Image segmentation for improved consistency in image-interpretation of opium poppy

The image-interpretation of opium poppy crops from very high resolution satellite imagery forms part of the annual Afghanistan opium surveys conducted by the United Nations Office on Drugs and Crime and the United States Government. We tested the effect of generalization of field delineations on the final estimates of poppy cultivation using survey data from Helmand province in 2009 and an area frame sampling approach. The sample data was reinterpreted from pan-sharpened IKONOS scenes using two increasing levels of generalization consistent with observed practice. Samples were also generated from manual labelling of image segmentation and from a digital object classification. Generalization was found to bias the cultivation estimate between 6.6% and 13.9%, which is greater than the sample error for the highest level. Object classification of image-segmented samples increased the cultivation estimate by 30.2% because of systematic labelling error. Manual labelling of image-segmented samples gave a similar estimate to the original interpretation. The research demonstrates that small changes in poppy interpretation can result in systematic differences in final estimates that are not included within confidence intervals. Segmented parcels were similar to manually digitized fields and could provide increased consistency in field delineation at a reduced cost. The results are significant for Afghanistan’s opium monitoring programmes and other surveys where sample data are collected by remote sensing.     

Nearest neighbour analysis applied to synthetic aperture radar images for the description of urban land cover and land use

This article presents an analysis method for the creation of an image variable that represents built-up land cover and land use within the urban fabric. The method is inspired by the nearest neighbour analysis and the data are from the synthetic aperture radar systems COSMO-SkyMed (CSK) and Radarsat-2 (RS2). Point features were identified from the extreme high backscattering values for each image and the spatial pattern extracted to represent the proportion of built-up land cover as clustered, random, or dispersed. The coefficient of association between the continuous nearest neighbour ratio image and the land-cover percentage cover in four classes are ?0.9 and ?0.8 with the CSK and the RS2 images, respectively. Considering a two-class land-cover scheme, the coefficient of association between variables approaches ?0.9 for both images. Clustered features highlight individual buildings that are mixed in various neighbouring land-cover and land-use types. Residential land use is particularly well outlined using the CSK image, while large institutional, commercial, and light industry buildings are enhanced through the RS2 cross-polarization nearest neighbour ratio images.     

Oxidation Behaviour of NiCrAl and NiCoCrAl Bond Coatings Under Industrial Gas Turbine Conditions

Model bond coatings were deposited with a wide range of compositions and their oxidation behaviour investigated at 900 °C. These Ni–Co–Cr–Al coatings were deposited using magnetron sputtering (a physical vapour deposition technique) onto 10 mm diameter sapphire substrates. A range of compositions was generated by co-sputtering from a combination of two or three sources: Ni–10 wt% Cr, Ni–20Cr, Ni–50Cr, Ni–20Co–40Cr and/or Ni–40Co–20Cr combined with pure Al. The coatings were oxidised at 900 °C and the scales formed characterised. These data have been summarised into oxide predominance diagrams to show the relationships between coating compositions and the formation of protective Cr₂O₃ or Al₂O₃ scales, or the formation of other, less protective oxides (or mixed oxides). Both coating composition and exposure temperature (by comparison with earlier published research) were found to influence the oxide scale growth rate and oxide type, and thus the resulting degree of protection.     

To use or not to use: Clinicians' perceptions of telemental health.

Equal access to mental health services is necessary for healthy individuals and communities. However, due to geographical distances and other barriers, some clients cannot easily access mental health professionals. Technologies such as videoconferencing for clinical purposes (i.e., telemental health) may help to bridge these gaps to connect clients and clinicians at geographically diverse locations. However, despite its potential utility, telemental health has not been widely adopted in Canada. This study is an exploratory investigation into mental health professionals' attitudes toward telemental health, factors that affect the frequency with which they use this technology, and their perceptions of individual characteristics that make clients more or less suitable candidates for telemental health. This study has a particular focus on remote and rural and Operational Stress Injury (OSI) contexts. One hundred sixty mental health workers across Canada participated in an online survey, and 25 mental health workers from Operational Stress Injury clinics across Canada participated in in-person interviews. The data were examined using qualitative and quantitative analysis methods. Findings suggest that mental health workers have overall positive attitudes toward the use of telemental health—particularly for clients in remote and rural locations. Additionally, receiving training in telemental health, being in the mental health field for longer, and perceiving the technology as easy to use are associated with more frequent use of telemental health. Finally, clinicians reported specific client characteristics that they perceive to make some clients unsuitable candidates for telemental health. Implications of these findings and directions for future research are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A meta-analytic investigation of the structure of posttraumatic stress disorder symptoms.

Converging lines of evidence have called into question the validity of conceptualizations of posttraumatic stress disorder (PTSD) based on the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000) and suggested alternative structural models of PTSD symptomatology. We conducted a meta-analysis of 40 PTSD studies (N = 14,827 participants across studies) that used a DSM-based measure to assess PTSD severity. We aggregated correlation matrices across studies and then applied confirmatory factor analysis to the aggregated matrices to test the fit of competing models of PTSD symptomatology that have gained support in the literature. Results indicated that both prominent 4-factor models of PTSD symptomatology yielded good model fit across subsamples of studies; however, the model comprising Intrusions, Avoidance, Hyperarousal, and Dysphoria factors appeared to fit better across studies. Results also indicated that the best fitting models were not moderated by measure or sample type. Results are discussed in the context of structural models of PTSD and implications for the diagnostic nosology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of substrate curvature on residual stresses and failure modes of an air plasma sprayed thermal barrier coating system

A set of aerofoil shaped air plasma sprayed thermal barrier coated (APS-TBC) specimens were adopted in this paper to investigate the stress distributions in the ceramic top coat (TC) and the thermally grown oxide (TGO), the mechanism of local crack generation and propagation at the TC/BC (bond coat) interface. The failure mode of the TBC system, the distribution of asperities at TC/BC interface, thickness of the TC and BC, and the TC microstructure were found to be influenced by substrate curvature. Residual stress was therefore measured across the thickness of the TC, along the undulating TGO and mapped at locations of asperities where failure tended to occur to interpret the initiation of local failure. The role of the TGO was investigated via its chemical bonding with the TC and the decohesion occurring at the TGO/BC interface. The crack propagation at the interface has been discussed with respect to the macro-failure of the TBC system.