Prediction error identification of linear dynamic networks with rank-reduced noise

Dynamic networks are interconnected dynamic systems with measured node signals and dynamic modules reflecting the links between the nodes. We address the problem of \red{identifying a dynamic network with known topology, on the basis of measured signals}, for the situation of additive process noise on the node signals that is spatially correlated and that is allowed to have a spectral density that is singular. A prediction error approach is followed in which all node signals in the network are jointly predicted. The resulting joint-direct identification method, generalizes the classical direct method for closed-loop identification to handle situations of mutually correlated noise on inputs and outputs. When applied to general dynamic networks with rank-reduced noise, it appears that the natural identification criterion becomes a weighted LS criterion that is subject to a constraint. This constrained criterion is shown to lead to maximum likelihood estimates of the dynamic network and therefore to minimum variance properties, reaching the Cramer-Rao lower bound in the case of Gaussian noise.Comment: 17 pages, 5 figures, revision submitted for publication in Automatica, 4 April 201

Exploring Patterns of Activities of Daily Living in the Home Environment

Background: Senior citizens tend to live longer and longer independently. Judging whether a senior person is still capable of living on his own is often based on the occurrence of incidents, with all consequences thereof. In the specific case of early dementia, the symptoms are not immediately apparent and the occurrence and severity of incidents progress gradually over time. In this case, the children or grandchildren are burdened by the question whether or not the elderly adult can still live safely and independently in his or her own home. This decision is only based on input obtained through incidental visits. We believe that the capability of independent living can only be objectively judged, by a health professional, if long term objective information on the elderly person's daily activities of living (ADL) is available

Wind and boundary layers in Rayleigh-Benard convection. Part 2: boundary layer character and scaling

The effect of the wind of Rayleigh-Benard convection on the boundary layers is studied by direct numerical simulation of an L/H=4 aspect-ratio domain with periodic side boundary conditions for Ra={10^5, 10^6, 10^7} and Pr=1. It is shown that the kinetic boundary layers on the top- and bottom plate have some features of both laminar and turbulent boundary layers. A continuous spectrum, as well as significant forcing due to Reynolds stresses indicates undoubtedly a turbulent character, whereas the classical integral boundary layer parameters -- the shape factor and friction factor (the latter is shown to be dominated by the pressure gradient) -- scale with Reynolds number more akin to laminar boundary layers. This apparent dual behavior is caused by the large influence of plumes impinging onto and detaching from the boundary layer. The plume-generated Reynolds stresses have a negligible effect on the friction factor at the Rayleigh numbers we consider, which indicates that they are passive with respect to momentum transfer in the wall-parallel direction. However, the effect of Reynolds stresses cannot be neglected for the thickness of the kinetic boundary layer. Using a conceptual wind model, we find that the friction factor C_f should scale proportional to the thermal boundary layer thickness as C_f ~ lambda_Theta, while the kinetic boundary layer thickness lambda_u scales inversely proportional to the thermal boundary layer thickness and wind Reynolds number lambda_u ~ lambda_Theta^{-1} Re^{-1}. The predicted trends for C_f and \lambda_u are in agreement with DNS results

Spectral analysis of boundary layers in Rayleigh-Benard convection

A combined experimental and numerical study of the boundary layer in a 4:1 aspect-ratio Rayleigh-B\'{e}nard cell over a four-decade range of Rayleigh numbers has been undertaken aimed at gaining a better insight into the character of the boundary layers. The experiments involved the simultaneous Laser Doppler Anemometry (LDA) measurements of fluid velocity at two locations, i.e. in the boundary layer and far away from it in the bulk, for Rayleigh numbers varying between $1.6 \times 10^7$ and $2.4 \times 10^9$. In parallel, direct numerical simulations (DNS) have been performed for the same configuration for Rayleigh numbers between $7.0 \times 10^4$ and $7.7 \times 10^7$. The temperature and velocity probability density functions and the power spectra of the horizontal velocity fluctuations measured in the boundary layer and in the bulk flow are found to be practically identical. Except for the smallest Rayleigh numbers, the spectra in the boundary layer and in the bulk central region are continuous and have a wide range of active scales. This indicates that both the bulk and the boundary layers are turbulent in the $\textrm{Ra}$ number range considered. However, molecular effects can still be observed and the boundary layer does not behave like a classical shear-driven turbulent boundary layer.Comment: 10 pages, 6 figures, Accepted for publication in Phys. Rev.

Diffusion weighted imaging in cystic fibrosis disease: beyond morphological imaging

To explore the feasibility of diffusion-weighted imaging (DWI) to assess inflammatory lung changes in patients with Cystic Fibrosis (CF) METHODS: CF patients referred for their annual check-up had spirometry, chest-CT and MRI on the same day. MRI was performed in a 1.5 T scanner with BLADE and EPI-DWI sequences (b = 0-600 s/mm(2)). End-inspiratory and end-expiratory scans were acquired in multi-row scanners. DWI was scored with an established semi-quantitative scoring system. DWI score was correlated to CT sub-scores for bronchiectasis (CF-CTBE), mucus (CF-CTmucus), total score (CF-CTtotal-score), FEV1, and BMI. T-test was used to assess differences between patients with and without DWI-hotspots

How strong is the relationship between general phonological processes and pseudo-word reading? (51st Academy of Aphasia Proceedings)

Phonological dyslexia (PD) is an acquired reading disorder characterised by an abnormally strong lexicality effect, i.e., with impaired pseudo-word reading contrasting with relatively preserved real word reading (Beauvois & Derouesne, 1979). Parallel distributed models of reading aloud (Harm & Seidenberg, 2001) have made the strong claim that PD is due to a general, non-reading specific deficit to central phonological representations which manifests during pseudo-word reading due to the inherently high demands they place on the phonological system. Under this account, patients with impaired phonology should show impaired pseudo-word reading and vice-versa. Consistent with this view, phonological deficits frequently co-occur with PD (Friedman, 1996). In contrast, dual route models posit that PD may result from a deficit to grapheme-phoneme conversion processes (sublexical reading process) that does not have to implicate a general phonological deficit. We present two cases that directly challenge the phonological deficit view

A Context-Aware Adaptive Feedback System for Activity Monitoring

An active lifestyle is an important factor in the prevention of deconditioning and many negative secondary effects in chronic diseases (e.g. COPD). A number of studies have been conducted with the aim of gaining insight into the daily activity patterns of these patients. Current research is focussing on motivating patients to stay physically active and balancing their activity patterns by using an activity sensor combined with remote monitoring and smart, personalised feedback