Electromagnetic modeling of conformal wideband and multi-band patch antennas by bridging a solid-object modeler with MoM software

The advantages of antennas that can resemble the shape of the body to which they are attached are obvious. However, electromagnetic modeling of such unusually shaped antennas can be difficult. In this paper, the commercially available software SolidWorks(TM) is used for accurately drawing complex shapes in conjunction with the electromagnetic software FEKO(TM) to model the EM behavior of conformal antennas. The application of SolidWorks and custom-written software allows all the required information that forms the analyzed structure to be automatically inserted into FEKO, and gives the user complete control over the antenna being modeled. This approach is illustrated by a number of simulation examples of single, wideband, multi-band planar and curved patch antennas.

Patch and whole of surface mass-transfer rate measurements on a stepped rotating cylinder electrode

A recently developed whole of surface electroplating technique was used to obtain mass-transfer rates in the separated flow region of a stepped rotating cylinder electrode. These data are compared with previously reported mass-transfer rates obtained with a patch electrode. It was found that the two methods yield different results, where at lower Reynolds numbers, the mass-transfer rate enhancement was noticeably higher for the whole of the surface electrode than for the patch electrode. The location of the peak mass transfer behind the step, as measured with a patch electrode, was reported to be independent of the Reynolds number in previous studies, whereas the whole of the surface electrode shows a definite Reynolds number dependence. Large eddy simulation results for the recirculating region behind a step are used in this work to show that this difference in behavior is related to the existence of a much thinner fluid layer at the wall for which the velocity is a linear junction of distance from the wall. Consequently, the diffusion layer no longer lies well within a laminar sublayer. It is concluded that the patch electrode responds to the wall shear stress for smooth wall flow as well as for the disturbed flow region behind the step. When the whole of the surface is electro-active, the response is to mass transfer even when this is not a sole function of wall shear stress. The results demonstrate that the choice of the mass-transfer measurement technique in corrosion studies can have a significant effect on the results obtained from empirical data.

Patch dynamics in grazed subtropical native pastures in south-east Queensland

Patch formation is common in grazed grasslands but the mechanisms involved in the formation and maintenance of patches are not clear. To increase our knowledge on this subject we examined possible reasons for patch formation and the influence of management on changes between patch states in three experiments in native pasture communities in the Crows Nest district, south-east Queensland. In these communities, small-scale patches (tall grassland (dominated by large and medium tussock grasses), short swards (dominated by short tussock grasses and sedges), and lawns (dominated by stoloniferous and/or rhizomatous grasses)) are readily apparent. We hypothesized that the formation of short sward and lawn patches in areas of tall grassland was due to combinations of grazing and soil fertility effects. This was tested in Experiment 1 by applying a factorial combination of defoliation, nutrient application and transplants of short tussock and stoloniferous species to a uniform area of tall grassland. Total species density declined during the experiment, was lower with high nutrient applications, but was not affected by defoliation. There were significant changes in abundance of species that provided support for our hypotheses. With light defoliation and low nutrients, the tall grassland remained dominated by large tussock grasses and contained considerable amounts of forbs. With heavy defoliation, the pastures were dominated by medium tussock grasses and there were significant decreases in forbs and increases in sedges (mainly with low nutrients) and stoloniferous grasses (mainly with high nutrients). Total germinable seed densities and those of most species groups were significantly lower in the heavy defoliation than the light defoliation plots. Total soil seed numbers were not affected by nutrient application but there were fewer seeds of the erect forbs and more sedge seeds in plots with high nutrients. The use of resting from grazing and fire to manage transitions between patches was tested. In Experiment 2, changes in species density and abundance were measured for 5 years in the three patch types with and without grazing. Experiment 3 examined the effects of fire, grazing and resting on short sward patches over 4 years. In Experiment 2, total species density was lower in lawn than short sward or tall grassland patches, and there were more species of erect forbs than other plant groups in all patch types. The lawn patches were originally dominated by Cynodon spp. This dominance continued with grazing but in ungrazed patches the abundance of Cynodon spp. declined and that of forbs increased. In the short sward patches, dominance of short tussock grasses continued with grazing but in ungrazed plots their abundance declined while that of large tussock grasses increased. The tall grassland patches remained dominated by large and medium tussock species. In Experiment 3, fire had no effect on species abundance. On the grazed plots the short tussock grasses remained dominant but where the plots were rested from grazing the small tussock grasses declined and the large tussock grasses increased in abundance. The slow and relatively small changes in these experiments over 4 or 5 years showed how stable the composition of these pastures is, and that rapid changes between patch types are unlikely.

PBG-assisted shared-aperture dual-band aperture-coupled patch antenna for satellite communication

Design and development of a photonic bandgap (PBG)-assisted shared-aperture dual-band orthogonal aperture-fed rectangular microstrip patch antenna element, which is suitable for a portable very small aperture terminal (VSAT), are presented in this paper. The dual-band dual-polarized antenna element achieves 21% input impedance bandwidth at the S- and C-bands. A comparison of the antenna with and without 2D PBG grids shows that the inclusion of PBG structures (PBGSs) improves the antenna performances. (c) 2005 Wiley Periodicals, Inc.

The role of CD4(+) and CD8(+) T cells on antibody production by murine Peyer's patch cells following mucosal presentation of Actinomyces viscosus

The aim of this study was to determine the role of CD4 and CD8 cells on specific antibody production by murine Peyer's patch (PP) cells after oral immunization with Actinomyces viscosus in mice. Female DBA/2 mice were orally immunized with three low doses of heat-killed A. viscosus. Sham-immunized mice served as a control group. Mice were depleted of CD4 or CD8 cells by intraperitoneal injection of anti-CD4 or anti-CD8 antibodies daily for 3 days before oral immunization. One week after the last oral immunization, PPs were removed and cell suspensions were cultured with A. viscosus. Specific antibody production in the culture supernatants was assessed by enzyme-linked immunosorbent assay. The results showed that oral immunization with A. viscosus induced a predominant specific immunoglobulin A (IgA) response by PP cells and, to a lesser extent, IgM antibodies. Depletion of CD4 but not CD8 cells suppressed the production of specific antibodies. These results suggest that oral immunization with low doses of A. viscosus may induce the production of specific antibodies by murine PP cells in a CD4-cell-dependent fashion.

A passive reflect array with dual-feed microstrip patch elements

The design, development, and testing of an X-band 137-element passive reflect away capable of incorporating active devices such as transistor amplifiers is presented. In order to avoid grating lobes in the radiation pattern, the interelement spacing is minimized using dual-feed aperture-coupled patch antenna elements. Far-field radiation pattern results are presented and compared with the predicted radiation patterns. (C) 1999 John Wiley & Sons, Inc.

A dual band 2.4/5.2GHz antenna including a radial line slot array and a patch

The design of an antenna that combines a radial line slot array and a circular patch to operate as a dual band (2.4/5.2 GHz) antenna at the access point of a WLAN is presented. The design has been accomplished using commercially available Ansoft HFSS and in-house developed software. The designed antenna shows good performance in terms of return losses, radiation pattern and circular polarization in the two, 2.4 and 5.2 GHz, frequency bands. Due to its good electrical performance and a relatively low profile and low developmental cost, it should be found attractive for use as an access point antenna for dual band operation.

3D protein structure matching by patch signatures

For determining functionality dependencies between two proteins, both represented as 3D structures, it is an essential condition that they have one or more matching structural regions called patches. As 3D structures for proteins are large, complex and constantly evolving, it is computationally expensive and very time-consuming to identify possible locations and sizes of patches for a given protein against a large protein database. In this paper, we address a vector space based representation for protein structures, where a patch is formed by the vectors within the region. Based on our previews work, a compact representation of the patch named patch signature is applied here. A similarity measure of two patches is then derived based on their signatures. To achieve fast patch matching in large protein databases, a match-and-expand strategy is proposed. Given a query patch, a set of small k-sized matching patches, called candidate patches, is generated in match stage. The candidate patches are further filtered by enlarging k in expand stage. Our extensive experimental results demonstrate encouraging performances with respect to this biologically critical but previously computationally prohibitive problem.