Seismic Tomography by Monte Carlo Sampling     

Wojciech Dȩbski 《Pure and Applied Geophysics》2010,167(1-2):131-152

The paper discusses the performance and robustness of the Bayesian (probabilistic) approach to seismic tomography enhanced by the numerical Monte Carlo sampling technique. The approach is compared with two other popular techniques, namely the damped least-squares (LSQR) method and the general optimization approach. The theoretical considerations are illustrated by an analysis of seismic data from the Rudna (Poland) copper mine. Contrary to the LSQR and optimization techniques the Bayesian approach allows for construction of not only the “best-fitting” model of the sought velocity distribution but also other estimators, for example the average model which is often expected to be a more robust estimator than the maximum likelihood solution. We demonstrate that using the Markov Chain Monte Carlo sampling technique within the Bayesian approach opens up the possibility of analyzing tomography imaging uncertainties with minimal additional computational effort compared to the robust optimization approach. On the basis of the considered example it is concluded that the Monte Carlo based Bayesian approach offers new possibilities of robust and reliable tomography imaging.  相似文献   

A Model to Predict Granular Activated Carbon Backwash Curves     

Wojciech Dabrowski  Marta Spaczyńska  R. Ian Mackie 《洁净——土壤、空气、水》2008,36(1):103-110

A mathematical model that produces curves for predicting the expansion of granular activated carbon (GAC) filter beds has been developed and applied to several widely used commercial GAC products. Initially, the hydraulic load required to produce a given bed expansion was assumed to be inversely proportional to the viscosity. This assumption was then modified by assuming a power law for the dependence on viscosity. The errors were sufficiently small to allow practical application of the formulae presented in this paper. The potential for application of the method was tested and is illustrated by an example.  相似文献   

Advantages and limitations of an α-plasticity model for sand     

Sun  Yifei  Sumelka  Wojciech  Gao  Yufeng 《Acta Geotechnica》2020,15(6):1423-1437

Acta Geotechnica - The stress–strain response of sand was observed to depend on its material state, i.e., pressure and density. Successful modelling of such state-dependent response of sand...  相似文献   

The glacial landsystem of a tropical glacier: Charquini Sur,Bolivian Andes          下载免费PDF全文

Jakub Małecki  Harold Lovell  Wojciech Ewertowski  Łukasz Górski  Tomasz Kurczaba  Beata Latos  Michał Miara  Dorota Piniarska  Jacek Płocieniczak  Tomasz Sowada  Marcin Spiralski  Anna Warczachowska  Antoine Rabatel 《地球表面变化过程与地形》2018,43(12):2584-2602

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Reply to “Generation and propagation of transient nonlinear waves in a wave flume Wojciech Sulisz and Maciej Paprota 55:4 (2008) 277–287” [Coastal Engineering 56 (2009) 895–896]     

Wojciech Sulisz  Maciej Paprota 《Coastal Engineering》2010

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53Mn and 60Fe in iron meteorites—New data,model calculations     

Ingo Leya  Jean‐Christophe David  Thomas Faestermann  Michaela Froehlich  Niko Kivel  Dominik Koll  Gunther Korschinek  Sarah McIntyre  Silke Merchel  Stefan Pavetich  Georg Rugel  Dorothea Schumann  Thomas Smith  Anton Wallner 《Meteoritics & planetary science》2020,55(4):818-831

We measured specific activities of the long‐lived cosmogenic radionuclides ⁶⁰Fe in 28 iron meteorites and ⁵³Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for ⁵³Mn. This work doubles the number of existing individual ⁶⁰Fe data and quadruples the number of iron meteorites studied for ⁶⁰Fe. We also significantly extended the entire ⁵³Mn database for iron meteorites. The ⁵³Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of ⁶⁰Fe and ⁵³Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the ⁶⁰Fe activity concentrations are about a factor of 2 higher, for ⁵³Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data.  相似文献   

Generation and propagation of transient nonlinear waves in a wave flume     

Wojciech Sulisz  Maciej Paprota 《Coastal Engineering》2008

A semi-analytical nonlinear wavemaker model is derived to predict the generation and propagation of transient nonlinear waves in a wave flume. The solution is very efficient and is achieved by applying eigenfunction expansions and FFT. The model is applied to study the effect of the wavemaker and its motion on the generation and propagation of nonlinear waves. The results indicate that the linear wavemaker theory may be applied to predict only the generation of waves of low steepness for which the nonlinear terms in the kinematic wavemaker boundary condition and free-surface boundary conditions are of secondary importance. For waves of moderate steepness and steep waves these nonlinear terms have substantial effects on wave profile and wave spectrum just after the wavemaker. A wave spectrum corresponding to a sinusoidally moving wavemaker possesses a multi-peak form with substantial nonlinear components, which disturbs or may even exclude physical modeling in wave flumes. The analysis shows that the widely recognized weakly nonlinear wavemaker theory may only be applied to describe the generation and propagation of waves of low steepness. This is subject to further restrictions in shallow and deep waters because the kinematic wavemaker boundary condition as well as the nonlinear interaction of wave components and the evolution of wave energy spectrum is not properly described by weakly nonlinear wavemaker theory. Laboratory experiments were conducted in a wave flume to verify the nonlinear wavemaker model. The comparisons show a reasonable agreement between predicted and measured free-surface elevation and the corresponding amplitudes of Fourier series. A reasonable agreement between theoretical results and experimental data is observed even for fairly steep waves.  相似文献   

Distribution of compact object mergers around galaxies     

Tomasz Bulik  Krzysztof Belczy&#;ski  Wojciech Zbijewski 《Monthly notices of the Royal Astronomical Society》1999,309(3):629-635

Compact object mergers are one of the currently favoured models for the origin of gamma-ray bursts (GRBs). The discovery of optical afterglows and identification of the nearest, presumably host, galaxies allow the analysis of the distribution of burst sites with respect to these galaxies. Using a model of stellar binary evolution we synthesize a population of compact binary systems which merge within the Hubble time. We include the kicks in the supernovae explosions and calculate orbits of these binaries in galactic gravitational potentials. We present the resulting distribution of merger sites and discuss the results in the framework of the observed GRB afterglows.  相似文献   

Anisotropic Kepler and anisotropic two fixed centres problems     

Andrzej J. Maciejewski  Maria Przybylska  Wojciech Szumiński 《Celestial Mechanics and Dynamical Astronomy》2017,127(2):163-184

In this paper we show that the anisotropic Kepler problem is dynamically equivalent to a system of two point masses which move in perpendicular lines (or planes) and interact according to Newton’s law of universal gravitation. Moreover, we prove that generalised version of anisotropic Kepler problem as well as anisotropic two centres problem are non-integrable. This was achieved thanks to investigation of differential Galois groups of variational equations along certain particular solutions. Properties of these groups yield very strong necessary integrability conditions.  相似文献   

Non‐normality and induced plastic anisotropy under fractional plastic flow rule: a numerical study          下载免费PDF全文

Wojciech Sumelka  Marcin Nowak 《国际地质力学数值与分析法杂志》2016,40(5):651-675

In this paper, an implementation of fractional plastic flow rule in the framework of implicit and explicit procedures is under consideration. The fractional plastic flow rule is obtained from a generalisation of the classical plastic flow rule utilising fractional calculus. The key feature of this new concept is that in general, the non‐associative flow is obtained without necessity of additional potential assumption. If needed, the model can cover the anisotropy induced by plastic deformation. Illustrative examples showing the unusual flexibility of this model are also presented. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献