Exact propagator beyond and at caustics for isotropic time-dependent coupled and driven oscillators

Through a sequence of transformations we relate the propagator for the system of isotropic time-dependent, coupled and driven oscillators with time-varying mass, with those of free particles. We then derive the wave functions and the propagator beyond and at caustics. Finally we study a particular case which appears in quantum optics. © 1990.

Multiple-time higher-order perturbation analysis of the regularized long-wavelength equation

By considering the long-wavelength limit of the regularized long wave (RLW) equation, we study its multiple-time higher-order evolution equations. As a first result, the equations of the Korteweg-de Vries hierarchy are shown to play a crucial role in providing a secularity-free perturbation theory in the specific case of a solitary-wave solution. Then, as a consequence, we show that the related perturbative series can be summed and gives exactly the solitary-wave solution of the RLW equation. Finally, some comments and considerations are made on the N-soliton solution, as well as on the limitations of applicability of the multiple-scale method in obtaining uniform perturbative series.

Long-wave and short-wave asymptotics in nonlinear dispersive systems

In this paper we study the interplay between short- and long-space scales in the context of conservative dispersive systems. We consider model systems in (1 + 1) dimensions that admit both long- and short-wavelength solutions in the linear regime. A nonlinear analysis of these systems is constructed, making use of multiscale expansions. We show that the equations governing the lowest order involve only short-wave properties and that the long-wave effects to leading order are determined by a secularity elimination procedure. © 1999 The American Physical Society.

S-, P-, and D-wave resonances in positronium-lithium-atom scattering

We investigate ortho-positronium-lithium-atom (Ps-Li) scattering using static-exchange and three-Ps-state coupled-channel calculations. The present three-PS-state scheme, while closely agreeing with the resonance and binding energies in the Ps-H system, predicts S-, P-, and D-wave resonances at 4.25 eV, 4.9 eV, and, 5.25 eV. respectively, in the electronic spin-singlet channel of Ps-Li scattering. The present calculation also yields a Ps-Li binding in this attractive singlet channel with an approximate binding energy of 0.218 eV, which is in adherence with the recent findings of a chemically stable PsLi system using stocastic variational and quantum Monte Carlo calculations. We further report elastic, Ps(2s)-, and Ps(2p)-excitation cross sections at low to medium energies (0.068-30 eV).

Coherent atomic oscillations and resonances between coupled Bose-Einstein condensates with time-dependent trapping potential

The atomic tunneling between two tunnel-coupled Bose-Einstein condensates (BECs) in a double-well time-dependent trap was studied. For the slowly varying trap, synchronization of oscillations of the trap with oscillations of the relative population was predicted. Using the Melnikov approach, the appearance of the chaotic oscillations in the tunneling phenomena between the condensates was confirmed.

Numerical study of the coupled time-dependent Gross-Pitaevskii equation: Application to Bose-Einstein condensation

The Bose-Einstein condensate of several types of trapped bosons at ultralow temperature was described using the coupled time dependent Gross-Pitaevskii equation. Both the stationary and time evolution problems were analyzed using this approach. The ground state stationary wave functions were found to be sharply peaked near the origin for attractive interatomic interaction for larger nonlinearity while for a repulsive interatomic interaction the wave function extends over a larger region of space.

A method for the digital image analysis of ceramic grains based on shape factor segmentation

A very simple and robust method for ceramics grains quantitative image analysis is presented. Based on the use of optimal imaging conditions for reflective light microscopy of bulk samples, a digital image processing routine was developed for shading correction, noise suppressing and contours enhancement. Image analysis was done for grains selected according to their concavities, evaluated by perimeter ratio shape factor, to avoid consider the effects of breakouts and ghost boundaries due to ceramographic preparation limitations. As an example, the method was applied for two ceramics, to compare grain size and morphology distributions. In this case, most of artefacts introduced by ceramographic preparation could be discarded due to the use of perimeter ratio exclusion range.

Electromyographic analysis of the pectoralis major and deltoideus anterior muscles in horizontal flyer exercises with loads

The effective activity of the pectoralis major and deltoideus anterior muscles in horizontal flyer exercises with external loads of 25, 50, 75 and 100% of the maximum load was studied in 11 male volunteers. The electromyographic analysis was done by using MEDI-TRACE-200 surface electrodes connected to a biological signal acquisition mode coupled to a PC/AT computer. The electromyographic signals were processed and the values obtained were normalized through maximum voluntary isometric contraction. It was statistically observed that in all types and loads of this exercise, the muscles presented significant differences in the concentric and eccentric phases. In the concentric phase, when different loads were compared, the muscles were more active with 75 and 100% of the maximum load, while in the eccentric phase, higher activity was observed with 100% of the maximum load. By analyzing each load effect in the concentric phase, it was verified that the muscles on the left side were more active than those on the right side with 25, 75 and 100% of the maximum load.

Modal Analysis of a Beam with a Tip Rotor by Using a Fundamental Response

The shape modes of a damped-free beam model with a tip rotor are determined by using a dynamical basis that is generated by a fundamental spatial free response. This is a non-classical distributed model for the displacements in the transverse directions of the beam which turns out to be coupled through boundary conditions due to rotation. Numerical calculations are performed by using the Ritz-Rayleigh method with several approximating basis.

Modelling study of the impact of deep convection on the utls air composition - Part I: Analysis of ozone precursors

The aim of this work is to study the local impact on the upper troposphere/lower stratosphere air composition of an extreme deep convective system. For this purpose, we performed a simulation of a convective cluster composed of many individual deep convective cells that occurred near Bauru (Brazil). The simulation is performed using the 3-D mesoscale model RAMS coupled on-line with a chemistry model. The comparisons with meteorological measurements show that the model produces meteorological fields generally consistent with the observations. The present paper (part I) is devoted to the analysis of the ozone precursors (CO, NO x and non-methane volatile organic compounds) and HO x in the UTLS. The simulation results show that the distribution of CO with altitude is closely related to the upward convective motions and consecutive outflow at the top of the convective cells leading to a bulge of CO between 7 km altitude and the tropopause (around 17km altitude). The model results for CO are consistent with satellite-borne measurements at 700 hPa. The simulation also indicates enhanced amounts of NO x up to 2 ppbv in the 7-17 km altitude layer mainly produced by the lightning associated with the intense convective activity. For insoluble non-methane volatile organic compounds, the convective activity tends to significantly increase their amount in the 7-17km layer by dynamical effects. During daytime in the presence of lightning NO x, this bulge is largely reduced in the upper part of the layer for reactive species (e.g. isoprene, ethene) because of their reactions with OH that is increased on average during daytime. Lightning NO x also impacts on the oxydizing capacity of the upper troposphere by reducing on average HO x, HO 2, H 2O 2 and organic hydroperoxides. During the simulation time, the impact of convection on the air composition of the lower stratosphere is negligible for all ozone precursors although several of the simulated convective cells nearly reach the tropopause. There is no significant transport from the upper troposphere to the lower stratosphere, the isentropic barrier not being crossed by convection. The impact of the increase of ozone precursors and HO x in the upper troposphere on the ozone budget in the LS is discussed in part II of this series of papers.

Electromyographic analysis of the pectoralis major and deltoideus anterior in the inclined flying exercise with loads

Due to a shortage of textbooks with specific data on muscular activity concerning physical conditioning and sports, we analysed electromyographically the muscles pectoralis major and deltoideus anterior, bilaterally, in inclined flying exercises, during the concentric and eccentric phases, with external loads of 25, 50, 75 and 100% of the maximum load. The electromyographic analysis was performed in eleven male volunteers with MEDITRACE-200 surface electrodes connected to a six-channel biologic signal acquisition module coupled to a PC/AT computer. The electromyographic signals were processed and the obtained effective values were normalized through maximum voluntary isometric contraction. Statistically, the results showed that all the muscles studied presented significant differences between the concentric and the eccentric phases, with higher electromyographic activity during the concentric phase. By analysing the different loads for each muscle in both phases, significant electromyographic activity was observed for all muscles. When the effect of each load on each muscle during the concentric phase was analysed, it was noticed that the muscles on the left were more active than those on the right side, while in the eccentric phase the muscles had different behavior.

Comparative analysis of synchronization algorithms based on PLL, RDFT and Kalman Filter

This paper discusses the main characteristics and presents a comparative analysis of three synchronization algorithms based respectively, on a Phase-Locked Loop, a Kalman Filter and a Discrete Fourier Transform. It will be described the single and three-phase models of the first two methods and the single-phase model of the third one. Details on how to modify the filtering properties or dynamic response of each algorithm will be discussed in terms of their design parameters. In order to compare the different algorithms, these parameters will be set for maximum filter capability. Then, the dynamic response, during input amplitude and frequency deviations will be observed, as well as during the initialization procedure. So, advantages and disadvantages of all considered algorithms will be discussed. ©2007 IEEE.

Power losses analysis and cooling system design of three topologies of multilevel inverters

This paper presents the comparison of three topologies of multilevel inverters applied to drive an induction motor of 500 kVA/4.16 kV. The multilevel inverters analyzed are: a neutral point clamped inverter, a symmetrical cascaded multilevel inverter and a hybrid asymmetrical cascaded multilevel inverter. The performance indexes used in the comparison are total harmonic distortion, first order distortion factor, semiconductors power losses distribution and heat-sink volume. The comparison is developed with the purpose of finding the efficiency and the heat-sink volume where the three systems present the same output filter. ©2008 IEEE.

A comparative analysis of FBD, PQ and CPT current decompositions - Part II: Three-phase four-wire systems

This paper investigates the major similarities and discrepancies among three important current decompositions proposed for the interpretation of unbalanced and/or non linear three-phase four-wire power circuits. The considered approaches were the so-called FBD Theory, the pq-Theory and the CPT. Although the methods are based on different concepts, the results obtained under ideal conditions (sinusoidal and balanced signals) are very similar. The main differences appear in the presence of unbalanced and non linear load conditions. It will be demonstrated and discussed how the choice of the voltage referential and the return conductor impedance can influence in the resulting current components, as well as, the way of interpreting a power circuit with return conductor. Under linear unbalanced conditions, both FBD and pq-Theory suggest that the some current components contain a third-order harmonic. Besides, neither pq-Theory nor FBD method are able to provide accurate information for reactive current under unbalanced and distorted conditions, what can be done by means of the CPT. © 2009 IEEE.

Integrated analysis of halogenated organic pollutants in sub-millilitre volumes of venous and umbilical cord blood sera

A rapid, robust and economical method for the analysis of persistent halogenated organic compounds in small volumes of human serum and umbilical cord blood is described. The pollutants studied cover a broad range of molecules of contemporary epidemiological and legislative concern, including polychlorobiphenyls (PCBs), polychlorobenzenes (CBs), hexachlorocyclohexanes (HCHs), DDTs, polychlorostyrenes (PCSs) and polybromodiphenyl ethers (PBDEs). Extraction and clean-up with n-hexane and concentrated sulphuric acid was followed with analysis by gas chromatography coupled to electron capture (GC-ECD) and GC coupled to negative ion chemical ionisation mass spectrometry (GC-NICI-MS). The advantages of this method rest in the broad range of analytes and its simplicity and robustness, while the use of concentrated sulphuric acid extraction/clean-up destroys viruses that may be present in the samples. Small volumes of reference serum between 50 and 1000 μL were extracted and the limits of detection/quantification and repeatability were determined. Recoveries of spiked compounds for the extraction of small volumes (≥300 μL) of the spiked reference serum were between 90% and 120%. The coefficients of variation of repeatability ranged from 0.1-14%, depending on the compound. Samples of 4-year-old serum and umbilical cord blood (n = 73 and 40, respectively) from a population inhabiting a village near a chloro-alkali plant were screened for the above-mentioned halogenated pollutants using this method and the results are briefly described. © 2010 Springer-Verlag.