867 resultados para measurement and metrology
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A reliable assessment of relevant substance flows is very important for environmental risk assessments and efficiency analysis of measures to reduce or avoid emissions of micropollutants like drugs to water systems. Accordingly, a detailed preparation of monitoring campaigns should include an accuracy check for the sampling configuration to prove the reliability of the monitoring results and the subsequent data processing. The accuracy of substance flow analyses is expected to be particularly weak for substances having high short-term variations of concentrations in sewage. This is especially the case linked to the observation of substance flows close to source in waste water systems. The verification of a monitoring configuration in a hospital sewer in Luxembourg is in the centre of interest of the case study presented here. A tracer test in the sewer system under observation is an essential element of the suggested accuracy check and provides valuable information for an uncertainty analysis. The results illustrate the importance of accuracy checks as an essential element of the preparation of monitoring campaigns. Moreover the study shows that continuous flow proportional sampling enables a representative observation of short-term peak loads of the iodinated x-ray contrast media iobitridol close to source.
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This Master Final Project is intended to show the process developed to the functional and electrical characterization between different devices that use the SpaceWire space communications standard integrated into an evaluation board designed for this purpose. In order to carry out this characterization, firstly, a study to understand the SpaceWire standard is done. After that, another study for the understanding of the demonstration board with its different interfaces and IPs of SpW is done. According to this, it is expected to find out how the SpW devices are structured, especially at FPGA level, and how is the communication between them. Based on the knowledge obtained about SpaceWire and the SpW devices integrated into the evaluation board, the set of measurements and the strategy to validate electrical interoperability between the different devices are defined, as well as to perform functional checks required to ensure its proper understanding. Furthermore, it will let check whether the standard is met and search the limit of operation within a communication system representative of existing equipment in a satellite. Once finished the test plan and implemented on the representative hardware, the board will be considered characterized at SpW level and a report with the conclusions reached about the operation of the SpW interfaces in the board and constraints found will be done. RESUMEN. El presente Trabajo Fin de Máster pretende mostrar el proceso realizado para la caracterización eléctrica y funcional entre distintos dispositivos que utilizan el estándar de comunicaciones espaciales SpaceWire integrados en una tarjeta de evaluación diseñada para tal efecto. Para poder llevar a cabo dicha caracterización, en primer lugar, se realiza un estudio para el conocimiento del estándar SpaceWire. A continuación, se lleva a cabo otro estudio para el conocimiento de la tarjeta de demostración en la que se encuentran los distintos interfaces e IPs de SpW. Con esto último, se pretende conocer como están estructurados los dispositivos SpW, sobre todo a nivel de FPGA, y como se realiza la comunicación entre ellos. En base a los conocimientos adquiridos acerca de SpaceWire y los dispositivos SpW de la tarjeta de evaluación, se definen el conjunto de medidas y la estrategia a seguir para validar eléctricamente la interoperabilidad entre los distintos dispositivos, así como para realizar las comprobaciones funcionales necesarias para asegurar su correcto entendimiento. Además, con ello se podrá comprobar si se cumple el estándar y se podrá también buscar el límite de operación dentro de un sistema de comunicaciones representativo de los equipos existentes en un satélite. Realizado el plan de pruebas y aplicado sobre el hardware representativo se podrá dar por caracterizada la tarjeta a nivel SpW y realizar un informe con las conclusiones alcanzadas acerca del funcionamiento de los interfaces SpW de la tarjeta y las limitaciones encontradas.
Resumo:
BETs is a three-year project financed by the Space Program of the European Commission, aimed at developing an efficient deorbit system that could be carried on board any future satellite launched into Low Earth Orbit (LEO). The operational system involves a conductive tape-tether left bare to establish anodic contact with the ambient plasma as a giant Langmuir probe. As a part of this project, we are carrying out both numerical and experimental approaches to estimate the collected current by the positive part of the tether. This paper deals with experimental measurements performed in the IONospheric Atmosphere Simulator (JONAS) plasma chamber of the Onera-Space Environment Department. The JONAS facility is a 9- m3 vacuum chamber equipped with a plasma source providing drifting plasma simulating LEO conditions in terms of density and temperature. A thin metallic cylinder, simulating the tether, is set inside the chamber and polarized up to 1000 V. The Earth's magnetic field is neutralized inside the chamber. In a first time, tether collected current versus tether polarization is measured for different plasma source energies and densities. In complement, several types of Langmuir probes are used at the same location to allow the extraction of both ion densities and electron parameters by computer modeling (classical Langmuir probe characteristics are not accurate enough in the present situation). These two measurements permit estimation of the discrepancies between the theoretical collection laws, orbital motion limited law in particular, and the experimental data in LEO-like conditions without magnetic fields. In a second time, the spatial variations and the time evolutions of the plasma properties around the tether are investigated. Spherical and emissive Langmuir probes are also used for a more extensive characterization of the plasma in space and time dependent analysis. Results show the ion depletion because of the wake effect and the accumulation of- ions upstream of the tether. In some regimes (at large positive potential), oscillations are observed on the tether collected current and on Langmuir probe collected current in specific sites.
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"Serial no. 96-51."
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Previous editions published under title: The measurement of adult intelligence.
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National Highway Traffic Safety Administration, Washington, D.C.
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"March 1979."
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National Highway Traffic Safety Administration, Washington, D.C.
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"Printed for the use of the Joint Economic Committee."
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"January 1948."