Active vibration control for underwater signature reduction of a navy ship

Dutch navy ships are designed and built to have a low underwater signature. For low frequencies however, tonal vibrations of a gearbox can occur, which might lead to increased acoustic signatures. These vibrations are hard to reduce by passive means. To investigate the possibilities of active vibration control to reduce the underwater signature, a full scale experiment was performed with an active vibration control system on board of a navy ship. For this purpose six special, high efficiency, actuators were built and mounted on the gearbox. A MIMO adaptive feedforward control system was used to reduce the tonal vibrations of the gearbox which were excited by the diesel engine. Vibrations onboard and underwater acoustic pressures were used to monitor the performance of the system during full scale runs on the underwater acoustic range in Bergen, Norway. It can be concluded that the system is able to reduce the vibration and the acoustic signature significantly

Experimental study of the flow field in patient specific lower airways

In this study Particle Image Velocimetry (PIV) is used to visualize and measure airflow in the lower airways. Using Rapid Prototyping Manufacturing (RPM) technology, a hydraulic in vitro model was developed and constructed. Preliminary 2D PIV measurements compared successfully to Computational Fluid Dynamics (CFD) results

Constructing a no-reference H.264/AVC bitstream-based video quality metric using genetic programming-based symbolic regression

In order to ensure optimal quality of experience toward end users during video streaming, automatic video quality assessment becomes an important field-of-interest to video service providers. Objective video quality metrics try to estimate perceived quality with high accuracy and in an automated manner. In traditional approaches, these metrics model the complex properties of the human visual system. More recently, however, it has been shown that machine learning approaches can also yield competitive results. In this paper, we present a novel no-reference bitstream-based objective video quality metric that is constructed by genetic programming-based symbolic regression. A key benefit of this approach is that it calculates reliable white-box models that allow us to determine the importance of the parameters. Additionally, these models can provide human insight into the underlying principles of subjective video quality assessment. Numerical results show that perceived quality can be modeled with high accuracy using only parameters extracted from the received video bitstream

Cold and Warm Gas Outflows in Radio AGN

The study of the conditions and the kinematics of the gas in the central region of AGN provides important information on the relevance of feedback effects connected to the nuclear activity. Quantifying these effects is key for constraining galaxy evolution models. Here we present a short summary of our recent efforts to study the occurrence and the impact of gas outflows in radio-loud AGN that are in their first phase of their evolution. Clear evidence for AGN-induced outflows have been found for the majority of these young radio sources. The outflows are detected both in (warm) ionized as well in (cold) atomic neutral gas and they are likely to be driven (at least in most of the cases) by the interaction between the expanding jet and the medium. The mass outflow rates of the cold gas (HI) appear to be systematically higher than those of the ionized gas. The former reach up to ~50 Msun/yr, and are in the same range as "mild" starburst-driven superwinds in ULIRGs, whilst the latter are currently estimated to be a few solar masses per year. However, the kinetic powers associated with these gaseous outflow are a relatively small fraction (a few x 10^-4) of the Eddington luminosity of the galaxy. Thus, they do not appear to match the requirements of the galaxy evolution feedback models.Comment: Invited talk, to appear in the Proceedings of the IAU Symposium 267, "Co-Evolution of Central Black Holes and Galaxies", B.M. Peterson, R.S. Somerville, T. Storchi-Bergmann, eds., in pres

In Vitro Flow Modelling for Mitral Valve Leakage Quantification

In this study particle image velocimetry (PIV) is used to measure and visualise the blood flow through a leaking mitral heart valve. The results are compared with the results from Doppler echocardiography and computational fluid dynamics (CFD). Using CAD, five-axis milling and Rapid Prototyping Machining (RPM) technology, a hydraulic in vitro flow model was developed and constructed which is compatible with flow investigation with 2D normal speed PIV and 2D Doppler echocardiography. The same CAD model was used to conduct the CFD analysis. PIV results compared successfully with Doppler echo and CFD results, both in the upstream converging region and downstream the turbulent regurgitated jet zone. These results are expected to improve the assessment of mitral valve regurgitation severity with Doppler echocardiography in clinical practice