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81.
本文对我国的MB-2型和美国的TR-2型卵石推移质采样器的模型的水力特性和采样效率进行了对比试验研究。得到MB-2的水力效率为0.91,TR-2的水力效率为1.04;仪器置入水中后水流的紊动强度TR-2比MB-2大。TR-2的采校效率平均是MB-2的1.84倍,TR-2的采样效率方差平均是MB-2的1.67倍,即前者的采样效率比后者高,但其采样效率的稳定性比后者差。文中还给出了两种仪器的采样效率η 相似文献
82.
主要叙述HYS-1型原状取砂器的技术性能、基本结构工作原理有适用范围。同时介绍其在我国长江三峡及南水北调两大工程地基勘察中的应用技术 相似文献
83.
Jiangfeng She Chuang Li Jiaqi Li Qiujun Wei 《International journal of geographical information science》2018,32(3):476-497
With the extensive application of virtual geographic environments and the rapid development of 3D visualization analysis, the rendering of complex vector lines has attracted significant attention. Although there are many rendering algorithms in 3D geographic information system (GIS), they are not sufficiently flexible to meet the requirements for rendering linear symbols composed of diverse colors and shapes. However, the interactive rendering of a scene and the accuracy of the symbols are important components for large-scale, complex vector lines. In this paper, we propose a graphics processing unit (GPU)-accelerated algorithm for rendering linear symbols on 3D terrain. Symbol rendering is embedded within the terrain-rendering process, and vector lines are encoded in a 3D texture and then transferred to the GPU. A set of visual properties are used to enrich the expression of symbols with the help of geometric operations in the fragment shader. A series of experiments demonstrate that the proposed method can be utilized for drawing various pixel-exact linear symbols and can achieve real-time rendering efficiency. 相似文献
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Xavier Emery 《Mathematical Geosciences》2008,40(1):83-99
This paper presents random field models with Gaussian or gamma univariate distributions and isofactorial bivariate distributions,
constructed by composing two independent random fields: a directing function with stationary Gaussian increments and a stationary
coding process with bivariate Gaussian or gamma distributions. Two variations are proposed, by considering a multivariate
directing function and a coding process with a separable covariance, or by including drift components in the directing function.
Iterative algorithms based on the Gibbs sampler allow one to condition the realizations of the substitution random fields
to a set of data, while the inference of the model parameters relies on simple tools such as indicator variograms and variograms
of different orders. A case study in polluted soil management is presented, for which a gamma model is used to quantify the
risk that pollutant concentrations over remediation units exceed a given toxicity level. Unlike the multivariate Gaussian
model, the proposed gamma model accounts for an asymmetry in the spatial correlation of the indicator functions around the
median and for a spatial clustering of high pollutant concentrations. 相似文献
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We have constructed an artificial laboratory fumarole to calibrate the most common chemical volcanic gas sampling techniques and obtain a quantitative measure of their efficacy. We have also developed and tested a new rugged and portable venturi spray gas sampler. The venturi sampler reproduced the output gas composition most accurately, followed by the Giggenbach bottles, filter packs, and lastly alkaline traps. Passive alkaline traps, however, did better than filter packs when sampling more concentrated fumarole gases. Under ideal conditions, the accuracy of the Giggenbach bottles was identical to the venturi sampler, although there was slightly more scatter. The Giggenbach sampler was more susceptible to problems with condensation on the input train even in a laboratory setting, and this technique was only effective in relatively concentrated gas streams. Filter packs are also effective, but extreme care must be exercised to maintain strong undersaturation with respect to the acid gas. If strong undersaturation (high pH) is not maintained, the filter packs return erroneously low S/Cl and S/F ratios. Use of a pH indicator is an effective way of avoiding this problem. The passive alkaline traps also under-sample sulfur, resulting in low reported S/Cl and S/F ratios. It appears that the overall sampling efficiency of all techniques was not strongly affected by oxygen fugacity over the limited range tested. When detecting sulfate and sulfite simultaneously, we found no difference in total sulfur before and after oxidation. This suggests that all sulfur from the gas regardless of oxidation state was absorbed as sulfite or sulfate and/or was quickly oxidized in solution. This conclusion is supported by IC HS− reference samples. 相似文献
89.
Flume‐ and field‐based evaluation of a time‐integrated suspended sediment sampler for the analysis of sediment properties 下载免费PDF全文
Suspended sediment has been identified as a vector for nutrient and contaminant transport in the fluvial environment. A time‐integrated sampler (the Phillips sampler), which emerged over a decade ago as a cost‐effective tool for in situ suspended sediment collection, is increasingly being used to collect samples for the analysis of sediment properties such as particle size composition, and nutrient and contaminant concentrations. This study evaluates the sampler under both flume and field conditions for efficiency in the mass and grain size of the suspended sediment collected. The sampler was tested in a flume using both kaolinite and sediment samples (sieved to < 180 µm) collected from the Quesnel River, British Columbia, Canada. In the kaolinite trails, the sampler preferentially collected coarser grain sizes compared to the original sediment, probably due to finer sediment remaining in suspension and therefore passing through the sampler, and also possibly due to flocculation of the kaolinite upon introduction to the flume. Conversely, the sampler collected river sediment that was finer than the original sediment, probably due to some settling of coarser sediment observed at the bottom of the flume. Once allowance was made for these operational issues associated with the flume, maximum sediment mass efficiency for kaolinite and river sediment was 43% and 87%, respectively. Sediment collected by the time‐integrated sampler during field deployment and adjacent channel bed sediment were also compared. The sampler collected sediment with a representative grain size distribution. However, there were differences in the geochemical (arsenic and selenium) concentrations of channel bed sediment and sediment collected by the Phillips sampler which may be a function of differences in the behavior of geochemical elements associated with the two types of sediment. This work suggests that further research is needed to evaluate the role of the Phillips sampler in collecting sediment for contaminant and nutrient analysis. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
90.
本系统是国家“863”任务中818-02A项目的重要组成部 和高精度CTD测量仪联用,可以完成任意深度、任意时刻的采水控制功能,它采用国内外最新的技术和元器件,打破了原有的采水控制装置的设计思想,使采水器的动作完全合理准确。本文重点介绍其工作原理和关键技术。 相似文献