Slab

About: Slab is a research topic. Over the lifetime, 31617 publications have been published within this topic receiving 318693 citations.

Flat-panel camera

Abstract: A flat-panel camera comprises a tapered transparent slab 1, a prismatic sheet 3 for introducing light into one face of the slab at near the critical angle so that it is reflected along the slab towards the thick end, and a miniature camera 2 receiving light emerging from the thick end of the slab at an angle depending on where the light entered the slab. An image processor 7 eliminates distortion in the image such as gaps caused by the light missing the camera.

Guided modes with imaginary transverse wave number in a slab waveguide with negative permittivity and permeability

Abstract: The guidance conditions of modes with both real and imaginary transverse wave numbers inside a dielectric slab with negative permittivity and permeability are solved. We show that for real transverse wave numbers, cutoffs exist for all modes, unlike in conventional media where the first even mode is always propagating. In addition, we also show that guided modes exist for imaginary transverse wave numbers, with the power concentrated at the interfaces instead of having maxima inside the slab. A graphical method of determining the imaginary transverse wave numbers of the guided modes is introduced which clearly identifies the different conditions of propagation depending on the properties of the slab. In particular, propagation of guided waves inside less dense negative media is shown to be possible.

Mantle structure beneath Indonesia inferred from high-resolution tomographic imaging

Abstract: We investigated mantle structure beneath the Indonesian region by means of tomographic inversions of traveltime residuals of direct P and the surface-reflected depth phases pP and pwP. The hypocentres and phase data used in the inversions were derived from the reprocessing of data reported to international data centres, which include data from the Australian SKIPPY project. We used more than 6.0 × 10⁶ data from more than 50 000 globally distributed earthquakes recorded at a subset of nearly 3000 seismological stations worldwide. The use of depth phases improved the sampling of the upper-mantle structure, in particular beneath the back-arc regions. The mapping of distant aspherical mantle structure into the study region was minimized by combining a high-resolution regional with a low-resolution global inversion. The inversion was linearized around the ak135 reference velocity model, and a combination of minimum norm and gradient damping was applied to constrain the solution. Inversion of different subsets of the data and test inversions of synthetic data indicate that resolution is sufficient to substantiate the conclusions pertinent to the complex large-scale structure of the subducted slab beneath the Indonesian archipelago. The tomographic images confirm previous evidence for regional slab penetration into the upper part of the lower mantle but suggest a more complex trajectory of mantle flow beneath Indonesia. The implied lateral variation in the shape of the upper-mantle slab is generally in good agreement with inferences from seismicity. The data reveal a seismic anomaly beneath the Sunda arc, which is detected to at least 1500 km in depth and forms the eastern end of a deep anomaly associated with the past subduction of lithosphere of the Mesozoic Tethys ocean. Below Java the lithospheric slab is probably continuous from the Earth's surface to the lower mantle, but beneath Sumatra the deep slab seems to be detached from the seismogenic slab. The high-resolution images suggest that the subducted slab is deflected in the transition zone beneath the Banda arc and that the descending slabs form a spoon-shaped structure. North of the Banda Sea we detect the two opposing subducted slabs of the Molucca Sea plate; this is consistent with previous studies, but our images suggest that the westward subduction has a significantly steeper dip than the eastward subduction. Slab structure beneath the Banda and Molucca seas is explained in the context of the continent-arc collision between Australia and the southeast Indonesian Island arc, and the arc-arc collision between Sangihe and Halmahera. Inversion of traveltime residuals of direct S phases, a novelty for this region, largely confirms the inferences from the P-wave data, even though less detail is resolved.

Large negative Goos-Hänchen shift from a weakly absorbing dielectric slab.

Abstract: It is theoretically shown that the negative Goos–Hanchen shifts near resonance, Re[kzd]=m?, can be an order of magnitude larger than the wavelength for both TE- and TM-polarized beams reflected from a weakly absorbing dielectric slab if the absorption of the slab is sufficiently weak, which is different from the case for a lossless dielectric slab [Phys. Rev. Lett.91, 133903 (2003) ].