On the coupling in molecular motions: A novel molecular micro-structure approach to the physical meaning of the Ngai's coupling parameter

Summary The dielectric behaviour through DETA system has been studied for six PVC samples of distinct molecular microstructure in terms of content and associated surroundings and conformation of the local configurations mmr termini of isotactic sequences. Both the dielectric studies and the microstructure of the samples, as obtained by stereospecific substitution reaction of an additive-free commercial PVC are to be published in detail separately. For purposes of clarity some of the results are mentioned in Experimental section. The phenomenological correlation between the β parameter as defined by Ngai's theory and the microstructure of the samples, quantities both issued from the above quoted work, is considered in the present paper with the objective of providing some novel ideas on the physical meaning, at molecular level, of the Ngai's coupling parameter, in the light of mobility constraints and local free volume associated with mmr structure at its likely conformations. Received: 16 March 2001/Revised version: 18 June 2001/Accepted: 24 July 2001     

Finite element simulation to design constructive elements: An application to light gypsum plaster for partitions

In the past decade finite element simulation has become a very useful methodological tool in the different science fields. This article offers a specific application of this powerful mechanism used for analyzing the mechanical behaviour of constructive elements in the design phase, prior to the laboratory tests’ stage. The aim of applying this simulation is to minimize the high cost the real scale fabrication of these elements entails.This research focuses on the analysis by finite element simulations (FES) of several construction elements used as interior partitions and made of plaster lightened with cork. The results of the study will allow us to determine the most suitable thickness values and proportions to ensure that the requirements stated by the standards and norms for light partitions are fulfilled. These parameters will later be useful for the final laboratory tests.Two simulation groups have been developed using the ANSYS application: firstly, a partition leaf of 200 × 260 cm is studied exposing it to a superficial load and to an eccentric load following the EUAtc common directives for the technical appreciation of light panels, 1973). Second, the behaviour of a panel with a through opening is tested with the simulation regarding the different hypothesis of the structure deformation supporting and surrounding it.Finally, it is proved that the element of thickness 7 cm and proportions stated at the beginning ensure a good performance regarding strain without producing any visible fissures, and therefore are suitable for a further laboratory test on real models.     

Interpretation and generation incremental management in natural interaction systems

Human interaction develops as an exchange of contributions between participants. The construction of a contribution is not an activity unilaterally created by the participant who produces it, but rather it constitutes a combined activity between the producer and the rest of the participants who take part in the interaction, by means of simultaneous feedback. This paper presents an incremental approach (without losing sight of how turns are produced throughout time), in which the interpretation of contributions is done as they take place, and the final generated contributions are the result of constant rectifications, reformulations and cancellations of the initially formulated contributions. The Continuity Manager and the Processes Coordinator components are proposed. The integration of these components in natural interaction systems allow for a joint approach to these problems. Both have been implemented and evaluated in a real framework called LaBDA-Interactor System which has been applied to the “dictation domain”. We found that the degree of naturalness of this turn-taking approach is very close to the human one and it significantly improves the interaction cycle.     

A non-parametric method for estimating enthalpy-temperature functions of shape-stabilized phase change materials

A method for thermodynamic characterization of shape-stabilized phase change materials (PCM) based on one-single sample and one-single experiment has been proposed. The simplicity of the experimental device is comparable to that of the T-History method. However, instead of simple energy balances as in T-History method, a numerical heat transfer model is used to retrieve the whole set of parameters/functions characterizing the PCM from temperature measurements at one-single point within the PCM. An efficient inversion technique has been proposed for that. Its most striking feature is that it allows non-parametric identification of the enthalpy-temperature function in an easy way. Such a function is retrieved by solving a problem of nonhomogeneous heat source term estimation by inversion of a linear heat conduction model.     

New-type insulating sandwich panels

Many existing insulation panels employing foamed plastics raise questions about fire risk. The French National Coal Board has therefore been trying a new approach, using phenolic resins with aggregate from expanded shale, which is plentiful and cheap, to make sandwich panels with good fire resistance. Results so far are promising, but some technical and production problems remain, as described here by a research officer at the Board's research laboratories at Verneuil-en-Halette.     

Influence of Zn2+ doping on the morphotropic phase boundary in lead-free piezoelectric (1 – x)Na1/2Bi1/2TiO3-xBaTiO3

A series of morphotropic phase boundary (MPB) compositions of (1–x)Na_1/2Bi_1/2TiO₃-xBaTiO₃ (x = 0.05, 0.055, 0.06, 0.065, 0.07), with and without 0.5 mol% Zn-doping was synthesized using the solid-state route. The samples were characterized using X-ray diffraction, dielectric analysis, and electromechanical measurements (piezoelectric d₃₃ coefficient, coupling factor k_p, mechanical quality factor Q_m, and internal bias field E_bias). The increase in the ferroelectric-relaxor transition temperature upon Zn-doping was accompanied by a shift of the MPB toward the Na_1/2Bi_1/2TiO₃-rich side of the phase diagram. Higher tetragonal phase fraction and increased tetragonal distortion were noted for Zn-doped (1 – x)Na_1/2Bi_1/2TiO₃-xBaTiO₃. In addition, ferroelectric hardening and the presence of an internal bias field (E_bias) were observed for all doped compositions. The piezoelectric constant d₃₃ and the coupling coefficient k_p decreased by up to ∼30%, while a 4- to 6-fold increase in Q_m was observed for the doped compositions. Apart from establishing a structure–property correlation, these results highlight the chemically induced shift of the phase diagram upon doping, which is a crucial factor in material selection for optimal performance and commercialization.