57,439 research outputs found

    Policy compass: FCM-based policy impact evaluation using public open data

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    This paper presents how Fuzzy Cognitive Map (FCM) technique can be applied by a policy maker to support the policy impact evaluation using the example of Policy Compass, an EU research project. The practical usage example on interest rate policy shows the potential of FCMs as a policy impact modelling tool. Through the provision of a more intuitive and easier means of using open data based on FCM techniques, the Policy Compass project can play a critical role for both policy maker and lay public to evaluate the policy impact and prepare for future policy making

    L2L_2 boosting in kernel regression

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    In this paper, we investigate the theoretical and empirical properties of L2L_2 boosting with kernel regression estimates as weak learners. We show that each step of L2L_2 boosting reduces the bias of the estimate by two orders of magnitude, while it does not deteriorate the order of the variance. We illustrate the theoretical findings by some simulated examples. Also, we demonstrate that L2L_2 boosting is superior to the use of higher-order kernels, which is a well-known method of reducing the bias of the kernel estimate.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ160 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

    Pseudo-binary phase diagram for Zr-based in situ ß phase composites

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    The pseudo-binary (quasi-equilibrium) phase diagram for Zr-based bulk metallic glasses with crystalline in situ precipitates (ß phase) has been constructed from high-temperature phase information and chemical composition analysis. The phase evolution was detected in situ by high-energy synchrotron x-ray diffraction followed by Rietveld analysis of the data for volume fraction estimation. The phase diagram delineates phase fields and allows the control of phase fractions. Combined with related previous work by the authors, this diagram offers a unique opportunity to control both the morphology and volume of the dendritic ß phase precipitates to enhance the properties of the composites

    Effect of sintering temperature under high pressure in the uperconductivity for MgB2

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    We report the effect of the sintering temperature on the superconductivity of MgB2 pellets prepared under a high pressure of 3 GPa. The superconducting properties of the non-heated MgB2 in this high pressure were poor. However, as the sintering temperature increased, the superconducting properties were vastly enhanced, which was shown by the narrow transition width for the resistivity and the low-field magnetizations. This shows that heat treatment under high pressure is essential to improve superconducting properties. These changes were found to be closely related to changes in the surface morphology observed using scanning electron microscopy.Comment: 3 Pages including 3 figure

    Gravitating monopoles in SU(3) gauge theory

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    We consider the Einstein-Yang-Mills-Higgs equations for an SU(3) gauge group in a spherically symmetric ansatz. Several properties of the gravitating monopole solutions are obtained an compared with their SU(2) counterpart.Comment: 7 pages, Latex, 3 figure

    Scaling and memory in the return intervals of energy dissipation rate in three-dimensional fully developed turbulence

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    We study the statistical properties of return intervals rr between successive energy dissipation rates above a certain threshold QQ in three-dimensional fully developed turbulence. We find that the distribution function PQ(r)P_Q(r) scales with the mean return interval RQR_Q as PQ(r)=RQ1f(r/RQ)P_Q(r)=R_Q^{-1}f(r/R_Q) except for r=1r=1, where the scaling function f(x)f(x) has two power-law regimes. The return intervals are short-term and long-term correlated and possess multifractal nature. The Hurst index of the return intervals decays exponentially against RQR_Q, predicting that rare extreme events with RQR_Q\to\infty are also long-term correlated with the Hurst index H=0.639H_\infty=0.639.Comment: 5 pages, 5 figure

    New heat treatment to prepare high quality polycrystalline and single crystal MgB2 in single process

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    We report here on a new heat treatment to prepare both dense polycrystalline and single crystal MgB2 high quality samples in one single process. Resistivity measurements for polycrystalline part of the sample gives a residual resistivity ratio RRR=16.6 and a very low normal state resistivity rho(40K)= 0.28 microOhmcm. Both SEM and SQUID study on polycrystals reveal the high quality, dense character and well coupling of grain boundaries. On the other hand, the high quality single crystals have a unique shape that resembles the hexagonal crystal structure. SQUID measurements reveals very weak flux pinning character implying our single crystals to be very clean. In this study, we conclude that heat treatment is playing a major rule on the characteristics of both polycrystalline and single crystal MgB2. Samples are thoroughly characterized by x-ray, resistivity, dc SQUID and SEM
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