Dobbelaere D.,Ghent University |
De Zutter D.,Ghent University |
Van Hese J.,Keysight Technologies Belgium N.V. |
Sercu J.,Keysight Technologies Belgium N.V. |
And 2 more authors.
Journal of Computational Physics | Year: 2015
In the context of hybrid formulations, the Poincaré-Steklov operator acting on traces of solutions to the vector Helmholtz equation in a heterogeneous interior domain with a smooth boundary is regularized by a well-known boundary integral operator related to the homogeneous exterior domain. For the first time, this property allows us to simultaneously construct a Calderón multiplicative preconditioner for the discretized operator and for a 3-D hybrid finite/boundary element method formulation, applicable to electromagnetic scattering problems. Numerical examples demonstrate the effectiveness of this novel preconditioning scheme, even for heterogeneous domains with non-smooth boundaries. © 2015 Elsevier Inc.
He D.,University of Nottingham |
Morgan S.P.,University of Nottingham |
Trachanis D.,Keysight Technologies Belgium NV |
Hese J.V.,Keysight Technologies Belgium NV |
And 5 more authors.
Sensors (Switzerland) | Year: 2015
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring. © 2015 by the authors; licensee MDPI, Basel, Switzerland.