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21.
Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients 总被引:1,自引:0,他引:1
XUE Feng ZHAO Ming-fei WANG Yu-hang KANG Mu-yi XING Kai-xiong WANG Guo-yi SHI Jing-jing CHEN Chen JIANG Yuan 《山地科学学报》2019,(1):30-42
The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations(BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil(0-10 cm) samples across an elevational range of more than 2000 m(1243 ~ 3316 m a.s.l.),and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen(Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir(Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were nosignificant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature(MAT), growing season precipitation(GSP) and non-growing season precipitation(NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability. 相似文献
22.
不同开口比人工鱼礁体水动力特性及礁体稳定性研究 总被引:2,自引:0,他引:2
为研究方型人工鱼礁体开口比的变化对其水动力特性的影响,利用Fluent软件模拟了边长为3m、开口比为0~0.6之间7种不同方型鱼礁体周围水流场,通过分析水流场变化规律得到了礁体流场效应、阻力系数随开口比的变化情况;基于Morison方程计算了礁体在波流作用下的受力及其抗滑移、抗倾覆安全系数。研究结果表明:当礁体开口比小于0.2时,背涡区范围较大,流场效应明显;随着开口比的增大,礁体产生的上升流范围及竖直向最大速度分量逐渐减小;对于方形开口礁体,阻力系数与开口比的关系式为Cd=0.875φ+1.088(R2=0.963,P<0.01);随着开口比的增大,礁体所受最大波流作用力、抗滑移及抗倾覆安全系数逐渐减小,但礁体不会发生滑移和倾覆,可为实际礁体结构的设计提供参考。 相似文献
23.
介绍了一种高精度、高性价比的GPS定位定向仪的设计及实现(〈1mil,2σ)方法,系统利用了实际应用中的有利约束条件,对基于LAMBDA方法的载波相位整周模糊度解算算法进行了改进,经过系统工程设计,在实际应用中实现了单频、高精度、快速定向数据的输出。可以满足绝大多数环境下的使用需求,大大降低了系统成本。 相似文献
24.
分析了L2C码的主要作用,比较了GPS现代化后L2载波信噪比的变化特点,阐述了伪距观测值的噪声水平。 相似文献
25.
基于边缘分析的海面溢油检测 总被引:3,自引:2,他引:1
提出一种基于边缘检测的快速溢油信息提取方法, 首先对溢油图像进行ROA(radio of average)边缘检测, 根据检测结果进行AOI(area of interest)提取, 然后使用改进的Weibull-CFAR检测算法对AOI进行溢油检测, 并与全局CFAR检测结果进行对比。实验结果证明, 所提出的方法对于非均匀灰度SAR图像溢油检测准确性较好、效率较高, 特别适用于大图像的快速溢油检测。 相似文献
26.
Cindy Lee Robert A. Armstrong J. Kirk Cochran Anja Engel Scott W. Fowler Madeleine Goutx Pere Masqu Juan Carlos Miquel Michael Peterson Christian Tamburini Stuart Wakeham 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1363-1368
The MedFlux project was devised to determine and model relationships between organic matter and mineral ballasts of sinking particulate matter in the ocean. Specifically we investigated the ballast ratio hypothesis, tested various commonly used sampling and modeling techniques, and developed new technologies that would allow better characterization of particle biogeochemistry. Here we describe the rationale for the project, the biogeochemical provenance of the DYFAMED site, the international support structure, and highlights from the papers published here. Additional MedFlux papers can be accessed at the MedFlux web site (http://msrc.sunysb.edu/MedFlux/). 相似文献
27.
28.
In the identifying process of an oil spill accident, manual integral and artificial visual comparison are commonly used at present to determine the oil spill sources, these methods are time-consuming and easily affected by human factors. Therefore, it is difficult to achieve the purpose of rapid identification of an oil spill accident. In this paper, an intelligent method of automatic recognition, integration and calculation of diagnostic ratio of Gas Chromatography-Mass Spectrometer (GC/MS) spectrum are established. Firstly, four hundreds of samples collected around the world were analyzed using a standard method and Retention time locking technology (RTL) was applied to reduce the change of retention time of GC/MS spectrum. Secondly, the automatic identification, integration of n-alkanes, biomarker compounds, polycyclic aromatic hydrocarbons and calculation of the diagnostic ratios were realized by MATLAB software. Finally, a database of oil fingerprints were established and applied successfully in a spill oil accident. Based on the new method and database, we could acquire the diagnostic ratios of an oil sample and find out the suspected oil within a few minutes. This method and database can improve the efficiency in spilled oil identification. 相似文献
29.
The shape optimization of the 2-dimensional wing in ground effect (WIG) has been performed by the integration of CFD (computational fluid dynamics) and MOGA (multi-objective genetic algorithm). Because of the trade-off between the aerodynamic forces and the height stability, it is difficult to satisfy the design requirements of efficiency and stability at the same time. In this study, the lift coefficient, the lift-drag ratio and the static height stability are chosen as the objective functions to obtain the optimal wing profiles of a WIG craft. An NACA0015 airfoil is used for the baseline model; the aerodynamic characteristics of the base model are compared with that of the optimal solutions. The profile of the airfoil is constructed by four Bezier curves with fourteen control points resulting in the eighteen coordinates, which are adopted as the design variables. The optimal solutions of the multi-objective optimization are not unique but a set of the non-dominated optima: the Pareto frontiers or a Pareto set. As the results of the multi-objective optimization, the forty Pareto optima, which include high-lift, high-efficiency, and more stable airfoils on the edge of the 3-dimensional objective space, are obtained at thirty evolutions of the generation. 相似文献
30.