6,299 research outputs found

    On the simulation of space based manipulators with contact

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    An efficient method of simulating the motion of space based manipulators is presented. Since the manipulators will come into contact with different objects in their environment while carrying out different tasks, an important part of the simulation is the modeling of those contacts. An inverse dynamics controller is used to control a two armed manipulator whose task is to grasp an object floating in space. Simulation results are presented and an evaluation is made of the performance of the controller

    Hydrolytic effects of acid and enzymatic pre-treatment on the anaerobic biodegradability of <i>Ascophyllum nodosum</i> and <i>Laminaria digitata</i> species of brown seaweed

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    Abundant marine biomass in coastal regions has continued to attract increasing attention in recent times as a possible source of renewable energy. This study aimed to evaluate the effects of hydrolytic pre-treatment for the purpose of enhancing biogas yield of Laminaria digitata and Ascophyllum nodosum species found on the west coast of Scotland. Results show that L. digitata, in its natural and untreated form, appears to be more readily hydrolysable than A. nodosum. Two treatments were assessed: acid only and acid followed by enzyme. Both treatments enhanced the hydrolysis of both seaweed species, with acid-enzyme treatment providing a better performance

    Ethanol production from brown seaweed using non-conventional yeasts

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    The use of macroalgae (seaweed) as a potential source of biofuels has attracted considerable worldwide interest. Since brown algae, especially the giant kelp, grow very rapidly and contain considerable amounts of polysaccharides, coupled with low lignin content, they represent attractive candidates for bioconversion to ethanol through yeast fermentation processes. In the current study, powdered dried seaweeds (Ascophylum nodosum and Laminaria digitata) were pre-treated with dilute sulphuric acid and hydrolysed with commercially available enzymes to liberate fermentable sugars. Higher sugar concentrations were obtained from L. digitata compared with A. nodosum with glucose and rhamnose being the predominant sugars, respectively, liberated from these seaweeds. Fermentation of the resultant seaweed sugars was performed using two non-conventional yeast strains: Scheffersomyces (Pichia) stipitis and Kluyveromyces marxianus based on their abilities to utilise a wide range of sugars. Although the yields of ethanol were quite low (at around 6 g/L), macroalgal ethanol production was slightly higher using K. marxianus compared with S. stipitis. The results obtained demonstrate the feasibility of obtaining ethanol from brown algae using relatively straightforward bioprocess technology, together with non-conventional yeasts. Conversion efficiency of these non-conventional yeasts could be maximised by operating the fermentation process based on the physiological requirements of the yeasts

    Biophysics of magnetic orientation: strengthening the interface between theory and experimental design

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    The first demonstrations of magnetic effects on the behaviour of migratory birds and homing pigeons in laboratory and field experiments, respectively, provided evidence for the longstanding hypothesis that animals such as birds that migrate and home over long distances would benefit from possession of a magnetic sense. Subsequent identification of at least two plausible biophysical mechanisms for magnetoreception in animals, one based on biogenic magnetite and another on radical-pair biochemical reactions, led to major efforts over recent decades to test predictions of the two models, as well as efforts to understand the ultrastructure and function of the possible magnetoreceptor cells. Unfortunately, progress in understanding the magnetic sense has been challenged by: (i) the availability of a relatively small number of techniques for analysing behavioural responses to magnetic fields by animals; (ii) difficulty in achieving reproducible results using the techniques; and (iii) difficulty in development and implementation of new techniques that might bring greater experimental power. As a consequence, laboratory and field techniques used to study the magnetic sense today remain substantially unchanged, despite the huge developments in technology and instrumentation since the techniques were developed in the 1950s. New methods developed for behavioural study of the magnetic sense over the last 30 years include the use of laboratory conditioning techniques and tracking devices based on transmission of radio signals to and from satellites. Here we consider methodological developments in the study of the magnetic sense and present suggestions for increasing the reproducibility and ease of interpretation of experimental studies. We recommend that future experiments invest more effort in automating control of experiments and data capture, control of stimulation and full blinding of experiments in the rare cases where automation is impossible. We also propose new experiments to confirm whether or not animals can detect magnetic fields using the radical-pair effect together with an alternate hypothesis that may explain the dependence on light of responses by animals to magnetic field stimuli

    Love and hate across the U.S. political spectrum.

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    Twitter is a vast source of qualitative and quantitative data on human interaction. This proposed study examines group identity strength (GIS), measured as how strongly one identifies with a group, as a factor of positive and negative partisanship in the US by observing tweets and follower interactions. The top 10 words collocated with “love” and “hate” will be analyzed for each level of GIS for liberals and conservatives. Expected findings are that those with stronger GIS will display more in-group favoritism than out-group animosity, and that the top collocates of love and hate will be different for liberals and conservatives

    Evidence that fin whales respond to the geomagnetic field during migration

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    We challenge the hypothesis that fin whales use a magnetic sense to guide migration by testing for associations between geophysical parameters and the positions where fin whales were observed over the continental shelf off the northeastern United States. Monte Carlo simulations estimated the probability that the distribution of fin whale sighting was random with respect to bottom depth, bottom slope and the intensity and gradient of the geomagnetic field. The simulations demonstrated no overall association of sighting positions with any of these four geophysical parameters. Analysis of the data by season, however, demonstrated statistically reliable associations of sighting positions with areas of low geomagnetic intensity and gradient in winter and fall, respectively, but no association of sighting positions with bathymetric parameters in any season. An attempt to focus on migrating animals by excluding those observed feeding confirmed the associations of sighting positions with low geomagnetic intensity and gradient in winter and fall, respectively, and revealed additional associations with low geomagnetic gradients in winter and spring. These results are consistent with the hypothesis that fin whales, and perhaps other mysticete species, possess a magnetic sense that they use to guide migration

    Transforming Data into Meaning. Data-Driven approaches for Particle Physics, Nuclear Power Safety and Humanitarian Crisis Situations.

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    Machine learning and data intensive methods can be applied to a plethora of research domains. We apply supervised and unsupervised machine learning, Monte Carlo simulations and statistical tools to three diverse areas of research, tackling a range of computational and data analysis challenges unique to their respective environments. Using SHERPA-a Monte Carlo event generator-as a Standard Model machine we generate thousands of particle collision events. We employ a range of neural network architectures to determine the most powerful discriminating features which eliminate vast numbers of background events enabling us to calculate new constraints on the charm Yukawa coupling at the Large Hadron Collider and future projections. Hartlepool Nuclear Power Station has a rich array of instrumentation that continuously monitors reactor health as frequently as every second, at all times. We apply unsupervised machine learning and Bayesian tools to scrutinise anomalous behaviour in the data which is indicative of instrumentation degradation prior to instrumentation failure. JUNE-an agent based epidemiological simulation-is used to extract novel social mixing matrices at Cox's Bazar, a refugee camp in Bangladesh containing 600,000{\sim}600,000 displaced people. These contact matrices can be used to understand social interactions and disease spread and therefore provide better utilisation of limited resources
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