Results 1 - 10 of 5950
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[en] The nonlinear dynamical behavior of parametric wave-wave interactions is studied. The temporal dynamics of the model equations describing resonant coupling of two wave triplets in a quadratic nonlinear medium is analyzed. This Hamiltonian system is shown to undergo transition from regular to chaotic states via the route of quasi periodicity. Application to nonlinear optics in plasmas is exemplified. (author). 15 refs., 5 figs
[en] We analyze the 3-year WMAP data and look for a deviation from Gaussianity in the form of a 3-point function that has either of the two theoretically motivated shapes: local and equilateral. There is no evidence of departure from Gaussianity and the analysis gives the presently tightest bounds on the parameters fNLlocal and fNLequil., which define the amplitude of respectively the local and the equilateral non-Gaussianity: -36 < fNLlocal < 100, -256 < fNLequil. < 332 at 95% C.L. (author)
[en] In this paper, we aim to study the swimming performance of fish robots by using a statistical approach. A fish robot employing a carangiform swimming mode had been used as an experimental platform for the performance study. The experiments conducted aim to investigate the effect of various design parameters on the thrust capability of the fish robot with a flexible caudal fin. The controllable parameters associated with the fin include frequency, amplitude of oscillation, aspect ratio and the rigidity of the caudal fin. The significance of these parameters was determined in the first set of experiments by using a statistical approach. A more detailed parametric experimental study was then conducted with only those significant parameters. As a result, the parametric study could be completed with a reduced number of experiments and time spent. With the obtained experimental result, we were able to understand the relationship between various parameters and a possible adjustment of parameters to obtain a higher thrust. The proposed statistical method for experimentation provides an objective and thorough analysis of the effects of individual or combinations of parameters on the swimming performance. Such an efficient experimental design helps to optimize the process and determine factors that influence variability.
[en] The hysteresis curves of two Accumulator sample magnets have been measured, one large quadrupole and one small quadrupole. Based upon these measurements, a parameterization of hysteresis effects is deduced and generalized to other magnets. The goal is to incorporate the best knowledge of the magnets we have into the Accumulator model, on which lattice measurements are based and which is used to calculate an accurate first guess at the E-835 deceleration tables. Since a well-defined sequence of current cycles is performed during Accumulator operations, some simplifying hypotheses can be applied
[en] In this paper it is shown how the GARCH properties of oil price changes can be employed to forecast the oil price distribution over short-term horizons. The forecasting methodology is semiparametric and it is based on the bootstrap approach. The results of an out-of-sample forecasting exercise, carried out using the Brent oil price series, suggest that the forecasting approach can be used to obtain a performance measure for the forward price, in addition to compute interval forecasts for the oil price