3,575 research outputs found

    Seasonal Response of Workers of the Allegheny Mound Ant, \u3ci\u3eFormica Exsectoides\u3c/i\u3e (Hymenoptera: Formicidae) to Artificial Honeydews of Varying Nutritional Content

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    Field colonies of Allegheny mound ants, Formica exsectoides, were tested at monthly intervals throughout the summer to assess their preference for artificial honeydews containing varying compositions of sugars and amino acids. In choice tests, foragers significantly preferred high sugar honeydews early in the season, but shifted in mid-season to a strong preference for high amino acid honeydews. Late-season foragers slightly preferred sugars. When offered in equal concentrations, the honeydew sugar, melezitose, was consistently less attractive to foragers than sucrose. However both sugars were readily fed upon, and appeared to attract ants in an additive fashion. No single amino acid was significantly preferred; however the combination of asparagine, glutamine and serine was highly attractive during the mid-season sampling period. The seasonal switch in forager preference between sugars and amino acids coincides with an increase in the amount of actively growing brood

    Participation in domestic energy retrofit programmes: key spatio-temporal drivers

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    The Canadian government created the EcoENEGY Retrofit for Homes programme (2007–12) to improve residential energy efficiency and reduce emissions produced through energy use. The uptake of retrofits varied both spatially and temporally. This research examines spatio-temporal patterns of retrofit adoption to understand the drivers behind participation in the grant programme and assess how future grant-based programmes might improve the uptake of efficiency measures. Temporal analysis demonstrated continued growth of programme participation over its original period of availability, and this accelerated once the programme was extended for an additional year after its original closure date. However, some spatial correlations weakened, which may be attributable to changes in programme design during the extension period. Seasonal variation was also observed, with spikes in retrofit activity occurring in winter. A regression analysis for conversion rates in Ontario and British Columbia displayed significant positive correlations for high shelter costs (>30% of household income) and households occupied by usual residents (regular occupants). Population density, median property value (only in Ontario) and units that were recently occupied demonstrated negative correlations. Spatial variation at both the city and neighbourhood levels suggests a greater degree of programme customisation is required to ensure uniform building stock improvement

    Valuation of aircraft noise by time of day: a comparison of two approaches

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    This paper reports an innovative application of stated preference techniques to derive values of aircraft noise by time of day and day of week. Revealed preference techniques cannot provide such segmentations which would clearly be of use in policy development especially relating to airport operations. Given the lack of research on this issue the work reported here is highly experimental. Two stated preference experiments were designed. The first focussed on a single time period whilst the second asked respondents to trade between time periods. Both approaches yielded results that are plausible and mutually consistent in terms of relative values by time period. We conclude that stated preference techniques are particularly useful in this context where the use of aggregated values may lead to non-optimal policy decisions

    The Conditional Lucas & Kanade Algorithm

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    The Lucas & Kanade (LK) algorithm is the method of choice for efficient dense image and object alignment. The approach is efficient as it attempts to model the connection between appearance and geometric displacement through a linear relationship that assumes independence across pixel coordinates. A drawback of the approach, however, is its generative nature. Specifically, its performance is tightly coupled with how well the linear model can synthesize appearance from geometric displacement, even though the alignment task itself is associated with the inverse problem. In this paper, we present a new approach, referred to as the Conditional LK algorithm, which: (i) directly learns linear models that predict geometric displacement as a function of appearance, and (ii) employs a novel strategy for ensuring that the generative pixel independence assumption can still be taken advantage of. We demonstrate that our approach exhibits superior performance to classical generative forms of the LK algorithm. Furthermore, we demonstrate its comparable performance to state-of-the-art methods such as the Supervised Descent Method with substantially less training examples, as well as the unique ability to "swap" geometric warp functions without having to retrain from scratch. Finally, from a theoretical perspective, our approach hints at possible redundancies that exist in current state-of-the-art methods for alignment that could be leveraged in vision systems of the future.Comment: 17 pages, 11 figure
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