Photonic access concentrator for ATM gigabit switching fabrics

In future broadband communication networks the interest for purely photonic switches is due to the bandwidth mismatch between optical transmission networks and electronic switching nodes. Photonic ATM switching fabrics mainly based on wavelength-switching stages are therefore being studied, to implement high capacity switches with also concentration, multiplexing and demultiplexing functions, using state-of-the-art photonic technology. The architecture of an ATM photonic access concentrator is described in this paper, illustrating the design and implementation of its basic subsystems, the traffic concentrator and the cell multiplexer. The design guidelines are outlined in detail referring to an example, where 128 user lines at 622 Mb/s are given access to 4 outlets at 2.488 Gb/s. The corresponding implementation, based on the systematic use of cell wavelength encoding, makes use either of well-known photonic components, such as Fabry-Perot filters, fiber delay lines, splitters and combiners, either of recently developed devices, like high-speed optical gates and tunable filters and lasers. Finally, the system feasibility is demonstrated presenting the results obtained on a reduced size and speed experimental setup of the cell multiplexer     

Vitamin C Spray Drying: Study of the Thermal Constraint

Temperature variation in the spray drying method has no effect on the ascorbic acid molecule. No chemical interaction between the colloidal silica and the ascorbic acid could be determined, but a physicochemical interaction “absorption” was determined. Colloidal silica improved the final yield of spray drying in proportion to its concentration. No polymorphic forms could be determined in the spray-dried ascorbic acid. Drug release from the ascorbic acid spray dried was found to be dependent on the Aerosil content: highest release rates were obtained with Aerosil.     

Differences between organic and schizophrenic groups on the Halstead-Reitan battery: A reply to Watson.

Questions C. G. Watson's (see PA, Vol 52:Issue 3) attempt to explain apparent inconsistencies in findings between his and the present authors' studies in terms of sample differences. Despite Watson's reanalysis of his data by matched pairs, he fails adequately to control for differences in chronicity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling of bone conduction of sound in the human head using hp-finite elements: Code design and verification

We focus on the development of a reliable numerical model for investigating the bone-conduction of sound in the human head. The main challenge of the problem is the lack of fundamental knowledge regarding the transmission of acoustic energy through non-airborne pathways to the cochlea. A fully coupled model based on the acoustic/elastic interaction problem with a detailed resolution of the cochlea region and its interface with the skull and the air pathways, should provide an insight into this fundamental, long standing research problem. To this aim we have developed a 3D hp-finite element code that supports elements of all shapes (tetrahedra, prisms and pyramids) to better capture the geometrical features of the head. We have tested the code on a multilayered sphere and employed it to solve an idealized model of head. In the future we hope to attack a model with a more realistic geometry.     

10-Gb/s transmission of NRZ over 10000 km and solitons over 13500 km error-free in the same dispersion-managed system

A dispersion management scheme that is capable of supporting both dispersion-managed solitons and nonreturn-to-zero (NRZ) data formats as well as intermediate formats is demonstrated for error-free long-haul transmission at 10 Gb/s in excess of 9500 km. This experimental tool ran be used to directly compare the different data formats. Our results suggest that a format between standard solitons and standard NRZ, such as dispersion-managed solitons or phase-modulated NRZ, may have significant advantages.     

Non-uniform wavelets in electromagnetic scattering analysis

Non-uniform wavelets are constructed to benefit from both adaptively refined grids for modelling edge singularities and compression of moment matrices with wavelet bases. They are applied to the analysis of electromagnetic scattering problems     

Prediction and Measurement of Electron Density and Collision Frequency in a Weakly Ionised Pine Fire

Pine litter flame is a weakly ionised medium. Electron-neutral collisions are a dominant form of particle interaction in the flame. Assuming flame electrons to be in thermal equilibrium with neutrals and average electron-neutral collision frequency to be much higher than the plasma frequency, the propagation of microwaves through the flame is predicted to suffer signal intensity loss. A controlled fire burner was constructed where various natural vegetation species could be used as fuel. The burner was equipped with thermocouples and used as a cavity for microwaves with a laboratory quality network analyzer to measure wave attenuation. Electron density and collision frequency were then calculated from the measured attenuation. The parameters are important for numerical prediction of electromagnetic wave propagation in wildfire environments. A controlled pine litter fire with a maximum flame temperature of 1080 K was set in the burner and microwaves (8–10.5 GHz) were caused to propagate through the flame. A microwave signal loss of 1.6–5.8 dB was measured within the frequency range. Based on the measured attenuation, electron density and electron-neutral collision frequency in pine fire were calculated to range from 0.51–1.35?×?10¹⁶ m^?3 and 3.43–5.97?×?10¹⁰ s^?1 respectively.