Identification of temperature profile and heat transfer on a dielectric membrane for gas sensors by `COSMOS' program simulation

The application of commercial 3-D software `COSMOS' for the design and thermal analysis of the low power consumption test structures with dielectric membrane for gas microsensors is presented. Within this work, the simulation provides the estimation of the temperature profile on the active area and the whole membrane including the four bridges and the heating efficiency in the temperature range 20-500 °C. Unravelling of the heat loss mechanisms in terms of radiation, convection, conduction by air and solid materials during heat transfer on the dielectric membrane is reported for the first time as a mean to evaluate by 3-D simulation the contribution of technological processes and lay-out design to the total heat losses

Attention allocation in a language with post-focal prominences

Accentuation influences selective attention and the depth of semantic processing during online speech comprehension. We investigated the processing of semantically congruent and incongruent words in a language that presents cues to prosodic prominences in the region of the utterance occurring after the focussed information (the post-focal region). This language is Italian, in particular the variety spoken in Bari. In this variety, questions have a compressed, post-focal accent, whereas in statements there is a low-level pitch in this position. Using event-related potentials, we investigated the processing of congruent and incongruent target words with two prosodic realizations (focussed with accentuation, post-focal realization) and in two-sentence modalities (statement, question). Results indicate an N400 congruence effect that was modulated by position (focal, post-focal) and modality (statement, question): processing was deeper for questions in narrow focus than in post-focal position, while statements showed similar pronounced N400 effects across positions. The attenuated N400 difference for post-focal targets in questions was accompanied by a more enhanced late positivity when they were incongruent, indicating that attentional resources are allocated during updating of speech act information

The 2003 eclipse of EE Cep is coming. A review of past eclipses

EE Cep is an eclipsing binary with a period of 5.6 years. The next eclipse will occur soon, in May-June 2003, and all available past eclipses were collected and briefly analysed. EE Cep shows very large changes of the shape and the depth of minima during different eclipses, however it is possible to single out some persistent features. The analysis suggests that the eclipsing body should be a long object surrounded by an extended semi-transparent envelope. As an explanation, a model of a precessing optically thick disc, inclined to the plane of the binary orbit, is invoked. The changes of its spatial orientation, which is defined by the inclination of the disc and the tilt, induced most probably by precession of the disc spin axis with a period of about 50 years, produce strange photometric behaviour of this star. The H_alpha emission, and possibly the NaI absorptions, show significant changes during several months outside of the eclipse phase.Comment: 7 pages, 7 figures, LaTeX2e, accepted by A&

Variational Principles for Water Waves

We describe the Hamiltonian structures, including the Poisson brackets and Hamiltonians, for free boundary problems for incompressible fluid flows with vorticity. The Hamiltonian structure is used to obtain variational principles for stationary gravity waves both for irrotational flows as well as flows with vorticity.Comment: 20 page

Thermal modelling of a porous silicon-based pellistor-type catalytic flammable gas sensor with two supporting beams

A three-dimensional transient thermal mathematical model of a porous silicon based pellistor with two supporting beams was developed. The model was numerically solved using the implicit alternating-direction finite difference method. A computer program written in ANSI C and run on a VAX/VMS computer was utilized to study the influence of the power consumption and the main geometrical dimensions (membrane, beam and heater size) of the pellistor mentioned above on its transient and steady-state thermal behaviour. It was found that considerable improvement in the thermal behaviour of the pellistor could be achieved by reducing the membrane size (length and width). The optimal beam length was determined as 100 μm. By comparing the main sources of energy dissipation it was found that energy was lost predominantly through the heat conduction into the supporting beams

High Dielectric Permittivity in AFe1/2_{1 / 2}B1/2_{1 / 2}O3_{3} Nonferroelectric Perovskite Ceramics (A - Ba, Sr, Ca; B - Nb, Ta, Sb)

AFe$_{1 / 2}$B$_{1 / 2}$O$_{3}$(A- Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were synthesized and temperature dependencies of the dielectric permittivity were measured at different frequencies. The experimental data obtained show very high values of the dielectric permittivity in a wide temperature interval that is inherent to so-called high-k materials. The analyses of these data establish a Maxwell-Wagner mechanism as a main source for the phenomenon observed.Comment: 6 pages, 7 figure