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1.
A procedure is proposed for evaluating the functionality of acids and bases using data frompotentiometric titration.The sequential probability ratio test is used together with a numerical modelinvolving the ionic strength varying during the course of the titration.As in all sequential procedures,thenumber and extent of titrant additions are a function of the probabilistic discrimination level reachedafter each addition.This involves an important saving of time and reagents.The procedure has beenapplied for distinguishing monofunctional from difunctional acids and bases in real and simulatedexperiments,and always gives very good results even in routine analysis. 相似文献
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M. Stephenson J. Klaverkamp M. Motycka C. Baron W. Schwartz 《Journal of Paleolimnology》1996,15(1):99-106
Sediments of Lake 382, Experimental Lakes Area, Canada, were sampled at six sites using a 5-cm Wildco KB core sampler (KB), a similar device incorporating a ball check valve (BC), and a 0.2 m by 1.2 m flat-faced aluminum freeze core sampler (FC). Cores were sectioned at 1-cm intervals to a depth of 15 cm. Contaminant (210Pb and 137Cs) concentrations (Bq g-1) were measured by gamma spectroscopy, and inventories (Bq cm-2) were calculated following standard methods. Sediments collected using FC, BC and KB had similar contaminant concentrations, however, cores collected by FC and BC had lower estimated inventories than KB cores. Differences between estimates appear to be caused by differences in the water content (WC) of core material. Laboratory studies confirm that FC sediments have higher WC than tube-cored sediment. We hypothesize that ice crystal formation increases the WC of freeze cores, resulting in lower contaminant inventories. Loss of surficial sediment caused by a bow wave may have a similar effect on BC samples. We conclude that KB core gear is appropriate for sampling sediments to measure contaminant concentrations and inventories in recently deposited sediments. 相似文献
4.
Dario Albarello 《Geophysical Journal International》2000,140(3):535-542
Several methods have been proposed to constrain the stress field from fault plane orientations and slip directions within a crustal volume characterized by brittle deformation. All the methods are based on the assumption that the stress field is uniform in the volume considered. If this hypothesis is not checked in advance, however, the methodology may lead to misleading conclusions. In this work, a procedure is defined to check stress-field uniformity by a statistical analysis of the available fault data. Since, in most cases, the statistical features of the uncertainties that affect such data are not well known, a distribution-free approach is proposed. It is based on a simple search algorithm, devoted to selecting stress configurations compatible with available data, combined with a bootstrap resampling approach. The test results are more conservative than the ones so far proposed in the literature. When the test allows stress heterogeneities to be safely excluded, approximate confidence intervals for the principal stress directions can be obtained; otherwise, the level of stress heterogeneity present in the volume under study can be assessed. An application of the proposed procedure to a sample of fault data deduced from seismological data is presented. 相似文献
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Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results 总被引：59，自引：0，他引：59
Five test runs were performed to assess possible bias when performing the loss on ignition (LOI) method to estimate organic matter and carbonate content of lake sediments. An accurate and stable weight loss was achieved after 2 h of burning pure CaCO3 at 950 °C, whereas LOI of pure graphite at 530 °C showed a direct relation to sample size and exposure time, with only 40-70% of the possible weight loss reached after 2 h of exposure and smaller samples losing weight faster than larger ones. Experiments with a standardised lake sediment revealed a strong initial weight loss at 550 °C, but samples continued to lose weight at a slow rate at exposure of up to 64 h, which was likely the effect of loss of volatile salts, structural water of clay minerals or metal oxides, or of inorganic carbon after the initial burning of organic matter. A further test-run revealed that at 550 °C samples in the centre of the furnace lost more weight than marginal samples. At 950 °C this pattern was still apparent but the differences became negligible. Again, LOI was dependent on sample size.An analytical LOI quality control experiment including ten different laboratories was carried out using each laboratory's own LOI procedure as well as a standardised LOI procedure to analyse three different sediments. The range of LOI values between laboratories measured at 550 °C was generally larger when each laboratory used its own method than when using the standard method. This was similar for 950 °C, although the range of values tended to be smaller. The within-laboratory range of LOI measurements for a given sediment was generally small. Comparisons of the results of the individual and the standardised method suggest that there is a laboratory-specific pattern in the results, probably due to differences in laboratory equipment and/or handling that could not be eliminated by standardising the LOI procedure.Factors such as sample size, exposure time, position of samples in the furnace and the laboratory measuring affected LOI results, with LOI at 550 °C being more susceptible to these factors than LOI at 950 °C. We, therefore, recommend analysts to be consistent in the LOI method used in relation to the ignition temperatures, exposure times, and the sample size and to include information on these three parameters when referring to the method. 相似文献
7.
A new conglomerate test in palaeomagnetism 总被引：2，自引：0，他引：2
Stanislav V. Shipunov Anton A. Muraviev & Mikhail L. Bazhenov 《Geophysical Journal International》1998,133(3):721-725
The conglomerate test is widely used in palaeomagnetism to date components of natural remanent magnetization with respect to deposition of conglomerates. It has been demonstrated, however, that this test may be positive even if the data are strongly contaminated by a secondary remanence, especially for the commonly used small number of clasts Starkey & Palmer 1970). Here we show with the aid of numerical simulations that different statistical procedures employed in this test have similar low sensitivities to remagnetization. We suggest a new conglomerate test which incorporates additional information on the direction of a secondary palaeomagnetic component which is isolated from either clasts themselves or their host rocks. Numerical simulations show that this new test is about twice as sensitive to remagnetization as the previous procedures and is robust with respect to small errors in the direction of a secondary component. 相似文献
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The fold test as an analytical tool 总被引：1，自引：0，他引：1
P. L. McFadden 《Geophysical Journal International》1998,135(2):329-338
Two fold tests for palaeomagnetism have recently been proposed that rely on the assumption that the total population of magnetic vectors is most highly concentrated with the rocks in the orientation they had at the time of acquisition of the magnetization. This leads to appealing, simple tests based on parameter estimation. However, it is shown that the underlying assumption is flawed and can lead to incorrect conclusions. McFadden & Jones (1981 ) previously developed an inference test based on the concept that the between-group dispersion of magnetization should be consistent with the within-group dispersion when the rocks are in the orientation they had at the time of magnetic acquisition. That test made unrealistic demands upon the sampling scheme for typical, realistic folding geometries and so it has been under-utilized. The McFadden & Jones test is extended by recognizing that it is sufficient to use groups with similar bedding corrections and that it is not necessary to insist on groups with common bedding corrections. These groups may easily be determined with a clustering algorithm. The point is that with the rocks in the orientation at which the magnetization was acquired, it should be immaterial how the groups are chosen. 相似文献
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针对不同深度含水层,揭示其富水性,探讨地下水资源可恢复性、可利用性和浅层劣质水改造利用可能性。以国土资源部衡水地下水试验场为依托,在详细调查试验场影响区地下水开发利用状况、监测地下水年动态基础上,开展分层抽水试验和水化学同位素采样。通过对大量抽水水位动态数据过程、局部流场特征和水化学同位素的分析,得出结论:该区农业为影响地下水水位的主控因素;含水层系统承压性、补给强度从下到上分别呈减弱、增强趋势,除浅层外各含水层渗透性较强;各含水层渗流强度及方向不同等。提出实现地下水可持续开发利用建议:对浅层地下咸水适时进行抽咸换淡、混灌轮灌改造利用;170m、300m强含水层作为工农业用水主要开采层,深层地下水主要用于生活用水;按照水量平衡、分质用水原则开发地下水。 相似文献
11.
The seasonal variability and spatial distribution of precipitation are the main cause of flood and drought events. The study of spatial distribution and temporal trend of precipitation in river basins has been paid more and more attention. However, in China, the precipitation data are measured by weather stations (WS) of China Meteorological Administration and hydrological rain gauges (RG) of national and local hydrology bureau. The WS data usually have long record with fewer stations, while the RG data usually have short record with more stations. The consistency and correlation of these two data sets have not been well understood. In this paper, the precipitation data from 30 weather stations for 1958–2007 and 248 rain gauges for 1995–2004 in the Haihe River basin are examined and compared using linear regression, 5-year moving average, Mann-Kendall trend analysis, Kolmogorov-Smirnov test, Z test and F test methods. The results show that the annual precipitation from both WS and RG records are normally distributed with minor difference in the mean value and variance. It is statistically feasible to extend the precipitation of RG by WS data sets. Using the extended precipitation data, the detailed spatial distribution of the annual and seasonal precipitation amounts as well as their temporal trends are calculated and mapped. The various distribution maps produced in the study show that for the whole basin the precipitation of 1958–2007 has been decreasing except for spring season. The decline trend is significant in summer, and this trend is stronger after the 1980s. The annual and seasonal precipitation amounts and changing trends are different in different regions and seasons. The precipitation is decreasing from south to north, from coastal zone to inland area. 相似文献
12.
本研究对在中国和韩国采集的沙尘的粒径分布及质量浓度进行了测定,使用黄沙标准物质对基于静电沉降原理的等离子空气清洁系统的去除沙尘效率进行了评价。本研究所使用的黄沙采集于北京和汉城,其粒径中值在7.0~80μm之间,浓度范围为300~1462μg·m-3。在单通道测试中,沙尘去除效果随粒径增大和流速降低而增加。系统速度为1.0m·s-1时,去除率大于80%。在27m2的房间中,进行多通道测试时,浓度为300μg·m-3的大气颗粒物仅用10min即可降至150μg·m-3。因此,等离子空气清洁系统能够有效地去除沙尘及保持室内空气质量。 相似文献
13.
Angela L. Lamb Tim S. Brewer Melanie J. Leng Hilary J. Sloane Henry F. Lamb 《Journal of Paleolimnology》2007,37(4):499-516
The analysis of oxygen isotope ratios (δ18O) in biogenic silica (e.g. diatoms, sponge spicules, phytoliths) is an increasingly utilised palaeoclimatic proxy for lakes
and oceans, providing an alternative to carbonate δ18O. Currently, the problems associated with the cleaning and extraction of pure diatom silica, especially from lake sediments,
may compromise the precision associated with δ18Odiatom records. This is because, despite improvements in cleaning techniques, it is still difficult to remove silica-containing
contaminants (e.g. tephra, silts and clays) from biogenic silica. Where it has proved difficult to remove all the silica bearing
contaminants from a sample, mass balance calculations involving point counting have been used, but these are inherently inaccurate
as they only consider the surface area of the contaminant, rather than volume. The new method described here assesses the
volume of contamination in each sample of biogenic silica by using major and trace element geochemistry, allowing the δ18O of the contamination to be removed from the biogenic silica δ18O value by linear mass balance. In this case, diatom silica was contaminated with tephra, however the method should also be
applicable to other contaminants such as silts and clays. 相似文献
14.
J. Thibal A. Etchecopar J.-P. Pozzi V. Barthès & J. Pocachard 《Geophysical Journal International》1999,137(3):839-846
Precise time and facies correlations between drilled holes are fundamental for a better understanding of the geological evolution of sedimentary basins. A downhole magnetic measurement device called the geological high-sensitivity magnetic tool (GHMT) has been run within two wells drilled by Gaz de France in the Landes oil-field (southwest France) as part of a gas storage exploration program. The method of interpretation of downhole magnetic measurements yielded a magnetostratigraphy within each well, allowing absolute dating and time correlations between the wells.
Magnetic susceptibility and natural gamma ray intensity are useful parameters for establishing high-resolution lithological correlations at a basin scale. We present a correlation parameter established from a simultaneous analysis of the susceptibility and the gamma ray logs within each well. The correlation parameter appears to provide a new tool for delineating lithological elements when local lithological changes are too subtle to show clear well-to-well correlations either from susceptibility logs or from gamma ray logs. This new approach is interpreted as a sensitive way to detect relative variations between the detrital and clay content of the penetrated sediment. 相似文献
Magnetic susceptibility and natural gamma ray intensity are useful parameters for establishing high-resolution lithological correlations at a basin scale. We present a correlation parameter established from a simultaneous analysis of the susceptibility and the gamma ray logs within each well. The correlation parameter appears to provide a new tool for delineating lithological elements when local lithological changes are too subtle to show clear well-to-well correlations either from susceptibility logs or from gamma ray logs. This new approach is interpreted as a sensitive way to detect relative variations between the detrital and clay content of the penetrated sediment. 相似文献
15.
海河流域气象和水文降水资料对比分析及时空变异 总被引：11，自引：0，他引：11
选用海河流域上国家气象局30个气象站1958-2007年共50年的日降水资料,以及水文部门248个雨量站1995-2004年共10年的资料,采用线性回归、5年滑动平均、Mann-Kendall趋势分析、Kolmogorov-Smirnov检验、Z检验和F检验等方法,在充分考虑两套降水资料优势的基础上,分析了海河流域降水的时空变化特征。发现：(1) 海河流域气象站和雨量站的年降水量基本都符合正态分布,其均值和方差在统计意义上相等;两套资料的相关程度较高,气象站日降水资料可以用来延长水文站资料;(2) 在1958-2007年,除春季降水量略有增加外,海河流域的降水整体上呈减少趋势,夏季和全年减少趋势非常明显,而且1980年后呈加速减少;(3) 海河流域夏季和全年的降水分布形势相似,以太行山和燕山为界,分为山前多雨带、山前平原区少雨带以及山后少雨带,而且降水从南向北,从沿海到内陆逐渐减少;冬季水汽含量最少,基本上呈南多北少的分布;春秋季的分布特征相似,表现为冬夏季的过渡状态。近50年来,五台山地区和太行山前的部分地区降水减少趋势明显。 相似文献
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冀豫鄂三省农用地分等成果一致性检验 总被引：1，自引：0，他引：1
李小波 《地理与地理信息科学》2006,22(4):97-100
农用地省级分等成果是国家级成果汇总的基础,省级成果是否具有一致性,省际是否平衡协调是国家级汇总研究的重点内容。以冀豫鄂三省为例,标准样地为样本数据,分析标准粮产量与农用地等别关系,剖析农用地省级分等成果的内部一致性以及省际差异程度。检验结果表明:各省农用地分等结果与标准粮产量间具有相同的变化趋势,但相关程度与变化关系不具有整体一致性。 相似文献
17.
Construction of statistically reliable sclerochronology using subfossil shells of river pearl mussel
Sclerochronology is based on series of skeletal growth records that have been correctly aligned in time. These chronologies
have so far been derived from living bivalves and corals. Here we demonstrate the possibility of constructing the sclerochronology
from a suite of river pearl mussel (Margaritifera margaritifera (L.)) shells with unknown but at least partly overlapping geological age. Subsequent to measuring of the annual shell growth
increments, the sample series were iteratively compared to each other and to the mean series of other samples. This comparison
forms the basis of the applied procedure, termed cross-dating, in which more inter-correlative sample series can be progressively
added into the mean chronology in step-wise fashion. After cross-dating, the correlation of the 16 sample series (0.52) indicated
that the subfossil sclerochronology bore common growth signal that was comparable to previously recorded chronologies from
modern samples. The cross-dated sclerochronology represented growth variations over a time window of 91 years. Variability
in chronology was found to be statistically reliable, with sample replication in at least six series (this equalled to chronology
sub-interval of 78 years). In the wider paleontological context, these results show the possibility of constructing statistically
reliable sclerochronologies from fossil specimens at any given locality bearing an abundance of skeletal remains. Such chronologies
will be important in their ability to provide paleolimnological records with comparable quality to recent proxy and observational
series. Sclerochronologies can be numerically examined for paleolimnological variations using standard time-series analysis
tools: a dominant frequency-band at inter-annual and multi-annual time-scales was found in our sample by spectral analysis. 相似文献
18.
《自然地理学》2013,34(4):311-330
For a comprehensive bird inventory of Yukon-Charley Rivers National Preserve, Alaska, we stratified the 1 million hectare study area by large, physiographically defined regions known as ecological units. Point-count data from the bird inventory were used to test the ability of the ecological units to differentiate bird assemblages, and compare the effectiveness of ecological units to fine-scale vegetation types. The ecological units were a synthesis of geology, landforms, soils, and vegetation mapped at a scale of 1:250,000; the vegetation types were based on vegetation within 50 m of the sample points. Nonparametric multivariate statistical tests showed that ecological units and vegetation types had similar success in differentiating bird assemblages, despite their different scales and conceptual bases. Analyses of individual bird species showed that both ecological units and vegetation types provide useful and complementary information about bird habitat selection. Ecological units have several advantages over vegetation types as sample-area strata: they are stable over time, logistically easier to sample in a large roadless study area, and they allow one to obtain a larger bird sample size through inclusion of birds detected at greater distances. 相似文献
19.
Mapping landslide susceptibility from small datasets: A case study in the Pays de Herve (E Belgium) 总被引：3，自引：1，他引：3
A landslide susceptibility map is proposed for the Pays de Herve (E Belgium), where large landslides affect Cretaceous clay outcrop areas. Based on a Bayesian approach, this GIS-supported probabilistic map identifies the areas most susceptible to deep landslides. The database is comprised of the source areas of ten pre-existing landslides (i.e. a sample of 154 grid cells) and of six environmental data layers, namely lithology, proximity to active faults, slope angle and aspect, elevation and distance to the nearest valley-floor. A 30-m-resolution DEM from the Belgian National Geographical Institute is used for the analysis. Owing to the small size of the sample, a special cross-validation procedure of the susceptibility map is performed, which uses in an iterative way each of the landslides to test the predictive power of the map derived from the other landslides. Four different sets of variables are used to produce four susceptibility maps, whose prediction curves are compared. While the prediction rates associated with the models not involving the “proximity to active fault” criterion are comparable to those of the models considering this variable, strong weaknesses inherent in the fault data on which the latter rely suggest that the final susceptibility map should be based on a model that excludes any reference to fault. This highlights the difference between a triggering factor and determining factors, and in the same time broadens the scope of the produced map. A single reactivated slide is also used to test the possibility of predicting future reactivation of existing landslides in the area. Finally, the need for geomorphological control over the mathematical treatment is underlined in order to obtain realistic prediction maps. 相似文献
20.
中国次雨量特征及其区域分异 总被引：3，自引：0，他引：3
基于统计方法的降雨随机模拟已成为目前许多地表过程模型的重要组成部分,但多以日降雨模拟为主.为了进行次降雨随机模拟.必须揭示次降雨的统计特征.本文利用中国62个气象站1954-2001年5-9月逐日小时降水资料,整理出能够刻画次降雨特性的基本指标,分析了我国次降雨的基本特征,并利用卡方检验方法,验证了我国次雨量主要服从两参数Γ分布,个别未通过检验的站点主要是由于对次雨量极值模拟效果不好所致.进一步选择Γ分布两参数和90%、95%、99%次雨量百分位共5个指标.采用K均值动态聚类法将我国次降雨特征划分为5个类型区域,由东南向西北呈带状分布,各区次雨量的偏态性、非均匀性和分散度依次减弱.利用5个区Γ分布两参数的区域化参数值,可生成任一站点次雨量随机模拟序列,对于地表过程定量研究具有重要意义. 相似文献