Search results for " modelling"
showing 10 items of 1055 documents
La sopravvivenza immediata delle start-up italiane del settore manifatturiero sanitario: un'analisi multilevel
2017
The immediate survival of the Italian start-up businesses in healthcare industry: a multilevel analysis Objectives: The purpose of this contribution is to provide novel evidence about the main determinants of the short-run survival of pharmaceutical and medical device manufacturing start-up firms in Italy. In order to assess both the firm-specific determinants and the observed and unobserved regional and contextual characteristics, we model the three-year firm survival probability by means of a multilevel logistic framework. Methods and Results: The empirical analysis focuses on an internationally comparable database of the population of firms built up and managed by the Italian National In…
Simulation of extreme heat events over the Valencia coastal region: Sensitivity to initial conditions and boundary layer parameterizations
2019
The Valencia coastal region (Western Mediterranean) is especially sensitive to extreme heat events, where they are really common. However, due to its geophysical characteristics and climatic conditions, the incidence of high and extreme temperatures may still be modulated over this area by means of sea breeze circulations, defining a Sea Breeze Convergence Zone (SBCZ) due to the meet and interaction of these mesoscale conditions and Western synoptic-scale wind regimes. A proper definition of this convergence zone is of significant importance over the study area for the simulation and forecast of intense-heat meteorological events. This study analyses a week period in August 2010 over this a…
Stochastic model for electrical loads in Mediterranean residential building: validation and applications
2014
A major issue in modelling the electrical load of residential building is reproducing the variability between dwellings due to the stochastic use of different electrical equipment. In that sense and with the objective to reproduce this variability, a stochastic model to obtain load profiles of household electricity is developed. The model is based on a probabilistic approach and is developed using data from the Mediterranean region of Spain. A detailed validation of the model has been done, analysing and comparing the results with Spanish and European data. The results of the validation show that the model is able to reproduce the most important features of the residential electrical consum…
Impact of Initial Soil Temperature Derived from Remote Sensing and Numerical Weather Prediction Datasets on the Simulation of Extreme Heat Events
2016
Extreme heat weather events have received increasing attention and has become of special importance as they can remarkably affect sectors as diverse as public health, energy consumption, water resources, natural biodiversity and agricultural production. In this regard, summer temperatures have become a parameter of essential interest under a framework of a hypothetical increase in the number of intense-heat conditions. Thus, their forecast is a crucial aspect bearing in mind a mitigation of the effects and impacts that these intense-heat situations could produce. The current work tries to reach a better understanding of these sorts of situations that are really common over the Western Medit…
Numerical simulation of heat transfer, fluid flow and elements diffusion during laser welding of dissimilar steels
2017
The design of new steel grades offering equivalent mechanical performances for lower thicknesses and the added value with the possibility to join two different steel grades, require development and control of joining processes. Thanks to high precision and good flexibility, the laser welding became one of the most used processes for joining of dissimilar welded blanks. The prediction of local chemical composition in the weld formed between dissimilar steels in function of the welding parameters is essential because the dilution rate and the distribution of alloying elements in the melted zone determine the final tensile strength of the weld. The goal of the present study is to create and to…
Nitrogen recovery using a membrane contactor: Modelling nitrogen and pH evolution
2020
[EN] A hollow fibre membrane contactor has been applied for nitrogen recovery from anaerobic digestion supernatant at different operating conditions obtaining nitrogen recovery efficiencies over 99 %. A mathematical model able to represent the time evolution of pH and nitrogen concentration during the recovery process is presented in this paper. The developed model accurately reproduced the results obtained in 26 experiments carried out at different pH values (from 9 to 11), temperatures (from 25 to 35 degrees C), membrane surfaces (from 1.2 to 2.4 m(2)) and feed flow rates (from 0.33 x 10(-5) to 5.83 x 10(-5) m(3)/s) predicting the variations in nitrogen recovery rates measured at the diff…
Minimizing membrane bioreactor environmental footprint by multiple objective optimization.
2020
This paper presents a modelling study aimed at minimizing the environmental foot print of a membrane bioreactor (MBR) for wastewater treatment. Specifically, an integrated model for MBR was employed in view of the management optimization of an MBR biological nutrient removal (BNR) pilot plant in terms of operational costs and direct greenhouse gases emissions. The influence of the operational parameters (OPs) on performance indicators (PIs) was investigated by adopting the Extended-FAST sensitivity analysis method. Further, a multi-objective analysis was performed by applying the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The results show-up that the sludge …
Sensitivity and uncertainty analysis of an integrated ASM2d MBR model for wastewater treatment
2018
Abstract An integrated membrane bioreactor (MBR) model was previously proposed and tested. The model provides a comprehensive and detailed description of the nitrogen biological removal processes with respect to up-to-date literature. This paper presents a sensitivity and uncertainty analysis aimed at identifying the key factors affecting the variability of the model predictions. The Standardized Regression Coefficients (SRC) method was adopted for the sensitivity analysis. The uncertainty analysis was employed by running Monte Carlo simulations by varying only the value of the key factors affecting the model outputs. The sensitivity analysis combined with the uncertainty analysis applied h…
A comprehensive integrated membrane bioreactor model for greenhouse gas emissions
2018
Abstract A comprehensive integrated membrane bioreactor (MBR) model for wastewater treatment is here proposed. The model quantifies the main biological and physical processes. The model describes the biological removal of organic matter, nitrogen and phosphorus including greenhouse gases (carbon dioxide, CO 2 and nitrous oxide, N 2 O). The model takes into account the following main innovative aspects jointly: i. Two-step nitrification process; ii. N 2 O formation due to ammonia-oxidizing bacteria as a product of the hydroxylamine oxidation (NH 2 OH) and of the nitrite (NO 2 − ) reduction; iii. Soluble microbial product (SMP) formation/degradation due to microbial growth and endogenous resp…
Wait-and-switch relaxation model: Relationship between nonexponential relaxation patterns and random local properties of a complex system
2006
The wait-and-switch stochastic model of relaxation is presented. Using the ``random-variable'' formalism of limit theorems of probability theory we explain the universality of the short- and long-time fractional-power laws in relaxation responses of complex systems. We show that the time evolution of the nonequilibrium state of a macroscopic system depends on two stochastic mechanisms: one, which determines the local statistical properties of the relaxing entities, and the other one, which determines the number (random or deterministic) of the microscopic and mesoscopic relaxation contributions. Within the proposed framework we derive the Havriliak-Negami and Kohlrausch-Williams-Watts funct…