Observations of natural fluorescence with an underwater radiometer

Measurements of subsurface irradiance spectra in the ocean consistently indicate intensities of long-wavelength visible light (589 nm) greater than could be derived from the penetration of sunlight. This can be attributed to natural fluorescence and/or to spectral crosstalk due to light leakage through the blocking filters of each discrete detector. A comparison of observed profiles with modelled contributions from these two possible sources indicates that both factors are contributing. At 671 and 694 nm wavelength, the excess signal appears to be predominantly fluorescence while that at 589 nm is mostly crosstalk. Both effects appear to be important at 625 nm although the amount of excess light is small compared to the other wavelengths.The above observations and interpretations are consistent with the optical design of the instrument used and the shape of natural irradiance spectra. Fluorescence efficiencies derived from the irradiance measurements correlate well with measuredin situ fluorescence.     

Elastic lateral dynamic impedance functions for a rigid cylindrical shell type foundation

Elastic lateral dynamic impedance functions are defined as the ratio of the lateral dynamic force/moment to the corresponding lateral displacement/rotation at the top ending of a foundation at very small strains. Elastic lateral dynamic impedance functions have a defining influence on the natural frequencies of offshore wind turbines supported on cylindrical shell type foundations, such as suction caissons, bucket foundations, and monopiles. This paper considers the coupled horizontal and rocking vibration of a cylindrical shell type foundation embedded in a fully saturated poroelastic seabed in contact with a seawater half‐space. The formulation of the coupled seawater–shell–seabed vibration problem is simplified by treating the shell as a rigid one. The rigid shell vibration problem is approached by the integral equation method using ring‐load Green's functions for a layered seawater‐seabed half‐space. By considering the boundary conditions at the shell–soil interface, the shell vibration problem is reduced to Fredholm integral equations. Through an analysis of the corresponding Cauchy singular equations, the intrinsic singular characteristics of the problem are rendered explicit. With the singularities incorporated into the solution representation, an effective numerical method involving Gauss–Chebyshev method is developed for the governing Fredholm equations. Selected numerical results for the dynamic contact load distributions, displacements of the shell, and lateral dynamic impedance functions are examined for different shell length–radius ratio, poroelastic materials, and frequencies of excitation. Copyright © 2016 John Wiley & Sons, Ltd.     

Zur Schwefelisotopenzusammensetzung der Pb-Zn-Vererzung des Grazer Paläozoikums (Ostalpen)

Zusammenfassung Die Schwefelisotopenzusammensetzung von sulfidischen Erzmineralen und Baryten der unterdevonischen schichtgebundenen Bleiglanz-Zinkblende-Baryt-Erzvorkommen des Grazer Paläozoikums (Ostalpen, Österreich) wurde untersucht. Zur Analyse gelangten 64 Proben von etwa 15 Lokalitäten. Die Schwefelisotopenverteilung zeigt Ähnlichkeiten mit anderen an das Devon gebundenen schwerspatführenden Lagerstätten. Die Baryte ergaben ³⁴S-Werte von +23, 1 bis +27, 8, die dem Meerwassersulfat devonischen Alters entsprechen. Die untersuchten Galenite variieren von +2, 4 bis +6, 9 und die Sphalerite von +3, 3 bis +9, 1. Die Werte der Pyrite zeigen einen großen Streubereich (–27, 4 bis +37, 6). Eine massive buntmetallarme Pyritvererzung fällt durch sehr schweren Schwefel auf. Späte Mineralisationsphasen der Sulfide tendieren gleichfalls zur Anreicherung des schweren Schwefels.

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The sulphur isotope compositions of 64 samples of sulphide minerals and barites from the strata-bound Lower Devonian ore deposits of the Paleozoic Complex of Graz in the Eastern Alps (Austria) have been investigated. The ³⁴S-values of galenites and sphalerites show only small variations in the range of +2, 4 up to +6, 9 for PbS and +3, 3 up to +9, 1 for ZnS indicating abiogenic origin. Later remobilized sulphide minerals show a tendency to heavier sulphur. The deposition of pyrites is influenced partly by bacteriogenic processes (–27, 4 up to +37, 6). The enrichment of heavier sulphur characterizes massive pyrite mineralisations being poor on base metals. The sulphur isotope compositions of barites (+23, 1 up to 27, 8) correspond to Devonian sea water sulphate. An ore free barite characterized by increased strontium concentration shows heavier sulphur (+29, 6) than barites from ore beds.

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Derzeit Oberste Bergbehörde, Bundesministerium für Handel, Gewerbe und Industrie (Wien)     

Pore scale study of permeability and tortuosity for flow through particulate media using Lattice Boltzmann method

In this paper, Lattice Boltzmann method (LBM) has been used to study the effects of permeability and tortuosity on flow through saturated particulate media and identify the relationships between permeability and tortuosity with other parameters such as particles diameter, grain specific surface, and porosity. LBM is a simple kinematic model that can incorporate the essential physics of microscopic and mesoscopic processes involved in flow through granular soils. The obtained results indicate that the 2D LB model, due to its inherent theoretical advantages, is capable of demonstrating that the porosity and specific surface are the most influential parameters in determining the intrinsic permeability of granular media. The obtained results show that particles' size diameter has a two‐fold effect on the coefficient of permeability: one is through specific surface and the other is by tortuosity factor. Numerical study also reveals that tortuosity of granular soils decreases almost linearly with increasing the porosity. Copyright © 2010 John Wiley & Sons, Ltd.     

Weakly compressible SPH simulation of cnoidal waves with strong plunging breakers

Ocean Dynamics - Hydrodynamics of highly nonlinear cnoidal waves and their subsequent strong plunging breakers are among the least understood and most significant issues in coastal engineering. In...     

大地电磁测深与地震初至波走时交叉梯度反演

在地球物理勘探过程中,观测数据有限且存在误差,导致反演结果存在非唯一解。为了解决非唯一性问题,笔者研究了交叉梯度数学理论,实现了用交叉梯度约束2D 大地电磁和地震初至波走时的联合反演,并建立了2个模型。通过各自模型实验和不同模型间的对比,证明了交叉梯度联合反演比单独反演修复几何形态和物性参数的效果好,且交叉梯度与岩石物性无关;利用得到的交叉梯度图进一步证明了联合反演模型相似度高,也从交叉绘图中得到联合反演的物性关系更好的结论,反向证明了联合反演的正确性。     

PML solution of longitudinal wave propagation in heterogeneous media

This paper describes the development of a model for unbounded heterogeneous domains with radiation damping produced by an unphysical wave absorbing layer. The Perfectly Matched Layer (PML) approach is used along with a displacement-based finite element. The heterogeneous model is validated using the closed-form solution of a benchmark problem: a free rod with two-part modulus subjected to a specified time history. Both elastically supported and unsupported semi-infinite rods with different degrees of inhomogeneity and loading are considered. Numerical results illustrate the effects of inhomogeneity on the response and are compared with those for equivalent homogeneous domains. The effects of characteristic features of the inhomogeneous problem, presence of local maxima and cut-off frequency are determined. A degenerate case of a homogeneous semi-infinite rod on elastic foundations is produced by tending the magnitude of the foundation stiffness to zero. The response of the latter is compared with that of a free rod. The importance of proper selection of the PML parameters to highly accurate and efficient results is demonstrated by example problems.     

Experimental synthesis of seismic horizontal free-field motion of soil in finite-domain simulations with absorbing boundary

In this paper, a fundamental assessment of the method of physical wave-absorbing boundary and centrifuge modeling is presented in the context of experimental simulations of seismic free-field ground motion. Focusing on the characteristics of a sand stratum, a series of seismic tests on models of uniform density and a large width-to-depth ratio with Duxseal as the side boundary were performed using an in-box shake-table system. By means of the transfer function approach in the frequency domain, the complex three-dimensional nature of the dynamic response of the finite soil model with the boundary treatment is demonstrated in terms of its variable resonant frequency distribution at different g-levels. Apart from being helpful in quantifying the difficulty in interpreting the finite-domain response simulations using one-dimensional theories or homogenized representations, the measured data substantiates the need and usefulness of coupling the Duxseal boundary approach with a three-dimensional elastodynamic synthesis. With the aid of a corresponding boundary element implementation, the feasibility of identifying the soil's in-flight shear modulus variation, Poisson's ratio and horizontal-to-vertical earth pressure ratio from the centrifuge model's free-field measurements is also explored.     

Three‐dimensional time‐harmonic fundamental solutions for a fluid‐saturated poroelastic half‐space with partially permeable free surface

By virtue of a pair of scalar potentials for the displacement of the solid skeleton and the pore fluid pressure field of a saturated poroelastic medium, an alternative solution method to the Helmholtz decomposition is developed for the wave propagation problems in the framework of Biot's theory. As an application, a comprehensive solution for three‐dimensional response of an isotropic poroelastic half‐space with a partially permeable hydraulic free surface under an arbitrarily distributed time‐harmonic internal force field and fluid sources is developed. The Green's functions for the poroelastic fields, corresponding to point, ring, and disk loads, are reduced to semi‐infinite complex‐valued integrals that can be evaluated numerically by an appropriate quadrature scheme. Analytical and numerical comparisons are made with existing elastic and poroelastic solutions to illustrate the quality and features of the solution. Copyright © 2016 John Wiley & Sons, Ltd.