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- Ruiz-Huerta, Leopoldo, et al.
(författare)
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Investigacion del processo de corte por chorro de agua (wjc) y sus aplicaciones en micromecanica
- 2009
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Ingår i: IX Congreso iberoamericano de ingeniería mecánica: Cibim9, 17-20 de Noviembre del 2007, Las Palmas de Gran Canaria : memoria técnica, resúmenes. - Xalapa, Veracruz, Mexico : Universidad de Las Palmas de Gran Canaria. - 9788469285169
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Para la manufactura de dispositivos pequeños, también conocida como micromanufactura, se requiere del uso de herramientas de corte, sistemas de posicionamiento y sistemas de medición, proporcionales a lo que se desea maquinar. Utilizando técnicas convencionales de maquinado por arranque de material, se han logrado obtener las características dimensionales, tolerancias y acabado superficial necesarios para este propósito; pero siempre se tiene la limitante asociada al desarrollo de herramientas adecuadas al tamaño y a los materiales que se desean maquinar. Es por ello que en el Grupo de Micromecánica y Mecatrónica (GMM) de CCADET-UNAM decidió investigar el proceso de corte por chorro de agua (WJC) aplicado a la micromanufactura como una alternativa para cubrir la problemática antes mencionada, con lo cual, se podría ampliar la gama de materiales a manufacturar y se evita la necesidad de desarrollar herramientas de corte convencionales.
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- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 8. |
- Martin-Martin, Juan Diego, et al.
(författare)
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Extensive dickitization of the Permo-Triassic fluvial sandstones from the eastern Iberian Range, Spain
- 2007
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Ingår i: Clays and clay minerals. - 0009-8604 .- 1552-8367. ; 55:5, s. 481-490
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Tidskriftsartikel (refereegranskat)abstract
- Diagenetic kaolin minerals are very common in the Permo-Triassic succession from the SE Iberian Range, Spain. The morphology and crystal structure of kaolin minerals has been examined in four size fractions (< 1 mu m, < 2 mu m, < 6.3 mu m and < 20 mu m) of sandstone samples by means of scanning electron microscopy, X-ray diffraction, infrared spectroscopy, differential thermal analysis and thermogravimetry. Experimental data reveal that dickite is the dominant kaolin-type mineral in the entire range of size fractions, whereas small amounts of kaolinite coexists with dickite in all size fractions. Dickite appears typically as booklets of pseudo-hexagonal plates with blocky habit. The increase in size fraction is concomitant with the increase in the amount of dickite and the progressive improvement of its structural order. The extensive dickitization is attributed to the high paleogeothermal gradient recorded in the studied area and the increase in H+, presumably resulting from the flux of organic acids derived from the underlying Carboniferous rocks and/or the late Permian succession. These conditions are more likely to be associated with the late Cretaceous post-rift thermal stage of the eastern Iberian Basin. Lately, during the maximum burial depth, the fine crystalline kaolin minerals were slightly illitized. Given the very small feldspar content in the studied sequence, the results reflect the important contribution of mica alteration to the early diagenetic formation of kaolinite as well as the late conversion to dickite.
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