769 research outputs found

    Improved diamond coring bits developed for dry and chip-flush drilling

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    Two rotary diamond bit designs, one operating with a chip-flushing fluid, the second including auger section to remove drilled chips, enhance usefulness of tool for exploratory and industrial core-drilling of hard, abrasive mineral deposits and structural masonry

    Incorporating ecological functions in conservation decision making

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    Systematic conservation planning has become a standard approach globally, but prioritization of conservation efforts hardly considers species traits in decision making. This can be important for species persistence and thus adequacy of the conservation plan. Here, we developed and validated a novel approach of incorporating trophic information into a systematic conservation planning framework. We demonstrate the benefits of this approach using fish data from Europe's second largest river, the Danube. Our results show that adding trophic information leads to a different spatial configuration of priority areas at no additional cost. This can enhance identification of priority refugia for species in the lower position of the trophic web while simultaneously identifying areas that represent a more diverse species pool. Our methodological approach to incorporating species traits into systematic conservation planning is generally applicable, irrespective of realm, geographical area, and species composition and can potentially lead to more adequate conservation plans.SL was supported by ARC DECRA fellowship, project number DE130100565. VH was supported by a Ramon y Cajal contract (RYC‐2013‐13979) funded by the Spanish Government

    Loss Comparison of Small Delta- and Star-Connected Permanent Magnet Synchronous Machines

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    Delta-connected stator windings are often used in mass production of small Permanent Magnet Synchronous Machines (PMSMs). In comparison to star-connected stator windings, a delta-connected winding system offers advantages for manufacturing and lowers production costs. A main disadvantage of motors with such a winding system are additional losses caused by the Zero-Sequence Current Component (ZSCC). In this paper the ZSCC and its impact on the generated losses in a delta-connected PMSM used as a traction motor for a pedal electric cycle (Pedelec) is analysed. The calculated results are compared to those of a star-connected PMSM with the same design. We will show that the amplitude of the ZSCC depends on the operating point of the machine. As a result, the copper losses in the delta-connected machine are up to 5.8 % higher than the ones in the star-connected machine. On the other hand, the iron losses are 1 % smaller in the delta-connected machine. The efficiency of the delta-connected machine is still up to 4 % smaller

    Numerical Simulation Approach for a Dynamically Operated Sorption-Enhanced Water-Gas Shift Reactor

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    A dynamically operated sorption-enhanced water–gas shift reactor is modelled to leverage its performance by means of model-based process design. This reactor shall provide CO₂-free synthesis gas for e-fuel production from pure CO. The nonlinear model equations describing simultaneous adsorption and reaction are solved with three numerical approaches in MATLAB: a built-in solver for partial differential equations, a semi-discretization method in combination with an ordinary differential equation solver, and an advanced graphic implementation of the latter method in Simulink. The novel implementation in Simulink offers various advantages for dynamic simulations and is expanded to a process model with six reaction chambers. The continuous conditions in the reaction chambers and the discrete states of the valves, which enable switching between reactive adsorption and regeneration, lead to a hybrid system. Controlling the discrete states in a finite-state machine in Stateflow enables automated switching between reactive adsorption and regeneration depending on predefined conditions, such as a time span or a concentration threshold in the product gas. The established chemical reactor simulation approach features unique possibilities in terms of simulation-driven development of operating procedures for intensified reactor operation. In a base case simulation, the sorbent usage for serial operation with adjusted switching times is increased by almost 15%

    Re-examining the Effects of Medicaid Expansions for Pregnant Women

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    This paper analyzes the effect of Medicaid eligibility expansions on the health insurance coverage of women giving birth and on the use of prenatal care and infant health, controlling for year and state effects and state-specific trends that may be correlated with expansions in Medicaid eligibility. We combine estimates from the two sets of analyses to construct estimates of the effect of health insurance on use of prenatal care and infant health. We find that the eligibility expansions reduced the proportion of pregnant women who were uninsured by approximately 10 percent, although this decrease in uninsured came with the expense of a substantial reduction in private insurance coverage. Changes in Medicaid eligibility were associated with very small and statistically insignificant changes in prenatal care use, birth weight, and incidence of low-birth weight.

    The State of the Art in Tag Ontologies: A Semantic Model for Tagging and Folksonomies

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    There is a growing interest on how we represent and share tagging data for the purpose of collaborative tagging systems. Conventional tags, however, are not naturally suited for collaborative processes. Being free-text keywords, they are exposed to linguistic variations like case (upper vs lower), grammatical number (singular vs. plural) as well as human typing errors. Additionally, tags depend on the personal views of the world by individual users, and are not normalized for synonymy, morphology or any other mapping. The bottom line of the problem is that tags have no semantics whatsoever. Moreover, even if a user gives some semantics to a tag while using or viewing it, this meaning is not automatically shared with computers since it’s not defined in a machine-readable way. With tagging systems increasing in popularity each day, the evolution of this technology is hindered by this problem. In this paper we discuss approaches to represent tagging activities at a semantic level. We present criteria for the comparison of existing tag ontologies and discuss their strengths and weaknesses in relation to these criteria
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