13,770 research outputs found
Microstructural optimization of unalloyed ductile cast irons with a ferritic matrix used in the manufacture of wind turbine rotors
The aim of this work was the microstructural optimization of cast irons with nodular graphite for the manufacture of wind turbine hubs, paying preferential attention to the geometry and distribution of graphite spheroids to ensure the required mechanical properties for this application. The target was pursued based upon microstructure-properties correlation, in an environment of great competitiveness and exigency marked by current international standards. The methodology followed consisted of the generation of knowledge from tailor-made industrial castings, followed by the analysis of their microstructures, in order to extract valuable conclusions for the production process through the use of statistical analysis. The approach method employed was a Fractional Design of Experiments (DOE) with 7 factors, 16 experiments and resolution IV. The samples from each experiment were cubes of identical geometry, and designed to match a surface-to-volume module equal to 4 cm (1.57 in) found as the highest values in real hubs of 3 MW power wind turbines. It is concluded that the use of nodulizers with traces of lanthanum favour the reduction of the volume fraction of pearlite, although La has proved not to promote the spherical shape of primary graphite. The negative effect of pre-inoculants containing SiC on the spheroidal morphology of graphite has also been verified, and also that low-Mn bearing scrap favours graphite formation and the reduction of the volume fraction of pearlite, in spite of being a carbide forming element. The whitening effect of Mn was minimized with low carbon equivalent melts
Spin wave theory for 2D disordered hard-core bosons
A spin-wave (SW) approach for hard-core bosons is presented to treat the
problem of two dimensional boson localization in a random potential. After a
short review of the method to compute 1/S-corrected observables, the case of
random on-site energy is discussed. Whereas the mean-field solution does not
display a Bose glass (BG) phase, 1/S corrections do capture BG physics. In
particular, the localization of SW excitations is discussed through the inverse
participation ratio.Comment: TIDS15 conferenc
The Berry phase and the pump flux in stochastic chemical kinetics
We study a classical two-state stochastic system in a sea of substrates and
products (absorbing states), which can be interpreted as a single
Michaelis-Menten catalyzing enzyme or as a channel on a cell surface. We
introduce a novel general method and use it to derive the expression for the
full counting statistics of transitions among the absorbing states. For the
evolution of the system under a periodic perturbation of the kinetic rates, the
latter contains a term with a purely geometrical (the Berry phase)
interpretation. This term gives rise to a pump current between the absorbing
states, which is due entirely to the stochastic nature of the system. We
calculate the first two cumulants of this current, and we argue that it is
observable experimentally
LA BOTICA DE LOS JESUITAS: UNA DE LAS MEJORES INSTITUCIONES FARMACÉUTICAS DEL MUNDO EN EL CHILE COLONIAL
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