Fractal generation of surface area of porous media     

Hongbing Sun  Manfred Koch 《Stochastic Hydrology and Hydraulics》1998,12(2):83-96

Many natural porous geological rock formations, as well as engineered porous structures, have fractal properties, i.e., they are self-similar over several length scales. While there have been many experimental and theoretical studies on how to quantify a fractal porous medium and on how to determine its fractal dimension, the numerical generation of a fractal pore structure with predefined statistical and scaling properties is somewhat scarcer. In the present paper a new numerical method for generating a three-dimensional porous medium with any desired probability density function (PDF) and autocorrelation function (ACF) is presented. The well-known Turning Bands Method (TBM) is modified to generate three-dimensional synthetic isotropic and anisotropic porous media with a Gaussian PDF and exponential-decay ACF. Porous media with other PDF's and ACF's are constructed with a nonlinear, iterative PDF and ACF transformation, whereby the arbitrary PDF is converted to an equivalent Gaussian PDF which is then simulated with the classical TBM. Employing a new method for the estimation of the surface area for a given porosity, the fractal dimensions of the surface area of the synthetic porous media generated in this way are then measured by classical fractal perimeter/area relationships. Different 3D porous media are simulated by varying the porosity and the correlation structure of the random field. The performance of the simulations is evaluated by checking the ensemble statistics, the mean, variance and ACF of the simulated random field. For a porous medium with Gaussian PDF, an average fractal dimension of approximately 2.76 is obtained which is in the range of values of actually measured fractal dimensions of molecular surfaces. For a porous medium with a non-Gaussian quadratic PDF the calculated fractal dimension appears to be consistently higher and averages 2.82. The results also show that the fractal dimension is neither strongly dependent of the porosity nor of the degree of anisotropy assumed.  相似文献   

Ökochemische und toxikologische Daten für ausgewählte Halogenalkane und ihre Bewertung     

R. Koch  K. Strobel 《洁净——土壤、空气、水》1981,9(3):227-246

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A model for the evolution of photosynthetic oxygen     

Manfred Schidlowski 《Pure and Applied Geophysics》1978,116(2-3):234-238

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IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans: Vol. 18: Polychlorinated Biphenyls and Polybrominated Biphenyls. Lyon. International Agency for Research on Cancer, 1978, 140 S., 2 Abb., 11 Tab., 390 Lit.     

R. Koch 《洁净——土壤、空气、水》1979,7(6):626-627

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Geochronology of high-pressure rocks on Sifnos (Cyclades,Greece)     

Rainer Altherr  Manfred Schliestedt  Martin Okrusch  Eberhard Seidel  Hans Kreuzer  Wilhelm Harre  Heinz Lenz  Immo Wendt  Günther A. Wagner 《Contributions to Mineralogy and Petrology》1979,70(3):245-255

Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K-Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite+quartz+3T phengite, and omphacite+garnet +3T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote+2M ₁ phengite.K-Ar and Rb-Sr dates on phengites (predominantly 3T) of the best preserved high P/itTmetamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high P/T metamorphism. Phengites (2M ₁+3T) of less preserved high P/T assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb-Sr dates. The higher K-Ar dates are interpreted as being elevated by excess argon.K-Ar and Rb-Sr ages on 2M ₁ phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks.  相似文献   

Organohalogene als Karzinogene im Trinkwasser     

R. Koch  K. Strobel 《洁净——土壤、空气、水》1980,8(5):407-420

Ausgehend von bekannten Untersuchungsergebnissen über die Belastung von Trinkwässern mit Organohalogenen und den Ergebnissen tierexperimenteller Untersuchungen sowie epidemiologischen Studien wird versucht, den gegenwärtigen Kenntnisstand hinsichtlich eines Zusammenhanges zwischen Krebshäufigkeit und Belastung von Trinkwasser mit Organohalogenen darzustellen. Es ist nicht Ziel dieser Literaturstudie, eine Risikoeinschätzung für spezifische Karzinogene oder karzinogen suspekte Verbindungen zu geben, bzw. eine endgültige Bewertung der Substanzen unter den Aspekten der Umweltkarzinogenese vorzunehmen.  相似文献   

Component registration in two-dimensional model seismology     

Rolf Gutdeutsch  Manfred Koenig 《Studia Geophysica et Geodaetica》1966,10(3):314-322

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Eliminierung von p,p'-DDT,p,p'-DDE,p'p'-DDD und γ-HCH aus Wasser mittels Aluminiumsulfatflockung     

R. Koch 《洁净——土壤、空气、水》1976,4(4):315-325

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The influence of sea waves on the wind profile     

Lutz Krügermeyer  Manfred Grünewald  Michael Dunckel 《Boundary-Layer Meteorology》1978,14(3):403-414

From wind profile and wave measurements performed during the JONSWAP II experiment, relations between the dimensionless profile slope and the significant wave height are derived. It is shown that the wind profile is distorted by the waves especially in the vicinity of the water surface. The wave influence on the profile seems to be restricted to heights below about three wave heights. Above this level, the dimensionless profile slope is an approximately constant value corresponding to a drag coefficient of about 1.15 × 10^–3.  相似文献   

Nachweis von polychlorierten Biphenylen (PCB) im Oberflächenwasser     

R. Koch 《洁净——土壤、空气、水》1974,2(5):447-448

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