Radiation Pattern

... Instead, the undulations indicate an influence of the scattered SPs on the overall excitation of and radiation from the plasmon field. ... Electronic address: DP@ZURICH.IBM.COM [1] H. Raether, in Surface Plasmons on Smooth and Rough Surfaces and on Gratings, Springer ...

—In this paper, novel bandpass filter and tunable bandpass filter are designed based on half-mode substrate integrated waveguide (HMSIW) embedded with complementary resonators. Various passband characteristics are observed, and lumped equivalent circuit analysis models are developed. The configuration of the proposed bandpass filter is an open structure, and it is easy to load the active devices and build the bias/control networks on the signal plane. The tunable bandpass filter is presented based on the proposed novel bandpass filter loaded with semiconductor varactor diodes, and it has good spurious suppression characteristics and excellent out of band rejection. The prototype with overall size of 15.9 mm × 30.2 mm × 0.5 mm was designed and fabricated so as to validate the new structure. The measured central frequency is 1.538 GHz and 1.718 GHz, and the insertion loss is 5.1 dB and 3.3 dB, at 0 V and 30 V, respectively.

The effect of stress anisotropy on the brittle failure of granite is investigated under uniaxial compression. Non-standard asymmetric compression tests are performed on cores of Aue granite (diameter 52 mm, length 100 mm), in which 20 per cent of the core top surface remains unloaded. The edge of the asymmetric steel loading plate acts as a stress concentrator, from where a shear rupture is initiated. The propagation of the fracture-related process zone from top to bottom of the core is mapped by microcrack-induced acoustic emissions. Compared to standard uniaxial tests with symmetric loading, in the asymmetric tests both a greater quantity and more localized distributions of emission event hypocentres are observed. The maximum event density doubles for asymmetric (20 events per 10−6 m3) compared to symmetric tests. The cluster correlation coefficient, a measure of strain localization in the faulting process, reaches 0.15 for symmetric and 0.30 for asymmetric tests. The clustering of events, however, is found post-failure only. Three different amplitudes are used to determine b-values discussed as a possible failure precursor. Focal amplitudes determined at a 10 mm source distance and maximum amplitudes measured at eight piezoceramic sensors lead to b-values that drop before rock failure. First-pulse amplitudes automatically picked from emission wavelets show no anomaly. First-motion polarity statistics of amplitudes indicate that a shear-crack-type radiation pattern is responsible for 70 per cent of the failure of granite, irrespective of stress boundary conditions. For type-S events with an equal percentage of dilatational and compressional first motions, focal mechanisms are determined by fitting measured first-pulse amplitudes to an assumed double-couple radiation pattern. While hypocentres of large type-S events align parallel to the later fracture plane, their fault plane solutions show no coherent pattern. Spatial views of fracture planes reconstructed from X-ray computed tomograms reveal local small-scale changes in fracture plane orientation. Nodal planes from average fault plane solutions of the microscopic acoustic emission events coincide with the overall orientation of the macroscopic fracture plane azimuth (strike angle) determined from thin sections and tomograms.

Microlens array (MLA) diffusers for light-emitting diode (LED) backlight systems have been developed. A high fill-factor photoresist mold for the MLA was fabricated using three-dimensional diffuser lithography, and the patterns were transferred to a nickel master mold for UV-curable polymer replication. The fabricated microlens had various paraboloidal profiles, and its aspect ratio was controlled from 1.0 to 2.1. The MLA diffuser showed a batwing radiation pattern with a radiation angle of 150 degrees. The fabricated MLA diffuser may greatly enhance the color-mixing characteristics of LED backlight systems and help reduce the number of LEDs required.

Isolated granitic rock outcrops or ‘inselbergs’ may provide a window into the molecular ecology and genetics of continental radiations under simplified conditions, in analogy to the use of oceanic islands in studies of species radiations. Patterns of variability and gene flow in inselberg species have never been thoroughly evaluated in comparison to related taxa with more continuous distribution ranges, or to other species in the same kingdom in general. We use nuclear microsatellites to study population differentiation and gene flow in two diploid, perennial plants adapted to high-altitude neotropical inselbergs, Alcantarea imperialis and Alcantarea geniculata (Bromeliaceae). Population differentiation is pronounced in both taxa, especially in A. imperialis. Gene flow in this species is considerably lower than expected from the literature on plants in general and Bromeliaceae in particular, and too low to prevent differentiation due to drift (Nem < 1), unless selection coefficients/effect sizes of favourable alleles are great enough to maintain species cohesion. Low gene flow in A. imperialis indicates that the ability of pollinating bats to promote gene exchange between inselbergs is smaller than previously assumed. Population subdivision in one inselberg population of A. imperialis appears to be associated with the presence of two colour morphs that differ in the coloration of rosettes and bracts. Our results indicate a high potential for inselbergs as venues for studies of the molecular ecology and genetics of continental radiations, such as the one that gave rise to the extraordinary diversity of adaptive strategies and phenotypes seen in Bromeliaceae.