DEPRO - Departamento de Engenharia de Produção
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/515
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24 resultados
Resultados da Pesquisa
Item Inserção das afiliadas brasileiras na estrutura de P&D das suas matrizes.(2002) Camargos, Silvana Prata; Sbragia, RobertoDiscussão a respeito da internacionalização das atividades tecnológicas ampara-se, marcadamente, nos aspectos referentes à estruturação das atividades de P&D encaminhadas nas unidades estrangeiras. Uma linha de argumentação sinaliza para o caráter inevitável da internacionalização das atividades tecnológicas dentro dos moldes menos centralizadores. As principais causas apontadas são o surgimento de novas fontes de conhecimento e a importância crescente do atendimento às necessidades específicas dos diversos mercados locais e/ou regionais. Outra linha de pensamento defende que as vantagens associadas à maior descentralização das atividades de P&D não chegam a neutralizar suas desvantagens. Seus defensores argumentam que a necessidade de volumes significativos de investimentos nessas atividades requer ganhos de escala e manutenção da segurança quanto às novas tecnologias geradas, por exemplo, o que estaria seriamente ameaçado caso as empresas adotassem estruturas menos centralizadas. O objetivo do estudo foi analisar a estrutura de P&D Global adotada pelas empresas internacionais instaladas no Brasil. Foram estudados cinco casos, procurando abranger setores e modelos estruturais diferenciados, aspecto visto como importante por tratar-se de um estudo inicial sobre o assunto. Num primeiro momento, a análise baseou-se na caracterização de cada um dos arranjos encontrados e na identificação das suas vantagens e desvantagens. Posteriormente, foram levantados os fatores condicionantes da inserção da unidade brasileira nessa estrutura, além de alguns indicadores referentes ao desempenho do negócio e ao desempenho inovador dessa unidade.Item Application of an IT evaluation method.(2009) Ribeiro, Priscilla Cristina Cabral; Scavarda, Annibal José; Batalha, Mário Otávio; Bailey, DeeVonThis paper presents an application of an information technology (IT) evaluation method in three ranches in the American (United States) cattle chain. This method was built on some information systems (IS), IT, and Radio Frequency Identification (RFID) evaluation models, according to its focus (RFID technical aspects). Some IT is used to trace products from their source until their destination. Traceability systems are more general than identification systems, which are the central focus, RFID being the paradigm example. Although some ranchers have used RFID tags to help monitor animal health and quality, they frequently supplement RFID with plastic ear tags to reduce cost. Taking a qualitative approach, the results of this study are derived from case studies with interviews.Item Existence of mesons and mass splitting in strong coupling lattice quantum chromodynamics.(2004) Francisco Neto, Antônio; Veiga, Paulo Afonso Faria da; O’Carroll, MichaelWe consider one flavor lattice quantum chromodynamics in the imaginary time functional integral formulation for space dimensions d52, 3 with 434 Dirac spin matrices, small hopping parameter k, 0,k!1, and zero plaquette coupling. We determine the energy-momentum spectrum associated with four-component gauge invariant local meson fields which are composites of a quark and an antiquark field. For the associated correlation functions, we establish a Feynman–Kac formula and a spectral representation. Using this representation, we show that the mass spectrum consists of two distinct masses ma and mb , given by mc 522 lnk1rc(k), c5a,b, where rc is real analytic. For d52, ma and mb have multiplicity two and the mass splitting is k 41O(k 6); for d53, one mass has multiplicity one and the other three, with mass splitting 2k 41O(k 6). In the subspace of the Hilbert space generated by an even number of fermion fields the dispersion curves are isolated ~upper gap property! up to near the two-meson threshold of asymptotic mass 24 lnk.Item Meson-meson bound states in (2+1)-dimensional strongly coupled lattice QCD model.(2004) Veiga, Paulo Afonso Faria da; O'Carroll, Michael Louis; Francisco Neto, AntônioWe consider bound states of two mesons ~antimesons! in lattice quantum chromodynamics in an Euclidean formulation. For simplicity, we analyze an SU~3! theory with a single flavor in 211 dimensions and twodimensional Dirac matrices. For a small hopping parameter k and small plaquette coupling g0 22, such that 0 ,g0 22!k!1, recently we showed the existence of a ~anti!mesonlike particle, with an asymptotic mass of the order of 22 lnk and with an isolated dispersion curve—i.e., an upper gap property persisting up to near the meson-meson threshold which is of the order of 24 lnk. Here, in a ladder approximation, we show that there is no meson-meson ~or antimeson-antimeson! bound state solution to the Bethe-Salpeter equation up to the two-meson threshold. Remarkably the absence of such a bound state is an effect of a potential which is nonlocal in space at order k 2, i.e., the leading order in the hopping parameter k. A local potential appears only at order k 4 and is repulsive. The relevant spectral properties for our model are unveiled by considering the correspondence between the lattice Bethe-Salpeter equation and a lattice Schro¨dinger resolvent equation with a nonlocal potential.Item Meson-baryon bound states in a (2+1)-dimensional strongly coupled lattice QCD model.(2004) Francisco Neto, AntônioWe consider bound states of a meson and a baryon ~meson and antibaryon! in lattice QCD in a Euclidean formulation. For simplicity, considering the 1 parity sector we analyze an SU(3) theory with a single flavor in 211 dimensions and two-dimensional Dirac matrices. We work in the strong coupling regime, i.e., in a region of parameters such that the hopping parameter k is sufficiently small and k@g0 22, where g0 22 is the pure gauge coupling. There is a meson ~baryon! particle with asymptotic mass 22 lnk (23 lnk) and an isolated dispersion curve. Here, in a ladder approximation, we show that there is no meson baryon ~or meson-antibaryon! bound state solution to the Bethe-Salpeter equation up to the meson-baryon threshold (;25 lnk). The absence of such a bound state is an effect of a spatial range-one repulsive potential that is local in space at order k 3, i.e., the leading order in the hopping parameter k .Item A meson-baryon bound state in a 2 + 1 lattice QCD model with two flavours and strong coupling.(2007) Francisco Neto, AntônioWe consider the existence of bound states of one meson and one baryon in an imaginary-time formulation of lattice quantum chromodynamics (QCD). We analyse an SU(3) theory with two flavours in 2 + 1 dimensions and two-dimensional (2D) spin matrices. For small hopping parameter 0 < 1 and sufficiently large glueball mass, i.e., in the strong coupling limit, restricting our analysis to the 1/2 total isospin sector, we show the existence of a meson-baryon bound state solution to the Bethe–Salpeter (B–S) equation in a ladder approximation below the meson-baryon threshold ( −5ln ), and with binding energy of strength 0.1081 2. The existence of the bound state is an effect of two sources of attraction, a zero-range energy dependent potential and a space range-one potential associated with a quark anti-quark exchange.Item Meson-meson bound state in a 2 + 1 lattice QCD model with two flavors and strong coupling.(2005) Veiga, Paulo Afonso Faria da; O'Carroll, Michael Louis; Francisco Neto, AntônioWe consider the existence of bound states of two mesons in an imaginary-time formulation of lattice QCD. We analyze an SU(3) theory with two flavors in 2 1 dimensions and two-dimensional spin matrices. For a small hopping parameter and a sufficiently large glueball mass, as a preliminary, we show the existence of isoscalar and isovector mesonlike particles that have isolated dispersion curves (upper gap up to near the two-particle threshold 4 ln ). The corresponding meson masses are equal up to and including O 3 and are asymptotically of order 2 ln 2. Considering the zero total isospin sector, we show that there is a meson-meson bound state solution to the Bethe-Salpeter equation in a ladder approximation, below the two-meson threshold, and with binding energy of order b 2 ’ 0:02359 2. In the context of the strong coupling expansion in , we show that there are two sources of meson-meson attraction. One comes from a quark-antiquark exchange. This is not a meson exchange, as the spin indices are not those of the meson particle, and we refer to this as a quasimeson exchange. The other arises from gauge field correlations of four overlapping bonds, two positively oriented and two of opposite orientation. Although the exchange part gives rise to a space range-one attractive potential, the main mechanism for the formation of the bound state comes from the gauge contribution. In our lattice Bethe-Salpeter equation approach, this mechanism is manifested by an attractive distance-zero energy-dependent potential. We recall that no bound state appeared in the one-flavor case, where the repulsive effect of Pauli exclusion is stronger.Item Heat conduction in a weakly anharmonic chain : an analytical approach.(2006) Francisco Neto, Antônio; Lemos, Humberto César Fernandes; Pereira, Emmanuel AraújoThe analytical study of heat conduction in an anharmonic chain is considered here. We investigate an one-dimensional system (directly related to the Frenkel–Kontorova model) with anharmonic cosine on-site potential and harmonic interparticle interaction. We start with a stochastic thermal reservoir connected to each site of the system, and analyse the behaviour of the conductivity in the steady state with all the heat baths as we turn off the interior reservoirs, i.e., as we keep the heat baths at the boundaries only. For a weak interparticle potential and small anharmonicity, in a perturbative computation, we derive an analytic expression for the heat conductivity which indicates that the Fourier’s law holds only when each site is connected to a heat bath. To show the trustworthiness of our perturbative computation, we also derive an expression for the conductivity by starting from the exact solution of the linear part of the dynamics and compare with the result which comes from the previous perturbative analysis.Item Analytic approach to the (an)harmonic crystal chains with self-consistent stochastic reservoirs.(2008) Falcão, Ricardo de Carvalho; Francisco Neto, Antônio; Pereira, Emmanuel AraujoWe consider the harmonic and anharmonic chains of oscillators with self-consistent stochastic reservoirs and derive an integral representation (`a la Feynman–Kac) for the correlations, in particular, for the heat flow. For the harmonic chain, we give a new proof that its thermal conductivity is finite in the steady state. Based on this integral representation for the correlations and a perturbative analysis, the approach is quite general and can be extended to more intricate systems.Item Mesonic eightfold way from dynamics and confinement in strongly coupled lattice quantum chromodynamics.(2008) Francisco Neto, Antônio; O'Carroll, Michael Louis; Veiga, Paulo Afonso Faria daWe show the existence of all the 36 eightfold way mesons and determine their masses and dispersion curves exactly, from dynamical first principles such as directly from the quark-fluon dynamics. We also give a proof of confinement below the two-meson energy threshold. For this purpose, we consider an imaginary time functional integral representation of a 3 1 dimensional lattice QCD model with Wilson action, SU 3 f global and SU 3 c local symmetries. We work in the strong coupling regime, such that the hopping parameter 0 is small and much larger than the plaquette coupling 1/g0 2 0 1 . In the quantum mechanical physical Hilbert space H, a Feynman-Kac type representation for the two-meson correlation and its spectral representation are used to establish an exact rigorous connection between the complex momentum singularities of the two-meson truncated correlation and the energy-momentum spectrum of the model. The total spin operator J and its z-component Jz are defined by using /2 rotations about the spatial coordinate axes, and agree with the infinitesimal generators of the continuum for improper zero-momentum meson states. The mesons admit a labelling in terms of the quantum numbers of total isospin I, the third component I3 of total isospin, the z-component Jz of total spin and quadratic Casimir C2 for SU 3 f. With this labelling, the mesons can be organized into two sets of states, distinguished by the total spin J. These two sets are identified with the SU 3 f nonet of pseudo-scalar mesons (J=0 and the three nonets of vector mesons J=1,Jz= 1,0 . Within each nonet a further decomposition can be made using C2 to obtain the singlet state C2=0 and the eight members of the octet C2=3 . By casting the problem of determination of the meson masses and dispersion curves into the framework of the the anaytic implicit function theorem, all the masses m , are found exactly and are given by convergent expansions in the parameters and . The masses are all of the form m , =0 m =−2ln −3 2 /2+ 4r with r 0 0 and r real analytic; for 0,m , +2ln is jointly analytic in and . The masses of the vector mesons are independent of Jz and are all equal within each octet. All isospin singlet masses are also equal for the vector mesons. For each nonet and =0, up to and including O 4 , the masses of the octet and the singlet are found to be equal. But there is a pseudoscalar-vector meson mass splitting given by 2 4+O 6 and the splitting persists for 0. For =0, the dispersion curves are all of the form w p =−2 ln −3 2 /2+ 1 4 2 j=1 3 2 1−cos pj + 4r , p , with r , p const. For the pseudoscalar mesons, r , p is jointly analytic in and pj, for and Im pj small. We use some machinery from constructive field theory, such as the decoupling of hyperplane method, in order to reveal the gauge-invariant eightfold way meson states and a correlation subtraction method to extend our spectral results to all He, the subspace of H generated by vectors with an even number of Grassmann variables, up to near the two-meson energy threshold of −4 ln . Combining this result with a previously similar result for the baryon sector of the eightfold way, we show that the only spectrum in all H He Ho Ho being the odd subspace below −4 ln is given by the eightfold way mesons and baryons. Hence, we prove confinement up to near this energy threshold.
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