Factors affecting patch occupancy by the white-browed treecreeper Climacteris Affinis in an agricultural landscape in north-west Victoria, Australia

The survival of habitat-dependent fauna within agricultural mosaics depends on their ability to occupy remnant habitat patches and move through the modified landscape. In north-west Victoria, Australia, less than 10% of the pre-European extent of Selah Casuarina pauper woodland remains intact due to agricultural development. The White-browed Treecreeper Climacteris affinis, is a small, insectivorous passerine that, in this region, preferentially inhabits Selah woodland. To assess the ability of C. affinis to persist in an agricultural landscape, 30 woodland sites in the Millewa landscape (34°30'S, 141°30'E) were surveyed, and patterns of patch occupancy used to examine the influence of spatial characteristics, landscape context and grazing by stock on the suitability of remnants as C. affinis habitat. Sites occupied by C. affinis were larger and less likely to be grazed by stock than vacant patches. The area-dependency of patch occupancy represents a step-threshold: C. affinis were not detected in remnants with less than 18.5 ha of Selah woodland but above this threshold, density was not correlated with patch area. Measures of patch isolation, the existence of linking linear "corridors" and tree density were not reliable indicators of patch occupancy. The presence of the species in remnants entirely surrounded by agricultural land suggests they are capable of crossing up to 450 m of cultivated land to prospect for habitat. The extensive network of linear vegetation and the numerous small remnants and scattered trees appear to facilitate movements of C. affinis in this landscape. Increasing the size of existing remnants, creating new habitat to expand the area of occupancy and maintaining landscape connectivity are priorities for the long-term management of this threatened species.

Precoder design for multi-antenna systems with temporally and spatially correlated fading channels

This paper addresses the problem of the design of a precoder for multiple transmit antenna communication systems with spatially and temporally correlated fading channels. Using the theories of matrix differential calculus, the paper derives a precoder for unitary space-time codes that can exploit the spatio-temporal correlation in the time-varying fading channels. The design criterion is based on minimizing the mean square error of the channel estimates. Computer simulation results show that a significant performance gain can be achieved by using the designed precoder.

Differential encoding technique for multi-antenna systems with correlated Rayleigh fading channels

Differential space-time modulation (DSTM) techniques developed for multi-antenna systems allow the receiver to detect the transmitted signal without the knowledge of the fading channels. It can be viewed as an extension of differential phase-shift keying (DPSK) in single antenna systems. In this paper, we derived the pairwise error probability upper bound of differential space-time coded systems with spatially correlated Rayleigh fading channels. Based on the performance analysis, we develop a novel DSTM scheme which can exploit the spatial correlation in the fading channels. It is found that by carefully designing the initial transmitted signal matrix, the performance of the differential space-time coded systems can be significantly improved.

Retrodicting patch use by foraging swans in a heterogeneous environment using a set of functional responses

Effective conservation of important bird areas requires insight in the number of birds an area can support, and how this carrying capacity changes with habitat modifications. When food depletion is the dominant mechanism of competition, it should in principle be possible to calculate the total time foragers can spend per patch from their functional response (intake rate as a function of food density). However, in the field there are likely to be factors modulating the functional response. In this study previously published results of experiments on captive Bewick's swans were used to obtain functional responses of swans digging for tubers of Fennel pondweed on different foraging substrates: sandy and clayey sediment, and in shallow and deep water. In a field study, four 250×250 m sections belonging to different types (sandy–shallow, clayey–shallow, sandy–deep and clayey–deep) were delineated. Here tubers were sampled with sediment corers in three years, both before and after swan exploitation in autumn, and swans were observed and mapped from a hide in two of these years. Giving-up tuber biomass densities varied among sections. Substitution of these giving-up densities in the derived patch-type-specific functional responses yielded the quitting net energy intake rates in the four sections. As expected from the marginal value theorem, the quitting net energy intake rates did not vary among sections. Moreover, the observed foraging pressure (total foraging time per area) per patch type was in quantitative agreement with the integrated functional responses. These results suggest that in spatially heterogeneous environments, patch exploitation by foragers can be predicted from their functional responses after accounting for foraging substrate.

Antenna selection and channel estimation for hybrid relay systems

The research addressed performance issues for wireless signal transmission and has shown that performance improves with the help of relays due to increased diversity. Further, the areas of antenna selection and channel estimation and modelling has been investigated for improved cost and complexity and has shown to further enhance the performance of the wireless relay systems.

Seagrass patch size affects fish responses to edges

1. Patch area and proximity of patch edge can influence ecological processes across patchy landscapes and may interact with each other. Different patch sizes have different amounts of core habitat, potentially affecting animal abundances at the edge and middle of patches. In this study, we tested if edge effects varied with patch size.

2. Fish were sampled in 10 various-sized seagrass patches (114–5934 m²) using a small (0·5 m²) push net in three positions within each patch: the seagrass edge, 2 m into a patch and in the middle of a patch.

3. The two most common species showed an interaction between patch size and the edge–interior difference in abundance. In the smallest patches, pipefish (Stigmatopora nigra) were at similar densities at the edge and interior, but with increasing patch size, the density at the edge habitat increased. For gobies (Nesogobius maccullochi), the pattern was exactly the opposite.

4. This is the first example from a marine system of how patch size can influence the magnitude and pattern of edge effects.

5. Both patch area and edge effects need to be considered in the development of conservation and management strategies for seagrass habitats.

Adaptive patch size determination for patch-based image completion

Patch-based image completion proceeds by iteratively filling the target (unknown) region by the best matching patches in the source image. In most existing such algorithms, the size of the patches is either fixed and specified by a default number or simply chosen to be inversely proportional to the spatial frequency. However, it is noted that the patch size affects how well the filled patch captures the local characteristics of the source image and thus the final completion accuracy. Thus in this paper we propose a new method to compute appropriate patch sizes for image completion to improve its performance. In particular, we formulate the patch size determination as an optimization problem that minimizes an objective function involving image gradients and distinct and homogenous features. Experimental results show that our method can provide a significant enhancement to patch-based image completion algorithms.

Compact stacked planar inverted-F antenna for passive deep brain stimulation implants

A compact meandered three-layer stacked circular planar inverted-F antenna is designed and simulated at the UHF band (902.75 – 927.25 MHz) for passive deep brain stimulation implants. The UHF band is used because it offers small antenna size, and high data rate. The top and middle radiating layers are meandered, and low cost substrate and superstrate materials are used to limit the radius and height of the antenna to 5 mm and 1.64 mm, respectively. A dielectric substrate of FR-4 of εr= 4.7 and δ= 0.018, and a biocompatible superstrate of silicone of er= 3.7 and d= 0.003 with thickness of 0.2 mm are used in the design. The resonance frequency of the proposed antenna is 918 MHz with a bandwidth of 24 MHz at return loss of −10 dB in free space. The antenna parameter such as 3D gain pattern of the designed antenna within a skin-tissue model is evaluated by using the finite element method. The compactness, wide bandwidth, round shape, and stable characteristics in skin make this antenna suitable for DBS. The feasibility of the wireless power transmission to the implant in the human head is also examined.

Multi-layer implantable antenna for closed loop deep brain stimulation system

A multi-layer circular planar inverted-F antenna is designed and simulated at the industrial, scientific, and medical (ISM) band of 915 MHz for closed loop deep brain stimulation implant. The ISM band is considered due to the capabilities of small antenna size, high data rate, and long transmission range. In the proposed four-layer antenna, the top three radiating layers are meandered, and a high permittivity substrate and superstrate materials are used to limit the radius and the height of the antenna to 3.5 mm and 2.2 mm, respectively. The bottom layer works as a ground plate. The Roger RO3210 of εr = 10.2 and δ = 0.003 is used as a dielectric substrate and superstrate. The resonance frequency of the proposed antenna is 915 MHz with a bandwidth of 12 MHz at the return loss of -10 dB in free space. The stacked layered structure reduces the antenna size, and the circular shape makes it easily implantable into the human head. The antenna parameters (e.g. 3D gain pattern), SAR value, and electric field distribution within a six layers spherical head model are evaluated by using the finite element method (FEM). The feasibility of the wireless transmission of power, control and command signal to the implant in the human head is also examined. © 2012 IEEE.

Design and analysis of an antenna for wireless energy harvesting in head-mountable DBS device

This paper presents design and simulation of a circular meander dipole antenna at the industrial, scientific, and medical band of 915 MHz for energy scavenging in a passive head-mountable deep brain stimulation device. The interaction of the proposed antenna with a rat body is modeled and discussed. In the antenna, the radiating layer is meandered, and a FR-4 substrate is used to limit the radius and height of the antenna to 14 mm and 1.60 mm, respectively. The resonance frequency of the designed antenna is 915 MHz and the bandwidth of 15 MHz at a return loss of -10 dB in free space. To model the interaction of the antenna with a rat body, two aspects including functional and biological are considered. The functional aspect includes input impedance, resonance frequency, gain pattern, radiation efficiency of the antenna, and the biological aspect involves electric field distribution, and SAR value. A complete rat model is used in the finite difference time domain based EM simulation software XFdtd. The simulated results demonstrate that the specific absorption rate distributions occur within the skull in the rat model, and their values are higher than the standard regulated values for the antenna receiving power of 1W.

Design and analysis of an antenna for batteryless transcranial direct current stimulation devices

The purpose of this study is to design a low-cost planar Archimedean dipole antenna for batteryless transcranial direct current stimulation devices. The antenna parameters including resonance frequency, radiation efficiency, radiation pattern, and gain are simulated using finite difference time domain based electromagnetic simulation software XFdtd. The proposed antenna is simulated with low-cost FR4 PCB substrate of thickness of 1.6 mm. The antenna is designed with half wavelength of resonant frequency and fed with a matching line. The target frequency band is the industrial, scientific and medical (ISM) band of 915 MHz which is in the simulated band width of 31 MHz (903-934MHz). Moreover, since the bio-effect of specific absorption rate by radio frequency electromagnetic wave for power harvesting is an important concern, we try to find out the safety limit. Thus a quantitative analysis of distributions of electric field and power absorption in anatomical human head model by the far field radio frequency energy received by our designed antenna has been presented.