Search results for "equation"

2018

Smith and colleagues developed the Brief Resilience Scale (BRS) to assess the individual ability to recover from stress despite significant adversity. This study aimed to validate the German version of the BRS. We used data from a population-based (sample 1: n = 1.481) and a representative (sample 2: n = 1.128) sample of participants from the German general population (age ≥ 18) to assess reliability and validity. Confirmatory factor analyses (CFA) were conducted to compare one- and two-factorial models from previous studies with a method-factor model which especially accounts for the wording of the items. Reliability was analyzed. Convergent validity was measured by correlating BRS scores …

EMERGING PROPERTIES IN POPULATION DYNAMICS WITH DIFFERENT TIME SCALES

1995

The aim of this work is to show that at the population level, emerging properties may occur as a result of the coupling between the fast micro-dynamics and the slow macrodynamics. We studied a prey-predator system with different time scales in a heterogeneous environment. A fast time scale is associated to the migration process on spatial patches and a slow time scale is associated to the growth and the interactions between the species. Preys go on the spatial patches on which some resources are located and can be caught by the predators on them. The efficiency of the predators to catch preys is patch-dependent. Preys can be more easily caught on some spatial patches than others. Perturbat…

The measurement of economic, social and environmental performance of countries: a novel approach

2010

This paper presents a new analytical framework for assessing spatial disparities among countries. It takes for granted that the analysis of a country's performance cannot be limited solely to either economic or social factors. The aim of the paper is to combine relevant economic and 'non-economic' (mainly social) aspects of a country's performance in an integrated logical framework. Based on this idea, a structural simultaneous equation model will be presented and estimated in order to explore the direction of the causal relationship between economic and non-economic aspects of a country's performance. Furthermore, an exploration of the trajectory that each country has registered over time …

Population processes under the influence of disasters occurring independently of population size

1989

Markov branching processes and in particular birth-and-death processes are considered under the influence of disasters that arrive independently of the present population size. For these processes we derive an integral equation involving a shifted and rescaled argument. The main emphasis, however, is on the (random) probability of extinction. Its distribution density satisfies an equation which can be solved numerically at least up to a multiplicative constant. In an example it is also found by simulation.

Sex influences rat personality more than geographical origin

2011

Abstract The Norway rat is an indispensable model organism. Behavioral studies on rats usually concentrate on a single trait without considering how different behaviors are linked to each other and whether there are differences in this respect between rat strains or sexes. This study aims to describe the personality structure of the Norway rat, and investigate if the structure of personality varies between sexes or populations, using owner assessments of pet rats. Rat owners from three countries filled out a questionnaire which was analyzed using structural equation modeling. The data were divided between the sexes and populations, resulting in six groups. Preliminary exploratory factor ana…

A two-point boundary value formulation of a mean-field crowd-averse game

2014

Abstract We consider a population of “crowd-averse” dynamic agents controlling their states towards regions of low density. This represents a typical dissensus behavior in opinion dynamics. Assuming a quadratic density distribution, we first introduce a mean-field game formulation of the problem, and then we turn the game into a two-point boundary value problem. Such a result has a value in that it turns a set of coupled partial differential equations into ordinary differential equations.

Opinion dynamics and stubbornness through mean-field games

2013

This paper provides a mean field game theoretic interpretation of opinion dynamics and stubbornness. The model describes a crowd-seeking homogeneous population of agents, under the influence of one stubborn agent. The game takes on the form of two partial differential equations, the Hamilton-Jacobi-Bellman equation and the Kolmogorov-Fokker-Planck equation for the individual optimal response and the population evolution, respectively. For the game of interest, we establish a mean field equilibrium where all agents reach epsilon-consensus in a neighborhood of the stubborn agent's opinion.

Validation of the F-DBQ: A short (and accurate) risky driving behavior questionnaire for long-haul professional drivers

2021

Abstract Although the Driving Behavior Questionnaire (DBQ) remains the most known tool for assessing risky road behaviors among motor vehicle drivers, recent studies have raised several concerns on the specificity of both driving task conditions and behavioral repertory of certain segments of the driving population. Among them, long-haul (cargo) professional drivers constitute one of the “intensive driving” groups for which the existing adapted behavioral research tools are still very scarce. Purpose The aim of the present study was to test and validate the F-DBQ (or “Freight Driving Behavior Questionnaire”), a short version of the DBQ adapted to the occupational driving conditions and typi…

Comparison of non-Markovianity criteria in a qubit system under random external fields

2013

We give the map representing the evolution of a qubit under the action of non-dissipative random external fields. From this map we construct the corresponding master equation that in turn allows us to phenomenologically introduce population damping of the qubit system. We then compare, in this system, the time-regions when non-Markovianity is present on the basis of different criteria both for the non-dissipative and dissipative case. We show that the adopted criteria agree both in the non-dissipative case and in the presence of population damping.

A Side-by-Side Single Sex Age-Structured Human Population Dynamic Model: Exact Solution and Model Validation

2008

A side-by-side single sex age-structured population dynamic model is presented in this paper. The model consists of two coupled von Foerster-McKendrick-type quasi-linear partial differential equations, two initial conditions, and two boundary conditions. The state variables of the model are male and female population densities. The solutions of these partial differential equations provide explicit time and age dependence of the variables. The initial conditions define the male and female population densities at the initial time, while the boundary conditions compute the male and female births at zero-age by using fertility rates. The assumptions of the nontime-dependence of the death and fe…