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101.
102.
In situ Microphytobenthic community dynamics were combined with laboratory measurement of predominant species by fluorescence methods to estimate the areal primary production. Field investigation of community dynamics of microphytobenthos (MPB) was conducted from August 2006 to August 2007 in intertidal flats of the Nakdong River estuary, Korea. MPB Biomass varied between 0.47 and 16.58 μg cm?3 in the surface 1 cm sediment, with two dominant diatom species, Amphora coffeaeformis and Navicula sp., occupying average 77.2 ± 14.9% of total number of MPB cells. The biomass was higher in the slightly muddy sand sites than that in the sand site, and showed different pattern of seasonal variation. The profile of vertical distribution of biomass was an exponential decrease trend with depth in sediments. The biomass proportions in the uppermost 3 mm were 57.6% and 37.8% with and without the presence of biofilm, respectively. The two dominant species were cultured in laboratory, and their photosynthetic parameters, rETRmax (relative maximum electron transport rate), α (light utilization coefficient) and E k (light saturation parameter) were derived from rETR (relative ETR)-irradiance curves by Imaging- PAM (pulse amplitude modulated) fluorometry. The rETR-irradiance curves showed no significant difference of photosynthetic activities between the two species. The areal potential production ranged from 0.74 to 2.22 g C m?2 d?1. 相似文献
103.
海城7.3级地震前地震波动力学特征量的异常变化 总被引:1,自引:0,他引:1
本文给出对海城7.3级地震前地震波动力学特征量变化的一些最新研究结果。所研究的地震波包括体波(P,S波)、尾波和短周期地脉动三类。特征量有:体波与地脉动的波形时间线性度和空间线性度,平均半周期,频谱的峰值频率、拐角频率、相对频带宽度、相对频谱峰值、高频段的谱线斜率绝对值;尾波的时间熵、振幅比、持续时间、观测与计算持续时间差及其二阶差分、Q_c值、反映介质混浊度与震源特性的系数a_c等。所得结果表明,三类地震波的上述动力学特征量大都在震前一至半年左右出现、有的在6-10天乃至一天以内出现过不同形态的阶段性异常变化,因而可看作海城地震的中短期和临震的地震波前兆异常指标。 相似文献
104.
作为一种新颖的地图集,多媒体电子地图集具有超乎以往的多媒体可视效果。为此本文将多媒体电子地图集的媒体数据管理权由编制者转向用户,以地理信息为主体,多媒体为支撑,提出一种便捷灵活的数据管理思路。同时,根据目前用户需求及计算机信息化特点,设计并实现了图集数据开放式管理系统,提高了图集的安全性、开放性、灵活性和易用性,以推进多媒体电子地图集的发展和应用。 相似文献
105.
106.
东海表层水体中的多环芳烃及其沉积通量估算 总被引:2,自引:0,他引:2
以东海陆架水体中溶解态多环芳烃(PAHs)含量为基础,引入颗粒相-水相间的物质吸附系数(Koc)计算悬浮颗粒物中PAHs有机碳归一化含量,结合陆架沉积物有机碳的年埋藏通量,估算东海陆架沉积物中PAHs沉积通量。结果显示:水体中溶解态的15种PAHs总含量为(701±392)ng/L,变化范围为412~1 032ng/L,PAHs组成以3环为主。计算得到的悬浮颗粒物中15种PAHs有机碳归一化含量为20~28μg/g,对应的PAHs沉积通量为150~210t/a。估算结果与实测沉积物中PAHs含量和沉积通量结果基本吻合,表明实验室模拟实验获取的化合物Koc值适用于东海颗粒相-水相间的分配模型,证实悬浮颗粒物有机碳含量在控制PAHs两相分布过程中起着重要作用。同时,该方法为海洋沉积物中PAHs沉积通量的估算提供一种新途径。 相似文献
107.
Homologous feature point extraction is a key problem in the optical and synthetic aperture radar (SAR) image registration for islands. A new feature point extraction method using a threshold shrink operator and non-subsampled wavelet transform (TSO-NSWT) for optical and SAR image registration was proposed. Moreover, the matching for this proposed feature was different from the traditional feature matching strategies and was performed using a similarity measure computed from neighborhood circles in low-frequency bands. Then, a number of reliably matched couples with even distributions were obtained, which assured the accuracy of the registration. Application of the proposed algorithm to SPOT-5 (multi-spectral) and YG-1 (SAR) images showed that a large number of accurately matched couples could be identified. Additionally, both of the root mean square error (RMSE) patterns of the registration parameters computed based on the TSO-NSWT algorithm and traditional NSWT algorithm were analyzed and compared, which further demonstrated the effectiveness of the proposed algorithm. The algorithm can supply the crucial step for island image registration and island recognition. 相似文献
108.
The status of a fishery is often defined as the probability of fishing mortality rate exceeding a perilous level for long‐term sustainability. Lobster stock assessments are often subject to large uncertainty in input data and high levels of natural variability in lobster life history processes, which calls for incorporating uncertainty associated with both indicator and management reference points in an evaluation of biological risk of overfishing. Using a Monte Carlo simulation approach, we evaluated the impacts of uncertainty in modelling on the determination of the status of the Taitung spiny lobster (Panulirus penicillatus) fishery (Taiwan), which has not been quantitatively determined despite its commercial importance. The commonly used biological reference points derived from the per recruit model (F 0.1 the fishing mortality rate where the slope of the curve of yield‐per‐recruit model is 10% of the maximum slope and F 4Q%, the fishing mortality rate that reduces the expected egg production for a cohort of female lobsters to 40% of that produced in the absence of a fishery of the egg‐per‐recruit model) were influenced by uncertainties associated with lobster life history and fishery parameters. A large uncertainty in the current fishing mortality rate (F cnr) and estimates of biological reference points (F BRPs) increased the uncertainty in determining the risk of overexploitation throughout the confidence levels of the stochastic decision‐making framework. This simulation study suggests that the target reference point of F 40% is less sensitive to the input parameters’ uncertainty than F 0.1 We suggest a further evaluation of other F‐based references points and development of biomass‐based reference points before final selection and implementation for the management of the Taitung lobster fishery. 相似文献
109.
Gas-bearing sediments are widely distributed in five continents all over the world. Most of the gases exist in the soil skeleton in the form of discrete large bubbles. The existence of gas-phase may increase or decrease the strength of the soil skeleton. So far, bubbles’ structural morphology and evolution characteristics in soil skeleton lack research, and the influence of different gas reservoir pressures on bubbles are still unclear. The micro characteristics of bubbles in the same sediment sample were studied using an industrial CT scanning test system to solve these problems. Using the image processing software, the micro variation characteristics of gas-bearing sediments in gas reservoir pressure change are obtained. The results show that the number and volume of bubbles in different equivalent radius ranges will change regularly under different gas reservoir pressure. With the increase of gas reservoir pressure, the number and volume of tiny bubbles decrease. In contrast, the number and volume of large bubbles increase, and the gas content in different positions increases and occupies a dominant position, driving the reduction of pore water and soil skeleton movement. 相似文献
110.
利用百分位阈值方法定义极端事件,从极端事件再现时间的角度,研究了极端事件发生时间间隔的长程相关性.发现若原时间序列具有长程相关性,则它的极端事件再现时间序列也具有长程相关性;计算表明两者的标度指数α相当接近,这一特性与随机产生的再现时间序列有着本质的差别,再现时间序列的长程相关性是由原序列的长程相关性决定的.具有长程相关性的时间序列再现时间的概率分布明显不同于随机序列,其小值再现时间的概率较大,反映出极端事件的群发现象.本文根据这一特征定义了再现时间的群发性指数,发现时间序列的长程相关性是导 相似文献