Short-time scale variation of phytoplankton succession in Lisbon bay (Portugal) as revealed by microscopy cell counts and HPLC pigment analysis     

A. Silva  C.R. Mendes  S. Palma  V. Brotas 《Estuarine, Coastal and Shelf Science》2008

The phytoplankton distribution and composition in Lisbon bay was studied, at a short time scale based on a weekly sampling, during one year (April 2004 – May 2005), using microscopic examination and pigment analysis with high-performance liquid chromatography (HPLC). This work is a contribution to the knowledge on species succession and ecology of coastal communities. The frequency of the sampling permitted monitoring peak blooming and decaying, a process which frequently occurred within 1 –2 weeks.  相似文献   

The effects of vertical sampling resolution on estimates of plankton biomass and rate calculations in stratified water columns     

Malinda M. Sutor  Michael J. Dagg 《Estuarine, Coastal and Shelf Science》2008

The effects of vertical sampling resolution on estimates of plankton biomass and grazing calculations were examined using data collected in two different areas with vertically stratified water columns. Data were collected from one site in the upwelling region off Oregon and from four sites in the Northern Gulf of Mexico, three within the Mississippi River plume and one in adjacent oceanic waters. Plankton were found to be concentrated in discrete layers with sharp vertical gradients at all the stations. Phytoplankton distributions were correlated with gradients in temperature and salinity, but microzooplankton and mesozooplankton distributions were not. Layers of zooplankton were sometimes collocated with layers of phytoplankton, but this was not always the case. Simulated calculations demonstrate that when averages are taken over the water column, or coarser scale vertical sampling resolution is used, biomass and mesozooplankton grazing and filtration rates can be greatly underestimated. This has important implications for understanding the ecological significance of discrete layers of plankton and for assessing rates of grazing and production in stratified water columns.  相似文献   

深海取样绞车牵引卷筒上钢缆张力分析   总被引：4，自引：2，他引：2  

翟庆光  聂杰  康岳伟 《海洋技术学报》2008,27(2):28-30

文中根据深海取样绞车的钢缆和牵引卷筒之间力的关系,利用微积分学原理,对钢缆在牵引卷筒上的张力变化进行了分析,建立了钢缆张力、钢缆与卷筒间的摩擦系数、钢缆在卷筒上的包角等参数之间的关系式,并通过实例对该关系式进行了验证。  相似文献   

Sensitivity analyses of a distributed catchment model to verify the model structure   总被引：5，自引：0，他引：5  

Angela Sieber  Stefan Uhlenbrook   《Journal of Hydrology》2005,310(1-4):216-235

Sensitivity analyses are valuable tools for identifying important model parameters, testing the model conceptualization, and improving the model structure. They help to apply the model efficiently and to enable a focussed planning of future research and field measurement. Two different methods were used for sensitivity analyses of the complex process-oriented model TAC^D (tracer aided catchment model, distributed) that was applied to the meso-scale Brugga basin (40 km²) and the sub-basin St Wilhelmer Talbach (15.2 km²). Five simulations periods were investigated: two summer events, two snow melt induced events and one summer low flow period. The model was applied using 400 different parameter sets, which were generated by Monte Carlo simulations using latin hypercube sampling. The regional sensitivity analysis (RSA) allowed determining the most significant parameters for the complete simulation periods using a graphical method. The results of the regression-based sensitivity analysis were more detailed and complex. The temporal variability of the simulation sensitivity could be observed continuously and the significance of the parameters could be determined in a quantitative way. A dependency of the simulation sensitivity on initial- and boundary conditions and the temporal and spatial variability of the sensitivity to some model parameters was revealed by the regression-based sensitivity analysis. Thus, the difficulty of transferring the results to different time periods or model applications in other catchments became obvious. The analysis of the temporal course of the simulation sensitivity to parameter values in conjunction with simulated and measured additional data sets (precipitation, temperature, reservoir volumes etc.) gave further insight into the internal model behaviour and demonstrated the plausibility of the model structure and process conceptionalizations.  相似文献   

The reliability of an 'off-the-shelf' conceptual rainfall runoff model for use in climate impact assessment: uncertainty quantification using Latin hypercube sampling     

Conor Murphy  Rowan Fealy  Ro Charlton  John Sweeney 《Area》2006,38(1):65-78

Much uncertainty is derived from the application of conceptual rainfall runoff models. In this paper, HYSIM, an 'off-the-shelf' conceptual rainfall runoff model, is applied to a suite of catchments throughout Ireland in preparation for use in climate impact assessment. Parameter uncertainty is assessed using the GLUE methodology. Given the lack of source code available for the model, parameter sampling is carried out using Latin hypercube sampling. Uncertainty bounds are constructed for model output. These bounds will be used to quantify uncertainty in future simulations as they include error derived from data measurement, model structure and parameterization.  相似文献   

莫索湾南缘沙漠植物群落多样性抽样方法的研究   总被引：13，自引：3，他引：13  

刘彤  崔运河  翟伟  贾亚敏  张元杭  谢江波 《干旱区地理》2006,29(3):367-374

2005年9月中下旬,在莫索湾南缘沙漠设置的200m×40m样带内共观测到植物物种22个,其中草本物种占77．3%。通过种一面积方程拟合和临界抽样面积的求解发现要达到抽取群落60%以上物种,临界样方面积至少在518．33m~2以上,而草本物种在735．49m~2以上。样方间相似性指数分析发现样方布样经历的生境异质性越高,物种替代性增加,相似性降低,抽样效率提高。研究发现沿垂直于沙丘走向的方向布样,以4m×4m为基本样方,抽样272m~2即达到60%群落物种,远低于临界抽样面积的求解结果,表明基本样方大小和设置方向对抽样效率产生重要影响。由于沙漠物种偶见种多,频度和密度较低,并且分布的环境特异性强,认为对沙漠植物群落观测,样线法、巢式样方法以及对草本观测的梅花样方法均具有一定局限性,建议对草本和灌木物种多样性观测,在确定合理的布样方向基础上,以4m×4m为基本样方。提出对沙漠植物群落多样性结构和功能有全面了解,必须将局部抽样与区域抽样结合,增加抽样频率和强度。  相似文献   

Optimal decision-making model of spatial sampling for survey of China’s land with remotely sensed data   总被引：2，自引：0，他引：2  

Li?Lianfa?Email author  Jinfeng?Wang  Jiyuan?Liu 《中国科学D辑(英文版)》2005,48(6):752-764

In the remote sensing survey of the country land, cost and accuracy are a pair of conflicts, for which spatial sampling is a preferable solution with the aim of an optimal balance between economic input and accuracy of results, or in other words, acquirement of higher accuracy at less cost. Counter to drawbacks of previous application models, e.g. lack of comprehensive and quantitativecomparison, the optimal decision-making model of spatial sampling is proposed. This model first acquires the possible accuracy-cost diagrams of multiple schemes through initial spatial exploration, then regresses them and standardizes them into a unified reference frame, and finally produces the relatively optimal sampling scheme by using the discrete decision-making function (built by this paper) and comparing them in combination with the diagrams. According to the test result in the survey of the arable land using remotely sensed data, the Sandwich model, while applied in the survey of the thin-feature and cultivated land areas with aerial photos, can better realize the goal of the best balance between investment and accuracy. With this case and other cases, it is shown that the optimal decision-making model of spatial sampling is a good choice in the survey of the farm areas using remote sensing, with its distinguished benefit of higher precision at less cost or vice versa. In order to extensively apply the model in the surveys of natural resources, including arable farm areas, this paper proposes the prototype of development using the component technology, that could considerably improve the analysis efficiency by insetting program components within the software environment of GIS and RS.  相似文献   

Characterization of Coherent structures in the Atmospheric Surface Layer   总被引：3，自引：2，他引：3  

Nisia Krusche  Amauri P. De Oliveira 《Boundary-Layer Meteorology》2004,110(2):191-211

The ramplike coherent structures, observed in the temporal series of temperature and humidity in the atmospheric surface layer, are analyzed using the intermittency function and the wavelet transforms, with Haar, D4 and Mexican Hat functions as mother wavelets, in order to find the most efficient conditional sampling technique. It was found that the intermittency function and the wavelet transform, using Mexican Hat as mother wavelet, are the only ones that sample structures that fulfill the ramplike coherent structures definition of a slow rise followed by a sudden drop in the temporal series. The conditionally averaged structures detected by both techniques were similar for temperature, humidity, and vertical velocity at heights of 3, 5, and 9.4 m. Significant discrepancies were found among the conditional averaged structures detected by both techniques for zonal and meridional components of the wind at 11.5 m. Considering both techniques, it was observed that the averagedcoherent-structure duration ranged from 23.7 ± 0.5 s to 37.8 ± 3.0 s. Furthermore, the averaged number of events per 20-minute period ranged from 20.0 ± 1.0 to 28.5 ± 1.1, and the averaged intermittency factor from 45.0 ± 0.4% to 59.1 ± 1.3%. It was also observed that the averaged duration of the ramplike coherent structures increases with height, while their intensity, number, and intermittency factor decrease. Despite the good matching obtained for temperature and humidity, the coherent-structure properties did not show the expected variation with wind speed, stability parameter, and friction velocity. The Kolmogorov–Smirnov test indicated that the intermittent function and the wavelet transform did not detect coherent structures belonging to the same population.  相似文献   

QK-100型多功能全液压取样钻机的研制          下载免费PDF全文

黎毅力  孙建华  张永勤  张阳明  杨大根 《探矿工程》2005,32(1):43-45

QK-100型多功能全液压取样钻机是为满足我国厚覆盖地区地质填图取样而研制的。介绍了该钻机的技术参数、性能特点、主要结构以及试验试制情况。  相似文献   

浅议川南石屏井田SPMT-1号煤层气参数井采煤技术问题     

冯国文 《四川地质学报》2004,24(3):190-192

SPMT—1号煤层气参数井位于川南煤田古叙矿区石屏井田。该井田煤层普遍较薄，且为粉煤和粉煤夹块煤，取心较难。本文主要阐述了采好煤心的技术措施，通过认真的分析研究和技术措施的运用，煤样采取率高，质量好，保证了参数井对煤层的取样要求。  相似文献