Performance simulation of an absorption heat transformer operating with partially miscible mixtures

This paper proposes to study the thermodynamics performances of a new absorption heat-transformer cycle, where the separation step is obtained by the cooling and settling of a partially miscible mixture at low temperature. This new cycle has been called an absorption-demixing heat transformer (ADHT) cycle. A numerical simulation code has been written, and has allowed us to evaluate the temperature lift and thermal yield of 2 working pairs. Both high qualitative and quantitative performances have been obtained, so demonstrating the feasibility and industrial interest for such a cycle. Moreover a comparison of the simulation results with performances really obtained on an experimental ADHT has confirmed the pertinence of the simulation code.     

IAda: A language for robot programming based on Ada

We present a programming language for robots which we have implemented based on the Ada language. It is an interpreted language which permits dynamic configuration of software. It manipulates Ada tasks and subroutines. One of the Ada tasks is an inference engine of a logic programming language adapted to real-time constraints. We show how the conjunction of Ada tasks, to perform perception and action functions on the robot, to logic programs, for the control of these tasks, both manipulated by the IAda language, gives a powerful environment for robot programming.     

Protection contre les erreurs en enregistrement magnétique numérique de télévision

In this paper the authors present the main problem of operating video tape recorders for television production, viz. picture degradations through multiple generations, which could be cancelled by using digital machines. Efficient error protection is mandatory. Burst error statistics are given as collected on a laboratory digital recorder as well as a physical interpretation. Different protection methods are used for luminance and colour differences, which results in sharing the available redundancy between two distinct coding systems. Adequate codes are selected through the use of two bounds stated as theorems. The main parameters of a possible system are presented. They are likely to be improved when further information is available to make an operating system practical.     

Une exploration de nouveaux équilibres du marché des télécommunications

The economy of telecommunications is presently characterized by differentiation of services. This paper explores this differentiation in different institutionnal situations starting from very simple but realistic assumptions. It is established that the most efficient situation should associate a technical monopoly of the network with a competitive supply of services.     

Crystallization and Properties of a Si-Y-Al-O-N Glass-Ceramic

Glasses have been prepared in the Si -Y-Al O-N system by melting mixtures of silica, alumina, yttria, and silicon nitride. One particular glass containing 17 equiv% N has been investigated to Observe the crystallization at temperatures in the range 1050^o-1300^oC. The major crystalline phase observed is Y₂Si₂O₇, existing as the α form below 1200^oC and the β form above this temperature. Properties of the glass-ceramic, including thermal expansion coefficient, hardness, electrical resistivity, and creep have been assessed.     

Permeation and Sorption of Water and Gases Through EVA Copolymers Films

The transport of water and gases (pure oxygen and carbon dioxide) through poly(ethylene-co-vinyl acetate) (EVA) films of different VA contents and through a low density polyethylene LDPE (used as reference with 0 wt.% VA), was analysed by permeation and sorption measurements. In the case of water, for EVA of 70 wt.% VA, a plasticization effect on the material was observed. For EVA of 19 wt.% VA, there was no plasticization, while for EVA of 4.5 wt.% VA and for LDPE, the water diffusion coefficient decreases with increasing water. An empirical law was then found to account for the reduction of the water diffusivity. A negative plasticization effect was attributed to the formation of water clusters in these rather non polar polymers. This latter result was confirmed by sorption measurements and infra-red spectroscopy. The increase in water sorption extent with the VA content leads to a steady increase in the water permeability in the EVA copolymers. In the case of gas permeation, both for O₂ and CO₂ and whatever the VA content of the copolymer used, the experimental curves are characterized by a constant diffusion coefficient. This is confirmed by sorption experiments. In terms of gas permeability, EVA copolymers are characterized by low coefficients especially for oxygen. In the EVA rubbery copolymers, The O₂ solubility coefficient does not increase with the VA content due to the lack of polar interactions, while the CO₂ one increases due to the overall interactions between CO₂ induced dipoles and the polar the VA carbonyl groups. For these copolymers, the H₂O/CO₂ and H₂O/O₂ selectivities are very high. The experimental values of the selectivities indicate that these EVA copolymers appear as good candidates for applications using high perm-selectivity properties. Electronic Publication     

Abstracts of invited papers

Abstracts of invited papers