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1.
为了保证建筑物在沉降过程中变形观测点的观测成果的连续性、可比性，对沉降监测中基准网与监测网的观测精度匹配问题进行了详细的探讨，得出了有参考价值的结论。 相似文献
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Gary C. Matlock 《Estuaries and Coasts》1984,7(2):185-189
The relative capture efficiencies for fish in 732-m trammel nets using three striking methods were compared using nets set in open-water and along the shoreline in Texas bays in fall and spring. When compared to noise, sublethal concentrations of rotenone and KMnO4 did not increase the catches of 9 of the 12 species tested at either shoreline or open-water stations in either the fall or spring. Some effect of strike type was noted for hardhead catfish (Arius felis), gizzard shad (Dorosoma cepedianum), and striped mullet (Mugil cephalus) at stations struck with noise or rotenone, but catches were not consistently greater for either striking method. The catches of some species were different between station types and seasons. However, the total catch at shoreline stations was the same as at open-water stations in both the fall and spring. 相似文献
3.
By following a simple set of rules, a flow net can be manually constructed to obtain a graphical solution to the Laplace equation for simple two‐dimensional (2‐D) flow problems. With the advent of numerical solutions such as the finite difference and finite element methods, it is more common to generate a flow net automatically using the nodal head and flow values output by the computer program. Two methods have been published for automatically generating flow nets from finite element solutions: the stream‐function method and the particle‐tracking method. The stream‐function method works well for many cases, but it does not work for problems with holes in the mesh or internal sources or sinks. The particle‐tracking method works for all cases, but previously published algorithms that utilize this method do not result in the properly sized flow channels. A new approach is presented in this paper that is a hybrid of the stream‐function and particle‐tracking approaches. This method works for all cases and generates the properly sized flow channels. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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人工神经网络在区域地质调查中的应用--反向传播模型(BP网)建立与应用 总被引：1，自引：0，他引：1
类比与识别是１∶５ 万区调工作中应用的基本方法之一。把人工神经网络技术———反向传播模型（ＢＰ网） 应用于这些基本方法中,不但有助于区调技术人员使脑科学朝向定量、精确和理论化方向发展,而且有助于我们对神经网络及其成为一种崭新的信息处理方法的理解,从而提高１∶５ 万区调理论研究水平。 相似文献
5.
大中型企业网络的安全形势越来越严峻,在分析企业网络安全的基础上,从防病毒技术、防火墙技术、入侵检测技术及主机防护等方面阐述了网络安全防护技术,基于安全平台的构建与应用,给出了配套的软件及解决方案。 相似文献
6.
This paper analyses the spatial patterns of internal migration in Russia using data on net migration gain/loss in 2200 municipal formations (MFs) in Russia for the 2012–2013 period. These MFs are grouped into age categories that correspond with different life-course stages. We define 16 classes of MFs with similar migration balance patterns for multiple age groups and characterize the most typical classes. The results of our analysis show that age-specific migration patterns are determined by the spatial characteristics of MFs—in particular, a municipality’s localization in the centreperiphery system and the advantages of the geographic location (e.g., resort area, natural resources). We find that a city’s population size and administrative status are also important migration factors. In addition, we reveal differences in inter-regional and intra-regional migration and define their structural characteristics. An analysis of age-specific net migration contributes to our understanding of internal migration factors and allows us to assess the impact of migration on a municipality’s age structure. In large cities and regional centres, migration results in younger populations, while in peripheral areas, it speeds up population ageing. In most of the MFs that we analysed, the migration of youth and adults ‘moves’ in opposite directions. This factor accelerates the impact of migration on the population age structure in areas of destination and origin and significantly influences a municipality’s current and prospective demographic parameters as well as the population’s patterns of settlement and spatial concentration or de-concentration both nationally and regionally. 相似文献
7.
Y. P. Hsieh 《Estuaries and Coasts》1996,19(1):82-85
Information of aboveground net primary production (ANPP) in marshes has been limited by the lack of accurate methods for assessment. Most popular methods have weaknesses that cause either underestimates or overestimates of ANPP values. The nondestructive growth kinetics monitoring method used by Williams and Murdoch (W-M) has provided, perhaps, a most ideal and reasonable assessment of ANPP inJuncus roemerianus marshes Unfortunately, the W-M procedure is difficult to carry out and it is restricted toJuncus marshes. I present here a modification of the W-M procedure. The modified procedure applies the principle of the original W-M method while eliminating the need to monitor growth kinetics of individual plants. The modified ANPP procedure requires monthly harvests of the above-ground plant biomass over a period of 1 yr and the estimation of mean residence time of the plant. The modified W-M procedure was comparable to the original procedure inJ. roemerianus marshes of northern Florida. This modified procedure has the potential to be applied to marshes other than those dominated byJuncus. 相似文献
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利用MATLAB语言编写M文件,可以读取指定文件名下的Excel文档中基点网平差时所运用的基本参数进行计算,得到准确的平差结果;该M文件使用时不需要打开源程序,在Excel文件中输入相关数据后,打开MATLAB运行界面中直接输入M文件名就可以进行平差计算,使用简单方便. 相似文献
10.
《Applied Geochemistry》2005,20(10):1941-1964
The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples.Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5–4) or near neutral (pH 6–7); ≈ 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6.The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze.The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= −net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH < 6.3 after oxidation had positive Hot Acidity. Samples with similar pH values before oxidation had dissimilar Hot Acidities due to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. Hot Acidity was approximately equal to net acidity calculated based on initial pH and dissolved concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity calculated from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was equivalent to that calculated based on complete aqueous speciation of FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the Hot Acidities were comparable for fresh and most aged samples.A meaningful “net” acidity can be determined from a measured Hot Acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. The use of net alkalinity = (Alkalinitymeasured − Hot Aciditymeasured) to design mine drainage treatment can lead to systems with insufficient Alkalinity to neutralize metal and H+ acidity and is not recommended. The use of net alkalinity = −Hot Acidity titration is recommended for the planning of mine drainage treatment. The use of net alkalinity = (Alkalinitymeasured − Aciditycalculated) is recommended with some cautions. 相似文献