Bondgraph modelling and simulation of the dynamic behaviour of above-knee prostheses

A mathematical model was used to investigate the dynamic behaviour of an above-knee (AK) prosthesis in the swing phase and to analyse the influence of mass and mass distribution on the maximal stump load and the required energy. The model consists of a bondgraph model of the prosthesis and a “walking” model which predicts the walking velocity, step length and the femoral trajectory. Equipment was developed to measure the inertial properties of the components of the prosthesis. \ud \ud Through computer simulation, stickdiagrams of the swing phase and graphs of the variation with time of the hip and stump forces were obtained. It was found that for a normal AK prosthesis with a knee-lock mechanism the axial stump load is greatest at the beginning and at the end of the swing phase. At a walking velocity of 5 km/hr the maximum axial stump load amounts to 2.1 times the static weight of the prosthesis. \ud \ud The maximum axial stump force appeared to be almost directly proportional to the total mass of the prosthesis but independent of the mass distribution. The required energy also increased with the mass of the prosthesis but is' dependent on mass distribution. \ud \ud Because of their comparable weights the influence of the shoe is almost equal to the influence of the prosthetic foot. Thus lightweight shoes should be used with lightweight prosthetic feet in order to add to their advantages

Global interlaboratory assessments of perfluoroalkyl substances under the Stockholm Convention on persistent organic pollutants

The Global Monitoring Plan (GMP) according to article 16 of the Stockholm Convention on Persistent Organic Pollutants (POPs) requires that POP laboratories must be capable – at any time – to analyse samples for POPs within a variation of ±25%. Based on this target error of 25%, a statistical model using z-scores was applied to assess the performance of analytical laboratories for POPs and a number of matrices. Since the second round of these ‘Bi-ennial Global Interlaboratory Assessment on Persistent Organic Pollutants (POPs)’, carried out in 2012/2013, perfluoroalkyl substances (PFASs) have been included into the proficiency tests. The third round was carried out in 2016/2017. The test materials included test solutions of PFASs analytical standards, the abiotic matrices sediment, air (extract) and water and the biotic matrices fish, human milk and human plasma. The number of laboratories submitting results for PFASs remained quite stable (IL2 = 27 laboratories; IL3 = 29), but there was broader geographic distribution observed in IL3: in addition to the laboratories from Asia and the Western Europe/other groups, two laboratories from Africa participated, two from Central-Eastern Europe and one from the Latin American/Caribbean region. Considering that PFASs were introduced for the first time in round 2, the results were good to reasonable compared to those of a number of other POPs included in the same study. However, it shall also be mentioned that for some matrices and PFASs, the number of laboratories submitting results was too small and the results too scattered to derive a consensus value. This was especially true for the PFOS precursor compounds and the air matrix. Also, laboratories struggle with the analysis of the branched PFOS isomers. These interlaboratory assessments on PFASs gave promising results and demonstrated the importance of proficiency tests in an international environment to generate trust in laboratory results. The need to participate regularly in such intercomparison assessments is highlighted. The results show the current level of PFAS analysis, which varies by laboratory and by matrix rather than per geographic region

Water kent geen grenzen : samen werken aan agrarisch waterbeheer

Waterbeheer door boeren, waarbij het nog de vraag is of grootschalige toepassing op boerenbedrijven mogelijk is. Voorbeelden zijn het project Functionele Agrobiodiversiteit (FAB) Hoeksche Waard (p. 9) en demonstratieprojecten bij individuele boeren, zoals het agrarische informatiebedrijf Helder Water (pag 8.) en het project Boeren met water (p. 9). Stuwbeheer, waterzuivering en rietteelt zijn andere voorbeelden van waterbeheer door boere

ABLooM: Location behaviour, spatial patterns, and agent-based modelling

This paper presents an Agent-based LOcation Model (ABLOoM). ABLOoM simulates the location decisions of two main types of agents, namely households and firms. The model contains multiple interactions that are crucial in understanding land use changes, such as interactions of agents with other agents, of agents with their environment and of agents with emerged patterns. In order to understand the mechanisms that are at the basis of land use changes and the formation of land use patterns, ABLOoM allows us to study human behaviour at the microlevel in a spatial context. The models, which include economic theory, aspects of complexity theory and decision rules, show that it is possible to generate macrolevel land use patterns from microlevel spatial decision rules

Low-bitrate video coding with third order geometric transformations

This paper describes low-bitrate video compression based upon the characterization of the new frame as a set of geometric transformations of objects of the previous frame. Objects with motion are detected and the motion is estimated. The estimated motion (motion field) is used to obtain the parameters for the geometric transformations. The pertinent geometric transformations are rotation, translation, zooming and isotropic and anisotropic distortion. The motivation for choosing this set of third-order transformations is that we have at our disposal special ASICS for real-time video processing. We only want to transform moving objects and therefore the boundaries of the moving objects must be known. The boundaries of the objects are represented by closed contours