Formula manipulation in the bond graph modelling and simulation of large mechanical systems

A multibond graph element for a general single moving body is derived. A multibody system can easily be described as an interconnection of these elements. 3-D mechanical systems usually contain dependent inertias having both differential and integral causality. A method is described for the transformation of inertias with differential causality to an integral form, using formula manipulation. The program also helps to find experimentally the optimal choice for the generalized coordinates. The resulting explicit differential equation may be solved using a standard integration routine or simulation program

Modelling the dynamics and kinematics of mechanical systems with multibond graphs

A method to model mechanical systems with multibond graphs is described. The method is based on the description of the vector velocity relation of a moving point in a rotating system. This relation is incorporated in a bond graph. Since bond graphs are based on the power conserving concept, the force or momenta relations are then available too. By repeating the same bond graph structure for every point (which is of interest within a chosen coordinate frame), where each point has the same rotational velocity, a systematic way of modelling mechanical systems is achieved. It is explained how connected mechanical linkages have to be handled. Two simple examples are given

Revealing causal heterogeneity using time series analysis of ambulatory assessments: application to the association between depression and physical activity after myocardial infarction

Objective: Studies in psychosomatic medicine are characterized by analyses that typically compare groups. This nomothetic approach leads to conclusions that apply to the average group member but not necessarily to individual patients. Idiographic studies start at the individual patient and are suitable to study associations that differ between time points or between individuals. We illustrate the advantages of the idiographic approach in analyzing ambulatory assessments, taking the association between depression and physical activity after myocardial infarction as an example. Methods: Five middle-aged men who had myocardial infarction with mild to moderate symptoms of depression were included in this study. Four of these. participants monitored their physical activity and depressive symptoms during a period of 2 to 3 months using a daily self-registration form. The time series of each individual participant were investigated using vector autoregressive modeling, which enables the analysis of temporal dynamics between physical activity and depression. Results: We found causal heterogeneity in the association between depression and physical activity. Participants differed in the predominant direction of effect, which was either from physical activity to depression (n = 1,85 observations, unstandardized effect size = -0.183, p=.03) or from depression to physical activity (n = 2, 65 and 59 observations, unstandardized effect sizes = -0.038 and -0.381, p<.001 and p=.04). Also, the persistency of effects differed among individuals. Conclusions: Vector autoregressive models are suitable in revealing causal heterogeneity and can be easily used to analyze ambulatory assessments. We suggest that these models might bridge the gap between science and clinical practice by translating epidemiological results to individual patients

Risk assessment on the possible introduction of three predatory snails (Ocinebrellus inornatus, Urosalpinx cinerea, Rapana venosa in the Dutch Wadden Sea

Recently three alien invasive predatory snails have been found in the Dutch marine waters, which are identified by the Ministry of Agriculture, Nature and Food Quality as potential high risk species due to their possible impact on bivalve species (TRCPD/2009/3587). These are: Japanese oyster drill Ocinebrellus inornatus (syn: Ceratostoma inornatum, Ocenebra japonica), American oyster drill Urosalpinx cinerea and Asian rapa whelk Rapana venosa. In this report we describe the potential ecological and economical risks of introduction of the three alien invasive predatory snails in the Nature 2000 Wadden Sea area

An in-line dye tracer experiment to measure the residence time in continuous concrete processing

This paper introduces an in-line dye tracer experiment to measure the residence time functions in continuous concrete processing. These functions quantify the material-system interdependency and can be used to compare different material-system combinations and for quality and process control. A Rhodamine B solution was used as the tracer material and detected by measuring the color intensity using a digital image processing technique. The experiment was validated on a 3D concrete printing system by comparing the results of impulse, step-up and step-down inputs with different tracer quantities. The results show that a high signal-to-noise ratio can be obtained with low tracer concentrations. For the examined combination of material and system, an impact on the original process was only observed for the step-up inputs at high tracer quantities. It is concluded that the presented method is cost-effective and non-labor-intensive and, therefore, has the potential for wide adoption and integration in automated workflows

Automated image segmentation of 3D printed fibrous composite micro-structures using a neural network

A new, automated image segmentation method is presented that effectively identifies the micro-structural objects (fibre, air void, matrix) of 3D printed fibre-reinforced materials using a deep convolutional neural network. The method creates training data from a physical specimen composed of a single, straight fibre embedded in a cementitious matrix with air voids. The specific micro-structure of this strain-hardening cementitious composite (SHCC) is obtained from X-ray micro-computed tomography scanning, after which the 3D ground truth mask of the sample is constructed by connecting each voxel of a scanned image to the corresponding micro-structural object. The neural network is trained to identify fibres oriented in arbitrary directions through the application of a data augmentation procedure, which eliminates the time-consuming task of a human expert to manually annotate these data. The predictive capability of the methodology is demonstrated via the analysis of a practical SHCC developed for 3D concrete printing, showing that the automated segmentation method is well capable of adequately identifying complex micro-structures with arbitrarily distributed and oriented fibres. Although the focus of the current study is on SHCC materials, the proposed methodology can also be applied to other fibre-reinforced materials, such as fibre-reinforced plastics. The micro-structures identified by the image segmentation method may serve as input for dedicated finite element models that allow for computing their mechanical behaviour as a function of the micro-structural composition