Search results for " modeling"
showing 10 items of 2411 documents
Introduction to: Enabling Collaborative Governance through Systems Modeling Methods
2020
This opening chapter sets out a structure for considering collaborative governance for public policy and managerial problem-solving through systemic principles, as well as through the use of group processes to facilitate agreement and buy-in in collective strategies. Such a collection of tools, techniques, and frameworks is needed to establish the value of these approaches and to accelerate their dissemination through the field.
Applying Numerical Weather Prediction Models to the Production of New European Wind Atlas : Sensitivity studies of the wind climate to the planetary …
2018
Reliable and precise information about the wind speed climate is crucial for the development of wind energy. Meteorological processes in the mesoscale (2 – 200 km) can be represented using Numerical Weather Prediction (NWP) models such as the Weather Research and Forecast model (WRF), but before their application for creating wind energy atlases, their results and sensitivity to modelling parameters should be investigated. Here the WRF model wind speed results for the year 2015 for the Baltic Sea region are investigated, and the effect of the planetary boundary layer parametrization scheme is analyzed.
Modeling an X-ray Flare on Proxima Centauri: evidence of two flaring loop components and of two heating mechanisms at work
2003
We model in detail a flare observed on Proxima Centauri with the EPIC-PN on board XMM-Newton at high statistics and high time resolution and coverage. Time-dependent hydrodynamic loop modeling is used to describe the rise and peak of the light curve, and a large fraction of the decay, including its change of slope and a secondary maximum, over a duration of more than 2 hours. The light curve, the emission measure and the temperature derived from the data allow us to constrain the loop morphology and the heating function and to show that this flare can be described with two components: a major one triggered by an intense heat pulse injected in a single flaring loop with half-length ~1.0 10^{…
Towards Stable Radial Basis Function Methods for Linear Advection Problems
2021
In this work, we investigate (energy) stability of global radial basis function (RBF) methods for linear advection problems. Classically, boundary conditions (BC) are enforced strongly in RBF methods. By now it is well-known that this can lead to stability problems, however. Here, we follow a different path and propose two novel RBF approaches which are based on a weak enforcement of BCs. By using the concept of flux reconstruction and simultaneous approximation terms (SATs), respectively, we are able to prove that both new RBF schemes are strongly (energy) stable. Numerical results in one and two spatial dimensions for both scalar equations and systems are presented, supporting our theoret…
A probabilistic approach to radiant field modeling in dense particulate systems
2016
Radiant field distribution is an important modeling issue in many systems of practical interest, such as photo-bioreactors for algae growth and heterogeneous photo-catalytic reactors for water detoxification.In this work, a simple radiant field model suitable for dispersed systems showing particle size distributions, is proposed for both dilute and dense two-phase systems. Its main features are: (i) only physical, independently assessable parameters are involved and (ii) its simplicity allows a closed form solution, which makes it suitable for inclusion in a complete photo-reactor model, where also kinetic and fluid dynamic sub-models play a role. A similar model can be derived by making us…
Particle flow modelling in slurry-fed stirred vessels
2004
In this paper experimental information on the retention time distribution (RTD) of solid particles in a high-aspect-ratio vessel, stirred by three equally spaced Rushton turbines, is presented. The relevant data were obtained by a special technique named twin system approach (TSA) that greatly simpli+es the handling of particle-laden streams and is therefore particularly suited for investigating particle RTD in 9ow systems. The technique fundamentals are +rst summarized, together with the data analysis procedure. This lastly requires a numerical deconvolution operation that is easily performed with the help of Z-transforms. Two di;erent approaches for excluding the spurious contributions of…
On the mechanisms involved in the tensile strength of a dissimilar Ti6Al4V/316L laser welded assembly
2021
International audience; The aim of the present work is to analyze the thermomechanical behavior of dissimilar laser seams by means of FE modeling. The case of a Ti6Al4V/316L assembly with vanadium insert was considered. Effective mechanical properties of the main materials and cords were first estimated from NHT measurements. Modeling of the double pass laser welding process was performed first by considering shrinking of the two weld seams during manufacturing, to get the residual stress state in the welded assembly. Modeling of the tensile test was performed in a second step to study the assembly behavior during loading. In these modeling results, the mesh was the cross-section of the mic…
Kramers potential study of the Rouse-like dynamics of short alkane chains.
1999
In this work we present a Kramers potential study of the orientational dynamics and shear viscosity of short chain alkanes. In this approach the determination of the orientational relaxation time is reduced to the calculation of static moments of single chain conformations. We study a chemically realistic alkane model that asymptotically produces Gaussian chain conformations by means of a Monte Carlo simulation. Our results are applicable to single chain descriptions of polymer melt dynamics and to the intrinsic viscosity of molecules in a Theta solvent. When we map the unknown time unit of our relaxation time result for one particular chain length and temperature to the value obtained for …
Job Characteristics, Recovery Experiences and Occupational Well-being: Testing Cross-lagged Relationships across 1 Year
2013
The aim of the present study conducted among 274 Finnish employees was to examine the relationships between job characteristics, recovery experiences and occupational well-being across 1 year. We hypothesized that these relationships would follow normal causation, that is, job characteristics at T1 predict recovery experiences (detachment, relaxation, mastery and control at off-job time) and well-being (fatigue at work and work engagement) at T2, and recovery experiences at T1 predict well-being at T2. The structural equation modelling analyses lent support to the hypothesized normal causation model compared with the reversed causation and reciprocal models. However, only the longitudinal r…
Positive parenting and parenting stress among working mothers in Finland, the UK and the Netherlands : Do working time patterns matter?
2017
This study explored the effects of working time patterns on positive parenting and parenting stress, and the moderating effects of working hours, the unpredictability of work schedules, and autonomy over working time in a European context. This cross-national survey study compared Finnish (n = 337), Dutch (n = 283) and British (n = 317) mothers with children under the age of 13, using structural equation modeling with a multigroup procedure. We found a connection between working time patterns and positive parenting but the nature of the connection differed between countries. In all three countries, no relationship was found between working time pattern and parenting stress, while unpredict…