Showing papers by "Altran published in 1999"

Ground-penetrating radar for concrete bridge health monitoring applications

Abstract: Ground penetrating radar, often used for geophysics investigation and land mine detection, has been developed as a non-destructive means of concrete bridge health monitoring for nearly a decade. However, the commercially available systems are limited to estimating the location and gross quantities of the deterioration. The objective of this research is to develop a GPR system that can provide a more accurate method for obtaining detailed information, so that the location and magnitude of the delaminations and deterioration can be decided. A frequency band of 500 MHz to 6 GHz, was used for this system. A corresponding antenna with high resolution and radiation efficiency, Good Impedance Match Antenna, was developed for this frequency range. The system is able to distinguish features that are at least 360 mm deep in concrete. The GPR system, antenna, and experimental results from field investigations are presented.

Recovery and characterization of biofilm bacteria associated with medical devices.

Abstract: Publisher Summary Bacteria colonizing medical devices exhibit a number of phenotypic and genotypic characteristics that are distinct from planktonic organisms and provide them with an adaptive advantage in an otherwise hostile environment replete with antibiotics and cellular and humoral antagonistic agents. The incidence of device-related bacterial infections is increasing with the more widespread application of implants in medicine. The methods described in this chapter focuses on both clinical and research laboratory techniques used for the recovery and evaluation of bacterial biofilms. Many of the techniques, such as including scanning confocal laser microscopy and Fourier transform infrared spectrometry (FTIR) have great potential for application to studies of device-associated biofilms. There are also a number of interesting surface analytical techniques that have been applied to the study of biofilms on various medical devices. These include X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis, and static secondary ion mass spectrometry.

Hybrid linear/bilinear time-scale analysis

Abstract: The introduce a new method for the time-scale analysis of nonstationary signals. Our work leverages the success of the "time-frequency distribution series/cross-term deleted representations" into the time-scale domain to match wideband signals that are better modeled in terms of time shifts and scale changes than in terms of time and frequency shifts. Using a wavelet decomposition and the Bertrand time-scale distribution, we locally balance linearity and bilinearity in order to provide good resolution while suppressing troublesome interference components. The theory of frames provides a unifying perspective for cross-term deleted representations in general.

Simulation and analysis of ghost images for the megajoule laser

Abstract: The amplification of the Megajoule Laser will be made with a multi-pass cavity. This technical principle can generate many ghost images. In fact, beam reflections occur on lens faces, propagate in the whole system and may focus in several points. Some of these reflections can also be amplified. Furthermore, focusing points may be located near or inside optical elements and their fluence may be over the glass damage threshold. So the amplification cavity can not be realized without studying beam reflections. In consequence, OPTIS developed a new and specific software with the help and scientifical advice of the CEA/DAM.

Growth of large KDP crystals in the form of plates

Abstract: This paper suggests a new technique of growth-oriented KDP crystals in the form of plates. The technique includes: using small oriented seeds spaced between two parallel platforms with a rapid growth of crystals between these two platforms, in a tank containing a KDP solution. As a result, crystals in the form of plates can be obtained. The thickness of the crystal plate depends on the distance between platforms. The horizontal dimensions of the plate depend on the volume of solution and the diameter of the platforms. The orientation of the plates are defined by the orientation of the seed. KDP crystals in the form of plates of two orientations are grown. The peculiarities of morphology and some characteristics of crystals are discussed.

Case Studies of Inadvertent Interactions Between Polymers and Devices in Field Applications

Abstract: Publisher Summary This chapter provides the case studies of inadvertent interactions between polymers and devices in field applications. Polymeric compounds are selected for a wide range of applications. Development of thermoplastic and thermoset polymer compounds is a mature science that continues to grow with the development of new types of additives, changing regulatory requirements, and proprietary considerations. It is important that the total life cycle of polymeric compounds be considered in context of the end-use application. The corrective measures are implemented so that predictable and consistent performance of the pressure relief device can be attained. Compound reformulation took place that included the careful selection of a clean homopolymer base resin, a specially designed and compounded antioxidant and a low aspect ratio, small particle size reinforcement. The compound simplification, in combination with highly functional components, allowed for exceptional performance and reliability. Finally for the pharmaceutical container component example, reformulation of the raw polymer compound, as well as substitution of machine lubricant with a food-grade aliphatic mineral oil was necessary, followed by substitution of increased purity raw materials, before use of this material could be continued.