Michael Catrysse

A telemetry system for the detection of hip prosthesis loosening by vibration analysis

This paper proposes a system for the detection of hip prosthesis loosening by means of a vibration analysis technique. Although this technique has been adapted before, the novelty presented here lies in the fact that the monitoring is done inside the prosthesis itself, offering better measurement results. Thus, an implantable monitoring system is required, involving low power consumption and miniaturization. Monitoring is done by a miniature, capacitive accelerometer. The monitoring system is equipped with a telemetric link, to provide data transmission from the implant to a PC, where the data are analyzed. The system is powered inductively, since it is intended for long-term implantation.

WIRELESS INDUCTIVE TRANSFER OF POWER AND DATA

This text discusses the possibilities when designing a wireless inductive link that works both as an energy link, to power up a remote device, as well as a communication link to retrieve data and to write data to the same remote device, using the same set of inductive coils. Datatransmission from the measurement system to a base unit is achieved by applying absorption modulation, datatransmission to the measurement system by applying amplitude modulation. Some basic formulae and design considerations are given, and a full example applicable to an implantable device is given.

The impact of influent total ammonium nitrogen concentration on nitrite-oxidizing bacteria inhibition in moving bed biofilm reactor

The application of nitrification-denitrification over nitrite (nitritation-denitritation) with municipal (i.e. diluted and cold (or low-temperature)) wastewater can substantially improve the energy balance of municipal wastewater treatment plants. For the accumulation of nitrite, it is crucial to inhibit nitrite-oxidizing bacteria (NOB) with simultaneous proliferation of ammonium-oxidizing bacteria (AOB). The present study describes the effect of the influent total ammonium nitrogen (TAN) concentration on AOB and NOB activity in two moving bed biofilm reactors operated as sequencing batch reactors (SBR) at 15 °C (SBR I) and 21 °C (SBR II). The reactors were fed with diluted reject water containing 600, 300, 150 and 75 mg TAN L(-1). The only factor limiting NOB activity in these reactors was the high concentrations of free ammonia and/or free nitrous acid (FNA) during the SBR cycles. Nitrite accumulation was observed with influents containing 600, 300 and 150 mg TAN L(-1) in SBR I and 600 and 300 in SBR II. Once nitrate production established in the reactors, the increase of influent TAN concentration up to the original 600 mg TAN L(-1) did not limit NOB activity. This was due to the massive development of NOB clusters throughout the biofilm that were able to cope with faster formation of FNA. The results of the fluorescence in situ hybridization analysis preliminarily showed the stratification of bacteria in the biofilm.

Design of a microphone array for near-field conferencing applications

Microphone arrays are becoming increasingly popular for conferencing applications and near-field speech recording. In this work, a 16-element cylindrical microphone array is designed for beamforming towards a nearby speaker, while reducing the influence of competing talkers. A two-stage approach is used to obtain the desired array directivity pattern, optimizing both microphone locations and filter weights. The positions of the microphones are optimized by using a hybrid optimization technique, taking into account the influence of the nearby acoustic environment. FIR filter coefficients for each microphone are derived from a regularized leastsquares (LSQR) solution, combined with null-steering. The performance of the design is evaluated experimentally and compared with a classically used goose-neck microphone.

How biomass growth mode affects ammonium oxidation start-up and NOB inhibition in the partial nitritation of cold and diluted reject water

ABSTRACT The inhibition of undesirable nitrite oxidizing bacteria (NOB) and desirable ammonium oxidizing bacteria (AOB) by free ammonia (FA) and free nitrous acid (FNA) in partial nitritation (PN) is crucially affected by the biomass growth mode (suspended sludge, biofilm, encapsulation). But, the limitations of these modes towards less concentrated reject waters (≤600 mg-N L−1) are unclear. Therefore, this work compares the start-up and stability of three PN sequencing batch reactors (SBRs) with biomass grown in one of the three modes: suspended sludge, biofilm and biomass encapsulated in polyvinyl alcohol (PVA) pellets. The SBRs were operated at 15°C with influent total ammonium nitrogen (TAN) concentrations of 75–600 mg-TAN L−1. PN start-up was twice as fast in the biofilm and encapsulated biomass SBRs than in the suspended sludge SBR. After start-up, PN in the biofilm and suspended sludge SBRs was stable at 150–600 mg-TAN L−1. But, at 75 mg-TAN L−1, full nitrification gradually developed. In the encapsulated biomass SBR, full nitrification occurred even at 600 mg-TAN L−1, showing that NOB in this set-up can adapt even to 4.3 mg-FA L−1 and 0.27 mg-FNA L−1. Thus, PN in the biofilm was best for the treatment of an influent containing 150–600 mg-TAN L−1.