217 research outputs found

    Conflict in Russian Genitive Plural Assignment: a Solution Represented in DATR

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    Inflectional endings are assigned in languages by general principles, but these can come into conflict. We address the question of how such conflict is resolved. A particularly complex example is the Russian genitive plural, where we find that with soft-stem nouns there is a conflict between exponent assignment according to declension class and a default exponent assignment for soft-stem nouns. What is specially interesting is that the conflict here can be resolved by reference to subsystems over and above the paradigm, such as stress. We present an explicit account of the conflict and its mediation by basing our study on default inheritance. For this purpose we make use of the lexical knowledge representation language DATR. This allows us to demonstrate in the output provided that the correct forms are indeed predicted by our theory

    An analytical model of momentum availability for predicting large wind farm power

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    Turbine-wake and farm-atmosphere interactions influence wind farm power production. For large offshore farms, the farm-atmosphere interaction is usually the more significant effect. This study proposes an analytical model of the `momentum availability factor' to predict the impact of farm-atmosphere interactions. It models the effects of net advection, pressure gradient forcing and turbulent entrainment, using steady quasi-1D flow assumptions. Turbulent entrainment is modelled by assuming self-similar vertical shear stress profiles. We used the model with the `two-scale momentum theory' to predict the power of large finite-sized farms. The model compared well with existing results of large-eddy simulations (LES) of finite wind farms in conventionally neutral boundary layers. The model captured most of the effects of atmospheric boundary layer (ABL) height on farm performance by considering the undisturbed vertical shear stress profile of the ABL as an input. In particular, the model predicted the power of staggered wind farms with a typical error of 5% or less. The developed model provides a novel way of instantly predicting the power of large wind farms, including the farm blockage effects. A further simplification of the model to analytically predict the 'wind extractability factor' is also presented. This study provides a novel framework for modelling farm-atmosphere interactions. Future studies can use the framework to better model large wind farms.Comment: 22 pages, 12 figures, 4 table

    Nautilus pompilius Life History and Demographics at the Osprey Reef Seamount, Coral Sea, Australia

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    Nautiloids are the subject of speculation as to their threatened status arising from the impacts of targeted fishing for the ornamental shell market. Life history knowledge is essential to understand the susceptibility of this group to overfishing and to the instigation of management frameworks. This study provides a comprehensive insight into the life of Nautilus in the wild. At Osprey Reef from 1998–2008, trapping for Nautilus was conducted on 354 occasions, with 2460 individuals of one species, Nautilus pompilius, captured and 247 individuals recaptured. Baited remote underwater video systems (BRUVS) were deployed on 15 occasions and six remotely operated vehicle (ROV) dives from 100–800 m were conducted to record Nautilus presence and behavior. Maturity, sex and size data were recorded, while measurements of recaptured individuals allowed estimation of growth rates to maturity, and longevity beyond maturity. We found sexual dimorphism in size at maturity (males: 131.9±SD = 2.6 mm; females: 118.9±7.5 mm shell diameter) in a population dominated by mature individuals (58%). Mean growth rates of 15 immature recaptured animals were 0.061±0.023 mm day−1 resulting in an estimate of around 15.5 years to maturation. Recaptures of mature animals after five years provide evidence of a lifespan exceeding 20 years. Juvenile Nautilus pompilius feeding behavior was recorded for the first time within the same depth range (200–610 m) as adults. Our results provide strong evidence of a K-selected life history for Nautilus from a detailed study of a ‘closed’ wild population. In conjunction with population size and density estimates established for the Osprey Reef Nautilus, this work allows calculations for sustainable catch and provides mechanisms to extrapolate these findings to other extant nautiloid populations (Nautilus and Allonautilus spp.) throughout the Indo-Pacific

    Maïs à rendement élevé pour les paysans du Burundi

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    Version anglaise disponible dans la BibliothÚque numérique du CRDI: High maize yields offer hope for Burundi farmer

    Data‐driven modelling of turbine wake interactions and flow resistance in large wind farms

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    Turbine wake and local blockage effects are known to alter wind farm power production in two different ways: (1) by changing the wind speed locally in front of each turbine and (2) by changing the overall flow resistance in the farm and thus the so-called farm blockage effect. To better predict these effects with low computational costs, we develop data-driven emulators of the ‘local’ or ‘internal’ turbine thrust coefficient as a function of turbine layout. We train the model using a multi-fidelity Gaussian process (GP) regression with a combination of low (engineering wake model) and high-fidelity (large eddy simulations) simulations of farms with different layouts and wind directions. A large set of low-fidelity data speeds up the learning process and the high-fidelity data ensures a high accuracy. The trained multi-fidelity GP model is shown to give more accurate predictions of compared to a standard (single-fidelity) GP regression applied only to a limited set of high-fidelity data. We also use the multi-fidelity GP model of with the two-scale momentum theory (Nishino & Dunstan 2020, J. Fluid Mech. 894, A2) to demonstrate that the model can be used to give fast and accurate predictions of large wind farm performance under various mesoscale atmospheric conditions. This new approach could be beneficial for improving annual energy production (AEP) calculations and farm optimization in the future

    Use of unmanned aerial vehicles (UAVs) for mark-resight nesting population estimation of adult female green sea turtles at Raine Island

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    Nester abundance is a key measure of the performance of the world's largest green turtle rookery at Raine Island, Australia, and has been estimated by mark-resight counts since 1984. Nesters are first marked by painting their carapace with a longitudinal white stripe. Painted and unpainted turtles are then counted by a surface observer on a small boat in waters adjacent to the reef. Unmanned aerial vehicles (UAV) and underwater video may provide more cost-effective and less biased alternatives to this approach, but estimates must be comparable with historical estimates. Here we compare and evaluate the three methods. We found comparatively little variation in resighting probabilities between consecutive days of sampling or time of day, which supports an underlying assumption of the method (i.e. demographic closure during sampling). This lack of bias in the location availability for detection of painted versus unpainted turtles and further supported by a parallel satellite tracking study of 40 turtles at Raine Island. Our results demonstrated that surface observers consistently reported higher proportions of marked turtles than either the UAV or underwater video method. This in turn yielded higher population estimates with UAV or underwater video compared to the historical surface observer method, which suggested correction factors of 1.53 and 1.73 respectively. We attributed this to observer search error because a white marked turtle is easier to spot than the non-marked turtle. In contrast, the UAV and underwater video methods allowed subsequent frame-by-frame review, thus reducing observer search error. UAVs were the most efficient in terms of survey time, personnel commitment and weather tolerance compared to the other methods. However, underwater video may also be a useful alternative for in-water mark-resight surveys of turtles

    Data‐driven modelling of turbine wake interactions and flow resistance in large wind farms

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    Turbine wake and local blockage effects are known to alter wind farm power production in two different ways: (1) by changing the wind speed locally in front of each turbine and (2) by changing the overall flow resistance in the farm and thus the so-called farm blockage effect. To better predict these effects with low computational costs, we develop data-driven emulators of the ‘local’ or ‘internal’ turbine thrust coefficient C_{*}^{T} as a function of turbine layout. We train the model using a multi-fidelity Gaussian process (GP) regression with a combination of low (engineering wake model) and high-fidelity (large eddy simulations) simulations of farms with different layouts and wind directions. A large set of low-fidelity data speeds up the learning process and the high-fidelity data ensures a high accuracy. The trained multi-fidelity GP model is shown to give more accurate predictions of C_{*}^{T} compared to a standard (single-fidelity) GP regression applied only to a limited set of high-fidelity data. We also use the multi-fidelity GP model of C_{*}^{T} with the two-scale momentum theory (Nishino & Dunstan 2020, J. Fluid Mech. 894, A2) to demonstrate that the model can be used to give fast and accurate predictions of large wind farm performance under various mesoscale atmospheric conditions. This new approach could be beneficial for improving annual energy production (AEP) calculations and farm optimization in the future

    Monitoring and management of a landslide on the main motorway between Sydney and Wollongong, NSW Australia

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    The Mount Ousley Road section of the M1 Princes Motorway is one of the main transportation links between the cities of Sydney and Wollongong, New South Wales (NSW), on the east coast of Australia. The road was originally constructed during World War II as an alternative defense route and now supports approximately 50,000 vehicle movements per day. The road negotiates 4.4km of the Illawarra escarpment at grades up to 1:8. A section of the road traverses the largest landslide in the Wollongong Landslide Inventory, Site 141. The surface area of the landslide is 67,000m2, which includes a 350m section of Mount Ousley Road affecting all six lanes. The landslide is a deep seated, episodically active translational debris slide with a maximum depth of sliding of 20.5m. The landslide is managed by a continuous real-time monitoring system and is dewatered by nine 30m deep pumping wells to maintain lower ground water levels. The dewatering system was installed in 1988, but has been upgraded three times to enhance serviceability and most recently to provide a further 10 years of landslide management. This paper presents some analysis of data collected from the continuous real-time monitoring system established by the University of Wollongong Landslide Research Team, in partnership with NSW Government organizations including Roads and Maritime Services (RMS) and NSW Public Works and highlights the troubleshooting work associated. Periodic and continuous monitoring has been successful in identifying needs for the dewatering system upgrades, assessing thresholds for slope movement and evaluating the overall effectiveness of the remedial measures installed

    Effects of a sugar-sweetened beverage tax on prices and affordability of soft drinks in Chile : A time series analysis

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    Chile is one of several countries that recently implemented a fiscal policy to reduce soft drink (SD) intake and obesity. In 2014 the government increased the existing ad-valorem tax on high-sugar SD by 5% and decreased by 3% the tax on low-sugar SD, based on a 6.25gr/100 ml sugar threshold. This study aims to evaluate the tax modification passed-on to consumers through prices, and to calculate changes in affordability of SDs. We analysed nationally representative consumer price index data of 41 soft drinks within 6 beverage categories between 2009 and 2016. Price change post-tax implementation was estimated for different categories (carbonates, juices, concentrates, waters and energy-sport drinks), using time-series analyses. In addition, changes in affordability were evaluated by estimating the changes in prices relative to wages. The price of carbonates increased by 5.60% (CI 95% 3.18–8.03%) immediately after the tax was implemented. A sustained increase in the prices of concentrates was observed after the implementation. Unexpectedly, a smaller increase was also seen for the price of bottled water – a category that saw no tax change. There were no effects for juices and energy-sports drinks. There was a reduction in affordability for carbonates, concentrates and waters. Overall, the fiscal policy was effective in increasing prices and there are some signs of reduced affordability. Results varied substantially among categories directly affected by the tax policy. While for carbonates the price increase exceeded the tax change (‘over-shifting’), in other categories subject to a tax cut, a price reduction was expected but the opposite occurred. As the effect of the tax on prices differed between categories, the effects of the tax policy on consumption patterns are likely to be mixed. Our findings underline the need to better understand and anticipate price setting behaviour of firms in response to a tax

    Vertical Distribution and Migration Patterns of Nautilus pompilius

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    Vertical depth migrations into shallower waters at night by the chambered cephalopod Nautilus were first hypothesized early in the early 20th Century. Subsequent studies have supported the hypothesis that Nautilus spend daytime hours at depth and only ascend to around 200 m at night. Here we challenge this idea of a universal Nautilus behavior. Ultrasonic telemetry techniques were employed to track eleven specimens of Nautilus pompilius for variable times ranging from one to 78 days at Osprey Reef, Coral Sea, Australia. To supplement these observations, six remotely operated vehicle (ROV) dives were conducted at the same location to provide 29 hours of observations from 100 to 800 meter depths which sighted an additional 48 individuals, including five juveniles, all deeper than 489 m. The resulting data suggest virtually continuous, nightly movement between depths of 130 to 700 m, with daytime behavior split between either virtual stasis in the relatively shallow 160–225 m depths or active foraging in depths between 489 to 700 m. The findings also extend the known habitable depth range of Nautilus to 700 m, demonstrate juvenile distribution within the same habitat as adults and document daytime feeding behavior. These data support a hypothesis that, contrary to previously observed diurnal patterns of shallower at night than day, more complex vertical movement patterns may exist in at least this, and perhaps all other Nautilus populations. These are most likely dictated by optimal feeding substrate, avoidance of daytime visual predators, requirements for resting periods at 200 m to regain neutral buoyancy, upper temperature limits of around 25°C and implosion depths of 800 m. The slope, terrain and biological community of the various geographically separated Nautilus populations may provide different permutations and combinations of the above factors resulting in preferred vertical movement strategies most suited for each population
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