PEM single fuel cell as a dedicated power source for high-inductive superconducting coils

In practice, the voltage of a hydrogen–oxygen fuel cell is around 1 V at open circuit and from 0.6 V to 0.7 V at full rated load and it can be considered as a low-voltage energy source. Moreover, preliminary investigations undertaken on a single proton exchange membrane fuel cell (PEMFC) highlighted its behavior as a DC current source, that can be directly controlled by the H₂ flow rate when the operating point is at very low voltage. In this paper, we present an innovative application of PEMFC that relies on taking advantage of both low voltage level and current source operating mode to feed a high inductive superconducting coil. Such a coil has no resistance and among others, is very sensitive to current ripples. Thus, specific power supplies are designed to feed them but they exhibit in most cases a huge volume and/or a low energy yield. Connecting a superconducting coil to a PEMFC implies to operate in short-circuit, which is an unusual use of PEMFC. To this end, requirements of such an application are defined, by making use of a PEMFC electrical model based on a 1D analog representation of mass transport phenomena. This model, that enables to take into account the influence of gas supply conditions, notably diffusion limit operation, is directly implemented in a standard simulation software used in electrical engineering. Then, simulation results and experimental results obtained by supplying a 10 H superconducting coil cooled by liquid helium by means of a single 100 cm² PEMFC are compared and discussed.     

Slowness and the preceding preparatory interval effect in schizophrenia.

Measured the reaction times (RTs) of 25 schizophrenic (SCZ), 69 matched normal, and 14 bipolar Ss to a tone preceded by a preparatory interval (PI) of varying length. RTs increase when the PI for the immediately preceding trial (PPI) is longer than the PI for the current trial. Several studies have shown that this PPI effect is heightened in schizophrenia. The authors replicated this finding. However, they found that the size of the PPI effect within groups increased with overall slowness and that the least squares regression line relating the PPI effect difference score to overall slowness did not differ between groups, nor did SCZ Ss' regression line differ from that of normal Ss. Group differences on the PPI effect were also analyzed by taking residuals for members of all groups from the normal Ss' regression line of the PPI effect difference score on overall slowness. Groups did not differ on these residuals, nor did SCZ Ss differ from normal Ss. The authors conclude that the heightening of the PPI effect in schizophrenia is like that observed in equally slow normal Ss. This finding suggests that the PPI effect does not appear to be a promising marker of a distinctive SCZ pathology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Precision metrology for studying thin films and surfaces

Evaluation techniques that are appropriate for characterizing the surface topography of optical thin films and surfaces are briefly described. These include microscopes ranging from low power optical microscopes to scanning probe microscopes that can measure topography of individual atoms or groups of atoms, optical non-contact and mechanical contact profilers, some of which can give topographic maps of surface areas, and total integrated scattering and angle-resolved scattering that yield statistical properties of surfaces. Theories are needed to relate scattering to surface topography; these are valid only for certain types of topographies. Examples are given showing how various surface evaluation techniques can be applied to selected surfaces.     

Approche stochastique de l’analyse de la propagation des erreurs d’arrondi et de données dans les algorithmes numériques

Any result of algorithms provided by a computer always contains an error resulting from floating-point arithmetic round-off error propagation. Furthermore signal processing algorithms are also generally performed with data containing errors. The permutationperturbation method, also known under the name CESTAC (contrôle et estimation stochastique d’arrondi de calcul) is a very efficient practical method for evaluating these errors and consequently for estimating the exact significant decimal figures of any result of algorithms performed on a computer. The stochastic approach of this method, its probabilistic proof, and the perfect agreement between the theoretical and practical aspects are described in this paper.     

Use of analogies in therapeutic situations: An analogue study.

141 participants read vignettes that described stressors encountered by college students. Each vignettes also included information about the students' hobby and therapeutic advice the students might follow to deal with their stressors. This advice was expressed in either a literal or an analogical form. Ss were asked to read the vignettes from the perspective of a therapist, a patient, or an observer, and to rate the advice component of each vignette for helpfulness. Analogical advice was rated as significantly more helpful than literal advice on a variety of questions. A surprise cued-recall memory test showed that Ss in the analogical condition but not in the literal condition remembered information according to their assigned role. In the role of patients, Ss showed greatest recall for the therapeutic advice, but in the role of therapists, they showed greatest recall for the students' stressors. In line with a growing literature in cognitive psychology, these results show that the impact of analogies in therapeutic interactions is a combined is a combined function of the material to be processed and the role of the person processing it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A coherent approach to stationary stimulated Brillouin fiber amplifiers

An analytical stationary solution is proposed for the collinear Brillouin fiber mirror in the frame of the 1-D-coherent 3-wave model, in which decoupled phases allow side-resonance interaction, the conservation of the impulsion being insured by a nonlinear phase gradient. The Lorentzian shape of the gain curve of low efficiency stationary SBS amplifiers is then justified, even when the interaction is strong enough to stimulate an acoustic wave with a narrow spectral width. It is shown that, when SBS efficiency increases, the gain curve first exhibits some gain narrowing, then saturates, yielding for high pump powers a spectral band larger than the spontaneous Brillouin bandwidth.