Analysis of multipath channel delay estimation using subspace fitting

The presence of rich scattering in indoor and urban radio propagation scenarios may cause a high arrival density of multipath components (MPCs). Often the MPCs arrive in clusters at the receiver, where MPCs within one cluster have similar angles and delays. The MPCs arriving within a single cluster are typically unresolvable in the delay domain....

How to measure diffusion coefficients in biofilms: A critical analysis

Biofilm and granular sludge processes depend on diffusion of substrates. Despite their importance for the kinetic description of biofilm reactors, biofilm diffusion coefficients reported in literature vary greatly. The aim of this simulation study was to determine to what extent the methods that are used to measure diffusion coefficients...

A combined experimental with simulation approach to calibrated 3D strain measurement using shearography

This paper is concerned with the development of a calibrated 3D shearography strain measurement instrument, calibrated iteratively, using a combined mechanical-optical model and specially designed test objects. The test objects are a cylinder loaded by internal pressure and a flat plate under axial load. Finite element models of the samples,...

Error analysis of 3D shearography using finite-element modelling

This paper describes the development of an opto-mechanical simulation of a complete shearography system, including the shearography instrument, the samples and the test environment. This simulation is applied to the measurement of 3D strains in engineering samples. The samples are a cylinder loaded by internal pressure and a flat plate under...

Improved manometric setup for the accurate determination of supercritical carbon dioxide sorption

An improved version of the manometric apparatus and its procedures for measuring excess sorption of supercritical carbon dioxide are presented in detail with a comprehensive error analysis. An improved manometric apparatus is necessary for accurate excess sorption measurements with supercritical carbon dioxide due to the difficulties associated...

Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations

The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing radius and the level of approximation by...

A posteriori error analysis for stochastic finite element solutions of fluid flows with parametric uncertainties

Accounting for uncertainty in numerical simulations is a growing concern and a great deal of methods have recently been developed, such as the Polynomial Chaos which basically consists in a spectral approximation of the surface response of the solution by stochastic finite elements. However, criteria for refinement of the spectral space have so...

Radar interferometry: Data interpretation and error analysis

Overview of the POINT SAND model

A position reference system for flight test, based on GPS/IRS integration

Nowadays, several flight test organizations recognize the potential of the Navstar Global Positioning System (GPS) for flight test trajectorydetermination. In 1990 the National Aerospace Laboratory of the Netherlands (NLR) started the development of a Position Reference System (PRS) based on an Inertial Reference System (IRS), updated by GPS...

A study on methods to compare measured and calculated modal data

Fokker Space and Systems and the National Aerospace Laboratory NLR performed a study to integrate more systematically the experimental and analytical analysis of the dynamic behaviour of structures. The study focused on the correlation of experimental and analytical data, matrix and parameter updating methods. In this paper an overview will be...

Some aerospace applications of estimation theory

In this report, the application of estimation theory to three problems from aerospace research is described. The applications considered deal with spacecraft attitude estimation, software reliability modelling and estimation, and with a satellite-based navigation algorithm. Maximum likelihood estimation is used in the software reliability case...

De plaats van de wiskundige bij de ontwikkeling van digitale simulatie-systemen voor toepassingen uit de "Computational physics"

NLR mainly performs applied scientific research for use in the aerospace industry. In many cases the product has the form of an information system for the design, production and usage of aerospace vehicles. Within this context, the mathematician contributes, in cooperation with specialists from other disciplines such as aerodynamics, structures,...

Correlation, error-localisation and updating of the second problem defined in GARTEUR AG11

A description is given of the second problem, a clamped-free truss structure, defined in the GARTEUR Action Group 11. The measured and calculated modal data of the structure are correlated, the locations of the errors are determined and finally the finite element model of the structure is updated. These analyses are performed with the B2000...

Determination of the resin content in DSC prepreg samples using thermal analysis techniques

Determination of the heat of reaction during the cure of the resin in carbon fibre reinforced epoxy prepreg using Differential Scanning Calorimetry resulted in considerable scatter with the measurements were done on prepreg samples. Differences in resin content between the DSC prepreg samples were suspected to be the main cause of the observed...

Reliability aspects of software for digital avionics

Modern commercial transport aircraft contain digital avionics systems for more and more safety critical functions. The reliability and safety of those new systems depend on the hardware reliability and on the reliability of the embedded software. In this report, an overview is given of available methods and techniques to develop reliable...

Evaluation of a method to extract performance data from dynamic maneuvers for a jet transport aircraft

A very accurate measurement system and a data reduction method have been developed to extract performance data from a single dynamic maneuver, in order to reduce the large amoimt of flight hours required for the determination of these data by means of measurements in steady flight. In order to evaluate the applicability of this method to a modem...

A statistical method for error reduction in an integration process involving experimental data

The numerical integration of a non-linear function f(a (t), ap(t),.. a (t)) vith mutually independent variaties a, is considered for the case that the initial conditions for the integration process and time series of a, are determined by experiment. In order to minimize the error in the result of the integration process a technique is developed...