Experimental stylolites in quartz and modeled application to natural structures.

Experimental stylolites have been observed at stressed contacts between quartz grains loaded for a period of several months in presence of aqueous silica solution, at 350°C under 50 MPa of differential stress. Stereoscopic analysis of pairs of SEM images, processed in the same way as earth-surface elevation data gives the stylolites topography. Coupled with observations of closed interactions between dissolution pits and stylolitic peaks, these data illuminate the mechanism of stylolite formation. The complex geometry of stylolite surfaces is imposed by the interplay between the development of dissolution peaks in favored locations (fast dissolution pits) and the mechanical properties of the solid-fluid-solid interfaces. Simple mechanical modeling expresses the crucial competition that could rule the development of stylolites: (i) a stress related process (modeled as the stiffness of springs (N/m3) activates the heterogeneous dissolution rates of the solid interface that promotes the deflection. In parallel, (ii) the strength of the solid interface, modeled as the stiffness of a membrane (N/m) and equivalent to a surface tension) limits the deflection and is opposed to its development. The modeling produces stylolitic surfaces with characteristic geometries that vary from conical to columnar shaped stylolites when both the effect of dissolution-rate heterogeneity and the strength properties of the rock are included

Efficient sequence detection for multicarrier transmissions over doubly dispersive channels

Multicarrier modulation (MCM) over a doubly dispersive (DD) channel yields complicated inter-carrier interference (ICI) and intersymbol interference (ISI) responses. With appropriately designed MCM pulse shapes, however, ISI can be mostly suppressed, as can ICI outside a small subcarrier radius. In this case, the channel can be well described by a quasi-banded subcarrier coupling matrix. Several sequence detectors (SDs) have been proposed to leverage this quasi-banded structure, including linear, decision feedback (DF), and maximum likelihood (ML) schemes. Relative to linear and DF schemes, the ML schemes offer superior performance, but are significantly more complex, even when efficient Viterbi or sphere-detection algorithms are used. In this paper, we propose a new SD algorithm for the quasi-banded application with a frame error rate (FER) that is nearly indistinguishable from ML and an average complexity that is on par with DF SD. 1 1