衰落能力。
