PyFMI: A Python Package for Simulation of Coupled Dynamic Models with the Functional Mock-up Interface

With the advent of the Functional Mock-up Interface (FMI) standard, exchanging dynamic models between modeling and simulation tools has been greatly simplified. At the core of it, FMI is a standardized and unified model execution interface for dynamic models. FMI has gained widespread adoption among users and numerous commercial and open source tools implement support for the standard. In this article, the Python package PyFMI is introduced. PyFMI supports loading and execution of models compliant with the FMI standard, called Functional Mock-up Units (FMUs). It includes a master algorithm for simulation of coupled FMUs together with connections to both Assimulo, for simulation of single FMUs, and to SciPy, for performing parameter estimation. Accessing models compliant with FMI in Python, which is an open and accessible scripting language, is intended to further spread the standard and also promote and facilitate future development of the standard. This is due to Python being a convenient language for experimentation and prototyping of numerical algorithms. PyFMI is also demonstrated on a number of problems that highlights its viability for solving industrial grade simulation problems with FMUs

Efficient Predictor for Co-Simulation with Multistep Sub-System Solvers

An industrial model of a dynamic system is usually not just a set of differential equations. External inputs acting on the system are common, such as an external force acting on a body or wind pressing on a car. Update of these inputs needs to be handled by the numerical solver in an efficient way.In dynamical simulation, multistep methods are commonly used. A multistep method uses the solution history in order to predict the future solution. When an input is changed, the history is no longer a good approximation for the future solution which may result in order reductions and simulation failure.In this paper, a modification of the predictor is presented. Modifying the predictor, instead of restarting the method, results in an increased performance of the method. The cost of the modification must be weighed with the cost of restarting the method. Experiments show that the benefit of modifying the predictor outweighs the cost of a restart

Improving Newton's method for Initialization of Modelica models

Initializing a model written in Modelica translates to finding consistent initial values to the underlying DAE. Adding initial equations and conditions creates a system of non-linear equations that can be solved for the initial configuration. This paper reports an implementation of Newton's method to solve the non-linear initialization system. This implementation also uses a regularization method to deal with singular Jacobians as well as sparse solvers to exploit the sparsity structure of the Jacobian. The implementation is based on the open-source projects JModelica.org and Assimulo, KINSOL from the SUNDIALS suite and SuperLU

A Study on Variation Technique in Courses on Scientific Computing

The background of this study is a project aiming at assessing the quality of teaching and learning in scientific computing in different cultural settings. This, we hope will lead us to constructing standards, which can provide outcomes of comparable quality in scientific computing in different countries and societies. Specifically we want to gain insight which quality benchmarks are suitable for the project. The tool we use in teaching is a set of variation techniques. The presented pilot study aims at the examination of the role variation theory for the quality of elementary courses in scientific computing. Earlier studies by others confirmed that variation theory offers a comprehensive set of variables characterizing teaching, well described and easy to follow and measure and which can result in improving teaching. The main data for this investigation was collected via interviewing students

Restarting algorithms for simulation problems with discontinuities

Modelica has in its language support for describing discontinuities; so-called events. Modern integrating environments; like Assimulo; provide elaborated event detection and event handling methods. In addition; the overall performance of a simulation of models with discontinuities (hybrid models) depends strongly on methods for restarting integration after event detection. The presented paper reviews two restarting methods; based oRunge--Kutta starters for multistep methods; and presents first experiments on a hybrid system described in Modelica and simulated by JModelica.org/PyFMI and Assimulo

Associations of Migration, Socioeconomic Position and Social Relations With Depressive Symptoms – Analyses of the German National Cohort Baseline Data

Objectives: We analyze whether the prevalence of depressive symptoms differs among various migrant and non-migrant populations in Germany and to what extent these differences can be attributed to socioeconomic position (SEP) and social relations.Methods: The German National Cohort health study (NAKO) is a prospective multicenter cohort study (N = 204,878). Migration background (assessed based on citizenship and country of birth of both participant and parents) was used as independent variable, age, sex, Social Network Index, the availability of emotional support, SEP (relative income position and educational status) and employment status were introduced as covariates and depressive symptoms (PHQ-9) as dependent variable in logistic regression models.Results: Increased odds ratios of depressive symptoms were found in all migrant subgroups compared to non-migrants and varied regarding regions of origins. Elevated odds ratios decreased when SEP and social relations were included. Attenuations varied across migrant subgroups.Conclusion: The gap in depressive symptoms can partly be attributed to SEP and social relations, with variations between migrant subgroups. The integration paradox is likely to contribute to the explanation of the results. Future studies need to consider heterogeneity among migrant subgroups whenever possible

The interplay of family history of depression and early trauma: associations with lifetime and current depression in the German national cohort (NAKO)

INTRODUCTION: Family history of depression and childhood maltreatment are established risk factors for depression. However, how these factors are interrelated and jointly influence depression risk is not well understood. The present study investigated (i) if childhood maltreatment is associated with a family history of depression (ii) if family history and childhood maltreatment are associated with increased lifetime and current depression, and whether both factors interact beyond their main effects, and (iii) if family history affects lifetime and current depression via childhood maltreatment. METHODS: Analyses were based on a subgroup of the first 100,000 participants of the German National Cohort (NAKO), with complete information (58,703 participants, mean age = 51.2 years, 53% female). Parental family history of depression was assessed via self-report, childhood maltreatment with the Childhood Trauma Screener (CTS), lifetime depression with self-reported physician's diagnosis and the Mini-International Neuropsychiatric Interview (MINI), and current depressive symptoms with the depression scale of the Patient Health Questionnaire (PHQ-9). Generalized linear models were used to test main and interaction effects. Mediation was tested using causal mediation analyses. RESULTS: Higher frequencies of the childhood maltreatment measures were found in subjects reporting a positive family history of depression. Family history and childhood maltreatment were independently associated with increased depression. No statistical interactions of family history and childhood maltreatment were found for the lifetime depression measures. For current depressive symptoms (PHQ-9 sum score), an interaction was found, with stronger associations of childhood maltreatment and depression in subjects with a positive family history. Childhood maltreatment was estimated to mediate 7%–12% of the effect of family history on depression, with higher mediated proportions in subjects whose parents had a depression onset below 40 years. Abuse showed stronger associations with family history and depression, and higher mediated proportions of family history effects on depression than neglect. DISCUSSION: The present study confirms the association of childhood maltreatment and family history with depression in a large population-based cohort. While analyses provide little evidence for the joint effects of both risk factors on depression beyond their individual effects, results are consistent with family history affecting depression via childhood maltreatment to a small extent

Integration av numeriska metoder i kemiteknikutbildningen

Kemiteknikprogrammet fick en ny utbildningsplan 2001. Enligt den gamla utbildningsplanen fanns det en valfri kurs i numerisk analys under årskurs 4 med ett fåtal studenter. I den nya utbildningsplanen integrerades numeriska metoder med kemiteknik redan under första terminen. Metoder undervisas där problemställningen finns. Vi har valt att kalla undervisningen i numeriska metoder för beräkningsteknik. Den beräkningsmässiga delen av kursen i kemiteknik tillsammans med beräkningsteknik omfattar ca 6 poäng av en 12 poängs kurs. I kemiteknik tränas teknologerna att ställa upp modeller för kemitekniska system. För att lösa dessa krävs i flera fall hjälp av numeriska metoder. I kemiteknik används huvudsakligen färdiga funktioner för att lösa modellerna. Beräkningsteknik lär ut principen bakom de använda metoderna. Vi diskuterar de fördelar vi ser i integrerade och ämnesövergripande upplägg av kursen samt våra erfarenheter av undervisningen efter kursen har gått i fyra år. Vi avslutar med att diskutera hur denna ändring har påverkat programmet i sin helhet

A wavelet semidiscretisation of elastic multibody systems

In this paper we consider a coupled system of elastic and rigid bodies. It can be mathematically formulated as a coupled system of ordinary and partial differential equations, often written in its weak form. The discretisation is performed by a Galerkin-type ansatz in connection with a finite element approach or known eigenfunctions. Here, we demonstrate instead the use of a recently published Galerkin-wavelet method and its application to obtain a reasonable,small number of elastic modes

Evaluation of the compression process diagram in presence of magnesium stearate

In the pharmaceutical industry is no longer worked without instrumented tablet presses. The recording of the press information at different parameters of each test series and batches in the development of tablets and an online measurement and control of pressing forces during the production process is becoming increasingly important. Eccentric tablet presses were equipped with sensors for the upper and lower punch force and upper punch way. As sample quantity 100g were selected. All fillers lubricant mixtures were prepared in Turbula lab mixtures with 68 rpm. The bulk and tap density of the excipients were determined according to DIN of 53912 and 53194 on a tap density testers into a 250 ml graduated cylinder. It is to be expected that compression diagrams are changed by lubricant additives. This should give itself to recognize in the different section of the force relationship. This study also showed that the lubricant properties of a lubricant can be greatly influenced by the interaction between the lubricant and ingredient formulation to be exposed