183 research outputs found
The Use of a Viscous Cysteamine Eyedrop in a Belgian Cohort: Early 3-Year Results
No full textIntroduction With the life expectancy of patients with cystinosis increasing (ORPHA213), the corneal burden and the objective assessment of corneal crystal deposition have become increasingly important. Previous research highlights the disadvantages of hospital-prepared cysteamine solutions (HPCS), including limited efficacy, which can lead to visual decline. Cystadrops (R) is a viscous topical treatment in cystinosis care that counteracts these disadvantages. Methods A total of 14 patients with cystinosis and corneal involvement are being followed in the multidisciplinary cystinosis clinic of the University Hospital of Leuven. Data retrieved between September 2014 and March 2023 were analyzed. All patients were initially treated with HPCS before switching to Cystadrops (R). Patients were assessed yearly according to the standard clinical ophthalmological examination for patients with cystinosis developed by Pinxten et al. Photophobia, corneal crystal deposition, and corneal crystal deposition depth were measured by the Liang cystinosis photophobia score, Gahl score, and anterior segment optical coherence tomography (OCT) respectively. Corneal densitometry was assessed with Scheimpflug imaging. Results OCT mean crystal depth was 83% of total corneal thickness. The mean corneal density was 28.9 grayscale units. We found a positive trend (F = 0.20, p = 0.65) in corneal densitometry despite the use of HPCS, with a decreasing trend (F = 3.30, p = 0.08) after switching to Cystadrops (R). Photophobia scores significantly reduced after switching treatments (p = 0.008). In total, seven patients developed anterior segment complications while using HPCS. No new anterior segment complications developed while using Cystadrops (R). Conclusions This study underscores previous research, demonstrating HPCS' limited effectiveness in reducing corneal crystal deposition due to unachievable dosing frequencies and poor stability. Our data highlights the effectiveness of Cystadrops (R) in treating the ocular symptoms of cystinosis. The data demonstrates the difficulty of reversing high levels of corneal crystal deposition and anterior segment complications. Starting Cystadrops (R) early in the disease course may prevent high rates of crystal deposition, thus reducing complications and their impact on vision and quality of life.The rapid service fees of this article were funded by Recordati Rare Diseases
Axiomatic Projective Geometry
No full textStarting with the three axioms of projective geometry, this paper explores concepts such as perspectives, projective maps, and harmonic additions that are unique to this geometry. In addition, important theorems such as Pappus's Theorem, Desargue's Theorem, and the Fundamental Property are mentioned and worked with extensively.Applied Mathematic
The ℓ <sup>s</sup>-boundedness of a family of integral operators on UMD banach function spaces
No full textWe prove the ℓs-boundedness of a family of integral operators with an operator-valued kernel on UMD Banach function spaces. This generalizes and simplifies earlier work by Gallarati, Veraar and the author, where the ℓs-boundedness of this family of integral operators was shown on Lebesgue spaces. The proof is based on a characterization of ℓs-boundedness as weighted boundedness by Rubio de Francia.Analysi
Data and analysis scripts for Thermal soaring over the North Sea and implications for wind farm interactions
No full textData and analysis scripts used for manuscript: Thermal soaring over the North Sea and implications for wind farm interactions by Jens A. van Erp, Elspeth Sage, Willem Bouten, E. Emiel van Loon, Kees (C.) J. Camphuysen, Judy Shamoun-Baranes. “File description.docx” describes each individual data file. The scripts require RStudio and listed libraries to run.van Erp* J, Sage* E, Bouten W, van Loon E, Camphuysen KCJ, Shamoun-Baranes J, 2023. Thermal soaring over the North Sea and implications for wind farm interactions. Marine Ecology Progress Series 723:185-200. doi: https://doi.org/10.3354/meps14315.*joint first author
Sparse domination implies vector-valued sparse domination
No full textWe prove that scalar-valued sparse domination of a multilinear operator
implies vector-valued sparse domination for tuples of quasi-Banach function
spaces, for which we introduce a multilinear analogue of the UMD condition.
This condition is characterized by the boundedness of the multisublinear
Hardy-Littlewood maximal operator and goes beyond examples in which a UMD
condition is assumed on each individual space and includes e.g. iterated
Lebesgue, Lorentz, and Orlicz spaces. Our method allows us to obtain sharp
vector-valued weighted bounds directly from scalar-valued sparse domination,
without the use of a Rubio de Francia type extrapolation result.
We apply our result to obtain new vector-valued bounds for multilinear
Calder\'on-Zygmund operators as well as recover the old ones with a new sharp
weighted bound. Moreover, in the Banach function space setting we improve upon
recent vector-valued bounds for the bilinear Hilbert transform.Comment: 31 pages. Corrected author nam
Analyzing the wake of a wind turbine actuated with Dynamic Induction Control
No full textTo meet current renewable energy demands, there is a major increase in global wind power capacity. Wind turbines are commonly clustered in wind farms. When operating, wind turbines extract energy from the wind, creating a region characterized by a low velocity, called the wake. The wake negatively impacts the power production of downstream wind turbines. This power loss can be alleviated with wind farm control, where an upstream wind turbine deviates from optimal individual operation to improve the power production of the total wind farm. A novel wind farm control concept is dynamic induction control. While the results of dynamic control look promising, the working principles behind the increase in energy are not yet well understood. This thesis provides a framework to evaluate the transport of kinetic energy into a cylindrical control volume in a wind turbine wake using the instantaneous Navier Stokes energy equation. This approach can provide insight into the time behaviour of kinetic energy transport and can be used in conjunction with the Reynolds Averaged Navier Stokes energy equation. The wake is analyzed using Proper Orthogonal Decomposition to identify the dominant phenomena. The working principle of dynamic induction control is qualitatively described by dividing the wake into three regions: region I, dominated by pressure, region II, dominated by a vortex ring and region III, dominated by turbulence. The peak of transport of kinetic energy occurs in region II, as is confirmed by analysis through the instantaneous Navier Stokes energy equations. Finally, this thesis shows that for a simulation with uniform inflow and where the effect of the nacelle is not modelled, the transition from region II to region III is triggered by the interaction of the vortex ring with an inner vortex ring that forms around the nacelle wake. The nacelle wake is a result of not modelling the nacelle and deemed non-physical, so the ring vortex breakdown location that arises from this simulation does not have much physical meaning. While there remains a lot of work to be done, this thesis confirms the potential of dynamic induction control shown in previous research. A particularly interesting aspect of dynamic induction control shown in this thesis is that a high amount of wake recovery is compressed into a short distance in the order of . This property makes dynamic induction control a potential way to decrease turbine spacing in wind farms, allowing the placement of more wind turbines on the same area.European Wind Energy Masters (EWEM
Stability of stones on mild slopes
No full textThe static stability of stones on mild slopes under wave attack is investigated in this research. The first part of the research is focused on reproducing the physical scale model tests regarding profile change of Kramer (2016) numerically with the model XBeach-G. The erosion profiles modelled with the bed-load transport formulas of Nielsen (2006) and Van Rijn (2007) in XBeach-G do not match the erosion profiles of the profile change experiments of Kramer (2016). The bed-load transport formulas of Nielsen (2006) and Van Rijn (2007) are not able to model the sediment transport in XBeach-G accurately. Furthermore, XBeach-G cannot determine the velocity and acceleration near the bed, because the model solves the flow due to currents and waves for a single layer. Therefore, it can be concluded that XBeach-G should not be used to describe static stability of stones on mild slopes under wave attack. For the application of dynamically stable structures (which is not investigated in this research), XBeach-G functions satisfactorily (Postma, 2016). For further research, a model that solves the hydrodynamics for multiple layers should be applied. In this way, the hydrodynamics near the bed can be used to describe the static stability of stones. The aim of the second part of the research is to develop a design method that describes the static stability of stones on mild slopes under wave attack. The basis of this design method is the initiation of motion of a stone and the hydrodynamic forces that initiate this movement. The hydrodynamic forces and corresponding mobility parameters are determined with the velocity and the acceleration near the bottom. Using Bubble Image Velocimetry (BIV), the velocity and the acceleration are derived from the videos of the BIV experiments of Kramer (2016) with regular waves breaking on a slope. It is found from the results of the BIV analysis that the effective, adapted Shields parameter θ’McCall can be used to describe movements of stones on mild slopes under wave attack. This mobility parameter has been determined with the bed shear stress of McCall (2015), which added an inertia term to include the influence of accelerations. For initiation of motion of stones, it appears that the stability parameter θcr could be a value of 0.024 (in case no slope correction factor has been applied). To substantiate a design method that describes the static stability of stones on mild slopes under wave attack, the value of 0.024 could be used to define a threshold for initiation of motion of stones. More experiments need to be executed to optimize this value of the stability parameter. Moreover, a statistical value for the stability parameter could be used (like θcr,1%) to describe the static stability of stones by means of a certain number of stones that are allowed to move for a certain number of waves
Stability for Discrete Event Max-Min-Plus (MMP) and Max-Min-Plus-Scaling (MMPS) Systems: Max-Plus Lyapunov Functions for Stability Analysis and Control
No full textThis research presents a framework for analysing the stability and control of discrete-event systems, specifically emphasising max-min-plus (MMP) and max-min-min-plus-scaling (MMPS) systems. These systems are valuable modelling tools for various applications, including production systems and urban railway traffic management, respectively. However, a critical challenge in discrete-event systems is the lack of a generalised approach to assessing the stability of time signals, particularly in the context of MMPS systems. To address this challenge,this research will use max-plus Lyapunov functions already used to study the buffer stability in discrete-event switching-max-plus-linear (SMPL) systems.This thesis provides a framework to use max-plus Lyapunov functions to determine buffer stability of MMP and MMPS systems, focusing on their time signals. The max-plus Lyapunov function uses a buffer for each pair of states. The system is considered stable if the difference converges to the buffer levels for every pair of states. Given the structure of MMP and MMPS systems, the difference between the states after one state update will often be bounded. To determine this boundedness of the buffer levels, a novel concept of "fully correlated" MMP and MMPS systems is introduced. Using the properties of fully correlated systems, an algorithm is proposed to determine the buffer levels for both MMP and MMPS systems. We also derive analytical methods using Markov properties to assess the additive eigenvalue of fully correlated time-invariant monotonic MMPS systems. Using the property of fully correlatedness, it is also derived that fully correlated time-invariant non-monotonic MMPS systems will always have a bounded buffer and growth rate and can have multiple additive eigenvalues. The findings show that fully correlated time-invariant systems consistently exhibit bounded growth rates. In addition to providing theoretical insights, this study demonstrates the practical use of max-plus Lyapunov functions as a control Lyapunov function (CLF) in model predictive control (MPC). A novel control technique is proposed to stabilise naturally unstable discrete event systems. This approach has been effectively applied to stabilise inherently unstable discrete-event max-plus-linear (MPL) and MMP systems, indicating the practical significance of the proposed framework.Mechanical Engineering | Systems and Contro
- …
