102,274 research outputs found

    Design, analysis and test verification of advanced encapsulation systems

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    Analytical models were developed to perform optical, thermal, electrical and structural analyses on candidate encapsulation systems. Qualification testing, specimens of various types, and a finalized optimum design are projected

    Deep inelastic scattering, diffraction, and all that

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    These lectures include an introduction to the partonic description of the proton, the photon and the `colour singlet', as seen in inclusive and semi-inclusive DIS, in e+ee^+e^- collisions, and in diffractive processes, respectively. Their formal treatment using structure, fragmentation, and fracture functions is outlined giving an insight into the perturbative QCD framework for these functions. Examples and comparisons with experimental data from LEP, HERA, and Tevatron are also covered.Comment: 46 pages, 52 postscript figures, LaTeX, aipproc.sty. To be published in the proceedings of VII Mexican Workshop on Particles and Field

    NLO Scale Dependence of Semi-Inclusive Processes

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    We discuss the order \alpha_s^2 gluon initiated QCD corrections to one particle inclusive deep inelastic processes. We focus in the NLO evolution kernels relevant for the non homogeneous QCD scale dependence of these cross sections and factorization.Comment: Poster presentation at the XXIII Physics in Collision Conference (PIC03), Zeuthen, Germany, June 2003, 3 pages, LaTeX, 4 eps figures, PSN FRAP1

    Space-time defects :Domain walls and torsion

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    The theory of distributions in non-Riemannian spaces is used to obtain exact static thin domain wall solutions of Einstein-Cartan equations of gravity. Curvature δ \delta -singularities are found while Cartan torsion is given by Heaviside functions. Weitzenb\"{o}ck planar walls are caracterized by torsion δ\delta-singularities and zero curvature. It is shown that Weitzenb\"{o}ck static thin domain walls do not exist exactly as in general relativity. The global structure of Weitzenb\"{o}ck nonstatic torsion walls is investigated.Comment: J.Math.Phys.39,(1998),Jan. issu

    Optimal boundary geometry in an elasticity problem: a systematic adjoint approach

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    p. 509-524In different problems of Elasticity the definition of the optimal geometry of the boundary, according to a given objective function, is an issue of great interest. Finding the shape of a hole in the middle of a plate subjected to an arbitrary loading such that the stresses along the hole minimizes some functional or the optimal middle curved concrete vault for a tunnel along which a uniform minimum compression are two typical examples. In these two examples the objective functional depends on the geometry of the boundary that can be either a curve (in case of 2D problems) or a surface boundary (in 3D problems). Typically, optimization is achieved by means of an iterative process which requires the computation of gradients of the objective function with respect to design variables. Gradients can by computed in a variety of ways, although adjoint methods either continuous or discrete ones are the more efficient ones when they are applied in different technical branches. In this paper the adjoint continuous method is introduced in a systematic way to this type of problems and an illustrative simple example, namely the finding of an optimal shape tunnel vault immersed in a linearly elastic terrain, is presented.Garcia-Palacios, J.; Castro, C.; Samartin, A. (2009). Optimal boundary geometry in an elasticity problem: a systematic adjoint approach. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/654

    Collapse of the Gd3+Gd^{3+} ESR fine structure throughout the coherent temperature of the Gd-doped Kondo Semiconductor CeFe4P12CeFe_{4}P_{12}

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    Experiments on the Gd3+Gd^{3+} Electron Spin Resonance (ESR) in the filled skutterudite Ce1xGdxFe4P12Ce_{1-x}Gd_{x}Fe_{4}P_{12} (x0.001x \approx 0.001), at temperatures where the host resistivity manifests a smooth insulator-metal crossover, provides evidence of the underlying Kondo physics associated with this system. At low temperatures (below TKT \approx K), Ce1xGdxFe4P12Ce_{1-x}Gd_{x}Fe_{4}P_{12} behaves as a Kondo-insulator with a relatively large hybridization gap, and the Gd3+Gd^{3+} ESR spectra displays a fine structure with lorentzian line shape, typical of insulating media. The electronic gap is attributed to the large hybridization present in the coherent regime of a Kondo lattice, when Ce 4f-electrons cooperate with band properties at half-filling. Mean-field calculations suggest that the electron-phonon interaction is fundamental at explaining the strong 4f-electron hybridization in this filled skutterudite. The resulting electronic structure is strongly temperature dependent, and at about T160KT^{*} \approx 160 K the system undergoes an insulator-to-metal transition induced by the withdrawal of 4f-electrons from the Fermi volume, the system becoming metallic and non-magnetic. The Gd3+Gd^{3+} ESR fine structure coalesces into a single dysonian resonance, as in metals. Still, our simulations suggest that exchange-narrowing via the usual Korringa mechanism, alone, is not capable of describing the thermal behavior of the ESR spectra in the entire temperature region (4.24.2 - 300300 K). We propose that temperature activated fluctuating-valence of the Ce ions is the missing ingredient that, added to the usual exchange-narrowing mechanism, fully describes this unique temperature dependence of the Gd3+Gd^{3+} ESR fine structure observed in Ce1xGdxFe4P12Ce_{1-x}Gd_{x}Fe_{4}P_{12}.Comment: 19 pages, 6 figure
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