The noise and mode-locking phenomena of a hybrid soliton pulse source (HSPS) utilizing different fiber Bragg gratings (FBG) with or without linear chirp are described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise, and relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that transform-limited pulses over a wide tuning range around the fundamental mode-locking frequency are generated from mode-locked HSPS with linearly chirped uniform and Gaussian apodized FBGs. Mode-locked pulses that are not transform-limited are generated over a wide tuning range from HSPS with Gaussian apodized and uniform FBGs. These gratings can give transform-limited pulses only over a limited tuning range around the fundamental mode-locking frequency. It is also found that RIN reduction is possible for the mode-locked HSPS by selecting a suitable apodization function such as Gaussian and linear chirp rate.

This work describes the application of the Lattice Fringe Spacing Measurement (LFSM) method to the study of complex multiquantum well heterostructures containing both low-misfit and strain compensated short period superlattices in barriers and wells, respectively. 90°-wedge cross-sectional samples have been used. The adequate choice of both experimental conditions and digitized sampling allows the whole heterostructure to be visualized and studied in a single High Resolution Transmission Electron Microscopy (HRTEM) image. Sample preparation and image processing technique are simple and inexpensive, resulting a fast procedure particularly suited for the analysis of large areas. By this way, in a single HRTEM image we have measured, in the growth direction, the lattice spacings at either side of the multiple grown interfaces as well as the period variations of both types of superlattices; in addition, we have measure on the same image the lattice strain in a direction perpendicular to the growth direction by using the LFSM and the Cumulative Sum methods. We have observed local lateral variations within the wells, with regions tensile or compressively strained, while a vestige of the grown SL remains, indicating the occurrence of a strain induced lateral composition modulation process spontaneously produced during the growth of strain compensated short-period superlattices. This is further confirmed in cross-section prepared by the tripod mechanical polisher method.

Calculated values of viscosity, thermal conductivity, electrical conductivity, density and specific enthalpy of plasma formed in five different insulators vapours (PE, POM, PMMA, PC and PA66) are presented. The calculations, which assume local thermodynamic equilibrium, are performed for three pressures (1 atm, 10 atm, 100 atm) in the temperature range from 5000 to 30000 K. The results for PE, PMMA and PA66 are compared with those of other authors at atmospheric pressure. Significant discrepancies are found; these are attributed both to differences in the collision integrals and to the formulation used in calculating the transport coefficients. We give all the data for the potential interaction and the formulation necessary to obtain reliable values of transport coefficients.

A new fast method is used to analyze positron annihilation lifetime spectra. The regularization procedure to solve the inverse problem of finding parameters of useful signals present in the data is formulated. A new approach to determine the number of components in a spectrum is proposed. Results on simulated spectra demonstrate the high resolution capability of the method.

We propose a new method of molecular microwave spectroscopy together with analysis ofresonance line shapes, based on the fast passage effect. The fast passage effect isthe excitation of coherent spontaneous radiation of tested molecules using a fastfrequency sweep over the absorption line. We show that the line shape can bereconstructed from the received detector signal with the use of Hilbert and Fouriertransformations. We find that sensitivity of a fast passage spectrometer is higherthan that of an ordinary pulsed Fourier-transform spectrometer. The proposed method isa useful tool for fast analysis of gas mixtures.

A new indirect method of determining the rheological behavior of a non-Newtonian fluid, modeled by a two parameter power law, flowing in a tube with a geometrical singularity is proposed which makes it possible to indirectly estimate the rheology. Due to this singularity, the shape of the velocity profiles can be strongly dependent on the fluid rheology, which makes it possible to obtain indirectly the required viscosity estimation. Non-Newtonian fluid flows were simulated numerically with various flow conditions. Based on the results of these calculations, plots were drawn emphasizing the dependence of the dimensionless velocity on the dimensionless rheological parameters. On the other hand, dimensionless velocities were also obtained by measuring velocity profiles with an ultrasonic Doppler velocimeter. These experimental values were put on the plots and the rheological parameters of the actual fluid were thus determined. Comparisons were made with viscometer measurements in order to assess the accuracy of the method and its range of validity. This method is of great potential interest for application to industrial processes when it is necessary to know the viscosity of a fluid undergoing a transformation without interrupting the process by taking fluid samples.