8,224 research outputs found

    A model for the submarine depthkeeping team

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    The most difficult task the depthkeeping team must face occurs during periscope-depth operations during which they may be required to maintain a submarine several hundred feet long within a foot of ordered depth and within one-half degree of ordered pitch. The difficulty is compounded by the facts that wave generated forces are extremely high, depth and pitch signals are very noisy and submarine speed is such that overall dynamics are slow. A mathematical simulation of the depthkeeping team based on the optimal control models is described. A solution of the optimal team control problem with an output control restriction (limited display to each controller) is presented

    Vector boson production at hadron colliders: hard-collinear coefficients at the NNLO

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    We consider QCD radiative corrections to vector-boson production in hadron collisions. We present the next-to-next-to-leading order (NNLO) result of the hard-collinear coefficient function for the all-order resummation of logarithmically-enhanced contributions at small transverse momenta. The coefficient function controls NNLO contributions in resummed calculations at full next-to-next-to-leading logarithmic accuracy. The same coefficient function is used in applications of the subtraction method to perform fully-exclusive perturbative calculations up to NNLO.Comment: 13, pages, no figures. arXiv admin note: text overlap with arXiv:1106.465

    Investigation of metal flow in bridge die extrusion of Alloy 6063 and subsequent effect on surface quality and weld seam integrity

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    This paper describes a detailed study of tube extrusion by simulation using finite element method (FEM). The finite element model used one-sixth of symmetry. The extrusion load, emperature evolution and metal flow were predicted. Innovative methods, combining both grid and surface tools, were used to define in detail the flow of material. These showed clearly the inner and outer surface formation mechanisms of the tube extrusion. The seam weld, an important quality indicator, was also evaluated by selecting an appropriate criterion

    Diversidad genética de las razas porcinas ibérica y alentejana mediante el genotipado de variantes genéticas en genes mayores y genes candidatos

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    Las razas porcinas ibérica y alentejana se encuentran biogeográficamente localizadas en el suroeste de la península Ibérica. Estas razas comparten un conjunto de características comunes. Ambas son fenotípicamente muy similares; muestran un bajo índice de crecimiento y una elevada deposición grasa y tienen un sistema común de producción al aire libre en el que se explotan los recursos de la Dehesa. El objetivo del presente trabajo, dentro del marco del proyecto TREASURE, consistió en caracterizar la diversidad genética de ambas razas usando los datos de genotipado de 39 polimorfismos localizados en 34 genes previamente asociados a distintos caracteres de interés económico. Estos polimorfismos fueron genotipados en 950 cerdos pertenecientes a las razas ibérica y alentejana y a 18 razas europeas autóctonas adicionales. Los bajos valores para heterozigosidad observada y esperada indican una baja diversidad genética en ibéricos y alentejanos. Las distancias genéticas estimadas usando DS y FST fueron cercanas a 0 (0.007 y 0.039, respectivamente), sugieren que estas razas son genéticamente muy similares. Asimismo, las técnicas de análisis multivariante utilizadas como análisis de componentes principales y asignación a grupos mostraron que los individuos de estas razas están muy próximos formando clusters diferenciados del resto de razas. Estos resultados concuerdan con los de otros autores que ya mostraron distancias genéticas cortas entre ambas razas usando secuencias de ADN mitocondrial

    A Study of Charged P-wave D Meson Production in Semileptonic B Decays

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    A Study of Charged P-wave D Meson Production in Semileptonic B Decays. A search for the semileptonic decay of B mesons into final states involving charged D** as well as non resonant D0-pi is performed in a sample of approximately 3 million hadronic Z decays recorded with the ALEPH detector at LEP. Topological vertex criteria are used to separate the B -> D**+ l nu X signal from background as well as to search for the non-resonant component B -> D0 pi l nu X. Preliminary results for the branching fraction into resonant and non-resonant components are presented

    Scalar Particle Contribution to Higgs Production via Gluon Fusion at NLO

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    We consider the gluon fusion production cross section of a scalar Higgs boson in models where fermion and scalar massive colored particles are present. We report analytic expressions for the matrix elements of ggHggg\to Hg, qqˉHgq\bar{q}\to Hg, and qgHqqg\to Hq processes completing the calculation of the NLO QCD corrections in these extended scenarios. The formulas are written in a complete general case, allowing a flexible use for different theoretical models. Applications of our results to two different models are presented: i) a model in which the SM Higgs sector is augmented by a weak doublet scalar in the SU(Nc)SU(N_c) adjoint representation. ii) The MSSM, in the limit of neglecting the gluino contribution to the cross section.Comment: 20 pages, 5 figures. Minor changes. Refs. adde

    Heavy-quark mass effects in Higgs boson production at the LHC

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    We study the impact of heavy-quark masses in Higgs boson production through gluon fusion at the LHC. We extend previous computations of the fully differential cross section and of the transverse momentum spectrum of the Higgs boson by taking into account the finite top- and bottom-quark masses up to O(alpha_S^3). We also discuss the issues arising when the heavy-quark mass is much smaller than the Higgs mass. Our results are implemented in updated versions of the HNNLO and HRes numerical programs.Comment: Minor modifications, results unchanged. Discussion on uncertainties added. Version published on JHE

    Ultrastructure of endogenous stages of Eimeria ninakohlyakimovae Yakimoff & Rastegaieff, 1930 Emend. Levine, 1961 in experimentally infected goat.

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    Abstract: The ultrastructure of endogenous stages of Eimeria ninakohlyakimovae was observed in epithelial cells of cecum and colon crypts from a goat experimentally infected with 2.0 x 10(5) oocysts/kg. The secondary meronts developed above the nucleus of the host cell. The nucleus first divides and merozoites then form on the surface of multinucleated meronts. Free merozoites in the parasitophorous vacuole present a conoid, double membrane, one pair of rhoptries, micronemes, micropore, anterior and posterior polar ring, a nucleus with a nucleolus and peripheral chromatin. The microgamonts are located below the nucleus of the host cell and contain several nuclei at the periphery of the parasite. The microgametes consist of a body, a nucleus, three flagella and mitochondria. The macrogamonts develop below the nucleus of the host cell and have a large nucleus with a prominent nucleolus. The macrogametes contain a nucleus, wall-forming bodies of type I and type II. The young oocysts present a wall containing two layers and a sporont

    VBFNLO: A parton level Monte Carlo for processes with electroweak bosons -- Manual for Version 2.7.0

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    VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), QCD induced single and double vector boson production plus two jets, and double and triple vector boson production (plus jet) in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two jet production via gluon fusion at the one-loop level. For the new version -- Version 2.7.0 -- several major enhancements have been included into VBFNLO. The following new production processes have been added: WγjjW\gamma jj in VBF, HHjjHHjj in VBF, WW, WjWj, WHWH, WHjWHj, ppSpin-2jjpp\to \text{Spin-2}jj in VBF (with Spin-2WW/ZZleptons\text{Spin-2}\to WW/ZZ\to\text{leptons}) and the QCD induced processes WZjjWZjj, WγjjW\gamma jj, W±W±jjW^\pm W^\pm jj and WjjWjj production. The implementation of anomalous gauge boson couplings has been extended to all triboson and VBF VVjjVVjj processes, with an enlarged set of operators yielding anomalous couplings. Finally, semileptonic decay modes of the vector bosons are now available for many processes, including VVjjVVjj in VBF, VVVVVV and VVγVV\gamma production.Comment: 83 pages, 23 tables; new code available at http://www.itp.kit.edu/vbfnlo/; v3: update to version 2.7.

    Differential Cross Sections for Higgs Boson Production at Tevatron Collider Energies

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    The transverse momentum QTQ_T distribution is computed for inclusive Higgs boson production at S=1.96\sqrt{S} = 1.96 TeV. We include all-orders resummation of large logarithms associated with emission of soft gluons at small QTQ_T. We provide results for Higgs boson and ZZ^* masses from MZM_Z to 200 GeV. The relatively hard transverse momentum distribution for Higgs boson production suggests possibilities for improvement of the signal to background ratio.Comment: 12 pages, latex, 7 figure
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