Search results for "equation"

Predicting change in middle school students’ leisure‐time physical activity participation: A prospective test of the trans‐contextual model

2020

We applied the trans-contextual model (TCM) to examine the effects of middle school students’ perceived autonomy support from their physical education (PE) teachers on autonomous motivation toward PE in school and, critically, autonomous motivation toward, and actual participation in, leisure-time physical activity (PA). The research adopted a three-wave prospective design enabling the modeling of change in the TCM constructs over time. Middle school students (N = 248) aged from 12 to 16 years reported their perceived autonomy support, autonomous motivation in PE, autonomous motivation toward leisure-time PA, attitudes, subjective norms, perceived behavioral control (PBC), intentions for PA…

Exploring working conditions as determinants of job satisfaction: an empirical test among Catalonia service workers

2011

Job satisfaction is particularly important in the service industries since it involves direct contact with customers and thus has a direct influence on company performance. This paper analyses the impact of 10 working conditions on job satisfaction by means of structural equation modeling in a representative stratified random sample of 1553 service sector employees in Catalonia, Spain. Significant effects in social aspects (recognition of a job well done and social support) were found, followed by psychological loads (emotional demands and job insecurity) and by task contents (development and meaning, and predictability). These variables explained 50% of the variance in job satisfaction.

Uncertainty quantification analysis of the biological Gompertz model subject to random fluctuations in all its parameters

2020

[EN] In spite of its simple formulation via a nonlinear differential equation, the Gompertz model has been widely applied to describe the dynamics of biological and biophysical parts of complex systems (growth of living organisms, number of bacteria, volume of infected cells, etc.). Its parameters or coefficients and the initial condition represent biological quantities (usually, rates and number of individual/particles, respectively) whose nature is random rather than deterministic. In this paper, we present a complete uncertainty quantification analysis of the randomized Gomperz model via the computation of an explicit expression to the first probability density function of its solution s…

Nonsmooth Penalty Techniques in Control of the Continuous Casting Process

1991

We introduce a mathematical model which is used to simulate the continuous casting process and to control the secondary cooling water sprays. The main object is to minimize the defects in the final products. The problem is formulated as an optimal control problem where the cost function is constructed according to certain metallurgical criteria and constraints. The temperature distribution of the strand is calculated by solving a nonlinear heat equation with free boundaries between solid and liquid phases.

UNIVERSITY STUDENTS’ GROWTH GOALS, OPPORTUNITIES FOR GOAL FULFILLMENT, AND PERCEIVED UNIVERSITY AND MESOSYSTEM SUPPORT

2021

This study assessed the relationship between students’ growth goals and perceived opportunities to achieve these goals in Latvia and the perceived support from the university and the mesosystem. Socialization models emphasize that the setting of personal goals occurs in continuous interaction with the sociocultural context, which includes perceived opportunities to achieve these goals and the interpersonal environment. Both – perceived support from close people (mesosystems) and perceived support from the university – are significant for students. The study involved 432 university students between 18 and 49. We have assessed the extent to which students’ goals regarding education, work, and…

Three periodic solutions for perturbed second order Hamiltonian systems

2009

AbstractIn this paper we study the existence of three distinct solutions for the following problem−u¨+A(t)u=∇F(t,u)+λ∇G(t,u)a.e. in [0,T],u(T)−u(0)=u˙(T)−u˙(0)=0, where λ∈R, T is a real positive number, A:[0,T]→RN×N is a continuous map from the interval [0,T] to the set of N-order symmetric matrices. We propose sufficient conditions only on the potential F. More precisely, we assume that G satisfies only a usual growth condition which allows us to use a variational approach.

The interrelation between stochastic differential inclusions and set-valued stochastic differential equations

2013

Abstract In this paper we connect the well established theory of stochastic differential inclusions with a new theory of set-valued stochastic differential equations. Solutions to the latter equations are understood as continuous mappings taking on their values in the hyperspace of nonempty, bounded, convex and closed subsets of the space L 2 consisting of square integrable random vectors. We show that for the solution X to a set-valued stochastic differential equation corresponding to a stochastic differential inclusion, there exists a solution x for this inclusion that is a ‖ ⋅ ‖ L 2 -continuous selection of X . This result enables us to draw inferences about the reachable sets of solutio…

Role of conditional probability in multiscale stationary markovian processes.

2010

The aim of the paper is to understand how the inclusion of more and more time-scales into a stochastic stationary Markovian process affects its conditional probability. To this end, we consider two Gaussian processes: (i) a short-range correlated process with an infinite set of time-scales bounded from below, and (ii) a power-law correlated process with an infinite and unbounded set of time-scales. For these processes we investigate the equal position conditional probability P(x,t|x,0) and the mean First Passage Time T(L). The function P(x,t|x,0) can be considered as a proxy of the persistence, i.e. the fact that when a process reaches a position x then it spends some time around that posit…

The Master Equation

2009

Ambit processes and stochastic partial differential equations

2011

Ambit processes are general stochastic processes based on stochastic integrals with respect to Levy bases. Due to their flexible structure, they have great potential for providing realistic models for various applications such as in turbulence and finance. This papers studies the connection between ambit processes and solutions to stochastic partial differential equations. We investigate this relationship from two angles: from the Walsh theory of martingale measures and from the viewpoint of the Levy noise analysis.