107 research outputs found
PRF Sampling Strategies for SwarmSAR Systems
No full textThe work investigates staggered and random PRF (Pulse Repetition Frequency) strategies for a close formation of small Synthetic Aperture Radar (SAR) satellites operating in a multistatic configuration. The satellites are positioned within a fraction of the along-track critical baseline, hence allowing for the application of Displaced Phase Center image formation approaches. The performance of regular and random pulse sampling schemes is in particular assessed for a single-input multiple-output (SIMO) S-Band constellation, whose feasibility is further analyzed in relation to the number of satellites and their antenna size.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Optical and Laser Remote SensingMicrowave Sensing, Signals & SystemsMathematical Geodesy and PositioningAtmospheric Remote Sensin
Are the asserted advantages of organic solvents in capillary electrophoresis real? A critical discussion
No full textIncreased Carotid Thickness in Subjects with Recently-Diagnosed Diabetes from Rural Cameroon
No full textPMCID: PMC3423396This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Non-occupational exposure to trace elements in Finland – Urinary and blood biomonitoring study
No full textThe aim of this study was to assess the exposure to trace elements of the non-occupationally exposed, non-smoking, working-age population in Finland, and to provide reference values for these trace elements in the urine and blood. Urine samples were analysed for 30 trace elements and blood samples for eight elements. The samplings took place in 2020.In the urine samples (n = 147), most of the studied trace elements were quantifiable; only the indium and iridium results were below the limit of quantification. In the blood samples (n = 143), all the trace elements were quantifiable. The results regarding four trace elements in the urine and five trace elements in the blood were statistically different among the females to those among the males. In most cases, exposure was higher among the females than the males. An age-dependent trend was only observed in the results regarding lead in blood and copper in urine. In comparison to data from other countries, the blood lead levels were lower in Finland, but urinary arsenic and selenium levels were generally higher.The results of this study will be used to set reference values for use in occupational health. We emphasize that it is important to use an appropriate reference population to identify occupational exposure to trace elements when setting reference values. Especially when considering a reduction in occupational exposure limit values and the corresponding health-based biological limit values for trace elements, it is essential to understand that the background population exposure varies to correctly interpret the data from occupationally exposed populations
A novel control architecture for floating wind turbines
No full textThe control of Floating Wind Turbines (FWTs) is challenging, as they possess much lower natural frequencies related to the structure's rigid body motion, which creates an undesirable coupling between tower motion and the blade pitch control. As a result, the tower motion is negatively damped triggering instability. This is because of the presence of Right Half Plane Zeros (RHPZs) imposing fundamental limitation on the control bandwidth. To address this problem, different solutions were proposed with varying control structures ranging from Single-Input, Single-Output (SISO) controllers to Multiple-input, Multiple-output (MIMO) ones. In this paper, a new control structure, of Single-Input, Multiple-Output (SIMO) is proposed that is able to lift the bandwidth limitation, while using simple elements that match the industry demands.Team Jan-Willem van WingerdenShip Hydromechanics and Structure
Discontinuous modelling of strain localisation and failure
No full textThe computational simulation of failure in solids poses many challenges. A proper understanding of how structures respond under loading, both before and past the peak load, is important for safe and economical constructions. This requires numerical models for failure which are both faithful to the physical reality and mathematically well founded. A serious computational issue is that of objectivity with respect to the spatial discretisation of a problem. This requires that upon refinement of the spatial discretisation of a problem, a unique, physically meaningful result is approached. One approach to ensure objectivity with respect to spatial discretisation when simulating failure in solids is to allow displacement discontinuities in the solution. In this work, different techniques, of varying complexity, are developed to simulate displacement discontinuities which are independent of the spatial discretisation using finite elements. The different techniques are then critically evaluated. The first model examined involves adding only the effect of a displacement discontinuity to a finite element as an incompatible strain mode. This allows a traction–separation relationship to be applied at an interface and can be implemented simply in a standard finite element code. It is however shown that this type of model can be cast in an equivalent continuum format, a form which is known to be sensitive to the spatial discretisation. The second approach developed involves the addition of the Heaviside function to the underlying finite element interpolation basis. This method is based on the partition of unity concept, and allows the Heaviside function to be added locally to a finite element mesh to simulate a propagating displacement discontinuity. The approach is formulated for geometrically linear, geometrically nonlinear, quasi-static and dynamic problems. It is shown to be completely independent of the spatial discretisation. The partition of unity-based model is used also to simulate failure using a regularised strain softening model. When a critical level of inelastic deformation is reached, a displacement discontinuity is inserted. This model is better suited to modelling the entire failure process than a continuum or discontinuous model alone. Through numerical examples, it is shown that the inclusion of a displacement discontinuity during the failure process can lead to a different failure mode than for a continuum-only model
Semi-blind adaptive beamforming for high-throughput quadrature amplitude modulation systems
No full textA semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrays elements, are first utilised to provide a rough initial least squares estimate of the beamformer's weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study
Medium effect (transfer activity coefficient) of methanol and acetonitrile on beta-cyclodextrin/benzoate complexation in capillary zone electrophoresis
No full textCitation chain aggregation: An interaction model to support citation cycling
No full textThis is the postprint version of the conference paper.Citation chaining is a powerful means of exploring the academic literature. Starting from just one or two known relevant items, a
naïve researcher can cycle backwards and forwards through the citation graph to generate a rich overview of key works, authors and journals relating to their topic. Whilst online citation indexes
greatly facilitate this process, the size and complexity of the search space can rapidly escalate. In this paper, we propose a
novel interaction model called citation chain aggregation (CCA). CCA employs a simple three-list view which highlights the
overlaps that occur between the first-generation relations of known relevant items. As more relevant articles are identified, differences in the frequencies of citations made by or to unseen articles provide strong relevance feedback cues. The benefits of this technique are illustrated using a simple case study
- …
