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Markku Pirttijärvi Risto Pietilä Aimo Hattula Sven-Erik Hjelt 《Geophysical Prospecting》2002,50(5):425-440
This paper presents a computational method for the interpretation of electromagnetic (EM) profile data in the frequency domain using a thin plate model within a two-layer earth. The modelling method is based on an integral equation formulation, where the conductor is represented by a lattice structure composed of two-dimensional surface elements. Several approximations are used to simplify the theoretical basis and to decrease the computation time. The simple parametric model allows efficient use of optimization methods. We employ a linearized inversion scheme based on singular value decomposition and adaptive damping. The new forward computation method and the parameter optimization are combined in the computer program, emplates . The modelling examples demonstrate that the approximate method is capable of describing the characteristic behaviour of the EM response of a thin plate-like conductor in conductive surroundings. The efficacy of the inversion is demonstrated using both synthetic and field data. An optional depth compensation method is used to improve the interpreted values of the depth of burial. The results show that the method is cost effective and suitable for interactive interpretation of EM data. 相似文献
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David Hodgkinson Hakim Benabderrahmane Mark Elert Aimo Hautojärvi Jan-Olof Selroos Yasuharu Tanaka Masahiro Uchida 《Hydrogeology Journal》2009,17(5):1035-1049
An overview is presented of a 4-year study by the Äspö Task Force on Modelling of Groundwater Flow and Transport of Solutes, whose primary aim was to build a bridge between the approaches used for site characterisation (SC) and performance assessment (PA) associated with nuclear waste repositories. Eleven modelling teams representing six national radioactive waste organisations participated in eight modelling exercises whose objectives were: to assess simplifications used in PA models; to determine how, and to what extent, experimental tracer and flow experiments can constrain the range of parameters used in PA models; to support the design of SC programmes to assure that the results have optimal value for PA calculations; and to improve the understanding of site-specific flow and transport behaviour at different scales using SC models. The modelling tasks were concerned with flow and transport through single and multiple near-planar features on SC and PA timescales, including the diffusion of solutes into multiple immobile zones adjacent to fracture surfaces. In general, tracer tests provide only limited quantitative constraints on retention parameter values relevant to PA but nevertheless provide insight about the flow and transport processes, which is a key element of the bridge between SC and PA. 相似文献
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The stratigraphy of resin acids (pimaric, isopimaric, sandaracopimaric, dehydroabietic and abietic acids) and base neutral compounds (retene, tetrahydroretene, dehydroabietin and fichtelite) in sediments of a lake recovering after the mill closure from exposure to effluents from sulphite pulp mill was studied. The highest concentrations of these compounds were detected 1.5 km downstream from the effluent pipe in sediment depth of 7–11 cm. This sediment layer is approximately 30 yrs old. The highest concentration of resin acids was 1100 and of retene 3300 g/g d.w. The retene concentration observed is the highest reported in the literature so far. The results imply that high concentrations of retene may be common in sediments of Finnish lakes polluted by pulp mill effluents. 相似文献
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Sterols and their metabolites are recognized as hormonally active compounds in many earlier studies. Therefore, identification and quantification of selected phytosterols related to developments in pulping and wastewater treatment of pulp and paper industry were studied from sediment cores of two Finnish lakes. Indicating the period of maximal emissions, the highest total concentration of sterols, 1970 μg/g dry weight, was detected in the stratified sediment of central Lake Päijänne, dated to the mid-1970s (depth 12–15 cm). After notable changes in processes and effluent treatment, the amounts of sterols in effluents must have diminished, as shown by the sterol content in the sediment downstream from the mills. Therefore, the concentrations were about 10% of the historical maximum in the surface sediment (depth 0–3 cm) in both downstream sites investigated at Lake Päijänne. However, these concentrations were clearly over the natural background (10–50 μg/g) occurring in the subsamples of the pre-industrial phase (depth 36–44 cm) as well as in the reference site of southern Lake Saimaa, the second investigated lake. At a nearby site of a pulp and paper mill in southern Lake Saimaa, sterols were most abundant (1760 μg/g dry weight) in the sediment layer 0–5 cm despite the improved process control during last few decades. This study showed the abundance of ecotoxicologically harmful compounds in downstream sediment sites of pulp and paper industry. 相似文献
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Simultaneous linear and circular polarization observations of blazars 3C 66A,OJ 287 and Markarian 421 总被引：1，自引：0，他引：1
We present the first ever simultaneous optical linear and circular polarization observations of blazars. These polarizations have been measured simultaneously inUBVRI-bands in three blazars; 3C 66A, OJ 287 and Markarian 421. Measured linear polarization in 3C 66A was the largest ever observed, at PR = 33.1 ± 0.5 per cent. In 3C 66A we detected small circular polarization in the other bands, exceptU. In OJ 287 we detected variable circular polarization in theU-band. 相似文献
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An Archean age for Finnish rocks in the range 2500–3000 Ma has been determined north of the NW-striking Ladoga—Raahe shear belt. The Archean may be divided into two main units: the granitoid association and the greenstone-belt association. The complex is characterized by stockwork tectonics. The granitoid association forms the basement infrastructure and the greenston-belt association forms the suprastructure which is present in synforms between granitoid diapirs. The infrastructure has been subjected to ultrametamorphism, and the second and third generation palingenetic magmas so formed have intruded the suprastructure. The granitoid association contains widespread migmatized relicts of the greenstone-belt association, indicating that the latter originally covered much larger areas, but the granitoids are also thought to be partly transformed primitive ensialic crust on which rocks of the greenstone-belt association were deposited. The Archean rocks have been deformed in at least four subsequent phases, of which part developed in Proterozoic time. The youngest deformation is the overthrust of the granulite belt of Lapland towards SSW. NWSE striking transcurrent faults played a major role in Proterozoic time and affected cratonized Archean crust. On the whole the greenstone belts in eastern and northern Finland form a NNW-trending zone 750 km long. On a geochemical basis the volcanic rocks of the greenstone belts can be divided into two groups: tholeiites with a low potassium content and extremely low aluminium content and a calc-alkalic group with some alkalic affinities. 相似文献
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The aim of this study was to examine the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, given intraperitoneally) alone and together with bleached kraft pulpmill effluents (BKME) on fish biotransformation reactions and testosterone levels in mature male rainbow trout (Salmo gairdneri Richardson). The results show extremely high induction in liver and kidney monooxygenase (PSMO) activities in 3 weeks caused by TCDD alone or TCDD together with BKME. BKME alone did not cause significant effects. 7-Pentoxyresorufin O-dealkylase activity, previously shown to be an indicator of phenobarbital-type induction, was shown to be highly inducible by TCDD in fish. Plasma testosterone levels, although decreased in another subacute exposure to BKME, showed only slight changes due to TCDD and TCDD + BKME. 相似文献
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A simplifying concept of modelling of transport of dissolved species through a clay backfill from the disposal canister to a fissure in rock, or vice versa, is presented to describe the transport fairly well with a wide range of parameter values. The modelling is an improvement to the previously used simplifying expressions.
The new approach is very illustrative and conserves the volume of the clay section under consideration. Conservation of the volume gives the right time dependency in the case of a well mixed volume. The nonstationary phase of transport can thus be modelled using in principle the presented simplifying concept as a starting point.
Comparisons of stationary mass transport calculations with previous and present simplifying expressions to more accurate calculations are presented. 相似文献
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Aimo Kiviniemi 《Journal of Geodesy》1975,49(2):177-181
Summary Global variations in gravity caused by the general variation in the mass distribution of the Earth can be investigated by
measuring gravity differences around the Earth. When the gravity differences to be measured are small and special arrangements
are applied, the gravity differences can be measured with an accuracy of some microgals. Measurement of this kind needs effective
and extensive international cooperation. 相似文献
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