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In this paper, the feasibility of structured H∞ control design is demonstrated in representative environment for flexible launcher control during non-stationary ascent phase. Robust control is achieved and performances are improved with respect to non structured H∞ controller; furthermore, numerous simplifications in control design process are highlighted providing flight control development cost reduction perspectives. These results pave the way towards industrial application of structured H∞ framework for existing and future European launcher control. Further research axes are currently under investigation in the frame of co-funded AIRBUS DS and CNES researches.

The present paper exposes a novel description of the effect of a pulse generator on a double integrator representing one axis of rotation for a space vehicle. By considering the difference between the angular velocity obtained with zero-order-hold (ZOH) actuator and the one with a PWM actuator, a perturbation operator expressing the influence of the PWM on the angular speed is defined. Using this configuration in a linear fractional representation (LFR), a stability analysis allows comparing LMI-based and IQC-based stability results for a one degree of freedom rotating body with uncertain PWM and saturation and permits dwelling on improvements to make for further analyses.

Polynomial surrogate models of an industrial standard, closed-loop launcher model during an atmospheric flight phase are developed. A probabilistic collocation method is applied to derive surrogate models of varying complexity for wind perturbations occurring at different time instances during the atmospheric flight phase. These models are employed in optimisation-based worst-case analysis to significantly reduce the computational overhead while maintaining the accuracy of the computed worst-case uncertain parameter combinations. Comparisons of worst-case analysis results obtained using standard simulation models and their polynomial surrogate equivalents demonstrate significant potential of the proposed approach for radically reducing the computational burden associated with the industrial verification and validation process.

The robustness of an industrial standard, closed-loop launcher model during an atmospheric flight phase is assessed in terms of robust safety margins in a multi-dimensional parameter space made up of various rigid and bending mode uncertainties. A single-axis launcher model with time-varying aerodynamic and thruster efficiency parameters, along with an H∞controller and bending mode filter is considered. A constrained hybrid optimisation approach is adopted to determine the safety margins for different wind perturbations acting at different time instances of the flight. In addition, optimisation-based analysis is performed to determine the worst-case uncertain parameter combination for the launcher during the atmospheric flight phase. Probability constraints on the uncertain parameter combination satisfying the dispersion requirements are considered during the analysis.

The integral quadratic separation (IQS) framework is a specialization of topological separation theory to the case where operators are described by (or embedded in) integral quadratic constraints. IQS applies both to regular and descriptor system representations. Thanks to this feature, IQS provides a methodology for deriving sequences of LMI conditions with reducing conservatism. It has been applied for robust performance analysis of systems with uncertainties and delays. In this paper the methodology is adapted for the first time for region of attraction evaluation in the case of systems with saturations. Results are illustrated on a launcher attitude control example with saturated inputs.

An investigation of the stability of the transfer function of the European Southern Observatory's Very Large Telescope Interferometer has been carried out through observations of Fomalhaut, which was observed over a range in hour angle from 21:50–05:24 on 20 October 2002. No significant variation in the transfer function was found for the zenith angle range 5°–70°. The projected baseline varied between 139.7 m and 49.8 m during the observations and, as an integral part of the determination of the transfer function, a new accurate limb-darkened angular diameter for Fomalhaut of 2.109 ± 0.013 mas has been established. This has led to improved values for the emergent flux = (3.43 ± 0.10)×108 Wm−2, effective temperature = 8819 ± 67 K and radius = (1.213 ± 0.011)×109 m (R/R⊙ = 1.744 ± 0.016). The luminosity has been found to be (6.34 ± 0.20)×1027 W (L/L⊙ = 16.5 ± 0.5). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract:  The rate of seroconversion for antibody to Chlamydia pneumoniae was analysed in blood samples of 26 vertically HIV-1 infected children and 14 seroreverter children (HIV-negative children born to HIV-positive mothers) during a 3-year study period. Seroconversion for Chlamydia pneumoniae was found in 13 of 26 HIV-1 infected children and in 1 of 14 in the seroreverter group (P=0.013). A lower mean CD4+ cell count and p24 antigen positivity at enrolment were significantly associated with seroconversion for Chlamydia pneumoniae. Signs and symptoms of acute respiratory infection were recorded in the 30 to 40 days preceding collection of the blood samples showing seroconversion for Chlamydia pneumoniae in 8 of 13 HIV-1 infected children and in the single seroreverter. This study confirms the potential role of Chlamydia pneumoniae in the pathogenesis of respiratory tract infections in HIV-1 infected subjects.

To determine whether granulocyte-colony stimulating factor and erythropoietin are effective in the therapy of neutropenia and anaemia related to human immunodeficiency virus (HIV) infection and to anti-retroviral agents, we recruited 11 HIV-infected children (mean age 4 years 10 months). All the children were given granulocyte-colony stimulating factor at a dosage of 5 μ-g/kg twice or three times a week while erythropoietin was administered additionally to three patients at a dosage of 50 U/kg twice a week. Both agents were administered subcutaneously for at least 4 months. Leukocyte and neutrophil counts significantly increased during the treatment (after 1 month, P= 0.003 and P= 0.009, respectively). Erythropoietin prevented blood transfusions and increased haemoglobin levels in the three children treated. No side-effects were recorded during the administration of either agent. Granulocyte-colony stimulating factor and erythropoietin appear to be safe and useful agents in the management of HIV-infected children.

We have compared the variable region 3 sequences from 10 human immunodeficiency virus type 1 (HIV-1)-infected infants to virus sequences from the corresponding mothers. The sequences were derived from DNA of uncultured peripheral blood mononuclear cells (PBMC), DNA of cultured PBMC, and RNA from serum collected at or shortly after delivery. The infected infants, in contrast to the mothers, harbored homogeneous virus populations. Comparison of sequences from the children and clones derived from DNA of the corresponding mothers showed that the transmitted virus represented either a minor or a major virus population of the mother. In contrast to an earlier study, we found no evidence of selection of minor virus variants during transmission. Furthermore, the transmitted virus variant did not show any characteristic molecular features. In some cases the transmitted virus was more related to the virus RNA population of the mother and in other cases it was more related to the virus DNA population. This suggests that either cell-free or cell-associated virus may be transmitted. These data will help AIDS researchers to understand the mechanism of transmission and to plan strategies for prevention of transmission.

This paper presents the development of an H∞ robust control law for the atmospheric flight phase of a future Ariane's type launcher. Some particular points of the development are the launcher control problem transcription into H∞ methodology framework, the take into account of system non-stationary features and the problem of finding a simplified on-board implementation of H∞ controllers. Satisfactory results were obtained in terms of a synthesis methodology definition, H∞ law performances compared to an LQG control law reference and implementation solutions with an LQG type structure for H∞ controllers.

In order to evaluate the response to immunization of HIV-infected children we studied the humoral response to an enhanced potency inactivated poliovaccine (E-IPV) of 43 children born of HIV seropositive mothers. All these subjects have been followed for 32 (15–48) months in order to ascertain their infection status.

The province of Aquitaine contains very abundant water supplies which are only being tapped very locally. More over, as it is bounded by the shores of the Gironde estuary and the Atlantic coast, salt water encroaches inland right up to the vicinity of the tapping points. This synthesis is the result of teamwork which, by geological, geophysical and hydrodynamics research and the use of natural radioactive tracers has shown that in tapping these ground water resources, one cannot consider each aquifer separately even where the local formations between them are relatively impervious. It was necessary to consider that whole sedimentary mass if one was to reliably estimate the effects of pumping on the aquifers and the accomanying risks of salt water contamination of the ground water. And lastly, the separation between surface and ground water no longer has any physical meaning at that scale. In its concrete form, the synthesis is provided by mathematical and multi-layer analogue models representing all the Tertiary aquifers and impervious formations between them north of the Western Aquitaine region, covering a total area of some 15,000 sq.kms.

The province of Aquitaine contains very abundant water supplies which are only being tapped very locally. More over, as it is bounded by the shores of the Gironde estuary and the Atlantic coast, salt water encroaches inland right up to the vicinity of the tapping points. This synthesis is the result of teamwork which, by geological, geophysical and hydrodynamics research and the use of natural radioactive tracers has shown that in tapping these ground water resources, one cannot consider each aquifer separately even where the local formations between them are relatively impervious. It was necessary to consider that whole sedimentary mass if one was to reliably estimate the effects of pumping on the aquifers and the accomanying risks of salt water contamination of the ground water. And lastly, the separation between surface and ground water no longer has any physical meaning at that scale. In its concrete form, the synthesis is provided by mathematical and multi-layer analogue models representing all the Tertiary aquifers and impervious formations between them north of the Western Aquitaine region, covering a total area of some 15,000 sq.kms.

The PMN, thanks to its ability to engulf and kill microorganisms, works as first defence against invading bacteria,whether or not antibiotics are administered. Because of the so-called “postantibiotic effect”, antibiotics in vitro slow down bacterial growth and metabolism for a period stretching beyond the exposure.Our study aims at assaying the capacity of E to influence PMN activity against microorganisms. PMN function was evaluated by chemotaxis,using the modified Boyden technique,and by Candida Albicans phagocytosis and killing using Lehre and Cline technique.PMN's were isolated from the peripheral blood of 9 healthy children(mean age 7,16±2,82) treated with a single oral dose of 25mg/Kg of E. Blood wase drawn prior to the administration of the antibiotic(reference value of PMN activity),2 hrs. later (when E blood levels reach their peak) and 8 hrs. later(2 hrs. after disappearance of E from the blood).The results show that,from the 8th hour on,there is a considerable increase in PMN phagocytic and killer activity(phF 0,17±0,04 before;0,40±0,08 after 8 hrs.;p&z.Lt;0,001 - % killing 23,08±4,16 before;32,6±5,1 after 8 hrs.;p< 0,001).Chemotaxis is unchanged (I.C. 78,52+7,73 before; 77,72+8,28 after 8 hrs.).