共查询到20条相似文献，搜索用时 484 毫秒
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O. M. Rozental 《Water Resources》2012,39(6):685-699
Analysis is given to the source of errors, invalidating the results of laboratory studies of water and the standards, norms, and regulations for ensuring the accuracy (validity and accuracy) of methods and results of measurements. The accreditation of laboratories, and their use of the means of measurements and reference standards, admitted for use in accordance with the established order, as well as the participation in interlaboratory comparison tests are shown to be necessary but not sufficient conditions for providing customers with reliable measurement data. To obtain measurement results with an error satisfying the established standards, one should demonstrate conscious and competent attitude toward the measurement problem in accordance with the basic ISO/MEK 17025 standard. It is shown that, under the conditions of increasing value of fresh water in the world, the metrological support of water-environmental control becomes an urgent and specific scientific problem. Therefore, it is proposed to develop water qualimetry??the direction of scientific and applied studies, making it possible to evaluate the characteristics of measurement errors in the characteristics under control to ensure their lying within the established limits with a specified probability. 相似文献
3.
The gel-permeation chromatography system with multicomponent detection of organic carbon, organic nitrogen, organic halogen, and UV/vis absorption measurement is shown to be a useful tool for characterization of industrial wastewaters and wastewater treatment processes. The proposed system was used to investigate biologically treated wastewater from chemical industry, whereby one branch stream was identified to be the main source of persistent halogenated organics. Various treatment processes of pulp mill wastewater were also evaluated revealing that precipitation with aluminium is very effective for the removal of the high molecular fraction whereas the biological treatment is generally less selective. In the biological treatment of tannery wastewaters, it has been shown that the aerobic treatment, in contrast to anaerobic step, causes evident alterations of the composition of the polar DOC fraction. The nitrogen containing compounds are also better decomposed in the aerobic step compared to the anaerobic one. 相似文献
4.
单项资料异常变化信息提取的一种新方法：多点组信息法 总被引：1，自引：0，他引：1
在前人工作的基础上提出了多点组信息法，包容了以前各种各样的数据处理方法，并赋予了新的内容，以４点组斜率信息法为例，做了系统的论述，并以小水峪垂直基线资料为例，给出了初步的处理结果，证明该方法在各种数据的分析处理、提取地震前兆异常信息的应用中有较大的价值，最后给出了标准化信息流，对多项不同量纲的异常信息合成提供了方便。 相似文献
5.
Tim W. Geerits Xiaoming Tang Olaf Hellwig Thomas Bohlen 《Journal of Applied Geophysics》2010,70(2):113-143
In recent years the emphasis in acoustic logging has been shifting from the wireline to the Logging While Drilling (LWD) environment, the latter being far different from the former in that both tool rigidity and tool radius are considerably greater. In this paper we present a generic mathematical formulation for the multipole borehole acoustic measurement (alternate and equal polarity case), including a detailed analysis on the effects of multipole source amplitude imbalances. It is shown that source imbalance induced mode contaminants have excitation amplitudes that are scaled by the sum of the relative source imbalances between diametrically opposed sources. Furthermore it is shown that for mode contaminants with odd modal number there can be a significant offset in the associated directivity pattern, even at low levels of source imbalance. However, it is also shown that source imbalance induced mode contaminants can be completely eliminated if the multipole source is accompanied with a ‘vertically’ (but not azimuthally) offset multipole receiver. Mathematically, it is demonstrated (for a centered tool) that a polarity weighted stack of these multipole receivers completely eliminates the source imbalance induced mode contaminants. Excitation amplitudes and phase slowness of borehole guided modes are presented for the most common excitation regimes, i.e., monopole, dipole, quadrupole and the hexapole excitation, the latter one showing to have the advantage of a higher formation shear cut-off frequency than the quadrupole mode. Special emphasis will be on the analysis of the dipole excitation and the differences that occur due to variations in tool rigidity, tool diameter and (isotropic) formation properties with the resulting conclusion that a formation flexural mode is not observable as a result of a LWD dipole excitation (this opposed to its dipole wireline counterpart). The guided mode excitation amplitudes are calculated as residues using a Laurent series expansion. This (unconventional) way of calculating the residue has the advantage that it is independent of the pole order, does not require the numerical evaluation of derivatives with respect to the vertical wavenumber and allows for an accurate and efficient FFT implementation. 相似文献
6.
对均匀大地和二层大地的频率域电场差分法理论曲线进行的计算和研究表明,电场差分法是一种以目标地质体和围岩在电阻率和极化率方面的差异为基础,根据测量到的能明显反映激电响应与电磁耦合响应的比值随频率变化的P参数曲线在性态上的差异来圈划油气藏的一种电法勘探方法. 因为它圈划油气藏的物理基础是油气藏上方与围岩上方测量到的电磁耦合响应和激电响应的差异,所以在圈划油气藏方面,该方法与复电阻率法类似,同样具有找油气的优良性能. 此外,该方法与复电阻率法相比,具有对目标地质体和围岩的电阻率和极化率差异反映灵敏、效率高、成本低等优点,所以它是一种值得推广的找油气的电法勘探方法. 相似文献
7.
与传统阶跃源激励方式相比,采用m序列伪随机编码对发射源波形进行编码,提高了电磁探测的深度和分辨能力.然而受这种编码源发射波形自相关旁瓣效应的影响,使得对大地冲激响应的精细辨识效果受到一定限制.为了解决这一问题,在以往相关辨识方法研究的基础上,进一步考虑发射自相关旁瓣的影响,首先提出一种由收发互相关中高精度提取大地冲激响应的数学方法;然后通过数值模拟给出了m序列编码源大地冲激响应的精细辨识结果;同时对以m序列为发射波形的勘探系统相关参数选择进行了分析;最后利用本文提出的方法对野外实测数据进行辨识处理,通过与其他EM方法结果进行对比,证明了本文提出方法的可靠性. 相似文献
8.
一个基于扫频与混频相结合的多频EIT数据采集系统 总被引：1，自引：0，他引：1
采用多频率组合与扫频技术相结合的方式,建立了一个32电极多频电阻抗断层成像数据采集系统,该系统具有四种工作模式,在程序控制下,最多步采集四种频率下的组织阻抗信息,工作频率可在1．6KHZ到380KHZ间程控选择。为从含多种频率分量的测量信号中解调出各频率下的组织阻抗,我们设计了一种新的具有高速和高精度特点的解调方法,正交序列数字解调法,对含有n个频率分别的信号,若对其每周期采样N点,则总运算量可降低到2nN次乘法和2n(N-1)次加法运算,信号的信噪比可提高（N／2）^-0．5倍。 相似文献
9.
《Journal of Atmospheric and Solar》2005,67(10):907-912
We availed hourly data of four middle and high cut-off rigidity neutron monitors recorded over 21 years and then discussed various measures of the CR variability and simplified estimates of the CR anisotropy in relation to the Dst time history. The correlation of Dst with the prehistory of CR variability at these cut-offs is shown. A different distribution of the CR indices for 24 h before the sharp Dst decreases in comparison with that for geomagnetically quiet periods is found. The relation of CR variability with the solar wind speed appeared but neither with the solar wind density nor with the Bz component of the interplanetary magnetic field. The multiple regression of Dst with the prehistory of CR variability resulted to be significant, suggesting that the parameters describing CR variability/anisotropy are potentially useful to be implemented into the schemes of forecasting of geomagnetic activity, performed with interplanetary medium data obtained before their arrival at the Earth (e.g. at the L1 point). 相似文献
10.
The integration of geophysical data into the subsurface characterization problem has been shown in many cases to significantly improve hydrological knowledge by providing information at spatial scales and locations that is unattainable using conventional hydrological measurement techniques. In particular, crosshole ground-penetrating radar (GPR) tomography has shown much promise in hydrology because of its ability to provide highly detailed images of subsurface radar wave velocity, which is strongly linked to soil water content. Here, we develop and demonstrate a procedure for inverting together multiple crosshole GPR data sets in order to characterize the spatial distribution of radar wave velocity below the water table at the Boise Hydrogeophysical Research Site (BHRS) near Boise, Idaho, USA. Specifically, we jointly invert 31 intersecting crosshole GPR profiles to obtain a highly resolved and consistent radar velocity model along the various profile directions. The model is found to be strongly correlated with complementary neutron porosity-log data and is further corroborated by larger-scale structural information at the BHRS. This work is an important prerequisite to using crosshole GPR data together with existing hydrological measurements for improved groundwater flow and contaminant transport modeling. 相似文献
11.
A seven year event-based study partitioning of rainfall into throughfall, stemflow, and interception was conducted in a dry sclerophyll eucalypt forest and a Pinus radiata plantation. Resulting information will be of use for process modelling. Stemflow was influenced by event type, rain angle having a major effect; and the yields of the different species are compared. Tree characteristics that influenced stemflow yields are outlined and discussed. The canopy storage capacity of the eucalypt forest was determined and the influence of species composition is shown. The likely influence of climate variations is discussed. The canopy storage capacity is compared to the interception values estimated for continuous events of various sizes. The interception of the eucalypt forest and the pine plantation are compared on event basis for event size classes and on an annual basis. The comparative interceptions for continuous events are also discussed, while the effect of thinning the pine plantation on throughfall, stemflow, and interception is shown. The hydrological consequences of this study are: more informed judgment can be made about techniques for measurement of throughfall, tree structural characteristics (species related) can more adequately be considered when selecting trees for measurement of stemflow, and the stemflow yields can in some cases be better understood from the information about effect of event type. This paper deals with the influence of measurement method, species composition, and tree characteristics on the estimation of throughfall in the eucalypt forest. The site is near Canberra, lat. 35°S, 145°E, with annual rainfall about 650 mm. Two methods of measuring throughfall are compared: randomly placed, 200 mm cylindrical gauges (standard) and 50 mm square opening wedge type gauges (plastic), and randomly placed 5 × 0–22 m troughs. Despite the high placement density (150 to 225 ha?1), throughfall estimates from gauges has high variance and consistently underestimated those of the troughs, which had a total opening equivalent to 2325 raingauges (200 mm diameter) per hectare. Local concentration of stemflow into drip points provided by detaching bark pieces of one smooth barked species, Eucalyptus mannifera, is believed to be the principal cause of the lower collection and greater variance of the gauges. The low leaf area index (1–3) and large wood area of the forest together with a pendulous vertical habit of the leaves also contributed. The presence of E. mannifera is shown to substantially affect the relative values of throughfall as measured by troughs and gauges. The plastic receivers were found to underestimate rainfall or throughfall relative to the standard gauges, particularly for fine drop rainfall in multiperiod events. 相似文献
12.
角反射器精确定位是角反射器微形变获取的前提,文中从研究角反射器影像特征入手,详细介绍了角反射器强度、相关性和光谱离散指数（MSR-Mean to Standard deviation Ratio）影像特征：1）角反射器强度影像特征明显,其影像扩散在多个像素上,Envisat数据中角反射器表现为亮点,而TerraSAR数据中角反射器呈明显的十字型;2）角反射器MSR影像特征不明显;3）不同带宽多视处理后统计得到的角反射器相关性聚焦在一个像素内,而且相关值明显高于周边像素。将角反射器强度、相关性和MSR作为衡量光谱稳定性的参数,对比分析不同参数定位出的角反射器像素位置及其对应的相位信息,结果表明：角反射器强度易受背景干扰,此参数定位角反射器容易产生偏差;角反射器MSR值与背景差别小,不能单独用于角反射器定位;角反射器相关性聚焦性好,相关性参数能准确定位角反射器的像素位置,对应的相位值比其他参数定位得到的相位值相对稳定。 相似文献
13.
Kostelecký J. Kostelecký J. Pešek I. Šimek J. Švábenský O. Weigel J. Zeman A. 《Studia Geophysica et Geodaetica》2004,48(3):503-518
Several quasigeoid models for the Czech Republic have been developed for different purposes since mid-seventies using different data sources: gravimetric, astronomical and GPS/levelling observations, as well as data gained from the territories of neighbouring countries. Two of the recent solutions, namely the VUGTK96 quasigeoid obtained from heterogeneous data and gravimetric quasigeoid CR2000 are described and compared. Accuracies of the models were estimated with the help of accuracy characteristics resulting from the processing, by comparison with GPS/levelling results available for most of the territory, and, finally, tested on a special GPS/levelling profile across the steepest slope of the quasigeoid surface in the south-eastern part of the territory. It is shown that the CR2000 gravimetric quasigeoid is suitable for transformation of ellipsoidal GPS heights to the gravity related heights with an accuracy of 3 cm. 相似文献
14.
Historical seismology suggests certain recommendations to assess the reliability of macroseismic information. These recommendations are quite general and have proved their efficiency in many cases. But they should be very carefully applied, because the formal approach used in them is not always reasonable. Based on the analysis of sources relevant to the 1542 earthquake in the north of Russia, it is shown that though the distribution of priorities for sources relying on how close they are to the event works well, it can not be considered a universal rule. Many other details, such as characteristic of the person compiling the document, one’s interests, how free one could access the non-public achirves, and the goal of writing the document, have to be taken into account. 相似文献
15.
It has been indicated that the Rao-Cramer inequality can be used to estimate the resolvability of intervals with opposite geomagnetic field polarity based on marine anomalies and for measurement planning. Specifically, it has been elucidated that the width of a detected interval of one polarity is determined more exactly than its center. 相似文献
16.
R. T. Gushchina A. V. Belov V. N. Obridko B. D. Shelting 《Geomagnetism and Aeronomy》2010,50(4):436-442
Based on observations of long-term variations in galactic cosmic rays (CRs) on Earth and in the near-Earth space, we have
determined, using our own semiempirical model, modulation of galactic CRs during solar cycles 19–23. The modulation model
relates CR variations to the characteristics of the solar magnetic field obtained for the surface of the solar wind source
at distances of 2.50 and 3.25 solar radii. The main focus is CR behavior at the minimums of cycles 19–23 and specific features
of CR modulation at a prolonged (as compared to previous cycles) minimum of cycle 23, which is still ongoing. CR modulation
at minimums related to a change in the solar field dipole component during this period of the cycle has been considered. It
is indicated that the long-term variations in CRs are better described if the last two years (2007 and 2008) of cycle 23 with
anomalously low solar activity (SA) are included in the model. The role and value of the contribution of the cyclic variations
in each index used in the proposed CR modulation model to the observed CR modulation have been estimated. 相似文献
17.
Recent research in fluvial geomorphology has emphasized the spatially distributed feedbacks amongst river channel topography, flow hydraulics and sediment transport. Although understanding of the behaviour of dynamic river channels has been increased markedly through detailed within-channel process studies, less attention has been given to the accurate monitoring and terrain modelling of river channel form using three-dimensional measurements. However, such information is useful in two distinct senses. Firstly, it is one of the necessary boundary conditions for a physically based, deterministic modelling approach in which three-dimensional topography and river discharge drive within-channel flow hydraulics and ultimately spatial patterns of erosion and deposition and therefore channel change. Secondly, research has shown that an alternative means of estimating the medium-term bedload transport rate can be based upon monitoring spatial patterns of erosion and deposition within the river channel. This paper presents a detailed assessment of the distributed monitoring and terrain modelling of river bed topography using a technique that combines rigorous analytical photogrammetry with rapid ground survey. The availability of increasingly sophisticated terrain modelling packages developed for civil engineering application allows the representation of topographic information as a landform surface. Intercomparison of landform surfaces allows visualization and quantification of spatial patterns of erosion and deposition. A detailed assessment is undertaken of the quality of the morphological information acquired. This allow some general comments to be made concerning the use of more traditional methods to monitor and represent small-scale river channel morphology. 相似文献
18.
This paper presents a geostatistical approach to multi-directional aquifer stimulation in order to better identify the transmissivity
field. Hydraulic head measurements, taken at a few locations but under a number of different steady-state flow conditions,
are used to estimate the transmissivity. Well installation is generally the most costly aspect of obtaining hydraulic head
measurements. Therefore, it is advantageous to obtain as many informative measurements from each sampling location as possible.
This can be achieved by hydraulically stimulating the aquifer through pumping, in order to set-up a variety of flow conditions.
We illustrate the method by applying it to a synthetic aquifer. The simulations provide evidence that a few sampling locations
may provide enough information to estimate the transmissivity field. Furthermore, the innovation of, or new information provided
by, each measurement can be examined by looking at the corresponding spline and sensitivity matrix. Estimates from multi-directional
stimulation are found to be clearly superior to estimates using data taken under one flow condition. We describe the geostatistical
methodology for using data from multi-directional simulations and address computational issues. 相似文献
19.
M. F. Snodgrass P. K. Kitanidis 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(5):299-316
This paper presents a geostatistical approach to multi-directional aquifer stimulation in order to better identify the transmissivity
field. Hydraulic head measurements, taken at a few locations but under a number of different steady-state flow conditions,
are used to estimate the transmissivity. Well installation is generally the most costly aspect of obtaining hydraulic head
measurements. Therefore, it is advantageous to obtain as many informative measurements from each sampling location as possible.
This can be achieved by hydraulically stimulating the aquifer through pumping, in order to set-up a variety of flow conditions.
We illustrate the method by applying it to a synthetic aquifer. The simulations provide evidence that a few sampling locations
may provide enough information to estimate the transmissivity field. Furthermore, the innovation of, or new information provided
by, each measurement can be examined by looking at the corresponding spline and sensitivity matrix. Estimates from multi-directional
stimulation are found to be clearly superior to estimates using data taken under one flow condition. We describe the geostatistical
methodology for using data from multi-directional simulations and address computational issues. 相似文献
20.
Using previous results on extended Petri Nets (EPN), we present the relations between various hydrological dynamical systems (HDSys) derived from the water budget. Once the water budget has been implemented, there is a consistent way of getting the equations for backward travel time distributions, for forward response time distributions and for the concentration of a solute or tracer. We show that the water budget has a correspondence of one to many with the backward travel time distributions. In fact, to any one of the water budget equations there correspond as many equations as there are input precipitation events. The backward travel time distributions are related to the response time distributions by Niemi's relationship and, if there are n outputs, by the definition of n − 1 partition functions. These determine what fraction of the water volume injected into the control volume at a specific time tin goes asymptotically to a specific output. Given the backward travel time distributions, the output concentration of a solute or tracer also depends on the input concentration. The paper clarifies the complicated relations described above by taking [Hydrology and Earth System Sciences, 20, 299–328] as an example from literature. Once the appropriate information is presented, it is shown how these HDSys can be solved simultaneously without duplicating calculations. Then, it is also shown that, under the hypothesis of uniform mixing of water ages within each reservoir, these systems can be solved exactly. 相似文献