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Perneel L.,Vrije Universiteit Brussel | Fayyad-Kazan H.,Vrije Universiteit Brussel | Timmerman M.,Vrije Universiteit Brussel | Timmerman M.,Royal Military Academy Brussels
2012 International Conference on Computer Systems and Industrial Informatics, ICCSII 2012 | Year: 2012

Android is thought as being yet another operating system! In reality, it is a software platform rather than just an OS; in practical terms, it is an application framework on top of Linux, which facilitates its rapid deployment in many domains. Android was originally designed to be used in mobile computing applications, from handsets to tablets to e-books. But developers are also looking to employ Android in a variety of other embedded systems that have traditionally relied on the benefits of true real-time operating systems performance, boot-up time, real-time response, reliability, and no hidden maintenance costs. In this paper, we present a preliminary conclusion about Android's real-time behavior and performance based on experimental measurements such as thread switch latency, interrupt latency, sustained interrupt frequency, and finally the behavior of mutex and semaphore. All these measurements were done on the same ARM platform (Beagleboard-XM). Our testing results showed that Android in its current state cannot be qualified to be used in real-time environments. © 2012 IEEE.


Lesage K.,Catholic University of Leuven | Cizer O.,Catholic University of Leuven | Desmet B.,Royal Military Academy Brussels | Vantomme J.,Royal Military Academy Brussels | And 2 more authors.
Advances in Cement Research | Year: 2015

In this research, the plasticising mechanism of sodium gluconate (SG) retarder in cement paste containing a superplasticiser has been investigated in order to clarify the performance of the admixture combination in concrete. From adsorption and zeta-potential measurements, it is found that a lower viscosity occurs owing to (a) the electrostatic repulsion and (b) a lower particle volume fraction. Moreover, the gluconate anion is expected to enhance the formation of a homogenous polymer network on the cement grain surface, which explains the viscosity stabilisation time. In situ investigations of hydration using environmental scanning electron microscopy showed that SG induced modifications of the ettringite crystal morphology by reducing the amount and size of the ettringite needles. From pore solution analysis and energy-dispersive X-ray spectra, a mineral similar to syngenite is detected. These morphological changes lower the shear resistance and the paste viscosity. A thorough understanding of the plasticising mechanism will lead eventually to a more predictable concrete flow behaviour, which is particularly useful for concrete practitioners facing concerns related to combined use of admixtures.


Tellez H.F.,Free University of Brussels | Tellez H.F.,Royal Military Academy of Brussels | Morrison S.A.,Jozef Stefan Institute | Morrison S.A.,University of Ljubljana | And 15 more authors.
Sleep | Year: 2016

Study Objectives: Exposure to hypoxia elevates chemosensitivity, which can lead to periodic breathing. Exercise impacts gas exchange, altering chemosensitivity; however, interactions between sleep, exercise and chronic hypoxic exposure have not been examined. This study investigated whether exercise exacerbates sleep-related periodic breathing in hypoxia. Methods: Two experimental phases. Short-Term Phase: a laboratory controlled, group-design study in which 16 active, healthy men (age: 25 ± 3 y, height: 1.79 ± 0.06 m, mass: 74 ± 8 kg) were confined to a normobaric hypoxic environment (FIO2 = 0.139 ± 0.003, 4,000 m) for 10 days, after random assignment to a sedentary (control, CON) or cycle-exercise group (EX). Long-Term Phase: conducted at the Concordia Antarctic Research Station (3,800 m equivalent at the Equator) where 14 men (age: 36 ± 9 y, height: 1.77 ± 0.09 m, mass: 75 ± 10 kg) lived for 12-14 months, continuously confined. Participants were stratified post hoc based on self-reported physical activity levels. We quantified apnea-hypopnea index (AHI) and physical activity variables. Results: Short-Term Phase: mean AHI scores were significantly elevated in the EX group compared to CON (Night1 = CON: 39 ± 51, EX: 91 ± 59; Night10 = CON: 32 ± 32, EX: 92 ± 48; P = 0.046). Long-Term Phase: AHI was correlated to mean exercise time (R2 = 0.4857; P = 0.008) and the coefficient of variation in night oxyhemoglobin saturation (SpO2; R2 = 0.3062; P = 0.049). Conclusions: Data indicate that exercise (physical activity) per se affects night SpO2 concentrations and AHI after a minimum of two bouts of moderateintensity hypoxic exercise, while habitual physical activity in hypobaric hypoxic confinement affects breathing during sleep, up to 13+ months' duration. © Copyright 2016 Associated Professional Sleep Societies, LLC.

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