Search

The Dutch peatlands are a notoriously difficult region to monitor using InSAR. Low temporal coherence and signal-to-clutter levels necessitate the extraction of collective behaviour by the suppression of noise and clutter. Conventional techniques used to accomplish this include multilooking and phase-linking. The t-distributed Stochastic Neighbour Embedding (t-SNE) algorithm is a dimensionality reduction technique that aids in the analysis of large datasets. In this paper, we present an initial investigation into the suitability of the t-SNE algorithm to take the idea of extracting collective behaviour further. Similarly-behaved patches of land are automatically grouped together by the algorithm which aids in the specification of a functional model for that group. Our initial results show that the algorithm is able to successfully identify and group together areas in a scene which display similar behaviour over time. We also find that groups which display the same behaviour may also contain the same kinds of processing errors (for example unwrapping errors or cycle slips) and that these can also be automatically detected by the algorithm. We present this result as the first building block in an approach to smart InSAR data analysis which can learn from the data it is processing.

Noise correlation matrices and noise parameters are useful for low-noise amplifier designers seeking to achieve the best noise performance out of their circuits. In some applications, such as radio astronomy, antennas and antenna arrays are part of receivers and, thus, modeling of the antenna noise is useful. Currently, antenna noise is modeled through antenna efficiency. A more accurate information on the highest-possible antenna efficiency is obtained from its $S$ -parameters or noise parameters. In this letter, we show how the two-port $S$ -parameters of an antenna can be determined by measuring its reflection coefficients inside two specifically sized Wheeler caps, in addition to a free-space measurement. We use the measurement to determine the noise correlation matrices and noise parameters of an antenna. The challenges of constructing appropriately sized Wheeler caps are discussed, and a new way of constructing a Wheeler cap is shown.

An optical communications system employing intradyne reception and offline digital signal processing is tested over a 10.45 km link through the atmosphere. 40 GBaud transmission using binary phase-shift keying in the C-band is demonstrated and compared with laboratory measurements. Simultaneous photodetector measurements show that the turbulence in the atmospheric channel is representative for relevant and worst-case conditions in the geostationary satellite uplink scenario.

The noise correlation matrix and noise parameters are parameters of interest for antennas, and antenna arrays, particularly in the radio-astronomy context. For a passive network, such as an antenna, 2-port scattering parameters can be used to establish a noise correlation matrix and consequently the antenna noise parameters. In this paper we show how the 2-port scattering parameters of an antenna can be completely determined by measuring its reflection coefficient inside two specifically sized Wheeler caps, in addition to a free space measurement. We use the measurement to determine the noise correlation matrices and noise parameters of an antenna.

(1999). Informal carers of aphasic stroke patients: stresses and interventions. Aphasiology: Vol. 13, No. 12, pp. 889-900.

Background: Communication difficulties due to aphasia following stroke are particularly stressful to caregivers. Objective: To examine the impact of a psychoeducation programme on caregivers’ burden and stress and communication between the caregiver and aphasic stroke patient. Design: Randomized wait-list controlled trial with immediate or three-month delayed treatment. Setting: Three public hospital rehabilitation services in Sydney, Australia. Subjects: Thirty-nine caregivers of aphasic stroke patients, up to 12 months post stroke: 19 given immediate treatment and 20 in a delayed treatment control group. Interventions: Four-session weekly caregiver programme that included elements of education, support and communication skills conducted by a speech pathologist, social worker and clinical psychologist. Main measures: The General Health Questionnaire (GHQ) was used to measure caregiver stress, the Relatives’ Stress Scale was used to measure caregiver burden and a communication questionnaire was designed specifically for this project. Results: Thirty-one caregivers completed the study. Caregivers in the immediate treatment group had significant reductions in GHQ measured stress (GHQ mean (SD) at baseline= 6.26 (5.67), GHQ post treatment 3.21 (SD 4.20), P = 0.006). There was no improvement in wait-listed caregivers. Improvement was not maintained at three-month follow-up. There were no significant effects of the programme on communication skills or on caregiver burden. Conclusions: Stroke caregiver support, education and training programmes have short-term effects on caregiver stress levels but are likely to require ongoing involvement to maintain their effect.