A staggered scheme for nonconvex hyperbolic systems of conservation laws

Electrical Engineering, Mathematics and Computer Scienc

On the accuracy of different boundary integral formulations for dielectric bodies using RWG and BC functions

Different formulations of the boundary integral method for dielectric bodies are evaluated on their accuracy. The formulations apply RWG and/or BC functions both as basis functions and as test functions. A systematic evaluation, measuring the order of accuracy of the different formulations, is performed for low-contrast test cases. The conclusion is that for low-contrast dielectric bodies, the CTF and Müller formulation (tested with BC functions) provide the best choice

Full wave analysis of the influence of the jet engine air intake on the radar signature of modern fighter aircraft

Radar cross section prediction techniques are used to determine the radar signature of a military platform when the radar signature can not be determined experimentally, because the platform is not available or for reasons of time and cost. For classic jet aircraft the radar cross section for forward observation angles is dominated by the contribution of the open ended cavity formed by the jet engine air intake and compressor fan. This cavity is characterized by its large depth (L/d>3), curved centerline and nonuniform cross section, for which the scattering characteristics can not by analyzed by approximate high frequency methods. Jin et al. have published a numerical method based on a higher order finite element discretisation of the Maxwell equations, where the resulting linear system is solved by means of a frontal solution method. The method takes full advantage of the topology of the cavity scattering problem and has been successfully applied for the analysis of cavities of intermediate size. In this paper an adaptation of their algorithm is discussed that can efficiently compute the electric field scattered by very large cavities, in particular the jet engine air intake cavity for X-band radar frequencies

Segregated solution methods for compressible flow

Electrical Engineering, Mathematics and Computer Scienc

Evaluation of the interface-capturing algorithm of OpenFoam for the simulation of incompressible immiscible two-phase flow

The Mass-Conserving Level-Set method combines the efficiency of a Level-Set algorithm with the mass conserving properties of the Volume Of Fluid method. It avoids the work intensive interface construction of the former method and imposes a mass-conserving correction to the distance function of the latter. The interface capturing algorithm implemented in OpenFOAM uses a compressive convection scheme for the evolution of the VOF colour function, as opposed to an interface reconstruction algorithm. Therefore, it can be assumed to match the efficiency of the MCLS method. Further analysis of the accuracy of the algorithm is required to make a fair comparison. In this report the accuracy will be evaluated for the simulation of incompressible, immiscible two-phase flow in two and three spatial dimensions. Three representative test cases are considered: The advection of a spherical bubble for an imposed, constant velocity field (2D), a rising (buoyant) bubble in a quiescent fluid (2D and 3D) and a stationary bubble in a stationary fluid (2D and 3D). The computed results are compared with results obtained with the Mass-Conserving Level-Set method of [8], benchmark results of [5] and other references. The compressive scheme accurately conserves mass, but shows large spurious currents for the test cases with surface tension. Additionally, the error in the predicted rise velocity of the gas bubble is large in comparison with that of the MCLS method.Electrical Engineering, Mathematics and Computer Scienc

Feeding and Swallowing Problems in Infants with Spinal Muscular Atrophy Type 1: an Observational Study

Contains fulltext : 220780.pdf (Publisher’s version ) (Closed access)BACKGROUND: Infantile hereditary proximal spinal muscular atrophy (SMA) type 1 is characterized by onset in the first 6 months of life and severe and progressive muscle weakness. Dysphagia is a common complication but has not been studied in detail. OBJECTIVE: To study feeding and swallowing problems in infants with SMA type 1, and to explore the relation between these problems and functional motor scores. METHODS: We prospectively included 16 infants with SMA type 1 between September 2016 and October 2018. Eleven infants received palliative care and five infants best supportive care in combination with nusinersen. We compiled and used an observation list with feeding related issues and observed feeding sessions during inpatient and outpatient visits. The Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) was used as a measure of motor function. RESULTS: All infants in the palliative care group (median onset of disease 14 days (range 1-56); median inclusion in the study 52 days (range 16-252) demonstrated symptoms of fatigue during feeding and unsafe swallowing. Symptoms were short nursing sessions (10-15 minutes), and not being able to finish the recommended feeding volumes (72%); increased frequency of feeding sessions (55%); coughing when drinking or eating (91%), and wet breathing during and after feeding (64%).Two out of five infants in the nusinersen group (median onset of disease 38 days (range 21-90); inclusion in the study at 63 days (range 3-218) were clinically pre-symptomatic at the start of treatment. The other three infants showed symptoms of fatigue and unsafe swallowing at inclusion in the study. These symptoms initially decreased after the start of the treatment, but (re)appeared in all five infants between the ages of 8 to 12 months, requiring the start tube of feeding. In the same period motor function scores significantly improved (median increase CHOP INTEND 16 points). CONCLUSION: Impaired feeding and swallowing remain important complications in infants with SMA type 1 after the start of nusinersen. Improvement of motor function does not imply similar gains in bulbar function