Distributions and sources of total organic carbon （TOC）in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects ...Distributions and sources of total organic carbon （TOC）in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects of estuary water on the continuously increasing terrigenous organic carbon from the Changjiang River are also explored through variations of organic carbon content and water quality indicators. Results show that, hydrodynamics exert important influences on distributions of organic carbon in the tur- bidity maximum of Changjiang Estuary. For their redistribution effect of terrigenous organic carbon within the moving layer in the whole region, variations from land to sea are not indicated by surficial and vertical average values of TOC and total nitrogen （TN） contents in core sediment, as well as organic stable carbon isotopes in surface sediments. However, on the long-time scale, the trend of terrigenous organic carbon decreasing from land to sea is still displayed by variations of stable carbon isotopic average values becoming heavier from land to sea. Previous studies have shown that high content of Chl a cannot appear in the Changjiang Estuary in despite of adequate nourishment supply, because photosynthesis of phytoplankton is constrained by high suspended sediment concentration（SSC）. However, an area with a high content of Chl a occurs, which may be caused by resuspended benthic algae with bottom fine grain-size sediments. Tremendous pressures are imposed on the environment of Changjiang Estuary, because of uhrophication trends and special hydrodynamics. Phytoplankton bloom area tends to extend from the outer sea to the mouth of Changjiang River.展开更多
Sediment cores were collected from the subaqueous delta of the Changjiang Estuary. Sediment grain-size profiles and their fractal dimensions were analyzed, to elucidate responses to long-term sedimentary processes. In...Sediment cores were collected from the subaqueous delta of the Changjiang Estuary. Sediment grain-size profiles and their fractal dimensions were analyzed, to elucidate responses to long-term sedimentary processes. In addition, the environmental sensitive populations of grain size have been extracted. The sediment cores can be divided into two parts, according to the sedimentary structures present. The upper part （0-12 cm） is interpreted as being the active layer, which is influenced frequently by changes in the short-term hydrodynamic environment. The lower part extends from a depth of 12 cm, to the bottom of the core. The pattern of fluctuation is linked to sediment grain size. Moreover, two grain-size sensitive populations can be identified. The fine sensitive population is 6.0-7.2 μm, which is a similar grain size to the suspended sediment from up-river. The coarse sensitive population varies from 40.7 to 57.5 μm, revealing complex changes. Thus, the riverine inputs from the Changjiang River may be an important source, which contributes to seasonal fluctuations of grain-size distribution, over the area. The sediments, with grain-sizes ranging from 0.9 to 20.3 μm, are characterised by self-similar in the fractal non-scale region. The fraetal dimension is eonsistant with the grain-size parameter varatioins, which could be used as a replacement index to reveal and reconstruct the sedimentary environmental evolution.展开更多
The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area co...The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotopes in sediments show linear correlations with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratios can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （up to 50%） of terrestrial organic carbon appears near the Changjiang Estuary with isolines projecting towards northeast, indicating the influence of the Changjiang dilution water. Terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.展开更多
介绍一种主要为室内定位提供测距基础的系统。该系统由两个对等的节点组成,节点1发送通过无线发出的同步握手信号,节点2收到同步信号后开始计时并回应握手信号,节点1确认握手成功后开始发送声波脉冲信号,节点2收到脉冲信号后停止计时,...介绍一种主要为室内定位提供测距基础的系统。该系统由两个对等的节点组成,节点1发送通过无线发出的同步握手信号,节点2收到同步信号后开始计时并回应握手信号,节点1确认握手成功后开始发送声波脉冲信号,节点2收到脉冲信号后停止计时,定时器的时间就是声波在空气中的传播时间,进而确定点和点之间的距离。节点主要是由声波发射接收电路、CC1100无线电模块和STC12C5A0S2单片机等组成。STC12C5A0S2内部带有捕获定时器的功能,能准确地抓住定时器的值。声波发射接收电路主要由NE555,LM386和NE5532构成,能高频喇叭发送和接收10.25 k Hz声波信号。系统在测试的过程中,随着距离的增大,误差会有所加大,在10 m范围内误差小于10%,可以满足定位测距的需求。在实际的应用过程中还可以通过系统标定等数据处理手段,进一步提高测量精度,满足更高的测距要求。展开更多
针对用户访问服务负载均衡的分布存储要求和磁盘连续读取的合并存储要求之间的矛盾,提出一种基于用户访问行为的综合考虑存储节点连续读取效率和网络负载均衡效率的空间数据存储组织方法(combined strategy of data placement and load ...针对用户访问服务负载均衡的分布存储要求和磁盘连续读取的合并存储要求之间的矛盾,提出一种基于用户访问行为的综合考虑存储节点连续读取效率和网络负载均衡效率的空间数据存储组织方法(combined strategy of data placement and load balance,CSDL)。该方案根据用户访问行为,通过空间数据的访问相关性计算,将热点数据分布存储在不同的服务器上,以实现用户并发访问时的负载均衡;同时,通过对存储在相同服务器内数据的并发度计算,将并发度高的数据存储在连续的磁盘空间上,以实现磁盘存储服务的连续读取。CSDL方法试图同时从上层应用的负载均衡和底层磁盘效率两个方面对空间数据的存储进行分布组织,以提高地理信息系统服务效率。试验结果表明,该方案可有效提高45.2%～245.3%的系统平均请求响应时间,与此同时,分布式服务器节点的负载均衡度可提高约0.5%～440.9%,能满足大规模分布式环境的应用需求。展开更多
基金the National Key Basic Research Program of China under contract No.2002CB412401the National Natural Science Foundation of China under contract Nos40506022 and 40506013
文摘Distributions and sources of total organic carbon （TOC）in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects of estuary water on the continuously increasing terrigenous organic carbon from the Changjiang River are also explored through variations of organic carbon content and water quality indicators. Results show that, hydrodynamics exert important influences on distributions of organic carbon in the tur- bidity maximum of Changjiang Estuary. For their redistribution effect of terrigenous organic carbon within the moving layer in the whole region, variations from land to sea are not indicated by surficial and vertical average values of TOC and total nitrogen （TN） contents in core sediment, as well as organic stable carbon isotopes in surface sediments. However, on the long-time scale, the trend of terrigenous organic carbon decreasing from land to sea is still displayed by variations of stable carbon isotopic average values becoming heavier from land to sea. Previous studies have shown that high content of Chl a cannot appear in the Changjiang Estuary in despite of adequate nourishment supply, because photosynthesis of phytoplankton is constrained by high suspended sediment concentration（SSC）. However, an area with a high content of Chl a occurs, which may be caused by resuspended benthic algae with bottom fine grain-size sediments. Tremendous pressures are imposed on the environment of Changjiang Estuary, because of uhrophication trends and special hydrodynamics. Phytoplankton bloom area tends to extend from the outer sea to the mouth of Changjiang River.
基金The National Basic Research Program of China under contract No 2002CB412401the National Natural Science Foundation of China under contract Nos 40876043 & 40106009+1 种基金the Jiangsu Natural Science Foundation under contract NoBK2006131the NCET Program under contract NoNCET-06-0446
文摘Sediment cores were collected from the subaqueous delta of the Changjiang Estuary. Sediment grain-size profiles and their fractal dimensions were analyzed, to elucidate responses to long-term sedimentary processes. In addition, the environmental sensitive populations of grain size have been extracted. The sediment cores can be divided into two parts, according to the sedimentary structures present. The upper part （0-12 cm） is interpreted as being the active layer, which is influenced frequently by changes in the short-term hydrodynamic environment. The lower part extends from a depth of 12 cm, to the bottom of the core. The pattern of fluctuation is linked to sediment grain size. Moreover, two grain-size sensitive populations can be identified. The fine sensitive population is 6.0-7.2 μm, which is a similar grain size to the suspended sediment from up-river. The coarse sensitive population varies from 40.7 to 57.5 μm, revealing complex changes. Thus, the riverine inputs from the Changjiang River may be an important source, which contributes to seasonal fluctuations of grain-size distribution, over the area. The sediments, with grain-sizes ranging from 0.9 to 20.3 μm, are characterised by self-similar in the fractal non-scale region. The fraetal dimension is eonsistant with the grain-size parameter varatioins, which could be used as a replacement index to reveal and reconstruct the sedimentary environmental evolution.
基金National Basic Research Program of China, No.2002CB412401 National Natural Science Foundation of China, No.40506022+1 种基金 No.40506013 Natural Science Foundation of Jiangsu Province, No.BK2006131
文摘The spatial distribution patterns of total organic carbon and total nitrogen show significant correlations with currents of the East China Sea Shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotopes in sediments show linear correlations with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratios can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （up to 50%） of terrestrial organic carbon appears near the Changjiang Estuary with isolines projecting towards northeast, indicating the influence of the Changjiang dilution water. Terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.
文摘介绍一种主要为室内定位提供测距基础的系统。该系统由两个对等的节点组成,节点1发送通过无线发出的同步握手信号,节点2收到同步信号后开始计时并回应握手信号,节点1确认握手成功后开始发送声波脉冲信号,节点2收到脉冲信号后停止计时,定时器的时间就是声波在空气中的传播时间,进而确定点和点之间的距离。节点主要是由声波发射接收电路、CC1100无线电模块和STC12C5A0S2单片机等组成。STC12C5A0S2内部带有捕获定时器的功能,能准确地抓住定时器的值。声波发射接收电路主要由NE555,LM386和NE5532构成,能高频喇叭发送和接收10.25 k Hz声波信号。系统在测试的过程中,随着距离的增大,误差会有所加大,在10 m范围内误差小于10%,可以满足定位测距的需求。在实际的应用过程中还可以通过系统标定等数据处理手段,进一步提高测量精度,满足更高的测距要求。
文摘针对用户访问服务负载均衡的分布存储要求和磁盘连续读取的合并存储要求之间的矛盾,提出一种基于用户访问行为的综合考虑存储节点连续读取效率和网络负载均衡效率的空间数据存储组织方法(combined strategy of data placement and load balance,CSDL)。该方案根据用户访问行为,通过空间数据的访问相关性计算,将热点数据分布存储在不同的服务器上,以实现用户并发访问时的负载均衡;同时,通过对存储在相同服务器内数据的并发度计算,将并发度高的数据存储在连续的磁盘空间上,以实现磁盘存储服务的连续读取。CSDL方法试图同时从上层应用的负载均衡和底层磁盘效率两个方面对空间数据的存储进行分布组织,以提高地理信息系统服务效率。试验结果表明,该方案可有效提高45.2%～245.3%的系统平均请求响应时间,与此同时,分布式服务器节点的负载均衡度可提高约0.5%～440.9%,能满足大规模分布式环境的应用需求。
