Report on "Scheduling in a factory"

In order to carry out their orders of shoe soles, this company has a number of tasks T_1, ..., T_n of different lengths to be assigned to groups of machines. Each group is operated by one worker (two in one case), and an operation cycle corresponds to injection, cooling, and removal of the sole. The time taken at each step varies from one order to another, and when starting a new task a machine needs to be tuned, which takes some extra time. Machines are working in parallel. At the moment the assignment is carried out empirically, and the problem proposed is to optimize the procedure

Regge-model predictions for K+Sigma photoproduction from the nucleon

We present Regge-model predictions for the p(gamma,K+)Sigma0 and n(gamma,K+)Sigma- differential cross sections and photon-beam asymmetries in the resonance region. The reaction amplitude encompasses the exchange of K+(494) and K*+(892) Regge-trajectories, introducing a mere three free parameters. These are fitted to the available p(gamma,K+)Sigma0 data beyond the resonance region. The n(gamma,K+)Sigma- amplitude is obtained from the p(gamma,K+)Sigma0 one through SU(2) isospin symmetry considerations.Comment: 4 pages, 2 figures; Proceedings Tenth Conference on the Intersections of Particle and Nuclear Physics, San Diego, 200

Quantum Electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell's equations due to vacuum polarization. Our multidimensional solver reproduced in one dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of counter-propagating configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities

Symmetries in two-dimensional dilaton gravity with matter

The symmetries of generic 2D dilaton models of gravity with (and without) matter are studied in some detail. It is shown that $\delta_2$, one of the symmetries of the matterless models, can be generalized to the case where matter fields of any kind are present. The general (classical) solution for some of these models, in particular those coupled to chiral matter, which generalizes the Vaidya solution of Einstein Gravity, is also given.Comment: Minor changes have been made; the references have been updated and some added; 11 pages. To appear in Phys. Rev.

Integrable models and degenerate horizons in two-dimensional gravity

We analyse an integrable model of two-dimensional gravity which can be reduced to a pair of Liouville fields in conformal gauge. Its general solution represents a pair of ``mirror'' black holes with the same temperature. The ground state is a degenerate constant dilaton configuration similar to the Nariai solution of the Schwarzschild-de Sitter case. The existence of $\phi=const.$ solutions and their relation with the solution given by the 2D Birkhoff's theorem is then investigated in a more general context. We also point out some interesting features of the semiclassical theory of our model and the similarity with the behaviour of AdS$_2$ black holes.Comment: Latex, 16 pages, 1 figur

Exhaustive Gaussian Approach for performance evaluation of direct-detection OFDM systems employing square and cross QAM

An exhaustive Gaussian approach (EGA) is proposed to evaluate, through numerical simulation, the bit error ratio (BER) of direct-detection orthogonal frequency division multiplexing systems employing square and cross quadrature amplitude modulation. Excellent agreement between the BER estimates from the direct error counting (DEC) and the EGA is shown for different levels of optical signal-to-noise ratio and signal distortion. It is shown that the EGA requires about three orders of magnitude less in computation time than the DEC method for BER levels around 10-6, with the difference getting higher for lower BER levels.info:eu-repo/semantics/publishedVersio

Tolerância ao déficit hídrico em acessos de Brachiaria brizantha: taxa de alongamento foliar.

Em virtude das dimensões continentais do Brasil, o país apresenta áreas com precipitação pluvial média variando de mais de 3.000 mm/ano (região Norte) a menos de 500 mm/ano (região Nordeste). Em algumas áreas, não são registrados períodos de estiagem (região Sul), enquanto em outras este período pode ser superior a nove meses por ano (região Nordeste). Essas condições são, em parte, responsáveis pelos baixos níveis de produtividade de sistemas de produção animal exclusivamente a pasto. O gênero Brachiaria têm sido um dos mais utilizados na formação de pastagens no Brasil. O conhecimento da resposta de cultivares e acessos de Brachiaria brizantha ao estresse por déficit hídrico, auxiliarão no desenvolvimento de gramíneas forrageiras mais eficientes no uso da água, proporcionando menor estacionalidade de produção e redução da necessidade de água por unidade de carne produzida. O objetivo do presente trabalho foi avaliar o efeito do déficit hídrico sobre a taxa de alongamento foliar de três acessos de Brachiaria brizantha