Search results for "Model parameters"
showing 10 items of 37 documents
Modelling of light transmittance and reflectance in flat fluidized photoreactors
1992
In recent years several photon induced chemical reactions involving the use of a solid catalyst have been studied. Flat fluidized beds have proved to be promising devices for carrying out these photocatalytic reactions. There is therefore a need for the modelling of light interactions within such kinds of photoreactors. In this paper, a phenomenological model is proposed for simulating the light transmission and reflection in flat fluidized gas-solid photoreactors. A detailed description of the model is presented. The model predictions were compared with experimental data and a satisfactory agreement was found. Correlations were also suggested for the estimation of model parameters. Depuis …
Viscoelastic Behavior of an Epoxy Resin Modified with Recycled Waste Particles Analyzed through a Fractional Model
2021
It is well-known that the addition of randomly dispersed particles in polymers influences their linear viscoelastic behavior and dynamic mechanical properties. The aim of this study was to describe the viscoelastic behavior of an epoxy resin modified by waste glass and rubber particles using the linear fractional spring-pot model. Unlike complex classical exponential models, fractional models, being only two-parameter dependent, make it easier to characterize the viscoelastic behavior of materials. Isothermal relaxation and single frequency sweep temperature dynamic tests were carried out in a dynamic mechanical analyzer DMA150 by varying the content of the particles from 0 to 20% by weight…
Petri Net Modelling of the Starch Enzymatic Liquefaction
2012
This paper investigates the use of the Petri Net modelling language for the description and analysis of the enzymatic reactions that are used for the starch liquefaction. The Coloured Petri Net formalism supported by the CPN Tools modelling and simulation environment is used. The pools of substrates and products are represented as the places and the possible reactions as the transition of the net. The concurrent reactions are modelled trough transitions that are enabled at the same time. The occurrence probabilities associated with each of these concurrent transitions are chosen as the model parameters. The analysis of the specific properties of the model is used to fit the model to data fr…
Effect of temperature on ammonium removal in Scenedesmus sp
2015
The effect of temperature on microalgal ammonium uptake was investigated by carrying out four batch experiments in which a mixed culture of microalgae, composed mainly of Scenedesmus sp., was cultivated under different temperatures within the usual temperature working range in Mediterranean climate (15-34 ºC). Ammonium removal rates increased with temperature up to 26 ºC and stabilized thereafter. Ratkowsky and Cardinal Temperatures models successfully reproduced the experimental data. Optimum (31.3 ºC), minimum (8.8 ºC) and maximum (46.1 ºC) temperatures for ammonium removal by Scenedesmus sp. under the studied conditions were obtained as model parameters. These temperature-related paramet…
Offshoring along the production chain
2009
Recent contributions on offshoring often assume that firms can freely split their production process into separate steps which can be ranked according to the cost savings from producing abroad. We replace this assumption by the notion of a technologically determined sequence of production steps. In our model, cost savings from offshoring fluctuate along the production chain, and moving unfinished goods across borders causes transport costs. We show that, in such a setting, firms may refrain from offshoring even if relocating individual steps would be advantageous in terms of offshoring costs, or they may offshore (almost) the entire production chain to save transport costs. Small variations…
A nonlinear mixed model approach to predict energy expenditure from heart rate.
2021
Abstract Objective. Heart rate (HR) monitoring provides a convenient and inexpensive way to predict energy expenditure (EE) during physical activity. However, there is a lot of variation among individuals in the EE-HR relationship, which should be taken into account in predictions. The objective is to develop a model that allows the prediction of EE based on HR as accurately as possible and allows an improvement of the prediction using calibration measurements from the target individual. Approach. We propose a nonlinear (logistic) mixed model for EE and HR measurements and an approach to calibrate the model for a new person who does not belong to the dataset used to estimate the model. The …
The Multiscale Stochastic Model of Fractional Hereditary Materials (FHM)
2013
Abstract In a recent paper the authors proposed a mechanical model corresponding, exactly, to fractional hereditary materials (FHM). Fractional derivation index 13 E [0,1/2] corresponds to a mechanical model composed by a column of massless newtonian fluid resting on a bed of independent linear springs. Fractional derivation index 13 E [1/2, 1], corresponds, instead, to a mechanical model constituted by massless, shear-type elastic column resting on a bed of linear independent dashpots. The real-order of derivation is related to the exponent of the power-law decay of mechanical characteristics. In this paper the authors aim to introduce a multiscale fractance description of FHM in presence …
Analysis of the spawning stock-recruitment relationship of vendace (Coregonus albula (L.)) with evaluation of alternative models, additional variable…
2004
– Spawning biomass and recruitment data for vendace from a central Finnish lake were analysed by fitting various recruitment models and comparing the fits statistically. The compensatory models of Ricker, Cushing and Beverton & Holt fitted the data better than the H0 hypothesis of constant proportionality, but model and parameter uncertainties were high. Additional variables were included in an attempt to reduce uncertainties. Heavy wind forcing during the first month after hatching of larvae reduced the recruitment success. For the Ricker and the Cushing models, recruitment seemed to be also negatively associated with the density of the previous year-class. The r2 increased considerably w…
Does GRS 1915+105 exhibit "canonical" black-hole states?
2003
We have analysed RXTE data of the superluminal source GRS 1915+105 in order to investigate if, despite its extreme variability, it also exhibits the canonical source states that characterise other black-hole candidates. The phenomenology of GRS 1915+105 has been described in terms of three states (named A, B and C) based on their hardness ratios and position in the colour-colour diagram. We have investigated the connection between these states and the canonical behaviour and found that the shape of the power spectral continuum and the values of the best-fit model parameters to the noise components in all three states indicate that the source shows properties similar to the canonical very hi…
General parametrization of Majorana neutrino mass models
2020
We discuss a general formula which allows to automatically reproduce experimental data for Majorana neutrino mass models, while keeping the complete set of the remaining model parameters free for general scans, as necessary in order to provide reliable predictions for observables outside the neutrino sector. We provide a proof of this master parametrization and show how to apply it for several well-known neutrino mass models from the literature. We also discuss a list of special cases, in which the Yukawa couplings have to fulfill some particular additional conditions.