3,426 research outputs found

    Techniques for Forecasting the Cessation of Lightning at Cape Canaveral Air Station and the Kennedy Space Center

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    The focus of this research effort is directed toward identifying new methods of forecasting the cessation of lightning along the Central Atlantic Coast of Florida. Cloud-to-ground lightning flashes place Air Force (AF) personnel and assets at risk almost daily at this location. Providing a more accurate method of forecasting the cessation of lightning would allow for safer and more efficient execution of AF operations. A data set consisting of 40 thunderstorm cases was identified within a 90 nautical miles (nmi) region surrounding the Melbourne, Florida WSR-88D (KMLB) site. Each case falls between the months of May and September and the years of 1995 through 1997. Simple and multiple linear regression models are built using this dataset. Variables included max Vertically Integrated Liquid water (VIL), max reflectivity, max peak current, peak cumulative flash rate, peak negative flash rate, and peak positive flash rate. Results indicate that three of the simple linear regression models to some extent accurately represent the data. Additionally, when the data set is separated by thunderstorm cell type (multi or single) and cell specific regressions are built, results indicate that the regressions based on the single-cell data set produce a substantial increase in forecast skill compared to that of climatology. In fact, some regressions are shown to improve forecast accuracy by 90% over that of climatology. Moreover, multiple linear regression models are shown to produce similar results and further reinforce the notion that each thunderstorm cell type (multi or single) behaves substantially different from the other with respect to forecasting the cessation of lightning

    Knots and Links in Three-Dimensional Flows

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    The closed orbits of three-dimensional flows form knots and links. This book develops the tools - template theory and symbolic dynamics - needed for studying knotted orbits. This theory is applied to the problems of understanding local and global bifurcations, as well as the embedding data of orbits in Morse-smale, Smale, and integrable Hamiltonian flows. The necesssary background theory is sketched; however, some familiarity with low-dimensional topology and differential equations is assumed

    Mining modern repositories with elasticsearch

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    Organizations are generating, processing, and retaining data at a rate that often exceeds their ability to analyze it effec-tively; at the same time, the insights derived from these large data sets are often key to the success of the organi-zations, allowing them to better understand how to solve hard problems and thus gain competitive advantage. Be-cause this data is so fast-moving and voluminous, it is in-creasingly impractical to analyze using traditional offline, read-only relational databases. Recently, new “big data ” technologies and architectures, including Hadoop and NoSQL databases, have evolved to better support the needs of organizations analyzing such data. In particular, Elasticsearch — a distributed full-text search engine — explicitly addresses issues of scalability, big data search, and performance that relational databases were simply never designed to support. In this paper, we reflect upon our own experience with Elasticsearch and highlight its strengths and weaknesses for performing modern mining software repositories research

    Effects of a simulated motion environment upon the physical demands of heavy materials handling operators

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    Maritime shipping, commercial fishing, passenger and cargo shipping and offshore oil and gas industries are all major contributors to the economies of Atlantic Canada. These industries require workers to perform heavy materials handling under harsh environmental conditions, particularly extreme deck motions. The purpose of this study was to better understand the demands of a moving environment on the ability of a person to perform specific lifting tasks. -- Nineteen healthy male subjects volunteered for this study. Each subject was required to lift a 15 kg load under four lifting conditions. While performing these lifting tasks, a ship's motion simulator was used to create deck motions under foot. Three deck motions were considered: pitch, quartering and roll. A stable laboratory condition was also collected for all lifting conditions. Electromyography (EMG) histories of four muscles (erector spinae, latissimus dorsi, external oblique and trapezius) were collected bilaterally and thoracolumbar kinematics was measured throughout the experimental protocol. -- A repeated measures ANOVA was employed to assess trunk motions and muscle activities across the lifting and motion conditions. There were no significant differences found due to the motion effect for any of the muscles monitored in this study. However, the lifting task did produce differences in the EMG activities for some muscles. The maximal sagittal velocities were significantly smaller for all motion states in comparison to the stable lab condition (p≤0.01) while maximum twisting and lateral bending velocities increased in the motion conditions compared to the stable lab condition (p≤0.05). Results suggest that working in a moving environment will likely increase the operator's risk for overexertion injuries, particularly to the spine

    Non--Newtonian viscosity of interacting Brownian particles: comparison of theory and data

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    A recent first-principles approach to the non-linear rheology of dense colloidal suspensions is evaluated and compared to simulation results of sheared systems close to their glass transitions. The predicted scenario of a universal transition of the structural dynamics between yielding of glasses and non-Newtonian (shear-thinning) fluid flow appears well obeyed, and calculations within simplified models rationalize the data over variations in shear rate and viscosity of up to 3 decades.Comment: 6 pages, 2 figures; J. Phys. Condens. Matter to be published (Jan. 2003

    Cyclical 'flipping' of morphology in block copolymer films

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    We studied the kinetics of nanopattern evolution in (polystyrene-b-polyethylene oxide) diblock copolymer thin films. Using scanning force microscopy, a highly unexpected cylindrical flipping of morphology from normal to parallel to the film plane was detected during solvent annealing of the film (with average thickness of 30 nm) at high vapor pressure. Using an in situ time-resolved light scattering device combined with an environmental cell enabled us to obtain kinetic information at different vapor pressures. The data indicated that there is a threshold value for the vapor pressure necessary for the structural transition. We propose a swelling and deswelling mechanism for the orientation flipping of the morphology. The cyclic transition occurs faster in thick films (177 nm) where the mass uptake and solvent volume fraction is smaller and therefore the driving force for phase separation is higher. We induced a stronger segregation by confining the chains in graphoepitaxially patterned substrates. As expected, the cyclic transition occurred at higher rate. Our work is another step forward to understanding the structure evolution and also controlling the alignment of block copolymer nanocylinders independently of thickness and external fields

    Psychometric properties of standardized balance confidence, fear of falling, and falls-efficacy measures in people with lower limb amputations

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    Background: In Canada, \u3e50% of community-dwelling lower limb amputees (LLA) fall at least once each year, a rate that is almost twice that of community-dwelling older adults. While the physical consequences of falls may be readily apparent, psychological sequelae that follow may be just as, if not more, detrimental than an actual fall itself. Current measures of balance confidence show no change in LLA following discharge from rehabilitation. The limited detectable change may be due to content validity challenges of the measures as they were not developed for the unique challenges faced by LLA. Objectives: 1) Review items from standardized scales measuring falls-related concerns with participants to determine the applicability of test items to the LLA population. 2) Solicit novel examples of relevant activities from participants to inform the development of an LLA-specific balance confidence scale. Proposed Methods: This cross-sectional study will include adult unilateral/bilateral LLA (n=60) recruited through the Outpatient Amputee Rehabilitation Program at Parkwood Institute. Falls-related concerns will be evaluated using seven relevant clinical measures of a concern for falling. Participants will be asked to identify inapplicable questions and to provide i) a list of activities they are physically able to do but are avoiding; and ii) a list of activities they currently do but are worried about becoming unsteady or falling when performed. Future Directions/Implications: The results of this project could provide important details for the creation of an amputee-specific measurement tool to better quantify psychological concerns related to falls

    Critical fluctuations in cortical models near instability

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    Australian Research Council, the National Health and Medical Research Council, the Brain Network Recovery Group Grant JSMF22002082, and Netherlands Organization for Scientific Research (NWO #451–10-030

    Modeling Treatment Strategies to Inform Yaws Eradication.

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    Yaws is a neglected tropical disease targeted for eradication by 2030. To achieve eradication, finding and treating asymptomatic infections as well as clinical cases is crucial. The proposed plan, the Morges strategy, involves rounds of total community treatment (i.e., treating the whole population) and total targeted treatment (TTT) (i.e., treating clinical cases and contacts). However, modeling and empirical work suggests asymptomatic infections often are not found in the same households as clinical cases, reducing the utility of household-based contact tracing for a TTT strategy. We use a model fitted to data from the Solomon Islands to predict the likelihood of elimination of transmission under different intervention schemes and levels of systematic nontreatment resulting from the intervention. Our results indicate that implementing additional treatment rounds through total community treatment is more effective than conducting additional rounds of treatment of at-risk persons through TTT
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