[Show abstract][Hide abstract] ABSTRACT: Polyelectrolyte membrane used in proton exchange membrane fuel cell (PEMFC) should act as a barrier to hydrogen and electrons. In the present work, fast and robust specific tools were developed both to characterize these properties and localize defects, such as pinholes or short-circuits, within the membrane electrode assembly (MEA). The identification of defective cells without disassembling the Axane's stack was performed in a single step through a passive electrical technique so-called “relaxometry” and by internal gas leak measurements. The flaws were further tracked inside MEA using Infrared Thermography in order to obtain their precise location. The latter, performed after stack disassembly, permitted to reveal the defects responsible for the Fuel Cell shutdown. A third step dealt with SEM examinations of the flaws in order to identify the origin and nature of the membrane failure.
[Show abstract][Hide abstract] ABSTRACT: The Belgian Society for Medical Informatics (MIM) organized a survey in 1986 in order to assess the present state of development of medical informatics in Belgium. Questionnaires were sent to hospitals, laboratories, private practitioners and pharmacists, as well as to social security organizations and software industries. The response rate was higher in hospitals (93%) than in any other category. Results showed a large number of computerized hospitals (93% of general acute care hospitals and 91% of psychiatric hospitals). There has been a sharp increase (+ 15%) in computerization of the admission, accounting and billing procedures since 1985, most likely in relation with administrative rules issued by the Belgian Government. The same trend (+ 20%) has been observed for computer applications in clinical laboratories, between 1984 and 1985. There is almost one computer terminal for ten beds in the hospitals with more than 200 beds in 1986. This figure exemplifies the present trend to on-line access to data. Computerized instrumental aids to medicine such as text processing, imaging or computerized interpretation of signals have known a rapid extension during recent years, although less comprehensive than administrative applications in hospitals and in social security organizations. The present state of other applications in medicine (general practice, pharmacy, etc.) was more difficult to assess as those information systems remain more pinpointed. In all medical fields, there appears to be a new rise in computer programs offered by software companies.
Medical informatics = Médecine et informatique 07/2009; 12(4):249-62. DOI:10.3109/14639238709010063
[Show abstract][Hide abstract] ABSTRACT: The main thrust of the HAPEX-MOBILHY experiment was towards investigating techniques involved in integrating the turbulent surface fluxes measured at local sites to a larger scale approaching that used in general circulation models.Some aspects of the field data collected at various times and spatial scales are presented. Annual cycle of the soil moisture at many sites is discussed in relation with outputs of a large scale hydrological model. At shorter time scales, the spatial variability of surface energy partition is examined with regard to spatial contrasts in albedo, surface roughness and plant properties related to the two main vegetation classes found in the HAPEX square: A pine forest and the nearby agricultural area.Finally, examples of daily spatial integration with an atmospheric mesoscale model including a comprehensive treatment of land surface processes are presented.
Surveys in Geophysics 01/1991; 12(1):31-61. DOI:10.1007/BF01903411 · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effect of forests on local meteorological circulations is discussed with particular regard to the consequence of their lower albedo, enhanced roughness and larger minimal stomatal resistance when compared with agricultural crops. The effect of these is determined by numerical simulation using two different mesoscale atmospheric models. Emphasis is given to the surface energy budget because this is the driving mechanism behind atmospheric circulation at the mesoscale. Experimental measurements taken during the "HAPEX-MOBILHY' programme are shown to be consistent with the conclusions drawn from this numerical simulation. -Authors
Philosophical Transactions of The Royal Society B Biological Sciences 08/1989; 324(1223). DOI:10.1098/rstb.1989.0055 · 7.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The possibility of forecasting seeing quality from routine
meteorological data used as input to a numerical model of the boundary
layer is discussed after demonstrating examples of reasonably good
agreement between observed and calculated seeing on three nights when
observed image diameter did not exceed 2 arc sec. Under poor seeing
conditions (5 arc sec) agreement was not achieved. The comparisons were
made between optical measurements by the Anglo-Australian Observatory
and calculations based on temperature soundings from an aircraft and an
empirical relationship for estimating dome seeing effects. It is argued
that even limited seeing forecasts would assist in optimizing the
observing schedules of highly utilized telescopes. A numerical model
appears useful to predict C2(N) profiles of the atmosphere but cannot
handle dome seeing effects, which often constitute a significant
contribution to overall image quality.
Publications of the Astronomical Society of the Pacific 02/1986; 98:376-387. DOI:10.1086/131769 · 3.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The parameterization of pressure effects on triple correlations is shown
to be an important part of the closure problem. Based on arguments
relevant to homogeneous and isotropic turbulence, it is argued that
pressure effects are not only of a relaxative nature. In the case of
turbulent thermal convection, a parameterization scheme including
nonlinear and rapid effects is proposed and used within the framework of
a third-order model. Comparison with experimental results by Ferreira
(1978) indicates that the rapid part of pressure effects represents an
important contribution to the budget of triple correlations and that it
prevents the development of spurious stable stratification in the
interior of the convective layer.
[Show abstract][Hide abstract] ABSTRACT: A high-order model is proposed for the study of the 24 h evolution of clear planetary boundary layers. The model includes the rate equations of correlations up to the third order, as required for an accurate description of daytime convective phenomena, but it also takes into account interactions between radiative transfer and turbulence in order to achieve a physically reasonable description of the nocturnal structure of the boundary layer. This numerical model is tested against the Wangara boundary layer data of Day 33 and Night 33-34 (Clarke et al., 197l). The computed daytime mean structure of the boundary layer compares favorably with the Wangara data, while the daytime turbulent structure, expressed in the framework of the convective similarity theory, is in particularly good quantitative agreement with a number of experimental and numerical data concerning convection in the boundary layer, with particular concern to the production of turbulence at the top of the mixed layer. The computed nocturnal mean structure is shown to be driven principally by radiative transfer and the mesoscale pressure gradient. It agrees with the observed nocturnal structure with the exception that the height of the turbulent surface layer is underestimated in the model, but it is shown that this height is very sensitive to the imposed boundary conditions. The computed nocturnal turbulent structure is explained on a qualitative basis by the interactions between shear generation of turbulence, thermal stratification and radiative phenomena. It is also shown that generation and vertical propagation of nocturnal turbulence, which are of primary interest for environmental purposes, are strongly influenced by turbulence and radiative transfer interactions.
Journal of the Atmospheric Sciences 10/1978; 35(10):1861-1883. DOI:10.1175/1520-0469(1978)035<1861:MTHEOT>2.0.CO;2 · 3.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new treatment of third order moments is proposed for the study of inhomogeneous turbulence: the equations for the rate of change of third order correlations should be used in conjunction with the quasi-normal approximation and with the enforcement of some generalized Schwarz inequalities ('clipping' mechanism) relating third and second order moments, the clipping mechanism being intended to preserve realizability. Together with rather classical formulations for pressure and dissipative terms, this approximation is used for numerical modeling of a penetrative convection experiment and of an asymmetric channel flow experiment.
[Show abstract][Hide abstract] ABSTRACT: The quasi-normal theory modified by the clipping approximation is used
to construct a numerical model of vertically inhomogeneous turbulence in
a Boussinesq fluid. The pressure-correlation terms are expressed
according to recently proposed formulations. With the aid of the
horizontal homogeneity assumption the model is applied to the
description of a laboratory experiment on penetrative convection and the
numerical results are compared to the experimental data. It is found
that the model does reproduce the measured vertical variations of mean
temperature, turbulent beat flux, eddy kinetic energy and temperature
variance, as well as a third-order correlation such as the vertical flux
of eddy kinetic energy. The stationarity of the vertical profiles of
various turbulent quantities, when scaled by the convective velocity and
temperature, is also verified.
Journal of the Atmospheric Sciences 02/1976; 33(3):482-491. DOI:10.1175/1520-0469(1976)033<0482:TAFIFP>2.0.CO;2 · 3.14 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A modification of the quasi-normal theory is proposed for the study of
inhomogeneous turbulent flows. In this approximation realizability
conditions for third-order correlations are enforced. These conditions
are based on generalized Schwarz' inequalities which limit the growth of
triple correlations and the approximation consists in `clipping' these
last quantities when they violate their respective inequalities. By
requiring that the inequalities be satisfied, we take into account the
damping effect of fourth-order correlations. The equations corresponding
to this approximation are derived for the case of inhomogeneous
turbulence in a Boussinesq fluid with the aid of a recently proposed
hypothesis for pressure correlation terms.
Journal of the Atmospheric Sciences 02/1976; 33(3):476-481. DOI:10.1175/1520-0469(1976)033<0476:TAFIFP>2.0.CO;2 · 3.14 Impact Factor