Search results for "equation"
showing 10 items of 4219 documents
Time Scale Effects and Interactions of Rainfall Erosivity and Cover Management Factors on Vineyard Soil Loss Erosion in the Semi-Arid Area of Souther…
2019
Several authors describe the effectiveness of cover crop management practice as an important tool to prevent soil erosion, but at the same time, they stress on the high soil loss variability due to the interaction of several factors characterized by large uncertainty. In this paper the Revised Universal Soil Loss Equation (RUSLE) model is applied to two Sicilian vineyards that are characterized by different topographic factors
Finite-Element Modeling of Floodplain Flow
2000
A new methodology for a robust solution of the diffusive shallow water equations is proposed. The methodology splits the unknowns of the momentum and continuity equations into one kinematic and one parabolic component. The kinematic component is solved using the slope of the water level surface computed in the previous time-step and a zero-order approximation of the water head inside the mass-balance area around each node of the mesh. The parabolic component is found by applying a standard finite-element Galerkin procedure, where the source terms can be computed from the solution of the previous kinematic problem. A simple 1D case, with a known analytical solution, is used to test the accur…
Testing alternative erosivity indices to predict event soil loss from bare plots in Southern Italy
2009
Methods for predicting unit plot soil loss for the ‘Sparacia’ Sicilian (Southern Italy) site were developed using 316 simultaneous measurements of runoff and soil loss from individual bare plots varying in length from 11 to 44 m. The event unit plot soil loss was directly proportional to an erosivity index equal to (QREI30)1·47, being QREI30 the runoff ratio (QR) times the single storm erosion index (EI30). The developed relationship represents a modified version of the USLE-M, and therefore it was named USLE-MM. By the USLE-MM, a constant erodibility coefficient was deduced for plots of different lengths, suggesting that in this case the calculated erodibility factor is representative of a…
Eckhaus instability of stationary patterns in hyperbolic reaction–diffusion models on large finite domains
2022
AbstractWe have theoretically investigated the phenomenon of Eckhaus instability of stationary patterns arising in hyperbolic reaction–diffusion models on large finite domains, in both supercritical and subcritical regime. Adopting multiple-scale weakly-nonlinear analysis, we have deduced the cubic and cubic–quintic real Ginzburg–Landau equations ruling the evolution of pattern amplitude close to criticality. Starting from these envelope equations, we have provided the explicit expressions of the most relevant dynamical features characterizing primary and secondary quantized branches of any order: stationary amplitude, existence and stability thresholds and linear growth rate. Particular em…
Improved Hölder regularity for strongly elliptic PDEs
2019
We establish surprising improved Schauder regularity properties for solutions to the Leray-Lions divergence type equation in the plane. The results are achieved by studying the nonlinear Beltrami equation and making use of special new relations between these two equations. In particular, we show that solutions to an autonomous Beltrami equation enjoy a quantitative improved degree of H\"older regularity, higher than what is given by the classical exponent $1/K$.
Associations between parental rules, style of communication and children's screen time
2015
Background Research suggests an inverse association between parental rules and screen time in pre-adolescents, and that parents’ style of communication with their children is related to the children’s time spent watching TV. The aims of this study were to examine associations of parental rules and parental style of communication with children’s screen time and perceived excessive screen time in five European countries. Methods UP4FUN was a multi-centre, cluster randomised controlled trial with pre- and post-test measurements in each of five countries; Belgium, Germany, Greece, Hungary and Norway. Questionnaires were completed by the children at school and the parent questionnaire was brough…
Modelling of a hydro-pneumatic system for heave compensation
2018
This paper presents a mathematical model of the dynamic behaviour of a passive heave compensation system. The main purpose is to develop a model that enables cost-efficient prototyping and testing of the control system in an active heave compensator. The physics are described by first principles, and result in 21 ordinary differential equations. Temperature calculations are included as an option during simulation in order to investigate its effect on the results. Similarly is a non-ideal gas law (Redlich-Kwong equation) implemented and compared to the ideal gas law. Verification against field data shows that the model is in good accordance with real-life drilling operations. It is further s…
Numerical methods to compute sentinels for parabolic systems with an application to source terms identification
1994
We apply the method of sentinels to the identification of source terms in parabolic systems. We present two numerical approaches; the first one is based on the solution of an optimal control problem, and the second one is based on the solution of a linear system of equations. In numerical experiments, we compare these approaches in terms of accuracy and computational cost.
Reliability of Parameter Estimation Methods Applied to the Identification of Biomedical Multicompartment Systems
1985
Abstract The reliability of parameter estimation in biomedical multicompartment models is influenced by the chosen mathematical representation of the model, by the sensitivity of the output on the relevant parameters to be identified and by the experimental conditions, e.g. choice of the data-set. this paper the reliability of different parameter estimation methods applied in a multi-compartment model of the circulatory system has been studied under the assumption that there exists a partially system output insensitivity against the compliance parameters. Suitable conditions for efficient parameter estimation have been found by simulation of sensitivity equations of the system, which is of …
Technique of Statistical Validation of Rival Models for Fatigue Crack Growth Process and Its Identification
2011
The development of suitable models of stochastic crack growth process is important for the reliability analysis of fatigued structures as well as the scheduling of inspection and repair/replacement maintenance. Based on modifications of the solution of the deterministic differential equation for the crack growth rate, where a stochastic nature of this rate is expressed by a random disturbance embedded in the solution of the differential equation, the simple stochastic models are presented for practical applications. Each of these models represents a stochastic version of the solution of the Paris-Erdogan law equation. The models take into account the random disturbance parameters while main…